Adipose Tissue Explants Research Articles

Anti-inflammatory effect of resveratrol on adipokine expression and secretion in human adipose tissue explants

Human obesity is closely associated with a state of chronic low-grade inflammation, which also involves the adipose tissue with enhanced production of bioactive substances (adipokines). Calorie restriction (CR) reduces adipocytokine production and improves metabolic profile in rodents. Some of these effects are mediated through activation of the sirtuin 1 (Sirt1) enzyme, and in this study, we investigate whether the natural phytoalexin, resveratrol (RSV), which is a potent Sirt1 activator, has anti-inflammatory effects in human adipose tissue explants. The effect of RSV on interleukin 1β (IL1β)-induced change of adipokine mRNA gene expression and secretion were measured in human adipose tissue explants. Exposure of human adipose tissue in vitro to IL1β for 24 h increased secretion of the proinflammatory adipokines IL6, IL8 and monocyte chemoattractant protein 1 (MCP-1) 3-7.7-fold (P<0.05) and increased IL6, IL8, MCP-1, IL1β and PAI-1 mRNA expression 1.3-7.2-fold (P<0.05) accordingly. Concomitant incubations with RSV reversed the IL1β-stimulated secretion (16-36%) and gene expression (25-48%) of these adipokines. IL1β reduced adiponectin mRNA expression (40%), a decrement that was reversed by RSV treatment. Similar effects were observed in differentiated human preadipocytes in primary culture, indicating that human adipocytes are a potential target for RSV effects. Finally, the effects were neutralized by sirtinol, a Sirt1 inhibitor. This study is the first to show anti-inflammatory effects of RSV on adipokine expression and secretion in human adipose tissue in vitro through the SIRT1 pathway. Thus, RSV is hypothesized to possess beneficial effects and might improve the metabolic profile in human obesity.

Identification of Nesfatin-1 in Human and Murine Adipose Tissue: A Novel Depot-Specific Adipokine with Increased Levels in Obesity

Nesfatin-1 is a recently identified anorexigenic peptide derived from its precursor protein, nonesterified fatty acid/nucleobindin 2 (NUCB2). Although the hypothalamus is pivotal for the maintenance of energy homeostasis, adipose tissue plays an important role in the integration of metabolic activity and energy balance by communicating with peripheral organs and the brain via adipokines. Currently no data exist on nesfatin-1 expression, regulation, and secretion in adipose tissue. We therefore investigated NUCB2/nesfatin-1 gene and protein expression in human and murine adipose tissue depots. Additionally, the effects of insulin, dexamethasone, and inflammatory cytokines and the impact of food deprivation and obesity on nesfatin-1 expression were studied by quantitative RT-PCR and Western blotting. We present data showing NUCB2 mRNA (P < 0.001), nesfatin-1 intracellular protein (P < 0.001), and secretion (P < 0.01) were significantly higher in sc adipose tissue compared with other depots. Also, nesfatin-1 protein expression was significantly increased in high-fat-fed mice (P < 0.01) and reduced under food deprivation (P < 0.01) compared with controls. Stimulation of sc adipose tissue explants with inflammatory cytokines (TNFalpha and IL-6), insulin, and dexamethasone resulted in a marked increase in intracellular nesfatin-1 levels. Furthermore, we present evidence that the secretion of nesfatin-1 into the culture media was dramatically increased during the differentiation of 3T3-L1 preadipocytes into adipocytes (P < 0.001) and after treatments with TNF-alpha, IL-6, insulin, and dexamethasone (P < 0.01). In addition, circulating nesfatin-1 levels were higher in high-fat-fed mice (P < 0.05) and showed positive correlation with body mass index in human. We report that nesfatin-1 is a novel depot specific adipokine preferentially produced by sc tissue, with obesity- and food deprivation-regulated expression.

