Stimulation of PAI-1 and adipokines by glucose in human adipose tissue in vitro

ApoA-I Mimetic Peptide Reduces Vascular and White Matter Damage After Stroke in Type-2 Diabetic Mice

Diabetes leads to an elevated risk of stroke and worse functional outcome compared to the general population. We investigate whether L-4F, an economical ApoA-I mimetic peptide, reduces neurovascular and white-matter damage in db/db type-2 diabetic (T2DM) stroke mice. L-4F (16 mg/kg, subcutaneously administered initially 2 h after stroke and subsequently daily for 4 days) reduced hemorrhagic transformation, decreased infarct-volume and mortality, and treated mice exhibited increased cerebral arteriole diameter and smooth muscle cell number, decreased blood-brain barrier leakage and white-matter damage in the ischemic brain as well as improved neurological functional outcome after stroke compared with vehicle-control T2DM mice (p < 0.05, n = 11/group). Moreover, administration of L-4F mitigated macrophage infiltration, and reduced the level of proinflammatory mediators tumor necrosis factor alpha (TNFα), high-mobility group box-1 (HMGB-1)/advanced glycation end-product receptor (RAGE) and plasminogen activator inhibitor-1 (PAI-1) in the ischemic brain in T2DM mice (p < 0.05, n = 6/group). In vitro, L-4F treatment did not increase capillary-like tube formation in mouse-brain endothelial cells, but increased primary artery explant cell migration derived from C57BL/6-aorta 1 day after middle cerebral artery occlusion (MCAo), and enhanced neurite-outgrowth after 2 h of oxygen-glucose deprivation and axonal-outgrowth in primary cortical neurons derived from the C57BL/6-embryos subjected to high-glucose condition. This study suggests that early treatment with L-4F provides a potential strategy to reduce neuroinflammation and vascular and white-matter damage in the T2DM stroke population.

Effect of ezetimibe on plasma adipokines: a systematic review and meta-analysis

AIMS

Statins are known to influence the status of adipokines, which play a key role in the pathophysiology of cardiometabolic diseases. As the effect of ezetimibe as an add-on to statin therapy on the impact of statins on plasma adipokines levels is currently unclear, the aim of the present study was to investigate this through a meta-analysis of controlled trials.

METHODS

A systematic review was performed, followed by a bibliographic search in PubMed, Medline, SCOPUS, Web of Science and Google Scholar databases. Quantitative data synthesis was performed using a fixed- or random-effects model (based on the level of interstudy heterogeneity) and the generic inverse variance weighting method. Effect sizes were expressed as standardized mean difference (SMD) and 95% confidence interval (CI).

RESULTS

Meta-analysis of 23 controlled trials did not suggest any significant effect of adding ezetimibe on top of statin therapy on plasma concentrations of adiponectin (SMD 0.34, 95% CI -0.28, 0.96; P = 0.288), leptin (SMD -0.75, 95% CI: -2.35, 0.85; P = 0.360), plasminogen activator inhibitor 1 (SMD -1.06, 95% CI: -2.81, 0.69; P = 0.236) and interleukin 6 (SMD 0.30, 95% CI: -0.08, 0.67; P = 0.124). However, significantly greater reductions in plasma concentrations of tumour necrosis factor α (TNF-α) (SMD -0.48, 95% CI -0.87, -0.08; P = 0.018) were achieved with ezetimibe/statin combination therapy.

CONCLUSIONS

The results suggested that ezetimibe add-on to statin therapy is associated with an enhanced TNF-α-lowering effect compared with statin monotherapy. Owing to the emerging role of TNF-α in the pathogenesis of metabolic disorders, further investigations are required to unveil the translational relevance of this TNF-α-lowering effect.

