Programming of cardiac metabolism by miR-15b-5p, a miRNA released in cardiac extracellular vesicles following ischemia-reperfusion injury.

OBJECTIVE: We investigated the potential involvement of miRNAs in the developmental programming of cardiovascular diseases (CVD) by maternal obesity. METHODS: Serum miRNAs were measured in individuals from the Helsinki Birth Cohort (with known maternal body mass index), and a mouse model was used to determine causative effects of maternal obesity during pregnancy and ischemia-reperfusion on offspring cardiac miRNA expression and release. RESULTS: miR-15b-5p levels were increased in the sera of males born to mothers with higher BMI and in the hearts of adult mice born to obese dams. In an ex-vivo model of perfused mouse hearts, we demonstrated that cardiac tissue releases miR-15b-5p, and that some of the released miR-15b-5p was contained within small extracellular vesicles (EVs). We also demonstrated that release was higher from hearts exposed to maternal obesity following ischaemia/reperfusion. Over-expression of miR-15b-5p in vitro led to loss of outer mitochondrial membrane stability and to repressed fatty acid oxidation in cardiomyocytes. CONCLUSIONS: These findings suggest that miR-15-b could play a mechanistic role in the dysregulation of cardiac metabolism following exposure to an in utero obesogenic environment and that its release in cardiac EVs following ischaemic damage may be a novel factor contributing to inter-organ communication between the programmed heart and peripheral tissues.

Large-scale exome sequence analysis identifies sex- and age-specific determinants of obesity.

Obesity contributes substantially to the global burden of disease and has a significant heritable component. Recent large-scale exome sequencing studies identified several genes in which rare, protein-coding variants have large effects on adult body mass index (BMI). Here we extended such work by performing sex-stratified associations in the UK Biobank study (N∼420,000). We identified genes in which rare heterozygous loss-of-function increases adult BMI in women (DIDO1, PTPRG, and SLC12A5) and in men (SLTM), with effect sizes up to ∼8 kg/m2. This is complemented by analyses implicating rare variants in OBSCN and MADD for recalled childhood adiposity. The known functions of these genes, as well as findings of common variant genome-wide pathway enrichment analyses, suggest a role for neuron death, apoptosis, and DNA damage response mechanisms in the susceptibility to obesity across the life-course. These findings highlight the importance of considering sex-specific and life-course effects in the genetic regulation of obesity.

Early life impacts of maternal obesity: a window of opportunity to improve the health of two generations.

The number of pregnancies complicated by obesity is increasing in line with the worldwide obesity crisis; recent estimates suggest that in developed countries more than 50% of pregnancies are in women who are overweight or have obesity. Maternal obesity is associated with an increased risk of many adverse outcomes for both the mother and baby during pregnancy and birth. In addition to these immediate outcomes, maternal obesity before and during pregnancy is associated with an increased risk of offspring cardio-metabolic disease later in life. Studies comparing siblings discordant for in utero exposure to maternal obesity suggest this is not simply due to transmission of 'obesogenic genes' between mother and child or current lifestyle factors, but reflects a direct impact of the obese intrauterine environment on fetal development. This review will describe the long-term consequences of exposure to maternal obesity during development for the cardio-metabolic health of the offspring. It will also discuss the potential molecular mechanisms that underlie the increased risk of metabolic disease in offspring of mothers with obesity, and explore interventions that may be implemented during pregnancy to limit the impact of obesity on offspring long-term health. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part I)'.

Sex-specific effects of maternal metformin intervention during glucose-intolerant obese pregnancy on body composition and metabolic health in aged mouse offspring.

