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Chubb SAP, Hyde Z, Almeida OP, Flicker L, Norman PE, Jamrozik K, Hankey GJ, Yeap BB. Lower sex hormone-binding globulin is more strongly associated with metabolic syndrome than lower total testosterone in older men: the Health in Men Study. Eur J Endocrinol 2008; 158:785-92. [PMID: 18505902 DOI: 10.1530/eje-07-0893] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BACKGROUND Reduced circulating testosterone and sex hormone-binding globulin (SHBG) are implicated as risk factors for metabolic syndrome. As SHBG increases with age while testosterone declines, we examined the relative contributions of SHBG and testosterone to the risk of metabolic syndrome in older men. METHODS We conducted a cross-sectional study of 2502 community-dwelling men aged > or = 70 years without known diabetes. Metabolic syndrome was defined using the National Cholesterol Education Program-Third Adult Treatment Panel (NCEP-ATPIII) criteria. Early morning fasting sera were assayed for total testosterone, SHBG and LH. Free testosterone was calculated using mass action equations. RESULTS There were 602 men with metabolic syndrome (24.1%). The risk of metabolic syndrome increased for total testosterone < 20 nmol/l, SHBG < 50 nmol/l and free testosterone < 300 pmol/l. In univariate analyses SHBG was associated with all five components of metabolic syndrome, total testosterone was associated with all except hypertension, and free testosterone was associated only with waist circumference and triglycerides. In multivariate analysis, both total testosterone and especially SHBG remained associated with metabolic syndrome, with odds ratios of 1.34 (95% confidence interval (CI): 1.18-1.52) and 1.77 (95% CI: 1.53-2.06) respectively. Men with hypogonadotrophic hypogonadism (total testosterone < 8 nmol/l, LH < or = 12 IU/l) had the highest prevalence of metabolic syndrome (53%, P<0.001). CONCLUSIONS Lower SHBG is more strongly associated with metabolic syndrome than lower total testosterone in community-dwelling older men. SHBG may be the primary driver of these relationships, possibly reflecting its relationship with insulin sensitivity. Further studies should examine whether measures that raise SHBG protect against the development of metabolic syndrome in older men.
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Almeida OP, Yeap BB, Hankey GJ, Jamrozik K, Flicker L. Low free testosterone concentration as a potentially treatable cause of depressive symptoms in older men. ACTA ACUST UNITED AC 2008; 65:283-9. [PMID: 18316674 DOI: 10.1001/archgenpsychiatry.2007.33] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
CONTEXT Serum concentrations of gonadal hormones have been associated with various measures of well-being, but it is unclear whether their association with mood is confounded by concurrent physical morbidity. OBJECTIVE To determine whether the association between serum testosterone concentration and mood in older men is independent of physical comorbidity. DESIGN Cross-sectional study. SETTING Community of Perth, Western Australia. PARTICIPANTS A community sample of men aged 71 to 89 years. MAIN OUTCOME MEASURES We used the 15-item Geriatric Depression Scale (GDS-15) to assess depressed mood. Clinically significant depression was defined a priori as a GDS-15 score of 7 or greater. Physical health was assessed using the weighted Charlson index and the Physical Component Summary score of the 36-Item Short Form Health Survey. RESULTS Of 3987 men included in the study, 203 (5.1%; 95% confidence interval [CI], 4.4%-5.8%) had depression. Participants with depression had significantly lower total and free testosterone concentrations than nondepressed men (P < .001 for both). However, they were also more likely to smoke and to have low educational attainment, a body mass index categorized as obese, a Mini-Mental State Examination score less than 24, a history of antidepressant drug treatment, and greater concurrent physical morbidity. After adjusting for these factors and for age, men with depression were 1.55 (95% CI, 0.91-2.63) and 2.71 (95% CI, 1.49-4.93) times more likely to have total and free testosterone concentrations, respectively, in the lowest quintile. CONCLUSIONS A free testosterone concentration in the lowest quintile is associated with a higher prevalence of depression, and this association cannot be adequately explained by physical comorbidity. A randomized controlled trial is required to determine whether the link between low free testosterone level and depression is causal because older men with depression may benefit from systematic screening of free testosterone concentration and testosterone supplementation.
