Corticotropin-releasing (CRF) factor plays a central role in the orchestration of behavioral and neuroendocrine responses to stress. The family of CRF-related peptides (CRF and paralogs: Urocortin (Ucn) -I,-II and -III) and associated receptors (CRF-R1 and CRF-R2) are also expressed in peripheral tissues such as the skin and gastrointestinal tract (GIT). Local signaling may exert multiple effects of stress-induced exacerbation of many complex syndromes including psoriasis and visceral hypersensitivity. Interstitial cystitis/painful bladder syndrome (IC/PBS), a chronic visceral pain syndrome characterized by urinary frequency, urgency and pelvic pain, is reported to be exacerbated by stress. Functional changes in the epithelial lining of the bladder, a vital blood-urine barrier called the urothelium, may play a role in IC/PBS. This study investigated the expression and functional activity of CRF-related peptides in the urothelium of normal cats and cats with feline interstitial cystitis (FIC), a chronic idiopathic cystitis exhibiting similarities to humans diagnosed with IC/PBS. Western blots showed urothelial (UT) expression of CRF-R1 and CRF-R2. Enzyme immunoassay revealed release of endogenous ligands (CRF and Ucn) by UT cells in culture. Evidence of functional activation of CRF-R1 and CRF-R2 by receptor selective agonists (CRF and UCN3 respectively) was shown by: (1)-measurement of ATP release using the luciferin-luciferase assay and (2)-the use of membrane impermeant fluorescent dyes (FM dyes) for fluorescence microscopy to assess membrane exocytotic responses in real-time. Our findings show evidence of CRF-related peptide signaling in the urothelium. Differences in functional responses between FIC and normal UT indicate that this system is altered in IC/PBS.
Urothelium; CRF-signaling; Stress; Interstitial Cystitis
Diabetic nephropathy (DN) is the most common cause of end-stage kidney disease worldwide, and is associated with increased morbidity and mortality in patients with both type 1 and type 2 diabetes. Increasing prevalence of diabetes has made the need for effective treatment of DN critical, and identifying new therapeutic targets to improve clinical management. Autophagy is a highly conserved “self-eating” pathway by which cells degrade and recycle macromolecules and organelles. Autophagy serves as an essential mechanism to maintain homeostasis of glomeruli and tubules, and plays important roles in human health and diseases. Impairment of autophagy is implicated in the pathogenesis of DN. Emerging body of evidence suggests that targeting the autophagic pathway to activate and restore autophagy activity may be renoprotective. Here we review current advances in our understanding of the roles of autophagy in diabetic kidney injury, focusing on studies in renal cells in culture, human kidney tissues, and experimental animal models of diabetes. We discuss the major nutrient-sensing signal pathways, and diabetes-induced altered intracellular metabolism and cellular events, including accumulation of advanced glycation end-products, increased oxidative stress, endoplasmic reticulum stress, hypoxia, and activation of the renin angiotensin system, which modulate autophagic activity and contribute to the development of DN. We also highlight recent studies of autophagy and transforming growth factor-β in renal fibrosis, the final common response to injury that ultimately leads to end-stage kidney failure in both type 1 and type 2 diabetes. These findings suggest the possibility that autophagy can be a therapeutic target against DN.
diabetes mellitus; macroautophagy; autophagy; kidney; nephropathy
Stress-induced activation of hypothalamic paraventricular nucleus (PVN) corticotropin releasing hormone (CRH) neurons triggers CRH release and synthesis. Recent findings suggest that this process depends on the intracellular activation (phosphorylation) of extracellular-regulated kinase 1 and 2 (ERK1/2) within CRH neurons. We have recently shown that the presence of glucocorticoids constrains stress-stimulated phosphorylation of PVN ERK1/2. In some peripheral cell types, dephosphorylation of ERK has been shown to be promoted by direct glucocorticoid upregulation of the MAP-kinase phosphatase-1 (Mkp-1) gene. In this study we tested the prospect that glucocorticoids regulate Mkp-1 mRNA expression in neural forebrain (medial-prefrontal cortex,mPFC, and PVN) and endocrine tissue (anterior pituitary) by subjecting young adult male Sprague-Dawley rats to various glucocorticoid manipulations ± acute psychological stress (restraint). Restraint led to a rapid increase in Mkp-1 mRNA within the mPFC, PVN and anterior pituitary, and this increase did not require glucocorticoid activity. In contrast to glucocorticoid upregulation of Mkp-1 gene expression in peripheral tissues, we found that the absence of glucocorticoids (via adrenalectomy) augmented basal mPFC and stress-induced PVN and anterior pituitary Mkp-1 gene expression. Taken together, this study indicates that the presence of glucocorticoids may constrain Mkp-1 gene expression in neural forebrain and endocrine tissues. This possible constraint may be an indirect consequence of the inhibitory influence of glucocorticoids on stress-induced activation of ERK1/2, a known upstream positive regulator of Mkp-1 gene transcription.