AIMS/HYPOTHESIS: Metformin is increasingly used to treat gestational diabetes (GDM) and pregnancies complicated by pregestational type 2 diabetes or polycystic ovary syndrome but data regarding long-term offspring outcome are lacking in both human studies and animal models. Using a mouse model, this study investigated the effects of maternal metformin intervention during obese glucose-intolerant pregnancy on adiposity, hepatic steatosis and markers of metabolic health of male and female offspring up to the age of 12 months. METHODS: C57BL/6J female mice were weaned onto either a control diet (Con) or, to induce pre-conception obesity, an obesogenic diet (Ob). The respective diets were maintained throughout pregnancy and lactation. These obese dams were then randomised to the untreated group or to receive 300 mg/kg oral metformin hydrochloride treatment (Ob-Met) daily during pregnancy. In male and female offspring, body weights and body composition were measured from 1 month until 12 months of age, when serum and tissues were collected for investigation of adipocyte cellularity (histology), adipose tissue inflammation (histology and quantitative RT-PCR), and hepatic steatosis and fibrosis (histochemistry and modified Folch assay). RESULTS: At 12 months of age, male Ob and Ob-Met offspring showed increased adiposity, adipocyte hypertrophy, elevated expression of proinflammatory genes, hyperleptinaemia and hepatic lipid accumulation compared with Con offspring. Male Ob-Met offspring failed to show hyperplasia between 8 weeks and 12 months, indicative of restricted adipose tissue expansion, resulting in increased immune cell infiltration and ectopic lipid deposition. Female Ob offspring were relatively protected from these phenotypes but Ob-Met female offspring showed increased adiposity, adipose tissue inflammation, hepatic lipid accumulation, hyperleptinaemia and hyperinsulinaemia compared with Con female offspring. CONCLUSIONS/INTERPRETATION: Maternal metformin treatment of obese dams increased offspring metabolic risk factors in a sex- and age-dependent manner. These observations highlight the importance of following up offspring of both sexes beyond early adulthood after interventions during pregnancy. Our findings illustrate the complexity of balancing short-term benefits to mother and child vs any potential long-term metabolic effects on the offspring when prescribing therapeutic agents that cross the placenta.

Programming of cardiometabolic health: the role of maternal and fetal hyperinsulinaemia.

Obesity and gestational diabetes during pregnancy have multiple short- and long-term consequences for both mother and child. One common feature of pregnancies complicated by maternal obesity and gestational diabetes is maternal hyperinsulinaemia, which has effects on the mother and her adaptation to pregnancy. Even though insulin does not cross the placenta insulin can act on the placenta as well affecting placental growth, angiogenesis and lipid metabolism. Obese and gestational diabetic pregnancies are often characterised by maternal hyperglycaemia resulting in exposure of the fetus to high levels of glucose, which freely crosses the placenta. This leads to stimulation of fetal ß-cells and insulin secretion in the fetus. Fetal hyperglycaemia/hyperinsulinaemia has been shown to cause multiple complications in fetal development, such as altered growth trajectories, impaired neuronal and cardiac development and early exhaustion of the pancreas. These changes could increase the susceptibility of the offspring to develop cardiometabolic diseases later in life. In this review, we aim to summarize and review the mechanisms by which maternal and fetal hyperinsulinaemia impact on (i) maternal health during pregnancy; (ii) placental and fetal development; (iii) offspring energy homeostasis and long-term cardiometabolic health; (iv) how interventions can alleviate these effects.

Mechanisms mediating the impact of maternal obesity on offspring hypothalamic development and later function.

As obesity rates have risen around the world, so to have pregnancies complicated by maternal obesity. Obesity during pregnancy is not only associated with negative health outcomes for the mother and the baby during pregnancy and birth, there is also strong evidence that exposure to maternal obesity causes an increased risk to develop obesity, diabetes and cardiovascular disease later in life. Animal models have demonstrated that increased weight gain in offspring exposed to maternal obesity is usually preceded by increased food intake, implicating altered neuronal control of food intake as a likely area of change. The hypothalamus is the primary site in the brain for maintaining energy homeostasis, which it coordinates by sensing whole body nutrient status and appropriately adjusting parameters including food intake. The development of the hypothalamus is plastic and regulated by metabolic hormones such as leptin, ghrelin and insulin, making it vulnerable to disruption in an obese in utero environment. This review will summarise how the hypothalamus develops, how maternal obesity impacts on structure and function of the hypothalamus in the offspring, and the factors that are altered in an obese in utero environment that may mediate the permanent changes to hypothalamic function in exposed individuals.

