| 1. |
- Bass, Joseph J., et al.
(författare)
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The mechanisms of skeletal muscle atrophy in response to transient knockdown of the vitamin D receptor in vivo
- 2021
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Ingår i: Journal of Physiology. - : John Wiley & Sons. - 0022-3751 .- 1469-7793. ; 599:3, s. 963-979
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Tidskriftsartikel (refereegranskat)abstract
- KEY POINTS:Reduced vitamin D receptor (VDR) expression prompts skeletal muscle atrophy.Atrophy occurs through catabolic processes, namely the induction of autophagy, while anabolism remains unchanged.In response to VDR-KD mitochondrial function and related gene-set expression is impaired.In vitro VDR knockdown induces myogenic dysregulation occurring through impaired differentiation.These results highlight the autonomous role the VDR has within skeletal muscle mass regulation.Objective: Vitamin-D deficiency is estimated to affect ∼40% of the world's population and has been associated with impaired muscle maintenance. Vitamin-D exerts its actions through the Vitamin-D-receptor (VDR), the expression of which was recently confirmed in skeletal muscle, and its down-regulation is linked to reduced muscle mass and functional decline. To identify potential mechanisms underlying muscle atrophy, we studied the impact of VDR knockdown (KD) on mature skeletal muscle in vivo, and myogenic regulation in vitro in C2C12 cells.Methods: Male Wistar rats underwent in vivo electrotransfer (IVE) to knock down the VDR in hind-limb tibialis anterior (TA) muscle for 10 days. Comprehensive metabolic and physiological analysis was undertaken to define the influence loss of the VDR on muscle fibre composition, protein synthesis, anabolic and catabolic signalling, mitochondrial phenotype, and gene expression. Finally, in vitro lentiviral transfection was used to induce sustained VDR-KD in C2C12 cells to analyse myogenic regulation.Results: Muscle VDR-KD elicited atrophy through a reduction in total protein content, resulting in lower myofibre area. Activation of autophagic processes was observed, with no effect upon muscle protein synthesis or anabolic signalling. Furthermore, RNA-Seq analysis identified systematic down-regulation of multiple mitochondrial respiration related protein and genesets. Finally, in vitro VDR-knockdown impaired myogenesis (cell cycling, differentiation and myotube formation).Conclusion: Taken together, these data indicate a fundamental regulatory role of the VDR in the regulation of myogenesis and muscle mass; whereby it acts to maintain muscle mitochondrial function and limit autophagy.
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| 2. |
- Deane, Colleen S., et al.
(författare)
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The acute transcriptional response to resistance exercise : impact of age and contraction mode
- 2019
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Ingår i: Aging. - : Impact Journals LLC. - 1945-4589 .- 1945-4589. ; 11:7, s. 2111-2126
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Tidskriftsartikel (refereegranskat)abstract
- Optimization of resistance exercise (RE) remains a hotbed of research for muscle building and maintenance. However, the interactions between the contractile components of RE (i.e. concentric (CON) and eccentric (ECC)) and age, are poorly defined. We used transcriptomics to compare age-related molecular responses to acute CON and ECC exercise. Eight young (21 +/- 1 y) and eight older (70 +/- 1 y) exercise-naive male volunteers had vastus lateralis biopsies collected at baseline and 5 h post unilateral CON and contralateral ECC exercise. RNA was subjected to next-generation sequencing and differentially expressed (DE) genes tested for pathway enrichment using Gene Ontology (GO). The young transcriptional response to CON and ECC was highly similar and older adults displayed moderate contraction-specific profiles, with no GO enrichment. Age-specific responses to ECC revealed 104 DE genes unique to young, and 170 DE genes in older muscle, with no GO enrichment. Following CON, 15 DE genes were young muscle-specific, whereas older muscle uniquely expressed 147 up-regulated genes enriched for cell adhesion and blood vessel development, and 28 down-regulated genes involved in mitochondria! respiration, amino acid and lipid metabolism. Thus, older age is associated with contraction-specific regulation often without clear functional relevance, perhaps reflecting a degree of stochastic age-related dysregulation.
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| 3. |
- Lebeaux, Rebecca M, et al.
(författare)
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Maternal serum perfluoroalkyl substance mixtures and thyroid hormone concentrations in maternal and cord sera : The HOME Study
- 2020
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Ingår i: Environmental Research. - : Elsevier. - 0013-9351 .- 1096-0953. ; 185
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Per- and polyfluoroalkyl substances (PFAS) are ubiquitous. Previous studies have found associations between PFAS and thyroid hormones in maternal and cord sera, but the results are inconsistent. To further address this research question, we used mixture modeling to assess the associations with individual PFAS, interactions among PFAS chemicals, and the overall mixture.METHODS: We collected data through the Health Outcomes and Measures of the Environment (HOME) Study, a prospective cohort study that between 2003 and 2006 enrolled 468 pregnant women and their children in the greater Cincinnati, Ohio region. We assessed the associations of maternal serum PFAS concentrations measured during pregnancy with maternal (n = 185) and cord (n = 256) sera thyroid stimulating hormone (TSH), total thyroxine (TT4), total triiodothyronine (TT3), free thyroxine (FT4), and free triiodothyronine (FT3) using two mixture modeling approaches (Bayesian kernel machine regression (BKMR) and quantile g-computation) and multivariable linear regression. Additional models considered thyroid autoantibodies, other non-PFAS chemicals, and iodine deficiency as potential confounders or effect measure modifiers.RESULTS: PFAS, considered individually or as mixtures, were generally not associated with any thyroid hormones. A doubling of perfluorooctanesulfonic acid (PFOS) had a positive association with cord serum TSH in BKMR models but the 95% Credible Interval included the null (β = 0.09; 95% CrI: -0.08, 0.27). Using BKMR and multivariable models, we found that among children born to mothers with higher thyroid peroxidase antibody (TPOAb), perfluorooctanoic acid (PFOA), PFOS, and perfluorohexanesulfonic acid (PFHxS) were associated with decreased cord FT4 suggesting modification by maternal TPOAb status.CONCLUSIONS: These findings suggest that maternal serum PFAS concentrations measured in the second trimester of pregnancy are not strongly associated with thyroid hormones in maternal and cord sera. Further analyses using robust mixture models in other cohorts are required to corroborate these findings.
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