Differences in AMPK expression between subcutaneous and visceral adipose tissue in morbid obesity

Adenine monophosphate (AMP) activated protein kinase (AMPK) is an important regulator of obesity. The objective of the present work was to study and compare AMPK protein expression in visceral vs. subcutaneous adipose tissue of morbid obese subjects and to correlate it with adipose tissue characteristics. We selected a total population of 17 extreme obese (BMI ≥ 40 kg/m 2) aged 42.8 ± 10.2 years were included in this study. We measured anthropometric and body composition parameters. Adiponectin expression by qRT-PCR, isoproterenol-stimulated lipolytic rates, and AMPK alpha subunits expression by Western blot in adipose tissue explants were determined. Finally plasma concentrations of glucose, triacylglycerols, total cholesterol, HDL-c, LDL-c and insulin were also measured. Our results showed that AMPK alpha expression was higher in subcutaneous than in visceral tissue. A positive correlation between AMPK expression and adiponectin expression in human subcutaneous adipose tissue was observed. Furthermore, a positive correlation between AMPK expression and isoproterenol evoked upregulation of lipolysis rate was also observed. In conclusion, AMPK alpha expression differed according to adipose tissue location. The positive correlation between subcutaneous adipose tissue AMPK and adiponectin or the evoked lipolysis rate could indicate a protective role of AMPK in this tissue, counteracting insulin resistance in morbid obese patients.

Release of 12 Adipokines by Adipose Tissue, Nonfat Cells, and Fat Cells From Obese Women

The relative release in vitro of endothelin-1, zinc-alpha2-glycoprotein (ZAG), lipocalin-2, CD14, RANTES (regulated on activation, normal T cell expressed and secreted protein), lipoprotein lipase (LPL), osteoprotegerin (OPG), fatty acid-binding protein 4 (FABP-4), visfatin/PBEF/Nampt, glutathione peroxidase-3 (GPX-3), intracellular cell adhesion molecule 1 (ICAM-1), and amyloid A was examined using explants of human adipose tissue as well as the nonfat cell fractions and adipocytes from obese women. Over a 48-h incubation the majority of the release of LPL was by fat cells whereas that of lipocalin-2, RANTES, and ICAM-1 was by the nonfat cells present in human adipose tissue. In contrast appreciable amounts of OPG, amyloid A, ZAG, FABP-4, GPX-3, CD14, and visfatin/PBEF/Nampt were released by both fat cells and nonfat cells. There was an excellent correlation (r = 0.75) between the ratios of adipokine release by fat cells to nonfat cells over 48 h and the ratio of their mRNAs in fat cells to nonfat cells at the start of the incubation. The total release of ZAG, OPG, RANTES, and amyloid A by incubated adipose tissue explants from women with a fat mass of 65 kg was not different from that by women with a fat mass of 29 kg. In contrast that of ICAM-1, FABP-4, GPX-3, visfatin/PBEF/Nampt, CD14, lipocalin-2, LP, and endothelin-1 was significantly greater in tissue from women with a total fat mass of 65 kg.

Simultaneous presence of Ins2C96Y mutation uncovers the insulin resistance phenotype in the adipose tissue of PPARγP465L female mice

Mutations in Peroxisome Proliferator Activated Receptor‐γ (PPARγ) affect adipose tissue and insulin sensitivity. The heterozygous PPARγP467L (L/+) mutation was originally identified in insulin resistant patients. Yet, L/+ mice have normal plasma glucose and insulin sensitivity. They have mild hyperinsulinemia and increased pancreatic islet mass, especially on high‐fat diet. We hypothesized that L/+ mutation leads to insulin resistance; however the hyperinsulinemia in mice compensates for it to retain normal plasma glucose. Thus, we introduced Ins2C96Y (akita, A/+) mutation, which reduces plasma insulin, in L/+ mice. Unlike +/+;A/+ littermates, male L/+;A/+ mice have dramatically reduced life span. When compared with +/+;A/+ mice, female L/+;A/+ mice have significant hyperglycemia, smaller pancreatic islets, reduced plasma insulin levels and upregulated gluconeogenesis. In an Insulin Tolerance Test, female L/+;A/+ mice have a smaller reduction in plasma glucose indicating impaired sensitivity to insulin. Adipose tissue explants from L/+;A/+ mice have impaired glucose uptake in response to exogenous insulin. Thus, insulin resistance phenotype can indeed be attributable to L/+ mutation. Our data also provides an excellent mouse model to study diabetes in the context of gender specific physiology.

