Effect of insulin sensitivity on SHBG levels in premenopausal versus postmenopausal obese women

The association of menopause with cardiometabolic disease risk factors in low- and middle-income countries: a systematic review and meta-analyses

IMPORTANCE

Menopause is an integral part of women's health, and studies in high-income countries have shown an increase in cardiometabolic disease (CMD) risk factors in postmenopausal compared with premenopausal women. However, to date, no study has combined and assessed such studies across low- and middle-income countries. This would better inform early monitoring and intervention strategies for reducing CMD risk factor levels in midlife women in these regions.

OBJECTIVE

This study aimed to evaluate evidence from the literature on differences in CMD risk factors between premenopausal and postmenopausal midlife women living in low- and middle-income countries.

EVIDENCE REVIEW

A systematic review with meta-analysis of original articles of all study designs from the databases PubMed, PubMed Central, Scopus, and ISI Web of Science was conducted from conception until April 24, 2023. Studies that met the inclusion criteria were included in the analysis. Quality assessment of the articles was done using the Newcastle-Ottawa Scale, adapted for each study design. The study protocol was registered with the International Prospective Register of Systematic Reviews and adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis. For the meta-analysis, fixed-effects models were used to pool the odds ratios (OR), as measures of association.

FINDINGS

Our search identified 4,849 relevant articles: 44 for the systematic review and 16 for the meta-analysis, in accordance with our inclusion criteria. Compared with premenopausal women, the postmenopausal stage was associated with metabolic syndrome (OR, 1.18 [95% CI, 1.11-1.27]), high waist-to-hip ratio (OR, 1.22 [95% CI, 1.12-1.32]), hypertension (OR, 1.10 [95% CI, 1.04-1.16]), elevated triglycerides (OR, 1.16 [95% CI, 1.11-1.21]), and elevated plasma glucose (OR, 1.21 [95% CI, 1.15-1.28]).

CONCLUSIONS AND RELEVANCE

This study confirmed that CMD risk factors are present at higher levels in postmenopausal than premenopausal women. This demonstrates an urgent need for public health policies that focus on early monitoring and interventions targeted at reducing CMD risk and related adverse outcomes in midlife women in these nations.

Molecular biomarkers for gestational diabetes mellitus and postpartum diabetes

ABSTRACT

Gestational diabetes mellitus (GDM) is a growing public health problem worldwide that threatens both maternal and fetal health. Identifying individuals at high risk for GDM and diabetes after GDM is particularly useful for early intervention and prevention of disease progression. In the last decades, a number of studies have used metabolomics, genomics, and proteomic approaches to investigate associations between biomolecules and GDM progression. These studies clearly demonstrate that various biomarkers reflect pathological changes in GDM. The established markers have potential use as screening and diagnostic tools in GDM and in postpartum diabetes research. In the present review, we summarize recent studies of metabolites, single-nucleotide polymorphisms, microRNAs, and proteins associated with GDM and its transition to postpartum diabetes, with a focus on their predictive value in screening and diagnosis.

Whey Protein Supplementation Improves the Glycemic Response and May Reduce Non-Alcoholic Fatty Liver Disease Related Biomarkers in Women with Polycystic Ovary Syndrome (PCOS)

Polycystic ovary syndrome (PCOS) increases type 2 diabetes and non-alcoholic fatty liver disease (NAFLD) with insulin resistance. We hypothesized that a 35 g whey preload would improve insulin sensitivity and glucose handling while reducing biomarkers associated with NAFLD. Twenty-nine age-matched women (CON = 15, PCOS = 14) completed oral glycemic tolerance tests following baseline (Day 0) as well as an acute (Day 1) and short-term whey supplementation (Day 7). Whey had an interaction effect on glucose (p = 0.02) and insulin (p = 0.03), with glucose remaining stable and insulin increasing with whey supplementation. Insulin sensitivity (p < 0.01) improved with whey associated with increased glucagon secretion (p < 0.01). Alanine aminotransferase (ALT), and aspartate aminotransferase (AST) remained unchanged, but “day” had an effect on the AST:ALT ratio (p = 0.04), whereas triglycerides and sex hormone binding globulin overall were greater in the PCOS group (p < 0.05). Total cholesterol decreased in PCOS (by 13%) and CON (by 8%) (NS). HepG2 cells treated with plasma from participants before and after whey decreased lipid accumulation in the PCOS group after whey (p < 0.05). Whey provided an insulinogenic and glycemic homeostatic effect in women with PCOS with the potential to combat NAFLD-consequences.

Socioeconomic Deprivation as Measured by the Index of Multiple Deprivation and Its Association with Low Sex Hormone Binding Globulin in Women

Objective:

Sex hormone binding globulin (SHBG) is a marker of insulin resistance. Given established links between BMI and socioeconomic disadvantage, we investigated how SHBG varies by index of multiple deprivation (IMD).

Research Design and Methods:

Using laboratory data from a Midlands UK population of mixed ethnicity, we examined the relation between blood concentrations of SHBG and IMD in 1160 women aged between 17 and 71 years. Women with a serum SHBG >250 nmol/L were excluded.