MKP-1; ACTH; paraventricular nucleus of hypothalamus; medial prefrontal cortex; corticosterone; ERK1/2
Treatment with anti-inflammatory glucocorticoids is associated with osteoporosis. Many of the treated patients are postmenopausal women, who even without treatment have an increased risk of osteoporosis. Lymphocytes have been shown to play a role in postmenopausal and arthritis-induced osteoporosis, and they are targeted by glucocorticoids. The aim of this study was to investigate the mechanisms behind effects of glucocorticoids on bone during health and menopause, focusing on lymphocytes. Female C57BL/6 or SCID mice were therefore sham-operated or ovariectomized and 2 weeks later treatment with dexamethasone (dex), the nonsteroidal anti-inflammatory drug carprofen, or vehicle was started and continued for 2.5 weeks. At the termination of experiments, femurs were phenotyped using peripheral quantitative computed tomography and high-resolution micro-computed tomography, and markers of bone turnover were analyzed in serum. T and B lymphocyte populations in bone marrow and spleen were analyzed by flow cytometry. Dex-treated C57BL/6 mice had increased trabecular bone mineral density, but lower cortical content and thickness compared with vehicle-treated mice. The dex-treated mice also had lower levels of bone turnover markers and markedly decreased numbers of spleen T and B lymphocytes. In contrast, these effects could not be repeated when mice were treated with the nonsteroidal anti-inflammatory drug carprofen. In addition, dex did not increase trabecular bone in ovariectomized SCID mice lacking functional T and B lymphocytes. In contrast to most literature, the results from this study indicate that treatment with dex increased trabecular bone density, which may indicate that this effect is associated with corticosteroid-induced alterations of the lymphocyte populations.
glucocorticoid; osteoporosis; immune system; estrogen
Survivin (BIRC5) is a cell survival gene that is overexpressed in endometrial cancer and has been implicated to have a physiological role in normal endometrial function. To determine whether survivin gene expression is regulated by reproductive steroid hormones in the human endometrium, RNA was prepared from normal cycling women in the proliferative and secretory phases of the menstrual cycle. RNA was also isolated from 21 endometrial biopsies from premenopausal women at baseline and following 3 months of treatment with depot medroxyprogesterone acetate. Finally, RNA was isolated from endometrial biopsies from ten healthy postmenopausal women participating in a clinical trial of estrogen replacement therapy at baseline and following 6 months of treatment with conjugated equine estrogen. Quantitative RT-PCR analysis was used to determine survivin, insulin-like growth factor binding protein 1 (IGFBP1), Ki67, and IGF1 gene expression levels. Survivin gene expression was highest in the proliferative phase of the menstrual cycle and showed a statistically significant 4-fold increase in expression following chronic treatment with estrogens; this was strongly correlated with increased Ki67, a marker of proliferation. Survivin gene expression decreased 4·6-fold following chronic progestin treatment in the human endometrium. These data suggest that survivin transcript is regulated by estrogens and progestins in the disease-free human endometrium. The data also suggest that survivin transcript may be used as a biomarker of estrogen and progestin treatment efficacy, but validation studies must be conducted to support this conclusion.
