Visceral fat and metabolic inflammation: the portal theory revisited

Body weight predicts Nicotinamide N-Methyltransferase activity in mouse fat

AIM

Nicotinamide N-methyltransferase (NNMT) is a novel regulator of energy homeostasis in adipose tissue. NNMT expression is higher in obese mice than in lean mice, and NNMT knockdown prevents diet-induced obesity. Little is known about the regulation of enzyme activity during the development of obesity. The aim of this study was to analyze NNMT activity in tissues of mice with incipient and established obesity.

METHODS

A fluorescence-based, sensitive, low-volume, high-throughput method was developed to assay NNMT activity. C57BL/6 mice were fed a high-fat diet for 4 weeks (incipient obesity) and for 12 weeks (established obesity). Tissues and serum were harvested and analyzed.

RESULTS

NNMT activity was highest in subcutaneous white fat (55.0 µU/mg), followed by epididymal white fat (35.6 µU/mg), brown adipose tissue (7.8 µU/mg), liver (7.6 µU/mg), and lung (7.3 µU/mg). Little activity was detected in heart, skeletal muscle, and kidney. No activity was found in serum samples. Body weight predicted NNMT activity in white fat, but not in brown fat or any other tissue, and only in incipient obesity. With established obesity, this association was lost.

CONCLUSIONS

As obesity develops, body weight predicts NNMT activity in white adipose tissue, but not in any other tissue, consistent with a specific role of adipose-tissue NNMT in the regulation of body weight.

Obesity phenotypes: depot-differences in adipose tissue and their clinical implications

Obesity, defined as excess fat mass, increases risks for multiple chronic diseases, such as type 2 diabetes, cardiovascular disease, and several types of cancer. Beyond adiposity per se, the pattern of fat distribution, android or truncal as compared to gynoid or peripheral, has a profound influence on systemic metabolism and hence risk for obesity complications. Not only factors as genetics, environment, gender, and age account for the apparent compartmentalization of white adipose tissue (WAT) in the body. Indeed, the heterogeneity among different anatomical depots also appears to stem from their intrinsic diversity, including cellular developmental origin, proliferative capacity, glucose and lipid metabolism, insulin sensitivity, cytokine pattern, thermogenic ability, and vascularization. Under the obese condition, these depot-specific differences translate into specific WAT distribution patterns, giving rise to different cardiometabolic consequences. This review summarizes the clinical and mechanistic evidence for the depot-specific differences and the phenotypic characteristics of different WAT depots that link their depot-specific biology to obesity-specific complications.

Sedentary Time and MRI-Derived Measures of Adiposity in Active Versus Inactive Individuals

OBJECTIVE

The aim of this study was to examine cross-sectional associations between objectively measured sedentary time and magnetic resonance imaging (MRI)-assessed adiposity in a population at high risk for type 2 diabetes (T2DM) and to determine whether associations are modified by the recommended levels of moderate-to-vigorous physical activity (MVPA).

METHODS

Sedentary time and MVPA were measured objectively by using accelerometers. Linear regression models examined the association of sedentary time with liver, visceral, subcutaneous, and total abdominal fat (quantified by using MRI). Interaction terms determined whether results were consistent across activity categories (active [> 150 min/wk of MVPA] vs. inactive [< 150 min/wk of MVPA]).

RESULTS

One hundred and twenty-four participants (age = 64.0 ± 7.1 years; male = 65.3%; BMI = 31.8 ± 5.6 kg/m² ) were included. Following adjustment, each 60 minutes of sedentary time was associated with 1.74 L higher total abdominal fat, 0.62 L higher visceral fat, 1.14 L higher subcutaneous fat, and 1.86% higher liver fat. When results were stratified by MVPA (active vs. inactive), sedentary time was associated with greater liver, visceral, and total abdominal fat in the inactive group only.

CONCLUSIONS

These findings suggest that sedentary time is associated with higher levels of inter- and intraorgan fat, but associations with liver, visceral, and total abdominal fat were stronger in those who do not reach the current exercise recommendations for health.

Effect of Distinct Lifestyle Interventions on Mobilization of Fat Storage Pools: CENTRAL Magnetic Resonance Imaging Randomized Controlled Trial

BACKGROUND

We aimed to assess whether distinct lifestyle strategies can differentially affect specific body adipose depots.

METHODS

We performed an 18-month randomized controlled trial among 278 sedentary adults with abdominal obesity (75%) or dyslipidemia in an isolated workplace with a monitored provided lunch. Participants were randomized to isocaloric low-fat or Mediterranean/low-carbohydrate (MED/LC) diet+28 g walnuts/day with/without added moderate physical activity (PA; 80% aerobic; supervised/free gym membership). Overall primary outcome was body fat redistribution, and the main specific end point was visceral adipose tissue (VAT). We further followed the dynamics of different fat depots (deep and superficial subcutaneous, liver, pericardial, muscle, pancreas, and renal sinus) by magnetic resonance imaging.

RESULTS

Of 278 participants (age, 48 years, 89% men, body mass index, 30.8 kg/m²), 86% completed the trial with good adherence. The low-fat group preferentially decreased reported fat intake (-21.0% versus -11.5% for the MED/LC; P<0.001), and the MED/LC group decreased reported carbohydrates intake (-39.5% versus -21.3% for the low-fat group; P<0.001). The PA⁺ groups significantly increased the metabolic equivalents per week versus the PA^- groups (19.0 versus 2.1; P=0.009). Whereas final moderate weight loss was indifferent, exercise attenuated the waist circumference rebound with the greatest effect in the MED/LC^PA+ group (P<0.05). VAT (-22%), intrahepatic (-29%), and intrapericardial (-11%) fats declines were higher than pancreatic and femur intermuscular fats (1% to 2%) loss. Independent of weight loss, PA⁺ with either diet had a significantly greater effect on decreasing VAT (mean of difference, -6.67cm²; 95% confidence interval, -14.8 to -0.45) compared with PA^-. The MED/LC diet was superior to the low-fat diet in decreasing intrahepatic, intrapericardial, and pancreatic fats (P<0.05 for all). In contrast, renal sinus and femoral intermuscular fats were not differentially altered by lifestyle interventions but by weight loss per se. In multivariate models further adjusted for weight loss, losing VAT or intrahepatic fat was independently associated with improved lipid profile, losing deep subcutaneous adipose tissue with improved insulin sensitivity, and losing superficial subcutaneous adipose tissue remained neutral except for an association with decreased leptin.

CONCLUSIONS

Moderate weight loss alone inadequately reflects the significant lifestyle effects on atherogenic and diabetogenic fat depots. The MED/LC diet mobilizes specific ectopic fat depots, and exercise has an independent contribution to VAT loss. Fat depots exhibit diverse responsiveness and are differentially related to cardiometabolic markers. Distinct lifestyle protocols may uniquely induce fat mobilization from specific anatomic sites.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT01530724.

Physical activity and central adiposity in a cohort of African-American adults

Background

Visceral adipose tissue (VAT) is known as an independent predictor of cardiometabolic risk and all-cause mortality, while increased physical activity has been shown to improve cardiometabolic risk. The purpose of the present study was to determine whether or not there is an association between objectively-measured physical activity and VAT in a community-based cohort of African-American adults, a population at higher-than-average risk for cardiometabolic diseases.

Methods

Free-living physical activity was quantified using accelerometry while VAT and abdominal subcutaneous fat were estimated using dual x-ray absorptiometry in a cohort of African Americans, ages 30–50 years, enrolled in the Modeling the Epidemiologic Transition Study. Univariate and multivariate analyses were used to determine the degree of association comparing moderate-to-vigorous physical activity (MVPA), vigorous activity, and sedentary behavior with measures of central adiposity including VAT, subcutaneous fat, and waist circumference.

Results

A total of 271 individuals with complete data were included in the analyses. Women, on average, had significantly more VAT and abdominal subcutaneous fat than men. There were statistically significant inverse univariate correlations between MVPA and measures of abdominal adiposity (−0.30, p < 0.001) and activity counts and adiposity (−0.31, p < 0.001) among both sexes. These significant associations remained after controlling for age, sex, and smoking status; neither alcohol consumption nor employment status were associated with abdominal adiposity. Time in sedentary behavior was not meaningfully associated with central adiposity in either sex (women: −0.02, p = 0.79; men: −0.21, p = 0.04).

