Protection from diabetic cardiomyopathy - putative role of the retinoid receptor-mediated signaling

Retinoic acid attenuates cardiac injury induced by hyperglycemia in pre- and post-delivery mice

The aim of the present study is to explore the effect of retinoic acid (RA) on cardiac injury induced by gestational diabetes mellitus (GDM). GDM mice were given 3 mg/kg RA once daily until the 19th day of pregnancy or the 7th day of post-partum. Compared to normal control and normal pregnant control mice, GDM mice before and after delivery showed significantly cardiac injury. RA treatment attenuated cardiac injury as evidenced by decreased heart mass and left ventricular mass, mRNA expressions of ANP and BNP, and cardiac fibrosis compared with that in GDM mice. The protective effect of RA on GDM cardiomyopathy was related to the decreased MDA content and ROS generation, the increased GSH-Px and SOD content as well as the reduced TNF-α and IL-1β content and inhibition of NF-κB signaling. In addition, RA treatment delayed the continuous rise of blood glucose before delivery and decreased the higher level of glucose after delivery. In conclusion, RA treatment could increase the activity of the antioxidant enzyme and suppress the oxidative stress, inflammation response, and activation of NF-κB signaling, thereby improving blood glucose level and cardiac injury of GDM mice before and after delivery.

A Doxorubicin-induced Cardiomyopathy Model in Adult Zebrafish

The genetically accessible adult zebrafish (Danio rerio) has been increasingly used as a vertebrate model for understanding human diseases such as cardiomyopathy. Because of its convenience and amenability to high throughput genetic manipulations, the generation of acquired cardiomyopathy models, such as the doxorubicin-induced cardiomyopathy (DIC) model in adult zebrafish, is opening the doors to new research avenues, including discovering cardiomyopathy modifiers via forward genetic screening. Different from the embryonic zebrafish DIC model, both initial acute and later chronic phases of cardiomyopathy can be determined in the adult zebrafish DIC model, enabling the study of stage-dependent signaling mechanisms and therapeutic strategies. However, variable results can be obtained with the current model, even in the hands of experienced investigators. To facilitate future implementation of the DIC model, we present a detailed protocol on how to generate this DIC model in adult zebrafish and describe two alternative ways of intraperitoneal (IP) injection. We further discuss options on how to reduce variations to obtain reliable results and provide suggestions on how to appropriately interpret the results.

A modifier screen identifies DNAJB6 as a cardiomyopathy susceptibility gene

Mutagenesis screening is a powerful forward genetic approach that has been successfully applied in lower-model organisms to discover genetic factors for biological processes. This phenotype-based approach has yet to be established in vertebrates for probing major human diseases, largely because of the complexity of colony management. Herein, we report a rapid strategy for identifying genetic modifiers of cardiomyopathy (CM). Based on the application of doxorubicin stress to zebrafish insertional cardiac (ZIC) mutants, we identified 4 candidate CM-modifying genes, of which 3 have been linked previously to CM. The long isoform of DnaJ (Hsp40) homolog, subfamily B, member 6b (dnajb6b(L)) was identified as a CM susceptibility gene, supported by identification of rare variants in its human ortholog DNAJB6 from CM patients. Mechanistic studies indicated that the deleterious, loss-of-function modifying effects of dnajb6b(L) can be ameliorated by inhibition of ER stress. In contrast, overexpression of dnajb6(L) exerts cardioprotective effects on both fish and mouse CM models. Together, our findings establish a mutagenesis screening strategy that is scalable for systematic identification of genetic modifiers of CM, feasible to suggest therapeutic targets, and expandable to other major human diseases.