Secretion of angiogenic and antiapoptotic factors by human adipose stromal cells.

BACKGROUND: The delivery of autologous cells to increase angiogenesis is emerging as a treatment option for patients with cardiovascular disease but may be limited by the accessibility of sufficient cell numbers. The beneficial effects of delivered cells appear to be related to their pluripotency and ability to secrete growth factors. We examined nonadipocyte stromal cells from human subcutaneous fat as a novel source of therapeutic cells. METHODS AND RESULTS: Adipose stromal cells (ASCs) were isolated from human subcutaneous adipose tissue and characterized by flow cytometry. ASCs secreted 1203+/-254 pg of vascular endothelial growth factor (VEGF) per 10(6) cells, 12 280+/-2944 pg of hepatocyte growth factor per 10(6) cells, and 1247+/-346 pg of transforming growth factor-beta per 10(6) cells. When ASCs were cultured in hypoxic conditions, VEGF secretion increased 5-fold to 5980+/-1066 pg/10(6) cells (P=0.0016). The secretion of VEGF could also be augmented 200-fold by transfection of ASCs with a plasmid encoding VEGF (P<0.05). Conditioned media obtained from hypoxic ASCs significantly increased endothelial cell growth (P<0.001) and reduced endothelial cell apoptosis (P<0.05). Nude mice with ischemic hindlimbs demonstrated marked perfusion improvement when treated with human ASCs (P<0.05). CONCLUSIONS: Our experiments delineate the angiogenic and antiapoptotic potential of easily accessible subcutaneous adipose stromal cells by demonstrating the secretion of multiple potentially synergistic proangiogenic growth factors. These findings suggest that autologous delivery of either native or transduced subcutaneous ASCs, which are regulated by hypoxia, may be a novel therapeutic option to enhance angiogenesis or achieve cardiovascular protection.

Obesity is associated with increased levels of circulating hepatocyte growth factor.

OBJECTIVES: This study evaluated whether obesity in humans was associated with an increase in circulating hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) levels. BACKGROUND: Obesity acts as a cardiovascular risk factor by mechanisms that are not fully understood. Adipose tissue is able to secrete multiple cytokines and growth factors ex vivo. We hypothesized that the increased presence of adipose tissue in obese subjects results in systemic elevations of the mitogenic factors HGF and VEGF. METHODS: Blood samples were obtained from lean (n = 21) and obese (n = 44) volunteers. Serum HGF and VEGF levels were assessed by enzyme-linked immunoadsorbent assay. Insulin and fasting glucose levels were measured to evaluate insulin sensitivity. Conditioned medium of adipose cells was assayed for HGF secretion. RESULTS: Serum HGF levels in obese subjects were more than three-fold higher than those of lean subjects (2,462 +/- 184 pg/ml vs. 765 +/- 48 pg/ml, p < 0.0001). The VEGF levels were not significantly elevated in obese subjects (135 +/- 31 pg/ml vs. 128 +/- 37 pg/ml). The HGF concentrations, but not VEGF concentrations, were significantly correlated with body mass index (BMI) (p < 0.0001, r = 0.74). The observed increases in HGF concentrations of obese subjects were not secondary to insulin resistance or hypertension. Freshly isolated human adipose cells secreted HGF. CONCLUSIONS: Our results indicate that obesity is associated with a marked increase in circulating HGF levels, which correlate linearly with BMI. Because vascular growth factors have been associated with the pathogenesis of atherosclerosis, the possible role of such humoral factors as a link between obesity and cardiovascular disease is very intriguing.

Serum resistin (FIZZ3) protein is increased in obese humans.

The role of resistin in obesity and insulin resistance in humans is controversial. Therefore, resistin protein was quantitated by ELISA in serum of 27 lean [13 women/14 men, body mass index (BMI) 21.7 +/- 0.4 kg/m(2), age 33 +/- 2 yr] and 50 obese (37 women/13 men, BMI 49.8 +/- 1.5 kg/m(2), age 47 +/- 1 yr) subjects. There was more serum resistin protein in the obese (mean +/- SEM: 5.3 +/- 0.4 ng/ml; range 1.8-17.9) than lean subjects (3.6 +/- 0.4 ng/ml; range 1.5-9.9; P = 0.001). The elevation of serum resistin in obese humans was confirmed by Western blot as was expression of resistin protein in human adipose tissue and isolated adipocytes. There was a significant positive correlation between resistin and BMI (r = 0.37; P = 0.002). Multiple regression analysis with predictors BMI and resistin explained 25% of the variance in homeostasis model assessment of insulin resistance score. BMI was a significant predictor of insulin resistance (P = 0.0002), but resistin adjusted for BMI was not (P = 0.11). The data demonstrate that resistin protein is present in human adipose tissue and blood, and that there is significantly more resistin in the serum of obese subjects. Serum resistin is not a significant predictor of insulin resistance in humans.

Adipose tissue production of hepatocyte growth factor contributes to elevated serum HGF in obesity.

