Visceral Fat: Higher Responsiveness of Fat Mass and Gene Expression to Calorie Restriction than Subcutaneous Fat

Impact of baseline adipose tissue characteristics on change in adipose tissue volume during a low calorie diet in people with obesity-results from the LION study

BACKGROUND/OBJECTIVES

Weight loss outcomes vary individually. Magnetic resonance imaging (MRI)-based evaluation of adipose tissue (AT) might help to identify AT characteristics that predict AT loss. This study aimed to assess the impact of an 8-week low-calorie diet (LCD) on different AT depots and to identify predictors of short-term AT loss using MRI in adults with obesity.

METHODS

Eighty-one adults with obesity (mean BMI 34.08 ± 2.75 kg/m², mean age 46.3 ± 10.97 years, 49 females) prospectively underwent baseline MRI (liver dome to femoral head) and anthropometric measurements (BMI, waist-to-hip-ratio, body fat), followed by a post-LCD-examination. Visceral and subcutaneous AT (VAT and SAT) volumes and AT fat fraction were extracted from the MRI data. Apparent lipid volumes based on MRI were calculated as approximation for the lipid contained in the AT. SAT and VAT volumes were subdivided into equidistant thirds along the craniocaudal axis and normalized by length of the segmentation. T-tests compared baseline and follow-up measurements and sex differences. Effect sizes on subdivided AT volumes were compared. Spearman Rank correlation explored associations between baseline parameters and AT loss. Multiple regression analysis identified baseline predictors for AT loss.

RESULTS

Following the LCD, participants exhibited significant weight loss (11.61 ± 3.07 kg, p < 0.01) and reductions in all MRI-based AT parameters (p < 0.01). Absolute SAT loss exceeded VAT loss, while relative apparent lipid loss was higher in VAT (both p < 0.01). The lower abdominopelvic third showed the most significant SAT and VAT reduction. The predictor of most AT and apparent lipid losses was the normalized baseline SAT volume in the lower abdominopelvic third, with smaller volumes favoring greater AT loss (p < 0.01 for SAT and VAT loss and SAT apparent lipid volume loss).

CONCLUSIONS

The LCD primarily reduces lower abdominopelvic SAT and VAT. Furthermore, lower abdominopelvic SAT volume was detected as a potential predictor for short-term AT loss in persons with obesity.

Cross-talk between adipose tissue and microbiota-gut-brain-axis in brain development and neurological disorder

The gut microbiota is an important factor responsible for the physiological processes as well as pathogenesis of host. The communication between central nervous system (CNS) and microbiota occurs by different pathways i.e., chemical, neural, immune, and endocrine. Alteration in gut microbiota i.e., gut dysbiosis causes alteration in the bidirectional communication between CNS and gut microbiota and linked to the pathogenesis of neurological and neurodevelopmental disorder. Therefore, now-a-days microbiota-gut-brain-axis (MGBA) has emerged as therapeutic target for the treatment of metabolic disorder. But, experimental data available on MGBA from basic research has limited application in clinical study. In present study we first summarized molecular mechanism of microbiota interaction with brain physiology and pathogenesis via collecting data from different sources i.e., PubMed, Scopus, Web of Science. Furthermore, evidence shows that adipose tissue (AT) is active during metabolic activities and may also interact with MGBA. Hence, in present study we have focused on the relationship among MGBA, brown adipose tissue, and white adipose tissue. Along with this, we have also studied functional specificity of AT, and understanding heterogeneity among MGBA and different types of AT. Therefore, molecular interaction among them may provide therapeutic target for the treatment of neurological disorder.

Visceral Adiposity and Cancer: Role in Pathogenesis and Prognosis

The prevalence of being overweight and obese has been expanded dramatically in recent years worldwide. Obesity usually occurs when the energetic introit overtakes energy expenditure from metabolic and physical activity, leading to fat accumulation mainly in the visceral depots. Excessive fat accumulation represents a risk factor for many chronic diseases, including cancer. Adiposity, chronic low-grade inflammation, and hyperinsulinemia are essential factors of obesity that also play a crucial role in tumor onset. In recent years, several strategies have been pointed toward boundary fat accumulation, thus limiting the burden of cancer attributable to obesity. While remodeling fat via adipocytes browning seems a tempting prospect, lifestyle interventions still represent the main pathway to prevent cancer and enhance the efficacy of treatments. Specifically, the Mediterranean Diet stands out as one of the best dietary approaches to curtail visceral adiposity and, therefore, cancer risk. In this Review, the close relationship between obesity and cancer has been investigated, highlighting the biological mechanisms at the basis of this link. Finally, strategies to remodel fat, including browning and lifestyle interventions, have been taken into consideration as a major perspective to limit excess body weight and tumor onset.

Comparison of Visceral Fat Reduction by Ipragliflozin and Metformin in Elderly Type 2 Diabetes Patients: Sub-Analysis of a Randomized-Controlled Study

INTRODUCTION

To compare the effects of ipragliflozin, a sodium-glucose transporter 2 inhibitor, with those of metformin on visceral fat (as well as muscles and bones) in Japanese elderly patients with type 2 diabetes (T2D), we conducted a sub-analysis of a prospective, multicenter, blinded-endpoint randomized-controlled study.

METHODS

In total, 103 patients with T2D (body mass index ≥ 22 kg/m²; glycated hemoglobin, 7-10%) and being treated with sitagliptin (a dipeptidyl peptidase-4 inhibitor) were included and randomized to receive ipragliflozin or metformin. The primary outcome was the change in visceral fat area measured using computed tomography 24 weeks following treatment. The secondary outcomes included changes in subcutaneous and total fat area, muscle volume, bone density measured using computed tomography, handgrip strength, bone markers, plasma glucose, insulin, homeostasis model assessment (HOMA)2-beta, HOMA2-R, glycated hemoglobin, lipid panel, uric acid, blood pressure, adiponectin, and high-sensitivity C-reactive protein. All patients aged 65-74 years were selected for sub-analysis.

RESULTS

The sub-analysis included 15 and 14 patients in the ipragliflozin and metformin groups, respectively. The patients' backgrounds were well balanced. Visceral fat area reduction was greater in the ipragliflozin group than in the metformin group (- 10.58% vs. - 6.93%; P = 0.034). There were significant differences in the changes in bone absorption markers, uric acid, and total cholesterol levels between the groups.

CONCLUSION

Ipragliflozin significantly reduced the visceral fat area compared with metformin when added to sitagliptin in elderly patients with T2D. Long-term and large-scale studies are required to elucidate whether ipragliflozin is suitable for elderly patients.

TRIAL REGISTRATION

The study was registered at https://www.umin.ac.jp/ctr/ (UMIN-ID: UMIN 000015170).

Change in body composition in patients with achalasia before and after peroral endoscopic myotomy

BACKGROUND AND AIM

Patients with achalasia experience weight loss because of dysphagia caused by impaired relaxation of the lower esophageal sphincter. This study aimed to use dual bioelectrical impedance analysis (BIA) to determine the change in bodyweight and body composition in patients with achalasia before and after peroral endoscopic myotomy (POEM).

METHODS

Patients with achalasia who underwent POEM from 2013 to 2018 (n = 72) were retrospectively analyzed for change in bodyweight before and after 3 months. Additionally, change in body composition was prospectively investigated in the final 10 of 72 patients using non-radiation dual BIA.

RESULTS

Twenty patients (27.8%) were underweight (body mass index < 18.5) before undergoing POEM. No clinical parameters were identified to be associated with the underweight condition before POEM and be predictive of an increase in bodyweight after POEM. Low visceral fat volume observed on dual BIA correlated closely with the result obtained using computed tomography (Pearson correlation coefficient: r = 0.850, P < 0.01). Patients with achalasia had a statistically significant increase in visceral (P < 0.01) and subcutaneous fat volumes (P < 0.01) after POEM. Skeletal muscle mass index slightly increased (P = 0.02), although the value after POEM was still low. No blood biomarkers were indicators for low bodyweight or low visceral fat volume.

