Adipokine inflammation and insulin resistance: the role of glucose, lipids and endotoxin

Adipose tissue is an active endocrine organ, and our knowledge of this secretory tissue, in recent years, has led us to completely rethink how our body functions and becomes dysregulated with weight gain. Human adipose tissue appears to act as a multifunctional secretory organ with the capacity to control energy homoeostasis through peripheral and central regulation of energy homoeostasis. It also plays an important role in innate immunity. However, the capability to more than double its original mass to cope with positive energy balance in obesity leads to many pathogenic changes. These changes arise within the adipose tissue as well as inducing secondary detrimental effects on other organs like muscle and liver, including chronic low-grade inflammation mediated by adipocytokines (adipokine inflammation). This inflammation is modulated by dietary factors and nutrients including glucose and lipids, as well as gut bacteria in the form of endotoxin or LPS. The aim of this current review is to consider the impact of nutrients such as glucose and lipids on inflammatory pathways, specifically within adipose tissue. Furthermore, how nutrients such as these can influence adipokine inflammation and consequently insulin resistance directly through their effects on secretion of adipocytokines (TNFα, IL6 and resistin) as well as indirectly through increases in endotoxin is discussed.

Identification of a novel heterozygous mutation in exon 50 of the COL1A1 gene causing osteogenesis imperfecta

A 19-year-old woman was diagnosed with osteogenesis imperfecta (OI). She had sustained numerous low-trauma fractures throughout her childhood, including a recent pelvic fracture (superior and inferior ramus) following a low-impact fall. She had the classical blue sclerae, and dual energy X-ray absorptiometry (DEXA) bone scanning confirmed low bone mass for her age in the lumbar spine (Z-score was −2.6). However, despite these classical clinical features, the diagnosis of OI had not been entertained throughout the whole of her childhood. Sequencing of her genomic DNA revealed that she was heterozygous for the c.3880_3883dup mutation in exon 50 of the COL1A1 gene. This mutation is predicted to result in a frameshift at p.Thr1295, and truncating stop codon 3 amino acids downstream. To our knowledge, this mutation has not previously been reported in OI.

Glucose oscillations, more than constant high glucose, induce p53 activation and a metabolic memory in human endothelial cells

AIMS/HYPOTHESIS

Damage persists in HUVECs exposed to a constant high glucose concentration long after glucose normalisation, a phenomenon termed 'metabolic memory'. Evaluation of the effects of exposure of HUVECs to oscillating high glucose on the induction of markers of oxidative stress and DNA damage (phospho-γ-histone H2AX and PKCδ) and onset of metabolic memory, and the possible role of the tumour suppressor transcriptional factor p53 is of pivotal interest.

METHODS

HUVECs were incubated for 3 weeks in 5 or 25 mmol/l glucose or oscillating glucose (24 h in 5 mmol/l glucose followed by 24 h in 25 mmol/l glucose) or for 1 week in constant 5 mmol/l glucose after being exposed for 2 weeks to continuous 25 mmol/l high glucose or oscillating glucose. Transcriptional activity of p53 was also evaluated in the first 24 h after high glucose exposure.

RESULTS

High constant glucose upregulated phospho-γ-histone H2AX and protein kinase C (PKC)δ compared with control. Oscillating glucose was even more effective than both normal and constant high glucose. Both constant and oscillating glucose resulted in a memory effect, which was more pronounced in the oscillating condition. Transcriptional activity of p53 peaked 6 h after glucose exposure, showing a predicted oscillatory behaviour.

CONCLUSIONS/INTERPRETATION

Exposure to oscillating glucose was more deleterious than constant high glucose and induced a metabolic memory after glucose normalisation. Hyperactivation of p53 during glucose oscillation might be due to the absence of consistent feedback inhibition during each glucose spike and might account for the worse outcome of this condition.

Ghrelin promotes nuclear factor kappa-B activation in a human B-lymphocyte cell line

Ghrelin, an orexigenic hormone of gastric origin that stimulates growth hormone secretion, may modulate inflammation. This experimental study examines the effect of ghrelin on NFκB (p65 subunit), a transcriptional factor involved in inflammation on a human B-lymphocyte cell (WILCL). After confirming the expression of ghrelin receptor protein using western blotting the cells were transferred to wells maintaining a density of 1 × 10(6) cells per ml and a proportion activated with phytohaemagluttinin. Activated and resting cells were exposed to octanoyl-, desoctanoyl ghrelin and a non-peptide ghrelin agonist (Pfizer CP-464709) in increasing concentrations for 6 h. Cell protein extracts were analyzed for NFκB activation using Trans AM NFκB p65 assay. IL-6, IL-8, IL-10, IL-13 and TNFα were measured in the media using Lincoplex human cytokine assay. In octanoyl ghrelin treated resting cells, NFκB activity (Optical Density OD(450 nm)) (mean ± SEM) in control cells was 0.42 ± 0.10 and increased to 0.61 ± 0.20 (P = 0.044), 0.54 ± 0.10 (P = 0.043), 0.52 ± 0.08 at 1, 10 and 100 nM concentrations respectively. No effect was detected with desoctanoyl ghrelin or ghrelin agonist and no specific change in cytokine production. In conclusion, Octanoyl ghrelin increased NFκB activation by up to 50% in a B-lymphocyte cell line suggesting an effect on the inflammatory process.

Low serum adiponectin predicts 10-year risk of type 2 diabetes and HbA1c independently of obesity, lipids, and inflammation: Whitehall II study

Our aim of the present work was to study the effect of serum adiponectin on incident diabetes and HbA1c values. We measured baseline serum adiponectin levels in a nested case-control selection (n=140) of the Whitehall II Cohort. Participants (mean [SD] age 50.9 [6.3] years) had no prevalent diabetes or CHD at baseline. Cases (n=55) had incident diabetes according to an oral glucose tolerance test during follow-up (mean: 11.5+/-3.0 years). Adiponectin levels were lower among cases (9.3 microg/ml, 3.2 [median; IQR] vs. 10.5; 3.6, p=0.01). The risk of incident diabetes decreased by 11% (p=0.03) for 1 microg/ml higher adiponectin levels. Higher adiponectin levels were associated with lower HbA1c at follow-up (p<0.05). Both associations were stable to adjustment for age, sex, body mass index, systolic blood pressure, and serum lipids, and for the case of HbA1c, also for C-reactive protein (all p<0.05). The observed robust, prospective associations support that adiponectin is an independent predictor of diabetes and the degree of glycaemic impairment.

DPP-IV inhibition enhances the antilipolytic action of NPY in human adipose tissue

CONTEXT

Dipeptidyl peptidase IV (DPP-IV) inactivates the incretin hormone glucagon-like peptide. It can also affect the orexigenic hormone neuropeptide Y (NPY(1-36)) which is truncated by DPP-IV to NPY(3-36), as a consequence NPY's affinity changes from receptor Y1, which mediates the antilipolytic function of NPY, to other NPY receptors. Little is known whether DPP-IV inhibitors for the treatment of type 2 diabetic (T2DM) patients could influence these pathways.

