Subdivision of the subcutaneous adipose tissue compartment and lipid-lipoprotein levels in women

Plasma adiponectin/leptin ratio associates with subcutaneous abdominal and omental adipose tissue characteristics in women

BACKGROUND

A better understanding of adipose tissue (AT) dysfunction, which includes morphological and functional changes such as adipocyte hypertrophy as well as impaired adipogenesis, lipid storage/mobilization, endocrine and inflammatory responses, is needed in the context of obesity. One dimension of AT dysfunction, secretory adiposopathy, often assessed as a low plasma adiponectin (A)/leptin (L) ratio, is commonly observed in obesity. The aim of this study was to examine markers of AT development and metabolism in 67 women of varying age and adiposity (age: 40-62 years; body mass index, BMI: 17-41 kg/m2) according to levels of adiponectinemia, leptinemia or the plasma A/L ratio.

METHODS

Body composition, regional AT distribution and circulating adipokines were determined. Lipolysis was measured from glycerol release in subcutaneous abdominal (SCABD) and omental (OME) adipocytes under basal, isoproterenol-, forskolin (FSK)- and dibutyryl-cyclic AMP (DcAMP)-stimulated conditions. Adipogenesis (C/EBP-α/β/δ, PPAR-γ2 and SREBP-1c) and lipid metabolism (β2-ARs, HSL, FABP4, LPL and GLUT4) gene expression (RT-qPCR) was assessed in both fat depots. Participants in the upper versus lower tertile of adiponectin, leptin or the A/L ratio were compared.

RESULTS

Basal lipolysis was similar between groups. Women with a low plasma A/L ratio were characterized by higher adiposity and larger SCABD and OME adipocytes (p<0.01) compared to those with a high ratio. In OME adipocytes, women in the low adiponectinemia tertile showed higher isoproterenol-stimulated lipolysis (0.01

CONCLUSIONS

Secretory adiposopathy assessed as the plasma A/L ratio, more so than adiponectin or leptin levels alone, discriminates low and elevated lipolysis in OME and SCABD adipocytes despite similar AT expression of selected genes involved in lipid metabolism.

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Key Words

• Adipogenesis
• Adipokines
• Adipose cell lipolysis
• Adipose tissue gene expression
• Lipid metabolism

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MESH Headings

• Female
• Humans
• Adult
• Middle Aged
• Adiponectin/metabolism
• Leptin/metabolism
• Isoproterenol/metabolism
• Adipose Tissue/metabolism
• Obesity/metabolism

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Grants

• MOP-64182 and MOP-102642 CIHR
• Canadian Institutes of Health Research
• Centre de Recherche de l'Institut Universitaire de Cardiologie et de Pneumologie de Québec

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Affiliation(s)

Eve-Julie Tremblay École de Nutrition, Faculté des sciences de l'agriculture et de l'alimentation, Université Laval, Québec City, Canada Centre de recherche de l'Institut Universitaire de Cardiologie et Pneumologie de Québec (CRIUCPQ), Université Laval, Québec City, Canada
André Tchernof École de Nutrition, Faculté des sciences de l'agriculture et de l'alimentation, Université Laval, Québec City, Canada Centre de recherche de l'Institut Universitaire de Cardiologie et Pneumologie de Québec (CRIUCPQ), Université Laval, Québec City, Canada
Mélissa Pelletier Centre de recherche de l'Institut Universitaire de Cardiologie et Pneumologie de Québec (CRIUCPQ), Université Laval, Québec City, Canada
Denis R Joanisse Centre de recherche de l'Institut Universitaire de Cardiologie et Pneumologie de Québec (CRIUCPQ), Université Laval, Québec City, Canada Département de kinésiologie, Faculté de médecine, Université Laval, Québec City, Canada
Pascale Mauriège Centre de recherche de l'Institut Universitaire de Cardiologie et Pneumologie de Québec (CRIUCPQ), Université Laval, Québec City, Canada. Département de kinésiologie, Faculté de médecine, Université Laval, Québec City, Canada.

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17β-hydroxysteroid dehydrogenase type 2 activity, expression and cellular localization in abdominal adipose tissues from women

CONTEXT

17β-hydroxysteroid dehydrogenase type 2 (17β-HSD2) may be involved in the local modulation of estradiol (E2) availability in adipose tissues.

OBJECTIVE

To assess the conversion of E2 into estrone (E1) as well as the expression of 17β-HSD2 and its localization in omental (OM) and subcutaneous (SC) adipose tissues obtained from women.

METHODS

Rates of ¹⁴ C-E1 formation from ¹⁴ C-E2 were measured in OM and SC adipose tissue homogenates from 29 women. Specific 17β-HSD2 inhibitor EM-919 was tested in OM and SC adipose tissue homogenates (n = 6). 17β-HSD2 mRNA expression was measured in whole OM and SC adipose tissues (n = 14). Cellular localization of the enzyme was examined using immunohistochemistry. Anthropometric measurements were obtained and body composition as well as body fat distribution were measured.

RESULTS

Significant ¹⁴ C-E1 formation from ¹⁴ C-E2 in OM and SC tissue homogenates was detected. The rate of ¹⁴ C-E1 formation was significantly higher in OM than SC adipose tissue (p < .0001). The conversion of ¹⁴ C-E2 to ¹⁴ C-E1 was significantly inhibited by EM-919 in OM (p < .05) and SC (p < .05) adipose tissues. Significantly higher expression of 17β-HSD2 mRNA in OM versus SC fat was found (p = .03). 17β-HSD2 was localized in the vasculature of OM and SC tissues. Significant negative associations were detected between OM 17β-HSD2 activity and body mass index, WC, lean body mass as well as SC adipose tissue areas.

CONCLUSION

17β-HSD2 converts E2 to E1 in OM and SC adipose tissues of women. The activity of this enzyme decreases with increasing adiposity.

Contribution of markers of adiposopathy and adipose cell size in predicting insulin resistance in women of varying age and adiposity

Adipose tissue (AT) dysfunctions, such as adipocyte hypertrophy, macrophage infiltration and secretory adiposopathy (low plasma adiponectin/leptin, A/L, ratio), associate with metabolic disorders. However, no study has compared the relative contribution of these markers to cardiometabolic risk in women of varying age and adiposity. Body composition, regional AT distribution, lipid-lipoprotein profile, glucose homeostasis and plasma A and L levels were determined in 67 women (age: 40-62 years; BMI: 17-41 kg/m2). Expression of macrophage infiltration marker CD68 and adipocyte size were measured from subcutaneous abdominal (SCABD) and omental (OME) fat. AT dysfunction markers correlated with most lipid-lipoprotein levels. The A/L ratio was negatively associated with fasting insulinemia and HOMA-IR, while SCABD or OME adipocyte size and SCABD CD68 expression were positively related to these variables. Combination of tertiles of largest adipocyte size and lowest A/L ratio showed the highest HOMA-IR. Multiple regression analyses including these markers and TAG levels revealed that the A/L ratio was the only predictor of fasting insulinemia and HOMA-IR. The contribution of the A/L ratio was superseded by adipose cell size in the model where the latter replaced TAGs. Finally, leptinemia was a better predictor of IR than adipocyte size and the A/L ratio in our participants sample.

The Potential of the Mediterranean Diet to Improve Mitochondrial Function in Experimental Models of Obesity and Metabolic Syndrome

The abnormal expansion of body fat paves the way for several metabolic abnormalities including overweight, obesity, and diabetes, which ultimately cluster under the umbrella of metabolic syndrome (MetS). Patients with MetS are at an increased risk of cardiovascular disease, morbidity, and mortality. The coexistence of distinct metabolic abnormalities is associated with the release of pro-inflammatory adipocytokines, as components of low-to-medium grade systemic inflammation and increased oxidative stress. Adopting healthy lifestyles, by using appropriate dietary regimens, contributes to the prevention and treatment of MetS. Metabolic abnormalities can influence the function and energetic capacity of mitochondria, as observed in many obesity-related cardio-metabolic disorders. There are preclinical studies both in cellular and animal models, as well as clinical studies, dealing with distinct nutrients of the Mediterranean diet (MD) and dysfunctional mitochondria in obesity and MetS. The term "Mitochondria nutrients" has been adopted in recent years, and it depicts the adequate nutrients to keep proper mitochondrial function. Different experimental models show that components of the MD, including polyphenols, plant-derived compounds, and polyunsaturated fatty acids, can improve mitochondrial metabolism, biogenesis, and antioxidant capacity. Such effects are valuable to counteract the mitochondrial dysfunction associated with obesity-related abnormalities and can represent the beneficial feature of polyphenols-enriched olive oil, vegetables, nuts, fish, and plant-based foods, as the main components of the MD. Thus, developing mitochondria-targeting nutrients and natural agents for MetS treatment and/or prevention is a logical strategy to decrease the burden of disease and medications at a later stage. In this comprehensive review, we discuss the effects of the MD and its bioactive components on improving mitochondrial structure and activity.

Increasing changes in visceral adiposity is associated with higher risk for colorectal adenoma: Multilevel analysis in a prospective cohort

BACKGROUND AND AIM

While many studies demonstrated an association between visceral adiposity and colorectal adenoma (CRA), the effect of longitudinal changes in body fat composition on CRA is unclear. We investigated the longitudinal association between changes in visceral adiposity and CRA occurrence.

METHODS

Between 2006 and 2018, 732 (62.8%) of the 1165 subjects in a prospective cohort voluntarily underwent follow-up abdominal fat computed tomography and colonoscopy. We defined incident and recurrent CRA as adenoma detected at follow-up colonoscopy from negative and positive adenoma at baseline colonoscopy, respectively. Multilevel survival analysis examined the longitudinal association between changes in visceral fat and CRA.

RESULTS

During a median follow-up of 7.4 years, 400 (54.6%) subjects developed CRA. In multivariable analysis, increasing changes in visceral adipose tissue (VAT) area were associated with higher risk of incident adenoma (hazard ratio [HR] 1.21, 95% confidence interval [CI] 1.00-1.46 for change per 10 cm² increase; HR 1.79, 95% CI 1.08-2.97 for highest vs lowest quartile, P values for trend = 0.045). Likewise, increasing changes in VAT area were independently associated with a higher risk of recurrent adenoma (HR 1.35, 95% CI 1.13-1.62 for change per 10 cm² increase; HR 1.62, 95% CI 1.04-2.52 for highest vs lowest quartile, P values for trend = 0.001). Changes in subcutaneous adipose tissue area were not independently associated with CRA.

