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n-3 Fatty acids preserve muscle mass and insulin sensitivity in a rat model of energy restriction

Abstract : In obese subjects, the loss of fat mass during energy restriction is often accompanied by a loss of muscle mass. The hypothesis that n-3 PUFA, which modulate protein homoeostasis via effects on insulin sensitivity, could contribute to maintain muscle mass during energy restriction was tested in rats fed a high-fat diet (4 weeks) rich in 18 : 1 n-9 (oleic acid, OLE-R), 18 : 3 n-3 (alpha-linolenic acid, ALA-R) or n-3 long-chain (LC-R) fatty acid and then energy restricted (8 weeks). A control group (OLE-ad libitum (AL)) was maintained with AL diet throughout the study. Rats were killed 10 min after an i.v. insulin injection. All energy-restricted rats lost weight and fat mass, but only the OLE-R group showed a significant muscle loss. The Gastrocnemius muscle was enriched with ALA in the ALA-R group and with LC-PUFA in the ALA-R and LC-R groups. The proteolytic ubiquitin-proteasome system was differentially affected by energy restriction, with MAFbx and muscle ring finger-1 mRNA levels being decreased in the LC-R group (-30 and -20 %, respectively). RAC-a serine/threonine-protein kinase and insulin receptor substrate 1 phosphorylation levels increased in the LC-R group (+ 70 %), together with insulin receptor mRNA (+ 50 %). The ALA-R group showed the same overall activation pattern as the LC-R group, although to a lesser extent. In conclusion, dietary n-3 PUFA prevent the loss of muscle mass associated with energy restriction, probably by an improvement in the insulin-signalling pathway activation, in relation to enrichment of plasma membranes in n-3 LC-PUFA.
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Submitted on : Monday, March 13, 2017 - 4:17:11 PM
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Guillaume Galmiche, Jean-François Huneau, Veronique Mathe, Jacques Mourot, Noëmie Simon, et al.. n-3 Fatty acids preserve muscle mass and insulin sensitivity in a rat model of energy restriction. British Journal of Nutrition, Cambridge University Press (CUP), 2016, 116 (7), pp.1141-1152. ⟨10.1017/S0007114516003111⟩. ⟨hal-01488440⟩



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