Tai-Yu Huang1, Donghai Zheng2, Robert C Hickner3, Jeffrey J Brault4, Ronald N Cortright5. 1. Department of Kinesiology, East Carolina University, Greenville, NC, United States of America. 2. Department of Kinesiology, East Carolina University, Greenville, NC, United States of America; Diabetes and Obesity Institute, East Carolina University, Greenville, NC, United States of America. 3. Department of Kinesiology, East Carolina University, Greenville, NC, United States of America; Department of Physiology, East Carolina University, Greenville, NC, United States of America; Diabetes and Obesity Institute, East Carolina University, Greenville, NC, United States of America; College of Human Sciences, Florida State University, Tallahassee, FL, United States of America; School of Health Sciences, University of KwaZulu-Natal, Westville, South Africa. 4. Department of Kinesiology, East Carolina University, Greenville, NC, United States of America; Department of Physiology, East Carolina University, Greenville, NC, United States of America; Diabetes and Obesity Institute, East Carolina University, Greenville, NC, United States of America. 5. Department of Kinesiology, East Carolina University, Greenville, NC, United States of America; Department of Physiology, East Carolina University, Greenville, NC, United States of America; Department of Surgery, East Carolina University, Greenville, NC, United States of America; Diabetes and Obesity Institute, East Carolina University, Greenville, NC, United States of America. Electronic address: cortrightr@ecu.edu.
Abstract
Peroxisomes are essential for lipid metabolism and disruption of liver peroxisomal function results in neonatal death. Little is known about how peroxisomal content and activity respond to changes in the lipid environment in human skeletal muscle (HSkM). AIMS: We hypothesized and tested that increased peroxisomal gene/protein expression and functionality occur in HSkM as an adaptive response to lipid oversupply. MATERIALS AND METHODS: HSkM biopsies, derived from a total of sixty-two subjects, were collected for 1) examining correlations between peroxisomal proteins and intramyocellular lipid content (IMLC) as well as between peroxisomal functionality and IMLC, 2) assessing peroxisomal gene expression in response to acute- or 7-day high fat meal (HFM), and in human tissue derived primary myotubes for 3) treating with high fatty acids to induce peroxisomal adaptions. IMLC were measured by both biochemical analyses and fluorescent staining. Peroxisomal membrane protein PMP70 and biogenesis gene (PEX) expression were assessed using western blotting and realtime qRT-PCR respectively. 1-14C radiolabeled lignocerate and palmitate oxidation assays were performed for peroxisomal and mitochondrial functionality respectively. RESULTS: 1) Under fasting conditions, HSkM tissue demonstrated a significant correlation (P ≪ 0.05) between IMCL and the peroxisomal biogenesis factor 19 (PEX19) protein as well as between lipid content and palmitate and lignocerate complete oxidation. 2) Similarly, post-HFM, additional PEX genes (Pex19, PEX11A, and PEX5) were significantly (P ≪ 0.05) upregulated. 3) Increments in PMP70, carnitine octanoyl transferase (CrOT), PGC-1α, and ERRα mRNA were observed post-fatty acid incubation in HSkM cells. PMP70 protein was significantly (P ≪ 0.05) elevated 48-h post lipid treatment. CONCLUSIONS: These results are the first to associate IMLC with peroxisomal gene/protein expression and function in HSkM suggesting an adaptive role for peroxisomes in lipid metabolism in this tissue.
Peroxisomes are essential for lipid metabolism and disruption of liver peroxisomal function results in neonatal death. Little is known about how peroxisomal content and activity respond to changes in the lipid environment in human skeletal muscle (HSkM). AIMS: We hypothesized and tested that increased peroxisomal gene/protein expression and functionality occur in HSkM as an adaptive response to lipid oversupply. MATERIALS AND METHODS: HSkM biopsies, derived from a total of sixty-two subjects, were collected for 1) examining correlations between peroxisomal proteins and intramyocellular lipid content (IMLC) as well as between peroxisomal functionality and IMLC, 2) assessing peroxisomal gene expression in response to acute- or 7-day high fat meal (HFM), and in human tissue derived primary myotubes for 3) treating with high fatty acids to induce peroxisomal adaptions. IMLC were measured by both biochemical analyses and fluorescent staining. Peroxisomal membrane protein PMP70 and biogenesis gene (PEX) expression were assessed using western blotting and realtime qRT-PCR respectively. 1-14C radiolabeled lignocerate and palmitate oxidation assays were performed for peroxisomal and mitochondrial functionality respectively. RESULTS: 1) Under fasting conditions, HSkM tissue demonstrated a significant correlation (P ≪ 0.05) between IMCL and the peroxisomal biogenesis factor 19 (PEX19) protein as well as between lipid content and palmitate and lignocerate complete oxidation. 2) Similarly, post-HFM, additional PEX genes (Pex19, PEX11A, and PEX5) were significantly (P ≪ 0.05) upregulated. 3) Increments in PMP70, carnitine octanoyl transferase (CrOT), PGC-1α, and ERRα mRNA were observed post-fatty acid incubation in HSkM cells. PMP70 protein was significantly (P ≪ 0.05) elevated 48-h post lipid treatment. CONCLUSIONS: These results are the first to associate IMLC with peroxisomal gene/protein expression and function in HSkM suggesting an adaptive role for peroxisomes in lipid metabolism in this tissue.
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