Protective role of adiponectin against ethanol-induced gastric injury in mice

Adiponectin is an anti-inflammatory molecule released from adipocytes, and serum adiponectin concentrations are reduced in obesity. We previously reported that gastric erosion occurs in association with obesity and low serum adiponectin levels. In the present study, we examined adiponectin-knockout (APN-KO) mice to elucidate the role of adiponectin in gastric mucosal injury. Gastric injury was induced by oral administration of ethanol in wild-type (WT) and APN-KO mice. Ethanol treatment induced severe gastric injury in APN-KO mice compared with WT mice. In APN-KO mice, increased apoptotic cells and decreased expression of prostaglandin E(2) (PGE(2)) were detected in the injured stomach. We next assessed the effect of adiponectin on the cellular response to ethanol treatment and wound repair in rat gastric mucosal cells (RGM1). Adiponectin induced the expression of PGE(2) and cyclooxygenase 2 (COX-2) in ethanol-treated RGM1 cells. RGM1 cells exhibited efficient wound repair accompanied by increased PGE(2) expression in the presence of adiponectin. Coadministration of adiponectin with celecoxib, a COX-2 inhibitor, inhibited efficient wound repair. These findings indicate that adiponectin has a protective role against ethanol-induced gastric mucosal injury in mice. This effect may be partially mediated by the efficient wound repair of epithelial cells via increased PGE(2) expression.     

Functional Effects of Adiponectin on Endothelial Progenitor Cells

Adiponectin is an adipokine whose plasma levels are inversely correlated to metabolic syndrome components. Adiponectin protects against atherosclerosis and decreases risks in myocardial infarction. Endothelial progenitor cells (EPCs) are a heterogeneous population of circulating cells involved in vascular repair and neovascularization. EPCs number is reduced in patients with cardiovascular disease. We hypothesize that the positive effects of adiponectin against atherosclerosis are explained in part by its interactions with EPCs. Cells were obtained from healthy volunteers' blood by mononuclear cell isolation and plating on collagen‐coated dishes. Three sub‐populations of EPCs were identified and characterized using flow cytometry. EPCs' expression of adiponectin receptors, AdipoR1, and AdipoR2 was evaluated by quantitative PCR. The effects of recombinant adiponectin on EPCs' susceptibility to apoptosis were assessed. Finally, expression of neutrophil elastase by EPCs and activity of this enzyme on adiponectin processing were assessed. Quantitative PCR analysis of EPCs mRNAs showed that AdipoR1 mRNA is expressed at higher levels than AdipoR2. Expression of AdipoR1 protein was confirmed by western blot. Adiponectin significantly increased survival of two sub‐populations of EPCs in conditions of serum deprivation. Such effect could not be demonstrated in the third EPCs sub‐population. We also demonstrated that EPCs, particularly one sub‐population, express neutrophil elastase. Neutrophil elastase activity was confirmed in EPCs' conditioned media. Adiponectin protects some EPCs sub‐populations against apoptosis and therefore could modulate EPCs ability to induce repair of vascular damage. Neutrophil elastase activity of EPCs could locally modulate adiponectin activity by its involvement in the generation of the globular form of adiponectin.     

Adiponectin ameliorates doxorubicin-induced cardiotoxicity through Akt protein-dependent mechanism