Exploring Telomere Dynamics in Aging Male Rat Tissues: Can Tissue-Specific Differences Contribute to Age-Associated Pathologies?

INTRODUCTION: Due to increasing lifespan, global aging rates are rising rapidly and age-associated diseases are increasing. To ensure that health span is concomitant with life span, a greater understanding of cellular mechanisms of aging is important. METHODS: Telomere length analysis from a wide range of tissues from weaning, young adult, and middle-aged (3, 12 and 52 week) male Wistar rats were conducted using Southern blotting. Telomere lengths were compared between tissues and ages using regression models based on the ratios of longest-to-shortest telomere fragments. RESULTS: Robust linear age-dependent telomere attrition was observed in the liver; 3 versus 12 weeks, 3 versus 52 weeks (p < 0.01), 12 versus 52 weeks (p < 0.05) and the heart; 3 versus 12 weeks (p < 0.05) and 3 versus 52 weeks (p < 0.001). More subtle shortening was observed in aorta and epididymal fat; 3 and 12 versus 52 weeks (p < 0.001) and in skeletal muscle; 3 versus 52 weeks (p < 0.05), 12 versus 52 weeks (p < 0.01). Young thymus telomeres increased in length (3 vs. 12 weeks) and then shortened between 12 and 52 weeks (p < 0.001). We also reported disparity in telomere shortening within tissues: telomeres in aging brain cortex significantly shortened; 3 versus 52 weeks (p < 0.05), 12 versus 52 weeks (p < 0.01). This was not seen in the hypothalamic region. A robust stepwise shortening was observed in the renal cortex; 3 versus 12 weeks, 12 versus 52 weeks (p < 0.05), and 3 versus 52 weeks (p < 0.001), which was not as apparent in the renal medulla; 3 versus 12 weeks (p < 0.01) and 3 versus 52 weeks (p < 0.01). The vastus lateralis skeletal muscle demonstrated the shortest telomere length at weaning and underwent robust age-associated attrition; 3 versus 52 weeks (p < 0.05), 12 versus 52 weeks (p < 0.01). We demonstrated that specific tissues exhibit unique telomere attrition profiles which may partially explain why certain diseases are more prevalent in aged individuals. DISCUSSION/CONCLUSION: We show wide variations between tissues in vulnerability to the aging process. In the future, this may help target potential interventions to improve health span.

Nutritional and developmental programming effects of insulin.

The discovery of insulin in 1921 was a major breakthrough in medicine and for therapy in patients with diabetes. The dramatic rise in the prevalence of overweight and obesity has been tightly linked to an increased prevalence of gestational diabetes mellitus (GDM), which poses major health concerns. Babies born to GDM mothers are more likely to develop obesity, type 2 diabetes and cardiovascular disease later in life. Evidence accumulated during the past two decades has revealed that high levels insulin, such as those observed during GDM, can have a widespread effect on the development and function of a variety of organs. This review summarises our current knowledge on the role of insulin in the placenta, cardiovascular system and brain during critical periods of development, as well as how it can contribute to lifelong metabolic regulation. We also discuss possible intervention strategies to ameliorate and hopefully reverse the developmental defects associated with obesity and GDM.

Maternal exercise intervention in obese pregnancy improves the cardiovascular health of the adult male offspring.

