Evaluation of isoflavone-containing kudzu root and inonotus obliquus extract on experimentally induced diabetes

Purpose: Studies support health benefits of isoflavones, but antidiabetic effects of these naturally occurring compounds remains largely unknown. Inonotus obliquus (chaga) extract is a mushroom extract used in traditional Russian and Chinese medicine for the treatment of inflammatory diseases. This pilot study investigates isoflavones and Inonotus obliquus (chaga) extract effects on rodent diabetes model. Methods: Diabetes was induced (streptozotocin 65 mg/kg, nicotinamide 110 mg/kg) in 9 male Wistar rats (12 weeks old). 9 additional rats were healthy controls. 4 weeks was allowed for the establishment of the pathology before animals were treated for 4 weeks with vehicle, isoflavone (200 mg/kg/day), or Inonotus obliquus (100 mg/kg/day). Weekly weight, blood pressure, and metabolic caging measurements were recorded. Glucose tolerance, regeneration of β-cells, renal function (serum creatinine, blood urea nitrogen (BUN) level, creatinine clearance rate) and heart and kidney weight index were estimated at the end-point. Results: Untreated diabetic rats showed impaired glucose tolerance (area under curve (AUC)= 64.87±9.71min×mmol/L) which was remediated with isoflavone (AUC=14.78±1.1min×mmol/L, p<0.001) and chaga extract (AUC=30.4 ±13.5 min×mmol/L, p<0.001). Plasma insulin concentration was significantly different in untreated diabetic rats (26±1µlU/ml) versus chaga (80±34 µlU/ml p<0.05) but not with isoflavone treatment (43±8 µlU/ml, p>0.05). Body weight was lower but not significantly different in untreated diabetes (491±35g) versus isoflavone (521±7g, p>0.05) and chaga treatment (552±92 g, p>0.05). Kidney weight index was greater in untreated diabetic rats (0.51±0.06%) compared to isoflavone (0.36±0.02%, p< 0.05) but not significantly different in chaga (0.39±0.06%, p >0.05) treatment. Food and water intake and 24 hr urine output, serum creatinine, BUN, and creatinine clearance rate were not significantly different for the sample size studied. Conclusions: Initial results show improved renal function and glycaemic control in diabetic rats treated with isoflavone and chaga extract but without other cardiovascular impact. The study was underpowered to detect all potential differences and further work, including translating results to humans, is required.