Weight Loss Is Associated With Increased NAD(+)/SIRT1 Expression But Reduced PARP Activity in White Adipose Tissue

CONTEXT

Sirtuins (SIRTs) and poly(ADP-ribose) polymerases (PARPs) are 2 important nicotinamide adenine dinucleotide (NAD)(+)-dependent enzyme families with opposing metabolic effects. Energy shortage increases NAD(+) biosynthesis and SIRT activity but reduces PARP activity in animals. Effects of energy balance on these pathways in humans are unknown.

OBJECTIVE

We compared NAD(+)/SIRT pathway expressions and PARP activities in sc adipose tissue (SAT) between lean and obese subjects and investigated their change in the obese subjects during a 12-month weight loss.

DESIGN, SETTING AND PARTICIPANTS

SAT biopsies were obtained from 19 clinically healthy obese subjects (mean ± SE body mass index, 34.6 ± 2.7 kg/m(2)) during a weight-loss intervention (0, 5, and 12 mo) and from 19 lean reference subjects (body mass index, 22.7 ± 1.1 kg/m(2)) at baseline.

MAIN OUTCOME MEASURES

SAT mRNA expressions of SIRTs 1-7 and the rate-limiting gene in NAD(+) biosynthesis, nicotinamide phosphoribosyltransferase (NAMPT) were measured by Affymetrix, and total PARP activity by ELISA kit.

RESULTS

SIRT1, SIRT3, SIRT7, and NAMPT expressions were significantly lower, whereas total PARP activity was increased in obese compared with lean subjects. SIRT1 and NAMPT expressions increased in obese subjects between 0 and 5 months, after a mean weight loss of 11.7%. In subjects who continued to lose weight between 5 and 12 months, SIRT1 expression increased progressively, whereas in subjects with weight regain, SIRT1 reverted to baseline levels. PARP activity significantly decreased in all subjects upon weight loss.

CONCLUSIONS

Calorie restriction is an attractive strategy to improve the NAD(+)/SIRT pathway and decrease PARPs in SAT in human obesity.

Obesity Is Associated With Low NAD(+)/SIRT Pathway Expression in Adipose Tissue of BMI-Discordant Monozygotic Twins

CONTEXT

Sirtuins (SIRTs) regulate cellular metabolism and mitochondrial function according to the energy state of the cell reflected by NAD(+) levels.

OBJECTIVE

Our aim was to determine whether expressions of SIRTs and NAD(+) biosynthesis genes are affected by acquired obesity and how possible alterations are connected with metabolic dysfunction while controlling for genetic and familial factors.

DESIGN AND PARTICIPANTS

We studied a cross-sectional sample of 40 healthy pairs of monozygotic twins, including 26 pairs who were discordant for body mass index (within-pair difference > 3 kg/m(2)), from the FinnTwin12 and FinnTwin16 cohorts.

MAIN OUTCOME MEASURES

Subcutaneous adipose tissue (SAT) transcriptomics was analyzed by using Affymetrix U133 Plus 2.0 chips, total SAT (poly-ADP) ribose polymerase (PARP) activity by an ELISA kit, body composition by dual-energy x-ray absorptiometry and magnetic resonance imaging/spectroscopy, and insulin sensitivity by an oral glucose tolerance test.

RESULTS

SIRT1, SIRT3, SIRT5, NAMPT, NMNAT2, NMNAT3, and NRK1 expressions were significantly down-regulated and the activity of main cellular NAD(+) consumers, PARPs, trended to be higher in the SAT of heavier co-twins of body mass index-discordant pairs. Controlling for twin-shared factors, SIRT1, SIRT3, NAMPT, NMNAT3, and NRK1 were significantly negatively correlated with adiposity, SIRT1, SIRT5, NMNAT2, NMNAT3, and NRK1 were negatively correlated with inflammation, and SIRT1 and SIRT5 were positively correlated with insulin sensitivity. Expressions of genes involved in mitochondrial unfolded protein response were also significantly down-regulated in the heavier co-twins.

CONCLUSIONS

Our data highlight a strong relationship of reduced NAD(+)/SIRT pathway expression with acquired obesity, inflammation, insulin resistance, and impaired mitochondrial protein homeostasis in SAT.

Long-term outcome in anorexia nervosa in the community

OBJECTIVE

Few studies have assessed outcomes of anorexia nervosa (AN) outside clinical settings. We aimed to assess mortality, recovery, and socio-demographic outcomes of AN in a community sample.

METHOD

Women in the nationwide FinnTwin16 cohort (born 1975-1979) were followed for 10 years after baseline diagnostic assessment (mean age at follow-up 34 years, N = 2188). We compared women with lifetime DSM-IV AN (N = 40) with unaffected women from the same cohort.

