Linking the genetics of type 2 diabetes with low birth weight: a role for prenatal islet maldevelopment?

Mapping the Cord Blood Transcriptome of Pregnancies Affected by Early Maternal Anemia to Identify Signatures of Fetal Programming

CONTEXT

Anemia during early pregnancy (EP) is common in developing countries and is associated with adverse health consequences for both mothers and children. Offspring of women with EP anemia often have low birth weight, which increases risk for cardiometabolic diseases, including type 2 diabetes (T2D), later in life.

OBJECTIVE

We aimed to elucidate mechanisms underlying developmental programming of adult cardiometabolic disease, including epigenetic and transcriptional alterations potentially detectable in umbilical cord blood (UCB) at time of birth.

METHODS

We leveraged global transcriptome- and accompanying epigenome-wide changes in 48 UCB from newborns of EP anemic Tanzanian mothers and 50 controls to identify differentially expressed genes (DEGs) in UCB exposed to maternal EP anemia. DEGs were assessed for association with neonatal anthropometry and cord insulin levels. These genes were further studied in expression data from human fetal pancreas and adult islets to understand their role in beta-cell development and/or function.

RESULTS

The expression of 137 genes was altered in UCB of newborns exposed to maternal EP anemia. These putative signatures of fetal programming, which included the birth weight locus LCORL, were potentially mediated by epigenetic changes in 27 genes and associated with neonatal anthropometry. Among the DEGs were P2RX7, PIK3C2B, and NUMBL, which potentially influence beta-cell development. Insulin levels were lower in EP anemia-exposed UCB, supporting the notion of developmental programming of pancreatic beta-cell dysfunction and subsequently increased risk of T2D in offspring of mothers with EP anemia.

CONCLUSIONS

Our data provide proof-of-concept on distinct transcriptional and epigenetic changes detectable in UCB from newborns exposed to maternal EP anemia.

Prevention of Post-Transplant Diabetes Mellitus: Towards a Personalized Approach

Post-transplant diabetes is a frequent complication after transplantation. Moreover, patients suffering from post-transplant diabetes have increased cardiovascular morbidity and reduced survival. Pathogenesis mainly involves beta-cell dysfunction in presence of insulin resistance. Both pre- and post-transplant risk factors are well-described, and some of them may be corrected or prevented. However, the frequency of post-transplant diabetes has not decreased in recent years. We realized a critical appraisal of preventive measures to reduce post-transplant diabetes.

Revisiting Regulators of Human β-cell Mass to Achieve β-cell-centric Approach Toward Type 2 Diabetes

Type 2 diabetes (T2DM) is characterized by insulin resistance and β-cell dysfunction. Because patients with T2DM have inadequate β-cell mass (BCM) and β-cell dysfunction worsens glycemic control and makes treatment difficult, therapeutic strategies to preserve and restore BCM are needed. In rodent models, obesity increases BCM about 3-fold, but the increase in BCM in humans is limited. Besides, obesity-induced changes in BCM may show racial differences between East Asians and Caucasians. Recently, the developmental origins of health and disease hypothesis, which states that the risk of developing noncommunicable diseases including T2DM is influenced by the fetal environment, has been proposed. It is known in rodents that animals with low birthweight have reduced BCM through epigenetic modifications, making them more susceptible to diabetes in the future. Similarly, in humans, we revealed that individuals born with low birthweight have lower BCM in adulthood. Because β-cell replication is more frequently observed in the 5 years after birth, and β cells are found to be more plastic in that period, a history of childhood obesity increases BCM. BCM in patients with T2DM is reduced by 20% to 65% compared with that in individuals without T2DM. However, since BCM starts to decrease from the stage of borderline diabetes, early intervention is essential for β-cell protection. In this review, we summarize the current knowledge on regulatory factors of human BCM in health and diabetes and propose the β-cell–centric concept of diabetes to enhance a more pathophysiology-based treatment approach for T2DM.

Metabolic Diseases and Down Syndrome: How Are They Linked Together?

Down syndrome is a genetic disorder caused by the presence of a third copy of chromosome 21, associated with intellectual disabilities. Down syndrome is associated with anomalies of both the nervous and endocrine systems. Over the past decades, dramatic advances in Down syndrome research and treatment have helped to extend the life expectancy of these patients. Improved life expectancy is obviously a positive outcome, but it is accompanied with the need to address previously overlooked complications and comorbidities of Down syndrome, including obesity and diabetes, in order to improve the quality of life of Down syndrome patients. In this focused review, we describe the associations between Down syndrome and comorbidities, obesity and diabetes, and we discuss the understanding of proposed mechanisms for the association of Down syndrome with metabolic disorders. Drawing molecular mechanisms through which Type 1 diabetes and Type 2 diabetes could be linked to Down syndrome could allow identification of novel drug targets and provide therapeutic solutions to limit the development of metabolic and cognitive disorders.

