What this is
- This review explores the relationship between and type 2 diabetes mellitus (T2D).
- , an iron-dependent form of cell death, contributes to the pathogenesis of T2D.
- It highlights the role of (miRNAs) in regulating and suggests potential therapeutic strategies targeting this pathway.
Essence
- significantly impacts insulin secretion and the progression of type 2 diabetes mellitus (T2D). Targeting through specific inhibitors and modulation may offer new therapeutic avenues for managing T2D.
Key takeaways
- contributes to pancreatic β-cell dysfunction in T2D by promoting oxidative stress and lipid peroxidation, leading to impaired insulin secretion.
- (miRNAs) regulate and influence T2D progression. Specific miRNAs can either promote or inhibit , presenting potential targets for therapeutic intervention.
- Therapeutic strategies targeting include the use of inhibitors and -guided therapies, which may improve β-cell function and insulin secretion in diabetic patients.
Caveats
- Clinical evidence supporting the efficacy of -targeted therapies in T2D is currently limited, necessitating further research.
- Challenges in translating preclinical findings to clinical settings include issues with drug delivery, stability, and specificity of inhibitors.
Definitions
- ferroptosis: A regulated form of cell death characterized by iron accumulation and lipid peroxidation, distinct from apoptosis.
- microRNA (miRNA): Small noncoding RNA molecules that regulate gene expression by binding to messenger RNAs, influencing various biological processes.
AI simplified
Introduction
One of the earliest illnesses to be documented was diabetes, which dates back to an Egyptian book written around 1500 before Common Era [1]. The incidence of Type 2 diabetes (T2D) has significantly increased since 1960, primarily due to sedentary lifestyles and excessive calorie intake, particularly from diets high in saturated fat and carbohydrates. This has led to obesity and T2D, especially in young and old people and ethnic communities with higher genetic risk. About 38.4 million Americans, or 11.6% of the country's total population, have diabetes as of 2021; 29.7 million of these cases are diagnosed, while 8.7 million are not [2]. Recent estimates indicate that by 2050, the number of Americans with diabetes will have more than doubled, potentially affecting up to 33% of the adult population [3].
Ferroptosis is a unique and newly discovered kind of cell death that has been connected to several illnesses, such as lung cancer [4], infections [5], inflammatory bowel disease [6], diabetes [7], neurological disorders [8], and acute kidney disease [8]. It is characterized by iron buildup, lipid peroxidation, excessive reactive oxygen species (ROS), and depletion of glutathione. Ferroptosis is considered a non-apoptotic controlled cell death process as it does not require caspases (aspartate-specific cysteine proteases). The process is triggered by an iron-dependent buildup of ROS, followed by the peroxidation of membrane polyunsaturated fatty acid phospholipids, causing significant damage [9]. Ferroptosis differs from other programmed cell death due to smaller mitochondria, rupture of the outer mitochondrial membrane, preservation of the plasma membrane, normal nuclear size, and lack of chromatin condensation [9 –11].
Ferroptosis significantly contributes to the development and progression of T2D. Iron metabolism plays a role in various aspects of glucose metabolism, including insulin production [12], hepatic metabolism [12], and lipid metabolism [13] while sustaining blood glucose homeostasis across multiple organs and tissues. Therefore, understanding the relationship between ferroptosis and diabetes may result in the development of novel pharmaceutical therapies. Thus, the purpose of this review is to offer fresh insights into possible therapeutic targets and diagnostic biomarkers that could enhance diabetes care and lessen its consequences. In addition, the growing significance of epigenetic regulators, including microRNAs and N6-methyladenosine (m6A), in regulating ferroptosis-related gene expression in type 2 diabetes will be emphasized.
Type 2 diabetes mellitus (T2D)
Overview of type 2 diabetes mellitus (T2D)
T2D, earlier referred to as diabetes of adulthood, is distinguished by elevated blood glucose levels, insulin resistance, and inadequate production of insulin [14]. Common symptoms include exhaustion, more frequent urination and thirst, unexplained weight loss, increased hunger, a burning sensation in the body, and sores that do not heal [15]. Furthermore, long-term consequences and complications from elevated blood glucose levels include coronary artery disease, stroke, and diabetic retinal degeneration, which can cause blindness, kidney damage, and inadequate circulation in the lower extremities which may result in amputations [16]. Moreover, the sudden development of hyperosmolarity and hyperglycemic status [17, 18].
T2D is primarily caused by obesity, a sedentary lifestyle, and hereditary variables, which are accountable for the altered glucose homeostasis observed in T2D [19]. In addition, T2D has been linked to gut dysbiosis, such as Bacteroides vulgatus and Prevotella copri [20, 21]. Approximately 90% of occurrences of diabetes are T2D, and the remaining 10% are mostly caused by type 1 diabetes and pregnancy-related diabetes [22]. Diabetes is diagnosed using blood tests, such as glycated hemoglobin (HbA1C) levels, glucose tolerance testing, and plasma glucose levels during fasting [23]. T2D can be prevented by maintaining a healthy weight, getting regular exercise, and eating a balanced diet rich in fruits and vegetables and low in harmful fats and carbs [24], and if blood sugar levels are not sufficiently reduced, the medicine metformin is usually advised [25].
Alarming findings from epidemiological statistics point to a concerning future for T2D. The International Diabetes Federation (IDF) reports that among diabetic patients, diabetes killed 4.2 million people in 2019, and that 463 million people aged and increased to 700 million diabetic patients in 2045 [26]. The development of T2D is driven by many risk factors, including genetic predisposition, involving dysfunction in liver function and insulin secretion. The need for better risk factors is highlighted by the excessively high glucose levels caused by this malfunction, which is further worsened by β-cell failure [27, 28]. Improving modifiable variables such as obesity, inactivity, and bad diets can prevent many instances, whereas non-modifiable ones such as ethnicity and family history contribute to the prevalence [29, 30].
