Glucose metabolism is altered in the adequately-nourished grand-offspring (F3 generation) of rats malnourished during gestation and perinatal life

Changed mitochondrial function by pre- and/or postpartum diet alterations in sheep

In a sheep model, we investigated diet effects on skeletal muscle mitochondria to look for fetal programming. During pregnancy, ewes were fed normally (N) or were 50% food restricted (L) during the last trimester, and lambs born to these ewes received a normal (N) or a high-fat diet (H) for the first 6 mo of life. We examined mitochondrial function in permeabilized muscle fibers from the lambs at 6 mo of age (adolescence) and after 24 mo of age (adulthood). The postpartum H diet for the lambs induced an approximately 30% increase (P < 0.05) of mitochondrial VO(2max) and an approximately 50% increase (P < 0.05) of the respiratory coupling ratio (RCR) combined with lower levels of UCP3 and PGC-1alpha mRNA levels (P < 0.05). These effects proved to be reversible by a normal diet from 6 to 24 mo of age. However, at 24 mo, a long-term effect of the maternal gestational diet restriction (fetal programming) became evident as a lower VO(2max) (approximately 40%, P < 0.05), a lower state 4 respiration (approximately 40%, P < 0.05), and lower RCR ( approximately 15%, P < 0.05). Both PGC-1alpha and UCP3 mRNA levels were increased (P < 0.05). Two analyzed muscles were affected differently, and muscle rich in type I fibers was more susceptible to fetal programming. We conclude that fetal programming, seen as a reduced VO(2max) in adulthood, results from gestational undernutrition. Postnatal high-fat diet results in a pronounced RCR and VO(2max) increase in adolescence. However, these effects are reversible by diet correction and are not maintained in adulthood.

Maternal high-fat diet promotes body length increases and insulin insensitivity in second-generation mice

Maternal obesity and diet consumption during pregnancy have been linked to offspring adiposity, cardiovascular disease, and impaired glucose metabolism. Furthermore, nutrition during development is clearly linked to somatic growth. However, few studies have examined whether phenotypes derived from maternal high-fat diet exposure can be passed to subsequent generations and by what mechanisms this may occur. Here we report the novel finding of a significant body length increase that persisted across at least two generations of offspring in response to maternal high-fat diet exposure. This phenotype is not attributable to altered intrauterine conditions or maternal feeding behavior because maternal and paternal lineages were able to transmit the effect, supporting a true epigenetic manner of inheritance. We also detected a heritable feature of reduced insulin sensitivity across two generations. Alterations in the GH secretagogue receptor (GHSR), the GHSR transcriptional repressor AF5q31, plasma IGF-I concentrations, and IGF-binding protein-3 (IGFBP3) suggest a contribution of the GH axis. These studies provide evidence that the heritability of body length and glucose homeostasis are modulated by maternal diet across multiple generations, providing a mechanism where length can increase rapidly in concert with caloric availability.

The Elephant in the Room: The Invisibility of Poverty in Research on Type 2 Diabetes

Over two hundred years of anecdotal, epidemiological, and experimental evidence indicate that poverty breeds disease. This holds true for type 2 diabetes, which both in the United States and other developed nations disproportionately occurs, cripples, and kills among the poor. In this article we examine rhetorical strategies used in 30 journal articles indexed under type 2 diabetes and poverty. As we show, poverty is rarely highlighted in this literature as a causal factor. Instead, explanations for diabetes among poor people overwhelmingly emphasize features of patients—their biology, behaviors, psychology, culture, or other “risk factors”—while ignoring, reframing or neglecting the links between poverty and disease. By so doing, these discursive strategies naturalize higher rates of diabetes among poor persons, legitimize relations of domination in the larger society, and encourage only research projects, treatment practices and health and social policies that do not challenge existing social relations. We discuss the implications of these discursive practices for medical research and care, and for social and public health policies.

Intergenerational transmission of glucose intolerance and obesity by in utero undernutrition in mice

OBJECTIVE

Low birth weight (LBW) is associated with increased risk of obesity, diabetes, and cardiovascular disease during adult life. Moreover, this programmed disease risk can progress to subsequent generations. We previously described a mouse model of LBW, produced by maternal caloric undernutrition (UN) during late gestation. LBW offspring (F(1)-UN generation) develop progressive obesity and impaired glucose tolerance (IGT) with aging. We aimed to determine whether such metabolic phenotypes can be transmitted to subsequent generations in an experimental model, even in the absence of altered nutrition during the second pregnancy.

