Progressive accumulation of mitochondrial DNA mutations and decline in mitochondrial function lead to beta-cell failure

Detection of expressional changes induced by intrauterine growth restriction in the developing rat mammary gland via exploratory pathways analysis

Background

Intrauterine growth restriction (IUGR) is thought to lead to fetal programming that in turn contributes to developmental changes of many organs postnatally. There is evidence that IUGR is a risk factor for the development of metabolic and cardiovascular disease later in life. A higher incidence of breast cancer was also observed after IUGR. This could be due to changes in mammary gland developmental pathways. We sought to characterise IUGR-induced alterations of the complex pathways of mammary development at the level of the transcriptome in a rat model of IUGR, using pathways analysis bioinformatics.

Methodology/Principal Findings

We analysed the mammary glands of Wistar rats with IUGR induced by maternal low protein (LP) diet at the beginning (d21) and the end (d28) of pubertal ductal morphogenesis. Mammary glands of the LP group were smaller in size at d28, however did not show morphologic changes. We identified multiple differentially expressed genes in the mammary gland using Agilent SurePrint arrays at d21 and d28. In silico analysis was carried out using Ingenuity Pathways Analysis. In mammary gland tissue of LP rats at d21 of life a prominent upregulation of WT1 and CDKN1A (p21) expression was observed. Differentially regulated genes were associated with the extracellular regulated kinase (ERK)-1/-2 pathway. Western Blot analysis showed reduced levels of phosphorylated ERK-1/-2 in the mammary glands of the LP group at d21. To identify possible changes in circulating steroid levels, serum LC-Tandem mass-spectrometry was performed. LP rats showed higher serum progesterone levels and an increased corticosterone/dehydrocorticosterone-ratio at d28.

Conclusions/Significance

Our data obtained from gene array analysis support the hypothesis that IUGR influences pubertal development of the rat mammary gland. We identified prominent differential regulation of genes and pathways for factors regulating cell cycle and growth. Moreover, we detected new pathways which appear to be programmed by IUGR.

Maternal diabetes, programming of beta-cell disorders and intergenerational risk of type 2 diabetes

A substantial body of evidence suggests that an abnormal intra-uterine milieu elicited by maternal metabolic disturbances as diverse as malnutrition, placental insufficiency, diabetes and obesity may be able to programme susceptibility of the foetus to later develop chronic degenerative diseases such as obesity, hypertension, cardiovascular diseases and type 2 diabetes (T2D). As insulin-producing cells have been placed centre stage in the development of T2D, this review examines developmental programming of the beta-cell mass (BCM) in various rodent models of maternal protein restriction, calorie restriction, overnutrition and diabetes. The main message is that whatever the initial maternal insult (F0 generation) and whether alone or in combination, it gives rise to the same programmed BCM outcome in the daughter generation (F1). The altered BCM phenotype in F1 females prohibits normal BCM adaptation during pregnancy and, thus, diabetes (gestational diabetes) ensues. This gestational diabetes is then passed from one generation (F1) to the next (F2, F3 and so on). This review highlights a number of studies that have identified epigenetic mechanisms that may contribute to altered BCM development and beta-cell failure, as observed in diabetes. In addition to their role in instilling the programmed defect, these non-genomic mechanisms may also be involved in its intergenerational transmission.

Mechanisms by which maternal obesity programs offspring for obesity: evidence from animal studies

Maternal obesity can profoundly affect offspring phenotype and predisposition to obesity and metabolic disease. Carefully controlled studies in precocial and altricial mammalian species provide insights into the involved mechanisms. These include programming of hypothalamic appetite-regulating centers to increase orexigenic relative to anorexigenic drive; increasing maternal, fetal, and offspring adrenal and peripheral tissue glucocorticoid production; and increasing maternal oxidative stress. Outcomes often show offspring sex differences that may play a role in the differential susceptibility of males and females to later-life obesity and other related metabolic diseases.

Exercise as an intervention to improve metabolic outcomes after intrauterine growth restriction

Individuals born after intrauterine growth restriction (IUGR) are at an increased risk of developing diabetes in their adult life. IUGR impairs β-cell function and reduces β-cell mass, thereby diminishing insulin secretion. IUGR also induces insulin resistance, with impaired insulin signaling in muscle in adult humans who were small for gestational age (SGA) and in rodent models of IUGR. There is epidemiological evidence in humans that exercise in adults can reduce the risk of metabolic disease following IUGR. However, it is not clear whether adult IUGR individuals benefit to the same extent from exercise as do normal-birth-weight individuals, as our rat studies suggest less of a benefit in those born IUGR. Importantly, however, there is some evidence from studies in rats that exercise in early life might be able to reverse or reprogram the long-term metabolic effects of IUGR. Studies are needed to address gaps in current knowledge, including determining the mechanisms involved in the reprogramming effects of early exercise in rats, whether exercise early in life or in adulthood has similar beneficial metabolic effects in larger animal models in which insulin resistance develops after IUGR. Human studies are also needed to determine whether exercise training improves insulin secretion and insulin sensitivity to the same extent in IUGR adults as in control populations. Such investigations will have implications for customizing the recommended level and timing of exercise to improve metabolic health after IUGR.

Neutralizing Th2 inflammation in neonatal islets prevents β-cell failure in adult IUGR rats

Intrauterine growth restriction (IUGR) leads to development of type 2 diabetes (T2D) in adulthood. The mechanisms underlying this phenomenon have not been fully elucidated. Inflammation is associated with T2D; however, it is unknown whether inflammation is causal or secondary to the altered metabolic state. Here we show that the mechanism by which IUGR leads to the development of T2D in adulthood is via transient recruitment of T-helper 2 (Th) lymphocytes and macrophages in fetal islets resulting in localized inflammation. Although this immune response is short-lived, it results in a permanent reduction in islet vascularity and impaired insulin secretion. Neutralizing interleukin-4 antibody therapy given only in the newborn period ameliorates inflammation and restores vascularity and β-cell function into adulthood, demonstrating a novel role for Th2 immune responses in the induction and progression of T2D. In the neonatal stage, inflammation and vascular changes are reversible and may define an important developmental window for therapeutic intervention to prevent adult-onset diabetes.

[Epigenetic mechanisms in physiologic and pathologic pregnancies]

Epigenetic factors are nowadays in the focus of scientific interest in medicine including obstetrics. The environment in utero and early neonatal life may induce a permanent response in the fetus and the newborn leading to enhanced susceptibility to later diseases. There is now growing evidence that the effects of developmental programming may also manifest themselves in the next generations without further suboptimal exposure. The so-called fetal programming may also highlight a tight connection between pathological conditions in pregnancy, environmental factors and the development of chronic diseases in adulthood. Investigation of epigenetic factors may yield new possibilities for the prevention of chronic diseases affecting a significant part of the population.