Pathophysiology of type 2 diabetes (T2D)
T2D is a long-term metabolic condition characterized by tissue insulin resistance (IR), insufficient insulin compensatory secretion response, and insufficient insulin secretion by islet β-cells of the pancreas [31, 32]. The liver, kidneys, brain, skeletal muscle, adipose tissue, small intestine, and pancreas (β-cells and α-cells) are among the organs implicated in the development of T2D [33]. Adipokine dysregulation, inflammation, and alterations in gut microbiota have been identified as significant pathophysiological contributors, according to evolving research [34].
Genetic susceptibility and overnutrition states, i.e., chronic hyperglycemia and hyperlipidemia, are the causes of insulin resistance and low-grade chronic inflammation. These metabolic stressors induce endoplasmic reticulum (ER) stress via activation of the apoptotic unfolded protein response (UPR), posing toxic pressure on pancreatic β-cells. Furthermore, β-cells increase proinsulin and islet amyloid polypeptide (IAPP) synthesis after chronic hyperglycemia to enhance the intracellular retention of misfolded insulin and IAPP in the ER. Oxidative protein folding catalytically increases this misfolding, generating ROS that further destabilize cellular structure. The resulting stressful environment attracts macrophages that trigger local inflammation in the islet. To satisfy the increased demand for metabolism, β-cells attempt to secrete extra insulin. This adaptive response, though, can destroy islet architecture, impair cell-to-cell communication, and disrupt concerted release of insulin and glucagon and thereby worsen hyperglycemia during pathologic states. Ultimately, insulin secretory malfunction due to impaired insulin biosynthesis, structural flaws in insulin, and impaired exocytosis represents an important mechanism of β-cell failure and T2D (Fig. 1B) [39].
Even when hyperglycemia is managed, diabetic problems may still arise, because hyperglycemia causes mitochondria to produce too many ROS [40]. When proper glycemic control is started very early, the damage caused by oxidative stress due to hyperglycemia can be avoided; nevertheless, if inadequate control continues for an extended period, it is difficult to reverse [41, 42]. Hyperglycemia, oxidative stress elevation, and excessive advanced glycation end products (AGEs) production are all related to the initial phases of T2D. The respiratory chain's components experience chronic protein glycation as the illness worsens, which, when combined with the damaged DNA of mitochondria, can cause a series of events that are independent of hyperglycemia and result in a synergy between oxidative stress and AGEs [43]. Through receptors, the consequences of this metabolic disequilibrium trigger inflammatory processes, low-grade inflammation, and nuclear factor kappa B (NF-κB) [44]. Insulin resistance is a feature of T2D, but the primary mechanisms by which it is associated with ferroptosis are increased oxidative stress and lipid peroxidation. Hyperglycemia and impaired insulin signaling contribute to the accumulation of ROS, which increases the susceptibility of cells to ferroptosis via iron-dependent lipid damage mechanisms [45].
Mechanisms of-cell insulin secretion under normal and diabetic conditions. The insulin secretion from the-cells, under normal settings (), is triggered by high glucose concentration. Glucose enters the cell through glucose transporter 2 (GLUT2). The adenosine triphosphate (ATP)/adenosine diphosphate (ADP) ratio rises as a result of glucose catabolism. ATP-dependent potassium channels are shut, causing membrane depolarization with subsequent stimulation of phospholipase C (PLC) activity and activation of voltage-dependent Cachannels. The latter permits the entry of Ca, which in turn causes the exocytosis of insulin. Camobilization and insulin secretion are facilitated by additional Cachannels, such as purinergic receptor X and Y (P2X and P2Y), Sarco-endoplasmic reticulum Ca-ATPase (SERCA), and ryanodine receptor channel (RYR). Furthermore, PLC hydrolyzes PIP₂ (phosphatidylinositol 4,5-bisphosphate) into DAG (diacylglycerol) and IP₃ (inositol 1,4,5-trisphosphate). IP₃ binds to IP₃ receptors (IP₃R) on the endoplasmic reticulum (ER), causing Ca⁺ release from ER stores into the cytoplasm. In contrast, hyperglycemia and lipotoxicity () induce oxidative stress and ER stress, triggering unfolded protein response (UPR), reduced Ca⁺ signaling, accumulation of misfolded proteins, and activation of proapoptotic pathways. These disturbances stimulate proapoptotic signaling, resulting in β-cell dysfunction and impaired insulin secretion. ROS: reactive oxygen species; FFAs: free fatty acid β β A B 2+ 2+ 2+ 2+ 2+ 2 2
Ferroptosis
Overview of ferroptosis
Ferroptosis is a recently identified kind of iron-dependent cellular death marked by iron accumulation and an accumulation of lipid peroxidation. In 2003, Dolma, Lessnick [46] first found that the chemical erastin was found, which demonstrated specific lethality towards cancer cells expressing renin–angiotensin system (RAS); nonetheless, it was observed that the cells succumbed by a mechanism distinct from conventional programmed cell death. As this research progresses, Dixon, Lemberg [47] first developed ferroptosis in 2012, an iron-dependent variant of regulated cell death (RCD) characterized by unique morphological and biochemical attributes relative to other forms of cell death. Ferroptosis is a specific type of cell death triggered by the presence of ROS that rely on iron [46], it is a distinct form of controlled cell death that lacks the involvement of caspases, which are crucial in inducing apoptosis by cleaving specific intracellular substrates [48, 49]. Unlike other forms of controlled cell death, such as parthanatos and necroptosis, ferroptosis operates independently of apoptotic effectors, such as caspases, Bcl-2 homologous antagonist/killer (BAK), and Bcl-2-associated X protein (BAX) [50]. Notably, ferroptosis relies on intracellular iron and lipid peroxide buildup, setting it apart from other forms of controlled cell death. Unlike necroptosis, ferroptosis does not require vital components, such as receptor-interacting protein kinase 1 (RIPK1), RIPK3, and mixed lineage kinase domain-like protein (MLKL). Ferroptosis also results in the inhibition of oxidoreductase, particularly glutathione peroxidase 4 (GPX4), which is a scavenger of lipid peroxides [7]. Furthermore, downstream of p53, ferroptosis may function as an intrinsic tumor-inhibitory mechanism in the cancer setting [51]. It is still debatable whether or not small molecules of ferroptosis stimulants can be employed to specifically kill cancer cells with anomalies in the RAS–RAF–MEK pathway [46, 52]. Furthermore, ferroptosis is linked to damaged mitochondria in specific cells, such as kidney cells, which exhibit smaller organelles, no longer visible mitochondrial cristae, and ruptured outer membranes [53].
