Kin-Chuen Leung

Estrogen inhibits GH signaling by suppressing GH-induced JAK2 phosphorylation, an effect mediated by SOCS-2

Oral estrogen administration attenuates the metabolic action of growth hormone (GH) in humans. To investigate the mechanism involved, we studied the effects of estrogen on GH signaling through Janus kinase (JAK)2 and the signal transducers and activators of transcription (STATs) in HEK293 cells stably expressing the GH receptor (293GHR), HuH7 (hepatoma) and T-47D (breast cancer) cells. 293GHR cells were transiently transfected with an estrogen receptor-α expression plasmid and luciferase reporters with binding elements for STAT3 and STAT5 or the β-casein promoter. GH stimulated the reporter activities by four- to sixfold. Cotreatment with 17β-estradiol (E2) resulted in a dose-dependent reduction in the response of all three reporters to GH to a maximum of 49–66% of control at 100 nM (P < 0.05). No reduction was seen when E2 was added 1–2 h after GH treatment. Similar inhibitory effects were observed in HuH7 and T-47D cells. E2 suppressed GH-induced JAK2 phosphorylation, an effect attenuated by actinomycin D, suggesting a requirement for gene expression. Next, we investigated the role of the suppressors of cytokine signaling (SOCS) in E2 inhibition. E2 increased the mRNA abundance of SOCS-2 but not SOCS-1 and SOCS-3 in HEK293 cells. The inhibitory effect of E2 was absent in cells lacking SOCS-2 but not in those lacking SOCS-1 and SOCS-3. In conclusion, estrogen inhibits GH signaling, an action mediated by SOCS-2. This paper provides evidence for regulatory interaction between a sex steroid and the GH/JAK/STAT pathway, in which SOCS-2 plays a central mechanistic role.

The Effects of Growth Hormone on Body Composition and Physical Performance in Recreational Athletes: A Randomized Trial

BACKGROUND Growth hormone is widely abused by athletes, frequently with androgenic steroids. Its effects on performance are unclear. OBJECTIVE To determine the effect of growth hormone alone or with testosterone on body composition and measures of performance. DESIGN Randomized, placebo-controlled, blinded study of 8 weeks of treatment followed by a 6-week washout period. Randomization was computer-generated with concealed allocation. (Australian-New Zealand Clinical Trials Registry registration number: ACTRN012605000508673) SETTING Clinical research facility in Sydney, Australia. PARTICIPANTS 96 recreationally trained athletes (63 men and 33 women) with a mean age of 27.9 years (SD, 5.7). INTERVENTION Men were randomly assigned to receive placebo, growth hormone (2 mg/d subcutaneously), testosterone (250 mg/wk intramuscularly), or combined treatments. Women were randomly assigned to receive either placebo or growth hormone (2 mg/d). MEASUREMENTS Body composition variables (fat mass, lean body mass, extracellular water mass, and body cell mass) and physical performance variables (endurance [maximum oxygen consumption], strength [dead lift], power [jump height], and sprint capacity [Wingate value]). RESULTS Body cell mass was correlated with all measures of performance at baseline. Growth hormone significantly reduced fat mass, increased lean body mass through an increase in extracellular water, and increased body cell mass in men when coadministered with testosterone. Growth hormone significantly increased sprint capacity, by 0.71 kJ (95% CI, 0.1 to 1.3 kJ; relative increase, 3.9% [CI, 0.0% to 7.7%]) in men and women combined and by 1.7 kJ (CI, 0.5 to 3.0 kJ; relative increase, 8.3% [CI, 3.0% to 13.6%]) when coadministered with testosterone to men; other performance measures did not significantly change. The increase in sprint capacity was not maintained 6 weeks after discontinuation of the drug. LIMITATIONS Growth hormone dosage may have been lower than that used covertly by competitive athletes. The athletic significance of the observed improvements in sprint capacity is unclear, and the study was too small to draw conclusions about safety. CONCLUSION Growth hormone supplementation influenced body composition and increased sprint capacity when administered alone and in combination with testosterone. PRIMARY FUNDING SOURCE The World Anti-Doping Agency.