Polycystic ovary syndrome is a common endocrine disorder in females of reproductive age and is believed to have a developmental origin in which gestational androgenization programs reproductive and metabolic abnormalities in offspring. During gestation, both male and female fetuses are exposed to potential androgen excess. We determined the consequences of developmental androgenization in male mice exposed to neonatal testosterone (NTM). Adult NTM displayed hypogonadotropic hypogonadism with decreased serum testosterone and gonadotropins. Hypothalamic KiSS1 neurons are believed to be critical in the onset of puberty and are the target of leptin. Adult NTM showed lower hypothalamic Kiss1 expression and a failure of leptin to upregulate Kiss1 expression. NTM displayed an early reduction in lean mass, decreased locomotor activity and decreased energy expenditure. They developed a delayed increase in subcutaneous white adipose tissue. Thus, excessive neonatal androgenization disrupts reproduction and energy homeostasis and predisposes to hypogonadism and obesity in adult male mice.
Androgens; Reproduction; Energy homeostasis
The prevalence of diabetes is increasing rapidly world-wide. A cardinal feature of most forms of diabetes is the lack of insulin-producing capability, due to the loss of insulin-producing β-cells, impaired glucose-sensitive insulin secretion from the β-cell, or a combination thereof, the reasons for which largely remain elusive. Reversible phosphorylation is an important and versatile mechanism for regulating the biological activity of many intracellular proteins, which, in turn, controls a variety of cellular functions. For instance, significant changes in protein kinase activities and in protein phosphorylation patterns occur subsequent to stimulation of insulin release by glucose. Therefore, the molecular mechanisms regulating phosphorylation of proteins involved in the insulin secretory process by the β-cell have been extensively investigated. However, far less is known about the role and regulation of protein dephosphorylation by various protein phosphatases. Herein we review extant data implicating serine/threonine and tyrosine phosphatases in various aspects of healthy and diabetic islet biology, ranging from control of hormonal stimulus-secretion coupling to mitogenesis and apoptosis.
Diabetes; Islet; Protein phosphatase; High-fat diet; Knockout mouse; Obesity; Insulin
Anorexia nervosa (AN) is a condition of severe low weight that is associated with low bone mass, impaired bone structure and reduced bone strength, all of which contribute to increased fracture risk., Adolescents with AN have decreased rates of bone accrual compared with normal-weight controls, raising addition concerns of suboptimal peak bone mass and future bone health in this age group. Changes in lean mass and compartmental fat depots, hormonal alterations secondary to nutritional factors contribute to impaired bone metabolism in AN. The best strategy to improve bone density is to regain weight and menstrual function. Oral estrogen-progesterone combinations are not effective in increasing bone density in adults or adolescents with AN, and transdermal testosterone replacement is not effective in increasing bone density in adult women with AN. However, physiologic estrogen replacement as transdermal estradiol with cyclic progesterone does increase bone accrual rates in adolescents with AN to approximate that in normal-weight controls, leading to a maintenance of bone density Z-scores. A recent study has shown that risedronate increases bone density at the spine and hip in adult women with AN. However, bisphosphonates should be used with great caution in women of reproductive age given their long half-life and potential for teratogenicity, and should be considered only in patients with low bone density and clinically significant fractures when non-pharmacological therapies for weight gain are ineffective. Further studies are necessary to determine the best therapeutic strategies for low bone density in AN.
Anorexia nervosa; eating disorders; adolescents; adults; bone density; microarchitecture; strength; fracture; growth hormone; IGF-1; estrogen; testosterone; bisphosphonates; leptin; ghrelin; PYY; adipokines
Metformin is a first-line, anti-diabetic agent prescribed to over 150 million people worldwide. The main effect of metformin is to suppress glucose production in the liver; however, there is no reliable biomarker to assess the effectiveness of metformin administration. Our previous studies have shown that phosphorylation of CBP at S436 is important for the regulation of hepatic glucose production by metformin. In current study, we found that CBP could be phosphorylated in white blood cells (WBCs), and CBP phosphorylation in the liver and in WBCs of mice had a similar pattern of change during a fasting time course experiment. These data suggests that CBP phosphorylation in WBCs may be used as a biomarker of metformin action in the liver.