The G 0/G 1 Switch Gene 2 Regulates Adipose Lipolysis through Association with Adipose Triglyceride Lipase

Adipose triglyceride lipase (ATGL) is the rate-limiting enzyme for triacylglycerol (TAG) hydrolysis in adipocytes. The precise mechanisms whereby ATGL is regulated remain uncertain. Here, we demonstrate that a protein encoded by G(0)/G(1) switch gene 2 (G0S2) is a selective regulator of ATGL. G0S2 is highly expressed in adipose tissue and differentiated adipocytes. When overexpressed in HeLa cells, G0S2 localizes to lipid droplets and prevents their degradation mediated by ATGL. Moreover, G0S2 specifically interacts with ATGL through the hydrophobic domain of G0S2 and the patatin-like domain of ATGL. More importantly, interaction with G0S2 inhibits ATGL TAG hydrolase activity. Knockdown of endogenous G0S2 accelerates basal and stimulated lipolysis in adipocytes, whereas overexpression of G0S2 diminishes the rate of lipolysis in both adipocytes and adipose tissue explants. Thus, G0S2 functions to attenuate ATGL action both in vitro and in vivo and by this mechanism regulates TAG hydrolysis.

Cathepsins in Human Obesity: Changes in Energy Balance Predominantly Affect Cathepsin S in Adipose Tissue and in Circulation

Context: Recent studies in humans and mice suggest the implication of the cysteine proteases cathepsins S, L, and K in vascular and metabolic complications of obesity. Objective: Our objective was to identify clinically relevant forms of cathepsin in human obesity. Design and Setting: We conducted a prospective study on two independent cohorts. Participants and Interventions: The first cohort includes 45 obese women eligible for gastric surgery (age, 39 ± 1.6 yr; body mass index, 47 ± 0.99 kg/m2) and 17 nonobese women (age, 38 ± 1.8 yr; body mass index, 21 ± 0.44 kg/m2). The second cohort comprises 29 obese women (age, 57 ± 0.8 yr; body mass index, 34 ± 0.69 kg/m2) undergoing 6 months of medically supervised caloric restriction. Main Outcomes: Cathepsin S, L, and K mRNA levels were determined in surgical adipose tissue biopsies. The proteins were measured in conditioned medium of adipose tissue explants and in circulation. Results: Obese subjects had a 2-fold increase in cathepsin S mRNA in adipose tissue...

Cathepsins in Human Obesity: Changes in Energy Balance Predominantly Affect Cathepsin S in Adipose Tissue and in Circulation

Recent studies in humans and mice suggest the implication of the cysteine proteases cathepsins S, L, and K in vascular and metabolic complications of obesity. Our objective was to identify clinically relevant forms of cathepsin in human obesity. We conducted a prospective study on two independent cohorts. The first cohort includes 45 obese women eligible for gastric surgery (age, 39 +/- 1.6 yr; body mass index, 47 +/- 0.99 kg/m(2)) and 17 nonobese women (age, 38 +/- 1.8 yr; body mass index, 21 +/- 0.44 kg/m(2)). The second cohort comprises 29 obese women (age, 57 +/- 0.8 yr; body mass index, 34 +/- 0.69 kg/m(2)) undergoing 6 months of medically supervised caloric restriction. Cathepsin S, L, and K mRNA levels were determined in surgical adipose tissue biopsies. The proteins were measured in conditioned medium of adipose tissue explants and in circulation. Obese subjects had a 2-fold increase in cathepsin S mRNA in adipose tissue as compared with normal-weight subjects and an increased rate (1.5-fold) of cathepsin S release in adipose tissue explants. Cathepsin S circulating concentrations were increased with obesity (+30%) and reduced after weight reduction (P < 0.05 for both). By contrast, cathepsin L was unaffected in adipose tissue and serum; cathepsin K was undetectable in circulation and unchanged in adipose tissue. In humans, cathepsin S is more influenced than cathepsins L and K by changes in energy balance in adipose tissue and circulation. This opens new avenues to explore whether selective inhibition of this protease could reduce cardiovascular risk and ameliorate metabolic status in obese subjects.

