A genetic study of sex hormone--binding globulin measured before and after a 20-week endurance exercise training program: the HERITAGE Family Study

The HERITAGE Family Study: A Review of the Effects of Exercise Training on Cardiometabolic Health, with Insights into Molecular Transducers

The aim of the HERITAGE Family Study was to investigate individual differences in response to a standardized endurance exercise program, the role of familial aggregation, and the genetics of response levels of cardiorespiratory fitness and cardiovascular disease and diabetes risk factors. Here we summarize the findings and their potential implications for cardiometabolic health and cardiorespiratory fitness. It begins with overviews of background and planning, recruitment, testing and exercise program protocol, quality control measures, and other relevant organizational issues. A summary of findings is then provided on cardiorespiratory fitness, exercise hemodynamics, insulin and glucose metabolism, lipid and lipoprotein profiles, adiposity and abdominal visceral fat, blood levels of steroids and other hormones, markers of oxidative stress, skeletal muscle morphology and metabolic indicators, and resting metabolic rate. These summaries document the extent of the individual differences in response to a standardized and fully monitored endurance exercise program and document the importance of familial aggregation and heritability level for exercise response traits. Findings from genomic markers, muscle gene expression studies, and proteomic and metabolomics explorations are reviewed, along with lessons learned from a bioinformatics-driven analysis pipeline. The new opportunities being pursued in integrative -omics and physiology have extended considerably the expected life of HERITAGE and are being discussed in relation to the original conceptual model of the study.

Linking Physical Activity to Breast Cancer via Sex Hormones, Part 1: The Effect of Physical Activity on Sex Steroid Hormones

The effect of physical activity on breast cancer risk may be partly mediated by sex steroid hormones. This review synthesized and appraised the evidence for an effect of physical activity on sex steroid hormones. Systematic searches were performed using MEDLINE (Ovid), EMBASE (Ovid), and SPORTDiscus to identify experimental studies and prospective cohort studies that examined physical activity and estrogens, progestins, and/or androgens, as well as sex hormone binding globulin (SHBG) and glucocorticoids in pre- and postmenopausal women. Meta-analyses were performed to generate effect estimates. Risk of bias was assessed, and the GRADE system was used to appraise quality of the evidence. Twenty-eight randomized controlled trials (RCT), 81 nonrandomized interventions, and six observational studies were included. Estrogens, progesterone, and androgens mostly decreased, and SHBG increased, in response to physical activity. Effect sizes were small, and evidence quality was graded moderate or high for each outcome. Reductions in select sex steroid hormones following exercise supports the biological plausibility of the first part of the physical activity-sex hormone-breast cancer pathway. The confirmed effect of physical activity on decreasing circulating sex steroid hormones supports its causal role in preventing breast cancer.See related reviews by Lynch et al., p. 11 and Drummond et al., p. 28.

The effects of three types of exercise training on steroid hormones in physically inactive middle-aged adults: a randomized controlled trial

PURPOSE

Physical inactivity and ageing are associated with imbalances in anabolic/catabolic steroid hormones, jeopardizing health. We investigated the effects of three types of training on plasma steroid hormone levels in physically inactive, middle-aged adults.

METHODS

A 12-week randomized controlled trial was performed with a parallel-group design. A total of 67 (36 women) middle-aged adults (45-65 years old) were randomly assigned to (1) no exercise (control), (2) concurrent training based on the international physical activity recommendations (PAR), (3) high-intensity interval training (HIIT), or (4) HIIT plus whole-body electromyostimulation (HIIT + EMS). The training volume in the PAR group was 150 min/week at 60-65% of the heart rate reserve for aerobic training and ~ 60 min/week at 40-50% of the one-repetition maximum for resistance training. The training volume in the HIIT and HIIT + EMS groups was 40-65 min/week at > 95% of the maximum oxygen uptake in long interval sessions, and > 120% of the maximum oxygen uptake in short interval sessions.