Insulin resistance (IR) in skeletal muscle is an important component of both type 2 diabetes and the syndrome of sarcopaenic obesity, for which there are no effective therapies. Urocortins (UCNs) are not only well established as neuropeptides but also have their roles in metabolism in peripheral tissues. We have shown recently that global overexpression of UCN3 resulted in muscular hypertrophy and resistance to the adverse metabolic effects of a high-fat diet. Herein, we aimed to establish whether short-term local UCN3 expression could enhance glucose disposal and insulin signalling in skeletal muscle. UCN3 was found to be expressed in right tibialis cranialis and extensor digitorum longus muscles of rats by in vivo electrotransfer and the effects studied vs the contralateral muscles after 1 week. No increase in muscle mass was detected, but test muscles showed 19% larger muscle fibre diameter (P=0.030), associated with increased IGF1 and IGF1 receptor mRNA and increased SER256 phosphorylation of forkhead transcription factor. Glucose clearance into the test muscles after an intraperitoneal glucose load was increased by 23% (P=0.018) per unit mass, associated with increased GLUT1 (34% increase; P=0.026) and GLUT4 (48% increase; P=0.0009) proteins, and significantly increased phosphorylation of insulin receptor substrate-1, AKT, AKT substrate of 160 kDa, glycogen synthase kinase-3β, AMP-activated protein kinase and its substrate acetyl coA carboxylase. Thus, UCN3 expression enhances glucose disposal and signalling in muscle by an autocrine/paracrine mechanism that is separate from its pro-hypertrophic effects, implying that such a manipulation may have promised for the treatment of IR syndromes including sarcopaenic obesity.
skeletal muscle; urocortin 3; glucose disposal; GLUT4; AMPK; PI3K signalling
Resveratrol (RES) and curcumin (CUR) are polyphenols that are found in fruits and turmeric, and possess medicinal properties that are beneficial in various diseases, such as heart disease, cancer, and type 2 diabetes mellitus (T2DM). Results from recent studies have indicated that their therapeutic properties can be attributed to their anti-inflammatory effects. Owing to reports stating that they protect against β-cell dysfunction, we studied their mechanism(s) of action in β-cells. In T2DM, cAMP plays a critical role in glucose- and incretin-stimulated insulin secretion as well as overall pancreatic β-cell health. A potential therapeutic target in the management of T2DM lies in regulating the activity of phosphodiesterases (PDEs), which degrade cAMP. Both RES and CUR have been reported to act as PDE inhibitors in various cell types, but it remains unknown if they do so in pancreatic β-cells. In our current study, we found that both RES (0.1–10 μmol/l) and CUR (1–100 pmol/l)-regulated insulin secretion under glucose-stimulated conditions. Additionally, treating β-cell lines and human islets with these polyphenols led to increased intracellular cAMP levels in a manner similar to 3-isobutyl-1-methylxanthine, a classic PDE inhibitor. When we investigated the effects of RES and CUR on PDEs, we found that treatment significantly downregulated the mRNA expression of most of the 11 PDE isozymes, including PDE3B, PDE8A, and PDE10A, which have been linked previously to regulation of insulin secretion in islets. Furthermore, RES and CUR inhibited PDE activity in a dose-dependent manner in β-cell lines and human islets. Collectively, we demonstrate a novel role for natural-occurring polyphenols as PDE inhibitors that enhance pancreatic β-cell function.
type 2 diabetes; resveratrol; curcumin; phosphodiesterase; β-cell
Glucocorticoids (Gc) are potent anti-inflammatory agents with wide clinical application. We have previously shown that increased serum concentration significantly attenuates regulation of a simple Gc-responsive reporter. We now find that glucocorticoid receptor (GR) regulation of some endogenous transactivated but not transrepressed genes is impaired, suggesting template specificity. Serum did not directly affect GR expression, activity or trafficking, implicating GR crosstalk with other signalling pathways. Indeed, a JNK inhibitor completely abolished the serum effect. We identified the Gc modulating serum component as cholesterol. Cholesterol loading mimicked the serum effect, which was readily reversed by JNK inhibition. Chelation of serum cholesterol with methyl-β-cyclodextrin or inhibition of cellular cholesterol synthesis with simvastatin potentiated the Gc response. To explore the effect in vivo we used ApoE
−/− mice, a model of hypercholesterolaemia. Consistent with our in vitro studies, we find no impact of elevated cholesterol on the expression of GR, or on the hypothalamic–pituitary–adrenal axis, measured by dexamethasone suppression test. Instead we find selective Gc resistance on some hepatic target genes in ApoE
−/− mice. Therefore, we have discovered an unexpected role for cholesterol as a selective modulator of Gc action in vivo. Taken together these findings reveal a new environmental constraint on Gc action with relevance to both inflammation and cancer.