Consequently, the regulation of ferroptosis is intricately linked to the metabolism of iron, lipids, amino acids, and glutathione. In the last 10 years, a growing body of research has substantiated the notion that ferroptosis is significantly involved in the pathophysiology of T2DM and associated consequences [54 –56].
Mechanism of ferroptosis
Iron metabolism and ferroptosis
In the extracellular environment, pancreatic β cells secrete hepcidin, which binds to transferrin and facilitates its internalization [60, 61]. Research indicates that transferrin facilitates a positive feedback mechanism for iron control during glucose-stimulated insulin production [62]. Fe2+ in the Labile Iron Pool (LIP) participates in insulin production. Iron is present in nearly all intracellular organelles; however, it is mostly utilized by mitochondria, the main site of cellular iron metabolism. Production of heme and Fe–S clusters, utilized in electron transport proteins, occurred in the mitochondrial organelle [45].
Iron metabolism, ferroptosis pathway, and regulatory miRNAs. Iron overload and ferritinophagy expand the labile iron pool, ROS generation triggers lipid peroxidation, and impaired GPX4/GSH antioxidant defense accelerates-cell death. Mechanisms of ferroptosis involving iron, lipid, and amino acid metabolism. Excess Fe⁺ accumulation, lipid peroxidation, and reduced GPX4/GSH activity promote ferroptosis, while ferritinophagy contributes to labile iron pool expansion. ACSL4: acyl-CoA synthetase long-chain family 4, DMT1: divalent metal transporter 1; GPX4: glutathione peroxidase 4, GSH: glutathione, LOX: lipoxygenase, LPCAT3: lysophosphatidylcholine acyltransferase 3, NCOA4: nuclear receptor coactivator 4, PUFA: polyunsaturated fatty acid, SLC7A11: cystine/glutamate antiporter, PE: phosphatidylethanolamine, STEAP3: six-transmembrane epithelial antigen of prostate 3 metallo-reductase, SLC7A11: solute carrier family 7 member 11, TF: transferrin, TFR1: transferrin receptor β 2
Amino acid metabolism
Glutathione (GSH) is a tripeptide composed of glycine, cysteine, and glutamic acid, featuring Y-amido-hexapeptide and sulfhydryl groups, and serves as a crucial antioxidant [63]. GSH operates intracellularly as an essential substrate for GPX4 [64]. The cell membrane has a type of heterodimer referred to as System Xc-, consisting of Solute Carrier Family 7 Member 11 (SLC7A11) and Solute Carrier Family 3 Member 2 (SLC3A2) [65]. The system Xc- facilitates the transfer of extracellular cystine to intracellular glutamate in a 1:1 ratio, subsequently leading to the synthesis of GSH from intracellular cystine, supported by the functions of glutamate–cysteine ligase (GCL) and glutathione (GSS) [64]. The majority of mammalian cells mediate cysteine absorption by SLC7A11, subsequently undergoing a reduction reaction that consumes nicotinamide adenine dinucleotide phosphate (NADPH) to generate cysteine. Cysteine can be synthesized from methionine via the trans-sulfuration route [66]. In addition, the GPX4 coenzyme of GSH facilitates the conversion of phospholipid peroxides into phospholipids, thus protecting cells from ferroptosis [11, 66]. Thus, inhibition of System Xc⁻ increases susceptibility to ferroptosis by lowering intracellular cysteine and GSH levels [67] (Fig. 2).
Moreover, the modulation of ferroptosis can be affected by mitochondrial tricarboxylic acid (TCA), and the suppression of the TCA cycle in mitochondria can obstruct the voltage-dependent channel 2/3 (VDAC2/3) to protect cells against ferroptosis [68].
Lipid metabolism
Polyunsaturated fatty acids (PUFAs) are essential constituents of the phospholipid bilayer and play a vital role in modulating cell membrane fluidity. However, PUFAs (including arachidonic acid and epinephrine) are susceptible to the Fenton reaction, resulting in the generation of excessive peroxides that disrupt the phospholipid bilayer structure, hence undermining cell membrane functionality [69]. PUFAs interact with coenzyme A to generate acyl-CoA via the catalytic activity of acyl-CoA synthetase long-chain family member 4 (ACSL4). Lysophosphatidylcholine acyltransferase 3 (LPCAT3) subsequently catalyzes the conversion of acyl-CoA to membrane phosphatidylcholine (PE) via esterification, yielding PUFA-PE [70]. The oxidation of PUFA-PE by lipoxygenase (LOX) leads to cellular ferroptosis [71] (Fig. 2).
