Adiponectin: Are Measurements Clinically Useful in Pregnancy?

Adiponectin (AdpN) is an abundant protein that circulates in blood in microgram quantities. Although AdpN is primarily produced by adipose tissue, the paradox of AdpN is that plasma concentrations decrease with increasing adiposity (1,2). AdpN concentrations are decreased in obesity (3) and obesity-related complications—for example, diabetes, cardiovascular diseases, nonalcoholic fatty liver disease, and in pregnancy (4,5). AdpN exerts pleiotropic actions including potent insulin sensitizing properties. Studies in obesity, type 2 diabetes, and gestational diabetes mellitus (GDM) suggest that the deficiency of AdpN triggers the progression to insulin resistance and the development of metabolic inflammation (recently reviewed in ref. 6). This has encouraged numerous groups to investigate whether AdpN could serve as a systemic biomarker that would predict the risk of diabetes. A link between hypoadiponectinemia and reduced insulin action also exists in pregnancy. In healthy women, AdpN levels reach their lowest concentrations in the third trimester when maternal insulin resistance is greatest (5,7). The low AdpN concentrations in the third trimester are further accentuated in GDM (8). Total AdpN and high molecular weight AdpN and the high molecular weight-to-AdpN ratio are inversely related to insulin resistance as estimated by clamp studies in early and late pregnancy (5). Maternal AdpN does not cross the placenta and consequently does not contribute to fetal adiponectinemia (9). Contrary to other cytokines, AdpN is not expressed nor produced by the placenta (10–12). Similar to the nonpregnant state, these characteristics underscore that maternal adipose tissue is the major source of maternal plasma AdpN, which thus can be assessed as an independent maternal biomarker (Fig. 1). …