Melanie M. van der Klauw

The prevalence of metabolic syndrome and metabolically healthy obesity in Europe: a collaborative analysis of ten large cohort studies

BackgroundNot all obese subjects have an adverse metabolic profile predisposing them to developing type 2 diabetes or cardiovascular disease. The BioSHaRE-EU Healthy Obese Project aims to gain insights into the consequences of (healthy) obesity using data on risk factors and phenotypes across several large-scale cohort studies. Aim of this study was to describe the prevalence of obesity, metabolic syndrome (MetS) and metabolically healthy obesity (MHO) in ten participating studies.MethodsTen different cohorts in seven countries were combined, using data transformed into a harmonized format. All participants were of European origin, with age 18–80xa0years. They had participated in a clinical examination for anthropometric and blood pressure measurements. Blood samples had been drawn for analysis of lipids and glucose. Presence of MetS was assessed in those with obesity (BMIu2009≥u200930xa0kg/m2) based on the 2001 NCEP ATP III criteria, as well as an adapted set of less strict criteria. MHO was defined as obesity, having none of the MetS components, and no previous diagnosis of cardiovascular disease.ResultsData for 163,517 individuals were available; 17% were obese (11,465 men and 16,612 women). The prevalence of obesity varied from 11.6% in the Italian CHRIS cohort to 26.3% in the German KORA cohort. The age-standardized percentage of obese subjects with MetS ranged in women from 24% in CHRIS to 65% in the Finnish Health2000 cohort, and in men from 43% in CHRIS to 78% in the Finnish DILGOM cohort, with elevated blood pressure the most frequently occurring factor contributing to the prevalence of the metabolic syndrome. The age-standardized prevalence of MHO varied in women from 7% in Health2000 to 28% in NCDS, and in men from 2% in DILGOM to 19% in CHRIS. MHO was more prevalent in women than in men, and decreased with age in both sexes.ConclusionsThrough a rigorous harmonization process, the BioSHaRE-EU consortium was able to compare key characteristics defining the metabolically healthy obese phenotype across ten cohort studies. There is considerable variability in the prevalence of healthy obesity across the different European populations studied, even when unified criteria were used to classify this phenotype.

A Meta-Analysis of Thyroid-Related Traits Reveals Novel Loci and Gender-Specific Differences in the Regulation of Thyroid Function

Thyroid hormone is essential for normal metabolism and development, and overt abnormalities in thyroid function lead to common endocrine disorders affecting approximately 10% of individuals over their life span. In addition, even mild alterations in thyroid function are associated with weight changes, atrial fibrillation, osteoporosis, and psychiatric disorders. To identify novel variants underlying thyroid function, we performed a large meta-analysis of genome-wide association studies for serum levels of the highly heritable thyroid function markers TSH and FT4, in up to 26,420 and 17,520 euthyroid subjects, respectively. Here we report 26 independent associations, including several novel loci for TSH (PDE10A, VEGFA, IGFBP5, NFIA, SOX9, PRDM11, FGF7, INSR, ABO, MIR1179, NRG1, MBIP, ITPK1, SASH1, GLIS3) and FT4 (LHX3, FOXE1, AADAT, NETO1/FBXO15, LPCAT2/CAPNS2). Notably, only limited overlap was detected between TSH and FT4 associated signals, in spite of the feedback regulation of their circulating levels by the hypothalamic-pituitary-thyroid axis. Five of the reported loci (PDE8B, PDE10A, MAF/LOC440389, NETO1/FBXO15, and LPCAT2/CAPNS2) show strong gender-specific differences, which offer clues for the known sexual dimorphism in thyroid function and related pathologies. Importantly, the TSH-associated loci contribute not only to variation within the normal range, but also to TSH values outside the reference range, suggesting that they may be involved in thyroid dysfunction. Overall, our findings explain, respectively, 5.64% and 2.30% of total TSH and FT4 trait variance, and they improve the current knowledge of the regulation of hypothalamic-pituitary-thyroid axis function and the consequences of genetic variation for hypo- or hyperthyroidism.

