Loss of LEPR function (LOF) in mammals leads to diverse phenotypes including morbid obesity and infertility while zebrafish show relatively minor phenotypes. This however allows the study of LEPR LOF in the absence of the detrimental effects of hyperglycemia or obesity. Here, we show evidence that leptin plays a role in the central as well as peripheral regulation of the hypothalamic–pituitary–gonadal (HPG) axis in zebrafish. Animals with a Lepr LOF show dysregulated pituitary HPG genes as well as evidence that oocytes mature slower and/or exhibit an increased rate of atresia. In culture, Lepr LOF attenuates the effect of 17α-20β-dihydroxy-4 pregnen-3-one in promoting germinal vesicle breakdown (GVBD) and increases the rate of GVBD as well as attenuates the rate of oocyte atresia.
Amrutha Bagivalu Lakshminarasimha, Madhuri Puvvada, Matthias Hammerschmidt, and Maximilian Michel
Laura L Gathercole, Nikolaos Nikolaou, Shelley E Harris, Anastasia Arvaniti, Toryn M Poolman, Jonathan M Hazlehurst, Denise V Kratschmar, Marijana Todorčević, Ahmad Moolla, Niall Dempster, Ryan C Pink, Michael F Saikali, Liz Bentley, Trevor M Penning, Claes Ohlsson, Carolyn L Cummins, Matti Poutanen, Alex Odermatt, Roger D Cox, and Jeremy W Tomlinson
Steroid 5β-reductase (AKR1D1) plays important role in hepatic bile acid synthesis and glucocorticoid clearance. Bile acids and glucocorticoids are potent metabolic regulators, but whether AKR1D1 controls metabolic phenotype in vivo is unknown. Akr1d1–/– mice were generated on a C57BL/6 background. Liquid chromatography/mass spectrometry, metabolomic and transcriptomic approaches were used to determine effects on glucocorticoid and bile acid homeostasis. Metabolic phenotypes including body weight and composition, lipid homeostasis, glucose tolerance and insulin tolerance were evaluated. Molecular changes were assessed by RNA-Seq and Western blotting. Male Akr1d1–/– mice were challenged with a high fat diet (60% kcal from fat) for 20 weeks. Akr1d1–/– mice had a sex-specific metabolic phenotype. At 30 weeks of age, male, but not female, Akr1d1–/– mice were more insulin tolerant and had reduced lipid accumulation in the liver and adipose tissue yet had hypertriglyceridemia and increased intramuscular triacylglycerol. This phenotype was associated with sexually dimorphic changes in bile acid metabolism and composition but without overt effects on circulating glucocorticoid levels or glucocorticoid-regulated gene expression in the liver. Male Akr1d1–/– mice were not protected against diet-induced obesity and insulin resistance. In conclusion, this study shows that AKR1D1 controls bile acid homeostasis in vivo and that altering its activity can affect insulin tolerance and lipid homeostasis in a sex-dependent manner.
Michal Hubert Wrobel, Jaroslaw Mlynarczuk, and Magdalena Karolina Kowalik
This study aimed to investigate the effect of pyrethroid insecticides on the regulation of bovine cervical function. Cervical cells or strips obtained from cows during the periovulation period were treated with cypermethrin and fenvalerate (0.1–10 ng/mL). None of the pyrethroids exerted a cytotoxic effect, whereas only fenvalerate increased the cervical contraction force and mRNA expression of receptor of oxytocin and prostaglandin (PG) synthases. Both pyrethroids inhibited PG secretion and decreased the amount of diacylglycerol, which is the second messenger involved in oxytocin signal transmission, and fenvalerate decreased the myosin light-chain kinase level. These findings indicate that fenvalerate induces greater disruption of cervical function than cypermethrin.
Nikshay Karthigan, Siobhan Lockwood, Anthony White, Jun Yang, and Morag J Young
The mineralocorticoid receptor is a steroid hormone receptor that is well known for its involvement in fluid and electrolyte homeostasis in epithelial cells present in the distal nephron. The inappropriate activation of this receptor is now known to be implicated in various pathophysiological mechanisms in heart failure. Mineralocorticoid receptor antagonists offer substantial clinical benefit in patients with heart failure with reduced ejection fraction; however, for patients with heart failure with preserved ejection fraction, the treatment benefit is less clear. Biomarkers that can predict response to mineralocorticoid receptor antagonist treatment do not currently exist. Potential biomarkers may be modulated either directly by the mineralocorticoid receptor or indirectly via downstream effects and be able to reflect treatment outcomes, particularly changes in key parameters of cardiac health and function. A biomarker or set of biomarkers that can reliably predict responsiveness to mineralocorticoid receptor antagonist treatment at an early stage may allow for the selection of patients who are most likely to benefit from treatment thereby avoiding any unnecessary side effects associated with the use of these medications.
