Brain and systemic glucose metabolism in the healthy elderly following fish oil supplementation S. Nugent a,b , E. Croteau c,e , F. Pifferi a , M. Fortier a , S. Tremblay a,e , E. Turcotte c,e , S.C. Cunnane a,b,d,n a Research Center on Aging, Universite´ de Sherbrooke, Sherbrooke, Que., Canada J1H 4C4 b Department of Physiology and Biophysics, Universite´ de Sherbrooke, Sherbrooke, Que., Canada J1H 4C4 c Department of Nuclear Medicine and Radiobiology, Universite´ de Sherbrooke, Sherbrooke, Que., Canada J1H 4C4 d Department of Medicine, Universite´ de Sherbrooke, Sherbrooke, Que., Canada J1H 4C4 e Sherbrooke Molecular Imaging Center, E ´ tienne-LeBel Clinical Research Center, CHUS, Sherbrooke, Que., Canada J1H 4C4 abstract Cerebral metabolic rate of glucose (CMRg) is lower in individuals affected by cognitive decline and dementia, especially in Alzheimer’s disease. However, as yet there is no consensus as to whether CMRg decreases during healthy aging. Epidemiological studies show that weekly consumption of fish abundant in o3 fatty acids has a protective effect on cognition during aging. Thus, the primary objective of this human study was to use positron emission tomography analysis with 18 F-fluorodeox- yglucose to evaluate whether supplementation with a fish oil rich in o3 fatty acids increases cerebral glucose metabolism in young or elderly adults. Healthy young (23 75 y old; n ¼5) and elderly (76 73y old; n ¼6) women and men were included in the study. Semi-quantitative expression of the data as ‘standardized uptake values’ showed that elderly participants had significantly lower cerebral glucose metabolism compared with the young group. However, when expressed quantitatively a CMRg, there was no effect of age or o3 supplementation on glucose metabolism in any of the brains regions studied. Higher plasma triglyceride levels and higher plasma insulin levels were associated with lower CMRg in several regions, suggesting that a trend towards the metabolic syndrome may be associated with cerebral hypometabolism. We conclude that under these experimental conditions, o3 supplementation did not affect brain glucose metabolism in the healthy elderly. Future studies in this area should address whether glucose intolerance or other conditions linked to the metabolic syndrome impact negatively on brain glucose metabolism and cognition. & 2011 Elsevier Ltd. All rights reserved. 1. Introduction The elderly are particularly susceptible to cognitive decline but why this is the case is still uncertain. There is an emerging body of evidence suggesting that cerebral glucose hypometabolism is pre- sent well in advance of the onset of any measurable cognitive decline associated with aging, and may at least partly contribute to the risk of cognitive decline associated with aging [1]. Several studies have examined glucose metabolism during normal aging using positron emission tomography (PET) with the tracer— 18 fluorodeoxyglucose ( 18 F-FDG). 18 F-FDG provides a reliable measure of glucose metabolism, the uptake of which by the brain is commonly expressed as the cerebral metabolic rate of glucose (CMRg). CMRg represents glucose utilization per volume of cerebral tissue as a function of time (mmol/100 g/min). As yet there is no consensus as to whether CMRg decreases during healthy aging [1]. Epidemiological studies show that weekly consumption of fish has a protective effect on cognition during aging [2]. Omega-3 polyunsaturated fatty acids, primarily docosahexaenoic acid (DHA), are particularly abundant in fish and could play an important role in determining the effect of aging on cognitive status [3]. DHA appears to have a role in brain glucose uptake because rats deficient in o3 fatty acids have lower brain glucose utilization as measured by the 2-deoxyglucose method [4]. GLUT1 in brain microvessels is also reduced in rats fed an o3 deficient diet [5,6]. Dietary supplementation with DHA increases GLUT1 expression in the rat brain endothelial cells and astrocytes [7]. A recent in vitro study found that glucose uptake was positively correlated with DHA levels in rat brain endothelial cells [8]. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/plefa Prostaglandins, Leukotrienes and Essential Fatty Acids 0952-3278/$ - see front matter & 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.plefa.2011.04.008 Abbreviations: PET, positron emission tomography; 18 F-FDG, 18 fluorodeoxyglu- cose; CMRg, cerebral metabolic rate of glucose; DHA, docosahexaenoic acid; MMSE, Mini-Mental State Examination; OGTT, oral glucose tolerance test; SUV, standardized uptake values; HOMA-IR, homeostasis model of insulin resistance; QUICKI, quantitative insulin sensitivity check index n Corresponding author at: Research Center on Aging, 1036 Belvedere St. South, Sherbrooke, Que., Canada J1H 4C4. Tel.: þ1 819 780 2220x45670; fax: þ1 819 829 4171. E-mail address: stephen.cunnane@usherbrooke.ca (S.C. Cunnane). Prostaglandins, Leukotrienes and Essential Fatty Acids 85 (2011) 287–291