Endocrine Abstracts

Sex hormone-binding globulin (SHBG) is a circulating plasma glycoprotein produced by the liver, which in the blood binds estrogens and androgens with high affinity and regulates its bioavailability. Low plasma SHBG levels are associated with obesity, metabolic syndrome and non-alcoholic fatty liver disease. Importantly, epidemiological studies have demonstrated that low plasma SHBG levels is a risk factor for developing type 2 diabetes and cardiovascular disease. In the last years, we have described the molecular mechanisms by which several nutritional factors including high carbohydrate diets, olive oil, red wine (resveratrol) and caffeine regulate hepatic SHBG production. In the present work we have studied the effects of Rooibos tea on hepatic SHBG production since Rooibos (Aspalathus linearis), a South African herbal tea, has been shown to possess anti-diabetic and cardiovascular protective effects. For this objective, we performed in vitro and in vivo studies. The results showed that Rooibos treatment increases SHBG production in HepG2 cells. These results were corroborated in vivo using SHBG transgenic mice. Our results showed for the first time that Rooibos consumption increases hepatic SHBG production. These results suggest that the anti-diabetic and cardiovascular beneficial effects of Rooibos may be explained by increasing hepatic SHBG production.