CONCLUSION

Increasing changes in VAT area were longitudinally associated with a higher risk of incident and recurrent CRA, independent of risk factors, suggesting that visceral adiposity may be an important target in CRA prevention.

Effects of short-term dietary restriction on plasma metabolites and the subcutaneous fat area according to metabolic status in obese individuals: a case-control study

BACKGROUND

Research elucidating the metabolic mechanisms that differentiate subtypes of obesity has been increasing. We aimed to investigate the effects of a 12-week dietary intervention on the metabolomic profiles of obese subjects.

METHODS

Subjects followed a 12-week dietary restriction protocol consisting of a 300 kcal/day reduction in their usual caloric intake. Twenty-nine obese subjects were included and divided into two groups: the metabolic status maintenance group (n = 17, controls) and the metabolic status improvement group (n = 12, tests). We analyzed the somatometric and biochemical parameters and performed ultra-performance liquid chromatography-mass spectrometry analysis of the plasma metabolites.

RESULTS

At 12 weeks, the fat percentage, whole fat area (WFA), subcutaneous fat area (SFA) at the L1 vertebra, and the levels of triglycerides, gamma-glutamyltransferase (gamma-GT), and leptin were markedly decreased in the metabolic status improvement group, while the level of high-density lipoprotein cholesterol increased compared with that in the metabolic status maintenance group. Metabolomic profiling at 12 weeks showed substantial differences in 4-aminobutyraldehyde (p = 0.005) and 4'-apo-β-carotenal (p = 0.024) between the two groups. Furthermore, an AUC value of 0.89 was obtained for the following seven featured biomarkers: triglycerides, gamma-GT, leptin, fat percentage, WFA, and SFA at the L1 vertebra, and 4-aminobutyraldehyde.

CONCLUSIONS

We demonstrated that 4-aminobutyraldehyde and related regional fat distribution parameters were strongly associated with obesity according to metabolic status. Thus, these biomarkers are potentially valuable in confirming the efficacy of short-term interventions and predicting metabolic status in obese individuals.

TRIALS REGISTRATION

This study was registered at ClinicalTrials.gov under NCT03135132 (registered 1 May 2017-retrospectively registered).

Association of abdominal fat with metabolic syndrome components in overweight women: effect of menopausal status

BACKGROUND

The association between abdominal fat distribution and metabolic syndrome (MetSyn) components by menopausal status has yet to be explicated. The purpose of this study was to examine a cross-sectional association between abdominal fat compartments and MetSyn components in pre- and post-menopausal overweight Japanese women.

METHODS

Of 212 overweight Japanese women, 76 pre-menopausal overweight (BMI ≥ 25) women (PreM age, 42.1 ± 5.9 years) and 87 post-menopausal overweight women (PostM: age, 56.2 ± 4.5 years) were analyzed in this study. Measurements were taken for body mass index (BMI), abdominal compartments [visceral fat (VF), subcutaneous fat (SF), superficial subcutaneous fat (SSF), and deep subcutaneous fat (DSF)], serum high-density lipoprotein cholesterol (HDLC), low-density lipoprotein cholesterol, triglycerides (TG), and fasting plasma glucose (FPG). Abdominal compartments were assessed using computed tomography.

RESULTS

No significant differences were found for BMI, SF, SSF, or DSF between the PreM and PostM. Despite this, the PreM had a significantly smaller VF area than that of the PostM. However, the difference in VF area disappeared when age was adjusted for. VFA significantly correlated with HDLC, TG, and FPG independently of menopause status.

CONCLUSIONS

These results suggest that the effect of menopause status on the association between VF and MetSyn components is negligible. Abdominal subcutaneous fat compartments were not associated with MetSyn components in overweight women regardless of menopausal status.

Circulating steroid levels as correlates of adipose tissue phenotype in premenopausal women

Background Obesity-related alterations in the circulating steroid hormone profile remain equivocal in women. Our objective was to identify circulating steroid levels that relate to increased adiposity and altered adipose phenotype in premenopausal women. Materials and methods In a sample of 42 premenopausal women [age 46 ± 3 years; body mass index (BMI) 27.1 ± 4.2 kg/m2], 19 plasma steroids were quantified by electrospray ionization-liquid chromatography-tandem mass spectroscopy (ESI-LC-MS/MS). Body composition and fat distribution were assessed by dual-energy X-ray absorptiometry (DXA) and computed tomography (CT), respectively. Markers of adipose tissue function including adipocyte size distributions, radiological attenuation and macrophage infiltration were also analyzed in surgically obtained visceral and subcutaneous fat samples. Results Many negative correlations were observed between adiposity measurements such as BMI, body fat percentage or total abdominal adipose tissue area and plasma levels of androstenedione (Δ4) (r = -0.33 to -0.39, p ≤ 0.04), androsterone (ADT) (r = -0.30 to -0.38, p ≤ 0.05) and steroid precursor pregnenolone (PREG) (r = -0.36 to -0.46, p ≤ 0.02). Visceral adipocyte hypertrophy was observed in patients with low PREG concentrations (p < 0.05). Visceral adipose tissue radiologic attenuation, a potential marker of adipocyte size, was also positively correlated with PREG levels (r = 0.33, p < 0.05). Low levels of PREG were related to increased number of macrophages infiltrating visceral and subcutaneous adipose tissue (p < 0.05). Conclusion Plasma levels of androgens and their precursors are lower in women with increased adiposity and visceral adipocyte hypertrophy. Low circulating PREG concentration may represent a marker of adipose tissue dysfunction.

Survival benefit of a low ratio of visceral to subcutaneous adipose tissue depends on LDL clearance versus production in sepsis

Background

Patients with sepsis with a high ratio of visceral adipose tissue (VAT) to subcutaneous adipose tissue (SAT) have increased mortality. Our goal was to investigate the mechanism of this effect, noting that low LDL levels are also associated with increased sepsis mortality. Accordingly we tested for association between VAT/SAT, low-density lipoprotein (LDL) levels, and mortality. Then we examined the effect of statin treatment, which decreases LDL production, and the effect of PCSK9 genotype, which increases LDL clearance.

Methods

We performed retrospective analysis of a cohort of patients with sepsis from a tertiary care adult intensive care unit in Vancouver, Canada, who underwent abdominal computed tomography (CT) (n = 75) for clinical reasons. We compared LDL levels in patients with sepsis according to high versus low VAT/SAT and 90-day survival. We next examined the effects of statin therapy and PCSK9 loss-of-function genotype on survival.

Results

Patients with a low VAT/SAT had increased 90-day survival and were relatively protected against low LDL levels in sepsis compared to high VAT/SAT. Statin treatment abrogated the beneficial effects of low VAT/SAT; eliminating the difference in LDL levels and survival between patients with low and high VAT/SAT. PSCK9 loss-of-function genotype similarly eliminated the increased LDL levels in low VAT/SAT patients but, in contrast, increased the survival advantage of low VAT/SAT compared to high VAT/SAT.

Conclusions

Low LDL levels per se are not simply associated with decreased sepsis survival because lowering LDL levels by inhibiting LDL production (statin treatment) is associated with adverse outcomes, while increased LDL clearance (PCSK9 loss-of-function genotype) is associated with improved outcomes in patients with low VAT/SAT.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-1985-1) contains supplementary material, which is available to authorized users.

Obesity phenotypes and their paradoxical association with cardiovascular diseases

The pro-inflammatory state of the visceral adipose tissue (VAT) is supposed to accelerate cardiovascular (CV) and metabolic diseases in obese subjects. Some studies have recently reported an improved CV prognosis in certain obese and overweight patients as compared with leaner ones. This phenomenon, known as the "obesity paradox" (OP), has been described in many chronic diseases. This narrative review is based on the material searched for and obtained via PubMed and Web of Science up to May 2017. The search terms we used were: "obesity, paradox, adipose tissue" in combination with "cardiovascular, coronary heart disease, heart failure, arrhythmias". Using the current Body Mass Index (BMI)-based obesity definition, individuals with different clinical and biochemical characteristics are gathered together in the same category. Emerging evidence point to the existence of many "Obesity phenotypes" with different association with CV risk, accordingly to physical and life-style features. In this narrative review, we discussed if obesity phenotypes may be associated with a different CV risk, potentially explaining the OP. As a globally accepted definition of obesity is still lacking, we emphasized the need of a new approach, which should consider the heterogeneity of obesity. Better defining "obesities" and related CV risk is critical to markedly improve the classical BMI-based definition of obesity.

Adipose tissue and liver

Adipose tissue and liver are central tissues in whole body energy metabolism. Their composition, structure, and function can be noninvasively imaged using a variety of measurement techniques that provide a safe alternative to an invasive biopsy. Imaging of adipose tissue is focused on quantitating the distribution of adipose tissue in subcutaneous and intra-abdominal (visceral) adipose tissue depots. Also, detailed subdivisions of adipose tissue can be distinguished with modern imaging techniques. Adipose tissue (or adipocyte) accumulation or infiltration of other organs can also be imaged, with intramuscular adipose tissue a common example. Although liver fat content is now accurately imaged using standard magnetic resonance imaging (MRI) techniques, inflammation and fibrosis are more difficult to determine noninvasively. Liver imaging efforts are therefore concerted on developing accurate imaging markers of liver fibrosis and inflammatory status. Magnetic resonance elastography (MRE) is presently the most reliable imaging technique for measuring liver fibrosis but requires an external device for introduction of shear waves to the liver. Methods using multiparametric diffusion, perfusion, relaxometry, and hepatocyte-specific MRI contrast agents may prove to be more easily implemented by clinicians, provided they reach similar accuracy as MRE. Adipose tissue imaging is experiencing a revolution with renewed interest in characterizing and identifying distinct adipose depots, among them brown adipose tissue. Magnetic resonance spectroscopy provides an interesting yet underutilized way of imaging adipose tissue metabolism through its fatty acid composition. Further studies may shed light on the role of fatty acid composition in different depots and why saturated fat in subcutaneous adipose tissue is a marker of high insulin sensitivity.