Effect of Triiodothyronine on Adiponectin Expression and Leptin Release by White Adipose Tissue of Normal Rats

Previous studies have shown that alterations in thyroid status may lead to changes in serum leptin and adiponectin, both in humans and rodents. The mechanisms, especially for adiponectin, are unclear. In the present study, we investigated the effect of triiodothyronine (T3) on the expression of adiponectin mRNA and the release of leptin and adiponectin by white adipose tissue (WAT) explants obtained from epididymal (visceral) or inguinal (subcutaneous) depots from normal rats. We also analyzed the effects of other known regulators of adiponectin and leptin release, such as rosiglitazone and dexamethasone. T3 acted directly at rat WAT explants in a depot-specific manner and in a unique fashion to each hormone. T3 was able to inhibit leptin release only by epididymal explants, and to reduce adiponectin mRNA expression only in inguinal explants. However, T3 was incapable of modifying adiponectin release by both explants. Additionally, rosiglitazone exhibited an inhibitory effect on adiponectin release by both WAT explants, even though adiponectin mRNA was importantly upregulated only in inguinal explants. Rosiglitazone acted as an inhibitor of leptin release by both studied fat depots, while only epididymal explants responded to the stimulatory effect of dexamethasone on leptin release. Therefore, the present model of isolated rat white adipose tissue explants highlights the fact that the regulation of hormonal production by white adipose tissue depends on the type of depot and its anatomical location. In this context, our results show for the first time a potential inhibitory effect of T3 on adiponectin mRNA expression specifically on WAT from a subcutaneous depot.

Effects of androgens on adipocyte differentiation and adipose tissue explant metabolism in men and women

To examine the effects of aromatizable or nonaromatizable androgens on abdominal subcutaneous (SC) and omental (OM) adipose tissue lipid metabolism and adipogenesis in men and women. Primary organ and preadipocyte cultures were established from surgical samples obtained in men (n = 22) and women undergoing biliopancreatic diversions (n = 12) or gynaecological surgeries (n = 8). Cultures were treated with testosterone, dihydrotestosterone (DHT) and methyltrienolone (R1881). Heparin-releasable lipoprotein lipase (HR-LPL) activity, glycerol release, adiponectin secretion, glycerol-3-phosphate dehydrogenase activity and lipid accumulation were measured. In organ cultures from men, DHT had a statistically significant inhibitory effect on HR-LPL activity in the OM compartment. Testosterone significantly inhibited HR-LPL activity in SC and OM cultures. In women, high DHT concentrations tended to inhibit HR-LPL activity in OM cultures. Minor androgenic effects were observed for basal and isoproterenol-stimulated lipolysis as well as adiponectin release in men. On the other hand, adipocyte differentiation was significantly and dose-dependently inhibited by DHT, testosterone and R1881 in SC and OM cultures from both sexes. These effects did not differ according to adipose tissue depot but appeared to be more pronounced in women than in men. Androgens slightly decreased HR-LPL activity in adipose tissue organ cultures, but markedly inhibited adipogenesis in SC and OM primary preadipocyte cultures in both sexes. Androgenic effects on adipose tissue in men vs. women may not differ in terms of direction but in the magnitude of their negative impact on adipogenesis and lipid synthesis.

The inflammatory response seen when human omental adipose tissue explants are incubated in primary culture is not dependent upon albumin and is primarily in the nonfat cells

