T2DM: Why Epigenetics?

Comprehensive treatment of diabetic endothelial dysfunction based on pathophysiological mechanism

Vascular endothelium is integral to the regulation of vascular homeostasis and maintenance of normal arterial function in healthy individuals. Endothelial dysfunction is a significant contributor to the advancement of atherosclerosis, which can precipitate cardiovascular complications. A notable correlation exists between diabetes and endothelial dysfunction, wherein chronic hyperglycemia and acute fluctuations in glucose levels exacerbate oxidative stress. This results in diminished nitric oxide synthesis and heightened production of endothelin-1, ultimately leading to endothelial impairment. In clinical settings, it is imperative to implement appropriate therapeutic strategies aimed at enhancing endothelial function to prevent and manage diabetes-associated vascular complications. Various antidiabetic agents, including insulin, GLP-1 receptor agonists, sulfonylureas, DPP-4 inhibitors, SGLT2 inhibitors, α-glucosidase inhibitors, thiazolidinediones (TZDs), and metformin, are effective in mitigating blood glucose variability and improving insulin sensitivity by lowering postprandial glucose levels. Additionally, traditional Chinese medicinal compounds, such as turmeric extract, resveratrol, matrine alkaloids, tanshinone, puerarin, tanshinol, paeonol, astragaloside, berberine, and quercetin, exhibit hypoglycemic properties and enhance vascular function through diverse mechanisms. Consequently, larger randomized controlled trials involving both pharmacological and herbal interventions are essential to elucidate their impact on endothelial dysfunction in patients with diabetes. This article aims to explore a comprehensive approach to the treatment of diabetic endothelial dysfunction based on an understanding of its pathophysiology.

DNA Methylation and Type 2 Diabetes: Novel Biomarkers for Risk Assessment?

Diabetes is a severe threat to global health. Almost 500 million people live with diabetes worldwide. Most of them have type 2 diabetes (T2D). T2D patients are at risk of developing severe and life-threatening complications, leading to an increased need for medical care and reduced quality of life. Improved care for people with T2D is essential. Actions aiming at identifying undiagnosed diabetes and at preventing diabetes in those at high risk are needed as well. To this end, biomarker discovery and validation of risk assessment for T2D are critical. Alterations of DNA methylation have recently helped to better understand T2D pathophysiology by explaining differences among endophenotypes of diabetic patients in tissues. Recent evidence further suggests that variations of DNA methylation might contribute to the risk of T2D even more significantly than genetic variability and might represent a valuable tool to predict T2D risk. In this review, we focus on recent information on the contribution of DNA methylation to the risk and the pathogenesis of T2D. We discuss the limitations of these studies and provide evidence supporting the potential for clinical application of DNA methylation marks to predict the risk and progression of T2D.

Phytochemicals as Potential Epidrugs in Type 2 Diabetes Mellitus

Type 2 diabetes Mellitus (T2DM) prevalence has significantly increased worldwide in recent years due to population age, obesity, and modern sedentary lifestyles. The projections estimate that 439 million people will be diabetic in 2030. T2DM is characterized by an impaired β-pancreatic cell function and insulin secretion, hyperglycemia and insulin resistance, and recently the epigenetic regulation of β-pancreatic cells differentiation has been underlined as being involved. It is currently known that several bioactive molecules, widely abundant in plants used as food or infusions, have a key role in histone modification and DNA methylation, and constituted potential epidrugs candidates against T2DM. In this sense, in this review the epigenetic mechanisms involved in T2DM and protein targets are reviewed, with special focus in studies addressing the potential use of phytochemicals as epidrugs that prevent and/or control T2DM in vivo and in vitro. As main findings, and although some controversial results have been found, bioactive molecules with epigenetic regulatory function, appear to be a potential replacement/complementary therapy of pharmacological hypoglycemic drugs, with minimal side effects. Indeed, natural epidrugs have shown to prevent or delay the T2DM development and the morbidity associated to dysfunction of blood vessels, eyes and kidneys due to sustained hyperglycemia in T2DM patients.

