Hyperglycemia-mediated microvascular damage has been proposed to originate from excessive generation of mitochondrial
superoxide in endothelial cells and is the suggested mechanism by which the pathogenesis of diabetes-induced renal damage occurs.
C-peptide has been shown to ameliorate diabetes-induced renal impairment. Yet, the mechanisms underlying this protective benefit remain unclear. The objective of this study was to determine whether
C-peptide affords protection to renal microvascular endothelial cell mitochondria during
hyperglycemia. Conditionally immortalized murine renal microvascular endothelial cells (MECs) were exposed to low (5.5 mM) or high
glucose (25 mM) media with either
C-peptide (6.6 nM) or its scrambled sequence control
peptide for 24 or 48 hours. Respiratory control ratio, a measure of mitochondrial electrochemical coupling, was significantly higher in high
glucose renal MECs treated with
C-peptide than those of high
glucose alone.
C-peptide also restored high
glucose-induced renal MEC mitochondrial membrane potential changes back to their basal low
glucose state. Moreover,
C-peptide prevented the excessive mitochondrial
superoxide generation and concomitant reductions in mitochondrial complex I activity which are mediated by the exposure of the renal MECs to high
glucose. Together, these data demonstrate that
C-peptide protects against high
glucose-induced generation of mitochondrial
superoxide in renal MECs via restoration of basal mitochondrial function.