AIMS

To investigate the in vitro effects of NPY with DPP-IV inhibition in isolated abdominal subcutaneous (AbdSc) adipocytes on fat metabolism, and assessment of NPY receptor and DPP-IV expression in adipose tissue (AT).

METHODS

Ex vivo human AT was taken from women undergoing elective surgery (body mass index: 27.5 (mean +/- s.d.) +/- 5 kg/m2, age: 43.7 +/- 10 years, n = 36). Isolated AbdSc adipocytes were treated with human recombinant (rh)NPY (1-100 nM) with and without DPP-IV inhibitor (1 M); glycerol release and tissue distribution of DPP-IV, Y1 and Y5 messenger RNA (mRNA) were measured and compared between lean and obese subjects.

RESULTS AND CONCLUSION

rhNPY reduced glycerol release, an effect that was further enhanced by co-incubation with a DPP-IV inhibitor [control: 224 (mean +/- s.e.) +/- 37 micromol/l; NPY, 100 nM: 161 +/- 27 micromol/l**; NPY 100 nM/DPP-IV inhibitor, 1 M: 127 +/- 14 micromol/l**; **p < 0.01, n = 14]. DPP-IV was expressed in AbdSc AT and omental AT with relative DPP-IV mRNA expression lower in AbdSc AT taken from obese [77 +/- 6 signal units (SU)] vs. lean subjects (186 +/- 29 SU*, n = 10). Y1 was predominantly expressed in fat and present in all fat depots but higher in obese subjects, particularly the AbdSc AT-depot (obese: 1944 +/- 111 SU vs. lean: 711 +/- 112 SU**, n = 10). NPY appears to be regulated by AT-derived DPP-IV. DPP-IV inhibitors augment the antilipolytic effect of NPY in AT. Further studies are required to show whether this explains the lack of weight loss in T2DM patients treated with DPP-IV inhibitors.

Ghrelin and the differential regulation of des-acyl (DSG) and oct-anoyl ghrelin (OTG) in human adipose tissue (AT)

OBJECTIVES

Ghrelin, an important central acting orexigenic hormone, is predominantly secreted in the gastrointestinal tract. However little is known about the action of ghrelin in human adipose tissue (AT).

AIM

To study the expression of ghrelin in AT, the effects of octanoyl-(OTG) and des-acyl (DSG) ghrelin on lipolysis and lipogenesis, leptin release and potential peripheral signalling through the Y1 receptor.

METHODS

Ex vivo human AT was obtained from women undergoing elective surgery (46 (mean +/- SD) 6.8 years, body mass index (BMI): 25.6 +/- 5.0 kg/m(2), n = 20). Abdominal-subcutaneous (AbdSc) adipocytes were isolated and treated with recombinant human (rh) OTG and DSG to assess lipid metabolism leptin release and the influence of Y1-receptor blocker.

RESULTS

Ghrelin was expressed in AbdScAT and negatively correlated with BMI (lean: 3.6 +/- 0.74 optical-density-units (OD), obese: 1.64 +/- 0.45 OD, *P < 0.05). Only DSG significantly suppressed glycerol release (Control (C): 286 +/- 58 microl/l; DSG 1 nm: 224 +/- 38 microl/l downward arrow*; DSG 100 nm: 172 +/- 13 microl/l downward arrow*,* downward arrow P < 0.05, n = 7) and reduced hormone sensitive lipase expression (C: 1.0 +/- 0.3 OD; DSG 1 nm: 0.8 +/- 0.3 OD downward arrow*; DSG 100 nm: 0.6 +/- 0.1 OD downward arrow*, n = 4). However, both isoforms increased lipoprotein lipase expression (C: 1.0 +/- 0.3OD; DSG 100 nm: 0.2 +/- 0.4 OD upward arrow*; OTG 100 nm: 2.5 +/- 0.3 OD upward arrow*, n = 4), whilst blockade of Y1 eliminated this effect in both. Leptin was down-regulated by DSG only (DSG 1 nm: 5.3 +/- 0.7 ng/ml; DSG 100 nm: 4.1 +/- 0.7 ng/ml*) and was significant after BMI adjustment (P = 0.029).

CONCLUSION

Ghrelin was expressed in human AbdSc AT. In vitro, both OGT and DSG appear to mediate fat deposition with the lipogenic effects in part mediated by the Y1 receptor, whilst the influence of DSG affected lipolysis, lipogenesis and leptin secretion. Taken together, these studies support a local action for ghrelin isoforms on lipid and adipokine metabolism that further supports a cross talk between organs.

Increased plasma ghrelin following infliximab in Crohn's disease

BACKGROUND

Ghrelin, a potent orexigenic peptide produced by the stomach, may be affected by circulating inflammatory mediators.

AIM

To assess the effect of an anti-TNFα antibody on ghrelin in patients with Crohn's disease (CD).

METHODS

Fifteen patients with Crohn's receiving infliximab were studied before and 1 week after infusion. Following an overnight fast, blood was sampled before a meal and then every 20 min for 2 h. Total ghrelin and CRP were measured using ELISA. Acylated ghrelin and TNFα, IFNγ, IL-1β and IL-6 were measured with bioplex. Harvey Bradshaw Activity Index was assessed.

RESULTS

Median (95% CI) 2-h integrated plasma total ghrelin increased from 162 (99-311) before infliximab to 200 (128-387) pg/mL h, (P = 0.02) after. Following infliximab, 20 min postmeal, median acylated ghrelin decreased from 50.3 (24-64) to 38.6 (26-82) pg/mL, (P = 0.04) thus reverting to a traditional meal related ghrelin curve. Median (range) disease activity decreased from 5 (2-28) before to 3 (0-22), (P = 0.0001) and Median (95% CI) TNFα decreased from 2.8 (1.89-4.48) to 1.31 (0.73-2.06) pg/mL (P = 0.002).

CONCLUSIONS

Infliximab increases circulating total ghrelin by 25% in CD and restores the postprandial response of acylated ghrelin to food intake. Acylated and de-sacyl ghrelin remain unchanged, suggesting that an alternate isoform could be affected by infliximab.

Epicardial adipose tissue as a source of nuclear factor-kappaB and c-Jun N-terminal kinase mediated inflammation in patients with coronary artery disease

CONTEXT

Visceral adipose tissue (AT) is known to confer a significantly higher risk of type 2 diabetes and cardiovascular disease. Epicardial AT has been shown to be related to cardiovascular disease and myocardial function through unidentified mechanisms. Epicardial AT expresses an inflammatory profile of proteins; however, the mechanisms responsible are yet to be elucidated.

OBJECTIVES

The objectives of the study were to: 1) examine key mediators of the nuclear factor-kappaB (NFkappaB) and c-Jun N-terminal kinase (JNK) pathways in paired epicardial and gluteofemoral (thigh) AT from coronary artery disease (CAD) and control patients and 2) investigate circulating endotoxin levels in CAD and control subjects.

