Dehydroepiandrosterone up-regulates resistin gene expression in white adipose tissue

Role of the Steroid Sulfate Uptake Transporter Soat (Slc10a6) in Adipose Tissue and 3T3-L1 Adipocytes

In addition to the endocrine and paracrine systems, peripheral tissues such as gonads, skin, and adipose tissue are involved in the intracrine mechanisms responsible for the formation of sex steroids via the transformation of dehydroepiandrosterone and dehydroepiandrosterone sulfate (DHEA/DHEAS) into potent androgenic and estrogenic hormones. Numerous studies have examined the relationship between overweight, central obesity, and plasma levels of DHEA and DHEAS. The sodium-dependent organic anion transporter Soat (Slc10a6) is a plasma membrane uptake transporter for sulfated steroids. Significantly increased expression of Slc10a6 mRNA has been previously described in organs and tissues of lipopolysaccharide (LPS)-treated mice, including white adipose tissue. These findings suggest that Soat plays a role in the supply of steroids in peripheral target tissues. The present study aimed to investigate the expression of Soat in adipocytes and its role in adipogenesis. Soat expression was analyzed in mouse white intra-abdominal (WAT), subcutaneous (SAT), and brown (BAT) adipose tissue samples and in murine 3T3-L1 adipocytes. In addition, adipose tissue mass and size of the adipocytes were analyzed in wild-type and Slc10a6^−/− knockout mice. Soat expression was detected in mouse WAT, SAT, and BAT using immunofluorescence. The expression of Slc10a6 mRNA was significantly higher in 3T3-L1 adipocytes than that of preadipocytes and was significantly upregulated by exposure to lipopolysaccharide (LPS). Slc10a6 mRNA levels were also upregulated in the adipose tissue of LPS-treated mice. In Slc10a6^−/− knockout mice, adipocytes increased in size in the WAT and SAT of female mice and in the BAT of male mice, suggesting adipocyte hypertrophy. The serum levels of adiponectin, resistin, and leptin were comparable in wild-type and Slc10a6^−/− knockout mice. The treatment of 3T3-L1 adipocytes with DHEA significantly reduced lipid accumulation, while DHEAS did not have a significant effect. However, following LPS-induced Soat upregulation, DHEAS also significantly inhibited lipid accumulation in adipocytes. In conclusion, Soat-mediated import of DHEAS and other sulfated steroids could contribute to the complex pathways of sex steroid intracrinology in adipose tissues. Although in cell cultures the Soat-mediated uptake of DHEAS appears to reduce lipid accumulation, in Slc10a6^−/− knockout mice, the Soat deletion induced adipocyte hyperplasia through hitherto unknown mechanisms.

Adrenal Androgen Predictive Effects on Clinical and Metabolic Abnormalities of Polycystic Ovary Syndrome

OBJECTIVE

 To examine the possible effects of adrenal prohormones in the prediction of clinical and metabolic abnormalities in women with polycystic ovary syndrome (PCOS).

METHODS

 The present study enrolled 299 normal cycling non-PCOS, 156 normoandrogenemic, and 474 hyperandrogenemic women with PCOS. Baseline characteristics were compared using a chi-squared test or analysis of variance (ANOVA) as appropriate. The roles of adrenal prohormones and their ratios with total testosterone in predicting co-occurring morbidities in women PCOS were evaluated using univariate and multivariate logistic regression analyses.

RESULTS

 Adrenal hyperandrogenism per dehydroepiandrosterone sulfate (DHEAS) levels were found in 32% of women with PCOS. In non-PCOS women, dehydroepiandrosterone (DHEA) and its sulfate had no predictive role concerning clinical, anthropometric, and metabolic parameters. In PCOS women, mainly in the hyperandrogenemic group, DHEA showed to be a significant predictor against most anthropometric-metabolic index abnormalities (odds ratio [OR] = 0.36-0.97; p < 0.05), and an increase in triglycerides (TG) levels (OR = 0.76; p = 0.006). Dehydroepiandrosterone sulfate presented a few predictive effects regarding PCOS-associated disorders. In controls, DHEAS predicted against the increase in estimated average glucose (OR= 0.38; p = 0.036). In the normoandrogenic group, it predicted against elevation in the waist/hip ratio (WHR) (OR= 0.59; p = 0.042), and in hyperandrogenemic PCOS women, it predicted against abnormality in the conicity index (CI) (OR = 0.31; p = 0.028).

CONCLUSION

 Dehydroepiandrosterone was shown to be a better predictor of abnormal anthropometric and biochemical parameters in women with PCOS than DHEAS. Thus, regarding adrenal prohormones, DHEA measurement, instead of DHEAS, should be preferred in PCOS management. The effects of androgen prohormones on the prediction of PCOS abnormalities are weak.

