The C282Y polymorphism of the hereditary hemochromatosis gene is associated with increased sex hormone-binding globulin and normal testosterone levels in men.

BACKGROUND: Hereditary hemochromatosis resulting either from homozygosity for the C282Y polymorphism of the HFE gene, or compound heterozygosity for C282Y and H63D, manifests with liver disease and hypogonadism. However, it is unclear whether men who are heterozygotes for C282Y or H63D exhibit subtle abnormalities of sex hormone status. AIMS: To evaluate whether heterozygosity for either of the HFE gene polymorphisms C282Y or H63D is associated with circulating testosterone and SHBG in men. SUBJECTS AND METHODS: We performed a cross-sectional analysis of 388 community-dwelling men. Men were genotyped for C282Y and H63D. Sera were analysed for testosterone and SHBG, and insulin resistance was estimated using a homeostatic model (HOMA2-IR). RESULTS: Mean age of men in the cohort was 56.9 yr. Men who were heterozygous for the C282Y polymorphism in the HFE gene had higher SHBG levels than men who did not carry this polymorphism (mean ± SE, 38.2 ± 1.64 vs 32.8 ± 0.71 nmol/l, p=0.006). Total and free testosterone levels did not differ in the two groups. In multivariate analysis adjusting for potential confounders including age, waist circumference, testosterone, and HOMA2-IR, C282Y heterozygosity remained associated with SHBG levels (p<0.001). CONCLUSION: The C282Y polymorphism is associated with SHBG levels in men who do not manifest iron overload. Further studies are needed to clarify potential mechanisms and determine the clinical relevance of this finding.

Serum testosterone levels correlate with haemoglobin in middle-aged and older men.

BACKGROUND: Lower testosterone levels are associated with anaemia in older men and women. The relation between testosterone and haemoglobin (Hb) in younger and middle-aged men is less well defined. The aim of the study was to examine the association between testosterone and Hb levels in men spanning middle to older ages. METHODS: A cross-sectional analysis of 492 men aged 30.7-94.5 years from the Busselton Health Survey, Western Australia, was carried out. Haemoglobin (Hb), early-morning serum total testosterone and sex hormone-binding globulin (SHBG) were measured. Free testosterone was calculated using mass action equations. RESULTS: Haemoglobin correlated to total and free testosterone concentrations (r= 0.13, P= 0.003 and r= 0.20, P < 0.001, respectively). Hb and SHBG were inversely correlated (r=-0.14, P= 0.001). Hb increased across lowest to highest quartiles of total testosterone (P= 0.02) and free testosterone (P < 0.001), but not SHBG. After adjusting for age, waist circumference, smoking status, alcohol consumption, renal function and ferritin, total testosterone was associated with Hb (beta= 0.037, P= 0.003) as was free testosterone (beta= 2.32, P < 0.001), whereas SHBG was not associated. CONCLUSION: Testosterone concentration modulates Hb levels in community-dwelling men across a wide age range. Further studies are needed to clarify implications of this association between testosterone and Hb in men.

A case-control study of the androgen receptor gene CAG repeat polymorphism in Australian prostate carcinoma subjects.

BACKGROUND: The development of prostate carcinoma is androgen-dependent. The coding sequence of the androgen receptor (AR) gene contains a CAG repeat polymorphism that has been shown to influence AR activity in vitro. Studies of this polymorphism as a prostate carcinoma risk factor have been conflicting. METHODS: A matched case-control design was used in a clinic-based multicenter study of Australian prostate carcinoma subjects. Cancer subjects were matched by age and locality with controls, all of whom had a serum prostate specific antigen (PSA) level of less than 4 mg/L. Conditional logistic regression was used to determine the relative risk of prostate carcinoma dependent on AR gene CAG number. The association of disease characteristics at diagnosis with the polymorphism also was assessed. RESULTS: Five hundred forty-five cases of prostate carcinoma and 456 matched case-control pairs were recruited. Association studies of disease characteristics at diagnosis showed age at diagnosis to be associated with AR CAG number by univariate (P = 0.004) and multivariate (adjusting for PSA, stage, and grade) linear regression (P = 0.018). No association was observed between the polymorphism and disease stage (TNM-based categories; P = 0.277), histologic grade (P = 0.41), or PSA level at diagnosis (P = 0.48). In the pairwise case-control analysis, the odds ratio of prostate carcinoma for a change of 5 CAG repeats gave an odds ratio of 0.9821 (95% confidence interval, 0.84-1.15). CONCLUSIONS: In this Australian study population, the AR CAG repeat polymorphism was not a risk factor for prostate carcinoma, but a shorter repeat sequence was associated with earlier age at diagnosis.

