Objective Essential amino acids and unsaturated fatty acids, rich in rice germ (RG), have been shown to improve glucose metabolism. This study aims to investigate the effects of RG on glucose metabolism in a rat model of diabetes mellitus (DM).
Methods Male SD rats (n=100) were randomly divided into a normal control group (n=10) and a DM model group (n=90). After high-fat and high-carbohydrate diet and intraperitoneal injection of 35 mg/kg streptozotocin, a diabetic rat model was established. Fifty-five DM model rats were further divided into five groups:model group, drug control group, and low-, medium-, and highdose RG groups. Three RG groups were fed with 2.5%, 10%, and 40% (w/w) RG respectively for 12 weeks, and the remaining groups were given basal diet; the drug control group was additionally given 500mg/kg metformin hydrochloride. After the designed treatment, fasting blood glucose (FBG) and fasting insulin (FINS) levels were measured, and insulin sensitivity index (ISI) was calculated. The ultrastructure of islet B cells was observed. The mRNA expressions of glucose kinase (GCK) in liver and glucose transporter-4 (GLUT-4) and adiponectin (APN) in fat were detected.
Results The levels of essential amino acids in RG were higher than those in milled rice (white rice), especially lysine(7 200±88) mg/kg vs (2 530±33) mg/kg, P < 0.05, so were fat acids, 30-43 times as much as those in white rice. Compared with the model group, the low-, medium-, and high-dose RG groups showed lower FBG(2 493.7±473.0), (1 935.1±318.0), and (1 583.8±345.9) mg/L and FINS(4.08±0.19), (3.53±0.16), and (3.29±0.21) mU/L levels, and higher ISI(-6.93±0.29), (-6.53±0.25), and (-6.26±0.23), as well as relieved injury of pancreatic tissues, increased number of pancreatic islets, and alleviated injury of islet B cell ultrastructure. The mRNA expressions of GLUT-4 and GCK increased in the medium-and high-dose RG groups (P < 0.05); the APN mRNA expression increased in the high-dose RG group (P < 0.05).
Conclusion The mechanism by which RG improves glucose metabolism in diabetic rats may relate to the up-regulation APN and GLUT-4 mRNA expressions in adipose tissues and GCK mRNA expression in liver tissues. These findings suggest that RG is a potential therapeutic agent for DM.
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