Adipocyte and steroidogenic cell cross-talk in polycystic ovary syndrome

BACKGROUND

Metabolic and endocrine alterations in women with polycystic ovary syndrome (PCOS) affect adipose tissue mass and distribution. PCOS is characterised by hyperandrogenism, obesity and adipocyte dysfunction. Hyperandrogenism in PCOS drives dysfunctional adipocyte secretion of potentially harmful adipocytokines. Glucocorticoids and sex-steroids modulate adipocyte development and function. For their part, adipocyte products interact with adrenal and ovarian steroidogenic cells. Currently, the relationship between adipocyte and steroidogenic cells is not clear, and for these reasons, it is important to elucidate the interrelationship between these cells in women with and without PCOS.

OBJECTIVE AND RATIONALE

This comprehensive review aims to assess current knowledge regarding the interrelationship between adipocytes and adrenal and ovarian steroidogenic cells in animal models and humans with or without PCOS.

SEARCH METHODS

We searched for articles published in English and Portuguese in PubMed. Keywords were as follows: polycystic ovary syndrome, steroidogenesis, adrenal glands, theca cells, granulosa cells, adipocytes, adipocytokines, obesity, enzyme activation, and cytochrome P450 enzymes. We expanded the search into the references from the retrieved articles.

OUTCOMES

Glucocorticoids and sex-steroids modulate adipocyte differentiation and function. Dysfunctional adipocyte products play important roles in the metabolic and endocrine pathways in animals and women with PCOS. Most adipokines participate in the regulation of the hypothalamic-pituitary-adrenal and ovarian axes. In animal models of PCOS, hyperinsulinemia and poor fertility are common; various adipokines modulate ovarian steroidogenesis, depending on the species. Women with PCOS secrete unbalanced levels of adipocyte products, characterised by higher levels of leptin and lower levels of adiponectin. Leptin expression positively correlates with body mass index, waist/hip ratio and levels of total cholesterol, triglyceride, luteinising hormone, oestradiol and androgens. Leptin inhibits the production of oestradiol and, in granulosa cells, may modulate 17-hydroxylase and aromatase enzyme activities. Adiponectin levels negatively correlate with fat mass, body mass index, waist-hip ratio, glucose, insulin and triglycerides, and decrease androgen production by altering expression of luteinising hormone receptor, steroidogenic acute regulatory protein, cholesterol-side-chain cleavage enzyme and 17-hydroxylase. Resistin expression positively correlates with body mass index and testosterone, and promotes the expression of 17-hydroxylase enzyme in theca cells. The potential benefits of adipokines in the treatment of women with PCOS require more investigation.

WIDER IMPLICATIONS

The current data regarding the relationship between adipocyte products and steroidogenic cells are conflicting in animals and humans. Polycystic ovary syndrome is an excellent model to investigate the interrelationship among adipocyte and steroidogenic cells. Women with PCOS manifest some pathological conditions associated with hyperandrogenism and adipocyte products. In animals, cross-talk between cells may vary according to species, and the current review suggests opportunities to test new medications to prevent or even reverse several harmful sequelae of PCOS in humans. Further studies are required to investigate the possible therapeutic application of adipokines in women with obese and non-obese PCOS. Meanwhile, when appropriate, metformin use alone, or associated with flutamide, may be considered for therapeutic purposes.

Circulating resistin and follistatin levels in obese and non-obese women with polycystic ovary syndrome: A systematic review and meta-analysis

This meta-analysis was performed to resolve the inconsistencies regarding resistin and follistatin levels in women with polycystic ovary syndrome (PCOS) by pooling the available evidence. A systematic literature search using PubMed and Scopus was carried out through November 2020 to obtain all pertinent studies. Weighted mean differences (WMDs) with corresponding 95% confidence intervals (CIs) were calculated to evaluate the strength of the association between the levels of resistin and follistatin with PCOS in the overall and stratified analysis by obesity status. A total of 47 publications, 38 for resistin (2424 cases; 1906 controls) and 9 studies for follistatin (815 cases; 328 controls), were included in the meta-analysis. Resistin levels were significantly higher in PCOS women compared with non-PCOS controls (WMD = 1.96 ng/ml; 95%CI = 1.25–2.67, P≤0.001) as well as in obese PCOS women vs. obese controls, and in non-obese PCOS women compared with non-obese controls, but not in obese PCOS vs. non-obese PCOS patients,. A significantly increased circulating follistatin was found in PCOS patients compared with the controls (WMD = 0.44 ng/ml; 95%CI = 0.30–0.58, P≤0.001) and in non-obese PCOS women compared with non-obese controls and in obese PCOS women vs. obese controls, but, no significant difference in follistatin level was observed in obese PCOS compared with non-obese PCOS women. Significant heterogeneity and publication bias was evident for some analyses. Circulating levels of resistin and follistatin, independent of obesity status, are higher in women with PCOS compared with controls, showing that these adipokines may contribute to the pathology of PCOS.

