Role of human adipose tissue in the production and metabolism of steroid hormones

Radioimmunological methods have been employed for the simultaneous determination of dehydroepiandrosterone, androstenedione, testosterone, oestrogens (oestradiol + oestrone), progesterone, 17 alpha-hydroxyprogesterone and cortisol in human adipose tissue and peripheral blood to compare the hormone pool of adipose tissue with that in the general circulation. Extremely high steroid concentrations in the adipose tissue and hormone pool in the fat of obese subjects were observed. For adipose tissue/serum steroid ratios, the highest values were obtained for dehydroepiandrosterone and the lowest ones for cortisol. A preliminary study showed a great accumulation of steroids in adjacent adipose tissue of breast tumors. Striking differences were observed in the adipose tissue steroid concentrations between benign and malignant mammary tumors. The present findings revealed that blood hormone determinations may be insufficient to consider the steroid hormone availability in various endocrinopathies or steroid responsive tumors, especially when the endocrine state of extremely obese subjects is observed.     

Dynamic appearance of [4-14C] dehydroepiandrosterone and [7 alpha-3H] dehydroepiandrosterone sulphate metabolites in urine of normal and obese female subjects.

[4-14C]-Dehydroepiandrosterone and [7 alpha-3H]-Dehydroepiandrosterone sulphate were injected simultaneously to normal and obese female subjects. The percentage recovery of 14C and 3H radioactivies in dehydroepiandrosterone sulphate, androsterone sulphate, etiocholanolone sulphate, androsterone glucuronoside and etiocholanolone glucuronoside was determined in the day-to-day urine collections for 72 hr. Results showed a normal total 3H recovery and a poor 14C recovery in urinary conjugates of obese patients. The rate of appearance of 3H activity was not identical in the individual metabolites of normal subjects, and it was not normal in obesity. Overweight subjects exhibited an acceleration in [7 alpha-3H]-Dehydroepiandrosterone sulphate metabolism to androsterone glucuronoside. The observation regarding the rate of appearance of urinary conjugates bearing 14C isotope correlate with our previous finding in which a glandular overproduction of free dehydroepiandrosterone was found and an uptake of this steroid by the adipose tissue was suggested. Our results showed that the poor recovery of 14C radioactivity in urine of obese female subjects was not an aspecific consequence of illness.     

Omental and subcutaneous adipose tissue steroid levels in obese men

We examined plasma and fat tissue sex steroid levels in a sample of 28 men aged 24.8-62.2 years (average BMI value of 46.3 +/- 12.7 kg/m(2)). Abdominal adipose tissue biopsies were obtained during general or obesity surgery. Omental and subcutaneous adipose tissue steroid levels were measured by gas chromatography and chemical ionization mass spectrometry after appropriate extraction procedures. BMI and waist circumference were negatively correlated with plasma testosterone (r = -0.49 and -0.50, respectively, p < 0.01) and dihydrotestosterone (r = -0.58 and -0.56, respectively, p < 0.01), and positively associated with estrone levels (r = 0.64 and 0.62, respectively, p < 0.001). Regional differences in adipose tissue steroid levels were observed for dihydrotestosterone (p < 0.005), androstenedione (p < 0.0001) and dehydroepiandrosterone levels (p < 0.05), which were all significantly more concentrated in omental versus subcutaneous fat. Positive significant associations were found between circulating level of a steroid and its concentration in omental and subcutaneous adipose tissue, for estrone (r = 0.72 and 0.57, respectively, p < 0.01), testosterone (r = 0.66 and 0.58, respectively, p < 0.01) and dihydrotestosterone (r = 0.58 and 0.45, respectively, p < 0.05). Positive correlations were observed between plasma dehydroepiandrosterone-sulfate and omental (r = 0.56, p < 0.01) as well as subcutaneous adipose tissue dehydroepiandrosterone level (r = 0.38, p = 0.05). Positive significant associations were found between omental adipocyte responsiveness to positive lipolytic stimuli (isoproterenol, dibutyryl cyclic AMP and forskolin) and plasma or omental fat tissue androgen levels. In conclusion, although plasma androgen or estrogen levels are strong correlates of adipose tissue steroid content both in the omental and subcutaneous fat depots, regional differences may be observed. Androgen concentration differences in omental versus subcutaneous adipose tissue suggest a depot-specific impact of these hormones on adipocyte function and metabolism.     