Also, FPT is driven by lipid peroxidation (LPOX) levels, which are only able to happen in situations, where there is either no enzymatic inhibition of phospholipid hydroperoxides (PHL-OOH) or a severely restricted amount of it relative to the rate at which it forms [72]. The process by which LPOX causes ferroptosis completely overlaps with that of iron-dependent lipid peroxidation, which was first described over 50 years ago. Ferrous iron complexes and pre-existing lipid hydroperoxides are catalysts for the oxidative breakdown of polyunsaturated phospholipids, known as membrane LPOX [66, 73]. Thus, reducing PL-OOH to a nontoxic alcoholic substance by GPx4 utilizing GSH as a reducing substrate is solely an enzymatic process capable of stopping the entire peroxidative process [72]. When glutathione-dependent antioxidant systems are deactivated, harmful lipid reactive oxygen species (L-ROS) build up and cause ferroptosis [47, 74]. To put it another way, GPx4's impact is clear proof that PL-OOH is the source of LPOX. Since PL-OOH is a byproduct of LPOX, it could seem contradictory, but this problem is resolved by keeping in mind that residues of PL-OOH can occur independently of the start and advancement of rapid peroxidative reactions [75]. Without particular obstacles, GPx4 and GSH continue to catalyze the conversion of phospholipid alcohols (PL-OH) into their equivalent PL-OOH, which are created in trace quantities during aerobic metabolism. In addition, lipoxygenases may also create PL-OOH [76], with particular attention paid to lipoxygenase 12/15 (ALOX-12/15), and this appears to be pertinent to FPT [77]. Nevertheless, GPx4 activity regulates this lipoxygenase's function as well, since it needs lipid hydroperoxides to activate [73]. The LPOX of biological membranes includes the following free radical reactions: initiation, which starts with the removal of a hydrogen atom from polyunsaturated fatty acid by creating free radical, resulting in a phospholipid carbon-centered radical (PL); (ii) chain development, which interact with molecular oxygen to form radical of lipid peroxy PL-OO [78] then reaction between PL-OO and another PL, yielding a phospholipid hydroperoxide (PL-OOH); and (iii) arrest, which is caused by the capture or interactions of radical–radical [79]. Within the framework of this streamlined process scheme, Fe2+ from PL-OOH initiates LPO. Fe2+ may readily break the weak O–O link in PL-OOH, resulting in the highly reactive alkoxyl radical (PL-O), capable of initiation [78]. Therefore, PL-O initiates LPO, and PL-OO drives propagation [80].
Role of ferroptosis in T2DM
Ferroptosis is a regulated form of cell death driven by iron-dependent lipid peroxidation. It plays a critical role in pancreatic diseases due to the pancreas's vulnerability to oxidative stress and iron accumulation [81, 82]. The imbalance of iron and Fe–S clusters FV in β-cells leads to mitochondrial iron buildup [83, 84]. Research indicated that pancreatic β cells exhibit minimal expression of antioxidant enzymes, including superoxide dismutase (SOD), GSH, and catalase [85]. This can result in ROS generation, stress in the endoplasmic reticulum, ferroptosis, and insulin production failure [86]. In addition, it plays a role in diabetes complications, such as endothelial dysfunction and myocardial ischemia [7, 87].
External stimuli, such as chronic arsenic exposure, induce mitochondrial damage and generate excess mitochondrial ROS, which then trigger mitochondrial ROS-dependent autophagy and ferroptosis, culminating in an elevation of intracellular iron levels. This leads to elevated Fe2+ production in pancreatic β cells and compromised insulin secretion. Experimental verification showed that the inhibition of the mitochondrial ROS-mediated pathway enhances insulin production from pancreatic β cells [88], subsequently causing ferroptosis due to the accumulation of lipid peroxides [89].
In conclusion, ferroptosis, driven by iron overload and lipid peroxidation, contributes to pancreatic β-cell failure due to weak antioxidant defenses. Mitochondrial ROS and iron accumulation impair insulin secretion, linking ferroptosis to diabetes onset and its complications.
Therapeutic strategies targeting ferroptosis in T2D
Ferroptosis contributes to the development of T2DM and its consequences; therefore, it represents a prospective therapeutic avenue for the treatment and prevention of T2DM and metabolic disorders. This section summarizes various compounds that can suppress ferroptosis and their roles in the metabolic and molecular pathways associated with ferroptosis.
Pharmacological agents and natural compounds
| Category (natural vs pharmaceutical) | Agent | Chemical structure | Mechanism of action | Model of study | Adverse effects | Therapeutic uses | Evidence level | References |
|---|---|---|---|---|---|---|---|---|
| Natural | Quercetin | It is one of the flavonoids that is most commonly found in plants. (3,3′,4′,5,7-pentahydroxyflavone) | -It reduces oxidative damage in the tissues of the pancreas by scavenging free radicals -It inhibits lipid peroxidation by controlling glutathione peroxidase 4 (GPX4) and maintaining glutathione (GSH) levels -Quercetin decreases the oxidative stress induced by iron by lowering iron levels in the pancreatic islets -It reduces the symptoms of T2D by protecting pancreatic β cells and enhancing insulin production and β cell activity | Mice models | - No possible side effects, - It is safe, but if it is taken in high dosages, thus may cause allergy and gastrointestinal problems | - restoring normal β cell activity by reducing ferroptosis in type 2 diabetes | preclinical | [] [106] |
| Pharmaceutical | Erythropoietin (EPO) | A kind of glycoprotein with 165 amino acids that weighs 30.4 kDa | -EPO promotes the survival and development of neurons by exhibiting neuroprotective and neurotrophic effects -EPO lowers fasting blood sugar levels -EPO helps control ferroptosis-related proteins by lowering iron levels and lipid peroxidation -EPO improves mental performance | -Animal mice model -Cell culture PC12 model | -Safe but require monitoring Especially at high dosages or in specific groups, hypertension, and thromboembolic complications are possible negative consequences. [] [112] | EPO is mostly used for the treatment of anemia, particularly in cases with chronic renal disease Potentially neuroprotective roles in neurodegenerative diseases EPO may lessen the cognitive decline brought on by diseases like type 2 diabetes | Preclinical | |
| Pharmaceutical | Liraglutide | It is glucagon-like peptide-1 (GLP-1), an analog of the 30-amino acids acid hormonal peptide | -Liraglutide alleviates T2D-related NAFLD, presumably via inhibiting ferroptosis and activating the AMPK/ACC pathway which prevents ferroptosis and encourages lipid metabolism - Causing an increase in insulin production by mimicking the actions of GLP-1 and inhibiting the release of glucagon - Increasing fullness by delaying stomach emptying | -Mice model, T2D induction by high-fat diet followed by STZ injection | Liraglutide is usually tolerated without problems, although some notable side effects include Feeling queasy and throwing up | Controlling T2D (enhancing glycemic control) Its capacity to mitigate liver damage and prevent ferroptosis in the setting of T2D suggests that it may improve the condition of the liver in NAFLD | Preclinical | [] [105] |
