Non-alcoholic fatty liver disease (NAFLD) with its more progressive form non-alcoholic steatohepatitis (NASH) has become the most common chronic liver disease, thereby representing a great burden for patients and healthcare systems. Specific pharmacological therapies for NAFLD are still missing. Inflammation is an important driver in the pathogenesis of NASH, and the mechanisms underlying inflammation in NAFLD represent possible therapeutic targets. In NASH, various intra- and extrahepatic triggers involved in the metabolic injury typically lead to the activation of different immune cells. This includes hepatic Kupffer cells, i.e. liver-resident macrophages, which can adopt an inflammatory phenotype and activate other immune cells by releasing inflammatory cytokines. As inflammation progresses, Kupffer cells are increasingly replaced by monocyte-derived macrophages with a distinct lipid-associated and scar-associated phenotype. Many other immune cells, including neutrophils, T lymphocytes – such as auto-aggressive cytotoxic as well as regulatory T cells – and innate lymphoid cells balance the progression and regression of inflammation and subsequent fibrosis. The detailed understanding of inflammatory cell subsets and their activation pathways prompted preclinical and clinical exploration of potential targets in NAFLD/NASH. These approaches to target inflammation in NASH include inhibition of immune cell recruitment via chemokine receptors (e.g. cenicriviroc), neutralization of CD44 or galectin-3 as well as agonism to nuclear factors like peroxisome proliferator-activated receptors and farnesoid X receptor that interfere with the activation of immune cells. As some of these approaches did not demonstrate convincing efficacy as monotherapies, a rational and personalized combination of therapeutic interventions may be needed for the near future.
Leke Wiering and Frank Tacke
Mariana Rosolen Tavares, Renata Frazao, and Jose Donato Jr
Growth hormone (GH) is secreted by the anterior pituitary gland and plays a key role in controlling tissue and body growth. While basal GH secretion is considerably reduced along adulthood and aging, several situations of metabolic stress can lead to robust increases in circulating GH levels. The objective of the present review is to summarize and discuss the importance of GH regulating different physiological functions in situations of metabolic stress, including prolonged food restriction, hypoglycemia, exercise, pregnancy, and obesity. The presented data indicate that GH increases hunger perception/food intake, fat mobilization, blood glucose levels, and insulin resistance and produces changes in energy expenditure and neuroendocrine responses during metabolic challenges. When all these effects are considered in the context of situations of metabolic stress, they contribute to restore homeostasis by (1) helping the organism to use appropriate energy substrates, (2) preventing hypoglycemia or increasing the availability of glucose, (3) stimulating feeding to provide nutrients in response to energy-demanding activities or to accelerate the recovery of energy stores, and (4) affecting the activity of neuronal populations involved in the control of metabolism and stress response. Thus, the central and peripheral effects of GH coordinate multiple adaptations during situations of metabolic stress that ultimately help the organism restore homeostasis, increasing the chances of survival.
Stuart A Morgan, Laura L Gathercole, Zaki K Hassan-Smith, Jeremy Tomlinson, Paul M 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.
Lara H Sattgast, Adam J Branscum, Natali Newman, Steven W Gonzales, Mary Lauren Benton, Erich J Baker, Kathleen A Grant, Russell T Turner, and Urszula T Iwaniec
Insulin-like growth factor 1 (IGF-1) influences bone turnover. Transient decreases in IGF-I levels and/or bioavailability may contribute to the detrimental effects of alcohol on bone. The goals of this non-human primate study were to i) evaluate the 20-h response of bone turnover markers to ethanol consumption and ii) assess how ethanol consumption influences the relationship between IGF-1 and these markers. Osteocalcin (bone formation), carboxyterminal cross-linking telopeptide of type 1 collagen (CTX, bone resorption), IGF-1, and IGF binding protein 1 (IGFBP-1) were measured in plasma from male rhesus macaques (N = 10, 8.4 ± 0.3 years) obtained at 12:00, 16:00, and 06:00 h during two phases: pre-ethanol (alcohol-naïve) and ethanol access. During the ethanol access phase, monkeys consumed 1.5 g/kg/day ethanol (4% w/v) beginning at 10:00 h. Osteocalcin and CTX were lower, and the ratio of osteocalcin to CTX was higher at each time point during ethanol access compared to the pre-ethanol phase. Pre-ethanol marker levels did not vary across time points, but markers varied during ethanol access. IGF-1 levels, but not IGFBP-1 levels, varied during the pre-ethanol phase. In contrast, IGF-1 levels were stable during ethanol access but IGFBP-1 levels varied. There were positive relationships between IGF-1 and turnover markers during the pre-ethanol phase, but not during ethanol access. In conclusion, chronic ethanol consumption reduces levels of bone turnover markers and blocks the normal positive relationship between IGF-1 and turnover markers and alters the normal relationship between IGF-1 and IGFBP-1. These findings support the hypothesis that chronic alcohol consumption leads to growth hormone/IGF-1 resistance.
