The competition for nutrients that arises when pregnancy coincides with continuing or incomplete growth in young adolescent girls increases the risk of preterm delivery and low birthweight with negative after-effects for mother and child extending beyond the perinatal period. Sheep paradigms involving nutritional management of weight and adiposity in young, biologically immature adolescents have allowed the consequences of differential maternal growth status to be explored. Although nutrient reserves at conception play a modest role, it is the dietary manipulation of the maternal growth trajectory thereafter which has the most negative impact on pregnancy outcome. Overnourishing adolescents to promote rapid maternal growth is particularly detrimental as placental growth, uteroplacental blood flows and fetal nutrient delivery are perturbed leading to a high incidence of fetal growth restriction and premature delivery of low birthweight lambs, whereas in undernourished adolescents further maternal growth is prevented, and depletion of the maternal body results in a small reduction in birthweight independent of placental size. Maternal and placental endocrine systems are differentially altered in both paradigms with downstream effects on fetal endocrine systems, organ development and body composition. Approaches to reverse these effects have been explored, predominantly targeting placental growth or function. After birth, growth-restricted offspring born to overnourished adolescents and fed to appetite have an altered metabolic phenotype which persists into adulthood, whereas offspring of undernourished adolescents are largely unaffected. This body of work using ovine paradigms has public health implications for nutritional advice offered to young adolescents before and during pregnancy, and their offspring thereafter.
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Stephen G Matthews and Patrick O McGowan
It has been approximately 30 years since the seminal discoveries of David Barker and his colleagues, and research is beginning to unravel the mechanisms that underlie developmental programming. The early environment of the embryo, foetus and newborn have been clearly linked to altered hypothalamic–pituitary–adrenal (HPA) function and related behaviours through the juvenile period and into adulthood. A number of recent studies have shown that these effects can pass across multiple generations. The HPA axis is highly responsive to the environment, impacts both central and peripheral systems and is critical to health in a wide variety of contexts. Mechanistic studies in animals are linking early exposures to adversity with changes in gene regulatory mechanisms, including modifications of DNA methylation and altered levels of miRNA. Similar associations are emerging from recent human studies. These findings suggest that epigenetic mechanisms represent a fundamental link between adverse early environments and developmental programming of later disease. The underlying biological mechanisms that connect the perinatal environment with modified long-term health outcomes represent an intensive area of research. Indeed, opportunities for early interventions must identify the relevant environmental factors and their molecular targets. This new knowledge will likely assist in the identification of individuals who are at risk of developing poor outcomes and for whom early intervention is most effective.
Kok Lim Kua, Shanming Hu, Chunlin Wang, Jianrong Yao, Diana Dang, Alexander B Sawatzke, Jeffrey L Segar, Kai Wang and Andrew W Norris
Offspring exposed in utero to maternal diabetes exhibit long-lasting insulin resistance, though the initiating mechanisms have received minimal experimental attention. Herein, we show that rat fetuses develop insulin resistance after only 2-day continuous exposure to isolated hyperglycemia starting on gestational day 18. Hyperglycemia-induced reductions in insulin-induced AKT phosphorylation localized primarily to fetal skeletal muscle. The skeletal muscle of hyperglycemia-exposed fetuses also exhibited impaired in vivo glucose uptake. To address longer term impacts of this short hyperglycemic exposure, neonates were cross-fostered and examined at 21 days postnatal age. Offspring formerly exposed to 2 days late gestation hyperglycemia exhibited mild glucose intolerance with insulin signaling defects localized only to skeletal muscle. Fetal hyperglycemic exposure has downstream consequences which include hyperinsulinemia and relative uteroplacental insufficiency. To determine whether these accounted for induction of insulin resistance, we examined fetuses exposed to late gestational isolated hyperinsulinemia or uterine artery ligation. Importantly, 2 days of fetal hyperinsulinemia did not impair insulin signaling in murine fetal tissues and 21-day-old offspring exposed to fetal hyperinsulinemia had normal glucose tolerance. Similarly, fetal exposure to 2-day uteroplacental insufficiency did not perturb insulin-stimulated AKT phosphorylation in fetal rats. We conclude that fetal exposure to hyperglycemia acutely produces insulin resistance. As hyperinsulinemia and placental insufficiency have no such impact, this occurs likely via direct tissue effects of hyperglycemia. Furthermore, these findings show that skeletal muscle is uniquely susceptible to immediate and persistent insulin resistance induced by hyperglycemia.