| Natural | Poliumoside | It is derived from Callicarpa kwangtungensis Chun | Poliumoside can interfere with ferroptosis by activating the Nrf2/GPX | -murine model -Invitro stem cells of bone mesenchyma(BMSCs) | – | -Treatment of T2D with bone degradation | Preclinical | [] [111] |
Metformin
Among the first-line medicines against diabetes, metformin can inhibit oxidative stress and affect ferroptosis. Although in widespread practice, its chronic administration is marred by gut intolerance and lactic acidosis risk in some populations. The natural flavonoid quercetin showed encouraging antidiabetic activity by mechanisms, such as antioxidant, insulin-sensitising, and ferroptosis-related pathway modulating activity. However, there is sparse human clinical data and low availability (< 1 μM plasma levels) [91]. a synthetic biguanide that improves glucose management in diabetics by activating the AMP-activated protein kinase (AMPK) signaling system, inhibiting gluconeogenesis in the liver and increasing insulin-stimulated peripheral glucose absorption [92]. The liver kinase B1 (LKB1)/AMPK signaling pathway is crucial for glucose regulation [93]. A prior investigation demonstrated that LKB1 and its downstream AMPK inhibited ferroptosis by obstructing the phosphorylation of acetyl-CoA carboxylase 1 (ACC1) and fatty acid synthase (FAS) [94]. Metformin decreased the accumulation of iron in the liver's cells through the AMPK–ferroportin pathway in a preclinical model of non-alcoholic fatty liver disease [95]. Metformin preserves cells by activating the AMPK system, modulating metabolism, and safeguarding them against degradation and pathogenic alterations at the molecular level. Consequently, we suggest that metformin's efficacy in enhancing T2D is linked to the suppression of ferroptosis and the mitigation of IR. Metformin's anti-ferroptosis properties reduced the calcification of vascular smooth muscle cells in a rat model of calcification via nuclear factor erythroid 2-related factor 2 (Nrf2) signal activation [96]. Ferroptosis was also inhibited by metformin's alteration of the gut microbiota, which was marked by a rise in bacteria that produce gamma-aminobutyric acid (GABA) [97].
SGLT2 inhibitors
A family of medications known as SGLT2 inhibitors, such as empagliflozin, dapagliflozin, and canagliflozin, can lower blood glucose levels by preventing the reabsorption of glucose in the proximal tubules. Once-daily dosing is possible with SGLT2 inhibitors, because they are orally bioavailable, have long half-lives (10–13 h), and high absorption rates [98]. Moreover, they lower ferroptosis, protect the heart and kidneys. According to preclinical research, in diabetic mice, the medications improve cardiac function in heart failure models, stimulate tubular kidney function, and increase revascularization. Because of their possible advantages, their use has grown [99, 100]. The decline in ferroptosis is brought about by increasing intracellular glutathione levels and inducing sirtuin-1, both of which strengthen glutathione-dependent glutathione peroxidase 4 [101].
Liraglutide
The common medications for T2D, glucagon-like peptide-1 receptor agonists (GLP-1 RA) are known to enhance the balance of glucose and encourage weight loss in people who are overweight. It is administered by injection, because it has poor oral absorption and has a short biological half-life. It may be useful to use it loaded in nanochitosan, which increases the bioavailability by ten times when administered orally [102]. According to preclinical research, liraglutide, a drug used to regulate blood sugar, may lessen ferroptosis, because it reduces the hepatic iron buildup seen in db/db mice, which in turn lessens IR [103]. In addition, another research revealed a decrease in iron deposition in the hippocampus, which improved synaptic plasticity and decreased damage to hippocampus neurons, encouraging the restoration of cognitive function in db/db mice [104]. Furthermore, T2D frequently results in non-alcoholic fatty liver disease (NAFLD), which is impacted by oxidative stress, inflammation, insulin resistance, and heredity. It has been discovered that liraglutide improves NAFLD in mice. According to the study, liraglutide reduced liver tissue damage and enhanced glucose metabolism. In addition, it preserved the viability of liver cells in high-glucose circumstances. According to the results, liraglutide may alleviate NAFLD by blocking ferroptosis and triggering the AMPK/ACC2 pathway [105].
Quercetin
Quercetin, a prevalent flavonoid, is found in fruits, vegetables, and medicinal plants and has garnered interest due to its potential benefits in treating metabolic disorders, which are significant global public health concerns. Quercetin has been shown in animal studies to increase insulin secretion, improve insulin resistance, reduce blood cholesterol levels, decrease inflammation, decrease hepatic fat accumulation, and control diseases associated with the gut microbiota. Nevertheless, there are not many human clinical investigations; therefore, more investigation is required to increase bioavailability and confirm its efficacy in people [91]. In T2D diabetic mice, quercetin, an inhibitor of ferroptosis, enhanced insulin secretion and reduced oxidative stress [106]. Research indicates that quercetin administration markedly reinstates GSH levels and SOD activity in pancreatic β cells [106]. According to the study, ferrous-chelating deferoxamine, ferroptosis suppressor ferrostatin-1, and quercetin may all be useful T2D management methods for preventing ferroptosis and pancreatic iron accumulation [106]. The findings suggest that quercetin may have a favorable impact on T2D by decreasing ferroptosis in pancreatic β cells, underscoring its potential therapeutic efficacy in T2D.
Erythropoietin (EPO)
Moreover, erythropoietin (EPO) can alleviate cognitive deficits in T2D mice and lower fasting blood glucose. In mice with T2D, EPO also enhanced cognitive performance and decreased hippocampus damage [107, 108]. EPO also controlled the production of proteins linked to ferroptosis and decreased lipid peroxidation and iron levels. These results imply that by reducing iron overload and preventing ferroptosis, EPO may mitigate cognitive impairment linked to T2D [108].
Poliumoside
The idea of Traditional Chinese Medicine asserts that Poliumoside (Pol), mostly located in Callicarpa kwangtungensis Chun, improves blood circulation, stimulates Qi movement, and alleviates pain [109, 110]. Pol counteracts ferroptosis by mitigating oxidative stress via the Nrf2/GPX4 pathway in diabetic mice with osteoporosis [111].
