calpain and Diabetes-Mellitus--Type-1

Calpain plays a critical role in cardiomyopathic changes in type 1 diabetes (T1D). This study investigated how calpain regulates mitochondrial reactive oxygen species (ROS) generation in the development of diabetic cardiomyopathy. T1D was induced in transgenic mice overexpressing calpastatin, in mice with cardiomyocyte-specific capn4 deletion, or in their wild-type littermates by injection of streptozotocin. Calpain-1 protein and activity in mitochondria were elevated in diabetic mouse hearts. The increased mitochondrial calpain-1 was associated with an increase in mitochondrial ROS generation and oxidative damage and a reduction in ATP synthase-α (ATP5A1) protein and ATP synthase activity. Genetic inhibition of calpain or upregulation of ATP5A1 increased ATP5A1 and ATP synthase activity, prevented mitochondrial ROS generation and oxidative damage, and reduced cardiomyopathic changes in diabetic mice. High glucose concentration induced ATP synthase disruption, mitochondrial superoxide generation, and cell death in cardiomyocytes, all of which were prevented by overexpression of mitochondria-targeted calpastatin or ATP5A1. Moreover, upregulation of calpain-1 specifically in mitochondria induced the cleavage of ATP5A1, superoxide generation, and apoptosis in cardiomyocytes. In summary, calpain-1 accumulation in mitochondria disrupts ATP synthase and induces ROS generation, which promotes diabetic cardiomyopathy. These findings suggest a novel mechanism for and may have significant implications in diabetic cardiac complications.

Topics: Animals; Apoptosis; Calcium-Binding Proteins; Calpain; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Diabetic Cardiomyopathies; Disease Models, Animal; Mice; Mice, Transgenic; Mitochondria, Heart; Mitochondrial Proton-Translocating ATPases; Myocardium; Myocytes, Cardiac; Reactive Oxygen Species; Superoxides

Recently we have shown that calpain-1 activation contributes to cardiomyocyte apoptosis induced by hyperglycemia. This study was undertaken to investigate whether targeted disruption of calpain would reduce myocardial hypertrophy and fibrosis in mouse models of type 1 diabetes.. Diabetes in mice was induced by injection of streptozotocin (STZ), and OVE26 mice were also used as a type 1 diabetic model. The function of calpain was genetically manipulated by cardiomyocyte-specific knockout Capn4 in mice and the use of calpastatin transgenic mice. Myocardial hypertrophy and fibrosis were investigated 2 and 5 months after STZ injection or in OVE26 diabetic mice at the age of 5 months. Cultured isolated adult mouse cardiac fibroblast cells were also investigated under high glucose conditions.. Calpain activity, cardiomyocyte cross-sectional areas, and myocardial collagen deposition were significantly increased in both STZ-induced and OVE26 diabetic hearts, and these were accompanied by elevated expression of hypertrophic and fibrotic collagen genes. Deficiency of Capn4 or overexpression of calpastatin reduced myocardial hypertrophy and fibrosis in both diabetic models, leading to the improvement of myocardial function. These effects were associated with a normalization of the nuclear factor of activated T-cell nuclear factor-κB and matrix metalloproteinase (MMP) activities in diabetic hearts. In cultured cardiac fibroblasts, high glucose-induced proliferation and MMP activities were prevented by calpain inhibition.. Myocardial hypertrophy and fibrosis in diabetic mice are attenuated by reduction of calpain function. Thus targeted inhibition of calpain represents a potential novel therapeutic strategy for reversing diabetic cardiomyopathy.

