Gestational Diabetes and the Metabolic Syndrome

Abstract

The metabolic syndrome is a clustering of traditional cardiometabolic risk factors that include central obesity, dysglycemia, hypertension, hypertriglyceridemia, and reduced high-density lipoprotein (HDL) cholesterol. In recent years, its clinical utility, diagnostic criteria and underlying etiology have been the subject of continuous debate and controversy. While the debate continues, it remains incontrovertible that those identified with the metabolic syndrome are at high risk for the future development of type 2 diabetes (T2DM) and cardiovascular disease (CVD). In addition, an expanding body of evidence has linked the metabolic syndrome with several emerging non-traditional risk factors, including markers of hepatic fat, chronic inflammation (such as C-reactive protein (CRP)), and adipocyte dysregulation (such as low circulating levels of adiponectin). Interestingly, many of these features of the metabolic syndrome are also common to gestational diabetes mellitus (GDM). Indeed, GDM has also been the subject of longstanding debate throughout its history and it too identifies women who are at high risk of developing T2DM and CVD in the future. Moreover, in recent years, GDM has been similarly linked to an array of non-traditional cardiometabolic risk factors, including CRP and hypoadiponectinemia. A series of studies have demonstrated that women with GDM are at risk of developing the metabolic syndrome in the years following their index pregnancy. Furthermore, emerging evidence shows that components of the metabolic syndrome identified in early gestation and even prior to pregnancy can predict the subsequent development of GDM. Taken together, these findings have raised the intriguing possibility that women who develop GDM may have an underlying latent metabolic syndrome that warrants clinical evaluation and risk factor modification. Though intricate and still incompletely understood, the gradual expansion of knowledge about inter-relationships between the metabolic syndrome, GDM and T2DM may provide us with opportunities to screen for and detect metabolic dysfunction at various stages of disease progression. In this way, GDM represents an important and early “metabolic flag” for an affected mother and, perhaps, her offspring. Thus, in this chapter, we explore the emerging relationship between GDM and the metabolic syndrome. We review the definitions of each condition, their limitations and controversies, and their utility and predictive value in identifying T2DM and CVD risk. The clinical evidence for metabolic syndrome as a precursor to the development of GDM and, in turn, T2DM is also discussed.