Microbiome–metabolomics analysis reveals the potential effect of verbascoside in alleviating cognitive impairment in db/db mice

Cognitive impairment is the main central nervous system complication of diabetes, affecting the quality of life of patients. Herba Cistanche is a homologous plant widely used as a health food and therapeutic drug. Verbascoside, a signature component of Herba Cistanche, has anti-diabetic and neuroprotective effects. However, it is quickly metabolized by the gut microbiota, and the mechanism of its neuroprotection and improvement of learning and memory remains unclear. We investigated the effectiveness and potential mechanisms of verbascoside on cognitive dysfunction in db/db mice using a 16S rRNA microbiome and serum metabolomics approach. We found that 12-week treatment with verbascoside significantly inhibited insulin resistance, reduced blood glucose and lipids, and improved cognitive deficits. In addition, verbascoside increased the gut microbiota diversity, improved intestinal dysbiosis, attenuated intestinal barrier disruption, reduced the levels of inflammatory factors, regulated the expression of the metabolites associated with cognitive function, and enhanced the central insulin sensitivity and hippocampal synaptogenesis signaling. We revealed that verbascoside induced the enrichment of Alistipes, Roseburia, and Intestinimonas in the gut, suppressed the abundance of Escherichia-Shigella, increased the serum levels of gamma-aminobutyric acid, L-glutamic acid, and L-lysine, and decreased taurine expression. Finally, a strong association between gut microbes, serum metabolites, and cognitive performance affected by verbascoside was observed. Our research suggests that alterations in gut microbes/metabolites are involved in the development of diabetic cognitive dysfunction, which is alleviated by verbascoside in the db/db mice through restructuring the gut microbiota composition, ameliorating diabetic metabolic disorders, and attenuating pathological brain damage.