glucocorticoid receptor; inflammatory disease; cholesterol; transcription factors; signal transduction
Dienogest, a synthetic progestin, has been shown to be effective against endometriosis, although it is still unclear as to how it affects the ectopic endometrial cells. Decorin has been shown to be a powerful endogenous tumor repressor acting in a paracrine fashion to limit tumor growth. Our objectives were to examine the direct effects of progesterone and dienogest on the in vitro proliferation of the human ectopic endometrial epithelial and stromal cell lines, and evaluate as to how decorin contributes to this effect. We also examined DCN mRNA expression in 50 endometriosis patients. The growth of both cell lines was inhibited in a dose-dependent manner by both decorin and dienogest. Using a chromatin immunoprecipitation assay, it was noted that progesterone and dienogest directly induced the binding of the decorin promoter in the EMOsis cc/TERT cells (immortalized human ovarian epithelial cells) and CRL-4003 cells (immortalized human endometrial stromal cells). Progesterone and dienogest also led to significant induced cell cycle arrest via decorin by promoting production of p21 in both cell lines in a dose-dependent manner. Decorin also suppressed the expression of MET in both cell lines. We confirmed that DCN mRNA expression in patients treated with dienogest was higher than that in the control group. In conclusion, decorin induced by dienogest appears to play a crucial role in suppressing endometriosis by exerting anti-proliferative effects and inducing cell cycle arrest via the production of p21 human ectopic endometrial cells and eutopic endometrial stromal cells.
decorin; progesterone; dienogest; endometriosis; cell cycle arrest; p21
Epidermal growth factor (EGF) is a key regulator of cell survival and proliferation involved in the pathogenesis and progression of different types of cancer. The EGF receptor (EGFR) is activated by binding of the specific ligand but also by transactivation triggered by different growth factors including GH. Chronically, elevated GH levels have been associated with the progression of hepatocellular carcinoma. Considering EGF and GH involvement in cell proliferation and their signaling crosstalk, the objective of the present study was to analyze GH modulatory effects on EGF signaling in liver. For this purpose, GH receptor-knockout (GHR-KO) and GH-overexpressing transgenic mice were used. EGFR content was significantly decreased in GHR-KO mice. Consequently, EGF–induced phosphorylation of EGFR, AKT, ERK1/2, STAT3, and STAT5 was significantly decreased in these mice. In contrast, EGFR content as well as its basal tyrosine phosphorylation was increased in transgenic mice overexpressing GH. However, EGF stimulation caused similar levels of EGFR, AKT, and ERK1/2 phosphorylation in normal and transgenic mice, while EGF induction of STAT3 and STAT5 phosphorylation was inhibited in the transgenic mice. Desensitization of the STATs was related to decreased association of these proteins to the EGFR and increased association between STAT5 and the tyrosine phosphatase SH2-containing phosphatase-2. While GHR knockout is associated with diminished expression of the EGFR and a concomitant decrease in EGF signaling, GH overexpression results in EGFR overexpression with different effects depending on the signaling pathway analyzed: AKT and ERK1/2 pathways are induced by EGF, while STAT3 and STAT5 activation is heterologously desensitized.
The suppressor of cytokine signalling (Socs2
−/−)-knockout mouse is characterised by an overgrowth phenotype due to enhanced GH signalling. The objective of this study was to define the Socs2
−/− bone phenotype and determine whether GH promotes bone mass via IGF1-dependent mechanisms. Despite no elevation in systemic IGF1 levels, increased body weight in 4-week-old Socs2
−/− mice following GH treatment was associated with increased cortical bone area (Ct.Ar) (P<0.01). Furthermore, detailed bone analysis of male and female juvenile and adult Socs2
−/− mice revealed an altered cortical and trabecular phenotype consistent with the known anabolic effects of GH. Indeed, male Socs2
−/− mice had increased Ct.Ar (P<0.05) and thickness associated with increased strength. Despite this, there was no elevation in hepatic Igf1 expression, suggesting that the anabolic bone phenotype was the result of increased local GH action. Mechanistic studies showed that in osteoblasts and bone of Socs2
−/− mice, STAT5 phosphorylation was significantly increased in response to GH. Conversely, overexpression of SOCS2 decreased GH-induced STAT5 signalling. Although an increase in Igf1 expression was observed in Socs2
−/− osteoblasts following GH, it was not evident in vivo. Igf1 expression levels were not elevated in response to GH in 4-week-old mice and no alterations in expression was observed in bone samples of 6-week-old Socs2
−/− mice. These studies emphasise the critical role of SOCS2 in controlling the local GH anabolic bone effects. We provide compelling evidence implicating SOCS2 in the regulation of GH osteoblast signalling and ultimately bone accrual, which maybe via mechanisms that are independent of IGF1 production in vivo.
