Date of Award

2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Pharmaceutical and Chemical Sciences

First Advisor

Melanie A. Felmlee

First Committee Member

William K. Chan

Second Committee Member

Miki S. Park

Third Committee Member

John C. Livesey

Fourth Committee Member

Robert Jones

Abstract

Proton-coupled and sodium-dependent monocarboxylate transporters are encoded by the SLC16A and SLC5A gene family of solute carriers, and are responsible for the transport of essential nutrients such as L-lactate, pyruvate, and ketone bodies. Basigin, or CD147, acts as an ancillary protein for MCT1 and MCT4, and is involved in membrane surface expression of transporters. MCT's are also involved in the shuttling of monocarboxylic xenobiotics across cell membranes, including the drugs valproate and gamma hydroxybutyrate. MCT’s are also important for normal mammalian development, particularly during embryogenesis and early neonatal life. Previous studies have shown that ketogenic diets increase MCT expression in the brain, and the obesity biomarker leptin increases MCT1 and CD147 expression and colocalization in colonocytes. Clinical studies in post-mortem tissue demonstrated that hepatic MCT1 expression changes nonlinearly from birth to adulthood. We hypothesize that age and high fat dietary intake regulate monocarboxylate transporter and ancillary protein expression in the liver, and other organs of drug disposition during childhood obesity.

The purpose of this study was to elucidate just how diet and ontogeny regulate MCT1, MCT4, CD147, and SMCT1 mRNA and protein expression in the liver, kidney, and ileum. Timed-pregnant rats were fed either normal or high fat diet, and tissue was harvested from the progeny of both cohorts at predetermined postnatal timepoints. Serum leptin levels were measured, and MCT1, MCT4, CD147, and SMCT1 transcripts were evaluated using real time quantitative PCR. Whole cell and total membrane proteins were extracted and transporter expression was analyzed via western blot.

In summary, we have demonstrated age, diet, and sex dependent regulation of MCT1, MCT4, CD147, and SMCT1 expression in the liver, kidneys, and intestine, and that these effects are tissue specific. Pediatric drug-dosing is both a pressing and understudied clinical field, with the possibility of altered pharmacokinetics in obese children. Changes in hepatic, renal, and intestinal monocarboxylate transporter expressions during mammalian development may affect functional activity of these transporters and lead to altered metabolism and drug disposition. Further studies of this animal model can shine new light on the dynamic and highly-variable nature of drug pharmacokinetics in pediatric obesity.

Pages

149

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