Association of the SHBG gene promoter polymorphism with early markers of atherosclerosis in apparently healthy women

Impaired protective role of HLA-B*57:01/58:01 in HIV-1 CRF01_AE infection: a cohort study in Vietnam

OBJECTIVES

Human Leukocyte Antigen HLA-B*57:01 and B*58:01 are considered anti-HIV-1 protective alleles. HLA-B*57:01/58:01-restricted HIV-1 Gag TW10 (TSTLQEQIGW, Gag residues 240-249) epitope-specific CD8⁺ T cell responses that frequently select for a Gag escape mutation, T242N, with viral fitness cost are crucial for HIV-1 control. Although this finding has been observed in cohorts where HIV-1 subtype B or C predominates, the protective impact of HLA-B*57:01/58:01 has not been reported in Southeast Asian countries where HIV-1 CRF01_AE is the major circulating strain. Here, the effect of HLA-B*57:01/58:01 on CRF01_AE infection was investigated.

METHODS

The correlation of HLA-B*57:01/58:01 with viral load and CD4 counts were analyzed in the CRF01_AE-infected Vietnamese cohort (N = 280). The impact of the T242N mutation on CRF01_AE replication capacity was assessed.

RESULTS

HLA-B*57:01/58:01-positive individuals mostly had HIV-1 with T242N (62/63) but showed neither a significant reduction in viral load nor increased CD4 counts relative to B*57:01/58:01-negative participants. In vitro and in vivo analyses revealed a significant reduction in viral fitness of CRF01_AE with T242N. In silico analysis indicated reduced presentation of epitopes in the context of CRF01_AE compared to subtype B or C in 10/16 HLA-B*57:01/58:01-restricted HIV-1 epitopes.

CONCLUSION

The protective impact of HLA-B*57:01/58:01 on CRF01_AE infection is impaired despite strong suppressive pressure by TW10-specific CD8⁺ T cells.

Biomediators in Polycystic Ovary Syndrome and Cardiovascular Risk

Polycystic ovary syndrome (PCOS) is extremely heterogeneous in terms of clinical manifestations. The variability of the syndrome's phenotype is derived from the genetic and molecular heterogeneity, with a great deal of environmental factors that may have long-term health consequences, such as metabolic and cardiovascular (CV) diseases. There is no doubt that women with PCOS suffer from metabolic complications more than their age-matched counterparts in the general population and at an earlier age. Obesity, low steroid hormone-binding globulin (SHBG), hyperandrogenemia, insulin resistance, and compensatory hyperinsulinemia are biomediators and early predictors of metabolic complications in PCOS. Doubts remain about the real risk of CV diseases in PCOS and the molecular mechanisms at the basis of CV complications. Based on that assumption, this review will present the available evidence on the potential implications of some biomediators, in particular, hyperandrogenism, estrogen-progesterone imbalance, insulin resistance, and low SHBG, in the processes leading to CV disease in PCOS, with the final aim to propose a more accurate CV risk assessment.

Research progress on the relationship between sex hormone-binding globulin and male reproductive system diseases

Sex hormone-binding globulin, also known as testosterone-estradiol-binding globulin, is a multifunctional protein synthesised by hepatocytes. Sex hormone-binding globulin specifically binds and transports sex hormones to regulate plasma bioactive sex hormone levels and affects their bioavailability. As male sex hormone expression is dominated by testosterone, the binding of sex hormone-binding globulin with testosterone leads to the reduction in bioavailable testosterone, which cannot fulfil its physiological roles, thereby resulting in male infertility, erectile and gonadal dysfunction, prostate cancer and other male reproductive system diseases. Sex hormone-binding globulin may be involved in the pathogenesis of male reproductive system diseases, seriously affecting the quality of life of men. In this article, we review the association between sex hormone-binding globulin and male reproductive system diseases.

Association of rs6259 polymorphism with SHBG levels and Poly Cystic Ovary Syndrome in Indian population: a case control study

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy of reproductive-aged women. PCOS reflects a number of possible etiologies but its pathophysiology is still unclear. The principal abnormality of the syndrome is hyperandrogenism (70-80%). The access of androgens to target tissues is regulated by sex hormone-binding globulin (SHBG), a transport protein secreted by liver i.e. specific for androgens. Present study was done to find the association of rs6259 polymorphism with SHBG levels and Poly Cystic Ovary Syndrome in Indian population. Present study was a case control study. 400 subjects were enrolled for the study and serum SHBG levels and D327N polymorphism were measured. The D327N polymorphism (wild-type and variant allele) was detected using PCR-RFLP method (restriction enzyme Bbs-I). PCOS group was found to have significantly lower SHBG levels than healthy controls. There was no significant difference in genotype distribution between PCOS and controls (χ² = 1.0335, p = 0.59). Significant difference in SHBG levels of PCOS and control group highlights the potential of SHBG as a biomarker for PCOS. However, no significant difference in genotype distribution between PCOS and controls provided an insight that rs6259 polymorphism is not associated with the risk of PCOS and SHBG levels.