DESIGN

Serums and AT biopsies (epicardial and thigh) were obtained from CAD (n = 16) and non-CAD (n = 18) patients. Inflammation was assessed in tissue and serum samples through Western blot, real-time PCR, ELISAs, and activity studies.

RESULTS

Western blotting showed epicardial AT had significantly higher NFkappaB, inhibitory-kappaB kinase (IKK)-gamma, IKKbeta, and JNK-1 and -2 compared with thigh AT. Epicardial mRNA data showed strong correlations between CD-68 and toll-like receptor-2, toll-like receptor-4, and TNF-alpha. Circulating endotoxin was elevated in patients with CAD compared with matched controls [CAD: 6.80 +/- 0.28 endotoxin unit(EU)/ml vs. controls: 5.52 +/- 0.57 EU/ml; P<0.05].

CONCLUSION

Epicardial AT from patients with CAD shows increased NFkappaB, IKKbeta, and JNK expression compared with both CAD thigh AT and non-CAD epicardial AT, suggesting a depot-specific as well as a disease-linked response to inflammation. These studies implicate both NFkappaB and JNK pathways in the inflammatory profile of epicardial AT and highlight the role of the macrophage in the inflammation within this tissue.

Effects of menopausal status on circulating calcitonin gene-related peptide and adipokines: implications for insulin resistance and cardiovascular risks

OBJECTIVES

To determine, first, the effects of menopausal status on circulating calcitonin gene-related peptide (CGRP) levels and, second, the correlation between circulating CGRP levels and biomarkers for cardiovascular disease.

METHODS

Cross-sectional study of healthy premenopausal and postmenopausal women volunteers and women admitted for elective benign abdominal surgery in a district general hospital. All women were non-smokers, had no history of endocrinological problems and were not receiving any hormone therapy. Fasting blood samples (premenopausal (n = 45): follicle stimulating hormone (FSH) < 20 IU/l, estradiol (mean +/- SEM) 440.33 +/- 51.82 pmol/l; postmenopausal women (n = 28): FSH > 20 IU/l, estradiol 93.79 +/- 17.40 pmol/l) were analyzed for CGRP, resistin, leptin, adiponectin, insulin and lipids using ELISA and immunoassays.

RESULTS

Mean circulating CGRP levels were higher in the postmenopausal women compared with premenopausal women (pre: 41.79 +/- 9.01 pg/ml, post: 138.14 +/- 45.75 pg/ml; p = 0.047). Among women who were experiencing hot flushes, the postmenopausal women had significantly higher CGRP levels than the premenopausal women (pre: 21.98 +/- 4.95 pg/ml, post: 171.08 +/- 61.80 pg/ml; p = 0.028). Serum CGRP levels positively correlated with serum insulin levels (r = 0.652, p = 0.016) and HOMA index (r = 0.54, p < 0.001).

CONCLUSION

These data show that circulating CGRP levels are influenced by menopausal status and suggest additional mechanisms through which increased risk of hyperinsulinemia and cardiovascular disease may arise in postmenopausal women.

MRI total sagittal abdominal diameter as a predictor of metabolic syndrome compared to visceral fat at L4-L5 level

OBJECTIVE

To compare associations between anteroposterior (AP) diameter or sagittal abdominal diameter - a measure of total central fat, and visceral fat alone with the metabolic syndrome as defined by ATPIII criteria.

RESEARCH DESIGN AND METHODS

Twenty-four Caucasian male with type 2 diabetes and 24 non-diabetic Caucasian male subjects [body mass index (BMI) (+/-SD): 32.23 +/- 7.52 kg/m(2), age (+/-SD): 51.35 +/- 13.80 years] were studied by magnetic resonance imaging (MRI) scan to measure central fat at L4-L5 level. The visceral and total central adipose tissue was calculated in cm(2) and total sagittal MRI diameter and visceral sagittal MRI diameters in cm. Components of the ATPIII definition of the metabolic syndrome and circulating adipocytokine concentrations were also measured.

RESULTS

MRI total sagittal abdominal diameter was positively associated with waist circumference in controls (r=0.62, p=0.007) and in diabetic subjects (r=0.81, p<0.001). Binary logistic regression analysis showed that MRI-calculated total sagittal diameter (r=0.61, p=0.002) was a more significant predictor of the adverse metabolic profile of the metabolic syndrome than MRI-assessed visceral fat. Receiver operating characteristic curves revealed that MRI-calculated total sagittal diameter most effectively identified subjects with the metabolic syndrome.

CONCLUSIONS

MRI-calculated total sagittal abdominal diameter is a non-validated MRI method that predicts the adverse metabolic profile of the ATPIII definition of the metabolic syndrome. Antero-posterior fat is a dimension of central fat that seems to be more closely associated with cardiovascular risk compared to visceral fat.

Effect of the orlistat on serum endotoxin lipopolysaccharide and adipocytokines in South Asian individuals with impaired glucose tolerance

BACKGROUND

Orlistat has been shown to increase adiponectin and reduce progression to type 2 diabetes in obese Caucasians. Some effects of orlistat are thought to be independent of weight loss by altering gut flora and the production of endotoxin lipopolysaccharide (LPS). We studied the effect of dietary treatment with and without orlistat in South Asian individuals with impaired glucose tolerance (IGT) on adiponectin and inflammatory markers including LPS.

METHODS

South Asian individuals were randomised to either dietary treatment with orlistat or dietary treatment alone. At the end of 12 months, a comparison was made between the two groups for differences in anthropomorphic measurements and serum markers.

RESULTS

Three hundred and five individuals underwent oral glucose tolerance test of whom 40 had IGT. Complete baseline and 1-year data was available for 31 patients. After 1 year, patients in the orlistat group demonstrated a greater but insignificant decrease in weight (4.5 +/- 0.1 kg), and a significant increase in adiponectin (6.73 +/- 3.2 microg/ml) and decrease in LPS (4.55 +/- 1.98 EU/ml) compared with- the diet-alone group. In the orlistat group the reduction in LPS was correlated with the increase in adiponectin (p < 0.005).

CONCLUSION

The increase in adiponectin levels in the orlistat group would suggest that orlistat may reduce the progression to type 2 diabetes in South Asian individuals by raising serum adiponectin. The finding that LPS levels are also reduced by orlistat and that this reduction correlates with the increase in adiponectin raises the possibility that the increase in adiponectin may be mediated via an effect on LPS levels.

Dydrogesterone and norethisterone regulate expression of lipoprotein lipase and hormone-sensitive lipase in human subcutaneous abdominal adipocytes

AIM

In premenopausal women, hyperandrogenicity is associated with central obesity and an increased cardiovascular risk. The aim of this study was to investigate the effects of dydrogesterone (DYD) (a non-androgenic progestogen) and norethisterone (NET) (an androgenic progestogen) on lipoprotein lipase (LPL), hormone-sensitive lipase (HSL) and glycerol release in adipocytes isolated from subcutaneous abdominal adipose tissue.

