Nutritional effects on T-cell immunometabolism.

T cells are highly influenced by nutrient uptake from their environment, and changes in overall nutritional status, such as malnutrition or obesity, can result in altered T-cell metabolism and behavior. In states of severe malnutrition or starvation, T-cell survival, proliferation, and inflammatory cytokine production are all decreased, as is T-cell glucose uptake and metabolism. The altered T-cell function and metabolism seen in malnutrition is associated with altered adipokine levels, most particularly decreased leptin. Circulating leptin levels are low in malnutrition, and leptin has been shown to be a key link between nutrition and immunity. The current view is that leptin signaling is required to upregulate activated T-cell glucose metabolism and thereby fuel T-cell activation. In the setting of obesity, T cells have been found to have a key role in promoting the recruitment of inflammatory macrophages to adipose depots along with the production of inflammatory cytokines that promote the development of insulin resistance leading to diabetes. Deletion of T cells, key T-cell transcription factors, or pro-inflammatory T-cell cytokines prevents insulin resistance in obesity and underscores the importance of T cells in obesity-associated inflammation and metabolic disease. Altogether, T cells have a critical role in nutritional immunometabolism.