GH/IGF1; bone; SOCS2; osteoblast
Establishing sufficient skeletal muscle mass is essential for lifelong metabolic health. The intrauterine environment is a major determinant of the muscle mass that is present for the life course of an individual, because muscle fiber number is set at the time of birth. Thus, a compromised intrauterine environment from maternal nutrient restriction or placental insufficiency that restricts development of muscle fiber number can have permanent effects on the amount of muscle an individual will live with. Reduced muscle mass due to fewer muscle fibers persists even after compensatory or “catch up” postnatal growth occurs. Furthermore, muscle hypertrophy can only partially compensate for this limitation in fiber number. Compelling associations link low birth weight and decreased muscle mass to future insulin resistance, which can drive the development of the metabolic syndrome and type 2 diabetes, and risk for cardiovascular events later in life. There are gaps in knowledge about the origins of reduced muscle growth at the cellular level and how these patterns are set during fetal development. By understanding the nutrient and endocrine regulation of fetal skeletal muscle growth and development, we can direct research efforts towards improving muscle growth early in life in order to prevent the development of chronic metabolic disease later in life.
muscle; insulin; IGF1; amino acids; protein synthesis; myogenesis
Angiotensin II (Ang II) is involved in induction and progression of renal damage in diabetes. Angiotensin converting enzyme 2 (ACE2) is highly expressed in the kidney and has been shown to be renoprotective by degrading Ang II to Ang-(1–7). Disintegrin and Metalloproteinase (ADAM) 17 mediated shedding of renal ACE2 contribute to diabetic nephropathy pathogenesis. Lifestyle modification and metformin are recommended as initial therapies for most patients with type 2 diabetes. The aim of the study was to investigate whether exercise training and/or metformin improve glucose homeostasis, albuminuria and downregulate renal ADAM17 and ACE2 shedding in db/db mice. Seven wk old normal and db/db mice were subjected either to sedentary or exercise training with and without metformin (150 mg/kg/day) for 10 wks. Exercise training significantly lowered blood glucose, urinary albumin and ACE2 excretion in db/db mice. ADAM17 and ACE2 proteins were co-localized in cortical tubules of the kidney, suggesting a possible interaction. Metformin treatment was effective in lowering hyperglycemia only during the first 2 weeks of treatment. Increased renal ADAM17 in 17 wk old db/db mice was corrected by physical exercise but not metformin. In addition, exercise training reduced plasma triglycerides and enhanced insulin levels of db/db mice. In conclusion, exercise training alone and in combination with metformin prevented shedding of renal ACE2 by decreasing ADAM17 protein. Urinary ACE2 could serve as a prognostic tool in the progression of kidney damage and its attenuation by exercise may partially contribute to its renal protection.
Type 2 diabetes; Urinary ACE2; ADAM17; Diabetic nephropathy; Metformin; Exercise
Ganitumab is a fully human MAB to the human type 1 IGF receptor (IGF1R). Binding assays showed that ganitumab recognized murine IGF1R with sub-nanomolar affinity (KD=0.22 nM) and inhibited the interaction of murine IGF1R with IGF1 and IGF2. Ganitumab inhibited IGF1-induced activation of IGF1R in murine lungs and CT26 murine colon carcinoma cells and tumors. Addition of ganitumab to 5-fluorouracil resulted in enhanced inhibition of tumor growth in the CT26 model. Pharmacological intervention with ganitumab in naïve nude mice resulted in a number of physiological changes described previously in animals with targeted deletions of Igf1 and Igf1r, including inhibition of weight gain, reduced glucose tolerance and significant increase in serum levels of GH, IGF1 and IGFBP3. Flow cytometric analysis identified GR1/CD11b-positive cells as the highest IGF1R-expressing cells in murine peripheral blood. Administration of ganitumab led to a dose-dependent, reversible decrease in the number of peripheral neutrophils with no effect on erythrocytes or platelets. These findings indicate that acute IGF availability for its receptor plays a critical role in physiological growth, glucose metabolism and neutrophil physiology and support the presence of a pituitary IGF1R-driven negative feedback loop that tightly regulates serum IGF1 levels through Gh signaling.