CONCLUSIONS

Dual BIA is an effective non-invasive tool to evaluate the change in body composition of underweight patients with achalasia. Skeletal muscle volume was not enough after POEM, although a rapid increase in the intra-abdominal fat volume was observed. Additional studies are warranted to understand the pathological implications.

Effect of Daily Ingestion of Quercetin-Rich Onion Powder for 12 Weeks on Visceral Fat: A Randomised, Double-Blind, Placebo-Controlled, Parallel-Group Study

Quercetin, which is frequently found in vegetables such as onion, is widely found to have biological activities such as visceral fat reduction. Therefore, we performed this randomised double-blind placebo-controlled parallel-group study and analysed the effects of daily intake of quercetin-rich onion on visceral fat for 12 weeks. Seventy healthy Japanese subjects whose body mass index (BMI) was ≥23 and <30 were recruited and randomly assigned to either the quercetin-rich onion group or placebo group. The subjects ingested 9 g of onion powder per day for 12 weeks. We conducted medical interviews, hematological and biological tests; measured body composition and vital signs; and analysed the Food Frequency Questionnaire weeks 0, 4, 8, and 12. Abdominal fat area was measured using computed tomography scanning at weeks 0 and 12. No significant differences in visceral fat area (VFA) were observed between the two groups. However, in subjects whose high-density lipoprotein cholesterol was lower, VFA was significantly lower in the quercetin-rich onion group. In addition, alanine aminotransferase was significantly lower in the quercetin-rich onion group than in the placebo group. Thus, the results suggest that quercetin-rich onion may be beneficial for preventing obesity and improving liver function.

Interaction of lipid accumulation product and family history of hypertension on hypertension risk: a cross-sectional study in the Southern Chinese population

OBJECTIVES

This study aimed at investigating the applicability of a novel index based on waist circumference (WC) and triglyceride (TG) which was named lipid accumulation product (LAP) in the Southern Chinese population, and compared the predictive effects of LAP and other obesity indicators on hypertension risk. Moreover, this study investigated the interactive effects of LAP and family history of hypertension.

METHODS

A total number of 2079 of community-dwelling adults in Southern China were enrolled in this cross-sectional study. The participants underwent questionnaire surveys, anthropometric tests and laboratory examinations. Themultinomial logistic regression model and receiver operating characteristic curves, including LAP, body mass index (BMI), waist-to-hip ratio (WHR), WC and TG, were used to assess the association between hypertension risk and obesity indexes. The interaction effects were evaluated by relative excess risk of interaction (RERI), attributable proportion due to interaction (AP) and synergy index (SI).

RESULTS

Higher LAP levels have a relatively higher risk of having hypertension in both sexes (males: adjusted OR=2.79 per SD increase, 95% CI 1.43 to 5.44, p<0.001; females: adjusted OR=3.15, 95% CI 1.56 to 6.39, p<0.001). LAP (area under the curve=0.721; 95% CI 0.680 to 0.761) is a better indicator in identifying hypertension risk than BMI, WHR and TG in females, but WC performed better in males. A significant interaction between LAP and family history of hypertension was observed in males (RERI=1.652, 95% CI 0.267 to 3.037; AP=0.516, 95% CI 0.238 to 0.794; SI=3.998, 95% CI 0.897 to 17.820), but there is no statistically significant difference in females.

CONCLUSIONS

LAP significantly associates with hypertension risk in the Southern Chinese population. It has better performance than BMI, WHR and TG on predicting hypertension risk of the Southern Chinese female population. Moreover, LAP and family history of hypertension might synergistically increase the risk of hypertension.

The effect of lipid accumulation product and its interaction with other factors on hypertension risk in Chinese Han population: A cross-sectional study

OBJECTIVES

Lipid accumulation product (LAP) is a simple and effective indicator that reflects visceral obesity. This study aimed to compare the significance of LAP in predicting hypertension risk with other obesity indices, and to evaluate the interactive effects of LAP and smoking, family history of hypertension on hypertension risk in Chinese Han adults.

METHODS

A community based cross-sectional study was performed in Bengbu, China. Participants received face-to-face questionnaire survey, anthropometric tests and laboratory examinations. Relevant indicators that reflect obesity including BMI (body mass index), waist-to-height ratio (WHtR) and LAP were calculated. Multivariate logistic regression analysis was applied to explore the association between LAP and hypertension risk. The area under the receiver-operating characteristics curves (AUC) of LAP, BMI, and WHtR were calculated and then compared. Interactive effect was evaluated by relative excess risk due to interaction (RERI), attributable proportion due to interaction (AP) and synergy index (SI).

RESULTS

A total of 1777 participants were enrolled, and the prevalence of hypertension was 24.4% (n = 433). There was a significant increase in hypertension risk with LAP levels in the fourth quartile as compared with the bottom quartile (OR: 3.31, 95%CI: 1.76-6.25). The AUC of LAP was significantly different than that of BMI in males (Z = 2.158, p = 0.0309) and females (Z = 3.570, p = 0.0004), while only performed better in females as compared with that of WHtR (Z = 2.166, p = 0.0303). LAP was significantly interacted with family history of hypertension on hypertension risk both in males (RERI: 1.07, 95%CI: 0.09-2.05; AP: 0.33, 95%CI: 0.23-0.44; SI: 1.92, 95%CI: 1.53-2.41) and females (RERI: 0.80, 95%CI: 0.07-1.53; AP: 0.25, 95%CI: 0.11-0.39; SI: 1.59, 95%CI: 1.16-2.19). However, a significant interaction between LAP and smoking was only observed in males (RERI: 1.32, 95%CI: 0.15-2.75; AP: 0.40, 95% CI: 0.14-0.73).

CONCLUSION

Increased LAP was significantly associated with a higher risk of hypertension in Chinese Han adults. Moreover, the effect of LAP on predicting hypertension risk was better than that of other obesity indices. Our results also demonstrated interactive effects of LAP with smoking, family history of hypertension on hypertension risk.

Factors Associated with Visceral Fat Loss in Response to a Multifaceted Weight Loss Intervention

Background

Visceral adipose tissue is more metabolically active than other fat depots and is more closely associated with obesity-related diseases, such as cardiovascular disease and type 2 diabetes, than indicators of obesity, such as body mass index. Across various strategies to promote weight loss, including energy-reduced diet and exercise, variable effects on VAT compared to loss of total body fat have been reported.

Methods

To examine the effect of a behavioral weight loss intervention using portion-controlled prepackaged entrées on VAT, we examined data and measurements from overweight/obese men and women (N=183) who were assigned to a weight loss intervention and prescribed a reduced-energy diet with either portion-controlled prepackaged entrées or self-selected meals in a randomized clinical trial. VAT was estimated with dual-energy X-ray absorptiometry at baseline and study end (12 weeks).

Results

VAT loss was greater for the prepackaged entrees group (p=0.02), with an average loss of 29% compared to an average loss of 19% among participants consuming self-selected meals. VAT (mean [SEM]) was 1651 (71) g and 1546 (157) g at baseline and 1234 (59) g and 1278 (118) g at study end in the prepackaged entrees and self-selected meal groups, respectively. Greater VAT loss was associated with higher baseline weight and VAT, and greater weight loss, but not associated with age or physical activity.

Conclusion

Prescribing portion-controlled prepackaged entrees in a behavioral weight loss intervention promotes a reduction in VAT, which should promote improved metabolic profile and reduced cardiovascular disease risk.

Loss of skeletal muscle mass and its predictors in type 2 diabetes patients under a multifaceted treatment approach

Background

Weight loss, which is an effective method for reducing visceral fat, may cause a concomitant loss of skeletal muscle mass. The aim of this study was to elucidate the changes in visceral fat and skeletal muscle mass in response to diabetes treatment including weight control.

Methods

For 6 months we observed the changes in the body compositions of 72 Japanese patients with type 2 diabetes who underwent multifaceted treatment including educational hospitalization. Visceral fat area (VFA) and appendicular skeletal muscle mass (ASM) were measured using a bioelectrical impedance method and dual-energy X-ray absorptiometry, respectively.

