Effects of rebaudioside A on the β cell function and lipid metabolism in rats fed high–fat diets

Objective To study the effect of high–fat diet and rebaudioside(RA) intervention on the function of β cell and lipid metabolism of SD rats. Methods Ten–week–old male SD rats were randomly divided into 3 groups, i. e., the normal group (NC, n=10), the high–fat diet group (HF, n=10), and the high–fat diet plus RA intervention group (HF+ R, n=10). Rats in HF+ R group was administered RA 30 mg·kg–1·d–1 by intra–peritoneal injection, while rats in HF group was injected same volume of saline.Intraperitoneal glucose tolerance test (IPGTT) were carried out after eight weeks of feeding. Triglycerides (TG) content in liver and in muscle was calculated. The mRNA expression of genes involved in fatty acid metabolism was measured by using reverse transcription and real–time PCR. Results (1) At the 30 min of the IPGTT, the insulin levels in NC, HF, HF+ R group were (16.0±6.1), (5.4±0.8) and (23.9±7.1) μg/L, respectively (F=3.77, all P<0.05); the blood glucose at the 30 min in rats of HF+ R increased significantly as compared with NC group and HF group(F=3.83, P<0.05). (2)TG content of muscle and liver in HF and HF + R group increased significantly than NC group (F=4.39, P<0.05 in muscle, F=5.97, P<0.01 in liver). (3)The expression of acetyl coenzyme A carboxylase –2 (ACC–2) in rat muscle of HF group and HF+ R group was 1.74 fold and 19.97 fold higher than that in NC group, respectively (F=13.48, P<0.01); Compared with the NC group, the muscle carnitine acyltransferase 1(M–CPT–1) was increased only in HF group . Conclusion RA preserved early phase insulin secretion in rats feeding with high–fat diet, however, the blood glucose level was higher. The increased TG contents and the change of gene expression in muscle may account for the increased glucose level. Key words: Rebaudioside A; Dietary fats; Beta cell