Bela Bendlova

Association of Insulin Gene VNTR Polymorphism with Polycystic Ovary Syndrome

Abstract: Variability in the number of tandem repeats of the insulin gene (INS VNTR) is known to influence several phenotypes, including polycystic ovary syndrome (PCOS), diabetes mellitus type 1, diabetes mellitus type 2, and birth weight. The presence of the class III allele of INS VNTR has been reported to be protective in diabetes mellitus type 1, but in contrary it increases the disease risk of PCOS and diabetes mellitus type 2. PCOS is a very common endocrinopathy in women of reproductive age. The etiology of PCOS is uncertain, but family history of this syndrome suggests a major genetic cause. The aim of this pilot study was to investigate the possible association of INS VNTR polymorphism with PCOS in Czech women. In PCOS, significantly higher WHR, BMI, G0, G180, I30, Cp0, Cp30, Cp60, AUC‐I, AUC‐Cp, and insulinogenic index and significantly lower AUC‐G/AUC‐I were found. No significant differences in INS VNTR genotype, phenotype, or allele frequencies were found between PCOS and controls. In spite of several differences in anthropometric and biochemical parameters (abdominal fat localization, increased β‐cell function, and lower insulin sensitivity in PCOS women), no effect of INS VNTR polymorphism was found on insulin secretion, insulin action, or any other screened parameter.

Incretin levels in polycystic ovary syndrome

OBJECTIVE Polycystic ovary syndrome (PCOS) has been linked to a high risk of type 2 diabetes mellitus. Disturbances in the secretion of the incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) have been observed in states with impaired glucose regulation. This paper considers the secretion of GIP and GLP-1 after oral glucose load in a group of lean, glucose-tolerant PCOS women in comparison with age- and body mass index (BMI)-matched healthy women. DESIGN Case control. METHODS PCOS (n=21, 25.8+/-4.1 years, BMI 21.6+/-1.7 kg/m(2)) and control healthy women (CT, n=13, 28.5+/-7.2 years, BMI 20.3+/-2.5 kg/m(2)) underwent oral glucose tolerance test (OGTT) with blood sampling for glucose, insulin, C-peptide, total GIP, and active GLP-1. Insulin sensitivity was determined both at fasting and during the test. STATISTICS Repeated measures ANOVA. RESULTS Glucose levels and insulin sensitivity did not differ between PCOS and CT. PCOS had significantly higher levels of C-peptide (P<0.05) and tended to have higher insulin levels. The levels of total GIP were significantly higher in PCOS than in CT (P<0.001). Active GLP-1 levels exhibited a significantly different time-dependent pattern in PCOS (P<0.002 for PCOS versus time interaction). GLP-1 concentrations were similar in PCOS and CT in the early phase of OGTT and then reached significantly lower levels in PCOS than in CT at 180 min (P<0.05). CONCLUSIONS Increased total GIP and lower late phase active GLP-1 concentrations during OGTT characterize PCOS women with higher C-peptide secretion in comparison with healthy controls, and may be the early markers of a pre-diabetic state.

Prevalence of insulin resistance and prediction of glucose intolerance and type 2 diabetes mellitus in women with polycystic ovary syndrome.

Abstract Background: Diabetes mellitus type 2 (DM2) affects 10% of women with polycystic ovary syndrome (PCOS). We evaluated the sensitivity and specificity of clinical and fasting biochemical parameters in screening for impaired glucose tolerance (IGT) and DM2. Methods: Women with PCOS [n=244, age 27.4±7.5 years, body mass index (BMI) 27.5±6.9 kg/m2] and healthy women (n=57, age 26.8±5.8 years, BMI 21.3±2.1 kg/m2) underwent basal blood sampling and an oral glucose tolerance test (oGTT). Results: Insulin resistance was identified in 40.2% of PCOS women. Impaired fasting glucose (5.6–6.9 mmol/L) was found in 30 subjects (12.3%), but the oGTT revealed IGT in only six of these cases and DM2 in one subject. IGT was found in 23 (9.4%) and DM2 in four (1.6%) of the women with PCOS. The conventional upper limits for total cholesterol, triglycerides, systolic and diastolic blood pressure and fasting glucose revealed low sensitivity for the identification of impaired glucose metabolism. Conclusions: No single parameter nor any combination of them showed an accuracy sufficient for screening of IGT or DM2 in PCOS patients. All PCOS patients should be screened using an oGTT to identify disturbances in glucose metabolism. Clin Chem Lab Med 2007;45:639–44.