Accumulating evidence shows that obesity is associated with doxorubicin cardiac toxicity in the heart, but the molecular mechanisms that contribute to this pathological response are not understood. Adiponectin is an adipose-derived, cardioprotective factor that is down-regulated in obesity. Here, we investigated the effect of adiponectin on doxorubicin (DOX)-induced cardiotoxicity and assessed the mechanisms of this effect. A single dose of DOX was intraperitoneally injected into the abdomen of adiponectin knock-out (APN-KO) and wild-type (WT) mice. APN-KO mice had increased mortality and exacerbated contractile dysfunction of left ventricle compared with WT mice. APN-KO mice also showed increased apoptotic activity and diminished Akt signaling in the failing myocardium. Systemic delivery of adenoviral vector expressing adiponectin improved left ventricle dysfunction and myocardial apoptosis following DOX injection in WT and APN-KO mice but not in Akt1 heterozygous KO mice. In cultured rat neonatal cardiomyocytes, adiponectin stimulated Akt phosphorylation and inhibited DOX-stimulated apoptosis. Treatment with sphingosine kinase-1 inhibitor or sphingosine 1-phosphate receptor antagonist diminished adiponectin-induced Akt phosphorylation and reversed the inhibitory effects of adiponectin on myocyte apoptosis. Pretreatment with anti-calreticulin antibody reduced the binding of adiponectin to cardiac myocytes and blocked the adiponectin-stimulated increase in Akt activation and survival in cardiomyocytes. Interference of the LRP1/calreticulin co-receptor system by siRNA or blocking antibodies diminished the stimulatory actions of adiponectin on Akt activation and myocyte survival. These data show that adiponectin protects against DOX-induced cardiotoxicity by its ability to promote Akt signaling.     

Adiponectin protects against myocardial ischemia-reperfusion injury through AMPK- and COX-2-dependent mechanisms

Obesity-related disorders are associated with the development of ischemic heart disease. Adiponectin is a circulating adipose-derived cytokine that is downregulated in obese individuals and after myocardial infarction. Here, we examine the role of adiponectin in myocardial remodeling in response to acute injury. Ischemia-reperfusion in adiponectin-deficient (APN-KO) mice resulted in increased myocardial infarct size, myocardial apoptosis and tumor necrosis factor (TNF)-alpha expression compared with wild-type mice. Administration of adiponectin diminished infarct size, apoptosis and TNF-alpha production in both APN-KO and wild-type mice. In cultured cardiac cells, adiponectin inhibited apoptosis and TNF-alpha production. Dominant negative AMP-activated protein kinase (AMPK) reversed the inhibitory effects of adiponectin on apoptosis but had no effect on the suppressive effect of adiponectin on TNF-alpha production. Adiponectin induced cyclooxygenase (COX)-2-dependent synthesis of prostaglandin E(2) in cardiac cells, and COX-2 inhibition reversed the inhibitory effects of adiponectin on TNF-alpha production and infarct size. These data suggest that adiponectin protects the heart from ischemia-reperfusion injury through both AMPK- and COX-2-dependent mechanisms.     

Adiponectin deficiency exacerbates age-related hearing impairment

Obesity-related disorders are closely associated with the development of age-related hearing impairment (ARHI). Adiponectin (APN) exerts protective effects against obesity-related conditions including endothelial dysfunction and atherosclerosis. Here, we investigated the impact of APN on ARHI. APN-knockout (APN-KO) mice developed exacerbation of hearing impairment, particularly in the high frequency range, compared with wild-type (WT) mice. Supplementation with APN prevented the hearing impairment in APN-KO mice. At 2 months of age, the cochlear blood flow and capillary density of the stria vascularis (SV) were significantly reduced in APN-KO mice as compared with WT mice. APN-KO mice also showed a significant increase in terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive apoptotic cells in the organ of Corti in the cochlea at 2 months of age. At the age of 6 months, hair cells were lost at the organ of Corti in APN-KO mice. In cultured auditory HEI-OC1 cells, APN reduced apoptotic activity under hypoxic conditions. Clinically, plasma APN levels were significantly lower in humans with ARHI. Multiple logistic regression analysis identified APN as a significant and independent predictor of ARHI. Our observations indicate that APN has an important role in preventing ARHI.     

