High-hydroxypropylated tapioca starch improves insulin resistance in genetically diabetic KKAy mice

The hypoglycemic and antidiabetic effect of hydroxypropyl tapioca starch (HPTS) with a varying degree of substitution (DS: 0.058, 0.091, and 0.180) was investigated in rats and KKAy mice, an animal model of type 2 diabetes. The positive incremental area under the curve (IAUC) for glucose significantly decreased as the DS of HPTS increased. The IAUC after intragastric intubation of the highest HPTS (HPTS-III, DS = 0.180) was 55% of the IAUC of tapioca starch (TS). After 28 d, fasting blood glucose and insulin concentrations were significantly lower in rats fed HPTS-III (50 g/kg diet) than in those fed TS (P < 0.05). In KKAy mice fed HPTS-III (50 or 100 g/kg diet) for 33 d, as compared with TS, there was a delay in the detection of glucose in urine and also a decreased incidence of finding glucose in urine on days 7, 21, and 28; in addition, the AUCs for glucose in the oral glucose tolerance test on days 14 and 28 were significantly lower (P < 0.05 and P < 0.05, respectively). The plasma adiponectin concentration and the quantitative insulin sensitivity check index (QUICKI) were significantly higher in mice fed HPTS-III than in those fed TS (P < 0.01), whereas the homeostasis model assessment of insulin resistance (HOMA-IR) was lower (P < 0.01). Energy intake was significantly lower in mice fed HPTS-III than in those fed TS. These findings show that HPTS with a high DS resists digestion by alpha-amylase and improves insulin resistance in KKAy mice by decreasing energy intake. However, the potential mechanism by which HPTS-III decreases energy intake is unclear at present.