RESULTS

Compared to the control group, dehydroepiandrosterone sulfate increased in the PAR, HIIT, and HIIT + EMS groups (~ 14%, ~ 14%, and ~ 20%, respectively; all P < 0.01). Cortisol decreased in the PAR, HIIT, and HIIT + EMS groups (~ - 17%, ~ - 10%, and ~ - 23%, respectively; all P ≤ 0.05). Testosterone increased in the HIIT and HIIT + EMS groups (~ 28%, and ~ 16%, respectively; all P ≤ 0.01). Free testosterone increased in the HIIT and HIIT + EMS groups (~ 30% and ~ 18% respectively; all P ≤ 0.01). No significant increase in sex hormone-binding globulin was observed (P = 0.869).

CONCLUSION

Our findings suggest that HIIT, with or without whole-body EMS, can significantly enhance steroid hormones status in previously physically inactive middle-aged adults. The PAR program led to slight improvements than the HIIT and HIIT + EMS groups despite the application of a higher training volume.

CLINICAL TRIAL REGISTRY

NCT03334357 (ClinicalTrials.gov). November 7, 2017 retrospectively registered.

Effect of Physical Exercise on Endometriosis Experimentally Induced in Rats

Objective:

Endometriosis is characterized by the growth of endometrial tissue outside the uterine cavity. The prevalence of endometriosis among women experiencing pain, infertility, or both is as high as 35% to 50%. The most common symptoms of endometriosis are dysmenorrhea, dyspareunia, chronic pelvic pain, and infertility. Evidence has suggested that endometriosis symptoms result from a local inflammatory peritoneal reaction caused by ectopic endometrial implants that undergo cyclic bleeding. On the other hand, regular physical exercise seems to have protective effects against diseases that involve inflammatory processes such as type 2 diabetes and colon and breast cancer. On this basis, it is possible that the practice of physical exercise may have beneficial effects on endometriosis. Therefore, the objective of this study was to evaluate the possible anti-inflammatory effect of physical exercise on endometriosis experimentally induced in rats.

Study Design:

Seventy female Wistar rats were divided into 7groups of 10 animals each. Animals performed light exercise (swimming once a week), moderate exercise (swimming 3 times a week), and intense exercise (swimming 5 times a week) before or after endometriosis induction.

Results:

At the end of the experimental protocol, a reduction in the size of endometriotic lesions was observed after physical exercise regardless of its frequency, with a greater reduction in the groups practicing moderate and intense activity; an increase in FAS levels and a decrease in matrix metalloproteinases 9 and proliferating cell nuclear antigen (PCNA)levels was also observed. The immunohistochemistry results did not lead to conclusive results. As expected, oxidative stress was reduced in all groups. These results show that the practice of physical exercise could be beneficial, at least in part, for the treatment of endometriosis.

Risk for and consequences of endometriosis: A critical epidemiologic review

Endometriosis affects approximately 10% of women of reproductive age. Characteristics robustly associated with a greater risk for endometriosis include early age at menarche, short menstrual cycle length, and lean body size, whereas greater parity has been associated with a lower risk. Relationships with other potential characteristics including physical activity, dietary factors, and lactation have been less consistent, partially because of the need for rigorous data collection and a longitudinal study design. Critical methodologic complexities include the need for a clear case definition; valid selection of comparison/control groups; and consideration of diagnostic bias and reverse causation when exploring demographic characteristics, medical history, and lifestyle factors. Reviewers and editors must demand a detailed description of rigorous methods to facilitate comparison and replication to advance our understanding of endometriosis.

Adolescent Physical Activity and Endometriosis Risk

Background

In the one study examining the relationship, adolescent physical activity was not associated with risk for endometriosis. Case-control studies have shown 40–80% reductions in risk for adult activity, while only an 11% reduction in endometriosis risk was observed in a recent prospective analysis.

Methods

Using data collected from the Nurses’ Health Study II, a prospective cohort study of premenopausal US nurses that began in 1989, we have attempted to clarify this relation. Data are updated every 2 yrs with follow-up for these analyses through to 2001. Women reported the average amount of time per week spent in moderate and strenuous recreational activity during three age periods: ages 12–13, ages 14–17, and ages 18–22. A metabolic equivalent (MET) score was assigned to each activity and these were summed to estimate total activity.

Results

During 637,747 person-years of follow-up, 1,481 cases of laparoscopically confirmed endometriosis were reported among women with no past infertility. After adjusting for age, calendar time, birth weight, age at menarche, parity, oral contraceptive use, and body mass index (BMI), we observed a 16% increase in the risk for endometriosis comparing the greatest amount of activity (≥80 MET-h/wk) with the least (<20 MET-h/wk) during ages 12–13 (RR=1.16, 95% CI=0.98–1.37, p-value test for trend=0.02), and no associations for ages 14–17 or ages 18–22. In analyses of the individual activity types within each time period, only strenuous activity during ages 12–13 was associated with endometriosis.