Patrycja A Jazwiec and Deborah M Sloboda
It is well established that early life environmental signals, including nutrition, set the stage for long-term health and disease risk – effects that span multiple generations. This relationship begins early, in the periconceptional period and extends into embryonic, fetal and early infant phases of life. Now known as the Developmental Origins of Health and Disease (DOHaD), this concept describes the adaptations that a developing organism makes in response to early life cues, resulting in adjustments in homeostatic systems that may prove maladaptive in postnatal life, leading to an increased risk of chronic disease and/or the inheritance of risk factors across generations. Reproductive maturation and function is similarly influenced by early life events. This should not be surprising, since primordial germ cells are established early in life and thus vulnerable to early life adversity. A multitude of ‘modifying’ cues inducing developmental adaptations have been identified that result in changes in reproductive development and impairments in reproductive function. Many types of nutritional challenges including caloric restriction, macronutrient excess and micronutrient insufficiencies have been shown to induce early life adaptations that produce long-term reproductive dysfunction. Many pathways have been suggested to underpin these associations, including epigenetic reprogramming of germ cells. While the mechanisms still remain to be fully investigated, it is clear that a lifecourse approach to understanding lifetime reproductive function is necessary. Furthermore, investigations of the impacts of early life adversity must be extended to include the paternal environment, especially in epidemiological and clinical studies of offspring reproductive function.
Miguel A Velazquez, Tom P Fleming and Adam J Watkins
The concept emerging from Professor David Barker’s seminal research on the developmental origins of later-life disease has progressed in many directions since it was first published. One critical question being when during gestation might environment alter the developmental programme with such enduring consequences. Here, we review the growing consensus from clinical and animal research that the period around conception, embracing gamete maturation and early embryogenesis might be the most vulnerable period. We focus on four types of environmental exposure shown to modify periconceptional reproduction and offspring development and health: maternal overnutrition and obesity; maternal undernutrition; paternal diet and health; and assisted reproductive technology. These conditions may act through diverse epigenetic, cellular and physiological mechanisms to alter gene expression and cellular signalling and function in the conceptus affecting offspring growth and metabolism leading to increased risk for cardiometabolic and neurological disease in later life.
Trassanee Chatmethakul and Robert D Roghair
Consistent with the paradigm shifting observations of David Barker and colleagues that revealed a powerful relationship between decreased weight through 2 years of age and adult disease, intrauterine growth restriction (IUGR) and preterm birth are independent risk factors for the development of subsequent hypertension. Animal models have been indispensable in defining the mechanisms responsible for these associations and the potential targets for therapeutic intervention. Among the modifiable risk factors, micronutrient deficiency, physical immobility, exaggerated stress hormone exposure and deficient trophic hormone production are leading candidates for targeted therapies. With the strong inverse relationship seen between gestational age at delivery and the risk of hypertension in adulthood trumping all other major cardiovascular risk factors, improvements in neonatal care are required. Unfortunately, therapeutic breakthroughs have not kept pace with rapidly improving perinatal survival, and groundbreaking bench-to-bedside studies are urgently needed to mitigate and ultimately prevent the tsunami of prematurity-related adult cardiovascular disease that may be on the horizon. This review highlights our current understanding of the developmental origins of hypertension and draws attention to the importance of increasing the availability of lactation consultants, nutritionists, pharmacists and physical therapists as critical allies in the battle that IUGR or premature infants are waging not just for survival but also for their future cardiometabolic health.
Holly M Johnson, Erin Stanfield, Grace J Campbell, Erica E Eberl, Gregory J Cooney and Kim S Bell-Anderson
Poor nutrition plays a fundamental role in the development of insulin resistance, an underlying characteristic of type 2 diabetes. We have previously shown that high-fat diet-induced insulin resistance in rats can be ameliorated by a single glucose meal, but the mechanisms for this observation remain unresolved. To determine if this phenomenon is mediated by gut or hepatoportal factors, male Wistar rats were fed a high-fat diet for 3 weeks before receiving one of five interventions: high-fat meal, glucose gavage, high-glucose meal, systemic glucose infusion or portal glucose infusion. Insulin sensitivity was assessed the following day in conscious animals by a hyperinsulinaemic-euglycaemic clamp. An oral glucose load consistently improved insulin sensitivity in high-fat-fed rats, establishing the reproducibility of this model. A systemic infusion of a glucose load did not affect insulin sensitivity, indicating that the physiological response to oral glucose was not due solely to increased glucose turnover or withdrawal of dietary lipid. A portal infusion of glucose produced the largest improvement in insulin sensitivity, implicating a role for the hepatoportal region rather than the gastrointestinal tract in mediating the effect of glucose to improve lipid-induced insulin resistance. These results further deepen our understanding of the mechanism of glucose-mediated regulation of insulin sensitivity and provide new insight into the role of nutrition in whole body metabolism.
