Milk intake and incident stroke and CHD in populations of European descent: a Mendelian randomisation study.

Higher milk intake has been associated with a lower stroke risk, but not with risk of CHD. Residual confounding or reverse causation cannot be excluded. Therefore, we estimated the causal association of milk consumption with stroke and CHD risk through instrumental variable (IV) and gene-outcome analyses. IV analysis included 29 328 participants (4611 stroke; 9828 CHD) of the European Prospective Investigation into Cancer and Nutrition (EPIC)-CVD (eight European countries) and European Prospective Investigation into Cancer and Nutrition-Netherlands (EPIC-NL) case-cohort studies. rs4988235, a lactase persistence (LP) SNP which enables digestion of lactose in adulthood was used as genetic instrument. Intake of milk was first regressed on rs4988235 in a linear regression model. Next, associations of genetically predicted milk consumption with stroke and CHD were estimated using Prentice-weighted Cox regression. Gene-outcome analysis included 777 024 participants (50 804 cases) from MEGASTROKE (including EPIC-CVD), UK Biobank and EPIC-NL for stroke, and 483 966 participants (61 612 cases) from CARDIoGRAM, UK Biobank, EPIC-CVD and EPIC-NL for CHD. In IV analyses, each additional LP allele was associated with a higher intake of milk in EPIC-CVD (ß = 13·7 g/d; 95 % CI 8·4, 19·1) and EPIC-NL (36·8 g/d; 95 % CI 20·0, 53·5). Genetically predicted milk intake was not associated with stroke (HR per 25 g/d 1·05; 95 % CI 0·94, 1·16) or CHD (1·02; 95 % CI 0·96, 1·08). In gene-outcome analyses, there was no association of rs4988235 with risk of stroke (OR 1·02; 95 % CI 0·99, 1·05) or CHD (OR 0·99; 95 % CI 0·95, 1·03). Current Mendelian randomisation analysis does not provide evidence for a causal inverse relationship between milk consumption and stroke or CHD risk.

Established BMI-associated genetic variants and their prospective associations with BMI and other cardiometabolic traits: the GLACIER Study.

BACKGROUND: Recent cross-sectional genome-wide scans have reported associations of 97 independent loci with body mass index (BMI). In 3541 middle-aged adult participants from the GLACIER Study, we tested whether these loci are associated with 10-year changes in BMI and other cardiometabolic traits (fasting and 2-h glucose, triglycerides, total cholesterol, and systolic and diastolic blood pressures). METHODS: A BMI-specific genetic risk score (GRS) was calculated by summing the BMI-associated effect alleles at each locus. Trait-specific cardiometabolic GRSs comprised only the loci that show nominal association (P⩽0.10) with the respective trait in the original cross-sectional study. In longitudinal genetic association analyses, the second visit trait measure (assessed ~10 years after baseline) was used as the dependent variable and the models were adjusted for the baseline measure of the outcome trait, age, age(2), fasting time (for glucose and lipid traits), sex, follow-up time and population substructure. RESULTS: The BMI-specific GRS was associated with increased BMI at follow-up (ß=0.014 kg m(-2) per allele per 10-year follow-up, s.e.=0.006, P=0.019) as were three loci (PARK2 rs13191362, P=0.005; C6orf106 rs205262, P=0.043; and C9orf93 rs4740619, P=0.01). Although not withstanding Bonferroni correction, a handful of single-nucleotide polymorphisms was nominally associated with changes in blood pressure, glucose and lipid levels. CONCLUSIONS: Collectively, established BMI-associated loci convey modest but statistically significant time-dependent associations with long-term changes in BMI, suggesting a role for effect modification by factors that change with time in this population.

Inverse relationship between a genetic risk score of 31 BMI loci and weight change before and after reaching middle age.

