ODP007 Nephron Specific ATP6AP2 Knockout Increases Urinary Excretion of Fatty Acids while Decreasing Renal Cortical Megalin Expression

Abstract

Abstract We recently reported that mice with inducible nephron specific knockout of ATP6AP2 are resistant to diet induced obesity while demonstrating significant increases in urine glucose and albumin excretion. It is not known whether urinary loss of other metabolites such as lipids contributes to impaired weight gain in this model. Nonesterified fatty acids (NEFA) are filtered by the glomerulus bound to albumin and are normally reabsorbed in the proximal tubule via the megalin-cubulin complex. We hypothesized that nephron specific ATP6AP2 knockout reduces megalin expression leading to increased urinary NEFA excretion. Eight-week-old male inducible nephron specific ATP6AP2 knockout mice underwent either induction with oral doxycycline or received sucrose water as controls before being placed on either normal diet (ND) or high fat diet (HFD) for 6 months. At the end of this period, organic lipid extraction was performed on 24-hour urine samples to determine 24-hour NEFA excretion. RT-PCR was utilized to determine renal cortical expression of LRP2, the gene for megalin. Similar to prior reports, HFD alone increased body weight by 76% at 6 months compared to ND controls (p<0. 01) while HFD fed knockout mice had 53% lower body weight than HFD controls (p<0. 01). There was no significant change in 24-hour NEFA excretion between ND and HFD controls, but knockout mice on ND had 79% greater 24-hour urine NEFA excretion than ND controls while HFD fed knockout mice had 142% greater 24-hour NEFA excretion compared to HFD controls (p<0. 05). RT-PCR for renal cortical expression of LRP2, the gene for megalin, revealed 55% and 76% reduction in expression in ND and HFD fed knockout mice respectively compared to their respective ND and HFD fed controls (p<0. 01). These results indicate that nephron ATP6AP2 knockout results in increased urinary NEFA excretion via decreased megalin expression in the renal cortex. Further investigation is warranted into how ATP6AP2 may regulate the activity of the megalin-cubulin complex and what effects this may have on lipid reabsorption by the kidney. Presentation: No date and time listed