RhoA/ROCK I signalling downstream of the P2Y13 ADP-receptor controls HDL endocytosis in human hepatocytes

Cell surface receptors for high-density lipoprotein (HDL) on hepatocytes are major partners in the regulation of cholesterol homeostasis. We have previously demonstrated on human hepatocytes that apolipoprotein A-I binding to an ectopic F(1)-ATPase stimulates the production of extracellular ADP that activates a P2Y(13)-mediated high-density lipoprotein (HDL) endocytosis pathway. However, P2Y(13)-dependent signalling pathway has never been described yet. The current study demonstrates a major role of cytoskeleton reorganization in F(1)-ATPase/P2Y(13)-dependent HDL endocytosis under the control of the small GTPase RhoA and its effector ROCK I. Indeed human hepatocytes (HepG(2) cells) stimulated by ADP or AR-C69931MX (both P2Y(13) agonists) showed a high specific activation of RhoA; in addition, inhibition of Rho proteins by C3 exoenzyme impairs HDL endocytosis whereas a constitutively active form of RhoA stimulates HDL endocytosis at the same level as under F(1)-ATPase/P2Y(13) activation. Pharmacological inhibition of ROCK activity decreased HDL endocytosis following stimulation by apoA-I (F(1)-ATPase ligand), ADP or AR-C69931MX and specific siRNA ROCK I extinction prevented the stimulation of HDL endocytosis without effect of ROCK II extinction. The functional involvement of ROCK I downstream F(1)-ATPase/P2Y(13) was confirmed by the strong enrichment of the membrane fraction in ROCK I and by the requirement of actin polymerization in hepatocyte HDL endocytosis. These results allow the identification of the molecular events downstream P2Y(13) receptor activation for a better understanding of hepatocyte HDL endocytosis, the latest step in reverse cholesterol transport.

Genetic and pharmacological targeting of phosphoinositide 3-kinase-gamma reduces atherosclerosis and favors plaque stability by modulating inflammatory processes

BACKGROUND

The role of inflammation at all stages of the atherosclerotic process has become an active area of investigation, and there is a notable quest for novel and innovative drugs for the treatment of atherosclerosis. The lipid kinase phosphoinositide 3-kinase-gamma (PI3Kgamma) is thought to be a key player in various inflammatory, autoimmune, and allergic processes. These properties and the expression of PI3Kgamma in the cardiovascular system suggest that PI3Kgamma plays a role in atherosclerosis.

METHODS AND RESULTS

Here, we demonstrate that a specific PI3Kgamma inhibitor (AS605240) is effective in murine models of established atherosclerosis. Intraperitoneal administration of AS605240 (10 mg/kg daily) significantly decreased early atherosclerotic lesions in apolipoprotein E-deficient mice and attenuated advanced atherosclerosis in low-density lipoprotein receptor-deficient mice. Furthermore, PI3Kgamma levels were elevated in both human and murine atherosclerotic lesions. Comparison of low-density lipoprotein receptor-deficient mice transplanted with wild-type or PI3Kgamma-deficient bone marrow demonstrated that functional PI3Kgamma in the hematopoietic lineage is required for atherosclerotic progression. Alleviation of atherosclerosis by targeting of PI3Kgamma activity was accompanied by decreased macrophage and T-cell infiltration, as well as increased plaque stabilization.

CONCLUSIONS

These data identify PI3Kgamma as a new target in atherosclerosis with the potential to modulate multiple stages of atherosclerotic lesion formation, such as fatty streak constitution, cellular composition, and final fibrous cap establishment.