Is a Pro12Ala Polymorphism of the PPARγ2 Gene Related to Obesity and Type 2 Diabetes Mellitus in the Czech Population

Abstract: The peroxisome proliferator‐activated receptors (PPARs) are members of the nuclear hormone receptor subfamily of transcription factors. PPARγ2 plays a key role in regulation of adipocyte differentiation and energy homeostasis. Recent studies provide evidence that the Pro12Ala polymorphism is linked to obesity and type 2 diabetes mellitus, but the results are controversial and depend on ethnicity. The aim of this study was to determine allele frequencies and to study the influence of the polymorphism on biochemical and anthropometric parameters in a Czech healthy adult population, in type 2 diabetics, and in a group of obese women. Results: The frequency of the Pro12Ala PPARγ2 gene polymorphism in Czech probands is similar to other central European populations. Frequency of the Pro12Ala substitution tends to be higher in obese women and diabetics compared with controls. The fasting insulin levels in the 12Ala carriers were significantly lower within the group of diabetics even after adjustment for age, BMI, and the length of diabetes duration. In obese women, higher WHR was found in subjects with the 12Ala allele. Conclusions: This study indicates that the substitution Pro12Ala is not associated with a decreased obesity or diabetes risk in the Czech population. However, the present data show that fasting insulin concentrations are lower in diabetics with the 12Ala allele than in those without it. This finding provides evidence that the polymorphism may influence glucose homeostasis.

Determinants of circulating adiponectin in women with polycystic ovary syndrome.

Background and Aim: Adiponectin is regarded as a possible link between adiposity and insulin resistance. Ghrelin and leptin are considered as signals of energy status. We evaluated the relationships between these peptides, androgens and insulin sensitivity in women affected by polycystic ovary syndrome. Methods: Thirty-six women with PCOS were examined with euglycemic hyperinsulinemic clamp (to determine M/I, index of insulin sensitivity). Leptin, ghrelin, adiponectin, androgens, and SHBG were determined. Statistics was done using correlation analysis and backward stepwise multiple regression. Results: The positive correlation of adiponectin with testosterone remains significant even after adjustment for BMI (p = 0.01), M/I (p = 0.009) and for both M/I and BMI (p = 0.02). In multiple regression with testosterone, M/I, leptin and ghrelin as independent variables, the model including testosterone (p = 0.03) and ghrelin (p = 0.002) explained 49% of the variability (p < 0.0012) of adiponectin. Conclusions: Both adiponectin and ghrelin can be involved in the pathophysiology of PCOS but their relation must be delineated further.

RET mutation Tyr791Phe the genetic cause of different diseases derived from neural crest

Activating germline RET mutations are presented in patients with familial medullary thyroid carcinoma (FMTC) and multiple endocrine neoplasia (MEN) types 2A and 2B, whereas inactivating germline mutations in patients with Hirschsprung’s disease (HSCR). The aim of this study was to evaluate genotype–phenotype correlations of the frequently discussed Tyr791Phe mutation in exon 13 of the RET proto-oncogene. Screening of three groups of patients was performed (276 families with medullary thyroid carcinoma (MTC), 122 families with HSCR, and 29 patients with pheochromocytoma). We found this mutation in 3 families with apparently sporadic MTC, 3 families with FMTC/MEN2, 1 patient with pheochromocytoma, and 3 families with HSCR. All gene mutation carriers have a silent polymorphism Leu769Leu in exon 13. In three families second germline mutations were detected: Cys620Phe (exon 10) in MEN2A family, Met918Thr (exon 16) in MEN2B family, and Ser649Leu (exon 11) in HSCR patient. Detection of the Tyr791Phe mutation in MEN2/MTC and also in HSCR families leads to the question whether this mutation has a dual character (gain-of-function as well as loss-of-function). A rare case of malignant pheochromocytoma in a patient with the Tyr791Phe mutation is presented. This study shows various clinical characteristics of the frequently discussed Tyr791Phe mutation.

Routine OGTT: A Robust Model Including Incretin Effect for Precise Identification of Insulin Sensitivity and Secretion in a Single Individual

In order to provide a method for precise identification of insulin sensitivity from clinical Oral Glucose Tolerance Test (OGTT) observations, a relatively simple mathematical model (Simple Interdependent glucose/insulin MOdel SIMO) for the OGTT, which coherently incorporates commonly accepted physiological assumptions (incretin effect and saturating glucose-driven insulin secretion) has been developed. OGTT data from 78 patients in five different glucose tolerance groups were analyzed: normal glucose tolerance (NGT), impaired glucose tolerance (IGT), impaired fasting glucose (IFG), IFG+IGT, and Type 2 Diabetes Mellitus (T2DM). A comparison with the 2011 Salinari (COntinuos GI tract MOdel, COMO) and the 2002 Dalla Man (Dalla Man MOdel, DMMO) models was made with particular attention to insulin sensitivity indices ISCOMO, ISDMMO and kxgi (the insulin sensitivity index for SIMO). ANOVA on kxgi values across groups resulted significant overall (P<0.001), and post-hoc comparisons highlighted the presence of three different groups: NGT (8.62×10−5±9.36×10−5 min−1pM−1), IFG (5.30×10−5±5.18×10−5) and combined IGT, IFG+IGT and T2DM (2.09×10−5±1.95×10−5, 2.38×10−5±2.28×10−5 and 2.38×10−5±2.09×10−5 respectively). No significance was obtained when comparing ISCOMO or ISDMMO across groups. Moreover, kxgi presented the lowest sample average coefficient of variation over the five groups (25.43%), with average CVs for ISCOMO and ISDMMO of 70.32% and 57.75% respectively; kxgi also presented the strongest correlations with all considered empirical measures of insulin sensitivity. While COMO and DMMO appear over-parameterized for fitting single-subject clinical OGTT data, SIMO provides a robust, precise, physiologically plausible estimate of insulin sensitivity, with which habitual empirical insulin sensitivity indices correlate well. The kxgi index, reflecting insulin secretion dependency on glycemia, also significantly differentiates clinically diverse subject groups. The SIMO model may therefore be of value for the quantification of glucose homeostasis from clinical OGTT data.

