The fractionation of phosphorus in UK chalk stream surface waters and its relevance to the regulation and management of water quality.

The regulatory management of river water quality requires measurements of phosphorus that are operationally viable and meaningful in terms of insight into its effects. This need is a particular concern in globally rare and ecologically sensitive chalk streams. P data pertaining to rivers are commonly limited to soluble reactive P; other fractions of P may be of concern but are not routinely monitored. This study seeks to establish the nature and extent of non-regulated forms of P in UK chalk streams. Whilst soluble reactive P in two southern English chalk streams was found to comprise the majority of reactive P in surface waters in the majority of samples, 15-20% of the total reactive P was within other size fractions greater than 0.22 µm. The contribution of reactive P to the total P was highly variable. We conclude that, with some adjustments, the established method of regulatory monitoring of P in UK rivers is viable and valuable. In cases where the levels of reactive P are not consistent with ecological status and/or expected outcomes of programmes of measures, we recommend that targeted analysis of non-regulated forms of P is undertaken as a means to guide and focus management interventions.

Simultaneous pancreas and kidney transplantation as the standard surgical treatment for diabetes mellitus patients with end-stage renal disease.

OBJECTIVES: To review the outcome following simultaneous pancreas and kidney transplantation in patients with type 1 diabetes mellitus and end-stage renal disease, as well as those with type 2 diabetes mellitus, and to discuss the applicability of this treatment in this locality. METHODS: A systematic literature review was performed by searching the PubMed and Elsevier databases. The search terms used were "simultaneous pancreas and kidney transplantation", "diabetes", "pancreas transplant" and "SPK". Original and major review articles related to simultaneous pancreas and kidney transplantation were reviewed. Papers published in English after 1985 were included. Clinical outcomes following transplantation were extracted for comparison between different treatment methods. Outcomes of simultaneous pancreas and kidney transplant and other transplantation methods were identified and categorised into patient survival, graft survival, diabetic complications, and quality of life. Patient survivals and graft survivals were also compared. RESULTS: Currently available clinical evidence shows good outcomes for type 1 diabetes mellitus in terms of patient survival, graft survival, diabetic complications, and quality of life. For type 2 diabetes mellitus, the efficacy and application of the procedure remain controversial but the outcomes are possibly comparable with those in type 1 diabetes mellitus. CONCLUSIONS: Simultaneous pancreas and kidney transplantation is a technically demanding procedure that is associated with significant complications, and it should be regarded as a 'last resort' treatment in patients whose diabetic complications have become life-threatening or severely burdensome despite best efforts in maintaining good diabetic control through lifestyle modifications and medications.

Attitude toward the out-patient cardiac rehabilitation program and facilitators for maintenance of exercise behavior.

OBJECTIVE: This study examined the attitudes of Chinese patients with coronary heart disease (CHD) toward the outpatient cardiac rehabilitation program (OCRP), as well as their exercise behavior, intention, maintenance and related factors. METHOD: A qualitative descriptive study design was used, and 22 CHD patients were recruited in Hong Kong in 2014. In-depth interviews and content analyses were conducted. The tripartite model of attitudes was adopted as research framework. RESULT: Two themes were identified: (1) informant attitude (perception, affection, and practice) toward the OCRP and (2) Exercise Behavior - intention, maintenance and its related factors. Most informants showed positive perception and affection regarding the outpatient rehabilitation program, leading to regular practice of exercise in the program and at home. Peer, group dynamic, social support and Chinese culture influences on exercise behavior may serve as major facilitators to maintain exercise behavior. CONCLUSION: Positive attitude toward the OCRP enhanced the participation rate, whereas peer and social support from the family and workplace were useful to improve the maintenance of exercise behavior. Overall, this study provides insights into strategic planning for the OCRP and continual support for CHD patients in the community.

A territory-wide real-world efficacy and toxicity analysis of abiraterone acetate versus docetaxel in 574 Asian patients with metastatic hormone-sensitive prostate cancer.