Association of APOC3 polymorphisms with both dyslipidemia and lipoatrophy in HAART-receiving patients

The incidence and the magnitude of lipodystrophy and dyslipidemia in HIV-treated people reported in previous studies are very variable. Several predisposing factors have been identified, but there are few data on genetic factors. To search for a correlation between APOC3 polymorphisms and lipid disorders and lipodystrophy in HIV patients under d4T and protease inhibitors (PI)-containing HAART, we designed a monocenter, cross-sectional study in a University Hospital in Southern France during the period 2001-2004. Forty patients under HAART were included, with d4T for > or = 2 years and PI for > or = 1 year. We determined body mass composition by DXA, lipoprotein markers, and the -455/-482 apo C3 genotypes. Carriers of APOC3 variant alleles (-455 1/-482 1) displayed higher levels of triglycerides (3.72 vs. 2.57 mmol/liter), apo C3 (45.3 vs. 34.5 mg/liter), and apo E (130.2 vs. 66.5 mg/liter) and a lower fat mass (13.9 vs. 19.7%) than patients with nonvariant alleles (-455 0/-482 0). APOC3 polymorphisms might be associated with both dyslipidemia and lipoatrophy in HAART-treated patients.

High consumptions of grain, fish, dairy products and combinations of these are associated with a low prevalence of metabolic syndrome

OBJECTIVE

To analyse the relation between various food groups and the frequency of insulin resistance syndrome (IRS).

DESIGN

A sample of 912 men aged 45-64 years was randomly selected. Questionnaires on risk factors and a three consecutive day food diary were completed. Height, weight, waist circumference, and blood pressure were measured. A fasting blood sample was analysed for lipid and glucose measurements. The NCEP-ATP-III definition was used to assess IRS. Data were analysed according to quintiles of food groups and medians of dairy products, fish, or cereal grains.

RESULTS

The prevalence of IRS was 23.5%. It reached 29.0%, 28.1% and 28.1% when the intake was below the median for fish, dairy products, and grain, respectively. When consumptions of all three types of food were higher than the median, the prevalence reached 13.1%, and when they were lower, the prevalence was 37.9% (p<0.001). In logistic regression adjusted for confounders (centre, age, physical activities, education level, smoking, dieting, alcohol intake, treatments for hypertension and dyslipidaemia, energy intake, and diet quality index) the odds ratios for IRS (above median value v below) were 0.51 (95% confidence interval, 0.36 to 0.71) for fish, 0.67 (0.47 to 0.94) for dairy products, and 0.69 (0.47 to 1.01) for grain. When intakes of all three kinds of food were high, the OR was 0.22 (0.10 to 0.44).

CONCLUSIONS

A high consumption of dairy products, fish, or cereal grains is associated with a lower probability of IRS. The probability decreases when intakes of all three types of food were high.

Impact of HIV infection on total body composition in treatment-naive men evaluated by dual-energy X-ray absorptiometry comparison of 90 untreated HIV-infected men to 241 controls

The aim of this study was to establish the contribution of human immunodeficiency virus (HIV) itself on body composition changes evaluated by dual-energy X-ray absorptiometry (DXA). Body composition evaluated by DXA in 90 HIV never treated men, without comorbidity, or current or past opportunistic infections were compared with 241 healthy volunteers. The mean duration of seropositivity from HIV diagnosis was 41+/-62 mo, mean CD4 and viral load at the time of DXA were 402/mm(3)+/-263 (control values 500-1200/mm(3)) and 4.2 log copies/mL+/-1.3. Mean age (41 vs 39 yr, respectively, for HIV never treated patients and controls) and mean height (174.5 vs 176 cm) were not different, but mean weight was lower among HIV never treated patients (69.8 vs 78.7 kg). Mean total body bone mineral density (BMD) of naive HIV-infected patients was lower than that of controls (1.20 vs 1.23 g/cm(2), p=0.01) but not after adjustment on age, height, lean mass (LM), and fat mass ratio (FMR=% trunk fat mass/% lower limb fat mass). Fat mass (13.2 vs 16.5 kg, p<0.0001) and LM (53.5 vs 59 kg, p<0.0001) of naive HIV-infected patients were lower whatever the adjustment variables. The FMR was lower in naive HIV-infected men (1.0 vs 1.3, p<0.0001) because of a decreased trunk fat mass. After adjustment on age, height, LM, and fat mass, the lower limbs fat mass percentage was higher in HIV-infected men. The profile of naïve HIV-infected patients displayed low lean and fat masses, and a fat mass repartition characterized by a predominant loss in the trunk. Those alterations may result from the catabolic effect of the chronic HIV infection.