Results

During the follow-up period, VFA reduced significantly whereas the average ASM did not change. Changes in ASM were strongly positively associated with changes in body weight (r = 0.50). Additionally, in an analysis of covariance, an above-median BMI (27 kg/m²) and above-median VFA (110 cm²) at baseline were found to be independent predictors of ASM reduction prevention. Of the 55 patients who lost weight, those who had a baseline VFA of ≥110 cm² had significantly greater reductions in VFA than those with a baseline VFA of <110 cm² (p < 0.01). ASM reduced significantly in patients with a VFA of <110 cm² (p < 0.01), but not in those with a VFA of ≥110 cm² (p = 0.98).

Conclusions

Baseline accumulation of visceral fat may predict a preferential reduction of visceral fat rather than skeletal muscle during weight control programs in type 2 diabetes patients.

Differential sympathetic outflow to adipose depots is required for visceral fat loss in response to calorie restriction

The sympathetic nervous system (SNS) regulates energy homeostasis in part by governing fatty acid liberation from adipose tissue. We first examined whether SNS activity toward discrete adipose depots changes in response to a weight loss diet in mice. We found that SNS activity toward each adipose depot is unique in timing, pattern of activation, and habituation with the most dramatic contrast between visceral and subcutaneous adipose depots. Sympathetic drive toward visceral epididymal adipose is more than doubled early in weight loss and then suppressed later in the diet when weight loss plateaued. Coincident with the decline in SNS activity toward visceral adipose is an increase in activity toward subcutaneous depots indicating a switch in lipolytic sources. In response to calorie restriction, SNS activity toward retroperitoneal and brown adipose depots is unaffected. Finally, pharmacological blockage of sympathetic activity on adipose tissue using the β3-adrenergic receptor antagonist, SR59230a, suppressed loss of visceral adipose mass in response to diet. These findings indicate that SNS activity toward discrete adipose depots is dynamic and potentially hierarchical. This pattern of sympathetic activation is required for energy liberation and loss of adipose tissue in response to calorie-restricted diet.

Resveratrol derivative BTM-0512 mitigates obesity by promoting beige remodeling of subcutaneous preadipocytes

Recent studies revealed that sirtuin 1 (SIRT1) is involved in the regulation of energy metabolism and its agonist resveratrol showed anti-obesity effect. This study aims to determine whether BTM-0512, a novel derivative of resveratrol, acts as an antagonist of obesity and to explore its possible mechanisms. High-fat diet (HFD)-induced obese mice were intragastrically administered with BTM-0512 (5, 10, and 20 mg/kg/day) or resveratrol (10 mg/kg/day). It was found that the body weight, Lee's index, ratio of visceral adipose tissue (VAT) to body weight, and blood glucose were significantly reduced in BTM-0512-treated mice when compared with those in mice treated with resveratrol. BTM-0512 up-regulated the expressions of SIRT1, full length PRDM16 (fPRDM16), total PRDM16 (tPRDM16, including fPPRDM16 and other PRDM16 isoforms), and uncoupling protein 1 (UCP1) in both brown and subcutaneous adipose tissues. Although BTM-0512 and resveratrol also up-regulated SIRT1 and tPRDM16 levels in VAT of HFD-induced obese mice, the expressions of fPRDM16, UCP1, and TMEM26 were down-regulated. In mouse primary subcutaneous preadipocytes cultured with or without adipogenic medium, BTM-0512 up-regulated fPRDM16, tPRDM16, and UCP1 expressions, which was reversed by SIRT1 antagonists. But in cultured brown and visceral adipocytes, the UCP1 protein level showed no significant change after treatment with 1 μM of BTM-0512. Moreover, transfection with human SIRT1 plasmid reduced lipid deposit, as well as the mRNA levels of fPRDM16, UCP1, and TMEM26, in cultured human visceral adipose-derived stem cells. In conclusion, BTM-0512 has stronger anti-obesity effect than resveratrol, which might be associated with activation of beige remodeling in subcutaneous adipose tissue.

Revascularization Determines Volume Retention and Gene Expression by Fat Grafts in Mice

Autologous fat transplantation is a popular and useful technique in plastic and reconstructive surgery. The efficiency and survival of such grafts is predictable in many cases, but there are still issues to be resolved, such as how to improve graft volume retention. To address the issue of volume retention, we studied the effect of revascularization from the recipient on the size and function of adipocytes in fat grafts. Treatment of mice with TNP-470, an angiogenesis inhibitor, reduced blood flow from the recipient into the graft after subcutaneous transplantation of epididymal fat. The weight of transplanted tissues and the size of adipocytes in the grafts were significantly lower in mice treated with TNP-470 (TNP mice) than in control mice. Expression of genes for enzymes related to lipid accumulation was decreased in the grafts of TNP mice compared with control mice. Moreover, the expression of adipocyte-derived angiogenic peptides, VEGF and leptin, was significantly lower in the grafts of TNP mice than in grafts from control animals. The expression of VEGF and leptin by cultured human adipocytes was increased in the presence of conditioned medium from cultured vascular endothelial cells. These results show that the inhibition of the revascularization of fat grafts after transplantation reduces graft volume retention and cellular function. Early and adequate revascularization may be important for both the supply of nutrients and vasoactive interactions between vascular endothelial cells and adipocytes in graft.

Quantification of abdominal fat depots in rats and mice during obesity and weight loss interventions

Background & Aims

Obesity is a leading healthcare issue contributing to metabolic diseases. There is a great interest in non-invasive approaches for quantitating abdominal fat in obese animals and humans. In this work, we propose an automated method to distinguish and quantify subcutaneous and visceral adipose tissues (SAT and VAT) in rodents during obesity and weight loss interventions. We have also investigated the influence of different magnetic resonance sequences and sources of variability in quantification of fat depots.

Materials and Methods

High-fat diet fed rodents were utilized for investigating the changes during obesity, exercise, and calorie restriction interventions (N = 7/cohort). Imaging was performed on a 7T Bruker ClinScan scanner using fast spin echo (FSE) and Dixon imaging methods to estimate the fat depots. Finally, we quantified the SAT and VAT volumes between the L1–L5 lumbar vertebrae using the proposed automatic hybrid geodesic region-based curve evolution algorithm.

Results

Significant changes in SAT and VAT volumes (p<0.01) were observed between the pre- and post-intervention measurements. The SAT and VAT were 44.22±9%, 21.06±1.35% for control, −17.33±3.07%, −15.09±1.11% for exercise, and 18.56±2.05%, −3.9±0.96% for calorie restriction cohorts, respectively. The fat quantification correlation between FSE (with and without water suppression) sequences and Dixon for SAT and VAT were 0.9709, 0.9803 and 0.9955, 0.9840 respectively. The algorithm significantly reduced the computation time from 100 sec/slice to 25 sec/slice. The pre-processing, data-derived contour placement and avoidance of strong background–image boundary improved the convergence accuracy of the proposed algorithm.

Conclusions

We developed a fully automatic segmentation algorithm to quantitate SAT and VAT from abdominal images of rodents, which can support large cohort studies. We additionally identified the influence of non-algorithmic variables including cradle disturbance, animal positioning, and MR sequence on the fat quantification. There were no large variations between FSE and Dixon-based estimation of SAT and VAT.