Relationship between metabolic syndrome and metabolic syndrome score with β-cell function by gender in non-diabetic Korean populations

Aims: The present study was conducted to assess the association of metabolic syndrome (MetS) and the MetS score (MSS) with β-cell function by gender in Korean non-diabetic populations. Methods: This study used the data from the 2015 Korean National Health and Nutrition Examination Survey including 4380 adults, aged 20 or older. Results: After adjusting for related variables (with exception of body mass index [BMI]), MetS (p < 0.001) and MSS (p < 0.001) were positively associated with homeostasis model assessment of β-cell function (HOMA-B), in both men and women. When further adjusting for BMI, MetS (p = 0.002) and MSS (p = 0.006) were positively associated with HOMA-B in women, whereas the association of MetS (p = 0.140) or MSS (p = 0.697) and HOMA-B was no longer significant in men. Conclusion: MetS and MSS increases were positively associated with β-cell function in non-diabetic Korean women, but not in non-diabetic Korean men.

Public health research needs for molecular epidemiology and to emphasize homeostasis - could the omnipotent endopeptidase inhibitor α-2-macroglobulin be a meaningful biomarker?

Public health authorities in low- and middle-income countries face dramatic challenges in handling rapidly increasing non-communicable diseases (NCDs), due to the epidemiological- and particularly nutritional transition. Among major reasons for the development of NCDs are smoking and alcohol, but overnutrition and obesity are also major threats to population health. Obesity is related to diabetes and cancer, but also has a genetic background. It is difficult to recommend a healthy nutrition. This is because of conflicting nutritional conceptions, and given the complexity of human metabolism understanding this topic can be difficult for the laymen.  Public health measures advocating physical activity and refraining from high intake of energy, sugar and soft drinks need to be enhanced by supporting the ‘intrinsic motivation’ to preserve a good health. The mission of public health should be to increase awareness about the complexity of human metabolism, and the involvement of genetic and epigenetics in health and diseases. To maintain homeostasis, means to keep an optimal relationship between catabolism and synthesis, seems to be of particular interest. Preconditions for this is, that public health institutions within the administration- and academic sector follow up developments in life science and molecular biology and conduct population-based research making use of molecular epidemiology, especially those related to key metabolic steps and maintenance of ‘homeostasis’, in balancing catabolism and anabolism. A prospective biomarker for this situation might be α-2-macroglobulin.

Improved control of non-communicable diseases (NCDs) requires an additional advanced concept for public health - a perspective from a middle-income country

A major consequence of all elements of the 'epidemiological transition' is the rapid emergence of non-communicable diseases (NCDs) in low- and middle-income countries. In contrast to the outcomes of the 'Alma Ata Conference for Primary Health Care', it has not yet been possible to introduce an equally powerful health policy for the prevention and control of NCDs. Major strategies so far are to advise individuals not to smoke and drink alcohol in excess. Additionally, 'healthy' nutrition and increased physical activity are also advocated. Policy for preventing and working against NCDs is now part of the Sustainable Development Goals, specifically target 3.4. So far, attempts to soften the influence of NCDs on the health of the people in low- and middle-income countries have been unsuccessful. It is argued here that additional concepts on how public health could operate against NCDs are needed.  Major risk factors for NCDs interfere with and alter complex steps within the human metabolism.  This paper explores how human metabolism works by assessing advances in molecular biology and research in genetics, epigenetics and gerontology. Recent developments in these scientific disciplines shed light on the complexity of how human health is maintained and diseases are invoked. Public health bodies should be aware, interested and possibly contribute to the aforementioned areas of interest, as far as NCDs are concerned, and translate major developments in a way, that could be useful in improving population health.