METHODS

Adipose tissue was obtained from 12 non-diabetic women, mean age 51 years (range 37-78) and mean body mass index 25.4 kg/m(2) (range 20.3-26.4). Adipocytes were treated with increasing doses of DYD and NET for 48 h prior to protein extraction. Effects on lipogenesis and lipolysis were assessed using western blotting to determine the expression of key enzymes, LPL (56 kDa) and HSL (84 kDa) respectively. Measurement of glycerol release into the medium provided an assessment of lipolytic activity.

RESULTS

Expression of LPL was increased by DYD and NET (mean protein expression relative to control +/- s.e.), with greatest effect at 10(-8) M for DYD: 2.32 +/- 0.51 (p < 0.01) and 10(-8) M for NET: 2.06 +/- 0.19 (p < 0.01). In contrast, HSL expression was reduced by all concentrations of DYD, with maximal effect at 10(-9) M : 0.49 +/- 0.02 (p < 0.001). NET reduced HSL expression at all concentrations from 10(-9) M : 0.62 +/- 0.06 (p < 0.001) to 10(-7) M : 0.69 +/- 0.08 (p < 0.001). Glycerol measurements supported the HSL expression studies although they were not statistically significant (p > 0.05).

CONCLUSIONS

DYD and NET significantly increased LPL expression relative to control, while significantly reducing HSL expression. At the concentrations studied, similar effects were observed with the androgenic NET and the non-androgenic DYD despite differing effects on the lipid profile when taken orally in combination with oestrogen. Further work examining the effects of different progestogens on body fat distribution may enable progestogen use to be tailored to maximize benefits and minimize potential harm.

Lipopolysaccharide activates an innate immune system response in human adipose tissue in obesity and type 2 diabetes

Type 2 diabetes (T2DM) is associated with chronic low-grade inflammation. Adipose tissue (AT) may represent an important site of inflammation. 3T3-L1 studies have demonstrated that lipopolysaccharide (LPS) activates toll-like receptors (TLRs) to cause inflammation. For this study, we 1) examined activation of TLRs and adipocytokines by LPS in human abdominal subcutaneous (AbdSc) adipocytes, 2) examined blockade of NF-kappaB in human AbdSc adipocytes, 3) examined the innate immune pathway in AbdSc AT from lean, obese, and T2DM subjects, and 4) examined the association of circulating LPS in T2DM subjects. The findings showed that LPS increased TLR-2 protein expression twofold (P<0.05). Treatment of AbdSc adipocytes with LPS caused a significant increase in TNF-alpha and IL-6 secretion (IL-6, CONTROL: 2.7+/-0.5 vs. LPS: 4.8+/-0.3 ng/ml; P<0.001; TNF-alpha,

CONTROL

1.0+/-0.83 vs. LPS: 32.8+/-6.23 pg/ml; P<0.001). NF-kappaB inhibitor reduced IL-6 in AbdSc adipocytes (

CONTROL

2.7+/-0.5 vs. NF-kappaB inhibitor: 2.1+/-0.4 ng/ml; P<0.001). AbdSc AT protein expression for TLR-2, MyD88, TRAF6, and NF-kappaB was increased in T2DM patients (P<0.05), and TLR-2, TRAF-6, and NF-kappaB were increased in LPS-treated adipocytes (P<0.05). Circulating LPS was 76% higher in T2DM subjects compared with matched controls. LPS correlated with insulin in controls (r=0.678, P<0.0001). Rosiglitazone (RSG) significantly reduced both fasting serum insulin levels (reduced by 51%, P=0.0395) and serum LPS (reduced by 35%, P=0.0139) in a subgroup of previously untreated T2DM patients. In summary, our results suggest that T2DM is associated with increased endotoxemia, with AT able to initiate an innate immune response. Thus, increased adiposity may increase proinflammatory cytokines and therefore contribute to the pathogenic risk of T2DM.

Adiponectin complexes in human cerebrospinal fluid: distinct complex distribution from serum

AIMS/HYPOTHESIS

Adiponectin is an adipocyte-derived secretory factor that is specifically produced in adipocytes. It exerts effects on energy homeostasis via peripheral and central mechanisms. However, it is not clear whether adiponectin crosses the blood-brain barrier in humans. In serum, adiponectin circulates in several different complexes, each of which has distinct functions. Here, we wanted to test whether adiponectin can be found in human cerebrospinal fluid (CSF) and whether specific adiponectin complexes are enriched in CSF compared with peripheral serum samples. We also wanted to establish whether there is a sex-related difference with regard to the distribution of adiponectin oligomers in CSF.

MATERIALS AND METHODS

We studied 22 subjects (11 men, 11 women) in this study. Their average BMI was 28.0+/-4.7 kg/m2; average age was 70+/-7 years.

RESULTS

Analysis of total adiponectin revealed that adiponectin protein is present in human CSF at approximately 0.1% of serum concentration. The distribution of adiponectin oligomers differs considerably in CSF from that of serum within matched samples from the same patients. Only the adiponectin trimeric and low-molecular-mass hexameric complexes are found in CSF, with a bias towards the trimeric form in most patients. Male subjects have a higher CSF:serum ratio of total adiponectin (p<0.05; n=20) and have slightly higher trimer levels in serum and CSF than female subjects.

CONCLUSIONS/INTERPRETATION

We conclude that the adiponectin trimer is the predominant oligomer in human CSF.

Serum resistin is associated with C-reactive protein & LDL cholesterol in type 2 diabetes and coronary artery disease in a Saudi population

AIMS

Resistin is an adipocyte-derived factor implicated in obesity-associated type 2 diabetes (T2DM). This study examines the association between human serum resistin, T2DM and coronary heart disease.

METHODS

One hundred and fourteen Saudi Arabian patients (male: female ratio 46:68; age 51.4 (mean +/- SD)11.7 years; median and range: 45.59 (11.7) years and BMI: 27.1 (mean +/- SD) 8.1 Kgm2 median and range: 30.3 (6.3) were studied. Serum resistin and C-reactive protein (CRP), a marker of inflammation CRP levels, were measured in all subjects. (35 patients had type 2 diabetes mellitus (T2DM); 22 patients had coronary heart disease (CHD).

RESULTS

Serum resistin levels were 1.2-fold higher in type 2 diabetes and 1.3-fold higher in CHD than in controls (p = 0.01). In addition, CRP was significantly increased in both T2DM and CHD patients (p = 0.007 and p = 0.002 respectively). The use of regression analysis also determined that serum resistin correlated with CRP levels (p = 0.04, R2 0.045).

CONCLUSION

The findings from this study further implicate resistin as a circulating protein associated with T2DM and CHD. In addition this study also demonstrates an association between resistin and CRP, a marker of inflammation in type 2 diabetic patients.

