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Division of Endocrinology (A.G., V.V., S.G., F.T., U.P., R.P.), Department of Internal Medicine, and Centre for Applied Biomedical Research, S. Orsola-Malpighi Hospital, University of Bologna, 40138 Bologna, Italy; and Endocrinology Unit (B.R.W.), Centre for Cardiovascular Sciences, University of Edinburgh, Edinburgh EH8 9AG, United Kingdom
Address all correspondence and requests for reprints to: Alessandra Gambineri, M.D., Division of Endocrinology, Department of Internal Medicine, S. Orsola-Malpighi Hospital, via Massarenti 9, 40138 Bologna, Italy. E-mail: gambineri{at}aosp.bo.it.
| Abstract |
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Objective: Our objective was to investigate a functional polymorphism in HSD11B1 (T
G in the third intron rs12086634, which associates with lower 11ß-HSD1 activity) in PCOS with and without obesity.
Design and Setting: We conducted a case-control study in lean and obese PCOS patients and controls at an academic hospital.
Participants: Participants included 102 Caucasian PCOS patients and 98 controls comparable for age, weight, and race.
Main Outcome Measures: We assessed genotype distribution and influence of genotypes on clinical, hormonal, and metabolic parameters.
Results: The G allele was significantly related to PCOS status (P = 0.041), and this association was mainly attributable to lean (P = 0.025), rather than obese (P = 0.424), PCOS patients. The G allele was associated with lower 08000830 h plasma cortisol (P < 0.001) and higher cortisol response to ACTH124 (P < 0.001) in all women with PCOS and with higher dehydroepiandrosterone sulfate levels (P < 0.001), greater suppression of dehydroepiandrosterone sulfate by dexamethasone (P < 0.001), and lower fasting plasma low-density lipoprotein cholesterol (P = 0.002) levels in lean PCOS women.
Conclusions: Genetic variation in 11ß-HSD1 contributes to enhanced cortisol clearance and compensatory adrenal hyperandrogenism in lean patients with PCOS but may be protective against obesity and some features of the metabolic syndrome.
| Introduction |
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Polymorphisms in the HSD11B1 gene, which encodes 11ß-HSD1, have been associated with type 2 diabetes (10) and hypertension (11). A T
G polymorphism in the third intron (rs12086634) is protective against diabetes in Pima Indians (10). This polymorphism reduces HSD11B1 gene transcription in vitro (12), which is consistent with reduced cortisol generation within cells. However, when regeneration of cortisol in peripheral tissues is impaired, the overall metabolic clearance rate for cortisol is increased. Although any tendency for plasma cortisol concentrations to fall is compensated for by reduced negative feedback suppression of ACTH and hence increased adrenal cortisol secretion, this compensation occurs at the expense of increased ACTH-dependent adrenal androgen secretion. These mechanisms appear to operate in the rare syndrome of cortisone reductase deficiency, characterized by an inability to convert cortisone to cortisol (12, 13). This syndrome has been associated with the T
G polymorphism in the third intron (rs12086634), and female patients affected by cortisol reductase deficiency present with hyperandrogenism and a phenotype resembling polycystic ovary syndrome (PCOS) (hirsutism, irregular menses, and polycystic ovaries) (12, 13).
In patients with PCOS, lower ratios of cortisol/cortisone metabolites in urine have been reported (14), suggesting a reduced 11ß-HSD1 activity, albeit that this may be confounded by coexistent obesity.
These findings highlight the rs12086634 T
G HSD11B1 polymorphism as a candidate to explain the adrenal androgen excess in PCOS. However, any reduction in 11ß-HSD1 might paradoxically protect against obesity and associated metabolic dysfunction. We therefore hypothesized that the T
G HSD11B1 genotype would be enriched only in the subgroup of PCOS patients with adrenal androgen excess in whom hyperandrogenism is not associated with obesity and the metabolic syndrome; the association of these features is frequent, but not universal, in this heterogeneous condition (15, 16, 17). To test this hypothesis we characterized the T
G polymorphism in the third intron of HSD11B1 gene (rs12086634) and its association with hormonal and metabolic phenotype in women with PCOS who were either lean or obese.
| Subjects and Methods |
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We investigated 102 unmedicated Caucasian women with PCOS, aged 1845 yr, and 98 controls comparable for age, weight, and race. PCOS women had polycystic ovarian morphology at ultrasound and at least one of the following: chronic oligo-anovulation, with luteal serum progesterone less than 2 ng/ml (18), 100%; hirsutism with a Ferriman-Gallwey score of at least 8 (19), 68%; and elevated serum testosterone levels more than 2 SD above our reference mean values (20), 51%, according to the Rotterdam consensus (21). Hyperprolactinemia, Cushings syndrome, congenital adrenal hyperplasia, and androgen-secreting tumors were excluded by specific laboratory analysis (22). Controls had normal ovaries by ultrasound, no signs of hyperandrogenism, and regular and ovulatory menstrual cycles. Ovulation was documented by the presence of progesterone levels above 8 ng/ml during the luteal phase of the menstrual cycle, tested during the recruitment period (18). To better analyze the impact of obesity on T
G HSD11B1 genotype, we included only lean or obese subjects, excluding overweight women. The degree of obesity was established depending on the body mass index (BMI), and women were classified as lean if BMI was not more than 25 kg/m2 and obese if BMI was at least 30 kg/m2 (23). The protocol was approved by the local ethics committee, and written informed consent was obtained from each patient and control.
