Effect of brominated vegetable oils on heart lipid metabolism
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Normal rats fed for 105 days on an experimental diet made up of standard laboratory chow supplemented with 0.5% of a mixture of brominated sunflower-olive oil (BVO) developed a significant increase in the triacylglycerol content of the heart, liver and soleus muscle compared to controls. In addition, BVO-treated rats had a decrease in plasma levels of triacylglycerol and total and HDL cholesterol. Plasma fatty acid levels and plasma post-heparin lipolytic activities, such as H-TGL, LPL, T-TGL and MGH were similar to those of control animals fed the standard chow alone.
Heart PDHa (active portion of pyruvate dehydrogenase) was dramatically decreased in the BVO-fed rats. A faster rate of spontaneous lipolysis was recorded in the isolated perfused preparation of hearts from the experimental animals. The addition of 10−7 M of glucagon to the perfusate, however, revealed a lipolytic effect comparable to the one observed in the control rats. In summary, our findings of normal fatty acids and low triacylglycerol plasma levels associated with normal activities of the various PHLA (post-heparin lipolytic activity) enzymes suggest that accumulation of triacylglycerol in heart muscle may not be explained essentially in terms of an elevated uptake and/or increased delivery of plasma fatty acids or plasma triacylglycerol. A decreased in situ catabolism of tissue triacylglycerol also appears unlikely because the spontaneous as well as the glucagon induced lipolysis in the heart both were found to be unimpaired.
Our results suggest that the mechanisms involved in the toxicologic effects of a BVO diet on heart lipid metabolism could be exerted mainly at the level of triacylglycerol biosynthesis rather than a derangement in some known step of their catabolic pathway. Additional studies are necessary to clarify this matter.
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