Serum high molecular weight complex of adiponectin correlates better with glucose tolerance than total serum adiponectin in Indo-Asian males

AIMS/HYPOTHESIS

It is well established that total systemic adiponectin is reduced in type 2 diabetic subjects. To date most studies have been concerned with the singular full-length protein or proteolytically cleaved globular domain. It is, however, apparent that the native protein circulates in serum as a lower molecular weight hexamer and as larger multimeric structures of high molecular weight (HMW). In this study we address the clinical significance of each form of the protein with respect to glucose tolerance.

METHODS

Serum was obtained from 34 Indo-Asian male subjects (BMI 26.5+/-3.1; age 52.15+/-10.14 years) who had undertaken a 2-h oral glucose tolerance test. An aliquot of serum was fractionated using velocity sedimentation followed by reducing SDS-PAGE. Western blots were probed for adiponectin, and HMW adiponectin as a percentage of total adiponectin (percentage of higher molecular weight adiponectin [S(A)] index) was calculated from densitometry readings. Total adiponectin was measured using ELISA; leptin, insulin and IL-6 were determined using ELISA.

RESULTS

Analysis of the cohort demonstrated that total adiponectin (r = 0.625, p = 0.0001), fasting insulin (r = -0.354, p = 0.040) and age (r = 0.567, p = 0.0001) correlated with S(A). S(A) showed a tighter, inverse correlation with 2-h glucose levels (r = -0.58, p = 0.0003) than total adiponectin (r = -0.38, p = 0.0001).

CONCLUSIONS/INTERPRETATION

This study demonstrates the importance of the S(A) index as a better determinant of glucose intolerance than measurements of total adiponectin. Our findings suggest that HMW adiponectin is the active form of the protein.

11beta-hydroxysteroid dehydrogenase type 1 activity in lean and obese males with type 2 diabetes mellitus

Glucocorticoids play an important role in the pathogenesis of obesity and insulin resistance. Impaired conversion of cortisone (E) to cortisol (F) by the type 1 isoenzyme of 11beta-hydroxysteroid dehydrogenase (11beta-HSD) in obesity may represent a protective mechanism preventing ongoing weight gain and glucose intolerance. We have studied glucocorticoid metabolism in 33 male subjects with type 2 diabetes mellitus [age, 44.2 +/- 13 yr; body mass index (BMI), 31.1 +/- 7.5 kg/m(2) (mean +/- sd)] and 38 normal controls (age, 41.4 +/- 14 yr; BMI, 38.2 +/- 12.8 kg/m(2)). Circulating F:E ratios were elevated in the diabetic group and correlated with serum cholesterol and homeostasis model assessment-S. There was no difference in 11beta-HSD1 activity between diabetic subjects and controls. In addition, 11beta-HSD1 activity was unaffected by BMI in diabetic subjects. However, in control subjects, increasing BMI was associated with a reduction in the urinary tetrahydrocortisol+5alpha-tetrahydrocortisol:tetrahydrocortisone ratio (P < 0.05) indicative of impaired 11beta-HSD1 activity. The degree of inhibition correlated tightly with visceral fat mass. Changes in 11beta-HSD1 activity could not be explained by circulating levels of adipocytokines. Impaired E to F metabolism in obesity may help preserve insulin sensitivity and prevent diabetes mellitus. Failure to down-regulate 11beta-HSD1 activity in patients with diabetes may potentiate dyslipidemia, insulin resistance, and obesity. Inhibition of 11beta-HSD1 may therefore represent a therapeutic strategy in patients with type 2 diabetes mellitus and obesity.

Modest weight loss and reduction in waist circumference after medical treatment are associated with favorable changes in serum adipocytokines

Modest weight loss if maintained is associated with significant metabolic benefits and reduction in cardiovascular risk. Adipose tissue secretes cytokines believed to contribute to the pathogenesis of insulin resistance and cardiovascular risk. We therefore observed the effect of modest weight loss on serum adipocytokines and their relationship with changes in anthropometric and metabolic parameters within a period of 6 months in the setting of a routine obesity hospital clinic after various medical treatments. In this prospective, nonrandomized, nonblinded observational study, patients were first given treatment (sibutramine or orlistat) as decided by the treating clinician and then allocated into 1 of 2 groups according to the treatment prescribed. The first group included 21 Caucasian nondiabetic female subjects, with a mean (+/-SD) age of 43 +/- 11 years and a mean body mass index (BMI) of 46 +/- 8.6 kg/m(2); subjects were treated with sibutramine 10 or 15 mg/d for weight loss. The second group included 20 Caucasian nondiabetic female subjects, mean age 42 +/- 9 years and mean BMI 45.2 +/- 5.2 kg/m(2); orlistat was introduced after 1 month on a low-fat (</=30%) diet in this group. Blood pressure and anthropometric measurements were performed before and after weight loss by a single observer. Serum glucose, insulin, lipid profile, C-reactive protein (CRP), resistin, leptin, and adiponectin were measured before and after weight loss on a fasting sample. After 6 months, the sibutramine group had a modest mean weight loss of 5.4% (P =.0001), and waist circumference was reduced by 4.5 +/- 1.4 cm. There was a decrease in serum resistin, leptin, and CRP levels, and a rise in serum adiponectin (P <.05). Change (%) (Delta) in BMI (DeltaBMI%) was associated with Deltainsulin(%) (P =.02, r = 0.53) and Deltaleptin(%) (P =.01, r = 0.58). Change in waist was associated with Deltainsulin(%) (P =.005, r = 0.75) and Deltaresistin(%) (P =.03, r = -0.55). The orlistat-treated group had a mean weight loss of 2.5%. Although this group did not show significant change in metabolic parameters, surprisingly there was a greater decrease of resistin (P =.02) associated with comparable (%) increase in adiponectin and (%) reduction of waist circumference and CRP. We conclude that modest weight loss (>5%) after medical treatment in a routine obesity hospital clinic is associated with improvements in insulin sensitivity and lipid profile. Modest weight loss is also associated with potentially favourably changes in serum adipocytokines, particularly in a rise of serum adiponectin. Reduction of waist circumference is associated with a change in serum resistin.

Insulin increases angiotensinogen expression in human abdominal subcutaneous adipocytes

The renin-angiotensin system is an important regulator of blood pressure, and blockade of this system improves blood pressure in obesity and type 2 diabetes. Recently, components of the system have been described in adipose tissue. However, to date no study has investigated the influence of varying insulin concentrations on angiotensinogen (AGT) protein expression in human subcutaneous abdominal fat. Isolated subcutaneous adipocytes were treated with insulin (1-1000 nm) for 48 h. As part of the studies, a novel AGT antibody was developed and validated by Western blotting and immunohistochemistry. Western blotting was performed on the protein extracted from the adipocytes treated with insulin to determine AGT expression. Increasing doses of insulin raised AGT protein expression in a dose-dependent manner (control 1.0 +/- 0.0 (mean +/- s.e.) - protein expression standardized relative to control; 1 nm insulin: 2.64 +/- 0.0.32 upward arrow ***; 100 nm insulin: 4.37 +/- 0.57 upward arrow ***; 1000 nm insulin: 6.50 +/- 0.97 upward arrow ***; ***p < 0.001, n = 3). In conclusion, increasing insulin doses stimulates AGT production. In this study, protein analysis suggests that hyperinsulinaemia may be an important factor in obesity-related hypertension.

