Effect of age, breed and dietary omega-6 (n-6): omega-3 (n-3) fatty acid ratio on immune function, eicosanoid production, and lipid peroxidation in young and aged dogs

The focus of this study was to examine the influence of age and diet on var ious parameters of immune function in young and old Fox Terriers and Labrad or Retrievers. Eighteen young and old dogs were utilized for this study. Yo ung and old dogs were fed a basal diet containing an (n-6) : (n-3) ratio of 25 : 1 for sixty days (Phase I). Half of the dogs were then switched to a diet with an (n-6) : (n-3) ratio of 5 : 1, and all were maintained on their respective diets for an additional sixty days (Phase II). Results from the se studies revealed an age-associated decline in several immune parameters measured. Both these breeds demonstrated a reduction in sheep red blood cel l titers, as well as in their ability to respond to different mitogens. Int erestingly, this decline was greater in Fox Terriers, suggesting a decrease in cellular proliferative capacity in lymphocytes isolated from the larger breed. Neither cytokine production or DTH response was affected by age. Di et and breed interactions resulted in a significant increase in T- and B-ce ll mitogen responsiveness. In contrast, supplementation with n-3 fatty acid s did not affect IL-1, IL-6 or TNF-alpha production. Supplementation with n -3 fatty acids resulted in increased PGE(3) production from peritoneal macr ophages but had no effect on PGE(2) production from peripheral blood mononu clear cells or peritoneal macrophages. The n-3 fatty acid supplementation d id not influence alpha-tocopherol status although older dogs had significan tly lower serum alpha-tocopherol concentrations. Oxidative status of these does was assessed by serum levels of malondialdehyde (MDA) and 4-hydroxynon enal (4-HNE). Feeding an n-3-enriched diet did not affect 4-HNE levels but significantly decreased MA levels in old dogs. In summary, this study indic ates that feeding a diet containing an (n-6):(n-3) fatty acid ratio of 5:1 had a positive, rather than a negative, effect on the immune response of yo ung or geriatric dogs. (C) 1999 Elsevier Science B.V. All rights reserved.