Prenatal programming of insulin secretion in intrauterine growth restriction

Intrauterine growth restriction (IUGR) impairs insulin secretion in humans and in animal models of IUGR. Several underlying mechanisms have been implicated, including decreased expression of molecular regulators of β-cell mass and function, in some cases shown to be due to epigenetic changes initiated by an adverse fetal environment. Alterations in cell cycle progression contribute to loss of β-cell mass, whereas decreased islet vascularity and mitochondrial dysfunction impair β-cell function in IUGR rodents. Animal models of IUGR sharing similar insulin secretion outcomes as the IUGR human are allowing underlying mechanisms to be identified. This review will focus on models of uteroplacental insufficiency.

The impact of early nutrition on the ageing trajectory

Epidemiological studies, including those in identical twins, and in individuals in utero during periods of famine have provided robust evidence of strong correlations between low birth-weight and subsequent risk of disease in later life, including type 2 diabetes (T2D), CVD, and metabolic syndrome. These and studies in animal models have suggested that the early environment, especially early nutrition, plays an important role in mediating these associations. The concept of early life programming is therefore widely accepted; however the molecular mechanisms by which early environmental insults can have long-term effects on a cell and consequently the metabolism of an organism in later life, are relatively unclear. So far, these mechanisms include permanent structural changes to the organ caused by suboptimal levels of an important factor during a critical developmental period, changes in gene expression caused by epigenetic modifications (including DNA methylation, histone modification and microRNA) and permanent changes in cellular ageing. Many of the conditions associated with early-life nutrition are also those which have an age-associated aetiology. Recently, a common molecular mechanism in animal models of developmental programming and epidemiological studies has been development of oxidative stress and macromolecule damage, specifically DNA damage and telomere shortening. These are phenotypes common to accelerated cellular ageing. Thus, this review will encompass epidemiological and animal models of developmental programming with specific emphasis on cellular ageing and how these could lead to potential therapeutic interventions and strategies which could combat the burden of common age-associated disease, such as T2D and CVD.

Early environmental factors, alteration of epigenetic marks and metabolic disease susceptibility

The environmental conditions that are experienced in early life can profoundly influence human biology and long-term health. Early-life nutrition and stress are among the best documented examples of such conditions because they influence the adult risk of developing metabolic diseases, such as type 2 diabetes mellitus (T2D) and cardiovascular diseases. It is now becoming increasingly accepted that environmental compounds including nutrients can produce changes in the genome activity that in spite of not altering DNA sequence can produce important, stable and transgenerational alterations in the phenotype. Epigenetic changes, in particular DNA methylation and histone acetylation/methylation, provide a 'memory' of developmental plastic responses to early environment and are central to the generation of phenotypes and their stability throughout the life course. Their effects may only become manifest later in life, e.g. in terms of altered responses to environmental challenges.

Metabolic syndrome: role of maternal undernutrition and fetal programming

Development of metabolic syndrome is attributed to genes, dietary intake, physical activity and environmental factors. Fetal programming due to maternal nutrition is also an important factor especially in developing countries where intrauterine growth retardation followed by excess nutrition postnatally is causing mismatch predisposing individuals to development of metabolic syndrome and its components. Several epidemiological and animal studies have provided evidence for the link between intrauterine growth retardation and adult metabolic diseases. Deficiency of macronutrients, protein and carbohydrates, during pregnancy and gestation results in lower infant birth weight, a surrogate marker of fetal growth and subsequently insulin resistance, glucose intolerance, hypertension and adiposity in adulthood. The role of micronutrients is less extensively studied but however gaining attention with several recent studies focusing on this aspect. Several mechanisms have been proposed to explain the developmental origin of adult diseases important among them being alteration of hypothalamic pituitary axis, epigenetic regulation of gene expression and oxidative stress. All of these mechanisms may be acting at different time during gestation and contributing to development of metabolic syndrome in adulthood.

Cellular mechanisms underlying failed beta cell regeneration in offspring of protein-restricted pregnant mice

Low birth weight and poor foetal growth following low protein (LP) exposure are associated with altered islet development and glucose intolerance in adulthood. Additionally, LP-fed offspring fail to regenerate their β-cells following depletion with streptozotocin (STZ) in contrast to control-fed offspring that restore β-cell mass. Our objective was to identify signalling pathways and cellular functions that may be critically altered in LP offspring rendering them susceptible to developing long-term glucose intolerance and decreased β-cell plasticity. Pregnant Balb/c mice were fed a control (C; 20% protein) or an isocaloric LP (8% protein) diet throughout gestation and C diet thereafter. Female offspring were injected intraperitoneally with 35 mg/kg STZ or vehicle on days 1 to 5 for each dietary treatment. At 30 days of age, total RNA was extracted from pancreatic tissue for microarray analysis using the Affymetrix GeneChip Mouse Genome 430 2.0. Gene and protein expression were quantified from isolated islets. Finally, β-cell proliferation was determined in vitro following REG1α treatment. The microarray data and GO enrichment analysis indicated that foetal protein restriction alters the early expression of genes necessary for many cell functions, such as oxidative phosphorylation and free radical scavenging. Expression of Reg1 was upregulated following STZ, whereas protein content was decreased in LP + STZ islets. Furthermore, REG1α failed to stimulate β-cell proliferation in vitro in LP + STZ islets. Therefore, early nutritional insults may programme the Reg1 pathway resulting in a limited ability to increase β-cell mass during metabolic stress. In conclusion, this study implicates the Reg1 pathway in β-cell regeneration and describes altered programming of gene expression in LP offspring, which underlies later development of cell dysfunction and glucose intolerance in adulthood.

Genome-wide analysis reveals coating of the mitochondrial genome by TFAM

Mitochondria contain a 16.6 kb circular genome encoding 13 proteins as well as mitochondrial tRNAs and rRNAs. Copies of the genome are organized into nucleoids containing both DNA and proteins, including the machinery required for mtDNA replication and transcription. The transcription factor TFAM is critical for initiation of transcription and replication of the genome, and is also thought to perform a packaging function. Although specific binding sites required for initiation of transcription have been identified in the D-loop, little is known about the characteristics of TFAM binding in its nonspecific packaging state. In addition, it is unclear whether TFAM also plays a role in the regulation of nuclear gene expression. Here we investigate these questions by using ChIP-seq to directly localize TFAM binding to DNA in human cells. Our results demonstrate that TFAM uniformly coats the whole mitochondrial genome, with no evidence of robust TFAM binding to the nuclear genome. Our study represents the first high-resolution assessment of TFAM binding on a genome-wide scale in human cells.