Plasminogen Activator Inhibitor 1 Activity and Other Coronary Risk Factors

Because only some coronary risk factors have been evaluated for an association with plasma plasminogen activator inhibitor 1 (PAI-1) activity, this cross-sectional study examined the association between 27 coronary risk factors and PAI-1 in 24 healthy persons without coronary heart disease (control persons) and 22 patients who had survived myocardial infarction (cases). The coronary risk factors included major coronary risk factors such as age, anthropometric measures such as intraabdominal fat, and biochemical analytes such as serum concentration of triglyceride and plasma von Willebrand factor activity. The associations were analyzed in univariate and multiple linear regression analyses. For the control persons, triglyceride and von Willebrand factor were significantly associated with PAI-1 activity (p=0.0002, R2=0.55). In contrast for the 24 cases, age and intraabdominal adipose tissue were significantly associated with PAI-1 (p=0.0011, R2=0.51). Coronary risk factors explained more than half the variation of PAI-1 activity for both study groups. However, healthy persons and patients with previous myocardial infarction differed regarding coronary risk factors associated with PAI-1.

Involvement of CSE/ H2S in high glucose induced aberrant secretion of adipokines in 3T3-L1 adipocytes

BACKGROUND

Deregulated secretion of adipokines contributes to subclinical systemic inflammation associated with type 2 diabetes mellitus (T2DM). However, the mechanisms underlying are not fully understood. Hydrogen sulfide (H2S), as an endogenous gasotransmitter, possesses an anti-inflammation activity. The aim of this study was to examine the possible involvement of H2S in high glucose induced adipokine secretion in 3T3-L1 adipocytes.

METHODS

The expression of cystathionine-gamma-lyase (CSE), the H2S-forming enzyme, was evaluated by Western-blotting and real-time PCR. The secretion of TNF-α, MCP-1 and adiponectin was determined by radioimmunoassay and enzyme-linked immunosorbent assay (ELISA), respectively. Lentiviral empty vector and vector expressing mouse CSE were used for in vitro transduction.

RESULTS

High glucose (HG) significantly decreased CSE expression at both protein and mRNA levels in mature 3T3-L1 adipocytes. In parallel, HG significantly increased secretion of MCP-1 while decreasing secretion of adiponectin, but had no effect on secretion of TNF-α. HG induced changes in MCP-1 and adiponectin secretion were partly attenuated by forced expression of CSE or sodium hydrosulfide (NaHS), a source of exogenous H2S.

CONCLUSION

High glucose induces aberrant secretion of adipokines in mature 3T3-L1 adipocytes, favoring inflammation. The mechanism is partly related to inhibition of CSE/ H2S system.

Effect of atorvastatin and fenofibric acid on adipokine release from visceral and subcutaneous adipose tissue of patients with mixed dyslipidemia and normolipidemic subjects

Because of methodological limitations and conflicting results of studies conducted thus far, the possible involvement of human adipose tissue in pleiotropic effects of statins and fibrates requires better understanding. Samples of visceral and subcutaneous adipose tissue obtained from 23 mixed dyslipidemic patients and 23 normolipidemic subjects were treated in vitro for 48 h with atorvastatin, fenofibric acid or both these agents. Visceral and subcutaneous fat of mixed dyslipidemic patients released more leptin, resistin, interleukin-6, tumor necrosis factor alpha (TNFalpha and plasminogen activator inhibitor-1 (PAI-1), and less adiponectin than respective adipose tissue of patients without lipid abnormalities. In both groups of patients, visceral and subcutaneous tissue varied in the amount of secreted adipokines. In dyslipidemic patients both drugs administered alone affected adipose tissue adiponectin and resistin secretion. Additionally, atorvastatin decreased PAI-1 while fenofibric acid reduced leptin release. A combined administration of atorvastatin and fenofibric acid changed the release of all studied markers by visceral fat but did not affect interleukin-6 and TNFalpha release by subcutaneous tissue. In normolipidemic subjects the effect on adipokine release was more pronounced in visceral fat, in which it was strongest if the drugs were given together. Adipose tissue hormonal activity differs between mixed dyslipidemic and normolipidemic patients and between visceral and subcutaneous adipose tissue. Atorvastatin and fenofibrate exhibit their pleiotropic effects in part by changing the adipokine release by human adipose tissue, regardless of its origin. These effects are stronger in patients with mixed dyslipidemia and are particularly pronounced if atorvastatin and fenofibric acid are given together.