Pharmacodynamics of growth hormone abuse biomarkers and the influence of gender and testosterone: a randomized double-blind placebo-controlled study in young recreational athletes.

CONTEXT IGF axis proteins and collagen peptides are promising markers of GH abuse. OBJECTIVE Our objective was to investigate whether responses of serum IGF axis and collagen markers to GH differ between men and women, and are influenced by testosterone (T). DESIGN This was a randomized, double-blind, placebo-controlled study of 8-wk treatment followed by 6-wk washout. SETTING The study was performed at a clinical research facility. PARTICIPANTS A total of 96 recreationally trained healthy athletes (63 men, 33 women), aged 18-40 yr, were studied. INTERVENTION All subjects received GH (2 mg/d sc) or placebo for 8 wk; men also received T (250 mg/wk im) or placebo for 5 wk. MAIN OUTCOME MEASURES Serum IGF axis proteins (IGF-I, IGF binding protein-3, and acid labile subunit) and collagen peptides (N-terminal propeptide of type I procollagen, C-terminal telopeptide of type I collagen, and N-terminal propeptide of type III procollagen) were measured. RESULTS GH induced significant increases in IGF axis and collagen markers that were greater in men than women (P < 0.001). Of the IGF axis markers, IGF-I showed the greatest increase. The relative incremental responses of the collagen markers in general were greater than the IGF markers, especially for PIIINP. The collagen markers increased and decreased more slowly with most remaining elevated (P < 0.01) after 6 wk, in comparison to IGF markers, which returned to baseline within 1 wk. Addition of T to GH amplified the response of PIIINP by more than 1.5-fold but did not affect any other marker. T alone did not affect IGF axis markers but modestly increased collagen markers. CONCLUSIONS These markers of GH abuse are less responsive in women. The increases in collagen markers have a different time course to the IGF markers and extend the window of detection in both sexes. The response of PIIINP is increased by coadministration of T.

Modulation by progestogens of the effects of oestrogen on hepatic endocrine function in postmenopausal women

objective  Oral but not transdermal oestrogen administration reduces IGF‐I, and increases GH binding protein (GHBP) reflecting effects on hepatic endocrine function in postmenopausal women. As progestogens attenuate the effects of oestrogen on circulating lipid levels according to their androgenic properties, we have investigated the impact of progestogen types on the hepatic endocrine effects of oestrogen.

Adiponectin isoform distribution in women—relationship to female sex steroids and insulin sensitivity

Little is known about the associations between adiponectin and its oligomeric isoforms with female sex steroids, and the relevance of these relationships to insulin sensitivity in women. In a cross-sectional study of 32 healthy women (12 premenopausal, 10 postmenopausal, and 10 early pregnant), we investigated the correlations of total adiponectin and the high-, medium-, and low-molecular weight oligomers (HMW, MMW, and LMW, respectively) with estrogen, progesterone, adiposity, and insulin resistance. Fat mass and serum concentrations of estradiol, progesterone, insulin, glucose, and total and isoform adiponectin were measured. The homeostasis model assessment of insulin resistance (HOMA-IR) was calculated. Serum concentrations of total and HMW adiponectin were highest in postmenopausal women and lowest in pregnant women. Concentrations of the MMW and LMW isoforms were not significantly different between the 3 groups. Total adiponectin, HMW adiponectin, and MMW adiponectin were negatively associated with estradiol and progesterone; but no associations between the LMW isoform and female sex steroids were observed. Fat mass and HOMA-IR were highest in pregnant women and lowest in premenopausal women. The HOMA-IR was positively associated with fat mass, estradiol, and progesterone, and negatively associated with total, HMW, and MMW adiponectin. Multivariate stepwise regression analysis revealed that fat mass explained 34% of the variance in HOMA-IR and that total and isoform adiponectin contributed an additional 10% to 15%. In the multivariate linear regression analysis, there were significant interactions of estradiol and progesterone with adiponectin or fat mass in the associations with HOMA-IR. In conclusion, there are strong negative associations of serum adiponectin and some of its isoforms with estradiol and progesterone. Female sex steroids are likely to affect insulin sensitivity through modulation of adiponectin and body fat.

