Impact of Obesity and Metabolic Syndrome on Immunity

Abstract

Obesity is associated with metabolic disturbances that cause tissue stress and dysfunction. Obese individuals are at a greater risk for chronic disease and often present with clinical parameters of metabolic syndrome (MetS), insulin resistance, and systemic markers of chronic low-grade inflammation. It has been well established that cells of the immune system play an important role in the pathogenesis of obesity- and MetS-related chronic diseases, as evidenced by leukocyte activation and dysfunction in metabolic tissues such as adipose tissue, liver, pancreas, and the vasculature. However, recent findings have highlighted the substantial impact that obesity and MetS parameters have on immunity and pathogen defense, including the disruption of lymphoid tissue integrity; alterations in leukocyte development, phenotypes, and activity; and the coordination of innate and adaptive immune responses. These changes are associated with an overall negative impact on chronic disease progression, immunity from infection, and vaccine efficacy. This review presents an overview of the impact that obesity and MetS parameters have on immune system function.

FIGURE 1

The impact of obesity and MetS on immune system function. Obesity and MetS are associated with stress and dysfunction of metabolic tissues, including adipose tissue, liver, skeletal muscle, and pancreas. Systemic physiological dysfunction that arises from obesity-related complications leads to fat accumulation in primary lymphoid organs (bone marrow and thymus), resulting in a breakdown of tissue architecture and integrity. Obesity-induced changes in lymphoid tissues are further associated with an altered distribution of leukocyte subsets and populations and greater numbers of leukocytes with proinflammatory phenotypes. Obesity-induced disruptions in the immune system impair immunity and contribute to the progression of metabolic dysfunction and chronic disease. Chronic disease can further perpetuate dysfunction throughout the immune system. MetS, metabolic syndrome.