Magnesium's role in controlling energy use, metabolism, and aging through mitochondrial function

Systemic magnesium balance relies on a dynamic equilibrium between intestinal absorption, renal excretion, and skeletal storage. While the glomerulus filters a substantial load of magnesium daily, and the thick ascending limb (TAL) reabsorbs the majority via passive paracellular routes (de Baaij et al. 2015; Khan and Khan 2025), the definitive fine‐tuning of urinary excretion occurs exclusively in the distal convoluted tubule (DCT). Here, transport is active, transcellular, and dependent on a highly specialized apical entry system. The primary molecular entities mediating this influx are the Transient Receptor Potential Melastatin (TRPM) family members, specifically TRPM6 and TRPM7 (Dimke et al. 2011). While TRPM7 is ubiquitously expressed and essential for cell viability, TRPM6 expression is strictly confined to the apical membranes of the DCT and intestinal epithelia (Mittermeier et al. 2019; Vargas‐Poussou et al. 2023). Cryo‐electron microscopy (cryo‐EM) studies have resolved that, under physiological conditions in the DCT, the functional apical channel assembles predominantly as a heterotetrameric complex comprising both TRPM6 and TRPM7 subunits (Chubanov et al. 2016; Schmidt et al. 2022). These proteins exhibit a unique chanzyme architecture that represents an evolutionary fusion of an N terminal ion channel pore with a C terminal alpha kinase domain. The channel pore displays high selectivity for divalent cations, with magnesium favored over calcium, and functions broadly as a constitutively active channel (Zhang et al. 2023). The driving force for this apical entry is strictly electrochemical; the intracellular potential of the DCT cell is maintained at a negative value relative to the tubular lumen, creating a gradient that favors the passive entry of Mg²⁺ through the open pore (Voets et al. 2004; Figure 2). The clinical indispensability of this specific machinery is evidenced by Hypomagnesemia with Secondary Hypocalcemia (HSH), where loss‐of‐function mutations in TRPM6 cause severe renal magnesium wasting that cannot be compensated by TRPM7 homomers alone (Schlingmann et al. 2002; Walder et al. 2002).

Following apical entry, intracellular Mg²⁺ must be extruded across the basolateral membrane into the renal interstitium against both chemical and electrical gradients. This thermodynamically unfavorable step constitutes the rate‐limiting barrier in transepithelial magnesium transport. The molecular identity of this extrusion system has been confirmed as the Cyclin M (CNNM) family of proteins, specifically CNNM2 (Funato and Miki 2022). Genetic studies have causally linked CNNM2 mutations to dominant familial hypomagnesemia, confirming its non‐redundant role in renal magnesium retention (Liu, Wang, Wang, et al. 2025). Structurally, CNNM2 contains a transmembrane DUF21 domain and a cytosolic cystathionine‐β‐synthase (CBS) pair domain (Gimenez‐Mascarell et al. 2019). While the precise stoichiometry of transport, specifically whether CNNM2 functions as a sodium magnesium exchanger that exploits the inward sodium gradient generated by the sodium potassium ATPase, remains under active biophysical investigation, the requirement of CNNM2 for magnesium efflux is well established (Yamazaki et al. 2013; Figure 2). A critical regulatory layer at this interface involves the phosphatases of regenerating liver (PRLs), which directly engage the CBS pair module of CNNM transporters (Gimenez‐Mascarell et al. 2017; Gulerez et al. 2016). Biochemical analyses indicate that dimerization of the CBS pair in solution is tightly coupled to Mg–ATP binding and can be further enhanced by PRL association, consistent with PRLs reshaping, rather than abolishing, the nucleotide‐dependent conformational landscape of CNNMs (Chen et al. 2020). Functionally, PRL binding has been most consistently linked to suppression of CNNM‐mediated Mg²⁺ efflux and consequent intracellular Mg²⁺ accumulation, positioning PRLs as modulators that tune epithelial magnesium handling capacity rather than as constitutive activators of export (Gulerez et al. 2016).

