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Long ‐ term, but not short ‐ term high ‐ fat diet induces fiber composition changes and impaired contractile force in mouse fast ‐ twitch skeletal muscle

View Article: PubMed Central - PubMed

ABSTRACT

In this study, we investigated the effects of a short‐term and long‐term high‐fat diet (HFD) on morphological and functional features of fast‐twitch skeletal muscle. Male C57BL/6J mice were fed a HFD (60% fat) for 4 weeks (4‐week HFD) or 12 weeks (12‐week HFD). Subsequently, the fast‐twitch extensor digitorum longus muscle was isolated, and the composition of muscle fiber type, expression levels of proteins involved in muscle contraction, and force production on electrical stimulation were analyzed. The 12‐week HFD, but not the 4‐week HFD, resulted in a decreased muscle tetanic force on 100 Hz stimulation compared with control (5.1 ± 1.4 N/g in the 12‐week HFD vs. 7.5 ± 1.7 N/g in the control group; P < 0.05), whereas muscle weight and cross‐sectional area were not altered after both HFD protocols. Morphological analysis indicated that the percentage of type IIx myosin heavy chain fibers, mitochondrial oxidative enzyme activity, and intramyocellular lipid levels increased in the 12‐week HFD group, but not in the 4‐week HFD group, compared with controls (P < 0.05). No changes in the expression levels of calcium handling‐related proteins and myofibrillar proteins (myosin heavy chain and actin) were detected in the HFD models, whereas fast‐troponin T‐protein expression was decreased in the 12‐week HFD group, but not in the 4‐week HFD group (P < 0.05). These findings indicate that a long‐term HFD, but not a short‐term HFD, impairs contractile force in fast‐twitch muscle fibers. Given that skeletal muscle strength largely depends on muscle fiber type, the impaired muscle contractile force by a HFD might result from morphological changes of fiber type composition.

No MeSH data available.


Expression levels of muscle calcium‐regulated proteins in mice after a high‐fat diet. Protein levels in control mice (CONT) and high‐fat diet‐fed mice (HFD; upper panel: 4 weeks; lower panels: 12 weeks). Left: representative western blots of RyR, DHPR, CSQ, SERCA1 and PV proteins (A: 4 weeks; C: 12 weeks). A protein expression levels expressed relative to the value of CONT mice (B: 4 weeks; D: 12 weeks). Values are means ± SE (n = 7).
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phy213250-fig-0005: Expression levels of muscle calcium‐regulated proteins in mice after a high‐fat diet. Protein levels in control mice (CONT) and high‐fat diet‐fed mice (HFD; upper panel: 4 weeks; lower panels: 12 weeks). Left: representative western blots of RyR, DHPR, CSQ, SERCA1 and PV proteins (A: 4 weeks; C: 12 weeks). A protein expression levels expressed relative to the value of CONT mice (B: 4 weeks; D: 12 weeks). Values are means ± SE (n = 7).

Mentions: Proteins playing an important role in skeletal muscle Ca2+ regulation were analyzed by western blotting. No significant differences in the protein expression levels of RyR, DHPR, CSQ, SERCA1, and PV were noted between both HFD groups and the CONT group (Fig. 5). Next, we assessed the expression levels of myofibrillar proteins in HFD groups and the CONT group. Neither the MHC nor actin content were altered in HFD groups compared with CONT groups (Fig. 6). We also evaluated troponin T, a component of the regulatory troponin complex that plays a role in Ca2+ sensitivity and contractile function in skeletal muscle (Ogut et al. 1999). Expression levels of fast‐TnT was approximately 20% lower in the 12‐week HFD than in the CONT group (P < 0.05), but not in the 4‐week HFD group. Expression levels of slow‐TnT was relatively higher after 12‐week HFD compared with CONT (Fig. 6).