INTRODUCTION: Abiraterone acetate (ABI) or docetaxel (DOC), in addition to androgen-deprivation therapy (ADT), are current treatment options for metastatic hormone-sensitive prostate cancer (mHSPC). No randomized head-to-head trial has compared these 2 mHSPC treatments, and real-world data regarding their outcomes in Asian patients are lacking. PATIENTS AND METHODS: The medical records of mHSPC patients who began upfront ABI or DOC treatment in addition to ADT at seven public oncology centers in Hong Kong between 2015 and 2021 were reviewed. The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), prostate-specific antigen (PSA) response, and toxicities. Kaplan-Meier and multivariate Cox regression analyses were performed. RESULTS: A total of 574 patients were included, of whom 419 received DOC and 155 received ABI. The median follow-up duration was 22.4 (DOC group: 23.8; ABI group: 17.3) months. The ABI group demonstrated significantly better PFS than the DOC group (not reached vs. 15.1 months: hazard ratio = 0.37; 95% confidence interval = 0.28-0.50; P < .001). No significant OS difference was observed (P = .58). Failure to achieve a ≥ 90% decline in PSA level at 3 months and failure to achieve an undetectable PSA nadir were each associated with unfavorable PFS and OS. Patients who received DOC had a higher rate of febrile neutropenia, whereas those who received ABI had higher rates of grade ≥ 3 hypokalemia and elevated alanine transaminase. Treatment discontinuation due to toxicities was more common in the DOC (3.6%) than the ABI (0.6%) group. CONCLUSION: In Asian mHSPC patients, upfront ABI + ADT was associated with better PFS than DOC + ADT, with no significant OS difference. PSA kinetics may help stratify the prognosis for treatment intensification. Toxicity profiles were different, with a higher rate of toxicity-related treatment discontinuation in the DOC group.

Docetaxel chemotherapy for Chinese patients with castrate-resistant prostate cancer.

OBJECTIVE. To determine the effectiveness and toxicity of docetaxel for Chinese patients with castrate-resistant prostate cancer in a local Hong Kong hospital. DESIGN. Case series. SETTING. A tertiary cancer centre in Hong Kong. PATIENTS. In all, 39 castrate-resistant prostate cancer patients were treated with 3-weekly docetaxel at 75 mg/m(2) and prednisolone 10 mg daily between January 2006 and December 2011 in Queen Elizabeth Hospital. MAIN OUTCOME MEASURES. Prostate-specific antigen control rate, pain control rate, progression-free survival, overall survival, and complication rates. RESULTS. The prostate-specific antigen response rate was 36%, and 27 (69%) of the patients had improved pain control after chemotherapy. The median progression-free survival, cancer-specific survival, and overall survival was 7.8 (95% confidence interval, 4.9-10.8) months, 13.0 (95% confidence interval, 9.6-16.3) months, and 12.2 (95% confidence interval, 9.3-15.1) months, respectively. The grade 3 anaemia and thrombocytopenia rates were 5%, and the neutropenic fever rate was 8%. CONCLUSIONS. Chemotherapy with docetaxel at a dose of 75 mg/m(2) given once every 3 weeks together with daily prednisolone is well tolerated in Chinese and can offer good symptom palliation in suitable patients with castrate-resistant prostate cancer.

A Systematic Review and Meta-analysis of the Effect of Oral Exercises on Masticatory Function.

The aim of the current systematic review was to summarize and to evaluate the available information on the effectiveness of oral exercise in improving the masticatory function of people ≥18 y. Electronic databases (Medline, Embase, CENTRAL) and gray literatures were searched (up to December 2020) for relevant randomized and nonrandomized controlled clinical trials. Two reviewers independently conducted the study selection, data extraction, and quality assessments. Meta-analysis was conducted for the comparison of bite force and masticatory performance using mean difference (MD) and standardized mean difference (SMD), respectively. GRADE (Grading of Recommendations Assessment, Development, and Evaluation) assessment was adopted for collective grading of the overall body of evidence. Of the 1,576 records identified, 18 studies (21 articles) were included in the analysis. Results of meta-analysis indicated that oral exercise could significantly improve the mean bite force of the participants (parallel comparison: MD, 41.2; 95% CI, 11.6-70.7, P = 0.006; longitudinal comparison: MD, 126.5; 95% CI, 105.2-144.9, P < 0.001). However, the improvement in masticatory performance was not significant (parallel comparison: SMD, 0.11; 95% CI, -0.20 to 0.42, P = 0.48; longitudinal comparison: SMD, 0.4; 95% CI, -0.11 to 0.91, P = 0.13). Results of meta-regression showed that greater improvements in bite force can be achieved among younger adults and with more intensive exercise. Chewing exercise is the most effective oral exercise, followed by clenching exercise, while simple oral exercise may not have a significant effect. Based on the results of the meta-analysis and GRADE assessment, a weak recommendation for people with declined masticatory function to practice oral exercise is made.