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Davis TME, Yeap BB, Davis WA, Bruce DG. Lipid-lowering therapy and peripheral sensory neuropathy in type 2 diabetes: the Fremantle Diabetes Study. Diabetologia 2008; 51:562-6. [PMID: 18193189 DOI: 10.1007/s00125-007-0919-2] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2007] [Accepted: 12/12/2007] [Indexed: 10/22/2022]
Abstract
AIMS/HYPOTHESIS The aim of this study was to assess the relationships between lipid-lowering therapy and the prevalence and incidence of peripheral sensory neuropathy in type 2 diabetes mellitus. METHODS We analysed data from an observational cohort study, the Fremantle Diabetes Study (FDS), specifically, (1) a cross-sectional sample comprising 1,237 FDS participants with type 2 diabetes mellitus, and (2) a longitudinal subgroup of 531 individuals who had attended six consecutive annual assessments. Neuropathy was identified using the clinical portion of the Michigan Neuropathy Screening Instrument. RESULTS At entry, the cross-sectional sample had a mean +/- SD age of 63.8+/-11.3 years, 48.7% were men, median (interquartile range) diabetes duration was 4.0 (1.0-9.0) years, and 30.9% had peripheral neuropathy. Fibrates and statins were used by 3.5 and 6.8%, respectively. Multiple logistic regression analysis showed that older age, longer diabetes duration, central adiposity, increased height, higher fasting serum glucose, albuminuria and aboriginality were significant independent positive predictors of prevalent neuropathy, while systolic blood pressure and fibrate use (odds ratio 0.30, 95% CI 0.10-0.86; p=0.025) were negatively associated. In the longitudinal subgroup, fibrate and statin use increased to 10.4 and 36.5%, respectively, over 5 years. In time-dependent Cox proportional hazards modelling, fibrate use [hazard ratio (HR) 0.52, 95% CI 0.27-0.98] and statin use (HR 0.65, 95% CI 0.46-0.93) were significant determinants of incident neuropathy (p <or= 0.042). CONCLUSIONS/INTERPRETATION These preliminary observational data suggest that therapy with a statin or a fibrate may protect against the development of diabetic peripheral sensory neuropathy, but there is a need for additional confirmatory evidence, preferably from randomised clinical trials.
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Yeap BB, Almeida OP, Hyde Z, Chubb SAP, Hankey GJ, Jamrozik K, Flicker L. Higher serum free testosterone is associated with better cognitive function in older men, while total testosterone is not. The Health In Men Study. Clin Endocrinol (Oxf) 2008; 68:404-12. [PMID: 17888021 DOI: 10.1111/j.1365-2265.2007.03055.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
OBJECTIVE To determine the relationship of total and free serum testosterone to cognitive performance in older men. DESIGN Cross-sectional study of a population-based sample. Participants A total of 2932 men aged 70-89 years. MEASUREMENTS Cognitive function was assessed using the Standardized Mini-Mental State Examination (SMMSE). Early morning sera were assayed for total testosterone, SHBG and LH. Free testosterone was calculated using the Vermeulen method. RESULTS There were weak positive correlations between SMMSE score and serum free testosterone (Spearman's rho = 0.06, P = 0.001) and total testosterone (r = 0.04, P = 0.027), and a weak negative correlation with LH (r = -0.07, P < 0.001). Men with SMMSE scores in the top quintile had higher serum free testosterone compared with those in the lowest quintile [median (interquartile range, IQR): 278 (228-335) vs. 262 (212-320) pmol/l, P = 0.003], but similar total testosterone [15.2 (11.9-18.8) vs. 14.8 (11.6-18.3) nmol/l, P = 0.118]. Increasing age, non-English-speaking background, lower educational attainment, presence of clinically significant depressive symptoms, and cardiovascular morbidity were associated with the lowest cognitive performance quintile. After their effects were taken into account in a multivariate analysis, serum free testosterone > or = 210 pmol/l was associated with reduced likelihood of poor cognitive performance on the SMMSE [odds ratio (OR) 0.71, 95% confidence interval (CI) 0.52-0.97]. CONCLUSIONS In community-dwelling older men, serum free testosterone > or = 210 pmol/l is associated with better cognitive performance. In this context, calculated free testosterone seems to be a more informative measure of androgen status than total testosterone. Studies examining the contribution of androgens to age-related cognitive decline should incorporate an assessment of free testosterone concentration.