Lipoprotein (a) and risk of ischemic stroke in young adults

Lipoprotein (a) [Lp(a)] is a LDL-particle linked to apoprotein (a) [apo(a)]. High Lp(a) plasma level is a risk factor for coronary heart disease and, in older men, for ischemic stroke. The role of Lp(a) as a risk factor for ischemic stroke in young adults is uncertain.

METHODS

Lp(a) concentration was prospectively measured in 100 consecutive patients with acute ischemic stroke (58 men and 42 women) aged 18-55 years, and in 100 controls matched for age and gender.

RESULTS

The distribution of Lp(a) concentration was skewed toward the highest and median tertiles in male patients. In multivariate logistic regression analyses adjusting on classical risk factors for ischemic stroke and lipid variables, Lp(a) concentration in the highest and medium tertiles compared with the lowest tertile was significantly associated with ischemic stroke in men (OR 3.55, 95% CI 1.33-9.48, p = 0.012), but was not in women (OR 0.42, 95% CI 0.14-1.26, p = 0.12). Although large vessel atherosclerosis was more common in men than in women, there were no differences in Lp(a) concentration according to the cause of ischemic stroke.

CONCLUSION

Among subjects aged 18-55 years, a slightly elevated Lp(a) concentration was strongly and independently associated with ischemic stroke in men, but not in women. Further studies are required to elucidate the mechanisms underlying this gender-specific association.

Impact of genetic polymorphisms on the risk of lipid disorders in patients on anti-HIV therapy

Active anti-HIV therapy can induce hypertriglyceridemia, low high-density lipoprotein (HDL) and insulin resistance, eventually accompanied by clinical lipodystrophy, associated loss of subcutaneous adipose tissue and an increase in abdominal adiposity. The frequency of these metabolic disorders is approximately 50% and host genetic factors might confer particular susceptibility. Variants of apolipoproteins (apo) A5 and C3, interacting with

Clin Chem Lab Med 2007;45:815–21.

Cell surface adenylate kinase activity regulates the F(1)-ATPase/P2Y (13)-mediated HDL endocytosis pathway on human hepatocytes

We have previously demonstrated on human hepatocytes that apolipoprotein A-I binding to an ecto-F(1)-ATPase stimulates the production of extracellular ADP that activates a P2Y(13)-mediated high-density lipoprotein (HDL) endocytosis pathway. Therefore, we investigated the mechanisms controlling the extracellular ATP/ADP level in hepatic cell lines and primary cultures to determine their impact on HDL endocytosis. Here we show that addition of ADP to the cell culture medium induced extracellular ATP production that was due to adenylate kinase [see text] and nucleoside diphosphokinase [see text] activities, but not to ATP synthase activity. We further observed that in vitro modulation of both ecto-NDPK and AK activities could regulate the ADP-dependent HDL endocytosis. But interestingly, only AK appeared to naturally participate in the pathway by consuming the ADP generated by the ecto-F(1)-ATPase. Thus controlling the extracellular ADP level is a potential target for reverse cholesterol transport regulation.

Exosome lipidomics unravels lipid sorting at the level of multivesicular bodies

Exosomes are part of the family of "bioactive vesicles" and appear to be involved in distal communications between cells. They vehiculate bioactive lipids and lipolytic enzymes and their biogenesis require specific lipids and a membrane reorganisation. Their biogenesis pathway could be a way to secrete enzymes involved in lipid signalling and to generate "particulate agonists". However, this pathway seems also to be used by pathogens such as HIV. This review will consider several aspects of lipidomics studies which might help to understand the fate and role of these fascinating vesicles.

