Adipose tissue depot-specific differences in adipocyte apolipoprotein E expression

Important differences in gene expression have been documented in adipocytes derived from specific adipose tissue depots. We have previously documented an important role for adipocyte apolipoprotein E (apoE) in modulating adipocyte and adipose tissue triglyceride and lipoprotein metabolism. We now evaluate the endogenous expression of apoE in adipocytes isolated from unique adipose tissue depots in 4 different species. Adipocyte apoE expression is higher in subcutaneous fat compared with visceral fat in humans, mice, rats, and baboons. In baboons, evaluation of apoE expression in 5 adipose tissue depots (subcutaneous abdominal, subcutaneous gluteal, visceral, pericardial, epicardial) showed that, compared with subcutaneous abdominal adipocytes, the level of apoE expression is similar in subcutaneous gluteal, lower in visceral and pericardial, and higher in epicardial adipocytes. Consistent with previously demonstrated suppression of adipocyte apoE by adipose tissue inflammation, adipose tissue depots with lower apoE expression demonstrated greater infiltration of macrophages and an increased expression of tumor necrosis factor–α messenger RNA. Depot-specific differences in apoE expression were maintained after in vitro differentiation. Adipocytes isolated from depots with lower apoE expression manifested lower rates of triglyceride synthesis in the absence and presence of triglyceride-rich lipoproteins. Adenoviral-mediated increase of apoE expression in omental adipocytes increased triglyceride synthesis in these cells. Our results demonstrate significant heterogeneity in adipocyte apoE expression across adipose tissue depots in several species. Because of its role in modulating adipocyte triglyceride and lipoprotein metabolism, depot-specific differences in endogenous adipocyte apoE could have important implications for modulating the accumulation of lipid in these depots.     

Tumor necrosis factor-alpha-mediated suppression of adipocyte apolipoprotein E gene transcription: primary role for the nuclear factor (NF)-kappaB pathway and NFkappaB p50

The adipose tissue inflammation accompanying obesity has important consequences for adipocyte lipid metabolism, and increased adipose tissue TNFalpha plays an important role for mediating the effect of inflammation on adipocyte function. Recent studies have shown that apolipoprotein E (apoE) is highly expressed in adipose tissue where it plays an important role in modulating adipocyte triglyceride metabolism, triglyceride mass, and adipocyte size. We have previously reported that TNFalpha reduces adipocyte apoE, and the current studies were undertaken to evaluate the molecular mechanism for this regulation. TNFalpha repression of adipocyte apoE gene expression required an intact nuclear factor (NF)-kappaB binding site at -43 in the apoE promoter. Site-directed mutagenesis at this site completely eliminated TNFalpha regulation of an apoE gene reporter. TNFalpha treatment activated binding of NFkappaB p50, isolated from adipocyte nuclei, to the apoE promoter. Two structurally distinct inhibitors of NFkappaB complex activation or translocation abrogated the TNFalpha effect on the apoE gene. Using chromatin immunoprecipitation assays, we demonstrated that treatment of adipocytes with TNFalpha led to increased binding of NFkappaB p50, and decreased binding of p65 and Sp1, to this region of the apoE promoter in living cells. The key role played by increased p50 binding was confirmed by p50 knockdown experiments. Reduction of p50 expression using small interference RNA completely eliminated TNFalpha-mediated reduction of endogenous adipocyte apoE gene expression. These results establish the molecular link between adipose tissue inflammation and apoE gene expression in adipocytes. The suppression of adipocyte apoE by the proinflammatory adipose tissue milieu associated with obesity will have important downstream effects on adipocyte triglyceride turnover and content.     

Human adipose tissue cannabinoid receptor 1 gene expression is not related to fat cell function or adiponectin level

CONTEXT: The cannabinoid receptor 1 gene (CNR1) is implicated in adipocyte function. OBJECTIVE: We investigated human adipose tissue CNR1 mRNA in relation to obesity, clinical and metabolic variables, adipocyte function, and adiponectin (ADIPOQ) levels. METHODS: We assessed sc fat biopsies from 96 obese and nonobese subjects and omental fat biopsies from 82 obese and nonobese subjects. RESULTS: The sc and omental adipose CNR1 gene expression were similar in obese and nonobese subjects. No association between either sc or omental adipose CNR1 mRNA levels and body mass index, waist circumference, plasma levels of glucose and insulin, lipids, or blood pressure was found. The sc and omental maximal adrenergic lipolytic activation as well as lipolytic adrenoceptor sensitivity were not related to CNR1 gene expression. Lipogenesis in sc adipocytes also showed no association with CNR1 mRNA levels. Finally, no relation was found between adipose CNR1 gene expression and ADIPOQ mRNA, adipose tissue adiponectin secretion, or circulating adiponectin. CONCLUSION: We found no association of human adipose tissue CNR1 mRNA expression with measures of body fat, metabolic parameters, fat cell function, or ADIPOQ expression. These data do not suggest a major role of human adipose CNR1 in fat cell function or metabolic disease development.     