Body Fat Distribution and the Risk of Incident Metabolic Syndrome: A Longitudinal Cohort Study

The effect of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) area on metabolic syndrome (MS) has been debated. We aimed to evaluate the effects of VAT and SAT on the incidence of MS and its components in a large and apparently healthy Asian population. We performed a longitudinal cohort study of 1,964 subjects who received health screenings over a 5-year follow-up period; 317 incidents of MS (16.1%) were observed during a median follow-up of 4.5 years. The VAT area was significantly associated with a higher incidence of MS; the adjusted HR for incident MS per 1 SD of VAT was 1.50 (95% CI 1.29-1.74), and the adjusted HR of the 5th VAT quintile compared with the 1st quintile was 3.73 (95% CI 2.22-6.28). However, the SAT area was not associated with incident MS. Although the VAT area was longitudinally associated with the incidence of each component of MS, the SAT area was inversely associated with the risk of high blood pressure, fasting blood sugar, and triglycerides, with marginal significance. In conclusion, the VAT area is longitudinally associated with an increased risk of incident MS, while SAT may have a protective effect against the incidence of individual MS components.

Comparative analysis of three human adipocyte size measurement methods and their relevance for cardiometabolic risk

OBJECTIVE

To determine whether adipocyte diameters from three measurement methods are similarly associated with adiposity measurements and cardiometabolic variables.

METHODS

Surgical samples of omental and abdominal subcutaneous adipose tissue were obtained in a sample of 60 women (age 35-59 years; body mass index 20.3-41.1 kg/m² ). Median adipocyte diameter of the main cell population was determined by collagenase digestion, osmium tetroxide fixation, and histological analysis. Adiposity and cardiometabolic risk factors were assessed.

RESULTS

Adipocyte diameter was consistently smaller with formalin fixation than with collagenase digestion, whereas osmium-fixed cells were larger (P < 0.0001, for all). Median adipocyte diameters derived from all methods were intercorrelated (r = 0.46-0.83, P < 0.001 for all). Positive associations were found between adipocyte diameters from all techniques and regional or total adiposity measurements (P < 0.01 for all). Omental adipocyte diameter was positively associated with fasting glucose, insulin, and homeostatic model assessment of insulin resistance (r = 0.30-0.52, P < 0.05 for all), with osmium-fixed cell size as a stronger correlate. Osmium-fixed cell diameter was also a better correlate of plasma adiponectin and leptin.

CONCLUSIONS

Although measurement techniques generated systematic differences in adipocyte size, associations with adiposity were only slightly affected by the technique. Osmium fixation generated stronger associations with cardiometabolic risk factors than collagenase digestion and histological analysis.

Quantitative analysis of rat adipose tissue cell recovery, and non-fat cell volume, in primary cell cultures

BACKGROUND

White adipose tissue (WAT) is a complex, diffuse, multifunctional organ which contains adipocytes, and a large proportion of fat, but also other cell types, active in defense, regeneration and signalling functions. Studies with adipocytes often require their isolation from WAT by breaking up the matrix of collagen fibres; however, it is unclear to what extent adipocyte number in primary cultures correlates with their number in intact WAT, since recovery and viability are often unknown.

EXPERIMENTAL DESIGN

Epididymal WAT of four young adult rats was used to isolate adipocytes with collagenase. Careful recording of lipid content of tissue, and all fraction volumes and weights, allowed us to trace the amount of initial WAT fat remaining in the cell preparation. Functionality was estimated by incubation with glucose and measurement of glucose uptake and lactate, glycerol and NEFA excretion rates up to 48 h. Non-adipocyte cells were also recovered and their sizes (and those of adipocytes) were measured. The presence of non-nucleated cells (erythrocytes) was also estimated.

RESULTS

Cell numbers and sizes were correlated from all fractions to intact WAT. Tracing the lipid content, the recovery of adipocytes in the final, metabolically active, preparation was in the range of 70-75%. Cells showed even higher metabolic activity in the second than in the first day of incubation. Adipocytes were 7%, erythrocytes 66% and other stromal (nucleated cells) 27% of total WAT cells. However, their overall volumes were 90%, 0.05%, and 0.2% of WAT. Non-fat volume of adipocytes was 1.3% of WAT.

CONCLUSIONS

The methodology presented here allows for a direct quantitative reference to the original tissue of studies using isolated cells. We have also found that the "live cell mass" of adipose tissue is very small: about 13 µL/g for adipocytes and 2 µL/g stromal, plus about 1 µL/g blood (the rats were killed by exsanguination). These data translate (with respect to the actual "live cytoplasm" size) into an extremely high metabolic activity, which make WAT an even more significant agent in the control of energy metabolism.

Relevance of omental pericellular adipose tissue collagen in the pathophysiology of human abdominal obesity and related cardiometabolic risk

BACKGROUND

Adipose tissue fibrosis is a relatively new notion and its relationship with visceral obesity and cardiometabolic alterations remains unclear, particularly in moderate obesity.

OBJECTIVE

Our objective was to examine if total and pericellular collagen accumulation are relevant for the pathophysiology of visceral obesity and related cardiometabolic risk.

SUBJECTS AND METHODS

Surgical omental (OM) and subcutaneous (SC) fat samples were obtained in 56 women (age: 47.2±5.8 years; body mass index (BMI): 27.1±4.4 kg/m²). Body composition and fat distribution were measured by dual-energy X-ray absorptiometry and computed tomography, respectively. Total and pericellular collagen were measured using picrosirius red staining. CD68+ cells (total macrophages) and CD163+ cells (M2-macrophages) were identified using immunohistochemistry.

RESULTS

We found that only pericellular collagen percentage, especially in OM fat, was associated with higher BMI, body fat mass and adipose tissue areas as well as lower radiologic attenuation of visceral adipose tissue and altered cardiometabolic risk variables. Strong correlations between peri-adipocyte collagen percentage and total or M2-macrophage percentages were observed in both depots. Total collagen percentage in either compartment was not related to adiposity, fat distribution or cardiometabolic risk.

CONCLUSIONS

As opposed to whole tissue-based assessments of adipose tissue fibrosis, collagen deposition around the adipocyte, especially in the OM fat compartment is related to total and regional adiposity as well as altered cardiometabolic risk profile.

Relative abdominal adiposity is associated with chronic low back pain: a preliminary explorative study

Background

Although previous research suggests a relationship between chronic low back pain (cLBP) and adiposity, this relationship is poorly understood. No research has explored the relationship between abdominal-specific subcutaneous and visceral adiposity with pain and disability in cLBP individuals. The aim of this study therefore was to examine the relationship of regional and total body adiposity to pain and disability in cLBP individuals.

Methods

A preliminary explorative study design of seventy (n = 70) adult men and women with cLBP was employed. Anthropometric and adiposity measures were collected, including body mass index, waist-to-hip ratio, total body adiposity and specific ultrasound-based abdominal adiposity measurements. Self-reported pain and disability were measured using a Visual Analogue Scale (VAS) and the Oswestry Disability Index (ODI) questionnaires respectively. Relationships between anthropometric and adiposity measures with pain and disability were assessed using correlation and regression analyses.

Results

Significant correlations between abdominal to lumbar adiposity ratio (A-L) variables and the waist-to-hip ratio with self-reported pain were observed. A-L variables were found to predict pain, with 9.1–30.5 % of the variance in pain across the three analysis models explained by these variables. No relationships between anthropometric or adiposity variables to self-reported disability were identified.

Conclusions

The findings of this study indicated that regional distribution of adiposity via the A-L is associated with cLBP, providing a rationale for future research on adiposity and cLBP.

Abdominal fat sub-depots and energy expenditure: Magnetic resonance imaging study

BACKGROUND & AIMS

We aimed to assess the association between the distinct abdominal sub-depots and resting energy expenditure (REE).

METHODS

We performed magnetic resonance imaging (MRI) to quantify abdominal visceral-adipose-tissue (VAT), deep-subcutaneous-adipose-tissue (deep-SAT), and superficial-subcutaneous-adipose-tissue (superficial-SAT). We measured REE by indirect-calorimetry. Non-exercise activity thermogenesis (NEAT) [1-3 metabolic equivalents (METs)] and exercise thermogenesis (activities of 4+MET_S) were estimated based on 6-days of accelerometry to assess total physical activity energy expenditure (PAEE).

RESULTS

We studied 282 participants: 249 men [mean age = 47.4 years, body-mass-index (BMI) = 31 kg/m², mean VAT proportion from total abdominal fat = 34.5%, mean superficial-SAT proportion from total abdominal fat = 24.3%] and 33 women (mean age = 51.2 years, BMI = 30.1 kg/m², mean VAT proportion from total abdominal fat = 22.8%, mean superficial-SAT proportion from total abdominal fat = 37.8%). As expected, women had lower REE [by 32.4% (1488 ± 234 kcal/day vs. 1971 ± 257 kcal/day; p < 0.01)] and lower REE/kg [by 8% (19.6 ± 3 kcal/kg vs. 21.2 ± 2 kcal/kg; p < 0.01)] than men. Exercise and total PAEE were positively associated with REE/kg (p < 0.01 for both) and a positive correlation between NEAT and REE/kg was borderline (p = 0.056). Participants, in whom abdominal VAT was the dominant proportional depot, had higher REE (1964 ± 297 kcal/day vs. 1654 ± 352 kcal/day; p < 0.01) and higher REE∖kg (22.2 ± 2.3 kcal/kg/day vs. 19.6 ± 2.5 kcal/kg/day; p < 0.01) than participants in whom superficial-SAT was the largest proportional depot. In multivariate models, adjusted for age, gender and residual BMI, increased VAT proportion was independently associated with higher REE (β = 0.181; p = 0.05). Likewise, increased VAT proportion (β = 0.482; p < 0.01) remained independently associated with higher REE/kg. In this model younger age (β = -0.329; p < 0.01) was associated with higher REE/kg.