Effect of Postnatal Nutritional Environment Due to Maternal Diabetes on Beta Cell Mass Programming and Glucose Intolerance Risk in Male and Female Offspring

Besides the fetal period, the suckling period is a critical time window in determining long-term metabolic health. We undertook the present study to elucidate the impact of a diabetic suckling environment alone or associated with an in utero diabetic environment on beta cell mass development and the risk of diabetes in the offspring in the long term. To that end, we have compared two experimental settings. In setting 1, we used Wistar (W) rat newborns resulting from W ovocytes (oW) transferred into diabetic GK rat mothers (pGK). These oW/pGK neonates were then suckled by diabetic GK foster mothers (oW/pGK/sGK model) and compared to oW/pW neonates suckled by normal W foster mothers (oW/pW/sW model). In setting 2, normal W rat newborns were suckled by diabetic GK rat foster mothers (nW/sGK model) or normal W foster mothers (nW/sW model). Our data revealed that the extent of metabolic disorders in term of glucose intolerance and beta cell mass are similar between rats which have been exposed to maternal diabetes both pre- and postnatally (oW/pGK/sGK model) and those which have been exposed only during postnatal life (nW/sW model). In other words, being nurtured by diabetic GK mothers from birth to weaning was sufficient to significantly alter the beta cell mass, glucose-induced insulin secretion and glucose homeostasis of offspring. No synergistic deleterious effects of pre-and postnatal exposure was observed in our setting.

Beta-cell failure in type 2 diabetes: mechanisms, markers, and clinical implications

It is well known that type 2 diabetes mellitus (T2D) is a globally increasing health burden. Despite recent therapeutic advances and the availability of many different classes of antihyperglycemic therapy, a large proportion of people do not achieve glycemic control. A decline in pancreatic beta-cell function has been defined as a key contributing factor to progression of T2D. In fact, a significant proportion of beta-cell secretory capacity is thought to be lost well before the diagnosis of T2D is made. Several models have been proposed to explain the reduction in beta-cell function, including reduced beta-cell number, beta-cell exhaustion, and dedifferentiation or transdifferentiation into other cell types. However, there have been reports that suggest remission of T2D is possible, and it is believed that beta-cell dysfunction may be, in part, reversible. As such, the question of whether beta cells are committed to failure in people with T2D is complex. It is now widely accepted that early restoration of normoglycemia may protect beta-cell function. Key to the successful implementation of this approach in clinical practice is the appropriate assessment of individuals at risk of beta-cell failure, and the early implementation of appropriate treatment options. In this review, we discuss the progression of T2D in the context of beta-cell failure and describe how C-peptide testing can be used to assess beta-cell function in primary care practice. In conclusion, significant beta-cell dysfunction is likely in individuals with certain clinical characteristics of T2D, such as long duration of disease, high glycated hemoglobin (≥9%), and/or long-term use of therapies that continuously stimulate the beta cell. In these people, measurement of beta-cell status could assist with choice of appropriate therapy to delay or potentially reverse beta-cell dysfunction and the progression of T2D.

Precision medicine in type 2 diabetes

The Precision Medicine Initiative defines precision medicine as 'an emerging approach for disease treatment and prevention that takes into account individual variability in genes, environment and lifestyle for each person'. This approach will facilitate more accurate treatment and prevention strategies in contrast to a one-size-fits-all approach, in which disease treatment and prevention strategies are developed for generalized usage. Diabetes is clearly more heterogeneous than the conventional subclassification into type 1 and type 2 diabetes. Monogenic forms of diabetes like MODY and neonatal diabetes have paved the way for precision medicine in diabetes, as carriers of unique mutations require unique treatment. Diagnosis of diabetes in the past has been dependent upon measuring one metabolite, glucose. By instead including six variables in a clustering analysis, we could break down diabetes into five distinct subgroups, with better prediction of disease progression and outcome. The severe insulin-resistant diabetes (SIRD) cluster showed the highest risk of kidney disease and highest prevalence of nonalcoholic fatty liver disease, whereas patients in the insulin-deficient cluster 2 (SIDD) had the highest risk of retinopathy. In the future, this will certainly be improved and expanded by including genetic, epigenetic and other biomarker to allow better prediction of outcome and choice of more precise treatment.

