Consequences of high dietary fructose in the islet-transplanted rat with suboptimal beta-cell mass

Fructose (FR) feeding in rats provides a model of dietary-induced insulin resistance that has been used to examine interactions among the cluster of metabolic disorders including insulin resistance, hyperinsulinemia, hypertension, and dyslipidemia known as Syndrome X. In animals with reduced beta-cell mass, however, insulin resistance may not have similar associated disorders. Therefore this study examined the consequences of FR feeding in rats with a reduced beta-cell mass. Formerly diabetic islet-transplanted (TX) or shamoperated (SHAM) male Wistar Furth rats were fed a purified control (CNTL) diet or a diet containing either 40 or 70% (wt/wt) FR for 3-5 wk. FR feeding in SHAM animals resulted in elevated triglyceride levels but did not affect fed or fasting glucose and insulin concentrations, blood pressure, glucose tolerance, and the acute insulin response to a glucose bolus compared with CNTL-fed animals. Among TX animals, hypertriglyceridemia and fasting hyperglycemia were observed only in those fed FR. Thus the effects of diet-induced insulin resistance are limited to dyslipidemia, if insulin secretory capacity is adequate, but are detrimental to both glucose and lipid metabolism in combination with a reduced beta-cell mass.