Impact of high fat diet and krill oil supplementation on spatial memory, microglia migration and neurogenesis in aged rats

Objective: Investigate the potential of krill oil (KO), a marine-based, long chain, omega-3 ( n-3) polyunsaturated fatty acid (PUFA), to negate the deleterious effects of high fat diet and aging on spatial learning, microglia migration and neurogenesis. Hypothesis: KO exhibits beneficial, anti-inflammatory properties comparable to other sources of n-3 PUFA, but with several biochemical advantages. KO contains phospholipid-bound fatty acids, improving bioavailability when compared to triacylglyceride bound n-3 PUFA, astaxanthin, a powerful antioxidant, and choline which is an essential neurotransmitter precursor exhibiting neuroprotective properties. Hence, we hypothesized that KO supplementation would improve deficiencies in spatial learning, hippocampal neurogenesis and unwarranted microglia migration induced by high fat diet and normal aging in rats. Methods: Thirty-two male, Sprague Dawley rats, aged 15 months were divided into four dietary groups consisting of varying amounts of saturated fats, with and without krill oil supplementation: Control (CON), Control with krill oil (CONKO), High fat (HF), High fat with krill oil (HFKO). High fat and control diets consisted of 60% and 23% calories from fats, respectively, while 8% krill oil was added to both experiment KO diets. Food intake and body weight were assessed weekly. After 12-weeks of dietary interventions, spatial learning was assessed utilizing Morris Water Maze testing, followed by cortex and hippocampus tissue analysis. Microglia migration and neurogenesis was quantified by immunostaining and stereology techniques utilizing doublecortin (DCX) and ionized calcium-binding adaptor protein (Iba-1). Results: Despite evidence of learning by each group over the course of MWM testing, no significant difference in time-to-platform or probe trial times between dietary groups was identified. Total food consumption was significantly less in the HF group when compared to CON (p=0.047) and CONKO (p=0.030), whereas body weight was significantly higher in the HFKO group when compared to CON (p=0.024) and CONKO (p=0.030). Otherwise, no other differences in food consumption or body weight were identified. Furthermore, no significant difference was found in cortex (p=0.623) or hippocampus (p=0.863) microglia counts between dietary groups. Similarly, DCX totals were not significantly different (p=0.454). Conclusions: KO supplementation did not significantly alter the effects of aging and high fat diet consumption on spatial memory, microglia migration or hippocampal neurogenesis. Some evidence suggests that the unique properties of KO have the potential to positively influence brain health. Therefore, considering the negative effects of aging and fatty foods and the associated risks of neurodegenerative diseases, exploration of neuroprotective dietary interventions such as krill oil is paramount and warrants further investigation. This work was supported by the Central Michigan University Office of Research and Graduate Studies and College of Health Professions This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.