Intrauterine hyperglycemia induces intergenerational Dlk1-Gtl2 methylation changes in mouse placenta

An intrauterine hyperglycemic environment has long-lasting effects on the offspring. Recent studies focused on fetal tissues, whereas we studied the development and molecular alteration of the placenta. By intercrossing male and female adult control (C) and first-generation offspring mice with gestational diabetes mellitus (F1-GDM), we obtained four groups of second generation (F2) offspring: 1) C♂-C♀, 2) C♂-GDM♀, 3) GDM♂-C♀, 4) GDM♂- GDM♀. Placental weights in F1-GDM offspring were lower than in the control group. Placental weights in F2-offspring decreased through the paternal line. Placental RNA was extracted and analyzed using microarrays on day18.5 of pregnancy. This revealed 35 upregulated imprinted genes and 10 down-regulated imprinted genes. Dlk1and Gtl2 were especially down-regulated and up-regulated, respectively, due to their abnormal methylation status. These findings suggest that intrauterine hyperglycemia decreased placental weight in the first generation, and this was transmitted paternally to the second generation in mice. They also suggest intrauterine hyperglycemia leads to abnormal placental Dlk1-Gtl2 expression due to DNA methylation in first and second generation mice.

Metabolic Stress and Compromised Identity of Pancreatic Beta Cells

Beta cell failure is a central feature of type 2 diabetes (T2D), but the molecular underpinnings of the process remain only partly understood. It has been suggested that beta cell failure in T2D involves massive cell death. Other studies ascribe beta cell failure to cell exhaustion, due to chronic oxidative or endoplasmic reticulum stress leading to cellular dysfunction. More recently it was proposed that beta cells in T2D may lose their differentiated identity, possibly even gaining features of other islet cell types. The loss of beta cell identity appears to be driven by glucotoxicity inhibiting the activity of key beta cell transcription factors including Pdx1, Nkx6.1, MafA and Pax6, thereby silencing beta cell genes and derepressing alternative islet cell genes. The loss of beta cell identity is at least partly reversible upon normalization of glycemia, with implications for the reversibility of T2D, although it is not known if beta cell failure reaches eventually a point of no return. In this review we discuss current evidence for metabolism-driven compromised beta cell identity, key knowledge gaps and opportunities for utility in the treatment of T2D.

Effects of prenatal low protein and postnatal high fat diets on visceral adipose tissue macrophage phenotypes and IL-6 expression in Sprague Dawley rat offspring

Adipose tissue macrophages (ATM) are implicated in adipose tissue inflammation and obesity-related insulin resistance. Maternal low protein models result in fetal programming of obesity. The study aims to answer whether maternal undernutrition by protein restriction affects the ATM M1 or M2 phenotype under postnatal high fat diet in F1 offspring. Using a rat model of prenatal low protein (LP, 8% protein) diet followed by a postnatal high fat energy diet (HE, 45% fat) or low fat normal energy diet (NE, 10% fat) for 12 weeks, we investigated the effects of these diets on adiposity, programming of the offspring ATM phenotype, and the associated inflammatory response in adipose tissue. Fat mass in newborn and 12-week old LP fed offspring was lower than that of normal protein (20%; NP) fed offspring; however, the adipose tissue growth rate was higher compared to the NP fed offspring. While LP did not affect the number of CD68⁺ or CD206⁺ cells in adipose tissue of NE offspring, it attenuated the number of these cells in offspring fed HE. In offspring fed HE, LP offspring had a lower percentage of CD11c⁺CD206⁺ ATMs, whose abundancy was correlated with the size of the adipocytes. Noteworthy, similar to HE treatment, LP increased gene expression of IL-6 within ATMs. Two-way ANOVA showed an interaction of prenatal LP and postnatal HE on IL-6 and IL-1β transcription. Overall, both LP and HE diets impact ATM phenotype by affecting the ratio of CD11c⁺CD206⁺ ATMs and the expression of IL-6.

Down Syndrome-Associated Diabetes Is Not Due To a Congenital Deficiency in β Cells

Aims/Hypothesis:

We sought to establish whether the increased incidence of diabetes associated with Down syndrome was due to a congenital deficit in β cells.

Methods:

The pancreas was obtained at autopsy from nondiabetic subjects with Down syndrome (n = 29) and age-matched nondiabetic control subjects without Down syndrome (n = 28). The pancreas sections were evaluated for the fractional β-cell area.

Results:

No difference was found in the fractional β-cell area between the subjects with Down syndrome and the control subjects.