Insulin-Like Growth Factor Binding Protein 2 (IGFBP-2) and the Risk of Developing Type 2 Diabetes

Recent studies suggest that insulin-like growth factor binding protein 2 (IGFBP-2) may protect against type 2 diabetes, but population-based human studies are scarce. We aimed to investigate the prospective association of circulating IGFBP-2 concentrations and of differential methylation in the IGFBP-2 gene with type 2 diabetes risk.

Gender difference in the relationship between the ferritin and homeostasis model assessment of insulin resistance in non-diabetic Korean adults

Background

The present study was conducted to assess gender difference in the relationship between the ferritin and homeostasis model assessment of insulin resistance (HOMA-IR) and beta cell function (HOMA-B) in non-diabetic Korean adults.

Materials and methods

A sample including 5,414 adults (2,279 men, 1,529 postmenopausal women, and 1,606 premenopausal women) aged ≥ 20 years from the fifth Korean National Health and Nutrition Examination Survey (KNHANES V-1, 2010) was analyzed.

Results

There were several key findings in the present study. First, in men, HOMA-IR (β = 0.119, 95% confidence interval [CI], 3.304 to 8.003) constituted the independent factor determining ferritin, but this was not the case for HOMA-B (β = -0.042, 95% CI, -0.100 to 0.011). Second, in postmenopausal women, HOMA-IR (β = 0.087, 95% CI, 0.899 to 5.238) was the independent factor determining ferritin, but this was not the case for HOMA-B (β = -0.043, 95% CI, -0.065 to 0.010). Third, in premenopausal women, neither HOMA-IR (β = -0.050, 95% CI, -3.056 to 0.364) nor HOMA-B (β = -0.009, 95% CI, -0.028 to 0.020) constituted the independent factors determining ferritin.

Conclusions

Ferritin was positively associated with insulin resistance in non-diabetic Korean men and postmenopausal women, but not in non-diabetic Korean premenopausal women.

Relationship between homeostasis model assessment of insulin resistance and beta cell function and serum 25-hydroxyvitamin D in non-diabetic Korean adults

The purpose of this study is to look at these relationships in non-diabetic Korean adults. This study was based on data from the KNHANES V-1, which is representative of the population of Korea. A total of 5,492 participants (≥20 years in age) without type 1 or type 2 diabetes, assessed for serum 25-hydroxyvitamin D [25(OH)D], fasting blood glucose and insulin, as well as anthropometric variables, were included in the analyses. The key study results were as follows: First, vitamin D status [vitamin D deficient, 25(OH)D <25 nM; vitamin D insufficient, 25(OH)D ≥25, <50 nM; vitamin D sufficient, 25(OH)D ≥50 nM] was inversely associated with homeostasis model assessment of insulin resistance (HOMA-IR) and beta cell function (HOMA-B) in model 2 (adjusted for age and gender) and 3 (further adjusted for smoking, alcohol drinking, regular exercise, systolic and diastolic blood pressure, waist circumference, and body mass index). Second, in model 4, when further adjusted for total cholesterol, triglycerides, and HDL-C, vitamin D status was inversely associated with HOMA-B. However, association of vitamin D status and HOMA-IR was no longer significant. In conclusion, vitamin D was inversely associated with beta cell function in non-diabetic Korean adults but was not associated with insulin resistance.

Relationship between homeostasis model assessment of insulin resistance and beta cell function and serum 25-hydroxyvitamin D in non-diabetic Korean adults

The purpose of this study is to look at these relationships in non-diabetic Korean adults. This study was based on data from the KNHANES V-1, which is representative of the population of Korea. A total of 5,492 participants (≥20 years in age) without type 1 or type 2 diabetes, assessed for serum 25-hydroxyvitamin D [25(OH)D], fasting blood glucose and insulin, as well as anthropometric variables, were included in the analyses. The key study results were as follows: First, vitamin D status [vitamin D deficient, 25(OH)D <25 nM; vitamin D insufficient, 25(OH)D ≥25, <50 nM; vitamin D sufficient, 25(OH)D ≥50 nM] was inversely associated with homeostasis model assessment of insulin resistance (HOMA-IR) and beta cell function (HOMA-B) in model 2 (adjusted for age and gender) and 3 (further adjusted for smoking, alcohol drinking, regular exercise, systolic and diastolic blood pressure, waist circumference, and body mass index). Second, in model 4, when further adjusted for total cholesterol, triglycerides, and HDL-C, vitamin D status was inversely associated with HOMA-B. However, association of vitamin D status and HOMA-IR was no longer significant. In conclusion, vitamin D was inversely associated with beta cell function in non-diabetic Korean adults but was not associated with insulin resistance.