BACKGROUND/OBJECTIVE: Genome-wide-association studies have identified numerous body mass index (BMI)-associated variants, but it is unclear how these relate to weight gain in adults at different ages. METHODS: We examined the association of a genetic risk score (GRS), consisting of 31 BMI-associated variants, with an annual weight change (AWC) and a substantial weight gain (SWG) of 10% by comparing self-reported weight at 20 years (y) with baseline weight (mean: 58 y; s.d.: 8 y) in 21407 participants from the Malmö Diet and Cancer Study (MDCS), and comparing baseline weight to weight at follow-up (mean: 73 y; s.d.: 6 y) among 2673 participants. Association between GRS and AWG and SWG was replicated in 4327 GLACIER (Gene x Lifestyle interactions And Complex traits Involved in Elevated disease Risk) participants (mean: 45 y; s.d.: 7 y) with 10 y follow-up. Cohort-specific results were pooled by fixed-effect meta-analyses. RESULTS: In MDCS, the GRS was associated with increased AWC (ß: 0.003; s.e: 0.01; P: 7 × 10(-8)) and increased odds for SWG (odds ratio (OR) 1.01 (95% confidence interval (CI): 1.00, 1.02); P: 0.013) per risk-allele from age 20y, but unexpectedly with decreased AWC (ß: -0.006; s.e: 0.002; P: 0.009) and decreased odds for SWG OR 0.96 (95% CI: 0.93, 0.98); P: 0.001) between baseline and follow-up. Effect estimates from age 20 y to baseline differed significantly from those from baseline to follow-up (P: 0.0002 for AWC and P: 0.0001 for SWG). Similar to MDCS, the GRS was associated with decreased odds for SWG OR 0.98 (95% CI: 0.96, 1.00); P: 0.029) from baseline to follow-up in GLACIER. In meta-analyses (n=7000), the GRS was associated with decreased AWC (ß: -0.005; s.e.m. 0.002; P: 0.002) and decreased odds for SWG OR 0.97 (95% CI: 0.96, 0.99); P: 0.001) per risk-allele. CONCLUSIONS: Our results provide convincing evidence for a paradoxical inversed relationship between a high number of BMI-associated risk-alleles and less weight gain during and after middle-age, in contrast to the expected increased weight gain seen in younger age.

A novel interaction between the FLJ33534 locus and smoking in obesity: a genome-wide study of 14 131 Pakistani adults.

BACKGROUND: Obesity is a complex disease caused by the interplay of genetic and lifestyle factors, but identification of gene-lifestyle interactions in obesity has remained challenging. Few large-scale studies have reported use of genome-wide approaches to investigate gene-lifestyle interactions in obesity. METHODS: In the Pakistan Risk of Myocardial Infraction Study, a cross-sectional study based in Pakistan, we calculated body mass index (BMI) variance estimates (square of the residual of inverse-normal transformed BMI z-score) in 14 131 participants and conducted genome-wide heterogeneity of variance analyses (GWHVA) for this outcome. All analyses were adjusted for age, age(2), sex and genetic ancestry. RESULTS: The GWHVA analyses identified an intronic variant, rs140133294, in the FLJ33544 gene in association with BMI variance (P-value=3.1 × 10(-8)). In explicit tests of gene × lifestyle interaction, smoking was found to significantly modify the effect of rs140133294 on BMI (Pinteraction=0.0005), whereby the minor allele (T) was associated with lower BMI in current smokers, while positively associated with BMI in never smokers. Analyses of ENCODE data at the FLJ33534 locus revealed features indicative of open chromatin and high confidence DNA-binding motifs for several transcription factors, providing suggestive biological support for a mechanism of interaction. CONCLUSIONS: In summary, we have identified a novel interaction between smoking and variation at the FLJ33534 locus in relation to BMI in people from Pakistan.

Differences between men and women in the regulation of adipose 11ß-HSD1 and in its association with adiposity and insulin resistance.

This study explored sex differences in 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) activity and gene expression in isolated adipocytes and adipose tissue (AT), obtained via subcutaneous biopsies from non-diabetic subjects [58 M, 64 F; age 48.3 ± 15.3 years, body mass index (BMI) 27.2 ± 3.9 kg/m²]. Relationships with adiposity and insulin resistance (IR) were addressed. Males exhibited higher 11ß-HSD1 activity in adipocytes than females, but there was no such difference for AT. In both men and women, adipocyte 11ß-HSD1 activity correlated positively with BMI, waist circumference, % body fat, adipocyte size and with serum glucose, triglycerides and low-density lipoprotein:high-density lipoprotein (LDL:HDL) ratio. Positive correlations with insulin, HOMA-IR and haemoglobin A1c (HbA1c) and a negative correlation with HDL-cholesterol were significant only in males. Conversely, 11ß-HSD1 activity in AT correlated with several markers of IR and adiposity in females but not in males, but the opposite pattern was found with respect to 11ß-HSD1 mRNA expression. This study suggests that there are sex differences in 11ß-HSD1 regulation and in its associations with markers of obesity and IR.