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Hislop AL, Fegan PG, Schlaeppi MJ, Duck M, Yeap BB. Prevalence and associations of psychological distress in young adults with Type 1 diabetes. Diabet Med 2008; 25:91-6. [PMID: 18199136 DOI: 10.1111/j.1464-5491.2007.02310.x] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
AIMS To determine the prevalence of psychological distress in young adults with Type 1 diabetes and to explore associated factors. METHODS Ninety-two participants with Type 1 diabetes (46 male, 46 female) attending a young adult clinic completed two psychological self-report assessments; the Centre for Epidemiological Studies-Depression Scale (CES-D) and Adult Self-Report Scale (ASR). The mean age was 21.6 +/- 2.8 years (sd) and mean duration of diabetes was 9.3 +/- 5.4 years. A questionnaire identified the method of insulin delivery, the frequency of blood glucose monitoring and hypoglycaemia requiring third-party assistance. HbA(1c) was measured. RESULTS Of the participants, 35.2% reported depressive symptoms (CES-D > or = 16), 23.1% indicating severe depressive symptoms (CES-D > or = 24), and 32.2, 40.4 and 35.5% of participants reported significant distress (ASR > or = 60) on the ASR total problem scales, ASR internalizing and ASR externalizing scores, respectively. Mean HbA(1c) levels were higher in participants with depressive symptoms compared with those with normal scores (CES-D > or = 16, HbA(1c)= 9.4% vs. CES-D < 16, HbA(1c)= 8.4%, P = 0.01). Factors associated with psychological distress included use of continuous subcutaneous insulin infusion (CSII) (P = 0.02) and increased frequency of hypoglycaemic episodes (P = 0.03). CSII users had higher CES-D (21.3 vs. 11.9, P = 0.001) and ASR-Total (59.7 vs. 53.0, P = 0.02) scores than non-CSII users. CONCLUSIONS Approximately one-third of young adults with Type 1 diabetes experience psychological distress, which is associated with poorer glycaemic control. Psychological distress was related to frequency of hypoglycaemic episodes and method of insulin administration, with significantly greater distress being observed in those using CSII. These findings support inclusion of a psychologist in the diabetes team.
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Yeap BB, Almeida OP, Hyde Z, Norman PE, Chubb SAP, Jamrozik K, Flicker L. In men older than 70 years, total testosterone remains stable while free testosterone declines with age. The Health in Men Study. Eur J Endocrinol 2007; 156:585-94. [PMID: 17468195 DOI: 10.1530/eje-06-0714] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE An age-related decline in serum total and free testosterone concentration may contribute to ill health in men, but limited data are available for men > 70 years of age. We sought to determine the distribution and associations of reduced testosterone concentrations in older men. DESIGN The Health in Men Study is a community-representative prospective cohort investigation of 4263 men aged > or = 70 years. Cross-sectional hormone data from 3645 men were analysed. METHODS Early morning sera were assayed for total testosterone, sex hormone binding globulin (SHBG) and LH. Free testosterone was calculated using the Vermeulen method. RESULTS Mean (+/- s.d.) serum total testosterone was 15.4 +/- 5.6 nmol/l (444 +/- 162 ng/dl), SHBG 42.4 +/- 16.7 nmol/l and free testosterone 278 +/- 96 pmol/l (8.01 +/- 2.78 ng/dl). Total testosterone correlated with SHBG (Spearman's r = 0.6, P < 0.0001). LH and SHBG increased with age (r = 0.2, P < 0.0001 for both). Instead of declining, total testosterone increased marginally (r = 0.04, P = 0.007) whilst free testosterone declined with age (r = -0.1, P < 0.0001). Free testosterone was inversely correlated with LH (r = -0.1, P < 0.0001). In multivariate analyses, increasing age, body mass index (BMI) and LH were associated with lower free testosterone. CONCLUSIONS In men aged 70-89 years, modulation of androgen action may occur via an age-related increase in SHBG and reduction in free testosterone without a decline in total testosterone concentration. Increasing age, BMI and LH are independently associated with lower free testosterone. Further investigation would be required to assess the clinical consequences of low serum free testosterone, particularly in older men in whom total testosterone may be preserved.