Persistent Chromatin Modifications Induced by High Fat Diet

Obesity is a highly heritable complex disease that results from the interaction of multiple genetic and environmental factors. Formerly obese individuals are susceptible to metabolic disorders later in life, even after lifestyle changes are made to mitigate the obese state. This is reminiscent of the metabolic memory phenomenon originally observed for persistent complications in diabetic patients, despite subsequent glycemic control. Epigenetic modifications represent a potential mediator of this observed memory. We previously demonstrated that a high fat diet leads to changes in chromatin accessibility in the mouse liver. The regions of greatest chromatin changes in accessibility are largely strain-dependent, indicating a genetic component in diet-induced chromatin alterations. We have now examined the persistence of diet-induced chromatin accessibility changes upon diet reversal in two strains of mice. We find that a substantial fraction of loci that undergo chromatin accessibility changes with a high fat diet remains in the remodeled state after diet reversal in C57BL/6J mice. In contrast, the vast majority of diet-induced chromatin accessibility changes in A/J mice are transient. Our data also indicate that the persistent chromatin accessibility changes observed in C57BL/6J mice are associated with specific transcription factors and histone post-translational modifications. The persistent loci identified here are likely to be contributing to the overall phenotype and are attractive targets for therapeutic intervention.

The early life origin theory in the development of cardiovascular disease and type 2 diabetes

Life expectancy has been examined from a variety of perspectives in recent history. Epidemiology is one perspective which examines causes of morbidity and mortality at the population level. Over the past few 100 years there have been dramatic shifts in the major causes of death and expected life length. This change has suffered from inconsistency across time and space with vast inequalities observed between population groups. In current focus is the challenge of rising non-communicable diseases (NCD), such as cardiovascular disease and type 2 diabetes mellitus. In the search to discover methods to combat the rising incidence of these diseases, a number of new theories on the development of morbidity have arisen. A pertinent example is the hypothesis published by David Barker in 1995 which postulates the prenatal and early developmental origin of adult onset disease, and highlights the importance of the maternal environment. This theory has been subject to criticism however it has gradually gained acceptance. In addition, the relatively new field of epigenetics is contributing evidence in support of the theory. This review aims to explore the implication and limitations of the developmental origin hypothesis, via an historical perspective, in order to enhance understanding of the increasing incidence of NCDs, and facilitate an improvement in planning public health policy.

Twin methodology in epigenetic studies

Since the final decades of the last century, twin studies have made a remarkable contribution to the genetics of human complex traits and diseases. With the recent rapid development in modern biotechnology of high-throughput genetic and genomic analyses, twin modelling is expanding from analysis of diseases to molecular phenotypes in functional genomics especially in epigenetics, a thriving field of research that concerns the environmental regulation of gene expression through DNA methylation, histone modification, microRNA and long non-coding RNA expression, etc. The application of the twin method to molecular phenotypes offers new opportunities to study the genetic (nature) and environmental (nurture) contributions to epigenetic regulation of gene activity during developmental, ageing and disease processes. Besides the classical twin model, the case co-twin design using identical twins discordant for a trait or disease is becoming a popular and powerful design for epigenome-wide association study in linking environmental exposure to differential epigenetic regulation and to disease status while controlling for individual genetic make-up. It can be expected that novel uses of twin methods in epigenetic studies are going to help with efficiently unravelling the genetic and environmental basis of epigenomics in human complex diseases.