RESEARCH DESIGN AND METHODS

We intercrossed female and male F(1) adult control (C) and UN mice and characterized metabolic phenotypes in F(2) offspring.

RESULTS

We demonstrate that 1) reduced birth weight progresses to F(2) offspring through the paternal line (Cfemale -Cmale = 1.64 g; Cfemale -UNmale = 1.57 g, P < 0.05; UNfemale -Cmale = 1.64 g; UNfemale -UNmale = 1.60 g, P < 0.05), 2) obesity progresses through the maternal line (percent body fat: Cfemale -Cmale = 22.4%; Cfemale -UNmale = 22.9%; UNfemale -Cmale = 25.9%, P < 0.05; UNfemale -UNmale = 27.5%, P < 0.05), and 3) IGT progresses through both parental lineages (glucose tolerance test area under curve Cfemale -Cmale = 100; Cfemale -UNmale = 122, P < 0.05; UNfemale -Cmale = 131, P < 0.05; UNfemale -UNmale = 151, P < 0.05). Mechanistically, IGT in both F(1) and F(2) generations is linked to impaired beta-cell function, explained, in part, by dysregulation of Sur1 expression.

CONCLUSIONS

Maternal undernutrition during pregnancy (F(0)) programs reduced birth weight, IGT, and obesity in both first- and second-generation offspring. Sex-specific transmission of phenotypes implicates complex mechanisms including alterations in the maternal metabolic environment (transmaternal inheritance of obesity), gene expression mediated by developmental and epigenetic pathways (transpaternal inheritance of LBW), or both (IGT).

Transgenerational epigenetic effects

Transgenerational epigenetic effects include all processes that have evolved to achieve the nongenetic determination of phenotype. There has been a long-standing interest in this area from evolutionary biologists, who refer to it as non-Mendelian inheritance. Transgenerational epigenetic effects include both the physiological and behavioral (intellectual) transfer of information across generations. Although in most cases the underlying molecular mechanisms are not understood, modifications of the chromosomes that pass to the next generation through gametes are sometimes involved, which is called transgenerational epigenetic inheritance. There is a trend for those outside the field of molecular biology to assume that most cases of transgenerational epigenetic effects are the result of transgenerational epigenetic inheritance, in part because of a misunderstanding of the terms. Unfortunately, this is likely to be far from the truth.

Insulin sensitivity is normalized in the third generation (F3) offspring of developmentally programmed insulin resistant (F2) rats fed an energy-restricted diet

Background/Aims

The offspring and grandoffspring of female rats fed low protein diets during pregnancy and lactation, but fed nutritionally adequate diets thereafter, have been shown to exhibit altered insulin sensitivity in adulthood. The current study investigates the insulin sensitivity of the offspring and grandoffspring of female rats fed low protein diets during pregnancy, and then maintained on energy-restricted diets post weaning over three generations.

Methods

Female Sprague Dawley rats (F0) were mated with control males and protein malnourished during pregnancy/lactation. F1 offspring were then weaned to adequate but energy-restricted diets into adulthood. F1 dams were fed energy-restricted diets throughout pregnancy/lactation. F2 offspring were also fed energy-restricted diets post weaning. F2 pregnant dams were maintained as described above. Their F3 offspring were split into two groups; one was maintained on the energy-restricted diet, the other was maintained on an adequate diet consumed ad libitum post weaning.

Results

F2 animals fed energy-restricted diets were insulin resistant (p < 0.05), while the insulin sensitivity of their F3 offspring equaled and surpassed that of controls on both the energy-restricted and adequate ad libitum postweaning diets (p < 0.05).

Conclusion

Maternal energy-restriction did not consistently program reduced insulin sensitivity in offspring over three consecutive generations. The reasons for this remain unclear. It is possible that the intergenerational transmission of developmentally programmed insulin resistance is determined in part by the relative insulin sensitivity of the mother during pregnancy/lactation.

