[New pathophysiological mechanisms of metabolic syndrome: implication of orphan nuclear receptors?]

This review focuses on a number of new data on biology and pathophysiology of the metabolic syndrome (MetS) and the involvement of nuclear receptors that have been presented during the last Endocrine Society meeting, held in Houston in June 2012. Several studies have reported beneficial effects of various orphan nuclear receptors, including SHP (Small Heterodimeric Partner, NR0B2) and LXR (Liver X Receptor, NR1H3 and NR1H2), on various components of MetS. By using an inactivation model of SHP, David Moore has shown that SHP exerts "antidiabetic" effects but associated with hepatic steatosis development. He also showed that DLPC (dilauroyl phosphatidylcholine), an unconventional phospholipid, exhibited anti-diabetic properties through its binding to LRH-1 (Liver Receptor Homolog-1, NR5A2), a molecular partner of SHP. Interestingly, Carolyn Cummins investigated LXR α and β isoforms knock-out mice and provided experimental evidence for the detailed mechanisms involved in the deleterious metabolic effects of glucocorticoids, pointing out to the functional interaction between LXRβ, and the glucocorticoid receptor. These new and original studies open new therapeutic opportunities for the management of metabolic disorders in humans by selective modulators of these receptors.

The acute effect of IABP-induced pulsatility on coronary vascular resistance and graft flow in critical ill patients during ECMO

AIM

The combination of the two cardiac support mechanisms of intra-aortic balloon pumping (IABP) and non-pulsatile circulatory extracorporeal membrane oxygenation (ECMO) has been confirmed to improve efficacy of the cardiac support as a whole. However, reports on benefits of diastolic augmentation on coronary vascular bed and graft flowmetry during concomitant use of IABP and ECMO are lacking. The aim of this study was to evaluate the acute impact of IABP support on coronary vascular resistance (CVR) and coronary bypass flows (CBF) in high-risk patients with peripheral ECMO following coronary artery bypass grafting (CABG).

METHODS

In eight emergency CABG patients (mean age=67.8±1.9 years; gender: six male and two female; EF=25.5±2.4%) requiring mechanical circulatory support with ECMO hemodynamic parameters, CVR, CBF, diastolic filling index (DFI), graft flow reserve (GFR), and pulsatility index (PI) were analyzed with and without diastolic augmentation using a transit time flowmeter.

RESULTS

The addition of IABP to ECMO decreased CVR significantly by 6.5%±1.9% compared to baseline with ECMO alone (1.62±0.2 versus 1.78±0.2; P<0.0045). Accordingly, significant higher mean CBF were found during IABP assist, resulting in a 21.6%±2.6% increase (60.7±8.7 mL/min with versus 51.3±7.4 mL/min without IABP; P<0.0001). IABP also significantly increased DFI by 9.8±0.9% (73.2%±1.4% with versus 66.7%±1.3% without IABP; P<0.0001). GFR was recruited during IABP in all grafts (GFR>1). There were no statistically significant differences in PI with and without IABP assistance (2.6±0.1 versus 2.5±0.2).

CONCLUSION

IABP-induced pulsatility significantly improves diastolic filling index and mean coronary bypass graft flows by lowering coronary vascular resistance during non-pulsatile peripheral ECMO. The combination of ECMO with IABP may provide more optimal myocardial oxygen conditions resulting in an improved efficacy of the cardiac support as a whole in critical ill patients with postcardiotomy myocardial dysfunction following CABG.

Sequence dependent antitumour efficacy of the vascular disrupting agent ZD6126 in combination with paclitaxel

The clinical success of small-molecule vascular disrupting agents (VDAs) depends on their combination with conventional therapies. Scheduling and sequencing remain key issues in the design of VDA-chemotherapy combination treatments. This study examined the antitumour activity of ZD6126, a microtubule destabilising VDA, in combination with paclitaxel (PTX), a microtubule-stabilising cytotoxic drug, and the influence of schedule and sequence on the efficacy of the combination. Nude mice bearing MDA-MB-435 xenografts received weekly cycles of ZD6126 (200 mg kg(-1) i.p.) administered at different times before or after PTX (10, 20, and 40 mg kg(-1) i.v.). ZD6126 given 2 or 24 h after PTX showed no significant benefit, a result that was attributed to a protective effect of PTX against ZD6126-induced vascular damage and tumour necrosis, a hallmark of VDA activity. Paclitaxel counteracting activity was reduced by distancing drug administrations, and ZD6126 given 72 h after PTX potentiated the VDA's antitumour activity. Schedules with ZD6126 given before PTX improved therapeutic activity, which was paralleled by a VDA-induced increase in cell proliferation in the viable tumour tissue. Paclitaxel given 72 h after ZD6126 yielded the best response (50% tumours regressing). A single treatment with ZD6126 followed by weekly administration of PTX was sufficient to achieve a similar response (57% remissions). These findings show that schedule, sequence and timing are crucial in determining the antitumour efficacy of PTX in combination with ZD6126. Induction of tumour necrosis and increased proliferation in the remaining viable tumour tissue could be exploited as readouts to optimise schedules and maximise therapeutic efficacy.