AGING AND DIETARY MODULATION OF ELASTASE AND INTERLEUKIN-1-BETA SECRETION

Aging is associated with diminished immune function that may stem from alterations in arachidonic acid metabolism and lipid peroxidation. Th is study sought to determine if dietary modification of fatty acids in fluenced neutrophil and monocyte secretion after an in vivo inflammato ry stress in older human subjects. Volunteers participated in protocol s that forced their quadriceps muscles to lengthen during tension deve lopment (eccentric stress). These protocols can cause inflammatory foc i in the muscle as well as alterations in circulating leukocyte functi on. In this study, in vivo neutrophil degranulation was assessed by pl asma elastase concentrations, and mononuclear cell function was assess ed by interleukin-1 beta (IL-1 beta) secretion in vitro. In response t o eccentric stress, older subjects (>60 yr old) taking a placebo had n o apparent elastase response, whereas those taking fish oil supplement s responded with a 142% increase in plasma elastase (P = 0.011), simil ar to responses of younger reference subjects (<33 yr old) taking no s upplement. Overall, elastase responses correlated with individual plas ma arachidonic acid-to-eicosapentaenoic acid ratios (r = -0.881, P = 0 .004). Thus apparent age-related differences in elastase release were reconciled by individual differences in fatty acid nutriture. No signi ficant temporal changes in urinary lipid peroxide excretion or IL-1 be ta secretion were observed; however, age-associated differences were f ound.