Serum concentrations of high-molecular weight adiponectin and their association with sex steroids in premenopausal women

The mysterious association between adiponectin and endometriosis

Adiponectin is a pleiotropic cytokine predominantly derived from adipose tissue. In addition to its role in regulating energy metabolism, adiponectin may also be related to estrogen-dependent diseases, and many studies have confirmed its involvement in mediating diverse biological processes, including apoptosis, autophagy, inflammation, angiogenesis, and fibrosis, all of which are related to the pathogenesis of endometriosis. Although many researchers have reported low levels of adiponectin in patients with endometriosis and suggested that it may serve as a protective factor against the development of the disease. Therefore, the purpose of this review was to provide an up-to-date summary of the roles of adiponectin and its downstream cytokines and signaling pathways in the aforementioned biological processes. Further systematic studies on the molecular and cellular mechanisms of action of adiponectin may provide novel insights into the pathophysiology of endometriosis as well as potential therapeutic targets.

Estrogen Impairs Adipose Tissue Expansion and Cardiometabolic Profile in Obese-Diabetic Female Rats

It has been reported that 17β-estradiol (E2) can exert beneficial effects against the development of obesity, providing women with a healthier metabolic profile and conferring cardiovascular protection. However, a growing body of evidence questions this role in the context of obesity and diabetes. We focus on the adipose tissue–heart axis to address the question of whether E2 can have metabolically detrimental effects in an obese-diabetic rat model. Female Zucker Diabetic Fatty rats were used: LEAN, fa/+; SHAM, sham-operated fa/fa; OVA, ovariectomized fa/fa, and OVA+E2, ovariectomized and E2 treated fa/fa. The secretory expression profile, tissue expansion parameters and composition of visceral adipose tissue, as well as systemic and cardiac parameters related to insulin resistance, fibrosis, and inflammation were analyzed. Ovariectomy induced an attenuation of both diabetic condition and metabolic dysfunction of adipose tissue and cardiac muscle in fa/fa rats, suggesting that E2, in the context of diabetes and obesity, loses its cardioprotective role and could even contribute to greater metabolic alterations. Adipose tissue from OVA rats showed a healthier hyperplastic expansion pattern, which could help maintain tissue function, increase adiponectin expression, and decrease pro-inflammatory adipokines. These findings should be taken into account when considering hormone replacement therapy for obese-diabetic women.

Insulin resistance and high molecular weight adiponectin in obese and non-obese patients with Polycystic Ovarian Syndrome (PCOS)

BACKGROUND

Polycystic ovarian syndrome (PCOS) is the most common endocrinopathy among young women. Insulin resistance is a key feature in the pathogenesis of PCOS; also high molecular weight adiponectin is a marker of insulin resistance. The aim of this study was to evaluate the insulin resistance, metabolic and androgenic profiles and high molecular weight adiponectin in obese and non-obese PCOS patients.

METHODS

In this cross-sectional study in outpatient endocrinology clinics of Shiraz University of Medical Sciences, 80 women aged 17-43 years old with PCOS were enrolled. Biochemical and hormonal assay was done on fasting blood sample on the third day of follicular phase.

RESULTS

The individuals had a mean age of 28.39 ± 6.56 years, mean weight of 65.41 ± 12.59 Kg, mean BMI of 25.5 ± 4.9, and mean waist circumference of 88.0 ± 13.1 cm. Of all individuals 20% had frank insulin resistance with HOMA-IR > 3.8. Although the obese PCOS patients had lower levels of high molecular weight adiponectin (P = 0.03) than the normal weight PCOS individuals, the level of insulin and insulin resistance was not different in them (P = 0.13, 0.13). Patients with classic PCOS phenotype significantly had higher levels of insulin resistance and free androgen index (P < 0.001, 0.001). We found a significant correlation between the insulin level and free androgen index (correlation coefficient: 0.266 and P = 0.018) after adjusting for BMI.

CONCLUSION

This cross-sectional study showed a high incidence of insulin resistance in PCOS patients independent of obesity, and determined BMI related lower level of high molecular weight adiponectin in obese PCOS individuals. More detailed studies are warranted for evaluation of insulin resistance and its pathophysiologic role in PCOS.

