Historically, insulin resistance during pregnancy has been ascribed to increased production of placental hormones and cortisol. The purpose of this study was to test this hypothesis by correlating the longitudinal changes in insulin sensitivity during pregnancy with changes in placental hormones, cortisol, leptin, and tumor necrosis factor (TNF)-␣. Insulin resistance was assessed in 15 women (5 with gestational diabetes mellitus [GDM] and 10 with normal glucose tolerance) using the euglycemic-hyperinsulinemic clamp procedure, before pregnancy (pregravid) and during early (12-14 weeks) and late (34 -36 weeks) gestation. Body composition, plasma TNF-␣, leptin, cortisol, and reproductive hormones (human chorionic gonadotropin, estradiol, progesterone, human placental lactogen, and prolactin) were measured in conjunction with the clamps. Placental TNF-␣ was measured in vitro using dually perfused human placental cotyledon from five additional subjects. Compared with pregravid, insulin resistance was evident during late pregnancy in all women (12.4 ؎ 1.2 vs. 8.1 ؎ 0.8 10 ؊2 mg ⅐ kg ؊1 fat-free mass ⅐ min ؊1 ⅐ U ؊1 ⅐ ml ؊1 ). TNF-␣, leptin, cortisol, all reproductive hormones, and fat mass were increased in late pregnancy (P < 0.001). In vitro, most of the placental TNF-␣ (94%) was released into the maternal circulation; 6% was released to the fetal side. During late pregnancy, TNF-␣ was inversely correlated with insulin sensitivity (r ‫؍‬ ؊0.69, P < 0.006). Furthermore, among all of the hormonal changes measured in this study, the change in TNF-␣ from pregravid to late pregnancy was the only significant predictor of the change in insulin sensitivity (r ‫؍‬ ؊0.60, P < 0.02). The placental reproductive hormones and cortisol did not correlate with insulin sensitivity in late pregnancy. Multivariate stepwise regression analysis revealed that TNF-␣ was the most significant independent predictor of insulin sensitivity (r ‫؍‬ ؊0.67, P < 0.0001), even after adjustment for fat mass by covariance (r ‫؍‬ 0.46, P < 0.01). These observations challenge the view that the classical reproductive hormones are the primary mediators of change in insulin sensitivity during gestation and provide the basis for including TNF-␣ in a new paradigm to explain insulin resistance in pregnancy. Diabetes 51:2207-2213, 2002

Obese pregnant women develop severe insulin resistance and enhanced systemic and placental inflammation, suggesting associated modifications of endocrine and immune functions. Activation of innate immunity by endotoxins/lipopolysaccharides (LPS) has been proposed as a mechanism for enhancing metabolic alterations in disorders with insulin resistance. The aim of this study was to characterize the immune responses developed by the adipose tissue AT and their potential links to maternal endotoxemia in pregnancy with obesity. Blood and subcutaneous abdominal AT were obtained from 120 lean and obese women (term pregnancy) recruited at delivery. Gene expression was assessed in AT and stromal vascular cells isolated from a subset of 24 subjects from the same cohort. Doubling of plasma endotoxin concentrations indicated subclinical endotoxemia in obese compared with lean women. This was associated with significant increase in systemic CRP and IL-6 but not TNF-alpha concentrations. AT inflammation was characterized by accumulation of CD68+ macrophages with a 3-fold increased gene expression of the macrophage markers CD68, EMR1 and CD14. Gene expression for cytokines IL-6, TNF-α, IL-8, and MCP1 and for LPS - sensing CD14, TLR4, TRAM2 was 2.5-5 fold higher in stromal cells of obese compared to lean. LPS-treated cultured stromal cells of obese women expressed a 5-16 fold stimulation of the same cytokines up-regulated in vivo. Our data demonstrate that subclinical endotoxemia is associated with systemic and AT inflammation in obese pregnant women. Recognition of bacterial pathogens may contribute to the combined dysfunction of innate immunity and the metabolic systems in AT.

The initial steps of primitive hematopoiesis and endothelial vascular formation in the human embryo remain to be defined. Here, we report the identification of a novel marker, namely the nonclassical HLA-G class I molecule, which targets both primitive erythroid cells of the yolk sac and endothelial cells from developing vessels. Moreover, HLA-G was present in its soluble form in the erythropoietic lineage in all organs sustaining primitive to definitive erythropoiesis (ie, aorta-gonad-mesonephros, liver, spleen, and bone marrow). The alternatively spliced transcript coding the soluble HLA-G5 molecule was detected in erythroid cells. The corresponding intron 4-retaining 37-kDa HLA-G5 isoform was secreted from the erythroid progenitor stage to the reticulocyte but was lost in mature erythrocytes and in endothelial cells from differentiated vessels. This study constitutes the first description of an HLA class I antigen expression on the primitive erythroid lineage and provides a way of seeking both primitive and definitive erythropoiesis using HLA-G5. This new marker, previously known by its immunotolerogeneic properties, may be involved in erythroid differentiation, angiogenesis, or both. IntroductionOver the past few years, studies have been carried out aimed at understanding the spatial and temporal generation and organization of the human hematopoietic system during ontogeny. Current research has identified 2 independent generations of hematopoietic progenitor cells which differ in their potential for self-renewal and differentiation, and which are produced in the embryo at distinct times and in specific locations. 1 The first hematopoietic precursors originate from the extraembryonic yolk sac (YS) in the first stages of development and only lead to short-term erythromyeloid reconstitution, referred to as primitive hematopoiesis. Later, the intraembryonic para-aortic splanchnopleura/aorta-gonad-mesonephros (PSp/AGM) region produces the hematopoietic stem cells (HSCs), corresponding to the self-renewing, multipotent precursors that further colonize the fetal liver (FL) and thymus. This later process is referred to as the definitive hematopoiesis, which starts in the bone marrow (BM) from the second trimester of intraembryonic life and continues throughout adult life. However, works in mice, for which ontogeny of hematopoiesis is similar to that of humans, has demonstrated that HSC activity also arises from the yolk sac. [2][3][4] We here identify a novel pattern of distribution of the nonclassical HLA class I molecule, HLA-G, namely the erythroid cells in all organs sustaining primitive and definitive hematopoiesis and the endothelial cells forming developing vessels. This double expression of HLA-G in both endothelial and erythroid cells is of particular interest in the context of the proposed precursor common to both lineages, called the hemangioblast. 5 The nonclassical HLA class I molecule, HLA-G, plays a major role in human reproduction because it is expressed from oocyte to blastocyst stages in the human...