Adipose tissue and adrenal glands: novel pathophysiological mechanisms and clinical applications

Hormones produced by the adrenal glands and adipose tissues have important roles in normal physiology and are altered in many disease states. Obesity is associated with changes in adrenal function, including increase in adrenal medullary catecholamine output, alterations of the hypothalamic-pituitary-adrenal (HPA) axis, elevations in circulating aldosterone together with changes in adipose tissue glucocorticoid metabolism, and enhanced adipocyte mineralocorticoid receptor activity. It is unknown whether these changes in adrenal endocrine function are in part responsible for the pathogenesis of obesity and related comorbidities or represent an adaptive response. In turn, adipose tissue hormones or "adipokines" have direct effects on the adrenal glands and interact with adrenal hormones at several levels. Here we review the emerging evidence supporting the existence of "cross talk" between the adrenal gland and adipose tissue, focusing on the relevance and roles of their respective hormones in health and disease states including obesity, metabolic syndrome, and primary disorders of the adrenals.

Serum concentrations of resistin and adiponectin and their relationship to insulin resistance in subjects with impaired glucose tolerance

OBJECTIVES

This study measured the serum concentrations of resistin and adiponectin in Chinese subjects with impaired glucose tolerance (IGT) and investigated their association with insulin resistance, metabolic parameters and circulating inflammatory markers.

METHODS

A total of 124 subjects participated in the study (44 with IGT and 80 with normal glucose tolerance [NGT]). Fasting serum concentrations of lipids, glucose, insulin and adipocytokines (resistin, adiponectin, leptin, tumour necrosis factor-α [TNF-α], interleukin-6 and C-reactive protein) were measured.

RESULTS

Serum resistin concentrations were similar in the IGT and NGT groups but were significantly higher in overweight/ obese IGT subjects than in those of normal weight. Serum adiponectin concentrations were significantly lower in the IGT group than in the NGT group. In the IGT group, resistin was positively correlated with age, body mass index and TNF-α, and adiponectin was correlated positively with high-density lipoprotein cholesterol and negatively with TNF-α and waist/hip ratio.

CONCLUSIONS

Circulating resistin is unlikely to be a major mediator of glucose tolerance in humans but it may have an inflammatory role in IGT. The data support the theory that circulating adiponectin has an anti-inflammatory and anti-insulin resistance function.

Fat-reducing effects of dehydroepiandrosterone involve upregulation of ATGL and HSL expression, and stimulation of lipolysis in adipose tissue

Dehydroepiandrosterone (DHEA) reduces body fat in rodents and humans, and increases glycerol release from isolated rat epididymal adipocytes and human visceral adipose tissue explants. It suggests that DHEA stimulates triglyceride hydrolysis in adipose tissue; however, the mechanisms underlying this action are still unclear. We examined the effects of DHEA on the expression of adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL), the key enzymes of lipolysis, in rat epididymal white adipose tissue (eWAT). Male Wistar rats were fed a diet containing 0.6% DHEA for 2 weeks and eWAT was analyzed for mRNA and protein expression of ATGL and HSL, as well as mRNA expression of peroxisome proliferator-activated receptor γ 2 (PPARγ2) and its downstream target fatty acid translocase (FAT). Glycerol release from eWAT explants and serum free fatty acids (FFA) were also measured. Rats that received DHEA gained less weight, had 23% lower eWAT mass and 31% higher serum FFA levels than controls. Cultured explants of eWAT from DHEA-treated rats released 81% more glycerol than those from control rats. DHEA administration upregulated ATGL mRNA (1.62-fold, P<0.05) and protein (1.78-fold, P<0.05) expression as well as augmented HSL mRNA levels (1.36-fold, P<0.05) and Ser660 phosphorylation of HSL (2.49-fold, P<0.05). PPARγ2 and FAT mRNA levels were also increased in DHEA-treated rats (1.61-fold, P<0.05 and 2.16-fold, P<0.05; respectively). Moreover, ATGL, HSL, and FAT mRNA levels were positively correlated with PPARγ2 expression. This study demonstrates that DHEA promotes lipid mobilization in adipose tissue by increasing the expression and activity of ATGL and HSL. The effects of DHEA appear to be mediated, at least in part, via PPARγ2 activation, which in turn upregulates ATGL and HSL gene expression.

