Objective: Excess intramyocellular triacylglycerol (IMTG), found especially in obese women, is slowly metabolized and, therefore, prone to longer exposure to intracellular desaturases. Accordingly, it was hypothesized that IMTG content correlates inversely with IMTG fatty acid (FA) saturation in sedentary subjects. In addition, it was validated if IMTG palmitic acid is associated with insulin resistance as suggested earlier.
Design: Cross-sectional human study.
Subjects: In skeletal muscle biopsies, which were obtained from sedentary subjects (34 women, age 48+/-2 years (27 obese including 7 type 2 diabetes (T2DM), body mass index (BMI)=35.5+/-0.8 kg m(-2)) and 25 men, age 49+/-2 years (20 obese including 6 T2DM, BMI=35.8+/-0.8 kg m(-2))), IMTG FA composition was determined by gas-liquid chromatography after separation from phospholipids by thin-layer chromatography.
Results: Independently of gender saturated FA correlated inversely with IMTG (P<0.001) and monounsaturated FA (P<0.001) including total unsaturation of FA (P<0.002) correlated positively with IMTG. Obese women exhibited lower total saturated FA (P<0.001) and palmitic acid (P<0.001) than obese men independent of IMTG, the latter of which, however, was increased twofold in obese women compared to obese men (P<0.001). Polyunsaturated and long-chain polyunsaturated FA did not correlate with IMTG. Palmitic acid correlated positively with insulin resistance (homeostasis insulin resistance index, P<0.05), fasting glucose (P<0.01) and glycosylated hemoglobin (P<0.002) both in univariate analysis and after correction for gender and IMTG.
Conclusion: IMTG content correlates inversely with IMTG saturated FA, potentially reflecting a low turnover of excess IMTG prone to in situ desaturation probably by the ubiquitous stearoyl-CoA desaturase-1. IMTG FA composition is gender specific and implicates on insulin sensitivity and glycemic control.
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http://dx.doi.org/10.1038/ijo.2009.264 | DOI Listing |
Appl Physiol Nutr Metab
January 2025
Nagoya University, Graduate School of Education and Human Development, Nagoya, Japan.
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October 2024
Programa de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte 31310-250, MG, Brazil.
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Program in Physical Therapy, Washington University School of Medicine, St. Louis, MO.
Observational studies have shown correlations between intramyocellular lipid (IMCL) content and muscle strength and contractile function in people with metabolically abnormal obesity. However, a clear physiologic mechanism for this association is lacking, and causation is debated. We combined immunofluorescent confocal imaging with force measurements on permeabilized muscle fibers from metabolically normal and metabolically abnormal mice and people with metabolically normal (defined as normal fasting plasma glucose and glucose tolerance) and metabolically abnormal (defined as prediabetes and type 2 diabetes) overweight/obesity to evaluate relationships among myocellular lipid droplet characteristics (droplet size and density) and biophysical (active contractile and passive viscoelastic) properties.
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Long-term high-fat feeding results in intramyocellular lipid accumulation, leading to insulin resistance. Intramyocellular lipid accumulation is related to an energy imbalance between excess fat intake and fatty acid consumption. Alternating current electromagnetic field exposure has been shown to enhance mitochondrial metabolism in the liver and sperm.
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June 2023
Department of Metabolism & Endocrinology, Juntendo University Graduate School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
A short-term high-calorie high-fat diet (HCHFD) impairs insulin sensitivity in non-obese South Asian but not Caucasian men; however, the effect of short-term HCHFD on insulin sensitivity in East Asians is unknown. We recruited 21 healthy non-obese Japanese men to evaluate metabolic parameters and gut microbiota before and after 6-day HCHFD consisting of a regular diet plus a 45% energy excess with dairy fat supplementation. We evaluated tissue-specific insulin sensitivity and metabolic clearance rate of insulin (MCRI) using a two-step hyperinsulinemic euglycemic clamp, glucose tolerance using the glucose tolerance test, and measured ectopic fat in muscle and the liver using ¹H-magnetic resonance spectroscopy.
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