Enterovirus infection induces cytokine and chemokine expression in insulin-producing cells.

Despite evidence supporting an association between enterovirus (EV) infection and type 1 diabetes, the etiological mechanism(s) for EV‐induced beta cell destruction is(are) not well understood. In this study, the effects of Coxsackievirus B (CVB) 1–6 on cell lysis and cytokine/chemokine expression in the insulinoma‐1 (INS‐1) beta cell line were investigated. Cytolysis was assessed using tissue culture infectious dose 50 (TCID50). Quantitative RT‐PCR was used to measure viral RNA and mRNA of cytokines interferon (IFN)‐α, IFN‐β, IFN‐γ, tumor necrosis factor (TNF)‐α, and chemokine (C–X–C motif) ligand 10 (CXCL10), chemokine (C–C motif) ligand 2 (CCL2), and chemokine (C–C motif) ligand 5 (CCL5) in infected INS‐1 cells. CVB2, 4, 5, and 6 lysed and replicated in INS‐1 cells; TCID50 was lowest for CVB5 and highest for CVB6. IFN‐γ, CXCL10, and CCL5 mRNA levels all increased significantly following infection with CVB2, 4, 5, and 6 (P < 0.05). CCL2 mRNA increased with CVB2, 5, and 6 (P < 0.05), IFN‐α mRNA increased with CVB5 infection (P < 0.05), while TNF‐α mRNA and IFN‐β mRNA (P < 0.001) increased with CVB2 infection. Dose‐dependent effects of infection on cytokine mRNA levels were observed for all (P < 0.01) except IFN‐γ. Following inoculation of INS‐1 cells with CVB1 and 3, viral RNA was not detected and cytokine/chemokine mRNA levels were unchanged. In conclusion, CVB2, 4, 5, and 6 induce dose‐dependent cytokine and chemokine mRNA production from INS‐1 cells suggesting that pro‐inflammatory cytokine and chemokine secretion by beta cells is a potential mechanism for EV‐induced beta cell damage in type 1 diabetes. J. Med. Virol. 82:1950–1957, 2010.

Galanin in human pituitary adenomas: frequency and clinical significance

objectives Galanin (GAL) is a neuropeptide widely expressed in the central and peripheral nervous system and in neuroendocrine tissue, including the adenohypophysis where, in humans, it is expressed in corticotrophs and in ACTH‐producing adenomas. Previous analyses of human tissue have used antiserum against porcine GAL for detection of GAL immunoreactivity (GAL‐IR) and no pathophysiological correlates have been reported. Given significant differences between the sequence of porcine and human GAL peptides, the aim of this study was to use antiserum raised against synthetic human GAL to investigate GAL‐IR in non tumorous pituitaries and in pituitary adenomas, and to correlate GAL‐IR with the clinical and hormonal characteristics of patients with Cushing’s disease.

Measurement of growth hormone, insulin-like growth factor I and their binding proteins: the clinical aspects.