Conclusions/Interpretations:

The increased incidence and prevalence of diabetes in individuals with Down syndrome is not due to an underlying congenital deficiency of β cells.

Sex-Specific Metabolic Outcomes in Offspring of Female Rats Born Small or Exposed to Stress During Pregnancy

Low birth weight increases adult metabolic disease risk in both the first (F1) and second (F2) generation. Physiological stress during pregnancy in F1 females that were born small induces F2 fetal growth restriction, but the long-term metabolic health of these F2 offspring is unknown. Uteroplacental insufficiency (restricted) or sham (control) surgery was performed in F0 rats. F1 females (control, restricted) were allocated to unstressed or stressed pregnancies. F2 offspring exposed to maternal stress in utero had reduced birth weight. At 6 months, F2 stressed males had elevated fasting glucose. In contrast, F2 restricted males had reduced pancreatic β-cell mass. Interestingly, these metabolic deficits were not present at 12 month. F2 males had increased adrenal mRNA expression of steroidogenic acute regulatory protein and IGF-1 receptor when their mothers were born small or exposed to stress during pregnancy. Stressed control F2 males had increased expression of adrenal genes that regulate androgen signaling at 6 months, whereas expression increased in restricted male and female offspring at 12 months. F2 females from stressed mothers had lower area under the glucose curve during glucose tolerance testing at 12 months compared with unstressed females but were otherwise unaffected. If F1 mothers were either born small or exposed to stress during her pregnancy, F2 offspring had impaired physiological outcomes in a sex- and age-specific manner. Importantly, stress during pregnancy did not exacerbate disease risk in F2 offspring of mothers born small, suggesting that they independently program disease in offspring through different mechanisms.

Assignment of Functional Relevance to Genes at Type 2 Diabetes-Associated Loci Through Investigation of β-Cell Mass Deficits

Type 2 diabetes (T2D) has been associated with a large number of genomic loci, many of which encompass multiple genes without a definitive causal gene. This complexity has hindered efforts to clearly identify functional candidate genes and interpret their role in mediating susceptibility to disease. Here we examined the relevance of individual genes found at T2D-associated loci by assessing their potential contribution to a phenotype relevant to the disease state: production and maintenance of β-cell mass. Using transgenic zebrafish in which β-cell mass could be rapidly visualized in vivo, we systematically suppressed the expression of orthologs of genes found at T2D-associated genomic loci. Overall, we tested 67 orthologs, many of which had no known relevance to β-cell mass, at 62 human T2D-associated loci, including eight loci with multiple candidate genes. In total we identified 25 genes that were necessary for proper β-cell mass, providing functional evidence for their role in a physiological phenotype directly related to T2D. Of these, 16 had not previously been implicated in the regulation of β-cell mass. Strikingly, we identified single functional candidate genes at the majority of the loci for which multiple genes were analyzed. Further investigation into the contribution of the 25 genes to the adaptive capacity of β-cells suggested that the majority of genes were not required for glucose-induced expansion of β-cell mass but were significantly necessary for the regeneration of β-cells. These findings suggest that genetically programmed deficiencies in β-cell mass may be related to impaired maintenance. Finally, we investigated the relevance of our findings to human T2D onset in diabetic individuals from the Old Order Amish and found that risk alleles in β-cell mass genes were associated with significantly younger age of onset and lower body mass index. Taken together, our study offers a functional approach to assign relevance to genes at T2D-associated loci and offers experimental evidence for the defining role of β-cell mass maintenance in genetic susceptibility to T2D onset.

Metabolic predictors of impaired glucose tolerance and type 2 diabetes in a predisposed population--A prospective cohort study

BACKGROUND

We characterized in detail (oral and intravenous glucose tolerance tests (OGTT and IVGTT), euglycemic hyperinsulinemic clamp, adipose tissue biopsy), healthy first-degree relatives (FDR) of individuals with type 2 diabetes (T2D), to examine predictive factors for future development of impaired glucose tolerance (IGT) or T2D.

METHODS

Non-diabetic FDR (n = 138, mean age 40.5 ± 6.5 years, 57 % women) underwent an extended OGTT every 3 years to assess any deterioration in glucose tolerance status. Differences between groups were assessed by logistic fit for continuous variables and by contingency analysis for categorical variables. Multiple logistic regression analysis was applied to adjust for confounding variables.

