Epigenetics of the non-coding RNA nc886 across blood, adipose tissue and skeletal muscle in offspring exposed to diabetes in pregnancy

BACKGROUND

Diabetes in pregnancy is associated with increased risk of long-term metabolic disease in the offspring, potentially mediated by in utero epigenetic variation. Previously, we identified multiple differentially methylated single CpG sites in offspring of women with gestational diabetes mellitus (GDM), but whether stretches of differentially methylated regions (DMRs) can also be identified in adolescent GDM offspring is unknown. Here, we investigate which DNA regions in adolescent offspring are differentially methylated in blood by exposure to diabetes in pregnancy. The secondary aim was to characterize the RNA expression of the identified DMR, which contained the nc886 non-coding RNA.

METHODS

To identify DMRs, we employed the bump hunter method in samples from young (9-16 yr, n = 92) offspring of women with GDM (O-GDM) and control offspring (n = 94). Validation by pyrosequencing was performed in an adult offspring cohort (age 28-33 years) consisting of O-GDM (n = 82), offspring exposed to maternal type 1 diabetes (O-T1D, n = 67) and control offspring (O-BP, n = 57). RNA-expression was measured using RT-qPCR in subcutaneous adipose tissue and skeletal muscle.

RESULTS

One significant DMR represented by 10 CpGs with a bimodal methylation pattern was identified, located in the nc886/VTRNA2-1 non-coding RNA gene. Low methylation status across all CpGs of the nc886 in the young offspring was associated with maternal GDM. While low methylation degree in adult offspring in blood, adipose tissue, and skeletal muscle was not associated with maternal GDM, adipose tissue nc886 expression was increased in O-GDM compared to O-BP, but not in O-T1D. In addition, adipose tissue nc886 expression levels were positively associated with maternal pre-pregnancy BMI (p = 0.006), but not with the offspring's own adiposity.

CONCLUSIONS

Our results highlight that nc886 is a metastable epiallele, whose methylation in young offspring is negatively correlated with maternal obesity and GDM status. The physiological effect of nc886 may be more important in adipose tissue than in skeletal muscle. Further research should aim to investigate how nc886 regulation in adipose tissue by exposure to GDM may contribute to development of metabolic disease.

Impact of BMI and comorbidities on efficacy of once-weekly semaglutide: Post hoc analyses of the STEP 1 randomized trial

OBJECTIVE

This study assessed the effects of semaglutide on body weight, cardiometabolic risk factors, and glycemic status in individuals categorized by baseline BMI with or without additional obesity-related comorbidities, including prediabetes and high risk of cardiovascular disease (CVD).

METHODS

This was a post hoc exploratory subgroup analysis of the Semaglutide Treatment Effect in People with Obesity (STEP) 1 trial (NCT03548935), in which participants without diabetes and BMI ≥30 kg/m2 , or BMI ≥27 kg/m2 with ≥1 weight-related comorbidity, were randomized to once-weekly subcutaneous semaglutide 2.4 mg or placebo for 68 weeks. For this analysis, individuals were categorized into subgroups based on baseline BMI <35 versus ≥35 kg/m2 (with no additional criteria, with ≥1 comorbidity, with prediabetes, and with prediabetes and high risk of CVD).

RESULTS

Mean changes in body weight from baseline to week 68 with semaglutide were -16.2% and -14.0% in the subgroups with baseline BMI <35 and ≥35 kg/m2 , respectively (both p < 0.0001 vs. placebo). Similar changes were observed in individuals with comorbidities, with prediabetes, and with prediabetes plus high CVD risk. The beneficial effects of semaglutide on cardiometabolic risk factors were consistent across all subgroups.

CONCLUSIONS

This subgroup analysis confirms that semaglutide is effective in individuals with baseline BMI <35 and ≥35 kg/m2 , including in those with comorbidities.

DNA Methylation and Gene Expression in Blood and Adipose Tissue of Adult Offspring of Women with Diabetes in Pregnancy—A Validation Study of DNA Methylation Changes Identified in Adolescent Offspring

