Obesity status and obesity-associated gut dysbiosis effects on hypothalamic structural covariance.

BACKGROUND: Functional connectivity alterations in the lateral and medial hypothalamic networks have been associated with the development and maintenance of obesity, but the possible impact on the structural properties of these networks remains largely unexplored. Also, obesity-related gut dysbiosis may delineate specific hypothalamic alterations within obese conditions. We aim to assess the effects of obesity, and obesity and gut-dysbiosis on the structural covariance differences in hypothalamic networks, executive functioning, and depressive symptoms. METHODS: Medial (MH) and lateral (LH) hypothalamic structural covariance alterations were identified in 57 subjects with obesity compared to 47 subjects without obesity. Gut dysbiosis in the subjects with obesity was defined by the presence of high (n = 28) and low (n = 29) values in a BMI-associated microbial signature, and posthoc comparisons between these groups were used as a proxy to explore the role of obesity-related gut dysbiosis on the hypothalamic measurements, executive function, and depressive symptoms. RESULTS: Structural covariance alterations between the MH and the striatum, lateral prefrontal, cingulate, insula, and temporal cortices are congruent with previously functional connectivity disruptions in obesity conditions. MH structural covariance decreases encompassed postcentral parietal cortices in the subjects with obesity and gut-dysbiosis, but increases with subcortical nuclei involved in the coding food-related hedonic information in the subjects with obesity without gut-dysbiosis. Alterations for the structural covariance of the LH in the subjects with obesity and gut-dysbiosis encompassed increases with frontolimbic networks, but decreases with the lateral orbitofrontal cortex in the subjects with obesity without gut-dysbiosis. Subjects with obesity and gut dysbiosis showed higher executive dysfunction and depressive symptoms. CONCLUSIONS: Obesity-related gut dysbiosis is linked to specific structural covariance alterations in hypothalamic networks relevant to the integration of somatic-visceral information, and emotion regulation.

Ferritin levels throughout childhood and metabolic syndrome in adolescent stage.

BACKGROUND AND AIM: Increased ferritin levels have been widely associated with cardiovascular risk in adults. Whether ferritin levels and their changes during childhood are related to metabolic syndrome (MetS) at adolescence is unknown. We aimed to evaluate these associations using levels of ferritin at 5, 10 and 16 years and their linear increases and patterns of sustained increased levels across childhood. METHODS AND RESULTS: There were four samples evaluated according to non-missing values for study variables at each stage (5 years: 562; 10 years: 381; and 16 years: 567 children; non-missing values at any stage: 379). MetS risk was evaluated as a continuous Z score. Patterns of sustained increased ferritin (highest tertile) and slope of the change of ferritin per year across the follow-up were calculated. Ferritin levels in the highest versus lowest tertile at five and 16 years were significantly positively associated with MetS risk Z score at adolescence in boys and these associations were unaffected by adjustment for covariates. Having high, compared to low/moderate ferritin level at 2 or more time periods between 5 and 16 years was related to higher Mets Z-score in boys only [e.g. 5-10 years adjusted-beta (95 %CI):0.26 (0.05-0.48),P < 0.05]. In girls, ferritin Z score at 10 and 16 years was positively and independently associated with HOMA-IR Z score. In girls, the slope of ferritin per year in the highest tertile was positively associated with MetS risk Z-score [adjusted-beta (95 %CI):0.21 (0.05-0.38),P < 0.05]. CONCLUSIONS: Ferritin levels throughout childhood are positively related to cardiometabolic risk in adolescence, with associations varying by sex.

Adipose tissue and serum CCDC80 in obesity and its association with related metabolic disease.

