The Impact of Long-term Physical Inactivity on Adipose Tissue Immunometabolism

Abstract

Context Adipose tissue and physical inactivity both influence metabolic health and systemic inflammation, but how adipose tissue responds to chronic physical inactivity is unknown. Objective This work aimed to characterise the impact of chronic physical inactivity on adipose tissue in healthy, young males. Methods We collected subcutaneous adipose tissue from twenty healthy, young men before and after 60 days of complete bed rest with energy intake reduced to maintain energy balance and fat mass. We used RNA-sequencing, flow cytometry, ex vivo tissue culture, and targeted protein analyses to examine adipose tissue phenotype. Results: Our results indicate that the adipose tissue transcriptome, stromal cellular compartment, and insulin signalling protein abundance is largely unaffected by bed rest when fat mass is kept stable. However, there was an increase in the circulating concentration of several adipokines, including plasma leptin, which was associated with inactivity-induced increases in plasma insulin and absent from adipose tissue cultured ex vivo under standardised culture conditions. Conclusion Physical inactivity-induced disturbances to adipokine concentrations such as leptin, without changes to fat mass, could have profound metabolic implications outside a clinical facility when energy intake is not tightly controlled.

Long-duration head-down tilt bed rest confirms the relevance of the neutrophil to lymphocyte ratio and suggests coupling it with the platelet to lymphocyte ratio to monitor the immune health of astronauts

“…It was originally designed to evaluate the efficiency of dietary supplementation with a cocktail of antioxidant substances. However, independent studies carried out on these subjects demonstrated that this supplementation had no effect on B-cell homeostasis ( 11 ), biomarkers of calcium homeostasis, bone formation and resorption ( 21 ), lumbar vertebral fat fraction ( 22 ), hemolysis and CO elimination ( 23 ), muscle deconditioning, oxidative damage, mitochondrial content and protein balance ( 24 ), neurobehavior ( 25 ), cardiac circadian rhythm ( 26 ) or adipose tissue immunometabolism ( 27 ). Therefore, individuals from the supplemented and non-supplemented groups could be pooled, allowing access to a group of 20 participants, which is quite a large group to have experienced long-duration head-down tilt bed rest.…”