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Senanayake S, Brownrigg LM, Panicker V, Croft KD, Joyce DA, Steer JH, Puddey IB, Yeap BB. Monocyte-derived macrophages from men and women with Type 2 diabetes mellitus differ in fatty acid composition compared with non-diabetic controls. Diabetes Res Clin Pract 2007; 75:292-300. [PMID: 16908084 DOI: 10.1016/j.diabres.2006.07.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Accepted: 07/10/2006] [Indexed: 10/24/2022]
Abstract
We examined whether macrophages from men and women with Type 2 diabetes mellitus (T2DM) exhibited differences in expression of key genes involved in fatty acid metabolism and in fatty acid composition compared with macrophages from non-diabetic controls. Peripheral blood monocytes from subjects with T2DM (n=9) and non-diabetic controls (n=10) were differentiated into macrophages in 10% autologous serum and normal (5mM) or high (22mM) glucose. Levels of PPARalpha, PPARgamma, LXRalpha, SCD and ABCA1 mRNAs were similar in macrophages from subjects with T2DM and controls. At 5mM glucose, macrophage stearic acid (C18:0) was 12.6+/-1.0% of total fatty acids for T2DM compared with 18.1+/-2.0% for controls (p=0.03). Macrophage linoleic acid (C18:2) was 15.5+/-0.8% for T2DM and 9.3+/-2.0% for controls (p=0.005). The ratio of macrophage stearic acid (C18:0)/oleic acid (C18:1) was 0.29 [0.25,0.48] for T2DM versus 0.54 [0.36,0.82] for controls (p=0.04). Compared with non-diabetic controls, macrophages from men and women with T2DM had significantly different fatty acid profiles consistent with increased stearoyl-CoA desaturase (SCD) activity and increased C18:2 accumulation. This pattern of altered macrophage fatty acid composition may be relevant to diabetic atherogenesis.
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Nguyen HV, Mollison LC, Taylor TW, Chubb SAP, Yeap BB. Chronic hepatitis C infection and sex hormone levels: effect of disease severity and recombinant interferon-alpha therapy. Intern Med J 2006; 36:362-6. [PMID: 16732861 DOI: 10.1111/j.1445-5994.2006.01093.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND We aimed to investigate the associations between androgen status and markers of liver disease severity and to determine the effect of interferon-alpha (IFN-alpha) treatment on sex hormone levels in the context of hepatitis C infection. METHODS We audited liver biopsy and sex hormone data from 35 men with chronic hepatitis C and a separate group of 11 men with hepatitis C who received IFN-alpha treatment at Fremantle Hospital. RESULTS We found that men with low fibrosis scores (0-2) on the modified Knodell histological activity index were more likely to have lower sex hormone-binding globulin (SHBG) levels (38.2 +/- 13.2 vs 66.6 +/- 43.3 nmol/L, P < 0.001) and higher free testosterone levels (380.4 +/- 102.0 vs 255.9 +/-83.0 pmol/L, P = 0.01) than those with higher fibrosis scores (3-6). SHBG directly correlated with fibrosis scores (r = 0.37, P = 0.032). Free testosterone levels inversely correlated with liver fibrosis scores (r = -0.43, P = 0.011). A transient reduction in total testosterone of 5.7 +/- 4.2 nmol/L (P = 0.014) occurred within the first 6 months of IFN-alpha therapy although free testosterone was unaffected. CONCLUSION More severe liver disease was associated with lower free testosterone and higher SHBG. IFN-alpha therapy reduced total testosterone but not to hypogonadal levels, with no decline in free testosterone. These data suggest that liver disease in hepatitis C infection modulates androgen status indirectly via increased SHBG. Screening for androgen deficiency in the context of hepatitis C infection should selectively target men with more severe liver disease or documented higher grade fibrosis.
