Effect of a Diet Rich in Sunflower Oil on Aspects of Lipid Metabolism in the Genetically-obese Rat

Aspects of the lipid metabolism of male, obese and lean Zucker rats were compared using animals which had been fed ad libitum for 32 days on a diet (HS) which contained 200 g sunflowerseed oil/kg or one (LS) which contained 50 g/kg of the oil. When compared with the LS diet, the HS diet decreased the characteristic lipid accretion in the liver of obses rats from 126 mg (LS) to 81 mg (HS)/g wet weight; corresponding values for the lean rats were 39 mg and 56 mg/g wet weight of liver, respectively. The HS diet depressed lipid synthesis de novo by liver homogenates and decreased the delta9-desaturase activity of liver microsomes from obese and lean rats by about 50%. delta9-Desaturase activity in vitro was also depressed by the addition of linoleic acid to liver microsomes from both obese and lean rats fed ad libitum on a standard laboratory diet. Depressed delta9-desaturase activity, due to ingestion of the HS diet, was reflected in lower ratios of 16:1/16:0 and 18:1/18:0 fatty acids in tissue lipids from obese and lean rats. Ingestion of the HS compared with the LS diet resulted in increased proportions of 18:2omega6 in liver lipids and adipose tissue triacylglycerols of obese and lean rats. The HS diet also increased the proportions of 20:4omega6 in adipose triacylglycerols of obese and lean rats and in liver lipids of obese animals but not in their lean littermates.