Normal menstrual cycle steroid hormones variation does not affect the blood levels of total adiponectin and its multimer forms

Objective

Plasma total adiponectin reveals a sexual dimorphism indicating that gonadal steroids may be involved in its secretion and/or metabolism. However, results from previous reports are conflicting and data regarding the influence of ovarian steroids on adiponectin's multimer forms are scarce. The objective of the study was to assess if total adiponectin and its isoforms are affected by the changes of estradiol and progesterone during the normal menstrual cycle and the association of total adiponectin and its isoforms with the gonadal steroid levels.

Materials/methods

Quantitative determination of plasma adiponectin and its multimers was conducted in the three phases of an ovulatory cycle in 13 premenopausal women, in the follicular phase of 10 more premenopausal women, in 20 postmenopausal women and in 21 men. Moreover, serum levels of FSH, LH, prolactin, estradiol, progesterone, and testosterone, sex hormone binding globulin, glucose, and insulin were measured.

Results

The circulating levels of total adiponectin and its multimers were not affected by the normal variation of estradiol and progesterone across the ovulatory menstrual cycle. In the whole number of participants, the total adiponectin and high molecular weight adiponectin levels were significantly different between genders and associated positively with age and sex hormone binding globulin levels, and negatively with testosterone and progesterone levels and the waist/hip ratio. In the multiple logistic regression analysis, after adjustment for age, gender, and sex hormone binding globulin and progesterone levels, significant predictors of total adiponectin levels were the waist/hip ratio and testosterone levels, and of high molecular weight adiponectin the testosterone levels.

Conclusions

Normal menstrual cycle ovarian steroids are not involved directly in the regulation of secretion and/or metabolism of total adiponectin and its multimers. Testosterone seems to be responsible for the adiponectin's sexual dimorphism.

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Adiponectin and its multimers were assessed in the three-step hormonal model of normal menstrual cycle.

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Estrogens may not be involved directly in the regulation of adiponectin's secretion and/or metabolism.

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Androgens appear to be responsible for the sexual dimorphism of adiponectin.

Circulating apelin level in relation to nutritional status in polycystic ovary syndrome and its association with metabolic and hormonal disturbances

OBJECTIVE

The aim of the study was to analyse relationships between plasma apelin-36 and apelin-12 levels, nutritional status, insulin resistance and hormonal disturbances, as well as plasma adiponectin, leptin and resistin concentrations in PCOS women.

STUDY DESIGN PATIENTS AND MEASUREMENTS

A cross-sectional study involving 87 PCOS (48 obese) and 67 non-PCOS women (36 obese). Anthropometric parameters and body composition were determined. Serum glucose, androgens, FSH, LH, SHBG, insulin, apelin-36, apelin-12, adiponectin, leptin and resistin were measured in the fasting state.

RESULTS

Plasma apelin-36 and apelin-12 levels were significantly higher in normal weight women than in the obese women with PCOS (3·1 ± 2·2 vs 1·2 ± 0·7 μg/l, P < 0·001; 2·9 ± 2·4 vs 0·5 ± 0·7 μg/l; P < 0·001 respectively). Both plasma apelin-36 and -12 levels correlated positively with adiponectin levels, and inversely with leptin or resistin levels. There was a negative correlation between plasma apelin-36, apelin-12 and serum LH levels. In addition, an inverse correlation between apelin-12 level and LH to FSH ratio was found. In multiple regression analysis 9% of LH variability was explained by apelin-12 levels (β = -0·14; P < 0·001).

CONCLUSIONS

Nutritional status seems to have different effects on apelin release, particularly, its active isoform, in women with PCOS compared with women without PCOS. This may be partially caused by changes in leptin and resistin secretion and may enhance pituitary-ovarian axis disturbances. The association between both isoforms of apelin and insulin resistance seems to be bidirectional.

Associations of testosterone and sex hormone binding globulin with adipose tissue hormones in midlife women

OBJECTIVE

Regulators of adipose tissue hormones remain incompletely understood, but may include sex hormones. As adipose tissue hormones have been shown to contribute to numerous metabolic and cardiovascular disorders, understanding their regulation in midlife women is of clinical importance. Therefore, we assessed the associations between testosterone (T) and sex hormone binding globulin (SHBG) with leptin, high molecular weight (HMW) adiponectin, and the soluble form of the leptin receptor (sOB-R) in healthy midlife women.

