Prostaglandin (PG) F2 alpha synthesis in human subcutaneous and omental adipose tissue: modulation by inflammatory cytokines and role of the human aldose reductase AKR1B1.

INTRODUCTION: PGF2α may be involved in the regulation of adipose tissue function. OBJECTIVES: 1) To examine PGF2α release by primary preadipocytes, mature adipocytes and whole tissue explants from the subcutaneous and omental fat compartments; 2) To assess which PGF synthase is the most relevant in human adipose tissue. METHODS: Fat samples were obtained by surgery in women. PGF2α release by preadipocytes, adipocytes and explants under stimulation by TNF-α, IL-1ß or both was measured. Messenger RNA expression levels of AKR1B1 and AKR1C3 were measured by RT-PCR in whole adipose tissue and cytokine-treated preadipocytes. The effect of AKR1B1 inhibitor ponalrestat on PGF2α synthesis was investigated. RESULTS: PGF2α release was significantly induced in response to cytokines compared to control in omental (p = 0.01) and to a lesser extent in subcutaneous preadipocytes (p = 0.02). Messenger RNA of COX-2 was significantly higher in omental compared to subcutaneous preadipocytes in response to combined TNF-α and IL-1ß (p = 0.01). Inflammatory cytokines increased AKR1B1 mRNA expression and protein levels (p≤0.05), but failed to increase expression levels of AKR1C3 in cultured preadipocytes. Accordingly, ponalrestat blunted PGF2α synthesis by preadipocytes in basal and stimulated conditions (p≤0.05). Women with the highest PGF2α release by omental adipocytes had a higher BMI (p = 0.05), waist circumference (p≤0.05) and HOMAir index (p≤0.005) as well as higher mRNA expression of AKR1B1 in omental (p<0.10) and subcutaneous (p≤0.05) adipose tissue compared to women with low omental adipocytes PGF2α release. Positive correlations were observed between mRNA expression of AKR1B1 in both compartments and BMI, waist circumference as well as HOMAir index (p≤0.05 for all). CONCLUSION: PGF2α release by omental mature adipocytes is increased in abdominally obese women. Moreover, COX-2 expression and PGF2α release is particularly responsive to inflammatory stimulation in omental preadipocytes. Yet, blockade of PGF synthase AKR1B1 inhibits most of the PGF2α release.

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.

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.

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.

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.

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. 11ß-Hydroxysteroid dehydrogenase type 1 (11ß-HSD1), 2 (11ß-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 11ß-HSD2, H6PDH and GRα were higher in omental adipose tissue while 11ß-HSD1 expression was similar between fat compartments. Subcutaneous and omental 11ß-HSD1 mRNA abundances were positively associated with total and visceral adiposity whereas omental H6PDH mRNA abundance was negatively associated with these measures. Only omental 11ß-HSD1 mRNA expression remained significantly associated with visceral adipose tissue area following statistical adjustment for fat mass, age and menopausal status. Omental 11ß-HSD1 mRNA expression explained 19.1% of the variance in visceral adipose tissue area. Omental fat tissue 11ß-HSD-1 protein and cortisol levels were higher in visceral obese women, supporting findings obtained with 11ß-HSD-1 mRNA. These results suggest that among the transcripts examined only omental 11ß-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.

Differential estrogenic 17beta-hydroxysteroid dehydrogenase activity and type 12 17beta-hydroxysteroid dehydrogenase expression levels in preadipocytes and differentiated adipocytes.

Estradiol (E2) is produced locally in adipose tissue and could play an important role in fat distribution and accumulation, especially in women. It is well recognized that aromatase is expressed in adipose tissue; however the identity of its estrogenic 17beta-hydroxysteroid dehydrogenase (17beta-HSD) partner is not identified. To gain a better knowledge about the enzyme responsible for the conversion of estrone into estradiol, we determined the activity and expression levels of known estrogenic 17beta-HSDs, namely types 1, 7 and 12 17beta-HSD in preadipocytes before and after differentiation into mature adipocytes using an adipogenic media. Estrogenic 17beta-HSD activity was assessed using [(14)C]-labelled estrone, while mRNA expression levels of types 1, 7 and 12 17beta-HSD were quantified using real-time PCR and protein expression levels of type 12 17beta-HSD was determined using immunoblot analysis. The data indicate that there is a low conversion of E1 into E2 in preadipocytes; however this activity is increased approximately 5-fold (p<0.0001) in differentiated adipocytes. The increased estrogenic 17beta-HSD activity is consistent with the increase in protein expression levels of 17beta-HSD12.