CONCLUSIONS

Abdominal fat distribution patterns are associated with varying levels of resting energy expenditure, potentially reflecting different metabolic rates of adipose sub-depots and providing an anatomic/anthropometric link to physiological obese sub-phenotypes.

Relationship between deep subcutaneous abdominal adipose tissue and metabolic syndrome: a case control study

BACKGROUND

The deep subcutaneous adipose tissue (dSAT) is closely related to the obesity-associated complications similarly to the characteristics of visceral adipose tissue (VAT). However, the association between dSAT and metabolic syndrome (MS) is unclear. The purpose of our study was to evaluate the association of distinct abdominal adipose tissue with the cardiometabolic risk factors and MS.

METHODS

Abdominal computed tomography (CT) images were obtained in 365 asymptomatic subjects (187 subjects with MS and 178 without MS). The axial images segmented into superficial and deep SAT by manually tracing the fascia superficialis at L4-5 levels. The concentrations of serum inflammatory cytokines and adipokines were also measured.

RESULTS

The MS group had significantly lower adiponectin levels but significantly higher levels of resistin, leptin, tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), intercellular adhesion molecule (ICAM), monocyte chemotactic protein-1 (MCP-1), and oxLDL than the control group (p < 0.05). All inflammatory cytokines and adipokines were associated with the sum of VAT and dSAT areas (VDAT) (P for trend < 0.05), but no significant correlation was found between inflammatory cytokines and sSAT. dSAT was significantly associated with MS in both men and women (OR 2.371; p < 0.001) whereas the ORs between sSAT and MS were not significant (p = 0.597). The age-adjusted ORs between VDAT and MS (OR of 8.359 in men and 3.183 in women, p < 0.001) were higher than those of VAT (OR of 7.941 in men and 2.570 in women, p < 0.05) and dSAT (OR of 2.954 in men and 1.856 in women, p < 0.05).

CONCLUSIONS

We demonstrated that dSAT was associated with increased inflammation and oxidative stress, suggesting that dSAT is an important determinant of MS. Therefore, abdominal subcutaneous fat should be considered as two functionally distinct compartments rather than a single entity.

Abdominal fat depots associated with insulin resistance and metabolic syndrome risk factors in black African young adults

Background

Individuals of black African ethnicity tend to have less visceral adipose tissue (VAT) but more subcutaneous-abdominal adipose tissue (SCAT) than white Caucasians. However, it is unclear whether such distribution of abdominal fat is beneficial for metabolic disease risk in black individuals. Here we compared the associations between these specific abdominal fat depots, insulin sensitivity and metabolic syndrome risk.

Methods

A cross-sectional analysis of 76 black South African young adults (36 men; 40 women) aged 18–19 years participating in the Birth to Twenty Cohort Study had VAT and SCAT measured by MRI. The metabolic syndrome traits (blood pressure, lipid profile, fasting glucose and insulin) were measured and the values were combined into a metabolic syndrome risk score. Fasting glucose and insulin were used to derive the HOMA-index of insulin resistance (HOMA-IR).

Results

Compared to men, women had greater VAT (mean: 16.6 vs. 12.5 cm²) and SCAT (median 164.0 vs. 59.9 cm²). In men, SCAT (r = 0.50) was more strongly correlated to the metabolic syndrome score (MetS) than was VAT (r = 0.23), and was associated with both MetS (P = 0.001) and HOMA-IR (P = 0.001) after adjustment for VAT and total fat mass. In women, both abdominal fat compartments showed comparable positive correlations with MetS (r = 0.26 to 0.31), although these trends were weaker than in men.

Conclusions

In young black South African adults, SCAT appears to be more relevant than VAT to metabolic syndrome traits.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-015-2147-x) contains supplementary material, which is available to authorized users.

Omental adipocyte hypertrophy relates to coenzyme Q10 redox state and lipid peroxidation in obese women

Occurrence of oxidative stress in white adipose tissues contributes to its dysfunction and the development of obesity-related metabolic complications. Coenzyme Q10 (CoQ10) is the single lipophilic antioxidant synthesized in humans and is essential for electron transport during mitochondrial respiration. To understand the role of CoQ10 in adipose tissue physiology and dysfunction, the abundance of the oxidized and reduced (CoQ10red) isoforms of the CoQ10 were quantified in subcutaneous and omental adipose tissues of women covering the full range of BMI (from 21.5 to 53.2 kg/m(2)). Lean women displayed regional variations of CoQ10 redox state between the omental and subcutaneous depot, despite similar total content. Obese women had reduced CoQ10red concentrations in the omental depot, leading to increased CoQ10 redox state and higher levels of lipid hydroperoxide. Women with low omental CoQ10 content had greater visceral and subcutaneous adiposity, increased omental adipocyte diameter, and higher circulating interleukin-6 and C-reactive protein levels and were more insulin resistant. The associations between abdominal obesity-related cardiometabolic risk factors and CoQ10 content in the omental depot were abolished after adjustment for omental adipocyte diameter. This study shows that hypertrophic remodeling of visceral fat closely relates to depletion of CoQ10, lipid peroxidation, and inflammation.

Circulating 5α-dihydrotestosterone, abdominal obesity and adipocyte characteristics in women

Abstract Background: The association between circulating androgen levels and fat distribution in women has been widely inconsistent among existing studies.

OBJECTIVE

We sought to investigate the relation between plasma adrenal and gonadal androgen levels and body fat distribution, as well as abdominal adipocyte characteristics.

METHODS

Paired omental and subcutaneous adipose tissue samples were surgically obtained from 60 women (age, 47±5 years; body mass index, 26±5 kg/m2) undergoing gynecological surgery. Body composition and fat distribution were measured by dual-energy X-ray absorptiometry and computed tomography, respectively. Adipocyte diameter, basal lipolysis, and heparin-releasable lipoprotein lipase activity were measured. Steroids were quantified using high-performance gas chromatography and mass spectrometry.

RESULTS

Significant negative associations were found between plasma dihydrotestosterone (DHT) levels and total adiposity (body mass index, r=-0.35, p<0.05; fat mass, r=-0.31, p<0.05) as well as computed tomography assessments of abdominal adiposity (r=-0.30, p<0.05 and r=-0.44, p<0.005 for subcutaneous and visceral adipose tissue area, respectively). The association between DHT levels and visceral adipose tissue area was independent of total body fat mass. A significant negative association was also observed between plasma DHT and omental adipocyte diameter (r=-0.27, p<0.05). When expressed as the omental/subcutaneous ratio, heparin-releasable lipoprotein lipase activity was negatively and significantly related to plasma DHT, androstenedione, and dehydroepiandrosterone (DHEA) levels.

CONCLUSION

Abdominally obese women with large, metabolically active omental adipocytes appear to be characterized by reduced endogenous levels of DHT. The assumption that high androgen levels are associated with an android body fat distribution pattern in women should be critically re-examined.

Expression of genes related to prostaglandin synthesis or signaling in human subcutaneous and omental adipose tissue: depot differences and modulation by adipogenesis

OBJECTIVES

(1) To examine depot-specific PGE2 and PGF2α release and mRNA expression of enzymes or receptors involved in PG synthesis or signaling in human adipose tissues; (2) to identify changes in expression of these transcripts through preadipocyte differentiation; and (3) to examine associations between adipose tissue mRNA expression of these transcripts and adiposity measurements.

METHODS

Fat samples were obtained surgically in women. PGE2 and PGF2α release by preadipocytes and adipose tissue explants was measured. Expression levels of mRNA coding for enzymes or receptors involved in PG synthesis or signaling were measured by RT-PCR.

RESULTS

Cultured preadipocytes and explants from omental fat released more PGE2 and PGF2α than those from the subcutaneous depot and the corresponding transcripts showed consistent depot differences. Following preadipocyte differentiation, expression of PLA2G16 and PTGER3 mRNA was significantly increased whereas COX-1, COX-2, PTGIS, and PTGES mRNA abundance were decreased in both compartments (P ≤ 0.01 for all). Transcripts that were stimulated during adipogenesis were those that correlated best with adiposity measurements.

CONCLUSION

Cells from the omental fat compartment release more PGE2 and PGF2α than those from the subcutaneous depot. Obesity modulates expression of PG-synthesizing enzymes and PG receptors which likely occurs through adipogenesis-induced changes in expression of these transcripts.

Comparison of T1 relaxation times in adipose tissue of severely obese patients and healthy lean subjects measured by 1.5 T MRI

Subcutaneous (SAT) and visceral adipose tissue (VAT) differ in composition, endocrine function and localization in the body. VAT is considered to play a role in the pathogenesis of insulin resistance, type 2 diabetes, fatty liver disease, and other obesity-related disorders. It has been shown that the amount, distribution, and (cellular) composition of adipose tissue (AT) correlate well with metabolic conditions. In this study, T1 relaxation times of AT were measured in severely obese subjects and compared with those of healthy lean controls. Here, we tested the hypothesis that T1 relaxation times of AT differ between lean and obese individuals, but also between VAT and SAT as well as superficial (sSAT) and deep SAT (dSAT) in the same individual. Twenty severely obese subjects (BMI 41.4 ± 4.8 kg/m(2) ) and ten healthy lean controls matched for age (BMI 21.5 ± 1.9 kg/m(2) ) underwent MRI at 1.5 T using a single-shot fast spin-echo sequence (short-tau inversion recovery) at six different inversion times (TI range 100-1000 ms). T1 relaxation times were computed for all subjects by fitting the TI -dependent MR signal intensities of user-defined regions of interest in both SAT and VAT to a model function. T1 times in sSAT and dSAT were only measured in obese patients. For both obese patients and controls, the T1 times of SAT (275 ± 14 and 301 ± 12 ms) were significantly (p < 0.01) shorter than the respective values in VAT (294 ± 20 and 360 ± 35 ms). Obese subjects also showed significant (p < 0.01) T1 differences between sSAT (268 ± 11 ms) and dSAT (281 ± 19 ms). More important, T1 differences in both SAT and VAT were highly significant (p < 0.001) between obese patients and healthy subjects. The results of our pilot study suggest that T1 relaxation times differ between severely obese patients and lean controls, and may potentially provide an additional means for the non-invasive assessment of AT conditions and dysfunction.

