[Genetic background in common forms of obesity - from studies on identical twins to candidate genes of obesity]. / Genetické pozadí bezných forem obezity - od studií identických dvojcat po studium kandidátních genu obezity*

Common obesity is a result of interaction between genes and environmental/lifestyle factors, with heritability estimates 40-70%. Not only the susceptibility to obesity but also the success of weight management depends on the genetic background of each individual. This paper summarizes the up-to-date knowledge on genetic causes of common obesities. Introduction of genome-wide association studies (GWAS) led to an identification of a total of 32 variants associated with obesity/BMI and 14 with body fat distribution. Further, a great progress in revealing the mechanisms regulating the energy balance was also noted. However, the proportion of explained variance for BMI is still low, suggesting other mechanisms such as gene-gene and gene-environment interactions, rare gene variants, copy number variants polymorphisms, or epigenetic modifications and microRNAs regulating gene transcription. In summary, we present results of our studies on obesity risk variants in Czech adults, children and adolescents including those evaluating the influence of selected gene variants on the outcomes of weight management.

[The prevalence of metabolic syndrome in women with polycystic ovary syndrome]. / Výskyt metabolického syndromu u zen se syndromem polycystických ovarií.

BACKGROUND: Polycystic ovary syndrome (PCOS) affects between 4-10% women of fertile age and is often connected with insulin resistance. We aimed to ascertain the prevalence of metabolic syndrome in Czech women with PCOS and to describe relations of different features of metabolic syndrome with insulin sensitivity. METHODS AND RESULTS: 179 women with PCOS. Clinical examination was done and blood lipid spectrum was measured. Euglycaemic hyperinsulinaemic clamp was done in 114 subjects. Metabolic syndrome (according to ATP III criteria) was detected in 28.7% women. The most frequent features were an increased waist circumference, decreased concentration of HDL - cholesterol (both in 96%), and increased blood pressure (88%). Increased triglycerides (49%) and impaired fasting blood glucose or diabetes mellitus type 2 (37.3%) were less common. The average insulin sensitivity described as corrected glucose disposal (Mk) was 34.9 +/- 12.70 micromol/kg/min. The most tight correlations was that of Mk and waist circumference (r = -0.896), weight (r = -0.875) and BMI (r = -0.844). CONCLUSION: The increased risk of metabolic syndrome and the decreased insulin sensitivity in polycystic ovary syndrome is tightly connected with obesity, especially with its abdominal type.

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

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/m(2)] and healthy women (n=57, age 26.8+/-5.8 years, BMI 21.3+/-2.1 kg/m(2)) 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.

Insulin sensitivity and counter-regulatory hormones in hypothyroidism and during thyroid hormone replacement therapy.

We examined insulin sensitivity and secretion, together with the levels of selected glucoregulatory hormones, in 15 female patients with severe hypothyroidism (H) and during subsequent thyroid hormone replacement therapy (HRT) using the euglycaemic hyperinsulinaemic clamp technique. Insulin action, as evaluated by glucose disposal, the insulin sensitivity index, and fasting post-hepatic insulin delivery rate were established. The basal levels of insulin, C-peptide and counter-regulatory hormones were measured in basal condition. In H, glucose disposal (p<0.01), the insulin sensitivity index (p<0.01) and post-hepatic insulin delivery rate (p<0.05) were significantly lower than during HRT. No significant changes in the levels of fasting insulin and C-peptide were observed. The levels of counter-regulatory hormones in patients with H were significantly higher than during HRT (glucagon, p<0.05; epinephrine, p<0.01; cortisol, p<0.05; growth hormone, p<0.05). In H, an inverse correlation between insulin sensitivity and insulin secretion was observed (p<0.05). Cortisol was the most important factor affecting the variability of insulin sensitivity values, regardless of thyroid function (p=0.0012). In conclusion, H altered both insulin sensitivity and the levels of selected counter-regulatory hormones. The situation was restored by HRT, as manifested not only by normalisation of insulin sensitivity, secretion and levels of glucoregulatory hormones, but also by improvement of their relationships.

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.

Insulin sensitivity in women with polycystic ovary syndrome.

The aim of our study was to compare insulin sensitivity in lean and obese European polycystic ovary syndrome (PCOS) women with lean healthy women. We performed the euglycemic hyperinsulinemic clamp in 83 women with PCOS [53 lean with body mass index (BMI) of 21.5 +/- 1.8 kg/m2 and 30 obese with BMI of 29.6 +/- 3.7 kg/m2] and in 15 healthy women with BMI of 21.6 +/- 1.8 kg/m2 to determine glucose disposal (M) and the insulin sensitivity index (ISI). Statistical evaluation was done using Kruskal-Wallis ANOVA followed by Kruskal-Wallis multiple-comparison z-value test. The basal blood glucose was significantly higher in lean and obese PCOS women than in controls (P < 0.02). Fasting insulin was significantly higher in both lean and obese PCOS women than in controls (P < 0.000001). Obese PCOS women were more insulin resistant than controls (P < 0.02 for M and P < 0.0008 for ISI); lean PCOS women did not differ from controls in M or ISI. Posthepatic insulin delivery was significantly higher in both lean and obese PCOS women compared with controls (P < 0.000008). We conclude that lean PCOS women are not more insulin resistant than healthy controls. Insulin hypersecretion, on the other hand, is present even in lean PCOS women.

New methodology of influential point detection in regression model building for the prediction of metabolic clearance rate of glucose.

Identifying outliers and high-leverage points is a fundamental step in the least-squares regression model building process. The examination of data quality involves the detection of influential points, outliers and high-leverages, which cause many problems in regression analysis. On the basis of a statistical analysis of the residuals (classical, normalized, standardized, jackknife, predicted and recursive) and diagonal elements of a projection matrix, diagnostic plots for influential points indication are formed. The identification of outliers and high leverage points are combined with graphs for the identification of influence type based on the likelihood distance. The powerful procedure for the computation of influential points characteristics written in S-Plus is demonstrated on the model predicting the metabolic clearance rate of glucose (MCRg) that represents the ratio of the amount of glucose supplied to maintain blood glucose levels during the euglycemic clamp and the blood glucose concentration from common laboratory and anthropometric indices. MCRg reflects insulin sensitivity filtering-off the effect of blood glucose. The prediction of clamp parameters should enable us to avoid the demanding clamp examination, which is connected with a higher load and risk for patients.

Levels of testosterone, allopregnanolone and homocysteine in severe hypothyroidism.

Hypothyroidism is very often associated with cardiovascular diseases and neurological complications. Recently, homocysteine has been studied as an independent risk factor for atherosclerosis which negatively affects vascular endothelial cells. Because homocysteine metabolism is related to thyroid and steroid hormones, we studied these relationships in severe hypothyroidism and in euthyroid state. Homocysteine, testosterone and allopregnanolone concentrations were measured in the fasting plasma from 16 women who underwent total thyroidectomy, and who were either hypothyroid or euthyroid. Although all women used oral contraceptives, they were not protected against hyperhomocysteinemia during hypothyroid state. With the normalization of thyroid hormone concentrations homocysteine levels decreased to normal levels. There was a positive correlation between testosterone and homocysteine in the euthyroid state which suggests that not only estrogens but also androgen state should be considered in future studies on homocysteine.