Intracellular magnesium homeostasis is tightly compartmentalized, with a substantial fraction of total cellular Mg²⁺ sequestered in organelles where it is largely buffered by phospholipids, nucleotides, and proteins. Within this landscape, mitochondria act as a major, dynamically exchangeable Mg²⁺ pool that couples cation availability to bioenergetic demand (Yamanaka et al. 2016). Importantly, quantitative statements must distinguish between total Mg (dominated by the bound pool) and free Mg²⁺ (the signaling and catalytic pool). Accordingly, comparisons of mitochondrial Mg content with cytosolic Mg²⁺ should be framed as differences in buffering capacity and exchange dynamics, rather than as a simple free concentration gradient (Yamanaka et al. 2016). The best characterized entry route for Mg²⁺ across the inner mitochondrial membrane is Mitochondrial RNA Splicing 2 (MRS2), a eukaryotic homolog of the bacterial CorA family (Li et al. 2023). Recent cryo‐EM studies converge on a homo‐pentameric architecture that defines a central ion conduction pathway and a gated permeation mechanism, providing a structural basis for Mg²⁺ translocation through the inner membrane (Lai, Balaraman, et al. 2023; Li et al. 2023). Notably, electrophysiological analyses of human MRS2 indicate that channel activity is regulated by Ca²⁺ and that the pore can conduct multiple cations, including Mg²⁺, rather than operating as a strictly Mg²⁺‐selective conduit under all conditions (He et al. 2025). This revised view is mechanistically important, because it places MRS2 at the intersection of mitochondrial cation flux, signaling context, and membrane energization (He et al. 2025; Li et al. 2023). In energetic terms, net cation influx through an inner‐membrane channel is ultimately shaped by the ΔΨm, which provides the electrical component of the driving force for positively charged ions. Therefore, when ΔΨm collapses, the electrical incentive for mitochondrial Mg²⁺ accumulation diminishes, functionally uncoupling Mg²⁺ uptake from oxidative metabolism (Yamanaka et al. 2016). In this sense, MRS2‐mediated Mg²⁺ entry is best described as channel permeation that is gated by channel state and constrained by the prevailing electrochemical landscape, rather than as an ATP‐driven pumping process (He et al. 2025; Li et al. 2023; Madaris et al. 2023). As illustrated in Figure 3, mitochondrial magnesium uptake through MRS2 directly couples membrane potential to functional energy availability.

The physiological imperative for mitochondrial Mg²⁺ uptake lies in how Mg integrates catalysis, nucleotide chemistry, and respiratory performance. Magnesium is an obligate cofactor for numerous metabolic enzymes, and in mitochondria it supports reaction chemistry across central carbon metabolism and oxidative phosphorylation (Yamanaka et al. 2016). A particularly consequential constraint is that ATP is predominantly used in cells as a MgATP complex, meaning that “ATP sufficiency” is inseparable from Mg availability at the site of ATP synthesis and utilization (Yamanaka et al. 2016). Thus, mitochondrial Mg handling is not a passive bookkeeping exercise in ion balance, but a prerequisite for sustaining the chemical currency that powers phosphorylation networks and transport work (Yamanaka et al. 2016). Consistent with this logic, genetic or functional impairment of MRS2 compromises mitochondrial Mg homeostasis and disrupts mitochondrial metabolism. In cellular systems, MRS2 depletion reduces mitochondrial Mg uptake and undermines bioenergetic resilience under stress (Yamanaka et al. 2016). In vivo, inducible loss of MRS2 has been linked to profound mitochondrial dysfunction, including loss of respiratory chain integrity with severe consequences for cell viability (Li et al. 2023). Together with the recent structural and functional dissection of human MRS2, these findings support the concept that MRS2 is a necessary determinant of mitochondrial Mg homeostasis that helps preserve oxidative phosphorylation capacity in demanding contexts (Madaris et al. 2023; Mastrototaro et al. 2016; Figure 3). Finally, Mg²⁺ flux is bidirectional at the organelle level. A mitochondrial Mg²⁺ efflux pathway has been attributed to SLC41A3, providing a mechanism to extrude Mg²⁺ and thereby prevent pathological accumulation. In aggregate, current evidence positions MRS2 as the core, best established molecular entity required for mitochondrial Mg²⁺ influx, with efflux mechanisms such as SLC41A3 shaping steady‐state set points and adaptive dynamics (He et al. 2025; Madaris et al. 2023). Collectively, these transport layers define how much Mg²⁺ is available to form Mg–ATP and to support Mg‐dependent enzymatic reactions. TRPM6/TRPM7 sets the entry capacity, CNNM2‐centered regulation determines the efficiency of basolateral export, and MRS2 couples cytosolic supply to matrix sufficiency under bioenergetic constraints. This architecture provides a mechanistic bridge to the next section, where we examine how Mg–ATP coupling and Mg‐sensitive enzyme kinetics translate ion handling into metabolic regulation and disease vulnerability.