BACKGROUND Growth hormone (GH) secreted from the pituitary stimulates the production of insulin-like growth factor I (IGF-I) from the liver and extrahepatic tissues, which in turn regulates tissue proliferation and differentiation in an endocrine or autocrine/paracrine manner. Both GH and IGF-I circulates as complexes with specific binding proteins. The GH binding protein (GHBP) corresponds to the extracellular, ligand-binding domain of the GH receptors in tissues and its serum concentration may reflect the status of the tissue receptors. Most serum IGF-I associates with IGF binding protein 3 (IGFBP-3) and another protein, the acid labile subunit (ALS). Like IGF-I, serum concentrations of IGFBP-3 and ALS are tightly regulated by GH. GH secretion (both spontaneous and stimulated), IGF-I, IGFBP-3, and ALS have been assessed as potential biochemical markers for diagnosis of GH-related disorders. CONCLUSIONS In acromegaly, IGF-I is the most reliable marker. The peak GH response to insulin tolerance test is the diagnostic test of choice, GH deficiency. GHBP has no diagnostic value in acromegaly or GH deficiency. However, it may be a potential biochemical marker for GH insensitivity syndrome as serum GHBP concentrations are undetectable or reduced in >75% of these patients. Other biochemical tests may also prove to be useful in these disorders, but require further validation.

Human growth hormone fragment (hGH44–191) produces insulin resistance and hyperinsulinemia but is less potent than the 22 kDa hGH in the rat

A 17 kDa fragment of human growth hormone (22 kDa hGH), identified as hGH44–191, has lower binding affinity for growth hormone receptors (GHRs), but has been reported to be more potent in producing glucose intolerance in yellow obese mice. Our aim was to investigate this anomaly by comparing acute development of hyperinsulinemia and insulin resistance (“diabetogenic activity”) during hGH44–191 or 22 kDa hGH infusion in normal rats. Fasted awake male rats (350–370 g) were infused via a carotid cannula with saline (CON), 22 kDa hGH (at 0.125 μg/min), or hGH44–191 (at 0.64 or 0.32 μg/min) for 5.75 h. Over the last 2 h, a euglycemic hyperinsulinemic clamp (insulin infusion rate 0.25 U/kg/h) was performed. After 3.75 h infusion, 22 kDa hGH at 0.125 and hGH44–191) at 0.64 μg/min produced basal (preclamp) hyperinsulinemia compared to CON. During the clamp, insulin resistance was consistently produced by 22 kDa hGH at 0.125 and hGH44–191 at 0.64 μg/min compared to CON. Using specific radio-immunoassays for 22 kDa hGH and hGH44–191 we determined that under conditions of equivalent diabetogenic activity, molar circulating levels of hGH44–191 were 50–60-fold higher than 22 kDa hGH. It was concluded that whereas 22 kDa hGH and hGH44–191 are both capable of generating acute hyperinsulinemia and insulin resistance in the normal rat, the diabetogenic potency of hGH44–191 is not enhanced compared to 22 kDa hGH, and that diabetogenic potency is in accord with the reported lower binding affinity of hGH44–191 to the GHR.

Congenital Cytomegalovirus among Children with Cerebral Palsy

Objectives To determine the proportion of children with cerebral palsy (CP) and cytomegalovirus (CMV) DNA detected retrospectively in their newborn screening cards (NBSC), to compare the proportion of children with CMV DNA in their NBSC across spastic subtypes of CP, and to compare the sex and other characteristics of children with CP and CMV detected on their NSBC with those in whom CMV DNA was not detected. Study design Retrospective observational study. Data were extracted from patient records on children with CP (birth years 1996‐2014) from 2 Australian state CP registers and state‐wide paediatric rehabilitation services with consent. NBSCs were retrospectively analyzed for CMV DNA by nested polymerase chain reaction (PCR) using primers against gB. Positive samples were validated using real time PCR for CMV UL83. Results Of 401 children recruited, 323 (80.5%) had an available NBSC. Of these, 31 (9.6%; 95% CI, 6.8‐13.3) tested positive for CMV DNA by nested PCR for CMV gB, of whom 28 (8.7%; 95% CI, 6.1‐12.2) also had CMV DNA detected by real‐time PCR for CMV UL83. Detection of CMV DNA was significantly associated with epilepsy, but not with clinical or epidemiologic characteristics, including sex and pattern of spasticity. Conclusions CMV viremia in the newborn period, indicating congenital CMV infection, is highly prevalent among children with CP. Further research is needed to investigate the mechanisms and contribution of congenital CMV to the causal pathways to CP.