Serum androgen concentrations and subclinical measures of cardiovascular disease in men and women

OBJECTIVES

Most of the observed associations of androgens and sex hormone-binding globulin (SHBG) with subclinical cardiovascular disease (CVD) stem from selected study samples with immunoassay-based hormone measurements. Thus, we used a large population-based sample with total testosterone (TT) and androstenedione (ASD) concentrations measured by liquid chromatography-tandem mass spectrometry.

DESIGN

Data of 2140 individuals (mean age: 60,8 years) from the cohort Study of Health in Pomerania were assessed at baseline and 5-year follow-up.

METHODS

Multivariable regression models were implemented to assess cross-sectional and longitudinal associations of TT, free testosterone (fT), ASD, SHBG and dehydroepiandrosterone-sulphate (DHEAS) with measures of subclinical CVD including intima media thickness (IMT), carotid plaques, left ventricular mass (LVM), fractional shortening (FS), relative wall thickness (RWT), and left ventricular geometry.

RESULTS

Cross-sectional analyses yielded an association of TT with IMT in women (β-coefficient per log unit increase: 0.02; 95% CI: 0.007; 0.45) and ASD with FS in both sexes (men: β-coefficient: -2.94; 95% CI: -4.75; -1.12; women: β-coefficient: 1.64; 95% CI: 0.55; 2.73). In longitudinal analyses, DHEAS was positively associated with FS change (β-coefficient: 2.34; 95% CI: -0.59; 4.08). In women, SHBG was positively associated with incident plaques (Q1 vs. Q3 (Ref.): β-coefficient: 1.35; 95% CI: 1.04; 1.74). In both sexes, longitudinal analyses showed no consistent association of TT with subclinical CVD.

CONCLUSIONS

Despite several sex-specific associations of androgens and SHBG with subclinical CVD, the present representative study for the age group ≥45 years among men and women from the general population detected no consistent associations in longitudinal analyses.

Association between serum levels and pentanucleotide polymorphism in the sex hormone binding globulin gene and cardiovascular risk factors in females with polycystic ovary syndrome

The objective of the present study was to evaluate the influence of TAAAA repeat allele length on the levels of serum sex hormone binding globulin (SHBG) and cardiovascular risk factors in patients with polycystic ovary syndrome (PCOS). The study included 91 females with PCOS and 99 healthy controls. Phenotypic hyperandrogenism, body mass index and waist‑to‑hip ratio (WHR) were recorded. Hormonal profiles, fasting insulin and glucose levels, lipid profiles and C‑reactive protein (CRP) levels were measured. Genotyping of TAAAA repeat polymorphisms in the SHBG gene was performed. No significant difference was found in the frequency and distribution of TAAAA repeat alleles between PCOS patients and controls (P=0.739). In PCOS patients, SHBG levels were inversely correlated with serum C‑reactive protein (CRP) levels (R=-0.489, P<0.001). PCOS patients with long TAAAA repeat alleles had significantly lower serum SHBG and free testosterone levels, yet higher CRP levels than patients with short allele repeats. A multiple linear regression model using the number of TAAAA repeats, waist‑to‑hip ratio, a homeostatic model assessment of insulin resistance and age as independent predictors explained 44.8% of the variability in serum SHBG levels. In this model, TAAAA repeat polymorphism was found to be the only reliable predictor of serum SHBG levels (P<0.001). In conclusion, the TAAAA repeat polymorphism was shown to not be a major determinant of the PCOS status, although it influenced serum SHBG levels in females with PCOS. A strong independent association existed between serum SHBG and CRP levels. CRP is an established risk factor of cardiovascular disease and a marker of low‑grade inflammation, typical of atherogenesis. This may be one of the pathways by which low SHBG levels affect cardiovascular risk.

SHBG and endothelial function in older subjects

BACKGROUND

Endothelial dysfunction is predictor of cardiovascular diseases that have different prevalence in men and women before menopause. Sex hormones and sex hormone binding globulin (SHBG), novel risk factors for diabetes and cardiovascular diseases even in older individuals, might explain this difference. However, the relationship between these hormones and endothelial function has never been addressed in the elderly.