Sacrococcygeal teratoma in adults: case report and literature review.

Sacrococcygeal teratoma is one of the most common tumours in infants but rare in adults. We present a case of sacrococcygeal teratoma in a female adult. The clinical presentation, radiological and histological findings, management, and outcome are described.

Topical Fluoride to Prevent Root Caries: Systematic Review with Network Meta-analysis.

The aim of this systematic review and network meta-analysis was to summarize the direct and indirect clinical evidence on the effectiveness of professionally applied and self-applied topical fluorides in preventing dental root caries. Controlled clinical trials with any follow-up duration were included. MEDLINE, PubMed, Embase, Scopus, and Cochrane Library were searched. Two reviewers independently carried out the selection of studies, data extraction, risk-of-bias assessments, and assessment of the certainty in the evidence using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. Fixed effects model and frequentist approach were used in the network meta-analyses. Nine clinical trials involving 4,030 participants were included. Five professionally applied and 7 self-applied topical fluoride agents or combinations were included in the meta-analyses. Compared to control group, 38% silver diamine fluoride solution, 5% sodium fluoride varnish, and 1.2% acidulated phosphate fluoride reduced root caries increment after 2 y (ranging from 0.59 to 0.85 mean decayed or filled root [DF-root]). Fluoride mouth rinse and fluoride toothpaste, used alone or in combination, reduced root caries increment after 1 y (ranging from 0.29 to 1.90 mean DF-root). Among the professionally applied topical fluorides reviewed, an annually applied 38% silver diamine fluoride (SDF) solution combined with oral health education is most likely to be the most effective in preventing dental root caries. Among the reviewed self-applied topical fluoride methods, daily use of a 0.2% sodium fluoride (NaF) mouth rinse is most likely to be the most effective, followed by 1100 ppm to 1500 ppm fluoride toothpaste plus 0.05% NaF mouth rinse, and 1100 ppm to 1500 ppm fluoride toothpaste.

Factors Associated with Dental Root Caries: A Systematic Review.

OBJECTIVES: The objectives of this review were to identify the factors associated with root caries and to describe their relationship with the presence and extent of root caries. METHODS: A search was carried out on the PubMed, Medline, Embase, and Scopus databases for articles published between January 1990 and October 2018. Information was extracted on the factors associated with the presence or extent of decayed or filled root surfaces and/or decayed root surfaces. Factors were sorted into 6 categories: social-demographic background, general health, health behaviors, fluoride exposure, oral health habits, and oral health condition. RESULTS: The quality of the 127 identified relevant papers was assessed, and those of low methodological quality were excluded. Finally, 44 articles reporting on 40 cross-sectional studies were included. The total sample size comprised 78,183 participants from different countries around the world. Positive correlations were detected between root caries and age, gingival recession, and use of tobacco, while negative correlations were found for social position, use of fluoride toothpaste, and oral hygiene status. Mixed findings were reported for association with the number of teeth and dental visit behaviors. CONCLUSION: This systematic review found a number of factors in different categories to be associated with root caries. People who are older, of lower socioeconomic status, or tobacco users and those with more gingival recession and poorer oral hygiene have higher risk of root caries. KNOWLEDGE TRANSFER STATEMENT: This systematic review found a number of factors associated with root caries, including age, social position, exposure to fluoride, and oral hygiene status. This information helps dental public health workers and clinicians identify the groups at high risk of caries and the factors to act on for more effective prevention and management of root caries (e.g., use fluoride toothpaste and improve oral hygiene).

Activation of pro-urokinase and plasminogen on human sarcoma cells: a proteolytic system with surface-bound reactants.

