Triacylglycerol secretion in rats: effects of essential fatty acids and influence of dietary sucrose, glucose or fructose.

The rate of triacylglycerol (TG) secretion into plasma was determined in vivo in essential-fatty-acid(EFA)-adequate and EFA-deficient rats fed for 8-10 weeks on diets containing either sucrose, glucose or fructose (66.5% wt/wt) as the sole source of carbohydrate. The rate of TG secretion was increased in EFA-deficient rats, irrespective of the type of dietary carbohydrate. The secretion rate in EFA-deficient rats fed fructose was 50% higher than the rate in similar animals fed glucose or sucrose, although in the EFA-adequate rats, the secretion rate with fructose was not significantly higher than with sucrose or glucose. The concentrations of triacylglycerols and cholesteryl esters in plasma were generally reduced in EFA deficiency, whereas the concentrations of these lipids in liver were increased. Plasma free fatty acid concentrations were unchanged. The fatty acid composition of plasma and hepatic lipids was altered both by EFA deficiency and to a smaller extent by the type of dietary carbohydrate. The concentration of plasma glucagon was reduced in the deficient animals, although plasma insulin concentration was not affected. The resulting increase in the plasma insulin:glucagon molar ratio may explain some of the alterations in lipid concentrations and in lipid metabolism observed in EFA deficiency.