RESULTS

At follow-up (mean 5.6 ± 2.4 years) 19 subjects had IGT and 4 had T2D. At baseline these 23 subjects had more family members with T2D, higher fasting plasma glucose, higher OGTT plasma glucose at 120 min, higher HbA1c, lower M-value and higher total cholesterol compared to subjects with normal glucose tolerance (NGT). There were significantly larger changes in weight, BMI, fasting plasma glucose, OGTT plasma glucose at 120 min and HbA1c in individuals developing IGT or T2D during the follow-up period than the subjects remaining NGT. Crude predictors of deteriorating glucose tolerance were age, family history of diabetes and of hypertension, OGTT plasma glucose levels at 60 min, 90 min, and 120 min, as well as serum bilirubin, ALP and creatinine (p-values <0.05). A multiple nominal logistic regression model revealed that male sex, low M-value and high physical exercise (p-values <0.05) predicted development of IGT/T2DM.

CONCLUSION

In sum, genetically predisposed individuals for T2D with deteriorating glucose tolerance exhibit insulin resistance as well as beta-cell and signs of adipose tissue dysfunction, emphasizing the multifactorial pathophysiology in the development of IGT and T2D.

Maternal health issues and cardio-metabolic outcomes in the offspring: a focus on Indigenous populations

Non-communicable diseases (NCDs) including diabetes, obesity and cardiovascular disease are the leading causes of death worldwide. Indigenous populations are disproportionally affected. In an effort to halt the increasing disease burden, the mechanisms underlying the increasing rate of NCDs are an important area of study. Recent evidence has focused on the perinatal period as an influential period impacting the future cardio-metabolic health of the offspring. This concept has been defined as metabolic foetal programming and supports the importance of the developmental origins of health and disease in research and clinical practice, specifically in prevention efforts to protect future generations from NCDs. An understanding of the underlying mechanisms involved is not clear as of yet. However, an understanding of these mechanisms is imperative in order to plan effective intervention strategies. As much of the discussion below is gleaned from large epidemiological studies and animal studies, further research with prospective cohorts is necessary.

Indices of insulin resistance and dyslipidemia are correlated with lymphocyte proneness to apoptosis in obese or overweight low birth weight children

AIMS

Our aim was to study the relationship between markers of cell proneness to apoptosis and indices of insulin resistance and dyslipidemia in children born with low birth weight (LBW).

METHODS

The study comprised 177 prepubertal children stratified by birth weight and their nutritional status into LBW (n = 138) and normal birth weight (NBW; n = 39) groups. We analyzed DNA from peripheral blood lymphocytes, separated by pulsed-field gel electrophoresis (PFGE), as well as the serum levels of cholesterol, HDL-cholesterol, triglycerides, fasting insulin and glucose, caspase 3, and BCL2.

RESULTS

LBW children with a BMI SDS >1.55 demonstrated increased content of the large fragments of the lymphocyte DNA [300-500 kb (DNA300-500 kb)] in electrophoretic slides (a marker of decreased chromatin stability and susceptibility of cells to apoptosis) compared to the NBW group. In these children the level of DNA300-500 kb exhibited a strong negative correlation with the serum level of antiapoptotic protein of BCL2 (r = -0.901). DNA300-500 kb significantly correlated with calculated indices of insulin resistance: HOMA-IR and QUICKI as well as with the indices of lipid homeostasis (Castelli and AIP).

CONCLUSIONS

Increased susceptibility of lymphocytes to apoptosis correlated with a higher risk of insulin resistance and lipid disturbance in overweight or obese LBW children. A comprehensive study of the proneness of cells to apoptosis should be implemented to further investigate the pathomechanism of the metabolic syndrome in these children.

A four-stage model explaining the higher risk of Type 2 diabetes mellitus in South Asians compared with European populations

With approximately 1.5 billion people at risk, the staggeringly high risk of Type 2 diabetes in South Asians comprises a global problem. The causes of this high risk are complex, with 23 major risk factors identified in a Lancet seminar. This paper proposes a four-stage explanatory model: (1) the birth of a small, adipose, lowlean mass South Asian baby--the phenotype tracking through life; (2) in childhood and early adulthood, the deposition of any excess energy intake preferentially in upper body and ectopic fat stores rather than in the lower body or superficial subcutaneous fat stores; (3) as a consequence of points 1 and 2, and exacerbated by an environment of low physical activity and excess calories, the accelerated appearance of high levels of plasma insulin, triglycerides and glucose, and the fatty-liver vicious cycle; (4) β-cell failure as a result of fewer β-cells at birth, exposure to apoptotic triggers such as fat in the pancreas, and high demand from insulin resistance, which causes diabetes. Other risk factors--especially energy-dense hyperglycaemic diet and low physical activity--play into this pathway. The recommended behavioural changes fit with this model, which brings clarity to guide future research, policy, practice and health promotion.

