Recent studies indicated an important role of connexins, gap junction proteins, in the regulation of metabolism. However, most of these studies focused on the glial expression of connexins, whereas the actions of connexins in neurons are still poorly investigated. Thus, the present study had the objective to investigate the possible involvement of gap junctions, and in particular connexin 43 (CX43), for the central regulation of energy homeostasis. Initially, we demonstrated that hypothalamic CX43 expression was suppressed in fasted mice. Using whole-cell patch-clamp recordings, we showed that pharmacological blockade of gap junctions induced hyperpolarization and decreased the frequency of action potentials in 50–70% of agouti-related protein (AgRP)-expressing neurons, depending on the blocker used (carbenoxolone disodium, TAT-Gap19 or Gap 26). When recordings were performed with a biocytin-filled pipette, this intercellular tracer was detected in surrounding cells. Then, an AgRP-specific CX43 knockout (AgRPΔCX43) mouse was generated. AgRPΔCX43 mice exhibited no differences in body weight, adiposity, food intake, energy expenditure and glucose homeostasis. Metabolic responses to 24 h fasting or during refeeding were also not altered in AgRPΔCX43 mice. However, AgRPΔCX43 male, but not female mice, exhibited a partial protection against high-fat diet-induced obesity, even though no significant changes in energy intake or expenditure were detected. In summary, our findings indicate that gap junctions regulate the activity of AgRP neurons, and AgRP-specific CX43 ablation is sufficient to mildly prevent diet-induced obesity specifically in males.
Gabriel O de Souza, Fernanda M Chaves, Josiane N Silva, João A B Pedroso, Martin Metzger, Renata Frazão, and Jose Donato
Jordan E Hamden, Katherine M Gray, Melody Salehzadeh, and Kiran K Soma
The profound programming effects of early life stress (ELS) on brain and behavior are thought to be primarily mediated by adrenal glucocorticoids (GCs). However, in mice, stressors are often administered between postnatal days 2 and 12 (PND2–12), during the stress hyporesponsive period (SHRP), when adrenal GC production is greatly reduced at baseline and in response to stressors. During the SHRP, specific brain regions produce GCs at baseline, but it is unknown if brain GC production increases in response to stressors. We treated mice at PND1 (pre-SHRP), PND5 (SHRP), PND9 (SHRP), and PND13 (post-SHRP) with an acute stressor (isoflurane anesthesia), vehicle control (oxygen), or neither (baseline). We measured a panel of progesterone and six GCs in the blood, hippocampus, cerebral cortex, and hypothalamus via liquid chromatography tandem mass spectrometry. At PND1, baseline corticosterone levels were high and did not increase in response to stress. At PND5, baseline corticosterone levels were very low, increases in brain corticosterone levels were greater than the increase in blood corticosterone levels, and stress had region-specific effects. At PND9, baseline corticosterone levels were low and increased similarly and moderately in response to stress. At PND13, blood corticosterone levels were higher than those at PND9, and corticosterone levels were higher in blood than in brain regions. These data illustrate the rapid and profound changes in stress physiology during neonatal development and suggest that neurosteroid production is a possible mechanism by which ELS has enduring effects on brain and behavior.
James I Raeside and Heather L Christie
Current heightened recognition of the importance of sulfated steroids led to the examination of conjugates in media from incubations of estrogens in tissues from the reproductive tract of stallions. Previously, we had reported a ‘new’ unidentified metabolite of estrone (E1) and [3H]-E1, located between 17β-estradiol (E2) and E1 reference standards on chromatography (HPLC) and identified tentatively as a stable 5α,6α-estrone epoxide. Stallion tissues were minced and incubated for 2 h with [3H]-E1 (1 × 106 cpm). Solid-phase extraction of unconjugated and conjugated steroids from media was followed by liquid scintillation counting (LSC), where radioactivity was mostly in the conjugate fractions (>80%). HPLC of conjugated steroids used an isocratic solvent system of acetonitrile/water (8:92) at 700 µL/min with detection by LSC. A radioactive peak between reference standards of E1 and E2 sulfates was examined, after solvolysis, in a second solvent system. Sulfated steroids yielded largely E1, whereas acid treatment of the unconjugated E1 epoxide had earlier formed 6α-OH-E1 almost exclusively. With sulfatase enzyme, at neutral pH, radioactivity was also seen mostly as E1 with trace amounts of polar material. Reduction with KBH4, however, led also to desulfation; radioactivity had alignment with E2 but even more had low retention times as for 6α/6β-OH-E2. These findings point to a different hydrolysis for desulfation; even more, they reveal an additional oxygen atom at C6 and are supportive of biological formation of 5α,6α-epoxides of E1 and E2. As possible alternatives to catechol estrogens, implicated in cancer, the ‘new’ estrogen metabolites and their sulfated forms may have special interest.