Conclusions

To our knowledge, this study is the first to identify significant inverse associations between MVPA and measures of central adiposity among African American adults from a community-based cohort using an objective measure of physical activity and a validated quantitative imaging technique.

Ovarian hormones and obesity

BACKGROUND

Obesity is caused by an imbalance between energy intake, i.e. eating and energy expenditure (EE). Severe obesity is more prevalent in women than men worldwide, and obesity pathophysiology and the resultant obesity-related disease risks differ in women and men. The underlying mechanisms are largely unknown. Pre-clinical and clinical research indicate that ovarian hormones may play a major role.

OBJECTIVE AND RATIONALE

We systematically reviewed the clinical and pre-clinical literature on the effects of ovarian hormones on the physiology of adipose tissue (AT) and the regulation of AT mass by energy intake and EE.

SEARCH METHODS

Articles in English indexed in PubMed through January 2016 were searched using keywords related to: (i) reproductive hormones, (ii) weight regulation and (iii) central nervous system. We sought to identify emerging research foci with clinical translational potential rather than to provide a comprehensive review.

OUTCOMES

We find that estrogens play a leading role in the causes and consequences of female obesity. With respect to adiposity, estrogens synergize with AT genes to increase gluteofemoral subcutaneous AT mass and decrease central AT mass in reproductive-age women, which leads to protective cardiometabolic effects. Loss of estrogens after menopause, independent of aging, increases total AT mass and decreases lean body mass, so that there is little net effect on body weight. Menopause also partially reverses women's protective AT distribution. These effects can be counteracted by estrogen treatment. With respect to eating, increasing estrogen levels progressively decrease eating during the follicular and peri-ovulatory phases of the menstrual cycle. Progestin levels are associated with eating during the luteal phase, but there does not appear to be a causal relationship. Progestins may increase binge eating and eating stimulated by negative emotional states during the luteal phase. Pre-clinical research indicates that one mechanism for the pre-ovulatory decrease in eating is a central action of estrogens to increase the satiating potency of the gastrointestinal hormone cholecystokinin. Another mechanism involves a decrease in the preference for sweet foods during the follicular phase. Genetic defects in brain α-melanocycte-stimulating hormone-melanocortin receptor (melanocortin 4 receptor, MC4R) signaling lead to a syndrome of overeating and obesity that is particularly pronounced in women and in female animals. The syndrome appears around puberty in mice with genetic deletions of MC4R, suggesting a role of ovarian hormones. Emerging functional brain-imaging data indicates that fluctuations in ovarian hormones affect eating by influencing striatal dopaminergic processing of flavor hedonics and lateral prefrontal cortex processing of cognitive inhibitory controls of eating. There is a dearth of research on the neuroendocrine control of eating after menopause. There is also comparatively little research on the effects of ovarian hormones on EE, although changes in ovarian hormone levels during the menstrual cycle do affect resting EE.

WIDER IMPLICATIONS

The markedly greater obesity burden in women makes understanding the diverse effects of ovarian hormones on eating, EE and body adiposity urgent research challenges. A variety of research modalities can be used to investigate these effects in women, and most of the mechanisms reviewed are accessible in animal models. Therefore, human and translational research on the roles of ovarian hormones in women's obesity and its causes should be intensified to gain further mechanistic insights that may ultimately be translated into novel anti-obesity therapies and thereby improve women's health.

Overexpression of C-type Natriuretic Peptide in Endothelial Cells Protects against Insulin Resistance and Inflammation during Diet-induced Obesity

The endogenous peptide C-type natriuretic peptide (CNP) binds its receptor, guanylyl cyclase B (GCB), and is expressed by endothelial cells in diverse tissues. Because the endothelial cells of visceral adipose tissue have recently been reported to play a role in lipid metabolism and inflammation, we investigated the effects of CNP on features of obesity by using transgenic (Tg) mice in which CNP was placed under the control of the Tie2 promoter and was thus overexpressed in endothelial cells (E-CNP). Here we show that increased brown adipose tissue thermogenesis in E-CNP Tg mice increased energy expenditure, decreased mesenteric white adipose tissue (MesWAT) fat weight and adipocyte hypertrophy, and prevented the development of fatty liver. Furthermore, CNP overexpression improved glucose tolerance, decreased insulin resistance, and inhibited macrophage infiltration in MesWAT, thus suppressing pro-inflammation during high-fat diet–induced obesity. Our findings indicate an important role for the CNP produced by the endothelial cells in the regulation of MesWAT hypertrophy, insulin resistance, and inflammation during high-fat diet–induced obesity.

Muscle and adipose tissue morphology, insulin sensitivity and beta-cell function in diabetic and nondiabetic obese patients: effects of bariatric surgery

Obesity is characterized by insulin-resistance (IR), enhanced lipolysis, and ectopic, inflamed fat. We related the histology of subcutaneous (SAT), visceral fat (VAT), and skeletal muscle to the metabolic abnormalities, and tested their mutual changes after bariatric surgery in type 2 diabetic (T2D) and weight-matched non-diabetic (ND) patients. We measured IR (insulin clamp), lipolysis (²H₅-glycerol infusion), ß-cell glucose-sensitivity (ß-GS, mathematical modeling), and VAT, SAT, and rectus abdominis histology (light and electron microscopy). Presurgery, SAT and VAT showed signs of fibrosis/necrosis, small mitochondria, free interstitial lipids, thickened capillary basement membrane. Compared to ND, T2D had impaired ß-GS, intracapillary neutrophils and higher intramyocellular fat, adipocyte area in VAT, crown-like structures (CLS) in VAT and SAT with rare structures (cyst-like) ~10-fold larger than CLS. Fat expansion was associated with enhanced lipolysis and IR. VAT histology and intramyocellular fat were related to impaired ß-GS. Postsurgery, IR and lipolysis improved in all, ß-GS improved in T2D. Muscle fat infiltration was reduced, adipocytes were smaller and richer in mitochondria, and CLS density in SAT was reduced. In conclusion, IR improves proportionally to weight loss but remains subnormal, whilst SAT and muscle changes disappear. In T2D postsurgery, some VAT pathology persists and beta-cell dysfunction improves but is not normalized.

Shortcuts to a functional adipose tissue: The role of small non-coding RNAs

Metabolic diseases such as type 2 diabetes are a major public health issue worldwide. These diseases are often linked to a dysfunctional adipose tissue. Fat is a large, heterogenic, pleiotropic and rather complex tissue. It is found in virtually all cavities of the human body, shows unique plasticity among tissues, and harbors many cell types in addition to its main functional unit - the adipocyte. Adipose tissue function varies depending on the localization of the fat depot, the cell composition of the tissue and the energy status of the organism. While the white adipose tissue (WAT) serves as the main site for triglyceride storage and acts as an important endocrine organ, the brown adipose tissue (BAT) is responsible for thermogenesis. Beige adipocytes can also appear in WAT depots to sustain heat production upon certain conditions, and it is becoming clear that adipose tissue depots can switch phenotypes depending on cell autonomous and non-autonomous stimuli. To maintain such degree of plasticity and respond adequately to changes in the energy balance, three basic processes need to be properly functioning in the adipose tissue: i) adipogenesis and adipocyte turnover, ii) metabolism, and iii) signaling. Here we review the fundamental role of small non-coding RNAs (sncRNAs) in these processes, with focus on microRNAs, and demonstrate their importance in adipose tissue function and whole body metabolic control in mammals.

Relationship between Nonalcoholic Fatty Liver Disease and Vitamin D Nutritional Status in Extreme Obesity

AIM

To evaluate the relationship of nonalcoholic fatty liver disease (NAFLD) with nutritional status of vitamin D in extreme obesity.

METHODS

Descriptive cross-sectional study in individuals with class III obesity (BMI ≥ 40 kg/m2), aged ≥ 20 years to < 60 years. Data were obtained for weight, height, waist circumference (WC), and serum 25-hydroxyvitamin D (25(OH)D) levels. Vitamin D analysis was performed by high performance liquid chromatography (HPLC) and the cutoff points used for its classification were < 20 ng/mL for deficiency and 20-29.9 ng/ml for insufficiency. NAFLD gradation was conducted through histological evaluation by liver biopsy.

