Roasted licorice extracts prevent chronic high glucose‐induced accumulation of glomerular mesangial matrix

Abstract

Diabetic nephropathy (DN) characterized as glomerulosclerosis can cause renal failure and end‐stage renal disease. Expansion of glomerular mesangial matrix mainly comprised of type IV collagen is a prominent feature of DN. Enhanced expression and secretion of connective tissue growth factor (CTGF) contribute an important role in this process. The present study is to investigate whether roasted licorice extracts (rLE) at non‐toxic doses can inhibit production of high glucose‐induced type IV collagen as well as CTGF in human mesangial cells (HRMC). Serum starved HRMC were cultured in media containing 5.5 mM glucose plus 27.5 mM mannitol as an osmotic control or 33 mM glucose for 3 days in the presence of 10 µg/mL rLE. Exposure of HRMC to high glucose resulted in a significant increase in collagen type IV secretion and CTGF expression, which was reversed by rLE. These effects were much greater than raw licorice extracts that exhibited a weak inhibition when extracted in ethanol. Isoliquiritigenin, a bioactive component of rLE, appeared to attenuate high glucose‐stimulated mesangial matrix accumulation. The results demonstrate that rLE may be potential therapeutic agents for the prevention and treatment of diabetic nephropathy. Supported by Brain Korea 21 from Korea Research Foundation and the grant (R01‐2006‐000‐10896‐0) from Korea Science and Engineering Foundation.