Metabolic syndrome and coronary heart disease risk in a population-based study of middle-aged men from France and Northern Ireland

Metabolic Syndrome (MetS) was found associated with an increased CHD risk in several studies but data about this relationship in Southern Europe are lacking. We studied the association of MetS according to three different indexes (the National Cholesterol Education Program's definition (NCEP), a modified World Health Organization's definition (WHO) and the recent International Diabetes Federation's definition (IDF)) with CHD risk in a case-control study nested within the PRIME cohort, composed of subjects from France (Southern Europe) and Belfast (Northern Europe). The PRIME prospective study is composed of 10 592 men, aged 50-59 at baseline and followed for 5 years. Subjects included in this nested case-control study were 296 cases of incident CHD and 540 controls, who remained free of CHD during the 5 years of follow-up of the PRIME cohort and matched for age, recruitment centre and recruitment date. All subjects had questionnaires and a medical examination at baseline, and a blood sample was taken. Using the IDF's, the WHO's and the NCEP's definitions respectively, the frequency of MetS was 38.9%, 35.5% and 29.7% in cases and 32.4%, 28.7% and 22.6% in controls. After adjustment for physical activity, smoking and drinking habits, MetS was associated with CHD risk whichever the definition used (ORIDF=1.41 [1.02-1.95], P<0.04, ORWHO=1.40 [1.01-1.94], P<0.05 and ORNCEP=1.46[1.04-2.04], P<0.04). These results were homogeneous in France (low risk of CHD) and Belfast (high risk of CHD). Our results add further evidence that MetS is predictive of CHD risk in middle-aged men from Northern and Southern Europe, and highlight differences between the three definitions studied.

Influence of Dyslipidemia on Moxidectin Distribution in Plasma Lipoproteins and on its Pharmacokinetics

PURPOSE

We studied the influence of dyslipemia on the distribution of moxidectin, a potent antiparasitic drug of the macrocyclic lactone (ML) family, in plasma lipoproteins and on its pharmacokinetic behaviour.

MATERIALS AND METHODS

Plasma samples from normolipidemic or dyslipidemic subjects were spiked with moxidectin (20 ng/ml). Rabbits fed with standard (n = 5) or cholesterol-enriched diet (n = 5) were injected subcutaneously with moxidectin (300 microg/kg) and blood samples were collected over 32 days. Lipoproteins were separated from plasma samples by ultracentrifugation on density gradients. Moxidectin and lipids were measured in plasma and in lipoproteins and the pharmacokinetic parameters calculated.

RESULTS

In normolipidemic subjects or rabbits, the drug bound preferentially to HDL. In hyperlipidemic samples, moxidectin shifted to the VLDL-LDL fraction. In addition, hyperlipidemic rabbits had a 2.8-fold higher area under the plasma concentration versus time curve (AUC) and a lower clearance and volume of distribution when compared with controls.

CONCLUSION

Dyslipidemia led to major changes in moxidectin plasma distribution and in drug disposition. Therefore, a high variability in moxidectin disposition might be expected in humans or animals liable to develop dyslipidemia, with a possible impact on the efficacy and safety of this class of drugs.

The adaptor protein Gab1 couples the stimulation of vascular endothelial growth factor receptor-2 to the activation of phosphoinositide 3-kinase