Regional muscle and adipose tissue amino acid metabolism in lean and obese women

The effect of obesity on regional skeletal muscle and adipose tissue amino acid metabolism is not known. We evaluated systemic and regional (forearm and abdominal subcutaneous adipose tissue) amino acid metabolism, by use of a combination of stable isotope tracer and arteriovenous balance methods, in five lean women [body mass index (BMI) <25 kg/m(2)] and five women with abdominal obesity (BMI 35.0-39.9 kg/m(2); waist circumference >100 cm) who were matched on fat-free mass (FFM). All subjects were studied at 22 h of fasting to ensure that the subjects were in net protein breakdown during this early phase of starvation. Leucine rate of appearance in plasma (an index of whole body proteolysis), expressed per unit of FFM, was not significantly different between lean and obese groups (2.05 +/- 0.18 and 2.34 +/- 0.04 micromol x kg FFM(-1) x min(-1), respectively). However, the rate of leucine release from forearm and adipose tissues in obese women (24.0 +/- 4.8 and 16.6 +/- 6.5 nmol x 100 g(-1) x min(-1), respectively) was lower than in lean women (66.8 +/- 10.6 and 38.6 +/- 7.0 nmol x 100 g(-1) x min(-1), respectively; P < 0.05). Approximately 5-10% of total whole body leucine release into plasma was derived from adipose tissue in lean and obese women. The results of this study demonstrate that the rate of release of amino acids per unit of forearm and adipose tissue at 22 h of fasting is lower in women with abdominal obesity than in lean women, which may help obese women decrease body protein losses during fasting. In addition, adipose tissue is a quantitatively important site for proteolysis in both lean and obese subjects.     

Sulphation of contraceptive steroids

The sulphation of a number of contraceptive steroids by rabbit tissue in vitro was investigated. With liver tissue the three synthetic gestagens (norethisterone, norgesterel and lynestrenol) were sulphated at different rates and none was sulphated as rapidly as dehydroepiandrosterone; sulphation occurred at the tertiary 17 beta-hydroxyl group. The synthetic oestrogen ethynyloestradiol was sulphated more rapidly than dehydroepiandrosterone, both mono and disulphates being formed. Of the other tissues studied, sulphation occurred with stomach and lung but not with heart, spleen, muscle, kidney or adipose tissue. These in vitro studies provide confirmation of in vivo findings regarding sulphate conjugates of the synthetic steroids.     

Enhanced glycerol 3-phosphate dehydrogenase activity in adipose tissue of obese humans

The primary purpose of this investigation was to determine whether adipose tissue glycerol 3-phosphate dehydrogenase activity is associated with human obesity. The data presented in this paper indicate that the glycerol 3-phosphate dehydrogenase activity in adipose tissue from morbidly obese subjects is approximately 2-fold higher than from lean individuals. Moreover, positive correlation between adipose tissue glycerol 3-phosphate dehydrogenase activity and body mass index (BMI) (r = 0.5; p < 0.01) was found. In contrast, the adipose tissue fatty acid synthase (FAS) and ATP-citrate lyase (ACL) activities in morbidly obese patients are significantly lower than in lean subjects. Furthermore, negative correlation between adipose tissue FAS activity and BMI (r = –0.3; p < 0.05) as well as between ACL activity and BMI (r = –0.3; p < 0.05) was found.These data indicate that elevated glycerol 3-phosphate dehydrogenase might contribute to the increase of triacylglycerol (TAG) synthesis in obese subjects, however, fatty acids necessary for glycerol 3-phosphate esterification must be derived (because of lower FAS and ACL activities) mainly from TAG in circulating lipoproteins formed in liver (VLDL), and/or from the intake with food (chylomicrons).The conclusion is, that the enhanced activity of glycerol 3-phosphate dehydrogenase, and hence the generation of more glycerol 3-phosphate in adipose tissue offers a novel explanation for increased TAG production in adipose tissue of obese subjects.     