Serum HGF is elevated in obese individuals. This study examined the contribution of excess adipose tissue to increased circulating HGF levels in obesity. Serum HGF was measured by ELISA before and after weight loss due to bariatric surgery or a 24-h fast. At 6.1 +/- 0.1 mo following surgery, BMI (50.6 +/- 1.6 vs. 35.1 +/- 1.3 kg/m(2); P < 0.0001) and serum HGF were significantly decreased (1,164 +/- 116 vs. 529 +/- 39 pg/ml, P < 0.001). A 24-h fast did not change serum HGF, but serum leptin was significantly reduced (67.7 +/- 7.1 vs. 50.3 +/- 8.3 ng/ml, P = 0.02). HGF secretion in vitro from adipocytes of obese (BMI 40.3 +/- 2.8 kg/m(2)) subjects was significantly greater (80.9 +/- 10.4 vs. 21.5 +/- 4.0 pg/10(5) cells, P = 0.008) than release from adipocytes of lean (BMI 23.3 +/- 1.4 kg/m(2)) subjects. HGF mRNA levels determined by real-time RT-PCR were not different in adipocytes from lean (BMI 24.0 +/- 0.8 kg/m(2)) and obese (45.7 +/- 3.0 kg/m(2)) subjects, but serum HGF was significantly elevated in the obese individuals studied (787 +/- 61 vs. 489 +/- 49 pg/ml, P = 0.001). TNF-alpha (24 h treatment) significantly increased HGF release from subcutaneous adipocytes 23.6 +/- 8.3% over control (P = 0.02). These data suggest that elevated serum HGF in obesity is in part attributable to excess adipose tissue and that this effect can be reversed by reducing adipose tissue mass through weight loss. Increased HGF secretion from adipocytes of obese subjects may be due to posttranscriptional events possibly related to adipocyte size and stimulation by elevated TNF-alpha in the adipose tissue of obese individuals.

Regulation of adiponectin expression in human adipocytes: effects of adiposity, glucocorticoids, and tumor necrosis factor alpha.

OBJECTIVE: Adiponectin mRNA expression in isolated subcutaneous and omental adipocytes was examined across a wide range of adiposity to determine whether adiponectin synthesis is impaired in these adipose tissue depots in obese humans. Tumor necrosis factor (TNF)alpha and dexamethasone were tested for inhibitory effects on adiponectin release from human adipocytes in vitro. RESEARCH METHODS AND PROCEDURES: Adipocytes were isolated by collagenase digestion of abdominal adipose tissue obtained from subjects undergoing surgical procedures or outpatient needle biopsy. Adiponectin and leptin mRNA were quantitated by real-time reverse transcriptase-polymerase chain reaction. Adiponectin and leptin secretion from isolated adipocytes treated with dexamethasone or TNFalpha were determined by radioimmunoassay. RESULTS: There was a significant negative correlation between adiponectin gene expression and BMI in subcutaneous adipocytes from 32 women (r = 0.420; p = 0.02). Adiponectin mRNA was also significantly correlated with serum adiponectin (r = 0.44; p = 0.03; n = 25). There was no correlation between adiponectin mRNA expression and BMI in omental adipocytes from 29 women. Leptin mRNA was significantly and positively correlated (r = 0.484; p = 0.01) with BMI in the same omental adipocyte mRNA preparations. In subcutaneous adipocytes from lean subjects, TNFalpha inhibited adiponectin release by 7.4 +/- 1.2% (n = 9, p < 0.05) but had no effect on adiponectin release from subcutaneous or omental adipocytes from obese subjects. Dexamethasone significantly inhibited adiponectin release with 24 hours of treatment. DISCUSSION: The data suggest that reduced adiponectin synthesis in subcutaneous adipocytes contributes to lower serum adiponectin levels in obesity and that glucocorticoids regulate adiponectin gene expression in human adipocytes. TNFalpha does not seem to directly inhibit adiponectin synthesis in human adipocytes.

Lower serum adiponectin levels in African-American boys.

OBJECTIVE: To examine adiponectin, an adipocyte-secreted hormone with anti-inflammatory and insulin-sensitizing effects, in relation to race or gender in younger subjects. RESEARCH METHODS AND PROCEDURES: The relationship of adiponectin, quantitated by radioimmunoassay, to anthropometric and metabolic factors (fasting insulin, glucose, and leptin) and reproductive hormones was examined in 46 healthy African Americans (25 girls/21 boys) and 40 whites (20 girls/20 boys) ranging in age from 12 to 21 years. RESULTS: There was no statistical difference in BMI or in BMI percentile among the four groups. Sums of skinfolds, but not skinfold percentile, were significantly lower in boys than girls (p = 0.001 and p = 0.896, respectively), whereas there was no difference between racial groups. Leptin was significantly greater in girls (p = 0.0002). There was no difference in fasting serum glucose, insulin, or homeostasis model assessment score among any of the groups. There was a significant negative univariate relationship between serum adiponectin and both BMI and BMI percentile for the entire group (p = 0.006 and p = 0.005). In a multivariate model, BMI percentile (p = 0.005) and the interaction between race and gender (p = 0.026) were significant predictors of serum adiponectin. In this model, African-American boys had the lowest serum adiponectin level, 37% less than white boys, who had the highest adiponectin levels. DISCUSSION: Serum adiponectin levels are reduced in young obese subjects (African Americans and whites) and are lower in African-American boys than white boys. A lower adiponectin level in African-American boys may predispose this group to a greater risk of diabetes and cardiovascular disease.