Visceral Adipose Tissue Inflammatory Factors (TNF-Alpha, SOCS3) in Gestational Diabetes (GDM): Epigenetics as a Clue in GDM Pathophysiology

Gestational diabetes (GDM) is among the most challenging diseases in westernized countries, affecting mother and child, immediately and in later life. Obesity is a major risk factor for GDM. However, the impact visceral obesity and related epigenetics play for GDM etiopathogenesis have hardly been considered so far. Our recent findings within the prospective 'EaCH' cohort study of women with GDM or normal glucose tolerance (NGT), showed the role, critical factors of insulin resistance (i.e., adiponectin, insulin receptor) may have for GDM pathophysiology with epigenetically modified expression in subcutaneous (SAT) and visceral (VAT) adipose tissues. Here we investigated the expression and promoter methylation of key inflammatory candidates, tumor necrosis factor-alpha (TNF-α) and suppressor of cytokine signaling 3 (SOCS3) in maternal adipose tissues collected during caesarian section (GDM, n = 19; NGT, n = 22). The mRNA expression of TNF-α and SOCS3 was significantly increased in VAT, but not in SAT, of GDM patients vs. NGT, accompanied by specific alterations of respective promoter methylation patterns. In conclusion, we propose a critical role of VAT and visceral obesity for the pathogenesis of GDM, with epigenetic alterations of the expression of inflammatory factors as a potential factor

Visceral adipose tissue alteration of PI3KR1 expression is associated with gestational diabetes but not promoter DNA methylation

Obesity and diabetes are at an epidemic rate, as well as growing incidences of gestational diabetes mellitus (GDM) which causes pregnancy risks, and harm in both maternal and child health. It remains unclear which molecular mechanisms are driving the functional differences between visceral and subcutaneous fat and how these types directly affect an individual's health outcome. Paired abdominal subcutaneous and omental visceral adipose tissue were collected from women with GDM (n = 20) and with normal glucose tolerance (NGT, n = 22) during planned caesarian section. Both groups had similar maternal age (average 32.5 years) and BMI at delivery (average 33.3 kg/m2). Adipose tissue mRNA expression analyses of insulin signalling genes: PI3KCA, PI3KR1, IRS1 and IRS2 showed significantly decreased PI3KR1 expression (-23%) in visceral fat in GDM with no association to promoter DNA methylation. Reduced visceral fat PI3KR1 expression appears to be a pathogenic factor in GDM but not through altered promoter methylation

Alterations of adiponectin gene expression and DNA methylation in adipose tissues and blood cells are associated with gestational diabetes and neonatal outcome

BACKGROUND: Adiponectin critically contributes to metabolic homeostasis, especially by insulin-sensitizing action. Gestational diabetes mellitus (GDM) is characterized by insulin resistance leading to materno-fetal hyperglycemia and detrimental birth outcomes. By investigating paired subcutaneous (SAT) and visceral adipose tissue (VAT) as well as blood (cell) samples of GDM-affected (n = 25) vs. matched control (n = 30) mother-child dyads of the prospective "EaCH" cohort study, we addressed whether alterations of adiponectin plasma, mRNA, and DNA methylation levels are associated with GDM and offspring characteristics. RESULTS: Hypoadiponectinemia was present in women with GDM, even after adjustment for body mass index (BMI). This was accompanied by significantly decreased mRNA levels in both SAT and VAT (P < 0.05), independent of BMI. Maternal plasma adiponectin showed inverse relations with glucose and homeostatic model assessment of insulin resistance (both P < 0.01). In parallel to reduced mRNA expression in GDM, significant (P < 0.05) yet small alterations in locus-specific DNA methylation were observed in maternal fat (~ 2%) and blood cells (~ 1%). While newborn adiponectin levels were similar between groups, DNA methylation in GDM offspring was variously altered (~ 1-4%; P < 0.05). CONCLUSIONS: Reduced adiponectin seems to be a pathogenic co-factor in GDM, even independent of BMI, affecting materno-fetal metabolism. While altered maternal DNA methylation patterns appear rather marginally involved, functional, diagnostic, and/or predictive implications of cord blood DNA methylation should be further evaluated

Acquired alterations of hypothalamic gene expression of insulin and leptin receptors and glucose transporters in prenatally high-glucose exposed three-week old chickens do not coincide with aberrant promoter DNA methylation.