Coiled-coil domain-containing 80 (CCDC80) is an adipocyte-secreted protein that modulates glucose homeostasis in response to diet-induced obesity in mice. The objective of this study is to analyze the link between human CCDC80 and obesity. CCDC80 protein expression was assessed in paired visceral (VAT) and subcutaneous (SAT) adipose tissue from 10 subjects (BMI range 22.4-38.8 kg/m2). Circulating CCDC80 levels were quantified in serum samples from two independent cross-sectional cohorts comprising 33 lean and 15 obese (cohort 1) and 32 morbid obese (cohort 2) male subjects. Insulin sensitivity, insulin secretion and blood neutrophil count were quantified in serum samples from both cohorts. Additionally, circulating free IGF-1 levels and oral glucose tolerance tests (OGTT) were assessed in cohort 1 whereas C-reactive protein levels and degree of atherosclerosis and hepatic steatosis were studied in cohort 2. In lean subjects, total CCDC80 protein content assessed by immunoblotting was lower in VAT than in SAT. In obese patients, CCDC80 was increased in VAT (P<0.05), but equivalent in SAT compared with lean counterparts. In cohort 1, serum CCDC80 correlated negatively with the acute insulin response to glucose and IGF1 levels, and positively with blood neutrophil count, independently of BMI, but not with insulin sensitivity. In cohort 2, serum CCDC80 was positively linked to the inflammatory biomarker C-reactive protein (r=0.46; P=0.009), atherosclerosis (carotid intima-media thickness, r=0.62; P<0.001) and hepatic steatosis (ANOVA P=0.025). Overall, these results suggest for the first time that CCDC80 may be a component of the obesity-altered secretome in VAT and could act as an adipokine whose circulant levels are linked to glucose tolerance derangements and related to inflammation-associated chronic complications.

Decreased lipid metabolism but increased FA biosynthesis are coupled with changes in liver microRNAs in obese subjects with NAFLD.

BACKGROUND/OBJECTIVE: Many controversies regarding the association of liver miRNAs with obesity and nonalcoholic fatty liver diseases (NAFLD) call for additional validations. This study sought to investigate variations in genes and hepatic miRNAs in a sample of obese patients with or without NAFLD and human hepatocytes (HH). SUBJECTS/METHODS: A total of 60 non-consecutive obese women following bariatric surgery were recruited. Subjects were classified as NAFLD (n=17), borderline (n=24) and controls (n=19) with normal enzymatic profile, liver histology and ultrasound assessments. Profiling of 744 miRNAs was performed in 8 obese women with no sign of hepatic disease and 11 NAFLD patients. Additional validation and expression of genes related to de novo fatty acid (FA) biosynthesis, uptake, transport and ß-oxidation; glucose metabolism, and inflammation was tested in the extended sample. Induction of NAFLD-related genes and miRNAs was examined in HepG2 cells and primary HH treated with palmitic acid (PA), a combination of palmitate and oleic acid, or high glucose, and insulin (HG) mimicking insulin resistance in NAFLD. RESULTS: In the discovery sample, 14 miRNAs were associated with NAFLD. Analyses in the extended sample confirmed decreased miR-139-5p, miR-30b-5p, miR-122-5p and miR-422a, and increased miR-146b-5p in obese subjects with NAFLD. Multiple linear regression analyses disclosed that NAFLD contributed independently to explain miR-139-5p (P=0.005), miR-30b-5p (P=0.005), miR-122-5p (P=0.021), miR-422a (P=0.007) and miR-146a (P=0.033) expression variance after controlling for confounders. Decreased miR-122-5p in liver was associated with impaired FA usage. Expression of inflammatory and macrophage-related genes was opposite to decreased miR-30b-5p, miR-139-5p and miR-422a, whereas increased miR-146b-5p was associated with FABP4 and decreased glucose metabolism and FA mobilization. In partial agreement, PA (but not HG) led to decreased miR-139-5p, miR-30b-5p, miR-422a and miR-146a in vitro, in parallel with increased lipogenesis and FA transport, decreased glucose metabolism and diminished FA oxidation. CONCLUSION: This study confirms decreased liver glucose and lipid metabolism but increased FA biosynthesis coupled with changes in five unique miRNAs in obese patients with NAFLD.

Neuroinflammation in obesity: circulating lipopolysaccharide-binding protein associates with brain structure and cognitive performance.