Adriana María Belén Abiuso, María Luisa Varela, Trinidad Raices, Griselda Irusta, Juan Manuel Lazzati, Marcos Besio Moreno, Alina Cavallotti, Alicia Belgorosky, Omar Pedro Pignataro, Esperanza Berensztein, and Carolina Mondillo
Recent reports indicate an increase in Leydig cell tumor (LCT) incidence. Radical orchiectomy is the standard therapy in children and adults, although it entails physical and psychosocial side effects. Testis-sparing surgery can be a consideration for benign LCT of 2.5 cm or less in size. Malignant LCTs respond poorly to conventional chemotherapy, so new treatment modalities are needed. In this study, we observed increased histidine decarboxylase expression and pro-angiogenic potential in LCT surgically resected from pediatric patients (fetal to pubertal) vs control samples from patients without endocrine or metabolic disorders which were collected at necropsy. We, therefore, evaluated for the first time the antitumor efficacy of two histidine decarboxylase inhibitors (α-methyl-dl-histidine dihydrochloride (α-MHD) and epigallocatechin gallate (EGCG)), alone and combined with carboplatin, in two preclinical models of LCT. MA-10 and R2C Leydig tumor cells, representing two different LCT subtypes, were used to generate syngeneic and xenograft mouse LCT models, respectively. In the syngeneic model, monotherapy with α-MHD effectively reduced tumor growth and angiogenesis. In the xenografts, which showed co-expression of histidine decarboxylase and CYP19, the combination of EGCG plus carboplatin was the most effective therapy, leading to LCT growth arrest and undetectable levels of plasmatic estradiol. Testicular and body weights remained unaltered. On the basis of this study, histidine decarboxylase may emerge as a novel pharmacological target for LCT treatment.
Ying Sze, Joana Fernandes, Zofia M Kołodziejczyk, and Paula J Brunton
Stress during pregnancy negatively affects the fetus and increases the risk for affective disorders in adulthood. Excess maternal glucocorticoids are thought to mediate fetal programming; however, whether they exert their effects directly or indirectly remains unclear. During pregnancy, protective mechanisms including maternal hypothalamic–pituitary–adrenal (HPA) axis hyporesponsiveness and placental 11β-hydroxysteroid dehydrogenase (11βHSD) type 2, which inactivates glucocorticoids, limit mother-to-fetus glucocorticoid transfer. However, whether repeated stress negatively impacts these mechanisms is not known. Pregnant rats were exposed to repeated social stress on gestational days (GD) 16–20 and several aspects of HPA axis and glucocorticoid regulation, including concentrations of glucocorticoids, gene expression for their receptors (Nr3c1, Nr3c2), receptor chaperones (Fkbp51, Fkbp52) and enzymes that control local glucocorticoid availability (Hsd11b1, Hsd11b2), were investigated in the maternal, placental and fetal compartments on GD20. The maternal HPA axis was activated following stress, though the primary driver was vasopressin, rather than corticotropin-releasing hormone. Despite the stress-induced increase in circulating corticosterone in the dams, only a modest increase was detected in the circulation of female fetuses, with no change in the fetal brain of either sex. Moreover, there was no change in the expression of genes that mediate glucocorticoid actions or modulate local concentrations in the fetal brain. In the placenta labyrinth zone, stress increased Hsd11b2 expression only in males and Fkbp51 expression only in females. Our results indicate that any role glucocorticoids play in fetal programming is likely indirect, perhaps through sex-dependent alterations in placental gene expression, rather than exerting effects via direct crossover into the fetal brain.
Juan Bernal, Beatriz Morte, and Diego Diez
Brain development is critically dependent on the timely supply of thyroid hormones. The thyroid hormone transporters are central to the action of thyroid hormones in the brain, facilitating their passage through the blood–brain barrier. Mutations of the monocarboxylate transporter 8 (MCT8) cause the Allan–Herndon–Dudley syndrome, with altered thyroid hormone concentrations in the blood and profound neurological impairment and intellectual deficit. Mouse disease models have revealed interplay between transport, deiodination, and availability of T3 to receptors in specific cells. However, the mouse models are not satisfactory, given the fundamental differences between the mouse and human brains. The goal of the present work is to review human neocortex development in the context of thyroid pathophysiology. Recent developments in single-cell transcriptomic approaches aimed at the human brain make it possible to profile the expression of thyroid hormone regulators in single-cell RNA-Seq datasets of the developing human neocortex. The data provide novel insights into the specific cellular expression of thyroid hormone transporters, deiodinases, and receptors.
Gabriel O de Souza, Fernanda M Chaves, Josiane N Silva, João A B Pedroso, Martin Metzger, Renata Frazão, and Jose Donato
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.
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.