Effect of the androgen receptor CAG repeat polymorphism on transcriptional activity: specificity in prostate and non-prostate cell lines.

The action of androgens is essential for the development of benign prostatic hyperplasia and carcinoma of the prostate. The androgen receptor is a ligand-dependent nuclear transcription factor. The transcriptional activation domain of the androgen receptor gene contains a polymorphic CAG repeat sequence. A shorter CAG repeat sequence within the normal range has been reported to be associated with increased risk of prostate cancer and symptomatic benign prostatic hyperplasia. Here, we examine the in vitro transcriptional activity of the androgen receptor (AR) with different numbers of CAG repeats within the normal range in a number of different cell lines of prostatic (LNCaP, PC3) and non-prostatic (COS-1, MCF7) origin. We utilize a luciferase reporter driven by the rat probasin promoter (-286/+28) containing two androgen receptor binding sites. Transcriptional activation of the androgen responsive reporter was observed to be greater with the AR containing 15 vs 31 CAG repeats in COS-1 cells (123.2+/-16.6 vs 78.2+/-10.9, P value 0.01) and the well differentiated prostate cancer cell line LNCaP (103.4+/-17.7 vs 81.4+/-7.7, P value 0.045). No difference was observed in the poorly differentiated prostate cancer cell line, PC3 (106.9+/-21.9 vs 109. 6+/-21.4, P>0.5) or the breast cancer cell line MCF7 (120.4+/-39.4 vs 103.1+/-23.1, P value >0.5). Dose-response experiments with varying quantities of ligand (0.01, 0.1, 1 and 10 nM dihydrotestosterone) or AR cDNA did not demonstrate significant differences in transactivation of the androgen responsive reporter in PC3 cells by the different AR constructs. This suggests that the lack of influence of CAG number in this prostatic cell line is not related to dose of ligand or quantity of androgen receptor. Western immunoblot analysis of androgen receptor protein in transiently transfected COS-1 cells did not demonstrate a difference in the expression of the androgen receptor protein with different numbers of CAG repeats following incubation in the presence or absence of androgen. Gel shift assay did not demonstrate increased DNA binding by androgen receptor with a shorter CAG repeat sequence. These experiments using a relatively androgen- and prostate-specific reporter provide evidence for an inverse relationship between androgen receptor transcriptional activity and the number of CAG repeats in the transcriptional activation domain. The effect of CAG repeat number was cell specific suggesting the involvement of accessory factors expressed differentially between different cell lines.

Androgen receptor gene polymorphism and prostate zonal volumes in Australian and Chinese men.