BACKGROUND/OBJECTIVES: Growing evidence implicates neuroinflammation in the pathogenesis of diet-induced obesity and cognitive dysfunction in rodent models. Obesity is associated with reduced white matter integrity and cognitive decline. Circulating lipopolysaccharide binding protein (LBP) concentration is known to be increased in patients with obesity. Here, we aimed to evaluate whether circulating LBP is associated longitudinally with white matter structure and cognitive performance according to obesity status. SUBJECTS/METHODS: This longitudinal study analyzed circulating LBP (ELISA), DTI-metrics (axial diffusivity (L1), fractional anisotropy (FA) and radial diffusivity (RD)) in specific regions of the white matter of 24 consecutive middle-aged obese subjects (13 women) and 20 healthy volunteers (10 women) at baseline and two years later. Digit Span Test (DST) was used as a measure of working memory/short-term verbal memory. RESULTS: Circulating LBP concentration was associated with FA and L1 values of several white matter regions both at baseline and follow-up. The associations remained significant after controlling for age, BMI, fat mass and plasma high sensitivity C-reactive protein. Importantly, the increase in LBP over time impacted negatively on FA and L1 values and on DST performance. CONCLUSIONS: Circulating LBP associates with brain white matter integrity and working memory/short-term verbal memory in both obese and non-obese subjects.

Reduced circulating levels of sTWEAK are associated with NAFLD and may affect hepatocyte triglyceride accumulation.

CONTEXT: Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome and is strongly associated with obesity, dyslipidaemia and altered glucose regulation. Previous data demonstrated that low circulating levels of tumour necrosis factor weak inducer of apoptosis (sTWEAK) were associated with obesity, diabetes and insulin resistance, all traits associated with an increased risk of NALFD. Circulating sTWEAK levels are expected to be reduced in the presence of NAFLD. OBJECTIVE: We aimed to explore the relationship between NAFLD and circulating sTWEAK levels in obese patients, and to evaluate the effect of sTWEAK on hepatocyte triglyceride accumulation.Design setting and patients:This is an observational case-control study performed in n=112 severely obese patients evaluated for NAFLD by abdominal ultrasound and n=32 non-obese patients without steatosis. Serum sTWEAK concentrations were measured by ELISA. Multivariable analyses were performed to determine the independent predictors of NAFLD. We analysed TWEAK and Fn14 protein expression in liver biopsies by western blotting and immunohistochemistry. An immortalized primary human hepatocyte cell line (HHL) was used to evaluate the effect of sTWEAK on triglyceride accumulation. RESULTS: We observed a reduction in serum circulating sTWEAK concentrations with the presence of liver steatosis. On multivariable analysis, lower sTWEAK concentrations were independently associated with the presence of NAFLD (odds ratio (OR)=0.023; 95% confidence interval: 0.001-0.579; P<0.022). In human hepatocytes, sTWEAK administration reduced fat accumulation as demonstrated by the reduction in palmitic acid-induced accumulation of triglyceride and the decreased expression of cluster of differentiation 36 (CD36) and perilipin 1 and 2 (PLIN1 and PLIN2) genes. CONCLUSIONS: Decreased sTWEAK concentrations are independently associated with the presence of NAFLD. This is concordant with the observation that TWEAK reduces lipid accumulation in human liver cells.

Circulating irisin levels and coronary heart disease: association with future acute coronary syndrome and major adverse cardiovascular events.

INTRODUCTION: Irisin is a newly discovered myokine, associated with 'browning' of the white adipose tissue, obesity, insulin resistance and metabolic syndrome. The purpose of this study is to evaluate circulating irisin as a predictor of acute coronary syndromes (ACSs) and major adverse cardiovascular events (MACE). METHODS: Sub-study 1: a case-control study, nested within the Veteran's Affairs Normative Ageing Study, evaluating circulating irisin levels in 88 ACS cases and 158 age- and sampling year-matched controls, as a predictor of ACS. Sub-study 2: a prospective cohort study, where 103 participants with established coronary artery disease were stratified by circulating irisin levels at the time they received percutaneous coronary interventions (PCIs) and were followed for the development of MACE. RESULTS: Study 1: there was no association between irisin levels and ACS in otherwise healthy individuals (odds ratio: 1.00 95% confidence interval: (0.99-1.00)). Study 2: the incidence of MACE was significantly lower in the first irisin tertile compared with the second and third (incidence rate 0 vs 0.92 (0.51-1.61) vs 0.57 (0.28-1.14) events per 1000 person-days; P < 0.01). This was primarily driven by the lower incidence of unstable angina (incidence rate 0 vs 0.61 (0.31-1.22) vs 0.43 (0.19-0.96) per 1000 person-days; P = 0.01). CONCLUSION: This is the first study to date that demonstrates that, although circulating irisin levels do not predict the development of ACS in healthy individuals, increased irisin levels are associated with the development of MACE in patients with established coronary artery disease after PCI.