The rs11705701 G>A polymorphism of IGF2BP2 is associated with IGF2BP2 mRNA and protein levels in the visceral adipose tissue - a link to type 2 diabetes susceptibility

BACKGROUND

Insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2) regulates translation of IGF2, a growth factor that plays a key role in controlling fetal growth and organogenesis including adipogenesis and pancreatic development. In Caucasians, the rs4402960 G>T polymorphism of IGF2BP2 has been shown to predispose to type 2 diabetes (T2D) in multiple populations. In this study, we tested whether rs4402960 G>T and rs11705701 G>A contribute to the development of T2D in a Russian population.

METHODS

Both markers were genotyped in Russian diabetic (n = 1,470) and non-diabetic patients (n = 1,447) using a Taqman allele discrimination assay. The odds ratio (OR) for the risk of developing T2D was calculated using logistic regression assuming an additive genetic model adjusted for age, sex, HbA1c, hypertension, obesity, and body mass index (BMI). Multivariate linear regression analyses were used to test genotype-phenotype correlations, and adjusted for age, sex, hypertension, obesity, and BMI. Expression of IGF2BP2 in the visceral adipose tissue was quantified using real-time PCR. The content of IGF2BP2 protein and both its isoforms (p58 and p66) in the adipose tissue was measured using Western blot analysis.

RESULTS

There was no significant association between rs4402960 and T2D. Whereas, allele A of rs11705701 was associated with higher T2D risk (OR = 1.19, p < 0.001). Diabetic and non-diabetic carriers of genotype TT (rs4402960) had significantly increased HOMA-IR (p = 0.033 and p = 0.031, respectively). Non-diabetic patients homozygous for AA (rs11705701) had higher HOMA-IR (p = 0.04), lower HOMA-β (p = 0.012), and reduced 2-h insulin levels (p = 0.016). Non-obese individuals (diabetic and non-diabetic) homozygous for either AA (rs11705701) or TT (rs4402960) had higher levels of IGF2BP2 mRNA in the adipose tissue than other IGF2BP2 variants. Also, allele A of rs11705701 was associated with reduced amounts of the short isoform (p58) and increased levels of the long isoform (p66) of the IGF2BP2 protein in adipose tissue of non-obese diabetic and non-diabetic subjects.

CONCLUSIONS

IGF2BP2 genetic variants contribute to insulin resistance in Russian T2D patients. The short protein isoform p58 of IGF2BP2 is likely to play an anti-diabetogenic role in non-obese individuals.

The ontogeny of the endocrine pancreas in the fetal/newborn baboon

Erratic regulation of glucose metabolism including hyperglycemia is a common condition in premature infants and is associated with increased morbidity and mortality. The objective of this study was to examine histological and ultrastructural differences in the endocrine pancreas in fetal (throughout gestation) and neonatal baboons. Twelve fetal baboons were delivered at 125 days (d) gestational age (GA), 140d GA, or 175d GA. Eight animals were delivered at term (185d GA); half were fed for 5 days. Seventy-three nondiabetic adult baboons were used for comparison. Pancreatic tissue was studied using light microscopy, confocal imaging, and electron microscopy. The fetal and neonatal endocrine pancreas islet architecture became more organized as GA advanced. The percent areas of α-β-δ-cell type were similar within each fetal and newborn GA (NS) but were higher than the adults (P<0.05) regardless of GA. The ratio of β cells within the islet (whole and core) increased with gestation (P<0.01). Neonatal baboons, which survived for 5 days (feeding), had a 2.5-fold increase in pancreas weight compared with their counterparts killed at birth (P=0.01). Endocrine cells were also found in exocrine ductal and acinar cells in 125, 140 and 175d GA fetuses. Subpopulation of tissue that coexpressed trypsin and glucagon/insulin shows the presence of cells with mixed endo-exocrine lineage in fetuses. In summary, the fetal endocrine pancreas has no prevalence of a α-β-δ-cell type with larger endocrine cell percent areas than adults. Cells with mixed endocrine/exocrine phenotype occur during fetal development. Developmental differences may play a role in glucose homeostasis during the neonatal period and may have long-term implications.