OBJECTIVE: Obesity during pregnancy is associated with an elevated risk of cardiovascular disease in the offspring. With increased numbers of women entering pregnancy overweight or obese, there is a requirement for targeted interventions to reduce disease risk in future generations. Using an established murine model of maternal obesity during pregnancy, we investigated if a treadmill exercise intervention in the mother could improve offspring cardiac health and explored potential underlying mechanisms. METHODS: A 20-minute treadmill exercise intervention protocol was performed 5 days a week in diet-induced obese female C57BL/6 mice 1 week prior to, and up to E17 of pregnancy. All male offspring were weaned onto a control diet and studied at 8 weeks of age when their cardiovascular physiology was assessed by in vivo echocardiography and non-invasive tail cuff plethysmography. Cardiomyocyte cell area, re-expression of fetal genes and the expression of calcium handling and sympathetic activation proteins were determined. RESULTS: At 8 weeks, there was no difference in bodyweight or fat mass between groups. Offspring of obese dams developed pathologic cardiac hypertrophy, hypertension and cardiac dysfunction characterized by reduced ejection fraction (p < 0.001). Maternal exercise prevented cardiac hypertrophy and dysfunction but failed to prevent hypertension. These offspring of exercised dams also had enhanced (p < 0.001) levels of calcium handling proteins and a sympathetic-activated inotropic response. CONCLUSIONS: Exercise in obese pregnancy was beneficial to offspring cardiac function and structure but did not influence hypertension suggesting they are programmed by separate mechanistic pathways. These data suggest combination interventions in obese pregnancies will be required to improve all aspects of the cardiovascular health of the next generation.

Programming of central and peripheral insulin resistance by low birthweight and postnatal catch-up growth in male mice.

AIMS: Intra-uterine growth restriction (IUGR) followed by accelerated postnatal growth is associated with an increased risk of obesity and type 2 diabetes. We aimed to determine central and peripheral insulin sensitivity in mice that underwent IUGR followed by postnatal catch-up growth and investigate potential molecular mechanisms underpinning their physiology. METHODS: We used a C57BL/6J mouse model of maternal diet-induced IUGR (maternal diet, 8% protein) followed by cross-fostering to a normal nutrition dam (maternal diet, 20% protein) and litter size manipulation to cause accelerated postnatal catch-up growth. We performed intracerebroventricular insulin injection and hyperinsulinaemic-euglycaemic clamp studies to examine the effect of this early nutritional manipulation on central and peripheral insulin resistance. Furthermore, we performed quantitative real-time PCR and western blotting to examine the expression of key insulin-signalling components in discrete regions of the hypothalamus. RESULTS: IUGR followed by accelerated postnatal growth caused impaired glucose tolerance and peripheral insulin resistance. In addition, these 'recuperated' animals were resistant to the anorectic effects of central insulin administration. This central insulin resistance was associated with reduced protein levels of the p110ß subunit of phosphoinositide 3-kinase (PI3K) and increased serine phosphorylation of IRS-1 in the arcuate nucleus (ARC) of the hypothalamus. Expression of the gene encoding protein tyrosine phosphatase 1B (PTP1B; Ptpn1) was also increased specifically in this region of the hypothalamus. CONCLUSIONS/INTERPRETATION: Mice that undergo IUGR followed by catch-up growth display peripheral and central insulin resistance in adulthood. Recuperated offspring show changes in expression/phosphorylation of components of the insulin signalling pathway in the ARC. These defects may contribute to the resistance to the anorectic effects of central insulin, as well as the impaired glucose homeostasis seen in these animals.

Sex and gender differences in developmental programming of metabolism.

BACKGROUND: The early life environment experienced by an individual in utero and during the neonatal period is a major factor in shaping later life disease risk-including susceptibility to develop obesity, diabetes, and cardiovascular disease. The incidence of metabolic disease is different between males and females. How the early life environment may underlie these sex differences is an area of active investigation. SCOPE OF REVIEW: The purpose of this review is to summarize our current understanding of how the early life environment influences metabolic disease risk in a sex specific manner. We also discuss the possible mechanisms responsible for mediating these sexually dimorphic effects and highlight the results of recent intervention studies in animal models. MAJOR CONCLUSIONS: Exposure to states of both under- and over-nutrition during early life predisposes both sexes to develop metabolic disease. Females seem particularly susceptible to develop increased adiposity and disrupted glucose homeostasis as a result of exposure to in utero undernutrition or high sugar environments, respectively. The male placenta is particularly vulnerable to damage by adverse nutritional states and this may underlie some of the metabolic phenotypes observed in adulthood. More studies investigating both sexes are needed to understand how changes to the early life environment impact differently on the long-term health of male and female individuals.