Effects of biliopancreatic diversion on diurnal leptin, insulin and free fatty acid levels.

BACKGROUND: Free fatty acid (FFA) levels are raised in obesity as a consequence of increased production and reduced clearance. They may link obesity with insulin resistance. Bariatric surgery can result in considerable weight loss and reduced insulin resistance, but the mechanism of action is not well understood. Although drugs such as metformin that lower insulin resistance can contribute to weight loss, a better understanding of the links between obesity, weight loss and changes in insulin resistance might lead to new approaches to patient management. METHODS: Variations in circulating levels of leptin, insulin and FFAs over 24 h were studied in severely obese (body mass index over 40 kg/m(2) ) women before and 6 months after biliopancreatic diversion (BPD). Body composition was measured by dual-energy X-ray absorptiometry. A euglycaemic-hyperinsulinaemic clamp was used to assess insulin sensitivity. Levels of insulin, leptin and FFAs were measured every 20 min for 24 h. Pulsatile hormone and FFA analyses were performed. RESULTS: Among eight patients studied, insulin sensitivity more than doubled after BPD, from mean(s.d.) 39·78(7·74) to 96·66(27·01) mmol per kg fat-free mass per min, under plasma insulin concentrations of 102·29(9·60) and 93·61(9·95) µunits/ml respectively. The secretory patterns of leptin were significantly different from random but not statistically different before and after BPD, with the exception of the pulse height which was reduced after surgery. Both plasma insulin and FFA levels were significantly higher throughout the study day before BPD. Based on Granger statistical modelling, lowering of daily FFA levels was linked to decreased circulating leptin concentrations, which in turn were related to the lowering of daily insulin excursions. Multiple regression analysis indicated that FFA level was the only predictor of leptin level. CONCLUSION: Lowering of circulating levels of FFAs after BPD may be responsible for the reduction in leptin secretion, which in turn can decrease circulating insulin levels. Surgical relevance Insulin resistance is a common feature of obesity and type II diabetes. These patients are also relatively insensitive to the biological effects of leptin, a satiety hormone produced mainly in subcutaneous fat. Biliopancreatic diversion, a malabsorptive bariatric operation that drastically reduces circulating lipid levels, improves insulin resistance independently of weight loss. The mechanism of action, however, has still to be elucidated. This study demonstrated that normalization of insulin sensitivity after bariatric surgery was associated with a reduction in 24-h free fatty acid concentrations and changes in the pattern of leptin peaks in plasma. Bariatric surgery improves the metabolic dysfunction of obesity, and this may be through a reduction in circulating free fatty acids and modification of leptin metabolism.

Older type 2 diabetic patients are more likely to achieve glycaemic and cardiovascular risk factors targets than younger patients: analysis of a primary care database.

BACKGROUND: Older subjects with type 2 diabetes mellitus (T2DM) have differential characteristics compared with middle-aged or younger populations, and require tailored management of the disease. AIMS: To evaluate how clinical characteristics, degree of control of glycaemia and cardiovascular risk factors, presence of chronic complications and treatments differ between older T2DM patients and younger adults. METHODS: Cross-sectional study using data from a population-based electronic database. We retrieved data from 318,020 patients ≥ 30 years diagnosed with T2DM, attended during 2011 in primary care centres in Catalonia, Spain. We performed descriptive and comparative analyses stratified by gender and age subgroups: ≤ 65, 66-75, 76-85 and >85 years. RESULTS: Both men and women across older age subgroups (> 65 years) had longer diabetes duration than younger adults (8.0 vs. 5.6 in men and 8.4 vs. 6.9 years in women; p < 0.001), but better glycaemic control (mean glycated haemoglobin 7.1 vs. 7.7 in men and 7.1 vs. 7.4 in women; p < 0.001), and better combined control of different cardiovascular risk factors (p < 0.001). Moreover, older patients were more likely to achieve glycaemic targets irrespective of having cardiovascular disease. The use of oral antidiabetics decreased with increasing age, and insulin in monotherapy was more frequently prescribed among patients in the older age subgroups. Diabetes-related complications were more frequent in men of all group ages. In the older age subgroups, patients of both sexes had a longer duration of T2DM but better glycaemic control. In this context, the prevalence of diabetic retinopathy decreased unexpectedly with increasing age. CONCLUSION: Control of glycaemia and cardiovascular risk factors was better among older T2DM patients. There is a need for prospective studies to quantify the weight of risk factors in each complication to adapt the therapeutic and care approaches in elderly people.

