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Aims Knockout (KO) of the mitochondrial Ca2+ uniporter (MCU) in mice abrogates mitochondrial Ca2+ uptake and permeability transition pore (PTP) opening. However, hearts from global MCU-KO mice are not protected from ischaemic injury. We aimed to investigate whether adaptive alterations occur in cell death signalling pathways in the hearts of global MCU-KO mice. Methods and results First, we examined whether cell death may occur via an upregulation in necroptosis in MCU-KO mice. However, our results show that neither RIP1 inhibition nor RIP3 knockout afford protection against ischaemia-reperfusion injury in MCU-KO as in wildtype (WT) hearts, indicating that the lack of protection cannot be explained by upregulation of necroptosis. Instead, we have identified alterations in cyclophilin D (CypD) signalling in MCU-KO hearts. In the presence of a calcium ionophore, MCU-KO mitochondria take up calcium and do undergo PTP opening. Furthermore, PTP opening in MCU-KO mitochondria has a lower calcium retention capacity (CRC), suggesting that the calcium sensitivity of PTP is higher. Phosphoproteomics identified an increase in phosphorylation of CypD-S42 in MCU-KO. We investigated the interaction of CypD with the putative PTP component ATP synthase and identified an approximately 50% increase in this interaction in MCU-KO cardiac mitochondria. Mutation of the novel CypD phosphorylation site S42 to a phosphomimic reduced CRC, increased CypD-ATP synthase interaction by approximately 50%, and increased cell death in comparison to a phospho-resistant mutant. Conclusion Taken together these data suggest that MCU-KO mitochondria exhibit an increase in phosphorylation of CypD-S42 which decreases PTP calcium sensitivity thus allowing activation of PTP in the absence of an MCU-mediated increase in matrix calcium. [ABSTRACT FROM AUTHOR]

Metabolic syndrome is a cluster of risk factors, such as obesity, insulin resistance, and hyperlipidemia that increases the individual’s likelihood of developing cardiovascular diseases. Patients inflicted with metabolic disorders also suffer from tissue repair defect. Mitsugumin 53 (MG53) is a protein essential to cellular membrane repair. It facilitates the nucleation of intracellular vesicles to sites of membrane disruption to create repair patches, contributing to the regenerative capacity of skeletal and cardiac muscle tissues upon injury. Since individuals suffering from metabolic syndrome possess tissue regeneration deficiency and MG53 plays a crucial role in restoring membrane integrity, we studied MG53 activity in mice models exhibiting metabolic disorders induced by a 6 month high-fat diet (HFD) feeding. Western blotting showed that MG53 expression is not altered within the skeletal and cardiac muscles of mice with metabolic syndrome. Rather, we found that MG53 levels in blood circulation were actually reduced. This data directly contradicts findings presented by Song et. al that indict MG53 as a causative factor for metabolic syndrome (Nature 494, 375-379). The diminished MG53 serum level observed may contribute to the inadequate tissue repair aptitude exhibited by diabetic patients. Furthermore, immunohistochemical analyses reveal that skeletal muscle fibers of mice with metabolic disorders experience localization of subcellular MG53 around mitochondria. This clustering may represent an adaptive response to oxidative stress resulting from HFD feeding and may implicate MG53 as a guardian to protect damaged mitochondria. Therapeutic approaches that elevate MG53 expression in serum circulation may be a novel method to treat the degenerative tissue repair function of diabetic patients. [ABSTRACT FROM AUTHOR]

Background & Aims: A number of factors have been identified that influence the yield of screening colonoscopy. The perceived tolerability of bowel preparation has not been studied as a predictor of quality outcomes in colonoscopy. We aimed to characterize the association between patient-perceived tolerability of bowel preparation and polyp detection during colonoscopy. Methods: We performed a cross-sectional cohort study of 413 consecutive adult patients presenting for outpatient colonoscopy at two outpatient endoscopy centers at our institution. We developed a standardized questionnaire to assess the patient's experience with bowel preparation. Bowel preparation quality was measured using the validated Ottawa scale and colonoscopic findings were recorded for each patient. The primary outcome was polyp detection and the secondary outcome was the quality of bowel preparation. Results: Patient-reported clarity of effuent during bowel preparation correlated poorly with Ottawa score during colonoscopy, κ=0.15. Female gender was an independent risk factor for a poorly tolerated bowel prep (OR 3.93, 95% CI 2.30 - 6.72, p<0.001). Report of a poorly tolerated bowel prep was independently associated with the primary outcome, polyp detection (OR 0.39, 95% CI 0.18 - 0.84, p=0.02) and also with the secondary outcome, lower quality bowel preparation (OR 2.39, 95% CI 1.17 - 4.9, p=0.02). Conclusions: A patient-perceived negative experience with bowel preparation independently predicted both a lower quality bowel preparation and a lower rate of polyp of detection. Assessment of the tolerability of bowel preparation before colonoscopy may be a clinically useful predictor of quality outcomes during colonoscopy. [ABSTRACT FROM AUTHOR]