Plasminogen activator inhibitor-1 is associated with coronary artery calcium in Type 1 diabetes

BACKGROUND

Elevated levels of plasminogen activator inhibitor-1 (PAI-1), the major inhibitor of fibrinolysis, is associated with coronary artery disease (CAD). This association may not be independent of factors related to insulin resistance (IR). Patients with Type 1 diabetes mellitus have increased CAD and an increase in sub-clinical CAD which develops earlier in life. It is not known if PAI-1 is associated with sub-clinical CAD in Type 1 diabetes or if this association is independent of IR.

METHODS AND RESULTS

Type 1 diabetes patients (n=560) and participants without diabetes (n=693) were assessed for coronary artery calcium (CAC), a surrogate for subclinical CAD, by electron-beam computed tomography. PAI-1 was associated with CAC in both Type 1 diabetes (OR=1.32, 95% CI=1.12-1.58) and non-diabetes (OR=1.34, 95% CI=1.13-1.58), after controlling for traditional risk factors not associated with IR. In Type 1 diabetes, the relationship between PAI-1 and CAC was strongest for younger participants (P=.02 for PAI-1-by-age interaction) after controlling for factors related to IR. PAI-1 was positively associated with CAC for Type 1 diabetes participants younger than 45 years of age.

CONCLUSION

PAI-1 levels are independently related to CAC in younger Type 1 diabetes participants. PAI-1 levels were not independently related to CAC in non-diabetes participants.

Effect of hyperinsulinemia and very-low-calorie diet on interstitial cytokine levels in subcutaneous adipose tissue of obese women

Type 2 diabetes and obesity are associated with an enhanced release of a number of adipocytokines. Hyperinsulinemia, frequently present in type 2 diabetes and obesity, might be one of the drivers of the enhanced production of adipocytokines. The aim of this study was to investigate the interstitial levels of cytokines in subcutaneous adipose tissue (SCAT) in response to hyperinsulinemia and the effect of weight-reducing hypocaloric diet on this regulation in obese subjects. Thirteen obese premenopausal women participated in the study. Concentrations of seven cytokines were measured in plasma and in AT interstitial fluid collected by microdialysis during a euglycemic-hyperinsulinemic clamp and during control infusion of physiological saline. A subgroup of six women underwent a 4-wk very-low-calorie diet (VLCD). Microdialysis during the clamp was performed before and at the end of VLCD. Hyperinsulinemia induced an increase of monocyte chemoatractant protein (MCP-1) and IL-6 SCAT interstitial and plasma levels and elevated IL-8 levels in SCAT. The relative changes of IL-6 levels in the dialysate correlated with changes of IL-8 and MCP-1. The interstitial and plasma levels of IL-1β, IL-10, TNFα, and plasminogen activator inhibitor (PAI-1) remained unchanged in response to hyperinsulinemia. VLCD resulted in enhancement of the hyperinsulinemia-induced augmentation of MCP-1, IL-6, and IL-8 interstitial levels. In conclusion, hyperinsulinemia upregulates the interstitial levels of MCP-1, IL-6, and IL-8 in SCAT in obese women, whereas it does not affect IL-1β, IL-10, TNFα, and PAI-1 levels. Hypocaloric diet associated with weight reduction enhances the hyperinsulinemia-induced upregulation of MCP-1, IL-6, and IL-8 in SCAT.

Metformin decreases angiogenesis via NF-kappaB and Erk1/2/Erk5 pathways by increasing the antiangiogenic thrombospondin-1

AIMS

Polycystic ovary syndrome (PCOS) is associated with insulin resistance (IR), obesity, and cardiovascular complications. Thrombospondin-1 (TSP-1) is a novel antiangiogenic adipokine highly expressed in obese insulin-resistant subjects. We sought to assess TSP-1 levels in adipose tissue (AT) from PCOS women and matched controls. The effects of metformin treatment on circulating TSP-1 levels in PCOS subjects, the effects of serum from normal and PCOS women on in vitro migration and angiogenesis before and after metformin treatment, and ex vivo regulation of AT TSP-1 by D-glucose were also studied.

