Role of fatty acids in the transition from anaerobic to aerobic metabolism in skeletal muscle during exercise

Abstract

In moderate physical exercise, the transition from predominantly anaerobic towards predominantly aerobic metabolism is a key step to improve performance. Increase in the supply of oxygen and nutrients, such as free fatty acids (FFA) and glucose, which accompanies high blood flow, is required for this transition. The mechanisms involved in the vasodilation in skeletal muscle during physical activity are not completely known yet. In this article, we postulate a role of FFA and heat production in this process. The presence of uncoupling protein-2 and -3 (UCP-2 and -3) in skeletal muscle, whose activity is dependent on FFA, suggests that these metabolites can act as mitochondrial uncouplers in this tissue. Evidence indicates however that UCPs act as uncouplers only when coenzyme Q is predominantly in the reduced state (i.e. under nonphosphorylation conditions or state 4 respiration) as is observed in resting muscles and in the beginning of physical activity (predominantly anaerobic metabolism). The increase in the lipolytic activity in adipose tissue in the beginning of physical activity results in elevated plasma FFA levels. The FFA can then act on the UCPs, increasing the local heat production. We propose that this calorigenic effect of FFA is important to activate nitric oxide synthase, resulting in nitric oxide production and consequent vasodilation. Therefore, FFA would be important mediators for the changes that occur in muscle metabolism during prolonged physical activity, ensuring the appropriate supply of oxygen and nutrients by increasing blood flow at the beginning of exercise in the contracting skeletal muscles.

p53 Promotes Cardiac Dysfunction in Diabetic Mellitus Caused by Excessive Mitochondrial Respiration-Mediated Reactive Oxygen Species Generation and Lipid Accumulation

“…There were no alterations in state 2 (Vo) or state 4 (Voligomycin) respirations in p53 (ϩ/ϩ) and p53 (Ϫ/Ϫ) diabetic hearts ( Figure 3A). Considering that the state 4 respiration was reported to reflect uncoupling of mitochondrial oxidative phosphorylation, 6,16 the present findings raised the possibility that mitochondrial uncoupling was not involved in STZinduced diabetic hearts.…”

Moderate Physical Training Attenuates the Effects of Perinatal Undernutrition on the Morphometry of the Splenic Lymphoid Follicles in Endotoxemic Adult Rats

“…In trained animals, there was a lower body weight gain in comparison with nontrained animals. This result can be related to an increase in lean body mass as well as a higher utilization of fatty acids as fuel by skeletal muscles since the intensity of exercise was maintained at 65-70% of V O 2max [23] .…”

Regulação do metabolismo de glicose e ácido graxo no músculo esquelético durante exercício físico

“…Nosso grupo tem mostrado que, durante a contração muscular intensa, a produção de EROs é substancialmente elevada no músculo esquelético (8), um efeito mediado pelo consumo elevado de oxigênio mitocondrial (31,15). A mitocôndria, um importante sítio gerador de EROs durante a atividade muscular, pode também ser vulnerável às ações dessas espécies (32,33).…”

“…A lipólise nesses tecidos é regulada pela lipase sensível a hormônios, ativada pela estimulação beta-adrenérgica durante o exercício, particularmente pelas catecolaminas (15 acetil-CoA/CoA-SH como consequência de uma oxidação elevada de lipídios seguida por um aumento no conteúdo intracelular de citrato e glicose-6-P (G6-P). O acúmulo de acetil-CoA inibe a enzima piruvato desidrogenase (PDH), via ativação da PDH quinase, a enzima responsável pela fosforilação e inativação do complexo PDH, reduzindo a oferta de piruvato (glicose) como substrato oxidativo.…”