The effects of long- or medium-chain fat diets on glucose tolerance and myocellular content of lipid intermediates in rats

Johan de Vogel-van den Bosch, Joris Hoeks, Silvie Timmers, Sander M. Houten, Paul van Dijk, Wendy Boon, Denis van Beurden, Gert Schaart, Sander Kersten, Peter Voshol, Ronald J.A. Wanders, Matthijs Hesselink, Patrick Schrauwen. 2011. The effects of long- or medium-chain fat diets on glucose tolerance and myocellular content of lipid intermediates in rats. Obesity. April 12. 19
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Abstract / summary in English:

Accumulation of triacylglycerols (TAGs) and acylcarnitines in skeletal muscle upon high-fat (HF) feeding is the resultant of fatty acid uptake and oxidation and is associated with insulin resistance. As medium-chain fatty acids (MCFAs) are preferentially β-oxidized over long-chain fatty acids, we examined the effects of medium-chain TAGs (MCTs) and long-chain TAGs (LCTs) on muscle lipid storage and whole-body glucose tolerance. Rats fed a low-fat (LF), HFLCT, or an isocaloric HFMCT diet displayed a similar body weight gain over 8 weeks of treatment. Only HFLCT increased myocellular TAG (42.3 ± 4.9, 71.9 ± 6.7, and 48.5 ± 6.5 µmol/g for LF, HFLCT, and HFMCT, respectively, P < 0.05) and long-chain acylcarnitine content (P < 0.05). Neither HF diet increased myocellular diacylglycerol (DAG) content. Intraperitoneal (IP) glucose tolerance tests (1.5 g/kg) revealed a significantly decreased glucose tolerance in the HFMCT compared to the HFLCT-fed rats (802 ± 40, 772 ± 18, and 886 ± 18 area under the curve for LF, HFLCT, and HFMCT, respectively, P < 0.05). Finally, no differences in myocellular insulin signaling after bolus insulin injection (10 U/kg) were observed between LF, HFLCT, or HFMCT-fed rats. These results show that accumulation of TAGs and acylcarnitines in skeletal muscle in the absence of body weight gain do not impede myocellular insulin signaling or whole-body glucose intolerance.

Keywords in English: triacylglycerols (TAGs), skeletal muscle, high-fat (HF) feeding, fatty acids, insulin resistance, glucose tolerance, Type 2 Diabetes, Metabolic Syndrome, Pre-diabetes