METHODS AND RESULTS

Serum TSP-1 (ELISA), subcutaneous and omental AT TSP-1 mRNA (reverse transcriptase-polymerase chain reaction), and protein (western blotting) were significantly lower in PCOS women (P < 0.05). Corresponding plasminogen activator inhibitor-1 (PAI-1) and PAI-1 activity were significantly higher (P < 0.01). After 6 months of metformin treatment, there was a significant increase in serum TSP-1 (P < 0.05) and a corresponding decrease in PAI-1 and PAI-1 activity (P < 0.01). In vitro migration and angiogenesis were significantly increased in serum from PCOS women (P < 0.01); these effects were significantly attenuated by metformin treatment (P < 0.01) through the regulation of TSP-1 levels via nuclear factor-kappaB (NF-kappaB), extracellular regulated-signal kinase 1/2 (Erk1/2) and Erk5 pathways. Importantly, changes in the intima media thickness were predictive of changes in serum TSP-1 (P = 0.049). In AT explants, glucose significantly decreased TSP-1 protein production and secretion into conditioned media (ELISA) (P < 0.05, P < 0.001).

CONCLUSION

TSP-1 levels are lower in PCOS women. Metformin treatment increases serum TSP-1 in these women. Our findings provide novel insights into the relationship between obesity, IR, and angiogenesis.

The 4G/5G PAI-1 polymorphism influences the endothelial response to IL-1 and the modulatory effect of pravastatin

BACKGROUND

Increased plasminogen activator inhibitor (PAI-1) levels lead to impaired fibrinolytic function associated with higher cardiovascular risk. PAI-1 expression may be regulated by different inflammatory cytokines such as interleukin-1alpha (IL-1). Several polymorphisms have been described in the PAI-1 gene.

AIM

We examined the influence of the 4G/5G polymorphism in the promoter region on IL-1alpha-induced PAI-1 expression by human umbilical vein endothelial cells (HUVEC) in presence or absence of pravastatin.

METHODS AND RESULTS

Genotyped HUVEC were incubated with IL-1alpha (500 U mL(-1)) in presence or absence of pravastatin (1-10 microm). PAI-1 expression was analyzed by real time polymerase chain reaction (PCR), and PAI-1 antigen measured in supernatants by ELISA. IL-1alpha increased PAI-1 secretion in a genotype-dependent manner, and higher values were observed for 4G/4G compared with both 4G/5G and 5G/5G cultures (P < 0.05). Preincubation of HUVEC with 10 microm pravastatin significantly reduced IL-1-induced PAI-1 expression in 4G/4G HUVEC compared with untreated cultures (177.5% +/- 24.5% vs. 257.9% +/- 39.0%, P < 0.05). Pravastatin also attenuated the amount of secreted PAI-1 by 4G/4G HUVEC after IL-1 stimulation (5020.6 +/- 165.7 ng mL(-1) vs. 4261.1 +/- 309.8 ng mL(-1), P < 0.05). This effect was prevented by coincubation with mevalonate, indicating a dependence on HMG-CoA reductase inhibition.

CONCLUSIONS

The endothelial 4G/5G PAI-1 genotype influences the PAI-1 response to IL-1alpha and the modulatory effect of pravastatin. As increased PAI-1 levels have been linked to cardiovascular disease the observed endothelial modulation by pravastatin may have potential clinical implications.

Acute and prolonged effects of TNF-α on the expression and secretion of inflammation-related adipokines by human adipocytes differentiated in culture