Long ‐ term, but not short ‐ term high ‐ fat diet induces fiber composition changes and impaired contractile force in mouse fast ‐ twitch skeletal muscle
Expression levels of muscle calcium‐regulated proteins in mice after a high‐fat diet. Protein levels in control mice (CONT) and high‐fat diet‐fed mice (HFD; upper panel: 4 weeks; lower panels: 12 weeks). Left: representative western blots of RyR, DHPR, CSQ, SERCA1 and PV proteins (A: 4 weeks; C: 12 weeks). A protein expression levels expressed relative to the value of CONT mice (B: 4 weeks; D: 12 weeks). Values are means ± SE (n = 7).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5392533&req=5

phy213250-fig-0005: Expression levels of muscle calcium‐regulated proteins in mice after a high‐fat diet. Protein levels in control mice (CONT) and high‐fat diet‐fed mice (HFD; upper panel: 4 weeks; lower panels: 12 weeks). Left: representative western blots of RyR, DHPR, CSQ, SERCA1 and PV proteins (A: 4 weeks; C: 12 weeks). A protein expression levels expressed relative to the value of CONT mice (B: 4 weeks; D: 12 weeks). Values are means ± SE (n = 7).
Mentions: Proteins playing an important role in skeletal muscle Ca2+ regulation were analyzed by western blotting. No significant differences in the protein expression levels of RyR, DHPR, CSQ, SERCA1, and PV were noted between both HFD groups and the CONT group (Fig. 5). Next, we assessed the expression levels of myofibrillar proteins in HFD groups and the CONT group. Neither the MHC nor actin content were altered in HFD groups compared with CONT groups (Fig. 6). We also evaluated troponin T, a component of the regulatory troponin complex that plays a role in Ca2+ sensitivity and contractile function in skeletal muscle (Ogut et al. 1999). Expression levels of fast‐TnT was approximately 20% lower in the 12‐week HFD than in the CONT group (P < 0.05), but not in the 4‐week HFD group. Expression levels of slow‐TnT was relatively higher after 12‐week HFD compared with CONT (Fig. 6).

View Article: PubMed Central - PubMed

ABSTRACT

In this study, we investigated the effects of a short&#8208;term and long&#8208;term high&#8208;fat diet (HFD) on morphological and functional features of fast&#8208;twitch skeletal muscle. Male C57BL/6J mice were fed a HFD (60% fat) for 4&nbsp;weeks (4&#8208;week HFD) or 12&nbsp;weeks (12&#8208;week HFD). Subsequently, the fast&#8208;twitch extensor digitorum longus muscle was isolated, and the composition of muscle fiber type, expression levels of proteins involved in muscle contraction, and force production on electrical stimulation were analyzed. The 12&#8208;week HFD, but not the 4&#8208;week HFD, resulted in a decreased muscle tetanic force on 100&nbsp;Hz stimulation compared with control (5.1&nbsp;&plusmn;&nbsp;1.4&nbsp;N/g in the 12&#8208;week HFD vs. 7.5&nbsp;&plusmn;&nbsp;1.7&nbsp;N/g in the control group; P&nbsp;&lt;&nbsp;0.05), whereas muscle weight and cross&#8208;sectional area were not altered after both HFD protocols. Morphological analysis indicated that the percentage of type IIx myosin heavy chain fibers, mitochondrial oxidative enzyme activity, and intramyocellular lipid levels increased in the 12&#8208;week HFD group, but not in the 4&#8208;week HFD group, compared with controls (P&nbsp;&lt;&nbsp;0.05). No changes in the expression levels of calcium handling&#8208;related proteins and myofibrillar proteins (myosin heavy chain and actin) were detected in the HFD models, whereas fast&#8208;troponin T&#8208;protein expression was decreased in the 12&#8208;week HFD group, but not in the 4&#8208;week HFD group (P&nbsp;&lt;&nbsp;0.05). These findings indicate that a long&#8208;term HFD, but not a short&#8208;term HFD, impairs contractile force in fast&#8208;twitch muscle fibers. Given that skeletal muscle strength largely depends on muscle fiber type, the impaired muscle contractile force by a HFD might result from morphological changes of fiber type composition.

No MeSH data available.