Metabolic Flexibility to Lipid Availability During Exercise is Enhanced in Individuals with High Insulin Sensitivity

Metabolic Flexibility to Lipid Availability During Exercise is Enhanced in Individuals with High... Metabolic flexibility to lipid (MetFlex-lip) is the capacity to adapt lipid oxidation to lipid availability. Hypothetically, impaired MetFlex-lip in skeletal muscle induces accumulation of lipid metabolites that interfere insulin signaling. Our aim was to compare MetFlex-lip during exercise in subjects with low (Low_IS) vs. high (High_IS) insulin sensitivity. Twenty healthy men were designated as Low_IS or High_IS based on the median of the HOMA-IR. Groups had similar age, BMI and VO2max. Subjects cycled at 50% VO2max until expending 650 kcal. Adaptation in lipid oxidation was calculated as the drop in respiratory quotient (RQ) at the end of exercise vs. the maximum RQ (ΔRQ). Lipid availability was calculated as the increase in circulating non-esterified fatty acids (NEFA) at the end of exercise vs. the minimum NEFA (ΔNEFA). ΔRQ as a function of ΔNEFA was used to determine MetFlex-lip. On average, RQ and circulating NEFA changed similarly in both groups. However, ΔRQ correlated with ΔNEFA in High_IS (r = −0.83, P < 0.01), but not in Low_IS subjects (r = −0.25, P = 0.48). Thus, the slope of the relationship ΔRQ vs. ΔNEFA was steeper in High_IS vs. Low_IS (−0.139 {plus minus} 0.03 vs. −0.025 {plus minus} 0.03 RQ mmol−1 l−1, respectively; P < 0.05), with similar intercepts. We conclude that, in subjects with High_IS, lipid-to-carbohydrate oxidation ratio adapts to the increased circulating NEFA availability during exercise. Such MetFlex-lip appears impaired in subjects with Low_IS. Whether a cause-effect relationship exists between impaired MetFlex-lip and low insulin sensitivity remains to be determined. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png AJP - Endocrinology and Metabolism The American Physiological Society

Metabolic Flexibility to Lipid Availability During Exercise is Enhanced in Individuals with High Insulin Sensitivity

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ISSN
0193-1849
eISSN
1522-1555
D.O.I.
10.1152/ajpendo.00126.2018
Publisher site
See Article on Publisher Site

Abstract

Metabolic flexibility to lipid (MetFlex-lip) is the capacity to adapt lipid oxidation to lipid availability. Hypothetically, impaired MetFlex-lip in skeletal muscle induces accumulation of lipid metabolites that interfere insulin signaling. Our aim was to compare MetFlex-lip during exercise in subjects with low (Low_IS) vs. high (High_IS) insulin sensitivity. Twenty healthy men were designated as Low_IS or High_IS based on the median of the HOMA-IR. Groups had similar age, BMI and VO2max. Subjects cycled at 50% VO2max until expending 650 kcal. Adaptation in lipid oxidation was calculated as the drop in respiratory quotient (RQ) at the end of exercise vs. the maximum RQ (ΔRQ). Lipid availability was calculated as the increase in circulating non-esterified fatty acids (NEFA) at the end of exercise vs. the minimum NEFA (ΔNEFA). ΔRQ as a function of ΔNEFA was used to determine MetFlex-lip. On average, RQ and circulating NEFA changed similarly in both groups. However, ΔRQ correlated with ΔNEFA in High_IS (r = −0.83, P < 0.01), but not in Low_IS subjects (r = −0.25, P = 0.48). Thus, the slope of the relationship ΔRQ vs. ΔNEFA was steeper in High_IS vs. Low_IS (−0.139 {plus minus} 0.03 vs. −0.025 {plus minus} 0.03 RQ mmol−1 l−1, respectively; P < 0.05), with similar intercepts. We conclude that, in subjects with High_IS, lipid-to-carbohydrate oxidation ratio adapts to the increased circulating NEFA availability during exercise. Such MetFlex-lip appears impaired in subjects with Low_IS. Whether a cause-effect relationship exists between impaired MetFlex-lip and low insulin sensitivity remains to be determined.

Journal

AJP - Endocrinology and MetabolismThe American Physiological Society

Published: Mar 29, 2018

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