Aim: The aim of this report was to study the effect of high-fat (HF)/low-carbohydrate (CHO) diet on regulation of substrate metabolism in humans. Methods: Ten healthy men consumed either a HF (75% energy as fat) or control (35%) diet for 6 d in random order. On d 7, blood glucose disappearance rate (R(d)) was determined before and during a hyperinsulinemic euglycemic clamp. Substrate oxidation was determined by indirect calorimetry. Muscle biopsies were obtained prediet, postdiet, and postclamps. Results: R(d) was similar under basal conditions but slightly elevated ( approximately 10%, P < 0.05) during the last 30 min of the clamp after the HF diet. HF diet reduced CHO oxidation under basal (by approximately 40%, P < 0.05) and clamp conditions (by approximately 20%, P < 0.05), increased insulin-mediated whole-body nonoxidative glucose disposal (by 30%, P < 0.05) and muscle glycogen storage (by approximately 25%, P < 0.05). Muscle pyruvate dehydrogenase complex activity was blunted under basal and clamp conditions after HF compared with control (P < 0.05) and was accompanied by an approximately 2-fold increase (P < 0.05) in pyruvate dehydrogenase kinase 4 (PDK4) mRNA and protein expression. Conclusion: Short-term HF/low-CHO dietary intake did not induce whole-body insulin resistance, but caused a shift in im glucose metabolism from oxidation to glycogen storage. Insulin-stimulated CHO oxidation and muscle pyruvate dehydrogenase complex activity were blunted after the HF diet. Up-regulation of muscle PDK4 expression was an early molecular adaptation to these changes, and we showed for the first time in healthy humans, unlike insulin-resistant individuals, that insulin can suppress PDK4 but not PDK2 gene expression in skeletal muscle.
Chokkalingam, K., Jewell, K., Norton, L., Littlewood, J., van Loon, L. J., Mansell, P., Macdonald, I. A., & Tsintzas, K. (2007). High-fat/low-carbohydrate diet reduces insulin-stimulated carbohydrate oxidation but stimulates nonoxidative glucose disposal in humans: an important role for skeletal muscle pyruvate dehydrogenase kinase 4. Journal of Clinical Endocrinology & Metabolism, 92(1), 284-292. https://doi.org/10.1210/jc.2006-1592