Intrauterine Growth Retardation - A Developmental Model of Type 2 Diabetes

Intrauterine growth retardation has been linked to the development of type 2 diabetes later in life and the mechanisms underlying this phenomena are unknown. Epidemiological studies in humans show a distinct link with the exposure to an intrauterine insult that results in low birth weight and the development of type 2 diabetes in adulthood. Intrauterine growth retardation can be induced in rodent models by exposing the pregnant rat to a low protein diet, total calorie restriction, high dose glucocorticoids or inducing uteroplacental insufficiency, all which result in abnormalities in glucose homeostasis in the offspring later in life. Animal models of intrauterine growth retardation allow for a better characterization of changes in glucose homeostasis and corresponding changes in gene expression that can provide insight in the mechanisms by which intrauterine growth retardation leads to type 2 diabetes.

Neonatal exendin-4 reduces growth, fat deposition and glucose tolerance during treatment in the intrauterine growth-restricted lamb

Background

IUGR increases the risk of type 2 diabetes mellitus (T2DM) in later life, due to reduced insulin sensitivity and impaired adaptation of insulin secretion. In IUGR rats, development of T2DM can be prevented by neonatal administration of the GLP-1 analogue exendin-4. We therefore investigated effects of neonatal exendin-4 administration on insulin action and β-cell mass and function in the IUGR neonate in the sheep, a species with a more developed pancreas at birth.

Methods

Twin IUGR lambs were injected s.c. daily with vehicle (IUGR+Veh, n = 8) or exendin-4 (1 nmol.kg^-1, IUGR+Ex-4, n = 8), and singleton control lambs were injected with vehicle (CON, n = 7), from d 1 to 16 of age. Glucose-stimulated insulin secretion and insulin sensitivity were measured in vivo during treatment (d 12–14). Body composition, β-cell mass and in vitro insulin secretion of isolated pancreatic islets were measured at d 16.

Principal Findings

IUGR+Veh did not alter in vivo insulin secretion or insulin sensitivity or β-cell mass, but increased glucose-stimulated insulin secretion in vitro. Exendin-4 treatment of the IUGR lamb impaired glucose tolerance in vivo, reflecting reduced insulin sensitivity, and normalised glucose-stimulated insulin secretion in vitro. Exendin-4 also reduced neonatal growth and visceral fat accumulation in IUGR lambs, known risk factors for later T2DM.

Conclusions

Neonatal exendin-4 induces changes in IUGR lambs that might improve later insulin action. Whether these effects of exendin-4 lead to improved insulin action in adult life after IUGR in the sheep, as in the PR rat, requires further investigation.

From Mice to Men: research models of developmental programming

Developmental programming can be defined as a response to a specific challenge to the mammalian organism during a critical developmental time window that alters the trajectory of development with persistent effects on offspring phenotype and predisposition to future illness. We focus on the need for studies in relevant, well-characterized animal models in the context of recent research discoveries on the challenges, mechanisms and outcomes of developmental programming. We discuss commonalities and differences in general principles of developmental programming as they apply to several species, including humans. The consequences of these differences are discussed. Obesity, metabolic disorders and cardiovascular diseases are associated with the highest percentage of morbidity and mortality worldwide. Although many of the causes are associated with lifestyle, high-energy diets and lack of physical activity, recent evidence has linked developmental programming to the epidemic of metabolic diseases. A better understanding of comparative systems physiology of mother, fetus and neonate using information provided by rapid advances in molecular biology has the potential to improve the lifetime health of future generations by providing better women's health, diagnostic tools and preventative and therapeutic interventions in individuals exposed during their development to programming influences.

Two-dimensional intact mitochondrial DNA agarose electrophoresis reveals the structural complexity of the mammalian mitochondrial genome

The mitochondrial genome exists in numerous structural conformations, complicating the study of mitochondrial DNA (mtDNA) metabolism. Here, we describe the development of 2D intact mtDNA agarose gel electrophoresis (2D-IMAGE) for the separation and detection of approximately two-dozen distinct topoisomers. Although the major topoisomers were well conserved across many cell and tissue types, unique differences in certain cells and tissues were also observed. RNase treatment revealed that partially hybridized RNAs associated primarily with covalently closed circular DNA, consistent with this structure being the template for transcription. Circular structures composed of RNA:DNA hybrids contained only heavy-strand DNA sequences, implicating them as lagging-strand replication intermediates. During recovery from replicative arrest, 2D-IMAGE showed changes in both template selection and replication products. These studies suggest that discrete topoisomers are associated with specific mtDNA-directed processes. Because of the increased resolution, 2D-IMAGE has the potential to identify novel mtDNA intermediates involved in replication or transcription, or pathology including oxidative linearization, deletions or depletion.

Developmental origins of diabetes: The role of oxidative stress

The 'thrifty phenotype' hypothesis proposes that the fetus adapts to an adverse intrauterine milieu by optimizing the use of a reduced nutrient supply to ensure survival, but by favoring the development of certain organs over that of others, this leads to persistent alterations in the growth and function of developing tissues. This concept has been somewhat controversial, however recent epidemiological, clinical, and animal studies provide support for the developmental origins of disease hypothesis. Underlying mechanisms include reprogramming of the hypothalamic-pituitary-adrenal axis, islet development, and insulin signaling pathways. Emerging data suggests that oxidative stress and mitochondrial dysfunction may also play a critical role in the pathogenesis of type 2 diabetes in individuals who were growth retarded at birth.

Early determinants of type-2 diabetes

The global prevalence of type-2 diabetes (T2D) has more than doubled in the last 30 years and is predicted to continue to rise at an alarming rate. The associated health and financial burdens are considerable. The aetiology of common forms of T2D is multifactorial and involves a complex interplay between genetic, epigenetic and environmental factors. The influential role of the environment, in particular our diet and sedentary lifestyles, in diabetes risk is well established. Of major concern is the increasing prevalence of early onset T2D or pre-diabetic characteristics in children. In recent years, the role of the early life environment in programming diabetes risk has been the focus of numerous human and animal studies. Historical studies highlighted an association between low birthweight, a proxy for suboptimal in utero growth, and diabetes risk in adulthood. Over more recent years it has become apparent that a variety of expositions, including maternal obesity and/or maternal diabetes, can have a significant effect on offspring health outcomes. Further complicating matters, paternal and transgenerational transmission of T2D can occur thus mediating a perpetuating cycle of disease risk between generations. It is imperative for the underlying mechanisms to be elucidated so that interventions can be introduced. In doing so, it may be possible to prevent, delay or reverse a pre-programmed risk for T2D induced by pre- and/or postnatal environmental factors to improve health outcomes and curb premature metabolic decline. This review presents evidence for how the early life environment may programme T2D risk and suggests some mechanisms by which this may occur.

