miR-322 regulates insulin signaling pathway and protects against metabolic syndrome-induced cardiac dysfunction in mice.

We identified murine miR-322, orthologous to human miR-424, as a new regulator of insulin receptor, IGF-1 receptor and sirtuin 4 mRNA in vitro and in vivo in the heart and found that miR-322/424 is highly expressed in the heart of mice. C57Bl/6N mice fed 10weeks of high fat diet (HFD) presented signs of cardiomyopathy and a stable miR-322 cardiac level while cardiac function was slightly affected in 11week-old ob/ob which overexpressed miR-322. We thus hypothesized that mmu-miR-322 could be protective against cardiac consequences of hyperinsulinemia and hyperlipidemia. We overexpressed or knocked-down mmu-miR-322 using AAV9 and monitored cardiac function in wild-type C57Bl/6N mice fed a control diet (CD) or a HFD and in ob/ob mice. The fractional shortening progressively declined while the left ventricle systolic diameter increased in HFD mice infected with an AAVcontrol or with an AAVsponge (decreasing miR-322 bioavailability) but also in ob/ob mice infected with AAVsponge. Similar observations were also found in CD-fed mice infected with AAVsponge. On the contrary over-expressing miR-322 with AAVmiR-322 was efficient in protecting the heart from HFD effects in C57Bl/6N mice. This cardioprotection could be associated with the regulation of identified targets IGF1R, INSR and CD1, a decrease in insulin signaling pathway and an enrichment of genes involved in mitochondrial function and fatty acid oxidation as demonstrated by transcriptome analysis. Altogether, these results emphasize miR-322 as a new potential therapeutic target against cardiac consequences of metabolic syndrome, which represents an increasing burden in the western countries.

The differential tissue expression of inflammatory, oxidative stress, and apoptosis markers in human uncontrolled non-heart-beating donors.

BACKGROUND: Uncontrolled non-heart-beating donor (UNHBD) transplantation offers a major opportunity to ameliorate the effects of the donor shortage. However, little is known about the true status of the organs obtained from these donors. UNHBD transplantation is performed under unfavorable conditions and involves exposure to several harmful stimuli that have been identified as triggers for immediate inflammatory response, oxidative stress, and apoptotic phenomena. This adverse scenario could explain the higher rates of graft dysfunction due to primary nonfunction traditionally observed in NHBD. Our aim was to assess the expression of proinflammatory, oxidative, and apoptotic markers in liver, lung, and pancreas tissue samples obtained from UNHBD and to compare these expression levels with those observed in brain-dead donors (BDD). METHODS: Samples from human type 2 NHBD and BDD were obtained at the end of cold storage. Interleukin (IL)-1ß, tumor necrosis factor-α, IL-6, IL-10, endothelial nitric oxide synthase, inducible nitric oxide synthase, type 1 heme oxygenase, type 2 heme oxygenase, Bax, and Bcl-2 protein and mRNA expression, as well as catalase, glutathione peroxidase, and glutathione reductase tissue activity, were determined. RESULTS: UNHBD showed similar or lower expression of proinflammatory mediators and apoptosis markers in all three organs without modifications to the anti-inflammatory cytokines. Although the major oxidative stress marker levels were also comparable in both types of donors, the type 1 heme oxygenase mRNA expression and antioxidant enzyme activity were slightly diminished in UNHBD. CONCLUSIONS: The initial tissue damage generated during the UNHB donation process is at least comparable with that observed in BDD. However, although the expression of the immediate immune response and apoptosis markers is similar, a mild impairment of the local antioxidant activity was observed.