Gilvanildo Roberto da Silva, Mariane Gomes Carneiro, Miriam Pereira Barbosa, Jaciane de Almeida Costa, Ivone Antonia de Souza, Lisiane dos Santos Oliveira, Diogo Antonio Alves de Vasconcelos, Elizabeth do Nascimento, Rhowena Jane Barbosa Matos, Sandra Lopes de Souza, and Manuela Figueiroa Lyra de Freitas
Obesogenic diets are known to induce obesity and changes in food intake in experimental animals. Obesity negatively affects the peripheral metabolism and neural aspects, such as changes in eating behavior. In obese animals, dopamine (DA) receptor levels are reduced. DA is one of the main peptides involved in the motivation and pleasure of eating. A combination of naltrexone/bupropion (NB) has shown promise in controlling metabolic alterations, but there are few studies on how they modulate dopaminergic expression. NB, in addition to reducing food intake and body weight, can modify tyrosine hydroxylase (Th) and DA receptor D2 (Drd2) levels in the mesolimbic areas of rats submitted to a high-fat diet (HF). The study evaluated the effect of NB on food intake, body weight, and expression levels of Th, Drd1a, and Drd2, in the nucleus accumbens and striatum of rats fed on HF diet. Wistar rats were grouped according to diet: standard (n = 20) and HF diet (n = 20). The food intake and body weight were analyzed. The gene expression of Th, Drd1a, and Drd2 was evaluated using real-time PCR. NB combination of 1 mg/kg and 20 mg/kg reduced food intake and body weight, increased Drd2 expression in rats on HF diet, and increased Th in rats on both experimental diets. The level of Drd1a was unchanged. We concluded that bodyweight reduction may be associated with decreased food intake in response to the increased Drd2 expression in the mesolimbic areas of rats that received an HF diet.
Antonia Giacco, Teresa Peluso, Federica Cioffi, Stefania Iervolino, Giovanna Mercurio, Luca Roberto, Carla Reale, Marco Colella, Mario De Felice, Maria Moreno, Concetta Ambrosino, and Elena Silvestri
Thyroid dysfunctions are associated with liver diseases ranging, in severity, from insulin resistance (IR) to hepatocellular carcinoma. The pathogenic mechanisms appear complex and are not attributable, exclusively, to the impaired thyroid hormone (TH) signalling. Using a mouse model of human congenital hypothyroidism, young double heterozygote for both NK2 homeobox 1 (Nkx2-1)- and Paired box 8 (Pax8)-null mutations (DHTP) mice, and single heterozygous Pax8+/− and Nkx2-1+/− mice, we studied the liver pathways, the endocrine and metabolic factors affected in conditions of different dysthyroidisms. Young Nkx2-1+/− females displayed a slight hyperthyroidism and, in liver, increased TH signalling (i.e. increased expression of Dio1 and Trβ1) and lipogenic gene expression, with triglycerides accumulation. Hypothyroid DHTP and euthyroid Pax8+/− females shared liver and skeletal muscle IR and hepatic hypothyroidism (i.e. reduced expression of Mct8, Dio1 and TRβ1), activation of AKT and increased expression of glutathione peroxidase 4. Oxidative stress and reduced mitochondrial COX activity were observed in DHTP mice only. Pax8+/− females, but, unexpectedly, not DHTP ones, displayed transcriptional activation of the hepatic (and renal) gluconeogenic pathway, hypercortisolemia, fasting hyperglycaemia and hyperinsulinemia, reduced serum β-hydroxybutyrate, associated with hepatic AMPK activation. DHTP mice showed hypercholesterolemia and activation of mTOR. Collectively, the data indicate that heterozygote mutations of Pax8 and Nkx2-1 genes may produce multiple dysmetabolisms, even under systemic euthyroidism. Differential liver pathways and multiple hormonal axes are affected with implications for energy and nutrient homeostasis. The identified players may be specific target in the management of thyroid dysfunction-associated dysmetabolisms in terms of prevention/counteraction of IR, type 2 diabetes and related comorbidities.
Ling Cui, Chunlu Tan, Lili Huang, Weihao Wang, Zhengxiang Huang, Fang Geng, Mengjun Wu, Xiaolin Chen, Michael Cowley, Ferdinand Roelfsema, and Chen Chen
Obese women often have certain degree of reproductive dysfunction with infertility. Although the clinical impact of obesity on female infertility has been extensively studied, the effective and targeted treatment is still lacking. Melanocortin-4-receptor knock-out (MC4R KO) mouse is an over-eating obese model with hyperphagia, hyperinsulinemia, reduced growth hormone (GH), and insulin resistance. Dapagliflozin improved metabolic and hormonal parameters in MC4R KO mice. MC4R KO female mice were treated with dapagliflozin for 14 weeks from 14-week-age. Age-matched WT littermates and non-treated MC4R KO mice were used as control groups. Food intake was measured daily. Body weight was measured twice a week. Estrous cycles, GH and LH profiles were measured. Selected tissues were collected at the end of experiments for gene expression profiles and hematoxylin-eosin (HE) staining. Regularity and mode of hormonal profiles were restored by the dapagliflozin treatment. Estrous cycle was partially normalized; number of CL was significantly increased; and the expression of Kiss1 and Gnrh1 in hypothalamus and LH in pituitary was markedly increased by the dapagliflozin treatment. It is concluded that dapagliflozin may recover LH and GH profiles partially through modification of relevant gene expression at hypothalamus and pituitary, and result in an improved ovulation rate in obese mouse model. Dapagliflozin may therefore improve fertility in obese patients.