CIDEC/FSP27 and PLIN1 gene expression run in parallel to mitochondrial genes in human adipose tissue, both increasing after weight loss.

OBJECTIVE: FSP27 KO mice showed enhanced expression of mitochondrial genes, increased mitochondrial activity and smaller lipid droplets. Here, we aimed to investigate lipid droplet protein (CIDEC/FSP27 and perilipinA (PLIN1)) gene expression in human adipose tissue in association with obesity, insulin resistance and mitochondrial gene expression. DESIGN AND SUBJECTS: In cohort 1, CIDEC/FSP27, PLIN1, adipogenic (FASN, ACACA, PPARG, GLUT4) and mitochondrial (PPARGC1A, PPARGC1B, TFAM, MT-CO3) gene expression were analyzed in 171 adipose tissue samples (88 visceral adipose tissue (VAT) and 83 subcutaneous adipose tissue (SAT) depots) and in a time course experiment in human subcutaneous and visceral preadipocytes using real-time PCR. In cohort 2, the effects of bariatric surgery-induced weight loss were also evaluated in six caucasian morbidly obese women. Additionally, in cohort 2 FSP27 and PLIN1 protein levels were measured using western blotting. RESULTS: CIDEC/FSP27 (1.03±0.52 vs 0.49±0.23 relative gene expression unit (R.U.), P<0.0001) and PLIN1 (1.32±0.82 vs 0.63±0.42 R.U., P<0.0001) gene were significantly more expressed in SAT than in VAT. In VAT, CIDEC/FSP27 and PLIN1 gene expression decreased with body mass index, percent fat mass, fasting glucose, fasting insulin, HOMA and were positively associated with adipogenic (PPARG, GLUT4, FASN and ACACA) and mitochondrial biogenesis (PPARGC1A, PPARGC1B, TFAM and MT-CO3)-related genes. Mitochondrial gene expression increased during adipocyte differentiation in parallel to FSP27 and PLIN1 and other adipogenic genes. After bariatric surgery-induced weight loss, PLIN1 and CIDEC/FSP27 gene and protein expression in SAT increased significantly in parallel to adipogenic and mitochondrial genes. CONCLUSION: These findings suggest a positive functional interaction between CIDEC/FSP27, PLIN1 and mitochondrial biogenesis-related genes in human adipose tissue.

Inflammation and insulin resistance exert dual effects on adipose tissue tumor protein 53 expression.

OBJECTIVE: The purpose of this study was to investigate the expression of human adipose tissue protein 53 (p53) in subjects who varied widely in terms of obesity and insulin resistance. We also analyzed different in vivo and in vitro models to try to comprehend the associations found in humans. METHODS: p53 was analyzed in human adipose and isolated adipocytes, in high fat-fed and GLP-1R KO mice, during in vitro adipogenesis, and in adipocytes after high glucose, rosiglitazone and inflammatory conditions. The effects of surgery-induced weight loss and ex vivo metformin were also evaluated. RESULTS: Omental (OM) p53 gene expression (+27%, P=0.001) and protein (+11%, P=0.04) were increased in obese subjects and high fat diet-induced obese mice (+86%, P=0.018). Although the obesity-associated inflammatory milieu was associated with increased OM p53, this was negatively related to insulin resistance and glycated hemoglobin, and positively with biomarkers for insulin sensitivity. Multiple linear regression analyses revealed that glycated hemoglobin (P<0.0001) and body mass index (P=0.048) contributed independently to explain 13.7% (P<0.0001) of the OM p53 variance. Accordingly, the improvement of insulin sensitivity with surgery-induced weight loss (+51%, P=0.01) and metformin (+42%, P=0.02) led to increased adipose p53. While the glucose-intolerant GLP-1R KO mice showed decreased mesenteric p53 (-45.4%, P=0.017), high glucose led to decreased p53 in pre-adipocytes (-27%, P<0.0001). Inflammatory treatments led to increased p53 (+35%, P<0.0001), while Rs downregulated this expression (-40%, P=0.005) in mature adipocytes. CONCLUSION: Inflammation and insulin resistance exert dual effects on adipose p53, which seems to be the final result of these opposing forces.