Relation of lipoprotein lipase activity in adipose tissue to adipocyte volume and its influence in hypertriglyceridemia pathogenesis

In the subcutaneous adipose tissue of 20 normal weight and overweight subjects with normo- or hypertriglyceridemia, the relation is examined between the lipoprotein lipase activity (LPLA) per gram adipose tissue and adipocyte volume. The following findings were obtained: 1. Significant positive correlations between the LPLA per gram adipose tissue and the adipocyte volume were ascertained in the groups of subjects having normal triglyceridemia or exhibiting hypertriglyceridemia. 2. The negative relation between the LPLA in the adipose tissue and the triglyceride level in serum described in literature could not be verified. Across a glyceride span of 76 to 600 mg% in serum we found a correlation coefficient of +0.34. 3. It can therefore be assumed that the LPLA per gram adipose tissue with increasing adipocyte volume does not represent an inhibiting factor to the triglyceride in serum breakdown in the development of hypertriglyceridemia.     

Whole body and abdominal lipolytic sensitivity to epinephrine is suppressed in upper body obese women

We measured whole body and regional lipolytic and adipose tissue blood flow (ATBF) sensitivity to epinephrine in 8 lean [body mass index (BMI): 21 +/- 1 kg/m(2)] and 10 upper body obese (UBO) women (BMI: 38 +/- 1 kg/m(2); waist circumference >100 cm). All subjects underwent a four-stage epinephrine infusion (0.00125, 0.005, 0.0125, and 0.025 microgram. kg fat-free mass(-1). min(-1)) plus pancreatic hormonal clamp. Whole body free fatty acid (FFA) and glycerol rates of appearance (R(a)) in plasma were determined by stable isotope tracer methodology. Abdominal and femoral subcutaneous adipose tissue lipolytic activity was determined by microdialysis and (133)Xe clearance methods. Basal whole body FFA R(a) and glycerol R(a) were both greater (P < 0.05) in obese (449 +/- 31 and 220 +/- 12 micromol/min, respectively) compared with lean subjects (323 +/- 44 and 167 +/- 21 micromol/min, respectively). Epinephrine infusion significantly increased FFA R(a) and glycerol R(a) in lean (71 +/- 21 and 122 +/- 52%, respectively; P < 0.05) but not obese subjects (7 +/- 6 and 39 +/- 10%, respectively; P = not significant). In addition, lipolytic and ATBF sensitivity to epinephrine was blunted in abdominal but not femoral subcutaneous adipose tissue of obese compared with lean subjects. We conclude that whole body lipolytic sensitivity to epinephrine is blunted in women with UBO because of decreased sensitivity in upper body but not lower body subcutaneous adipose tissue.     

Differences in plasminogen activator inhibitor 1 in subcutaneous versus omental adipose tissue in non-obese and obese subjects.

Human adipose tissue can produce plasminogen activator inhibitor-1 (PAI-1). It has been suggested that high levels of PAI-1 are of importance in enhanced cardiovascular disease observed among obese subjects, especially abdominally obese individuals. In the present study, we investigated the level of mRNA and production of PAI-1 in adipose tissue from two adipose tissue depots (omental vs. subcutaneous). Adipose tissue from both depots was obtained from obese (mean BMI, 46.9 kg/m 2) and non-obese (mean BMI, 23.9 kg/m 2) women. PAI-1 mRNA was measured both in fresh adipose tissue obtained immediately after surgery and after the adipose tissue (fragments) had been incubated for up to 72 h. In immediately frozen adipose tissue, PAI-1 mRNA expression was similar in omental and subcutaneous adipose tissue. No differences between obese and non-obese women were found. However, when adipose tissue fragments were cultured, PAI-1 mRNA and PAI-1 production were significantly higher in omental than in subcutaneous adipose tissue (p < 0.05). In the culture system, the production of PAI-1 in obese subjects was higher than in non-obese subjects in both subcutaneous (p < 0.05) and in omental adipose tissue (p = 0.19). In order to test whether these regional differences observed after incubation of the adipose tissue were due to differences in local accumulation of cytokines that may stimulate PAI-1 by a paracrine or autocrine manner, we investigated the expression of transforming growth factor beta1 (TGF-beta1) mRNA and tumor necrosis factor alpha (TNF-alpha) mRNA and protein. No differences between the two fat depots were found. In conclusion, no differences in PAI-1 expression between omental and subcutaneous adipose tissue were observed in biopsies frozen immediately after removal, but after incubation of adipose tissue (which somehow stimulates PAI-1 production), higher levels of PAI-1 were found in omental adipose tissue than in subcutaneous adipose tissue. Finally, PAI-1 production in adipose tissue from obese women was higher in non-obese women after incubation for 72 h.     