DESIGN AND METHODS

Cross-sectional analyses were performed using data from 1,881 midlife women (average age 52.6 (±2.7) years) attending the sixth Annual follow-up visit of the multiethnic Study of Women's Health Across the Nation.

RESULTS

T was weakly negatively associated with both HMW adiponectin and sOB-R (r = -0.12 and r = -0.10, respectively; P < 0.001 for both), and positively associated with leptin (r = 0.17; P < 0.001). SHBG was more strongly and positively associated with both HMW adiponectin and sOB-R (r = 0.29 and r = 0.24, respectively; P < 0.001 for both), and more strongly and negatively associated with leptin (r = -0.27; P < 0.001). Adjustment for fat mass, insulin resistance, or waist circumference only partially diminished associations with HMW adiponectin and sOB-R, but attenuated associations with leptin. In conclusion, in these midlife women, lower SHBG values, and to a lesser extent, higher T levels, were associated with lower, or less favorable, levels of adiponectin and sOB-R, independent of fat mass.

CONCLUSIONS

These data suggest that variation in these adipose hormones resulting from lower SHBG levels, and possibly, though less likely, greater androgenicity, may contribute to susceptibility for metabolic and cardiovascular outcomes during midlife in women.

Influence of androgens on circulating adiponectin in male and female rodents

Several endocrine factors, including sex-steroid hormones are known to influence adiponectin secretion. Our purpose was to evaluate the influence of testosterone and of the synthetic non-aromatizable/non-5α reducible androgen 17β-hydroxyestra-4,9,11-trien-3-one (trenbolone) on circulating adiponectin and adiponectin protein expression within visceral fat. Young male and female F344 rats underwent sham surgery (SHAM), gonadectomy (GX), or GX plus supraphysiologic testosterone-enanthate (TE) administration. Total circulating adiponectin was 39% higher in intact SHAM females than SHAM males (p<0.05). GX increased total adiponectin by 29-34% in both sexes (p<0.05), while TE reduced adiponectin to concentrations that were 46-53% below respective SHAMs (p≤0.001) and ablated the difference in adiponectin between sexes. No differences in high molecular weight (HMW) adiponectin were observed between sexes or treatments. Adiponectin concentrations were highly and negatively associated with serum testosterone (males: r = -0.746 and females: r = -0.742, p≤0.001); however, no association was present between adiponectin and estradiol. In separate experiments, trenbolone-enanthate (TREN) prevented the GX-induced increase in serum adiponectin (p≤0.001) in young animals, with Low-dose TREN restoring adiponectin to the level of SHAMs and higher doses of TREN reducing adiponectin to below SHAM concentrations (p≤0.001). Similarly, TREN reduced adiponectin protein expression within visceral fat (p<0.05). In adult GX males, Low-dose TREN also reduced total adiponectin and visceral fat mass to a similar magnitude as TE, while increasing serum HMW adiponectin above SHAM and GX animals (p<0.05). Serum adiponectin was positively associated with visceral fat mass in young (r = 0.596, p≤0.001) and adult animals (r = 0.657, p≤0.001). Our results indicate that androgens reduce circulating total adiponectin concentrations in a dose-dependent manner, while maintaining HMW adiponectin. This change is directionally similar to the androgen-induced lipolytic effects on visceral adiposity and equal in magnitude between TE and TREN, suggesting that neither the aromatization nor the 5α reduction of androgens is required for this effect.

Localization of adiponectin and its receptor and its possible roles in the ovary of a vespertilionid bat, Scotophilus heathi

The aim of this study was to evaluate the seasonal variation in serum adiponectin levels and ovarian expression of adiponectin and its receptor in the Scotophilus heathi bat and their relationship to the changes in the body fat mass, serum insulin and luteinizing hormone (LH) levels, and ovarian activity. A very high level of circulating adiponectin was found during recrudescence, whereas a very low level of circulating adiponectin was observed during pre-ovulatory period. The increased circulating adiponectin level coincided with fat deposition, insulin resistance and hyperinsulinemia (HI) in S. heathi. Immunocytochemical study in the ovary of bat showed localization of adiponectin mainly in thecal-interstitial cells (TICs), and adiponectin receptor 1 (AdipoR1) in the granulosa cells of growing follicles, but showed no staining in atretic follicle. Seasonal changes in ovarian adiponectin and AdipoR1 levels showed two peaks (during recrudescence and ovulatory phases) coinciding with two periods of follicular development. Adiponectin in the absence of LH, as occur during recrudescence, stimulates androstenedione (A4) synthesis in vitro by up-regulating the insulin receptor (IR). Adiponectin in presence of LH, as occur during pre-ovulatory phase, inhibits A4 synthesis in vitro by down-regulating androgen receptor (AR). Further, the in vitro study showed that adiponectin, in presence of LH, also promotes luteinizing hormone receptor (LH-R) and steroidogenic acute regulatory protein (StAR) level in the ovary, which might help in development of ovulatory follicles. In brief, adiponectin in the absence of LH induces increased A4 synthesis and consequently the condition of delayed ovulation, whereas in the presence LH suppresses both synthesis and action of A4 and thus induces preovulatory condition in the ovary of S. heathi.