Effects of maternal protein or energy restriction during late gestation on antioxidant status of plasma and immune tissues in postnatal goats

Maternal malnutrition can have temporary or long-lasting effects on development and physiological function of offspring. Our objective was to investigate whether maternal protein or energy restriction in late gestation affects the antioxidant status of plasma, immune organs (thymus and spleen), and natural barrier organs (jejunum) in neonatal goats and whether the effects could be reversed after nutritional recovery. Forty-five pregnant goats (Liuyang Blacks) of similar age (2.0 ± 0.3 yr) and BW (22.2 ± 1.5 kg at d 90 of gestation) were assigned to 3 dietary treatments during late gestation: control (ME = 9.34 MJ/kg and CP = 12.5%, DM basis), 40% protein restricted (PR), and 40% energy restricted (ER) until parturition, after which offspring received the normal diet for nutritional recovery. Plasma and tissues of kids were sampled to determine antioxidant enzymes [superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC), and catalase (CAT)] and gene expression of antioxidant enzymes (Cu/Zn-SOD [SOD1], CAT, and peroxiredoxin 2 [PRDX2]). Maternal protein or energy restriction decreased (P < 0.05) SOD activities in plasma, liver, thymus, and spleen and SOD1 expression in thymus, and maternal energy restriction also decreased (P < 0.05) plasma GSH-Px activity and expressions of SOD1 and CAT in liver at birth. After nutritional recovery of 6 wk, SOD activities in thymus (both in PR and ER) and spleen (only in PR) were greater (P < 0.05), but CAT activity of thymus (both in PR and ER) and CAT expression (only in ER) were less (P < 0.01) than those in control. After nutritional recovery of 22 wk, SOD1 and PRDX2 expression in thymus (both in PR and ER) and SOD1 expression in liver (only in ER) were greater (P < 0.05) whereas CAT expression in thymus (both in PR and ER) was less (P < 0.001) than in control. The current results indicate that maternal protein or energy restriction can decrease the antioxidant capacity of the neonatal kids and result in an imbalance of SOD and hydrogen peroxide-inactivating systems in thymus, even after 6 or 22 wk of nutritional recovery.

Delayed myelination in an intrauterine growth retardation model is mediated by oxidative stress upregulating bone morphogenetic protein 4

Intrauterine growth retardation (IUGR) is associated with neurological deficits including cerebral palsy and cognitive and behavioral disabilities. The pathogenesis involves oxidative stress that leads to periventricular white matter injury with a paucity of mature oligodendrocytes and hypomyelination. The molecular mechanisms underlying this damage remain poorly understood. We used a rat model of IUGR created by bilateral ligation of the uterine artery at embryonic Day 19 that results in fetal growth retardation and oxidative stress in the developing brain. The IUGR rat pups showed significant delays in oligodendrocyte differentiation and myelination that resolved by 8 weeks. Bone morphogenetic protein 4 (BMP4), which inhibits oligodendrocyte maturation, was elevated in IUGR brains at postnatal time points and returned to near normal by adulthood. Despite the apparent recovery, behavioral deficiencies were found in 8-week-old female animals, suggesting that the early transient myelination defects have permanent effects. In support of these in vivo data, oligodendrocyte precursor cells cultured from postnatal IUGR rats retained increased BMP4 expression and impaired differentiation that was reversed with the BMP inhibitor noggin. Oxidants in oligodendrocyte cultures increased BMP expression, which decreased differentiation; however, abrogating BMP signaling with noggin in vitro and in BMP-deficient mice prevented these effects. Together, these findings suggest that IUGR results in delayed myelination through the generation of oxidative stress that leads to BMP4 upregulation.

Impact of oxidative stress in fetal programming

Intrauterine stress induces increased risk of adult disease through fetal programming mechanisms. Oxidative stress can be generated by several conditions, such as, prenatal hypoxia, maternal under- and overnutrition, and excessive glucocorticoid exposure. The role of oxidant molecules as signaling factors in fetal programming via epigenetic mechanisms is discussed. By linking oxidative stress with dysregulation of specific target genes, we may be able to develop therapeutic strategies that protect against organ dysfunction in the programmed offspring.

Developmental perturbation induced by maternal asthma during pregnancy: the short- and long-term impacts on offspring

Maternal asthma is a common disease to complicate human pregnancy. Epidemiological studies have identified that asthma during pregnancy increases the risk of a number of poor outcomes for the neonate including growth restriction, lower birthweight, preterm delivery, neonatal resuscitation, and stillbirth. Asthma therefore represents a significant health burden to society and could have an impact on the lifelong health of the children of women with asthma. Our research has identified that maternal asthma in pregnancy induces placental dysfunction and developmental perturbation in the fetus in a sex specific manner. These alterations in development could increase the risk of metabolic disease in adulthood of children of asthmatic mothers, especially females. In this paper, we will discuss the evidence currently available that supports the hypothesis that children of mothers with asthma may be at risk of lifelong health complications which include diabetes and hypertension.

Developmental origins of adult diseases

There is considerable evidence for the fact that early life environment in human beings are associated with future development of various metabolic diseases. Fetal programming and perinatal events appear to exert effects on later life that are independent of environmental risk factors in adults. Our understanding of the underlying mechanisms are limited and remains unclear. However several animal models and epidemiological studies have shown this association, and it is assumed secondary to the penalties of developmental plasticity. In this review, we amalgamate facts from several disciplines to support this hypothesis.

The ageing pancreas

Type 2 diabetes is historically associated with older adults, and glucose tolerance is known to decline with advancing age. During the course of natural ageing, changes in many peripheral tissues contribute to this deterioration of glucose homeostasis. Included in this process are changes to the structure and function of the pancreatic islets, which undergo deviation in endocrine responses to glycaemic challenge. Current knowledge about the changes seen in the ageing pancreas is reviewed here.

Molecular mechanisms underlying the fetal programming of adult disease

Adverse events in utero can be critical in determining quality of life and overall health. It is estimated that up to 50 % of metabolic syndrome diseases can be linked to an adverse fetal environment. However, the mechanisms linking impaired fetal development to these adult diseases remain elusive. This review uncovers some of the molecular mechanisms underlying how normal physiology may be impaired in fetal and postnatal life due to maternal insults in pregnancy. By understanding the mechanisms, which include epigenetic, transcriptional, endoplasmic reticulum (ER) stress, and reactive oxygen species (ROS), we also highlight how intervention in fetal and neonatal life may be able to prevent these diseases long-term.