Low abdominal subcutaneous preadipocyte adipogenesis is associated with visceral obesity, visceral adipocyte hypertrophy, and a dysmetabolic state

Subcutaneous adipose tissue expansion through adipogenesis is increasingly recognized as a major determinant of body fat distribution and obesity-related cardiometabolic alterations. Our objective was to assess whether adipogenic rates of cultured human primary preadipocytes from the visceral and subcutaneous compartments relate to visceral obesity and cardiometabolic alterations. We recruited 35 women undergoing gynecological surgery and assessed body fat distribution by CT as well as fasting plasma lipids and glycemia. Fat samples from the greater omentum and abdominal subcutaneous (SC) compartments were used to assess mature adipocyte cell size and establish primary preadipocyte cultures. Differentiation was induced using adipogenic media and adipogenic rates were assessed using Oil Red O (ORO) absorbance/DNA content ratio and glyceraldehyde 3-phosphate dehydrogenase (G3PDH) activity/DNA of differentiated cells. We found a lower adipogenic capacity of omental (OM) preadipocytes than SC preadipocytes originating from the same women (P < 0.05). Whereas only OM cell size was different among groups of low vs high OM adipogenic rate, SC adipogenic rates were clearly related to increased OM cell size and dyslipidemia when women were separated on median value of either ORO/DNA or G3PDH activity/DNA ratios. When matched for BMI, women with low SC preadipocyte adipogenic rates had a higher visceral adipose tissue area (P < 0.01), omental adipocyte hypertrophy (P < 0.05), higher VLDL-lipid content (P < 0.01) and higher fasting glycemia (P < 0.05) than those with low SC adipogenic rates. In conclusion, low abdominal subcutaneous preadipocyte differentiation capacity in vitro is associated with visceral obesity, visceral adipocyte hypertrophy, and a dysmetabolic state.

Interrelationships between changes in anthropometric variables and computed tomography indices of abdominal fat distribution in response to a 1-year physical activity–healthy eating lifestyle modification program in abdominally obese men

The objectives were to (i) measure the effects of a 1-year lifestyle modification program on body fat distribution/anthropometric variables; (ii) determine the interrelationships between changes in all these variables; and (iii) investigate whether there is a selective reduction in deep (DSAT) vs. superficial subcutaneous adipose tissue (SSAT) at the abdominal level following a 1-year lifestyle modification program. Anthropometric variables, body composition and abdominal and midthigh fat distribution were assessed at baseline and after 1 year in 109 sedentary, dyslipidemic and abdominally obese men. Reductions in anthropometric variables, skinfold thicknesses (except the trunk/extremity ratio) and fat mass as well as an increase in fat-free mass were observed after 1 year (p < 0.0001). Decreases in abdominal adipose tissue volumes were also noted (–23%, –26%, –18%, –19%, –17%, p < 0.0001 for total adipose tissue, visceral adipose tissue, subcutaneous adipose tissue, DSAT and SSAT, respectively). Adipose tissue areas at midthigh also decreased (–18%, –18%, –17%, p < 0.0001 for total, deep, and subcutaneous adipose tissue, respectively). A reduction (–9%, p < 0.0001) in low-attenuation muscle area and an increase (+1%, p < 0.05) in normal-attenuation muscle area were also observed. There was a positive relationship between changes in visceral adipose tissue and changes in DSAT (r = 0.65, p < 0.0001) or SSAT (r = 0.63, p < 0.0001). Although absolute changes in DSAT were greater than changes in SSAT, relative changes in both depots were similar, independent of changes in visceral adipose tissue. The 1-year lifestyle modification program therefore improved the body fat distribution pattern and midthigh muscle quality in abdominally obese men.

Abdominal subcutaneous and omental adipocyte morphology and its relation to gene expression, lipolysis and adipocytokine levels in women

OBJECTIVE

We tested the hypothesis that women with adipocyte hypertrophy in either omental (OM) or subcutaneous (SC) adipose tissue are characterized by alterations in adipocyte lipolysis and adipose tissue expression of genes coding for proteins involved in adipocyte metabolism or inflammation, independent of overall adiposity and fat distribution.

METHODS

OM and SC fat samples were obtained surgically in 44 women (age: 47.1±5.0years, BMI: 27.7±5.3kg/m(2)). In a given depot, women with larger adipocytes than predicted by the regression of adipocyte size vs. total and regional adiposity measurements were considered as having adipocyte hypertrophy, whereas women with smaller adipocytes than predicted were considered as having adipocyte hyperplasia.

RESULTS

Women with OM adipocyte hypertrophy had significantly lower SC GLUT4 mRNA abundance (p≤0.05), higher SC CEBPB mRNA expression (p≤0.05) as well as higher mRNA expression of OM PLIN (p≤0.05), CD68 (p≤0.10), CD14 (p≤0.10), CD31 (p≤0.05) and vWF (p≤0.05) compared to women with OM adipocyte hyperplasia. OM adipocyte isoproterenol- (10(-10) to 10(-5)mol/L), forskolin- (10(-5)mol/L) and dibutyryl cAMP- (10(-3)mol/L) stimulated lipolysis was higher in women with hypertrophic OM adipocytes (p≤0.05, for all). Women with SC adipocyte hypertrophy had lower SC mRNA expression of GLUT4 (p≤0.10), higher SC mRNA expression of CEBPB (p≤0.05), lower plasma adiponectin concentrations (p≤0.05) and higher SC adipocyte isoproterenol- (10(-9) to 10(-5)mol/L) stimulated lipolysis (p≤0.05) compared to women with SC adipocyte hyperplasia.

CONCLUSION

Hypertrophic adipocytes in both fat compartments are characterized by alterations in adipocyte lipolysis and adipose tissue expression of genes coding for proteins involved in adipocyte metabolism or inflammation.

Adipose tissue diacylglycerol acyltransferase activity and blood lipoprotein triglyceride enrichment in women with abdominal obesity

Previous studies have suggested altered triglyceride (TG) storage in patients with abdominal obesity and blood lipid disorders.

OBJECTIVE

We hypothesized that women with abdominal obesity and a dysmetabolic profile have low DGAT activity in their abdominal fat compartments.

METHODS

Paired omental (OM) and subcutaneous (SC) adipose tissue samples were obtained surgically from 39 women undergoing abdominal hysterectomies. Body composition and fat distribution were measured by dual energy x-ray absorptiometry and computed tomography. DGAT activity was measured by acylation of sn-l,2-diacylglycerol with [(14)C] oleoyl-CoA in microsomal fractions isolated from whole adipose tissue homogenates. DGAT activity was calculated on the basis of picomoles (pmol) TG synthesized in the assay per min per mg lipid, per μg protein or per 1000 cells.

RESULTS

No depot differences were found when DGAT activity was reported per μg microsomal protein or per 1000 cells. DGAT activity in either depot was not associated with adipocyte diameters and blood lipid profile variables. DGAT activity per mg lipid was higher in OM than in abdominal SC adipose tissue (0.43 ± 0.20 vs. 0.34 ± 0.18 pmol/min/mg lipid, p < 0.05). OM DGAT activity was negatively correlated with OM adipocyte diameter and visceral adipose tissue area (r = -0.43, p < 0.01 and r = -0.38, p < 0.05 respectively). Plasma total, LDL and HDL TG levels were negatively associated with OM DGAT activity independent of total body fat mass (r = -0.39, p < 0.05, r = -0.46, p < 0.001 and r = -0.40, p < 0.05 respectively).

CONCLUSION

A defect in adipose tissue DGAT activity is predictive of adiposity and blood lipoprotein TG enrichment only when considering activity per tissue lipid mass.

Molecular and morphologic characterization of superficial- and deep-subcutaneous adipose tissue subdivisions in human obesity

OBJECTIVE

Human abdominal subcutaneous white adipose tissue (SAT) is composed of two different subcompartments: a "superficial" SAT (SSAT), located between the skin and a fibrous-fascia plane; and a deeper SAT, located under this fibrous fascia plane, indicated as "deep" SAT (DSAT).

DESIGN AND METHODS

In order to investigate whether SSAT and DSAT have different molecular and morphological features, paired SSAT/DSAT biopsies were collected from 10 female obese patients and used for microarray and morphologic analysis. The stroma-vascular fraction cells were also isolated from both depots and cultured in vitro to assess the lipid accumulation rate.

RESULTS

SSAT and DSAT displayed different patterns of gene expression, mainly for metabolic and inflammatory genes, respectively. Detailed gene expression analysis indicated that several metabolic genes, including adiponectin, are preferentially expressed in SSAT, whereas inflammatory genes are over-expressed in DSAT. Despite a similar lipid accumulation rate in vitro, in vivo SSAT showed a significant adipocyte hypertrophy together with a significantly lower inflammatory infiltration and vascular vessel lumen mean size, when compared to DSAT.

CONCLUSIONS

These data show that, SSAT and DSAT are functionally and morphologically different and emphasize the importance of considering independent these two adipose depots when investigating SAT biology and obesity complications.

Markers of macrophage infiltration and measures of lipolysis in human abdominal adipose tissues

OBJECTIVE

We tested the hypothesis that high lipolytic responsiveness is related to increased expression of ATM genes in human adipose tissues.

DESIGN AND METHODS

Omental (OM) and subcutaneous (SC) fat samples were obtained surgically in 46 women (age: 47.2 ± 4.7 years, BMI: 26.9 ± 5.2 kg/m(2) ). Body composition and fat distribution were measured using dual energy X-ray absorptiometry and computed tomography. Lipolysis was measured by glycerol release in mature adipocytes isolated by collagenase digestion under basal-, isoproterenol (10(-5) M)-, and forskolin (10(-5) M)-stimulated conditions. Quantification of macrophage gene mRNA expression (CD11b, CD11c, and CD68) in whole adipose tissue was performed using real-time RT-PCR.

