Pdx1 regulates pancreas tubulogenesis and E-cadherin expression.

Current efforts in developing treatments for diabetes focus on in vitro generation of functional ß-cells for cell replacement therapies; however, these attempts have only been partly successful because factors involved in islet formation remain incompletely understood. The embryonic pancreas, which gives rise to ß-cells, undergoes early epithelial rearrangements, including transient stratification of an initially monolayered epithelium, followed by microlumen formation and later resolution into branches. Within the epithelium, a multipotent progenitor cell (MPC) population is specified, giving rise to three important lineages: acinar, ductal and endocrine. Pdx1 is a transcription factor required for pancreas development and lineage specification; however, few Pdx1 targets that regulate pancreatogenesis have been identified. We find that pancreatic defects in Pdx1(-/-) embryos initiate at the time when the progenitor pool is specified and the epithelium should resolve into branches. Pdx1(-/-) microlumen diameters expand aberrantly, resulting in failure of epithelial tubulogenesis and ductal plexus formation. Pdx1(-/-) epithelial cell proliferation is decreased and the MPC pool is rapidly lost. We identify two conserved Pdx1 binding sites in the epithelial cadherin (E-cad, Cdh1) promoter, and show that Pdx1 directly binds and activates E-cad transcription. In addition, Pdx1 is required in vivo for maintenance of E-cad expression, actomyosin complex activity and cell shape. These findings demonstrate a novel link between regulators of epithelial architecture, specification of pancreatic cell fate and organogenesis.

Aberrant DNA methylation as a diagnostic biomarker of diabetic embryopathy.

PURPOSE: Maternal diabetes is a known teratogen that can cause a wide spectrum of birth defects, collectively referred to as diabetic embryopathy (DE). However, the pathogenic mechanisms underlying DE remain uncertain and there are no definitive tests to establish the diagnosis. Here, we explore the potential of DNA methylation as a diagnostic biomarker for DE and to inform disease pathogenesis. METHODS: Bisulfite sequencing was used to identify gene regions with differential methylation between DE neonates and healthy infants born with or without prenatal exposure to maternal diabetes, and to investigate the role of allele-specific methylation at implicated sites. RESULTS: We identified a methylation signature consisting of 237 differentially methylated loci that distinguished infants with DE from control infants. These loci were found proximal to genes associated with Mendelian syndromes that overlap the DE phenotype (e.g., CACNA1C, TRIO, ANKRD11) or genes known to influence embryonic development (e.g., BRAX1, RASA3). Further, we identified allele-specific methylation (ASM) at 11 of these loci, within which 61.5% of ASM single-nucleotide variants are known expression quantitative trait loci (eQTLs). CONCLUSIONS: Our study suggests a role for aberrant DNA methylation and cis-sequence variation in the pathogenesis of DE and highlights the diagnostic potential of DNA methylation for teratogenic birth defects.

On the diabetic menu: zebrafish as a model for pancreas development and function.

Development of the vertebrate pancreas is a complex stepwise process comprising regionalization, cell differentiation, and morphogenesis. Studies in zebrafish are contributing to an emerging picture of pancreas development in which extrinsic signaling molecules influence intrinsic transcriptional programs to allow ultimate differentiation of specific pancreatic cell types. Zebrafish experiments have revealed roles for several signaling molecules in aspects of this process; for example our own work has shown that retinoic acid signals specify the pre-pancreatic endoderm. Time-lapse imaging of live zebrafish embryos has started to provide detailed information about early pancreas morphogenesis. In addition to modeling embryonic development, the zebrafish has recently been used as a model for pancreas regeneration studies. Here, we review the significant progress in these areas and consider the future potential of zebrafish as a diabetes research model.

YIPF5 mutations cause neonatal diabetes and microcephaly through endoplasmic reticulum stress.

