Tissue-Specific Remodeling of the Mitochondrial Proteome in Type 1 Diabetic Akita Mice

Abstract

OBJECTIVETo elucidate the molecular basis for mitochondrial dysfunction, which has been implicated in the pathogenesis of diabetes complications.RESEARCH DESIGN AND METHODSMitochondrial matrix and membrane fractions were generated from liver, brain, heart, and kidney of wild-type and type 1 diabetic Akita mice. Comparative proteomics was performed using label-free proteome expression analysis. Mitochondrial state 3 respirations and ATP synthesis were measured, and mitochondrial morphology was evaluated by electron microscopy. Expression of genes that regulate mitochondrial biogenesis, substrate utilization, and oxidative phosphorylation (OXPHOS) were determined.RESULTSIn diabetic mice, fatty acid oxidation (FAO) proteins were less abundant in liver mitochondria, whereas FAO protein content was induced in mitochondria from all other tissues. Kidney mitochondria showed coordinate induction of tricarboxylic acid (TCA) cycle enzymes, whereas TCA cycle proteins were repressed in cardiac mitochondria. Levels of OXPHOS subunits were coordinately increased in liver mitochondria, whereas mitochondria of other tissues were unaffected. Mitochondrial respiration, ATP synthesis, and morphology were unaffected in liver and kidney mitochondria. In contrast, state 3 respirations, ATP synthesis, and mitochondrial cristae density were decreased in cardiac mitochondria and were accompanied by coordinate repression of OXPHOS and peroxisome proliferator–activated receptor (PPAR)-γ coactivator (PGC)-1α transcripts.CONCLUSIONSType 1 diabetes causes tissue-specific remodeling of the mitochondrial proteome. Preservation of mitochondrial function in kidney, brain, and liver, versus mitochondrial dysfunction in the heart, supports a central role for mitochondrial dysfunction in diabetic cardiomyopathy.

Mitochondrial Morphology in Metabolic Diseases

“…This was not observed in the SSM samples. The reduced size of IFM could be explained by an enhanced fission, whereas the loss of internal complexity is consistent with the findings from Akita and OVE26 genetic models (19,143). Respiration analyses of ETC components of the augmented IFM revealed deficiencies in respiration from complexes I, II, and III.…”

“…In all models tested, except Akita mice where oxidative stress was not observed, cardiac and mitochondrial functions were decreased (9,10,16,18,19,41,53,73,80,96,122,123), and these decreases were associated with increases in oxidative stress (10,125,142,143). The OVE26 mouse model develops a type 1 diabetic phenotype through the overexpression of calmodulin, specifically in pancreatic b-cells, leading to damage and extremely low levels of insulin secretion (48).…”

“…In a follow-up study, the Epstein Lab further implicated the role of mitochondrial ROS production in cardiac morphological and physiological defects by demonstrating that the mitochondrial-specific ROS-scrubbing enzyme manganese superoxide dismutase (MnSOD) recovered the OVE26 cardiac maladies (122). Akita mice, which become diabetic by b-cell death in response to misfolded proinsulin (149), display a similar cardiac mitochondrial defect by EM (19). Despite their abnormal cardiac pathology, physiologically, they demonstrate very subtle contractile defects and retain mitochondrial coupling while lacking enhanced production of ROS and the resulting oxidative stress (18).…”

“…Despite their abnormal cardiac pathology, physiologically, they demonstrate very subtle contractile defects and retain mitochondrial coupling while lacking enhanced production of ROS and the resulting oxidative stress (18). Subsequent studies utilizing succinate and glutamate as substrates determined that Akita mice do have deficiencies in respiration in cardiac tissue, which results in suppressed ATP production (19). This suggests that ROS production may not be required for the development of DCM; however, it may exacerbate the physiological impairment upon metabolic insults, as type 2 models of diabetes demonstrate more robust impairment of contractile function and energetic deficiencies (16,85).…”

Toward Quantitative Proteomics of Organ Substructures: Implications for Renal Physiology

“…Many more studies used cell lines derived from various nephron regions with the major limitation that it remains unclear how far these cell lines reflect the in-vivo situation 88 . Most studies have applied proteomics to study disease processes using whole kidney tissue as material 55,[89][90][91][92][93][94] . Obviously, this approach is simple and fast but has major limitations due to the morphological diversity and complexity of the kidney.…”