Central sympathetic innervations to visceral and subcutaneous white adipose tissue

There is a link between visceral white adipose tissue (WAT) and the metabolic syndrome in humans, with health improvements produced with small visceral WAT reduction. By contrast, subcutaneous WAT provides a site for lipid storage that is rather innocuous relative to ectopic lipid storage in muscle or liver. The sympathetic nervous system (SNS) is the principal initiator for lipolysis in WAT by mammals. Nothing is known, however, about the central origins of the SNS circuitry innervating the only true visceral WAT in rodents, mesenteric WAT (MWAT), which drains into the hepatic portal vein. We tested whether the central sympathetic circuits to subcutaneous [inguinal WAT (IWAT)] and visceral WAT (MWAT) are separate or shared and whether they possess differential sympathetic drives with food deprivation in Siberian hamsters. Using two isogenic strains of pseudorabies virus, a retrograde transneuronal viral tract tracer within the same hamsters, we found some overlap (∼20-55% doubly infected neurons) between the two circuitries across the neural axis with lesser overlap proximal to the depots (spinal cord and sympathetic chain) and with more neurons involved in the innervation of IWAT than MWAT in some brain regions. Food deprivation triggered a greater sympathetic drive to subcutaneous (IWAT) than visceral (MWAT) depots. Collectively, we demonstrated both shared and separate populations of brain, spinal cord, and sympathetic chain neurons ultimately project to a subcutaneous WAT depot (IWAT) and the only visceral WAT depot in rodents (MWAT). In addition, the lipolytic stimulus of food deprivation only increased SNS drive to subcutaneous fat (IWAT).

Adiposopathy: how do diet, exercise and weight loss drug therapies improve metabolic disease in overweight patients?

An increase in bodyweight is generally associated with an increased risk of excessive fat-related metabolic diseases (EFRMD), including Type 2 diabetes mellitus, hypertension and dyslipidemia. However, not all patients who are overweight have EFRMD, and not all patients with EFRMD are significantly overweight. The adipocentric paradigm provides the basis for a unifying, pathophysiological process whereby fat gain in susceptible patients leads to fat dysfunction ('sick fat'), and wherein pathological abnormalities in fat function (adiposopathy) are more directly related to the onset of EFRMD than increases in fat mass (adiposity) alone. But just as worsening fat function worsens EFRMD, improved fat function improves EFRMD. Peroxisome proliferator-activated receptor-gamma agonists increase the recruitment, proliferation and differentiation of preadipocytes ('healthy fat') and cause apoptosis of hypertrophic and dysfunctional (including visceral) adipocytes resulting in improved fat function and improved metabolic parameters associated with EFRMD. Weight loss interventions, such as a hypocaloric diet and physical exercise, in addition to agents such as orlistat, sibutramine and cannabinoid receptor antagonists, may have favorable effects upon fat storage (lipogenesis and fat distribution), nutrient metabolism (such as free fatty acids), favorable effects upon adipose tissue factors involved in metabolic processes and inflammation, and enhanced 'cross-talk' with other major organ systems. In some cases, weight loss therapeutic agents may even affect metabolic parameters and adipocyte function independently of weight loss alone, suggesting that the benefit of these agents in improving EFRMD may go beyond their efficacy in weight reduction. This review describes how adiposopathy interventions may affect fat function, and thus improve EFRMD.

Rats perinatally exposed to food restriction and high-fat diet show differences in adipose tissue gene expression under chronic caloric restriction

The aim of this study is to analyze how maternal diet during the lactational period influences the adipose tissue response to chronic caloric restriction in offspring. Lactating dams were subjected to one of three treatments: 50% food restriction (FR), ad lib standard chow (AL), or ad lib high-fat diet (HF). Juveniles were first weaned onto standard chow, then in adulthood 50% calorically restricted and maintained at 90% of normal body weight for 60 d. HF animals showed increased percent body fat compared with AL and FR animals despite equivalent body weights. HF animals showed alterations in the balance of adipose tissue lipogenic (FAS, LPL) and lipolytic (HSL) gene expression that may underlie their propensity to maintain fat stores under caloric restriction.

Early changes of abdominal adiposity detected with weekly dual bioelectrical impedance analysis during calorie restriction

OBJECTIVE

To elucidate early change of intra-abdominal fat in response to calorie restriction in patients with obesity by weekly evaluation using a dual bioelectrical impedance analysis (Dual BIA) instrument.

METHODS

For 67 Japanese patients with obesity, diabetes, or metabolic syndrome, intra-abdominal fat area (IAFA), initially with both Dual BIA and computed tomography (CT), and in subsequent weeks of calorie restriction, with Dual BIA were measured.

RESULTS

IAFA by Dual BIA (Dual BIA-IAFA) correlated well with IAFA by CT (CT-IAFA) in obese patients (r = 0.821, P < .0001, n = 67). Ten males and 9 females (age 49.0 ± 14.4 years, BMI 33.2 ± 7.3 kg/m2) lost more than 5% of baseline body weight (BW) in 3 weeks, and their Dual BIA-IAFA, BW, and WC decreased by 18.9%, 5.3%, and 3.8%, respectively (P < .05, ANCOVA).

CONCLUSION

Dual BIA instrument could detect the weekly change of Dual BIA-IAFA under calorie restriction in obese patients and demonstrated a substantially larger change of IAFA compared with changes of BW and WC in early weeks. This observation corroborates the significance of evaluating IAFA as a biomarker for obesity, and indicates the clinical usefulness of the Dual BIA instrument.

Visceral adiposity is associated with SIRT1 expression in peripheral blood mononuclear cells: a pilot study

Sirtuin1 (SIRT1) is activated during calorie restriction and appears to be related to energy balance through glucose or lipid metabolism and insulin signaling. These findings suggest that SIRT1 may play a role in the pathophysiology of visceral obesity. Therefore, we investigated the relationship between SIRT1 gene expression in circulating peripheral blood mononuclear cells (PBMCs) and abdominal visceral adiposity as measured by computed tomography. We recruited 43 men and women without history of diabetes or cardiovascular disease Biomarkers of metabolic disease and body composition by computed tomography were assessed. SIRT1 gene expression was determined using isolated PBMCs. SIRT1 expression levels negatively correlated with body mass index, waist circumference, abdominal visceral fat area, and homeostasis model of assessment of insulin resistance (HOMA-IR) and positively correlated with adiponectin levels. Results of step-wise multiple regression analysis revealed that abdominal visceral fat area and HOMA-IR were independently associated with SIRT1 expression. The significant association between abdominal visceral fat accumulation and SIRT1 gene expression in PBMCs suggests that SIRT1 may be a new therapeutic target for the prevention of disease related to obesity, especially visceral obesity.

Food restriction and refeeding induces changes in lipid pathways and fat deposition in the adipose and hepatic tissues in rats with diet-induced obesity

The aim of this study was to determine the effects of successive cycles of a moderately restrictive diet and refeeding with a high-fat diet on the metabolism of the adipose and hepatic tissues of obese rats. Rats were assigned to the following groups: a chow diet; a high-fat diet; a moderate caloric restriction; or a moderate caloric restriction plus refeeding. Some animals in each group were given [1-(14)C]triolein intragastrically, while others received an intraperitoneal injection of 3 mCi (3)H(2)O. All animals were killed by decapitation. The retroperitoneal, visceral epididymal and omental white adipose tissues, brown adipose tissue, liver and blood were immediately removed. The lipid uptake from the diet, in vivo rate of lipogenesis, percentage of fat, lipid profile and leptin concentration were analysed. The high-fat diet promoted an increase in fatty liver (P ≤ 0.05), adiposity mass (P ≤ 0.05) and the plasma concentration of leptin (P ≤ 0.05) and a decreased lipid uptake in white adipose tissue depots (P ≤ 0.05) in relation to the chow diet. The moderate caloric restriction did not reverse the changes promoted by the high-fat diet but induced a small decrease in adiposity, which was reversed after refeeding, and the animals maintained a dyslipidaemic profile and high fat deposition in the liver. We can conclude that the high-fat diet and subsequent moderate caloric restriction plus refeeding increased the risks of developing visceral obesity, dyslipidaemia and non-alcoholic fatty liver disease, which suggests that this type of experimental protocol can be used to study mechanisms related to the metabolic syndrome.

