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Candice Marion, Philippe Zizzari, Raphael G P Denis, Rim Hassouna, Yacine Chebani, Thierry Leste-Lasserre, Hélène Doat, Gwenaëlle Le Pen, Daniela Cota, Florence Noble, Serge Luquet, and Jacques Pantel

The growth hormone secretagogue receptor (GHSR) mediates key properties of the gut hormone ghrelin on metabolism and behavior. Nevertheless, most recent observations also support that the GHSR is a constitutively active G protein-coupled receptor (GPCR) endowed with a sophisticated tuning involving a balance of endogenous ligands. Demonstrating the feasibility of shifting GHSR canonical signaling in vivo, we previously reported that a model with enhanced sensitivity to ghrelin (Ghsr Q343X mutant rats) developed fat accumulation and glucose intolerance. Herein, we investigated the contribution of energy homeostasis to the onset of this phenotype, as well as behavioral responses to feeding or pharmacological challenges, by comparing Ghsr M/M rats to WT littermate rats: (1) as freely behaving animals and (2) in feeding and locomotor paradigms. Herein, Ghsr M/M rats showed enhanced locomotor response to a GHSR agonist while locomotor or anorexigenic responses to amphetamine or cabergoline (dopamine receptor 2 agonist), respectively, were preserved. Ad libitum fedGhsr M/M rats consumed and conditioned for sucrose similarly to littermate control rats . In calorie-restricted conditions, Ghsr M/M rats retained food anticipatory activity and maintained better body weight and glycemia. Importantly, prior to fat accumulation, male Ghsr M/M rats preferentially used carbohydrates as fuel substrate without alterations of energy intake, energy expenditure or physical activity and showed alterations of the GHSR system (i.e. enhanced ratio of GHSR hormones LEAP2: acyl-ghrelin and increased Ghsr expression in the hypothalamus). Overall, the present study provides proof for the concept that shifted GHSR signaling can specifically alter nutrient partitioning resulting in modified balance of carbohydrate/lipid utilization.

Free access

Harleen Kaur, Beverly S Muhlhausler, Claire T Roberts, and Kathryn L Gatford

The growth hormone (GH)–insulin-like growth factor (IGF) axis is one of the main drivers of mammalian growth and development. Pituitary secretion of GH is pulsatile and under positive and negative hypothalamic control, as well as stimulation from gastric-secreted acyl-ghrelin. GH acts both directly via the GH-receptor (GHR) and indirectly via stimulation of IGF1 production to induce anabolic and metabolic responses at multiple target tissues. In this review, we describe the major changes to this axis during pregnancy, with increasing GH abundance in the maternal circulation across multiple species. This stimulates the secretion of IGFs, whose bioavailability is also increased by proteolytic cleavage of their circulating binding proteins during pregnancy. These changes in turn induce maternal metabolic adaptations to pregnancy and promote placental function and fetal growth, as does exogenous GH or IGF treatment in animal models of normal and compromised pregnancy. Finally, we explore alternative approaches to enhance maternal GH abundance during pregnancy to promote maternal adaptations, placental function and hence fetal growth.

Free access

Daniel J Tobiansky, George V Kachkovski, Reilly T Enos, Kim L Schmidt, E Angela Murphy, Stan B Floresco, and Kiran K Soma

Maternal diets can have dramatic effects on the physiology, metabolism, and behaviour of offspring that persist into adulthood. However, the effects of maternal sucrose consumption on offspring remain unclear. Here, female rats were fed either a sucrose diet with a human-relevant level of sucrose (25% of kcal) or a macronutrient-matched, isocaloric control diet before, during, and after pregnancy. After weaning, all offspring were fed a standard low-sucrose rodent chow. We measured indicators of metabolism (weight, adipose, glucose tolerance, and liver lipids) during development and adulthood (16–24 weeks). We also measured food preference and motivation for sugar rewards in adulthood. Finally, in brain regions regulating these behaviours, we measured steroids and transcripts for steroidogenic enzymes, steroid receptors, and dopamine receptors. In male offspring, maternal sucrose intake decreased body mass and visceral adipose tissue, increased preference for high-sucrose and high-fat diets, increased motivation for sugar rewards, and decreased mRNA levels of Cyp17a1 (an androgenic enzyme) in the nucleus accumbens. In female offspring, maternal sucrose intake increased basal corticosterone levels. These data demonstrate the enduring, diverse, and sex-specific effects of maternal sucrose consumption on offspring phenotype.