RESULTS

SC CD68 mRNA abundance was positively associated with isoproterenol-stimulated lipolysis (r = 0.36, P < 0.05). This association remained significant after adjustment for total body fat mass (r = 0.34, P ≤ 0.05). In the OM depot, CD11b mRNA abundance was positively associated with isoproterenol-stimulated lipolysis (r = 0.42, P ≤ 0.005). This association remained significant after adjustment for total body fat mass (r = 0.41, P ≤ 0.01). In subgroup analyses, high lipolytic rates in SC adipocytes were related to increased whole tissue expression of CD68 and CD11b in this compartment, independent of adiposity and fat cell size (P ≤ 0.001 and P ≤ 0.05). High lipolytic rates in OM adipocytes were related to increased whole tissue OM expression of CD11b, independent of adiposity and fat cell size (P ≤ 0.05).

CONCLUSIONS

High adipocyte lipolytic responsiveness is related to increased expression of ATM markers in the corresponding compartment, independent of adiposity and fat cell size.

Differences in subcutaneous abdominal adiposity regions in four ethnic groups

OBJECTIVE

Previous studies have identified ethnic specific differences in visceral adipose tissue (VAT), which may account for ethnic differences in cardio-metabolic risk. However, two distinctive sub-compartments of abdominal subcutaneous adipose tissue (SAT) have been recently identified that may also differ among ethnic groups. Therefore, the relationship between SAT compartments and body fat mass (BFM) between Aboriginal, Chinese, and South Asian cohorts compared to Europeans was investigated.

DESIGN AND METHODS

Healthy Aboriginal, Chinese, European, and South Asian (n = 822) men and women (30-65 years) were assessed for BFM via dual energy X-ray absorptiometry, and SAT areas using computer tomography. SAT was subdivided into superficial SAT (SSAT) and deep SAT (DSAT) via the fascia-superficialis. Linear regression was performed using DSAT and SSAT as separate dependent variables and BFM and ethnicity as primary independent variables adjusting for confounders.

RESULTS

Aboriginal (181.0 cm(2) ; p = 0.045) and South Asians (178.3 cm(2) ; p = 0.013) had significantly higher amounts of DSAT, whereas the Chinese cohort had significantly less when compared with Europeans (114.3 cm(2) ; p = <0.001). The Aboriginal cohort had a significantly higher amount of SSAT than Europeans (123.13 cm(2) vs. 108.7 cm(2) ; p = 0.04). Ethnicity modified the relationship between DSAT and BFM (p < 0.001 for interaction) such that Aboriginals and majority of South Asians had a significantly greater DSAT.

CONCLUSION

These data further demonstrate ethnic differences in body fat distribution such that Aboriginals and South Asians have greater amounts of DSAT. This may contribute to the increased cardio-metabolic risk in these groups.

The expression of FTO in human adipose tissue is influenced by fat depot, adiposity, and insulin sensitivity

OBJECTIVE

The fat mass and obesity associated (FTO) gene is related to obesity, but the regulation of FTO expression in adipose tissue is not fully understood. We investigated FTO expression in paired subcutaneous and omental adipose tissues (SAT and OAT) from healthy women undergoing gynecological surgeries, and its relation with adiposity and insulin sensitivity.

DESIGN AND METHODS

FTO expression in SAT of type 2 diabetic patients treated or not with Rosiglitazone was also compared.

RESULTS

Both the mRNA and protein levels of FTO were higher in OAT from women than in SAT. Only OAT FTO protein levels negatively correlated with BMI and body fat mass, whereas SAT FTO mRNA levels were negatively correlated with subcutaneous fat deposition. In addition, SAT FTO mRNA and protein levels were increased in insulin resistant women (high HOMA) compared to insulin sensitive women (low HOMA), whereas OAT FTO expression was not different between these two subgroups. Interestingly, FTO mRNA levels were increased in SAT of type 2 diabetic patients, and treatment of diabetics with Rosiglitazone improved insulin sensitivity and reduced SAT FTO mRNA levels. Lastly, FTO expression was transiently increased in the early phase of 3T3-L1 cell differentiation, which coincides with the induction of PPARγ2 expression. However, partial reduction of FTO did not impact PPARγ2 expression and adipocyte differentiation.

CONCLUSION

Therefore, FTO gene expression is higher in OAT than in SAT in lean to moderately obese women. OAT FTO expression is associated with adiposity, whereas SAT FTO expression is associated with insulin sensitivity. These associations are independent of an effect of FTO on adipocyte differentiation.

Visceral fat accumulation is an indicator of adipose tissue macrophage infiltration in women

We tested the hypothesis that visceral obesity is the best correlate of abdominal adipose tissue macrophage infiltration in women. Omental and subcutaneous fat samples were surgically obtained from 40 women (age, 47.0 ± 4.0 years; body mass index, 28.4 ± 5.8 kg/m(2)). CD68+ cells were identified using fluorescence immunohistochemistry. Expression of macrophage markers was measured by real-time reverse transcriptase polymerase chain reaction. Body composition and fat distribution were measured by dual-energy x-ray absorptiometry and computed tomography, respectively. Mean CD68+ cell percentage tended to be higher in subcutaneous (18.3%) compared with omental adipose tissue (15.5%, P = .07). Positive correlations were observed between CD68+ cell percentage as well as CD68 messenger RNA expression in a given depot vs the other (P ≤ .01). Visceral adipose tissue area and omental adipocyte diameter were positively related to CD68+ cell percentage in omental fat (r = 0.52 and r = 0.35, P ≤ .05). Total and visceral adipose tissue areas as well as subcutaneous adipocyte diameter were significantly correlated with CD68+ cell percentage in subcutaneous adipose tissue (0.32 ≤ r ≤ 0.40, P ≤ .05). Adipose tissue areas and subcutaneous adipocyte diameter were also significantly associated with expression of commonly used macrophage markers including CD68 in the subcutaneous fat compartment (0.32 ≤ r ≤ 0.57, P ≤ .05). Visceral adipose tissue area was the best correlate of CD68+ cell percentage in both omental and subcutaneous fat tissues, explaining, respectively, 20% and 12% of the variance in models also including subcutaneous adipose tissue area, adipocyte sizes, and total body fat mass. Visceral adipose tissue accumulation is the best correlate of macrophage infiltration in both the subcutaneous and omental fat compartments of lean to obese women.

Abdominal superficial subcutaneous fat: a putative distinct protective fat subdepot in type 2 diabetes

OBJECTIVE

Unlike visceral adipose tissue (VAT), the association between subcutaneous adipose tissue (SAT) and obesity-related morbidity is controversial. In patients with type 2 diabetes, we assessed whether this variability can be explained by a putative favorable, distinct association between abdominal superficial SAT (SSAT) (absolute amount or its proportion) and cardiometabolic parameters.

RESEARCH DESIGN AND METHODS

We performed abdominal magnetic resonance imaging (MRI) in 73 patients with diabetes (mean age 58 years, 83% were men) and cross-sectionally analyzed fat distribution at S1-L5, L5-L4, and L3-L2 levels. Patients completed food frequency questionnaires, and subgroups had 24-h ambulatory blood pressure monitoring and 24-h ambulatory electrocardiography.

RESULTS

Women had higher %SSAT (37 vs. 23% in men; P < 0.001) despite a similar mean waist circumference. Fasting plasma glucose (P = 0.046) and HbA(1c) (P = 0.006) were both lower with increased tertile of absolute SSAT. In regression models adjusted for age, waist circumference, and classes of medical treatments used in this patient population, increased %SSAT was significantly associated with decreased HbA(1c) (β = -0.317; P = 0.013), decreased daytime ambulatory blood pressure (β = -0.426; P = 0.008), and increased HDL cholesterol (β = 0.257; P = 0.042). In contrast, increased percent of deep SAT (DSAT) was associated with increased HbA(1c) (β = 0.266; P = 0.040) and poorer heart rate variability parameters (P = 0.030). Although total fat and energy intake were not correlated with fat tissue distribution, increased intake of trans fat tended to be associated with total SAT (r = 0.228; P = 0.05) and DSAT (r = 0.20; P = 0.093), but not with SSAT.

CONCLUSIONS

Abdominal SAT is composed of two subdepots that associate differently with cardiometabolic parameters. Higher absolute and relative distribution of fat in abdominal SSAT may signify beneficial cardiometabolic effects in patients with type 2 diabetes.

Stearic acid content of abdominal adipose tissues in obese women

Objective:

Subcutaneous (SC) adipose tissue stearic acid (18:0) content and stearoyl-CoA desaturase-1 (SCD1)-mediated production of oleic acid (18:1) have been suggested to be altered in obesity. The objective of our study was to examine abdominal adipose tissue fatty acid content and SCD1 mRNA/protein level in women.

Subjects and methods:

Fatty acid content was determined by capillary gas chromatography in SC and omental (OM) fat tissues from two subgroups of 10 women with either small or large OM adipocytes. Samples from 10 additional women were used to measure SCD1 mRNA and protein expression, total extracellular signal-regulated kinase 1/2 (ERK1/2) and phosphorylated ERK1/2 protein as well as insulin receptor (IR) expression levels.

Results:

OM fat 18:0 content was significantly lower in women with large OM adipocytes compared with women who had similar adiposity, but small OM adipocytes (2.37±0.45 vs 2.75±0.30 mg per 100 g adipose tissue, respectively, P⩽0.05). OM fat 18:0 content was negatively related to the visceral adipose tissue area (r=−0.44, P=0.05) and serum triglyceride levels (r=−0.56, P<0.05), while SC fat 18:0 content was negatively correlated with total body fat mass (BFM) (r=−0.48, P<0.05) and fasting insulin concentration (r=−0.73, P<0.005). SC adipose tissue desaturation index (18:1/18:0), SCD1 expression and protein levels were positively correlated with BFM. Moreover, obese women were characterized by a reduced OM/SC ratio of SCD1 mRNA and protein levels. A similar pattern was observed for ERK1/2 and IR expression.

Conclusion:

The presence of large adipocytes and increased adipose mass in a given fat compartment is related to reduced 18:0 content and increased desaturation index in women, independently of dietary fat intake. The depot-specific difference in ERK1/2 expression and activation, as well as in SCD1 and IR expression in obese women is consistent with the hypothesis that they may predominantly develop SC fat, which could in turn help protect from metabolic disorders.

