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Niacin supplementation induces type II to type I muscle fiber transition in skeletal muscle of sheep.

ABSTRACT: BACKGROUND: It was recently shown that niacin supplementation counteracts the obesity-induced muscle fiber transition from oxidative type I to glycolytic type II and increases the number of type I fibers in skeletal muscle of obese Zucker rats. These effects were likely mediated by the induction of key regulators of fiber transition, PPAR? (encoded by PPARD), PGC-1? (encoded by PPARGC1A) and PGC-1? (encoded by PPARGC1B), leading to type II to type I fiber transition and upregulation of genes involved in oxidative metabolism. The aim of the present study was to investigate whether niacin administration also influences fiber distribution and the metabolic phenotype of different muscles [M. longissimus dorsi (LD), M. semimembranosus (SM), M. semitendinosus (ST)] in sheep as a model for ruminants. For this purpose, 16 male, 11 wk old Rhoen sheep were randomly allocated to two groups of 8 sheep each administered either no (control group) or 1 g niacin per day (niacin group) for 4 wk. RESULTS: After 4 wk, the percentage number of type I fibers in LD, SM and ST muscles was greater in the niacin group, whereas the percentage number of type II fibers was less in niacin group than in the control group (P?

SUBMITTER: Khan M

PROVIDER: S-EPMC4176759 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Niacin supplementation induces type II to type I muscle fiber transition in skeletal muscle of sheep.

Khan Muckta M Couturier Aline A Kubens Johanna F JF Most Erika E Mooren Frank-Christoph FC Krüger Karsten K Ringseis Robert R Eder Klaus K

Acta veterinaria Scandinavica 20131122

<h4>Background</h4>It was recently shown that niacin supplementation counteracts the obesity-induced muscle fiber transition from oxidative type I to glycolytic type II and increases the number of type I fibers in skeletal muscle of obese Zucker rats. These effects were likely mediated by the induction of key regulators of fiber transition, PPARδ (encoded by PPARD), PGC-1α (encoded by PPARGC1A) and PGC-1β (encoded by PPARGC1B), leading to type II to type I fiber transition and upregulation of ge ...[more]

PMID: 24267720

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Project description:BackgroundA recent study showed that niacin supplementation counteracts the obesity-induced muscle fiber switching from oxidative type I to glycolytic type II and increases the number of type I fibers in skeletal muscle of obese Zucker rats. These effects were likely mediated by the induction of key regulators of fiber transition, PGC-1α and PGC-1β, leading to muscle fiber switching and up-regulation of genes involved in mitochondrial fatty acid import and oxidation, citrate cycle, oxidative phosphorylation, mitochondrial biogenesis. The aim of the present study was to investigate whether niacin supplementation causes type II to type I muscle and changes the metabolic phenotype of skeletal muscles in growing pigs.Results25 male, 11 wk old crossbred pigs (Danzucht x Pietrain) with an average body weight of 32.8 ± 1.3 (mean ± SD) kg were randomly allocated to two groups of 12 (control group) and 13 pigs (niacin group) which were fed either a control diet or a diet supplemented with 750 mg niacin/kg diet. After 3 wk, the percentage number of type I fibers in three different muscles (M. longissismus dorsi, M. quadriceps femoris, M. gastrocnemius) was greater in the niacin group and the percentage number of type II fibers was lower in the niacin group than in the control group (P < 0.05). The mRNA levels of PGC-1β and genes involved in mitochondrial fatty acid catabolism (CACT, FATP1, OCTN2), citrate cycle (SDHA), oxidative phosphorylation (COX4/1, COX6A1), and thermogenesis (UCP3) in M. longissimus dorsi were greater in the niacin group than in the control group (P < 0.05).ConclusionsThe study demonstrates that niacin supplementation induces type II to type I muscle fiber switching, and thereby an oxidative metabolic phenotype of skeletal muscle in pigs. Given that oxidative muscle types tend to develop dark, firm and dry pork in response to intense physical activity and/or high psychological stress levels preslaughter, a niacin-induced change in the muscle´s fiber type distribution may influence meat quality of pigs.

Project description:Hypoxia exposure is known to induce an alteration in skeletal muscle fiber-type distribution mediated by hypoxia-inducible factor (HIF)-?. The downstream pathway of HIF-? leading to fiber-type shift, however, has not been elucidated. The calcineurin pathway is one of the pathways responsible for slow muscle fiber transition. Because calcineurin pathway is activated by vascular endothelial growth factor (VEGF), one of the factors induced by HIF-1?, we hypothesized that the stabilization of HIF-1? may lead to slow muscle fiber transition via the activation of calcineurin pathway in skeletal muscles. To induce HIF-1? stabilization, we used a loss of function strategy to abrogate Prolyl hydroxylase domain protein (PHD) 2 responsible for HIF-1? hydroxylation making HIF-1? susceptible to ubiquitin dependent degradation by proteasome. The purpose of this study was therefore to examine the effect of HIF-1? stabilization in PHD2 conditional knockout mouse on skeletal muscle fiber-type transition and to elucidate the involvement of calcineurin pathway on muscle fiber-type transition.PHD2 deficiency resulted in an increased capillary density in skeletal muscles due to the induction of vascular endothelial growth factor. It also elicited an alteration of skeletal muscle phenotype toward the type I fibers in both of the soleus (35.8 % in the control mice vs. 46.7 % in the PHD2-deficient mice, p?<?0.01) and the gastrocnemius muscle (0.94 vs. 1.89 %, p?<?0.01), and the increased proportion of type I fibers appeared to correspond to the area of increased capillary density. In addition, calcineurin and nuclear factor of activated T cell (NFATc1) protein levels were increased in both the gastrocnemius and soleus muscles, suggesting that the calcineurin/NFATc1 pathway was responsible for the type I fiber transition regardless of PGC-1?, which responded minimally to PHD2 deficiency. Indeed, we found that tacrolimus (FK-506), a calcineurin inhibitor, successfully suppressed slow fiber-type formation in PHD2-deficient mice.Taken together, stabilized HIF-1? induced by PHD2 conditional knockout resulted in the transition of muscle fibers toward a slow fiber type via a calcineurin/NFATc1 signaling pathway. PHD2 conditional knockout mice may serve as a model for chronic HIF-1? stabilization as in mice exposed to low oxygen concentration.

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Niacin supplementation induces type II to type I muscle fiber transition in skeletal muscle of sheep.

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Niacin supplementation induces type II to type I muscle fiber transition in skeletal muscle of sheep.

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