Adiponectin deficiency suppresses ABCA1 expression and ApoA-I synthesis in the liver

Plasma high density lipoprotein (HDL)-cholesterol levels are inversely correlated with the incidence of cardiovascular diseases. HDL is mainly assembled in the liver through the ATP-binding cassette transporter (ABCA1) pathway. In humans, plasma HDL-cholesterol levels are positively correlated with plasma adiponectin (APN) concentrations. Recently, we reported that APN enhanced apolipoprotein A-I (apoA-I) secretion and ABCA1 expression in HepG2 cells. In the present study, we investigated HDL assembly in APN-knockout (KO) mice. The apoA-I protein levels in plasma and liver were reduced in APN-KO mice compared with wild-type-mice. The ABCA1 expression in liver was also decreased in APN-KO mice. APN deficiency might cause the impaired HDL assembly by decreasing ABCA1 expression and apoA-I synthesis in the liver.     

Antioxidants increase number of progenitor endothelial cells through multiple gene expression pathways

To date, there is no report on the effect of antioxidants on endothelial progenitor cells (EPCs). This study shows that in vitro incubation of EPCs with vitamin C and E reverted the already well documented lowering effect of TNF-alpha on EPC number and increased p-p38 expression levels. In order to document major changes of gene expression levels and gain insight into signalling pathways, microarray analysis was performed and a significant variation of the expression of 5389 genes in EPCs following antioxidant treatment was detected. Also in vivo evidence is provided about the positive effect of antioxidant vitamins on EPCs, since vitamin C and E supplementation potentiated the physical training-induced increase of EPC number and VEGF levels. Together, these data indicate that antioxidant treatment ameliorates EPC number and causes major changes of gene expression within these cells in vitro. Furthermore, concomitant antioxidant supplementation and physical training in vivo raised the levels of circulating EPCs and serum VEGF more than physical training alone.     

Adiponectin promotes migration activities of endothelial progenitor cells via Cdc42/Rac1

Adiponectin has anti-atherosclerotic effects through its direct actions on vascular cells. The present study investigates the molecular mechanisms of adiponectin in the migration of endothelial progenitor cells (EPCs) which play an important role in neovascularization and re-endothelization. The phosphorylation of Akt and the activations of Cdc42 and Rac1 were significantly increased by adiponectin. Adiponectin increased the migration activity of EPCs, which was completely inhibited by a PI3-kinase inhibitor. siRNA of Cdc42 or Rac1 completely inhibited the adiponectin-induced migration, but siRNA of Akt had no effects, indicating that adiponectin promotes the migration activities of EPCs mainly through PI3-kinase/Cdc42/Rac1.

Structured summary

MINT-7217629: PAK1 (uniprotkb:Q13153) physically interacts (MI:0914) with CDC42 (uniprotkb:P60953) by pull down (MI:0096)MINT-7217644: PAK1 (uniprotkb:Q13153) physically interacts (MI:0914) with Rac1 (uniprotkb:P63000) by pull down (MI:0096)     

Antioxidants increase number of progenitor endothelial cells through multiple gene expression pathways

To date, there is no report on the effect of antioxidants on endothelial progenitor cells (EPCs). This study shows that in vitro incubation of EPCs with vitamin C and E reverted the already well documented lowering effect of TNF-α on EPC number and increased p-p38 expression levels. In order to document major changes of gene expression levels and gain insight into signalling pathways, microarray analysis was performed and a significant variation of the expression of 5389 genes in EPCs following antioxidant treatment was detected. Also in vivo evidence is provided about the positive effect of antioxidant vitamins on EPCs, since vitamin C and E supplementation potentiated the physical training-induced increase of EPC number and VEGF levels. Together, these data indicate that antioxidant treatment ameliorates EPC number and causes major changes of gene expression within these cells in vitro. Furthermore, concomitant antioxidant supplementation and physical training in vivo raised the levels of circulating EPCs and serum VEGF more than physical training alone.     