High plasma lecithin: cholesterol acyltransferase activity does not predict low incidence of cardiovascular events: Possible attenuation of cardioprotection associated with high HDL cholesterol

The cholesterol esterifying enzyme, lecithin:cholesterol acyltransferase (LCAT), is crucial in high density lipoprotein (HDL) metabolism. The role of LCAT activity on incident cardiovascular disease (CVD) is unknown. We determined the association of incident CVD with plasma LCAT activity, and evaluated whether LCAT may modify the cardioprotective effect of higher HDL cholesterol. In a community-based prospective nested case-control study (PREVEND cohort), an exogenous substrate assay was used to measure plasma LCAT activity in 116 men who developed CVD (cases) and in 111 male controls. Plasma LCAT activity was 5% higher in cases (P=0.027) in association with higher total cholesterol, non-HDL cholesterol and triglycerides. Age-adjusted incident CVD was increased with higher LCAT activity (continuous variable: hazard ratio (HR) 1.23; 95% CI 1.01-1.49, P=0.037; upper quartile vs. lowest 3 quartiles: HR 1.60; 95% CI 1.07-2.39, P=0.021). This relationship was not significant after adjustment for lipids. Compared to subjects with HDL cholesterol above the median and lower LCAT activity (lowest 3 quartiles) the age-adjusted cardiovascular risk was elevated in subjects with similarly higher HDL cholesterol and higher LCAT activity (HR 2.38; 95% CI 1.27-4.49, P=0.007), lower HDL cholesterol and lower LCAT activity (HR 2.58; 95% CI 1.64-4.49, P<0.001) and lower HDL cholesterol and higher LCAT activity (HR 2.76; 95% CI 1.58-4.83, P<0.001). These HRs were unchanged after non-HDL cholesterol and triglyceride adjustment. In conclusion, high plasma LCAT activity does not predict reduced CVD risk, and may attenuate cardioprotection associated with higher HDL cholesterol.

Associations between smoking, components of metabolic syndrome and lipoprotein particle size

BackgroundThe clustering of metabolic and cardiovascular risk factors is known as metabolic syndrome (MetS). The risk of having MetS is strongly associated with increased adiposity and can be further modified by smoking behavior. Apolipoproteins (apo) associated with low-density lipoprotein-cholesterol (LDL-C) and high-density lipoprotein-cholesterol (HDL-C) may be altered in MetS. This study aimed to examine the association between smoking and the following parameters: MetS and its components, levels of apolipoproteins and estimated lipoprotein particle size, separately for men and women, and in different body mass index (BMI) classes.MethodsWe included 24,389 men and 35,078 women aged between 18 and 80 years who participated in the LifeLines Cohort Study between December 2006 and January 2012; 5,685 men and 6,989 women were current smokers. Participants were categorized into three different body mass index (BMI) classes (BMI <25; BMI 25 to 30; BMI ≥30 kg/m2). MetS was defined according to the National Cholesterol Education Program’s Adult Treatment Panel III (NCEP:ATPIII) criteria. Blood pressure, anthropometric and lipid measurements were rigorously standardized, and the large sample size enabled a powerful estimate of quantitative changes. The association between smoking and the individual MetS components, and apoA1 and apoB, was tested with linear regression. Logistic regression was used to examine the effect of smoking and daily tobacco smoked on risk of having MetS. All models were age adjusted and stratified by sex and BMI class.ResultsPrevalence of MetS increased with higher BMI levels. A total of 64% of obese men and 42% of obese women had MetS. Current smoking was associated with a higher risk of MetS in both sexes and all BMI classes (odds ratio 1.7 to 2.4 for men, 1.8 to 2.3 for women, all P values <0.001). Current smokers had lower levels of HDL cholesterol and apoA1, higher levels of triglycerides and apoB, and higher waist circumference than non-smokers (all P <0.001). Smoking had no consistent association with blood pressure or fasting blood glucose. In all BMI classes, we found a dose-dependent association of daily tobacco consumption with MetS prevalence as well as with lower levels of HDL cholesterol, higher triglyceride levels and lower ratios of HDL cholesterol/apoA1 and, only in those with BMI <30, LDL cholesterol/apoB (all P <0.001).ConclusionsSmoking is associated with an increased prevalence of MetS, independent of sex and BMI class. This increased risk is mainly related to lower HDL cholesterol, and higher triglycerides and waist circumference. In addition, smoking was associated with unfavorable changes in apoA1 and apoB, and in lipoprotein particle size.Please see related commentary: http://www.biomedcentral.com/1741-7015/11/196.

