A HIGH-SUCROSE DIET ALTERS THE LIPID-COMPOSITION AND FLUIDITY OF LIVER SINUSOIDAL MEMBRANES

Impaired insulin suppression of hepatic glucose production and accumul ation of hepatic triglycerides occur after 1 week on a high-sucrose di et. The purpose of this study was to ascertain whether changes in stru ctural lipids, fatty acid composition and/or fluidity occur after 1 we ek on a high-sucrose diet, and therefore might contribute to the sucro se-induced impairment in hepatic glucose metabolism. Male Wistar rats (n = 28) were fed a purified high starch (68% of energy) diet for a 2- week baseline period. Fourteen animals were then switched to a high su crose (68% of energy) diet for 1 (n = 7) or 5 (n = 7) weeks. Analyses were performed on liver sinusoidal membranes (due to this membrane's i nvolvement in nutrient transport) from overnight fasted rats. The degr ee of saturation of sinusoidal membrane phospholipids and liver trigly ceride fatty acids was significantly greater in sucrose vs, starch at 1 and 5 weeks. This resulted in significantly lower sinusoidal membran e fluidity at 1 and 5 weeks in the sucrose group. In contrast, hepatic sinusoidal membrane cholesterol content (0.60 +/- 0.05 vs. 0.42 +/- 0 .04 mu mol/mg protein) and the cholesterol to phospholipid molar ratio (0.66 +/- 0.04 vs. 0.50 +/- 0.03) were significantly greater in sucro se vs, starch animals at 5 weeks only. Minimal differences were observ ed in individual phospholipid species between groups. These data sugge st that changes in fatty acid composition and fluidity may contribute to the development of sucrose-induced hepatic insulin resistance.