Chronic consumption of trans-fat-rich diet increases hepatic cholesterol levels and impairs muscle insulin sensitivity without leading to hepatic steatosis and hypertriglyceridemia in female Fischer rats

Abstract

Background: The impact of industrial trans fatty acids (TFAs) on lipid metabolism and health remains elusive.

Methods: We compared the effect of long-term (52 weeks) ingestion of 10% partially hydrogenated vegetable oil, providing 4.2% of total energy from TFAs, on hepatic lipid metabolism and muscle insulin sensitivity in weanling female Fischer rats with that of palmolein (monounsaturated fatty acid, MUFA), sunflower (n-6 polyunsaturated fatty acid, PUFA), and a blend of sunflower and fish oil (n-3 PUFA).

Results: The proportion of plasma high-density lipoprotein cholesterol in total cholesterol and reverse cholesterol transport-associated protein expressions were similar in all the groups. Despite higher lipogenic-pathway protein levels, steatosis or hypertriglyceridemia was not observed in TFA-fed rats. Though TFA ingestion had no effect on fasting plasma glucose, insulin levels or oral glucose tolerance, it significantly decreased muscle insulin-stimulated glucose uptake as compared to PUFAs. Further, TFA ingestion increased adipose tissue retinol-binding protein 4 mRNA as compared to PUFAs (n-6 or n-3). The effects of MUFA (oleic acid) on all these parameters were comparable to those observed for TFAs.

Conclusions: Compared to PUFA-rich diets, chronic consumption of a TFA-rich diet did not lead to steatosis or hypertriglyceridemia; however, it significantly impaired muscle insulin sensitivity, while no changes were found in the oral glucose tolerance test.