Rosiglitazone inhibits the insulin-mediated increase in PAI-1 secretion in human abdominal subcutaneous adipocytes

OBJECTIVE

The aim of this study was to investigate the effect of insulin and an insulin-sensitizing agent, rosiglitazone (RSG), on the production of plasminogen-activator inhibitor-1 (PAI-1) in isolated subcutaneous abdominal adipocytes. Human tissue-type plasminogen activator (t-PA) was also measured to assess changes in overall thrombotic risk.

METHODS

The mean depot-specific expression of PAI-1 and t-PA mRNA (n = 42) in subcutaneous abdominal (n = 21), omental (n = 10) and thigh (n = 11) adipose tissue depots was examined. Furthermore, subcutaneous adipocytes were treated with insulin, RSG and insulin in combination with RSG (10-8 m) for 48 h. Conditioned media were collected and enzyme-linked immunosorbent assays performed for PAI-1 and t-PA (n = 12) antigen. PAI-1 and t-PA mRNA levels were also assessed.

RESULTS

PAI-1 mRNA levels were significantly higher in subcutaneous and omental abdominal tissue than in thigh fat (p = 0.037 and p = 0.014). No change in t-PA mRNA expression between the adipose tissue depots was observed. Insulin stimulated PAI-1 protein secretion in a concentration-dependent manner in adipocytes (control: 68.3 +/- 1.2 ng/ml (s.e.m.); 10 nm insulin: 73.7 +/- 3.8 ng/ml upward arrow; 100 nm insulin: 86.8 +/- 4.1 ng/ml upward arrow **; 1000 nm insulin: 102.0 +/- 4.8 ng/ml upward arrow ***; **p < 0.01, ***p < 0.001). In contrast, insulin + RSG (10-8 m) reduced PAI-1 production relative to insulin alone (***p < 0.001), whilst RSG alone reduced PAI-1 protein secretion in a concentration-dependent manner (RSG at 10-10 m: 50.4 +/- 2.87 ng/ml downward arrow ***; RSG at 10-5 m: 30.3 +/- 2.0 ng/ml downward arrow ***; p < 0.001). No difference was observed between control and treatments for t-PA secretion (range 7-11 ng/ml).

CONCLUSIONS

Insulin stimulated PAI-1 secretion, whilst RSG reduced both PAI-1 secretion alone and in combination with insulin. These data suggest that adipose tissue may contribute significantly to the elevated circulating PAI-1 in obesity. Therefore, RSG's effects on PAI-1 production in adipose tissue may contribute to the fall in circulating PAI-1 levels observed in patients receiving RSG therapy.

17Beta-estradiol and anti-estrogen ICI:compound 182,780 regulate expression of lipoprotein lipase and hormone-sensitive lipase in isolated subcutaneous abdominal adipocytes

We sought to investigate the influence of 17beta-estradiol (E(2)) on key enzymes of lipogenesis and lipolysis in subcutaneous (SC) abdominal adipocytes isolated from women. In addition, we wished to determine the influence of an anti-estrogen, ICI:compound 182,780 (anti-E), known to act via the estrogen receptor (ER), alone and in combination with E(2). Adipose tissue was obtained from 17 women undergoing elective surgery, with a mean age of 47 years (range, 34 to 62), mean weight of 65.4 kg (range, 58.1 to 75.0), and mean body mass index (BMI) of 25 kg/m(2) (range, 22 to 27). Isolated adipocytes were treated with varying doses of E(2), anti-E, or E(2) in combination with anti-E 10(-8) mol/L for 48 hours. Following treatment, proteins were extracted and the effects on lipogenesis and lipolysis were assessed, using Western blotting to determine the relative expression of the key enzymes of these processes, lipoprotein lipase (LPL; 56 kd), and hormone-sensitive lipase (HSL; 84 kd), respectively. Glycerol release into the medium was also measured as an index of lipolytic activity. The protein expression studies demonstrated that E(2) altered expression of LPL relative to control, with the highest dose significantly reducing LPL expression and the lower doses significantly increasing LPL expression (mean protein expression relative to control +/- SE): E(2) 10(-12) mol/L, 1.79 +/- 0.16 (P <.001); E(2) 10(-7) mol/L, 0.56 +/- 0.08 (P <.05). In contrast, HSL expression was increased relative to control at the higher doses of E(2) but was not significantly altered relative to control at the lower doses: E(2) 10(-12) mol/L, 1.02 +/- 0.14 (P >.05); E(2) 10(-7) mol/L, 1.55 +/- 0.17 (P <.01). Anti-E 10(-8) mol/L alone reduced LPL protein expression relative to control (P <.05) and increased HSL protein expression relative to control (P >.05). In combination with E(2) 10(-7) mol/L, anti-E 10(-8) mol/L did not abrogate the inhibitory effect on LPL expression relative to control (P <.05). Furthermore, E(2) 10(-7) mol/Lin combination with anti-E 10(-8) mol/L, displayed a stimulatory effect on HSL expression relative to control (P <.01). Glycerol release studies following the higher doses of E(2), and also following E(2) 10(-7) mol/L in combination with anti-E 10(-8) mol/L, provided support for the HSL protein expression studies. We conclude that the highest concentration of E(2) (10(-7) mol/L) significantly reduced LPL expression relative to control, while the lower concentrations significantly increased LPL expression relative to control. The highest concentration of E(2) also significantly increased both HSL expression and glycerol release relative to control. The effects of anti-E suggest that the in vitro effects of E(2) on lipogenesis and lipolysis occur, at least in part, through a receptor-mediated pathway. In addition, as recently observed in other tissues, ICI:compound 182,780 does not appear to behave as a pure anti-estrogen in isolated human adipocytes.

Fasting serum adiponectin concentration is reduced in Indo-Asian subjects and is related to HDL cholesterol

AIMS

Adiponectin is a 30-kDa protein secreted by adipose tissue. The aim of the present study was to compare serum adiponectin in male Indo-Asian and Caucasian subjects and examine its association with fat topography and metabolic parameters.

METHODS

Diabetic and non-diabetic male subjects (n = 48) were studied. A single observer carried out blood pressure and anthropometric measurements. Serum glucose, insulin, lipid profile and adiponectin (measured by RIA) were measured on a fasting sample.