Alarmin high-mobility group B1 (HMGB1) is regulated in human adipocytes in insulin resistance and influences insulin secretion in ß-cells.

BACKGROUND: The nuclear protein high-mobility group box 1 (HMGB1) can be passively released by necrotic cells or secreted actively by several cell types to regulate immune and inflammatory responses, as well as tissue remodeling. We herein aimed to characterize the effect of insulin resistance on HMGB1 in adipose tissue and to examine its potential role as a metabolic regulator in ß-pancreatic cells. DESIGN: Plasma HMGB1 concentration and adipose HMGB1 expression were assessed in relation to obesity and insulin resistance. Cultured adipocytes from lean and obese patients were used to investigate the intracellular distribution and factors regulating HMGB1 release, as well as to test its effects on adipogenesis and lipid metabolism. A regulatory role for HMGB1 in insulin secretion was also investigated. RESULTS: Circulating HMGB1 was positively associated with body mass index, while adipose HMGB1 mRNA levels correlated with the expression of inflammatory markers. Insulin resistance modified the intracellular distribution of HMGB1 in human adipocytes, with HMGB1 being predominantly nuclear in lean and obese normoglycemic individuals while localized to the cytosol in obese patients with type 2 diabetes. Adipocytes from lean individuals exposed to conditioned media from lipopolysaccharide-stimulated macrophages induced HMGB1 redistribution to the cytoplasm and release. HMGB1 treatment had no effect on differentiation and lipid metabolism in adipocytes. However, HMGB1, whose circulating levels correlated with postload insulin concentration, increased both insulin release and intracellular Ca(2+) concentration in INS-1 cells. CONCLUSIONS: These findings show, for the first time, that HMGB1 expression and release by human adipocytes is altered by inflammatory conditions as those imposed by obesity and insulin resistance. Our data reveal a novel role for HMGB1 as a stimulatory factor of insulin secretion of ß-pancreatic cells.

White fish reduces cardiovascular risk factors in patients with metabolic syndrome: the WISH-CARE study, a multicenter randomized clinical trial.

BACKGROUND AND AIMS: Reduction of cardiovascular risk with high consumption of fish in diet is still a matter of debate, and concerns about heavy metal contamination have limited consumption of oily fish. We aimed to evaluate the effect of regular ingestion of white fish on cardiovascular risk factors in patients with metabolic syndrome. METHODS AND RESULTS: Multicenter randomized crossover clinical trial including 273 individuals with metabolic syndrome. An 8-week only-one dietary intervention: 100 g/d of white fish (Namibia hake) with advice on a healthy diet, compared with no fish or seafood with advice on a healthy diet. Outcomes were lipid profile, individual components of the metabolic syndrome, serum insulin concentrations, homeostasis model of insulin resistance, serum C-reactive protein and serum fatty acid levels. We found a significant lowering effect of the intervention with white fish on waist circumference (P < 0.001) and diastolic blood pressure (P = 0.014). A significant lowering effect was also shown after the dietary intervention with fish on serum LDL concentrations (P = 0.048), whereas no significant effects were found on serum HDL or triglyceride concentrations. A significant rise (P < 0.001) in serum EPA and DHA fatty acids was observed following white fish consumption. Overall adherence to the intervention was good and no adverse events were found. CONCLUSION: In individuals with metabolic syndrome, regular consumption of hake reduces LDL cholesterol concentrations, waist circumference and blood pressure components of the metabolic syndrome. CLINICAL TRIAL REGISTRY: White Fish for Cardiovascular Risk Factors in Patients with Metabolic Syndrome Study, Registered under ClinicalTrials.gov Identifier: NCT01758601.

The lung innate immune gene surfactant protein-D is expressed in adipose tissue and linked to obesity status.