Depression and adipose polyunsaturated fatty acids in the survivors of the Seven Countries Study population of Crete

The purpose of the present study was to investigate the relation between adipose tissue polyunsaturated fatty acids, an index of long-term or habitual fatty acid dietary intake and depression. The sample consisted of 150 elderly males from the island of Crete. The subjects were survivors of the Greek Seven Countries Study group. The mean age was 84 years. The number of subjects with complete data on all variables studied was 63. Subjects were examined by the Preventive Medicine and Nutrition Clinic of the University of Crete. Depression was assessed through the use of the short form of the Geriatric Depression Scale (GDS-15). Depression correlated negatively with adipose tissue alpha-linolenic acid (C18:3n-3). Depressed subjects had significantly reduced (-10.5%) adipose tissue C18:3n-3 levels than non-depressed subjects. The observed negative relation between adipose tissue C18:3n-3 and depression, in the present study, appears to indicate increasing long-term dietary C18:3n-3 intakes with decreasing depression. This agrees with findings of other studies indicating an inverse relation between depression and consumption of fish and n-3 polyunsaturated fatty acids. This is the first literature report of a relation between adipose tissue C18:3n-3 and depression. Furthermore, this is the first report of a relation between adipose PUFA and depression in an elderly sample. Depression has been reported to be associated with elevated cytokines, such as, IL-1, IL-2, IL-6, INF-gamma and INF-alpha. Fish oil and omega-3 fatty acids, on the other hand, have been reported to inhibit cytokine production. The observed negative relation between adipose C18:3n-3 and depression, therefore, may stem from the inhibiting effect of C18:3n-3 or its long-chain metabolites on cytokine synthesis.     

Depression and adipose essential polyunsaturated fatty acids

The objective of the present study was to investigate the relation between adipose tissue polyunsaturated fatty acids, an index of long-term or habitual fatty acid dietary intake, and depression. The sample consisted of 247 healthy adults (146 males, 101 females) from the island of Crete. The number of subjects with complete data on all variables studied was 139. Subjects were examined at the Preventive Medicine and Nutrition Clinic of the University of Crete. Depression was assessed through the use of the Zung Self-rating Depression Scale. Mildly depressed subjects had significantly reduced (-34.6%) adipose tissue docosahexaenoic acid (DHA) levels than non-depressed subjects. Multiple linear regression analysis indicated that depression related negatively to adipose tissue DHA levels. In line with the findings of other studies, the observed negative relation between adipose tissue DHA and depression, in the present study, appears to indicate increasing long-term dietary DHA intakes with decreasing depression. This is the first literature report of a relation between adipose tissue DHA and depression. Depression has been reported to be associated with increased cytokine production, such as IL-1, IL-2, IL-6, INF-gamma and INF-alpha. On the other hand, fish oil and omega-3 fatty acids have been reported to inhibit cytokine synthesis. The observed negative relation between adipose DHA and depression, therefore, may stem from the inhibiting effect of DHA on cytokine synthesis.     

Increased lipolysis of subcutaneous abdominal adipose tissue and altered noradrenergic activity in patients with Cushing's syndrome: an in-vivo microdialysis study

Cushing's syndrome is associated with typical central redistribution of adipose tissue. The aim of the study was to assess lipolysis and catecholamines and their metabolites in subcutaneous abdominal adipose tissue using an in-vivo microdialysis technique. Nine patients with Cushing's syndrome and nine age-, gender- and body mass index (BMI)-matched control subjects were included in the study. Local glycerol concentrations were significantly increased in subcutaneous adipose tissue of patients with Cushing's syndrome (p<0.001). Plasma noradrenaline, dihydroxyphenylglycol and dihydroxyphenylalanine were decreased in patients with Cushing's syndrome (p<0.02, p<0.05, and p<0.02, respectively). Adrenaline, noradrenaline, dihydroxyphenylglycol and dihydroxyphenylalanine concentrations in subcutaneous abdominal adipose were non-significantly higher in patients with Cushing's syndrome. In conclusion, we showed that lipolysis in subcutaneous adipose tissue of patients with Cushing's syndrome is significantly increased as compared to healthy subjects. This finding together with non-significantly increased local catecholamine concentrations in these patients suggests a possible link between increased lipolysis and catecholaminergic activity in subcutaneous adipose tissue.     