Impaired Glucose Metabolism in Women with Polycystic Ovary Syndrome

Background: To compare the prevalence of impaired glucose tolerance (IGT) and type 2 diabetes mellitus (T2DM) in lean and overweight/obese women with polycystic ovary syndrome (PCOS), with the data from a normal population sample. Methods: PCOS-affected women fulfilling ESHRE diagnostic criteria underwent an oral glucose tolerance test. Prevalence of IGT and T2DM in control sample of white healthy females was extracted from the published data from NHANES II. Results: In 225 women with PCOS, IGT was present in 6/104 (5.8%) lean and in 15/121 (12.4%) overweight/obese women. T2DM was present in 1/104 (1.0%) lean and in 3/121 (2.5%) overweight/obese PCOS women. In a sample of 643 women from NHANES II, the crude rate of IGT was 5.9%. IGT was significantly more common only in the overweight/obese PCOS subgroup as compared to the NHANES II cohort (χ2 = 5.99, p < 0.01). Conclusions: IGT was found significantly more frequently only in overweight/obese PCOS subjects in comparison with healthy controls.

Beta cell function and insulin sensitivity in women with polycystic ovary syndrome: Influence of the family history of type 2 diabetes mellitus

Aim. To study the impact of family history (FH) of type 2 diabetes mellitus on β-cell compensatory mechanism in women with polycystic ovary syndrome (PCOS). Subjects and methods. A total of 70 women with PCOS, 14 with first-degree relative with type 2 diabetes mellitus (T2DM) (FH+), 56 with negative FH of T2DM (FH−) and 72 age and BMI matched control healthy women (CNT) underwent oral glucose tolerance test (OGTT). Insulin resistance was evaluated as oral glucose index (OGIS); insulin and C-peptide secretion as the insulinogenic index in 30th min of OGTT. Results. Fasting blood glucose levels were significantly higher in FH+ than in FH− (p < 0.05). Fasting insulin was higher in FH+ than in CNT (p < 0.05). Fasting C-peptide was significantly higher in both FH− and FH+ than in CNT (p < 0.05 and p < 0.01, respectively). OGIS was lower in FH+ than in FH− or in CNT (p < 0.05). Insulinogenic index calculated from C-peptide values (II-Cp) was lower in FH+ than in CNT (p < 0.05). Adaptation index calculated from the values of OGIS and insulinogenic index was significantly lower in FH+ than in CNT or in FH− (p < 0.0001 and p < 0.01, respectively). Conclusions. Insulin resistance and defective early-phase insulin secretion is present only in those PCOS-affected subjects who had positive FH of T2DM.

Hirschsprung's disease and medullary thyroid carcinoma: 15-year experience with molecular genetic screening of the RET proto-oncogene.

PurposeInactivating germline mutations in the RET proto-oncogene are the major genetic cause of Hirschsprung’s disease (HD). In some cases, HD can be associated with medullary thyroid carcinoma (MTC) that is commonly caused by activating RET mutations.MethodsThe retrospective and prospective genetic analyses of 157 patients with HD operated on between December 1979 and June 2011 were carried out. DNA was isolated from peripheral leukocytes. HD patients and family members were tested for RET mutations by direct sequencing and single-strand conformation polymorphism methods.ResultsRET mutations were detected in 16 patients (10%). Association with MTC was found in two families, other eight families had a mutation with potentially high risk of MTC development and four novel mutations were detected. Total colonic aganglionosis was noted to have a high mutation detection rate (40%). Three patients underwent total thyroidectomy (two had clinical manifestation of MTC, one C-cell hyperplasia).ConclusionResults show the benefit of systematic RET mutation screening in HD patients in order to identify the risk of MTC in the preclinical stage of the disease. All patients should be tested for RET mutations at least in exon 10, and now additionally in exon 11 and 13, as well.