Restoring Akt1 activity in outgrowth endothelial cells from South Asian men rescues vascular reparative potential.

Recent data suggest reduced indices of vascular repair in South Asian men, a group at increased risk of cardiovascular events. Outgrowth endothelial cells (OEC) represent an attractive tool to study vascular repair in humans and may offer potential in cell-based repair therapies. We aimed to define and manipulate potential mechanisms of impaired vascular repair in South Asian (SA) men. In vitro and in vivo assays of vascular repair and angiogenesis were performed using OEC derived from SA men and matched European controls, prior defining potentially causal molecular mechanisms. SA OEC exhibited impaired colony formation, migration, and in vitro angiogenesis, associated with decreased expression of the proangiogenic molecules Akt1 and endothelial nitric oxide synthase (eNOS). Transfusion of European OEC into immunodeficient mice after wire-induced femoral artery injury augmented re-endothelialization, in contrast with SA OEC and vehicle; SA OEC also failed to promote angiogenesis after induction of hind limb ischemia. Expression of constitutively active Akt1 (E17KAkt), but not green fluorescent protein control, in SA OEC increased in vitro angiogenesis, which was abrogated by a NOS antagonist. Moreover, E17KAkt expressing SA OEC promoted re-endothelialization of wire-injured femoral arteries, and perfusion recovery of ischemic limbs, to a magnitude comparable with nonmanipulated European OEC. Silencing Akt1 in European OEC recapitulated the functional deficits noted in SA OEC. Reduced signaling via the Akt/eNOS axis is causally linked with impaired OEC-mediated vascular repair in South Asian men. These data prove the principle of rescuing marked reparative dysfunction in OEC derived from these men.

A novel cardiopulmonary exercise test protocol and criterion to determine maximal oxygen uptake in chronic heart failure.

Cardiopulmonary exercise testing for peak oxygen uptake (Vo(2peak)) can evaluate prognosis in chronic heart failure (CHF) patients, with the peak respiratory exchange ratio (RER(peak)) commonly used to confirm maximal effort and maximal oxygen uptake (Vo(2max)). We determined the precision of RER(peak) in confirming Vo(2max), and whether a novel ramp-incremental (RI) step-exercise (SE) (RISE) test could better determine Vo(2max) in CHF. Male CHF patients (n = 24; NYHA class I-III) performed a symptom-limited RISE-95 cycle ergometer test in the format: RI (4-18 W/min; ∼10 min); 5 min recovery (10 W); SE (95% peak RI work rate). Patients (n = 18) then performed RISE-95 tests using slow (3-8 W/min; ∼15 min) and fast (10-30 W/min; ∼6 min) ramp rates. Pulmonary gas exchange was measured breath-by-breath. Vo(2peak) was compared within patients by unpaired t-test of the highest 12 breaths during RI and SE phases to confirm Vo(2max) and its 95% confidence limits (CI(95)). RER(peak) was significantly influenced by ramp rate (fast, medium, slow: 1.21 ± 0.1 vs. 1.15 ± 0.1 vs. 1.09 ± 0.1; P = 0.001), unlike Vo(2peak) (mean n = 18; 14.4 ± 2.6 ml·kg(-1)·min(-1); P = 0.476). Group Vo(2peak) was similar between RI and SE (n = 24; 14.5 ± 3.0 vs. 14.7 ± 3.1 ml·kg(-1)·min(-1); P = 0.407); however, within-subject comparisons confirmed Vo(2max) in only 14 of 24 patients (CI(95) for Vo(2max) estimation averaged 1.4 ± 0.8 ml·kg(-1)·min(-1)). The RER(peak) in CHF was significantly influenced by ramp rate, suggesting its use to determine maximal effort and Vo(2max) be abandoned. In contrast, the RISE-95 test had high precision for Vo(2max) confirmation with patient-specific CI(95) (without secondary criteria), and showed that Vo(2max) is commonly underestimated in CHF. The RISE-95 test was well tolerated by CHF patients, supporting its use for Vo(2max) confirmation.