Transmission of raised blood pressure and endothelial dysfunction to the F2generation induced by maternal protein restriction in the F0, in the absence of dietary challenge in the F1generation

We have previously demonstrated that maternal protein restriction during pregnancy leads to raised blood pressure and endothelial dysfunction in the offspring (F1). Here we show that these characteristics are transmitted to the F2offspring through the maternal line, in the absence of any additional challenges to the F1. Female Wistar rats were fed either a control (18 % casein) or protein-restricted diet (PR; 9 % casein) throughout pregnancy. Female F1offspring, maintained on standard chow postpartum, were mated with breeding males to produce F2progeny. Systolic blood pressure (SBP) in male F2offspring was assessed by tail-cuff plethysmography at age 100 d and vascular function of small mesenteric arteries by wire myography at age 80 and 200 d. SBP was raised in PR F2offspring compared with controls (control 122·1 (sem2·3) mmHg,n7; PR 134·7 (sem3·2) mmHg,n6;P < 0·01) and endothelial function, assessed by vasodilatation to acetylcholine, was impaired at both age 80 d (% maximal response: control 89·7 (sem2·6),n14; PR 72·7 (sem4·4),n15;P < 0·01) and 200 d (effective concentration equal to 50 % of maximum (pEC50): control 7·67 (sem0·10),n10; PR 7·33 (sem0·07),n8;P < 0·05). The present study demonstrates that both raised blood pressure and endothelial dysfunction are passed via the maternal line to grand-offspring in the absence of any additional dietary challenges to their F1mothers. Risk factors for chronic disease may therefore be heritable by non-genomic processes.

Transgenerational effects of prenatal exposure to the Dutch famine on neonatal adiposity and health in later life

OBJECTIVE

Maternal undernutrition during gestation is associated with increased metabolic and cardiovascular disease in the offspring. We investigated whether these effects may persist in subsequent generations.

DESIGN

Historical cohort study.

SETTING

Interview during a clinic or home visit or by telephone.

POPULATION

Men and women born in the Wilhelmina Gasthuis in Amsterdam between November 1943 and February 1947.

METHODS

We interviewed cohort members (F1) born around the time of the 1944-45 Dutch famine, who were exposed or unexposed to famine in utero, about their offspring (F2).

MAIN OUTCOME MEASURES

Birthweight, birth length, ponderal index and health in later life (as reported by F1) of the offspring (F2) of 855 participating cohort members, according to F1 famine exposure in utero.

RESULTS

F1 famine exposure in utero did not affect F2 (n = 1496) birthweight, but, among the offspring of famine-exposed F1 women, F2 birth length was decreased (-0.6 cm, P adjusted for F2 gender and birth order = 0.01) and F2 ponderal index was increased (+1.2 kg/m(3), P adjusted for F2 gender and birth order = 0.001). The association remained unaltered after adjusting for possible confounders. The offspring of F1 women who were exposed to famine in utero also had poor health 1.8 (95% CI 1.1-2.7) times more frequently in later life (due to miscellaneous causes) than that of F1 unexposed women.

CONCLUSIONS

We did not find transgenerational effects of prenatal exposure to famine on birthweight nor on cardiovascular and metabolic disease rates. F1 famine exposure in utero was, however, associated with increased F2 neonatal adiposity and poor health in later life. Our findings may imply that the increase in chronic disease after famine exposure in utero is not limited to the F1 generation but persists in the F2 generation.

Transgenerational epigenetic inheritance in health and disease

Over the past century, patterns of phenotypic inheritance have been observed that are not easily rationalised by Mendel's rules of inheritance. Now that we have begun to understand more about non-DNA based, or 'epigenetic', control of phenotype at the molecular level, the idea that the transgenerational inheritance of these epigenetic states could explain non-Mendelian patterns of inheritance has become attractive. There is a growing body of evidence that abnormal epigenetic states, termed epimutations, are associated with disease in humans. For example, in several cases of colorectal cancer, epimutations have been identified that silence the human mismatch repair genes, MLH1 and MSH2. But strong evidence that the abnormal epigenetic states are primary events that occur in the absence of genetic change and are inherited across generations is still absent.