Mitochondrial DNA polymerase editing mutation, PolgD257A, disturbs stem-progenitor cell cycling in the small intestine and restricts excess fat absorption

Changes in intestinal absorption of nutrients are important aspects of the aging process. To address this issue, we investigated the impact of accelerated mitochondrial DNA mutations on the stem/progenitor cells in the crypts of Lieberkühn in mice homozygous for a mitochondrial DNA polymerase gamma mutation, Polg(D257A), that exhibit accelerated aging phenotype. As early as 3-7 mo of age, the small intestine was significantly enlarged in the PolgD257A mice. The crypts of the PolgD257A mice contained 20% more cells than those of their wild-type littermates and exhibited a 10-fold increase in cellular apoptosis primarily in the stem/progenitor cell zones. Actively dividing cells were proportionally increased, yet a significantly smaller proportion of cells was in the S phase of the cell cycle. Stem cell-derived organoids from PolgD257A mice failed to develop fully in culture and exhibited fewer crypt units, indicating an impact of the mutation on the intestinal epithelial stem/progenitor cell maintenance. In addition, epithelial cell migration along the crypt-villus axis was slowed and less organized, and the ATP content in the villi was significantly reduced. On a high-fat, high-carbohydrate diet, PolgD257A mice showed significantly restricted absorption of excess lipids accompanied by an increase in fecal steatocrits. We conclude that the PolgD257A mutation causes cell cycle dysregulation in the crypts leading to the age-associated changes in the morphology of the small intestine and contributes to the restricted absorption of dietary lipids.

Mechanisms of early life programming: current knowledge and future directions

It has been >20 y since epidemiologic studies showed a relation between patterns of early growth and subsequent risk of diseases, such as type 2 diabetes, cardiovascular disease, and the metabolic syndrome. Studies of identical twins, individuals who were in utero during periods of famine, and animal models have provided strong evidence that the early environment, including early nutrition, plays an important role in mediating these relations. The concept of early life programming is therefore widely accepted. However, the mechanisms by which a phenomenon that occurs in early life can have long-term effects on the function of a cell and therefore on the metabolism of an organism many years later are only starting to emerge. These mechanisms include 1) permanent structural changes in an organ resulting from suboptimal concentrations of an important factor during a critical period of development, eg, the permanent reduction in β cell mass in the endocrine pancreas; 2) persistent alterations in epigenetic modifications (eg, DNA methylation and histone modifications) that lead to changes in gene expression (eg, several transcription factors are susceptible to programmed changes in gene expression through such mechanisms); and 3) permanent effects on the regulation of cellular aging (eg, increases in oxidative stress that lead to macromolecular damage, including that to DNA and specifically to telomeres, can contribute to such effects). Further understanding of such processes will enable the development of preventive and intervention strategies to combat the burden of common diseases such as type 2 diabetes and cardiovascular disease.

Maternal malnutrition programs the endocrine pancreas in progeny

Type 2 diabetes arises when the endocrine pancreas fails to secrete sufficient insulin to cope with metabolic demands resulting from β cell secretory dysfunction, decreased β cell mass, or both. Epidemiologic studies have shown strong relations between poor fetal and early postnatal nutrition and susceptibility to diabetes later in life. Animal models have been established, and studies have shown that a reduction in the availability of nutrients during fetal development programs the endocrine pancreas and insulin-sensitive tissues. We investigated several modes of early malnutrition in rats. Regardless of the type of diet investigated, whether there was a deficit in calories or protein in food or even in the presence of a high-fat diet, malnourished pups were born with a defect in their β cell population, with fewer β cells that did not secrete enough insulin and that were more vulnerable to oxidative stress; such populations of β cells will never completely recover. Despite the similar endpoint, the cellular and physiologic mechanisms that contribute to alterations in β cell mass differ depending on the nature of the nutritional insult. Hormones that are operative during fetal life, such as insulin, insulin-like growth factors, and glucocorticoids; specific molecules, such as taurine; and islet vascularization have been implicated as possible factors in amplifying this defect. The molecular mechanisms responsible for intrauterine programming of β cells are still elusive, but among them the programming of mitochondria may be a strong central candidate.

Brain metabolism in fetal intrauterine growth restriction: a proton magnetic resonance spectroscopy study

OBJECTIVE

The purpose of this study was to investigate alterations in brain metabolism in fetuses with intrauterine growth restriction (IUGR) and evidence of cerebral redistribution of blood flow.

STUDY DESIGN

Biometry and Doppler assessment of blood flow was assessed with ultrasound in 28 fetuses with IUGR and cerebral redistribution and in 41 appropriately grown control subjects. Proton magnetic resonance spectroscopy of the fetal brain was then performed to determine the presence of choline (Cho), creatine (Cr), N-acetylaspartate (NAA), and lactate and to generate ratios for NAA:Cho, NAA:Cr, and Cho:Cr.

RESULTS

Sixty-five percent of spectra were interpretable: N-acetylaspartate, choline, and creatine peaks were identified in all these spectra; lactate was present in 5 IUGR fetuses and in 3 appropriately grown fetuses. NAA:Cr and NAA:Cho ratios were significantly lower in IUGR fetuses with cerebral redistribution.

CONCLUSION

Cerebral redistribution is associated with altered brain metabolism that is evidenced by a reduction in NAA:Cho and NAA:Cr ratios.

Early-life origins of type 2 diabetes: fetal programming of the beta-cell mass

A substantial body of evidence suggests that an abnormal intrauterine milieu elicited by maternal metabolic disturbances as diverse as undernutrition, placental insufficiency, diabetes or obesity, may program susceptibility in the fetus to later develop chronic degenerative diseases, such as obesity, hypertension, cardiovascular diseases and diabetes. This paper examines the developmental programming of glucose intolerance/diabetes by disturbed intrauterine metabolic condition experimentally obtained in various rodent models of maternal protein restriction, caloric restriction, overnutrition or diabetes, with a focus on the alteration of the developing beta-cell mass. In most of the cases, whatever the type of initial maternal metabolic stress, the beta-cell adaptive growth which normally occurs during gestation, does not take place in the pregnant offspring and this results in the development of gestational diabetes. Therefore gestational diabetes turns to be the ultimate insult targeting the offspring beta-cell mass and propagates diabetes risk to the next generation again. The aetiology and the transmission of spontaneous diabetes as encountered in the GK/Par rat model of type 2 diabetes, are discussed in such a perspective. This review also discusses the non-genomic mechanisms involved in the installation of the programmed effect as well as in its intergenerational transmission.