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Hampel JKA, Brownrigg LM, Vignarajah D, Croft KD, Dharmarajan AM, Bentel JM, Puddey IB, Yeap BB. Differential modulation of cell cycle, apoptosis and PPARgamma2 gene expression by PPARgamma agonists ciglitazone and 9-hydroxyoctadecadienoic acid in monocytic cells. Prostaglandins Leukot Essent Fatty Acids 2006; 74:283-93. [PMID: 16647253 DOI: 10.1016/j.plefa.2006.03.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2005] [Revised: 02/15/2006] [Accepted: 03/12/2006] [Indexed: 12/22/2022]
Abstract
We sought to compare the effects of the thiazolidinedione ciglitazone with the endogenous fatty acid PPARgamma agonists 9- and 13-hydroxyoctadecadienoic acid (9- and 13-HODE), in U937 monocytic cells. Ciglitazone and 9-HODE inhibited cell proliferation and all three agonists increased cellular content of C18:0 fatty acids. Ciglitazone and 13-HODE resulted in an increased percentage of cells in S phase and ciglitazone reduced the percentage of cells in G2/M phase of cell cycle, whilst 9-HODE increased the percentage of cells in G0/1 and reduced the fraction in S and G2/M phases. 9-HODE selectively induced apoptosis in U937 cells, and increased PPARgamma2 gene expression. Induction of apoptosis by 9-HODE was not abrogated by the presence of the PPARgamma antagonist GW9662. Synthetic (TZD) and endogenous fatty acid ligands for PPARgamma, ciglitazone and 9- and 13-HODE, possess differential, ligand specific actions in monocytic cells to regulate cell cycle progression, apoptosis and PPARgamma2 gene expression.
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Burkhardt MS, Foster JK, Clarnette RM, Chubb SAP, Bruce DG, Drummond PD, Martins RN, Yeap BB. Interaction between testosterone and apolipoprotein E epsilon4 status on cognition in healthy older men. J Clin Endocrinol Metab 2006; 91:1168-72. [PMID: 16368754 DOI: 10.1210/jc.2005-1072] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Reduced testosterone levels have been implicated as a potential causative factor in cognitive decline with older age. Men who possess the apolipoprotein E (APOE) epsilon4 allele have an increased risk of developing Alzheimer's disease; however, no studies have examined whether the influence of testosterone on cognition in healthy older men may be modulated by this genetic predisposition. OBJECTIVE The objective of the study was to investigate the association between serum testosterone concentrations and cognitive performance in healthy older men, taking into account APOE epsilon4 status. DESIGN This was a cross-sectional study conducted from 2003 to 2004. SETTING The study population consisted of community-dwelling males residing in Perth, Western Australia. PARTICIPANTS Healthy men over 55 yr, free of cognitive impairment and dementia (n = 45), were included in the study. MAIN OUTCOME MEASURES Participants had fasting early morning blood samples for testosterone and SHBG and were assessed for mood as well as indices of general cognition, verbal and visual memory, executive functioning, working memory, and attention. RESULTS There was a significant interaction between calculated free testosterone (FT) and APOE epsilon4 on general cognition (P = 0.01) and executive functioning, working memory, and attention (P < 0.01). Higher levels of FT were associated with better general cognition in non-epsilon4 carriers (P = 0.01). By contrast, in epsilon4 carriers higher FT levels were associated with lower scores on tests of executive functioning, working memory, and attention (P = 0.02). In men at increased risk for Alzheimer's disease, higher testosterone levels were not associated with better cognitive function. CONCLUSIONS Cross-sectional and prospective studies of testosterone and cognition in older men should take into account APOE epsilon4 status.