Conclusions

We did not find evidence of a beneficial association between adolescent physical activity and laparoscopically confirmed endometriosis, but in fact found a small increase in risk.

Association of the (TAAAA)n repeat and Asp327Asn polymorphisms in the sex hormone-binding globulin (SHBG) gene with idiopathic male infertility and relation to serum SHBG concentrations

Sex hormone binding globulin (SHBG) is involved in delivering sex hormones to target tissues. We investigated the association between the (TAAAA)n repeat polymorphism, and Asp327Asn polymorphism in the SHBG gene with semen quality and idiopathic male infertility. We studied 168 men with idiopathic infertility [oligoasthenoteratozoospermia (OAT)] and equal number of age-matched normal controls. The serum levels of SHBG, reproductive and thyroid hormones, and Inhibin B were measured. Semen parameters were also assessed. The genotype assays for the SHBG polymorphism were done using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. Baseline SHBG levels tended to be lower in infertile men (21.1±7.2nmol/l) compared to normal fertile men (24.7±7.9nmol/l). SHBG levels tended to be higher among the subjects with the Asn/Asn (25.84±3.6nmol/l) and S/S (24.50±5.4nmol/l) genotypes compared to subjects with the Asp/Asn (24.38±3.2nmol/l) and L/L (18.44±4.2nmol/l) genotypes of the SHBG gene. The genotype frequencies of Asp/Asp were 80.9% in cases and 71.4% in controls (P=0.001). The variant Asp/Asn genotype was associated with a more than 50% reduced risk of infertility (OR: 0.46, 95% CI: 0.25-0.80, P=0.001). Genotype analysis demonstrated six SHBG (TAAAA)n alleles with 6-11 repeats. Long SHBG (TAAAA)n alleles (>8 repeats) were at greater frequency in infertile men than fertile subjects (P=0.001), whereas short SHBG (TAAAA)n alleles (≤8 repeats) tended to be more frequent in fertile men than cases (P=0.001). Men with the 9/X TAAAA repeat genotype displayed a 2.82-fold increased risk of infertility (95% CI: 1.27-4.79, P=0.01). There were strong and significant positive correlations between plasma SHBG and sperm count (r=0.672, P=0.01), sperm motility (r=0.721, P=0.01) and sperm morphology (r=0.574, P=0.02). We concluded that the SHBG Asp237Asn and (TAAAA)n polymorphisms may influence SHBG levels and as a result, male infertility. Multicenter large scale studies are warranted to better elucidate the role of SHBG gene polymorphism in male infertility.

Adult physical activity and endometriosis risk

BACKGROUND

Regular exercise has been associated with a 40%-80% reduction in risk for endometriosis in several case-control studies. However, women experiencing symptoms prior to their diagnosis may be less likely to exercise than healthy controls, thus biasing the observed association.

METHODS

Using data collected from the Nurses' Health Study II, a prospective cohort study of premenopausal US nurses that began in 1989, we have attempted to clarify this relation. Data are updated every 2 years with follow-up for these analyses through 2001. In 1989, 1991, and 1997 women reported average amount of time per week engaging in various physical activities. A metabolic equivalent (MET) score was assigned to each activity, and these were summed to estimate total activity.

RESULTS

A total of 102,197 premenopausal women contributed 996,422 person-years of follow-up with 2703 cases of laparoscopically confirmed endometriosis. After adjusting for BMI at age 18, current BMI, smoking, parity, infertility status, oral contraceptive use, age at menarche, and menstrual cycle length and pattern in college, we observed only a slight reduction in the incidence of endometriosis, comparing the highest level of activity (>or=42 MET hours/week) to the lowest (<3 MET hours/week) (rate ratio = 0.89 [95% confidence interval = 0.77-1.03]). The association was limited to participants with no past or concurrent infertility (P = 0.002, test for heterogeneity). No associations were seen with inactivity.

CONCLUSIONS

In this first prospective assessment, we did not find evidence of the strong inverse association previously reported, although we cannot rule out a modest inverse association.