RESULTS

None of the women with AN had died and 88% were weight-recovered (BMI ≥ 18.5 kg/m(2) ), but their mean BMI (22.0 kg/m(2) ) was lower than among unaffected women (24.0 kg/m(2) , p = 0.008). University degrees (38 vs. 29%, p = 0.26), sickness absence during the past year (median 5 vs. 3 days, p = 0.21), or unemployment or disability pension (5 vs. 4%, p = 0.62) did not significantly differ between AN probands and their unaffected peers. More women with AN were still studying (15 vs. 4%, p = 0.003), and half of them had children, as compared to 66% of unaffected women (p = 0.05).

DISCUSSION

The long-term prognosis of AN in the community appears promising. Weight-restoration is common and socio-demographic outcomes are generally favorable. However, women with a history of AN may be less likely to have children.

DNA methylation and gene expression patterns in adipose tissue differ significantly within young adult monozygotic BMI-discordant twin pairs

BACKGROUND

Little is known about epigenetic alterations associated with subcutaneous adipose tissue (SAT) in obesity. Our aim was to study genome-wide DNA methylation and gene expression differences in SAT in monozygotic (MZ) twin pairs who are discordant for body mass index (BMI). This design completely matches lean and obese groups for genetic background, age, gender and shared environment.

METHODS

14We analyzed DNA methylome and gene expression from SAT, together with body composition (magnetic resonance imaging/spectroscopy) and glucose tolerance test, lipids and C-reactive protein from 26 rare BMI-discordant (intrapair difference in BMI ⩾3 kg m(-2)) MZ twin pairs identified from 10 birth cohorts of young adult Finnish twins.

RESULTS

We found 17 novel obesity-associated genes that were differentially methylated across the genome between heavy and lean co-twins. Nine of them were also differentially expressed. Pathway analyses indicated that dysregulation of SAT in obesity includes a paradoxical downregulation of lipo/adipogenesis and upregulation of inflammation and extracellular matrix remodeling. Furthermore, CpG sites whose methylation correlated with metabolically harmful fat depots (intra-abdominal and liver fat) also correlated with measures of insulin resistance, dyslipidemia and low-grade inflammation, thus suggesting that epigenetic alterations in SAT are associated with the development of unhealthy obesity.

CONCLUSION

This is the first study in BMI-discordant MZ twin pairs reporting genome-wide DNA methylation and expression profiles in SAT. We found a number of novel genes and pathways whose methylation and expression patterns differ within the twin pairs, suggesting that the pathological adaptation of SAT to obesity is, at least in part, epigenetically regulated.

Impaired Mitochondrial Biogenesis in Adipose Tissue in Acquired Obesity

Low mitochondrial number and activity have been suggested as underlying factors in obesity, type 2 diabetes, and metabolic syndrome. However, the stage at which mitochondrial dysfunction manifests in adipose tissue after the onset of obesity remains unknown. Here we examined subcutaneous adipose tissue (SAT) samples from healthy monozygotic twin pairs, 22.8-36.2 years of age, who were discordant (ΔBMI >3 kg/m(2), mean length of discordance 6.3 ± 0.3 years, n = 26) and concordant (ΔBMI <3 kg/m(2), n = 14) for body weight, and assessed their detailed mitochondrial metabolic characteristics: mitochondrial-related transcriptomes with dysregulated pathways, mitochondrial DNA (mtDNA) amount, mtDNA-encoded transcripts, and mitochondrial oxidative phosphorylation (OXPHOS) protein levels. We report global expressional downregulation of mitochondrial oxidative pathways with concomitant downregulation of mtDNA amount, mtDNA-dependent translation system, and protein levels of the OXPHOS machinery in the obese compared with the lean co-twins. Pathway analysis indicated downshifting of fatty acid oxidation, ketone body production and breakdown, and the tricarboxylic acid cycle, which inversely correlated with adiposity, insulin resistance, and inflammatory cytokines. Our results suggest that mitochondrial biogenesis, oxidative metabolic pathways, and OXPHOS proteins in SAT are downregulated in acquired obesity, and are associated with metabolic disturbances already at the preclinical stage.

Genome-wide blood DNA methylation alterations at regulatory elements and heterochromatic regions in monozygotic twins discordant for obesity and liver fat

Background

The current epidemic of obesity and associated diseases calls for swift actions to better understand the mechanisms by which genetics and environmental factors affect metabolic health in humans. Monozygotic (MZ) twin pairs showing discordance for obesity suggest that epigenetic influences represent one such mechanism. We studied genome-wide leukocyte DNA methylation variation in 30 clinically healthy young adult MZ twin pairs discordant for body mass index (BMI; average within-pair BMI difference: 5.4 ± 2.0 kg/m²).