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Knight B, Yeap BB, Yeoh GC, Olynyk JK. Inhibition of adult liver progenitor (oval) cell growth and viability by an agonist of the peroxisome proliferator activated receptor (PPAR) family member gamma, but not alpha or delta. Carcinogenesis 2005; 26:1782-92. [PMID: 15917308 DOI: 10.1093/carcin/bgi138] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Multifaceted evidence links the development of liver tumours to the activation and proliferation of adult liver progenitor (oval) cells during the early stages of chronic liver injury. The aim of this study was to examine the role of the peroxisome proliferator activated receptors (PPARs): PPARalpha, delta and gamma, in mediating the behaviour of liver progenitor cells during pre-neoplastic disease and to investigate their potential as therapeutic targets for the treatment of chronic liver injury. We observed increased liver expression of PPARalpha and gamma in concert with expanding oval cell numbers during the first 21 days following commencement of the choline deficient, ethionine supplemented (CDE) dietary model of carcinogenic liver injury in mice. Both primary and immortalized liver progenitor cells were found to express PPARalpha, delta and gamma, but not gamma2, the alternate splice form of PPARgamma. WY14643 (PPARalpha agonist), GW501516 (PPARdelta agonist) and ciglitazone (PPARgamma agonist) were tested for their ability to modulate the behaviour of p53-immortalized liver (PIL) progenitor cell lines in vitro. Both PPARdelta and gamma agonists induced dose-dependent growth inhibition and apoptosis of PIL cells. In contrast, the PPARalpha agonist had no effect on PIL cell growth. None of the drugs affected the maturation of PIL cells along either the hepatocytic or biliary lineages, as judged by their patterns of hepatic gene expression prior to and following treatment. Administration of the PPARgamma agonist ciglitazone to mice fed with the CDE diet for 14 days resulted in a significantly diminished oval cell response and decreased fibrosis compared with those receiving placebo. In contrast, GW501516 did not affect oval cell numbers or liver fibrosis, but inhibited CDE-induced hepatic steatosis. In summary, PPARgamma agonists reduce oval cell proliferation and fibrosis during chronic liver injury and may be useful in the prevention of hepatocellular carcinoma.
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Abstract
Androgens (testosterone), acting via the androgen receptor (AR) a nuclear transcription factor, regulate male sexual development and body composition. In addition, AR expression plays an important role in the proliferation of human prostate cancer and confers a better prognosis in breast cancer. AR mRNA stability is central to the regulation of AR expression in prostate and breast cancer cells, and recent studies have demonstrated binding by members of the ELAV/Hu and poly(C) RNA-binding protein families to a highly conserved UC-rich element in the 3'-untranslated region of AR mRNA, with functional impact on AR protein expression. Remarkably, a CAG trinucleotide repeat in exon 1 of the AR, the length of which has been linked to prostate cancer survival, is also a target for multiple RNA-binding proteins from a variety of human and murine tissues. In this review, we will detail the current knowledge of the mechanisms involved in regulating AR mRNA stability, the nature, potential role and structural biology of several novel AR mRNA-protein interactions, and the implications for novel therapeutics in human prostate cancer.
