Metabolic Syndrome and the Lung

Abstract

A link between metabolic syndrome (MetS) and lung diseases has been observed in several cross-sectional and longitudinal studies. This syndrome has been identified as an independent risk factor for worsening respiratory symptoms, greater lung function impairment, pulmonary hypertension, and asthma. This review will discuss several potential mechanisms to explain these associations, including dietary factors and the effect of adiposity and fat-induced inflammation on the lungs, and the role of other comorbidities that frequently coexist with MetS, such as OSA and obesity. In contrast to the well-known association between asthma and obesity, the recognition that MetS affects the lung is relatively new. Although some controversy remains as to whether MetS is a unique disease entity, its individual components have independently been associated with changes in pulmonary function or lung disease. There is, however, uncertainty as to the relative contribution that each metabolic factor has in adversely affecting the respiratory system; also, it is unclear how much of the MetS-related lung effects occur independently of obesity. In spite of these epidemiological limitations, the proposed mechanistic pathways strongly suggest that this association is likely to be causal. Given the wide prevalence of MetS in the general population, it is imperative that we continue to further understand how this metabolic disorder impacts the lung and how to prevent its complications.

Keywords: COPD; asthma; metabolic syndrome; obesity; obstructive sleep apnea; pulmonary hypertension.

Figure 1

Potential mechanisms of the effect of metabolic syndrome on lung function are shown. Based on current data, multiple pathways related to metabolic syndrome may affect lung function, including changes in leptin and adiponectin, dietary effects of excess obesity, alterations in circulating growth hormone and subsequently insulin-like growth factor I, the effect of hyperglycemia and hyperinsulinemia, and the mechanical effect of abdominal obesity.