Human HT-1080 fibrosarcoma cells produce urokinase-type plasminogen activator (u-PA) and type 1 plasminogen activator inhibitor (PAI-1). We found that after incubation of monolayer cultures with purified native human plasminogen in serum-containing medium, bound plasmin activity could be eluted from the cells with tranexamic acid, an analogue of lysine. The bound plasmin was the result of plasminogen activation on the cell surface; plasmin activity was not taken up onto cells after deliberate addition of plasmin to the serum-containing medium. The cell surface plasmin formation was inhibited by an anticatalytic monoclonal antibody to u-PA, indicating that this enzyme was responsible for the activation. Preincubation of the cells with diisopropyl fluorophosphate-inhibited u-PA led to a decrease in surface-bound plasmin, indicating that a large part, if not all, of the cell surface plasminogen activation was catalyzed by surface-bound u-PA. In the absence of plasminogen, most of the cell surface u-PA was present in its single-chain proenzyme form, while addition of plasminogen led to formation of cell-bound two-chain u-PA. The latter reaction was catalyzed by cell-bound plasmin. Cell-bound u-PA was accessible to inhibition by endogenous PAI-1 and by added PAI-2, while the cell-bound plasmin was inaccessible to serum inhibitors, but accessible to added aprotinin and an anticatalytic monoclonal antibody. A model for cell surface plasminogen activation is proposed in which plasminogen binding to cells from serum medium is followed by plasminogen activation by trace amounts of bound active u-PA, to form bound plasmin, which in turn serves to produce more active u-PA from bound pro-u-PA. This exponential process is subject to regulation by endogenous PAI-1 and limited to the pericellular space.

Estrogenic phenol and catechol metabolites of PCBs modulate catechol-O-methyltransferase expression via the estrogen receptor: potential contribution to cancer risk.

Commercial PCB mixtures have been shown to induce liver tumors in female rats and this effect has been attributed to the effects of PCBs on estrogen metabolism. Catechol metabolites of PCBs are potent inhibitors of COMT activity and are likely to contribute significantly to reduced clearance of genotoxic catechol metabolites of estrogen. The effect of PCB metabolites on COMT expression in cultured cells was investigated to explore potential mechanisms by which PCB exposure alters catechol estrogen clearance. We hypothesize that estrogenic PCB metabolites may contribute to reduction of COMT expression via interaction with the estrogen receptor. To test this hypothesis, human MCF-7 cells were exposed to PCB analogues and the expression of COMT determined. Western blot analysis demonstrated that COMT protein levels were statistically significantly reduced by both the phenolic and the catechol compounds, an effect which was abolished by the anti-estrogen, ICI182780. The above suggests that COMT levels may be reduced by estrogenic PCB metabolites, via interactions between PCB metabolites and the ER. It supports the hypothesis that both phenolic and catechol metabolites of PCBs may contribute to PCB-mediated carcinogenesis through reduction of COMT levels and activities and subsequent reduction in clearance of endogenous and xenobiotic catechols.

The efficacy of cevimeline hydrochloride in the treatment of xerostomia in Sjögren's syndrome in southern Chinese patients: a randomised double-blind, placebo-controlled crossover study.

Cevimeline hydrochloride, a specific agonist of the M3 muscarinic receptor, is beneficial in the treatment of symptoms of xerostomia and xerophthalmia associated with Sjögren's syndrome (SS). Cevimeline has not been evaluated in southern Chinese patients. Furthermore, the effects of cevimeline on health-related quality of life and oral health status are not known. In this randomised, double-blind, placebo-controlled crossover study, patients received cevimeline 30 mg or matched placebo three times per day over 10 weeks followed by a 4-week washout period before treatment crossover. Participants self-completed the following questionnaires: Xerostomia Inventory (XI), the General Oral Health Assessment Index (GOHAI), the Ocular Surface Disease Index (OSDI) and the Medical Outcomes Short Form (SF-36). Clinical assessments included sialometry, examination of the oral cavity for the degree of xerostomia and dental complications of xerostomia. Fifty patients (22 primary SS and 28 secondary SS) were enrolled in the trial. Forty-four patients completed the study. There was a significant improvement in the XI and GOHAI scores as well as the objective rating of xerostomic signs of the oral cavity after treatment with cevimeline. However, there was no improvement in salivary flow rates and dry eye symptoms. SS patients had lower SF-36 scores, but these did not improve after treatment with cevimeline.