MicroRNAs and epigenetic regulators of ferroptosis
Interplay between microRNAs and ferroptosis in diabetes development and therapy
MicroRNAs (miRNAs) are small noncoding RNAs, approximately 22 nucleotides in length that have attracted significant research interest. They play a critical role in gene regulation by binding to specific sites in messenger RNAs (mRNAs), typically in the 3′-untranslated region (3′-UTR), which leads to either the degradation of mRNAs or the inhibition of their translation. Due to their exceptional stability compared to the more unstable transcriptome, miRNAs have emerged as potential biomarkers [113]. Research has established that miRNAs are associated with the regulation of iron through various specific targets, with key signaling pathways related to cell death predominantly influenced by miRNAs. Thus, ferroptosis is modulated by the expression levels of certain miRNAs, which target key genes involved in the ferroptotic process. This suggests a well-established connection between iron and miRNAs, leading to a new dual regulation framework for iron-dependent non-apoptotic programmed cell death. In this framework, miRNAs affect the signaling pathways related to iron or their principal regulators, while this type of cell death may, in turn, influence the cellular levels of miRNAs to some degree [114].
Molecular mechanisms of ferroptosis provide a basis for understanding its therapeutic targeting in T2D. The miRNAs have been shown to modulate ferroptosis in diabetic complications. These miRNAs influence key ferroptotic regulators, such as GPX4, SLC7A11, and ACSL4, suggesting their potential as therapeutic targets. According to these molecular insights, the next section explores how the miRNAs affect the ferroptosis regulation, with a focus on diabetic retinopathy and nephropathy.
MicroRNA and diabetic retinopathy (DR)
T2D is a progressive condition that, if unmanaged, can result in severe consequences, including macrovascular and microvascular disorders [115]. Diabetic retinopathy (DR) is a microvascular condition associated with T2D. It has been discovered that Astragaloside-IV, a naturally occurring substance from Astragalus, downregulates miR-138-5p in retinal pigment epithelial (RPE) cells of the DR model, leading to a boost in the expression of Nrf2, Sirtuin 1 (Sirt1), the antioxidant activity of GPX4, glutamate–cysteine ligase modifier subunit (GCLM) and glutamate–cysteine ligase catalytic subunit (GCLC), suggesting that the miR-138-5p/Sirt1/GPX4 axis helps mitigating ferroptosis and promotes cell survival in RPE cells exposed to high glucose conditions [116].
On the other hand, Zhu and Duan [117] explored that downregulating circ-PSEN1 increases cell survival rates and reduces ferroptosis in adult RPE-19 exposed to high glucose conditions. This suggests that targeting circ-PSEN1 could protect retinal cells from the damaging effects of high glucose levels. In addition, in DR, the miR-200b-3p plays an important role in regulating ferroptosis. It is sponged by circ-PSEN1, which means that circ-PSEN1 can bind to miR-200b-3p and prevent it from exerting its effects. This interaction implies that downregulating circ-PSEN1 could increase the availability of miR-200bp, which has protective effects against ferroptosis by targeting and inhibiting cofilin (CFL2), thereby reducing oxidative stress and cell death. The use of a miR-200b-3p inhibitor led to a significant decrease in GSH levels, an increase in MDA levels, and an elevation of ferrous ion contents. Under high glucose conditions, miR-200b-3p promotes the expression of transferrin receptor 1 (TFR1) while negatively regulating the expression of anti-ferroptosis genes, such as GPX4 and SLC7A11 [117]. In cells where miR-200b-3p is overexpressed, this change exacerbates ferroptosis. Therefore, treatments that lower circ-PSEN1 may indirectly alter the miR-200b-3p/CFL2 axis, improving DR cellular outcomes. The findings suggest that circ-PSEN1 knockdown may reduce ferroptosis. These findings suggested that targeting the circ-PSEN1/miR-200b-3p/CFL2 may reduce ferroptosis in DR [117].
Another work by Huang and Peng [118] used bioinformatics techniques to uncover ferroptosis-related genes in DR. The R software DESeq2 was used to analyze RNAseq data from retinas in DR and healthy controls. The protein–protein interaction network analysis found seven hub genes associated with ferroptosis in DR: HMOX1, PTGS2, EGFR, CAV1, TLR4, MAPK8, and CDKN2A. Upon verification with an alternative data set, only Heme Oxygenase 1 (HMOX1) and prostaglandin–endoperoxide synthase 2 (PTGS2) were identified as differentially expressed between the DR and control groups. In addition, they indicated that hsa-miR-873-5p has been identified as a key microRNA that regulates the expression of HMOX1, which is one of the hub genes implicated in the ferroptosis process within DR. While hsa-miR-624-5p and hsa-miR-542-3p are identified as the primary miRNAs that regulate the expression of PTGS2. MiR-542-3p is particularly noted for promoting the rapid degradation of PTGS2 mRNA, which supports the findings from bioinformatics predictions. Furthermore, HMOX1 and PTGS2 are regulated by 13 and 20 transcription factors, respectively. The involvement of these transcription factors suggests a complex regulatory network influencing the expression of these hub genes. The role of hsa-miR-624-5p in regulating PTGS2 is less clearly defined in the available literature. While it is categorized as a key miRNA influencing PTGS2, specific studies detailing whether it upregulates or downregulates PTGS2 have not been thoroughly investigated. Previous research on hsa-miR-624-5p suggests its involvement in cancer, but its precise impact on PTGS2 in the context of DR remains uncertain and requires further study [119]. These results underscore the need for additional research on the miR-873-5p/HMOX1 axis, specifically, its therapeutic potential and function within larger transcriptional networks that impact iron metabolism and oxidative stress.