Carmen Corciulo, Julia M Scheffler, Piotr Humeniuk, Alicia Del Carpio Pons, Alexandra Stubelius, Ula Von Mentzer, Christina Drevinge, Aidan Barrett, Sofia Wüstenhagen, Matti Poutanen, Claes Ohlsson, Marie K Lagerquist, and Ulrika Islander
Among patients with knee osteoarthritis (OA), postmenopausal women are over-represented. The purpose of this study was to determine whether deficiency of female sex steroids affects OA progression and to evaluate the protective effect of treatment with a physiological dose of 17β-estradiol (E2) on OA progression using a murine model. Ovariectomy (OVX) of female mice was used to mimic a postmenopausal state. OVX or sham-operated mice underwent surgery for destabilization of the medial meniscus (DMM) to induce OA. E2 was administered in a pulsed manner for 2 and 8 weeks. OVX of OA mice did not influence the cartilage phenotype or synovial thickness, while both cortical and trabecular subchondral bone mineral density (BMD) decreased after OVX compared with sham-operated mice at 8 weeks post-DMM surgery. Additionally, OVX mice displayed decreased motor activity, reduced threshold of pain sensitivity, and increased number of T cells in the inguinal lymph nodes compared to sham-operated mice 2 weeks after OA induction. Eight weeks of treatment with E2 prevented cartilage damage and thickening of the synovium in OVX OA mice. The motor activity was improved after E2 replacement at the 2 weeks time point, which was also associated with lower pain sensitivity in the OA paw. E2 treatment protected against OVX-induced loss of subchondral trabecular bone. The number of T cells in the inguinal lymph nodes was reduced by E2 treatment after 8 weeks. This study demonstrates that treatment with a physiological dose of E2 exerts a protective role by reducing OA symptoms.
Ryan A Lafferty, Laura M McShane, Zara J Franklin, Peter R Flatt, Finbarr P M O’Harte, and Nigel Irwin
Discerning modification to the amino acid sequence of native glucagon can generate specific glucagon receptor (GCGR) antagonists, that include desHis1Pro4Glu9-glucagon and the acylated form desHis1Pro4Glu9(Lys12PAL)-glucagon. In the current study, we have evaluated the metabolic benefits of once-daily injection of these peptide-based GCGR antagonists for 18 days in insulin-resistant high-fat-fed (HFF) mice with streptozotocin (STZ)-induced insulin deficiency, namely HFF-STZ mice. Administration of desHis1Pro4Glu9-glucagon moderately (P < 0.05) decreased STZ-induced elevations of food intake. Body weight was not different between groups of HFF-STZ mice and both treatment interventions delayed (P < 0.05) the onset of hyperglycaemia. The treatments reduced (P < 0.05–P < 0.001) circulating and pancreatic glucagon, whilst desHis1Pro4Glu9(Lys12PAL)-glucagon also substantially increased (P < 0.001) pancreatic insulin stores. Oral glucose tolerance was appreciably improved (P < 0.05) by both antagonists, despite the lack of augmentation of glucose-stimulated insulin release. Interestingly, positive effects on i.p. glucose tolerance were less obvious suggesting important beneficial effects on gut function. Metabolic benefits were accompanied by decreased (P < 0.05–P < 0.01) locomotor activity and increases (P < 0.001) in energy expenditure and respiratory exchange ratio in both treatment groups. In addition, desHis1Pro4Glu9-glucagon increased (P < 0.01–P < 0.001) O2 consumption and CO2 production. Together, these data provide further evidence that peptidic GCGR antagonists are effective treatment options for obesity-driven forms of diabetes, even when accompanied by insulin deficiency.
