Depressive symptoms in obesity: Relative contribution of low-grade inflammation and metabolic health

Background: Recent reports suggest that the risk of depressive symptoms in obesity is potentiated in subjects presenting a metabolically unhealthy phenotype. Inflammation is often considered a defining criteria of metabolic health. However, this factor may drive the association of metabolic health with depressive symptoms given its well-known role in the pathophysiology of depression. This study aimed at determining the relative contribution of inflammation and metabolic abnormalities to depressive symptoms in obesity. Methods: One-hundred severely obese adults (BMI >= 35-40 kg/m(2)) and 25 non-obese control individuals (BMI < 30 kg/m(2)) were recruited. Depressive symptoms were assessed using the Montgomery-Asberg Depression Rating Scale (MADRS) and Mini-International Neuropsychiatric Interview (MINI). Serum high-sensitive C-reactive protein (hs-CRP) was measured as a marker of systemic inflammation. Metabolically unhealthy obesity was defined as obesity associated with two or more metabolic alterations, including low high-density lipoprotein cholesterol, hypertriglyceridemia, high fasting glucose and hypertension. Results: Total MADRS scores were significantly higher in obese subjects with significant inflammation (hs-CRP >= 5 mg/L) compared to those with low inflammation (hs-CRP < 5 mg/L) and non-obese controls. Interestingly, hs-CRP levels significantly predicted MADRS scores in the whole population under study and in the group of obese subjects. Overall, no association was found between MADRS scores and individual metabolic alterations or the composite measure of metabolically unhealthy obesity. Similarly, the association of hs-CRP with MADRS scores in obese patients was not modulated by metabolic health factors. Conclusions: These results indicate that systemic inflammation represents a stronger contributor of obesity-related depressive symptoms than metabolic health per se. This supports the notion that inclusion of inflammation in the definition of metabolically unhealthy obesity drives the association found between poor metabolic health and depressive symptoms.