Metabolic dysregulation of trained immunity in immune aging and the impact of dietary patterns.

Trained immunity (TRIM) is the process through which the innate immune system undergoes memory-like epigenetic and metabolic reprogramming following an earlier infectious challenge. Trained immunity can be induced, in a similar fashion to microbial structures, by various endogenous compounds: oxidized low-density lipoproteins, lipoprotein(a), glucose and uric acid, and monosodium urate. Lipids, glucose, and protein metabolic dysfunction have the potential to perpetuate a proinflammatory feedback loop through the induction of maladaptive trained immunity programs, as shown in cardiovascular diseases, diabetes, and hyperuricemia. Molecular mechanisms leading to TRIM are susceptible to homeostatic disruptions of advanced age, and maladaptive TRIM may be the link between immune aging and age-associated pathologies. The present review discusses the current knowledge on metabolic pathways in adaptive and maladaptive trained immunity and its deleterious consequences of inappropriate activation during aging. Finally, we discuss how several dietary patterns modulate immunometabolism and influence trained immunity in aging.