Berberine, a plant alkaloid with lipid- and glucose-lowering properties : from in vitro evidence to clinical studies

Berberine (BBR) is an isoquinoline plant alkaloid endowed with several pharmacological activities, including anti-microbial, glucose- and cholesterol-lowering, anti-tumoral and immunomodulatory properties. The main mechanism by which BBR exerts a protective role in atherosclerosis relates to its cholesterol-lowering activity. BBR significantly increases hepatic low density lipoprotein receptor (LDLR) expression and reduces the expression and secretion of the LDLR modulator proprotein convertase subtilisin/kexin type 9 (PCSK9). In addition to this, several other atheroprotective effects have been ascribed to BBR, including anti-inflammatory and anti-oxidant properties, inhibition of vascular smooth muscle cell proliferation and improvement of endothelial dysfunction. BBR also increases glucose utilization in adipocytes and myocytes, while decreases glucose absorption in intestinal cells, resulting in a net hypoglycemic effect. In hypercholesterolemic animals, BBR significantly decreases LDL-C and total cholesterol (TC) levels and reduces aortic lesions, an effect similar to that of statins. In diabetic animals, BBR significantly reduces glucose levels, improves glucose tolerance, reduces body weight gain and adipose tissue mass. Several clinical studies have also tested the efficacy of BBR in humans. In hypercholesterolemic subjects, BBR induces a significant reduction of TC, triglycerides and LDL-C levels and a significant increase of HDL-C levels, without major adverse effects. BBR also reduces glycemia and plasma cholesterol in diabetic patients, improves lipid and glucose profile and decreases body mass index and waist circumference in subjects with metabolic syndrome. These findings, together with the good tolerability, suggest that BBR administration might be considered a potential therapeutic approach for the treatment of hypercholesterolemia or diabetes. Given the level of evidence available to date well-designed randomized controlled trials to test safety and efficacy of BBR are warranted.