METHODS AND RESULTS

430 men and,424 women 70 years older of Prospective Study of the Vasculature in Uppsala Seniors study, with complete data on SHBG, testosterone(T), estradiol(E2), endothelium-independent vasodilation (EIDV), endothelium-dependent vasodilation(EDV), flow-mediated vasodilation (FMD) and the pulse wave analysis (reflection index, RI) were evaluated. Multivariate regression analysis adjusted for confounders was used to assess the relationship between T, E2, SHBG and endothelial function. In men we found a positive relationship between SHBG and EDV (β ± SE 3.60 ± 0.83, p<0.0001), EIDV (2.42 ± 0.58, p<0.0001) but not with FMD. The relationship between SHBG and EDV and EIDV was maintained after adjustment for sex (1.64 ± 0.47, p<0.001 and 1.79 ± 0.35, p<0.0006, respectively). After adjustment for confounders, the relationship between SHBG and EDV and EIDV was still statistically significant (2.63 ± 0.90 and 1.86 ± 0.63, p = 0.004 for both). In women SHBG and EIDV were positively associated (1.58 ± 0.46; p = 0.0007), and this relationship was independent of sex (1.79 ± 0.35; p<0.001). No significant interaction SHBG * SEX was found for EIDV (p = 0.72). In a combined analysis in two sexes, SHBG and EIDV were positively associated (1.13 ± 0.45; p = 0.01). SHBG was not associated with EDV, FMD and RI. No significant relationship was found between T or E2 and EDV, EIDV, FMD or RI in both sexes.

CONCLUSIONS

In older men SHBG, but not T and E2, is positively and independently associated with EDV in resistance arteries. In both sexes, SHBG was positively and independently associated with EIDV.

The relationship between sex hormones, sex hormone binding globulin and peripheral artery disease in older persons

OBJECTIVE

The prevalence of peripheral artery disease (PAD) increases with aging and is higher in persons with metabolic syndrome and diabetes. PAD is associated with adverse outcomes, including frailty and disability. The protective effect of testosterone and sex hormone binding globulin (SHBG) for diabetes in men suggests that the biological activity of sex hormones may affect PAD, especially in older populations.

METHODS

Nine hundred and twenty-one elderly subjects with data on SHBG, testosterone (T), estradiol (E2) were selected from InCHIANTI study. PAD was defined as an Ankle-Brachial Index (ABI) < 0.90. Logistic regression models adjusted for age (Model 1), age, BMI, insulin, interleukin-6, physical activity, smoking, chronic diseases including metabolic syndrome (Model 2), and a final model including also sex hormones (Model 3) were performed to test the relationship between SHBG, sex hormones and PAD.

RESULTS

The mean age (±SD) of the 419 men and 502 women was 75.0 ± 6.8 years. Sixty two participants (41 men, 21 women) had ABI < 0.90. Men with PAD had SHBG levels lower than men without PAD (p = 0.03). SHBG was negatively and independently associated with PAD in men (p = 0.028) but not in women. The relationship was however attenuated after adjusting for sex hormones (p = 0.07). The E2 was not significantly associated with PAD in both men and women. In women, but not in men, T was positively associated with PAD, even after adjusting for multiple confounders, including E2 (p = 0.01).

CONCLUSIONS

Low SHBG and high T levels are significantly and independently associated with the presence of PAD in older men and women, respectively.

Evolving utility of sex hormone-binding globulin measurements in clinical medicine

PURPOSE OF REVIEW

Sex hormone-binding globulin (SHBG) regulates the plasma levels and biological actions of the sex steroids: testosterone and estradiol. Advances in our understanding of how plasma SHBG levels are determined, and how SHBG functions, have provided insight into how SHBG should be used to assess the actions of its sex-steroid ligands, and as a biomarker of metabolic and endocrine abnormalities.

RECENT FINDINGS

Plasma SHBG levels fluctuate throughout life in response to the changes in metabolic and physiologic states, and are altered by natural hormones and synthetic steroids. Interindividual differences in plasma SHBG levels and activity are also influenced by polymorphisms within the structural and regulatory regions of the SHBG gene.

SUMMARY

Measurements of SHBG are widely used to predict plasma free testosterone levels in patients suffering from excess androgen exposures, but have broader utility in assessing the risk for endocrine diseases and clinical sequelae of the metabolic syndrome, namely, type 2 diabetes and cardiovascular disease. It is anticipated that new genetic and functional data regarding SHBG will reveal whether SHBG is simply a biomarker of these diseases or participants in their cause.