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Gillett MJ, Martins RN, Clarnette RM, Chubb SAP, Bruce DG, Yeap BB. Relationship between testosterone, sex hormone binding globulin and plasma amyloid beta peptide 40 in older men with subjective memory loss or dementia. ACTA ACUST UNITED AC 2003; 5:267-9. [PMID: 14624021 DOI: 10.3233/jad-2003-5401] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In a group of 28 older men with either subjective memory loss or dementia, serum total testosterone and sex hormone binding globulin (SHBG) correlated inversely with plasma levels of amyloid beta peptide 40 (Abeta40, r=-0.5, P=0.01 and r=-0.4, P=0.04, respectively). Calculated free testosterone was also inversely correlated (r=-0.4, P=0.03), and all three relationships remained statistically significant after allowing for age. A similar but non-significant trend was seen with dehydroepiandrosterone sulphate (DHEAS), and neither luteinising hormone (LH) nor estradiol correlated with Abeta40. These data demonstrate that lower androgen levels are associated with increased plasma Abeta40 in older men with memory loss or dementia, suggesting that subclinical androgen deficiency enhances the expression of Alzheimer's disease-related peptides in vivo. An inverse correlation exists between SHBG and Abeta40, warranting further investigation.
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Yeap BB, Voon DC, Vivian JP, McCulloch RK, Thomson AM, Giles KM, Czyzyk-Krzeska MF, Furneaux H, Wilce MCJ, Wilce JA, Leedman PJ. Novel binding of HuR and poly(C)-binding protein to a conserved UC-rich motif within the 3'-untranslated region of the androgen receptor messenger RNA. J Biol Chem 2002; 277:27183-92. [PMID: 12011088 DOI: 10.1074/jbc.m202883200] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The androgen receptor (AR) mediates androgen action and plays a central role in the proliferation of specific cancer cells. We demonstrated recently that AR mRNA stability is a major determinant of AR gene expression in prostate and breast cancer cells and that androgens differentially regulate AR mRNA decay dependent on cell type (Yeap, B. B., Kreuger, R. G., Leedman, P. J. (1999) Endocrinology 140, 3282-3291). Here, we have identified a highly conserved UC-rich region in the 3-untranslated region of AR mRNA that contains a 5'-C(U)(n)C motif and a 3'-CCCUCCC poly(C)-binding protein motif. In transfection studies with LNCaP human prostate cancer cells, the AR UC-rich region reduced expression of a luciferase reporter gene. The AR UC-rich region was a target for cytoplasmic and nuclear RNA-binding proteins from human prostate and breast cancer cells as well as human testicular and breast cancer tissue. One of these proteins is HuR, a ubiquitously expressed member of the Elav/Hu family of RNA-binding proteins involved in the stabilization of several mRNAs. Poly(C)-binding protein-1 and -2 (CP1 and CP2), previously implicated in the control of mRNA turnover and translation, also bound avidly to the UC-rich region. Mutational analysis of the UC-rich region identified specific binding motifs for both HuR and the CPs. HuR and CP1 bound simultaneously to the UC-rich RNA and in a cooperative manner. Immunoprecipitation studies confirmed that each of these proteins associated with AR mRNA in prostate cancer cells. In summary, we have identified and characterized a novel complex of AR mRNA-binding proteins that target the highly conserved UC-rich region. The binding of HuR, CP1, and CP2 to AR mRNA suggests a role for each of these proteins in the post-transcriptional regulation of AR expression in cancer cells.
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Yeap BB. Primary care diabetes. What options are there? AUSTRALIAN FAMILY PHYSICIAN 2001; 30:1122-8. [PMID: 11838389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
BACKGROUND The recognised incidence of type 2 diabetes mellitus is increasing dramatically and the vital importance of good diabetes control in patients with both type 1 and type 2 diabetes is now well established. Weight reduction and oral hypoglycaemic therapy has been accompanied by new drug treatment options in type 2 diabetes, while refinements in insulin delivery are more relevant for patients with type 1 diabetes. OBJECTIVE To review currently available drug therapies and management strategies for type 2 diabetes, and optimal insulin treatment regimens for type 1 diabetes. DISCUSSION Weight reduction and regular exercise remain major lifestyle intervention priorities in type 2 diabetes. Metformin should be used early in overweight patients, and sulphonylureas as additive therapy. Acarbose, orlistat and the thiazolidinediones all have potential roles in the treatment of type 2 diabetes where cardiovascular risk factor reduction is also of vital importance. Insulin analogues and continuous subcutaneous insulin infusion via insulin pumps will help to optimise insulin replacement regimens for patients with type 1 diabetes mellitus.