Energy intake and adiponectin gene expression

Hypoadiponectinemia and decreased adiponectin gene expression in white adipose tissue (WAT) have been well observed in obese subjects and animal models. However, the mechanism for obesity-associated hypoadiponectinemia is still largely unknown. To investigate the regulatory role of energy intake, dietary fat, and adiposity in adiponectin gene expression and blood adiponectin level, a series of feeding regimens was employed to manipulate energy intake and dietary fat in obese-prone C57BL/6, genetically obese ob/ob, obese-resistant A/J and peroxisome proliferator-activated receptor-α gene knockout (PPARα KO) mice. Adiponectin gene expression in WAT and circulating adiponectin levels were studied in these dietary intervention-treated mice. Our study showed that calorie restriction (CR) robustly increased adiponectin gene expression in epididymal fat and blood adiponectin levels in both low-fat (LF) and high-fat (HF) diet-fed C57BL/6 mice. Although HF pair-fed C57BL/6 mice received the same amount of calories as LF ad libitum-fed mice, HF diet clearly increased adiposity but showed no significant effects on adiponectin gene expression and blood adiponectin level. CR also significantly increased blood adiponectin levels in ob/ob and A/J mice. Neither CR nor HF feeding displayed any significant effect on blood adiponectin half-life in C57BL/6 mice. Interestingly, CR increased PPARα expression in epididymal fat of C57BL/6 mice. Low levels of blood adiponectin and adiponectin gene expression in WAT were observed in PPARα KO mice. PPARα agonist treatment increased adiponectin mRNA levels in 3T3-L1 adipocytes. Furthermore, CR failed to increase adiponectin gene expression and blood adiponectin levels in PPARα KO mice. Therefore, our study demonstrated that energy intake, not dietary fat, plays an important role in regulating adiponectin gene expression and blood adiponectin level. PPARα mediates CR-enhanced adiponectin gene expression in WAT.

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) reverses hyperglycemia in a type II diabetes mellitus rat model by a mechanism unrelated to PPAR gamma

It has been asserted that exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) increases the risk for diabetes mellitus in humans, observable as hyperglycemia resulting from insulin resistance. There is no animal model for the induction of diabetes by TCDD. On the contrary, TCDD has been shown to increase insulin sensitivity in rats. Therefore, a diabetic rat model was used to study the effects of TCDD on preexisting diabetes. Type II diabetes was induced in male rats by a high-fat diet and streptozotocin. After manifestation of the disease, these rats received loading dose rates (LDRs) of 3.2, 6.4, and 12.8 microg/kg of TCDD p.o., followed by weekly maintenance dose rates. Rats fed a high-fat diet and not dosed with streptozotocin nor with TCDD served as nondiabetic controls. By day 2, serum-glucose levels in diabetic rats treated with the high LDR of 12.8 microg/kg TCDD were already significantly reduced. By day 8, serum-glucose levels had decreased to control levels and were maintained for the duration of the study (32 days). Thus, TCDD effectively counteracted hyperglycemia in this diabetic rat model. In healthy animals, TCDD induced PPAR gamma transcription and activity in a different dose range than that observed for the hypoglycemic effect.

Waist circumference reduction is more strongly correlated with the improvement in endothelial function after acute coronary syndrome than body mass index reduction

BACKGROUND

Endothelial function predicts recurrence of adverse cardiac events in patients with acute coronary syndromes (ACS). Moreover, the recovery of endothelial function correlates with cardiac event-free survival.

OBJECTIVES

The aim of this study was to determine which clinical factors correlate with the improvement in endothelial function after ACS.

METHODS

Vascular endothelial function was assessed in 98 patients with ACS by flow-mediated dilation (FMD) of the brachial artery using high-resolution ultrasound at 2 weeks and 6 months after ACS. We measured several risk parameters including plasma markers of glucose homeostasis, lipids, and blood pressure at baseline and at 6 months after ACS. Body mass index (BMI) and waist circumference (WC) were also measured as anthropometric assessments.

RESULTS

At baseline, FMD was significantly correlated with BMI, WC, high-density lipoprotein cholesterol, the homeostasis model assessment of insulin resistance, and brachial artery diameter (r=-0.32, p=0.001; r=-0.44, p<0.0001; r=0.34, p=0.0006; r=-0.21, p=0.04; r=-0.47, p<0.0001, respectively). In a stepwise multivariate regression analysis at baseline, larger WC and brachial artery diameter were independently correlated with lower brachial artery FMD (R(2)=0.319, p<0.0001). At 6 months, the change in FMD was significantly correlated with the change in WC and BMI (r=-0.59, p<0.0001; r=-0.33, p=0.001, respectively). In a stepwise multivariate regression analysis, WC reduction was independently correlated with improved FMD (R(2)=0.349, p<0.0001).

CONCLUSIONS

WC reduction is more strongly correlated with the improvement of endothelial function after ACS than BMI reduction.

Response to Fasting in an Unnaturally Obese Carnivore, the Captive European Polecat Mustela putorius

The European polecat ( Mustela putorius) is a naturally lean carnivore prone to excessive weight gain in captivity. This study assessed its suitability to investigate the natural history of the obese phenotype displayed in overweight humans, domestic animals, and seasonally obese wild mammals. Ten farm-bred polecats were subjected to a 5-day fast with 10 controls. Obesity (40% body fat) was associated with an unfavorable plasma lipid profile and high glucose and insulin concentrations. The polecats were in phase II of fasting with normoglycemia, low liver carbohydrate stores, and decreased plasma concentrations of urea and most amino acids. Although the plasma nonesterified fatty acid (NEFA) levels were elevated, the adipose tissue lipase activities suggested a blunted lipolytic response. Lipid mobilization was more efficient from intraabdominal fat. The animals developed hepatic lipidosis with elevated NEFA influx into the liver and losses of n-3 polyunsaturated fatty acids and arginine as hypothetical etiological factors. The plasma leptin, insulin, and triiodothyronine levels decreased but were not accompanied by reduced sex steroid or increased stress hormone concentrations. The blunted lipolytic response often encountered in obesity suggests that the organism is trying to defend the obese phenotype. Liver lipidosis and decreased insulin and triiodothyronine levels seem to be among the most consistent responses to fasting manifested in diverse mammalian orders and different levels of body fatness. The polecat could be recommended as an easily accessible carnivorean model to study the natural history of the obese phenotype and its comorbidities.

Analysis of knockout mice suggests a role for VGF in the control of fat storage and energy expenditure

Background

Previous studies of mixed background mice have demonstrated that targeted deletion of Vgf produces a lean, hypermetabolic mouse that is resistant to diet-, lesion-, and genetically-induced obesity. To investigate potential mechanism(s) and site(s) of action of VGF, a neuronal and endocrine secreted protein and neuropeptide precursor, we further analyzed the metabolic phenotypes of two independent VGF knockout lines on C57Bl6 backgrounds.

Results

Unlike hyperactive VGF knockout mice on a mixed C57Bl6-129/SvJ background, homozygous mutant mice on a C57Bl6 background were hypermetabolic with similar locomotor activity levels to Vgf+/Vgf+ mice, during day and night cycles, indicating that mechanism(s) other than hyperactivity were responsible for their increased energy expenditure. In Vgf-/Vgf- knockout mice, morphological analysis of brown and white adipose tissues (BAT and WAT) indicated decreased fat storage in both tissues, and decreased adipocyte perimeter and area in WAT. Changes in gene expression measured by real-time RT-PCR were consistent with increased fatty acid oxidation and uptake in BAT, and increased lipolysis, decreased lipogenesis, and brown adipocyte differentiation in WAT, suggesting that increased sympathetic nervous system activity in Vgf-/Vgf- mice may be associated with or responsible for alterations in energy expenditure and fat storage. In addition, uncoupling protein 1 (UCP1) and UCP2 protein levels, mitochondrial number, and mitochondrial cristae density were upregulated in Vgf-/Vgf- BAT. Using immunohistochemical and histochemical techniques, we detected VGF in nerve fibers innervating BAT and Vgf promoter-driven reporter expression in cervical and thoracic spinal ganglia that project to and innervate the chest wall and tissues including BAT. Moreover, VGF peptide levels were quantified by radioimmunoassay in BAT, and were found to be down-regulated by a high fat diet. Lastly, despite being hypermetabolic, VGF knockout mice were cold intolerant.

