Reduced Glucose Tolerance and Skeletal Muscle GLUT4 and IRS1 Content in Cyclists Habituated to a Long-Term Low-Carbohydrate, High-Fat Diet
| Autor: | Tertius Abraham Kohn, Timothy D. Noakes, Kathryn M. van Boom, Nur Armino, Kate Larmuth, Christopher C. Webster, James Smith |
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| Rok vydání: | 2019 |
| Předmět: |
0301 basic medicine
medicine.medical_specialty Medicine (miscellaneous) 030209 endocrinology & metabolism 03 medical and health sciences Glycogen phosphorylase 0302 clinical medicine Insulin resistance Internal medicine medicine Citrate synthase Orthopedics and Sports Medicine 030109 nutrition & dietetics Nutrition and Dietetics biology Chemistry Glucose transporter Skeletal muscle General Medicine medicine.disease Insulin receptor Endocrinology medicine.anatomical_structure biology.protein Creatine kinase GLUT4 |
| Zdroj: | International journal of sport nutrition and exercise metabolism. 30(3) |
| ISSN: | 1543-2742 |
| Popis: | Very little is known about how long-term (>6 months) adaptation to a low-carbohydrate, high-fat (LCHF) diet affects insulin signaling in healthy, well-trained individuals. This study compared glucose tolerance; skeletal muscle glucose transporter 4 (GLUT4) and insulin receptor substrate 1 (IRS1) content; and muscle enzyme activities representative of the main energy pathways (3-hydroxyacetyl-CoA dehydrogenase, creatine kinase, citrate synthase, lactate dehydrogenase, phosphofructokinase, phosphorylase) in trained cyclists who followed either a long-term LCHF or a mixed-macronutrient (Mixed) diet. On separate days, a 2-hr oral glucose tolerance test was conducted, and muscle samples were obtained from the vastus lateralis of fasted participants. The LCHF group had reduced glucose tolerance compared with the Mixed group, as plasma glucose concentrations were significantly higher throughout the oral glucose tolerance test and serum insulin concentrations peaked later (LCHF, 60 min; Mixed, 30 min). Whole-body insulin sensitivity was not statistically significantly different between groups (Matsuda index: LCHF, 8.7 ± 3.4 vs. Mixed, 12.9 ± 4.6;p = .08). GLUT4 (LCHF: 1.13 ± 0.24; Mixed: 1.44 ± 0.16;p = .026) and IRS1 (LCHF: 0.25 ± 0.13; Mixed: 0.46 ± 0.09;p = .016) protein content was lower in LCHF muscle, but enzyme activities were not different. We conclude that well-trained cyclists habituated to an LCHF diet had reduced glucose tolerance compared with matched controls on a mixed diet. Lower skeletal muscle GLUT4 and IRS1 contents may partially explain this finding. This could possibly reflect an adaptation to reduced habitual glucose availability rather than the development of a pathological insulin resistance. |
| Databáze: | OpenAIRE |
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