Reduced expression of PGC-1 and insulin-signaling molecules in adipose tissue is associated with insulin resistance

Peroxisome proliferator-activated receptor gamma (PPAR gamma) co-activator 1 (PGC-1) regulates glucose metabolism and energy expenditure and, thus, potentially insulin sensitivity. We examined the expression of PGC-1, PPAR gamma, insulin receptor substrate-1 (IRS-1), glucose transporter isoform-4 (GLUT-4), and mitochondrial uncoupling protein-1 (UCP-1) in adipose tissue and skeletal muscle from non-obese, non-diabetic insulin-resistant, and insulin-sensitive individuals. PGC-1, both mRNA and protein, was expressed in human adipose tissue and the expression was significantly reduced in insulin-resistant subjects. The expression of PGC-1 correlated with the mRNA levels of IRS-1, GLUT-4, and UCP-1 in adipose tissue. Furthermore, the adipose tissue expression of PGC-1 and IRS-1 correlated with insulin action in vivo. In contrast, no differential expression of PGC-1, GLUT-4, or IRS-1 was found in the skeletal muscle of insulin-resistant vs insulin-sensitive subjects. The findings suggest that PGC-1 may be involved in the differential gene expression and regulation between adipose tissue and skeletal muscle. The combined reduction of PGC-1 and insulin signaling molecules in adipose tissue implicates adipose tissue dysfunction which, in turn, can impair the systemic insulin response in the insulin-resistant subjects.     

Inhibition of 17 beta-hydroxysteroid dehydrogenase activity in human endometrium by adrenal androgens

The effect of dehydroepiandrosterone sulphate (DHA-S) and its metabolites dehydroepiandrosterone (DHA) and 5-androstene-3 beta, 17 beta-diol (ADIOL) on the activity of 17 beta-hydroxysteroid dehydrogenase in human endometrial tissue was investigated by an isotope ratio technique. The apparent KM for oestradiol was 1.59 X 10(-6) M. All three androgens inhibited the metabolism of oestradiol and the apparent Ki values were: ADIOL, 2.05 X 10(-6) M; DHA-S and DHA, 1.59 X 10(-6) M. However, ADIOL acted by direct competition with oestradiol for the active enzyme site whereas inhibition by DHA and its sulphate was non-competitive. DHA-S and DHA were more potent inhibitors of oestradiol metabolism than was ADIOL. These results support the hypothesis that adrenal androgens could be involved in the development of endometrial hyperplasia and adenocarcinoma. Inhibition of oestradiol metabolism could increase the concentration of oestradiol in endometrial tissue and if unopposed by progesterone, e.g. after the menopause or in subjects with ovulatory defects, could stimulate abnormal endometrial growth.     

MicroRNA expression in abdominal and gluteal adipose tissue is associated with mRNA expression levels and partly genetically driven

To understand how miRNAs contribute to the molecular phenotype of adipose tissues and related traits, we performed global miRNA expression profiling in subcutaneous abdominal and gluteal adipose tissue of 70 human subjects and characterised which miRNAs were differentially expressed between these tissues. We found that 12% of the miRNAs were significantly differentially expressed between abdominal and gluteal adipose tissue (FDR adjusted p<0.05) in the primary study, of which 59 replicated in a follow-up study of 40 additional subjects. Further, 14 miRNAs were found to be associated with metabolic syndrome case-control status in abdominal tissue and three of these replicated (primary study: FDR adjusted p<0.05, replication: p<0.05 and directionally consistent effect). Genome-wide genotyping was performed in the 70 subjects to enable miRNA expression quantitative trait loci (eQTL) analysis. Candidate miRNA eQTLs were followed-up in the additional 40 subjects and six significant, independent cis-located miRNA eQTLs (primary study: p<0.001; replication: p<0.05 and directionally consistent effect) were identified. Finally, global mRNA expression profiling was performed in both tissues to enable association analysis between miRNA and target mRNA expression levels. We find 22% miRNAs in abdominal and 9% miRNAs in gluteal adipose tissue with expression levels significantly associated with the expression of corresponding target mRNAs (FDR adjusted p<0.05). Taken together, our results indicate a clear difference in the miRNA molecular phenotypic profile of abdominal and gluteal adipose tissue, that the expressions of some miRNAs are influenced by cis-located genetic variants and that miRNAs are associated with expression levels of their predicted mRNA targets.     