ganitumab; GF1R; IGFBP3; receptor pituitary; human; murine
Age-related morphologic development of the human adrenal zona reticularis (ZR) has not been well-examined. Therefore, in this study, forty-four human young adrenal autopsy specimens retrieved from large archival files (n=252) were examined for immunohistochemical and morphometric analyses. Results demonstrated that ZR became discernible around 4 years old, and both thickness and ratio per total cortex of ZR increased in an age-dependent fashion thereafter, although there was no significant increment in total thickness of developing adrenal cortex. We further evaluated immunoreactivity of both Ki67 and Bcl-2 in order to clarify the equilibrium between cell proliferation and apoptosis in the homeostasis of developing human adrenals. Results demonstrated that proliferative adrenocortical cells were predominantly detected in the zona glomerulosa (ZG) and partly in outer zona fasciculata (ZF) before 4 years old and in ZR after 4 years old but the number of these cells markedly decreased around 20 years old. The number of Bcl-2 positive cells increased in ZR and decreased in ZF during development. Adrenal androgen synthesizing type 5 17β-hydroxysteroid dehydrogenase (HSD17B5) was almost confined to ZR of human adrenals throughout development. HSD17B5 immunoreactivity in ZR became discernible and increased from around 9 years old. Results of our present study support the theory of age-dependent adrenocortical cell migration and also indicated that ZR development is not only associated with adrenarche, but may play important roles in an initiation of puberty.
Adrenal gland; Zona reticularis; Adrenal hormones; Development; Apoptosis
Type 2 diabetes and obesity are very serious health problems in both developed and developing countries. Increased level of growth hormone (GH) is known to promote insulin resistance. Transgenic (Tg) mice over-expressing bovine GH are short-living and characterized, among others, by hyperinsulinemia and increased insulin resistance in comparison to normal (N) mice. Pioglitazone (PIO) is a member of the thiazolidinediones – group of insulin-sensitizing drugs which are selective agonists of peroxisome proliferator-activated receptor gamma (PPARγ). The aim of the study was to analyze the effects of PIO on the insulin signaling pathway in Tg and N mice. Plasma levels of insulin and glucose as well as hepatic levels of proteins involved in insulin signaling were analyzed by ELISA or western blot methods. Treatment with PIO decreased plasma level of glucose in N mice only. Similarly, PIO increased insulin sensitivity (expressed as the Relative Insulin Sensitivity Index; RISI) only in N mice. In the liver, PIO decreased the phosphorylation of IRS1 at a serine residue (Ser307-pS-IRS1), that inhibits insulin action, and had a tendency to increase tyrosine phosphorylation of IRS2 (Tyr-pY-IRS2) only in N mice but did not affect either of these parameters in Tg mice. Levels of total and phosphorylated mTOR were increased in Tg mice. Moreover, the AKT2 level was decreased by PIO in N mice only. In conclusion, the lack of improvement of insulin sensitivity in insulin-resistant Tg mice during PIO treatment suggests that chronically elevated GH level can inhibit the beneficial effects of PIO on insulin signaling.