A central implication of MgATP predominance is that fluctuations in free Mg²⁺ can uncouple total ATP abundance from ATP usability. When Mg²⁺ becomes limiting, the pool of MgATP contracts even if adenylate charge appears preserved, creating a state that can be conceptualized as functional ATP deficiency. This is particularly relevant for kinase networks, where the substrate is MgATP rather than ATP per se. Mechanistic enzymology has long established that many kinases coordinate Mg²⁺ in the active site to position the phosphates for in‐line transfer and to stabilize negative charge in the transition state (Gupta and Yushok 1980; Kleczkowski and Igamberdiev 2023). What is newly appreciated is how this chemistry scales into systems level regulation: Mg²⁺ can tune the balance between Mg complexed and Mg free nucleotide species, shifting reaction directionality and apparent affinities across nucleotide interconversion hubs such as adenylate kinase and nucleoside monophosphate kinases (Kleczkowski and Igamberdiev 2025; Nam et al. 2024; Run et al. 2015). A recent structural and enzymatic dissection of adenylate kinase shows that Mg²⁺ is not only an electrostatic cofactor but can induce a substrate reorganization that optimizes the phosphoryl transfer geometry, highlighting how Mg²⁺ can gate adenylate equilibration with direct kinetic consequences (Nam et al. 2024). Because adenylate kinase sets the interconversion between ATP, ADP, and AMP, Mg²⁺ at this node is positioned to influence both energetic buffering and downstream AMP sensitive signaling.

Within mitochondria, Mg²⁺ dependence intensifies because oxidative phosphorylation is simultaneously a generator and consumer of Mg coordinated nucleotides. MRS2 mediated Mg²⁺ uptake is increasingly viewed as a determinant of mitochondrial “cationic set point” that shapes bioenergetic resilience (He et al. 2025). Elegant work linking mitochondrial Mg²⁺ to Ca²⁺ handling further supports the idea that matrix Mg²⁺ is a rheostat for the mitochondrial Ca²⁺ uniporter, with reduced matrix Mg²⁺ associating with increased Ca²⁺ uptake and enhanced susceptibility to permeability transition (Ponnusamy et al. 2024; Uthayabalan et al. 2023; Yamanaka et al. 2016). These findings are conceptually important for bioenergetics because Ca²⁺ stimulated dehydrogenase activation can be beneficial, yet Ca²⁺ excess collapses membrane potential and ATP synthesis. Mg²⁺ therefore sits at the intersection of nucleotide chemistry and ion governed control of respiration, enforcing a permissive window in which mitochondrial activation does not tip into catastrophic overload. A striking illustration of this coupling comes from cell level Mg²⁺ dynamics triggered by lactate. In a study that repositioned lactate as a second messenger, L lactate promoted Mg²⁺ release from endoplasmic reticulum stores and subsequent mitochondrial Mg²⁺ uptake, in a process that depended on MRS2 and integrated glycolytic output with mitochondrial function (Daw et al. 2020; Wilde and Christofk 2020). This work reframes Mg²⁺ as a mobile signal that communicates carbon flux state to the mitochondrial matrix, rather than a static cofactor passively distributed by diffusion. It also implies that metabolic states commonly encountered in kidney physiology, including high glycolytic throughput in stressed epithelia, may dynamically reshape matrix Mg²⁺ and thus MgATP dependent enzymology.