Neonatal diabetes is caused by single gene mutations reducing pancreatic ß cell number or impairing ß cell function. Understanding the genetic basis of rare diabetes subtypes highlights fundamental biological processes in ß cells. We identified 6 patients from 5 families with homozygous mutations in the YIPF5 gene, which is involved in trafficking between the endoplasmic reticulum (ER) and the Golgi. All patients had neonatal/early-onset diabetes, severe microcephaly, and epilepsy. YIPF5 is expressed during human brain development, in adult brain and pancreatic islets. We used 3 human ß cell models (YIPF5 silencing in EndoC-ßH1 cells, YIPF5 knockout and mutation knockin in embryonic stem cells, and patient-derived induced pluripotent stem cells) to investigate the mechanism through which YIPF5 loss of function affects ß cells. Loss of YIPF5 function in stem cell-derived islet cells resulted in proinsulin retention in the ER, marked ER stress, and ß cell failure. Partial YIPF5 silencing in EndoC-ßH1 cells and a patient mutation in stem cells increased the ß cell sensitivity to ER stress-induced apoptosis. We report recessive YIPF5 mutations as the genetic cause of a congenital syndrome of microcephaly, epilepsy, and neonatal/early-onset diabetes, highlighting a critical role of YIPF5 in ß cells and neurons. We believe this is the first report of mutations disrupting the ER-to-Golgi trafficking, resulting in diabetes.

Diabetes and apoptosis: neural crest cells and neural tube.

Birth defects resulting from diabetic pregnancy are associated with apoptosis of a critical mass of progenitor cells early during the formation of the affected organ(s). Insufficient expression of genes that regulate viability of the progenitor cells is responsible for the apoptosis. In particular, maternal diabetes inhibits expression of a gene, Pax3, that encodes a transcription factor which is expressed in neural crest and neuroepithelial cells. As a result of insufficient Pax3, cardiac neural crest and neuroepithelial cells undergo apoptosis by a process dependent on the p53 tumor suppressor protein. This, then provides a cellular explanation for the cardiac outflow tract and neural tube and defects induced by diabetic pregnancy.

Cerebrovascular risk factors and incident depression in community-dwelling elderly.

OBJECTIVE: The 'vascular depression' hypothesis suggests that late-life depression results from vascular brain damage. We studied the longitudinal association between cerebrovascular risk factors and incident depression in a large population-based study. METHOD: Two thousand nine hundred and thirty-one persons with the age of > or =61 years were followed up. Data on a comprehensive set of cerebrovascular risk factors were collected at baseline. Participants received a psychiatric assessment 5 years later to establish DSM-IV diagnoses. RESULTS: Only current smoking and antihypertensive drug use were independently associated with incident depressive symptoms. Diabetes mellitus and the Framingham stroke risk score were related to incident depressive disorder. No relation with depression was observed for cholesterol, diastolic and systolic blood pressure, history of cardiovascular disease, atrial fibrillation, left ventricular hypertrophy or the use of statins and anticoagulants. CONCLUSION: These results moderately support the 'vascular depression' hypothesis.

Gestational diabetes mellitus manifests in all trimesters of pregnancy.

Screening for GDM is usually performed around 24-28 weeks of gestational age. We undertook a study to estimate the prevalence of glucose intolerance during different trimesters, as data in this aspect is sparse. A total of 4151 consecutive pregnant women irrespective of gestational weeks attending antenatal health posts across Chennai city underwent a 75 g OGTT recommended by WHO and diagnosed GDM if 2 hr PG value > or =140 mg/dl. Women who had normal OGTT at the first visit were screened with a repeat OGTT at the subsequent visits. Among the screened, 741 women (17.9%) had 2 hr PG> or =140 mg/dl and were identified to have gestational diabetes. Analysis based on gestational weeks revealed that out of the 741 GDM women, 121 (16.3%) were within 16 weeks, 166 (22.4%) were between 17 and 23 weeks and 454 (61.3%) were more than 24 weeks of gestation. Observation in this study was that 38.7% developed gestational diabetes even prior to 24th week of gestation. Out of the total 741 GDM women, 214 (28.9%) were diagnosed on repeat testing at subsequent visits. Glucose intolerance occurs in the early weeks of gestation. Women who had normal glucose tolerance in the first visit require repeat OGTT in the subsequent visits.

Embryonic oxidative stress as a mechanism of teratogenesis with special emphasis on diabetic embryopathy.