Maternal gestational diabetes and obesity are associated with adverse outcomes in offspring, including increased risk of diabetes and cardiovascular diseases. Previously, we identified a lower DNA methylation degree at genomic sites near the genes ESM1, MS4A3, and TSPAN14 in the blood cells of adolescent offspring exposed to gestational diabetes and/or maternal obesity in utero. In the present study, we aimed to investigate if altered methylation and expression of these genes were detectable in blood, as well in the metabolically relevant subcutaneous adipose tissue, in a separate cohort of adult offspring exposed to gestational diabetes and obesity (O-GDM) or type 1 diabetes (O-T1D) in utero, compared with the offspring of women from the background population (O-BP). We did not replicate the findings of lower methylation of ESM1, MS4A3, and TSPAN14 in blood from adults, either in O-GDM or O-T1D. In contrast, in adipose tissue of O-T1D, we found higher MS4A3 DNA methylation, which will require further validation. The adipose tissue ESM1 expression was lower in O-GDM compared to O-BP, which in turn was not associated with maternal pre-pregnancy BMI nor the offspring’s own adiposity. Adipose tissue TSPAN14 expression was slightly lower in O-GDM compared with O-BP, but also positively associated with maternal pre-pregnancy BMI, as well as offspring’s own adiposity and HbA1c levels. In conclusion, the lower DNA methylation in blood from adolescent offspring exposed to GDM could not be confirmed in the present cohort of adult offspring, potentially due to methylation remodeling with increased aging. In offspring adipose tissue, ESM1 expression was associated with maternal GDM, and TSPAN14 expression was associated with both maternal GDM, as well as pre-pregnancy BMI. These altered expression patterns are potentially relevant to the concept of developmental programming of cardiometabolic diseases and require further studies.

Increased expression of microRNA-15a and microRNA-15b in skeletal muscle from adult offspring of women with diabetes in pregnancy

Offspring of women with diabetes in pregnancy exhibit skeletal muscle insulin resistance and are at increased risk of developing type 2 diabetes, potentially mediated by epigenetic mechanisms or changes in the expression of small non-coding microRNAs. Members of the miR-15 family can alter the expression or function of important proteins in the insulin signalling pathway, affecting insulin sensitivity and secretion. We hypothesized that exposure to maternal diabetes may cause altered expression of these microRNAs in offspring skeletal muscle, representing a potential underlying mechanism by which exposure to maternal diabetes leads to increased risk of cardiometabolic disease in offspring. We measured microRNA expression in skeletal muscle biopsies of 26- to 35-year-old offspring of women with either gestational diabetes (O-GDM, n = 82) or type 1 diabetes (O-T1DM, n = 67) in pregnancy, compared with a control group of offspring from the background population (O-BP, n = 57) from an observational follow-up study. Expression of both miR-15a and miR-15b was increased in skeletal muscle obtained from O-GDM (both P < 0.001) and O-T1DM (P = 0.024, P = 0.005, respectively) compared with O-BP. Maternal 2 h post OGTT glucose levels were positively associated with miR-15a expression (P = 0.041) in O-GDM after adjustment for confounders and mediators. In all groups collectively, miRNA expression was significantly positively associated with fasting plasma glucose, 2 h plasma glucose and HbA1c. We conclude that fetal exposure to maternal diabetes is associated with increased skeletal muscle expression of miR-15a and miR-15b and that this may contribute to development of metabolic disease in these subjects.

DNA methylation and gene expression of TXNIP in adult offspring of women with diabetes in pregnancy

BACKGROUND

Fetal exposure to maternal diabetes increases the risk of type 2 diabetes (T2DM), possibly mediated by epigenetic mechanisms. Low blood TXNIP DNA methylation has been associated with elevated glucose levels and risk of T2DM, and increased skeletal muscle TXNIP gene expression was reported in subjects with impaired glucose metabolism or T2DM. Subcutaneous adipose tissue (SAT) and skeletal muscle play a key role in the control of whole body glucose metabolism and insulin action. The extent to which TXNIP DNA methylation levels are decreased and/or gene expression levels increased in SAT or skeletal muscle of a developmentally programmed at-risk population is unknown.

OBJECTIVE AND METHODS

The objective of this study was to investigate TXNIP DNA methylation and gene expression in SAT and skeletal muscle, and DNA methylation in blood, from adult offspring of women with gestational diabetes (O-GDM, n = 82) or type 1 diabetes (O-T1DM, n = 67) in pregnancy compared with offspring of women from the background population (O-BP, n = 57).

RESULTS

SAT TXNIP DNA methylation was increased (p = 0.032) and gene expression decreased (p = 0.001) in O-GDM, but these differences were attenuated after adjustment for confounders. Neither blood/muscle TXNIP DNA methylation nor muscle gene expression differed between groups.

CONCLUSION

We found no evidence of decreased TXNIP DNA methylation or increased gene expression in metabolic target tissues of offspring exposed to maternal diabetes. Further studies are needed to confirm and understand the paradoxical SAT TXNIP DNA methylation and gene expression changes in O-GDM subjects.

Differential adipokine DNA methylation and gene expression in subcutaneous adipose tissue from adult offspring of women with diabetes in pregnancy

BACKGROUND

Offspring of women with diabetes in pregnancy are at increased risk of type 2 diabetes mellitus (T2DM), potentially mediated by epigenetic mechanisms. The adipokines leptin, adiponectin, and resistin (genes: LEP, ADIPOQ, RETN) play key roles in the pathophysiology of T2DM. We hypothesized that offspring exposed to maternal diabetes exhibit alterations in epigenetic regulation of subcutaneous adipose tissue (SAT) adipokine transcription. We studied adipokine plasma levels, SAT gene expression, and DNA methylation of LEP, ADIPOQ, and RETN in adult offspring of women with gestational diabetes (O-GDM, N = 82) or type 1 diabetes (O-T1DM, N = 67) in pregnancy, compared to offspring of women from the background population (O-BP, N = 57).