Jocemara Patrícia Silva de Souza Parrela, Ingridys Regina Borkenhagen, Sarah Ramany Faria Salmeron, Thalyne Aparecida Leite Lima, Ginislene Dias Souza Miranda, Hercules de Oliveira Costermani, Camila Luiza Rodrigues dos Santos Ricken, Ester Vieira Alves, Rodrigo Mello Gomes, and Júlio Cezar de Oliveira
Herein, we assessed milk hormones, the biochemical composition of milk, and its association with neonatal body weight gain and metabolic homeostasis in weaned rats whose mothers were undernourished in the last third of pregnancy. From the 14th day of pregnancy until delivery, undernourished mothers had their food restricted by 50% (FR50), whereas control mothers were fed ad libitum. The litter size was adjusted to eight pups, and rats were weaned at 22 days old. Milk and blood from mothers, as well as blood and tissues from pups, were collected for further analyses. At birth, FR50 pups were smaller than control pups, and they exhibited hyperphagia and rapid catch-up growth during the suckling period. On day 12, the milk from FR50 mothers had higher energy content, glucose, total cholesterol, triglycerides, and acylated ghrelin but lower leptin and corticosterone levels. Interestingly, FR50 mothers were hypoglycemic and hyperleptinemic at the end of the nursing period. Weaned FR50 pups had an obese phenotype and exhibited insulin resistance, which was associated with hyperglycemia and hypertriglyceridemia; they also had high blood levels of total cholesterol, leptin, and acylated ghrelin. In addition, the protein expression of growth hormone secretagogue receptor (GHSR) in the hypothalamus was increased by almost 4-fold in FR50 pups. In summary, maternal calorie restriction during the last third of pregnancy disrupts energy and metabolic hormones in milk, induces pup hyperleptinemia and hyperghrelinemia, and upregulates their hypothalamic GHSR, thus suggesting that the hypothalamic neuroendocrine circuitry may be working to address the early onset of obesity.
Kirsty A Walters, Alba Moreno-Asso, Nigel K Stepto, Michael W Pankhurst, Valentina Rodriguez Paris, and Raymond J Rodgers
Polycystic ovary syndrome (PCOS) is a common endocrine condition characterised by a range of reproductive, endocrine, metabolic and psychological abnormalities. Reports estimate that around 10% of women of reproductive age are affected by PCOS, representing a significant prevalence worldwide, which poses a high economic health burden. As the origin of PCOS remains largely unknown, there is neither a cure nor mechanism-based treatments leaving patient management suboptimal and focused solely on symptomatic treatment. However, if the underlying mechanisms underpinning the development of PCOS were uncovered then this would pave the way for the development of new interventions for PCOS. Recently, there have been significant advances in our understanding of the underlying pathways likely involved in PCOS pathogenesis. Key insights include the potential involvement of androgens, insulin, anti-Müllerian hormone and transforming growth factor beta in the development of PCOS. This review will summarise the significant scientific discoveries on these factors that have enhanced our knowledge of the mechanisms involved in the development of PCOS and discuss the impact these insights may have in shaping the future development of effective strategies for women with PCOS.
Natalie K Y Wee, Thaísa F C de Lima, Narelle E McGregor, Emma C Walker, Ingrid J Poulton, Martha Blank, and Natalie A Sims
Bone strength is partially determined during cortical bone consolidation, a process comprising coalescence of peripheral trabecular bone and its progressive mineralisation. Mice with genetic deletion of suppressor of cytokine signalling 3 (Socs3), an inhibitor of STAT3 signalling, exhibit delayed cortical bone consolidation, indicated by high cortical porosity, low mineral content, and low bone strength. Since leptin receptor (LepR) is expressed in the osteoblast lineage and is suppressed by SOCS3, we evaluated whether LepR deletion in osteocytes would rectify the Dmp1cre.Socs3fl/fl bone defect. First, we tested LepR deletion in osteocytes by generating Dmp1cre.LepRfl/fl mice and detected no significant bone phenotype. We then generated Dmp1cre.Socs3fl/fl.LepRfl/fl mice and compared them to Dmp1cre.Socs3fl/fl controls. Between 6 and 12 weeks of age, both Dmp1cre.Socs3fl/fl.LepRfl/fl and control (Dmp1cre.Socs3fl/fl) mice showed an increasing proportion of more heavily mineralised bone, indicating some cortical consolidation with time. However, at 12 weeks of age, rather than resolving the phenotype, delayed consolidation was extended in female Dmp1cre.Socs3fl/fl.LepRfl/fl mice. This was indicated in both metaphysis and diaphysis by greater proportions of low-density bone, lower proportions of high-density bone, and greater cortical porosity than Dmp1cre.Socs3fl/fl controls. There was also no change in the proportion of osteocytes staining positive for phospho-STAT3, suggesting the effect of LepR deletion in Dmp1cre.Socs3fl/fl mice is STAT3-independent. This identifies a new role for leptin signalling in bone which opposes our original hypothesis. Although LepR in osteocytes has no irreplaceable physiological role in normal bone maturation, when STAT3 is hyperactive, LepR in Dmp1Cre-expressing cells supports cortical consolidation.