Phosphoinositide 3-kinase (PI3K) mediates essential functions of vascular endothelial growth factor (VEGF), including the stimulation of endothelial cell proliferation and migration. Nevertheless, the mechanisms coupling the receptor VEGFR-2 to PI3K remain obscure. We observed that the Grb2-bound adapter Gab1 is tyrosine-phosphorylated and relocated to membrane fractions upon VEGF stimulation of endothelial cells. We could detect the PI3K regulatory subunit p85 in immunoprecipitates of endogenous Gab1, and vice versa, and measure a Gab1-associated lipid kinase activity upon VEGF stimulation. Furthermore, transfection of the Gab1-YF3 mutant lacking all p85-binding sites strongly repressed PI3K activation measured in vitro. Moreover, Gab1-YF3 severely decreased the cellular amount of phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3) generated in response to VEGF. Furthermore, adenoviral expression of Gab1-YF3 suppressed both Akt phosphorylation and recovery of wounded human umbilical vein endothelial cell monolayers, a VEGF-dependent process involving cell migration and proliferation under PI3K control. Transfection of other Gab1 mutants, lacking Grb2-binding sites or the pleckstrin homology (PH) domain, also prevented Akt activation, further demonstrating Gab1 involvement in PI3K activation. These mutants were also used to show that interactions with both Grb2 and PtdIns(3,4,5)P3 mediate Gab1 recruitment by VEGFR-2. Importantly, Gab1 mobilization was impaired by (i) PI3K inhibitors, (ii) deletion of Gab1 PH domain, (iii) PTEN (phosphatase and tensin homolog deleted on chromosome 10) overexpression to repress PtdIns(3,4,5)P3 production, and (iv) overexpression of a competitor PH domain for PtdIns(3,4,5)P3 binding, which altogether demonstrated that PI3K is also an upstream regulator of Gab1. Gab1 thus appears as a primary actor in coupling VEGFR-2 to PI3K/Akt, recruited through an amplification loop involving PtdIns(3,4,5)P3 and its PH domain.

Selective activation of nuclear phospholipase D-1 by g protein-coupled receptor agonists in vascular smooth muscle cells

Recent studies highlight the existence of an autonomous nuclear lipid metabolism related to cellular proliferation. However, the importance of nuclear phosphatidylcholine (PC) metabolism is poorly understood. Therefore, we were interested in nuclear PCs as a source of second messengers and, particularly, nuclear phospholipase D (PLD) identification in membrane-free nuclei isolated from pig aorta vascular smooth muscle cells (VSMCs). Using immunoblot experiment, in vitro PLD assay with fluorescent substrate and confocal microscopy analysis, we demonstrated that only PLD1 is expressed in VSMC nucleus, whereas PLD1 and PLD2 are present in VSMC. Inhibition of RhoA and protein kinase Czeta (PKCzeta) by C3-exoenzyme and PKCzeta pseudosubstrate inhibitor, respectively, conducted a decrease of phosphatidylethanol production. On the other hand, treatment of intact VSMCs, but not nuclei, with phosphoinositide 3-kinase (PI3K) inhibitors prevented partially nuclear PLD1 activity, indicating for the first time that PI3K may have a role in nuclear PLD regulation. In addition, lysophosphatidic acid (LPA) or angiotensin II treatment of VSMCs resulted in an increase of intranuclear PLD activity, whereas platelet-derived growth factor and epidermal growth factor have no significant effect. Moreover, pertussis toxin induced a decrease of LPA-stimulated nuclear PLD1 activity, suggesting that heterotrimeric G(i)/G(0) protein involvement in intranuclear PLD1 regulation. We also show that LPA-induced nuclear PLD1 activation implied PI3K/PKCzeta pathway activation and PKCzeta nuclear translocation as well as nuclear RhoA activation. Thus, the characterization of an endogenous PLD1 that could regulate PC metabolism inside VSMC nucleus provides a new role for this enzyme in control of vascular fibroproliferative disorders.

Interleukin 6 is associated with subclinical atherosclerosis: a link with soluble intercellular adhesion molecule 1

BACKGROUND

Among the markers of inflammation, a cytokine, interleukin (IL)-6, promotes the expression of intercellular adhesion molecule 1 (ICAM-1), C-reactive protein (CRP) synthesis, and leads to a series of procoagulant actions with potential major implications on the progression of atherosclerosis.

AIM OF THE STUDY

To analyse in a population-based study, the relationship between IL-6 and atherosclerotic lesions and the role of serum ICAM-1 and CRP on this relationship.