pioglitazone; insulin signaling; growth hormone; transgenic mice
We investigated pregnancy-associated plasma protein-A (PAPP-A) in diabetic nephropathy. Normal human kidney showed specific staining for PAPP-A in glomeruli, and this staining was markedly increased in diabetic kidney. To assess possible contribution of PAPP-A in the development of diabetic nephropathy, we induced diabetes with streptozotocin in 14-month-old wild-type (WT) and PAPP-A knock-out (KO) mice. Renal histopathology was evaluated after four months of stable hyperglycemia. Kidneys from diabetic WT mice showed multiple abnormalities including thickening of Bowman’s capsule (100% of mice), increased glomerular size (80% of mice), tubule dilation (80% of mice), and mononuclear cell infiltration (90% of mice). Kidneys of age-matched non-diabetic WT mice had similar evidence of tubule dilation and mononuclear cell infiltration as diabetic WT mice indicating that these changes were predominantly age-related. However, thickened Bowman’s capsule and increased glomerular size appeared specific for the experimental diabetes. Kidneys from diabetic PAPP-A KO mice had significantly reduced or no evidence of changes in Bowman’s capsule thickening and glomerular size. There was also a shift to larger mesangial area and increased macrophage staining in diabetic WT compared to PAPP-A KO mice. In summary, elevated PAPP-A expression in glomeruli is associated with diabetic nephropathy in humans and absence of PAPP-A is associated with resistance to the development of indicators of diabetic nephropathy in mice. These data suggest PAPP-A as a potential therapeutic target for diabetic nephropathy.
Pregnancy-associated plasma protein-A; kidney; diabetes; Bowman’s capsule
Patients with critical illness or hepatic failure exhibit impaired cortisol responses to ACTH, a phenomenon known as ‘relative adrenal insufficiency’. A putative mechanism is that elevated bile acids inhibit inactivation of cortisol in liver by 5α-reductases type 1 and type 2 and 5β-reductase, resulting in compensatory downregulation of the hypothalamic–pituitary–adrenal axis and adrenocortical atrophy. To test the hypothesis that impaired glucocorticoid clearance can cause relative adrenal insufficiency, we investigated the consequences of 5α-reductase type 1 deficiency in mice. In adrenalectomised male mice with targeted disruption of 5α-reductase type 1, clearance of corticosterone was lower after acute or chronic (eightfold, P<0.05) administration, compared with WT control mice. In intact 5α-reductase-deficient male mice, although resting plasma corticosterone levels were maintained, corticosterone responses were impaired after ACTH administration (26% lower, P<0.05), handling stress (2.5-fold lower, P<0.05) and restraint stress (43% lower, P<0.05) compared with WT mice. mRNA levels of Nr3c1 (glucocorticoid receptor), Crh and Avp in pituitary or hypothalamus were altered, consistent with enhanced negative feedback. These findings confirm that impaired peripheral clearance of glucocorticoids can cause ‘relative adrenal insufficiency’ in mice, an observation with important implications for patients with critical illness or hepatic failure, and for patients receiving 5α-reductase inhibitors for prostatic disease.
glucocorticoids; 5α-reductases; adrenal insufficiency; HPA axis
Adaptation to the environment is essential for survival, in all wild animal species seasonal variation in temperature and food availability needs to be anticipated. This has led to the evolution of deep-rooted physiological cycles, driven by internal clocks, which can track seasonal time with remarkable precision. Evidence has now accumulated that a seasonal change in thyroid hormone (TH) availability within the brain is a crucial element. This is mediated by local control of TH-metabolising enzymes within specialised ependymal cells lining the third ventricle of the hypothalamus. Within these cells, deiodinase type 2 enzyme is activated in response to summer day lengths, converting metabolically inactive thyroxine (T4) to tri-iodothyronine (T3). The availability of TH in the hypothalamus appears to be an important factor in driving the physiological changes that occur with season. Remarkably, in both birds and mammals, the pars tuberalis (PT) of the pituitary gland plays an essential role. A specialised endocrine thyrotroph cell (TSH-expressing) is regulated by the changing day-length signal, leading to activation of TSH by long days. This acts on adjacent TSH-receptors expressed in the hypothalamic ependymal cells, causing local regulation of deiodinase enzymes and conversion of TH to the metabolically active T3. In mammals, the PT is regulated by the nocturnal melatonin signal. Summer-like melatonin signals activate a PT-expressed clock-regulated transcription regulator (EYA3), which in turn drives the expression of the TSHβ sub-unit, leading to a sustained increase in TSH expression. In this manner, a local pituitary timer, driven by melatonin, initiates a cascade of molecular events, led by EYA3, which translates to seasonal changes of neuroendocrine activity in the hypothalamus. There are remarkable parallels between this PT circuit and the photoperiodic timing system used in plants, and while plants use different molecular signals (constans vs EYA3) it appears that widely divergent organisms probably obey a common set of design principles.
pars tuberalis; melatonin; Eya3; thyroid hormone; thyrotrophin; photoperiod; circadian