Ovarian hormone status and abdominal visceral adipose tissue metabolism

We examined abdominal sc and visceral adipose tissue metabolism in a sample of 19 regularly cycling premenopausal women (age 46.3 +/- 3.7 yr) and 10 women with natural menopause or pharmacological ovarian suppression (age 51.1 +/- 9.2 yr). Subcutaneous and visceral (omental, epiploic) adipose tissue biopsies were obtained during abdominal hysterectomies. Body composition and adipose tissue distribution were measured before the surgery by dual x-ray absorptiometry and computed tomography, respectively. Ovarian hormone-deficient women tended to be older (P = 0.08) and were characterized by increased visceral adipose tissue area (P < 0.05). Subcutaneous adipocyte size, lipoprotein lipase (LPL) activity, and basal lipolysis were not significantly different between groups. On the other hand, omental fat cell size was significantly higher in ovarian hormone-deficient women, compared with premenopausal women (P < 0.05). The omental/sc LPL activity ratio and omental adipocyte basal lipolysis were also significantly higher in ovarian hormone-deficient women (P < 0.05 for both comparisons). Significant positive correlations were found between visceral adipose tissue area and omental LPL activity (r = 0.54, P < 0.003), omental adipocyte basal lipolysis (r = 0.66, P < 0.0001), and omental fat cell size (r = 0.81, P < 0.0001). In multivariate analyses, ovarian status was no longer a significant predictor of adipose cell metabolism variables after visceral adipose tissue area was entered into the model, with the exception of the omental/sc LPL activity ratio, which remained independently associated with ovarian status. In conclusion, although the size of the visceral adipose tissue compartment was an important determinant of adipocyte metabolism in this depot, the increased omental/sc LPL activity ratio in ovarian hormone-deficient women supports the notion of a predominant visceral fat storage in these women.     

Local androgen inactivation in abdominal visceral adipose tissue

We examined the expression and activity of two enzymes from the aldoketoreductase (AKR) family 1C, namely type 5 17beta-hydroxysteroid dehydrogenase (17beta-HSD-5, AKR1C3) and type 3 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD-3, AKR1C2) in female sc and omental adipose tissue and in preadipocyte primary cultures. 17beta-HSD-5 preferentially synthesizes testosterone from the inactive adrenal precursor androstenedione, whereas 3alpha-HSD-3 inactivates dihydrotestosterone. mRNAs of both enzymes were detected in adipose tissue from the omental and sc compartments. Real-time PCR quantification indicated a 3-fold higher 3alpha-HSD-3 expression compared with 17beta-HSD-5, and the expression of both enzymes tended to be higher in the sc vs. the omental depot. Accordingly, dose-response and time-course experiments performed in preadipocyte primary cultures indicated that 3alpha-HSD activity was higher than 17beta-HSD activity (13-fold maximum velocity difference). We measured 3alpha-HSD activity in omental and sc adipose tissue samples of 32 women for whom body composition and body fat distribution were evaluated by dual-energy x-ray absorptiometry and CT, respectively. We found that androgen inactivation in omental adipose tissue through 3alpha-HSD activity was significantly higher in women with elevated vs. low visceral adipose tissue accumulation (1.7-fold difference; P < 0.05). Moreover, omental adipose tissue 3alpha-HSD activity was positively and significantly associated with CT-measured visceral adipose tissue (r = 0.43; P < 0.02) and omental adipocyte diameter (r = 0.42; P < 0.02). These results indicate that local androgen inactivation is a predominant reaction in female abdominal adipose tissue, with the greatest conversion rates observed in the presence of abdominal visceral obesity. Increased androgen inactivation in omental adipose tissue of abdominally obese women may impact locally on the regulation of adipocyte metabolism.     