Alternative mechanism for anti-obesity effect of dehydroepiandrosterone: possible contribution of 11β-hydroxysteroid dehydrogenase type 1 inhibition in rodent adipose tissue

Dehydroepiandrosterone (DHEA) has been suggested to have an anti-obesity effect; however, the mechanism underlying this effect remains unclear. The effect of DHEA on adipocytes opposes that of glucocorticoids, which potentiate adipogenesis. The key to the intracellular activation of glucocorticoids in adipocytes is 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which catalyses the production of active glucocorticoids (cortisol in humans and corticosterone in rodents) from an inactive 11-keto form (cortisone in humans and 11-dehydrocorticosterone in rodents). In humans and rodents, intracellular glucocorticoid reactivation is exaggerated in obese adipose tissue. Using differentiated 3T3-L1 adipocytes, we demonstrated that DHEA inhibited about 15.6% of 11β-HSD1 activity at a concentration of 1 μM within 10min. Inhibition was also observed in a cell-free system composed of microsomes prepared from rat adipose tissue and NADPH, a coenzyme of 11β-HSD1. A kinetic study revealed that DHEA acted as a non-competitive inhibitor of 11β-HSD1. Moreover, conversion from DHEA to estrogens was not observed by sensitive semi-micro HPLC equipped with electrochemical detector. These results indicate that the inhibition of 11β-HSD1 by DHEA depends on neither the transcriptional pathway nor the nonspecific manner. This is the first demonstration that the anti-obesity effect of DHEA is exerted by non-transcriptional inhibition of 11β-HSD1 in rodent adipocytes.

Dehydroepiandrosterone (DHEA) treatment in vitro inhibits adipogenesis in human omental but not subcutaneous adipose tissue

Dehydroepiandrosterone (DHEA), a precursor sex steroid, circulates in sulphated form (DHEAS). Serum DHEAS concentrations are inversely correlated with metabolic syndrome components and in vivo/in vitro studies suggest a role in modulating adipose mass. To investigate further, we assessed the in vitro biological effect of DHEA in white (3T3-L1) and brown (PAZ6) preadipocyte cell lines and human primary preadipocytes. DHEA (from 10(-8)M) caused concentration-dependent proliferation inhibition of 3T3-L1 and PAZ6 preadipocytes. Cell cycle analysis demonstrated unaltered apoptosis but indicated blockade at G1/S or G2/M in 3T3-L1 and PAZ6, respectively. Preadipocyte cell-line adipogenesis was not affected. In human primary subcutaneous and omental preadipocytes, DHEA significantly inhibited proliferation from 10(-8)M. DHEA 10(-7)M had opposing effects on adipogenesis in the two fat depots. Subcutaneous preadipocyte differentiation was unaffected or increased whereas omental preadipocytes showed significantly reduced adipogenesis. We conclude that DHEA exerts fat depot-specific differences which modulate body composition by limiting omental fat production.

Adiponectin and resistin concentrations after glucose load in adolescents with polycystic ovary syndrome

Our aims were to evaluate the serum adiponectin and resistin levels at fasting and after glucose load and their interaction with risk of cardiovascular disease (CVD) in adolescents with polycystic ovary syndrome (PCOS). Twenty-two adolescents with PCOS and 16 healthy controls were included in the study. Oral glucose tolerance test (OGTT) was performed in all adolescents. Fasting lipids was measured. Insulin, glucose, adiponectin, and resistin levels were measured at 0 and 120 min of OGTT. Homeostasis model assessment of insulin resistance (HOMA-IR), quantitative insulin-sensitivity check index (QUICKI), fasting glucose-to-insulin ratio (FGIR), and the whole -body insulin sensitivity index (ISI) were calculated. Fasting adiponectin was correlated with ISI (r = 0.729, p < 0.0001), FGIR (r = 0.696, p < 0.0001), QUICKI (r = 0.592, p = 0.004) and HDL-C (r = 0.516, p = 0.028), systolic blood pressure (r = -0.732, p < 0.0001), body mass index (r = -0.738, p < 0.0001), waist circumference (r = -0.706, p < 0.0001), and HOMA-IR (r = -0.595, p = 0.003). No correlation was found between resistin and insulin resistance indexes. Obese adolescents with PCOS have increased CVD risk such as dyslipidemia, hypertension, and insulin resistance than normo-weight PCOS. Hypoadiponectinaemia could be increase risks levels in obese girls with PCOS.

Adiponectin is involved in the protective effect of DHEA against metabolic risk in aged rats

The aim of the present work was to analyze the effect of dehydroepiandrosterone (DHEA) on several metabolic risk factors, including cardiovascular health and insulin resistance, in aged rats submitted to a high-fat diet. For that, weaned rats were fed on a high-fat diet until 20 months of age. In the last 13 weeks of life, a group (n=11) received the diet supplemented with DHEA (0.5%, w/w), serving the rest (n=10) as controls. Body weight, body fat, serum lipids (triglycerides, total cholesterol and non-esterified fatty acids (NEFA)), HOMA index, n-6/n-3 polyunsaturated fatty acid (PUFA) ratios, serum adiponectin, leptin, resistin and TNF-alpha, as well as adiponectin expression in adipose tissue, were measured. A stepwise discriminant test was used to analyze these variables, and an index of overall metabolic risk was generated from them. DHEA treatment resulted in a significantly lower overall metabolic risk index, as generated by the discriminant test (P<0.01). The DHEA group had lower body fat and n-6/n-3 polyunsaturated fatty acid (PUFA) ratios than the control group (P<0.01), and the same trends were observed for serum cholesterol, triglycerides and HOMA index; in contrast, adiponectin expression in adipose tissue increased in DHEA-treated rats (P<0.05). The discriminant analysis revealed that adiponectin, both from serum and adipose tissue, was the most influencing factor, followed by n-6/n-3 ratios in adipose tissue, and by body fat. Our results then suggest that adiponectin is involved in the protective effect of DHEA against metabolic risk demonstrated in the present work.