Results

There were no differentially methylated cytosine-guanine (CpG) sites between the co-twins discordant for BMI. However, stratification of the twin pairs based on the level of liver fat accumulation revealed two epigenetically highly different groups. Significant DNA methylation differences (n = 1,236 CpG sites (CpGs)) between the co-twins were only observed if the heavier co-twins had excessive liver fat (n = 13 twin pairs). This unhealthy pattern of obesity was coupled with insulin resistance and low-grade inflammation. The differentially methylated CpGs included 23 genes known to be associated with obesity, liver fat, type 2 diabetes mellitus (T2DM) and metabolic syndrome, and potential novel metabolic genes. Differentially methylated CpG sites were overrepresented at promoters, insulators, and heterochromatic and repressed regions. Based on predictions by overlapping histone marks, repressed and weakly transcribed sites were significantly more often hypomethylated, whereas sites with strong enhancers and active promoters were hypermethylated. Further, significant clustering of differentially methylated genes in vitamin, amino acid, fatty acid, sulfur, and renin-angiotensin metabolism pathways was observed.

Conclusions

The methylome in leukocytes is altered in obesity associated with metabolic disturbances, and our findings indicate several novel candidate genes and pathways in obesity and obesity-related complications.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-015-0073-5) contains supplementary material, which is available to authorized users.

High prevalence of chronic kidney disease in Finnish patients with type 2 diabetes treated in primary care

OBJECTIVE

To examine the prevalence of chronic kidney disease (CKD) and related cardiovascular morbidity in a cross-sectional population in patients with type 2 diabetes (T2D) treated in a primary care setting in Finland.

RESEARCH DESIGN AND METHODS

Data were collected and recorded from 42 primary care centres, which recruited 629 patients diagnosed with type 2 diabetes (T2D) to this non-interventional study. Data including patient characteristics, kidney function and albuminuria, blood pressure, HbA1c, lipid and lipoprotein levels, and diabetes duration as well as current medication was collected in each patient.

RESULTS

In the final study population of 625 patients, the mean age was 67 years (range 29-92 years), BMI 32.8 kg/m(2) (95% CI 32-33), blood pressure 142/80 mmHg (140-143/80-81) and HbA1c 7.1% (7.0-7.2) (53.8 mmol/mol, 53-55) and the median duration of diabetes was 9.2 years ranging from newly diagnosed to 43 years. History of dyslipidemia had in 73.3% of patients, 27.8% had cardiovascular disease and 82.7% had hypertension. The primary endpoint, prevalence of CKD of any grade (1-5) or albuminuria, was 68.6%. Regarding declined renal function, 16.2% of patients had an estimated glomerular filtration rate (eGFR) <60 ml/min/1.72 m(2), classifying as CKD 3-5. Only one patient was within CKD5. Regarding renal damage, albuminuria was present in 24.3% of patients, with microalbuminuria in 17.1% and macroalbuminuria in 7.2%, respectively. Combining the patients with CKD 3-5 and/or the presence of albuminuria, 34.7% seemed to suffer from significant CKD. The proportion of patients with albuminuria increased with a decrease in glomerular filtration rate. Historically, diabetic nephropathy had been diagnosed in 24.3% of the patients.

CONCLUSIONS

Nearly 70% of patients with T2D treated in primary care in Finland have some sign of CKD and nearly half of all T2D patients have a significant CKD. However, only half of the latter had it diagnosed and documented in their patient charts, thus highlighting the importance of performing routine screening of nephropathy by measuring both albuminuria and eGFR in patients with T2D. Prevention of this complication with active therapy for risk factors, such as hypertension and dyslipidemia is warranted.

A break in the obesity epidemic? Explained by biases or misinterpretation of the data?

Recent epidemiologic papers are presenting prevalence data suggesting breaks and decreases in obesity rates. However, before concluding that the obesity epidemic is not increasing anymore, the validity of the presented data should be discussed more thoroughly. We had a closer look into the literature presented in recent reviews to address the major potential biases and distortions, and to develop insights about how to interpret the presented suggestions for a potential break in the obesity epidemic. Decreasing participation rates, the use of reported rather than measured data and small sample sizes, or lack of representativeness, did not seem to explain presented breaks in the obesity epidemic. Further, available evidence does not suggest that stabilization of obesity rates is seen in higher socioeconomic groups only, or that urbanization could explain a potential break in the obesity epidemic. However, follow-ups of short duration may, in part, explain the apparent break or decrease in the obesity epidemic. On the other hand, a single focus on body mass index (BMI) ⩾25 or ⩾30 kg m(-)(2) is likely to mask a real increase in the obesity epidemic. And, in both children and adults, trends in waist circumferences were generally suggesting an increase, and were stronger than those reported for trends in BMI. Studies concluding that there is a recent break in the obesity epidemic need to be interpreted with caution. Reported studies presenting a break were mostly of short duration. Further, focusing on trends in waist circumference rather than BMI leads to a less optimistic conclusion: the public health problem of obesity is still increasing.