Conclusion

We propose that VGF and/or VGF-derived peptides modulate sympathetic outflow pathways to regulate fat storage and energy expenditure.

Divergent regulation of adipose tissue metabolism by calorie restriction and inhibition of growth hormone signaling

Calorie restriction (CR) and a reduced growth hormone (GH) signal affect insulin sensitivity and lifespan in mammals in a similar manner. We investigated the effects of CR and moderate inhibition of GH on glucose-stimulated activation of insulin signaling and the expression of genes related to fat metabolism in white adipose tissue (WAT) in rats. We used 10-month-old male, wild-type (W) Wistar rats, fed ad libitum (AL) or a 30% CR diet from 6weeks of age, and transgenic (Tg) rats with moderately suppressed GH signaling. Rats were killed 15min after an intraperitoneal injection of glucose or saline. In control W-AL rats, the levels of serum insulin, phosphorylated (p) insulin receptor (pY-IR), p-Akt, and the expression of glucose transporter (Glut) 4 in the membrane fraction were greater in the glucose-injected group than in the saline-injected group, indicating significant activation of insulin signaling in response to glucose loading. In the W-CR and Tg-AL rats, the serum insulin and pY-IR levels were lower than those in the W-AL rats. The Akt-Glut pathway was up-regulated even after saline-injection. Expression levels of adipogenic and lipogenic genes including PPARgamma, adiponectin, and its receptors, were higher in the W-CR rats than in the W-AL and Tg-AL rats. The present findings indicate adipose tissue metabolic profiles specific to CR.

Daily exercise fluctuations and dietary patterns during training predict visceral fat regain in obese women

BACKGROUND

Visceral adiposity is an essential component of metabolic syndrome. Reduction of excessive visceral fat prevents metabolic syndrome and improves atherosclerotic diseases. This study aimed to identify dietary patterns and physical exercise during the training-education period that predict visceral adiposity regain during the follow-up period.

METHODS

One hundred one moderately obese Japanese women, 23 to 67 years of age, participated in 0- to 4-month training-education and 12-month follow-up periods. Dietary patterns of food groups during training-education were analyzed by principal components analysis, and 3 major dietary patterns were derived. The change in visceral fat over the follow-up, adjusted for 4-month visceral fat area (VFA) and 4- to 16-month body mass index change, was analyzed using stepwise multiple linear regression.

RESULTS

VFA and body weight decreased during training-education (P<0.001) and were maintained during follow-up. One major dietary pattern (of 3) (P=0.030) and standard deviations of daily exercise duration (P=0.012) during training-education predicted VFA regain during follow-up. This regain correlated negatively with combinations of bread, milk and dairy products, fruits, seeds and nuts, and mushrooms, but positively with combinations of rice, pickles, miso, alcohol, and meat. The large standard deviation of daily exercise duration during training-education showed greater VFA regain during follow-up than did the smaller standard deviation (P=0.023), but body mass index did not show a similar trend.

CONCLUSION

Our results revealed that daily exercise fluctuations and dietary patterns were useful predictors of visceral fat regain.

From chronic overnutrition to insulin resistance: the role of fat-storing capacity and inflammation

AIMS

We analyze how the inflammatory state in adipose tissue caused by a condition of chronically positive energy balance can lead to insulin resistance first in adipose tissue, then in all insulin-sensitive tissues.

DATA SYNTHESIS

Chronic nutrient overload causes an increase in adipose depots that, if adipose tissue expandability is low, are characterized by an increased presence of hypertrophic adipocytes. This adipocyte hypertrophy is a possible stress condition for the endoplasmic reticulum (ER) that would lead to a proinflammatory state in adipose tissue. In this condition, ER stress would activate metabolic pathways that trigger insulin resistance, release of macrophage chemoattractant proteins, and in chronic inflammation, the death of the hypertrophic adipocyte. The infiltrated macrophages in turn release inflammatory proteins causing further recruitment of macrophages to adipose tissue and the release of inflammatory cytokines. Following these events, insulin resistance becomes extended to all adipose tissue. Insulin-resistant adipocytes, characterized by low liposynthetic capacity and high lipolytic capacity, cause increased release of free fatty acids (FFA). FFA released by lipolitic adipocytes may also activate Toll-like receptors 4 and then chemokines and cytokines release amplifying insulin resistance, lipolysis and inflammation in all adipose tissue. Moreover, increased circulating FFA levels, reduced circulating adiponectin levels and leptin resistance lead to decreased lipid oxidation in non-adipose tissues, thereby triggering ectopic accumulation of lipids, lipotoxicity and insulin resistance.

CONCLUSION

All the conditions that increase circulating fatty acids and cause lipid overloading (obesity, lipoatrophy, lipodystrophy, catabolic states, etc.) induce a lipotoxic state in non-adipose tissues that gives rise to insulin resistance.

Assessment of diet-induced obese rats as an obesity model by comparative functional genomics

OBJECTIVE

We applied a comparative functional genomics approach to evaluate whether diet-induced obese (DIO) rats serve as an effective obesity model.

METHODS AND PROCEDURES

Gene-expression profiles of epididymal fat from DIO and lean rats were generated using microarrays and compared with the published array data of obese and non-obese human subcutaneous adipocytes.

RESULTS

Caloric intake and fuel efficiency were significantly higher in DIO rats, which resulted in increased body weight and adiposity. Circulating glucose, cholesterol, triglyceride, insulin, and leptin levels in DIO rats were significantly higher than those in the lean controls. DIO rats also exhibited impaired insulin sensitivity. A direct comparison of gene-expression profiles from DIO and lean rats and those from obese and non-obese humans revealed that global gene-expression patterns in DIO rat fat resemble those of obese human adipocytes. Differentially expressed genes between obese and non-obese subjects in both human and rat studies were identified and associated with biological pathways by mapping genes to Gene Ontology (GO) categories. Immune response-related genes and angiogenesis-related genes exhibited significant upregulation in both obese humans and DIO rats when compared with non-obese controls. However, genes in fatty acid metabolism and oxidation exhibited a broad downregulation only in obese human adipocytes but not in DIO rat epididymal fat.

DISCUSSION

Our study based on gene-expression profiling suggested that DIO rats in general represent an appropriate obesity model. However, the discrepancies in gene-expression alterations between DIO rats and obese humans, particularly in the metabolic pathways, may explain the limitations of using DIO rodent models in obesity research and drug discovery.

Caloric restriction and refeeding promoted different metabolic effects in fat depots and impaired dyslipidemic profile in rats

OBJECTIVE

We investigated the effects of severe caloric restriction and refeeding with a high-fat diet on lipid uptake by visceral adipose fat and lipid profile in rats.

METHODS

Rats were assigned to six groups: a chow diet (C), a high-fat diet (H), severe caloric restriction (SC and SH), and severe caloric restriction plus refeeding (SC-r and SH-r) during 8 wk. All animals were killed by decapitation 4 h after intragastric administration of [1-14C] triolein ( approximately 0.5 g, 0.3 muCi/rat). Liver; visceral retroperitoneal (RET), epididymal (EPI), and omental (VIS) white adipose tissues; brown adipose tissue; and intestine were immediately removed and weighed. The whole intestine was withdrawn and homogenized to determine lipid uptake. Total cholesterol, high-density lipoprotein (HDL), and triacylglycerol in plasma were determined enzymatically.

RESULTS

The SC and SH groups showed reduced visceral adiposity, although this effect was more evident in the SC group. The SC group had greater lipid absorption in the VIS than the C group. The SH treatment increased RET and VIS lipid uptake in relation to the H group. The SH-r treatment increased RET and VIS adiposity. HDL cholesterol decreased with caloric restriction in the SC and SH groups. The SH-r treatment did not increase HDL cholesterol.

CONCLUSION

Severe caloric restriction decreased visceral adiposity even in rats in the H group but did not reduce the risk of development of dyslipidemia. Therefore, food restriction plus refeeding with a high-fat diet increase the risk of development of visceral adiposity and dyslipidemia.