Expression of the mRNA coding for 11beta-hydroxysteroid dehydrogenase type 1 in adipose tissue from obese patients: an in situ hybridization study

Glucocorticoids play an important role in determining adipose tissue metabolism and distribution. Patients with Cushing's syndrome or receiving corticosteroid therapy develop a reversible visceral obesity. In obese patients, although circulating concentrations of cortisol are not consistently elevated, local conversion of inactive cortisone to active cortisol in adipose tissue, catalyzed by 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD-1), could amplify glucocorticoid signaling. We have studied, using semiquantitative in situ hybridization, 11beta-HSD-1 mRNA expression in the adipocyte and stromal compartments of sc abdominal adipose tissue obtained from 12 lean patients and sc abdominal and visceral adipose tissue obtained from 18 obese patients. 11beta-HSD-1 mRNA was expressed in adipocytes, stroma, and walls of vessels. Localization of 11beta-HSD-1 mRNA did not differ between lean sc and obese sc or visceral adipose tissue. 11beta-HSD-1 mRNA levels were significantly (P = 0.0106) increased in the adipocyte compartment of sc adipose tissue obtained from obese patients as compared with nonobese ones, whereas no significant change (P = 0.446) was found in the stromal compartment. In obese patients, 11beta-HSD-1 mRNA expression was increased (P = 0.0157) in the stromal compartment of visceral compared with sc tissue, whereas no significant change (P = 0.8767) was found in the adipocyte compartment. In summary, our data show that 11beta-HSD-1 mRNA is increased in adipose tissue from obese patients, in the abdominal sc fat in adipocytes and in the visceral fat in both adipocytes and stroma. This observation suggests that an overexpression of 11beta-HSD-1 may explain part of the glucocorticoid-induced metabolic disorders linked to obesity and may promote visceral fat deposition.     

Expression of six transmembrane protein of prostate 2 in human adipose tissue associates with adiposity and insulin resistance

CONTEXT: Six transmembrane protein of prostate 2 (STAMP2) is a counterregulator of adipose inflammation and insulin resistance in mice. Our hypothesis was that STAMP2 could be involved in human obesity and insulin resistance. OBJECTIVE: The objective of the study was to elucidate the role of adipose STAMP2 expression in human obesity and insulin resistance. DESIGN: The design was to quantify STAMP2 in human abdominal sc and omental white adipose tissue (WAT), isolated adipocytes, and stroma and in vitro differentiated preadipocytes and relate levels of STAMP2 in sc WAT to clinical and adipocyte phenotypes involved in insulin resistance. PARTICIPANTS: Nonobese and obese women and men (n = 236) recruited from an obesity clinic or through local advertisement. MAIN OUTCOME MEASUREMENT: Clinical measures included body mass index, body fat, total adiponectin, and homeostasis model assessment as measure of overall insulin resistance. In adipocytes we determined cell size, sensitivity of lipolysis and lipogenesis to insulin, adiponectin secretion, and inflammatory gene expression. RESULTS: STAMP2 levels in sc and visceral WAT and adipocytes were increased in obesity (P = 0.0008-0.05) but not influenced by weight loss. Increased WAT STAMP2 levels associated with a high amount of body fat (P = 0.04), high homeostasis model assessment (P = 0.01), and large adipocytes (P = 0.02). Subjects with high STAMP2 levels displayed reduced sensitivity of adipocyte lipogenesis (P = 0.04) and lipolysis (P = 0.03) to insulin but had normal adiponectin levels. WAT STAMP2 levels correlated with expression of the macrophage marker CD68 (P = 0.0006). CONCLUSION: Human WAT STAMP2 associates with obesity and insulin resistance independently of adiponectin, but the role of STAMP2 in obesity and its complications seems different from that in mice.     

The endogenous cannabinoid system stimulates glucose uptake in human fat cells via phosphatidylinositol 3-kinase and calcium-dependent mechanisms