Metabolome and fecal microbiota in monozygotic twin pairs discordant for weight: a Big Mac challenge

Postprandial responses to food are complex, involving both genetic and environmental factors. We studied postprandial responses to a Big Mac meal challenge in monozygotic co-twins highly discordant for body weight. This unique design allows assessment of the contribution of obesity, independent of genetic liability. Comprehensive metabolic profiling using 3 analytical platforms was applied to fasting and postprandial serum samples from 16 healthy monozygotic twin pairs discordant for weight (body mass index difference >3 kg/m(2)). Nine concordant monozygotic pairs were examined as control pairs. Fecal samples were analyzed to assess diversity of the major bacterial groups by using 5 different validated bacterial group specific denaturing gradient gel electrophoresis methods. No differences in fecal bacterial diversity were detected when comparing co-twins discordant for weight (ANOVA, P<0.05). We found that within-pair similarity is a dominant factor in the metabolic postprandial response, independent of acquired obesity. Branched chain amino acids were increased in heavier as compared with leaner co-twins in the fasting state, but their levels converged postprandially (paired t tests, FDR q<0.05). We also found that specific bacterial groups were associated with postprandial changes of specific metabolites. Our findings underline important roles of genetic and early life factors in the regulation of postprandial metabolite levels.

Telomere length in circulating leukocytes is associated with lung function and disease

Several clinical studies suggest the involvement of premature ageing processes in chronic obstructive pulmonary disease (COPD). Using an epidemiological approach, we studied whether accelerated ageing indicated by telomere length, a marker of biological age, is associated with COPD and asthma, and whether intrinsic age-related processes contribute to the interindividual variability of lung function. Our meta-analysis of 14 studies included 934 COPD cases with 15 846 controls defined according to the Global Lungs Initiative (GLI) criteria (or 1189 COPD cases according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria), 2834 asthma cases with 28 195 controls, and spirometric parameters (forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and FEV1/FVC) of 12 595 individuals. Associations with telomere length were tested by linear regression, adjusting for age, sex and smoking status. We observed negative associations between telomere length and asthma (β= -0.0452, p=0.024) as well as COPD (β= -0.0982, p=0.001), with associations being stronger and more significant when using GLI criteria than those of GOLD. In both diseases, effects were stronger in females than males. The investigation of spirometric indices showed positive associations between telomere length and FEV1 (p=1.07×10(-7)), FVC (p=2.07×10(-5)), and FEV1/FVC (p=5.27×10(-3)). The effect was somewhat weaker in apparently healthy subjects than in COPD or asthma patients. Our results provide indirect evidence for the hypothesis that cellular senescence may contribute to the pathogenesis of COPD and asthma, and that lung function may reflect biological ageing primarily due to intrinsic processes, which are likely to be aggravated in lung diseases.

Factors associated with recovery from anorexia nervosa: a population-based study

BACKGROUND

To examine factors associated with the outcome of anorexia nervosa among women from the general population.

METHOD

Women (N = 2,881) from the 1975-1979 birth cohorts of Finnish twins were screened for lifetime DSM-IV anorexia nervosa (N = 55 cases) using questionnaires and the SCID interview. Potential factors associated with the likelihood of recovery were addressed in the same assessment. Recovery was defined as restoration of weight, menstruation, and the absence of bingeing and purging for at least one year prior to assessment. Using two-tailed t tests and Pearson's chi-square tests, we contrasted recovered (N = 39) and unrecovered (N = 16) women. We then used logistic regression adjusted for duration of illness and Cox proportional hazard models to account for the variable lengths of illness on prognostic factors.

RESULTS

Unrecovered women were more likely to suffer from depressive symptoms prior to eating disorder onset (18.8% vs. 2.6%, p = 0.04), remain unemployed (18.8% vs. 2.6%, p = 0.04), report dissatisfaction with their current partner/spouse (p = 0.02), and report high perfectionism (p = 0.05) than were recovered women. When duration of illness was accounted for in the analyses, premorbid depression was the sole factor significantly associated with decreased likelihood of recovery (hazard ratio 0.17, 95% confidence interval: 0.03-0.89).

DISCUSSION

Predicting the course of anorexia remains fraught with difficulty, but premorbid depressive symptoms are associated with poor outcome of anorexia nervosa in the general population.

Adipocyte morphology and implications for metabolic derangements in acquired obesity

BACKGROUND

Adipocyte size and number have been suggested to predict the development of metabolic complications in obesity. However, the genetic and environmental determinants behind this phenomenon remain unclear.

METHODS

We studied this question in rare-weight discordant (intra-pair difference (Δ) body mass index (BMI) 3-10 kg m(-2), n=15) and concordant (ΔBMI 0-2 kg m(-)(2), n=5) young adult (22-35 years) monozygotic twin pairs identified from 10 birth cohorts of Finnish twins (n=5 500 pairs). Subcutaneous abdominal adipocyte size from surgical biopsies was measured under a light microscope. Adipocyte number was calculated from cell size and total body fat (D × A).