Involvement of ATP-sensitive potassium (K(ATP)) channels in the loss of beta-cell function induced by human islet amyloid polypeptide

Islet amyloid polypeptide (IAPP) is a major component of amyloid deposition in pancreatic islets of patients with type 2 diabetes. It is known that IAPP can inhibit glucose-stimulated insulin secretion; however, the mechanisms of action have not yet been established. In the present work, using a rat pancreatic beta-cell line, INS1E, we have created an in vitro model that stably expressed human IAPP gene (hIAPP cells). These cells showed intracellular oligomers and a strong alteration of glucose-stimulated insulin and IAPP secretion. Taking advantage of this model, we investigated the mechanism by which IAPP altered beta-cell secretory response and contributed to the development of type 2 diabetes. We have measured the intracellular Ca(2+) mobilization in response to different secretagogues as well as mitochondrial metabolism. The study of calcium signals in hIAPP cells demonstrated an absence of response to glucose and also to tolbutamide, indicating a defect in ATP-sensitive potassium (K(ATP)) channels. Interestingly, hIAPP showed a greater maximal respiratory capacity than control cells. These data were confirmed by an increased mitochondrial membrane potential in hIAPP cells under glucose stimulation, leading to an elevated reactive oxygen species level as compared with control cells. We concluded that the hIAPP overexpression inhibits insulin and IAPP secretion in response to glucose affecting the activity of K(ATP) channels and that the increased mitochondrial metabolism is a compensatory response to counteract the secretory defect of beta-cells.

Exendin-4 increases histone acetylase activity and reverses epigenetic modifications that silence Pdx1 in the intrauterine growth retarded rat

AIMS/HYPOTHESIS

The abnormal intrauterine milieu of intrauterine growth retardation (IUGR) permanently alters gene expression and function of pancreatic beta cells leading to the development of diabetes in adulthood. Expression of the pancreatic homeobox transcription factor Pdx1 is permanently reduced in IUGR islets suggesting an epigenetic mechanism. Exendin-4 (Ex-4), a long-acting glucagon-like peptide-1 (GLP-1) analogue, given in the newborn period increases Pdx1 expression and prevents the development of diabetes in the IUGR rat.

METHODS

IUGR was induced by bilateral uterine artery ligation in fetal life. Ex-4 was given on postnatal days 1-6 of life. Islets were isolated at 1 week and at 3-12 months. Histone modifications, PCAF, USF1 and DNA methyltransferase (Dnmt) 1 binding were assessed by chromatin immunoprecipitation (ChIP) assays and DNA methylation was quantified by pyrosequencing.

RESULTS

Phosphorylation of USF1 was markedly increased in IUGR islets in Ex-4 treated animals. This resulted in increased USF1 and PCAF association at the proximal promoter of Pdx1, thereby increasing histone acetyl transferase (HAT) activity. Histone H3 acetylation and trimethylation of H3K4 were permanently increased, whereas Dnmt1 binding and subsequent DNA methylation were prevented at the proximal promoter of Pdx1 in IUGR islets. Normalisation of these epigenetic modifications reversed silencing of Pdx1 in islets of IUGR animals.

CONCLUSIONS/INTERPRETATION

These studies demonstrate a novel mechanism whereby a short treatment course of Ex-4 in the newborn period permanently increases HAT activity by recruiting USF1 and PCAF to the proximal promoter of Pdx1 which restores chromatin structure at the Pdx1 promoter and prevents DNA methylation, thus preserving Pdx1 transcription.

Alteration of mitochondrial function in adult rat offspring of malnourished dams

Under-nutrition as well as over-nutrition during pregnancy has been associated with the development of adult diseases such as diabetes and obesity. Both epigenetic modifications and programming of the mitochondrial function have been recently proposed to explain how altered intrauterine metabolic environment may produce such a phenotype. This review aims to report data reported in several animal models of fetal malnutrition due to maternal low protein or low calorie diet, high fat diet as well as reduction in placental blood flow. We focus our overview on the β cell. We highlight that, notwithstanding early nutritional events, mitochondrial dysfunctions resulting from different alteration by diet or gender are programmed. This may explain the higher propensity to develop obesity and diabetes in later life.

Fetal origins of adult disease

Dr. David Barker first popularized the concept of fetal origins of adult disease (FOAD). Since its inception, FOAD has received considerable attention. The FOAD hypothesis holds that events during early development have a profound impact on one's risk for development of future adult disease. Low birth weight, a surrogate marker of poor fetal growth and nutrition, is linked to coronary artery disease, hypertension, obesity, and insulin resistance. Clues originally arose from large 20th century, European birth registries. Today, large, diverse human cohorts and various animal models have extensively replicated these original observations. This review focuses on the pathogenesis related to FOAD and examines Dr. David Barker's landmark studies, along with additional human and animal model data. Implications of the FOAD extend beyond the low birth weight population and include babies exposed to stress, both nutritional and nonnutritional, during different critical periods of development, which ultimately result in a disease state. By understanding FOAD, health care professionals and policy makers will make this issue a high health care priority and implement preventive measures and treatment for those at higher risk for chronic diseases.

Intestinal growth and morphology is associated with the increase in heat shock protein 70 expression in weaning piglets through supplementation with glutamine

The objectives of this study were to determine the effects of oral Gln supplementation on growth performance, intestinal morphology, and expression of heat shock protein (Hsp) 70 in weaning piglets. A total of 65 piglets after weaning at 21 d of age (d 0) were used in this experiment. Five piglets were randomly selected and euthanized initially at d 0 to determine baseline values for the expression of Hsp70 in the small intestine. The remaining piglets were randomly assigned to 1 of 2 treatments and received 0 or 1 g of oral Gln/kg of BW every 12 h. After piglets were humanely killed at d 3, 7, and 14 postweaning, the duodenum, jejunum, and ileum of piglets were sampled to evaluate intestinal morphology and the expression and localization of Hsp70. The results indicated that oral Gln supplementation increased plasma concentrations of Gln compared with those in control piglets (P < 0.05). Average daily gain and ADFI were greater in piglets orally supplemented with Gln than in control piglets during the whole period (P < 0.05). The incidence of diarrhea in piglets orally supplemented with Gln was 24% less than (P = 0.064) that in control piglets at 8 to 14 d after weaning. The weights of the jejunum and ileum were greater in piglets orally supplemented with Gln compared with those of control piglets relative to BW on d 14 postweaning (P < 0.05). The villus height and the villus height:crypt depth ratio in the jejunum and the ileum were greater in piglets receiving oral Gln on d 14 postweaning (P < 0.05) than in control piglets. These results indicate that Gln supplementation can influence the intestinal morphology of weaned piglets. The expression of hsp70 mRNA and Hsp70 proteins in the duodenum and jejunum was greater in piglets supplemented with Gln than in control piglets (P < 0.05). However, Gln supplementation had no effect on the expression of hsp70 mRNA and Hsp70 proteins in the ileum. Moreover, the localization of Hsp70 in the cytoplasm indicated that Hsp70 has a cytoprotective role in epithelial cell function and structure. These results indicate that Gln supplementation may be beneficial for intestinal health and development and may thus mitigate diarrhea and improve growth performance. The protective mechanisms of Gln in the intestine may be associated with the increase in Hsp70 expression.

