Sander Kersten

Promoter rearrangements cause species-specific hepatic regulation of the glyoxylate reductase/hydroxypyruvate reductase gene by the peroxisome proliferator-activated receptor alpha

In liver, the glyoxylate cycle contributes to two metabolic functions, urea and glucose synthesis. One of the key enzymes in this pathway is glyoxylate reductase/hydroxypyruvate reductase (GRHPR) whose dysfunction in human causes primary hyperoxaluria type 2, a disease resulting in oxalate accumulation and formation of kidney stones. In this study, we provide evidence for a transcriptional regulation by the peroxisome proliferator-activated receptor α (PPARα) of the mouse GRHPR gene in liver. Mice fed with a PPARα ligand or in which PPARα activity is enhanced by fasting increase their GRHPR gene expression via a peroxisome proliferator response element located in the promoter region of the gene. Consistent with these observations, mice deficient in PPARα present higher plasma levels of oxalate in comparison with their wild type counterparts. As expected, the administration of a PPARα ligand (Wy-14,643) reduces the plasma oxalate levels. Surprisingly, this effect is also observed in null mice, suggesting a PPARα-independent action of the compound. Despite a high degree of similarity between the transcribed region of the human and mouse GRHPR gene, the human promoter has been dramatically reorganized, which has resulted in a loss of PPARα regulation. Overall, these data indicate a species-specific regulation by PPARα of GRHPR, a key gene of the glyoxylate cycle.

Peroxisome Proliferator Activated Receptor Alpha Coordinates Intermediary Metabolism During Fasting

In response to repeated and long-lasting food shortages during evolution, humans have evolved with an intricate metabolic control system that allows them to survive prolonged period of food deprivation. One hallmark of this adaptive system is the ability to store large amounts of energy in the form of fat in times of plenty and mobilize this energy under conditions of food shortage such as fasting.