Impact of Hyperlipidemia on Plasma Protein Binding and Hepatic Drug Transporter and Metabolic Enzyme Regulation in a Rat Model of Gestational Diabetes

Abstract

It is currently unknown whether gestational diabetes mellitus (GDM), a prevalent obstetrical complication, compounds the changes in drug disposition that occur naturally in pregnancy. Hyperlipidemia occurs in GDM. Using a rat model of GDM, we determined whether excess lipids compete with drugs for plasma protein binding. Because lipids activate nuclear receptors that regulate drug transporters and metabolic enzymes, we used proteome analysis to determine whether hyperlipidemia indirectly leads to the dysregulation of these proteins in the liver. GDM was induced on gestational day 6 (GD6) via streptozotocin injection. Controls received either vehicle alone or streptozotocin with subsequent insulin treatment. Liver and plasma were collected on GD20. Glyburide and saquinavir protein binding was determined by ultrafiltration, and an established solvent method was used for plasma delipidation. Proteomics analysis was performed by using isobaric tags for relative and absolute quantitation methodology with membrane-enriched hepatic protein samples. Relative to controls, GDM rat plasma contained more cholesterol and triglycerides. Plasma protein binding of glyburide and saquinavir was decreased in GDM. Delipidation normalized protein binding in GDM plasma. Proteins linked to lipid metabolism were strongly affected in the GDM proteomics data set, with prohyperlipidemic and antihyperlipidemic changes observed, and formed networks that implicated several nuclear receptors. Up-regulation of drug transporters and metabolic enzymes was observed (e.g., multidrug resistance 1/2, CYP2A1, CYP2B9, and CYP2D3). In this study, GDM-induced hyperlipidemia decreased protein binding and was associated with drug transporter and metabolic enzyme up-regulation in the liver. Both of these findings could change drug disposition in affected pregnancies, compounding changes associated with pregnancy itself.

Mechanisms of Reduced Maternal and Fetal Lopinavir Exposure in a Rat Model of Gestational Diabetes

“…Although unbound serum concentrations were roughly equivalent in all of the groups, they represented a greater percentage of total serum concentrations in the GDM group. We have demonstrated previously that GDM-induced hyperlipidemia in rats, which was observed in this study (Table 1) and is observed clinically in GDM (Wiznitzer et al, 2009), leads to drug displacement (Anger and Piquette-Miller, 2010). Albumin concentrations in GDM also were reduced significantly, which means there were fewer LPV binding sites.…”

“…Induction of Mdr1 and Cyp3a has been observed in tissues from male rats with STZ-induced diabetes (Maeng et al, 2007;Kameyama et al, 2008;Hasegawa et al, 2010), but reports in female rats with STZ-induced diabetes or STZ-induced GDM are limited (Mulay and Varma, 1984;Anger et al, 2009;Anger and Piquette-Miller, 2010). We posit that disruptions to lipid and glucose homeostasis underlie the alterations to drug transporter and Cyp3a2 expression that were observed in STZ-induced GDM.…”

“…Whereas CYP3A4 is the dominant constitutive CYP3A subfamily isoform in humans, Cyp3a2 is the dominant constitutive Cyp3a subfamily isoform in rats (Nelson et al, 1993) and has been shown to metabolize prototypical human CYP3A4 substrates such as verapamil (Tracy et al, 1999;Choi and Burm, 2008;Hanada et al, 2008). Given our previous findings with this model (Anger and Piquette-Miller, 2010), we hypothesized that maternal LPV exposure would be reduced. Our hypothesis regarding fetal LPV exposure was dependent on whether protein binding or active feto-maternal transport dominated LPV transfer (and whether placental Mdr1 was up-regulated).…”

“…Studies indicate that the prevalence of GDM in HIV-positive pregnant women far exceeds that of HIV-negative pregnant women (Watts et al, 2004;Kourtis et al, 2006;Martí et al, 2007;González-Tomé et al, 2008), but to the best of our knowledge, it is unknown if this has an effect on the disposition of highly active antiretroviral therapy drugs. In rats with streptozotocin (STZ)-induced GDM, we have observed recently that the plasma protein binding of the protease inhibitor saquinavir decreases because of displacement by elevated lipids, whereas the expression of hepatic Mdr1 and a variety of cytochrome P450 and UDP-glucuronosyltransferase enzymes increases (Anger and Piquette-Miller, 2010). In addition, altered disposition has been observed for a variety of drugs in both nonpregnant humans with diabetes (reviewed in Gwilt et al, 1991) and nonpregnant rats with STZ-induced diabetes (reviewed in Lee et al, 2010).…”

“…Reports of drug disposition being sensitive to disease have appeared in the literature for nearly 40 years (reviewed in Morgan et al, 2008); however, only in the last decade have the effects of disease during pregnancy, including gestational diabetes mellitus (GDM), been investigated (Wang et al, 2005;Petrovic et al, 2008;Anger and Piquette-Miller, 2010). Studies indicate that the prevalence of GDM in HIV-positive pregnant women far exceeds that of HIV-negative pregnant women (Watts et al, 2004;Kourtis et al, 2006;Martí et al, 2007;González-Tomé et al, 2008), but to the best of our knowledge, it is unknown if this has an effect on the disposition of highly active antiretroviral therapy drugs.…”