Fatty acid desaturase regulation in adipose tissue by dietary composition is independent of weight loss and is correlated with the plasma triacylglycerol response

BACKGROUND

Atherogenic dyslipidemia associated with elevated plasma triacylglycerol concentrations and reduced HDL is improved by both caloric restriction and reduced carbohydrate consumption.

OBJECTIVE

We aimed to identify the molecular pathways responsive to both caloric restriction and dietary composition within adipose tissue by monitoring transcriptional expression.

DESIGN

Subcutaneous adipose tissue biopsy specimens were obtained from 131 moderately overweight men [body mass index (in kg/m2): 29.2 +/- 2.0] after 1 wk of a basal diet [54%, 16%, and 30% carbohydrate, protein, and fat, respectively; 7% saturated fat), after 3 wk with 1 of 4 randomized diets [basal diet; moderate-carbohydrate (39%) diet; low-carbohydrate (26%) and low-saturated-fat (9%) diet; low-carbohydrate (26%) and high-saturated-fat (15%) diet], after 5 wk of acute weight loss with a randomized diet (-1103.0 +/- 216.5 kcal/d, which resulted in a loss of 10.0 +/- 3.3 lb, or 4.5 +/- 1.5 kg), and after 4 wk of being stabilized at a reduced weight. Transcriptional response was identified by using expression array analysis and was confirmed by using real-time polymerase chain reaction analysis.

RESULTS

Of the 1473 transcripts significantly decreased in expression in response to acute weight loss, 30 were responsive to isocaloric alterations in dietary composition, including stearoyl-coenzyme A desaturase (SCD), fatty acid desaturases 1 and 2 (FADS1 and FADS2), and diacylglycerol transferase 2 (DGAT2). Response was confirmed by real-time polymerase chain reaction analysis for these genes (P < 0.003). SCD expression in response to isocaloric dietary change was most strongly correlated with carbohydrate intake (P = 0.019) and, with the low-carbohydrate diet, SCD expression was inversely correlated with saturated fat intake (P = 0.05). Triacylglycerol responses to changes in dietary composition were independently correlated with SCD (P = 0.003) and DGAT2 (P = 0.05) responses.

CONCLUSIONS

SCD expression in adipose tissue is independently regulated by weight loss and by carbohydrate and saturated fat intakes. Moreover, SCD and DGAT2 expression may be involved in dietary regulation of systemic triacylglycerol metabolism.

Adrenomedullin is a novel adipokine: adrenomedullin in adipocytes and adipose tissues

Adrenomedullin (AM) is a multifunctional regulatory peptide that is produced and secreted by various types of cells. The production and the secretion of AM have been demonstrated in cultured adipocytes and adipose tissues. Inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) and lipopolysaccharide are strong stimulators for AM expression in adipocytes. Furthermore, AM expression in the adipose tissue is increased in obesity, and plasma concentrations of AM are increased in obese subjects. One possible (patho)physiological role of AM secreted by adipose tissue may be actions against complications of the metabolic syndrome characterized by obesity, type 2 diabetic mellitus and hypertension, via its antioxidant and potent vasodilator effects. These findings indicate that AM is a new member of the adipokine family.

Comparison of mitochondrial and macrophage content between subcutaneous and visceral fat in db/db mice

Central (visceral) obesity is more closely associated with insulin resistance, type 2 diabetes, and cardiovascular disease than peripheral (subcutaneous) obesity, however the underlying differences in morphology and pathophysiology between subcutaneous and visceral adipose are largely unknown. To evaluate the effects of diabetes and rosiglitazone (RSG) treatment, the expression of mitochondrial Hsp60, UCP-1 and F4/80 in inguinal subcutaneous (SC) fat, composed of white and brown adipose tissues, and epididymal (EP) fat, mainly white adipose tissue, were evaluated. In diabetic db/db mice, there was significant increased number of aggregated macrophage foci compared to db/+ mice, especially in EP fat. On the other hand, the expression of mitochondrial Hsp60 protein was suppressed in both SC and EP fat of db/db mice compared to db/+ mice, and the expression level of mitochondrial Hsp60 in db/+ mice was lower in EP fat compared with SC. In db/db mice, RSG suppressed the number of aggregated macrophage foci in EP fat, but not in SC fat. RSG ameliorated the mitochondrial Hsp60 expression and induced the expression of UCP-1 in both SC and EP fat. Taken together, these data suggest that differences exist in mitochondrial and macrophage content, and in the response to RSG between visceral and subcutaneous adipose tissue, and adipose type and distribution may be important for obesity-linked insulin resistance.

Calcium and 1,25-dihydroxyvitamin D3 regulation of adipokine expression

OBJECTIVE

Obesity is associated with elevated oxidative stress and low-grade systemic inflammation. We have demonstrated recently that 1alpha,25-(OH)(2)-D(3) promotes reactive oxygen species production in cultured adipocytes, whereas suppression of 1alpha,25-(OH)(2)-D(3) by increasing dietary calcium down-regulates diet-induced oxidative stress in aP2-agouti transgenic mice. However, whether the anti-obesity effect of dietary calcium plays a role in regulation of obesity-associated inflammation is not clear.

RESEARCH METHODS AND PROCEDURES

We investigated the role of dietary calcium in the regulation of inflammatory cytokine production in aP2-agouti transgenic mice fed low- and high-calcium obesigenic diets and in the modulation of cytokine production by 1alpha,25-(OH)(2)-D(3) in cultured murine and human adipocytes.

RESULTS

The high-calcium diet inhibited the expression of pro-inflammatory factors tumor necrosis factor alpha and interleukin (IL)-6 by 64% and 51%, respectively (p < 0.001), in visceral fat, stimulated the expression of the anti-inflammatory factors IL-15 and adiponectin by 52% (p = 0.001) and 54% (p = 0.025), respectively, in visceral fat, and induced a 2-fold increase in IL-15 expression in soleus muscle (p = 0.01) compared with litter mate controls on a low-calcium diet. 1alpha,25-(OH)(2)-D(3) also markedly stimulated the expression of tumor necrosis factor alpha (p < 0.001) and IL-6 (p = 0.016) in differentiated 3T3-L1 adipocytes and increased IL-6 (p = 0.004) and IL-8 (p < 0.001) production in differentiated human adipocytes. These effects were blocked by calcium channel antagonism with nifedipine.

DISCUSSION

These data demonstrate that 1alpha,25-(OH)(2)-D(3) favors inflammatory cytokine expression and inhibits anti-inflammatory cytokine expression; accordingly, suppression of 1alpha,25-(OH)(2)-D(3) by dietary calcium inhibits adipocyte-derived inflammation associated with obesity.

Increased matrix metalloproteinase-3 mRNA expression in visceral fat in mice implanted with cultured preadipocytes

Using preadipocyte implantation methods, we recently demonstrated that adipocytes in the visceral area change their function, as the expression of tumor necrosis factor-alpha (TNF-alpha) increases, thereby causing insulin resistance. In order to clarify the mechanism for changes in the function of adipocytes in visceral area, we examined the mRNA expression profiles in visceral fat tissue specimens. Four weeks after cell implantation, we performed a microarray analysis using the RNA of fat tissue specimens implanted either with 3T3-L1 cells or PBS alone. Sixty-three genes were thus isolated and the expression of matrix metalloproteinase-3 (MMP-3) mRNA was found to dramatically increase in the fat tissue specimens. The neutralization of MMP-3 protein inhibited adipogenesis and the free fatty acid-induced TNF-alpha secretion in 3T3-L1 adipocytes. These results suggest a potential role of MMP-3, which promotes the TNF-alpha secretion, thus contributing to the disturbance of the functions in the adipocytes which accumulate in the visceral area.