肥胖者脂肪组织中TNF-α表达与脂肪细胞大小的相关性分析

目的探讨肥胖者网膜脂肪和皮下脂肪两处肿瘤坏死因子-α(TNF-α)蛋白的表达与脂肪细胞大小的相关性。方法选取正常体重者16名,中心型肥胖者32名拟行外科手术患者,术中取出网膜脂肪和皮下脂肪标本,测定脂肪细胞大小,采用western blot方法测定TNF-α蛋白表达。结果肥胖者网膜脂肪和皮下脂肪两处TNF-α蛋白的水平均比正常体重对照组表达高(P<0.01),肥胖者网膜脂肪组织TNF-α蛋白表达高于皮下脂肪(P<0.05),同时研究发现肥胖者皮下脂肪细胞和网膜脂肪细胞大小均明显大于正常体重组(P<0.05),且肥胖者网膜脂肪和皮下脂肪两处脂肪组织TNF-α蛋白表达与脂肪细胞大小呈正相关(网膜:r=0.808,P<0.01;皮下:r=0.452,P<0.05)。结论肥胖者网膜脂肪和皮下脂肪细胞增大,在肥胖相关胰岛素抵抗的发生中起到了重要的作用。     

Blood flow in subcutaneous adipose tissue depends on skin-fold thickness.

Blood flow in subcutaneous adipose tissue is reduced in obese compared to lean subjects. Limitations in vascular supply might interfere with adipose tissue function as a metabolic and endocrine organ. We tested the hypothesis that nutritive blood flow and tissue metabolism depends on subcutaneous adipose tissue thickness even in normal-weight subjects. Sixteen young, healthy, normal-weight subjects (8 men, 8 women) were included in the study. Abdominal subcutaneous adipose thickness was assessed by skin-fold measurements. The microdialysis technique was applied for monitoring basal adipose tissue blood flow (ethanol dilution technique) and metabolism. An increase in skin-fold thickness from 15 to 45 mm and from 8 to 37 mm was associated with a linear increase in basal ethanol ratio from 0.19 to 0.63 and 0.25 to 0.75 and linear decreases in dialysate glucose concentrations from 1.95 to 0.24 mM and 1.68 to 0.29 mM, and 152 to 42 microM and 172 to 49 microM for glycerol concentrations in men and women, respectively (p < 0.05). Isoproterenol-stimulated blood flow also inversely correlated to skin-fold thickness (p < 0.05). We conclude that increased adipose tissue thickness is associated with reduced tissue perfusion and metabolism, even in lean subjects. Skin-fold thickness is an important confounding variable in metabolic studies, particularly in microdialysis experiments.     

Insulin regulation of MCP-1 in human adipose tissue of obese and lean women

CCL2 (MCP-1, monocyte chemoattractant protein 1) and CCL3 (MIP-1alpha, macrophage inflammatory protein 1alpha) are required for macrophage infiltration in adipose tissue. Insulin increases CCL2 expression in adipose tissue and in serum more in insulin-resistant obese than in insulin-sensitive lean mice, but whether this is true in humans is unknown. We compared basal expression and insulin regulation of CCL2 and CCL3 in adipose tissue and MCP-1 and MIP-1alpha in serum between insulin-resistant and insulin-sensitive human subjects. Subcutaneous adipose tissue biopsies and blood samples were obtained before and at the end of 6 h of in vivo euglycemic hyperinsulinemia (maintained by the insulin clamp technique) in 11 lean insulin-sensitive and 10 obese insulin-resistant women, and before and after a 6-h saline infusion in 8 women. Adipose tissue mRNA concentrations of monocyte/macrophage markers CD68, EMR1, ITGAM, ADAM8, chemokines CCL2 and CCL3, and housekeeping gene ribosomal protein large P0 (RPLP0) were measured by means of real-time PCR at baseline. In addition, mRNA concentrations of CCL2, CCL3, and RPLP0 were measured after insulin infusion. Levels of MCP-1 and MIP-1alpha were determined in serum, and protein concentration of MCP-1 was determined in adipose tissue at baseline and after insulin infusion. Basally, expression of the macrophage markers CD68 and EMR1 were increased in adipose tissue of insulin-resistant subjects. Insulin increased MCP-1 gene and protein expression significantly more in the insulin-resistant than in the insulin-sensitive subjects. Basally expression of CCL2 and CCL3 and expression of macrophage markers CD68 and ITGAM were significantly correlated. In serum, MCP-1 decreased significantly in insulin-sensitive but not insulin-resistant subjects. MIP-1alpha was undetectable in serum. Insulin regulation of CCL2 differs between insulin-sensitive and -resistant subjects in a direction that could exacerbate adipose tissue inflammation.     