Combined effects of smoking and alcohol on metabolic syndrome: The LifeLines cohort study

Introduction The development of metabolic syndrome (MetS) is influenced by environmental factors such as smoking and alcohol consumption. We determined the combined effects of smoking and alcohol on MetS and its individual components. Methods 64,046 participants aged 18–80 years from the LifeLines Cohort study were categorized into three body mass index (BMI) classes (BMI<25, normal weight; BMI 25–30, overweight; BMI≥30 kg/m2, obese). MetS was defined according to the revised criteria of the National Cholesterol Education Program’s Adult Treatment Panel III (NCEP ATP III). Within each BMI class and smoking subgroup (non-smoker, former smoker, <20 and ≥20 g tobacco/day), the cross-sectional association between alcohol and individual MetS components was tested using regression analysis. Results Prevalence of MetS varied greatly between the different smoking-alcohol subgroups (1.7–71.1%). HDL cholesterol levels in all alcohol drinkers were higher than in non-drinkers (0.02 to 0.29 mmol/L, P values<0.001). HDL cholesterol levels were lower when they were also a former or current smoker (<20 and ≥20 g tobacco/day). Consumption of ≤1 drink/day indicated a trend towards lower triglyceride levels (non-significant). Concurrent use alcohol (>1 drink/day) and tobacco showed higher triglycerides levels. Up to 2 drinks/day was associated with a smaller waist circumference in overweight and obese individuals. Consumption of >2 drinks/day increased blood pressure, with the strongest associations found for heavy smokers. The overall metabolic profile of wine drinkers was better than that of non-drinkers or drinkers of beer or spirits/mixed drinks. Conclusion Light alcohol consumption may moderate the negative associations of smoking with MetS. Our results suggest that the lifestyle advice that emphasizes smoking cessation and the restriction of alcohol consumption to a maximum of 1 drink/day, is a good approach to reduce the prevalence of MetS.

Type 2 diabetes mellitus: prevention of macrovascular complications

Type 2 diabetes mellitus is a disease that affects a rapidly increasing number of patients. Most patients with Type 2 diabetes will develop vascular complications. This may be microvascular disease, such as nephropathy, retinopathy or polyneuropathy, and also macrovascular disease, such as coronary heart disease, stroke or peripheral artery disease. Optimal control of elevated blood glucose levels will reduce the symptoms of hyperglycemia and help to prevent the development of complications. In addition, treatment of hypertension and lipid disturbances has been shown to reduce the incidence and severity of vascular complications significantly. The current treatment goals focus on adequate and aggressive treatment of these three risk factors. The central dogma for treatment of blood glucose, blood pressure and cholesterol levels is ‘the lower the better’. Ongoing trials evaluate the effect of further lowering these treatment goals and of specific types of medication on cardiovascular events.

Lifestyle and clinical determinants of skin autofluorescence in a population-based cohort study

Skin autofluorescence (SAF) is a noninvasive marker of advanced glycation end products (AGEs). In diabetes, higher SAF levels have been positively associated with long‐term complications, cardiovascular morbidity and mortality. Because little is known about the factors that influence SAF in nondiabetic individuals, we assessed the association of clinical and lifestyle parameters with SAF as well as their interactions in a large‐scale, nondiabetic population and performed the same analysis in a type 2 diabetic subgroup.

GWAS identifies an NAT2 acetylator status tag single nucleotide polymorphism to be a major locus for skin fluorescence

Aims/hypothesisSkin fluorescence (SF) is a non-invasive marker of AGEs and is associated with the long-term complications of diabetes. SF increases with age and is also greater among individuals with diabetes. A familial correlation of SF suggests that genetics may play a role. We therefore performed parallel genome-wide association studies of SF in two cohorts.MethodsCohort 1 included 1,082 participants, 35–67xa0years of age with type 1 diabetes. Cohort 2 included 8,721 participants without diabetes, aged 18–90xa0years.Resultsrs1495741 was significantly associated with SF in Cohort 1 (pu2009<u20096u2009×u200910−10), which is known to tag the NAT2 acetylator phenotype. The fast acetylator genotype was associated with lower SF, explaining up to 15% of the variance. In Cohort 2, the top signal associated with SF (pu2009=u20098.3u2009×u200910−42) was rs4921914, also in NAT2, 440 bases upstream of rs1495741 (linkage disequilibrium r2u2009=u20091.0 for rs4921914 with rs1495741). We replicated these results in two additional cohorts, one with and one without type 1 diabetes. Finally, to understand which compounds are contributing to the NAT2–SF signal, we examined 11 compounds assayed from skin biopsies (nu2009=u2009198): the fast acetylator genotype was associated with lower levels of the AGEs hydroimidazolones of glyoxal (pu2009=u20090.017).Conclusions/interpretationWe identified a robust association between NAT2 and SF in people with and without diabetes. Our findings provide proof of principle that genetic variation contributes to interindividual SF and that NAT2 acetylation status plays a major role.