Free access

Hye-Jin Lee, Haifei Shi, Hella S Brönneke, Bo-Yeong Jin, Sang-Hyun Choi, Randy J Seeley, and Dong-Hoon Kim

Vascular reactivity of adipose tissue (AT) is hypothesized to play an important role in the development of obesity. However, the exact role of vascular reactivity in the development of obesity remains unclear. In this study, we investigated the chronological changes in vascular reactivity and the microenvironments of the visceral AT (VAT) and subcutaneous AT (SAT) in lean and obese mice. Changes in blood flow levels induced by a β-adrenoceptor agonist (isoproterenol) were significantly lower in the VAT of the mice fed a high-fat diet (HFD) for 1 and 12 weeks than those in the VAT of the mice fed a low-fat diet (LFD) for the same period; no significant change was observed in the SAT of any mouse group, suggesting depot-specific vascular reactivity of AT. Moreover, the hypoxic area and the expression of genes associated with angiogenesis and macrophage recruitment were increased in the VAT (but not in the SAT) of mice fed an HFD for 1 week compared with mice fed an LFD. These changes occurred with no morphological changes, including those related to adipocyte size, AT vessel density, and the diameter and pericyte coverage of the endothelium, suggesting a determinant role of vascular reactivity in the type of AT remodeling. The suppression of vascular reactivity was accompanied by increased endothelin1 (Edn1) gene expression and extracellular matrix (ECM) stiffness only in the VAT, implying enhanced contractile activities of the vasculature and ECM. The results suggest a depot-specific role of vascular reactivity in AT remodeling during the development of obesity.

Free access

Shang-Wu Shih, Jia-Jiun Yan, Yi-Hsing Wang, Yi-Ling Tsou, Ling Chiu, Yung-Che Tseng, Ming-Yi Chou, and Pung-Pung Hwang

Estrogen-related receptors (ERRs) are known to function in mammalian kidney as key regulators of ion transport-related genes; however, a comprehensive understanding of the physiological functions of ERRs in vertebrate body fluid ionic homeostasis is still elusive. Here, we used medaka (Oryzias melastigma), a euryhaline teleost, to investigate how ERRs are involved in ion regulation. After transferring medaka from hypertonic seawater to hypotonic freshwater (FW), the mRNA expression levels of errγ2 were highly upregulated, suggesting that Errγ2 may play a crucial role in ion uptake. In situ hybridization showed that errγ2 was specifically expressed in ionocytes, the cells responsible for Na+/Cl transport. In normal FW, ERRγ2 morpholino knockdown caused reductions in the mRNA expression of Na+/Cl cotransporter (Ncc), the number of Ncc ionocytes, Na+/Cl influxes of ionocytes, and whole-body Na+/Cl contents. In FW with low Na+ and low Cl, the expression levels of mRNA for Na+/H+ exchanger 3 (Nhe3) and Ncc were both decreased in Errγ2 morphants. Treating embryos with DY131, an agonist of Errγ, increased the whole-body Na+/Cl contents and ncc mRNA expression in Errγ2 morphants. As such, medaka Errγ2 may control Na+/Cl uptake by regulating ncc and/or nhe3 mRNA expression and ionocyte number, and these regulatory actions may be subtly adjusted depending on internal and external ion concentrations. These findings not only provide new insights into the underpinning mechanism of actions of ERRs, but also enhance our understanding of their roles in body fluid ionic homeostasis for adaptation to changing environments during vertebrate evolution.