The use of stable isotopes and gas chromatography/mass spectrometry in the identification of steroid metabolites in the equine

Stable isotope gas chromatography/mass spectrometry has been used successfully in the elucidation of structures of urinary steroid metabolites in the horse and in the identification of metabolites isolated from in vivo perfusion and in vitro incubation studies using equine tissue preparations. Deuterium-labeled steroids, testosterone, dehydroepiandrosterone, and 5-androstene-3 beta,17 beta-diol have been synthesized by base-catalyzed isotope exchange methods and the products characterized by gas chromatography/mass spectrometry. [16,16(-2)H2]Dehydroepiandrosterone (plus radiolabeled dehydroepiandrosterone) was perfused into a testicular artery of a pony stallion and was shown to be metabolized into 2H2-labeled testosterone, 4-androstenedione, isomers of 5-androstene-3,17-diol, 19-hydroxytestosterone, and 19-hydroxy-4-androstenedione. In further studies, equine testicular minces have been incubated with 2H2-labeled and radiolabeled dehydroepiandrosterone and 5-androstene-3 beta, 17 beta-diol. The metabolites, whose identity was confirmed by stable isotope gas chromatography/mass spectrometry, proved the interconversion of the two substrates, as well as formation of testosterone and 4-androstenedione. The aromatization of dehydroepiandrosterone was also confirmed, together with the formation of an isomer of 5(10)-estrene-3,17-diol from both substrates showing 19-demethylation without concomitant aromatization. In studies of the feto-placental unit, the allantochorion was shown to aromatize [2H5]testosterone to [2H4]estradiol, the loss of one 2H from the substrate being consistent with aromatization of the A ring. The formation of 6-hydroxyestradiol was also confirmed in this study. The same technique has been valuable in determining the structure of two metabolites of nandrolone isolated from horse urine.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inflammation may modulate IL-6 and C-reactive protein gene expression in the adipose tissue: the role of IL-6 cell membrane receptor

Only few studies have been addressed to the presence and regulation of C-reactive protein (CRP) gene expression in different districts of adipose tissue, and no study has investigated the role of adipose tissue in presence of inflammation. Therefore, the aim of this study was to investigate the inflammatory involvement of either adipose tissue or adipose cells (adipocytes and stromal cells, respectively) in patients with chronic inflammatory disease, focusing on regional adipose tissue CRP gene expression. Eighteen patients with inflammatory disease and 14 healthy controls were enrolled. All subjects underwent specific surgical procedures. Inflamed and noninflamed patients provided samples of subcutaneous and/or omental adipose tissue. All samples were analyzed by RT-PCR and real-time PCR for specific gene expression. In addition, both adipocytes and stromal cells were studied by real-time PCR and immunoprecipitation to evaluate either gene or protein expression of CRP. Our results (real-time PCR) demonstrated a higher gene expression of CRP, IL-6, and both IL-6 membrane receptors in subcutaneous samples of inflamed patients than in healthy controls. Furthermore, in omental fragments of inflamed patients, an enhanced mRNA abundance of the same genes, compared with subcutaneous, was observed. The results obtained at cellular level did not provide evidence of any difference between adipocytes and stromal cell CRP gene expression, whereas immunoprecipitation demonstrated the presence of CRP in inflamed subjects. These results provide first-time evidence of the involvement of adipose tissue in the course of chronic inflammatory diseases, with a different degree of participation of the different adipose tissue districts.