Influence of demographic factors and sport type on growth hormone-responsive markers in elite athletes.

CONTEXT: GH-responsive markers of the IGF system and of collagen turnover hold promise as the basis of a GH doping test. OBJECTIVE: The purpose of this study was to determine the influence of age, gender, body mass index (BMI), ethnicity, and sporting type on GH-responsive serum markers in a large cohort of elite athletes from different ethnic backgrounds. DESIGN: The study was designed as a cross-sectional study. PARTICIPANTS: A total of 1103 elite athletes (699 males, 404 females), aged 22.2 +/- 5.2 yr, from 12 countries and 10 major sporting categories participated in this study. MAIN OUTCOME MEASURES: Serum IGF-I, IGF binding protein-3 (IGFBP-3), acid labile subunit (ALS), and collagen markers [N-terminal propeptide of type I procollagen (PINP), C-terminal telopeptide of type I collagen (ICTP), N-terminal propeptide of type III procollagen (PIIINP)] were measured. RESULTS: There was a significant negative correlation (r = -0.14 to -0.58, P < 0.0005) between age and each of the GH-responsive markers. Serum IGF-I, IGFBP-3, and ALS were all lower (P < 0.05), whereas the collagen markers PINP, ICTP, and PIIINP were higher (P < 0.05) in men than in women. Multiple regression analysis indicated that age, gender, BMI, and ethnicity accounted for 23-54% of total between-subject variability of the markers. Age and gender cumulatively accounted for 91% of the attributable variation of IGF-I and more than 80% for PINP, ICTP, and PIIINP. Gender exerted the greatest effect on ALS (48%), and BMI accounted for less than 12% attributable variation for all markers. The influence of ethnicity was greatest for IGFBP-3 and ALS; however, for the other markers, it accounted for less than 6% attributable variation. Analysis of 995 athletes indicated that sporting type contributed 5-19% of attributable variation. CONCLUSIONS: Age and gender were major determinants of variability of GH-responsive markers except for IGFBP-3 and ALS. Ethnicity is unlikely to confound the validity of a GH doping test based on IGF-I and these collagen markers.

Antigenic determination fragments of alpha-momorcharin.

Alpha momorcharin is a protein isolated from the bitter gourd. It has a number of biological activities including induction of abortion, inhibition of tumor growth and anti-HIV. All these activities may be related to the ribosome-inhibiting activity of the protein. Repeated use of alphaMMC can elicit an antigenic response which may neutralize its biological activity. To overcome this problem, we need to know which part of the molecule is the antigenic determinant. In this study, we constructed a random fragment expression library from the alphaMMC cDNA and screened it with three anti-alphaMMC sera. A total of 9 positive clones were picked and sequenced. Based on the sequence information obtained, we were able to deduce three regions at which antibodies raised against native alphaMMC seem to interact. These regions are residues 1-14, residues 71-136 and residues 195-222. Mapping of these regions against a 3D model of alphaMMC indicates that they all are located on the surface of the molecule. As residues 71-136 are found to be in close proximity to the active site involved in ribosome inactivation, treatment with a monoclonal antibody directed to this area was shown to be effective in inactivating the inhibitory effect of alphaMMC on in vitro protein synthesis.

Characterization of a low affinity binding protein for growth hormone in rat serum.