POPULATION

Among 1015 individuals randomly recruited between 1995 and 1997 in Haute-Garonne, a French region with a low cardiovascular risk, 953 subjects with complete data for all measurements were analysed. Common carotid intima-media thickness (IMT) and the presence of plaques in the carotid and femoral arteries were assessed by ultrasonography.

RESULTS

Quartiles of IL-6, serum ICAM-1 and CRP were positively associated with plaques and IMT. After adjustment for traditional risk factors, IL-6 (P < 0.001) and serum ICAM-1 (P < 0.002) remained positively associated with plaques but not CRP (P = 0.20). Neither IL-6, nor serum ICAM-1, nor CRP were independently associated with IMT. When serum ICAM-1 was entered into the model in addition to traditional risk factors and IL-6, the percentage of variance in the number of plaques explained by the model did not increase significantly.

CONCLUSION

IL-6 levels are associated with subclinical atherosclerotic lesions independently of traditional risk factors; the influence of IL-6 on ICAM-1 secretion may play a role in this association. These results argue the interest of IL-6 in the stratification of cardiovascular risk.

Accelerated lipid absorption in mice overexpressing intestinal SR-BI

Dietary cholesterol absorption contributes to a large part of the circulating cholesterol. However, the mechanism of sterol intestinal uptake is not clearly elucidated. Scavenger receptor class B type I (SR-BI), major component in the control of cholesterol homeostasis, is expressed in the intestine, but its role in this organ remains unclear. We have generated transgenic mice overexpressing SR-BI primarily in the intestine by using the mouse SR-BI gene under the control of intestinal specific "apoC-III enhancer coupled with apoA-IV promoter." We found SR-BI overexpression with respect to the natural protein along the intestine and at the top of the villosities. After a meal containing [(14)C]cholesterol and [(3)H]triolein, SR-BI transgenic mice presented a rise in intestinal absorption of both lipids that was not due to a defect in chylomicron clearance nor to a change in the bile flow or the bile acid content. Nevertheless, SR-BI transgenic mice showed a decrease of total cholesterol but an increase of triglyceride content in plasma without any change in the high density lipoprotein apoA-I level. Thus, we described for the first time a functional role in vivo for SR-BI in cholesterol but also in triglyceride intestinal absorption.

High frequency of endothelial vasomotor dysfunction after acute coronary syndromes in non-culprit and angiographically normal coronary arteries: a reversible phenomenon

This study aimed to assess endothelium-dependent vasomotor function in non-culprit coronary vessels in patients with recent acute coronary syndrome (ACS). Endothelial dysfunction can also concern peripheral vessels during ACS, but the frequency of this phenomenon at coronary circulation level is unknown. Endothelial function was assessed by infusion of graded doses of acetylcholine (ACh) in a non-culprit coronary artery of normal appearance in 43 patients having recently suffered from non-ST ACS, and reassessed 6 months later. Endothelium-dependent vasoreactivity was impaired at baseline in 81% (35/43) of the patients, and only 19% (8/43) of patients showed a normal response to ACh. Among the 35 subjects with initial dysfunction, 77% showed a significant improvement 6 months later. All patients without initial endothelial dysfunction remained normal. C-reactive protein (CRP) level was elevated at month 0, and had declined at follow-up, tending towards normal levels. At that time, apolipoprotein A-I (apoA-I) levels were correlated with vasomotor improvement in univariate (p < 0.02) and multivariate analysis (p < 0.04). In conclusion, endothelium dysfunction is very frequently observed after recent ACS in non-culprit and angiographically normal coronary arteries, and an improvement occurs within 6 months in most cases. After resolution of the initial inflammation, apoA-I seems to play an important role in endothelial function.