Adiponectin expression in humans is dependent on differentiation of adipocytes and down-regulated by humoral serum components of high molecular weight

Adiponectin is an adipocytokine with profound anti-diabetic and anti-atherogenic effects. Even though adiponectin expression is restricted to adipocytes, serum levels are paradoxically decreased in obesity. We characterized how adiponectin expression and regulation relates to adipocyte differentiation in a human adipocyte cell culture model. Adiponectin was not expressed by human preadipocytes. Differentiation into adipocytes was necessary to induce an increasing expression of adiponectin (359 +/- 64-fold, P < 0.001) in parallel to an increasing expression of adipocyte differentiation markers. Adiponectin protein synthesis and secretion occurred specifically in mature adipocytes and may thus serve as a distinctive marker of adipocyte differentiation. Addition of serum during the course of differentiation as well as acutely to mature adipocytes significantly and concentration-dependently suppressed adiponectin to almost non-detectable levels (to 9.8 +/- 0.03%, P = 0.0043), suggesting a strong humoral serum component of adiponectin down-regulation. This serum component is present in both obese and lean individuals with a tendency to a stronger effect in obese men and women. Separation by molecular size suggests that higher molecular weight (>30 kDa) fractions exert inhibition of adiponectin. Withdrawal of adipogenic ingredients from the culture medium also resulted in a decrease of adiponectin expression and secretion to 62.01 +/- 0.09% and 70.86 +/- 0.05%, respectively. We identified insulin as a critical component to maintain adiponectin expression with a down-regulation to 61.6 +/- 0.1% (P = 0.0011) in the absence of insulin. These dynamic changes of adiponectin expression and regulation with adipocyte differentiation are of physiological interest in the light of the paradoxical decrease of adiponectin levels and the continuous recruitment of preadipocytes for differentiation in obesity.     

Thrombin bound to a fibrin clot confers angiogenic and haemostatic properties on endothelial progenitor cells

Recent data suggest that endothelial progenitor cells (EPCs) are involved in recanalizing venous thrombi. We examined the impact of a fibrin network, and particularly of adsorbed thrombin, on EPCs derived from cord blood CD34(+) cells. Fibrin networks generated in microplates by adding CaCl(2) to platelet-depleted plasma retained adsorbed thrombin at the average concentration of 4.2 nM per well. EPCs expressed high levels of endothelial cell protein C receptor and thrombomodulin, allowing the generation of activated protein C on the fibrin matrix in the presence of exogenous human protein C. The fibrin matrix induced significant EPC proliferation and, when placed in the lower chamber of a Boyden device, strongly enhanced EPC migration. These effects were partly inhibited by hirudin by 41% and 66%, respectively), which suggests that fibrin-adsorbed thrombin interacts with EPCs via the thrombin receptor PAR-1. Finally, spontaneous lysis of the fibrin network, studied by measuring D-dimer release into the supernatant, was inhibited by EPCs but not by control mononuclear cells. Such an effect was associated with a 10-fold increase in plasminogen activator inhibitor-1 (PAI-1) secretion by EPCs cultivated in fibrin matrix. Overall, our data show that EPCs, in addition to their angiogenic potential, have both anticoagulant and antifibrinolytic properties. Thrombin may modulate these properties and contribute to thrombus recanalization by EPCs.     

Adiponectin opposes endothelin-1-mediated vasoconstriction in the perfused rat hindlimb

Recent studies have shown that adiponectin is able to increase nitric oxide (NO) production by the endothelium and relax preconstricted isolated aortic rings, suggesting that adiponectin may act as a vasodilator. Endothelin-1 (ET-1) is a potent vasoconstrictor, elevated levels of which are associated with obesity, type 2 diabetes, hypertension, and cardiovascular disease. We hypothesized that adiponectin has NO-dependent vascular actions opposing the vasoconstrictor actions of ET-1. We studied the vascular and metabolic effects of a physiological concentration of adiponectin (6.5 μg/ml) on hooded Wistar rats in the constant-flow pump-perfused rat hindlimb. Adiponectin alone had no observable vascular activity; however, adiponectin pretreatment and coinfusion inhibited the increase in perfusion pressure and associated metabolic stimulation caused by low-dose (1 nM) ET-1. Adiponectin was not able to oppose vasoconstriction when infusion was commenced after ET-1. This is in contrast to the NO donor sodium nitroprusside, which significantly reduced the pressure due to established ET-1 vasoconstriction, suggesting dissociation of the actions of adiponectin and NO. In addition, adiponectin had no effect on vasoconstriction caused by either high-dose (20 nM) ET-1 or low-dose (50 nM) norepinephrine. Our findings suggest that adiponectin has specific, apparently NO-independent, vascular activity to oppose the vasoconstrictor effects of ET-1. The hemodynamic actions of adiponectin may be an important aspect of its insulin-sensitizing ability by regulating access of insulin and glucose to myocytes. Imbalance in the relationship between adiponectin and ET-1 in obesity may contribute to the development of insulin resistance and cardiovascular disease.     