Hydrochlorothiazide compared to candesartan treatment increases adipose tissue gene expression and circulating levels of serum amyloid A in hypertensive patients.

Treatment of hypertension with angiotensin receptor blockers has been shown to reduce the risk of developing type 2 diabetes in comparison to thiazide diuretics and beta adrenergic blockers. Therefore, we wanted to study the effect of antihypertensive drugs on adipose tissue with respect to insulin resistance. In the MEDICA (MEchanisms for the DIabetes preventing effects of CAndesartan) study, 22 hypertensive, nondiabetic patients with abdominal obesity (10 men, 12 women) were randomized into 12-week treatment periods with candesartan, hydrochlorothiazide, and placebo according to a 3-way cross-over design. Subcutaneous adipose tissue biopsies were taken after 8 weeks treatment to analyze gene expression, glucose uptake capacity, insulin-signaling, and adipocyte size. Adipose tissue gene expression of serum amyloid A (SAA) was higher after hydrochlorothiazide treatment compared to candesartan (p=0.036), and this was in accordance with our previous finding on circulating SAA levels. Serum levels of E selectin were increased after hydrochlorothiazide compared to candesartan treatment (p=0.002) and lower after candesartan compared to placebo (p=0.002). In adipocytes, there were no significant differences between the treatments with respect to cell size, glucose uptake capacity, or insulin-signaling. In comparison to candesartan, hydrochlorothiazide raised the adipose tissue gene expression of SAA and the serum level of SAA as well as E selectin in hypertensive patients. Less adipose and systemic inflammation may be one explanation why candesartan is favorable in comparison to thiazide diuretics with respect to development of insulin resistance and type 2 diabetes.

Evaluating the discriminative power of multi-trait genetic risk scores for type 2 diabetes in a northern Swedish population.

AIMS/HYPOTHESIS: We determined whether single nucleotide polymorphisms (SNPs) previously associated with diabetogenic traits improve the discriminative power of a type 2 diabetes genetic risk score. METHODS: Participants (n = 2,751) were genotyped for 73 SNPs previously associated with type 2 diabetes, fasting glucose/insulin concentrations, obesity or lipid levels, from which five genetic risk scores (one for each of the four traits and one combining all SNPs) were computed. Type 2 diabetes patients and non-diabetic controls (n = 1,327/1,424) were identified using medical records in addition to an independent oral glucose tolerance test. RESULTS: Model 1, including only SNPs associated with type 2 diabetes, had a discriminative power of 0.591 (p < 1.00 x 10(-20) vs null model) as estimated by the area under the receiver operator characteristic curve (ROC AUC). Model 2, including only fasting glucose/insulin SNPs, had a significantly higher discriminative power than the null model (ROC AUC 0.543; p = 9.38 x 10(-6) vs null model), but lower discriminative power than model 1 (p = 5.92 x 10(-5)). Model 3, with only lipid-associated SNPs, had significantly higher discriminative power than the null model (ROC AUC 0.565; p = 1.44 x 10(-9)) and was not statistically different from model 1 (p = 0.083). The ROC AUC of model 4, which included only obesity SNPs, was 0.557 (p = 2.30 x 10(-7) vs null model) and smaller than model 1 (p = 0.025). Finally, the model including all SNPs yielded a significant improvement in discriminative power compared with the null model (p < 1.0 x 10(-20)) and model 1 (p = 1.32 x 10(-5)); its ROC AUC was 0.626. CONCLUSIONS/INTERPRETATION: Adding SNPs previously associated with fasting glucose, insulin, lipids or obesity to a genetic risk score for type 2 diabetes significantly increases the power to discriminate between people with and without clinically manifest type 2 diabetes compared with a model including only conventional type 2 diabetes loci.

Assessing the effect of interaction between an FTO variant (rs9939609) and physical activity on obesity in 15,925 Swedish and 2,511 Finnish adults.