The pro-inflammatory cytokine TNF-alpha has multiple effects on adipocyte function, including the production of adipokines. In this paper, we have examined the acute vs prolonged effects of TNF-alpha on the expression and secretion of key inflammation-related adipokines by human adipocytes. Adipocytes differentiated in culture were treated with TNF-alpha for 1-24 h, mRNA quantitated by real-time polymerase chain reaction (PCR) and secreted adipokines by ELISA. Treatment of adipocytes with TNF-alpha for up to 24 h had little effect on MIF, MT-2 and PAI-1 mRNA levels. TNF-alpha decreased adiponectin, adipsin, haptoglobin and leptin mRNA levels by 24 h, but adiponectin and haptoglobin mRNA was initially increased. In contrast, TNF-alpha induced rapid and substantial increases in expression of the genes encoding IL-6, MCP-1, NGF and TNF-alpha itself; IL-6 and TNF-alpha mRNA levels peaked at 2 h with 75-fold and 600-fold increases, respectively. The elevated MCP-1, NGF and VEGF mRNA levels were sustained between 4 and 24 h. The adipokine secretion pattern largely paralleled cellular mRNA levels; IL-6 (transiently), MCP-1, NGF and VEGF release were stimulated by TNF-alpha, with an accelerating rate of MCP-1 secretion over 24 h. TNF-alpha has rapid and substantial effects on the synthesis of key inflammation-related adipokines in human adipocytes, with highly gene-specific responses.

Association of systemic chemokine concentrations with impaired glucose tolerance and type 2 diabetes: results from the Cooperative Health Research in the Region of Augsburg Survey S4 (KORA S4)

Chemokines are crucial immune mediators in many physiological and pathophysiological conditions. Chemokines have been hypothesized to be involved in macrophage infiltration into adipose tissue in obesity and might therefore play an important role in the development of obesity-related disorders like type 2 diabetes. Out of 1,653 individuals aged 55-74 years participating in a population-based survey in southern Germany (the Kooperative Gesundheitsforschung in der Region Augsburg [KORA] [Cooperative Health Research in the Region of Augsburg] Survey S4, 1999-2001), 236 individuals with type 2 diabetes, 242 subjects with impaired glucose tolerance (IGT), and 244 normoglycemic control subjects were studied for circulating concentrations of interleukin (IL)-8; RANTES (regulated on activation, normal T-cell expressed, and secreted); interferon-gamma-inducible protein-10 (IP-10), and eotaxin. Systemic concentrations of RANTES were higher in individuals with IGT or type 2 diabetes than in control subjects, whereas IL-8 levels were elevated in type 2 diabetic patients only (P < 0.001 for all comparisons). IP-10 and eotaxin were not significantly associated with IGT or type 2 diabetes. Adjustment for age, sex, BMI, hypertension, LDL cholesterol, HDL cholesterol, uric acid, C-reactive protein, and IL-6 did not alter these findings. Our findings indicate that RANTES and IL-8 may be involved in the development of type 2 diabetes independent of metabolic syndrome-related risk factors and of each other. There is no general upregulation of chemokine production in type 2 diabetes, but rather an association of the disease with specific members of the chemokine family.

Plasminogen activator inhibitor type 1 (PAI-1) in plasma and adipose tissue in HIV-associated lipodystrophy syndrome. Implications of adipokines

BACKGROUND

PAI-1, an important inhibitor of fibrinolysis, is increased in obese subjects and has been shown to be an independent risk factor for cardiovascular disease. In the present study, we investigated the association between circulating levels of PAI-1 and locally produced PAI-1 in adipose tissue and body fat distribution and adipokines (TNF-alpha, TNF receptors, IL-6, IL-8) in patients with and without HIV-associated lipodystrophy syndrome (HALS).

MATERIALS AND METHODS

Eighteen men with HALS and 18 men with HIV but without HALS were investigated. DEXA and computed tomography scan were performed to determine total body fat and visceral adipose tissue mass. Insulin sensitivity was determined by the euglycaemic clamp technique. Plasma levels of PAI-1 and cytokines were determined. In addition, PAI-1, TNF-alpha, IL-6 and IL-8 mRNA levels in subcutaneous adipose tissue were measured by real-time reverse transcriptase polymerase chain reaction.