RESULTS

Compared to O-BP, we found elevated plasma leptin and resistin levels in O-T1DM, decreased gene expression of all adipokines in O-GDM, decreased RETN expression in O-T1DM, and increased LEP and ADIPOQ methylation in O-GDM. In multivariate regression analysis, O-GDM remained associated with increased ADIPOQ methylation and decreased ADIPOQ and RETN gene expression and O-T1DM remained associated with decreased RETN expression after adjustment for potential confounders and mediators.

CONCLUSIONS

In conclusion, offspring of women with diabetes in pregnancy exhibit increased ADIPOQ DNA methylation and decreased ADIPOQ and RETN gene expression in SAT. However, altered methylation and expression levels were not reflected in plasma protein levels, and the functional implications of these findings remain uncertain.

Gene Expression and DNA Methylation of PPARGC1A in Muscle and Adipose Tissue From Adult Offspring of Women With Diabetes in Pregnancy

Prenatal exposure to maternal hyperglycemia is associated with an increased risk of later adverse metabolic health. Changes in the regulation of peroxisome proliferator-activated receptor-γ coactivator-1α (PPARGC1A) in skeletal muscle and subcutaneous adipose tissue (SAT) is suggested to play a role in the developmental programming of dysmetabolism based on studies of human subjects exposed to an abnormal intrauterine environment (e.g., individuals with a low birth weight). We studied 206 adult offspring of women with gestational diabetes mellitus (O-GDM) or type 1 diabetes (O-T1D) and of women from the background population (O-BP) using a clinical examination, oral glucose tolerance test, and gene expression and DNA methylation of PPARGC1A in skeletal muscle and SAT. Plasma glucose was significantly higher for both O-GDM and O-T1D compared with O-BP (P < 0.05). PPARGC1A gene expression in muscle was lower in O-GDM compared with O-BP (P = 0.0003), whereas no differences were found between O-T1D and O-BP in either tissue. PPARGC1A DNA methylation percentages in muscle and SAT were similar among all groups. Decreased PPARGC1A gene expression in muscle has previously been associated with abnormal insulin function and may thus contribute to the increased risk of metabolic disease in O-GDM. The unaltered PPARGC1A gene expression in muscle of O-T1D suggests that factors other than intrauterine hyperglycemia may contribute to the decreased PPARGC1A expression in O-GDM.

Gestational diabetes mellitus and long-term consequences for mother and offspring: a view from Denmark

Gestational diabetes mellitus (GDM) is defined as glucose intolerance of varying severity and is present in about 2-6% of all pregnancies in Europe, making it one of the most common pregnancy disorders. Aside from the short-term maternal, fetal and neonatal consequences associated with GDM, there are long-term consequences for both mother and child. Although maternal glucose tolerance often normalises shortly after pregnancy, women with GDM have a substantially increased risk of developing type 2 diabetes later in life. Studies have reported that women are more than seven times as likely to develop diabetes after GDM, and that approximately 50% of mothers with GDM will develop diabetes within 10 years, making GDM one of the strongest predictors of type 2 diabetes. In women with previous GDM, development of type 2 diabetes can be prevented or delayed by lifestyle intervention and/or medical treatment. Systematic follow-up programmes would be ideal to prevent progression of GDM to diabetes, but such programmes are unfortunately lacking in the routine clinical set-up in most countries. Studies have found that the risks of obesity, the metabolic syndrome, type 2 diabetes and impaired insulin sensitivity and secretion in offspring of mothers with GDM are two- to eightfold those in offspring of mothers without GDM. The underlying pathogenic mechanisms behind the abnormal metabolic risk profile in offspring are unknown, but epigenetic changes induced by exposure to maternal hyperglycaemia during fetal life are implicated. Animal studies indicate that treatment can prevent long-term metabolic complications in offspring, but this remains to be confirmed in humans. Thus, diabetes begets diabetes and it is likely that GDM plays a significant role in the global diabetes epidemic. This review summarises a presentation given at the 'Gestational diabetes: what's up?' symposium at the 2015 annual meeting of the EASD. It is accompanied by two other reviews on topics from this symposium (by Marja Vääräsmäki, DOI: 10.1007/s00125-016-3976-6 , and by Cuilin Zhang and colleagues, DOI: 10.1007/s00125-016-3979-3 ) and an overview by the Session Chair, Kerstin Berntorp (DOI: 10.1007/s00125-016-3975-7 ).