RESULTS

The concordant pairs were remarkably similar for adipocyte size and number (intra-class correlations 0.91-0.92, P<0.01), suggesting a strong genetic control of these measures. In the discordant pairs, the obese co-twins (BMI 30.6 ± 0.9 kg m(-2)) had significantly larger adipocytes (volume 547 ± 59 pl), than the lean co-twins (24.9 ± 0.9 kg m(-)(2); 356 ± 34 pl, P<0.001). In 8/15 pairs, the obese co-twins had less adipocytes than their co-twins. These hypoplastic obese twins had significantly higher liver fat (spectroscopy), homeostatic model assessment-index, C-reactive protein and low-density lipoprotein cholesterol than their lean co-twins. Hyperplastic obesity was observed in the rest (7/15) of the pairs, obese and lean co-twins having similar metabolic measures. In all pairs, Δadipocyte volume correlated positively and Δcell number correlated negatively with Δhomeostatic model assessment-index and Δlow-density lipoprotein, independent of Δbody fat. Transcripts most significantly correlating with Δadipocyte volume were related to a reduced mitochondrial function, membrane modifications, to DNA damage and cell death.

CONCLUSIONS

Together, hypertrophy and hypoplasia in acquired obesity are related to metabolic dysfunction, possibly through disturbances in mitochondrial function and increased cell death within the adipose tissue.

GLP-1 responses are heritable and blunted in acquired obesity with high liver fat and insulin resistance

OBJECTIVE Impaired incretin response represents an early and uniform defect in type 2 diabetes, but the contributions of genes and the environment are poorly characterized. RESEARCH DESIGN AND METHODS We studied 35 monozygotic (MZ) and 75 dizygotic (DZ) twin pairs (discordant and concordant for obesity) to determine the heritability of glucagon-like peptide 1 (GLP-1) responses to an oral glucose tolerance test (OGTT) and the influence of acquired obesity to GLP-1, glucose-dependent insulinotropic peptide (GIP), and peptide YY (PYY) during OGTT or meal test. RESULTS The heritability of GLP-1 area under the curve was 67% (95% CI 45-80). Cotwins from weight-concordant MZ and DZ pairs and weight-discordant MZ pairs but concordant for liver fat content demonstrated similar glucose, insulin, and incretin profiles after the OGTT and meal tests. In contrast, higher insulin responses and blunted 60-min GLP-1 responses during the OGTT were observed in the heavier as compared with leaner MZ cotwins discordant for BMI, liver fat, and insulin sensitivity. Blunted GLP-1 response to OGTT was observed in heavier as compared with leaner DZ cotwins discordant for obesity and insulin sensitivity. CONCLUSIONS Whereas the GLP-1 response to the OGTT is heritable, an acquired unhealthy pattern of obesity characterized by liver fat accumulation and insulin resistance is closely related to impaired GLP-1 response in young adults.

Characterising metabolically healthy obesity in weight-discordant monozygotic twins

AIMS/HYPOTHESIS

Not all obese individuals display the metabolic disturbances commonly associated with excess fat accumulation. Mechanisms maintaining this 'metabolically healthy obesity' (MHO) are as yet unknown. We aimed to study different fat depots and transcriptional pathways in subcutaneous adipose tissue (SAT) as related to the MHO phenomenon.

METHODS

Sixteen rare young adult obesity-discordant monozygotic (MZ) twin pairs (intra-pair difference (∆) in BMI ≥ 3 kg/m(2)), aged 22.8-35.8 years, were examined for detailed characteristics of metabolic health (subcutaneous, intra-abdominal and liver fat [magnetic resonance imaging/spectroscopy]), OGTT, lipids, adipokines and C-reactive protein (CRP). Affymetrix U133 Plus 2.0 chips were used to analyse transcriptomics pathways related to mitochondrial function and inflammation in SAT.

RESULTS

Based on liver fat accumulation, two metabolically different subgroups emerged. In half (8/16) of the pairs (∆weight 17.1 ± 2.0 kg), the obese co-twin had significantly higher liver fat (∆718%), 78% increase in AUC insulin during OGTT and CRP, significantly more disturbance in the lipid profile and greater tendency for hypertension compared with the lean co-twin. In these obese co-twins, SAT expression of mitochondrial oxidative phosphorylation, branched-chain amino acid catabolism, fatty acid oxidation and adipocyte differentiation pathways were downregulated and chronic inflammation upregulated. In the other eight pairs (∆weight 17.4 ± 2.8 kg), the obese co-twin did not differ from the non-obese co-twin in liver fat (∆8%), insulin sensitivity, CRP, lipids, blood pressure or SAT transcriptomics.

CONCLUSIONS/INTERPRETATION

Our results suggest that maintenance of high mitochondrial transcription and lack of inflammation in SAT are associated with low liver fat and MHO.

Association between habitual dietary intake and lipoprotein subclass profile in healthy young adults

BACKGROUND AND AIMS

Nutritional epidemiology is increasingly shifting its focus from studying single nutrients to the exploration of the whole diet utilizing dietary pattern analysis. We analyzed associations between habitual diet (including macronutrients, dietary patterns, biomarker of fish intake) and lipoprotein particle subclass profile in young adults.