Results:

Mean age was 28.7 (95% confidence interval (CI) 28.2–29.1) years. 48.2% of women were of Caucasian origin, 15.5% of Southern Asian ethnicity and 2.6% were of African or other origin (33.7% were of unknown origin).

SHBG increased with age (Spearman’s ρ=0.195; p<0.001). A higher proportion of women of South Asian origin versus other ethnic groups had an SHBG <30 nmol/L (OR 1.93 (95% CI 1.37–2.71)).

SHBG level was lower in individuals with greater socioeconomic disadvantage as measured by IMD (Spearman's ρ= -0.09; p=0.004 for SHBG versus IMD).

In multivariate logistic regression, IMD women in the quartiles 2–5 (higher socioeconomic disadvantage) were more likely to have an SHBG <30 nmol/L (compatible with significant insulin resistance) versus quartile 1 (odds ratio (OR) 1.71 (95% confidence interval (CI) 1.17–2.53), adjusted for age (OR=0.97 (95% CI 0.95–0.98)) and ethnicity (for South Asian ethnicity OR=2.00 (95% CI 1.42–2.81) versus the rest).

Conclusion:

Lower SHBG levels in women are associated with a higher level of socioeconomic disadvantage. Given the known association between lower SHBG and higher plasma glucose, our findings suggest a link between socioeconomic disadvantage and future risk of type 2 diabetes.

Cross-sectional study of factors influencing sex hormone-binding globulin concentrations in normally cycling premenopausal women

OBJECTIVE

To assess the relationship between SHBG and 18 other hormonal and metabolic parameters in well characterized, normally cycling premenopausal women.

DESIGN

Cross-sectional study.

SETTING

University general clinical research center.

SUBJECT(S)

A total of 319 young healthy women with ovulatory menstrual cycles.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Midfollicular serum SHBG concentrations.

RESULT(S)

In our final linear regression model, SHBG was negatively associated with bioavailable T and positively associated with adiponectin, associations that were independent from other parameters. SHBG was also positively associated with estrone sulfate, but only when taking into account confounding variables. Unexpectedly, there was no straightforward relationship between SHBG and insulin resistance according to homeostasis-model assessment.

CONCLUSION(S)

Our results highlight the link between androgen action, as reflected by bioavailable T, and circulating SHBG concentrations in all premenopausal women and speak to the importance of the relationship between SHBG and adiponectin, which is at least in part independent from androgen action.

CLINICAL TRIAL REGISTRATION NUMBER

NCT00393172.

Estrogen: a master regulator of bioenergetic systems in the brain and body

Estrogen is a fundamental regulator of the metabolic system of the female brain and body. Within the brain, estrogen regulates glucose transport, aerobic glycolysis, and mitochondrial function to generate ATP. In the body, estrogen protects against adiposity, insulin resistance, and type II diabetes, and regulates energy intake and expenditure. During menopause, decline in circulating estrogen is coincident with decline in brain bioenergetics and shift towards a metabolically compromised phenotype. Compensatory bioenergetic adaptations, or lack thereof, to estrogen loss could determine risk of late-onset Alzheimer's disease. Estrogen coordinates brain and body metabolism, such that peripheral metabolic state can indicate bioenergetic status of the brain. By generating biomarker profiles that encompass peripheral metabolic changes occurring with menopause, individual risk profiles for decreased brain bioenergetics and cognitive decline can be created. Biomarker profiles could identify women at risk while also serving as indicators of efficacy of hormone therapy or other preventative interventions.

Liver fat and SHBG affect insulin resistance in midlife women: the Study of Women's Health Across the Nation (SWAN)

OBJECTIVE

The liver is an insulin-responsive organ that contributes significantly to both whole body insulin sensitivity and availability of sex steroids through the production of sex hormone binding globulin (SHBG). Our objective was to explore whether lower SHBG was associated with ectopic liver fat and mediated its effect on insulin resistance in The Study of Women's Health Across the Nation (SWAN).

DESIGN AND METHODS

A subset of midlife African American and Caucasian women from SWAN (n = 208; 50.9 ± 0.18 yrs; 71% Caucasian) had computed tomography scans to quantify visceral, subcutaneous and liver fat. Blood samples were collected and assayed for hormonal and metabolic markers.

RESULTS

The cohort, while overweight, was generally healthy, and both liver fat and SHBG were unaffected by menopausal stage or race. Both higher liver fat and lower SHBG levels were significantly associated with higher insulin concentrations after adjustment for adiposity (r = -0.25, P < 0.001 and r = -0.18, P = 0.01). SHBG and liver fat had additive effects on insulin concentrations such that women with the lowest SHBG and the highest fat levels had the highest values (interaction P = 0.09). The association between SHBG and insulin was more apparent among women with fattier livers. SHBG and liver fat appear to have independent effects on insulin levels as adjustment for each other did not diminish the strength of either association (P = 0.023 and 0.001 respectively).