Heavy and moderate interval exercise training alters low-flow-mediated constriction but does not increase circulating progenitor cells in healthy humans.

Moderate-intensity endurance exercise training improves vascular endothelial vasomotor function; however, the impact of high-intensity exercise training has been equivocal. Thus, the effect of the physiological stress of the exercise remains poorly understood. Furthermore, enhanced vascular repair mediated by circulating progenitor cells may also be improved. To address whether the physiological stress of exercise training is an important factor contributing to these adaptations, 20 healthy participants trained for 6 weeks. Training involved either moderate (MSIT; n = 9) or heavy metabolic stress (HSIT; n = 11) interval exercise training programmes matched for total work and duration of exercise. Before and after training, flow-mediated dilatation, low-flow-mediated constriction and total vessel reactivity were measured at the brachial artery using Doppler ultrasound. Circulating progenitor cells (CD34(+), CD133(+) and CD309/KDR(+)) were measured by flow cytometry (means ± SD). Relative (MSIT pre- 5.5 ± 3.4 versus post-training 6.6 ± 2.5%; HSIT pre- 6.6 ± 4.1 versus post-training 7.0 ± 3.4%, P = 0.33) and normalized (P = 0.16) flow-mediated dilatation did not increase with either training programme. However, low-flow-mediated constriction was greater after training in both groups (MSIT pre- -0.5 ± 3.2 versus post-training -1.9 ± 3.1%; HSIT pre- -1.0 ± 1.7 versus post-training -2.9 ± 3.0%, P = 0.04) and contributed to greater total vessel reactivity (MSIT pre- 7.4 ± 3.3 versus post-training 10.1 ± 3.7%; HSIT pre- 10.9 ± 5.9 versus post-training 12.7 ± 6.2%, P = 0.01). Peak reactive hyperaemia and the area under the shear rate curve were not different between groups, either before or after training. Although circulating progenitor cell numbers increased following heavy-intensity interval exercise training, variability was great amongst participants [MSIT pre- 16 ± 18 versus post-training 14 ± 12 cells (ml whole blood)(-1); HSIT pre- 8 ± 6 versus post-training 19 ± 23 cells (ml whole blood)(-1), P = 0.50]. Overall, vasoconstrictor function may be augmented by moderate- and heavy-intensity interval exercise training in young adults. However, circulating progenitor cell numbers were not increased, suggesting that these cells are not likely to be upregulated as a result of training.

Association of diabetes with increased all-cause mortality following primary percutaneous coronary intervention for ST-segment elevation myocardial infarction in the contemporary era.

BACKGROUND: We investigated the association between diabetes mellitus (DM) and all-cause mortality in a large cohort of consecutive patients treated with primary percutaneous coronary intervention (PPCI) in the contemporary era. METHODS: We conducted a retrospective analysis of a single-centre registry of patients undergoing PPCI for ST-segment elevation myocardial infarction (STEMI) at a large regional PCI centre between 2005 and 2009. All-cause mortality in relation to patient and procedural characteristics was compared between patients with and without DM. RESULTS: Of 2586 patients undergoing PPCI, 310 (12%) had DM. Patients with DM had a higher prevalence of multi-vessel coronary disease (p<0.001) and prior myocardial infarction (p<0.001). Patients with DM were less commonly admitted directly to the interventional centre (p=0.002). Symptom-to-balloon (p<0.001) and door-to-balloon time (p=0.002) were longer in patients with DM. Final infarct-related-artery TIMI-flow grade was lower in patients with DM (p=0.031). All-cause mortality at 30 days (p=0.0025) and 1 year (p<0.0001) was higher in patients with DM. DM was independently associated with increased mortality after multivariate adjustment for potential confounders. CONCLUSIONS: Mortality remains substantially higher in patients with DM following reperfusion for STEMI in comparison with those without diabetes, despite contemporary management with PPCI. Greater co-morbidity, delayed presentation, longer times-to-reperfusion, and less optimal reperfusion may contribute to adverse outcomes.

