Epigenetic changes predisposing to type 2 diabetes in intrauterine growth retardation

Role of Hormones During Gestation and Early Development: Pathways Involved in Developmental Programming

Accumulating evidence suggests that an altered maternal milieu and environmental insults during the intrauterine and perinatal periods of life affect the developing organism, leading to detrimental long-term outcomes and often to adult pathologies through programming effects. Hormones, together with growth factors, play critical roles in the regulation of maternal-fetal and maternal-neonate interfaces, and alterations in any of them may lead to programming effects on the developing organism. In this chapter, we will review the role of sex steroids, thyroid hormones, and insulin-like growth factors, as crucial factors involved in physiological processes during pregnancy and lactation, and their role in developmental programming effects during fetal and early neonatal life. Also, we will consider epidemiological evidence and data from animal models of altered maternal hormonal environments and focus on the role of different tissues in the establishment of maternal and fetus/infant interaction. Finally, we will identify unresolved questions and discuss potential future research directions.

Epigenetics and In Utero Acquired Predisposition to Metabolic Disease

Epidemiological evidence has shown an association between prenatal malnutrition and a higher risk of developing metabolic disease in adult life. An inadequate intrauterine milieu affects both growth and development, leading to a permanent programming of endocrine and metabolic functions. Programming may be due to the epigenetic modification of genes implicated in the regulation of key metabolic mechanisms, including DNA methylation, histone modifications, and microRNAs (miRNAs). The expression of miRNAs in organs that play a key role in metabolism is influenced by in utero programming, as demonstrated by both experimental and human studies. miRNAs modulate multiple pathways such as insulin signaling, immune responses, adipokine function, lipid metabolism, and food intake. Liver is one of the main target organs of programming, undergoing structural, functional, and epigenetic changes following the exposure to a suboptimal intrauterine environment. The focus of this review is to provide an overview of the effects of exposure to an adverse in utero milieu on epigenome with a focus on the molecular mechanisms involved in liver programming.

Cardiovascular Programming During and After Diabetic Pregnancy: Role of Placental Dysfunction and IUGR

Intrauterine growth restriction (IUGR) is a condition whereby a fetus is unable to achieve its genetically determined potential size. IUGR is a global health challenge due to high mortality and morbidity amongst affected neonates. It is a multifactorial condition caused by maternal, fetal, placental, and genetic confounders. Babies born of diabetic pregnancies are usually large for gestational age but under certain conditions whereby prolonged uncontrolled hyperglycemia leads to placental dysfunction, the outcome of the pregnancy is an intrauterine growth restricted fetus with clinical features of malnutrition. Placental dysfunction leads to undernutrition and hypoxia, which triggers gene modification in the developing fetus due to fetal adaptation to adverse utero environmental conditions. Thus, in utero gene modification results in future cardiovascular programming in postnatal and adult life. Ongoing research aims to broaden our understanding of the molecular mechanisms and pathological pathways involved in fetal programming due to IUGR. There is a need for the development of effective preventive and therapeutic strategies for the management of growth-restricted infants. Information on the mechanisms involved with in utero epigenetic modification leading to development of cardiovascular disease in adult life will increase our understanding and allow the identification of susceptible individuals as well as the design of targeted prevention strategies. This article aims to systematically review the latest molecular mechanisms involved in the pathogenesis of IUGR in cardiovascular programming. Animal models of IUGR that used nutrient restriction and hypoxia to mimic the clinical conditions in humans of reduced flow of nutrients and oxygen to the fetus will be discussed in terms of cardiac remodeling and epigenetic programming of cardiovascular disease. Experimental evidence of long-term fetal programming due to IUGR will also be included.

Intrauterine diabetic milieu instigates dysregulated adipocytokines production in F1 offspring

Background

Intrauterine environment plays a pivotal role in the origin of fatal diseases such as the metabolic syndrome. Diabetes is associated with low-grade inflammatory state and dysregulated adipokines production. The aim of this study is to investigate the effect of maternal diabetes on adipocytokines (adiponectin, leptin and TNF-α) production in F1 offspring in rats.

Methods

The offspring groups were as follows: F1 offspring of control mothers under control diet (CD) (CF1-CD), F1 offspring of control mothers under high caloric diet (HCD) (CF1-HCD), F1 offspring of diabetic mothers under CD (DF1-CD), and F1 offspring of diabetic mothers under HCD (DF1-HCD). Every 5 weeks post-natal, 10 pups of each subgroup were culled to obtain blood samples for biochemical analysis.