Serum resistin and polymorphisms of androgen receptor GAGn and GGNn and aromatase TTTAn

There is evidence that androgens are regulators of insulin resistance (IR), and may be involved in the regulation of resistin, a cytokine that has been related with IR. Earlier studies found that androgen receptor length polymorphisms CAGn and GGNn and the aromatase polymorphism TTTAn may influence receptor or enzyme activity and serum concentrations of androgens. This study was designed to determine whether polymorphism length was related to serum resistin concentration and to other variables related with IR. In 1,580 persons chosen randomly from the general population of the Canary Islands (Spain), we measured polymorphism length, waist circumference, waist/hip ratio, BMI, and serum glucose concentration. In smaller subgroups, we also measured C-peptide (n = 677), resistin (n = 583), and leptin concentration (n = 754) and estimated IR (homeostasis model assessment-IR (HOMA2-IR)). In men, polymorphism length correlated with resistin concentration (CAGn, r = 0.13, P = 0.031; TTTAn, r = 0.15, P = 0.005; GGNn, r = -0.15, P = 0.026), and the correlations were confirmed in multivariate regression models. The length of CAGn and TTTAn correlated inversely with C-peptide (r = -0.13, P = 0.016 and r = -0.21, P < 0.001, respectively) and with estimated IR (r = -0.12, P = 0.032 and r = -0.19, P = 0.001, respectively). In men, length of the CAGn, GGNn, and TTTAn was associated with serum resistin concentration. These results support the hypothesis that androgens may be involved in the regulation of resistin. Resistin may be a link between IR and androgens.

Nutrigenomics, beta-cell function and type 2 diabetes

INTRODUCTION

The present investigation was designed to investigate the accuracy and precision of lactate measurement obtained with contemporary biosensors (Chiron Diagnostics, Nova Biomedical) and standard enzymatic photometric procedures (Sigma Diagnostics, Abbott Laboratories, Analyticon).

MATERIALS AND METHODS

Measurements were performed in vitro before and after the stepwise addition of 1 molar sodium lactate solution to samples of fresh frozen plasma to systematically achieve lactate concentrations of up to 20 mmol/l.

RESULTS

Precision of the methods investigated varied between 1% and 7%, accuracy ranged between 2% and -33% with the variability being lowest in the Sigma photometric procedure (6%) and more than 13% in both biosensor methods.

CONCLUSION

Biosensors for lactate measurement provide adequate accuracy in mean with the limitation of highly variable results. A true lactate value of 6 mmol/l was found to be presented between 4.4 and 7.6 mmol/l or even with higher difference. Biosensors and standard enzymatic photometric procedures are only limited comparable because the differences between paired determinations presented to be several mmol. The advantage of biosensors is the complete lack of preanalytical sample preparation which appeared to be the major limitation of standard photometry methods.

Gene modulation associated with inhibition of liver regeneration in hepatitis B virus X transgenic mice

AIM: To analyze the modulation of gene expression profile associated with inhibition of liver regeneration in hepatitis B X (HBx)-expressing transgenic mice.

METHODS: Microarray technology was performed on liver tissue obtained from 4 control (LacZ) and 4 transgenic mice (HBx-LacZ), 48 h after partial hepatectomy. The significance of the normalized log-ratios was assessed for each gene, using robust t-tests under an empirical Bayes approach. Microarray hybridization data was verified on selected genes by quantitative PCR.

RESULTS: The comparison of gene expression patterns showed a consistent modulation of the expression of 26 genes, most of which are implicated in liver regeneration. Up-regulated genes included DNA repair proteins (Rad-52, MSH6) and transmembrane proteins (syndecan 4, tetraspanin), while down-regulated genes were connected to the regulation of transcription (histone deacetylase, Zfp90, MyoD1) and were involved in the cholesterol metabolic pathway and isoprenoid biosynthesis (farnesyl diphosphate synthase, Cyp7b1, geranylgeranyl diphosphate synthase, SAA3).

CONCLUSION: Our results provide a novel insight into the biological activities of HBx, implicated in the inhibition of liver regeneration.

