Metformin-like effect of salvia officinalis (common sage) : is it useful in diabetes prevention?

Abstract

Common sage (Salvia officinalis L) is among the plants that are claimed to be beneficial to diabetic patients, and previous studies have suggested that some of its extracts have hypoglycaemic effects in normal and diabetic animals. In this study we purposed to verify the antidiabetic effects of the most common form of consumption of this plant as an infusion (tea). Replacing water with sage tea for 14 days lowered fasting plasma glucose in normal mice but had no effect on glucose clearance in response to an intraperitoneal glucose tolerance test. This indicated effects at level of the liver on gluconeogenesis. Hepatocyte primary cultures of healthy sage tea drinking rats showed, after stimulation, high glucose uptake capacity and a decreased gluconeogenesis in response to glucagon. Sage essential oil further increased hepatocyte sensitivity to insulin and inhibited gluconeogenesis. Overall these effects resemble those of the pharmaceutical drug metformin, a known inhibitor of gluconeogenesis used in the treatment and prevention of type 2 diabetes mellitus. In primary cultures of rat hepatocytes isolated from streptozotocin-induced diabetic rats none of these activities were observed. These results seem to indicate that sage tea does not possess antidiabetic effects at this level. However, its effects on fasting glucose levels in normal animals and the metformin-like effects on rat hepatocytes suggest that sage may be useful as food supplement in the prevention of type 2 diabetes mellitus by lowering plasma glucose of individuals at risk.