RESULTS

HALS patients were characterized by a 3-fold increased visceral adipose tissue (P < 0.001) and reduced limb fat (P < 0.01) as compared with non-HALS patients but with no difference in total fat mass between the groups. Plasma PAI-1 was increased in HALS patients (16.7 ng mL(-1) vs. 8.2 ng mL(-1), P < 0.05). Plasma PAI-1 was positively correlated with BMI (r = 0.74, P < 0.01), plasma TNF-alpha level (r = 0.64, P < 0.01), sTNFR-I (r = 0.38, P < 0.05), and visceral fat (r = 0.67, P < 0.01). Moreover, plasma PAI-1 was negatively associated with insulin sensitivity (r = -0.57, P < 0.01) and the percentage of limb fat (r = -0.57, P < 0.01). A positive correlation was found between plasma PAI-1 and TNF-alpha mRNA level. No association was, however, found between plasma PAI-1 and PAI-1 mRNA level in adipose tissue.

CONCLUSION

Plasma PAI-1 is increased in HALS patients and it is suggested that dysregulation of the TNF-system (high TNFalpha and high sTNFR1) may play a role in up-regulating PAI-1 in HALS.

Expression and secretion of inflammation-related adipokines by human adipocytes differentiated in culture: integrated response to TNF-alpha

The expression profile of a series of adipokine genes linked to inflammation has been examined by quantitative PCR during the differentiation of human preadipocytes to adipocytes in primary culture, together with the integrated effects of TNF-alpha on the expression of these adipokines in the differentiated adipocytes. Expression of the genes encoding adiponectin, leptin, and haptoglobin was highly differentiation dependent, the mRNA being undetectable predifferentiation with the level peaking 9-15 days postdifferentiation. Although angiotensinogen (AGT) and monocyte chemoattractant protein-1 (MCP-1) were both expressed before differentiation, the mRNA level increased markedly on differentiation. The expression of nerve growth factor (NGF) and plasminogen activator inhibitor-1 (PAI-1) fell after differentiation, whereas that of TNF-alpha and IL-6 changed little. Measurement of adiponectin, leptin, MCP-1, and NGF in the medium by ELISA showed that the protein secretion pattern paralleled cellular mRNA levels. Treatment of differentiated human adipocytes with TNF-alpha (5 or 100 ng/ml for 24 h) significantly decreased the level of adiponectin, AGT, and haptoglobin mRNA (by 2- to 4-fold), whereas that of leptin and PAI-1 was unchanged. In contrast, TNF-alpha induced substantial increases in IL-6, TNF-alpha, metallothionein, MCP-1, and NGF mRNAs, the largest increase being with MCP-1 (14.5-fold). MCP-1 and NGF secretion increased 8- to 10-fold with TNF-alpha, whereas leptin and adiponectin did not change. These results demonstrate that there are major quantitative changes in adipokine gene expression during differentiation of human adipocytes and that TNF-alpha has a pleiotropic effect on inflammation-related adipokine production, the synthesis of MCP-1 and NGF being highly induced by the cytokine.

TNF-alpha, but not IL-6, stimulates plasminogen activator inhibitor-1 expression in human subcutaneous adipose tissue

Plasminogen activator inhibitor-1 (PAI-1) is produced by adipose tissue, and elevated PAI-1 levels in plasma are a risk factor in the metabolic syndrome. We investigated the regulatory effects of TNF-alpha and IL-6 on PAI-1 gene induction in human adipose tissue. Twenty healthy men underwent a 3-h infusion of either recombinant human TNF-alpha (n = 8), recombinant human IL-6 (n = 6), or vehicle (n = 6). Biopsies were obtained from the subcutaneous abdominal adipose tissue at preinfusion, at 1, 2, and 3 h during the infusion, and at 2 h after the infusion. The mRNA expression of PAI-1 in the adipose tissue was measured using real-time PCR. The plasma levels of TNF-alpha and IL-6 reached 18 and 99 pg/ml, respectively, during the infusions. During the TNF-alpha infusion, adipose PAI-1 mRNA expression increased 2.5-fold at 1 h, 6-fold at 2 h, 9-fold at 3 h, and declined to 2-fold 2 h after the infusion stopped but did not change during IL-6 infusion and vehicle. These data demonstrate that TNF-alpha rather than IL-6 stimulates an increase in PAI-1 mRNA in the subcutaneous adipose tissue, suggesting that TNF-alpha may be involved in the pathogenesis of related metabolic disorders.