Type 2 diabetes mellitus in relation to global LINE-1 DNA methylation in peripheral blood: a cohort study

In the last years, epigenetic processes have emerged as a promising area of complex diseases research. DNA methylation measured in Long Interspersed Nucleotide Element 1 (LINE-1) sequences has been considered a surrogate marker for global genome methylation. New findings have suggested the potential involvement of epigenetic mechanisms in Type 2 diabetes (T2DM) as a crucial interface between the effects of genetic predisposition and environmental influences. Our study evaluated whether global DNA methylation predicted increased risk from T2DM or other carbohydrate metabolism disorders in a cohort study. We used a prospective cohort intervention study and a control group. We collected phenotypic, anthropometric, biochemical, and nutritional information from all subjects. Global LINE-1 DNA methylation was quantified by pyrosequencing technology. Subjects that did not improve their carbohydrate metabolism status showed lower levels of global LINE-1 DNA methylation (63.9 ± 1.7 vs. 64.7 ± 2.4) and they practiced less intense physical activity (5.8% vs. 21.5%). Logistic regression analyses showed a significant association between LINE-1 DNA methylation and metabolic status after adjustment for sex, age, BMI, and physical activity. Our study showed that lower LINE-1 DNA methylation levels were associated with a higher risk metabolic status worsening, independent of other classic risk factors. This finding highlights the potential role for epigenetic biomarkers as predictors of T2DM risk or other related metabolic disorders.

You are what you eat, or are you? The challenges of translating high-fat-fed rodents to human obesity and diabetes

Obesity and type 2 diabetes mellitus (T2DM) are rapidly growing worldwide epidemics with major health consequences. Various human-based studies have confirmed that both genetic and environmental factors (particularly high-caloric diets and sedentary lifestyle) greatly contribute to human T2DM. Interactions between obesity, insulin resistance and β-cell dysfunction result in human T2DM, but the mechanisms regulating the interplay among these impairments remain unclear. Rodent models of high-fat diet (HFD)-induced obesity have been used widely to study human obesity and T2DM. With >9000 publications on PubMed over the past decade alone, many aspects of rodent T2DM have been elucidated; however, correlation to human obesity/diabetes remains poor. This review investigates the reasons for this translational discrepancy by critically evaluating rodent HFD models. Dietary modification in rodents appears to have limited translatable benefit for understanding and treating human obesity and diabetes due—at least in part—to divergent dietary compositions, species/strain and gender variability, inconsistent disease penetrance, severity and duration and lack of resemblance to human obesogenic pathophysiology. Therefore future research efforts dedicated to acquiring translationally relevant data—specifically human data, rather than findings based on rodent studies—would accelerate our understanding of disease mechanisms and development of therapeutics for human obesity/T2DM.

Exposure to bisphenol-A during pregnancy partially mimics the effects of a high-fat diet altering glucose homeostasis and gene expression in adult male mice

Bisphenol-A (BPA) is one of the most widespread EDCs used as a base compound in the manufacture of polycarbonate plastics. The aim of our research has been to study how the exposure to BPA during pregnancy affects weight, glucose homeostasis, pancreatic β-cell function and gene expression in the major peripheral organs that control energy flux: white adipose tissue (WAT), the liver and skeletal muscle, in male offspring 17 and 28 weeks old. Pregnant mice were treated with a subcutaneous injection of 10 µg/kg/day of BPA or a vehicle from day 9 to 16 of pregnancy. One month old offspring were divided into four different groups: vehicle treated mice that ate a normal chow diet (Control group); BPA treated mice that also ate a normal chow diet (BPA); vehicle treated animals that had a high fat diet (HFD) and BPA treated animals that were fed HFD (HFD-BPA). The BPA group started to gain weight at 18 weeks old and caught up to the HFD group before week 28. The BPA group as well as the HFD and HFD-BPA ones presented fasting hyperglycemia, glucose intolerance and high levels of non-esterified fatty acids (NEFA) in plasma compared with the Control one. Glucose stimulated insulin release was disrupted, particularly in the HFD-BPA group. In WAT, the mRNA expression of the genes involved in fatty acid metabolism, Srebpc1, Pparα and Cpt1β was decreased by BPA to the same extent as with the HFD treatment. BPA treatment upregulated Pparγ and Prkaa1 genes in the liver; yet it diminished the expression of Cd36. Hepatic triglyceride levels were increased in all groups compared to control. In conclusion, male offspring from BPA-treated mothers presented symptoms of diabesity. This term refers to a form of diabetes which typically develops in later life and is associated with obesity.