RESULTS

The sample is comprised of 50 individuals (86% female). BMI and average weight were 44.1 ± 3.8 kg/m2 and 121.4 ± 21.4 kg, respectively. Sample distribution according to serum 25(OH)D levels showed 42% of deficiency and 48% of insufficiency. The diagnosis of NAFLD was confirmed in 100% of the individuals, of which 70% had steatosis and 30% had steatohepatitis. The highest percentage of 25(OH)D insufficiency was seen in individuals with steatosis (66%/n = 21) and steatohepatitis (93%/n = 16). All individuals with steatohepatitis presented VDD (p < 0.01).

CONCLUSION

The results of this study showed high prevalence of serum 25(OH)D inadequacy in individuals with class III obesity, which worsens as the stage of liver disease progresses.

Adipose tissue supports normalization of macrophage and liver lipid handling in obesity reversal

Adipose tissue inflammation and dysfunction are considered central in the pathogenesis of obesity-related dysmetabolism, but their role in the rapid metabolic recovery upon obesity reversal is less well defined. We hypothesized that changes in adipose tissue endocrine and paracrine mechanisms may support the rapid improvement of obesity-induced impairment in cellular lipid handling. C57Bl-6J mice were fed ad libitum either normal chow (NC) or high-fat diet (HFF) for 10 weeks. A dietary obesity reversal group was fed HFF for 8 weeks and then switched to NC for 2 weeks (HFF→NC). Whole-body glucose homeostasis rapidly nearly normalized in the HFF→NC mice (fasting glucose and insulin fully normalized, glucose and insulin tolerance tests reversed 82% to the NC group levels). During 2 weeks of the dietary reversal, the liver was significantly cleared from ectopic fat, and functionally, glucose production from pyruvate, alanine or fructose was normalized. In contrast, adipose tissue inflammation (macrophage infiltration and polarization) largely remained as in HFF, though obesity-induced adipose tissue macrophage lipid accumulation decreased by ~50%, and adipose tissue MAP kinase hyperactivation was reversed. Ex vivo, mild changes in adipose tissue adipocytokine secretion profile were noted. These corresponded to partial or full reversal of the excess cellular lipid droplet accumulation induced by HFF adipose tissue conditioned media in hepatoma or macrophage cells, respectively. We propose that early after initiating reversal of nutritional obesity, rapid metabolic normalization largely precedes resolution of adipose tissue inflammation. Nevertheless, we demonstrate a hitherto unrecognized contribution of adipose tissue to the rapid improvement in lipid handling by the liver and by macrophages.

Impact of fat mass and distribution on lipid turnover in human adipose tissue

Differences in white adipose tissue (WAT) lipid turnover between the visceral (vWAT) and subcutaneous (sWAT) depots may cause metabolic complications in obesity. Here we compare triglyceride age and, thereby, triglyceride turnover in vWAT and sWAT biopsies from 346 individuals and find that subcutaneous triglyceride age and storage capacity are increased in overweight or obese individuals. Visceral triglyceride age is only increased in excessively obese individuals and associated with a lower lipid removal capacity. Thus, although triglyceride storage capacity in sWAT is higher than in vWAT, the former plateaus at substantially lower levels of excess WAT mass than vWAT. In individuals with central or visceral obesity, lipid turnover is selectively increased in vWAT. Obese individuals classified as ‘metabolically unhealthy' (according to ATPIII criteria) who have small subcutaneous adipocytes exhibit reduced triglyceride turnover. We conclude that excess WAT results in depot-specific differences in lipid turnover and increased turnover in vWAT and/or decreased turnover in sWAT may result in metabolic complications of overweight or obesity.

Lipid turnover in tissues can be calculated from ratios of different carbon isotopes. Here the authors use this approach to study lipid turnover in two distinct adipose tissue depots and find that, in obese individuals, visceral fat is more lipolytic than subcutaneous fat.

A classification system for zebrafish adipose tissues

The zebrafish model system offers significant utility for in vivo imaging of adipose tissue (AT) dynamics and for screening to identify chemical and genetic modifiers of adiposity. In particular, AT can be quantified accurately in live zebrafish using fluorescent lipophilic dyes. Although this methodology offers considerable promise, the comprehensive identification and classification of zebrafish ATs has not been performed. Here, we use fluorescent lipophilic dyes and in vivo imaging systematically to identify, classify and quantify the zebrafish AT pool. We identify 34 regionally distinct zebrafish ATs, including five visceral ATs and 22 subcutaneous ATs. For each of these ATs, we describe detailed morphological characteristics to aid their identification in future studies. Furthermore, we quantify the areas for each AT and construct regression models to allow prediction of expected AT size and variation across a range of developmental stages. Finally, we demonstrate the utility of this resource for identifying effects of strain variation and high-fat diet on AT growth. Altogether, this resource provides foundational information on the identity, dynamics and expected quantities of zebrafish ATs for use as a reference for future studies.

Summary: A standardized nomenclature and classification system for zebrafish adipose tissues and regression models to predict expected adipose size during the course of zebrafish development.

The role of transplanted visceral fat from the long-lived growth hormone receptor knockout mice on insulin signaling

Growth hormone receptor knockout mice (GHRKO) are characterized by high insulin sensitivity and extended lifespan. Interestingly, the secretory activity of visceral fat in GHRKO mice is altered, stimulating whole body insulin sensitivity. In this study, we transplanted normal (N) mice with visceral fat pads from GHRKO or N mice to determine the role of visceral fat on the insulin signaling. We found that the transplant of visceral fat from GHRKO mice to N mice (N-GHRKO) improved whole body insulin sensitivity when comparing with sham-operated mice (N-S) and with mice that received visceral fat from N mice (N-N). This was associated with increased hepatic insulin sensitivity as observed by the increased phosphorylated insulin receptor and increased hepatic expression of Pparα and Pparγ. In conclusion, we demonstrated that visceral fat transplant from GHRKO mice into normal mice enhanced insulin sensitivity and glucose tolerance. These results further confirm the differential physiological role played by visceral adipose tissue from GH receptor deficient mice, indicating that the increase of this fat depot can be associated with beneficial effects on insulin signaling and longevity.

Sugar-Sweetened Beverage but Not Diet Soda Consumption Is Positively Associated with Progression of Insulin Resistance and Prediabetes

BACKGROUND

Previous studies have shown an inconsistent relation between habitual beverage consumption and insulin resistance and prediabetes.

OBJECTIVE

The objective of the present study was to test the hypothesis that the consumption of sugar-sweetened beverages (SSBs), rather than diet soda, is associated with long-term progression of insulin resistance and the development of prediabetes.

METHODS

We analyzed the prospective association between cumulative mean consumption of SSBs or diet soda and incident prediabetes (n = 1685) identified across a median of 14 y of follow-up in participants [mean ± SD age: 51.9 ± 9.2 y; 59.6% women; mean ± SD body mass index (BMI; kg/m²): 26.3 ± 4.4] of the Framingham Offspring cohort. The prospective association between beverage consumption and change in homeostasis model assessment of insulin resistance (HOMA-IR; n = 2076) over ∼7 y was also analyzed. The cumulative mean consumption of SSBs and diet soda was estimated by using food-frequency questionnaires. Multivariable Cox proportional hazards models and linear regression models were implemented to estimate the HRs of incident prediabetes and change in HOMA-IR, respectively.

RESULTS

After adjustment for multiple potential confounders, including baseline BMI, we observed that SSB intake was positively associated with incident prediabetes (P-trend < 0.001); the highest SSB consumers (>3 servings/wk; median: 6 servings/wk) had a 46% higher risk of developing prediabetes than did the SSB nonconsumers (HR: 1.46; 95% CI: 1.16, 1.83). Higher SSB intake was also associated with a greater increase in HOMA-IR (P-trend = 0.006). No prospective associations were observed between diet soda intake and risk of prediabetes (P-trend = 0.24) or changes in HOMA-IR (P-trend = 0.25). These associations were similar after additional adjustment for change in BMI.

CONCLUSION

Regular SSB intake, but not diet soda intake, is associated with a greater increase in insulin resistance and a higher risk of developing prediabetes in a group of middle-aged adults.

Acyl-CoA synthetase long-chain 5 genotype is associated with body composition changes in response to lifestyle interventions in postmenopausal women with overweight and obesity: a genetic association study on cohorts Montréal-Ottawa New Emerging Team, and Complications Associated with Obesity

BACKGROUND

Genetic studies on Acyl-CoA Synthetase Long-Chain 5 (ACSL5) demonstrate an association between rs2419621 genotype and rate of weight loss in women with obesity in response to caloric restriction. Our objectives were to (1) confirm results in two different populations of women with overweight and obesity (2) study rs2419621's influence on body composition parameters of women with overweight and obesity following lifestyle interventions.

