Rapeseed or fish oil protects muscle mass during energy restriction in the rat

Abstract : Background and Objectives: In obese subjects, the loss of fat mass during energy restriction is often accompanied by a loss of fat-free mass (mostly muscle), especially in the absence of physical activity. In other contexts leading to a muscle loss (immobilization, inflammation, cancer), several studies showed that n-3 polyunsaturated fatty acids (PUFA) modulate protein homeostasis, especially via effects on insulin sensitivity. The n-3 PUFA intake during weight loss could thus help protecting muscle mass. This hypothesis has been tested in rats with two sources of n-3 PUFA i.e. the vegetable precursor, -linolenic acid (18: 3 n-3) and its long-chain derivatives (LC, 20: 5 n-3 and 22: 6 n-3). Methods: Male adult Wistar rats (n=48) were fed for 4 weeks with a high-fat induction diet, then 3*12 rats were energy restricted during 8 weeks (50% of ad libitum intake) while the 12 remaining rats were fed ad libitum. During these two phases, the dietary lipids contained oleic sunflower oil (71% 18:1 n-9, ad libitum ADLIB and restricted OLE control groups), rapeseed oil (10% 18:3 n-3, RAPE group) or fish oil (10% LC n-3 PUFA, FISH group). At the end of the restriction phase, rats were anesthetized prior to intravenous insulin injection, sampling of the Gastrocnemius muscle, and euthanasia. Post-mortem analyses were as follows: body composition, expression of muscle genes involved in proteolysis by qPCR, and activation by phosphorylation of muscle proteins involved in insulin signalling by western blotting. Results: During the induction phase, the weight gain was similar in all groups. During the restriction phase, ADLIB group continued to gain weight while all energy- restricted rats lost weight (-20%) and fat mass (-50%). However, when compared to the ADLIB group, leg muscles significantly lost weight in the OLE group (-4 to -6%), but not in the RAPE and FISH groups. As concerns proteolysis key-enzymes, transcript levels involved in the ubiquitin/proteasome system were significantly decreased in the FISH group (-30% for MAFbx and -20% for MurF1), intermediary in the RAPE group and unchanged in the OLE group, when compared to the ADLIB group. The type of dietary fatty acids had no effect on calcium-dependent (calpain 2) and lysosomal (cathepsin D) systems. In response to insulin, phosphorylation levels of AKT and IRS1 (insulin receptor), known to stimulate protein synthesis, were significantly increased (+ 70%) in the FISH group, when compared to the ADLIB group. A similar result was observed for the transcript level of IRS1 (+ 50%), which promotes the transduction of insulin signal. The RAPE group exhibited the same activation pattern as the FISH one, with the exception of IRS1 phosphorylation level. No change was observed for OLE group. Conclusion: Dietary n-3 PUFAs prevent the loss of muscle mass associated with energy restriction. This beneficial effect is associated with an improved activation of the insulin-signalling pathway. Most importantly, the vegetable 18: 3 n-3, supplied by rapeseed oil, has the same overall efficiency as n-3 LC-PUFA from fish oil.
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12th european nutrition conference, Oct 2015, Berlin, Germany
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Contributeur : Jean-Francois Huneau <>
Soumis le : dimanche 6 août 2017 - 17:24:52
Dernière modification le : mardi 10 octobre 2017 - 11:11:57


  • HAL Id : hal-01572313, version 1


Dominique Hermier, Guillaume Galmiche, Coelho Stéphanie, Véronique Mathé, Jean-François Huneau, et al.. Rapeseed or fish oil protects muscle mass during energy restriction in the rat. 12th european nutrition conference, Oct 2015, Berlin, Germany. 〈hal-01572313〉



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