GH forms a high Mr complex in rat serum distinct from that with GH-binding protein (GHBP). The present study investigates the nature of this complex. When subjected to AcA44 filtration chromatography, 125I-labeled human GH (hGH) in rat serum eluted in four peaks. Peak 1 eluted at the void volume, whereas peaks 2, 3, and 4 corresponded to the GHBP complex, free hGH, and iodide, respectively. Stripping of GHBP in serum by immunoaffinity chromatography depleted peak 2 but did not affect peak 1. Peak 1 accounted for 11.4 +/- 1.2% of the total radioactivity (mean +/- SEM; n = 6) in stripped serum. Addition of unlabeled hGH (0.9-9 microM) demonstrated the binding of [125I]hGH to be specific, with Scatchard analysis revealing an affinity of 0.88 +/- 0.03 x 10(5) M(-1)(n = 3)and a capacity of 2.46 +/- 0.14 microM. Sepharose CL-6B filtration chromatography showed the complex to be 260 kDa in size. The distribution of GH binding to GHBP and this high Mr serum factor was investigated by incubating [125I]hGH in sera containing a low (5 nM) and a high (35 nM) concentration of GHBP over a range of physiological GH concentrations. In sera containing a low concentration of GHBP, the proportion of GH complexed in peak 1 increased with increasing GH concentrations. In sera with a high concentration of GHBP, GH was complexed mainly in peak 2. Studies with normal rat sera revealed that more GH was complexed in peak 1 in male than in female rats (3.4 +/- 0.4% and 1.4 +/- 0.1%, respectively; P < 0.006), in contrast to that of peak 2 (1.1 +/- 0.2% and 7.6 +/- 0.4%, respectively; P < 0.002). In summary, we provide strong evidence for the existence of a factor in rat serum that binds GH with low affinity and high capacity. It has a Mr of approximately 240 kDa, assuming a 1:1 binding stoichiometry, and is immunologically distinct from GHBP. This factor may provide supplementary capacity for GH binding when binding to GHBP is saturated.

Measurement of growth hormone-binding protein in the rat by a ligand immunofunctional assay.

We have developed a ligand immunofunctional assay (LIFA) for quantifying the circulating functional GH-binding protein (GHBP) in the rat. This two-site solid-phase assay uses a capture monoclonal antibody (4.3) specific to the hydrophilic C-terminal segment of rat GHBP (rGHBP), saturation of binding with human GH, and a detection system of rabbit antihuman GH polyclonal antibody and peroxidase-conjugated antirabbit immunoglobulin G antibody. Results were compared with Scatchard estimates derived by immuno-precipitation with monoclonal antibody 4.3. This assay was used to determine the GHBP levels in male and female rats and to investigate the diurnal properties and dynamics of GH and GHBP interaction in 15-min blood sampling over a 6-h period. The dynamic range of the rLIFA was 0.15-20.0 nM recombinant rGHBP, with intraassay and interassay coefficients of variation of 10.5% (n = 20) and 12.9% (n = 12), respectively. Serum GHBP levels determined by the rLIFA and those derived from Scatchard estimates were strongly correlated (n = 8; beta = 0.55; r2 = 0.89; P = 0.0005). Male rats had lower GHBP levels (6.5 +/- 0.7 nM; mean +/- SE; n = 14) than female rats (35.4 +/- 2.7 nM; n = 15; P = 0.0001). In the diurnal study, male rats had higher GH peaks (312.5 +/- 121.6 ng/ml; n = 7) than female rats (96.5 +/- 15.4 ng/ml; n = 9; P < 0.0001). In contrast to the pulsatile secretion of GH, GHBP levels in both sexes remained stable and showed no relationship to secretory pulses of GH. However, the GH bursts significantly altered the distribution of the GH-GHBP complex in male rats. By saturation and mass analysis, the greater GH pulsatile secretion in male rats resulted in occupancy of GHBP from less than 5% at nadir to about 80% at secretory peaks, in contrast to the less than 5-15% range of GHBP occupancy in female rats. In male rats, greater than 80% of GH at secretory peaks existed in the free form, whereas in female rats, 16-23% of GH existed in the free form during pulsatile secretion. In summary, the rLIFA shows good correlation to Scatchard analysis using an identical antibody. We conclude that this assay provides a rapid, sensitive, and accurate measurement of the circulating functional GHBP in the rat, and that it facilitates the study of GH and GHBP dynamics under a range of physiological conditions.

Stimulation of mitochondrial fatty acid oxidation by growth hormone in human fibroblasts.