CONCLUSION

These results confirmed the strong independent associations between increased liver fat and decreased SHBG with increased metabolic risk in midlife women. Further these data underscore the need for additional research into the role of liver fat in modifying SHBG's influence on insulin levels.

Sex hormone binding globulin and insulin resistance

Sex hormone binding globulin (SHBG) is a glycoprotein composed of two 373-amino-acid subunits. The SHBG gene and a promotor region have been identified. The SHBG receptor has yet to be cloned but is known to act through a G-protein-linked second-messenger system following plasma membrane binding. The principal function of SHBG has traditionally been considered to be that of a transport protein for sex steroids, regulating circulating concentrations of free (unbound) hormones and their transport to target tissues. Recent research suggests that SHBG has functions in addition to the binding and transport of sex steroids. Observational studies have associated a low SHBG concentration with an increased incidence of type 2 diabetes mellitus (DM) independent of sex hormone levels in men and women. Genetic studies using Mendelian randomization analysis linking three single nucleotide polymorphisms of the SHBG gene to risk of developing type 2 DM suggest SHBG may have a role in the pathogenesis of type 2 DM. The correlation between SHBG and insulin resistance that is evident in a number of cross-sectional studies is in keeping with the suggestion that the association between SHBG and incidence of type 2 DM is explained by insulin resistance. Several potential mechanisms may account for this association, including the identification of dietary factors that influence SHBG gene transcription. Further research to characterize the SHBG-receptor and the SHBG second messenger system is required. An interventional study examining the effects on insulin resistance of altering SHBG concentrations may help in determining whether this association is causal.

Sex hormone-binding globulin levels are not causally related to venous thrombosis risk in women not using hormonal contraceptives

BACKGROUND

Oral contraceptive use increases the risk of venous thrombosis as well as sex hormone-binding globulin (SHBG) levels. Furthermore, increased SHBG levels are positively associated with activated protein C (APC) resistance and thrombotic risk in oral contraceptive users.

OBJECTIVES

To determine whether increased SHBG levels are causally related to venous thrombosis in women not using hormonal contraceptives.

METHODS

Premenopausal women were selected from a case-control study on venous thrombosis, the Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis (MEGA) study (23 patients; 258 controls). Women using hormonal contraceptives were excluded. First, the risk of venous thrombosis with SHBG levels above the normal reference range (70 nm) was determined. Second, because multiple regulatory factors affect SHBG levels and residual confounding may remain, we determined six single-nucleotide polymorphisms (SNPs) in the SHBG gene and assessed the risk of venous thrombosis in a different case-control study, the Leiden Thrombophilia Study (LETS) (20 patients; 74 controls), and in the MEGA study. Finally, the association between SHBG levels and the normalized activated partial thromboplastin time-based APC resistance (an intermediate endpoint for venous thrombosis) was determined.

RESULTS

Elevated SHBG levels (> 70.0 nm) were associated with venous thrombosis (odds ratio 1.92; 95% confidence interval [CI] 0.74-5.00). However, this finding can be explained by residual confounding. Two SNPs in the SHBG gene affected SHBG levels, but not venous thrombosis risk. Furthermore, SHBG levels in controls were not associated with APC resistance (SHBG level, > 70.0 vs. ≤ 70.0 nm: mean difference in normalized APC sensitivity ratio, 0.03; 95% CI -0.05 to 0.10). Exclusion of women with FV Leiden did not materially change these results.

CONCLUSIONS

Increased SHBG levels are not causally related to the risk of venous thrombosis.

Relations between endogenous androgens and estrogens in postmenopausal women with suspected ischemic heart disease

CONTEXT

Because androgens are obligatory precursors of estrogens, it is reasonable to assume that their serum concentrations would exhibit positive correlations. If so, then epidemiologic studies that examine the association between androgens and pathological processes should adjust the results for the independent effect of estrogens.

OBJECTIVE

The objective of the study was to examine the interrelationships among testosterone (T), androstenedione, estradiol (E2), estrone, and SHBG in postmenopausal women.

DESIGN

This was a cross-sectional study of women participating in the National Heart, Blood, and Lung Institute-sponsored Women's Ischemia Syndrome Evaluation study.

SETTING

The study was conducted at four academic medical centers.

PATIENTS

A total of 284 postmenopausal women with chest pain symptoms or suspected myocardial ischemia.

MAIN OUTCOME MEASURES

Post hoc analysis of the relationships among sex steroid hormones with insulin resistance, body mass index (BMI), and presence or absence of coronary artery disease as determined by coronary angiography.

RESULTS

BMI was significantly associated with insulin resistance, total E2, free E2, bioavailable E2, and free T. Highly significant correlations were found for total T, free T, and androstenedione with total E2, free E2, bioavailable E2, and estrone and persisted after adjustment for BMI and insulin resistance. A significant relationship was present between total and free T and the presence of coronary artery disease after adjustment for the effect of E2.

CONCLUSIONS

Serum levels of androgens and estrogens track closely in postmenopausal women referred for coronary angiography for suspected myocardial ischemia. Epidemiological studies that relate sex steroid hormones to physiological or pathological processes need to control for the independent effect of both estrogens and androgens.