Insulin resistance impairs circulating angiogenic progenitor cell function and delays endothelial regeneration.

OBJECTIVE: Circulating angiogenic progenitor cells (APCs) participate in endothelial repair after arterial injury. Type 2 diabetes is associated with fewer circulating APCs, APC dysfunction, and impaired endothelial repair. We set out to determine whether insulin resistance adversely affects APCs and endothelial regeneration. RESEARCH DESIGN AND METHODS: We quantified APCs and assessed APC mobilization and function in mice hemizygous for knockout of the insulin receptor (IRKO) and wild-type (WT) littermate controls. Endothelial regeneration after femoral artery wire injury was also quantified after APC transfusion. RESULTS: IRKO mice, although glucose tolerant, had fewer circulating Sca-1(+)/Flk-1(+) APCs than WT mice. Culture of mononuclear cells demonstrated that IRKO mice had fewer APCs in peripheral blood, but not in bone marrow or spleen, suggestive of a mobilization defect. Defective vascular endothelial growth factor-stimulated APC mobilization was confirmed in IRKO mice, consistent with reduced endothelial nitric oxide synthase (eNOS) expression in bone marrow and impaired vascular eNOS activity. Paracrine angiogenic activity of APCs from IRKO mice was impaired compared with those from WT animals. Endothelial regeneration of the femoral artery after denuding wire injury was delayed in IRKO mice compared with WT. Transfusion of mononuclear cells from WT mice normalized the impaired endothelial regeneration in IRKO mice. Transfusion of c-kit(+) bone marrow cells from WT mice also restored endothelial regeneration in IRKO mice. However, transfusion of c-kit(+) cells from IRKO mice was less effective at improving endothelial repair. CONCLUSIONS: Insulin resistance impairs APC function and delays endothelial regeneration after arterial injury. These findings support the hypothesis that insulin resistance per se is sufficient to jeopardize endogenous vascular repair. Defective endothelial repair may be normalized by transfusion of APCs from insulin-sensitive animals but not from insulin-resistant animals.

Human exercise-induced circulating progenitor cell mobilization is nitric oxide-dependent and is blunted in South Asian men.

OBJECTIVE: Circulating progenitor cells (CPC) have emerged as potential mediators of vascular repair. In experimental models, CPC mobilization is critically dependent on nitric oxide (NO). South Asian ethnicity is associated with reduced CPC. We assessed CPC mobilization in response to exercise in Asian men and examined the role of NO in CPC mobilization per se. METHODS AND RESULTS: In 15 healthy, white European men and 15 matched South Asian men, CPC mobilization was assessed during moderate-intensity exercise. Brachial artery flow-mediated vasodilatation was used to assess NO bioavailability. To determine the role of NO in CPC mobilization, identical exercise studies were performed during intravenous separate infusions of saline, the NO synthase inhibitor L-NMMA, and norepinephrine. Flow-mediated vasodilatation (5.8%+/-0.4% vs 7.9%+/-0.5%; P=0.002) and CPC mobilization (CD34(+)/KDR(+) 53.2% vs 85.4%; P=0.001; CD133(+)/CD34(+)/KDR(+) 48.4% vs 73.9%; P=0.05; and CD34(+)/CD45(-) 49.3% vs 78.4; P=0.006) was blunted in the South Asian group. CPC mobilization correlated with flow-mediated vasodilatation and l-NMMA significantly reduced exercise-induced CPC mobilization (CD34(+)/KDR(+) -3.3% vs 68.4%; CD133(+)/CD34(+)/KDR(+) 0.7% vs 71.4%; and CD34(+)/CD45(-) -30.5% vs 77.8%; all P<0.001). CONCLUSIONS: In humans, NO is critical for CPC mobilization in response to exercise. Reduced NO bioavailability may contribute to imbalance between vascular damage and repair mechanisms in South Asian men.