The tricarboxylic acid cycle contains multiple enzymes that require divalent cations for catalysis and allosteric control, positioning Mg²⁺ as a determinant of flux rather than a background ion. Human NAD dependent isocitrate dehydrogenase (IDH3), which catalyzes oxidative decarboxylation of isocitrate to alpha ketoglutarate, has now been structurally resolved with detailed insights into assembly and allosteric regulation (Sun et al. 2020). These structures and accompanying kinetic analyses clarify how ligand binding and conformational coupling control active site function, and they reinforce that metal ion coordination is a core component of catalytic competence. Alpha ketoglutarate dehydrogenase (OGDH) is another major control point that connects carbon flux to NADH production. cryo EM of the human complex has advanced mechanistic understanding of its activity and regulation, providing a platform for mapping how cofactor occupancy and conformational states influence rate limitation in the cycle (Zhong et al. 2022). While these studies do not reduce regulation to Mg²⁺ alone, they underscore that cation coordinated chemistry is embedded in the key mitochondrial steps that produce reducing equivalents for the respiratory chain.

At the endpoint of mitochondrial energy conversion, the F₁F_o ATP synthase is often conceptualized as a proton driven machine, but its chemistry remains Mg²⁺ centric. High resolution structural work has provided snapshots of the catalytic cycle and conformational transitions, making explicit that nucleotide binding and release events occur within a Mg coordinated framework (Guo and Rubinstein 2022; Lai, Zhang, et al. 2023; Sobti et al. 2021). A complete rotational catalytic cycle of the F1 sector resolved by cryo EM captured ordered state transitions that clarify how nucleotide occupancy couples to mechanical steps. Complementary work examining ATP synthase under strain during catalysis reinforced that conformational energy landscapes, nucleotide binding states, and mechanical deformation are inseparable in the functioning enzyme (Guo and Rubinstein 2022). Human ATP synthase structures across multiple rotational states extend these principles to human mitochondria, providing a critical reference for disease relevant interpretation of OXPHOS dysfunction (Lai, Zhang, et al. 2023). Together, these studies support a mechanistic view in which Mg²⁺ availability can influence not only the chemical step of phosphoryl transfer but also the kinetics of nucleotide exchange, potentially sensitizing ATP production to Mg²⁺ limitation even before gross depolarization occurs. Once synthesized, ATP must be distributed and buffered between compartments. Here, Mg²⁺ dependence reappears in transport. The mitochondrial ATP Mg phosphate carrier SCaMC (SLC25A23 and related paralogs) transports MgATP. This distinguishes it from the standard ADP ATP carrier, which exchanges free nucleotides. Structural and functional analyses have defined an internal binding site that explains MgATP selectivity and identified residues essential for preference toward the Mg complex (Run et al. 2015). This selectivity is not an arcane biophysical feature; it is a design principle that enables mitochondria to traffic Mg coordinated energy currency in contexts where MgATP, rather than free ATP, is the biologically relevant species. In excitable cells, SCaMC family function has been linked to maintenance of mitochondrial ATP under stress, supporting the idea that MgATP transport can shape vulnerability to energetic collapse (Traba et al. 2012). In metabolically demanding epithelia such as kidney tubules, this axis may be particularly relevant because sustained ATP turnover requires not only synthesis but also proper chemical speciation and delivery of ATP.

A key translational insight is that Mg²⁺ regulation becomes most visible under stress, when homeostatic slack is lost. Limiting MRS2 dependent mitochondrial Mg²⁺ uptake has been shown to induce metabolic programming in the setting of prolonged dietary stress, indicating that mitochondrial Mg²⁺ influx is not redundant but instructive for metabolic remodeling (Madaris et al. 2023). More broadly, perturbations in mitochondrial Mg²⁺ handling can precipitate complex I dysfunction, reduce ATP output, and amplify susceptibility to injury, positioning Mg²⁺ not as an optional micronutrient but as a limiting factor for mitochondrial competence (Ponnusamy et al. 2024; Yamanaka et al. 2016). The emerging picture is that Mg²⁺ availability and compartmentalization define the operating range of oxidative metabolism by controlling MgATP abundance, the kinetics of phosphoryl transfer, and the stability of coupled respiration. This reframing has direct implications for kidney pathophysiology. Renal tubular cells operate near maximal energetic demand, with limited tolerance for inefficiency. In such a context, Mg²⁺ depletion can simultaneously weaken dehydrogenase driven NADH supply, slow ATP synthase chemistry through altered Mg nucleotide occupancy, and destabilize ion homeostasis through enhanced mitochondrial Ca²⁺ uptake and permeability transition susceptibility. These mechanisms provide a coherent bridge between Mg²⁺ handling proteins and downstream injury phenotypes, setting the stage for the Mg Ca mitochondria axis and its role in acute bioenergetic failure.