The nucleotide receptor P2Y13 is a key regulator of hepatic high-density lipoprotein (HDL) endocytosis

Cell surface receptors for high-density lipoprotein (HDL) on hepatocytes are major partners in the regulation of cholesterol homeostasis. We recently identified a cell surface ATP synthase as a high-affinity receptor for HDL apolipoprotein A-I (apoA-I) on human hepatocytes. Stimulation of this ectopic ATP synthase by apoA-I triggered a low-affinity-receptor-dependent HDL endocytosis by a mechanism strictly related to the generation of ADP. This suggests that nucleotide G-protein-coupled receptors of the P2Y family are molecular components in this pathway. Only P2Y1 and P2Y13 are present on the membrane of hepatocytes. Using both a pharmacological approach and small interference RNA, we identified P2Y13 as the main partner in hepatic HDL endocytosis, in cultured cells as well as in situ in perfused mouse livers. We also found a new important action of the antithrombotic agent AR-C69931MX as a strong activator of P2Y13-mediated HDL endocytosis.

Production of lysophosphatidic acid in blister fluid: involvement of a lysophospholipase D activity

Lysophosphatidic acid (LPA) is present in abundance in serum resulting from platelet activation and is also found in other biological fluids. LPA controls numerous cellular responses and plays a role in specific functions such as wound healing, especially in the skin. Nevertheless, its presence in the skin has never been investigated. Since re-epithelialization occurs after blister rupture, we tested the presence of endogenous LPA in blister fluid and investigated a possible mechanism for its biosynthesis and biological functions. Using a radioenzymatic assay, LPA was detected in 33 blister fluids originating from 24 bullous dermatoses, and at higher concentrations than in plasma. In parallel, blister fluids contained a lysophospholipase D (LPLD) activity but no detectable phospholipase A2 activity. The expressions of the LPLD autotaxin (ATX) and of LPA1-receptor (LPA1-R) were greatly increased in blister skin when compared with normal skin. Finally, LPA was found to have a positive effect on the migration of cultured keratinocytes. These results show that LPA is present in blister fluid synthesized by the LPLD ATX. Due to its ability to enhance keratinocyte migration, LPA in blister fluid could, via the LPA1-R, play an important role in re-epithelialization occurring after blister rupture.

Metabolic syndrome is associated with markers of subclinical atherosclerosis in a French population-based sample

Metabolic syndrome (MetS) is associated with increased risk of cardiovascular disease (CVD). The relation of MetS with early stages of atherosclerosis, more important from a prevention perspective, has not been evaluated extensively. We examined the association of MetS, using WHO and NCEP definitions, with number of carotid and femoral plaques; carotid intima-media thickness (IMT); pulse wave velocity (PWV) in a random population-based sample of 1153 French adults (35-65 year). Impact of inflammatory factors (C-reactive protein and soluble intercellular adhesion molecule-1) on these parameters was also evaluated. Prevalence of MetS was 14.5 (CI: 12.3-16.0) and 17.5 (CI: 15.1-20.2)%, using NCEP and WHO definitions, respectively. MetS significantly predicted number of plaques, IMT, and PWV after adjustment for traditional risk factors (P<0.05). Inflammatory factors predicted peripheral plaques only. The risk of subclinical atherosclerosis was considerably increased with MetS (P<0.05); odds ratios ranged 1.80-2.15 with NCEP definition, and 1.48-1.97 with WHO definition. Individuals meeting both NCEP and WHO definitions had slightly greater risk of increased plaques, IMT, and PWV. MetS was strongly associated with subclinical atherosclerosis and aortic stiffness, and can be used as a surrogate marker for high CVD risk, deserving aggressive treatment.

Fasting insulin concentrations and coronary heart disease incidence in France and Northern Ireland: the PRIME Study

BACKGROUND

Reports about the relationships between insulin concentrations and CHD risk are controversial. The objective of this survey was to study the association between insulin levels and CHD risk in middle-aged male participants of the PRIME Study after 5 years of follow-up.

METHODS

Our study adopted a nested case-control design including 294 cases of CHD and 536 controls randomly selected among healthy participants from the PRIME cohort. Data were obtained by questionnaires (medical history, lifestyle), standardised clinical measurements (blood pressure, anthropometric measurements), and a blood sample was obtained for biological measurements. Odds-Ratios for associations of four ordered classes of insulin concentration with CHD risk after adjustment for confounding factors were estimated using conditional logistic regression.