METHODS

rs2419621 genotype was determined in women with overweight and obesity who participated in the Montréal-Ottawa New Emerging Team (MONET n = 137) and Complications Associated with Obesity (CAO n = 37) studies. Genotyping was done using TaqMan MGB probe-based assay. Multiple linear regression analyses were used to test for associations.

RESULTS

When studying women with overweight and obesity, rs2419621 [T] allele carriers had a significantly greater decrease in visceral fat, absolute and percent fat mass and a greater increase in percent lean mass in response to lifestyle intervention in comparison to non-carriers. Studying only individuals with obesity showed similar results with rs2419621 [T] allele carriers also displaying a significantly greater decrease in body mass index following the lifestyle intervention in comparison to non-carriers.

CONCLUSION

Women with overweight and obesity carrying the ACSL5 rs2419621 [T] allele are more responsive to lifestyle interventions in comparison to non-carriers. Conducting such genetic association studies can aid in individualized treatments/interventions catered towards an individual's genotype.

Role of Serum Uric Acid and Ferritin in the Development and Progression of NAFLD

Nonalcoholic fatty liver disease (NAFLD), tightly linked to the metabolic syndrome (MS), has emerged as a leading cause of chronic liver disease worldwide. Since it is potentially progressive towards non-alcoholic steatohepatitis (NASH) and hepatic fibrosis, up to cirrhosis and its associated complications, the need for predictive factors of NAFLD and of its advanced forms is mandatory. Despite the current "gold standard" for the assessment of liver damage in NAFLD being liver biopsy, in recent years, several non-invasive tools have been designed as alternatives to histology, of which fibroscan seems the most promising. Among the different serum markers considered, serum uric acid (SUA) and ferritin have emerged as possible predictors of severity of liver damage in NAFLD. In fact, as widely described in this review, they share common pathogenetic pathways and are both associated with hepatic steatosis and MS, thus suggesting a likely synergistic action. Nevertheless, the power of these serum markers seems to be too low if considered alone, suggesting that they should be included in a wider perspective together with other metabolic and biochemical parameters in order to predict liver damage.

Heterogeneity of white adipose tissue: molecular basis and clinical implications

Adipose tissue is a highly heterogeneous endocrine organ. The heterogeneity among different anatomical depots stems from their intrinsic differences in cellular and physiological properties, including developmental origin, adipogenic and proliferative capacity, glucose and lipid metabolism, insulin sensitivity, hormonal control, thermogenic ability and vascularization. Additional factors that influence adipose tissue heterogeneity are genetic predisposition, environment, gender and age. Under obese condition, these depot-specific differences translate into specific fat distribution patterns, which are closely associated with differential cardiometabolic risks. For instance, individuals with central obesity are more susceptible to developing diabetes and cardiovascular complications, whereas those with peripheral obesity are more metabolically healthy. This review summarizes the clinical and mechanistic evidence for the depot-specific differences that give rise to different metabolic consequences, and provides therapeutic insights for targeted treatment of obesity.

Differential impacts of cardiac and abdominal ectopic fat deposits on cardiometabolic risk stratification

Background

Previous studies have shown that excessive abdominal visceral adipose tissue (AVAT) and epicardial adipose tissue (EAT) are risk factors of cardiometabolic disease; we hypothesized there is differential contribution of abdominal and cardiac fat deposits to the cardiometabolic profiles.

Methods

Two hundred eight consecutive subjects with clinical suspicion of coronary artery disease (CAD) who underwent cardiac and abdominal CT for Agatston score and abdominal visceral fat measurement were retrospectively analyzed. Regional thickness of EAT (EATth), total volume of EAT, total volume of paracardial adipose tissue (PAT) and total volume of AVAT from L2 to L5 level were measured. The relationships between abdominal and cardiac adipose tissue measurements, the number of components of metabolic syndrome, and the severity of Agatston score on a four ranking scale (0, 1–10,11–100, 101–400, >400) were investigated.

Results

The amounts of AVAT, EAT, PAT and EATth-LAVG showed a significant linear trend with increasing number (0–5) of components in metabolic syndrome (AVAT, EAT and PAT P for trend <0.0001; EATth-LVAG P for trend <0.001). EATth at left atrioventricular groove (EATth-LAVG) showed significant linear trend with the severity of Agatston score on a four ranking scale (P for trend <0.0001). In multivariate binary regression analysis, total volume of AVAT was the sole adiposity predictor for metabolic syndrome independent to age, gender, and waist circumference (odds ratio of 1.20, 95 % CI 1.08–1.32, p < 0.001) while total volume of EAT, PAT, and EATth-LAVG were not. In contrary, EATth-LAVG was the sole adiposity predictor for Agatston score >400 (odds ratio of 1.11, 95 % CI 1.034–1.184, p = 0.004).

Conclusions

Excessive total volume of AVAT appears to be preferentially associated with metabolic syndrome; while EAT, esp. EATth-LAVG is preferentially associated with coronary artery disease. This differential effect of the two adiposities deserves a large-scale cohort study for further investigation.

Anthropometric markers and their association with incident type 2 diabetes mellitus: which marker is best for prediction? Pooled analysis of four German population-based cohort studies and comparison with a nationwide cohort study

OBJECTIVE

To compare the association between different anthropometric measurements and incident type 2 diabetes mellitus (T2DM) and to assess their predictive ability in different regions of Germany.

METHODS

Data of 10,258 participants from 4 prospective population-based cohorts were pooled to assess the association of body weight, body mass index (BMI), waist circumference (WC), waist-to-hip-ratio (WHR) and waist-to-height-ratio (WHtR) with incident T2DM by calculating HRs of the crude, adjusted and standardised markers, as well as providing receiver operator characteristic (ROC) curves. Differences between HRs and ROCs for the different anthropometric markers were calculated to compare their predictive ability. In addition, data of 3105 participants from the nationwide survey were analysed separately using the same methods to provide a nationally representative comparison.

RESULTS

Strong associations were found for each anthropometric marker and incidence of T2DM. Among the standardised anthropometric measures, we found the strongest effect on incident T2DM for WC and WHtR in the pooled sample (HR for 1 SD difference in WC 1.97, 95% CI 1.75 to 2.22, HR for WHtR 1.93, 95% CI 1.71 to 2.17 in women) and in female DEGS participants (HR for WC 2.24, 95% CI 1.91 to 2.63, HR for WHtR 2.10, 95% CI 1.81 to 2.44), whereas the strongest association in men was found for WHR among DEGS participants (HR 2.29, 95% CI 1.89 to 2.78). ROC analysis showed WHtR to be the strongest predictor for incident T2DM. Differences in HR and ROCs between the different markers confirmed WC and WHtR to be the best predictors of incident T2DM. Findings were consistent across study regions and age groups (<65 vs ≥ 65 years).

CONCLUSIONS

We found stronger associations between anthropometric markers that reflect abdominal obesity (ie, WC and WHtR) and incident T2DM than for BMI and weight. The use of these measurements in risk prediction should be encouraged.

A role for exercise after bariatric surgery?

Obesity predisposes an individual to develop numerous comorbidities, including type 2 diabetes, and represents a major healthcare issue in many countries worldwide. Bariatric surgery can be an effective treatment option, resulting in profound weight loss and improvements in metabolic health; however, not all patients achieve similar weight loss or metabolic improvements. Exercise is an excellent way to improve health, with well-characterized physiological and psychological benefits. In the present paper we review the evidence to determine whether there may be a role for exercise as a complementary adjunct therapy to bariatric surgery. Objectively measured physical activity data indicate that most patients who undergo bariatric surgery do not exercise enough to reap the health benefits of exercise. While there is a dearth of data on the effects of exercise on weight loss and weight loss maintenance after surgery, evidence from studies of caloric restriction and exercise suggest that similar adjunctive benefits may be extended to patients who perform exercise after bariatric surgery. Recent evidence from exercise interventions after bariatric surgery suggests that exercise may provide further improvements in metabolic health compared with surgery-induced weight loss alone. Additional randomized controlled exercise trials are now needed as the next step to more clearly define the potential for exercise to provide additional health benefits after bariatric surgery. This valuable evidence will inform clinical practice regarding much-needed guidelines for exercise after bariatric surgery.