Computed tomographic evaluation of abdominal fat in minipigs

Computed tomography (CT) exams were conducted to determine the distribution of abdominal fat identified based on the CT number measured in Hounsfield Units (HU) and to measure the volume of the abdominal visceral and subcutaneous fat in minipigs. The relationship between the CT-based fat volumes of several vertebral levels and the entire abdomen and anthropometric data including the sagittal abdominal diameter and waist circumference were evaluated. Moreover, the total fat volumes at the T11, T13, L3, and L5 levels were compared with the total fat volume of the entire abdomen to define the landmark of abdominal fat distribution. Using a single-detector CT, six 6-month-old male minipigs were scanned under general anesthesia. Three radiologists then assessed the HU value of visceral and subcutaneous abdominal fat by drawing the region of interest manually at the T11, T13, L1, L3, and L5 levels. The CT number and abdominal fat determined in this way by the three radiologists was found to be correlated (intra-class coefficient = 0.9). The overall HU ranges for the visceral and subcutaneous fat depots were -147.47 to -83.46 and -131.62 to -90.97, respectively. The total fat volume of the entire abdomen was highly correlated with the volume of abdominal fat at the T13 level (r = 0.97, p < 0.0001). These findings demonstrate that the volume of abdominal adipose tissue measured at the T13 level using CT is a strong and reliable predictor of total abdominal adipose volume.

Visceral adipocyte hypertrophy is associated with dyslipidemia independent of body composition and fat distribution in women

OBJECTIVE

We assessed whether subcutaneous and omental adipocyte hypertrophy are related to metabolic alterations independent of body composition and fat distribution in women.

RESEARCH DESIGN AND METHODS

Mean adipocyte diameter of paired subcutaneous and omental adipose tissue samples was obtained in lean to obese women. Linear regression models predicting adipocyte size in both adipose tissue depots were computed using body composition and fat distribution measures (n = 150). In a given depot, women with larger adipocytes than predicted by the regression were considered as having adipocyte hypertrophy, whereas women with smaller adipocytes than predicted were considered as having adipocyte hyperplasia.

RESULTS

Women characterized by omental adipocyte hypertrophy had higher plasma and VLDL triglyceride levels as well as a higher total-to-HDL cholesterol ratio compared with women characterized by omental adipocyte hyperplasia (P < 0.05). Conversely, women characterized by subcutaneous adipocyte hypertrophy or hyperplasia showed a similar lipid profile. In logistic regression analyses, a 10% enlargement of omental adipocytes increased the risk of hypertriglyceridemia (adjusted odds ratio [OR] 4.06, P < 0.001) independent of body composition and fat distribution measures. A 10% increase in visceral adipocyte number also raised the risk of hypertriglyceridemia (adjusted OR 1.55, P < 0.02). Associations between adipocyte size and homeostasis model assessment of insulin resistance were not significant once adjusted for adiposity and body fat distribution.

CONCLUSIONS

These results suggest that omental, but not subcutaneous, adipocyte hypertrophy is associated with an altered lipid profile independent of body composition and fat distribution in women.

Ethnic-specific differences in abdominal subcutaneous adipose tissue compartments

South Asians have a higher prevalence of cardiovascular disease (CVD) than Europeans. Studies have identified distinct subcompartments of subcutaneous adipose tissue (SAT) that provide insight into the relationship between abdominal obesity and metabolic risk factors in different ethnic groups. Our objective was to determine the relationship between SAT compartments and fat-free mass (FFM) between South Asian and European cohorts, and between men and women. Healthy Europeans and South Asians (n = 408) were assessed for FFM via dual energy X-ray absorptiometry, and SAT areas by computed tomography (CT). SAT was subdivided into superficial subcutaneous abdominal adipose tissue (SSAT) and deep subcutaneous abdominal adipose tissue (DSAT). Linear regression analyses were performed using DSAT and SSAT as separate dependent variables and FFM and ethnicity as primary independent variables adjusting for age, gender, income, education, and smoking status. Results showed that South Asian men had significantly higher amounts of DSAT (median 187.65 cm(2) vs. 145.15 cm(2), P < 0.001), SSAT (median 92.0 cm(2) vs. 76.1 cm(2), P = 0.046), and body fat mass (BFM) (25.1 kg vs. 22.6 kg, P = 0.049) than European men. In a fully adjusted model, South Asians showed significantly greater DSAT at any FFM than Europeans. Women had more SSAT at any given FFM than men and less DSAT at any given FFM than men, irrespective of ethnic background. In conclusion, South Asians had more DSAT than Europeans and men had relatively more DSAT than women. These data suggest that specific fat depots are influenced by ethnicity and gender; therefore, could provide insight into the relationship between ethnicity, gender and subsequent risk for CVD.

Expression of genes related to glucocorticoid action in human subcutaneous and omental adipose tissue

Adipose tissue glucocorticoid action relies on local enzymatic interconversion and glucocorticoid receptor (GR) availability. 11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1), 2 (11β-HSD2) and hexose-6-phosphate dehydrogenase (H6PDH) are likely involved in glucocorticoid activation/inactivation within adipose tissue. We examined adipose tissue mRNA expression of genes related to glucocorticoid action and their association with total and visceral adiposity. Messenger RNA was measured in paired subcutaneous and omental fat samples obtained from 56 women (age: 47.3 ± 4.8 years, BMI: 27.1 ± 5.2 kg/m(2)) undergoing gynaecological surgery. Expression levels of 11β-HSD2, H6PDH and GRα were higher in omental adipose tissue while 11β-HSD1 expression was similar between fat compartments. Subcutaneous and omental 11β-HSD1 mRNA abundances were positively associated with total and visceral adiposity whereas omental H6PDH mRNA abundance was negatively associated with these measures. Only omental 11β-HSD1 mRNA expression remained significantly associated with visceral adipose tissue area following statistical adjustment for fat mass, age and menopausal status. Omental 11β-HSD1 mRNA expression explained 19.1% of the variance in visceral adipose tissue area. Omental fat tissue 11β-HSD-1 protein and cortisol levels were higher in visceral obese women, supporting findings obtained with 11β-HSD-1 mRNA. These results suggest that among the transcripts examined only omental 11β-HSD1 is independently associated with visceral obesity in women.

Adipose tissue lamin A/C messenger RNA expression in women

Mutations in the lamin A/C gene (LMNA) cause lipodystrophy. However, little data are available on lamin A/C expression in various fat depots in women. We recruited 34 women scheduled for gynecologic surgery. Blood samples were collected on the morning of surgery to obtain a detailed lipid profile. Radiological examinations were performed to measure total body fat mass and abdominal fat accumulation. Fat samples were taken from the subcutaneous (SC) fat depot and from the greater omentum (OM) during the surgical procedure. Whole adipose tissue samples were used for total messenger RNA (mRNA) extraction and real-time polymerase chain reaction quantification of the LMNA transcript. No association was observed between lamin A/C mRNA expression, either in SC or OM fat tissue, and adiposity measures. Women with low SC lamin A/C expression, identified on the basis of the median value of SC lamin A/C mRNA expression, had a significantly altered lipid profile including lower levels of high-density lipoprotein (HDL) cholesterol and HDL(2) cholesterol and reduced HDL(2) cholesterol to HDL(3) cholesterol ratio (P < .05 for all). These women were also characterized by higher cholesterol to HDL cholesterol, low-density lipoprotein-triglycerides, very low-density lipoprotein-apolipoprotein B, and low-density lipoprotein cholesterol to HDL cholesterol (P < .05 for all). Low SC lamin A/C mRNA expression levels were also associated with significantly increased lipolysis in isolated fat cells from this fat depot. Specifically, the response to lipolytic agent isoproterenol was significantly increased at doses ranging from 10(-5) to 10(-10) mol/L (P < .05). A similar trend was observed in OM fat cells but did not reach significance. In conclusion, low lamin A/C expression in SC adipose tissue is associated with significant alterations in the lipid profile and increased fat cell lipolysis, independent of the level of total or abdominal adiposity.

Omental adipose tissue type 1 11 beta-hydroxysteroid dehydrogenase oxoreductase activity, body fat distribution, and metabolic alterations in women

CONTEXT

Modulation of adipose tissue exposure to active glucocorticoids by type 1 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD1) is involved in abdominal obesity of rodent models, but only a few studies have related 11 beta-HSD1 oxoreductase activity to fat distribution in humans.

OBJECTIVE

The objective of the study was to examine the link between 11 beta-HSD1 oxoreductase activity, fat distribution patterns, and the metabolic profile in women.

METHODS

Omental (OM) and sc adipose tissue samples were obtained from 36 lean to obese women (aged 47.2 +/- 5.3 yr; body mass index 29.1 +/- 5.2 kg/m(2)) undergoing gynecological surgery. Measures of body composition, fat distribution, blood lipids, and insulin sensitivity were obtained. 11 beta-HSD1 oxoreductase activity was measured over a 24-h period by the reduction of [(14)C]cortisone in adipose tissue homogenates.

RESULTS

11 beta-HSD1 oxoreductase activity was higher in OM compared with sc adipose tissue (9.6 +/- 4.9 vs. 7.9 +/- 4.2 pmol/mg x h, P < 0.01). OM 11 beta-HSD1 oxoreductase activity was positively associated with OM adipocyte size (r = 0.67, P < 0.0001) and visceral adipose tissue area (r = 0.57, P < 0.0003). A positive correlation was also observed between the OM/sc 11 beta-HSD1 oxoreductase activity ratio and the OM/sc adipocyte size ratio (r = 0.37, P < 0.05) as well as the visceral/sc adipose tissue area ratio (r = 0.36, P < 0.05). Women in the highest tertile of OM 11 beta-HSD1 oxoreductase activity had larger OM adipocytes, increased OM lipolysis, increased lipoprotein lipase activity, decreased high-density lipoprotein cholesterol, decreased adiponectin levels, and an increased homeostasis model assessment of insulin resistance index compared with women in the lower tertile (P < 0.05).

CONCLUSIONS

These results suggest that a relatively higher 11 beta-HSD1 activity in OM vs. sc adipose tissue is associated with preferential visceral fat accumulation and concomitant metabolic alterations.

Gender differences in insulin resistance, body composition, and energy balance

BACKGROUND

Men and women differ substantially in regard to degrees of insulin resistance, body composition, and energy balance. Adipose tissue distribution, in particular the presence of elevated visceral and hepatic adiposity, plays a central role in the development of insulin resistance and obesity-related complications.

