New Insights into the Interaction of Carbohydrate and Fat Metabolism During Exercise

Abstract

Fat and carbohydrate are important fuels for aerobic exercise and there can be reciprocal shifts in the proportions of carbohydrate and fat that are oxidized. The interaction between carbohydrate and fatty acid oxidation is dependent on the intracellular and extracellular metabolic environments. The availability of substrate, both from inside and outside of the muscle, and exercise intensity and duration will affect these environments. The ability of increasing fat provision to downregulate carbohydrate metabolism in the heart, diaphragm and peripheral skeletal muscle has been well studied. However, the regulation of fat metabolism in human skeletal muscle during exercise in the face of increasing carbohydrate availability and exercise intensity has not been well studied until recently. Research in the past 10 years has demonstrated that the regulation of fat metabolism is complex and involves many sites of control, including the transport of fat into the muscle cell, the binding and transport of fat in the cytoplasm, the regulation of intramuscular triacylglycerol synthesis and breakdown, and the transport of fat into the mitochondria. The discovery of proteins that assist in transporting fat across the plasma and mitochondrial membranes, the ability of these proteins to translocate to the membranes during exercise, and the new roles of adipose triglyceride lipase and hormone-sensitive lipase in regulating skeletal muscle lipolysis are examples of recent discoveries. This information has led to the proposal of mechanisms to explain the downregulation of fat metabolism that occurs in the face of increasing carbohydrate availability and when moving from moderate to intense aerobic exercise.

Integrative Biology of Exercise

“…These factors are not only involved in mediating the acute response to exercise, but also activate signaling pathways critical for many of the chronic adaptations to regular exercise training. Recent reviews have summarized the various cellular and molecular factors involved in the regulation of skeletal muscle carbohydrate (Jensen and Richter, 2012;Richter and Hargreaves, 2013) and lipid (Jeppesen and Kiens, 2012) metabolism during exercise, as well as the interactions between them (Spriet, 2014). Oxygen Transport System At rest, whole-body O 2 consumption in healthy, young, adult humans averages about 3.5 ml/kg/min, with 20%-25% of this used by resting skeletal muscle.…”

Influence of a caffeine mouth rinse on sprint cycling following glycogen depletion

“…Exogenous supply of 38 CHO has the potential to improve exercise performance (Stellingwerff & Cox, 2014;Wilson, 39 2015), particularly high-intensity exercise that is more reliant on CHO than fat oxidation 40 (Spriet, 2014). Moreover, numerous studies have described attenuated performance during …”

Biochemical and functional modifications in biathlon athletes at medium altitude training / Modificările biochimice și funcționale ale atleților biatloniști după antrenament la altitudine medie

“…This determines the decrease of the glucose transport in muscles, increasing the reconversion into free fatty acids and saving the muscle glycogen [25,26].…”

“…The human body can compensate for the lack of O 2 up to an altitude of 5000 m, where the oxygen partial pressure (pO 2 ) reaches [25][26][27][28][29][30][31][32][33][34][35] mmHg, values that represent the minimum limit for survival [1][2][3].…”