Antidiabetic activity of Nigella sativa seed extract in cultured pancreatic β-cells, skeletal muscle cells, and adipocytes

The seeds of Nigella sativa L. (NS), a plant of the Runan-culaceae family, are used in traditional medicine in North Africa and the Middle East for the treatment of diabetes. Despite widespread use and a number of scientific studies, the target tissues and cellular mechanisms of action of this plant product are not well understood. This study evaluated the effects of NS seed crude ethanol extract on insulin secretion in INS832/13 and beta TC-tet lines of pancreatic beta-cells and on glucose disposal by C2C12 skeletal muscle cells and 3T3-L1 adipocytes. An 18-h treatment with NS amplified glucose-stimulated insulin secretion by more than 35% without affecting sensitivity to glucose. NS treatment also accelerated beta-cell proliferation. An 18-h treatment with NS increased basal glucose uptake by 55% (equivalent to approximately two-fold the effect of 100 nM insulin) in muscle cells and approximately by 400% (equal to the effect of 100 nM insulin) in adipocytes; this effect was perfectly additive to that of insulin in adipocytes. Finally, NS treatment of pre-adipocytes undergoing differentiation accelerated triglyceride accumulation comparably with treatment with 10 mu M rosiglitazone. It is concluded that the well-documented in vivo antihyperglycemic effects of NS seed extract are attributable to a combination of therapeutically relevant insulinotropic and insulin-like properties.