METHODS AND RESULTS

Complete dietary data (food-frequency questionnaire) and lipoprotein subclass profile (via nuclear magnetic resonance spectroscopy) were available for 663 subjects from the population-based FinnTwin12 study (57% women, age: 21-25 y). The serum docosahexaenoic to total fatty acid ratio was used as a biomarker of habitual fish consumption. Factor analysis identified 5 dietary patterns: "Fruit and vegetables", "Meat", "Sweets and desserts", "Junk food" and "Fish". After adjustment for sex, age, body mass index, waist circumference, physical activity, smoking status and alcohol intake, the "Junk food" pattern was positively related to serum triglycerides (r = 0.12, P = 0.002), a shift in the subclass distribution of VLDL toward larger particles (r = 0.12 for VLDL size, P < 0.001) and LDL toward smaller particles (r = -0.15 for LDL size, P < 0.001). In addition, higher scores on this pattern were positively correlated with concentrations of small, dense HDL (r = 0.16, P < 0.001). Habitual fish intake associated negatively with VLDL particle diameter ("Fish" pattern and biomarker) and positively with HDL particle diameter (biomarker).

CONCLUSIONS

Our results suggest that in young adults, higher habitual fish consumption is related to favorable subclass distributions of VLDL and HDL, while junk food intake is associated with unfavorable alterations in the distribution of all lipoprotein subclasses independent of adiposity and other lifestyle factors.

Blunted metabolic responses to cold and insulin stimulation in brown adipose tissue of obese humans

OBJECTIVE

Inactive brown adipose tissue (BAT) may predispose to weight gain. This study was designed to measure metabolism in the BAT of obese humans, and to compare it to that in lean subjects. The impact of weight loss on BAT and the association of detectable BAT with various metabolic characteristics were also assessed.

DESIGN AND METHODS

Using positron emission tomography (PET), cold- and insulin-stimulated glucose uptake and blood flow in the BAT of obese and lean humans were quantified. Further, cold-induced glucose uptake was measured in obese subjects before and after a 5-month conventional weight loss.

RESULTS

Mean responses in BAT glucose uptake rate to both cold and insulin stimulation were twice as large in lean as in obese subjects. Blood flow in BAT was also lower in obese subjects under cold conditions. The increase in cold-induced BAT glucose uptake rate after weight loss was not statistically significant. Subjects with cold-activated detectable BAT were leaner and had higher whole-body insulin sensitivity than BAT-negative subjects, irrespective of age and gender.

CONCLUSIONS

The effects of cold and insulin on BAT activity are severely blunted in obesity, and the presence of detectable BAT may contribute to a metabolically healthy status.

Acquired liver fat is a key determinant of serum lipid alterations in healthy monozygotic twins

OBJECTIVE

The effects of acquired obesity on lipid profile and lipoprotein composition in rare BMI-discordant monozygotic (MZ) twin pairs were studied.

DESIGN AND METHODS

Abdominal fat distribution, liver fat (magnetic resonance imaging and spectroscopy), fasting serum lipid profile (ultracentrifugation, gradient gel-electrophoresis, and colorimetric enzymatic methods), and lifestyle factors (questionnaires and diaries) were assessed in 15 BMI-discordant (within-pair difference [Δ] in BMI >3 kg/m2) and nin concordant (ΔBMI <3 kg/m2) MZ twin pairs, identified from two nationwide cohorts of Finnish twins.

RESULTS

Despite a strong similarity of MZ twins in lipid parameters (intra-class correlations 0.42-0.90, P < 0.05), concentrations of apolipoprotein B (ApoB), intermediate-density lipoprotein cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein 3a% (HDL3a%), and HDL3c% were higher (P < 0.05) and those of HDL cholesterol, HDL2-C, and HDL2b% were lower (P < 0.01) in the heavier co-twins of BMI-discordant pairs. The composition of lipoprotein particles was similar in the co-twins. When BMI-discordant pairs were further divided into liver fat-discordant and concordant (based on median for Δliver fat, 2.6%), the adverse lipid profile was only seen in those heavy co-twins who also had high liver fat. Conversely, BMI-discordant pairs concordant for liver fat did not differ significantly in lipid parameters. In multivariate analyses controlling for Δsubcutaneous, Δintra-abdominal fat, sex, Δsmoking and Δphysical activity, Δliver fat was the only independent variable explaining the variation in ΔApoB, Δtotal cholesterol, and ΔLDL-C concentration.

CONCLUSIONS

Several pro-atherogenic changes in the amounts of lipids but not in the composition of lipoprotein particles were observed in acquired obesity. In particular, accumulation of liver fat was associated with lipid disturbances, independent of genetic effects.