Pancreatic beta-cell function and type 2 diabetes risk: quantify the causal effect using a Mendelian randomization approach based on meta-analyses

The objective of the study is to quantify the causal effect of β-cell function on type 2 diabetes by minimizing residual confounding and reverse causation. We employed a Mendelian randomization (MR) approach using TCF7L2 variant rs7903146 as an instrument for lifelong levels of β-cell function. We first conducted two sets of meta-analyses to quantify the association of the TCF7L2 variant with the risk of type 2 diabetes among 55 436 cases and 106 020 controls from 66 studies by calculating pooled odds ratio (OR) and to quantify the associations with multiple direct or indirect measures of β-cell function among 35 052 non-diabetic individuals from 31 studies by calculating pooled mean difference. We further applied the method of MR to obtain the causal estimates for the effect of β-cell function on type 2 diabetes risk based on findings from the meta-analyses. The OR [95% confidence interval (CI)] was 0.87 (0.81-0.93) for each five unit increment in homeostasis model assessment of insulin secretion (HOMA-%B) (P = 3.0 × 10(-5)). In addition, for measures based on intravenous glucose tolerance test, ORs (95% CI) associated with type 2 diabetes risk were 0.24 (0.08-0.74) (P = 0.01) and 0.14 (0.04-0.48) (P = 0.002) for per 1 standard deviation increment in insulin sensitivity index and disposition index, respectively. Findings from the present study lend support to a causal role of pancreatic β-cell function itself in the etiology of type 2 diabetes.

Transgenerational glucose intolerance with Igf2/H19 epigenetic alterations in mouse islet induced by intrauterine hyperglycemia

Gestational diabetes mellitus (GDM) has been shown to be associated with high risk of diabetes in offspring. However, the mechanisms involved and the possibilities of transgenerational transmission are still unclear. We intercrossed male and female adult control and first-generation offspring of GDM (F1-GDM) mice to obtain the second-generation (F2) offspring in four groups: C♂-C♀, C♂-GDM♀, GDM♂-C♀, and GDM♂-GDM♀. We found that birth weight significantly increased in F2 offspring through the paternal line with impaired glucose tolerance (IGT). Regardless of birth from F1-GDM with or without IGT, high risk of IGT appeared as early as 3 weeks in F2 offspring and progressed through both parental lineages, especial the paternal line. IGT in male offspring was more obvious than that in females, with parental characteristics and sex-specific transmission. In both F1 and F2 offspring of GDM, the expression of imprinted genes Igf2 and H19 was downregulated in pancreatic islets, caused by abnormal methylation status of the differentially methylated region, which may be one of the mechanisms for impaired islet ultrastructure and function. Furthermore, altered Igf2 and H19 gene expression was found in sperm of adult F1-GDM, regardless of the presence of IGT, indicating that changes of epigenetics in germ cells contributed to transgenerational transmission.

The influence of parental history of diabetes and offspring birthweight on offspring glucose metabolism in adulthood

BACKGROUND

Links are well established between both family history of diabetes and reduced birthweight and increased risk of diabetes in adulthood.

OBJECTIVES

1) To investigate the influence of parental history of type 2 diabetes (T2DM) on offspring birthweight and adult offspring glucose tolerance status in non-diabetic offspring of patients with T2DM and 2) to study the associations of birthweight with measures of pancreatic beta-cell function and insulin sensitivity.

DESIGN

Family cohort study.

POPULATION

Offspring of patients with verified T2DM diagnosed after age 40 years with a spouse without known diabetes.

METHODS

Oral glucose tolerance tests and frequently sampled intravenous glucose tolerance tests (FSIGT) in non-diabetic offspring. Birthweight and length obtained from birth records.

RESULTS

Among 122 offspring with maternal history of T2DM, 14.8% had diabetes compared to 8.0% in 137 offspring with paternal history of diabetes, p=0.09. Offspring with maternal history of T2DM had a mean birthweight 196 g higher than offspring with paternal T2DM (3,651 ± 640 g (mean ± SD) vs. 3,456 ± 472g (p=0.01)). Non-diabetic offspring with birthweights in the lowest tertile had significantly higher plasma glucose levels after an oral glucose tolerance test (OGTT) [Area under the curve(glucOGTT) , mean (95%CI), 1 795 (1 725-1 866) vs. 1 683 (1 613-1 753) mmol/L/min, p=0.02], and lower insulin sensitivity index calculated from a frequently sampled intravenous glucose tolerance test - Si 9.60 [10(-5) (min*pmol/L)(-1) ] (8.23-10.97) vs. 11.79 (10.41-13.18), p=0.02 - in adulthood compared to offspring with birthweights in the upper tertile.

CONCLUSIONS

Offspring with a family history of maternal T2DM have higher birthweights than those with paternal T2DM. Low birthweight associates with elevated plasma glucose levels after an oral glucose load and decreased insulin sensitivity in adulthood.

