Abstract
Several studies link increasing body mass index (BMI) to cognitive decline both as a consequence of obesity per se and as a sequela of obesity-induced type 2 diabetes. Obese individuals are prone to a chronic low-grade inflammation as the metabolically active visceral fat produces proinflammatory cytokines. Animal studies indicate that these cytokines can cross the blood–brain barrier. Such crossover could potentially affect the immune system in the brain by inducing gene expression of proinflammatory genes. The relationship between obesity and neuroinflammation in the human brain is currently unknown. Therefore we aim to examine the relationship between BMI and gene expression of central inflammatory markers in the human frontal cortex. Microarray data of 141 neurologically and psychiatrically healthy individuals were obtained through the BrainCloud database. A simple linear regression analysis was performed with BMI as variable on data on IL10, IL1β, IL6, PTGS2 (COX2) and NOS2 (iNOS). Increasing BMI is associated with a decrease in the mRNA expression of IL10 (P=0.014) and an increase in the expression of NOS2 (iNOS; P=0.040). Expressions of IL10 and NOS2 (iNOS) were negatively correlated (P<0.001). The expression of IL10 was mostly affected by individuals with BMI ⩾40. Multiple linear regression analyses with BMI, age, sex and race as variables were performed in order to identify potential confounders. In conclusion, increasing BMI could affect the IL10-mediated anti-inflammatory defense in the brain and induce iNOS-mediated inflammatory activity.
Highlights
The World Health Organization (WHO) estimates that about 1.9 billion adults are currently overweight,[1] and obesity represents a massive economic burden on health-care systems worldwide.Much evidence links obesity in midlife to increased risk of dementia in later life.[2,3,4,5,6,7] a recent large-scale retrospective study of 2 million individuals reported that midlife obesity associates with a lower risk of dementia.[8]
The relationship between body mass index (BMI) and the mRNA expression of the investigated inflammatory cytokines was not affected by age, sex and race
BMI is associated with an altered mRNA expression of IL10 and IL10 and NOS2 (iNOS), whereas BMI does not significantly affect the expression level of IL1β, IL6 and PTGS2 (COX2) Performing a simple linear regression analysis, we found a significantly reduced IL10 expression P = 0.014 with increasing
Summary
The World Health Organization (WHO) estimates that about 1.9 billion adults are currently overweight,[1] and obesity represents a massive economic burden on health-care systems worldwide.Much evidence links obesity in midlife to increased risk of dementia in later life.[2,3,4,5,6,7] a recent large-scale retrospective study of 2 million individuals reported that midlife obesity associates with a lower risk of dementia.[8]. Obese individuals have a higher prevalence of atherosclerosis,[9] endothelial dysfunction and cerebral hypoperfusion. These are among the possible mechanisms of obesity-associated cognitive decline.[10,11] Obese individuals are more likely to develop diabetes, insulin resistance and/or metabolic syndrome (MetS). MetS is characterized by elevated plasma glucose levels, hypertension and dyslipidemia.[12] It is estimated that 20–25% of all adults suffer from MetS and about 1 in 11 adults have diabetes, of which 90% have type 2 diabetes.[13,14] Type 2 diabetes patients carry a two to five times increased risk of both Alzheimers disease and vascular dementia[15] and MetS is a known risk factor for cognitive decline and overall dementia risk.[16]
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