Objective. Zinc-alpha 2-glycoprotein (ZAG) has been proposed as a tumour-derived cancer cachexia factor. However, ZAGis produced by some normal tissues, including white adipose tissue (WAT), and high serum ZAG levels are present in nonmalignant conditions. We determined whether human WAT contributes to serum ZAG levels and how serum and WAT-secreted ZAG levels correlate with catabolism in patients with cancer and in obese subjects undergoing a very low-calorie diet (VLCD) for 11 days.Design/subjects. ZAG levels in serum and in conditioned medium from WAT/adipocytes were determined by enzyme-linked immunosorbent assay. ZAG release from WAT in vivo was determined in 10 healthy subjects. The correlation between ZAG and cachexia was studied in 34 patients with newly diagnosed gastrointestinal cancer. The impact of a VLCD on ZAG release and serum levels was assessed in 10 obese women.Results. ZAG was released from abdominal WAT and adipocytes in vitro. However, the arteriovenous differences in vivo showed that there was no significant contribution of WAT to the circulating levels. WAT-secreted but not serum ZAG correlated positively with poor nutritional status but not with fat mass (or body mass index) in patients with gastrointestinal cancer. In obese subjects on a VLCD, ZAG secretion from WAT increased significantly whereas serum levels remained unaltered.Conclusions. ZAGis released from human WAT, but this tissue does not contribute significantly to the circulating levels. WAT-secreted ZAG correlates with nutritional status but not with fat mass in both cancer and nonmalignant conditions. Adipose ZAG is therefore a local factor activated primarily by the catabolic state per se.

Objective: Tartrate-resistant acid phosphatase (TRAP) expressed by adipose tissue macrophages (ATMs) induces mice obesity and human adipocyte differentiation in vitro . This study aimed to investigate whether TRAP was secreted differently from human obese versus lean adipose tissues and to identify the cellular source of adipose tissue TRAP. Design: Subcutaneous adipose tissues obtained from healthy subjects. Enzyme-linked immunosorbent assays (ELISAs) for total (5a+5b) and cleaved TRAP (5b) were used. TRAP secretion was determined in adipose tissue biopsies, and mRNA expression was studied in cell types isolated from the same. Subjects: Results of 24 lean and 24 obese women ( in vitro ) and 8 subjects ( in vivo ) were compared. The main outcome measurements were TRAP expression and secretion in vitro and in vivo . Results: In-house total TRAP ELISA showed high sensitivity and a coefficient of variance of 11%. Adipose secretion of total TRAP was linear in vitro with time and was evident in vivo. Total TRAP secretion in vitro was similar in lean and obese women expressed per unit weight of the adipose tissue but correlated positively with the number/size of adipocytes ( P ⩽0.01) and with adipose secretion of tumor necrosis factor-α and interleukin-6 ( P <0.01). TRAP 5b was not secreted from the adipose tissue. ATMs displayed highest cellular expression of TRAP mRNA in adipose tissue cells derived from lean or obese women. Conclusions: TRAP is a novel human adipokine produced by macrophages and secreted from the subcutaneous adipose tissue in vivo and in vitro . Secretion is linked to the size and number of adipocytes, as well as to concomitant secretion of inflammatory mediators, suggesting that TRAP is involved in fat accumulation and adipose inflammation.

Long term effects of a diet intervention on adipose tissue blood flow, heart rate variability and endothelial function : a randomized controlled trial

To explore possible associations between adipose tissue (AT) blood flow (ATBF), AT depot sizes and adipocyte-derived hormones (adipokines) in women. In all, 43 healthy women were divided into four groups: normal-weight (n=11) and obese (n=11) pre-menopausal women and normal-weight (n=10) and obese (n=11) post-menopausal women. Fasting levels of adipokines were obtained, and a single-slice computed tomography scan at the level of L4–L5 was used to estimate fat depot sizes. ATBF was assessed by xenon washout while in a fasting state and after oral glucose load. We also measured glucose, insulin and non-esterified fatty acids. Total, subcutaneous and visceral AT areas strongly correlated with ATBF (all P<0.001). Circulating leptin levels strongly and inversely correlated with ATBF (P=0.001), but this association did not remain after adjustment for body mass index. Adiponectin was not associated with blood flow. ATBF is closely linked to subcutaneous and visceral AT size. Further analyses are needed to determine possible mediators of this association, including mechanistic studies to assess a putative role for leptin as a significant modulator of blood flow.

Objective: A putative link between abdominal obesity and metabolic-vascular complications after menopause may be due to a decreased adipose tissue blood flow (ATBF). The present work aimed to analyze possible changes in ATBF with being overweight and menopausal and its putative link to endothelial dysfunction and autonomic nervous system balance. Methods: Forty-three healthy women were classified into four groups according to weight and menopause status. The ATBF was measured by xenon washout while fasting and after oral glucose intake. The nitric oxide synthase inhibitor asymmetric dimethylarginine was used as a marker of endothelial function and heart rate variability-estimated autonomic nervous system activity. Results: Fasting ATBF was decreased in both overweight groups (P = 0.044 and P = 0.048) versus normal-weight premenopausal women. Normal-weight and overweight postmenopausal women exhibited lower maximum ATBF compared with normal-weight premenopausal women (P = 0.015 and P = 0.001, respectively), and overweight postmenopausal women exhibited lower maximum ATBF compared with normal-weight postmenopausal women (P = 0.003). A negative correlation was found between fasting ATBF and asymmetric dimethylarginine (P = 0.015), whereas maximum ATBF was negatively associated with sympathetic-parasympathetic nervous system balance (ratio of the power of the low frequency to the power of the high frequency; P = 0.002). Conclusions: Loss of ATBF flexibility in overweight postmenopausal women may contribute to the metabolic dysfunction seen in this group of women.

