Abdominal adipocyte populations in women with visceral obesity

BACKGROUND

Visceral obesity is independently related to numerous cardiometabolic alterations, with adipose tissue dysfunction as a central feature.

OBJECTIVE

To examine whether omental (OM) and subcutaneous (SC) adipocyte size populations in women relate to visceral obesity, cardiometabolic risk factors and adipocyte lipolysis independent of total adiposity.

DESIGN AND METHODS

OM and SC fat samples were obtained during gynecological surgery in 60 women (mean age, 46.1±5.9 years; mean BMI, 27.1±4.5 kg/m² (range, 20.3-41.  kg/m²)). Fresh samples were treated with osmium tetroxide and were analyzed with a Multisizer Coulter. Cell size distributions were computed for each sample with exponential and Gaussian function fits.

RESULTS

Computed tomography-measured visceral fat accumulation was the best predictor of larger cell populations as well as the percentage of small cells in both OM and SC fat (P<0.0001 for all). Accordingly, women with visceral obesity had larger cells in the main population and higher proportion of small adipocytes independent of total adiposity (P≤0.05). Using linear regression analysis, we found that women characterized by larger-than-predicted adipocytes in either OM or SC adipose tissue presented higher visceral adipose tissue area, increased percentage of small cells and homeostasis model assessment insulin resistance index as well as higher OM adipocyte isoproterenol-, forskolin- and dbcAMP-stimulated lipolysis compared to women with smaller-than-predicted adipocytes, independent of total adiposity (P≤0.05).

CONCLUSION

Excess visceral adipose tissue accumulation is a strong marker of both adipocyte hypertrophy and increased number of small cells in either fat compartment, which relates to higher insulin resistance index and lipolytic response, independent of total adiposity.

Evaluation of a novel high-intensity focused ultrasound device for ablating subcutaneous adipose tissue for noninvasive body contouring: safety studies in human volunteers

BACKGROUND

High-intensity focused ultrasound (HIFU) is an energy-based medical technology with many clinical applications. A device under clinical investigation in the United States (LipoSonix; Medicis Technologies Corporation, Bothell, Washington) uses HIFU to reduce localized deposits of abdominal adipose tissue.

OBJECTIVES

The authors describe the results from their clinical trial investigating the safety of this HIFU device in human patients.

METHODS

Over the course of three studies evaluating the safety of the HIFU device for ablating human subcutaneous adipose tissue (SAT), 152 healthy patients were treated with total HIFU energy doses of 47 to 331 J/cm(2)), including patients who presented for elective abdominoplasty and underwent treatment to areas identified for subsequent excision. The safety of each treatment regimen was confirmed before the energy levels were raised. Abdominoplasty was performed up to 14 weeks following the HIFU procedure, and a pathologist performed histopathological analyses of excised tissues. Safety evaluations included an assessment of clinical chemistry and hematology profiles, physical examinations, and adverse events.

RESULTS

Posttreatment ultrasound confirmed that the HIFU effects were limited to targeted SAT layers. Histopathology revealed well-demarcated disruption of adipocytes within the targeted SAT. Phagocytosis of released lipids and cellular debris occurred after 14 to 28 days. Phagocytized lipids underwent normal hepatic metabolism. Healing progressed normally and was 95% complete after eight to 14 weeks. Adverse events consisted primarily of temporary treatment discomfort, edema, erythema, dysesthesia, and ecchymosis. There were no changes in clinical laboratory parameters, and no serious device-related adverse events occurred. Optimal clinical outcomes were achieved with lower energy levels, which provided beneficial effects with the least amount of discomfort.

CONCLUSIONS

HIFU appears to provide a safe means for removing and remodeling unwanted deposits of abdominal SAT.

[Function of PAT family proteins in the lipid metabolism]

Triglycerides are stored in intracellular lipid droplets in mammalian cells. Current evidences suggest that the intracellular lipid droplets are active participants in a variety of metabolic processes, and thus are considered as functional organelles in cells. The lipid droplet is composed of a triglyceride core surrounded by a phospholipid monolayer in which several proteins are embedded. Four of these proteins belong to a family of structurally related PAT protein, which includes perilipin, ADRP, TIP47 and S3-12. In this review, we summarize the functions of these proteins in the modulation of lipolysis and lipid droplets formation.

Biological studies of radiolabeled glucose analogues iodinated in positions 3, 4 or 6

The aim of this study was to assess the biological behavior of new radiolabeled glucose analogues proposed as tracers of glucose uptake in vivo and iodinated in position 3, 4, or 6. Biological results obtained in vitro on adipocytes and erythrocytes and in vivo in mice were compared to those obtained with the gold-standard tracer of glucose uptake, 2-deoxy-D-glucose. None of these molecules had the same biological behavior than 2-deoxy-D-glucose. Therefore, these compounds cannot be considered as tracers of glucose uptake.

Ultrasonographic assessment of coronary flow reserve and abdominal fat in obesity

Recent technological advances in transthoracic Doppler echocardiography (TTDE) have provided noninvasive measurement of coronary flow velocity reserve (CFVR). We aimed to quantitate a correlation between endothelial dysfunction and fat distribution. In 36 patients with obesity, 16 with noninsulin-dependent diabetes mellitus (DM) and 12 healthy volunteers, coronary flow velocity was measured at the distal site of the left anterior descending branch. CFVR was defined as the ratio of hyperemic (IV infusion of 0.15 mg/kg/min adenosine) to basal peak diastolic flow velocity. Abdominal wall fat index (AWFI) was estimated by ultrasonography. Insulin resistance was quantified by the euglycemic hyperinsulinemic clump method. AWFI was significantly related to CFVR (r = -0.46, p = 0.011) and insulin resistance (r = -0.71, p < 0.0001). CFVR could be noninvasively evaluated using TTDE. Coronary endothelial dysfunction indicated as CFVR, body fat distribution and insulin resistance was quantitatively correlated in obesity.

Glucocorticoid-induced insulin resistance associates with activation of protein kinase C isoforms

We studied glucocorticoid-induced insulin resistance and possible role of protein kinase C (PKC). Pretreatment with dexamethasone, prednisolone and corticosterone for 60 min decreased insulin-induced [3H] 2-deoxyglucose (DOG) uptake in isolated rat adipocytes. Preincubation with Go6976, LY379196 or myristoylated PKC pseudosubstrate, conventional PKC inhibitor, but not cycloheximide or RU38486, recovered dexamethasone-induced insulin resistance. Dexamethasone activated immunoprecipitates with anti-PKC alpha, beta, and zeta antibodies. PKC zeta activity in adipocytes increased to 163%, and 264% from basal level (100%) with dexamethasone and insulin treatment, respectively. Dexamethasone provoked redistribution of both PKC beta and zeta from the cytosol to the membrane. These results indicate that dexamethasone activates both conventional and atypical PKC. However, conventional PKC is more important in glucocorticoid-induced insulin resistance.