BACKGROUND: The endogenous cannabinoid system participates in the regulation of energy balance, and its dysregulation may be implicated in the pathogenesis of obesity. Adipose tissue endocannabinoids may produce metabolic and endocrine effects, but very few data are available in human adipose tissue and in primary human fat cells. EXPERIMENTAL DESIGN: We measured expression of type 1 and type 2 cannabinoid receptors (CNR), enzymes of cannabinoids synthesis and degradation in human omental, sc abdominal, and gluteal adipose tissue from lean and obese subjects. Furthermore, we assessed the effect of CNR1 stimulation on glucose uptake and intracellular transduction mechanisms in primary human adipocytes. Then we assessed the reciprocal regulation between CNR1 and peroxisome proliferator-activated receptor-gamma (PPARgamma). Finally, we tested whether leptin and adiponectin are regulated by CNR1 in human adipocytes. RESULTS: We found that most genes of the endocannabinoid system are down-regulated in gluteal fat and up-regulated in visceral and sc abdominal adipose tissue of obese patients. Treatment of adipocytes with rosiglitazone markedly down-regulated CNR1 expression, whereas Win 55,212 up-regulated PPARgamma. Win 55,212 increased (+50%) glucose uptake, the translocation of glucose transporter 4, and intracellular calcium in fat cells. All these effects were inhibited by SR141716 and wortmannin and by removing extracellular calcium. Win 55,212 and SR141716 had no effect on expression of adiponectin and leptin. CONCLUSIONS: These results indicate a role for the local endocannabinoids in the regulation of glucose metabolism in human adipocytes and suggest a role in channeling excess energy fuels to adipose tissue in obese humans.     

Regional impact of adipose tissue morphology on the metabolic profile in morbid obesity

Aims/hypothesis

The aim of this study was to determine whether the mean size of fat cells in either visceral or subcutaneous adipose tissue has an impact on the metabolic and inflammatory profiles in morbid obesity.

Methods

In 80 morbidly obese women, mean visceral (omental) and subcutaneous fat cell sizes were related to in vivo markers of inflammation, glucose metabolism and lipid metabolism.

Results

Visceral, but not subcutaneous, adipocyte size was significantly associated with plasma apolipoprotein B, total cholesterol, LDL-cholesterol and triacylglycerols (p ranging from 0.002 to 0.015, partial r ranging from 0.3 to 0.4). Subcutaneous, but not visceral, adipocyte size was significantly associated with plasma insulin and glucose, insulin-induced glucose disposal and insulin sensitivity (p ranging from 0.002 to 0.005, partial r ranging from ?0.34 to 0.35). The associations were independent of age, BMI, body fat mass or body fat distribution. Adipose tissue hyperplasia (i.e. many small adipocytes) in both regions was significantly associated with better glucose, insulin and lipid profiles compared with adipose hypertrophy (i.e. few large adipocytes) in any or both regions (p ranging from <0.0001 to 0.04). Circulating inflammatory markers were not associated with fat cell size or corresponding gene expression in the fat cell regions examined.

Conclusions/interpretation

In morbidly obese women region-specific variations in mean adipocyte size are associated with metabolic complications but not systemic or adipose inflammation. Large fat cells in the visceral region are linked to dyslipidaemia, whereas large subcutaneous adipocytes are important for glucose and insulin abnormalities. Hyperplasia (many small adipocytes) in both adipose regions may be protective against lipid as well as glucose/insulin abnormalities in obesity.     

Attenuation of diet-induced weight gain and adiposity through increased energy expenditure in mice lacking angiotensin II type 1a receptor

Given that angiotensin II (AII) type 1 and 2 receptors (Agtr1 and Agtr2) are expressed in adipose tissue, AII may act directly on adipose tissue. However, regardless of whether AII directly modulates adipose tissue growth and metabolism in vivo and, if so, whether it is mediated via Agtr1 are still matters of debate. To understand the functional role of Agtr1 in adipose tissue growth and metabolism in vivo, we examined the metabolic phenotypes of mice lacking Agtr1a (Agtr1a-/- mice) during a high-fat diet. The Agtr1a-/- mice exhibited the attenuation of diet-induced body weight gain and adiposity, and insulin resistance relative to wild-type littermates (Agtr1a+/+ mice). They also showed increased energy expenditure accompanied by sympathetic activation, as revealed by increased rectal temperature and oxygen consumption, increased expression of uncoupling protein-1 mRNA in brown adipose tissue, and increased urinary catecholamine excretion. The heterozygous Agtr1a-deficient mice (Agtr1a+/- mice) also exhibited metabolic phenotypes similar to those of Agtr1a-/- mice. Using mouse embryonic fibroblasts derived from Agtr1a+/+ and Agtr1a-/- mice, we found no significant difference between genotypes in the ability to differentiate into lipid-laden mature adipocytes. In primary cultures of mouse mature adipocytes, AII increased the expression of mRNAs for some adipocytokines, which was abolished by pharmacological blockade of Agtr1. This study demonstrates that Agtr1a-/- mice exhibit attenuation of diet-induced weight gain and adiposity through increased energy expenditure. The data also suggest that AII does not affect directly adipocyte differentiation, but can modulate adipocytokine production via Agtr1.     