Effect of anti-TNFalpha treatment on circulating endothelial progenitor cells (EPCs) in rheumatoid arthritis

Rheumatoid arthritis (RA) is associated with increased cardiovascular morbidity and mortality, which may be attenuated by anti-inflammatory treatment. Endothelial progenitor cells (EPCs) have the ability to differentiate into mature endothelium and have a potentially reparative role protecting against ischemia and atherosclerosis. OBJECTIVE: To investigate the effect of treatment with infliximab on the number and functional capacity of endothelial progenitor cells (EPCs) in patients with RA, as a possible mechanism for reducing cardiovascular morbidity in this disorder. METHODS: Patients: Active seropositive RA patients (N = 14) considered candidates for starting infliximab treatment, were recruited. Assessment, based on DAS-28, was performed before treatment and 14 days later. Peripheral blood mononuclear cells were isolated and EPC numbers evaluated by the colony-forming unit (CFU) method. Endothelial phenotyping of CFU was performed by immunofluorescence employing antibodies to Tie-2 VEGF-receptor 2, and CD31. EPC Functional properties were evaluated by fibronectin adherance. RESULTS: A significant 33.4% increase (p < 0.001) in EPC levels was observed after infliximab. A 60% increase was noted in the EPC differentiation scale, (p < 0.002) while a 37.6% increase was observed in mean EPC adhesion (p < 0.001). These changes were associated with a 17.5% decrease in the DAS-28 (p < 0.0001). A significant correlation was observed between the clinical response, reflected by changes in DAS-28 and the degree of increase in EPC CFUs. CONCLUSION: A single dose of infliximab improved the number and functional properties of EPCs, in parallel with an early clinical effect, suggesting a possible mechanism by which anti-inflammatory treatment may reduce cardiovascular risk in RA patients.     

MKR mice are resistant to the metabolic actions of both insulin and adiponectin: discordance between insulin resistance and adiponectin responsiveness

Most rodent models of insulin resistance are accompanied by decreased circulating adiponectin levels. Adiponectin treatment improves the metabolic phenotype by increasing fatty acid oxidation in skeletal muscle and suppressing hepatic glucose production. Muscle IGF-I receptor (IGF-IR)-lysine-arginine (MKR) mice expressing dominant-negative mutant IGF-IRs in skeletal muscle are diabetic with insulin resistance in muscle, liver, and adipose tissue. Adiponectin levels are elevated in MKR mice, suggesting an unusual discordance between insulin resistance and adiponectin responsiveness. Therefore, we investigated the metabolic actions of adiponectin in MKR mice. MKR and ob/ob mice were treated both acutely (28 microg/g) and chronically (for 2 wk) with full-length adiponectin. Acute hypoglycemic effects of adiponectin were evident only in ob/ob mice but not in MKR mice. Chronic adiponectin treatment significantly improved both insulin sensitivity and glucose tolerance in ob/ob but not in MKR mice. Adiponectin receptor mRNA levels and adiponectin-stimulated phosphorylation of AMPK in skeletal muscle and liver were similar among MKR, wild-type, and ob/ob mice. Thus MKR mice are adiponectin resistant despite normal expression of adiponectin receptors and normal AMPK phosphorylation in muscle and liver. MKR mice may be a useful model for dissecting relationships between insulin resistance and adiponectin action in regulation of glucose homeostasis.     