Severity and outcome of acute stroke in women: relation to adrenal sex steroid levels

Adrenal sex steroids exert diverse metabolic and neurobiological actions. Their levels have been associated with cardiovascular disease, but data concerning cerebrovascular disease are lacking. The objective of our study was to investigate the role of adrenal sex steroids in a female population suffering an acute stroke. We addressed the question of whether their levels are associated with disease severity and prognosis. A 2-year cohort study was performed in 2 tertiary hospitals, where we prospectively studied 302 consecutive postmenopausal female patients hospitalized for an acute stroke. Neurological severity on admission was assessed by the National Institutes of Health Stroke Scale; and handicap 1 month after stroke, with the modified Rankin Scale. Δ4-androstenedione levels were positively and dehydroepiandrosterone sulfate was inversely associated with stroke severity (r = 0.142, P = .014 and r = -0.153, P = .008, respectively), and both parameters remained as significant determinants even after entering other confounders in the multivariate model (r = 0.118, P = .039 and r = -0.150, P = .011, respectively). Levels of Δ4-androstenedione were significantly associated with 1-month mortality in the multivariate analysis (odds ratio with 95% confidence intervals: 1.540 [1.107-2.138)], P = .010). Δ4-androstenedione and dehydroepiandrosterone sulfate levels were associated with poor outcome in the univariate analysis, that is, combined severe handicap (modified Rankin Scale ≥4) and death, 1 month poststroke, although this was not significant in the multivariate analysis. Adrenal sex steroids, and especially Δ4-androstenedione, are significantly associated with stroke severity on admission and short-term prognosis among female stroke subjects. Well-designed prospective studies will further clarify their role in cerebrovascular disease.

High-molecular-weight and total adiponectin levels and incident symptomatic peripheral artery disease in women: a prospective investigation

BACKGROUND

Adiponectin is linked to reduced diabetes risk and may be antiatherogenic, yet clinical data show no consistent relationship with incident cardiovascular events, especially among women. To our knowledge, no prior prospective studies have evaluated adiponectin, including high-molecular-weight (HMW) adiponectin, and incident peripheral artery disease (PAD).

METHODS AND RESULTS

We evaluated the relationship of total adiponectin, HMW adiponectin, and the HMW-to-total adiponectin ratio with incident symptomatic PAD in a prospective, nested case-control study conducted within the Women's Health Study (n=110 cases, n=230 controls, frequency matched in strata defined by 5-year age categories, smoking, fasting status, and follow-up time; median cohort follow-up=13.2 years). Baseline median levels of HMW and total adiponectin were significantly lower in women developing PAD than in those remaining event free (HMW: 3.3 versus 3.8 μg/mL, P=0.0005; total: 5.6 versus 7.4 μg/mL, P<0.0001). The ratio did not differ significantly between groups. Age-adjusted PAD odds ratios (95% confidence intervals) across tertiles were 1.0, 0.66 (0.39-1.13), and 0.40 (0.22-0.74) for HMW and 1.0, 0.74 (0.43-1.25), and 0.35 (0.18-0.65) for total adiponectin (P(trend)=0.004 and 0.001, respectively). Results were similar after adjustment for traditional cardiovascular risk factors, use of postmenopausal hormone therapy, high-sensitivity C-reactive protein, soluble intercellular adhesion molecule-1, leptin, hemoglobin A(1c), and fasting insulin (adjusted odds ratio and 95% confidence interval for HMW: 1.0, 0.62 [0.29-1.34], 0.30 [0.12-0.74]; total: 1.0, 0.46 [0.22-1.00], 0.30 [0.12-0.76]; P(trend)=0.01 for both).