Sexual dimorphism in non-Mendelian inheritance

There is accumulating evidence for nongenetic transgenerational inheritance with conspicuous marked sexual dimorphism for both the modes of transmission and the effects. Given the critical spatiotemporal windows, the role of the sex chromosomes, the regulatory pathways underlying sexual differentiation during gonad and brain development, and other developmental processes, as well as the lifelong impact of sex hormones, it is not surprising that most of the common diseases, which often take root in early development, display some degree of sex bias. The flexibility of epigenetic marks may make it possible for environmental and nutritional factors, or endocrine disruptors to alter-during a particular spatiotemporal window in a sex-specific manner-the sex-specific methylation or demethylation of specific CpGs and histone/chromatin modifications underlying sex-specific expression of a substantial proportion of genes. Thus, finely tuned developmental program aspects, specific to one sex, may be more sensitive to specific environmental challenges, particularly during developmental programming and gametogenesis, but also throughout the individual's life under the influence of sex steroid hormones. This review highlights the importance of studying both sexes in epidemiologic protocols or dietary interventions both in humans and in experimental models in animals.

Developmental origins of health and disease: new insights

Epidemiological and animal studies show that small changes in the developmental environment can induce phenotypic changes affecting an individual's responses to their later environment. These may alter the risk of chronic disease such as metabolic syndrome or cardiovascular disease. Recent research shows that animals exposed to such a mismatch between prenatal and postnatal environment develop obesity, reduced activity, leptin and insulin resistance, elevated blood pressure and vascular endothelial dysfunction. Epigenetic processes are involved in such effects, targeted to promoter regions of specific genes in specific tissues. Such fine control of gene expression suggests that the mechanisms have been retained through evolution through their adaptive advantage, rather than representing extreme effects of developmental disruption akin to teratogenesis. There may be adaptive advantage in a developmental cue inducing a phenotypic change in generations beyond the immediate pregnancy, and a range of data that support this concept. In animals, epigenetic effects such as DNA methylation can be passed to successive generations. Environmental toxins, including endocrine disruptors, may induce greater risk of chronic disease, even at low exposure levels, if they affect such normal developmental epigenetic processes. Appropriate interventions may have long-term multigenerational effects to reduce the risk of chronic disease.

Microcirculation in obesity: an unexplored domain

Obesity is traditionally linked to diabetes and cardiovascular diseases. Very recent experimental, clinical and epidemiological, sometimes provocative, data challenge this automaticity by showing that not the amount but the distribution of fat is the important determinant. Moderate abdominal fat accumulation may thus be more harmful than even consequent overweight. In view of the worldwide burden of obesity, factors leading to it in children and young adults must urgently be identified. Since obesity is a very complex cardiometabolic situation, this will require to focus investigations on uncomplicated obese subjects and adequate animal models. The recent discovery of intergenerational transmissions of obesity risk factors and also the key role played by gestational and perinatal events (epigenetic factors) give rise to completely new concepts and research avenues. Considering the potential close relationship between microcirculation and tissue metabolism, demonstrations of structural and/or functional abnormalities in microvascular physiology very early in life of subjects at risk for obesity might provide a solid basis for further investigations of such links. Microcirculation(arterioles, capillaries and venules) is conceivably a key compartment determining over one or several decades the translation of genetic and epigenetic factors into fat accumulation. Available animal models should serve to answer this cardinal question.

Metabolic programming in the pathogenesis of insulin resistance

This review focuses on different animal models of nutrient perturbations, inclusive of restrictive and excessive states mimicking human situations during pregnancy and lactation that cause aberrations in the offspring. These aberrations consist of diminished insulin sensitivity in the presence of defective insulin production. These phenotypic changes are due to altered peripheral tissue post-insulin receptor signaling mechanisms and pancreatic beta-islet insulin synthesis and secretion defects. While these changes during in utero or postnatal life serve as essential adaptations to overcome adverse conditions, they become maladaptive subsequently and set the stage for type 2 diabetes mellitus. Pregnancy leads to gestational diabetes with trans-generational propagation of the insulin resistant phenotype. This is in response to the metabolically aberrant maternal in utero environment, and tissue specific epigenetic perturbations that permanently alter expression of critical genes transmitted to future generations. These heritable aberrations consisting of altered DNA methylation and histone modifications remodel chromatin and affect transcription of key genes. Along with an altered in utero environment, these chromatin modifications contribute to the world-wide epidemic of type 2 diabetes mellitus, with nutrient excess dominating in developed and nutrient restriction in developing countries.