Reactive oxygen species (ROS) are involved in the etiology of numerous diseases including cardio-vascular diseases and diabetes mellitus. There is evidence that several teratogens affect the developing embryo by increasing its oxidative stress and, because of its relatively weak antioxidant defense, especially at the early stages of organogenesis, result in severe embryonic damage. This mechanism seems to operate in diabetes-induced embryonic damage as well as in the mechanism of teratogenicity caused by ionizing radiation, hypoxia, alcohol and cocaine use and cigarette smoking. We studied the role of oxidative stress in diabetic induced embryopathy, both in vivo and in vitro. Under diabetic condition there was a significant decrease in the activity of endogenous antioxidant enzymes and of vitamins C and E in the embryos and their yolk sacs. The lowest activity was observed in the malformed experimental embryos when compared to experimental embryos without anomalies. Similar results were obtained in the Cohen diabetic rats, where the diabetic prone (CDs) rats were unable to increase their antioxidant enzyme activity in spite of the diabetes. Studies performed by other investigators show similar results. Human and animal studies show that the main mechanism of fetal damage induced by high levels of ionizing irradiation, cocaine and alcohol abuse, hypoxia and cigarette smoking is also by increased embryonic oxidative stress. Similarly, several drugs exert their teratogenic activity via embryonic oxidative stress. Abnormal placentation may also cause enhanced placental oxidative stress, resulting in embryonic death, preeclampsia or congenital anomalies. Inability of the developing embryo to cope with that stress may result in embryonic death and/or congenital anomalies. Animal studies also show that a variety of antioxidants are effective in decreasing the damaging effects of heightened oxidative stress induced by teratogens. Effective antioxidants, which might also be of clinical use, include vitamins C and E, carotenoids, folic acid, as well as synthetic products. Appropriate clinical studies with antioxidants in pregnancies of high risk to develop oxidative stress are needed, since non-toxic antioxidants might prove an efficient and inexpensive way to reduce the rate of some serious and sometimes fatal congenital anomalies.

[Evidence and mechanisms of fetal origins of adult diseases].

This review focuses on the fetal origins of adult disease hypothesis put forward by David Barker and his colleagues, recent advances in epidemiological studies and experimental research in this field. Barker Hypothesis states that environmental factors, particularly intrauterine nutrition, as indicated by birth weight, operate in early life to program the risks for adverse health outcomes in adult life. A large growing body of reports described the association between the early development and adult diseases, such as diabetes, hypertension, coronary heart disease, abnormal lipids metabolism, obesity and cancer, etc. Experimental studies show that the changes of some key genes' expression, caused by epigenetic modifications, lead to a permanent alteration of cellular proliferation and differentiation and finally the genesis in key tissues and organs. These results bring about the impairment in structures and functions and the increased susceptibility to chronic diseases in adult life. The hypothesis provides a new perspective for the prevention and therapy of chronic diseases.

Intrauterine environment and later disease development: infertility treatment and the risk of diabetes in offspring.

The phenotype of an individual, including their susceptibility to disease, is governed by several factors including parental genes and intrauterine environment. Thus, the risk of developing Type 2 diabetes is modulated by the inheritance of specific genetic variants that are slowly being characterised by the techniques of linkage analysis and population association studies using either a candidate gene or genome-wide scan approach. At the same time, evidence has accrued that alterations in the nutritional status of the developing foetus also increase the risk of diabetes in later life. Restricting protein intake in pregnant dams or interfering with placental function increases the risk of diabetes in offspring and light weight babies are more likely to develop Type 2 diabetes as adults than heavier ones. The oocyte plays a key role, since it contains not only the maternal haplotype but other information such as mitochondrial DNA and factors that modulate the expression of genes in the developing foetus. Although the ovaries contain a huge number of primordial follicles, generally each month only one oocyte matures to ovulation. Little is known about the processes that control this phenomenon. Certainly, primordial follicles and oocytes are not all the same, differing especially in mitochondrial DNA content. As women age, the oocytes released are more likely to contain genetic errors, explaining the increased risk of Trisomy 21 with maternal age. It is generally assumed that primordial follicle development and the selection of a single ooctye for ovulation is a random process. This paper suggests that this may not be the case but that a carefully controlled system may allow the mother to release an oocyte that is best suited to the prevailing environment. This would represent an important mechanism for species adaptation. Many human infertility treatments involve pharmacological superovulation, egg harvesting and culture prior to in vitro fertilisation and reimplantation. These will bypass any system of controlled ovulation and therefore might alter the risk of diseases such as Type 2 diabetes mellitus in later life. Although the offspring of human infertility treatments are generally born healthy, it is important to note that the oldest "test-tube" baby is still less than 30-years old, so the risk of late-onset diseases is still unknown.

Diabetes Caused by Elastase-Cre-Mediated Pdx1 Inactivation in Mice.