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Yeap BB, Leedman PJ. Combined pituitary hormone deficiency - lessons from the murine models. Eur J Endocrinol 1999; 141:211-3. [PMID: 10474115 DOI: 10.1530/eje.0.1410211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Yeap BB, Krueger RG, Leedman PJ. Differential posttranscriptional regulation of androgen receptor gene expression by androgen in prostate and breast cancer cells. Endocrinology 1999; 140:3282-91. [PMID: 10385425 DOI: 10.1210/endo.140.7.6769] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Androgens, via the androgen receptor (AR), modulate the growth and proliferation of prostate and breast cancer cells. However, the molecular mechanisms underlying the regulation of AR gene expression by androgen in these cells remain to be fully elucidated. To explore differences in AR gene expression between these hormone-responsive tumor cell types, we studied androgen-responsive LNCaP prostate cancer and AR positive MDA453 breast cancer cells. Dihydrotestosterone (DHT) 10 nM increased LNCaP cell proliferation and the proportion of LNCaP cells in S-phase of the cell cycle but inhibited MDA453 cell proliferation and reduced the proportion of MDA453 cells in S-phase of cell cycle. In both these cell lines, DHT decreased total AR messenger RNA (mRNA) but increased AR protein. In LNCaP cells, DHT down-regulated AR mRNA transcription but stabilized AR mRNA. In contrast, in MDA453 cells, DHT had no effect on AR mRNA transcription but destabilized AR mRNA. In summary, transcriptional down-regulation induced by androgens in LNCaP cells results in down-regulation of steady-state AR mRNA despite an androgen-induced increase in AR mRNA stability. However, in MDA453 cells, posttranscriptional destabilization of AR mRNA appears to be the predominant mechanism resulting in down-regulation of AR mRNA by androgen. These results demonstrate cell-specific and divergent regulation of AR mRNA turnover by androgen and identify a novel pathway of androgen-induced posttranscriptional destabilization and down-regulation of AR mRNA in human breast cancer cells. Furthermore, these data establish an important role for posttranscriptional pathways in the regulation of AR gene expression by androgen in human prostate and breast cancer cells.
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Yeap BB, Russo A, Fraser RJ, Wittert GA, Horowitz M. Hyperglycemia affects cardiovascular autonomic nerve function in normal subjects. Diabetes Care 1996; 19:880-2. [PMID: 8842608 DOI: 10.2337/diacare.19.8.880] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
OBJECTIVE To evaluate the effect of acute hyperglycemia on autonomic nerve function in normal subjects. RESEARCH DESIGN AND METHODS Six healthy volunteers ages 19-32 years underwent paired studies during euglycemia (blood glucose 5.1 +/- 0.04 mmol/l) and hyperglycemia (blood glucose 15.7 +/- 0.48 mmol/l) induced by intravenous infusion of glucose and maintained for 150 min. The order of the two studies was randomized. In each experiment, supine heart rate, heart rate variation with respiration, ratio of the maximum to minimum R-R interval after standing ("30:15" ratio), systolic blood pressure response to standing, and diastolic blood pressure response to sustained handgrip were measured. Data were analyzed using repeated measures analysis of variance. RESULTS The supine heart rate was greater (P = 0.04) and the "30:15" ratio less (P = 0.03) during hyperglycemia than during euglycemia. Hyperglycemia had no significant effect on any of the other cardiovascular reflex tests. CONCLUSIONS These observations indicate that acute hyperglycemia affects autonomic nerve function in healthy humans.
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Burnet RB, Yeap BB, Chatterton BE, Gaffney RD. Chronic fatigue syndrome: is total body potassium important? Med J Aust 1996; 164:384. [PMID: 8606675 DOI: 10.5694/j.1326-5377.1996.tb122076.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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