Adipose Tissue Remodeling: Its Role in Energy Metabolism and Metabolic Disorders

The adipose tissue is a central metabolic organ in the regulation of whole-body energy homeostasis. The white adipose tissue functions as a key energy reservoir for other organs, whereas the brown adipose tissue accumulates lipids for cold-induced adaptive thermogenesis. Adipose tissues secrete various hormones, cytokines, and metabolites (termed as adipokines) that control systemic energy balance by regulating appetitive signals from the central nerve system as well as metabolic activity in peripheral tissues. In response to changes in the nutritional status, the adipose tissue undergoes dynamic remodeling, including quantitative and qualitative alterations in adipose tissue-resident cells. A growing body of evidence indicates that adipose tissue remodeling in obesity is closely associated with adipose tissue function. Changes in the number and size of the adipocytes affect the microenvironment of expanded fat tissues, accompanied by alterations in adipokine secretion, adipocyte death, local hypoxia, and fatty acid fluxes. Concurrently, stromal vascular cells in the adipose tissue, including immune cells, are involved in numerous adaptive processes, such as dead adipocyte clearance, adipogenesis, and angiogenesis, all of which are dysregulated in obese adipose tissue remodeling. Chronic overnutrition triggers uncontrolled inflammatory responses, leading to systemic low-grade inflammation and metabolic disorders, such as insulin resistance. This review will discuss current mechanistic understandings of adipose tissue remodeling processes in adaptive energy homeostasis and pathological remodeling of adipose tissue in connection with immune response.

Bardoxolone Methyl Prevents Mesenteric Fat Deposition and Inflammation in High-Fat Diet Mice

Mesenteric fat belongs to visceral fat. An increased deposition of mesenteric fat contributes to obesity associated complications such as type 2 diabetes and cardiovascular diseases. We have investigated the therapeutic effects of bardoxolone methyl (BARD) on mesenteric adipose tissue of mice fed a high-fat diet (HFD). Male C57BL/6J mice were administered oral BARD during HFD feeding (HFD/BARD), only fed a high-fat diet (HFD), or fed low-fat diet (LFD) for 21 weeks. Histology and immunohistochemistry were used to analyse mesenteric morphology and macrophages, while Western blot was used to assess the expression of inflammatory, oxidative stress, and energy expenditure proteins. Supplementation of drinking water with BARD prevented mesenteric fat deposition, as determined by a reduction in large adipocytes. BARD prevented inflammation as there were fewer inflammatory macrophages and reduced proinflammatory cytokines (interleukin-1 beta and tumour necrosis factor alpha). BARD reduced the activation of extracellular signal-regulated kinase (ERK) and Akt, suggesting an antioxidative stress effect. BARD upregulates energy expenditure proteins, judged by the increased activity of tyrosine hydroxylase (TH) and AMP-activated protein kinase (AMPK) and increased peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), and uncoupling protein 2 (UCP2) proteins. Overall, BARD induces preventive effect in HFD mice through regulation of mesenteric adipose tissue.

Surgical removal of inflamed epididymal white adipose tissue attenuates the development of non-alcoholic steatohepatitis in obesity

Background:

Non-alcoholic fatty liver disease (NAFLD) is strongly associated with abdominal obesity. Growing evidence suggests that inflammation in specific depots of white adipose tissue (WAT) has a key role in NAFLD progression, but experimental evidence for a causal role of WAT is lacking.

Methods:

A time-course study in C57BL/6J mice was performed to establish which WAT depot is most susceptible to develop inflammation during high-fat diet (HFD)-induced obesity. Crown-like structures (CLS) were quantified in epididymal (eWAT), mesenteric (mWAT) and inguinal/subcutaneous (iWAT) WAT. The contribution of inflamed WAT to NAFLD progression was investigated by surgical removal of a selected WAT depot and compared with sham surgery. Plasma markers were analyzed by enzyme-linked immunosorbent assay (cytokines/adipokines) and lipidomics (lipids).

Results:

In eWAT, CLS were formed already after 12 weeks of HFD, which coincided with maximal adipocyte size and fat depot mass, and preceded establishment of non-alcoholic steatohepatitis (NASH). By contrast, the number of CLS were low in mWAT and iWAT. Removal of inflamed eWAT after 12 weeks (eWATx group), followed by another 12 weeks of HFD feeding, resulted in significantly reduced NASH in eWATx. Inflammatory cell aggregates (−40% P<0.05) and inflammatory genes (e.g., TNFα, −37% P<0.05) were attenuated in livers of eWATx mice, whereas steatosis was not affected. Concomitantly, plasma concentrations of circulating proinflammatory mediators, viz. leptin and specific saturated and monounsaturated fatty acids, were also reduced in the eWATx group.

Conclusions:

Intervention in NAFLD progression by removal of inflamed eWAT attenuates the development of NASH and reduces plasma levels of specific inflammatory mediators (cytokines and lipids). These data support the hypothesis that eWAT is causally involved in the pathogenesis of NASH.

Association between serum zinc level and body composition: The Korean National Health and Nutrition Examination Survey

OBJECTIVE

The aim of this study was to examine the association between serum zinc levels and several body composition factors in Korean adults.

METHODS

We used data from the Korean National Health and Nutrition Examination Survey, a cross-sectional survey of Korean civilians. Data from 1896 adults were analyzed.

RESULTS

Serum zinc levels in men with elevated waist circumference were higher than in those with normal waist circumference (152.1 ± 3.7 μg/dL versus 137.8 ± 2.2 μg/dL; P < 0.001) and serum zinc levels increased with increasing tertiles of total body fat percentage (134.2 ± 2.8 μg/dL, 142 ± 2.9 μg/dL, and 148 ± 2.7 μg/dL; P = 0.001). Among men with a normal waist circumference, serum zinc levels of those with the highest total body fat percentage were higher than in those with the lowest or medium total body fat percentage values (145.4 μg/dL versus 135.2 μg/dL; P = 0.029). In contrast, in men with an elevated waist circumference, no difference in serum zinc levels according to total body fat percentage was detected. There was no relationship between serum zinc levels and body composition factors in women.

CONCLUSIONS

Body zinc status might be associated with the quantity and distribution of body fat in Korean men. Additional sex-specific studies are needed to determine whether the relationship of body zinc status with abdominal obesity and total body fat affects metabolic disorders and cardiovascular diseases.

Mesenteric Lymphatic-Perilymphatic Adipose Crosstalk: Role in Alcohol-Induced Perilymphatic Adipose Tissue Inflammation

BACKGROUND

The digestive tract lymphatics transport approximately two-thirds of all lymph produced in the body and have a key role in mucosal immunity through their contribution to antigen transport and immune cell trafficking. Mesenteric lymphatic pumping function integrity is critical for maintaining homeostasis and lipid transport. We previously demonstrated that acute alcohol intoxication (AAI) increases mesenteric lymphatic amplitude of contraction and ejection fraction, enhancing the ability of the lymphatic vessels to pump lymph. AAI has been shown to disrupt intestinal barrier integrity, which would be expected to increase the endotoxin content of mesenteric lymph. In this study, we tested the prediction that AAI increases lymphatic permeability directly affecting perilymphatic adipose tissue (PLAT) milieu.

METHODS

Male Sprague Dawley rats received an intragastric infusion of 2.5 g/kg of alcohol. Isovolumic administration of water (vehicle) served as control. PLAT was isolated for the determination of Evans Blue extravasation (permeability), cytokine content, and immunohistochemistry for inflammatory cell infiltration at 30 minutes and 24 hours after alcohol administration.

RESULTS

PLAT isolated from AAI animals had greater Evans Blue concentrations and cytokine expression (24 hours post-AAI) and mast cell and neutrophil density than that isolated from controls. AAI resulted in significantly higher plasma lipopolysaccharide (endotoxin) levels, lower plasma adiponectin levels (at 30 minutes), and unchanged plasma visfatin levels.

CONCLUSIONS

The data indicate that AAI induces mesenteric lymphatic hyperpermeability, promotes PLAT inflammatory milieu and disrupts the systemic adipokine profile. These findings suggest an association between alcohol-induced lymphatic hyperpermeability and early manifestations of metabolic dysfunction as a result of alcohol abuse. We propose that crosstalk between lymph and PLAT results in adipose inflammation and adipokine dysregulation during AAI.