Assessment program
Standard anthropometric data (height, weight, and waist circumference) and an L4L5 computerized tomography scan of body fat distribution (to estimate total, visceral, and sc adipose tissue areas) were obtained from each subject. Moreover, basal blood samples for hormonal [total testosterone, androstenedione, dehydroepiandrosterone sulfate (DHEA-S), SHBG, and cortisol] and metabolic [glucose, insulin, total cholesterol, high-density lipoprotein (HDL)-cholesterol, and triglycerides] determinations were collected at 08000830 h after overnight fast. All participants underwent also a fasting 75-g oral glucose tolerance test, an ACTH124 stimulation test (250 µg ACTH124 iv at 08000830 h with blood taken at 0 and 60 min), and a dexamethasone suppression test (0.5 mg orally every 6 h for 4 d with blood taken at 08000830 h on the fifth day). Samples were immediately chilled on ice and centrifuged; serum was stored at 20 C and plasma at 80 C until assayed. Studies were performed between d 5 and 10 of the menstrual cycle, or during amenorrhea, after excluding pregnancy by appropriate testing.
Biochemical assay
The assays employed for biochemical measurements have been reported elsewhere (22, 24, 25). Low-density lipoprotein (LDL)-cholesterol was calculated by the Friedewald equation (26). Insulin resistance was estimated using the quantitative insulin-sensitivity check index (QUICKI) and the insulin sensitivity index during the oral glucose tolerance test (ISI) (27, 28).
Genetic analysis
Blood samples were collected in tubes containing disodium-EDTA as anticoagulant and stored at 4 C until extraction. DNA was extracted using QIAGEN silica gel-based spin columns (QiaAmp DNA blood mini kit; QIAGEN, Hilden, Germany). DNA obtained gave a 260/280 absorbance ratio of 1.62.0, indicating high-quality DNA. Then samples were loaded in wells made in agarose gel 1% for separation by electrophoresis, to verify the DNA integrity and stored at 20 C until analysis. Genotyping of rs12086634 was performed by allelic discrimination real-time PCR on a TaqMan 7900 HT (Applied Biosystems, Foster City, CA) with probe sequences FAM CAGATGATTTCT and VIC CCCAGAGGATTTCT, forward primer 5'-GGAGGAGAATGGGAAAGGTATCAAC-3', and reverse primer 5'-TCCTCCTGCAAGAGATGGCTATATT-3'. Real-time PCR allelic discrimination was unsuccessful in 19 subjects, who were genotyped by direct sequencing using Big Dye Terminator and an automated capillary sequencer (3730 DNA analyzer; Applied Biosystems), using the forward primer 5'-TGAGCAATCTCTCATTTAAGCCC-3' and reverse primer 5'-TGTCCCTGTCCCACTTACCAGCC-3'. To evaluate whether real-time PCR and direct sequencing were comparable, we analyzed 10 samples with both techniques and obtained the same results.
Power analysis
The number of cases to be included in the study was calculated taking into account a G allele frequency in rs12086634 of 14% in the control Caucasian population (12) and assuming a frequency of 35% in PCOS (estimated from the frequency of adrenal hyperandrogenism in this disorder) (29); a case-control study of 200 subjects has a power of 90% to detect this difference at a significance level of P < 0.05.
Statistical analysis
Data are shown as means ± SD and frequencies. The data were evaluated by means of two-way ANOVA to analyze the overall effect of PCOS and of obesity in the entire population (each adjusted for the other) and to evaluate the interactions between them. The effects within groups were evaluated using the nested design of the two-way ANOVA. Two-way ANOVA with the same design was also applied to analyze the effects of T/G+G/G HSD11B1 genotype (rs12086634) and of obesity. Univariate and multivariate logistic regressions were used to relate the frequency of T/G+G/G HSD11B1 genotype (rs12086634) with the presence of PCOS and with the degree of obesity. The odds ratios (OR) evaluated by the logistic regression, together with their 95% confidence intervals (CI), were also reported. No post hoc analysis was performed. Statistical analyses were performed by running the SPSS/PC+ version 8 (Chicago, IL) software package. Two-tailed P values < 0.05 were considered statistically significant.
| Results |
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Table 1
shows clinical and biochemical characteristics in PCOS and controls, according to BMI (lean and obese), whereas Table 2
shows the effect attributable to PCOS status, to obesity, and to their interaction on all the characteristics analyzed.
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PCOS women had higher levels of androgens (testosterone, androstenedione, and DHEA-S) and lower levels of SHBG, independently of body weight. However, the difference between PCOS and controls in SHBG levels was more evident in lean than obese subjects.