BackgroundThe present studies were designed to investigate the changes in gene expression during in vitro incubation of human visceral omental adipose tissue explants as well as fat cells and nonfat cells derived from omental fat.MethodsAdipose tissue was obtained from extremely obese women undergoing bariatric surgery. Explants of the tissue as well as fat cells and the nonfat cells derived by digestion with collagenase were incubated for 20 minutes to 48 h. The expression of interleukin 1β [IL-1β], tumor necrosis factor α [TNFα], interleukin 8 [IL-8], NFκB1p50 subunit, hypoxia-inducible factor 1α [HIF1α], omentin/intelectin, and 11β-hydroxysteroid dehydrogenase 1 [11β-HSD1] mRNA were measured by qPCR as well as the release of IL-8 and TNFα.ResultsThere was an inflammatory response at 2 h in explants of omental adipose tissue that was reduced but not abolished in the absence of albumin from the incubation buffer for IL-8, IL-1β and TNFα. There was also an inflammatory response with regard to upregulation of HIF1α and NFκB1 gene expression that was unaffected whether albumin was present or absent from the medium. In the nonfat cells derived by a 2 h collagenase digestion of omental fat there was an inflammatory response comparable but not greater than that seen in tissue. The exception was HIF1α where the marked increase in gene expression was primarily seen in intact tissue. The inflammatory response was not seen with respect to omentin/intelectin. Over a subsequent 48 h incubation there was a marked increase in IL-8 mRNA expression and IL-8 release in adipose tissue explants that was also seen to the same extent in the nonfat cells incubated in the absence of fat cells.ConclusionThe marked inflammatory response seen when human omental adipose tissue is incubated in vitro is reduced but not abolished in the presence of albumin with respect to IL-1β, TNFα, IL-8, and is primarily in the nonfat cells of adipose tissue.

Effects of androgens on adipocyte differentiation and adipose tissue explant metabolism in men and women

Effects of androgens on adipocyte differentiation and adipose tissue explant metabolism in men and women

Human adenovirus-36 and non-alcoholic fatty liver disease

Human adenovirus-36 and non-alcoholic fatty liver disease

De novo fatty acid synthesis and NADPH generation in equine adipose and liver tissue

The lipogenic capacities of equine liver and adipose tissue explants were investigated in vitro. Preference for glucose or acetate as the primary carbon source for de novo fatty acid synthesis was determined using (14)C labeled substrates. Additional aims included determining the relative contribution of NADPH generating pathways to reducing equivalent generation and comparing the lipogenic activity of two adipose depots, mesenteric and subcutaneous harvested from the crest region of the neck. Mesenteric adipose tissue had greater lipogenic activity than subcutaneous adipose tissue, and liver tissue showed minimal (14)C incorporation into fatty acids, indicating a low hepatic lipogenic capacity. Acetate was found to be the primary carbon source for fatty acid synthesis due to both the appearance of the (14)C label in the lipid fraction and the low activity of ATP-citrate lyase. Finally, the pentose phosphate and isocitrate dehydrogenase enzymes contributed to NADPH production in equine adipose tissue.

Metabolic endotoxemia and saturated fat contribute to circulating NGAL concentrations in subjects with insulin resistance

Lipocalin-2 (neutrophil gelatinase-associated lipocalin, NGAL) is an innate immune system protein that has been linked to insulin resistance and obesity, but the mechanisms behind these associations are poorly known. We hypothesized that endotoxin (lipopolysaccharide, LPS) and fat intake were in the background of these associations. We studied four cohorts: (1) a cross-sectional study in 194 subjects; (2) the changes in NGAL concentration induced by diet and weight loss in 36 obese women (with circadian rhythm in 8 of them); (3) the effects of acute fat intake on circulating NGAL concentration in 42 morbidly obese subjects; and (4) LPS-induced NGAL secretion ex vivo (whole blood and adipose tissue explants). Serum NGAL concentration was significantly associated with fasting triglycerides and LPS-binding protein in patients with type 2 diabetes. In obese subjects, the intake of saturated fatty acids was the factor that best explained the variance of NGAL changes after weight loss (contributing independently to 14% of NGAL variance). In fact, weight loss significantly changed the circadian rhythm of NGAL. The acute increase in circulating NGAL after fat overload was significantly associated with fasting insulin (r=0.52, P<0.001), homeostasis model assessment of insulin resistance (HOMA-IR) (r=0.36, P=0.02) and post-load triglyceride concentrations (r=0.38, P=0.018). LPS-induced NGAL secretion from adipose tissue explants did not change significantly, but LPS led to a significant increase in NGAL concentration in the whole blood obtained from patients with type 2 diabetes. Metabolic endotoxemia and saturated fat might contribute to circulating NGAL concentration in patients with insulin resistance.