The gut-adipose-liver axis in the metabolic syndrome

Obesity is associated with altered gut microbiota composition and impaired gut barrier function. These changes, together with interrelated mesenteric adipose tissue inflammation, result in increased release of pro-inflammatory cytokines, bacteria-derived factors, and lipids into the portal circulation, promoting the development of (hepatic) insulin resistance. Herein, the potential impact of obesity-related changes in gut and visceral adipose tissue biology on the development of insulin resistance and Type 2 diabetes is reviewed.

Obesity, insulin resistance and comorbidities? Mechanisms of association

Overall excess of fat, usually defined by the body mass index, is associated with metabolic (e.g. glucose intolerance, type 2 diabetes mellitus (T2DM), dyslipidemia) and non-metabolic disorders (e.g. neoplasias, polycystic ovary syndrome, non-alcoholic fat liver disease, glomerulopathy, bone fragility etc.). However, more than its total amount, the distribution of adipose tissue throughout the body is a better predictor of the risk to the development of those disorders. Fat accumulation in the abdominal area and in non-adipose tissue (ectopic fat), for example, is associated with increased risk to develop metabolic and non-metabolic derangements. On the other hand, observations suggest that individuals who present peripheral adiposity, characterized by large hip and thigh circumferences, have better glucose tolerance, reduced incidence of T2DM and of metabolic syndrome. Insulin resistance (IR) is one of the main culprits in the association between obesity, particularly visceral, and metabolic as well as non-metabolic diseases. In this review we will highlight the current pathophysiological and molecular mechanisms possibly involved in the link between increased VAT, ectopic fat, IR and comorbidities. We will also provide some insights in the identification of these abnormalities.

Nonalcoholic Fatty Liver Disease Relationship with Metabolic Syndrome in Class III Obesity Individuals

INTRODUCTION

Obesity is represented mainly by abdominal obesity and insulin resistance (IR), both present in most individuals diagnosed with metabolic syndrome (MS). IR is the key risk factor in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Objective. To relate NAFLD to MS in class III obese individuals.

METHODOLOGY

A descriptive cross-sectional study with class III obese individuals, aged ≥ 20-60 years. Blood pressure measurement, weight, height, body mass index (BMI), waist circumference (WC) and blood glucose, insulin, high-density lipoprotein cholesterol (HDL-c), and triglycerides data were obtained. HOMA-IR (homeostatic model assessment insulin resistance) calculation was carried out with a cutoff value of 2.71 for IR evaluation. The diagnosis of NAFLD was performed by liver biopsy and the diagnosis of MS was performed in accordance with the National Cholesterol Education Program/Adult Treatment Panel III (NCEPATP III).

RESULTS

Of the 50 individuals evaluated, 86% were women and BMI means were 45.4 ± 3.6 Kg/m(2). The overall individuals had NAFLD, 70% steatosis, and 30% steatohepatitis. The diagnosis of MS occurred in 56% but showed no significant association with NAFLD (P = 0.254). Triglycerides (178 ± 65.5 mg/dL) and insulin (28.2 ± 22.6 mcU/mL) mean values were significantly higher in steatohepatitis (P = 0.002 and P = 0.042, resp.) compared to individuals with steatosis. IR was confirmed in 76% and showed a relationship with NAFLD severity.

CONCLUSION

NAFLD was not related to MS; however, MS components, evaluated in isolation, as well as IR, were related to the presence and severity of NAFLD.

Opposing effects of reduced kidney mass on liver and skeletal muscle insulin sensitivity in obese mice

Reduced kidney mass and/or function may result in multiple metabolic derangements, including insulin resistance. However, underlying mechanisms are poorly understood. Herein, we aimed to determine the impact of reduced kidney mass on glucose metabolism in lean and obese mice. To that end, 7-week-old C57BL/6J mice underwent uninephrectomy (UniNx) or sham operation. After surgery, animals were fed either a chow (standard) diet or a high-fat diet (HFD), and glucose homeostasis was assessed 20 weeks after surgery. Intraperitoneal glucose tolerance was similar in sham-operated and UniNx mice. However, insulin-stimulated glucose disposal in vivo was significantly diminished in UniNx mice, whereas insulin-stimulated glucose uptake into isolated skeletal muscle was similar in sham-operated and UniNx mice. Of note, capillary density was significantly reduced in skeletal muscle of HFD-fed UniNx mice. In contrast, hepatic insulin sensitivity was improved in UniNx mice. Furthermore, adipose tissue hypoxia-inducible factor 1α expression and inflammation were reduced in HFD-fed UniNx mice. Treatment with the angiotensin II receptor blocker telmisartan improved glucose tolerance and hepatic insulin sensitivity in HFD-fed sham-operated but not UniNx mice. In conclusion, UniNx protects from obesity-induced adipose tissue inflammation and hepatic insulin resistance, but it reduces muscle capillary density and, thus, deteriorates HFD-induced skeletal muscle glucose disposal.

Main characteristics of metabolically obese normal weight and metabolically healthy obese phenotypes

In this review, the influence of fat depots on insulin resistance and the main characteristics of metabolically obese normal-weight and metabolically healthy obese phenotypes are discussed. Medline/PubMed and Science Direct were searched for articles related to the terms metabolically healthy obesity, metabolically obese normal weight, adipose tissue, and insulin resistance. Normal weight and obesity might be heterogeneous in regard to their effects. Fat distribution and lower insulin sensitivity are the main factors defining phenotypes within the same body mass index. Although these terms are interesting, controversies about them remain. Future studies exploring these phenotypes will help elucidate the roles of adiposity and/or insulin resistance in the development of metabolic alterations.

Role of developmental transcription factors in white, brown and beige adipose tissues

In this review we discuss the role of developmental transcription factors in adipose tissue biology with a focus on how these developmental genes may contribute to regional variation in adipose tissue distribution and function. Regional, depot-specific, differences in lipid handling and signalling (lipolysis, lipid storage and adipokine/lipokine signalling) are important determinants of metabolic health. At a cellular level, preadipocytes removed from their original depot and cultured in vitro retain depot-specific functional properties, implying that these are intrinsic to the cells and not a function of their environment in situ. High throughput screening has identified a number of developmental transcription factors involved in embryological development, including members of the Homeobox and T-Box gene families, that are strongly differentially expressed between regional white adipose tissue depots and also between brown and white adipose tissue. However, the significance of depot-specific developmental signatures remains unclear. Developmental transcription factors determine body patterning during embryogenesis. The divergent developmental origins of regional adipose tissue depots may explain their differing functional characteristics. There is evidence from human genetics that developmental genes determine adipose tissue distribution: in GWAS studies a number of developmental genes have been identified as being correlated with anthropometric measures of adiposity and fat distribution. Additionally, compelling functional studies have recently implicated developmental genes in both white adipogenesis and the so-called 'browning' of white adipose tissue. Understanding the genetic and developmental pathways in adipose tissue may help uncover novel ways to intervene with the function of adipose tissue in order to promote health.

Comparing the effect of visceral fat and barley seed ash (hordeum vulgare L) with silversulfadiazine on burn wound healing in rats

BACKGROUND

Skin burn is one of the most common complications and remains a major public health issue worldwide.

OBJECTIVES

This experiment was conducted to study the effects of traditional medicine (Visceral Fat and Barely Seed Ash) compared with silversulfadiazine (SSD) cream on healing burn wounds in rats.

MATERIALS AND METHODS

Sixty adult male Wistar rats were randomly divided into four groups of equal numbers; each group consisted of 15 animals. After sedation, type II of skin burn with 1.5 cm diameter circle was created on the back of rats with a heated metal in boiling water. Group one was not treated and considered as control. The burned areas in the second, third and fourth groups were applied twice a day with normal saline, SSD cream and traditional preparation, respectively. Percentage of the burn wound concentration and histopathological examinations were used as parameters of our study on days 4, 9and 14. Obtained data were compared between the groups and days.

RESULTS

SSD cream and traditional preparation had better effects on burnt wound healing compared with control group. Furthermore, on the final day of study, the average percentage of wound concentration in traditional medicine group was significantly greater than other groups (P < 0.05). This finding was supported and confirmed by histological examination as well.

CONCLUSIONS

Traditional preparation significantly decreased inflammation and accelerated wound healing in treated rats. Furthermore, the findings of this study can be applied clinically in the future.

