BACKGROUND: Obesity is closely associated with cognitive dysfunction, and markedly increases the risk of developing neurodegenerative diseases. Currently, obesity-related cognitive impairment lacks effective therapeutic interventions. Shenling Baizhu Powder (SLBZ) is a classical formula used to strengthen the spleen and promote the ascent of clear qi in traditional Chinese medicine (TCM). According to the TCM, this formula has great potential for the treatment of obesity-related cognitive impairment. However, research on SLBZ has focused primarily on its gastrointestinal effects, leaving its neurocognitive mechanisms largely unexplored.
PURPOSE: This study aimed to elucidate the therapeutic mechanisms of SLBZ in obesity-related cognitive impairment.
MATERIALS AND METHODS: Obese mice were obtained by subjecting male mice to a 16-week high-fat diet (HFD, 60 kcal % fat). During the final four weeks of the study, a SLBZ decoction (10 and 20 g/kg/day) was administered orally. The mice were then subjected to two behavioral tests and a glucose tolerance test. To evaluate the therapeutic effects of HFD on metabolic dysregulation, neuroinflammation, and intestinal barrier impairment, a range of analytical techniques, including biochemical analysis, immunofluorescence, RT-qPCR, and Western blotting, were used. Subsequently, 16S rRNA gene sequencing and metabolomic profiling were used to detect changes in the gut microbes and metabolite levels. Finally, fecal microbiota transplantation was performed to assess the functional link between SLBZ remodeling of the gut microbiota, metabolic alterations, and hippocampal cognitive function.
RESULTS: Our study demonstrated that HFD-fed mice developed significant cognitive impairment, supporting the notion that obesity adversely affects cognitive function. In the Morris water maze and open-field tests, SLBZ administration effectively ameliorated HFD-induced cognitive dysfunction. This improvement was accompanied by the restoration of the hippocampal synaptic ultrastructure and the recovery of the key synaptic proteins BDNF and PSD95. In agreement with this, SLBZ suppressed microglial activation and associated neuroinflammatory responses in HFD-fed mice. In the colon, SLBZ administration markedly alleviated HFD-induced gut barrier impairment, as evidenced by increased colonic mucus thickness and elevated expression of tight junction proteins, ZO-1, Occludin, and Claudin-1. Furthermore, SLBZ reduced endotoxin translocation and downregulated the expression of pro-inflammatory cytokines TNF-α, IL-1β, and IL-6. Notably, HFD-induced gut microbiota dysbiosis was remodeled by the SLBZ treatment, which was characterized by an increased capacity for microbial vitamin B6 synthesis. SLBZ increased the serum levels of vitamin B6 in HFD-fed mice. Intriguingly, fecal microbiota transplantation from SLBZ-treated HFD-fed mice facilitated the amelioration of cognitive deficits, including superior performance in behavioral tests and synaptic repair in the hippocampus compared to recipients of HFD-microbiota.
CONCLUSION: Our findings highlight that SLBZ is a promising therapeutic agent mitigating obesity-related cognitive impairment via the "gut microbiota-vitamin B6-neuroprotection" axis.