BACKGROUND: Surfactant protein-D (SFTPD) is a component of the lung innate immunity that enhances clearance of pathogens and modulates inflammatory responses. An inverse association of putative, lung-derived circulating SFTPD with obesity has been reported but no information is available concerning possible SFTPD gene expression in human adipose tissue. METHODS: SFTPD gene expression was analyzed in human omental (OM; n=156) and subcutaneous (SC; n=106) adipose tissue, and in isolated fat cells (n=12) in association with measures of obesity and glucose tolerance. RESULTS: SFTPD gene was expressed in human adipose tissue and adipocytes. This expression was decreased in OM and SC adipose tissue from obese subjects with (-47%, P<0.0001; and -37%, P=0.048) and without (-34%, P=0.001; and -22%, P=0.08; respectively) type 2 diabetes when compared with the control group. Indeed, OM SFTPD was inversely associated with body mass index (r=-0.33, P<0.0001), percent fat mass (r=-0.36, P<0.0001), waist perimeter (r=-0.26, P=0.002), diastolic blood pressure (r=-0.21, P=0.018) and fasting glucose (r=-0.21, P=0.012); and positively linked to the expression of insulin receptor substrate 1 (IRS1; r=0.25, P=0.004), perilipin A (PLIN; r=0.38, P=0.007) and fatty acid synthase (FASN; r=0.36, P<0.0001). Accordingly, increased SFTPD (4.5-fold, P=0.02) was detected in isolated adipocytes when compared with the stromal-vascular cell fraction, in parallel to IRS1, FASN and PLIN. CONCLUSIONS: Both OM and SC adipose tissue (mainly mature adipocytes) express SFTPD. This expression decreases with obesity and impaired glucose tolerance.

Liver, but not adipose tissue PEDF gene expression is associated with insulin resistance.

OBJECTIVE: Recent studies linked circulating pigment epithelium-derived factor (PEDF) to obesity-associated insulin resistance, but the main source of circulating PEDF is unknown. We aimed to investigate liver and adipose tissue PEDF gene expression in association with obesity and insulin resistance. DESIGN, SUBJECTS AND METHODS: Three (two cross-sectional and one longitudinal) independent cohorts have been studied, for adipose tissue (n=80 and n=30) and liver gene expression (n=32 and n=14). Effects of high glucose and cytokines on HepG2 cell line were also investigated. PEDF gene expression and circulating PEDF were analyzed using real-time PCR and ELISA, respectively. RESULTS: In a first cohort of subjects, PEDF relative gene expression was higher in subcutaneous (SC) than in omental (OM) adipose tissue (P<0.0001) being also higher in mature adipocytes compared with stromo-vascular cells (P<0.0001). However, OM PEDF relative gene expression was decreased in morbidly obese subjects (P=0.01). Both OM PEDF and OM PEDF receptor (PEDFR) correlated positively with lipogenic and lipolytic genes, and with genes implicated in the lipid vacuole formation. Circulating PEDF levels were not associated with fat PEDF gene expression. In the second cohort, SC PEDF was decreased in subjects with type 2 diabetes and did not change significantly after weight loss. We next explored circulating PEDF in association with markers of liver-related insulin resistance injury (alanine aminotransferase, r=0.59, P=0.001). Interestingly, liver PEDF gene expression increased with obesity and insulin resistance in men, being significantly associated with fasting glucose and glycated hemoglobin in two independent cohorts. In fact, high glucose led to increased PEDF in HepG2 cells, while inflammatory stimuli present in the adipose tissue environment downregulated PEDF. CONCLUSION: Liver, but not adipose tissue, might be the source of increased circulating PEDF linked to insulin resistance.

Thyroid hormone receptor alpha gene variants increase the risk of developing obesity and show gene-diet interactions.

OBJECTIVE: Thyroid hormone receptor-beta resistance has been associated with metabolic traits. THRA gene sequencing of an obese woman (index case) who presented as empirical thyroid hormone receptor-α (THRA) resistance, disclosed a polymorphism (rs12939700) in a critical region involved in TRα alternative processing. DESIGN AND SUBJECTS: THRA gene variants were evaluated in three independent europid populations (i) in two population cohorts at baseline (n=3417 and n=2265), 6 years later (n=2139) and (ii) in 4734 high cardiovascular risk subjects (HCVR, PREDIMED trial). RESULTS: The minor allele of the index case polymorphism (rs12939700), despite having a very low frequency (4%), was significantly associated with higher body mass index (BMI) (P=0.042) in HCVR subjects. A more frequent THRA polymorphism (rs1568400) was associated with higher BMI in subjects from the population (P=0.00008 and P=0.05) after adjusting for several confounders. Rs1568400 was also strongly associated with fasting triglycerides (P dominant=3.99 × 10(-5)). In the same sample, 6 years later, age and sex-adjusted risk of developing obesity was significantly increased in GG homozygotes (odds ratio 2.93 (95% confidence interval, 1.05-6.95)). In contrast, no association between rs1568400 and BMI was observed in HCVR subjects, in whom obesity was highly prevalent. This might be explained by the presence of an interaction (P <0.001) among the rs1568400 variant, BMI and saturated fat intake. Only when saturated fat intake was high (>24.5 g d(-1)), GG carriers showed a significantly higher BMI than A carriers after controlling for energy intake and physical activity. CONCLUSIONS: THRA gene polymorphisms are associated with obesity development. This is a novel observation linking the THRA locus to metabolic phenotypes.