Higher plasma lipopolysaccharide concentrations are associated with less favorable phenotype in overweight/obese men

PURPOSE

Lipopolysaccharide (LPS) from the outer membrane of gram-negative bacteria might be an inflammation trigger in adipose tissue. It has recently been proposed that there is a link between adipose tissue distribution and blood LPS. However, the number of studies on this topic is scarce, and further investigation in humans is required. In this study, we explored the association between plasma LPS concentrations and body fat distribution, as well as the biochemical parameters that may indicate the presence of metabolic disorders.

METHODS

Sixty-seven young adult men with body mass index of 26-35 kg/m(2) were evaluated. Anthropometry, body composition and body fat distribution, blood pressure, energy expenditure, physical activity level, dietary intake, and biochemical parameters were assessed.

RESULTS

Men with median plasma LPS ≥ 0.9 EU/mL presented higher sagittal abdominal diameter, trunk fat percentage, and android fat percentage, and mass, insulin and alanine aminotransferase concentrations, homeostasis model assessment of insulin resistance (HOMA-IR), and beta cell dysfunction (HOMA-B) than those with lower plasma LPS. LPS correlated positively with the trunk fat percentage, and android fat percentage, and mass, insulin, aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase concentrations, as well as HOMA-IR and HOMA-B.

CONCLUSION

Our results suggest that a higher plasma LPS concentration is associated with a less favorable phenotype as characterized by higher central adiposity, higher values of HOMA-IR, and beta cell function impairment in overweight/obese men.

Leukotriene production is increased in abdominal obesity

Obesity is a major risk factor for insulin resistance and type-2 diabetes. A chronic low grade inflammatory state has been described during obesity and associated with insulin resistance pathogenesis. Results from animal studies are in favor of a role of the leukotriene (LT) pathway in obesity induced-insulin resistance. However, there is a paucity of data regarding this association in human obesity. Therefore, the aim of this study was to investigate whether LT production was associated with insulin resistance and other metabolic parameters in a cohort of obese subjects. Forty-six (70% females) obese subjects (BMI≧30 kg/m²) without known diabetes and without inflammatory disease (CRP<10 mg/l) were included. Median age was 44 years (16–80) with a median BMI of 36.8 kg/m² (30–51). Insulin resistance was evaluated by HOMA-IR index and glucose tolerance test. Urinary LTE₄ (U-LTE₄) concentration was measured by enzyme immune assay. Screening for obstructive sleep apnea was performed. There was a positive association of U-LTE₄ with waist to hip ratio, systolic blood pressure and HOMA-IR in univariate analysis. Further, waist to hip ratio remained the only parameter significantly correlated with U-LTE₄, in adjusted multivariate analysis. Taken together, these results confirm the previously established notion of chronic low grade inflammation in obesity and further suggests a role for the LT pathway in obesity-associated development of insulin resistance in humans.

Metabolic syndrome: is equine disease comparable to what we know in humans?

This review summarizes similarities and differences between the metabolic syndromes in humans and equines, concerning the anatomy, symptoms, and pathophysiological mechanisms. In particular, it discusses the structure and distribution of adipose tissue and its specific metabolic pathways. Furthermore, this article provides insights and focuses on issues concerning laminitis in horses and cardiovascular diseases in humans, as well as their overlap.

Hypercaloric diets with increased meal frequency, but not meal size, increase intrahepatic triglycerides: a randomized controlled trial

American children consume up to 27% of calories from high-fat and high-sugar snacks. Both sugar and fat consumption have been implicated as a cause of hepatic steatosis and obesity but the effect of meal pattern is largely understudied. We hypothesized that a high meal frequency, compared to consuming large meals, is detrimental in the accumulation of intrahepatic and abdominal fat. To test this hypothesis, we randomized 36 lean, healthy men to a 40% hypercaloric diet for 6 weeks or a eucaloric control diet and measured intrahepatic triglyceride content (IHTG) using proton magnetic resonance spectroscopy ((1) H-MRS), abdominal fat using magnetic resonance imaging (MRI), and insulin sensitivity using a hyperinsulinemic euglycemic clamp with a glucose isotope tracer before and after the diet intervention. The caloric surplus consisted of fat and sugar (high-fat-high-sugar; HFHS) or sugar only (high-sugar; HS) and was consumed together with, or between, the three main meals, thereby increasing meal size or meal frequency. All hypercaloric diets similarly increased body mass index (BMI). Increasing meal frequency significantly increased IHTG (HFHS mean relative increase of 45%; P = 0.016 and HS mean relative increase of 110%; P = 0.047), whereas increasing meal size did not (2-way analysis of variance [ANOVA] size versus frequency P = 0.03). Abdominal fat increased in the HFHS-frequency group (+63.3 ± 42.8 mL; P = 0.004) and tended to increase in the HS-frequency group (+46.5 ± 50.7 mL; P = 0.08). Hepatic insulin sensitivity tended to decrease in the HFHS-frequency group while peripheral insulin sensitivity was not affected.

CONCLUSION

A hypercaloric diet with high meal frequency increased IHTG and abdominal fat independent of caloric content and body weight gain, whereas increasing meal size did not. This study suggests that snacking, a common feature in the Western diet, independently contributes to hepatic steatosis and obesity. (

TRIAL REGISTRATION

www.clinicaltrials.gov; nr.NCT01297738.)

The complement system in human cardiometabolic disease

The complement system has been implicated in obesity, fatty liver, diabetes and cardiovascular disease (CVD). Complement factors are produced in adipose tissue and appear to be involved in adipose tissue metabolism and local inflammation. Thereby complement links adipose tissue inflammation to systemic metabolic derangements, such as low-grade inflammation, insulin resistance and dyslipidaemia. Furthermore, complement has been implicated in pathophysiological mechanisms of diet- and alcohol induced liver damage, hyperglycaemia, endothelial dysfunction, atherosclerosis and fibrinolysis. In this review, we summarize current evidence on the role of the complement system in several processes of human cardiometabolic disease. C3 is the central component in complement activation, and has most widely been studied in humans. C3 concentrations are associated with insulin resistance, liver dysfunction, risk of the metabolic syndrome, type 2 diabetes and CVD. C3 can be activated by the classical, the lectin and the alternative pathway of complement activation; and downstream activation of C3 activates the terminal pathway. Complement may also be activated via extrinsic proteases of the coagulation, fibrinolysis and the kinin systems. Studies on the different complement activation pathways in human cardiometabolic disease are limited, but available evidence suggests that they may have distinct roles in processes underlying cardiometabolic disease. The lectin pathway appeared beneficial in some studies on type 2 diabetes and CVD, while factors of the classical and the alternative pathway were related to unfavourable cardiometabolic traits. The terminal complement pathway was also implicated in insulin resistance and liver disease, and appears to have a prominent role in acute and advanced CVD. The available human data suggest a complex and potentially causal role for the complement system in human cardiometabolic disease. Further, preferably longitudinal studies are needed to disentangle which aspects of the complement system and complement activation affect the different processes in human cardiometabolic disease.

Aortic cholesterol accumulation correlates with systemic inflammation but not hepatic and gonadal adipose tissue inflammation in low-density lipoprotein receptor null mice

Inflammation is a major contributor to the development of atherosclerotic plaque, yet the involvement of liver and visceral adipose tissue inflammatory status in atherosclerotic lesion development has yet to be fully elucidated. We hypothesized that an atherogenic diet would increase inflammatory response and lipid accumulation in the liver and gonadal adipose tissue (GAT) and would correlate with systemic inflammation and aortic lesion formation in low-density lipoprotein (LDL) receptor null (LDLr-/-) mice. For 32 weeks, LDLr-/- mice (n = 10/group) were fed either an atherogenic (high saturated fat and cholesterol) or control (low fat and cholesterol) diet. Hepatic and GAT lipid content and expression of inflammatory factors were measured using standard procedures. Compared with the control diet, the atherogenic diet significantly increased hepatic triglyceride and total cholesterol (TC), primarily esterified cholesterol, and GAT triglyceride content. These changes were accompanied by increased expression of acyl-CoA synthetase long-chain family member 5, CD36, ATP-binding cassette, subfamily A, member 1 and scavenger receptor B class 1, and they decreased the expression of cytochrome P450, family 7 and subfamily a, polypeptide 1 in GAT. Aortic TC content was positively associated with hepatic TC, triglyceride, and GAT triglyceride contents as well as plasma interleukin 6 and monocyte chemoattractant protein-1 concentrations. Although when compared with the control diet, the atherogenic diet increased hepatic tumor necrosis factor α production, they were not associated with aortic TC content. These data suggest that the LDLr-/- mice responded to the atherogenic diet by increasing lipid accumulation in the liver and GAT, which may have increased inflammatory response. Aortic TC content was positively associated with systemic inflammation but not hepatic and GAT inflammatory status.