Prostate diseases are age and androgen dependent. The evolution of clinically overt pathology requires decades of exposure to adult male levels of circulating testosterone, but the precise relationship between age and androgen circulation remains poorly understood. A marker of integrated androgen action over prolonged periods would therefore be a valuable tool for clinical and epidemiologic research into the origins of prostate disease. In order to evaluate these 2 factors, we have studied the CAG-repeat length polymorphism of the androgen receptor gene and the size of the total, central, and peripheral zones of the prostate, estimated by planimetric ultrasound in 2 populations with widely different susceptibility to death from invasive prostate cancer. From a larger epidemiologic study of the effects of ethnicity and migration on the origins of prostate disease, a nested-case control study was undertaken with 50 Chinese men living in Yue Yang, China and 50 non-Chinese men living in Sydney, Australia. All men had undergone planimetric transrectal prostate ultrasound together with blood sampling to determine CAG-repeat length by polymerase chain reaction and immunoassay of plasma testosterone, estradiol, dihydrotestosterone (DHT), sex hormone-binding globulin (SHBG), and prostate-specific antigen (PSA). Australian men had larger central (7.9 +/- 0.4 vs 3.3 +/- 0.3 mL) and total (29.8 +/- 1.2 vs 25.5 +/- 1.1 mL) but not peripheral (22.0 +/- 0.9 vs 22.2 +/- 0.8 mL) prostate volumes compared with Chinese men. Even after adjustment for differences in body size (the Australian men were taller and heavier), the central-zone volume remained lower by approximately 50% in Chinese men (P < 0.001), whereas testis and total-prostate volumes were no longer significantly different. The length of CAG repeats was no different between Australian men (22.5 +/- 0.5 repeats) and Chinese men (22.5 +/- 0.5 repeats), and there was no correlation within or between populations in CAG repeats or any measure of prostate volume or hormones. DHT concentration was 20% lower in Chinese men compared with Australian men (1.6 +/- 0.1 vs 2.0 +/- 0.1 nmol/L, P = 0.005), a difference that persisted after age adjustment (P = 0.039) but that was removed by adjustment for differences in total-prostate size (P = 0.12). Blood testosterone, estradiol, SHBG, and PSA concentrations were not different between the 2 populations. Hence, the hypothesis is refuted that the CAG repeat polymorphism in the androgen receptor gene (within the nonpathologic range) and the central-prostate zone volume might be markers of long-term androgen sensitivity. Whether either factor alone may constitute a marker of androgen sensitivity remains to be established by other means, and a long-term marker of integrated androgen action suitable for clinical and epidemiologic research is still lacking.

Microalbuminuria in type 2 diabetes: an independent predictor of cardiovascular mortality.

BACKGROUND: Microalbuminuria has been shown to be associated with cardiovascular mortality in type 2 diabetic subjects. It is unclear to what extent this is due to the increased prevalence of other cardiac risk factors. AIMS: To examine the relationship of urine albumin excretion to cardiovascular mortality and to determine its status as an independent risk factor. METHODS: In a prospective longitudinal study from 1986-1993 we followed 666 type 2 diabetic subjects from a diabetes outpatient service. Cardiovascular risk factors including urine albumin concentration were measured at study entry. Cox proportional hazards regression was used to determine risk factors for mortality. The hazard ratios of microalbuminuria and macroalbuminuria for all cause, cardiovascular and coronary heart disease mortality were determined after accounting for other cardiac risk factors including blood pressure, glycated haemoglobin, total cholesterol, HDL cholesterol, triglycerides, urea, smoking, body mass index, patient age and disease duration. RESULTS: The prevalence of urine albumin of 30-300 mg/L at study entry was 31.7%. A total of 167 deaths occurred (80 from cardiovascular disease). Mortality hazard ratios in subjects with urine albumin of 30-300 mg/L as compared to < 30 mg/L, adjusted for age, sex and other cardiovascular risk factors were 1.77 (95% CI 1.22-2.57, p = 0.002) for all causes, 2.34 (95% CI 1.38-3.99, p = 0.002) for cardiovascular and 1.78 (95% CI 0.97-3.26, p = 0.061) for coronary heart disease (CHD) mortality. Other factors significantly associated with cardiovascular mortality included diastolic blood pressure, HDL cholesterol and glycated haemoglobin. Total cholesterol and log triglyceride were significantly associated with CHD mortality. Disease duration, age at diagnosis, smoking and body mass index were not related to cardiovascular or CHD mortality. CONCLUSIONS: We confirm microalbuminuria as an independent predictor of mortality in type 2 diabetes despite its association with a number of conventional cardiovascular risk factors.