Positive impact of DPP-4 or SGLT2 inhibitors on mild cognitive impairment in type 2 diabetes patients on metformin therapy: A metabolomic mechanistic insight

Mild cognitive impairment is increasingly recognized as a complication of type 2 diabetes (T2D). Although currently no disease-modifying treatments for cognitive disorders exist, interest surged in potential neuroprotective effects of newer anti-diabetic drugs. This study investigates the impact of newer anti-diabetic drug classes, dipeptidyl peptidase-4 (DPP-4i) and sodium-glucose cotransporter-2 inhibitors (SGLT2i) - on cognitive decline in T2D patients on metformin therapy. A prospective observational cohort study was conducted, with a follow-up duration of 6 months. The study compared the cognitive performance of T2D patients on metformin monotherapy to those on a combination of metformin with DPP-4i or SGLT2i, using the Montreal Cognitive Assessment Battery. A group of healthy volunteers served as a reference. At baseline, patients receiving combination therapy had a cognitive performance comparable to that of healthy volunteers, while those on metformin monotherapy scored lower. These differences persisted for patients who completed the follow-up, though there was no change within group. Baseline differences were independent of glycemic control, blood lipids, renal function, and serum inflammatory markers. Comprehensive metabolomics and lipidomics revealed that T2D patients on metformin monotherapy exhibited enriched purine, glutathione and sphingolipid metabolism, with alterations in xanthine, L-pyroglutamic acid, and several sphingomyelins. These changes suggest increased oxidative stress in T2D, mitigated in the combination therapy group, as evidenced by total serum antioxidant capacity. As such, we conclude that the combination of DPP-4i or SGLT2i with metformin positively impacts cognitive function in T2D patients by modulating metabolic pathways rather than improving glycemic control, peripheral diabetic complications, or systemic inflammation.