OBJECTIVE

This review summarizes published data on gender differences in insulin resistance, body composition, and energy balance, to provide insight into novel gender-specific avenues of research as well as gender-tailored treatments of insulin resistance, visceral adiposity, and obesity.

METHODS

English-language articles were identified from searches of the PubMed database through November 2008, and by reviewing the references cited in these reports. Searches included combinations of the following terms: gender, sex, insulin resistance, body composition, energy balance, and hepatic adipose tissue.

RESULTS

For a given body mass index, men were reported to have more lean mass, women to have higher adiposity. Men were also found to have more visceral and hepatic adipose tissue, whereas women had more peripheral or subcutaneous adipose tissue. These differences, as well as differences in sex hormones and adipokines, may contribute to a more insulin-sensitive environment in women than in men. When normalized to kilograms of lean body mass, men and women had similar resting energy expenditure, but physical energy expenditure was more closely related to percent body fat in men than in women.

CONCLUSION

Greater amounts of visceral and hepatic adipose tissue, in conjunction with the lack of a possible protective effect of estrogen, may be related to higher insulin resistance in men compared with women.

Computer tomographic investigation of subcutaneous adipose tissue as an indicator of body composition

BACKGROUND

Modern computer tomography (CT) equipment can be used to acquire whole-body data from large animals such as pigs in minutes or less. In some circumstances, computer assisted analysis of the resulting image data can identify and measure anatomical features. The thickness of subcutaneous adipose tissue at a specific site measured by ultrasound, is used in the pig industry to assess adiposity and inform management decisions that have an impact on reproduction, food conversion performance and sow longevity. The measurement site, called "P2", is used throughout the industry. We propose that CT can be used to measure subcutaneous adipose tissue thickness and identify novel measurement sites that can be used as predictors of general adiposity.

METHODS

Growing pigs (N = 12), were each CT scanned on three occasions. From these data the total volume of adipose tissue was determined and expressed as a proportion of total volume (fat-index). A computer algorithm was used to determined 10,201 subcutaneous adipose thickness measurements in each pig for each scan. From these data, sites were selected where correlation with fat-index was optimal.

RESULTS

Image analysis correctly identified the limits of the relevant tissues and automated measurements were successfully generated. Two sites on the animal were identified where there was optimal correlation with fat-index. The first of these was located 4 intercostal spaces cranial to the caudal extremity of the last rib, the other, a further 5 intercostal spaces cranially.

CONCLUSION

The approach to image analysis reported permits the creation of various maps showing adipose thickness or correlation of thickness with other variables by location on the surface of the pig. The method identified novel adipose thickness measurement positions that are superior (as predictors of adiposity) to the site which is in current use. A similar approach could be used in other situations to quantify potential links between subcutaneous adiposity and disease or production traits.

Glucose transporter 4 and insulin receptor substrate-1 messenger RNA expression in omental and subcutaneous adipose tissue in women

Insulin receptor substrate-1 (IRS-1) and glucose transporter 4 (GLUT4) expression may provide an indirect reflection of the capacity of adipocytes to respond to insulin stimulation. We examined messenger RNA (mRNA) expression of these genes in omental and subcutaneous adipose tissue of women. Paired omental and subcutaneous adipose tissue samples were obtained from 36 women (age, 47 +/- 5 years; body mass index, 28.0 +/- 5.4 kg/m(2)) undergoing gynecologic surgeries. Total adiposity and visceral adiposity were assessed by dual-energy x-ray absorptiometry and computed tomography. The GLUT4 and IRS-1 mRNA expression levels were both significantly higher in subcutaneous compared with omental adipose tissue. A negative correlation was observed between body fat percentage and subcutaneous adipose tissue GLUT4 (r = -0.39, P < .05) and IRS-1 (r = -0.30, P < .08) mRNA abundance. However, in omental fat, only GLUT4 mRNA was inversely associated with body fat percentage (r = -0.53, P < .001). Moreover, the homeostasis model assessment of insulin resistance index was associated with mRNA expression of subcutaneous GLUT4 (r = -0.56, P < .001), subcutaneous IRS-1 (r = -0.51, P < .01), and omental GLUT4 (r = -0.54, P < .001), but not omental IRS-1. Interestingly, plasma adiponectin was only associated with subcutaneous GLUT4 (r = 0.48, P < .01) and IRS-1 (r = 0.48, P < .05) mRNA expression. The GLUT4 protein, unlike mRNA expression, was higher in omental than in subcutaneous adipose tissue. However, abdominal obesity-related differences in protein or mRNA expression were similar. Omental IRS-1 expression was low and unaffected by visceral obesity. In contrast, omental and subcutaneous GLUT4 as well as subcutaneous IRS-1 were reduced in visceral obesity. This divergent pattern of expression may reflect a lower capacity of omental adipose tissue to respond to insulin stimulation at all adiposity levels.

Fat depot-specific impact of visceral obesity on adipocyte adiponectin release in women

Our objective was to examine omental and subcutaneous adipocyte adiponectin release in women. We tested the hypothesis that adiponectin release would be reduced to a greater extent in omental than in subcutaneous adipocytes of women with visceral obesity. Omental and subcutaneous adipose tissue samples were obtained from 52 women undergoing abdominal hysterectomies (age: 47.1 +/- 4.8 years; BMI: 26.7 +/- 4.7 kg/m(2)). Adipocytes were isolated and their adiponectin release in the medium was measured over 2 h. Measures of body fat accumulation and distribution were obtained using dual-energy X-ray absorptiometry and computed tomography, respectively. Adiponectin release by omental and subcutaneous adipocytes was similar in lean individuals; however, in subsamples of obese or visceral obese women, adiponectin release by omental adipocytes was significantly reduced while that of subcutaneous adipocytes was not affected. Omental adipocyte adiponectin release was significantly and negatively correlated with total body fat mass (r = -0.47, P < 0.01), visceral adipose tissue area (r = -0.50, P < 0.01), omental adipocyte diameter (r = -0.43, P < 0.01), triglyceride levels (r = -0.32, P < or = 0.05), cholesterol/high-density lipoprotein (HDL)-cholesterol (r = -0.31, P < or = 0.05), fasting glucose (r = -0.39, P < or = 0.01), fasting insulin (r = -0.36, P < or = 0.05), homeostasis model assessment index (r = -0.39, P < or = 0.01), and positively associated with HDL-cholesterol concentrations (r = 0.33, P < or = 0.05). Adiponectin release from subcutaneous cells was not associated with any measure of adiposity, lipid profile, or glucose homeostasis. In conclusion, compared to subcutaneous adipocyte adiponectin release, omental adipocyte adiponectin release is reduced to a greater extent in visceral obese women and better predicts obesity-associated metabolic abnormalities.

Sagittal abdominal diameter is more predictive of cardiovascular risk than abdominal fat compartments in severe obesity

OBJECTIVE

To compare the predictive role of abdominal fat distribution by computed tomography (CT) with that of total abdominal fat by sagittal abdominal diameter (SAD) on cardiovascular risk in severe obesity.

DESIGN

A cross-sectional, clinical study.

SUBJECTS

64 males and 64 females, aged 42+/-15 years (mean+/-s.d.; range 18-75 years), BMI (kg/m(2)) 41.7+/-5.3 (30.2-57.6).

MEASUREMENTS

Blood glucose, total cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, triglycerides (TGLs), insulin (IRI), insulin resistance (HOMA-IR), slice areas (cm(2)) of total (tSAT), superficial (sSAT) and deep subcutaneous adipose tissue (dSAT), visceral adipose tissue (VAT) and SAD (mm) by CT.

RESULTS

The sSAT depot was negatively associated with blood glucose, HOMA-IR, LDL cholesterol and TGLs, whereas dSAT was negatively associated with HDL cholesterol. VAT was associated with blood glucose and HOMA-IR, whereas SAD was associated with all variables evaluated. In males, VAT was associated with blood glucose (r(2)=0.12, P<0.01), SAD was associated with blood glucose (r(2)=0.67, P<0.01), IRI (r(2)=0.65, P<0.05), and HOMA-IR (r(2)=0.67, P<0.01). In females, sSAT was negatively associated with blood glucose (r(2)=0.63, P<0.05), whereas VAT was associated positively with blood glucose (r(2)=0.21, P< 0.001), total cholesterol (r(2)=0.16, P<0.01), LDL cholesterol (r(2)=0.20, P<0.001) and TGLs (r(2)=0.12, P<0.01). SAD was associated positively with IRI (r(2)=0.52, P<0.05), HOMA-IR (r(2)=0.53, P<0.05), total cholesterol (r(2)=0.52, P<0.05), LDL cholesterol (r(2)=0.54, P<0.01), TGLs (r(2)=0.52, P<0.05) and negatively to HDL cholesterol (r(2)=0.51, P<0.001).

CONCLUSION

When compared with CT-based measures of abdominal fat compartments, SAD is a more predictive indicator of cardiovascular risk in severe obesity.

[Metabolic profile according to leptin levels in obese patients]

Increased body mass index and waist circumference are related to cardiovascular risk factors. Leptin is an adipocyte-produced hormone and regulates body weight. Leptin is directly related to body fat. To evaluate the relationship between leptin and metabolic profile in obese subjects, we studied 119 patients. Anthropometric, laboratory, body composition (by bioelectrical impedance) and co-morbidity data were collected. The analysis was performed in the female population (86.6%): average age: 42 +/- 13 years; hypertension, type 2 diabetes and grade III obesity were present in 61.9%, 20.2% and 58.3%, respectively. Leptin levels were positively related to insulin resistance (IR). HOMA-IR was related to metabolic abnormalities of IR. No differences were demonstrated between lipid profile, glycemia, body composition and tertiles of leptin corrected by fat weight. A significant difference in HOMA-IR was present when the 2nd and 3rd tertiles of leptin corrected by fat weight [3.4 (2.8-4.1) vs. 5.3 (4.1-6.5), p=0.011] were compared. In conclusion, leptin corrected by fat weight did not influence lipid profile and glycemia in moderate to severe obese women with similar percent body fat. Leptin should not be considered an independent factor affecting lipid metabolism.