Inflammation in adipose tissue and fatty acid anabolism: when enough is enough!

Recent findings in adipose tissue (AT) have uncovered negative interactions among obesity, lipogenesis, and fatty acid (FA) storage, perhaps in response to the increased production of proinflammatory cytokines and transcription factors. Emerging evidence highlights that local hypoxia, generation of reactive oxygen and nitrogen species, increased immune cells infiltration and activation, senescence, inflammation, energy consumption, and decreased lipogenesis in the AT are interrelated and may lead to impaired cytokine and hormonal secretion by adipocytes, and ectopic fat deposition in obesity that strengths the increased risk of suffering metabolic disorders in obese subjects. The information summarized in this review attempts to defend the interdependent relationship of these proofs of concept, supporting the idea that "inflamed" and "dysfunctional" AT are synonymous when referring to obesity. This may happen in severe obese subjects with a large and long-lasting fat excess, when fat depots have reached the point in which excessive fat storage, cell density, and diminished oxygen availability promote decreased lipo/adipogenesis and increased lipolysis and FA release. This response may be induced by an important inflammatory component that promotes angiogenesis and insulin resistance, but also by leptin and the increase of T3 in hyperplastic AT.

Innate immunity, insulin resistance and type 2 diabetes.

In this edition of 'Then and now' the initial studies by J.C. Pickup and colleagues supporting the hypothesis that type 2 diabetes is caused by activated innate immunity, published in Diabetologia in 1997 (40:1286-1292), are discussed. These initial findings led to research that has uncovered links between insulin resistance, obesity, circulating immune markers, immunogenetic susceptibility, macrophage function and chronic infection. Genetic variations leading to the altered production or function of circulating innate immune proteins, cellular pattern recognition receptors and inflammatory cytokines are linked to obesity, insulin resistance and type 2 diabetes. Components of the innate immune system in the muscle, bone, liver and adipose tissue, as well as macrophages, have been revealed to play a role in systemic insulin action. Evolutionary pressures, such as acute infections at the population level (pandemics) and chronic low exposure to environmental products or infectious agents, may have contributed to increased susceptibility and to the current increase in the prevalence of insulin resistance and type 2 diabetes.

Type I iodothyronine 5'-deiodinase mRNA and activity is increased in adipose tissue of obese subjects.

Differentiation and metabolism of adipose tissue are modulated by thyroid hormones (THs), but relatively little is known about the metabolism of THs in this tissue. Expression of the genes for type I iodothyronine 5'-deiodinase (D1), leptin (LEP) and stearoyl-CoA desaturase 1 (SCD-1) was evaluated in omental (OM) and subcutaneous (SC) fat using a cohort of 70 humans. Activities of iodothyronine deiodinases (D1, D2 and D3) were assessed in a randomly selected subpopulation of 19 subjects. D1 expression was upregulated in both OM (P=0.011) and SC (P=0.003) fat of obese subjects. Concomitantly, OM (P=0.002) and SC (P=0.028) LEP expression were increased in obesity, associated with both D1 mRNA (r=0.315, P=0.014) and activity (r=0.647, P=0.023) and inversely related to SCD-1 (r=-0.266, P=0.034) expression in SC fat. Also D1 (but not D2 and D3) activity was increased in OM (∼fourfold, P=0.010) and SC (∼eightfold, P=0.004) fat of obese when compared with non-obese subjects and correlated in both OM (r=0.528, P=0.036) and SC (r=0.749, P=0.005) fat with body mass index. Our results document increased D1 gene expression and activity in adipose tissue of obese humans and suggest a role of 3,5,3'-triiodo-L-thyronine formed by D1 in response to leptin in the modulation of adipose tissue metabolism.