Kidney mitochondrial complex I dysfunction in a juvenile rat model of diabetic ketoacidosis

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Abstract
Background The pathobiology of acute kidney injury during diabetic ketoacidosis (DKA) is not completely understood. We hypothesized that mitochondrial function is impaired during DKA as a mechanism of acute kidney injury. Methods We isolated kidney samples from 4 to 5 week-old rats with normoglycemia (NG, controls; n = 7), hyperglycemia (HG; n = 5), acute DKA (DKA; n = 5), and after 24 h of DKA treatment (DKA-24; n = 5). Kidney tissue homogenates were prepared from frozen tissue for measurement of mitochondrial electron transport system (ETS) complex I + III, II + III, and IV activity and citrate synthase activity using spectrophotometry and ETS complex protein expression using Western blots. Results Mitochondrial ETS complex I + III activity (mean ± SD) exhibited a stepwise decrease from HG (113 ± 54 nmol/min/mg tissue protein) to DKA (64 ± 32; p < 0.05 compared to NG) and trended toward NG control levels (143 ± 37) in DKA-24 (135 ± 39). Mitochondrial content, including citrate synthase activity and ETS complex proteins I, II, IV, and V, did not differ between groups, except that ETS complex III increased in HG and DKA and subsequently decreased in DKA-24. Conclusions In a juvenile rat model of DKA, increasing glycemic stress caused a reversible change in kidney mitochondrial complex I function and complex III expression. Impact Acute kidney injury during diabetic ketoacidosis (DKA) increases risk of future diabetic kidney disease, but the underlying pathobiology is not understood. In a juvenile rat model of DKA, we found that increasing glycemic stress caused a reversible change in kidney mitochondrial complex I function and complex III expression. These data support further investigation to determine if mitochondrial dysfunction may contribute to DKA-related acute kidney injury.

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