Sex hormone-binding globulin and risk of type 2 diabetes in women and men

BACKGROUND

Circulating sex hormone-binding globulin levels are inversely associated with insulin resistance, but whether these levels can predict the risk of developing type 2 diabetes is uncertain.

METHODS

We performed a nested case-control study of postmenopausal women in the Women's Health Study who were not using hormone therapy (359 with newly diagnosed type 2 diabetes and 359 controls). Plasma levels of sex hormone-binding globulin were measured; two polymorphisms of the gene encoding sex hormone-binding globulin, SHBG, that were robustly associated with the protein levels were genotyped and applied in mendelian randomization analyses. We then conducted a replication study in an independent cohort of men from the Physicians' Health Study II (170 with newly diagnosed type 2 diabetes and 170 controls).

RESULTS

Among women, higher plasma levels of sex hormone-binding globulin were prospectively associated with a lower risk of type 2 diabetes: multivariable odds ratios were 1.00 for the first (lowest) quartile of plasma levels, 0.16 (95% confidence interval [CI], 0.08 to 0.33) for the second quartile, 0.04 (95% CI, 0.01 to 0.12) for the third quartile, and 0.09 (95% CI, 0.03 to 0.21) for the fourth (highest) quartile (P<0.001 for trend). These prospective associations were replicated among men (odds ratio for the highest quartile of plasma levels vs. the lowest quartile, 0.10; 95% CI, 0.03 to 0.36; P<0.001 for trend). As compared with homozygotes of the respective wild-type allele, carriers of a variant allele of the SHBG single-nucleotide polymorphism (SNP) rs6259 had 10% higher sex hormone-binding globulin levels (P=0.005), and carriers of an rs6257 variant had 10% lower plasma levels (P=0.004); variants of both SNPs were also associated with a risk of type 2 diabetes in directions corresponding to their associated sex hormone-binding globulin levels. In mendelian randomization analyses, the predicted odds ratio of type 2 diabetes per standard-deviation increase in the plasma level of sex hormone-binding globulin was 0.28 (95% CI, 0.13 to 0.58) among women and 0.29 (95% CI, 0.15 to 0.58) among men, a finding that suggests that sex hormone-binding globulin may have a causal role in the risk of type 2 diabetes.

CONCLUSIONS

Low circulating levels of sex hormone-binding globulin are a strong predictor of the risk of type 2 diabetes in women and men. The clinical usefulness of both SHBG genotypes and plasma levels in stratification and intervention for the risk of type 2 diabetes warrants further examination.

Heritability of blood concentrations of sex-steroids in relation to body composition in young adult male siblings

OBJECTIVE

Sex steroid concentrations in men are related to body composition and both are determined by genetic and environmental factors. This study investigates heritability estimates of sex steroid serum concentrations and body composition as well as the genetic and environmental components of their interrelation.

PATIENTS

Six hundred and seventy-four men (25-45 years) were included in this study with 274 independent pairs of brothers.

MEASUREMENTS

Body composition and regional fat mass estimates were determined using dual-energy X-ray absorptiometry. Serum testosterone (T), SHBG, oestradiol (E(2)) and LH levels were determined by immunoassay; free T and E(2) levels were calculated.

RESULTS

Both sex steroid hormone concentrations and indices of body composition exhibited significant heritability estimates. Among sex steroid hormones, T had the highest heritability (h(2) = 0.65), followed by free T (h(2) = 0.54). A heritability of 0.73 was observed for SHBG; a heritability estimate of 0.83 was obtained for body weight. Significant genetic correlations were found between whole body fat mass and serum T (rho(G) = -0.46), free T (rho(G) = -0.27) and SHBG (rho(G) = -0.48) concentrations. No genetic relationship was observed between total (F) E(2) or LH concentrations, respectively, and body composition.

CONCLUSION

Both sex steroid serum levels and body composition are under strong genetic control. Their interrelation is in part underlied by a genetic correlation, indicative of the action of shared genes.

Changes over 14 years in androgenicity and body mass index in a biracial cohort of reproductive-age women

BACKGROUND

Body mass index (BMI) is directly related to testosterone (total T and free T) and inversely to SHBG cross-sectionally, but little is known about how changes in body fat and androgen markers affect each other over time.