Prenatal exposures may have a distinct impact for long-term health, one example being exposure to maternal 'diabesity' during pregnancy increasing offspring 'diabesity' risk. Malprogramming of the central nervous regulation of body weight, food intake and metabolism has been identified as a critical mechanism. While concrete disrupting factors still remain unclear, growing focus on acquired epigenomic alterations have been proposed. Due to the independent development from the mother, the chicken embryo provides a valuable model to distinctively establish causal factors and mechanisms.The aim of this study was to determine the effects of prenatal hyperglycemia on postnatal hypothalamic gene expression and promoter DNA methylation in the chicken.To temporarily induce high-glucose exposure in chicken embryos, 0.5 ml glucose solution (30 mmol/l) were administered daily via catheter into a vessel of the chorioallantoic egg membrane from days 14 to 17 of incubation. At three weeks of postnatal age, body weight, total body fat, blood glucose, mRNA expression (INSR, LEPR, GLUT1, GLUT3) as well as corresponding promoter DNA methylation were determined in mediobasal hypothalamic brain slices (Nucleus infundibuli hypothalami). Although no significant changes in morphometric and metabolic parameters were detected, strongly decreased mRNA expression occurred in all candidate genes. Surprisingly, however, no relevant alterations were observed in respective promoter methylation.Prenatal hyperglycemia induces strong changes in later hypothalamic expression of INSR, LEPR, GLUT1, and GLUT3 mRNA. While the chicken provides an interesting approach for developmental malprogramming, the classical expression regulation via promoter methylation was not observed here. This may be due to alternative/interacting brain mechanisms or the thus far under-explored bird epigenome

Altered SOCS3 DNA methylation within exon 2 is associated with increased mRNA expression in visceral adipose tissue in gestational diabetes

Overweight/obesity is the main risk factor for gestational diabetes mellitus (GDM). In our cohort of pregnant women with GDM, n = 19, and without, n = 22, we previously reported a significant increase in SOCS3 mRNA expression (+62%) in visceral adipose tissue (VAT) according to GDM, without altered promoter DNA-methylation. Here, we examined methylation status of additional SOCS3 exon 2 regions in VAT and maternal blood. We found significantly altered methylation at specific CpG sites corresponding to aberrant mRNA expression levels of SOCS3 in VAT. We propose a potential regulatory element/region within exon 2; however, this region does not appear to be a good blood-marker representing VAT

Insulin receptor (<i>INSR</i>).

<p>Schematic illustration of sequence map of the insulin receptor (<i>INSR</i>) gene promoter region with chromosomal location of pyroassay <b>(A)</b>, and corresponding DNA methylation levels at individual CpG sites for prenatally NaCl-treated controls (black) and the prenatally glucose-treated group (gray) <b>(B)</b>.</p

Baseline characteristics, hypothalamic mRNA gene expression and overall promoter methylation in three-week-old chickens.

<p>Values are expressed as means ± SEM. Number of animals in parenthesis.</p><p><i>p-</i>values were calculated using Student’s t-test or Mann-Whitney U-test when appropriate.</p><p>*chi-square test</p><p>Abbreviations: <i>GLUT</i>, glucose transporter; <i>INSR</i>, insulin receptor, <i>LEPR</i>, leptin receptor; M/F, males/females</p><p>Baseline characteristics, hypothalamic mRNA gene expression and overall promoter methylation in three-week-old chickens.</p

Leptin receptor (<i>LEPR</i>).

<p>Schematic illustration of sequence map of the leptin receptor (<i>LEPR</i>) gene promoter region with chromosomal location of pyroassay <b>(A)</b>, and corresponding DNA methylation levels at individual CpG sites for prenatally NaCl-treated controls (black) and the prenatally glucose-treated group (gray) <b>(B)</b>.</p

Pyrosequencing assay information.

<p>* Chromosomal location is based on the UCSC Chicken Nov. 2011 (ICGSC Gallus_gallus-4.0/galGal4) Build.</p><p>Abbreviations: <i>GLUT</i>, glucose transporter; <i>INSR</i>, insulin receptor, <i>LEPR</i>, leptin receptor</p><p>Pyrosequencing assay information.</p

Correlation analyses.

<p>Relations between total DNA methylation levels and corresponding mRNA expression of the insulin receptor <b>(A)</b>, leptin receptor <b>(B)</b>, glucose transporter 1 <b>(C)</b> and glucose transporter 3 <b>(D)</b> in the <i>Nucleus infundibuli hypothalami</i> (NI) in three-week-old chickens of prenatally NaCl-treated controls (black) as compared to the prenatally glucose-treated group (gray).</p