Detection of adiponectin in cerebrospinal fluid in humans

Adiponectin circulates in the body in high concentrations, and 100-fold lower amounts were described in the cerebrospinal fluid (CSF) of mice, whereas in humans, contradictory results have been published. To clarify whether adiponectin is present in human CSF and is derived from the circulation, it was determined in human CSF and plasma of 52 nonselected patients. Adiponectin was detected by immunoblot in CSF and was quantified in CSF and serum by ELISA. CSF adiponectin was positively correlated to systemic levels, and the CSF/serum adiponectin ratio was correlated to the CSF/serum albumin ratio. Furthermore, disturbed function of the blood-brain barrier (BBB) was associated with an elevated CSF/serum adiponectin ratio. Adiponectin mRNA was not found in the brain, indicating that adiponectin crosses the BBB and/or the blood-cerebrospinal fluid barrier (BCB). Rat adiponectin with a COOH-terminal tag was injected into the tail vein of rats and was detected 3 h later in CSF. However, CSF adiponectin in humans and rats was approximately 0.1% of the serum concentration and therefore was below the 0.5% expected in the CSF because of the residual leakage of an undisturbed BBB/BCB. Taken together, data from the present study show that adiponectin in human CSF is far below the level expected by the baseline BBB/BCB permeability, indicating that adiponectin enters the brain much less efficiently than albumin, thus supporting recent data that exclude adiponectin transport to the CSF. Additional studies are needed to reveal whether these low levels of adiponectin in CSF have a physiological function.     

Shear stress augments the endothelial cell differentiation marker expression in late EPCs by upregulating integrins

Vascular endothelial cell injury has been implicated in the onset of atherosclerosis. A number of previous studies have demonstrated that endothelial progenitor cells (EPCs), in particular late EPCs, play important roles in endothelial maintenance and repair. Recent evidence has revealed shear stress as a key regulator for EPC differentiation. However, the detailed events that contribute to the shear stress-induced EPC differentiation, in particular the mechanisms of mechanotransduction, remain to be identified. The present study was undertaken to further confirm the effects of shear stress on the late EPC differentiation, and to investigate the role of integrins in this procedure. Shear stress was observed to increase the expression of endothelial cell differentiation markers, such as vWF and CD31, in late EPCs isolated from rat bone marrow. Shear stress moreover enhanced the mRNA expression of integrin subunits β(1) and β(3) in a time-dependent manner, and also upregulated specific integrins in late EPCs plated on substrates containing various extracellular matrix (ECM) proteins. In addition, the shear stress-induced vWF and CD31 expression were found to be related to the levels of integrin β(1) and β(3), and were inhibited in late EPCs treated with RGD peptide (Gly-Arg-Gly-Asp-Asn-Pro, GRGDNP) that blocks the binding of integrins to the extracellular matrix. Additionally, this increase was also attenuated by both anti-β(1) integrin and anti-β(3) integrin antibodies. The integrin subunits β(1) and β(3) thus play important roles in regulating the shear stress-induced endothelial cell differentiation marker expression in late EPCs. This may provide novel insights into the mechanisms of mechanotransduction in shear stress-mediated late EPC differentiation.     

