Skeletalmuscle is the major site for glucose uptake and thus plays an important role in initiating insulin resistance in type 2 diabetes mellitus. This study evaluated the effects of tocotrienols (TT) and greenteapolyphenols (GTP) individually or in combination on glucosehomeostasisand skeletalmusclemetabolism in obesemice with insulin resistance and elevation of blood glucose.
Forty-eight malemice were fed a high-fat diet and assigned to 4 groups in a 2 (no TT vs. 400 mg TT/kg diet) × 2 (no GTP vs. 0.5% vol/wt GTP in water) for 14 weeks. Both GTP and TT improved area under curve of insulin intolerance; while GTP increased serum insulin levels in obesemice, probably due to the addition of sweetener in drinking water. An interaction (TT×GTP) was observed in glucose tolerance test, total pancreas insulin concentration, and citrate synthase activity of soleus in mice. Neither TT nor GTP affected insulin and glucagon protein expression in pancreas based on immunohistochemistry.
Both TT and GTP individually increased soleus muscle weight of mice; while only GTP increased gastrocnemius muscle weight of mice. The TT+GTP group had the greatest gastrocnemius muscle cross sectional area than other groups. GTP, not TT, induced cytochrome c oxidase activity and reduced thiobarbituric acid reactive substances levels in soleus muscle.
Our results suggest that TT and GTP, individually or synergistically have the potential to improve skeletalmusclemetabolism in obesemice by improving glucosehomeostasis, reducing lipid peroxidation, and increasing rate limiting enzymes of oxidative phosphorylation.