In vivo administration of GH induces lipolysis and lipid oxidation. However, it is not clear whether the stimulation of lipid oxidation is a direct effect of GH or is driven by increased substrate supply secondary to lipolysis. An in vitro bioassay has been established for assessing beta-oxidation of fatty acids in mitochondria, based on the measurement of conversion of tritiated palmitic acid to 5H2O by fibroblasts in culture. We have modified this assay to investigate whether GH stimulates fatty acid oxidation. GH stimulated oxidation of palmitic acid maximally by 26.7 +/- 2.5% (mean +/- SEM; P < 0.0001). The stimulation was biphasic, with the oxidation rate increasing with increasing GH concentration to a peak response at 1.5 nmol/L and declining to a level not significantly different from control thereafter. Insulin-like growth factor-I at concentrations of up to 250 nmol/L had no significant effect on fatty acid oxidation. GH-binding protein attenuated the effect of GH. An anti-GH receptor (GHR) antibody (MAb263), which dimerizes the receptor and induces GH-like biological actions, significantly stimulated fatty acid oxidation. Another anti-GHR antibody (MAb5), which prevents receptor dimerization, suppressed GH action. In summary, GH directly stimulated fatty acid oxidation, an action not mediated by insulin-like growth factor-I. Dimerization of GHRs was necessary for this effect. This bioassay is a practical tool for studying the regulatory effects of GH on lipid oxidation.

Insulin regulation of human hepatic growth hormone receptors: divergent effects on biosynthesis and surface translocation.

Insulin modulates the biological actions of GH, but little is known about its effect on human hepatic GH receptors (GHRs). Using the human hepatoma cell line HuH7 as a model, we investigated insulin regulation of total, intracellular, and cell surface GHRs and receptor biosynthesis and turnover. Insulin up-regulated total and intracellular GHRs in a concentration-dependent manner. It increased surface GHRs in a biphasic manner, with a peak response at 10 nmol/L, and modulated GH-induced Janus kinase-2 phosphorylation in parallel with expression of surface GHRs. The abundance of GHR messenger ribonucleic acid and protein, as assessed by RT-PCR and Western analysis, respectively, markedly increased with insulin treatment. To examine whether insulin regulates GHRs at the posttranslational level, its effects on receptor surface translocation and internalization were investigated. Insulin suppressed surface translocation in a concentration-dependent manner, whereas internalization was unaffected. Moreover, insulin actions on total GHRs and surface translocation were inhibited by PD98059 and wortmannin, respectively. In conclusion, insulin regulates hepatic GHR biosynthesis and surface translocation in a reciprocal manner, with surface receptor availability the net result of the divergent effects. The divergent actions of insulin appear to be mediated by the mitogen-activated protein kinase and phosphatidylinositol 3-kinase pathways, respectively.

Distribution and abundance of messenger ribonucleic acid for growth hormone receptor isoforms in human tissues.

Two alternatively spliced exon 9 variants of human GH receptor (GHR) messenger ribonucleic acid (mRNA), GHR-(1-279) and GHR(1-277), were recently identified in liver. They encode receptor proteins lacking most of the intracellular domain and inhibit GH action in a dominant negative manner. Little is known about tissue distribution and abundance of these GHR isoforms. We have developed quantitative RT-PCR assays specific for the full-length and truncated GHRs and investigated their expression in various human tissues and cell lines. The mRNA of full-length GHR and GHR-(1-279) were readily detectable in all tissues investigated, with liver, fat, muscle, and kidney showing high levels of expression. These two receptor isoforms were also detected in a range of human cell lines, with strongest expression in IM9, a lymphoblastoid cell line. In contrast, GHR-(1277) message was expressed at low levels in liver, fat, muscle, kidney, and prostate and in trace amount in IM9 cells. Full-length GHR was the most abundant isoform, accounting for over 90% of total receptor transcripts in liver, fat, and muscle for quantitative RT-PCR. However, liver had 2- to 4-fold more full-length receptor mRNA and 16- to 40-fold more GHR-(1-277) mRNA than fat and muscle, whereas the mRNA levels of GHR-(1-279) were similar in the three tissues. GHR-(1-279) constituted less than 4% in liver and 7-10% in fat and muscle. GHR-(1-277) accounted for 0.5% of total GHR transcripts in liver and less than 0.1% in the other two tissues. These data suggest that the absolute and relative abundance of mRNA of the three GHR isoforms may be tissue specific. The regulation of expression of exon 9 alternatively spliced GHR variants may provide a potential mechanism for modulation of GH sensitivity at the tissue level.