The “Magnesium Clock” hypothesis originates from the observation that cytosolic magnesium is not static across the day. Instead, magnesium levels oscillate in a circadian manner and, by modulating global phosphorylation potential, can gate core timekeeping processes and energy balance (Feeney et al. 2016). This finding reframes magnesium as a temporal metabolite: it does not merely support enzymes; it periodically rewrites what ATP can do in vivo by tuning MgATP availability and kinase throughput. In aging organisms, circadian rhythms dampen and fragment, and mitochondrial output becomes noisier. A plausible extension is that magnesium oscillations also lose amplitude or become desynchronised across compartments, creating phases in which the cell's phosphorylation economy is intrinsically fragile. The key unresolved question is compartment specificity. If mitochondrial magnesium is the dominant buffer that stabilizes MgATP generation during fluctuating demand, then age‐related changes in mitochondrial membrane potential or transporter regulation could translate circadian misalignment into repeated episodes of “functional ATP insufficiency,” even when bulk ATP appears preserved. This sub‐aim therefore motivates a mechanistic map linking timekeeping, mitochondrial ion handling, and the progressive narrowing of bioenergetic resilience that precedes senescence.

Direct experimental evidence supports a causal role for magnesium deficiency in driving senescence‐like states. Magnesium restriction accelerates senescence in cultured human fibroblasts, consistent with the idea that inadequate magnesium is not a passive correlate of aging but an active modifier of fate (Killilea and Ames 2008). Similarly, perturbing magnesium entry pathways can be sufficient to trigger senescence programmes: targeted silencing of TRPM7, a major magnesium‐permeable chanzyme, induces replicative senescence in proliferative cancer cells (Yee et al. 2012). These data converge on a unifying principle: when magnesium supply is constrained, the cell can retain mitochondria yet lose the ability to sustain phosphorylation‐dependent homeostasis under stress, making growth arrest and secretory remodeling more likely outcomes. How does the mitochondrion enter this logic? Mitochondrial magnesium homeostasis is increasingly understood as a regulated variable that controls energetic vulnerability. Work in mammalian systems indicates that mitochondrial magnesium balance can determine cellular energy metabolism and stress susceptibility (Yamanaka et al. 2016). At the molecular level, the mitochondrial magnesium channel MRS2 provides the best‐defined portal for matrix magnesium control, and recent structural biology has transformed this topic from inference to mechanism. Multiple high‐resolution structures show that MRS2 forms a gated channel whose conformational states can be captured in closed and open configurations, revealing principles of selectivity and regulation that were previously assigned by analogy to bacterial CorA transporters (Lai, Balaraman, et al. 2023; Li, Liu, Wallerstein, et al. 2025; Uthayabalan et al. 2023). In parallel, functional studies position MRS2 as a node that links mitochondrial magnesium availability to broader metabolic programmes, including developmental metabolic programming (Ponnusamy et al. 2024) and feedback regulation through defined protein domains (Mastrototaro et al. 2016). Together, these studies suggest that matrix magnesium is not merely “stored” but actively governed, making it realistic to propose that aging could shift the set point of mitochondrial magnesium through altered gating, expression, or membrane potential, and thereby reshape the probability landscape for senescence initiation.

A second mechanistic bridge from mitochondrial magnesium to senescence is calcium control. Mitochondrial calcium handling is now recognized as a key determinant of whether cells enter senescence or proceed to death programmes, particularly under chronic stress (Wiley et al. 2016). Strikingly, mitochondrial magnesium has been proposed as a “cationic rheostat” that restrains MCU‐mediated calcium uptake (Gallage and Gil 2016), and reduced matrix magnesium is associated with increased calcium influx and permeability transition pore susceptibility in this framework. Complementary work further supports the concept that MRS2‐mediated magnesium uptake is required to prevent mitochondrial calcium overload and preserve viability (Herranz and Gil 2018). These findings place mitochondrial magnesium at a strategic interface: it simultaneously supports MgATP‐dependent bioenergetics and limits calcium‐triggered mitochondrial catastrophe. Senescence, in this view, can emerge when magnesium loss compresses both margins at once, lowering ATP‐linked repair capacity while increasing calcium‐linked damage signaling, thereby accelerating the engagement of p53 and p16 pathways and stabilizing arrest.