METHODS

Participants included 969 White and Black women from the Coronary Artery Risk Development in Young Adults (CARDIA) cohort, who were ages 18-30 at entry into the study and were pre- or perimenopausal 16 yr later at the time of the CARDIA Women's Study (CWS). Total T and SHBG were assayed from specimens drawn at the CWS examination and stored serum from the yr 2 and 10 CARDIA exams. Free T was calculated based on total T and SHBG. BMI and waist circumference were measured at yr 2, 10, and 16.

RESULTS

Despite clinically significant increases in BMI and waist circumference, total T and free T tended to decline, whereas SHBG remained relatively constant. BMI and waist circumference were directly correlated with free T and inversely correlated with SHBG in cross-sectional analyses. In longitudinal, multivariable analyses, an annualized increase in BMI was inversely related to a concurrent annualized decrease in SHBG (beta = -0.79 ng/dl, and se = 0.22 in Blacks; beta = -1.07 ng/dl; and se = 0.31 in Whites). However, early increases in BMI were not related to later decreases in SHBG.

CONCLUSION

Increases in adiposity are closely tied to decreases in SHBG, but changes in BMI and SHBG may occur concurrently rather than sequentially.

What makes a champion?

Variation in human athletic performance is determined by a complex interaction of socio-cultural, psychological, and proximate physiological factors. Human physiological trait variance has both an environmental and genetic basis, although the classic gene-environment dichotomy is clearly too simplistic to understand the full range of variation for most proximate determinants of athletic performance, e.g., body composition. In other words, gene and environment interact, not just over the short term, but also over the lifetime of an individual with permanent effects on the adult phenotype. To further complicate matters, gene and environment may also be correlated. That is, genetically gifted individuals may be identified as children and begin training pulmonary, cardiovascular, and muscle systems at an early critical age. This review covers evidence in support of a genetic basis to human athletic performance, with some emphasis on the recent explosion of candidate gene studies. In addition, the review covers environmental influences on athletic performance with an emphasis on irreversible environmental effects, i.e., developmental effects that may accrue during critical periods of development either before conception (epigenetic effects), during fetal life (fetal programming), or during childhood and adolescence. Throughout, we emphasize the importance of gene-environment interaction (G x E) as a means of understanding variation in human physiological performance and we promote studies that integrate genomics with developmental biology.

Heritability of plasma sex hormones and hormone binding globulin in adult male twins

Plasma sex hormone concentrations have been used as biomarkers in epidemiological studies of many conditions including cancer, obesity, bone density, and coronary heart disease. The objective of this analysis was to estimate genetic and nongenetic influences on endogenous sex hormones (testosterone, estradiol, estrone, and SHBG) in a large sample of 532 adult white male twins (134 monozygotic and 132 dizygotic twin pairs) from the National Heart, Lung, and Blood Institute Twin Study. Participants were aged 59-70 yr at the time of plasma collection, and hormone concentrations were determined with RIA. Genetic models were fitted by the method of maximum likelihood. Testosterone and SHBG concentrations have substantial genetic variation, with additive genetic factors accounting for 57 and 68% of the total phenotypic variation, respectively. In contrast, variation in estrone (37% shared environmental and 63% individual specific environmental effects) and estradiol concentrations (25% genetic effect, 44% shared environmental effects, and 31% individual specific environmental effects) were largely influenced by nongenetic factors. Assessment of the relative contribution of genetic and nongenetic influences on hormone concentrations may help in the search for genes underlying variation and covariation in complex traits affected by plasma sex hormone concentrations.

The Nurses' Health Study: lifestyle and health among women

The Nurses' Health Study has grown from a simple questionnaire-based study initiated in 1976 to a rich resource of information collected over 29 years. Important details about lifestyle have been collected throughout the study and, as the study has progressed, blood samples and DNA from buccal cells have been collected and stored. Tumour samples have also been collected from participants who developed cancer. Through analyses that integrate information from these various sources we are advancing our understanding of the causes of cancer and the potential for prevention.