Activation of diacylglycerol O-acyltransferase 1 gene results in increased tumor necrosis factor-alpha gene expression in 3T3-L1 adipocytes

The tumor necrosis factor-alpha (TNF-alpha) expression has been reported to be largely dependent on the size of adipocytes. We herein investigated the gene regulation of diacylglycerol O-acyltransferase (DGAT) in order to clarify the mechanism of TNF-alpha expression induced in large adipocytes. 3T3-L1 cells were cultured in the presence of 5 mM or 25 mM glucose to generate adipocytes from which the triglyceride content differs. The expression of TNF-alpha, DGAT1, and DGAT2 were upregulated in adipocytes cultured with 25 mM glucose. Furthermore, knockdown of DGAT1 gene significantly inhibited the TNF-alpha expression. Finally, the DGAT1 expression levels were closely related to the TNF-alpha level in 3T3-L1 adipocytes.

Involvement of AMP-activated protein kinase in fat depot-specific metabolic changes during starvation

The mechanisms controlling fat depot-specific metabolism are poorly understood. During starvation of mice, downregulation of lipogenic genes, suppression of fatty acid synthesis, and increases in lipid oxidation were all more pronounced in epididymal than in subcutaneous fat. In epididymal fat, relatively strong upregulation of uncoupling protein 2 and phosphoenolpyruvate carboxykinase genes was found. In mice maintained both at 20 and 30 degrees C, AMP-activated protein kinase was activated in epididymal but did not change in subcutaneous fat. Our results suggest that AMPK may have a role in the different response of various fat depots to starvation.

Quantitative trait loci for abdominal fat and BMI in Hispanic-Americans and African-Americans: the IRAS Family study

OBJECTIVE

To conduct linkage analysis for body mass index (BMI, kg/m2), waist-to-hip ratio (WHR), visceral adipose tissue mass (VAT, cm2) and subcutaneous adipose tissue mass (SAT, cm2) using a whole genome scan.

DESIGN

Cross-sectional family study.

STUDY SUBJECTS

African-American families from Los Angeles (AA, n=21 extended pedigrees) and Hispanic-American families (HA) from San Antonio, TX (HA-SA, n=33 extended pedigrees) and San Luis Valley, CO (HA-SLV, n=12 extended pedigrees), totaling 1049 individuals in the Insulin Resistance and Atherosclerosis (IRAS) Family Study.

MEASUREMENTS

VAT and SAT were measured using a computed tomography scan obtained at the fourth and fifth lumbar vertebrae. All phenotypes were adjusted for age, gender, and study center. VAT, SAT, and WHR were analyzed both unadjusted and adjusted for BMI.

RESULTS

Significant linkage to BMI was found at D3S2387 (LOD=3.67) in African-Americans, and at D17S1290 in Hispanic-Americans (LOD=2.76). BMI-adjusted WHR was linked to 12q13-21 (D12S297 (LOD=2.67) and D12S1052 (LOD=2.60)) in Hispanic-Americans. The peak LOD score for BMI-adjusted VAT was found at D11S2006 (2.36) in Hispanic families from San Antonio. BMI-adjusted SAT was linked to D5S820 in Hispanic families (LOD=2.64). Evidence supporting linkage of WHR at D11S2006, VAT at D17S1290, and SAT at D1S1609, D3S2387, and D6S1056 was dependent on BMI, such that the LOD scores became nonsignificant after adjustment of these phenotypes for BMI.

CONCLUSIONS

Our findings both replicate previous linkage regions and suggest novel regions in the genome that may harbor quantitative trait locis contributing to variation in measures of adiposity.

Caveolin-1 expression is essential for proper nonshivering thermogenesis in brown adipose tissue

Recently, we have shown that loss of caveolin-1 leads to marked alterations in insulin signaling and lipolysis in white adipose tissue. However, little is known about the role of caveolin-1 in brown adipose tissue (BAT), a tissue responsible for nonshivering thermogenesis. Here, we show that caveolin-1 null mice have a mildly, yet significantly, decreased resting core body temperature. To investigate this in detail, we next subjected the mice to fasting (for 24 h) or cold treatment (4 degrees C for 24 h), individually or in combination. Interestingly, caveolin-1 null mice showed markedly decreased body temperatures in response to fasting or fasting/cold treatment; however, cold treatment alone had no effect. In addition, under these conditions caveolin-1 null mice failed to show the normal increase in serum nonesterified fatty acids induced by fasting or fasting/cold treatment, suggesting that these mice are unable to liberate triglyceride stores for heat production. In accordance with these results, the triglyceride content of BAT was reduced nearly 10-fold in wild-type mice after fasting/cold treatment, but it was reduced only 3-fold in caveolin-1 null mice. Finally, electron microscopy of adipose tissue revealed dramatic perturbations in the mitochondria of caveolin-1 null interscapular brown adipocytes. Taken together, our data provide the first molecular genetic evidence that caveolin-1 plays a critical functional and structural role in the modulation of thermogenesis via an effect on lipid mobilization.

Omega-3 PUFA of marine origin limit diet-induced obesity in mice by reducing cellularity of adipose tissue

Omega-3 PUFA of marine origin reduce adiposity in animals fed a high-fat diet. Our aim was to learn whether EPA and DHA could limit development of obesity and reduce cellularity of adipose tissue and whether other dietary FA could influence the effect of EPA/DHA. Weight gain induced by composite high-fat diet in C57BL/6J mice was limited when the content of EPA/DHA was increased from 1 to 12% (wt/wt) of dietary lipids. Accumulation of adipose tissue was reduced, especially of the epididymal fat. Low ratio of EPA to DHA promoted the effect. A higher dose of EPA/DHA was required to reduce adiposity when admixed to diets that did not promote obesity, the semisynthetic high-fat diets rich in EFA, either alpha-linolenic acid (ALA, 18:3 n-3, the precursor of EPA and DHA) or linoleic (18:2 n-6) acid. Quantification of adipose tissue DNA revealed that except for the diet rich in ALA the reduction of epididymal fat was associated with 34-50% depression of tissue cellularity, similar to the 30% caloric restriction in the case of the high-fat composite diet. Changes in plasma markers and adipose gene expression indicated improvement of lipid and glucose metabolism due to EPA/DHA even in the context of the diet rich in ALA. Our results document augmentation of the antiadipogenic effect of EPA/DHA during development of obesity and suggest that EPA/DHA could reduce accumulation of body fat by limiting both hypertrophy and hyperplasia of fat cells. Increased dietary intake of EPA/DHA may be beneficial regardless of the ALA intake.

Impaired glucose tolerance is accompanied by decreased insulin sensitivity in tissues of mice implanted with cells that overexpress resistin

AIM/HYPOTHESIS

Resistin, the expression of which is suppressed by thiazolidinedione treatment in adipocytes, is one of the key molecules for the tight link between adiposity and insulin resistance. Here, we show the in vivo effects of resistin on insulin sensitivity in mature mice using a cell implantation method.

METHODS

Resistin cDNA was transfected into 3T3-L1 pre-adipocytes, which were then implanted into subcutaneous areas of nude mice. Metabolic analyses were performed 4 or 6 weeks after implantation.

RESULTS

The mice implanted with 3T3-L1 cells overexpressing resistin (R-mice) showed significantly (p<0.05) increased plasma resistin levels. After a glucose load plasma insulin levels were significantly greater in R-mice than in mice implanted with mock-transfected cells (M-mice). The AUC of insulin after glucose loading was positively correlated with circulating resistin levels. Significantly decreased glucose responses after insulin injection were observed in R-mice, compared to M-mice. The insulin-induced phosphorylation level of IRS-1 was significantly lower in muscles of R-mice than M-mice. The expression of TNF-alpha mRNA in intra-peritoneal fat tissues was significantly greater in R-mice than in M-mice, but there was no difference between the two groups with regard to subcutaneous fat tissues. The concentration of TNF-alpha in plasma was positively correlated with resistin levels in R-mice.

CONCLUSIONS/INTERPRETATION

Resistin, when actually secreted from cells in mature mice, causes disturbed glucose metabolism, possibly based on decreased insulin sensitivity in muscle. The in vivo effects of resistin on insulin sensitivity might be in part mediated by increased TNF-alpha expression in visceral fat tissues.