Metabolomics reveals relationship between plasma inositols and birth weight: possible markers for fetal programming of type 2 diabetes

Epidemiological studies in man and with experimental animal models have shown that intrauterine growth restriction (IUGR) resulting in low birth weight is associated with higher risk of programming welfare diseases in later life. In the pig, severe IUGR occurs naturally and contribute substantially to a large intralitter variation in birth weight and may therefore be a good model for man. In the present paper the natural form of IUGR in pigs was studied close to term by nuclear magnetic resonance (NMR-)based metabolomics. The NMR-based investigations revealed different metabolic profiles of plasma samples from low-birth weight (LW) and high-birth weight (HW) piglets, respectively, and differences were assigned to levels of glucose and myo-inositol. Further studies by GC-MS revealed that LW piglets had a significant higher concentration of myoinositol and D-chiro-inositol in plasma compared to larger littermates. Myo-inositol and D-chiro-inositol have been coupled with glucose intolerance and insulin resistance in adults, and the present paper therefore suggests that IUGR is related to impaired glucose metabolism during fetal development, which may cause type 2 diabetes in adulthood.

The long lifespan and low turnover of human islet beta cells estimated by mathematical modelling of lipofuscin accumulation

AIMS/HYPOTHESIS

Defects in pancreatic beta cell turnover are implicated in the pathogenesis of type 2 diabetes by genetic markers for diabetes. Decreased beta cell neogenesis could contribute to diabetes. The longevity and turnover of human beta cells is unknown; in rodents <1 year old, a half-life of 30 days is estimated. Intracellular lipofuscin body (LB) accumulation is a hallmark of ageing in neurons. To estimate the lifespan of human beta cells, we measured beta cell LB accumulation in individuals aged 1-81 years.

METHODS

LB content was determined by electron microscopical morphometry in sections of beta cells from human (non-diabetic, n = 45; type 2 diabetic, n = 10) and non-human primates (n = 10; 5-30 years) and from 15 mice aged 10-99 weeks. Total cellular LB content was estimated by three-dimensional (3D) mathematical modelling.

RESULTS

LB area proportion was significantly correlated with age in human and non-human primates. The proportion of human LB-positive beta cells was significantly related to age, with no apparent differences in type 2 diabetes or obesity. LB content was low in human insulinomas (n = 5) and alpha cells and in mouse beta cells (LB content in mouse <10% human). Using 3D electron microscopy and 3D mathematical modelling, the LB-positive human beta cells (representing aged cells) increased from >or=90% (<10 years) to >or=97% (>20 years) and remained constant thereafter.

CONCLUSIONS/INTERPRETATION

Human beta cells, unlike those of young rodents, are long-lived. LB proportions in type 2 diabetes and obesity suggest that little adaptive change occurs in the adult human beta cell population, which is largely established by age 20 years.

Glycemia and its relationship to outcomes in the metformin in gestational diabetes trial

OBJECTIVE

To determine how glucose control in women with GDM treated with metformin and/or insulin influenced pregnancy outcomes.

RESEARCH DESIGN AND METHODS

Women randomly assigned to metformin or insulin treatment in the Metformin in Gestational Diabetes (MiG) trial had baseline glucose tolerance test (OGTT) results and A1C documented, together with all capillary glucose measurements during treatment. In the 724 women who had glucose data for analysis, tertiles of baseline glucose values and A1C and of mean capillary glucose values during treatment were calculated. The relationships between maternal factors, glucose values, and outcomes (including a composite of neonatal complications, preeclampsia, and large-for-gestational-age [LGA] and small-for-gestational-age infants) were examined with bivariable and multivariate models.

RESULTS

Baseline OGTT did not predict outcomes, but A1C predicted LGA infants (P = 0.003). During treatment, fasting capillary glucose predicted neonatal complications (P < 0.001) and postprandial glucose predicted preeclampsia (P = 0.016) and LGA infants (P = 0.001). Obesity did not influence outcomes, and there was no interaction between glycemic control, randomized treatment, or maternal BMI in predicting outcomes. The lowest risk of complications was seen when fasting capillary glucose was <4.9 mmol/l (mean +/- SD 4.6 +/- 0.3 mmol/l) compared with 4.9-5.3 mmol/l or higher and when 2-h postprandial glucose was 5.9-6.4 mmol/l (6.2 +/- 0.2 mmol/l) or lower.

CONCLUSIONS

Glucose control in women with gestational diabetes mellitus treated with metformin and/or insulin is strongly related to outcomes. Obesity is not related to outcomes in this group. Targets for fasting and postprandial capillary glucose may need to be lower than currently recommended.