Decreased ovarian reserve, dysregulation of mitochondrial biogenesis, and increased lipid peroxidation in female mouse offspring exposed to an obesogenic maternal diet.

Maternal diet during pregnancy influences the later life reproductive potential of female offspring. We investigate the molecular mechanisms underlying the depletion of ovarian follicular reserve in young adult females following exposure to obesogenic diet in early life. Furthermore, we explore the interaction between adverse maternal diet and postweaning diet in generating reduced ovarian reserve. Female mice were exposed to either maternal obesogenic (high fat/high sugar) or maternal control dietin uteroand during lactation, then weaned onto either obesogenic or control diet. At 12 wk of age, the offspring ovarian reserve was depleted following exposure to maternal obesogenic diet (P< 0.05), but not postweaning obesogenic diet. Maternal obesogenic diet was associated with increased mitochondrial DNA biogenesis (copy numberP< 0.05; transcription factor A, mitochondrial expressionP< 0.05), increased mitochondrial antioxidant defenses [manganese superoxide dismutase (MnSOD)P< 0.05; copper/zinc superoxide dismutaseP< 0.05; glutathione peroxidase 4P< 0.01] and increased lipoxygenase expression (arachidonate 12-lipoxygenaseP< 0.05; arachidonate 15-lipoxygenaseP< 0.05) in the ovary. There was also significantly increased expression of the transcriptional regulator NF-κB (P< 0.05). There was no effect of postweaning diet on any measured ovarian parameters. Maternal diet thus plays a central role in determining follicular reserve in adult female offspring. Our observations suggest that lipid peroxidation and mitochondrial biogenesis are the key intracellular pathways involved in programming of ovarian reserve.-Aiken, C. E., Tarry-Adkins, J. L., Penfold, N. C., Dearden, L., Ozanne, S. E. Decreased ovarian reserve, dysregulation of mitochondrial biogenesis, and increased lipid peroxidation in female mouse offspring exposed to an obesogenic maternal diet.

Early life origins of metabolic disease: Developmental programming of hypothalamic pathways controlling energy homeostasis.

A wealth of animal and human studies demonstrate that perinatal exposure to adverse metabolic conditions - be it maternal obesity, diabetes or under-nutrition - results in predisposition of offspring to develop obesity later in life. This mechanism is a contributing factor to the exponential rise in obesity rates. Increased weight gain in offspring exposed to maternal obesity is usually associated with hyperphagia, implicating altered central regulation of energy homeostasis as an underlying cause. Perinatal development of the hypothalamus (a brain region key to metabolic regulation) is plastic and sensitive to metabolic signals during this critical time window. Recent research in non-human primate and rodent models has demonstrated that exposure to adverse maternal environments impairs the development of hypothalamic structure and consequently function, potentially underpinning metabolic phenotypes in later life. This review summarizes our current knowledge of how adverse perinatal environments program hypothalamic development and explores the mechanisms that could mediate these effects.

Sexual dimorphism in offspring glucose-sensitive hypothalamic gene expression and physiological responses to maternal high-fat diet feeding.