Free access

Jordan E Hamden, Melody Salehzadeh, Katherine M Gray, Brandon J Forys, and Kiran K Soma

Glucocorticoids (GCs) are secreted by the adrenal glands and locally produced by lymphoid organs. Adrenal GC secretion at baseline and in response to stressors is greatly reduced during the stress hyporesponsive period (SHRP) in neonatal mice (postnatal day (PND) 2–12). It is unknown whether lymphoid GC production increases in response to stressors during the SHRP. Here, we administered an acute stressor (isoflurane anesthesia) to mice before, during, and after the SHRP and measured systemic and local GCs via mass spectrometry. We administered isoflurane, vehicle control (oxygen), or neither (baseline) at PND 1, 5, 9, or 13 and measured progesterone and six GCs in blood, bone marrow, thymus, and spleen. At PND1, blood and lymphoid GC levels were high and did not respond to stress. At PND5, blood GC levels were very low and increased slightly after stress, while lymphoid GC levels were also low but increased greatly after stress. At PND9, blood and lymphoid GC levels were similar at baseline and increased similarly after stress. At PND13, blood GC levels were higher than lymphoid GC levels at baseline, and blood GC levels showed a greater response to stress. These data demonstrate the remarkable plasticity of GC physiology during the postnatal period, show that local steroid levels do not reflect systemic steroid levels, provide insight into the SHRP, and identify a potential mechanism by which early-life stressors can alter immunity in adulthood.

Free access

Andrew T Templin, Christine Schmidt, Meghan F Hogan, Nathalie Esser, Richard N Kitsis, Rebecca L Hull, Sakeneh Zraika, and Steven E Kahn

Apoptosis repressor with caspase recruitment domain (ARC) is an endogenous inhibitor of cell death signaling that is expressed in insulin-producing β cells. ARC has been shown to reduce β-cell death in response to diabetogenic stimuli in vitro, but its role in maintaining glucose homeostasis in vivo has not been fully established. Here we examined whether loss of ARC in FVB background mice exacerbates high fat diet (HFD)-induced hyperglycemia in vivo over 24 weeks. Prior to commencing 24-week HFD, ARC−/− mice had lower body weight than wild type (WT) mice. This body weight difference was maintained until the end of the study and was associated with decreased epididymal and inguinal adipose tissue mass in ARC−/− mice. Non-fasting plasma glucose was not different between ARC−/− and WT mice prior to HFD feeding, and ARC−/− mice displayed a greater increase in plasma glucose over the first 4 weeks of HFD. Plasma glucose remained elevated in ARC−/− mice after 16 weeks of HFD feeding, at which time it had returned to baseline in WT mice. Following 24 weeks of HFD, non-fasting plasma glucose in ARC−/− mice returned to baseline and was not different from WT mice. At this final time point, no differences were observed between genotypes in plasma glucose or insulin under fasted conditions or following intravenous glucose administration. However, HFD-fed ARC−/− mice exhibited significantly decreased β-cell area compared to WT mice. Thus, ARC deficiency delays, but does not prevent, metabolic adaptation to HFD feeding in mice, worsening transient HFD-induced hyperglycemia.

Open access

Antonio Gázquez, Francisca Rodríguez, María Sánchez-Campillo, Lidia E Martínez-Gascón, Marino B Arnao, Pedro Saura-Garre, María D Albaladejo-Otón, and Elvira Larqué

Gestational diabetes mellitus (GDM) reduces maternal adiponectin and docosahexaenoic acid (DHA) materno-fetal transfer, which may have negative consequences for the offspring. Our aim was to evaluate the effects of the administration of a novel adiponectin agonist (AdipoRon) to GDM rats on the long-term consequences in glycaemia and fatty acids (FA) profile in the offspring. Pregnant rats were randomized to three groups: GDM rats (GDM, n = 8), GDM rats treated with AdipoRon (GDM + ADI, n = 9), and control rats (n = 10). Diabetes was induced with streptozotocin (50 mg/kg) on day 12 of gestation. GDM+ADI received 50 mg/kg/day AdipoRon from day 14 until delivery. Glycaemia and FA profile were determined in mothers and adult offspring (12 weeks old). AdipoRon tended to reduce fasting glucose in diabetic mothers. Diabetic rats presented the foetus with intrauterine growth restriction and higher adiposity, which tried to be counteracted by AdipoRon. In the adult offspring, both GDM + ADI and control animals showed better glucose recovery after oral glucose overload with respect to GDM. DHA in offspring plasma was significantly reduced in both GDM and GDM + ADI compared to controls (P = 0.043). Nevertheless, n-6/n-3 polyunsaturated FA (PUFA) ratio improved in plasma of GDM + ADI adult offspring (GDM: 14.83 ± 0.85a%; GDM + ADI: 11.49 ± 0.58b%; control: 10.03 ± 1.22b%, P = 0.034). Inflammatory markers and oxidative stress were reduced in the adult offspring of AdipoRon-treated mothers. In conclusion, AdipoRon administration to pregnant diabetic rats improved glycaemia in the mothers and long-term glucose tolerance in the offspring. In addition, it tended to reduce excessive foetal fat accumulation and improved n-6/n-3 PUFA ratio significantly in offspring at the adult state.