Interleukin-6 regulates human adipose tissue lipid metabolism and leptin production in vitro

Adipose tissue IL-6 expression is increased in obesity and is a strong predictor of abnormalities in adipocyte and systemic metabolism. We used adipose tissue organ culture to test the direct effects of IL-6 on leptin expression, lipolysis, and lipoprotein lipase activity. To assess possible interactions with the hormonal milieu, IL-6 effects were tested in the presence or absence of insulin and/or glucocorticoid [dexamethasone (dex)]. Because omental (Om) and abdominal sc depots differ in IL-6 expression, their responses to exogenous IL-6 were compared. Although IL-6 had no significant effects under basal conditions, culture with the combination of IL-6 and dex, compared with dex alone, for 2 d increased leptin in both depots [+95 +/- 30% (sc) and +67 +/- 19% (Om), P < 0.01]; IL-6 did not affect leptin production when added in the presence of insulin. Culture with IL-6 in the absence of hormones moderately increased lipolysis during culture in both sc and Om [+79 +/- 23% (sc) and +26 +/- 9% (Om), each P < 0.01]. IL-6 markedly reduced the high levels of lipoprotein lipase activity in tissue cultured with insulin plus dex. We conclude that high local concentrations of IL-6 can modulate leptin production and lipid metabolism in human adipose tissue.     

Leptin production in adipocytes from morbidly obese subjects: stimulation by dexamethasone, inhibition with troglitazone, and influence of gender

This study examined the regulation of leptin production by dexamethasone and troglitazone. Subcutaneous and omental adipose tissue was obtained during bariatric surgical procedures (30 women and 16 men; body mass index, 52.5 +/- 1.7 kg/m2, age, 39 +/- 2 yr), and adipocytes were cultured in suspension. Subcutaneous adipocytes from females released significantly more leptin than did omental cells from the same subject (P < 0.05), but basal leptin release was not different in adipocytes from these depots in males. Dexamethasone (0.1 micromol/L) significantly increased leptin release within 24 h from sc (135 +/- 13% of control) and omental (227 +/- 53%) adipocytes of females, but not males. Dexamethasone-stimulated leptin production at 48 h was significantly greater in the omental adipocytes of females (398 +/- 64% of control) than in sc adipocytes of females (207 +/- 21%) or the omental (211 +/- 33%) and sc (180 +/- 23%) adipocytes of males. Troglitazone (10 micromol/L; 48 h) significantly inhibited dexamethasone-stimulated leptin release in sc (57 +/- 10.7% inhibition) and omental adipocytes (134 +/- 26% inhibition). There was no gender-related difference in the effect of troglitazone to inhibit dexamethasone-stimulated leptin release. Troglitazone significantly inhibited basal leptin production from omental adipocytes by 15.0 +/- 5.2%. The effect of dexamethasone and troglitazone to regulate leptin release was mediated through changes in ob gene expression, but did not involve changes in glucose uptake or metabolism to lactate. The data suggest that adipocytes from females are more responsive to the stimulatory effect of dexamethasone in vitro than are adipocytes from males. If adipocytes from females are more responsive to relevant in vivo stimuli for leptin secretion such as insulin or glucose, this could contribute to the gender difference in serum leptin. The data also suggest that leptin release from omental adipocytes may be more responsive to hormonal and nutrient regulation in vivo than are sc adipocytes.     

Raised serum, adipocyte, and adipose tissue retinol-binding protein 4 in overweight women with polycystic ovary syndrome: effects of gonadal and adrenal steroids