A wealth of animal and human studies demonstrate that early life environment significantly influences adult metabolic balance, however the etiology for offspring metabolic misprogramming remains incompletely understood. Here, we determine the effect of maternal diet per se on offspring sex-specific outcomes in metabolic health and hypothalamic transcriptome regulation in mice. Furthermore, to define developmental periods of maternal diet misprogramming aspects of offspring metabolic balance, we investigated offspring physiological and transcriptomic consequences of maternal high-fat/high-sugar diet feeding during pregnancy and/or lactation. We demonstrate that female offspring of high-fat/high-sugar diet-fed dams are particularly vulnerable to metabolic perturbation with body weight increases due to postnatal processes, whereas in utero effects of the diet ultimately lead to glucose homeostasis dysregulation. Furthermore, glucose- and maternal-diet sensitive gene expression modulation in the paraventricular hypothalamus is strikingly sexually dimorphic. In summary, we uncover female-specific, maternal diet-mediated in utero misprogramming of offspring glucose homeostasis and a striking sexual dimorphism in glucose- and maternal diet-sensitive paraventricular hypothalamus gene expression adjustment. Notably, female offspring metabolic vulnerability to maternal high-fat/high-sugar diet propagates a vicious cycle of obesity and type 2 diabetes in subsequent generations.

The deubiquitylase USP15 stabilizes newly synthesized REST and rescues its expression at mitotic exit.

Reversible ubiquitylation of proteins contributes to their integrity, abundance and activity. The RE1-silencing transcription factor (REST) plays key physiological roles and is dysregulated in a spectrum of disease. It is rapidly turned over and is phosphorylated, polyubiquitylated and degraded en masse during neuronal differentiation and cell cycle progression. Through siRNA screening we identified the deubiquitylase USP15 as a key regulator of cellular REST. Both antagonism of REST polyubiquitylation and rescue of endogenous REST levels are dependent on the deubiquitylase activity of USP15. However, USP15 depletion does not destabilize pre-existing REST, but rather specifically impairs de novo REST synthesis. Indeed, we find that a small fraction of endogenous USP15 is associated with polysomes. In accordance with these findings, USP15 does not antagonize the degradation of phosphorylated REST at mitosis. Instead it is required for the rapid accumulation of newly synthesized REST on mitotic exit, thus playing a key role in its cell cycle oscillations. Importantly, this study reveals a novel role for a DUB in specifically promoting new protein synthesis.

SENP3-mediated deSUMOylation of dynamin-related protein 1 promotes cell death following ischaemia.

Global increases in small ubiquitin-like modifier (SUMO)-2/3 conjugation are a neuroprotective response to severe stress but the mechanisms and specific target proteins that determine cell survival have not been identified. Here, we demonstrate that the SUMO-2/3-specific protease SENP3 is degraded during oxygen/glucose deprivation (OGD), an in vitro model of ischaemia, via a pathway involving the unfolded protein response (UPR) kinase PERK and the lysosomal enzyme cathepsin B. A key target for SENP3-mediated deSUMOylation is the GTPase Drp1, which plays a major role in regulating mitochondrial fission. We show that depletion of SENP3 prolongs Drp1 SUMOylation, which suppresses Drp1-mediated cytochrome c release and caspase-mediated cell death. SENP3 levels recover following reoxygenation after OGD allowing deSUMOylation of Drp1, which facilitates Drp1 localization at mitochondria and promotes fragmentation and cytochrome c release. RNAi knockdown of SENP3 protects cells from reoxygenation-induced cell death via a mechanism that requires Drp1 SUMOylation. Thus, we identify a novel adaptive pathway to extreme cell stress in which dynamic changes in SENP3 stability and regulation of Drp1 SUMOylation are crucial determinants of cell fate.

Enhanced SUMOylation and SENP-1 protein levels following oxygen and glucose deprivation in neurones.

Here, we show that oxygen and glucose deprivation (OGD) causes increased small ubiquitin-like modifier (SUMO)-1 and SUMO-2/3 conjugation to substrate proteins in cultured hippocampal neurones. Surprisingly, the SUMO protease SENP-1, which removes SUMO from conjugated proteins, was also increased by OGD, suggesting that the neuronal response to OGD involves a complex interplay between SUMOylation and deSUMOylation. Importantly, decreasing global SUMOylation in cultured hippocampal neurones by overexpression of the catalytic domain of SENP-1 increased neuronal vulnerability to OGD-induced cell death. Taken together, these results suggest a neuroprotective role for neuronal SUMOylation after OGD.