AIMS/HYPOTHESIS: Recent reports have suggested that genotypes at the FTO locus interact with physical activity to modify levels of obesity-related traits. We tested this hypothesis in two non-diabetic population-based cohorts, the first from southern Sweden and the second from the Botnia region of western Finland. METHODS: In total 2,511 Finnish and 15,925 Swedish non-diabetic middle-aged adults were genotyped for the FTO rs9939609 variant. Physical activity was assessed by questionnaires and standard clinical procedures were conducted, including measures of height and weight and glucose regulation. Tests of gene x physical activity interaction were performed using linear interaction effects to determine whether the effect of this variant on BMI is modified by physical activity. RESULTS: The minor A allele at rs9939609 was associated with higher BMI in both cohorts, with the per allele difference in BMI being about 0.13 and 0.43 kg/m(2) in the Swedish and Finnish cohorts, respectively (p < 0.0001). The test of interaction between physical activity and the rs9939609 variant on BMI was not statistically significant after controlling for age and sex in either cohort (Sweden: p = 0.71, Finland: p = 0.18). CONCLUSIONS/INTERPRETATION: The present report does not support the notion that physical activity modifies the effects of the FTO rs9939609 variant on obesity risk in the non-diabetic Swedish or Finnish adults studied here.

Factors in serum from type 2 diabetes patients can cause cellular insulin resistance.

This pilot study was aimed to investigate whether there are humoral factors in serum from type 2 diabetic subjects that, in addition to glucose, insulin and free fatty acids are able to induce or contribute to peripheral insulin resistance with respect to glucose transport. Isolated subcutaneous adipocytes from 11 type 2 diabetic subjects and 10 nondiabetic controls were incubated for 24-h in medium supplemented with 25 % serum from a control or a type 2 diabetic donor, in the presence of a low (5 mM) or a high (15 mM) glucose concentration, respectively. After the incubation period glucose uptake capacity was assessed. Serum from type 2 diabetic donors, compared to serum from controls, significantly reduced the maximal insulin eff ect to stimulate glucose uptake (approximately 40 %, p < 0.05) in adipocytes from control subjects, independent of surrounding glucose concentrations. Glucose uptake capacity in adipocytes isolated from type 2 diabetic subjects was similar regardless of culture condition. No significant alterations were found in cellular content of key proteins in the insulin signaling cascade (insulin receptor substrate-1 and -2, and glucose transporter 4) that could explain the impaired insulin-stimulated glucose transport in control adipocytes incubated with serum from type 2 diabetic donors. The present findings indicate the presence of biomolecules in the circulation of type 2 diabetic subjects, apart from glucose, insulin, and free fatty acids with the ability to induce peripheral insulin resistance. This further implies that even though normoglycemia is achieved other circulating factors can still negatively affect insulin sensitivity in type 2 diabetic patients.

Fat cell enlargement is an independent marker of insulin resistance and 'hyperleptinaemia'.

AIMS/HYPOTHESIS: The aim of this study was to explore whether fat cell size in human subcutaneous and omental adipose tissue is independently related to insulin action and adipokine levels. MATERIALS AND METHODS: Fat cells were prepared from abdominal subcutaneous biopsies obtained from 49 type 2 diabetic and 83 non-diabetic subjects and from omental biopsies obtained from 37 non-diabetic subjects. Cell size and insulin action on glucose uptake capacity in vitro were assessed in isolated fat cells. Insulin sensitivity in vivo was assessed with euglycaemic-hyperinsulinaemic clamps. Fasting blood samples were collected and adipokines and NEFA were measured. RESULTS: Negative correlations were found between subcutaneous fat cell size and insulin sensitivity assessed as M-value during clamp and as insulin action on glucose uptake in fat cells in vitro. This was seen in non-diabetic subjects after including age, sex and BMI in the analyses. No such relationship was found in type 2 diabetic subjects. In both groups, subcutaneous fat cell size correlated positively and independently with plasma levels of leptin but not to any of the other assessed adipokines. In non-diabetic subjects, omental fat cell size was independently and negatively correlated with insulin action in subcutaneous, but not omental, fat cells in vitro. CONCLUSIONS/INTERPRETATION: Fat cell enlargement is associated with insulin resistance in non-diabetic individuals independently of BMI. This was not seen in type 2 diabetic subjects, suggesting that after development of type 2 diabetes other factors, not related to fat cell size, become more important for the modulation of insulin resistance.