Abstract Vitamin D (VD) was reported to play protective roles in skeletal muscle. This study aimed to explore whether endoplasmic reticulum (ER) stress inhibition is associated with the protective effects of VD/VD receptor (VDR) signaling on skeletal muscle functions. C2C12 skeletal muscle cells were treated with palmitic acid (PA) and then incubated with different concentrations of 1,25-(OH)2-vitamin D3 (VD3), and we found that VD3 improved the impaired cell viability induced by PA and increased VDR expression in a dose-dependent manner. Then 100 nM VD3 treatment and VDR overexpression both ameliorated PA-induced ER stress, apoptosis, inflammation and glucose uptake inhibition in C2C12 myocytes. Furthermore, VDR knockdown reversed the protective effects of VD3 on C2C12 cell functions. Additionally, PA-treated C2C12 cells were treated with VD3 alone or together with AMPK signaling inhibitor Compound C. VD3 promoted phosphorylation of AMPK and SIRT1 expression, while Compound C reversed these effects and abolished the protective effects of VD3 in C2C12 cells. High-fat diet (HFD)-fed mice were treated with VD3, and VD3 alleviated skeletal muscle loss and insulin resistance in mice. In conclusion, VD inhibited AMPK/SIRT1-mediated ER stress by increasing VDR expression, and further ameliorated skeletal muscle loss and insulin resistance in mice.

OBJECTIVES: This study explored the relationship between skipping breakfast and physical fitness in a group of school-aged adolescents in China. METHODS: This cross-sectional study from the Chinese National Surveillance on Students’ Constitution and Health (CNSSCH) survey in Ningbo, China, used a standardized questionnaire to assess the frequency of breakfast consumption. Physical fitness was measured through standing long jump, 50-m sprint, 1,000 (or 800)-m run, and vital capacity tests. Multiple linear regression analysis was used to investigate the relationship between the frequency of breakfast consumption and physical fitness. RESULTS: Our study included a total of 1,849 school-aged adolescents (aged 15.53±1.80 years). Among boys, non-breakfast-skippers had good scores for 50-m sprints, 1,000-m run, and vital capacity tests when compared with breakfast skippers (all p<0.05). Among girls, non-breakfast-skippers had a good scores for the standing long jump test compared with breakfast skippers (p=0.003). The multiple linear regression model showed that not skipping breakfast was positively associated with vital capacity (β=-173.78, p=0.004) and inversely associated with 50-m sprint (β=-0.12, p=0.018) and 1,000-m run times (β=-8.08, p=0.001) in boys. CONCLUSION: The results of this cross-sectional study revealed that skipping breakfast might be associated with lower physical fitness in Chinese adolescents aged 13-18 years, especially boys. Breakfast consumption should be promoted among Chinese school-aged boys.

RESUMO A dor neuropática é uma condição de dor crônica causada por dano ou disfunção do sistema nervoso central ou periférico. A eletroacupuntura (EA) tem um efeito antinociceptivo durante a dor neuropática, que é parcialmente devido à inibição da ativação de astrócitos na medula espinhal. Descobrimos que a injeção intratecal de 8-ciclopentil-1,3-dipropilxantina (DPCPX), um antagonista seletivo do receptor de adenosina A1, reverteu os efeitos antinociceptivos da EA no modelo de dor neuropática induzida por lesão por constrição crônica (CCI). A expressão da GFAP na medula espinal L4-L6 foi significativamente melhorada, enquanto a DPCPX suprimiu o efeito da inibição mediadora da EA na ativação de astrócitos, bem como eliminou a supressão induzida pela EA do conteúdo de citocina (TNF-α). Esses resultados indicam que o receptor de adenosina A1 está envolvido nas ações da EA durante a dor neuropática, suprimindo a ativação astrocitária, bem como o aumento da TNF-α na EA, fornecendo esclarecimentos sobre os mecanismos de analgesia da acupuntura e o desenvolvimento de alvos terapêuticos para dor neuropática.

ABSTRACT Neuropathic pain is a chronic pain condition caused by damage or dysfunction of the central or peripheral nervous system. Electroacupuncture (EA) has an antinociceptive effect on neuropathic pain, which is partially due to inhibiting astrocyte activation in the spinal cord. We found that an intrathecal injection of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), a selective adenosine A1 receptor antagonist, reversed the antinociceptive effects of EA in a chronic constriction injury-induced neuropathic pain model. The expression of GFAP in L4-L6 spinal cord was significantly upgraded, while DPCPX suppressed the effect of the EA-mediating inhibition of astrocyte activation, as well as wiping out the EA-induced suppression of cytokine content (TNF-α). These results indicated that the adenosine A1 receptor is involved in EA actions during neuropathic pain through suppressing astrocyte activation as well as TNF-α upregulation of EA, giving enlightenment to the mechanisms of acupuncture analgesia and development of therapeutic targets for neuropathic pain.