Potential Contribution of Adipose Tissue to Elevated Serum Cystatin C in Human Obesity

Cystatin C, an endogenous inhibitor of cathepsin proteases has emerged as a biomarker of cardiovascular risk and reduced renal function. Epidemiological studies indicate that serum cystatin C increased in human obesity. Here, we evaluated the contribution of adipose tissue to this elevation, based on our previous observation that cystatin C is produced by in vitro differentiated human adipocytes. We measured serum cystatin C in 237 nonobese (age: 51 +/- 0.8 years; BMI: 22.8 +/- 0.11 kg/m(2)) and 248 obese subjects (age: 50 +/- 0.8 years; BMI: 34.7 +/- 0.29 kg/m(2)). Creatinine-based estimated glomerular filtration rate (eGFR) was calculated to account for renal status. Cystatin C gene expression and secretion were determined on surgical adipose tissue biopsies in a distinct group of subjects. Serum cystatin C is elevated in obese subjects of both genders, independently of reduced eGFR. Cystatin C mRNA is expressed in subcutaneous and omental adipose tissue, at twice higher levels in nonadipose than in adipose cells. Gene expression and cystatin C release by adipose tissue explants increase two- to threefold in obesity. These data confirm elevation of serum cystatin C in human obesity and strongly argue for a contribution of increased production of cystatin C by enlarged adipose tissue. Because cystatin C has the potential to affect adipose tissue and vascular homeostasis through local and/or systemic inhibition of cathepsins, this study adds a new factor to the list of adipose tissue secreted bioactive molecules implicated in obesity and obesity-linked complications.

Dexamethasone and the inflammatory response in explants of human omental adipose tissue

Dexamethasone is a synthetic glucocorticoid that is a potent anti-inflammatory agent. The present studies examined the changes in gene expression of 64 proteins in human omental adipose tissue explants incubated for 48 h both in the absence and presence of dexamethasone as well as the release of 8 of these proteins that are putative adipokines. The proteins were chosen because they are inflammatory response proteins in other cells, are key regulatory proteins or are proteins with known functions. About 50% were significantly up-regulated while about 10% were unchanged and the remaining 40% were down-regulated. Dexamethasone significantly up-regulated the expression of about 33% of the proteins but down-regulated the expression of about 12% of the proteins. We conclude that dexamethasone is a selective anti-inflammatory agent since it inhibits only about one-fourth of the proteins up-regulated during in vitro incubation of human omental adipose tissue.

Chemerin Is a Novel Adipocyte-Derived Factor Inducing Insulin Resistance in Primary Human Skeletal Muscle Cells

OBJECTIVEChemerin is an adipokine that affects adipogenesis and glucose homeostasis in adipocytes and increases with BMI in humans. This study was aimed at investigating the regulation of chemerin release and its effects on glucose metabolism in skeletal muscle cells.RESEARCH DESIGN AND METHODSHuman skeletal muscle cells were treated with chemerin to study insulin signaling, glucose uptake, and activation of stress kinases. The release of chemerin was analyzed from in vitro differentiated human adipocytes and adipose tissue explants from 27 lean and 26 obese patients.RESULTSHuman adipocytes express chemerin and chemokine-like receptor 1 (CMKLR1) differentiation dependently and secrete chemerin (15 ng/ml from 106 cells). This process is slightly but significantly increased by tumor necrosis factor-α and markedly inhibited by >80% by peroxisome proliferator–activated receptor-γ activation. Adipose tissue explants from obese patients are characterized by significantly higher chemerin secretion compared with lean control subjects (21 and 8 ng from 107 cells, respectively). Chemerin release is correlated with BMI, waist-to-hip ratio, and adipocyte volume. Furthermore, higher chemerin release is associated with insulin resistance at the level of lipogenesis and insulin-induced antilipolysis in adipocytes. Chemerin induces insulin resistance in human skeletal muscle cells at the level of insulin receptor substrate 1, Akt and glycogen synthase kinase 3 phosphorylation, and glucose uptake. Furthermore, chemerin activates p38 mitogen-activated protein kinase, nuclear factor-κB, and extracellular signal–regulated kinase (ERK)-1/2. Inhibition of ERK prevents chemerin-induced insulin resistance, pointing to participation of this pathway in chemerin action.CONCLUSIONSAdipocyte-derived secretion of chemerin may be involved in the negative cross talk between adipose tissue and skeletal muscle contributing to the negative relationship between obesity and insulin sensitivity.