Moreover, another study investigated the molecular processes involved in DR by administering high levels of glucose to the RPE. The findings indicated that excess glucose negatively impacts cell viability and proliferation, increases the levels of ROS, and promotes ferroptosis in the cells. The research showed that miR-338-3p targeted the 3'UTR of SLC1A5 for inhibition and degradation, while elevated glucose levels reduced SLC1A5 by enhancing miR-338-3p in RPE cells. By targeting miR-338-3p/SLC1A5, the researchers successfully prevented high glucose-induced ferroptosis in RPE cells [120].
| miRNA | Function | Target(s) | Ref | Ferroptotic effect |
|---|---|---|---|---|
| miR-138-5p | Pro-ferroptotic | Sirt1/GPX4 axis | [] [116] | ↑ Ferroptosis |
| miR-200b-3p | Pro-ferroptotic | GPX4, SLC7A11 | [] [117] | ↑ Ferroptosis |
| miR-338-3p | Pro-ferroptotic | SLC1A5 | [] [120] | ↑ Ferroptosis |
| miR-7-5p | Anti-ferroptotic | ACSL4 (via ZFAS1) | [] [121] | ↓ Ferroptosis |
| miR-873-5p | Anti-ferroptotic | HMOX1 | [] [129] | ↓ Ferroptosis |
| miR-223-3p | Anti-ferroptotic | ITPR3/GPX4/xCT | [] [123] | ↓ Ferroptosis |
| miR-144-3p | Pro-ferroptotic | β-cell ferroptosis regulators | [] [128] | ↑ Ferroptosis |
MicroRNA and diabetic nephropathy (DN)
Furthermore, diabetic nephropathy (DN), a serious consequence of diabetes, has become more prevalent. Although Circular ASAP2 mediates DN, nothing is known about its biological mechanism and function. A study by Li and Meng [122] showed that circular ASAP2 protein declines the sex-determining region Y-Box 2 (SOX2), solute carrier family 7 member 11 (SLC7A11), and miR-770-5p activity, which increased in mice with DN. Thus, ASAP2 inhibition exacerbates DN and increases oxidative stress and inflammation.
A recent study explores the role of ferroptosis and the miR-223-3p/inositol 1,4,5-trisphosphate receptor type 3 (ITPR3) pathway in diabetic kidney disease (DKD) using adenoviruses. Overexpression or silencing of MiR-223-3p was accomplished with adenoviruses. The findings showed that elevated glucose levels lead to the downregulation of miR-223-3p. This downregulation is possibly linked to the regulation of ITPR3 with subsequent reduction of GPX4 and the cystine/glutamate transporter (xCT) and an increment in long-chain ACSL4, thereby enhancing ferroptosis. These changes result in increased calcium levels and alterations in iron metabolism. Thus, understanding the miR-3p/ITPR3 pathway in DKD, particularly in the context of adenoviral research, provides insights into potential therapeutic strategies. By targeting miR-223-3p/ITPR3/GPX4/xCT, the researchers successfully prevented high glucose-induced ferroptosis [123] (Table 2).
Furthermore, circular RNAs (circRNAs) are essential in many human diseases. However, their function in DKD is still unclear. Circ-0069561 was up-regulated in kidney tissues from DKD patients using high-throughput RNA sequencing. Fluorescent in situ hybridization (FISH) and real-time PCR were used to validate this RNA in DKD patients and type 2 diabetic mice. Moreover, the circ-0069561 expression was significantly elevated and primarily localized in the glomerulus in the mouse podocyte clone 5. A higher risk of primary endpoints was linked to high expression of circ-0069561. Circ-0069561 may be the perfect biomarker and treatment target for the advancement of DKD [124].
By analyzing m6A RNA methylation, another epigenetic mechanism, and its impact on ferroptosis-related gene expression in type 2 diabetes and its microvascular complications, the next part expands on the role of non-coding RNAs, such as circRNAs, in regulating ferroptosis in diabetic complications.
Interplay between m6A RNA methylation and ferroptosis in diabetes development and therapy
N6-methyladenosine (m6A), a common RNA modulator, can affect critical genes related to ferroptosis, including cyclin-dependent kinase inhibitor 1A (CDKN1A), myo-inositol oxygenase (MIOX), proto-oncogene, BHLH transcription factor (MYCN), and cluster of differentiation 82 (CD82). They exhibit differential expression levels in diabetic conditions. These genes can negatively affect mitochondrial function, oxidative stress, and insulin secretion, all of which are crucial in the etiology of T2D. For example, MIOX overexpression during hyperglycemia accelerates ferroptosis and beta-cell damage by promoting lipid peroxidation and lowering antioxidant defense. Ferroptosis is further exacerbated by MYCN, which also alters redox balance and iron metabolism. The study reported that ferroptosis gene regulation by m6A may be a new target for diagnosis and treatment [125, 126].
Moreover, further research has demonstrated that the relationship between ferroptosis and m6A demethylation in the context of diabetic retinopathy (DR), a microvascular consequence of type 2 diabetes, using high-glucose-treated ARPE-19 cells and STZ-induced diabetic rats to examine the effect of alkylation repair homolog protein 5 (ALKBH5), a m6A demethylase, on ferroptosis in DR. The expression levels of ALKBH5, YTH N6-methyladenosine RNA binding protein 1 (YTHDF1), and ACSL4 were examined. The results showed that both models had elevated ferroptosis, with downregulated ALKBH5 and upregulated YTHDF1 and ACSL4. Interestingly, either YTHDF1 silencing or ALKBH5 expression restoration partially reversed ferroptosis. ALKBH5 mechanistically reduced the stability of ACSL4 mRNA through m6A demethylation in a manner that was reliant on YTHDF1. These results point to the m6A–YTHDF1–ACSL4 axis as a possible therapeutic target [127].