Dehydroepiandrosterone up-regulates the Adrenoleukodystrophy-related gene (ABCD2) independently of PPARα in rodents

X-linked adrenoleukodystrophy (X-ALD) is a neurodegenerative disease caused by mutations in the ABCD1 gene, which encodes a peroxisomal ABC transporter, ALDP, supposed to participate in the transport of very long chain fatty acids (VLCFA). The adrenoleukodystrophy-related protein (ALDRP), which is encoded by the ABCD2 gene, is the closest homolog of ALDP and is considered as a potential therapeutic target since functional redundancy has been demonstrated between the two proteins. Pharmacological induction of Abcd2 by fibrates through the activation of PPARalpha has been demonstrated in rodent liver. DHEA, the most abundant steroid in human, is described as a PPARalpha activator and also as a prohormone able to mediate induction of several genes. Here, we explored the in vitro and in vivo effects of DHEA on the expression of peroxisomal ABC transporters. We show that Abcd2 and Abcd3 but not Abcd4 are induced in primary culture of rat hepatocytes by DHEA-S. We also demonstrate that Abcd2 and Abcd3 but not Abcd4 are inducible by an 11-day treatment with DHEA in the liver of male rodents but not in brain, testes and adrenals. Finally and contrary to Abcd3, we show that the mechanism of induction of Abcd2 is independent of PPARalpha.

Effects of Dehydroepiandrosterone (DHEA) on Hepatic Lipid Metabolism Parameters and Lipogenic Gene mRNA Expression in Broiler Chickens

The aim of the present study was to identify the effects of dehydroepiandrosterone (DHEA) on hepatic lipid metabolism parameters and lipogenic gene mRNA expression in broiler chickens. A total of 72 1-day-old broiler chicks received a common basal diet with DHEA added at either 0 (control), 5 or 20 mg/kg feed. In the present study, the hepatic triglyceride (TG) concentration was significantly lower in male and female broilers that had bed administered DHEA than in control birds. In contrast, DHEA administration caused a marked rise in the hepatic non-esterified fatty acid (NEFA) concentration in both male and female broilers and also increased lipase (HL) activity in male broilers, while in female birds, no significant differences were observed in HL activity. The expression of peroxisome proliferators-activated receptor alpha (PPARalpha) and carnitine palmitoyl transferase I (CPTI) mRNA was decidedly enhanced following treatment with DHEA, and a similar tendency was also observed in the expression of acyl-Coenzyme A oxidase 1 (ACOX1). However, no significant differences were observed in the expression of either sterol regulatory element binding protein-1c (SREBP-1c) or acetyl CoA carboxylase (ACC) mRNA, except for a decline in the expression of ACC in females treated with 5 mg DHEA/kg. Numerous peroxisomes without a core and an increased number of peroxisomes were evident during morphological observations of broiler livers, in animals that had been treated with DHEA. Overall, the results of the present study indicated that DHEA accelerated lipid catabolism by direct regulation of hepatic lipid metabolism and by induction of relevant gene expression.

Dehydroepiandrosterone behavior and lipid profile in non-obese women undergoing abdominoplasty

BACKGROUND

The aim of this study was to determine any change in dehydroepiandrosterone (DHEA) and lipid profile in non-obese women after abdominoplasty.

METHODS

An auto-controlled clinical trial was carried out. 9 women aged 35 to 40 years with BMI 22-25 kg/m2 were studied. Basal lipid profile and DHEA were performed and repeated 1 month postoperatively. Statistical analysis used Wilcoxon signed-ranks test (two-tailed).

RESULTS

Weight of resected specimen was 606.11 +/- 143.4 grams. No significant changes were observed in high-density cholesterol (48.0 +/- 9.6 vs 48.8 +/- 11.0 mg/dl; P=0.106) or in triglycerides (119.2 +/- 50.9 vs 148.4 +/- 45.8 mg/dl; P = 0.139). Significant increases were obtained in DHEA (3.69 +/- 3.05 vs 11.09 +/- 6.3 ng/ml; P<0.008), low-density cholesterol (LDL) (87.4 +/- 23.5 vs 108.5 +/- 28.3 mg/dl; P<0.008 and total cholesterol (155.1 +/- 30.6 vs 186.6 +/- 33.1 mg/dl; P<0.008).

CONCLUSION

Excision of subcutaneous abdominal fat in studies 1 month later increased DHEA, whose role is controversial in visceral fat distribution, and increased LDL cholesterol and total cholesterol, both risk markers for cardiovascular illness.

Adipokines: implications for female fertility and obesity

Obesity is associated with a diverse set of metabolic disorders, and has reproductive consequences that are complex and not well understood. The adipose tissue-produced leptin has dominated the literature with regards to female fertility complications, but it is pertinent to explore the likely role of other adipokines--adiponectin and resistin--as our understanding of their biological functions emerge. Leptin influences the developing embryo, the functioning of the ovary and the endometrium, interacts with the release and activity of gonadotrophins and the hormones that control their synthesis. In this review such biological actions and potential roles of the adipokines leptin, adiponectin and resistin are explored in relation to female fertility and the complexity of the obese metabolic state.