Increased adiponectin is negatively linked to the local inflammatory process in patients with rheumatoid arthritis

Adiponectin has been shown to exert insulin-sensitizing, anti-atherogenic, and anti-inflammatory properties in metabolic diseases. It has been suggested that adiponectin may play a role in rheumatoid arthritis (RA). To assess adiponectin in serum and synovial fluid from patients with RA and osteoarthritis (OA), and in serum from healthy controls. Adiponectin and CRP levels were analyzed by ELISA. The clinical activity of RA patients was assessed according to the 28 joint count Disease Activity Score. Synovial fluid adiponectin was significantly higher in RA than in OA patients (p<0.001). Adiponectin was negatively associated with the leukocyte count in RA synovial fluid (r=-0.45, p<0.05). Serum adiponectin was higher in RA compared to healthy controls (p<0.02), however comparable to OA patients. Serum adiponectin was higher than in synovial fluid in both diseases (p<0.001). In general, women had higher adiponectin levels than men. Adiponectin was not related to age, disease duration, body mass index, or disease activity of RA patients. Adiponectin is decreased in synovial fluid compared to serum indicating that peripheral fat stores are major producers of adiponectin into the blood stream. However, increased synovial fluid adiponectin in RA patients may counterpart the local inflammatory process.     

Circulating endothelial progenitor cells and cellular membrane microparticles in db/db diabetic mouse: possible implications in cerebral ischemic damage

For determining the implications of circulating endothelial progenitor cells (cEPCs) and cellular membrane microparticles (MPs) in diabetic stroke, levels of EPCs, EPC-MPs, and endothelium-derived MPs (EMPs) and their correlations with blood glucose concentration, cerebral microvascular density (cMVD), and ischemic damage were investigated in type 2 diabetic db/db and db/+ (wild-type control) mice. Therapeutic efficacy of EPC infusion (preincubated with MPs) was also explored. Ischemic stroke was induced by middle cerebral artery occlusion (MCAO) surgery. Ischemic damage and cMVD were determined using histological analyses. The levels of cEPCs and MPs were determined using flow cytometric analyses. EPC generation and functions were evaluated by in vitro cell cultures. Results showed the following. 1) In db/db mice, the basal level of cEPCs was less and cMVDs were lower, but the levels of circulating EPC-MPs and EMPs were more; 2) MCAO induced a larger infarct volume and less of an increase in cEPCs in db/db mice; 3) the level of cEPCs correlated with blood glucose concentration (negatively), cMVD (positively), and ischemic damage (negatively), but the levels of EPC-MPs and EMPs correlated inversely with those parameters; 4) EPCs were reduced and dysfunctional in db/db mice, and preincubation with db/db MPs impaired EPC functions; and 5) infusion of EPCs preincubated with db/+ MPs increased the level of cEPCs and reduced ischemic damage, and these beneficial effects were reduced or lost in EPCs preincubated with db/db MPs. These data suggest that reduced cEPCs, impaired EPC generation/function, and increased production of MPs might be the mechanisms responsible for increased ischemic damage seen in db/db mice.     

Adiponectin expression in adipose tissue is reduced in first-degree relatives of type 2 diabetic patients

Adiponectin is suggested to be an important mediator of insulin resistance. Therefore, we investigated the association between adiponectin and insulin sensitivity in 22 healthy first-degree relatives (FDR) to type 2 diabetic patients and 13 matched control subjects. Subcutaneous adipose tissue biopsies were taken before and after a hyperinsulinemic euglycemic clamp. FDR subjects were insulin resistant, as indicated by a reduced M value (4.44 vs. 6.09 mg x kg(-1) x min(-1), P < 0.05). Adiponectin mRNA expression was 45% lower in adipose tissue from FDR compared with controls (P < 0.01), whereas serum adiponectin was similar in the two groups (6.4 vs. 6.6 microg/ml, not significant). Insulin infusion reduced circulating levels of adiponectin moderately (11-13%) but significantly in both groups (P < 0.05). In the control group, adiponectin mRNA levels were negatively correlated with fasting insulin (P < 0.05) and positively correlated with insulin sensitivity (P < 0.05). In contrast, these associations were not found in the FDR group. In conclusion, FDR have reduced adiponectin mRNA in subcutaneous adipose tissue but normal levels of circulating adiponectin. Adiponectin mRNA levels are positively correlated with insulin sensitivity in control subjects but not in FDR. These findings indicate dysregulation of adiponectin gene expression in FDR.