PCOS women had an exaggerated response of cortisol to ACTH124, were more insulin resistant, and had higher insulin responsiveness to the glucose load and lower HDL-cholesterol levels when compared with controls. Insulin resistance and insulin responsiveness to the glucose load were significantly higher, whereas HDL-cholesterol levels were significantly lower in obese than lean women in both PCOS and controls.
No effects of PCOS or obesity on basal cortisol levels, on the responsiveness of androgens to ACTH124, and on the suppression of adrenal steroids by dexamethasone were observed.
HSD11B1 genotype (rs12086634) in PCOS women compared with controls
The allelic frequency of the T
G polymorphism (rs1208664) in the third intron of HSD11B1 was 14% in the entire population. Sixty-seven percent (n = 68) of PCOS and 80% (n = 78) of controls were T/T; 33% (n = 34) of PCOS and 18% (n = 18) of controls were T/G; and 0% of PCOS and 2% (n = 2) of controls were G/G. Therefore, the G allele was significantly related to PCOS status, and this association was mainly attributable to lean, rather than obese, PCOS patients (Table 3
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Table 4
and Figs. 1
and 2
show clinical and biochemical characteristics in PCOS women, according to the HSD11B1 genotype (rs12086634) (T/T and T/G+G/G), whereas Table 5
shows the effect attributable to T/G+G/G HSD11B1 genotype (rs12086634), to obesity, and to their interaction on all the characteristics analyzed within the PCOS group.
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| Discussion |
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The association of the HSD11B1 genotype with PCOS was mainly attributable to lean, rather than obese, PCOS patients; lean patients are relatively enriched in this study cohort by the selection criteria for lean and obese groups. The lack of overweight subjects (BMI, 2629 kg/m2) distinguishes this study from that of San Millán et al. (30), performed in another population of Caucasian women, in which no association between HSD11B1 genotype and PCOS was found. In addition, ovarian morphology was not used in the diagnostic criteria by San Millán et al. (30), suggesting that different populations of PCOS and control subjects were included in the two studies and reinforcing that HSD11B1 polymorphisms may be relevant only in some subgroups of this heterogeneous condition. Also, data from White (31) did not show association between HSD11B1 genotype and PCOS. However, these data were from a multiethnic population, and the criteria used by the author to diagnose PCOS (only presence of more than 10 cysts detected by magnetic resonance imaging in one or both ovaries) are inadequate, because they are not in accordance with the diagnostic criteria recommended either by the National Institutes of Health (32) or the Rotterdam Consensus (21).
The finding of an association of HSD11B1 genotype with adrenal hyperandrogenism only in lean PCOS women suggests that in obese PCOS women, adrenal hyperandrogenism must have a different pathogenetic mechanism. This might involve abnormal adrenal steroidogenesis as a consequence of hyperinsulinemia (33) or may also be related to increased cortisol clearance, because obese patients have increased metabolic clearance of cortisol by 5
-reductase (34).
Among PCOS women, the apparent lower prevalence of rs1208664 T
G in the obese than lean patients also suggests that this genotype either reduces the chances of becoming obese or reduces the chance of developing PCOS in the presence of obesity. This could be attributed to lower intracellular cortisol levels, particularly in adipose tissue and liver, which are protective against features of the metabolic syndrome (1, 2). This is supported by the atheroprotective lipid profile observed in lean PCOS women carrying the G allele.
However, contrary to our expectations, we did not find any association of the HSD11B1 genotype with measures of insulin sensitivity. This result is in accordance with the study performed by San Millán et al. (30) but in apparent contrast with a previous report obtained in a large population of Pima Indians (10). This discrepancy might be attributed to ethnic and environmental differences between the cohorts or to the different methods used to asses insulin sensitivity. The principal association in the Pima Indians was with insulin sensitivity in a euglycemic hyperinsulinemic clamp rather than with fasting insulin levels and insulin responses to a glucose load, the methods used by us and by San Millán et al. (30 ).
The lack of association of HSD11B1 genotype with biochemical phenotype in control subjects may reflect the lack of statistical power or the presence of modifying environmental or genetic factors.
In conclusion, genetic variation in 11ß-HSD1 may underlie adrenal hyperandrogenism in lean patients with PCOS but may protect against obesity and associated metabolic dysfunction. These observations lend additional support to the concept that the pathogenesis of PCOS is different among the different phenotypes of the syndrome.
| Acknowledgments |
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| Footnotes |
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The authors have nothing to declare.
First Published Online March 21, 2006
Abbreviations: BMI, Body mass index; CI, confidence interval; DHEA-S, dehydroepiandrosterone sulfate; HDL, high-density lipoprotein; 11ß-HSD1, 11ß-hydroxysteroid dehydrogenase; ISI, insulin sensitivity index; LDL, low-density lipoprotein; OR, odds ratio; PCOS, polycystic ovary syndrome; QUICKI, quantitative insulin-sensitivity check index.
Received October 7, 2005.
Accepted March 13, 2006.
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