RESULTS

There was no statistically significant difference in serum adiponectin between diabetic and BMI-matched non-diabetic subjects. However, serum adiponectin was lower in Indo-Asians compared with BMI-matched Caucasians, [median adiponectin (interquartile range) 3.3 (2.1-3.9) vs. 4.9 (3.5-6.6) microg/ml respectively (p = 0.016)]. Univariate analysis showed serum adiponectin to be positively associated with HDL in diabetic (p = 0.039) and non-diabetic subjects (p = 0.0098). Waist circumference (p = 0.02), saggital diameter (p = 0.04) were negatively correlated with serum adiponectin in diabetic subjects. Multiple regression analysis including waist, HDL, fasting insulin, age, diabetes and ethnicity in all subjects showed HDL to be the best predictor of serum adiponectin.

CONCLUSIONS

Serum adiponectin is associated with HDL cholesterol and central obesity. Caucasians have higher serum adiponectin levels compared with Indo-Asians. Further studies are needed to explore basis for the association of adiponectin with HDL cholesterol and the reason for lower levels in Indo-Asians.

Differences in adiponectin protein expression: effect of fat depots and type 2 diabetic status

Adiponectin is an adipocyte-derived hormone associated with insulin sensitivity and atherosclerotic risk. As central rather than gluteofemoral fat is known to increase the risk of type 2 diabetes and cardiovascular disease, we investigated the mRNA and protein expression of adiponectin in human adipose tissue depots. RNA was extracted from 46 human adipose tissue samples from non-diabetic subjects aged 44.33 +/- 12.4 with a BMI of 28.3 +/- 6.0 (mean +/- SD). The samples were as follows: 21 abdominal subcutaneous, 13 omentum, 6 thigh; samples were also taken from diabetic subjects aged 66.6 +/- 7.5 with BMI 28.9 +/- 3.17; samples were: 6 abdominal subcutaneous; 3 thigh. Quantitative PCR and Western analysis was used to determine adiponectin content. Protein content studies determined that when compared with non-diabetic abdominal subcutaneous adipose tissue (Abd Sc AT) (values expressed as percentage relative to Abd Sc AT -100 %). Adiponectin protein content was significantly lower in non-diabetic omental AT (25 +/- 1.6 %; p < 0.0001, n = 6) and in Abd Sc AT from diabetic subjects (36 +/- 1.5 %; p < 0.0001, n = 4). In contrast, gluteal fat maintained high adiponectin protein content from non-diabetic patients compared with diabetic patients. An increase in BMI was associated with lower adiponectin protein content in obese ND Abd Sc AT (25 +/- 0.4 %; p < 0.0001). These findings were in agreement with the mRNA expression data. In summary, this study indicates that adiponectin protein content in non-diabetic subjects remains high in abdominal subcutaneous fat, including gluteal fat, explaining the high serum adiponectin levels in these subjects. Omental fat, however, expresses little adiponectin. Furthermore, abdominal and gluteal subcutaneous fat appears to express significantly less adiponectin once diabetic status is reached. In conclusion, the adipose tissue depot-specific expression of adiponectin may influence the pattern of serum adiponectin concentrations and subsequent disease risk.

The regulation of HSL and LPL expression by DHT and flutamide in human subcutaneous adipose tissue

Clinical observations suggest a role for testosterone in the accumulation of central adiposity and with an associated increased risk of disease. To date, no human study has analysed the role of dihydrotestosterone (DHT) on adipose tissue mass regulation in vitro. This study investigated the role of DHT and androgen receptors (AR) in the regulation of lipolysis and lipogenesis by examining the key enzymes hormone sensitive lipase (HSL) and lipoprotein lipase (LPL) respectively. Isolated abdominal subcutaneous adipocytes (Scad) (n = 15) were treated with either DHT (10(-7)-10(-9) m), an antiandrogen, flutamide (FLT: 10(-7)-10(-9) m) or a combination of DHT (10(-7)-10(-9) m) with FLT (10(-8) m). Relative protein expression of HSL, LPL and AR was determined. In Scad, DHT inhibited HSL expression maximally at 10(-9) m (0.7 +/- 0.4**; p < 0.01**) compared with control (control: 1.0 +/- (s.e.m.) 0.0), whereas LPL protein expression was stimulated at DHT10(-9) m (2.22 +/- 0.48*; p < 0.05*). Glycerol release assay results correlated with HSL expression data. LPL expression was reduced at all doses with combinations of DHT + FLT compared with DHT alone. Androgen receptor expression studies showed an inverse correlation with DHT, whereas DHT + FLT reduced AR expression. These studies indicate that DHT may alter HSL and LPL expression, whereas only LPL expression appears mediated by AR. These findings suggest a physiological role for DHT in the control of adipose tissue mass in women, and indicate that androgens may also play an important role in regulating lipid metabolism.

Resistin, central obesity, and type 2 diabetes

Resistin, an adipocyte-derived cytokine, causes insulin resistance and glucose intolerance in mice. We investigated whether resistin expression was higher in human abdominal adipose tissue than other adipose tissue depots. We extracted RNA from 32 adipose tissue samples (13 subcutaneous abdominal, seven omentum, six thigh, and six breast). Quantitative PCR was used to determine resistin mRNA expression. Resistin mRNA concentrations were similar in both the subcutaneous abdominal and omental depots. The abdominal depots showed a 418% increase in resistin mRNA expression compared with the thigh. Increased resistin expression in abdominal fat could explain the increased risk of type 2 diabetes associated with central obesity.

The effects of androgens and estrogens on preadipocyte proliferation in human adipose tissue: influence of gender and site

The gender-specific differences in body fat distribution suggest that sex steroids play an important role in regulating body fat distribution. Sex steroids may regulate adipose tissue mass by altering adipocyte number and size. The effects of various sex steroids on in vitro proliferation of preadipocytes from both sc and omental fat depots was investigated in men and women. Abdominal sc and omental preadipocytes from men (n = 14) and women (8 premenopausal and 7 postmenopausal) were cultured in the presence of 17beta-E2 (10(-7)-10(-9) M), estrone (10(-7)-10(-9) M), or dehydrotestosterone (DHT) (10(-7)-10(-9) M), and the rate of proliferation was measured over time (1-96 h) by DNA accumulation assays (micromoles per microg) and [(3)H]thymidine incorporation (disintegrations per min). In sc preadipocytes the rate of proliferation was increased between 24-48 h with E2 (10(-7) M) in both men (P = 0.028) and women (P = 0.017). Subcutaneous preadipocytes from women were more responsive to E2 in stimulating proliferation than those from men (women vs. men, DNA assay, 24 h, P = 0.014). In omental preadipocytes the increase in the rate of proliferation occurred at 24 h with E2 (10(-7) M) in women (P = 0.034) and at 48 h in men (P = 0.031). Gender appeared to influence the rate of proliferation by E2 in omental preadipocytes, with maximal stimulation of proliferation at 48 h in preadipocytes from women treated with E2 (10(-7) M; p = 0.007) compared with 72 h in preadipocyte cells from men (P = 0.048), as shown by DNA assay. Both estrone and the androgen DHT had no significant gender- or site-specific effect on the rate of proliferation at any time point. All DNA content data were further validated by thymidine incorporation analysis. In summary, E2 stimulates the rate of proliferation of preadipocytes in a dose-dependent manner, with significant gender- and site-specific differences. Neither estrone nor DHT affected adipocyte mass through proliferation of preadipocytes in this study. In conclusion, E2 may act as an important local factor influencing the proliferation of preadipocytes that may affect fat cell number in a depot- and gender-specific pattern in human abdominal sc and omental adipose tissue.

