Metformin enhances LDL-cholesterol uptake by suppressing the expression of the pro-protein convertase subtilisin/kexin type 9 (PCSK9) in liver cells

The association between circulatory, local pancreatic PCSK9 and type 2 diabetes mellitus: The effects of antidiabetic drugs on PCSK9

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a potent modulator of cholesterol metabolism and plays a crucial role in the normal functioning of pancreatic islets and the progression of diabetes. Islet autocrine PCSK9 deficiency can lead to the enrichment of low-density lipoprotein (LDL) receptor (LDLR) and excessive LDL cholesterol (LDL-C) uptake, subsequently impairing the insulin secretion in β-cells. Circulatory PCSK9 levels are primarily attributed to hepatocyte secretion. Notably, anti-PCSK9 strategies proposed for individuals with hypercholesterolemia chiefly target liver-derived PCSK9; however, these anti-PCSK9 strategies have been associated with the risk of new-onset diabetes mellitus (NODM). In the current review, we highlight a new direction in PCSK9 inhibition therapy strategies: screening candidates for anti-PCSK9 from the drugs used in type 2 diabetes mellitus (T2DM) treatment. We explored the association between circulating, local pancreatic PCSK9 and T2DM, as well as the relationship between PCSK9 monoclonal antibodies and NODM. We discussed the emergence of artificial and natural drugs in recent years, exhibiting dual benefits of antidiabetic activity and PCSK9 reduction, confirming that the diverse effects of these drugs may potentially impact the progression of diabetes and associated disorders, thereby introducing novel avenues and methodologies to enhance disease prognosis.

Insight into the role of PCSK9 in glucose metabolism

Diabetes mellitus (DM) is strongly associated with an increased risk of atherosclerotic cardiovascular disease (ASCVD). Proprotein convertase subtilisin/kexin type 9 (PCSK9) was recently identified as an important regulator of circulating low-density lipoprotein-cholesterol (LDL-C) levels via degradation of the LDL receptor, proving to be a valid target to improve lipoprotein profiles and cardiovascular outcomes in patients with ASCVD. Beyond LDL receptor processing and cholesterol homeostasis, the PCSK9 protein has recently been verified to be associated with glucose metabolism. Importantly, clinical trials suggest that treatment with PCSK9 inhibitors for patients with DM is more effective. Hence, in this review, we summarize the current findings derived from experimental, preclinical, and clinical studies regarding the association between PCSK9 and glucose metabolism, including the relationship of PCSK9 genetic mutations to glucose metabolism and diabetes, the link between plasma PCSK9 concentrations and glucose metabolic parameters, the effects of glucose-lowering drugs on plasma PCSK9 levels and the impacts of PCSK9 inhibitors on cardiovascular outcomes of patients with DM. Clinically, exploring this field may improve our understanding regarding the roles of PCSK9 in glucose metabolism and may offer an in-depth interpretation of how PCSK9 inhibitors exert effects on the treatment of patients with DM.

Lipid-lowering activity of metformin-soluble soybean polysaccharide nanoparticles

Soybean dregs are one of the most important albeit underutilized byproducts in soybean processing. In this study, soluble soybean polysaccharides with lipid-lowering activity were extracted from soybean dregs and used as a wall material for embedding metformin. Metformin-soluble soybean polysaccharide nanoparticles (MET-SSPS-NPs) were prepared by electrostatic interaction. The lipid-lowering activity and possible mechanism of MET-SSPS-NPs were investigated. Western blotting was used to detect the expression levels of cell-related protein proprotein convertase subtilisin/kexin type 9 (PCSK9) and low-density lipoprotein receptor (LDLR) in vitro. The results showed that MET-SSPS-NPs lowered the expression of PCSK9 and improved LDLR levels. A high-fat diet (HFD) animal model was established to study the lipid-lowering effect of MET-SSPS-NPs by real-time quantitative PCR and western blotting. MET-SSPS-NPs significantly upregulated peroxisome proliferator-activated receptor gamma (PPARγ) expression and downregulated PCSK9, fatty acid-binding protein (FABP)7 and FABP5 expression more strongly than MET or SSPS alone. In conclusion, MET-SSPS-NPs can inhibit PCSK9 expression and improve the level of adipokines, providing a theoretical basis for the application of MET-SSPS-NPs in lipid lowering.