Taurine supplementation restored the changes in pancreatic islet mitochondria in the fetal protein-malnourished rat

Intra-uterine growth retardation has been linked to the development of type 2 diabetes in later life. Mitochondrial changes have been suggested as a link between fetal malnutrition and adult insulin resistance. Taurine has been implicated in this process. We investigated whether protein malnutrition in early life alters mitochondria of the pancreatic islets in adulthood, and whether taurine supplementation restores these changes. Male offspring of rats fed a control diet, a low-protein diet or a low-protein diet supplemented with taurine during pregnancy and lactation were weaned onto the control diet. In each group, at 20 weeks of age, intravenous glucose tolerance tests, euglycaemic–hyperinsulinaemic clamp studies, morphometric analysis of the pancreatic islets and ultra-structural analysis of the mitochondria of the β-cells were performed. The expressions of cytochrome c oxidase (COX) I and mitochondrial respiratory chain complex II were also measured. Fetal protein-malnourished rats showed decreased pancreatic islet mass and reduced insulin-secretory responses to a glucose load. These rats also showed reduced mitochondrial DNA-encoded COX I gene expression in the islets. Electron microscopic examination showed abnormal mitochondrial shapes in the β-cells of fetal protein-malnourished rats. Taurine supplementation to the low-protein diet restored all these changes. Our findings indicate that a maternal protein-restriction diet causes long-lasting mitochondrial changes that may contribute to the development of type 2 diabetes later in life. The lack of taurine may be a key causative factor for these dysfunctional mitochondrial changes.

The interplay between mitochondrial dynamics and mitophagy

Mitochondrial dynamics and mitophagy are recognized as two critical processes underlying mitochondrial homeostasis. Morphological and bioenergetic characterization of the life cycle of an individual mitochondrion reveals several points where fusion, fission, and mitophagy interact. Mitochondrial fission can produce an impaired daughter unit that will be targeted by the autophagic machinery. Mitochondrial fusion, on the other hand, may serve to dilute impaired respiratory components and thereby prevent their removal. The inverse dependency of fusion and mitophagy on membrane potential allows them to act as complementary rather than competitive fates of the daughter mitochondrion after a fission event. We discuss the interplay between mitochondrial dynamics and mitophagy in different tissues and in different disease models under both stress-induced and steady-state conditions.

Mitochondrial DNA polymerase editing mutation, PolgD257A, reduces the diabetic phenotype of Akita male mice by suppressing appetite

Diabetes and the development of its complications have been associated with mitochondrial DNA (mtDNA) dysfunction, but causal relationships remain undetermined. With the objective of testing whether increased mtDNA mutations exacerbate the diabetic phenotype, we have compared mice heterozygous for the Akita diabetogenic mutation (Akita) with mice homozygous for the D257A mutation in mitochondrial DNA polymerase gamma (Polg) or with mice having both mutations (Polg-Akita). The Polg-D257A protein is defective in proofreading and increases mtDNA mutations. At 3 mo of age, the Polg-Akita and Akita male mice were equally hyperglycemic. Unexpectedly, as the Polg-Akita males aged to 9 mo, their diabetic symptoms decreased. Thus, their hyperglycemia, hyperphagia and urine output declined significantly. The decrease in their food intake was accompanied by increased plasma leptin and decreased plasma ghrelin, while hypothalamic expression of the orexic gene, neuropeptide Y, was lower and expression of the anorexic gene, proopiomelanocortin, was higher. Testis function progressively worsened with age in the double mutants, and plasma testosterone levels in 9-mo-old Polg-Akita males were significantly reduced compared with Akita males. The hyperglycemia and hyperphagia returned in aged Polg-Akita males after testosterone administration. Hyperglycemia-associated distal tubular damage in the kidney also returned, and Polg-D257A-associated proximal tubular damage was enhanced. The mild diabetes of female Akita mice was not affected by the Polg-D257A mutation. We conclude that reduced diabetic symptoms of aging Polg-Akita males results from appetite suppression triggered by decreased testosterone associated with damage to the Leydig cells of the testis.

Developmental programming of energy balance and its hypothalamic regulation

Developmental programming is an important physiological process that allows different phenotypes to originate from a single genotype. Through plasticity in early life, the developing organism can adopt a phenotype (within the limits of its genetic background) that is best suited to its expected environment. In humans, together with the relative irreversibility of the phenomenon, the low predictive value of the fetal environment for later conditions in affluent countries makes it a potential contributor to the obesity epidemic of recent decades. Here, we review the current evidence for developmental programming of energy balance. For a proper understanding of the subject, knowledge about energy balance is indispensable. Therefore, we first present an overview of the major hypothalamic routes through which energy balance is regulated and their ontogeny. With this background, we then turn to the available evidence for programming of energy balance by the early nutritional environment, in both man and rodent models. A wealth of studies suggest that energy balance can indeed be permanently affected by the early-life environment. However, the direction of the effects of programming appears to vary considerably, both between and within different animal models. Because of these inconsistencies, a comprehensive picture is still elusive. More standardization between studies seems essential to reach veritable conclusions about the role of developmental programming in adult energy balance and obesity.

Two tales of antioxidant enzymes on β cells and diabetes

Pancreatic islets contain low activities of catalase, selenium-dependent glutathione peroxidase 1 (GPX1), and Cu,Zn-superoxide dismutase 1 (SOD1). Thus, enhancing expression of these enzymes in islets has been unquestionably favored. However, such an attempt has produced variable metabolic outcomes. While β cell-specific overexpression of Sod1 enhanced mouse resistance to streptozotocin-induced diabetes, the same manipulation of catalase aggravated onset of type 1 diabetes in nonobese diabetic mice. Global overexpression of Gpx1 in mice induced type 2 diabetes-like phenotypes. Although knockouts of Gpx1 and Sod1 each alone or together decreased pancreatic β cell mass and plasma insulin concentrations, these knockouts improved body insulin sensitivity to different extents. Pancreatic duodenal homeobox 1, forkhead box A2, and uncoupling protein 2 are three key regulators of β cell mass, insulin synthesis, and glucose-stimulated insulin secretion. Phenotypes resulted from altering GPX1 and/or SOD1 were partly mediated through these factors, along with protein kinase B and c-jun terminal kinase. A shifted reactive oxygen species inhibition of protein tyrosine phosphatases in insulin signaling might be attributed to altered insulin sensitivity. Overall, metabolic roles of antioxidant enzymes in β cells and diabetes depend on body oxidative status and target functions. Revealing regulatory mechanisms for this type of dual role will help prevent potential pro-diabetic risk of antioxidant over-supplementation to humans.