CONTEXT: Polycystic ovary syndrome (PCOS) is associated with insulin resistance and obesity. Recent studies have shown that serum retinol-binding protein 4 (RBP4) levels increase with obesity. Currently, no data exist on the relative expression of RBP4 in either serum or adipose tissue of PCOS women. OBJECTIVES: mRNA expression of RBP4 from sc and omental (om) adipose tissue and sc adipocytes in overweight PCOS women were compared with matched controls; RBP4 protein in adipose tissue and serum RBP4 levels were also assessed. Additionally, we studied the effects of testosterone, 17beta-estradiol, androstenedione, and dehydroepiandrosterone sulfate on RBP4 expression in adipose tissue explants. DESIGN: Real-time RT-PCR and Western blotting were used to assess the relative mRNA and protein expression of RBP4. Biochemical measurements were also performed. RESULTS: Compared with controls, there was significant up-regulation of RBP4 mRNA in sc (P < 0.05) and om (P < 0.01) adipose tissue as well as isolated sc adipocytes (P < 0.01) of PCOS women. In addition to elevated serum RBP4 levels in PCOS women (P < 0.05), RBP4 protein levels were significantly greater in sc and om adipose tissue of PCOS women (P < 0.05 and P < 0.05, respectively). Furthermore, in human sc and om adipose tissue explants, 17beta-estradiol significantly increased RBP4 mRNA expression, protein levels, and secretion into the culture media (P < 0.05). CONCLUSIONS: The precise reason for elevated levels of RBP4 in overweight PCOS women is unknown, but it appears that 17beta-estradiol may play a role in their regulation in adipose tissue.     

Adipocyte precursor cells in obese and nonobese humans

Adipose precursors isolated from the stromal-vascular fraction of omental and subcutaneous adipose tissue, from defined hyperplastic obese and nonobese human adults were cultured in order to measure and compare replication rates. After multiplication to confluence these cells were also cultured in an enriched viscous suspension medium to optimize the expression of these cells to adipocytes, allowing an estimation of the number of cells having the ability to express an adipocyte phenotype. No difference in replication rate was seen between obese and nonobese donors or when adipocyte precursors from different depots were compared. When cells were allowed to develop fully in the enriched medium, approximately 6.5% of the original inoculated cell population exhibited an adipocyte morphology. Thus, these results suggest that environmental rather than genetic factors may be responsible for the hyperplasia seen in certain massively obese humans. Furthermore, the results indicate that fat-free cells found within the stromal-vascular fraction of adipose tissue have the ability to develop into adipocytes. However, it is suggested that the relatively low yield in obtaining fully differentiated fat cells under these conditions may be due to the heterogeneity of adipose related cells within the original stromal-vascular fraction from which these cultures were initially derived.     

Effects of systemic growth hormone (GH) administration on regional adipose tissue in children with non-GH-deficient short stature.

Chronic administration of exogenous GH to GH-deficient children is associated with a selective depletion of the abdominal sc fat depot and a resultant relative increase in gluteal, relative to abdominal, adipocyte lipid content. In GH-deficient children, the degree of this change in relative lipid content per adipocyte appears to be correlated with decreases in sensitivity of abdominal subcutaneous fat to the antilipolytic action of insulin. We studied abdominal and gluteal sc adipose tissue from 10 children with short stature (height less than 5% ile, growth velocity less than 5 cm/yr, bone age delayed at least 2 yr), who were not GH deficient based upon provocative testing (non-GH-deficient short stature) 1) before beginning and 2) after 3 months of therapy with exogenous GH (Humatrope, 0.1 mg/kg sc 3 times/week). In abdominal and gluteal adipocytes, we measured lipid content, rates of reesterification of fatty acids released by ongoing lipolysis and rates of in vitro lipolysis and lipogenesis in response to insulin, adenosine, and various adrenoreceptor agonists. These biochemical measures were correlated with measures of statural growth and adipose tissue distribution in each subject. We found that GH therapy was associated with a significant reduction in abdominal adipocyte size (0.48 microgram +/- 0.08 lipid per cell prior to therapy vs. 0.43 microgram +/- 0.08 lipid per cell after therapy, P less than 0.05) and a significant increase in responsiveness of gluteal sc adipose tissue to the lipogenic actions of insulin. The significant correlations of changes in abdominal adipocyte volume with changes in regional adipose tissue insulin sensitivity that were noted in GH-deficient children were not noted in this subject population, perhaps due to effects of endogenous GH on pretreatment insulin responsiveness of adipose tissue. These data reaffirm that GH has site-specific effects on regional adipose tissue depots.     

