ABSTRACT
OBJECTIVE: Sarcopenia-the loss of muscle mass and functionality occurring with age-is a pervasive problem with few effective treatments beyond exercise. We examined the ability of the green tea catechin, epigallocatechin-3-gallate (EGCg), to impact muscle mass and the molecular pathway involved in muscle atrophy in a rat model of sarcopenia. METHODS: 20-month-old Sprague-Dawley rats were treated for 8 weeks with control diet or control plus 200mg/kg body weight of EGCg diet. RESULTS: EGCg-supplemented animals had significantly greater gastrocnemius muscle mass than the aged controls, and showed a trend for increased muscle fiber cross-sectional areas (CSA) (p=0.06). These changes were associated with significantly lower protein expressions of the intramuscular 19S and 20S proteasome subunits and the MuRF1 and MAFbx ubiquitin ligases in the EGCg-treated animals. Proteasome activity as determined by 'Chymotrypsin-like' enzyme activity was also significantly reduced by EGCg. Muscle mRNA expression of IL-15 and IGF-1 were significantly increased in the EGCg group vs. the aged controls. In comparison to younger adult animals (6 month), the protein expression of 19S, 20S, MuRF1, MAFbx, and myostatin were increased between approximately 4- and 12-fold in the aged controls, but only up to ~2-fold in the aged EGCg animals. CONCLUSIONS: EGCg supplementation was able to preserve muscle in sarcopenic rats, partly through attenuating protein degradation via the ubiquitin-proteasome pathway, together with increased expression of anabolic factors.
ABSTRACT
Antioxidants are associated with reduced pro-inflammatory cytokine expression in immune cells and isolated tissues; however, no studies have examined whether short-term vitamin E administration is associated with reduced lipopolysaccharide (LPS)-induced cytokine expression in mouse skeletal and cardiac muscle, in vivo. These experiments tested the hypothesis that vitamin E administration attenuates nuclear factor kappaB (NF-kappaB), IL-6, IL-1beta and tumour necrosis factor alpha (TNFalpha) responses in skeletal and cardiac muscle to an inflammatory challenge induced by systemic LPS. We compared IL-6, IL-1beta and TNFalpha mRNA and protein, activated NF-kappaB and total oxidized proteins in skeletal and cardiac muscle 4 or 24 h after saline or LPS injection in mice receiving vitamin E or placebo for 3 days prior to the insult. Skeletal and cardiac IL-6 mRNA and protein were significantly elevated by LPS in both groups, but responses were significantly lower in vitamin E- compared with placebo-treated mice. In skeletal and cardiac muscle, LPS increased IL-1beta mRNA and protein in placebo- but not vitamin E-treated mice. Lipopolysaccharide-induced levels of cardiac IL-1beta mRNA and protein and skeletal IL-1beta mRNA were lower with vitamin E than placebo. Lipopolysaccharide-induced NF-kappaB activation and increases in total oxidized proteins were attenuated with vitamin E compared with placebo in both tissues. Vitamin E decreased LPS-induced increases in plasma IL-1beta but not IL-6 compared with placebo. The major results provide the first in vivo evidence that short-term vitamin E administration reduces IL-6 and IL-1beta responses to LPS in skeletal and cardiac muscle and prevents LPS-induced increases in NF-kappaB activation and total oxidized proteins.
Subject(s)
Anti-Inflammatory Agents/administration & dosage , Antioxidants/administration & dosage , Inflammation/prevention & control , Interleukin-1beta/metabolism , Interleukin-6/metabolism , Muscle, Skeletal/drug effects , Papillary Muscles/drug effects , Vitamin E/administration & dosage , Acute Disease , Animals , Disease Models, Animal , Inflammation/chemically induced , Inflammation/immunology , Interleukin-1beta/blood , Interleukin-1beta/genetics , Interleukin-6/blood , Interleukin-6/genetics , Lipopolysaccharides , Male , Mice , Mice, Inbred BALB C , Muscle, Skeletal/immunology , NF-kappa B/metabolism , Papillary Muscles/immunology , Protein Carbonylation/drug effects , RNA, Messenger/metabolism , Time Factors , Tumor Necrosis Factor-alpha/metabolismABSTRACT
Exaggerated proinflammatory cytokine responses can be observed with aging, and reduced levels of the anti-inflammatory cytokine IL-10 may contribute to these responses. IL-10 can reduce IL-6, IL-1beta, and TNF-alpha expression in nonmuscle tissues; however, no studies have examined the combined effects of IL-10 and age on cytokine responses in skeletal and cardiac muscle. These experiments tested the hypothesis that the absence of IL-10, in vivo, is associated with greater IL-6, TNF-alpha, and IL-1beta responses to an inflammatory challenge in skeletal and cardiac muscle and that aging exaggerates these responses. We compared IL-6, IL-1beta, and TNF-alpha mRNA and protein levels in skeletal and cardiac muscle of young (4 mo) and mature (10-11 mo) wild-type (IL-10(+/+)) and IL-10 deficient (IL-10(-/-)) mice following LPS. Skeletal and cardiac IL-6 mRNA and protein were elevated by LPS for IL-10(+/+) and IL-10(-/-) mice with greater responses in the IL-10(-/-) mice (P < 0.01). In skeletal muscle these effects were greater in mature than young mice (P < 0.01). IL-1beta mRNA and protein responses to LPS were greater in cardiac muscle of young but not mature IL-10(-/-) mice compared with IL-10(+/+) (P < 0.01). However, IL-1beta responses were greater in mature than young mice, but only in IL-10(+/+) groups (P < 0.05). The absence of IL-10 was associated with higher TNF-alpha protein levels in cardiac muscle (P < 0.05). The results provide the first in vivo evidence that the absence of IL-10 is associated with a greater IL-6 response to LPS in skeletal and cardiac muscles, and in skeletal muscle aging further exaggerates these responses.