A novel biopsy method to increase yield of subcutaneous abdominal adipose tissue

Collection of abdominal subcutaneous adipose tissue (SAT) for research testing is traditionally performed using punch biopsy or needle aspiration techniques, yielding small amounts of very superficial SAT (100-500 mg). Although liposuction techniques can be used to obtain large amounts of SAT, these approaches can compromise the integrity of the adipose tissue. Therefore, we investigated a novel method using a 6-mm Bergström side-cutting biopsy needle to acquire suitable amounts of intact abdominal SAT for multiple complex studies such as flow cytometry, RNA extraction, ex vivo expression of molecular and post-translational protein mediators, and histology. Fifty biopsies were obtained from 29 participants using a Bergström biopsy needle, applying transient manual suction and shearing large pieces of fat within the inner-cutting trochar. Eighteen of the biopsies were performed under ultrasound guidance, whereby we successfully sampled deep SAT (dSAT) from below Scarpa's fascia. The average weight of SAT sampled was 1.5 ± 0.4 g. There was no clinically important bleeding or ecchymosis on the abdominal wall and no infection occurred with this procedure. The 6-mm Bergström biopsy needle yielded substantially more SAT than what has been obtained from superficial procedures and, for the first time, allowed sampling of dSAT by a percutaneous approach.

Association of serum tumor necrosis factor-related apoptosis inducing ligand with body fat distribution as assessed by dual X-rays absorptiometry

A low chronic inflammation mediated by cytokine release is considered a major pathogenic mechanism accounting for the higher risk of cardiovascular disease in the overweight/obese population. In this context, although the existence of a possible interaction between soluble tumor necrosis factor- (TNF-) related apoptosis inducing ligand (TRAIL) and quantity and localization, of adiposity in the body has been hypothesized, no studies have yet investigated this link by radiologic techniques able to assess directly fat mass (FM) in different body regions. To address this issue, we assessed body fat distribution by dual X-rays absorptiometry (DXA) in a sample of 103 women and investigated the possible association between the derived adiposity measures and serum TRAIL concentration. The level of TRAIL showed a positive and independent correlation with arms FM (P < 0.05), trunk FM (P < 0.001) and trunk FM% (P < 0.05), total FM and total FM% (P < 0.001 for both), and an inverse association with legs FM% (P < 0.05). Only trunk FM retained a significant correlation (P < 0.05) with TRAIL after adjusting for all the other indices of regional adiposity. In conclusion, from our study it emerged a significant and independent association of serum TRAIL levels with overall, and, mainly, central adiposity. Further studies are needed to longitudinally investigate the cause-effect relationship between change in body fat distribution and TRAIL.

Bariatric endocrinology: principles of medical practice

Obesity, is a chronic, biological, preventable, and treatable disease. The accumulation of fat mass causes physical changes (adiposity), metabolic and hormonal changes due to adipose tissue dysfunction (adiposopathy), and psychological changes. Bariatric endocrinology was conceived from the need to address the neuro-endocrinological derangements that are associated with adiposopathy, and from the need to broaden the scope of the management of its complications. In addition to the well-established metabolic complications of overweight and obesity, adiposopathy leads to hyperinsulinemia, hyperleptinemia, hypoadiponectinemia, dysregulation of gut peptides including GLP-1 and ghrelin, the development of an inflammatory milieu, and the strong risk of vascular disease. Therapy for adiposopathy hinges on effectively lowering the ratio of orexigenic to anorexigenic signals reaching the the hypothalamus and other relevant brain regions, favoring a lower caloric intake. Adiposopathy, overweight and obesity should be treated indefinitely with the specific aims to reduce fat mass for the adiposity complications, and to normalize adipose tissue function for the adiposopathic complications. This paper defines the principles of medical practice in bariatric endocrinology-the treatment of overweight and obesity as means to treat adiposopathy and its accompanying metabolic and hormonal derangements.

Sleep fragmentation in mice induces nicotinamide adenine dinucleotide phosphate oxidase 2-dependent mobilization, proliferation, and differentiation of adipocyte progenitors in visceral white adipose tissue

BACKGROUND

Chronic sleep fragmentation (SF) without sleep curtailment induces increased adiposity. However, it remains unclear whether mobilization, proliferation, and differentiation of adipocyte progenitors (APs) occurs in visceral white adipose tissue (VWAT), and whether nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (Nox2) activity plays a role.

METHODS

Changes in VWAT depot cell size and AP proliferation were assessed in wild-type and Nox2 null male mice exposed to SF and control sleep (SC). To assess mobilization, proliferation, and differentiation of bone marrow mesenchymal stem cells (BM-MSC), Sca-1+ bone marrow progenitors were isolated from GFP+ or RFP+ mice, and injected intravenously to adult male mice (C57BL/6) previously exposed to SF or SC.

RESULTS

In comparison with SC, SF was associated with increased weight accrual at 3 w and thereafter, larger subcutaneous and visceral fat depots, and overall adipocyte size at 8 w. Increased global AP numbers in VWAT along with enhanced AP BrDU labeling in vitro and in vivo emerged in SF. Systemic injections of GFP+ BM-MSC resulted in increased AP in VWAT, as well as in enhanced differentiation into adipocytes in SF-exposed mice. No differences occurred between SF and SC in Nox2 null mice for any of these measurements.

CONCLUSIONS

Chronic sleep fragmentation (SF) induces obesity in mice and increased proliferation and differentiation of adipocyte progenitors (AP) in visceral white adipose tissue (VWAT) that are mediated by increased Nox2 activity. In addition, enhanced migration of bone marrow mesenchymal stem cells from the systemic circulation into VWAT, along with AP differentiation, proliferation, and adipocyte formation occur in SF-exposed wild-type but not in oxidase 2 (Nox2) null mice. Thus, Nox2 may provide a therapeutic target to prevent obesity in the context of sleep disorders.

Obesity-related inflammation: implications for older adults

The combination of age-related increases in obesity and inflammation can lead to chronic disease, decreased strength, and physical disability. Lifestyle interventions that include moderate caloric restriction along with aerobic and resistance exercise have shown improvements in metabolic outcomes, strength, and physical function in obese older adults. Although few weight loss studies have addressed diet quality, evidence summarized in this review suggests that encouraging intake of antioxidant-rich fruits and vegetables, high-quality protein, low-glycemic index carbohydrates, and omega-3 fatty acids may further ameliorate obesity-related inflammation. Future controlled trials are indicated to examine the effects of incorporating these foods into multimodal weight loss interventions.

Fat cell size and adipokine expression in relation to gender, depot, and metabolic risk factors in morbidly obese adolescents

OBJECTIVE

To understand the regulation of adipocyte size and adipokine expression in relation to gender, anatomic location, adiposity, and metabolic risk factors in adolescents with morbid obesity.

METHODS

Adipocyte size and adipokine expression in paired abdominal subcutaneous (SAT) and omental (VAT) surgical adipose tissues were related to gender, anatomic location, adiposity, and metabolic risk factors in a group of morbidly obese adolescents.

RESULTS

Significant depot- and/or gender-related differences in adipocyte size and adipokine expression were detected. Adjusted for body mass index, adipocyte size in both depots was larger in males than in females and was a major predictor of mRNA levels of leptin, plasminogen activator inhibitor-1, and adiponectin. Gender, but not adipocyte size, was significantly correlated with proinflammatory cytokine expression. Body mass index and waist circumference were correlated positively with VAT adipocyte size and negatively with SAT adipocyte size. VAT adiponectin and interleukin-6 expression levels were major predictors of high-density lipoprotein cholesterol concentrations, independent of gender, adiposity, and insulin sensitivity.

CONCLUSIONS

Adipose tissue morphology and function in obese adolescents are influenced by gender and anatomic location; the pattern of gender- and depot-related differences in adipocyte size and adipokine expression suggests that adolescent males, relative to the females, are at increased risk for obesity-related metabolic comorbidities.