Obesity Promotes Inflammation in Periaortic Adipose Tissue and Angiotensin II-Induced Abdominal Aortic Aneurysm Formation

Obesity promotes macrophage infiltration into adipose tissue and is associated with increases in several cardiovascular diseases. Infusion of angiotensin II (AngII) to mice induces formation of abdominal aortic aneurysms (AAAs) with profound medial and adventitial macrophage infiltration. We sought to determine whether obesity promotes macrophage infiltration and proinflammatory cytokines in periaortic adipose tissue surrounding abdominal aortas and increases AngII-induced AAAs. Hypertrophied white adipocytes surrounded abdominal aortas, whereas brown adipocytes surrounded thoracic aortas of obese mice. mRNA abundance of macrophage proinflammatory chemokines and their receptors were elevated with obesity to a greater extent in abdominal compared to thoracic periaortic adipose tissue. Periaortic adipose tissue explants surrounding abdominal aortas of obese mice released greater concentrations of MCP-1 and promoted more macrophage migration than explants from thoracic aortas. Male C57BL/6 mice were fed a high-fat (HF) diet for 1, 2, or 4 months and then infused with AngII (1000 ng/kg/min) for 28 days. AAA incidence increased progressively with the duration of HF feeding (18%, 36%,and 60%, respectively). Similarly, AngII-infused ob/ob mice exhibited increased AAAs compared to lean controls (76% compared to 32%, respectively, P<0.05). Infusion of AngII to obese mice promoted further macrophage infiltration into periaortic and visceral adipose tissue, and obese mice exhibiting AAAs had greater macrophage content in visceral adipose tissue than mice not developing AAAs. Increased macrophage accumulation in periaortic adipose tissue surrounding abdominal aortas of AngII-infused obese mice is associated with enhanced AAA formation.

Regulation of the Fibrosis and Angiogenesis Promoter SPARC/Osteonectin in Human Adipose Tissue by Weight Change, Leptin, Insulin, and Glucose

OBJECTIVEMatricellular Secreted Protein, Acidic and Rich in Cysteine (SPARC), originally discovered in bone as osteonectin, is a mediator of collagen deposition and promotes fibrosis. Adipose tissue collagen has recently been found to be linked with metabolic dysregulation. Therefore, we tested the hypothesis that SPARC in human adipose tissue is influenced by glucose metabolism and adipokines.RESEARCH DESIGN AND METHODSSerum and adipose tissue biopsies were obtained from morbidly obese nondiabetic subjects undergoing bariatric surgery and lean control subjects for analysis of metabolic markers, SPARC, and various cytokines (RT-PCR). Additionally, 24 obese subjects underwent a very-low-calorie diet of 1,883 kJ (450 kcal)/day for 16 weeks and serial subcutaneous-abdominal-adipose tissue (SCAT) biopsies (weight loss: 28 ± 3.7 kg). Another six lean subjects underwent fast-food–based hyperalimentation for 4 weeks (weight gain: 7.2 ± 1.6 kg). Finally, visceral adipose tissue explants were cultured with recombinant leptin, insulin, and glucose, and SPARC mRNA and protein expression determined by Western blot analyses.RESULTSSPARC expression in human adipose tissue correlated with fat mass and was higher in SCAT. Weight loss induced by very-low-calorie diet lowered SPARC expression by 33% and increased by 30% in adipose tissue of subjects gaining weight after a fast-food diet. SPARC expression was correlated with leptin independent of fat mass and correlated with homeostasis model assessment–insulin resistance. In vitro experiments showed that leptin and insulin potently increased SPARC production dose dependently in visceral adipose tissue explants, while glucose decreased SPARC protein.CONCLUSIONSOur data suggest that SPARC expression is predominant in subcutaneous fat and its expression and secretion in adipose tissue are influenced by fat mass, leptin, insulin, and glucose. The profibrotic effects of SPARC may contribute to metabolic dysregulation in obesity.