Antidiabetic effects of astaxanthin partly mediated by the inhibition of carbohydrate digestion and absorption and in vitro DPPH and lowering lipids in high-fat-fed albino mice

Astaxanthin (ASX) has been reported to reduce hyperglycemia by improving insulin secretion and insulin resistance. The present research aims to elucidate the antidiabetic effects as well as the mode of action of ASX, both in-vitro and in-vivo . Starch digestion, glucose diffusion, 2,2-Diphenyl-1-picrylhydrazyl (DPPH) were investigated in vitro, and oral glucose tolerance tests (OGTT), total residual unabsorbed sucrose contents in the gut, gastrointestinal (GI) motility were assessed in high-fat-fed (HFF) hyperlipidemic albino mice. Acute and chronic metabolic effects were evaluated by monitoring food and water intake, amount of urination and defecation. HFF-induced type 2 diabetic mice were treated for 33 days with ASX (30 and 60 mg/5 ml/kg b.w.) were used to assess chronic effects.

In the in vitro study, ASX (1.6 - 1000 µg/mL and 40 - 5,000 µg/ml) decreased ( p< 0.001) enzymatic digestion of starch and glucose diffusion by 45.14% and 32.50%, respectively and also showed a significant inhibitory effect on the DPPH ( p< 0.001) over a concentration range (1.6 - 5000 µg/mL) of ASX. During the in vivo experiments, oral administration of ASX (30 - 60 mg/5 ml/kg b.w.) improved oral glucose tolerance ( p< 0.001) as well as significantly increased ( p< 0.01) residual unabsorbed sucrose contents in the six segments of the gut. In addition, ASX (30 - 60 mg/5 ml/kg b.w.) significantly enhanced GI motility (p<0.05) in albino mice. Furthermore, ASX (60 mg/5 ml/kg b.w.) reduced food and fluid intake, and the amount of urine and stool formation significantly ( p< 0.001) both in chronic and acute metabolic studies, accordingly. In a chronic study, ASX, at (30 and 60 mg/5 ml/kg b.w.), substantially lowered blood glucose, total cholesterol, VLDL, triglycerides, LDL cholesterol and also improved liver glycogen content.

In conclusion, ASX shows effect on decreasing carbohydrate digestion, absorption, increasing GI motility, and inhibiting DPPH. Thus, ASX might be a potential drug for the management of diabetes and its complications.