Pathogenesis and therapeutic effect of sitagliptin in experimental diabetic model of COVID-19

This study evaluates the pathogenesis of COVID-19 and the therapeutic efficacy of sitagliptin in diabetic and obese mice. Using a novel double-transgenic mouse model (db/db and K18-hACE2), the findings demonstrates that SARS-CoV-2 infection (Delta variant) causes severe multi-organ damage, glucose metabolism abnormalities, insulin resistance, and pancreatic islet cell damage in diabetic mice. Infected diabetic mice displayed higher mortality, inflammation (elevated TNF-α, IL-6, IL-1β), and fibrinolytic activity (PAI-1), alongside dysregulated diabetes-related hormones (GLP-1, leptin, ghrelin, resistin) compared to non-diabetic controls. Sitagliptin treatment reduced organ injury, hyperglycemia, inflammation, and fibrinolytic activity while improving insulin resistance and glucose metabolism. This was evidenced by decreased fasting blood glucose levels, improved insulin sensitivity, and elevated insulin and GLP-1 levels. These findings suggest sitagliptin is a promising therapeutic strategy to mitigate the severity of COVID-19 in experimental diabetes by modulating inflammation and improving metabolic syndrome. Further mechanistic investigations revealed that the level of hACE2 expression, along with the activation of NF-κB and IRS-1, play critical roles in the development of SARS-CoV-2-induced diabetes, the exacerbation of pre-existing diabetes, and the therapeutic efficacy of sitagliptin.