Abstract 19549: Exercise Mitigates Calpain Induced Purkinje Cell Loss in Diabetes
Calpain 1 is a ubiquitous calcium dependent cysteine protease and found in cytoplasm as well as mitochondria. We have reported earlier that active calpain 1 is translocated from cytosol to mitochondria and activates MMP9. Calpain inhibition has been reported to restrict Purkinje cell damage however whether calpain 1 can degrade Purkinje cell protein (PCP4) and affect contractility in diabetes is unknown. Therefore, we hypothesize that calpain 1 degrades PCP4 in diabetes to cause contractile dysfunction and exercise can mitigate this. To test this hypothesis we recruited four groups of mice 1) db/+ control, 2) db/+ control with exercise, 3) db/db, 4) db/db with exercise. The mice were exercised on treadmill at 7m/min for 300m for 8 weeks. The echo data suggested significant improvement in cardiac function in terms of ejection fraction (~20%) and fractional shortening in db/db exercised mice. We treated the isolated cardiomyocytes with high calcium (40mM) till they lose their shape and become dead. We observed high levels of calpain 1 (~75% increase) and significantly downregulated PCP4 (~70%) along with upregulated levels of calmodulin and calmodulin kinase in dead myocyte as compared to live. We used the CRISPR/Cas9 plasmid to knock down calpain1 in HL-1 myocytes which restored the levels of PCP4 along with calmodulin and calmodulin kinase. In diabetic db/db mice, we found upregulated levels of calpain 1(~40% increase) as compared to controls which were mitigated in the exercised mice. We stained the Purkinje fibers with PCP4 and observed that exercised prevented Purkinje fiber loss (upto 40%) in the heart of diabetic mice. We transfected cadrdiomyocytes with CRISPR-calpain1 and observed improved contractility in transfected myocytes under calcium overload as compared to non-transfected. Conclusively our data strongly suggests that in diabetes there is high induction of calpain 1 with degrades PCP4, a protein important for contractility and exercise can mitigate this.
Author Disclosures: P. Chaturvedi: None. G.H. Kunkel: None. A. Familtseva: None. N. Jeremic: None. S.C. Tyagi: None.
- © 2016 by American Heart Association, Inc.