EFFECTS OF LONG-TERM LOW-GLYCEMIC INDEX STARCHY FOOD ON PLASMA-GLUCOSE AND LIPID CONCENTRATIONS AND ADIPOSE-TISSUE CELLULARITY IN NORMAL AND DIABETIC RATS

The present study aimed to assess the metabolic consequences of the ch ronic ingestion of two starches giving different postprandial glycaemi c responses in normal and diabetic rats. The two starches chosen were mung-bean (Phaseolus aureus) starch (97% pure starch) and wheat starch presented as ground French toast. First, we studied the characteristi cs of these two starches, In vitro the cr-amylase (EC 3.2.1.1) digesti bilities of these starches were 40 (SE 3) and 62 (SE 4)% respectively at 30 min, whereas the contents of resistant starch were 77 (SE 4) and 22 (SE 4) g/kg respectively, In vivo the mungbean starch produced low er postprandial glycaemic responses than the wheat starch (areas under the curve were: 91 (SE 28) and 208 (SE 33) mmol.min/l, P < 0.05) in n ormal rats (n 8). We then submitted twenty-eight normal and twenty-eig ht diabetic (neonatal streptozotocin on second day of birth) male Spra gue-Dawley rats (6 weeks old) to a diet containing 570 g starch/kg as either mung-bean starch or wheat starch (n 14 rats/group). After 5 wee ks on the diets food intakes and body weights were identical in each g roup. Liver and kidney weights were comparable when expressed as relat ive weight, The mungbean-starch diet slightly decreased epididymal fat -pad weight (P < 0.14, ANOVA) and led to a marked decrease in adipocyt e volume (P < 0.05). Plasma triacylglycerol and phospholipid concentra tions were lower after the mung-bean-starch diet than after the wheat- starch diet in both normal and diabetic rats, whereas free fatty acid concentrations were lower only in normal rats, Similarly, non-fasting plasma glucose concentrations decreased (P < 0.05) in normal rats fed on mung-bean starch but not in diabetic ones (P < 0.14), Insulin level s tended to be lower, but not significantly, after mung-bean-starch fe eding than after wheat starch, We conclude that the replacement of 570 g wheat starch/kg diet with mung-bean starch for 5 weeks resulted in (1) lowered non-fasting plasma glucose and free fatty acid levels in n ormal but not in diabetic rats, (2) a reduction in plasma triacylglyce rol concentration and adipocyte volume in both normal and diabetic rat s. Thus, the type of starch mixed into the diet may have important met abolic consequences in normal and diabetic rats.