Heleen I Jansen, Eveline Bruinstroop, Annemieke C Heijboer, and Anita Boelen
Currently, thyroid hormone status is predominantly determined by the measurement of serum thyroid-stimulating hormone and free thyroxine. Although it is assumed that serum thyroid hormone (TH) concentrations within the reference range represent euthyroidism, it is unknown whether this reflects euthyroidism in all tissues (e.g. brain, muscle, bone and liver). To date, no serum marker has been established for clinical use that represents TH status within tissues accurately. However, several biomarkers have been investigated and innovative techniques have been used to unravel new biomarkers. This review provides an overview of proposed serum biomarkers that reflect tissue TH status in humans. Furthermore, we discuss the feasibility of these serum markers in clinical practice.
Claire L Wood, Rob van ‘t Hof, Scott Dillon, Volker Straub, Sze C Wong, S Faisal Ahmed, and Colin Farquharson
Short stature and osteoporosis are common in Duchenne muscular dystrophy (DMD) and its pathophysiology may include an abnormality of the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis, which is further exacerbated by long-term glucocorticoid (GC) treatment. Hence, an agent that has anabolic properties and may improve linear growth would be beneficial in this setting and therefore requires further exploration. A 5-week-old x-linked muscular dystrophy (mdx) mice were used as a model of DMD. They were treated with prednisolone ± GH + IGF-1 for 4 weeks and then compared to control mdx mice to allow the study of both growth and skeletal structure. GC reduced cortical bone area, bone fraction, tissue area and volume and cortical bone volume, as assessed by micro computed tomography (CT) In addition, GC caused somatic and skeletal growth retardation but improved grip strength. The addition of GH + IGF-1 therapy rescued the somatic growth retardation and induced additional improvements in grip strength (16.9% increase, P < 0.05 compared to control). There was no improvement in bone microarchitecture (assessed by micro-CT and static histomorphometry) or biomechanical properties (assessed by three-point bending). Serum bone turnover markers (Serum procollagen 1 intact N-terminal propeptide (P1NP), alpha C-terminal telopeptide (αCTX)) also remained unaffected. Further work is needed to maximise these gains before proceeding to clinical trials in boys with DMD.
Yiran Zhou, Christine Neyt, Nicola J Batchelor, Rebecca L Kelley, Karmilla Jaafar Amsak, Greg M Anderson, Dorothy E Oorschot, Christine L Jasoni, Jane E Girling, and Michael W Pankhurst
Female anti-Müllerian hormone (AMH) overexpressing (Thy1.2-AMH Tg/0) mice experience fetal resorption (miscarriage) by mid-gestation. This study examined whether the ovary, uterine implantation sites and hypothalamus are potential sites of AMH action, as AMH type-2 receptor (AMHR2) expression is reported in each tissue. Pregnancy in Thy1.2-AMH Tg/0 mice was compared to wild-type (WT) mice via histological examination of implantation sites, hormone assays, embryo culture and embryo transfer. Uterine AMH and AMHR2 expression was examined by RT-qPCR and immunohistochemistry. The first signs of fetal resorption in the Thy1.2-AMH Tg/0 dams occurred at embryonic day 9.5 (E9.5) with 100% of fetuses resorbing by E13.5. Cultured embryos from Thy1.2-AMH Tg/0 dams had largely normal developmental rates but a small proportion experienced a minor developmental delay relative to embryos from WT dams. However, embryos transferred from WT donor females always failed to survive to term when transferred into Thy1.2-AMH Tg/0 dams. Amh and Amhr2 mRNA was detected in the gravid uterus but at very low levels relative to expression in the ovaries. Progesterone and estradiol levels were not significantly different between WT and Thy1.2-AMH Tg/0 dams during pregnancy but luteinizing hormone (LH) levels were significantly elevated in Thy1.2-AMH Tg/0 dams at E9.5 and E13.5 relative to WT dams. Collectively, these experiments suggest that AMH overexpression does not cause fetal resorption through an effect on oocytes or preimplantation embryo development. The Thy1.2-AMH Tg/0 fetal resorption phenotype is nearly identical to that of transgenic LH overexpression models, suggesting that neuroendocrine mechanisms may be involved in the cause of the miscarriage.