Yanqiu Wang, Zhou Jin, Jiajun Sun, Xinxin Chen, Pu Xie, Yulin Zhou, and Shu Wang
Graves’ disease (GD) is characterized by dysregulation of the immune system with aberrant immune cell function. However, there have been few previous studies on the role of monocytes in the pathology of GD. The object of this study was to investigate whether and how monocytes participate in GD pathology. CD14+ monocytes were isolated from untreated initial GD patients and healthy controls. Then, RNA-seq was performed to investigate changes in global mRNA expression in monocytes and found that type I interferon (IFN) signalling was among the top upregulated signalling pathways in GD monocytes. Type I IFN-induced sialic acid-binding immunoglobulin-like lectin1 (SIGLEC1) expression was significantly upregulated in untreated GD patients and correlated with thyroid parameters. Patient serum SIGLEC1 concentrations were reduced after anti-thyroid drug treatment. Inhibiting SIGLEC1 expression could inhibit proinflammatory cytokine (IL-1β, IL-6, IL-8, IL-10 and M-CSF) expression in monocytes. In conclusion, our study suggested that type I IFN-mediated monocyte activation could have a deleterious effect on the pathogenesis of GD. These observations indicated that the inhibition of type I IFN-activated monocytes/macrophages could have a therapeutic effect on GD remission.
Stuart Andrew Morgan, Laura L Gathercole, Zaki Hassan-Smith, Jeremy W Tomlinson, Paul Stewart, and Gareth G Lavery
The aged phenotype shares several metabolic similarities with that of circulatory glucocorticoid excess (Cushing’s syndrome), including type 2 diabetes, obesity, hypertension, and myopathy. We hypothesise that local tissue generation of glucocorticoids by 11β–hydroxysteroid dehydrogenase type 1 (11β-HSD1), which converts 11-dehydrocorticosterone to active corticosterone in rodents (corticosterone to cortisol in man), plays a role in driving age-related chronic disease. In this study, we have examined the impact of ageing on glucocorticoid metabolism, insulin tolerance, adiposity, muscle strength and blood pressure in both wildtype (WT) and transgenic male mice with a global deletion of 11β-HSD1 (11β-HSD1-/-) following 4 months high-fat feeding. We found that high fat-fed 11β-HSD1-/- mice were protected from age-related glucose intolerance and hyperinsulinemia when compared to age/diet-matched WTs. By contrast, aged 11β-HSD1-/- mice were not protected from the onset of sarcopenia observed in the aged WTs. Young 11β-HSD1-/- mice were partially protected from diet-induced obesity, however, this partial protection was lost with age. Despite greater overall obesity, the aged 11β-HSD1-/- animals stored fat in more metabolically safer adipose depots as compared to the aged WTs. Serum analysis revealed both WT and 11β-HSD1-/- mice had an age-related increase in morning corticosterone. Surprisingly, 11β-HSD1 oxo-reductase activity in the liver and skeletal muscle was unchanged with age in WT mice and decreased in gonadal adipose tissue. These data suggest that deletion of 11β-HSD1 in high fat-fed, but not chow-fed, male mice protects from age-related insulin resistance and supports a metabolically favourable fat distribution.