Glucosinolate Sinigrin Improves Insulin Resistance to Suppress Glutathione Consumption in Type 2 Diabetic Mice

Background: Sinigrin, an aliphatic glucosinolate, is absorbed from the intestine as allyl isothiocyanate (AITC) and conjugated with glutathione (GSH) followed by excretion as an N-acetylcysteine (AITC-NAC) into the urine. AITC is the crucial metabolized form which reflects the occurring bioavailability of dietary sinigrin. However, whether the anti-diabetic effects of dietary sinigrin and the quantitative of metabolic parameters AITC and AITC-NAC remain unknown in the type 2 diabetes model (T2D). Methods: A total of mice were divided into 6 groups: (i) normal control (ii) diabetic control, (iii) normal + 15 (μmol sinigrin/kg BW for all), (iv) diabetes + 15, (v) normal + 30 and (vi) diabetes + 30. After oral administration of sinigrin for 21 days, plasma, tissue, and urine were collected for analysis of metabolic parameters. Results: Administration of sinigrin reduced plasma glucose and significantly improved the insulin resistance of T2D mice. Besides, the treatment of sinigrin induced accumulates AITC levels in the liver and pancreas tissue results in enhancing GSH levels in these tissues (P<0.05). Sinigrin causes less elimination of AITC-NAC in T2D mice urine (below 10% excretion compared to 70% in normal mice P<0.05). These results indicated the collaboration of changeable sinigrin metabolism for its protective effect on T2D mice. Conclusions: Dietary intake of sinigrin possesses anti-diabetes and the changeable amount exposes AITC-NAC and AITC accumulation in the target tissue, enhancing the GSH levels may contribute to its protective effect. These findings may further justify the importance of sinigrin in phytomedicine.