Hypoxia plays a role in ischemic, toxic and sepsis-induced acute kidney injury. Evolving hypoxia triggers renal adaptive responses that may mitigate the insult, leading to sublethal forms of cell injury. The unique capability of the kidney to downregulate oxygen consumption for tubular transport could represent one such adaptive response which promotes maintenance of renal oxygenation, thereby preserving cellular integrity. Tran et al. recently explored a novel mechanism that might prevent tubular damage by downregulation of mitochondrial biogenesis and oxygen consumption. Using expression profiling of kidney RNA in endotoxemic rodents and complementary studies in vitro and in PGC-1α knockout mice, they found a sepsis-related decline in PPAR coactivator-1α (PGC-1α) expression and of PGC-1α-dependent genes involved in oxidative phosphorylation. This response may explain their observation of a paradoxical preservation of kidney oxygenation and structural integrity in sepsis, despite reduced renal blood flow and oxygen delivery. Thus, resetting of mitochondrial respiration and oxygen consumption during sepsis might be added to the growing list of adaptive responses that occur during hypoxic stress. This review will focus on these mechanisms that mitigate evolving hypoxic injury, even at the expense of transient renal dysfunction.

Primary hyperoxaluria Type 1 is a rare autosomal recessive inborn error of glyoxylate metabolism, caused by a deficiency of the liver-specific enzyme alanine:glyoxylate aminotransferase. The disorder results in overproduction and excessive urinary excretion of oxalate, causing recurrent urolithiasis and nephrocalcinosis. As glomerular filtration rate declines due to progressive renal involvement, oxalate accumulates leading to systemic oxalosis. The diagnosis is based on clinical and sonographic findings, urine oxalate assessment, enzymology and/or DNA analysis. Early initiation of conservative treatment (high fluid intake, pyridoxine, inhibitors of calcium oxalate crystallization) aims at maintaining renal function. In chronic kidney disease Stages 4 and 5, the best outcomes to date were achieved with combined liver–kidney transplantation.