Thyroid hormone status and health-related quality of life in the LifeLines Cohort Study

BACKGROUNDnThyroid disorders are prevalent in Western society, yet many subjects experience limited symptoms at diagnosis, especially in hypothyroidism. We hypothesize that health-related quality of life (HR-QOL) is more severely impaired in subjects with more abnormal thyroid hormone function tests.nnnMETHODSnThis is a cross-sectional study of Dutch adults participating in the LifeLines Cohort Study between December 2009 and August 2010. In 9491 Western European participants (median age 45 years; 3993 men and 5498 women), without current or former use of thyroid medication, we compared HR-QOL using the RAND 36-Item Health Survey between subjects with normal thyrotropin (TSH) values and subjects with disturbed thyroid hormone status (serum TSH, free thyroxine, and free triiodothyronine). The influence of possible confounders (age, smoking, co-morbidity) on HR-QOL was evaluated as well.nnnRESULTSnSuppressed TSH values (TSH < 0.5 mU/L) were found in 114 (1.2%), while 8334 (88.8%) had TSH within the normal range, 973 participants (10.3%) had TSH between 4 and 10 mU/L, and 70 (0.7%) had TSH > 10 mU/L. Men had a higher HR-QOL than women (70-92 vs. 65-89; p < 0.001), except for the domain general health (72 vs. 72; p = 0.692). Men with suppressed or elevated TSH values did not score significantly lower than euthyroid men for any of nine domains of the RAND 36-Item Health Survey. Compared with euthyroid women, women with suppressed TSH scored significantly lower in the domains physical functioning (84 vs. 89, p = 0.013) and general health (67 vs. 72, p = 0.036). Women with markedly elevated TSH (> 10 mU/L) had a score in all HR-QOL domains that was similar to that of women with normal TSH values. There were no differences in the physical component score and the mental component score between any of the TSH groups. Physical component score and mental component score were mainly determined by smoking status, co-morbidity, and body mass index or waist circumference.nnnCONCLUSIONSnIn this population-based study, HR-QOL scores of subjects with suppressed TSH values or markedly elevated TSH values were generally not significantly lower than those of subjects with normal or mildly elevated TSH values.

Health-Related Quality of Life in Relation to Obesity Grade, Type 2 Diabetes, Metabolic Syndrome and Inflammation

Background Health-related quality of life (HR-QoL) may be compromised in obese individuals, depending on the presence of other complications. The aim of this study is to assess the effect of obesity-related conditions on HR-QoL. These conditions are i) grade of obesity with and without type 2 diabetes (T2D), ii) metabolic syndrome (MetS), and iii) level of inflammation. Methods From the Dutch LifeLines Cohort Study we included 13,686 obese individuals, aged 18–80 years. HR-QoL was measured with the RAND 36-Item Health Survey which encompasses eight health domains. We calculated the percentage of obese individuals with poor HR-QoL, i.e. those scoring below the domain and sex specific cut-off value derived from the normal weight population. Logistic regression analysis was used to calculate the probability of having poor domain scores according to the conditions under study. Results Higher grades of obesity and the additional presence of T2D were associated with lower HR-QoL, particularly in the domains physical functioning (men: odds ratios (ORs) 1.48–11.34, P<0.005, and women: ORs 1.66–5.05, P<0.001) and general health (men: ORs 1.44–3.07, P<0.005, and women: ORs 1.36–3.73, P<0.001). A higher percentage of obese individuals with MetS had a poor HR-QoL than those without MetS. Furthermore, we observed a linear trend between inflammation and the percentage of obese individuals with poor scores on the HR-QoL domains. Individuals with MetS were more likely to have poor scores in the domains general health, vitality, social functioning and role limitations due to emotional problems. Obese women with increased inflammation levels were more likely to have poor scores on all domains except role limitations due to emotional problems and mental health. Conclusions The impact of obesity on an individual’s quality of life is enhanced by grade of obesity, T2D, MetS and inflammation and are mainly related to reduced physical health. The mental well-being is less often impaired.