Topics: Animals; Calcium-Binding Proteins; Calpain; Cardiomyopathy, Hypertrophic; Cell Proliferation; Cells, Cultured; Diabetes Mellitus, Type 1; Diabetic Cardiomyopathies; Disease Models, Animal; Fibrosis; Gene Expression Regulation; Heart; Hyperglycemia; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Molecular Targeted Therapy; Myocardium; Streptozocin

Pancreatic beta-cell death is a critical event in type 1 diabetes, type 2 diabetes, and clinical islet transplantation. We have previously shown that prolonged block of ryanodine receptor (RyR)-gated release from intracellular Ca(2+) stores activates calpain-10-dependent apoptosis in beta-cells. In the present study, we further characterized intracellular Ca(2+) channel expression and function in human islets and the MIN6 beta-cell line. All three RyR isoforms were identified in human islets and MIN6 cells, and these endoplasmic reticulum channels were observed in close proximity to mitochondria. Blocking RyR channels, but not sarco/endoplasmic reticulum ATPase (SERCA) pumps, reduced the ATP/ADP ratio. Blocking Ca(2+) flux through RyR or inositol trisphosphate receptor channels, but not SERCA pumps, increased the expression of hypoxia-inducible factor (HIF-1beta). Moreover, inhibition of RyR or inositol trisphosphate receptor channels, but not SERCA pumps, increased the expression of presenilin-1. Both HIF-1beta and presenilin-1 expression were also induced by low glucose. Overexpression of presenilin-1 increased HIF-1beta, suggesting that HIF is downstream of presenilin. Our results provide the first evidence of a presenilin-HIF signaling network in beta-cells. We demonstrate that this pathway is controlled by Ca(2+) flux through intracellular channels, likely via changes in mitochondrial metabolism and ATP. These findings provide a mechanistic understanding of the signaling pathways activated when intracellular Ca(2+) homeostasis and metabolic activity are suppressed in diabetes and islet transplantation.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Aryl Hydrocarbon Receptor Nuclear Translocator; Calcium; Calcium Signaling; Calpain; Cells, Cultured; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Endoplasmic Reticulum; Glucose; Homeostasis; Humans; Insulin-Secreting Cells; Islets of Langerhans Transplantation; Mitochondria; Presenilin-1; Protein Isoforms; Ryanodine Receptor Calcium Release Channel; Sarcoplasmic Reticulum Calcium-Transporting ATPases

Microalbuminuria in Type I diabetes involves a cell membrane abnormality and is associated with a large increase in cardiovascular risk. The hypothesis that the membrane abnormality alters granule exocytosis in neutrophils, which could contribute to the increased incidence of cardiovascular disease, was investigated. PMA-stimulated expression of CD11b and CD69 on neutrophils from normal controls (NC), long-term uncomplicated Type I diabetic control patients (DC) and diabetic nephropathy patients (DN) was determined by fluorescence activated cell scanning. Neutrophils from DN were faster than neutrophils from either NC or DC to exocytose primary granules with CD69 following initial expression of the adhesion molecule CD11b. However, a larger proportion of neutrophils from DN failed to withdraw CD11b from the cell membrane after 90 min incubation. The protein kinase C (PKC) inhibitor, bisindolylmaleimide (BIM), showed that a larger proportion of neutrophils from DN, compared with DC or NC, exocytosed primary granules independent of PKC. The calpain inhibitor, E64d, showed that a larger proportion of neutrophils from both groups of diabetic patients, compared with NC, exocytosed primary granules independent of calpain. Cytoskeletal disruption with cytochalasin D had an effect on CD11b and CD69 exocytosis similar to that of BIM and E64d. The pathways controlling granule exocytosis in neutrophils from diabetic patients are abnormal. A change characteristic of DN causes rapid exocytosis of primary granules, and also causes the adhesion molecule CD11b to persist on an increased proportion of neutrophils. This will make an important contribution to increased vascular damage in these patients.

Topics: Adult; Calpain; Case-Control Studies; Diabetes Mellitus, Type 1; Diabetic Nephropathies; Down-Regulation; Exocytosis; Female; Flow Cytometry; Humans; Macrophage-1 Antigen; Male; Middle Aged; Neutrophils; Normal Distribution; Protein Kinase C; Statistics, Nonparametric