Cellular senescence is not only a cell‐autonomous endpoint; it is a tissue‐level amplifier of aging through SASP‐driven inflammation, fibrosis, and metabolic rewiring. Mitochondrial dysfunction can induce a distinctive senescence state (MiDAS) with a specialized secretory output (Yarbro et al. 2020), and conceptual syntheses emphasize that senescence is heterogeneous and mechanistically plural, with metabolism functioning as both trigger and maintenance system (Margand et al. 2025; Wiley and Campisi 2021). Magnesium fits naturally into this pluralism as a modulator that can bias which senescence routes dominate in a given tissue: magnesium‐limited contexts may favor mitochondrial stress signaling and altered NAD and AMPK tone, whereas magnesium‐replete contexts may buffer transient mitochondrial insults and delay the consolidation of arrest. At the organismal level, associations between magnesium status and aging‐linked traits provide circumstantial but suggestive support for this model. Dietary and total magnesium intake has been analyzed in relation to frailty risk in older women (Struijk et al. 2024), consistent with magnesium availability tracking functional reserve at the whole‐body scale. In addition, recent work links magnesium‐related nutritional patterns to telomere dynamics in older adults (Dhillon et al. 2023), connecting magnesium to a canonical aging biomarker that integrates oxidative stress and replicative history.

While such studies align with a mechanistic narrative in which chronic, mild magnesium insufficiency increases the cumulative probability of senescence entry by weakening mitochondrial performance over time, they cannot yet resolve the direction of causality at the organismal level. It is essential to distinguish the mechanistic plausibility of this model from demonstrated lifespan causality. While the link between magnesium deficiency and cellular senescence is robustly supported in vitro, direct longitudinal evidence tracking mitochondrial magnesium dynamics across the natural aging process of a whole organism remains limited. Finally, inflammaging creates a feedback environment in which magnesium and senescence can reinforce each other. Aging is characterized by sterile, systemic inflammation, and macrophage immunometabolism has been highlighted as a critical axis linking mitochondrial dysfunction, senescence, CD38 activity, and NAD decline (Ponnusamy et al. 2024). Inflammatory signaling can promote renal magnesium wasting and impair cellular magnesium retention, while senescent cells amplify inflammatory tone, creating a loop that is plausibly magnesium‐sensitive (Ghosh‐Choudhary et al. 2021). Consequently, while we position mitochondrial magnesium as a “buffer of buffers” that stabilizes ATP‐linked repair and calcium‐linked tolerance, this framework should be viewed as a theoretical synthesis that necessitates future longitudinal studies to confirm its role as a primary driver of organismal aging. The implication is that mitochondrial magnesium may act as a “buffer of buffers,” stabilizing both ATP‐linked repair and calcium‐linked tolerance, thereby delaying not only senescence onset but also the inflammatory milieu that sustains senescence burden. As summarized in Figure 8, magnesium depletion initiates a self‐reinforcing cycle linking mitochondrial fragility, senescence‐associated inflammation, and systemic aging. In summary, the aging connection is not simply that magnesium “supports mitochondria,” but that mitochondrial magnesium may encode a time‐dependent constraint on metabolic fidelity. The circadian magnesium clock provides a conceptual entry point (Feeney et al. 2016), MRS2 biology supplies molecular levers, and calcium rheostat models define a catastrophe‐prevention mechanism (Lai, Balaraman, et al. 2023; Li, Liu, Wallerstein, et al. 2025; Mastrototaro et al. 2016; Ponnusamy et al. 2024; Uthayabalan et al. 2023). Translationally, this motivates a sharper distinction between serum magnesium and compartmental magnesium, and argues for aging research to incorporate mitochondrial magnesium state as both a biomarker and a candidate driver of senescence dynamics.