Exercise and the Regulation of Hepatic Metabolism

Abstract

The accelerated metabolic demands of the working muscle cannot be met without a robust response from the liver. If not for the hepatic response, sustained exercise would be impossible. The liver stores, releases, and recycles potential energy. Exercise would result in hypoglycemia if it were not for the accelerated release of energy as glucose. The energetic demands on the liver are largely met by increased oxidation of fatty acids mobilized from adipose tissue. Adaptations immediately following exercise facilitate the replenishment of glycogen stores. Pancreatic glucagon and insulin responses orchestrate the hepatic response during and immediately following exercise. Like skeletal muscle and other physiological systems, liver adapts to repeated demands of exercise by increasing its capacity to produce energy by oxidizing fat. The ability of regular physical activity to increase fat oxidation is protective and can reverse fatty liver disease. Engaging in regular physical exercise has broad ranging positive health implications including those that improve the metabolic health of the liver.

Metabolite Concentration Changes in Humans After a Bout of Exercise: a Systematic Review of Exercise Metabolomics Studies

“…When carbohydrates run out during prolonged exercise or when fasted, then especially the liver is synthesizing new substrates for energy metabolism through ketogenesis and gluconeogenesis [62]. Liver synthesizes ketone bodies from ketogenic amino acids such as leucine or lysine and glucose from glucogenic amino acids such as valine or glycine [54].…”

Effects of fasted vs fed‐state exercise on performance and post‐exercise metabolism: A systematic review and meta‐analysis

“…Regular aerobic exercise improves metabolism in different peripheral tissues, including skeletal muscle, liver, and adipose tissue . In skeletal muscle, exercising in the fasted state promotes utilization of fatty acids and intramuscular triglycerides as primary fuel sources while suppressing glucose metabolism compared with fed conditions, both after acute exercise and in response to a chronic training intervention .…”

“…9 Regular aerobic exercise improves metabolism in different peripheral tissues, including skeletal muscle, liver, and adipose tissue. [10][11][12] In skeletal muscle, exercising in the fasted state promotes utilization of fatty acids and intramuscular triglycerides as primary fuel sources while suppressing glucose metabolism compared with fed conditions, both after acute exercise and in response to a chronic training intervention. [13][14][15] This proposedly occurs via altered gene and protein expression of various downstream targets including pyruvate dehydrogenase kinase isozyme 4 (PDK4), AMP-activated protein kinase (AMPK), glucose transporter type 4 (GLUT4), uncoupling protein-3, and fatty acid translocase (CD36).…”

Intrinsic (Genetic) Aerobic Fitness Impacts Susceptibility for Metabolic Disease

“…As stated elegantly by Trefts, Williams, and Wasserman et al . (38) “The accelerated demands of working muscle cannot be met without a robust response from the liver. If not for the hepatic response, sustained exercise would be impossible.…”