Maternal malnutrition programs pancreatic islet mitochondrial dysfunction in the adult offspring

Accumulating evidence has shown that maternal malnutrition increases the risk of metabolic disease in the progeny. We previously reported that prenatal exposure to a low-protein diet (LP) leads to mitochondrial dysfunction in pancreatic islets from adult rodent offspring that could relate physiological and cellular alterations due to early diet. We aim to determine whether mitochondrial dysfunction could be a common consequence of prenatal nutritional unbalances. Pregnant Wistar rats received either a global food restriction (GFR), consisting in the reduction by 50% of the normal daily food intake, or a high-fat diet (HF) throughout gestation. GFR or HF diet during pregnancy leads to a lack of increase in insulin release and ATP content in response to glucose stimulation in islets from 3-month-old male and female offspring. These similar consequences originated from impairment in either glucose sensing or glucose metabolism, depending on the type of early malnutrition and on the sex of the progeny. Indeed, the glucose transport across β-cell membrane seemed compromised in female HF offspring, since GLUT-2 gene was markedly underexpressed. Additionally, for each progeny, consequences downstream the entry of glucose were also apparent. Expression of genes involved in glycolysis, TCA cycle and oxidative phosphorylations was altered in GFR and HF rats in a sex- and diet-dependent manner. Moreover, prenatal malnutrition affected the regulators of mitochondrial biogenesis, namely, PPAR coactivator 1 alpha (PGC-1α), since its expression was higher in islets from GFR rats. In conclusion, programming of mitochondrial dysfunction is a consequence of maternal malnutrition, which may predispose to glucose intolerance in the adult offspring.

Pathways linking the early environment to long-term health and lifespan

The intrauterine environment is a major contributor to normal physiological growth and development of an individual. Disturbances at this critical time can affect the long-term health of the offspring. Low birth weight individuals have strong correlations with increased susceptibility to type 2 diabetes and cardiovascular disease in later-life. These observations led to the Thrifty Phenotype Hypothesis which suggested that these associations arose because of the response of a growing fetus to a suboptimal environment such as poor nutrition. Animal models have shown that environmentally induced intrauterine growth restriction increases the risk of a variety of diseases later in life. These detrimental features are also observed in high birth weight offspring from mothers who were obese or consumed a high fat diet during gestation. Recent advances in our understanding of the mechanisms underlying this phenomenon have elucidated several potential candidates for the long-term effects of the early environment on the function and metabolism of a cell. These include: (1) Epigenetic alterations (e.g. DNA methylation and histone modifications), which regulate specific gene expression and can be influenced by the environment, both during gestation and early postnatal life and (2) Oxidative stress that changes the balance between reactive oxygen species generation (e.g. through mitochondrial dysfunction) and antioxidant defense capacity. This has permanent effects on cellular ageing such as regulation of telomere length. Further understanding of these processes will help in the development of therapeutic strategies to increase healthspan and reduced the burden of age-associated diseases.

ER stress is implicated in mitochondrial dysfunction-induced apoptosis of pancreatic beta cells

Mitochondrial dysfunction induces apoptosis of pancreatic β-cells and leads to type 2 diabetes, but the mechanism involved in this process remains unclear. Chronic endoplasmic reticulum (ER) stress plays a role in the apoptosis of pancreatic β-cells; therefore, in current study, we investigated the implication of ER stress in mitochondrial dysfunction-induced β-cells apoptosis. Metabolic stress induced by antimycin or oligomycin was used to impair mitochondrial function in MIN6N8 cells, which are mouse pancreatic β-cells. Impaired mitochondria dysfunction increased ER stress proteins such as p-eIF2α, GRP78 and GRP 94, as well as ER stress-associated apoptotic factor, CHOP, and activated JNK. AMP-activated protein kinase (AMPK) was also activated under mitochondria dysfunction by metabolic stress. However, the inhibition of AMPK by treatment with compound C, inhibitor of AMPK, and overexpression of mutant dominant negative AMPK (AMPKK45R) blocked the induction of ER stress, which was consist-ent with the decreased β-cell apoptosis and increase of insulin content. Furthermore, mitochondrial dysfunction increased the expression of the inducible nitric oxide synthase (iNOS) gene and the production of nitric oxide (NO), but NO production was prevented by compound C and mutant dominant negative AMPK (AMPK-K45R). Moreover, treatment with 1400W, which is an inhibitor of iNOS, prevented ER stress and apoptosis induced by mitochondrial dysfunction. Treatment of MIN6N8 cells with lipid mixture, physiological conditions of impaired mitochondria function, activated AMPK, increased NO production and induced ER stress. Collectively, these data demonstrate that mitochondrial dysfunction activates AMPK, which induces ER stress via NO production, resulting in pancreatic β-cells apoptosis.

Early life nutrition and metabolic programming

Research investigating the early programming of adult metabolic disease has in recent years provided much mechanistic insight into how the early environment impacts on long-term health. It includes studies addressing the roles of intrauterine nutrient availability, which is determined by maternal nutrition, maternal exposure to oxygen, toxic events, and infection; the placental interface; and also the early postnatal environment. This review will explore the epidemiological evidence for programming of metabolic disease and provide an overview of the various studies using animals to model metabolic phenotypic outcome. It will also discuss evidence for the proposed molecular mechanisms and the potential for intervention.

Maternal blood mitochondrial DNA content during normal and intrauterine growth restricted (IUGR) pregnancy

OBJECTIVE

We investigated mitochondrial DNA (mtDNA) content in the maternal circulation of normal pregnancies of different gestational ages and in pregnancies complicated by intrauterine growth restriction (IUGR).

STUDY DESIGN

We examined 70 maternal blood samples: 13 nonpregnant women; 45 normal pregnancies, divided into the 3 trimesters; and 12 pregnancies complicated by IUGR. MtDNA content was determined by real-time quantitative polymerase chain reaction, using a genomic control and a target gene.

RESULTS

A highly significant progressive reduction in circulating mtDNA was observed in pregnant women of first, second, and third trimesters and compared to nonpregnant women (mean value: 237, 188, 144, and 283, respectively; P < .001). Moreover, mtDNA was significantly increased in women carrying IUGR fetuses compared to women with normal pregnancies (430 vs 144; P < .001).

CONCLUSION

MtDNA could provide new insight into the mechanisms that occur during physiological gestation. Furthermore, mtDNA content may help recognize the IUGR disease in pregnancy.