Thirst deficits in aged rats are reversed by dietary omega-3 fatty acid supplementation

Abstract 

During heat waves many elderly individuals die as a consequence of dehydration. This is partially due to deficits in mechanisms controlling thirst. Reduced thirst following dipsogenic stimuli is well documented in aged humans and rodents. Low in vivo long-chain omega-3 fatty acid levels, as can occur in aging, have been shown to alter body fluid and sodium homeostasis. Therefore, the effect of dietary omega-3 fatty acid supplementation on drinking responses in aged rats was examined. Omega-3 fatty acids reversed thirst deficits in aged rats following dehydration and hypertonic stimuli; angiotensin (ANG) II induced drinking was unaffected in aged rats. Plasma atrial natriuretic peptide (ANP) and arginine vasopressin (AVP) were altered with age, but not affected by diet. Aged omega-3 fatty acid deficient animals displayed increased hypothalamic cytosolic phospholipase A₂ (cPLA₂), cyclooxygenase (COX)-2, and prostaglandin E (PGE) synthase messenger (m)RNA expression, compared with animals that received omega-3 fatty acids. The aged low omega-3 fatty acid fed animals had significantly elevated hypothalamic PGE₂ compared with all other groups. Hypothalamic PGE₂ was negatively correlated with drinking induced by both dehydration and hypertonicity. The results indicate that PGE₂ may be the underlying mechanism of the reduced thirst observed in aging.

Keywords:  Thirst , Fluid intake , Dehydration , Omega-3 polyunsaturated fatty acids , Cyclooxygenase , Prostaglandin E , Aging , Docosahexaenoic acid , Arachidonic acid