Insulin downregulates the expression of the Ca2+-activated nonselective cation channel TRPM5 in pancreatic islets from leptin-deficient mouse models

We recently proposed that the transient receptor potential melastatin 5 (TRPM5) cation channel contributes to glucose-induced electrical activity of the β cell and positively influences glucose-induced insulin release and glucose homeostasis. In this study, we investigated Trpm5 expression and function in pancreatic islets from mouse models of type II diabetes. Gene expression analysis revealed a strong reduction of Trpm5 mRNA levels in pancreatic islets of db/db and ob/ob mice. The glucose-induced Ca²⁺ oscillation pattern in db/db and ob/ob islets mimicked those of Trpm5^−/− islets. Leptin treatment of ob/ob mice not only reversed the diabetic phenotype seen in these mice but also upregulated Trpm5 expression. Leptin treatment had no additional effect on Trpm5 expression levels when plasma insulin levels were comparable to those of the vehicle-injected control group. In murine β cell line, MIN6, insulin downregulated TRPM5 expression in a dose-dependent manner, unlike glucose or leptin. In conclusion, our data show that increased plasma insulin levels downregulate TRPM5 expression in pancreatic islets from leptin-deficient mouse models of type 2 diabetes.

Cellular and molecular mechanisms of endothelial dysfunction in diabetes

In healthy individuals, the vascular endothelium regulates an intricate balance of factors that maintain vascular homeostasis and normal arterial function. Functional disruption of the endothelium is known to be an early event that underlies the development of subsequent cardiovascular disease (CVD) including atherosclerosis and coronary heart disease. In addition, the rising global epidemic of type 2 diabetes is a significant problem conferring a significantly higher risk of CVD to individuals in whom endothelial dysfunction is also notable. This review first summarises the role of endothelium in health and explores and evaluates the impact of diabetes on endothelial function. The characteristic features of insulin resistance and other metabolic disturbances that may underlie long-term changes in vascular endothelial function (metabolic memory) are described along with proposed cellular, molecular and epigenetic mechanisms. Through understanding the underlying mechanisms, novel targets for future therapies to restore endothelial homeostasis and 'drive' a reparative cellular phenotype are explored.

Variation in ultraviolet radiation and diabetes: evidence of an epigenetic effect that modulates diabetics' lifespan

Background

Published research has shown that month-of-birth variations modulate the incidence of adult human diseases. This article explores diabetes type 2 as one of those diseases. This study uses the death records of approximately 829,000 diabetics (approximately 90% were type-2) born before the year 1945 (and dying between 1979 and 2005) to show that variations in adult lifespan vary with ultraviolet radiation (UVR) at solar cycle peaks (MAX, approximately a three-year period) with less at non-peaks (MIN, approximately an eight-year period). The MAX minus MIN (in years) was our measure of sensitivity (for example, responsiveness) to long-term variations in UVR.

Results

Diabetics were less sensitive than non-diabetics, and ethnic minorities were more sensitive than whites. Diabetic males gained 6.1 years, and females 2.3 years over non-diabetics, with diabetic males gaining an average of 3.8 years over diabetic females. Most variation in lifespan occurred in those conceived around the seasonal equinoxes, suggesting that the human epigenome at conception is especially influenced by rapid variation in UVR. With rapidly decreasing UVR at conception, lifespan decreased in the better-nourished, white, female diabetic population.