Fazal Wahab, Ikram Ullah Khan, Ignacio Rodriguez Polo, Hira Zubair, Charis Drummer, Muhammad Shahab and Rüdiger Behr
Irisin, encoded by the FNDC5 gene, is a recently discovered endocrine factor mainly secreted as a myokine and adipokine. However, irisin/FNDC5 expression has also been reported in different other organs including components of the reproductive axis. Yet, there is the scarcity of data on FNDC5/irisin expression, regulation and its reproductive effects, particularly in primates. Here, we report the expression of FNDC5/irisin, along with PGC1A (peroxisome proliferator-activated receptor gamma coactivator 1-alpha) and ERRA (estrogen-related receptor alpha), in components of the reproductive axis of marmoset monkeys. Hypothalamic FNDC5 and ERRA transcript levels are developmentally regulated in both male and female. We further uncovered sex-specific differences in FNDC5, ERRA and PGC1A expression in muscle and the reproductive axis. Moreover, irisin and ERRα co-localize in the marmoset hypothalamus. Additionally, in the arcuate nucleus of rhesus monkeys, the number of irisin+ cells was significantly increased in short-term fasted monkeys as compared to ad libitum-fed monkeys. More importantly, we observed putative interaction of irisin-immunoreactive fibers and few GnRH-immunoreactive cell bodies in the mediobasal hypothalamus of the rhesus monkeys. Functionally, we noted a stimulatory effect of irisin on GnRH synthesis and release in mouse hypothalamic neuronal GT1-7 cells. In summary, our findings show that FNDC5 and irisin are developmentally, metabolic-status dependently and sex-specifically expressed in the primate hypothalamic–pituitary–gonadal axis and exert a stimulatory effect on GnRH expression and release in mouse hypothalamic cells. Further studies are required to confirm the reproductive effects of irisin in vivo and to illuminate the mechanisms of its regulation.
Shanqi Fu, Miho Kuwahara, Yoko Uchida, Sei Kondo, Daichi Hayashi, Yuji Shimomura, Asami Takagaki, Takashi Nishida, Yusuke Maruyama, Mika Ikegame, Atsuhiko Hattori, Satoshi Kubota and Takako Hattori
Endochondral ossification, including bone growth and other metabolic events, is regulated by circadian rhythms. Herein, we provide evidence that melatonin has a direct effect on the circadian rhythm of chondrocytes. We detected mRNA expression of the genes which encode the melatonin-synthesizing enzymes AANAT (arylalkylamine N-acetyltransferase) and HIOMT (hydroxyindole O-methyltransferase), as well as the melatonin receptors MT1 and MT2 in mouse primary chondrocytes and cartilage. Production of melatonin was confirmed by mass spectrometric analysis of primary rat and chick chondrocytes. Addition of melatonin to primary BALB/c mouse chondrocytes caused enhanced cell growth and increased expression of Col2a1, Aggrecan and Sox9, but inhibited Col10a1 expression. Addition of luzindole, an MT1 and MT2 antagonist, abolished these effects. These data indicate that chondrocytes produce melatonin, which regulates cartilage growth and maturation via the MT1 and MT2 receptors. Kinetic analysis showed that melatonin caused rapid upregulation of Aanat, Mt1, Mt2 and Pthrp expression, followed by Sox9 and Ihh. Furthermore, expression of the clock gene Bmal1 was induced, while that of Per1 was downregulated. Chronobiological analysis of synchronized C3H mouse chondrocytes revealed that melatonin induced the cyclic expression of Aanat and modified the cyclic rhythm of Bmal1, Mt1 and Mt2. In contrast, Mt1 and Mt2 showed different rhythms from Bmal1 and Aanat, indicating the existence of different regulatory genes. Our results indicate that exogenous and endogenous melatonin work in synergy in chondrocytes to adjust rhythmic expression to the central suprachiasmatic nucleus clock.
Kira G Slepchenko, Kathryn L Corbin and Craig S Nunemaker
Glucose-stimulated insulin secretion (GSIS) is a well-accepted method to investigate the physiological and pathophysiological function of islets. However, there is little consensus about which method is best for normalizing and presenting GSIS data. In this study, we evaluated the sufficiency of islet area, total protein, total DNA and total insulin content as parameters to normalize GSIS data. First, we tested if there is a linear correlation between each parameter and the number of islets (10, 20, 30 and 40 islets). Islet area, total protein and insulin content produced excellent linear correlations with islet number (R 2 > 0.9 for each) from the same islet material. Insulin secretion in 11 mM glucose also correlated reasonably well for islet area (R 2 = 0.69), protein (R 2 = 0.49) and insulin content (R 2 = 0.58). DNA content was difficult to reliably measure and was excluded from additional comparisons. We next measured GSIS for 18 replicates of 20 islets each, measuring 3 mM and 11 mM glucose to calculate the stimulation index and to compare each normalization parameter. Using these similar islet masses for each replicate, none of the parameters produced linear correlations with GSIS (R 2 < 0.05), suggesting that inherent differences in GSIS dominate small differences in islet mass. We conclude that when comparing GSIS for islets of reasonably similar size (<50% variance), normalization does not improve the representation of GSIS data. Normalization may be beneficial when substantial differences in islet mass are involved. In such situations, we suggest that using islet cross-sectional area is superior to other commonly used techniques for normalizing GSIS data.