Dietary protein restriction of pregnant rats in the F0 generation induces altered methylation of hepatic gene promoters in the adult male offspring in the F1 and F2 generations

Epidemiological studies and experimental models show that maternal nutritional constraint during pregnancy alters the metabolic phenotype of the offspring and that this can be passed to subsequent generations. In the rat, induction of an altered metabolic phenotype in the liver of the F1 generation by feeding a protein-restricted diet (PRD) during pregnancy involves the altered methylation of specific gene promoters. We therefore investigated whether the altered methylation of PPARalpha and glucocorticoid receptor (GR) promoters was passed to the F2 generation. Females rats (F0) were fed a reference diet (180 g/kg protein) or PRD (90 g/kg protein) throughout gestation, and AIN-76A during lactation. The F1 offspring were weaned onto AIN-76A. F1 females were mated and fed AIN-76A throughout pregnancy and lactation. F1 and F2 males were killed on postnatal day 80. Hepatic PPARalpha and GR promoter methylation was significantly (P<0 x 05) lower in the PRD group in the F1 (PPARalpha 8 %, GR 10 %) and F2 (PPARalpha 11 %, GR 8 %) generations. There were trends (P<0 x 1) towards a higher expression of PPARalpha, GR, acyl-CoA oxidase and phosphoenolpyruvate carboxykinase (PEPCK) in the F1 and F2 males, although this was significant only for PEPCK. These data show for the first time that the altered methylation of gene promoters induced in the F1 generation by maternal protein restriction during pregnancy is transmitted to the F2 generation. This may represent a mechanism for the transmission of induced phenotypes between generations

Non-genomic transgenerational inheritance of disease risk

That there is a heritable or familial component of susceptibility to chronic non-communicable diseases such as type 2 diabetes, obesity and cardiovascular disease is well established, but there is increasing evidence that some elements of such heritability are transmitted non-genomically and that the processes whereby environmental influences act during early development to shape disease risk in later life can have effects beyond a single generation. Such heritability may operate through epigenetic mechanisms involving regulation of either imprinted or non-imprinted genes but also through broader mechanisms related to parental physiology or behaviour. We review evidence and potential mechanisms for non-genomic transgenerational inheritance of 'lifestyle' disease and propose that the 'developmental origins of disease' phenomenon is a maladaptive consequence of an ancestral mechanism of developmental plasticity that may have had adaptive value in the evolution of generalist species such as Homo sapiens.

Epigenetic regulation of transcription: a mechanism for inducing variations in phenotype (fetal programming) by differences in nutrition during early life?

There is considerable evidence for the induction of different phenotypes by variations in the early life environment, including nutrition, which in man is associated with a graded risk of metabolic disease; fetal programming. It is likely that the induction of persistent changes to tissue structure and function by differences in the early life environment involves life-long alterations to the regulation of gene transcription. This view is supported by both studies of human subjects and animal models. The mechanism which underlies such changes to gene expression is now beginning to be understood. In the present review we discuss the role of changes in the epigenetic regulation of transcription, specifically DNA methylation and covalent modification of histones, in the induction of an altered phenotype by nutritional constraint in early life. The demonstration of altered epigenetic regulation of genes in phenotype induction suggests the possibility of interventions to modify long-term disease risk associated with unbalanced nutrition in early life.

Early life events and their consequences for later disease: a life history and evolutionary perspective

Biomedical science has little considered the relevance of life history theory and evolutionary and ecological developmental biology to clinical medicine. However, the observations that early life influences can alter later disease risk--the "developmental origins of health and disease" (DOHaD) paradigm--have led to a recognition that these perspectives can inform our understanding of human biology. We propose that the DOHaD phenomenon can be considered as a subset of the broader processes of developmental plasticity by which organisms adapt to their environment during their life course. Such adaptive processes allow genotypic variation to be preserved through transient environmental changes. Cues for plasticity operate particularly during early development; they may affect a single organ or system, but generally they induce integrated adjustments in the mature phenotype, a process underpinned by epigenetic mechanisms and influenced by prediction of the mature environment. In mammals, an adverse intrauterine environment results in an integrated suite of responses, suggesting the involvement of a few key regulatory genes, that resets the developmental trajectory in expectation of poor postnatal conditions. Mismatch between the anticipated and the actual mature environment exposes the organism to risk of adverse consequences-the greater the mismatch, the greater the risk. For humans, prediction is inaccurate for many individuals because of changes in the postnatal environment toward energy-dense nutrition and low energy expenditure, contributing to the epidemic of chronic noncommunicable disease. This view of human disease from the perspectives of life history biology and evolutionary theory offers new approaches to prevention, diagnosis and intervention.