Role of resistin in obesity, insulin resistance and Type II diabetes

Resistin is a member of a class of cysteine-rich proteins collectively termed resistin-like molecules. Resistin has been implicated in the pathogenesis of obesity-mediated insulin resistance and T2DM (Type II diabetes mellitus), at least in rodent models. In addition, resistin also appears to be a pro-inflammatory cytokine. Taken together, resistin, like many other adipocytokines, may possess a dual role in contributing to disease risk. However, to date there has been considerable controversy surrounding this 12.5 kDa polypeptide in understanding its physiological relevance in both human and rodent systems. Furthermore, this has led some to question whether resistin represents an important pathogenic factor in the aetiology of T2DM and cardiovascular disease. Although researchers still remain divided as to the role of resistin, this review will place available data on resistin in the context of our current knowledge of the pathogenesis of obesity-mediated diabetes, and discuss key controversies and developments.

Up-regulation of advanced glycated products receptors in the brain of diabetic rats is prevented by antioxidant treatment

Diabetics have at least twice the risk of stroke and may show performance deficit in a wide range of cognitive domains. The mechanisms underlying this gradually developing end-organ damage may involve both vascular changes and direct damage to neuronal cells as a result of overproduction of superoxide by the respiratory chain and consequent oxidative stress. The study aimed to assess the role of oxidative stress on the aldose reductase-polyol pathway, on advanced glycated end-product (AGE)/AGE-receptor interaction, and on downstream signaling in the hippocampus of streptozotocin-treated rats. Data show that, in diabetic rats, levels of prooxidant compounds increase, whereas levels of antioxidant compounds fall. Receptor for AGE and galectin-3 content and polyol flux increase, whereas glyceraldehyde-3-phosphate dehydrogenase activity is impaired. Moreover, nuclear factor kappaB (p65) transcription factor levels and S-100 protein are increased in the hippocampus cytosol, suggesting that oxidative stress triggers the cascade of events that finally leads to neuronal damage. Dehydroepiandrosterone, the most abundant hormonal steroid in the blood, has been reported to possess antioxidant properties. When dehydroepiandrosterone was administered to diabetic rats, the improved oxidative imbalance and the marked reduction of AGE receptors paralleled the reduced activation of nuclear factor kappaB and the reduction of S-100 levels, reinforcing the suggestion that oxidative stress plays a role in diabetes-related neuronal damage.

Adipocytokines: leptin--the classical, resistin--the controversical, adiponectin--the promising, and more to come

With the growing prevalence of obesity, scientific interest in the biology of adipose tissue has been extended to the secretory products of adipocytes, since they are increasingly shown to affect several aspects in the pathogenesis of obesity-related diseases. The cloning of the ob gene is consistent with this concept and suggests that body fat content in adult rodents is regulated by a negative feedback loop centred in the hypothalamus. In recent years, a number of additional signalling molecules secreted by adipose tissue have been discovered, commonly referred to as 'adipocytokines'. Among these, adiponectin is perhaps the most interesting and promising compound for the clinician since it has profound protective actions in the pathogenesis of diabetes and cardiovascular disease. Adiponectin is low in obese subjects and, in particular, insulin-resistant patients. In contrast, resistin seems to be of greater relevance in relation to the immune stress response than in the regulation of glucose homeostasis. However, inflammatory processes have recently been connected with the development of atherosclerosis. Finally, little is known regarding the clinical relevance of visfatin. Recent research has revealed many functions of adipocytokines extending far beyond metabolism, such as immunity, cancer and bone formation. This report aims to review some of the recent topics of adipocytokine research that may be of particular importance.

Effect of DHEA on endocrine functions of adipose tissue, the involvement of PPAR gamma

Dehydroepiandrosterone (DHEA), an adrenal steroid, is known to decrease body fat. Thus, it may also alter the endocrine functions of adipose tissue. The aim of this study was to determine if administration of DHEA might influence adiponectin gene expression and secretion from adipose tissue. We demonstrate here the inducing effect of exogenously administered DHEA on adiponectin gene expression in epididymal WAT and adiponectin levels in serum of rats fed a DHEA-containing diet (0.6%, w/w) for 2 weeks, accompanied by a reduction in epididymal adipose tissue mass. A corresponding increase in peroxisome proliferator-activated receptor gamma (PPAR(gamma)) mRNA expression suggests that PPAR(gamma) may be involved in the up-regulation of adiponectin gene expression after DHEA treatment. The presented observations indicate that the positive effects of DHEA, which seems to play a protective role against insulin resistance and atherosclerosis, may be in fact indirect and due to up-regulation of adiponectin gene expression and stimulation of adiponectin secretion from adipose tissue.

Resistin stimulation of 17alpha-hydroxylase activity in ovarian theca cells in vitro: relevance to polycystic ovary syndrome

CONTEXT

A newly discovered hormone resistin has been shown to be increased in women with polycystic ovary syndrome (PCOS).

OBJECTIVE

The purpose of this study was to confirm increased resistin concentrations in women with PCOS and to test the direct effect of resistin on human theca cell androgen production.

