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Cell therapy has been extensively investigated in heart disease but less so in the kidney. We considered whether cell therapy also might be useful in diabetic kidney disease. Cognizant of the likely need for autologous cell therapy in humans, we sought to assess the efficacy of donor cells derived from both healthy and diabetic animals. Eight-week-old db/db mice were randomized to receive a single intravenous injection of PBS or 0.5 × 106 early-outgrowth cells (EOCs) from db/m or db/db mice. Effects were assessed 4 weeks after cell infusion. Untreated db/db mice developed mesangial matrix expansion and tubular epithelial cell apoptosis in association with increased reactive oxygen species (ROS) and overexpression of thioredoxin interacting protein (TxnIP). Without affecting blood glucose or blood pressure, EOCs not only attenuated mesangial and peritubular matrix expansion, as well as tubular apoptosis, but also diminished ROS and TxnIP overexpression in the kidney of db/db mice. EOCs derived from both diabetic db/db and nondiabetic db/m mice were equally effective in ameliorating kidney injury and oxidative stress. The similarly beneficial effects of cells from healthy and diabetic donors highlight the potential of autologous cell therapy in the related clinical setting.

Hyperglycemia induces the production of reactive oxygen species (ROS) from mitochondria, which is closely related to diabetic vascular complications. Mammalian translocase of inner mitochondrial membrane (Tim)44 was identified by upregulation in streptozotocin (STZ)-induced diabetic mouse kidneys; Tim44 functions as a membrane anchor of mtHsp70 to TIM23 complex and is involved in the import of preproteins with mitochondria-targeted presequence into mitochondrial matrix. The process is dependent on inner membrane potential (Δψ) and ATP hydrolysis on ATPase domain of mtHsp70. Here, we show that the gene delivery of Tim44 using pcDNA3.1 vector (pcDNA3.1/TIM44) into the balloon injury model of STZ-induced diabetic rats ameliorated neointimal proliferation. ROS production, inflammatory responses, and cell proliferation in injured carotid artery were diminished by delivery of pcDNA3.1/TIM44. In vitro experiments using human aortic smooth muscle cells (HASMCs) revealed that the gene delivery of Tim44 normalized high-glucose–induced enhanced ROS production and increased ATP production, alterations in inner membrane potential, and cell proliferation. Transfection of siRNA and pcDNA3.1/TIM44 using HASMC culture clarified that import of antioxidative enzymes such as superoxide dismutase and glutathione peroxidase was facilitated by Tim44. Tim44 and its related molecules in mitochondrial import machinery complex are novel targets in the therapeutic interventions for diabetes and its vascular complications.

Cells in which insulin is not required for glucose uptake are susceptible to the long-term complications of diabetes. Even in these tissues, however, the major perturbations that would otherwise be engendered by the greatly increased intracellular glucose concentration are mollified by adaptive changes in the enzymes of intermediary metabolism. These include allosteric regulation, product inhibition, and covalent modification as well as alterations in gene transcription. More recently, advances in proteomic technology have shown that reversible acetylation of the ε-amino group of lysine provides an additional means of modulating protein function and, in particular, enzyme activity. Here, we explored the extent of protein acetylation in an organ susceptible to the long-term complications of diabetes, examining the kidneys of rats with streptozotocin-induced diabetes and kidney cells exposed to high glucose. Using high-resolution mass spectrometry coupled with immunoaffinity enrichment, we identified 47 lysine-acetylated proteins in the kidneys of diabetic rats compared with 11 in control kidneys. Bioinformatic interrogation of the acetylome from diabetic animals showed a predominance of metabolic pathway involvement including the citrate acid cycle, glycolysis/gluconeogenesis, and metabolism of branched chain amino acids. Increased lysine acetylation was also noted in mesangial and tubular cells exposed to 25 mmol/L compared with 5.6 mmol/L glucose. These findings highlight acetylation as a posttranslational modification affecting numerous proteins. Current drug discovery efforts to develop small molecule inhibitors and activators of various lysine acetylases and deacetylases offer a new potential strategy to reduce the likelihood of diabetes complications.