The Molecular Mechanisms of Metformin's Action on Blood Lipid Profile in Diabetic Patients

In this paper, we review the literature regarding metformin's action on blood lipid concentrations in metformin-treated diabetic patients. Published data indicate that metformin reduces serum total cholesterol (T-C), LDL-cholesterol (LDL-C) and triacylglycerol (TAG) concentrations and raises serum HDL-cholesterol (HDL-C) concentrations in diabetic patients. The beneficial effect of metformin on serum lipid profiles in diabetic patients can result from (a) its action on AMP-activated protein kinase, which inhibits lipogenesis and cholesterol synthesis and stimulates fatty acid oxidation; (b) decreased plasma TAG concentrations, via promoting VLDL-TAG clearance by brown adipose tissue; (c) the inhibition of nuclear factor erythroid 2-related factor 2 (Nrf2) gene expression, affecting lipid profile in diabetic patients; (d) the inhibition of the expression of genes encoding proprotein convertase subtilisin/kexin 9 (PCSK9) and lipogenic enzymes; (e) the downregulation of carbohydrate-response element-binding protein (ChREBP), which affects liver TAG and cholesterol synthesis from acetate formed by gut microbiota; (f) the inhibition of angiopoietin-like 3 protein (ANGPTL3) gene expression, and consequent effects on plasma TAG concentrations; (g) the activation of AMPK, which inhibits LXRα activity; and (h) reverse cholesterol transport. In conclusion, one can assume that beyond its primary antihyperglycemic effect, metformin exerts pleiotropic effects that modulate lipid metabolism and blood lipid profile in T2D patients. These beneficial effects of metformin on blood lipid profile may play a role in the reduction in cardiovascular risk in diabetic patients.