Endocrine and exocrine pancreas tissues are both derived from the posterior foregut endoderm, however, the interdependence of these two cell types during their formation is not well understood. In this study, we generated mutant mice, in which the exocrine tissue is hypoplastic, in order to reveal a possible requirement for exocrine pancreas tissue in endocrine development and/or function. Since previous studies showed an indispensable role for Pdx1 in pancreas organogenesis, we used Elastase-Cre-mediated recombination to inactivate Pdx1 in the pancreatic exocrine lineage during embryonic stages. Along with exocrine defects, including impaired acinar cell maturation, the mutant mice exhibited substantial endocrine defects, including disturbed tip/trunk patterning of the developing ductal structure, a reduced number of Ngn3-expressing endocrine precursors, and ultimately fewer ß cells. Notably, postnatal expansion of the endocrine cell content was extremely poor, and the mutant mice exhibited impaired glucose homeostasis. These findings suggest the existence of an unknown but essential factor(s) in the adjacent exocrine tissue that regulates proper formation of endocrine precursors and the expansion and function of endocrine tissues during embryonic and postnatal stages.

Developmental-stage-dependent teratogenic effects of maternal spontaneous diabetes in the chinese hamster.

The effect of maternal diabetes on teratogenesis was examined utilizing female Chinese hamsters with typical diabetic symptoms from our closed colony (CHA) and F13-F19 of the brother-sister mating generations of a diabetic strain (CHAD). Both groups were mated with nondiabetic males from CHA. Embryologic studies on day 2.5, 4.5, and 18.5 of gestation were performed with 30, 31, 71 diabetic females that were impregnated during a normal 4-day estrous cycle. The preimplantation embryos of day 2.5 and 4.5 were also karyotyped. The results indicated that: (1) There was no decrease in the number of ovulated ova, of collected embryos, and of implantation sites in the diabetic females. (2) As far as the preimplantation stages were concerned, there was no decrease in the cleavage activity and no increase in the incidence of developmental anomalies. (3) There was no increase of chromosomal aberrations in the preimplantation embryos. (4) With respect to the postimplantation development, however, there were significant increases in embryonic death (P less than 0.001), gross malformation (P less than 0.001), and fetal hypoplasia (P less than 0.001). Results (1), (2), and (3) indicated that in diabetic females capable of conceiving during a normal estrous cycle, the maternal diabetic milieu did not affect oogenesis, ovulation, fertilization, cleavage division, implantation, and chromosomal behavior. Result (4), however, showed definitely that maternal diabetes exerted deleterious effects on fetal development during the stage of organogenesis, and also markedly reduced fetal growth during later developmental stages.

Programming of the pancreas.

The pancreas, as most of the digestive tract, derives from the endoderm. Differentiation of these early gut endoderm cells into the endocrine cells forming the pancreatic islets of Langerhans depends on a cascade of gene activation events. These are controlled by different classes of transcription factors including the homeodomain, the basic helix-loop-helix (bHLH) and the winged helix proteins. Recently, considerable progress has been made delineating this cascade. The present review focuses on the role of the different transcription factors during pancreas development, with a particular emphasis on the newly identified bHLH transcription factor neurogenin3.

Short- and long-range complications in offspring of diabetic mothers.

The perinatal mortality rate of infants of diabetic mothers (IDMs) has declined dramatically from 250 per 1000 live births in the 1960s to a near-normal 20 per 1000 live births in the 1980s. Five to 8% of all IDMs suffer from major congenital malformations, and it is the latter that are responsible for 50% of these perinatal deaths. It has been shown that tight glycemic control prior to conception and during pregnancy can prevent an excess rate of congenital malformations, fetal macrosomia, birth trauma, and neonatal respiratory distress syndrome. We briefly review the short- and long-range complications that occur in offspring of diabetic mothers (ODMs) from gestation through young adulthood. Short-term neonatal complications, such as hypoglycemia, hypocalcemia, hypomagnesemia, hyperbilirubinemia, and polycythemia, are related mainly to fetal hyperinsulinemia, hypoxemia, and prematurity. They are readily controllable within the setup of modern neonatal intensive care units. Long-range complications include an increased rate of childhood and adolescent obesity, impaired glucose tolerance or diabetes mellitus, and subtle neuropsychological dysfunctions. These may be related to the severity of the maternal hyperglycemia during pregnancy, the consequent fetal hyperinsulinemia, and third trimester maternal lipid metabolism disturbances. Today we have at hand the knowledge and tools to properly treat both pregestational and gestational diabetes. Increased education of the general practitioner and the target population regarding early referral of pregestational diabetic mothers and the implementation of screening programs for gestational diabetes will further reduce diabetic pregnancy-related morbidity.

The fetal origins of adult hypertension.