Aging, Physical Activity, and Hormones in Women—A Review

Women experience significant changes in endocrine function during aging. Decreasing levels of anabolic hormones may be associated with musculoskeletal atrophy and decrease in function that is observed in older women and, as a result, there has been an increase in the use of pharmacological hormone therapies. It is difficult to distinguish, however, between physiological changes that are truly age related and those that are associated with lifestyle factors such as physical activity participation. Some research has shown that circulating levels of anabolic hormones such as DHEA(S) and IGF-I in older women are related to physical activity, muscle function, and aerobic power. Exercise-intervention studies have generally shown that increasing age blunts the acute hormonal response to exercise, although this might be explained by a lower exercise intensity in older women. There have been relatively few studies that examine hormonal adaptations to exercise training. Physical activity might have an effect on hormone action as a result of changes in protein carriers and receptors, and future research needs to clarify the effect of age and exercise on these other components of the endocrine system. The value and safety of hormone supplements must be examined, especially when used in combination with an exercise program.

Lack of pleiotropic genetic effects between adiposity and sex hormone-binding globulin concentrations before and after 20 weeks of exercise training: the HERITAGE family study

The relationship between sex hormone-binding globulin (SHBG) concentrations and body fat accumulation and distribution is governed by complex dynamic factors, which may involve common genetic and/or environmental factors. The current study investigated the genetic and environmental basis for the correlation between SHBG and body fat. Several measures of adiposity were investigated including body mass index (BMI) and a trunk to extremity skinfold thickness ratio (TER) assessed by anthropometry, body composition measured by hydrostatic weighing (total body fat mass [FM], fat-free mass [FFM], and percent body fat [%BF]), and abdominal fat measured by computerized tomography scanning (abdominal visceral fat [AVF]). The study comprised 501 white subjects from 99 families and 277 black subjects from 117 families participating in the HERITAGE Family Study. Familial correlations between traits and their cosegregation were investigated both at baseline and in response to endurance exercise training. Significant inverse phenotypic correlations were detected in both races between SHBG and adiposity measures at baseline and also in response to training. Significant cross-trait familial resemblance was found between SHBG and both BMI and FFM at baseline that accounted for 11% and 4% of maximal heritability, respectively, in white families. However, a joint segregation analysis of the traits failed to implicate shared genetic effects. Specifically, neither a pleiotropic major locus nor pleiotropic polygenic effects were detected between SHBG and BMI or FFM. A maximal cross-trait heritability of 45% was obtained for SHBG and TER at baseline in black families. However, no firm conclusions as to the etiology of this relationship could be drawn because of the limitations of small sample size. For the training response phenotypes, there was no significant cross-trait correlation between SHBG and any adiposity measures studied here, suggesting that their correlation may have an environmental basis. Therefore, this study fails to support the hypothesis of genetic pleiotropy between SHBG concentrations and body fat phenotypes, and suggests an environmental basis for the correlation, ie, SHBG concentrations are genetically independent of body composition and abdominal adiposity phenotypes.

Population differences in the pattern of familial aggregation for sex hormone-binding globulin and its response to exercise training: the HERITAGE Family Study

Familial influences were investigated for baseline sex hormone-binding globulin (SHBG) and its response (post-training minus baseline) to a 20-week endurance exercise training program. One hundred, eighty-four participants from 85 Black families in the HERITAGE Family Study (HERITAGE) were analyzed using a familial correlation model. Baseline SHBG values and the training response were adjusted for the effects of age, baseline BMI, testosterone, estradiol, and fasting insulin levels (plus baseline SHBG values for the training response) within four sex-by-generation groups prior to genetic analysis. Baseline SHBG levels were influenced by appreciable familial effects (maximum heritability h(2) = 54%) with neither spouse resemblance nor sex and generation differences in the correlations. This estimate is only slightly, but not significantly, smaller than the heritability of 64% reported previously in 428 participants from 99 White families in HERITAGE. In contrast to the modest familial effects for the training response in White participants in HERITAGE (h(2) = 25%), there were no evidence of familial resemblance in Blacks in the current study. Furthermore, there was heterogeneity for both baseline SHBG and the training response between Blacks and Whites in the pattern of familial aggregation. In conclusion, baseline SHBG levels are influenced by significant familial effects in both Blacks and Whites, independent of the effects of age, sex, and baseline values of BMI, testosterone, estradiol, and fasting insulin levels. Whereas modest familial effects were detected for the training response in Whites, the lack of similar effects in Blacks may be due to the smaller sample size.