Expression and activity of 20alpha-hydroxysteroid dehydrogenase (AKR1C1) in abdominal subcutaneous and omental adipose tissue in women

We examined the expression and activity of 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) in abdominal adipose tissue in women. This recently characterized enzyme from the aldoketoreductase 1C family is responsible for the conversion of progesterone into 20alpha-hydroxyprogesterone. Abdominal sc (SC) and omental (OM) adipose tissue biopsies were obtained from a sample of 32 women aged 47.7 +/- 5.9 yr (body mass index 27.6 +/- 5.0 kg/m(2)) undergoing abdominal hysterectomies. Body composition and body fat distribution measurements were performed before the surgery by dual-energy x-ray absorptiometry and computed tomography, respectively. The expression of 20alpha-HSD was determined by real-time RT-PCR, and its activity was measured in whole-tissue homogenates. mRNA and activity of the enzyme were detected in both the SC and OM fat depots, the two measures being significantly higher in the SC compartment. Women characterized by a visceral adipose tissue area of 100 cm(2) or greater had an increased 20alpha-HSD conversion rate in their OM adipose tissue, compared with women without visceral obesity (13.99 +/- 2.07 vs. 7.92 +/- 0.83 fmol/microg protein per 24 h, P < 0.05). Accordingly, a positive correlation was found between OM adipose tissue 20alpha-HSD activity and computed tomography-measured visceral adipose tissue area (r = 0.36, P < 0.05). Significant positive correlations were also found between OM 20alpha-HSD activity and OM adipocyte diameter (r = 0.49, P < 0.05) and OM adipose tissue LPL activity (r = 0.36, P = 0.06). In conclusion, 20alpha-HSD activity and mRNA were detected in SC and OM adipose tissue in women, and OM 20alpha-hydroxylation of progesterone was highest in women with visceral obesity. Additional studies are required to establish whether local conversion of progesterone may impact on the metabolism and function of adipocytes located within the abdominal cavity.     

De novo generation of white adipocytes from the myeloid lineage via mesenchymal intermediates is age,adipose depot,and gender specific

It is generally assumed that white adipocytes arise from resident adipose tissue mesenchymal progenitor cells. We challenge this paradigm by defining a hematopoietic origin for both the de novo development of a subset of white adipocytes in adults and a previously uncharacterized adipose tissue resident mesenchymal progenitor population. Lineage and cytogenetic analysis revealed that bone marrow progenitor (BMP)-derived adipocytes and adipocyte progenitors arise from hematopoietic cells via the myeloid lineage in the absence of cell fusion. Global gene expression analysis indicated that the BMP-derived fat cells are bona fide adipocytes but differ from conventional white or brown adipocytes in decreased expression of genes involved in mitochondrial biogenesis and lipid oxidation, and increased inflammatory gene expression. The BMP-derived adipocytes accumulate with age, occur in higher numbers in visceral than in subcutaneous fat, and in female versus male mice. BMP-derived adipocytes may, therefore, account in part for adipose depot heterogeneity and detrimental changes in adipose metabolism and inflammation with aging and adiposity.     

Increased visfatin messenger ribonucleic acid and protein levels in adipose tissue and adipocytes in women with polycystic ovary syndrome: parallel increase in plasma visfatin

CONTEXT: Polycystic ovary syndrome (PCOS) is a multifaceted metabolic disease linked with insulin resistance (IR) and obesity. Recent studies have shown that plasma levels of the insulin-mimetic adipokine visfatin increase with obesity. Currently, no data exist on the relative expression of visfatin in either plasma or adipose tissue of PCOS women. OBJECTIVES: We investigated the mRNA expression of visfatin from sc and omental (om) adipose tissue and sc adipocytes in women with PCOS compared with matched normal women, as well as visfatin protein in adipose tissue; plasma visfatin was also assessed. DESIGN: Real-time RT-PCR and Western blotting were used to assess the relative mRNA and protein expression of visfatin. Biochemical measurements were performed. RESULTS: There was significant up-regulation of visfatin mRNA in both sc (P < 0.05) and om (P < 0.05) adipose tissue of PCOS women, when compared with normal controls; these findings were also reflected in isolated sc adipocytes (PCOS > controls; P < 0.05). In addition to elevated plasma visfatin levels in women with PCOS (mean +/- sd, 30.2 +/- 10.4 vs. 11.2 +/- 6.2 ng/ml; P < 0.01) when compared with normal controls, visfatin protein levels were significantly greater in both sc and om adipose tissue of PCOS women (P < 0.05 and P < 0.01, respectively). CONCLUSIONS: The precise reason for the up-regulation of visfatin seen in women with PCOS, a proinflammatory state, is unknown. Additional studies are needed to clarify the potential role of visfatin in the pathophysiology of PCOS.