AIM: To elucidate the fetal origins of hypertension. METHODS: A systematic search was made for records of early growth, comprising measurements taken either at birth and/or during infancy, for groups of men and women now in middle-late life. Over 25,000 men and women born before 1931 were successfully traced. RESULTS: Retarded growth in fetal life was strongly related to high blood pressure in adult life. CONCLUSION: Hypertension is programmed by an adverse environment in utero. It is linked to impaired development in both early and late gestation.

Beyond pregnancy: modulation of trophoblast invasion and its consequences for fetal growth and long-term children's health.

Invasion of extravillous trophoblast cells (EVTs) into the maternal tissues is a key step in the development of a successful pregnancy, excessive and insufficient EVT invasion being associated with pregnancy complications. These pregnancy complications include preeclampsia and fetal growth restriction, both of which are associated with maternal and fetal morbidity and mortality at the time of birth and with increased risk of cardiovascular disease, diabetes and obesity in adult life for infants born from these conditions. In addition, women who develop preeclampsia are also at a greater risk of cardiovascular disease in later life. Many factors, protein and environmental, have been shown to both up- and down-regulate this process in vitro via different mechanisms. The redundancy observed in the regulation of this system suggests that dysregulation of one factor may not contribute to the pathological conditions of EVT invasion and that the relative local concentrations of many different factors may be more important. This review article explores the possibility that the modulation of EVT invasion as a therapeutic target for pregnancies affected by preeclampsia and fetal growth restriction may not be possible or needs to concentrate on the modulation of cell activity as a whole and not of one particular factor.

Racial/ethnic- and education-related disparities in the control of risk factors for cardiovascular disease among individuals with diabetes.

OBJECTIVE: There is limited information on whether recent improvements in the control of cardiovascular disease (CVD) risk factors among individuals with diabetes have been concentrated in particular sociodemographic groups. This article estimates racial/ethnic- and education-related disparities and examines trends in uncontrolled CVD risk factors among adults with diabetes. The main racial/ethnic comparisons made are with African Americans versus non-Latino whites and Mexican Americans versus non-Latino whites. RESEARCH DESIGN AND METHODS: The analysis samples include adults aged ≥20 years from the National Health and Nutrition Examination Survey (NHANES) 1988-1994 and the NHANES 1999-2008 who self-reported having diabetes (n = 1,065, NHANES 1988-1994; n = 1,872, NHANES 1999-2008). By use of logistic regression models, we examined the correlates of binary indicators measuring 1) high blood glucose, 2) high blood pressure, 3) high cholesterol, and 4) smoking. RESULTS: Control of blood glucose, blood pressure, and cholesterol improved among individuals with diabetes between the NHANES 1988-1994 and the NHANES 1999-2008, but there was no change in smoking prevalence. In the NHANES 1999-2008, racial/ethnic minorities and individuals without some college education were more likely to have poorly controlled blood glucose compared with non-Latino whites and those with some college education. In addition, individuals with diabetes who had at least some college education were less likely to smoke and had better blood pressure control compared with individuals with diabetes without at least some college education. CONCLUSIONS: Trends in CVD risk factors among individuals with diabetes improved over the past 2 decades, but racial/ethnic- and education-related disparities have emerged in some areas.

Generation of insulin-producing cells from pluripotent stem cells: from the selection of cell sources to the optimization of protocols.

The pancreas arises from Pdx1-expressing progenitors in developing foregut endoderm in early embryo. Expression of Ngn3 and NeuroD1 commits the cells to form endocrine pancreas, and to differentiate into subsets of cells that constitute islets of Langerhans. ß-cells in the islets transcribe gene-encoding insulin, and subsequently process and secrete insulin, in response to circulating glucose. Dysfunction of ß-cells has profound metabolic consequences leading to hyperglycemia and diabetes mellitus. ß-cells are destroyed via autoimmune reaction in type 1 diabetes (T1D). Type 2 diabetes (T2D), characterized by impaired ß-cell functions and reduced insulin sensitivity, accounts for 90% of all diabetic patients. Islet transplantation is a promising treatment for T1D. Pluripotent stem cells provide an unlimited cell source to generate new ß-cells for patients with T1D. Furthermore, derivation of induced pluripotent stem cells (iPSCs) from patients captures "disease-in-a-dish" for autologous cell replacement therapy, disease modeling, and drug screening for both types of diabetes. This review highlights essential steps in pancreas development, and potential stem cell applications in cell regeneration therapy for diabetes mellitus.