OBJECTIVE—11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) regenerates cortisol from cortisone. 11β-HSD1 mRNA and activity are increased in vitro in subcutaneous adipose tissue from obese patients. Inhibition of 11β-HSD1 is a promising therapeutic approach in type 2 diabetes. However, release of cortisol by 11β-HSD1 from adipose tissue and its effect on portal vein cortisol concentrations have not been quantified in vivo. RESEARCH DESIGN AND METHODS—Six healthy men underwent 9,11,12,12-[2H]4-cortisol infusions with simultaneous sampling of arterialized and superficial epigastric vein blood sampling. Four men with stable chronic liver disease and a transjugular intrahepatic porto-systemic shunt in situ underwent tracer infusion with simultaneous sampling from the portal vein, hepatic vein, and an arterialized peripheral vein. RESULTS—Significant cortisol and 9,12,12-[2H]3-cortisol release were observed from subcutaneous adipose tissue (15.0 [95% CI 0.4–29.5] and 8.7 [0.2–17.2] pmol · min−1 · 100 g−1 adipose tissue, respectively). Splanchnic release of cortisol and 9,12,12-[2H]3-cortisol (13.5 [3.6–23.5] and 8.0 [2.6–13.5] nmol/min, respectively) was accounted for entirely by the liver; release of cortisol from visceral tissues into portal vein was not detected. CONCLUSIONS—Cortisol is released from subcutaneous adipose tissue by 11β-HSD1 in humans, and increased enzyme expression in obesity is likely to increase local glucocorticoid signaling and contribute to whole-body cortisol regeneration. However, visceral adipose 11β-HSD1 activity is insufficient to increase portal vein cortisol concentrations and hence to influence intrahepatic glucocorticoid signaling.

OBJECTIVE:Visceral obesity increases risk of insulin resistance and type 2 diabetes. This may partly be due to a region-specific resistance to insulin's antilipolytic effect in visceral adipocytes. We investigated whether adipose tissue releases the vascular peptide endothelin-1 (ET-1) and whether ET-1 could account for regional differences in lipolysis.RESEARCH DESIGN AND METHODS:One group consisted of eleven obese and eleven nonobese subjects in whom ET-1 levels were compared between abdominal subcutaneous and arterialized blood samples. A second group included subjects undergoing anti-obesity surgery. Abdominal subcutaneous and visceral adipose tissues were obtained to study the effect of ET-1 on differentiated adipocytes regarding lipolysis and gene and protein expression.RESULTS:Adipose tissue had a marked net release of ET-1 in vivo, which was 2.5-fold increased in obesity. In adipocytes treated with ET-1, the antilipolytic effect of insulin was attenuated in visceral but not in subcutaneous adipocytes, which could not be explained by effects of ET-1 on adipocyte differentiation. ET-1 decreased the expression of insulin receptor, insulin receptor substrate-1 and phosphodiesterase-3B and increased the expression of endothelin receptor-B (ET(B)R) in visceral but not in subcutaneous adipocytes. These effects were mediated via ET(B)R with signals through protein kinase C and calmodulin pathways. The effect of ET-1 could be mimicked by knockdown of IRS-1.CONCLUSIONS:ET-1 is released from human adipose tissue and links fat accumulation to insulin resistance. It selectively counteracts insulin inhibition of visceral adipocyte lipolysis via ET(B)R signaling pathways, which affect multiple steps in insulin signaling.

Context: Low-grade inflammation in adipose tissue may contribute to insulin resistance in obesity. However, the roles of individual inflammatory mediators in adipose tissue are poorly understood.Objectives: The objective of this study was to determine which inflammation markers are most overexpressed at the gene level in adipose tissue in human obesity and how this relates to corresponding protein secretion.Design: We examined gene expression profiles in 17 lean and 20 obese subjects. The secretory pattern of relevant corresponding proteins was examined in human sc adipose tissue or isolated fat cells in vitro and in vivo in several obese or lean cohorts.Results: In ranking gene expression, defined pathways associated with obesity and immune and defense responses scored high. Among seven markedly overexpressed chemokines, only monocyte chemoattractant protein 1 (MCP1) was released from adipose tissue and isolated fat cells in vitro. In obesity, the secretion and expression of MCP1 in adipose tissue pieces were more than 6- and 2-fold increased, respectively, but there was no change in circulating MCP1 levels. There was no net release of MCP1, but there was a net release of leptin, in vivo from adipose tissue into the circulation.Conclusions: Obesity is associated with the increased expression of several chemokine genes in adipose tissue. However, only MCP1 is secreted into the extracellular space, where it primarily acts as a local factor, because little or no spillover into the circulation occurs. MCP1 influences the function of adipocytes, is a recruitment factor for macrophages, and may be a crucial link among chemokines between adipose tissue inflammation and insulin resistance.

Background: Despite advances in the treatment of atherosclerosis, cardiovascular disease is the leading cause of death worldwide. With the population getting older and more obese, the burden of car ...