Free access

Simon Travers, Laetitia Martinerie, Qiong-Yao Xue, Julie Perrot, Say Viengchareun, Kathleen M Caron, Elizabeth S Blakeney, Pascal Boileau, Marc Lombès, and Eric Pussard

Preterm birth is associated with immaturity of several crucial physiological functions notably those prevailing in the lung and kidney. Recently, a steroid secretion deficiency was identified in very preterm neonates, associated with a partial yet transient deficiency in 11β-hydroxylase activity, sustaining cortisol synthesis. However, the P450c11β enzyme is expressed in preterm adrenal glands, we hypothesized an inhibition of cortisol production by adrenomedullin (ADM), a peptide highly produced in neonates and whose effect on steroidogenesis remains poorly known. We studied the effects of ADM on three models: 104 cord-blood samples of the PREMALDO neonate cohort, genetically targeted mice overexpressing ADM, and two human adrenocortical cell lines (H295R and HAC15 cells). Mid-regional-proADM (MR-proADM) quantification in cord-blood samples showed strong negative correlation with gestational age (P = 0.0004), cortisol production (P < 0.0001), and 11β-hydroxylase activity index (P < 0.0001). Mean MR-proADM was higher in very preterm than in term neonates (1.12 vs 0.60 nmol/L, P < 0.0001). ADM-overexpression mice revealed a lower 11β-hydroxylase activity index (P < 0.05). Otherwise, aldosterone levels measured by LC-MS/MS were higher in ADM-overexpression mice (0.83 vs 0.46 ng/mL, P < 0.05). More importantly, the negative relationship between adrenal ADM expression and aldosterone production found in control was lacking in the ADM-overexpression mice. Finally, LC-MS/MS and gene expression studies on H295R and HAC15 cells revealed an ADM-induced inhibition of both cortisol secretion in cell supernatants and CYP11B1 expression. Collectively, our results converge toward an inhibitory effect of ADM on glucocorticoid synthesis in humans and should be considered to explain the steroid secretion deficiency observed at birth in premature newborns.

Open access

K L Davies, E J Camm, D J Smith, O R Vaughan, A J Forhead, A J Murray, and A L Fowden

In adults, glucocorticoids act to match the supply and demand for energy during physiological challenges, partly through actions on tissue mitochondrial oxidative phosphorylation (OXPHOS) capacity. However, little is known about the role of the natural prepartum rise in fetal glucocorticoid concentrations in preparing tissues for the increased postnatal energy demands. This study examined the effect of manipulating cortisol concentrations in fetal sheep during late gestation on mitochondrial OXPHOS capacity of two skeletal muscles with different postnatal locomotive functions. Mitochondrial content, biogenesis markers, respiratory rates and expression of proteins and genes involved in the electron transfer system (ETS) and OXPHOS efficiency were measured in the biceps femoris (BF) and superficial digital flexor (SDF) of fetuses either infused with cortisol before the prepartum rise or adrenalectomised to prevent this increment. Cortisol infusion increased mitochondrial content, biogenesis markers, substrate-specific respiration rates and abundance of ETS complex I and adenine nucleotide translocator (ANT1) in a muscle-specific manner that was more pronounced in the SDF than BF. Adrenalectomy reduced mitochondrial content and expression of PGC1α and ANT1 in both muscles, and ETS complex IV abundance in the SDF near term. Uncoupling protein gene expression was unaffected by cortisol manipulations in both muscles. Gene expression of the myosin heavy chain isoform, MHCIIx, was increased by cortisol infusion and reduced by adrenalectomy in the BF alone. These findings show that cortisol has a muscle-specific role in prepartum maturation of mitochondrial OXPHOS capacity with important implications for the health of neonates born pre-term or after intrauterine glucocorticoid overexposure.