Site-specific regulation of oestrogen receptor-alpha and -beta by oestradiol in human adipose tissue

AIM

To examine the expression of oestrogen receptors alpha and beta (ERalpha and ERbeta) and their regulation by 17beta-oestradiol (E2) in stromal cells and adipocytes from human subcutaneous (s.c.) and omental (o.m.) adipose tissue.

METHODS

Subcutaneous and o.m. abdominal adipose tissues were obtained from 10 women (mean age 63.5 +/- 4.8 years; mean weight 75.6 +/- 6.7 kg) undergoing elective or cosmetic surgery. Immunohistochemistry and RT-PCR analysis were used to detect the presence of ERalpha and ERbeta. The regulation of ERalpha and ERbeta by E(2) (10(-7) M to 10(-9) M) was examined using Western immunoblotting analysis in both s.c. and o.m. stromal cells and mature adipocytes cultured in serum-free, phenol red-free medium.

RESULTS

Immunostaining of s.c. and o.m. adipose tissue showed that the ER subtypes were localized predominantly within the nucleus. Western analysis demonstrated that E2 treatments differentially altered ERalpha and ERbeta expression in s.c. and o.m. adipocytes. In s.c. and o.m. stromal cells, E(2) (10(-8) M) produced a significant up regulation relative to control of 66 kDa ERalpha (s.c.:1.87 +/- 0.22; o.m.:1.97 +/- 0.17; p < 0.05) and 60 kDa ERbeta (s.c.:1.66 +/- 0.3; o.m.: 1.68 +/- 0.16; p < 0.05). In s.c. adipocytes, however, ERalpha expression significantly decreased with E(2) 10(-8) M relative to control while ERbeta expression increased (ERalpha 0.58 +/- 0.06, ERbeta: 1.47 +/- 0.11; p < 0.05). In o.m. adipocytes, the inhibition of ERalpha with E(2) was not observed (ERalpha 1.86 +/- 0.36, ERbeta:1.03 +/- 0.15, p < 0.05)

CONCLUSIONS

ERalpha and ERbeta are expressed but differentially regulated by E(2) in s.c. and o.m. adipocytes and stromal cells. The upregulation of ERbeta by E(2) suggests that E(2) maintains the expression of these receptors. The feed-back inhibition of ERalpha expression by E(2) in s.c. but not o.m. adipocytes observed in vitro is consistent with the data from ERalpha knock out mice where s.c. fat is increased. Selective ER modulators may have different effects in different adipose sites.

Gender differences in the regulation of P450 aromatase expression and activity in human adipose tissue

OBJECTIVE

To investigate the hormonal regulation of P450 aromatase activity (responsible for the conversion of C19 androgens to C18 oestrogens) in human adipose tissue from men and pre- and post-menopausal women.

SUBJECTS

Subcutaneous abdominal adipose tissue was obtained from 19 subjects: six pre-menopausal females (mean age 41.8+/-(s.e.m.) 2.5; mean weight 76.01+/-5.6 kg), eight post-menopausal females (mean age 59.9+/-2.0; mean weight 63.5+/-2.6 kg), and five males (mean age 35.8+/-8.8; mean weight 78.5+/-7.8 kg) undergoing elective or cosmetic surgery.

MEASUREMENTS

Cell viability and cell size were determined using staining techniques. RT-PCR was used to confirm the presence of aromatase. The regulation of aromatase activity was characterized using androstenedione as a substrate in a tritiated water release assay. Aromatase activity was analysed in abdominal subcutaneous stromal cells (ASC) and mature adipocytes (AD) cultured in serum-free medium with cortisol (10-6-10-7 M), insulin (500 nM) or a combination of both.

RESULTS

In ASC aromatase activity increased in females from 14.5+/-1.7 to 29. 3+/-2.6 pmol/mg/h (n=14, P<0.05) and to 25.2+/-2.1 pmol/mg/h with cortisol (10-7 M) and insulin, respectively (P<0.05). In males ASC basal aromatase activity (20.5+/-4.2 pmol/mg/h; n=5) was inhibited by cortisol (10-7 M) alone (12.3+/-1.8 pmol/mg/h) and in combination with insulin (6.6+/-1.2 pmol/mg/h; men vs women, P<0.005). Aromatase activity in mature adipocytes was stimulated by cortisol plus insulin (P<0.05) with no gender-specific differences. Treatment of ASC from both pre- and post-menopausal females with cortisol alone (10-6 M; 10-7 M) or in combination with insulin demonstrated significantly different aromatase regulation compared with male aromatase stromal cell regulation (P<0.05); however there were no differences in aromatase regulation between pre- and post-menopausal females either in stromal cells or adipocytes.

CONCLUSION

This study shows intrinsic gender differences in the regulation of aromatase, suggesting that differential enzyme regulation may affect sex steroid metabolism to alter the pattern of fat distribution between the sexes.

Hormone-induced changes in nuclear receptor stoichiometry in HL60 cells correlate with induction of monocyte or neutrophil differentiation

HL60 cells differentiate to monocytes or neutrophils in response to 1 alpha,25(OH)2-vitamin D3 (D3) and retinoids respectively. D3 and retinoid actions converge since their receptors (VDR, RAR) heterodimerise with a common partner, RXR, which also interacts with thyroid hormone (T3) receptors (T3R). HL60 cells were treated with combinations of D3 and retinoids to induce differentiation and to investigate whether increased VDR or RAR expression correlated with monocyte or neutrophil differentiation and whether altered receptor concentrations affected DNA-binding specificity. As assessed by Western blotting, VDR and RXR expression was unchanged in monocytes relative to controls but levels of RAR and T3R were reduced. In contrast, only VDR expression was reduced in neutrophils. T3 did not promote differentiation or influence its induction by D3 or retinoids and did not affect expression of any receptor. Gel mobility-shift analysis revealed that nuclear extracts from undifferentiated cells, monocytes and neutrophils interacted differently with VDRE-, RARE- and RXRE-binding sites. Monocyte nuclear protein/DNA complexes contain readily detectable VDR and RXR whereas neutrophil complexes contain RAR and RXR. Thus hormone-induced changes in receptor stoichiometry favour either VDR/RXR or RAR/RXR heterodimerisation and correlate with hormone-induced differentiation of HL60 cells to monocytes or neutrophils respectively.