In addition, recent findings highlight miR-144-3p as a critical regulator of ferroptosis in pancreatic β-cells, linking non-coding RNA biology to diabetes pathogenesis. In T2DM model mice, which were induced by a high-fat diet combined with streptozotocin injection, miR-144-3p was up-regulated under hyperglycemic conditions, where it promoted β-cell ferroptosis and impaired insulin secretion by directly targeting ubiquitin-specific peptidase 22 (USP22) and destabilizing the USP22/SIRT1 axis. Inhibition of miR-144-3p, conversely, restored antioxidant defenses (GPX4, GSH), preserved β-cell viability, and improved glycemic control in vivo. These findings suggest that miR-144-3p acts as a pro-ferroptosis driver in islet dysfunction, and its targeting may represent a promising therapeutic avenue to preserve β-cell function in type 2 diabetes [128].
| Type of study model | Ferroptosis mechanism | Type of miRNA | Target action of miRNA | Evidence level | References |
|---|---|---|---|---|---|
| In vitro, RPE cells | -HG increased the levels of ROS after damaged mitochondria and GSSG, and improved the mitochondrial membrane's lipid peroxidation density -Accumulation of iron and increased ferroptosis | miR-138-5p | -Increase the expression of Nrf2 and Sirt1, the antioxidant activity GPX4, GCLM, GCLC, and alleviate the DR | Preclinical | [] [116] |
| -In vivo study, C57BL/6 mice model | -HG increased the levels of ROS and lipid peroxide -Accumulation of iron and increased ferroptosis | miR-770-5p | -Decrease the SOX2 which can affect the SLC7A expression -Decrease the SLC7A and increase the oxidative stress damage | Preclinical | [] [122] |
| Bioinformatics study | -Increase the accumulated iron and lipid peroxides - p53 activation and regulation of ferroptosis | -Hsa-miR-873-5p | - Decrease the HMOX1 and PTGS2 expression | Computational detection | [] [118] |
| In vitro glomerular endothelial cells | -HG decreased the levels of miR-223-3p | -miR-223-3p | -Decrease the xCT and GPX4, and increase ACSL4 expression | Preclinical | [] [123] |
| In vitro retinal endothelial cells of diabetic human | -HG caused the ZFAS1 elevation | -miR-7-5p | - Regulating the expression of ACSL4 | Preclinical | [] [121] |
| In vitro retinal epithelium cells | HG increased the levels of ROS and ferroptosis activation | -miR-338-3p | -Inhibition of SLC1A5 | Preclinical | [] [120] |
| In vitro, ARPE19 | HG increased the levels of ROS and ferroptosis activation | -miR-200b-3p | Target CFL2 gene | Preclinical | [] [117] |
Ferroptosis-modulating medications from the lab to the clinic
Preclinical studies show a strong link between ferroptosis and type 2 diabetes, with evidence mainly from in vitro experiments and animal models. Ferroptosis contributes to insulin resistance and pancreatic β-cell dysfunction, but extrapolating these findings to the clinic remains a challenge. Small-molecule ferroptosis inhibitors face difficulties in preclinical trials, including limited efficacy, poor pharmacokinetics, low stability, low solubility, low targeting, low safety, and toxicity [130].
Challenges that preclinical experiments face
Without good diagnostic markers, it is difficult to monitor ferroptosis activity or assess therapeutic efficacy. In addition, most current investigations focus on single-target mechanisms, which may not capture the complexity of ferroptosis regulation in human metabolic disease. the clinical trials should be conducted to evaluate the safety and efficacy of ferroptosis inhibitors in T2D, develop markers of ferroptosis activity in diabetic tissues and investigate nanotechnology-based drug delivery techniques to enhance drug specificity and reduce toxicity. These challenges must be addressed if ferroptosis is to be used as a promising therapeutic target in the management of T2D.
Clinical evidence for treating T2D patients with ferroptosis-targeted therapy is still lacking. For instance, in animal models, Fer-1, the first synthetic inhibitor of ferroptosis, has been implicated in numerous diseases [131]. However, it is still in the experimental stage, which makes it challenging to transition to clinical trials.
In meantime, compound 51, a phenothiazine-based derivative, shows substantial hERG inhibitory activity despite having neuroprotective effects in IS animal models [132]. In a multicenter, randomised, double-blind, placebo-controlled trial of AD from 2007 to 2012, vitamin E was found to significantly reduce cognitive performance in patients with mild to moderate AD. On the other hand, some studies contend that vitamin E supplementation does not lower the risk of AD and slows down its pathogenesis [133]. Although iron chelators such as deferoxamine (DFO) and deferiprone (DFP) have been shown to reduce ferroptosis-mediated damage in other diseases, they have not been well-studied in diabetes in human subjects. Moreover, existing ferroptosis inhibitors are troubled by issues, such as short half-lives, poor bioavailability, and off-target effects, which compromise their therapeutic benefits. To overcome these restrictions, CN128, a novel oral iron chelator, has been created [134, 135].
While copper compound CuII (ATSM) has demonstrated neuroprotective effects in ALS and PD phase I studies, patients in the clinical trial phase have been discovered to have spinal cord immunocompromise. With Dabigatran in a Phase III clinical trial in IS and Argatroban in a Phase IV clinical trial, it has been discovered that thrombin inhibition reduces ferroptosis-mediated neurological damage. To treat ferroptosis-mediated diseases, decrease side effects, and increase treatment consumption, researchers must optimize medications [136].
Conclusion
Disorders in iron metabolism led to inadequate insulin secretion and insulin resistance. However, the connection between iron metabolism and T2D, along with its consequences, remained ambiguous until the identification of ferroptosis. Elevated concentrations of free reactive iron induce tissue damage and oxidative cellular demise with subsequent ferroptosis. This process is controlled at several levels, including iron equilibrium, cells with mitochondria, glutathione–GPX4 axis, and polyunsaturated fatty acid metabolism. Ferroptosis susceptibility is modulated by miRNAs, one important component of pathophysiological disorders associated with iron overload is the dysregulation of miRNA-regulated ferroptosis. Astragaloside-IV, a naturally occurring substance from Astragalus downregulates miR-138-5p in RPE cells of the DR model, leading to an increase in the expression of Nrf2, Sirt1, GPX4, GCLM, and GCLC. MiRNAs as hsa-miR-873-5p, hsa-miR-624-5p, hsa-miR-542-3p, and miR-338-3p, are critical regulators of essential ferroptosis-related genes. ZFAS1, a long noncoding RNA, may regulate ACSL4 expression in ferroptosis in human retinal endothelial cells. Future studies should focus on developing miRNA-based diagnostic assays for early ferroptosis-associated T2D alterations, clinical trials targeting ferroptosis pathways discussing therapeutic interventions, exploring ferroptosis's role in diabetic complications, and understanding the complex web of miRNA-dependent ferroptosis mechanisms for T2D diagnosis and therapy.