Results

The results indicate that DF1-CD and DF1-HCD groups exhibited hyperinsulinemia, dyslipidemia, insulin resistance and impaired glucose homeostasis compared to CF1-CD (p > 0.05). DF1-CD and DF1-HCD groups had high hepatic and muscular depositions of TGs. The significant elevated NEFA level only appeared in offspring of diabetic mothers that was fed HCD. DF1-CD and DF1-HCD groups demonstrated low serum levels of adiponectin, high levels of leptin, and elevated levels of TNF-α compared to CF1-CD (p > 0.05). These results reveal the disturbed metabolic lipid profile of offspring of diabetic mothers and could guide further characterization of the mechanisms involved.

Conclusion

Dysregulated adipocytokines production could be a possible mechanism for the transgenerational transmittance of diabetes, especially following a postnatal diabetogenic environment. Moreover, the exacerbating effects of postnatal HCD on NEFA in rats might be prone to adipcytokine dysregulation. Furthermore, dysregulation of serum adipokines is a prevalent consequence of maternal diabetes and could guide further investigations to predict the development of metabolic disturbances.

In Utero Nutritional Manipulation Provokes Dysregulated Adipocytokines Production in F1 Offspring in Rats

Background. Intrauterine environment plays a pivotal role in the origin of fatal diseases such as diabetes. Diabetes and obesity are associated with low-grade inflammatory state and dysregulated adipokines production. This study aims to investigate the effect of maternal obesity and malnutrition on adipokines production (adiponectin, leptin, and TNF-α) in F1 offspring in rats. Materials and Methods. Wistar rats were allocated in groups: F1 offspring of control mothers under control diet (CF1-CD) and under high-fat diet (CF1-HCD), F1 offspring of obese mothers under CD (OF1-CD) and under HCD (OF1-HCD), and F1 offspring of malnourished mothers under CD (MF1-CD) and under HCD (MF1-HCD). Every 5 weeks postnatally, blood samples were obtained for biochemical analysis. Results. At the end of the 30-week follow-up, OF1-HCD and MF1-HCD exhibited hyperinsulinemia, moderate dyslipidemia, insulin resistance, and impaired glucose homeostasis compared to CF1-CD and CF1-HCD. OF1-HCD and MF1-HCD demonstrated low serum levels of adiponectin and high levels of leptin compared to CF1-CD and CF1-HCD. OF1-CD, OF1-HCD, and MF1-HCD had elevated serum levels of TNF-α compared to CF1-CD and CF1-HCD (p < 0.05). Conclusion. Maternal nutritional manipulation predisposes the offspring to development of insulin resistance in their adult life, probably via instigating dysregulated adipokines production.

IGF2 methylation is associated with lipid profile in obese children

AIM

Our aim was to investigate the relationships between the degree of IGF2 methylation and the metabolic status in obese children and adolescents.

SUBJECTS AND METHODS

Eighty-five obese subjects aged 11.6 ± 2.1 years were studied. Anthropometry, metabolic parameters, blood pressure and body composition were assessed. DNA methylation analysis was performed by restriction enzyme digestion assay. The study population was subdivided into two groups according to the percentage of IGF2 cytidine-guanosine (CpG) island methylation.

RESULTS

Twenty-two subjects showed intermediate methylation (a percentage of CpG site methylation comprised between 10 and 60%), 56 were hypomethylated (percentage of methylation lower than 10%), and only 1 showed a high rate of hypermethylation (percentage of methylation above 60%). Children with intermediate methylation showed significantly higher levels of triglycerides (107.6 ± 41.99 vs. 76.6 ± 30.18 mg/dl, p < 0.005) and a higher triglyceride/high-density lipoprotein-cholesterol ratio (2.23 ± 0.98 vs. 1.79 ± 0.98, p < 0.02) compared with hypomethylated children.

CONCLUSIONS

These preliminary findings show for the first time a relationship between IGF2 methylation pattern and lipid profile in obese children. Although the correlation does not imply causation, if our findings are confirmed in further studies, IGF2 methylation might represent an epigenetic marker of metabolic risk.

Physiopathology of intrauterine growth retardation: from classic data to metabolomics

It is well known that adverse conditions during intrauterine life, such as intrauterine growth restriction (IUGR), can result in permanent changes in the physiology and metabolism of the newborn, which in turn leads to an increased risk of disease in adulthood (fetal origin of adult disease hypothesis). In the first part of this review the epidemiological studies in which a correlation between low birth weight and chronic pathologies in adulthood was observed are reported. The second part of the review is focused on metabolomics studies that have revealed an altered metabolism in IUGR patients compared to controls. Together with more classic biomarkers of IUGR, such as endothelin-1, leptin, protein S100B and visfatin, the new holistic metabolomics approach has assumed a crescent role in the identification of disorders in the neonatal metabolic profile, determined by the interconnection of the different processes.