Human Renal Xenobiotic Transporter Expression is Altered in Progression of Non‐Alcoholic Fatty Liver Disease as revealed by Quantitative Targeted Proteomics

Abstract

Alterations to hepatic function, including transporter expression, during progressive nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) are well documented. Recent evidence suggests that renal function, including glomerular filtration, is also perturbed during these diseases. To avoid adverse drug reactions, an accurate phenotype of renal xenobiotic transporters in NAFLD and NASH patients is critical. To evaluate this, formalin-fixed and paraffin-embedded kidney needle biopsies were acquired from patients (n=5-6/group) identified with paired diagnoses of NAFLD, NASH, or healthy liver. Protein was extracted and then digested with trypsin to generate unique surrogate peptides for 34 clinically relevant transporters; these surrogate peptides were then quantified against pure standards by LC-MS/MS. Trend analysis demonstrated transporter protein abundance decreases during disease progression from healthy to NASH of: BCRP (0.15 to 0.06 pmol/mg protein), OCT2 (157 to 17 pmol/mg protein), MRP3 (0.42 to 0.24 pmol/mg protein), ENT1 (28.5 to 10.8 pmol/mg protein), and CNT3 (0.19 to 0.09 pmol/mg protein). Only ASBT, a renal bile acid transporter, increased from 1.7 to 5.3 pmol/mg protein during disease progression. OAT4 expression decreased from healthy protein abundance of 1.72 to 0.78 in NAFLD and 0.47 pmol/mg protein in NASH patients. Interestingly, abundance of the alpha subunit of Na+/K+-ATPase decreased from 14.8 pmol/mg protein in healthy patients to 5.3 and 3.3 in NAFLD and NASH patients, respectively. These findings are the first to quantify alterations to renal xenobiotic transporters in patients with progressive stages of NAFLD. Notably, expression of transporters involved in renal secretion of organic anions (OAT4 and Na+/K+-ATPase) are considerably reduced, suggesting a novel mechanism by which these patients may be at greater risk of adverse drug reactions. As such, appropriate models recapitulating these changes are warranted to study their putative effects on the toxicokinetics of clinically relevant substrates.