Habitual dietary intake is associated with stool microbiota composition in monozygotic twins

The impact of diet on the gut microbiota has usually been assessed by subjecting people to the same controlled diet and thereafter following the shifts in the microbiota. In the present study, we used habitual dietary intake, clinical data, quantitative polymerase chain reaction, and denaturing gradient gel electrophoresis (DGGE) to characterize the stool microbiota of Finnish monozygotic twins. The effect of diet on the numbers of bacteria was described through a hierarchical linear mixed model that included the twin individuals, stratified by body mass index, and their families as random effects. The abundance and diversity of the bacterial groups studied did not differ between normal-weight, overweight, and obese individuals with the techniques used. Intakes of energy, monounsaturated fatty acids, n3 polyunsaturated fatty acids (PUFAs), n6 PUFAs, and soluble fiber had significant associations with the stool bacterial numbers (e.g., increased energy intake was associated with reduced numbers of Bacteroides spp.). In addition, co-twins with identical energy intake had more similar numbers and DGGE-profile diversities of Bacteroides spp. than did the co-twins with different intake. Moreover, the co-twins who ingested the same amounts of saturated fatty acids had very similar DGGE profiles of Bacteroides spp., whereas the co-twins with similar consumption of fiber had a very low bifidobacterial DGGE-profile similarity. In conclusion, our findings confirm that the diet plays an important role in the modulation of the stool microbiota, in particular Bacteroides spp. and bifidobacteria.

Influence of serotonin transporter gene polymorphism (5-HTTLPR polymorphism) on the relation between brain 5-HT transporter binding and heart rate corrected cardiac repolarization interval

Objective

Serotonin transporter gene polymorphism (5-HTTLPR polymorphism) predicts the degree of structural and functional connectivity in the brain, and less consistently the degree of vulnerability for anxiety and depressive disorders. It is less known how 5-HTTLPR polymorphism influences on the coupling between brain and neuronal cardiovascular control. The present study demonstrates the impact of 5-HTTLPR polymorphism on the relations between heart rate (HR) corrected cardiac repolarization interval (QTc interval) and the brain 5-HTT binding.

Material and Methods

Thirty healthy young adults (fifteen monozygotic twin pairs) (mean age 26±1.3 years, 16 females) were imagined with single-photon emission computed tomography (SPECT) using iodine-123 labeled 2β-carbomethoxy-3β-(4-iodophenyl) nortropane (nor-β-CIT). Continuous ECG recording was obtained from each participant at supine rest. Signal averaged QTc interval on continuous ECG was calculated and compared with the brain imaging results.

Results

In the two groups [l homozygotes (n = 16, 10 females), s carriers (n = 14, 8 female)] HR and the length of QTc interval were not influenced by 5-HTTLPR polymorphism. There were no significant relations between HR and 5-HTT binding in the brain. There were significant associations between QTc interval and nor-β-CIT binding in the brain in l homozygotes, but not in s carriers (correlations for QTc interval and nor-β-CIT binding of striatum, thalamus and right temporal region were −0.8–−0.9, (p<0.0005), respectively).

Conclusion

The finding of longer QTc interval with less 5-HTT binding availability in major serotonergic binding sites in l homozygotes, but not in s carriers, implicate to differentiated control of QTc interval by 5-HTTLPR polymorphism.

Adipose co-expression networks across Finns and Mexicans identify novel triglyceride-associated genes

Background

High serum triglyceride (TG) levels is an established risk factor for coronary heart disease (CHD). Fat is stored in the form of TGs in human adipose tissue. We hypothesized that gene co-expression networks in human adipose tissue may be correlated with serum TG levels and help reveal novel genes involved in TG regulation.

Methods

Gene co-expression networks were constructed from two Finnish and one Mexican study sample using the blockwiseModules R function in Weighted Gene Co-expression Network Analysis (WGCNA). Overlap between TG-associated networks from each of the three study samples were calculated using a Fisher’s Exact test. Gene ontology was used to determine known pathways enriched in each TG-associated network.

Results

We measured gene expression in adipose samples from two Finnish and one Mexican study sample. In each study sample, we observed a gene co-expression network that was significantly associated with serum TG levels. The TG modules observed in Finns and Mexicans significantly overlapped and shared 34 genes. Seven of the 34 genes (ARHGAP30, CCR1, CXCL16, FERMT3, HCST, RNASET2, SELPG) were identified as the key hub genes of all three TG modules. Furthermore, two of the 34 genes (ARHGAP9, LST1) reside in previous TG GWAS regions, suggesting them as the regional candidates underlying the GWAS signals.

Conclusions

This study presents a novel adipose gene co-expression network with 34 genes significantly correlated with serum TG across populations.

Effect of anti-IL-1β antibody (canakinumab) on insulin secretion rates in impaired glucose tolerance or type 2 diabetes: results of a randomized, placebo-controlled trial

AIMS

Evaluate anti-interleukin-1β (IL-1β) antibody, canakinumab, in patients with type 2 diabetes and impaired glucose tolerance (IGT) in whom hyperglycaemia may trigger IL-1β-associated inflammation leading to suppressed insulin secretion and β-cell dysfunction.

METHODS

This 4-week, parallel-group study randomized 190 patients with type 2 diabetes 2 : 1, canakinumab versus placebo, into the following treatment arms: metformin monotherapy, metformin + sulfonylurea, metformin + sulfonylurea + thiazolidinedione or insulin ± metformin. IGT population (n = 54) was randomized 1 : 1, canakinumab versus placebo. Primary efficacy assessment was change from baseline in insulin secretion rate (ISR) relative to glucose 0-2 h.