RESULTS

In Belfast, a significant trend (p<0.03) was observed between insulin classes and CHD risk in bivariate analyses, but this association lost its significance after multiple adjustments. In the French centres, a high risk of CHD (OR=3.24 [1.80-5.85], p<0.0001) was observed only for the second class of insulin concentration (6.5 to 9.9 mIU/l), compared with the reference class (<6.5 mIU/l). After multiple adjustments, this association remained highly significant (OR=2.92 [1.44-5.92], p<0.005).

CONCLUSIONS

In Belfast (high-risk population), a significant trend was observed between insulin concentration classes and CHD risk but hyperinsulinaemia lost its association with CHD risk in multivariate analyses. In the French centres (lower risk population), slightly increased insulin concentrations were associated with a high risk of CHD, independently of cardiovascular risk factors and other features of the metabolic syndrome, but very high insulin concentrations were not.

Tumor recognition following Vgamma9Vdelta2 T cell receptor interactions with a surface F1-ATPase-related structure and apolipoprotein A-I

Vgamma9Vdelta2 T lymphocytes, a major gammadelta T lymphocyte subset in humans, display cytolytic activity against various tumor cells upon recognition of yet uncharacterized structures. Here, we show that an entity related to the mitochondrial F1-ATPase is expressed on tumor cell surface and promotes tumor recognition by Vgamma9Vdelta2 T cells. When immobilized, purified F1-ATPase induces selective activation of this lymphocyte subset. The Vgamma9Vdelta2 T cell receptors (TCR) and the F1-ATPase also bind a delipidated form of apolipoprotein A-I (apo A-I), as demonstrated by surface plasmon resonance. Moreover, the presence of apo A-I in the culture medium is required for optimal activation of Vgamma9Vdelta2 T cells by tumors expressing F1-ATPase. This study thus describes an unanticipated tumor recognition mechanism by Vgamma9Vdelta2 lymphocytes and a possible link between gammadelta T cell immunity and lipid metabolism.

A Novel Role for Gab1 and SHP2 in Epidermal Growth Factor-induced Ras Activation

SHP2 was recently found to down-regulate PI3K activation by dephosphorylating Gab1 but the mechanisms explaining the positive role of the Gab1/SHP2 pathway in EGF-induced Ras activation remain ill defined. Substrate trapping experiments now suggest that SHP2 dephosphorylates other Gab1 phosphotyrosines located within a central region displaying four YXXP motifs. Because these sites are potential docking motifs for Ras-GAP, we tested whether SHP2 dephosphorylates them to facilitate Ras activation. We observed that a Gab1 construct preventing SHP2 recruitment promoted membrane relocation of RasGAP. Moreover, a RasGAP-inactive mutant restored the activation of Ras in cells transfected with SHP2-inactivating Gab1 mutant or in SHP2-deficient fibroblasts, supporting the hypothesis that RasGAP is a downstream target of SHP2. To determine whether Gab1 is a RasGAP-binding partner, a Gab1 mutant deleted of four YXXP motifs was produced. The deletion suppressed RasGAP redistribution and restored the defective Ras activation caused by SHP2-inactivating mutations. Moreover, Gab1 was found to interact with RasGAP SH2 domains, only under conditions where SHP2 is not activated. To identify Ras-GAP-binding sites, Tyr to Phe mutants of Gab1 YXXP motifs were produced. Gab1 constructs mutated on Tyr(317) were severely affected in RasGAP binding and were the most active in compensating for Ras-defective activation and blocking RasGAP redistribution induced by SHP2 inactivation. We have thus localized on Gab1 a Ras-negative regulatory tyrosine phosphorylation site involved in RasGAP binding and showed that an important SHP2 function is to down-regulate its phosphorylation to disengage RasGAP and sustain Ras activation.