Abstract
Older adults exhibit augmented renal vasoconstriction during orthostatic stress compared to young adults. Consumption of omega‐3 polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) found in fish oil (FO), modulates autonomic nerve activity. However, the effect of omega‐3 polyunsaturated fatty acid consumption on the renal vasoconstrictor response to orthostatic stress in young and older adults is unknown. Therefore, 10 young (25 ± 1 years; mean ± SEM) and 10 older (66 ± 2 years) healthy adults ingested 4 g FO daily for 12 weeks, and underwent graded lower body negative pressure (LBNP; −15 and −30 mmHg) pre‐ and post‐FO supplementation. Renal blood flow velocity (RBFV; Doppler ultrasound), arterial blood pressure (BP; photoplethysmographic finger cuff), and heart rate (electrocardiogram) were recorded. Renal vascular resistance (RVR), an index of renal vasoconstriction, was calculated as mean BP/RBFV. All baseline cardiovascular values were similar between groups and visits, except diastolic BP was higher in the older group (P < 0.05). FO supplementation increased erythrocyte EPA and DHA content in both groups (P < 0.05). FO did not affect RVR or RBFV responses to LBNP in either group, but attenuated the mean BP response to LBNP in the older group (older −30 mmHg: pre‐FO −4 ± 1 vs. post‐FO 0 ± 1 mmHg, P < 0.05; young −30 mmHg: pre‐FO −5 ± 1 vs. post‐FO −5 ± 2 mmHg). In conclusion, FO supplementation attenuates the mean BP response but does not affect the renal vasoconstrictor response to orthostatic stress in older adults.
Highlights
Aging is associated with a greater incidence of orthostatic hypotension (Rutan et al 1992), which is linked with greater mortality (Masaki et al 1998)
We recently showed that the renal vasoconstrictor response to orthostatic stress via lower body negative pressure (LBNP) is augmented in healthy older adults, while their blood pressure (BP) response is similar to healthy young adults (Clark et al 2015)
Our results indicate that fish oil (FO) supplementation does not affect Renal vascular resistance (RVR) or Renal blood flow velocity (RBFV) responses to LBNP in either healthy older or young adults
Summary
Aging is associated with a greater incidence of orthostatic hypotension (Rutan et al 1992), which is linked with greater mortality (Masaki et al 1998). Sympathetic neural outflow from the medulla oblongata in the brainstem directed towards the kidneys induces renal vasoconstriction, which reduces renal blood flow (Johns et al 2011). This reflex reduction in renal blood flow allows blood to be redistributed to other areas of the body where it is needed more critically at that time, such as the systemic circulation to maintain BP. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society
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