DESIGN

Resistin was measured in fasting serum samples by RIA. To test the direct effects of resistin on ovarian androgen biosynthesis, human theca cells were cultured with resistin for 3 d in the presence and absence of forskolin and insulin.

PATIENTS

Fasting serum samples were obtained from 45 women with PCOS and 74 regularly cycling premenopausal control women in the follicular phase of their menstrual cycles, and ovarian theca cell cultures were established from two control women.

RESULTS

The mean serum resistin concentration was increased (40%) in women with PCOS. Serum resistin concentrations correlated positively with body mass index and testosterone in PCOS women but not in controls. There were no significant correlations between resistin and fasting insulin or indicators of insulin resistance when corrected for body mass index. In cultured human theca cells, basal 17alpha-hydroxylase activity was unchanged by resistin alone, but resistin enhanced 17alpha-hydroxylase activity in the presence of forskolin or a combination of forskolin plus insulin. Resistin (> or =1 ng/ml) augmented forskolin and forskolin plus insulin stimulation of CYP17 mRNA expression in a concentration-dependent manner.

CONCLUSION

These data indicate that abnormal resistin secretion in PCOS may play a role in causing ovarian hyperandrogenism.

Dehydroepiandrosterone inhibits the amplification of glucocorticoid action in adipose tissue

Dehydroepiandrosterone (DHEA) exerts beneficial effects on blood glucose levels and insulin sensitivity in obese rodents and humans, resembling the effects of peroxisome proliferator-activated receptor-gamma (PPARgamma) ligands and opposing those of glucocorticoids; however, the underlying mechanisms remain unclear. Glucocorticoids are reactivated locally by 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1), which is currently considered as a promising target for the treatment of obesity and diabetes. Using differentiated 3T3-L1 adipocytes, we show that DHEA causes downregulation of 11beta-HSD1 and dose-dependent reduction of its oxoreductase activity. The effects of DHEA were comparable with those of the PPARgamma agonist rosiglitazone but not additive. Furthermore, DHEA reduced the expression of hexose-6-phosphate dehydrogenase, which stimulates the oxoreductase activity of 11beta-HSD1. These findings were confirmed in white adipose tissue and in liver from DHEA-treated C57BL/6J mice. Analysis of the transcription factors involved in the DHEA-dependent regulation of 11beta-HSD1 expression revealed a switch in CCAAT/enhancer-binding protein (C/EBP) expression. C/EBPalpha, a potent activator of 11beta-HSD1 gene transcription, was downregulated in 3T3-L1 adipocytes and in liver and adipose tissue of DHEA-treated mice, whereas C/EBPbeta and C/EBPdelta, attenuating the effect of C/EBPalpha, were unchanged or elevated. Our results further suggest a protective effect of DHEA on adipose tissue by upregulating PPARalpha and downregulating leptin, thereby contributing to the reduced expression of 11beta-HSD1. In summary, we provide evidence that some of the anti-diabetic effects of DHEA may be caused through inhibition of the local amplification of glucocorticoids by 11beta-HSD1 in adipose tissue.

Effect of tumor necrosis factor-alpha on resistin expression in 3T3-L1 adipocytes and its mechanism

In order to investigate the effect of tumor necrosis factor-alpha (TNFalpha) on resistin expression in 3T3-L1 adipocytes, and further explore its mechanisms, the differentiated 3T3-L1 adipocytes were incubated with 0, 1, 10, 100 ng/mL TNFalpha respectively for 24 h, and then the expression of resistin was determined. The differentiated 3T3-L1 adipocytes were incubated with 100 ng/ mL TNFalpha for 3, 6, 24 h respectively, and then the expression of resistin mRNA was analyzed. 3T3-L1 adipocytes were induced to differentiate into mature adipocytes. The cells were randomly divided into 4 groups for culture. In the control group, no drugs were added. Cells of TNFalpha group were treated with 100 ng/mL TNFalpha. In Ro-31-8220 group, 5 micromol/L protein kinase C inhibitor Ro-31-8220 was added. With TNFalpha+Ro-31-8220 group, 100 ng/mL TNFalpha were added 1 h after the addition of 5 micromol/L Ro-31-8220. All adipocytes were cultured for 24 h. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting were employed to detect the expression of resistin gene. Our results showed that resistin protein and mRNA in 3T3-L1 adipocytes were inhibited by TNFalpha at different concentrations (P<0.01), and the inhibitory effect increased with the concentration (P<0.01). At the same concentrations, the inhibitory effect increased with time (P <0.01). Ro-31-8220 could inhibit its expression and the inhibitive effect remained unchanged with addition of TNFalpha (P>0.05). It was concluded that TNFalpha could inhibit the expression of resistin in 3T3-L1 adipocytes. The mechanism may be that the expression of resistin is partly controlled by protein kinase C signal conduction pathway.