Conclusions

Rapidly changing UVR at the equinoxes modulates the expression of an epigenome involving the conservation of energy, a mechanism especially canalized in women. Decreasing UVR at conception and early gestation stimulates energy conservation in persons we consider ‘diabetic’ in today’s environment of caloric surfeit. In the late 19th and early 20th centuries ethnic minorities had poorer nutrition, laborious work, and leaner bodies, and in that environment a calorie-conserving epigenome was a survival advantage. Ethnic minorities with a similar epigenome lived long enough to express diabetes as we define it today and exceeded the lifespan of their non-diabetic contemporaries, while that epigenome in diabetics in the nutritional environment of today is detrimental to lifespan.

Epigenetic changes in diabetes

Diabetes is a multifactorial disease with numerous pathways influencing its progression and recent observations suggest that the complexity of the disease cannot be entirely accounted for by genetic predisposition. A compelling argument for an epigenetic component is rapidly emerging. Epigenetic processes at the chromatin template significantly sensitize transcriptional and phenotypic outcomes to environmental signaling information including metabolic state, nutritional requirements and history. Epigenetic mechanisms impact gene expression that could predispose individuals to the diabetic phenotype during intrauterine and early postnatal development, as well as throughout adult life. Furthermore, epigenetic changes could account for the accelerated rates of chronic and persistent microvascular and macrovascular complications associated with diabetes. Epidemiological and experimental animal studies identified poor glycemic control as a major contributor to the development of diabetic complications and highlight the requirement for early intervention. Early exposure to hyperglycemia can drive the development of complications that manifest late in the progression of the disease and persist despite improved glycemic control, indicating a memory of the metabolic insult. Understanding the molecular events that underlie these transcriptional changes will significantly contribute to novel therapeutic interventions to prevent, reverse or retard the deleterious effects of the diabetic milieu.

Twins for epigenetic studies of human aging and development

Most of the complex traits including aging phenotypes are caused by the interaction between genome and environmental conditions and the interface of epigenetics may be a central mechanism. Although modern technologies allow us high-throughput profiling of epigenetic patterns already at genome level, our understanding of genetic and environmental influences on the epigenetic processes remains limited. Twins are of special interest for genetic studies due to their genetic similarity and rearing-environment sharing. The classical twin design has made a great contribution in dissecting the genetic and environmental contributions to human diseases and complex traits. In the era of functional genomics, the valuable sample of twins is helping to bridge the gap between gene activity and the environments through epigenetic mechanisms unlimited by DNA sequence variations. We propose to extend the classical twin design to study the aging-related molecular epigenetic phenotypes and link them with environmental exposures especially early life events. Different study designs and application issues will be highlighted and novel approaches introduced with aim at making uses of twins in assessing the environmental impact on epigenetic changes during development and in the aging process.

Cytomegalovirus seropositivity is associated with glucose regulation in the oldest old. Results from the Leiden 85-plus Study

Background

Cytomegalovirus (CMV) infection has been reported to contribute to the pathogenesis of type 1 diabetes and post-transplantation diabetes. However, CMV infection has not been evaluated as a possible risk factor for type 2 diabetes. Our aim was to investigate potential associations between CMV seropositivity, CMV IgG antibody level and glucose regulation in the oldest old.

Results

CMV seropositive subjects were more likely to have type 2 diabetes (17.2% vs 7.9%, p = 0.016), had a higher level of HbA1c (p = 0.014) and higher non-fasting glucose (p = 0.024) in the oldest olds. These associations remained significant after adjustment for possible confounders. CMV IgG antibody level was not significantly associated with glucose regulation (all p > 0.05).

Conclusions

In the oldest old, CMV seropositivity is significantly associated with various indicators of glucose regulation. This finding suggests that CMV infection might be a risk factor for the development of type 2 diabetes in the elderly.