CONCLUSIONS

Total and HMW adiponectin are inversely associated with incident PAD among initially healthy women. These prospective data support a protective role for this adipokine in peripheral atherosclerosis development.

Alterations in total and high-molecular-weight adiponectin after 3 weeks of moderate alcohol consumption in premenopausal women

Moderate alcohol consumption is associated with increased concentrations of adiponectin. Whether this is the case for both total and high-molecular-weight (HMW) adiponectin is uncertain. Furthermore, the rate at which this increase occurs is unclear. Therefore, we examined the effect of moderate alcohol consumption on total and HMW adiponectin. In a randomized, crossover trial, 24 premenopausal women who were regular alcohol consumers received beer (∼26 g alcohol) or alcohol-free beer daily for 3 weeks preceded by a 1-week washout. Blood samples were collected weekly after an overnight fast for measurement of total and HMW adiponectin and markers of glucose and lipid metabolism. There was a significant interaction (P < .05) between the 2 treatments over time for both plasma HMW and total adiponectin concentrations. Within 3 weeks, plasma total (8.2%, P = .01) and HMW (8.2%, P = .02) adiponectin levels were higher after moderate alcohol consumption compared with abstention. Changes over time in total adiponectin were positively associated with changes in HMW adiponectin during the nonalcoholic beer (r = 0.80; 95% confidence interval, 0.55-0.92) and beer (r = 0.82; 0.58-0.93) intervention. Alcohol consumption did not affect the ratio of HMW to total adiponectin or the serum glucose, insulin, hemoglobin A(1c), or triglyceride levels compared with abstention during the intervention periods. Both total and HMW adiponectin concentrations are higher after moderate alcohol consumption compared with abstention in premenopausal women. These effects were evident after at least 3 weeks of consumption and occurred concomitantly.

Association between metabolic syndrome and carotid atherosclerosis: relevance of combined criteria including the serum adiponectin level for the general population

OBJECTIVE

The association between carotid atherosclerosis and the metabolic syndrome (MetS) was analyzed in the general population. The usefulness of the inclusion of the serum adiponectin concentration in the MetS criteria for the detection of atherosclerosis was also examined.

PATIENTS AND METHODS

The 825 participants of a comprehensive health checkup who underwent carotid ultrasonography and the measurement of serum adiponectin levels were studied.

RESULTS

The carotid plaque score (PLS) was significantly higher in the MetS group than in the non-MetS group in women, but not in men. In women, a significantly higher odds ratios was obtained for MetS, in terms of the current waist circumference criterion, and a high PLS (fourth quartile) (OR=2.64, p=0.040). In men, however, a waist circumference of around 85 cm did not reflect high a PLS, and even when the waist circumference criterion was varied, the odds ratio did not increase. When the waist circumference was replaced by hypoadiponectinemia in the current MetS criteria, the odds ratio was significantly increased in men (OR=1.82, p=0.032).

CONCLUSION

The current MetS criteria seem appropriate for women. In men, there was no significant evidence for the validity of the inclusion of the waist circumference criterion as an essential component. Incorporating hypoadiponectinemia into the current criteria would be useful for the early detection of atherosclerosis in men.

Metabolic and hormonal derangements in pulmonary hypertension: from mouse to man

Pulmonary arterial hypertension (PAH) is a complex disease with significant morbidity and mortality. Recent animal and human studies have highlighted abnormalities in regulation and metabolism of insulin, sex hormones, adipokines and lipids that may play a role in disease development. Mouse studies suggest features of the metabolic syndrome (MS) including insulin resistance, deficiencies in peroxisome proliferator-activated receptor γ and apolipoprotein E, and low adiponectin are linked to development of PAH. In humans, insulin resistance, the MS and low levels of high-density lipoprotein have been associated with PAH. In addition, abnormal metabolism of oestrogens has been demonstrated in human and animal models of PAH, suggesting an important relationship of sex hormones and pulmonary vascular disease. Improved understanding of how metabolic and hormonal derangements relate to development and progression of pulmonary hypertension may lead to better disease therapies and understanding of potential risk factors. This review will focus on the animal and human data regarding metabolic and sex hormone derangements in PAH.