Abstract and Introduction
Microgravity as experienced during spaceflight affects a number of physiological processes in various organs. However, effects on the liver have yet been poorly documented. Nevertheless, the liver is a metabolically highly active organ involved in carbohydrate metabolism, lipid metabolism and xenobiotic biotransformation. The present paper provides an overview of the effects of microgravity on the liver observed in experimental animals during actual spaceflight and upon simulation of microgravity on Earth. These include (i) induction of liver injury and inflammation associated with apoptosis and oxidative stress, (ii) changes in liver carbohydrate metabolism resulting in the onset of a diabetogenic phenotype, (iii) modifications in hepatic lipid metabolism leading to early non-alcoholic fatty liver disease and (iv) alterations of the hepatic xenobiotic biotransformation machinery. Although most of these observations remain to be fully validated in humans, appropriate measures to counteract liver pathogenesis should be considered, especially in view of long-term space missions.
Spaceflight considerably affects a number of physiological processes in astronauts. This does not come as a surprise considering the harsh environmental conditions in space. Most of these conditions are hardly, if at all, compatible with life on Earth, including radiation and microgravity. Microgravity in particular is gaining increasing attention, as weightlessness not only leads to the deterioration of bone and muscle, but also modifies body fluid distribution, the immuno-haematological system, cardiovascular functioning and the neurovestibular system.[1,2] Effects of microgravity on metabolically highly active organs have been poorly documented thus far. Among those is the liver, which is a major hub for carbohydrate metabolism, lipid metabolism and xenobiotic biotransformation in the human body. Research in this direction is still in its infancy, yet is expected to boom in the upcoming years given the advent of touristic space travel and long-term missions to Mars. The present paper gives a state-of-the-art overview of the reported effects of microgravity on the liver, as experienced during real-life spaceflight as well as experimentally simulated on Earth in laboratory settings.
Liver International. 2022;42(12):2599-2606. © 2022 Blackwell Publishing