RESULTS

Mean changes from baseline to week 4 in ISR relative to glucose at 0-2 h or other time points were not statistically significant for canakinumab versus placebo across groups. ISR (relative to glucose) at 0-0.5 h (first-phase insulin secretion) numerically favoured canakinumab versus placebo in insulin-treated patients {difference in mean change from baseline [point estimate (PE)] 3.81 pmol/min/m(2)/mmol/l; p = 0.0525} and in the IGT group (PE 3.92 pmol/min/m(2)/mmol/l; p = 0.1729). Mean change from baseline in fasting plasma glucose favoured canakinumab in the type 2 diabetes/metformin group and the IGT group; however, differences were not statistically significant. Mean change from baseline in peak insulin level and insulin AUC 0-4 h were statistically significantly higher in the canakinumab group in IGT patients. Canakinumab was well tolerated and consistent with known safety experience.

CONCLUSIONS

The trend towards improving ISR relative to glucose 0-0.5 h in patients treated with insulin supports the hypothesis that insulin secretion can be improved by blocking IL-1β.

Efficacy of rimonabant in obese patients with binge eating disorder

In obesity, a dysregulation of the endocannabinoid system has been shown. The endocannabinoid receptor blockage by rimonabant demonstrated interesting metabolic effects. However, the role of rimonabant in weight loss of patients with binge eating disorder has not been investigated. Thus, our aim was to evaluate the effects of rimonabant on body weight in obese patients with binge eating disorders. This multicenter, randomized, double-blind, placebo-controlled study included 289 obese subjects (age 18-70 years, body mass index 30-45 kg/m(2)) with binge eating disorders. Subjects were randomized (1:1) to receive rimonabant 20 mg/day or placebo for 6 months. In total, 289 participants (age: 43.2±10.5 yrs, 91% of women) were randomized. The completer rate was similar (71%) in both treatment and placebo groups. Participants treated with rimonabant lost 4.7±5.2% of their initial body weight, vs. 0.4±4.5% in the placebo group (difference between both groups: 4.4±0.6 kg, p<0.0001). The rimonabant group showed a greater reduction on the binge eating scale total score (mean±SD  - 40.9±35.2%) vs. placebo ( - 29.9±34.6%, p=0.02). The incidence of treatment emergent adverse events was comparable in both the rimonabant (82.5%) and placebo (76.0%) group. Discontinuations due to treatment emergent adverse events occurred in 13.3% rimonabant-treated vs. 6.2% placebo-treated participants. In conclusion, this is the only randomised, placebo-controlled, double-blind trial having assessed the effect of rimonabant in patients with binge eating disorders. The rimonabant treatment reduced body weight significantly more than placebo in obese subjects with binge eating. Trial registration number (clinicaltrials.gov): NCT00481975.

Effect of short-term carbohydrate overfeeding and long-term weight loss on liver fat in overweight humans

BACKGROUND

Cross-sectional studies have identified a high intake of simple sugars as an important dietary factor predicting nonalcoholic fatty liver disease (NAFLD).

OBJECTIVE

We examined whether overfeeding overweight subjects with simple sugars increases liver fat and de novo lipogenesis (DNL) and whether this is reversible by weight loss.

DESIGN

Sixteen subjects [BMI (kg/m²): 30.6 ± 1.2] were placed on a hypercaloric diet (>1000 kcal simple carbohydrates/d) for 3 wk and, thereafter, on a hypocaloric diet for 6 mo. The subjects were genotyped for rs739409 in the PNPLA3 gene. Before and after overfeeding and after hypocaloric diet, metabolic variables and liver fat (measured by proton magnetic resonance spectroscopy) were measured. The ratio of palmitate (16:0) to linoleate (18:2n-6) in serum and VLDL triglycerides was used as an index of DNL.

RESULTS

Carbohydrate overfeeding increased weight (±SEM) by 2% (1.8 ± 0.3 kg; P < 0.0001) and liver fat by 27% from 9.2 ± 1.9% to 11.7 ± 1.9% (P = 0.005). DNL increased in proportion to the increase in liver fat and serum triglycerides in subjects with PNPLA3-148IIbut not PNPLA3-148MM. During the hypocaloric diet, the subjects lost 4% of their weight (3.2 ± 0.6 kg; P < 0.0001) and 25% of their liver fat content (from 11.7 ± 1.9% to 8.8 ± 1.8%; P < 0.05).

CONCLUSIONS

Carbohydrate overfeeding for 3 wk induced a >10-fold greater relative change in liver fat (27%) than in body weight (2%). The increase in liver fat was proportional to that in DNL. Weight loss restores liver fat to normal. These data indicate that the human fatty liver avidly accumulates fat during carbohydrate overfeeding and support a role for DNL in the pathogenesis of NAFLD. This trial was registered at www.hus.fi as 235780.