Imbalance of Drug Transporter-CYP450s Interplay by Diabetes and Its Clinical Significance

The pharmacokinetics of a drug is dependent upon the coordinate work of influx transporters, enzymes and efflux transporters (i.e., transporter-enzyme interplay). The transporter-enzyme interplay may occur in liver, kidney and intestine. The influx transporters involving drug transport are organic anion transporting polypeptides (OATPs), peptide transporters (PepTs), organic anion transporters (OATs), monocarboxylate transporters (MCTs) and organic cation transporters (OCTs). The efflux transporters are P-glycoprotein (P-gp), multidrug/toxin extrusions (MATEs), multidrug resistance-associated proteins (MRPs) and breast cancer resistance protein (BCRP). The enzymes related to drug metabolism are mainly cytochrome P450 enzymes (CYP450s) and UDP-glucuronosyltransferases (UGTs). Accumulating evidence has demonstrated that diabetes alters the expression and functions of CYP450s and transporters in a different manner, disordering the transporter-enzyme interplay, in turn affecting the pharmacokinetics of some drugs. We aimed to focus on (1) the imbalance of transporter-CYP450 interplay in the liver, intestine and kidney due to altered expressions of influx transporters (OATPs, OCTs, OATs, PepTs and MCT6), efflux transporters (P-gp, BCRP and MRP2) and CYP450s (CYP3As, CYP1A2, CYP2E1 and CYP2Cs) under diabetic status; (2) the net contributions of these alterations in the expression and functions of transporters and CYP450s to drug disposition, therapeutic efficacy and drug toxicity; (3) application of a physiologically-based pharmacokinetic model in transporter-enzyme interplay.

Influence of hyperglycemia on liver inflammatory conditions in the early phase of non-alcoholic fatty liver disease in mice

OBJECTIVES

A non-alcoholic fatty liver disease (NAFLD) has high prevalence and now important issue of public health. In general, there exists strong interaction between NAFLD and diabetes, but the detailed mechanism is unclear. In this study, we determined the effects of hyperglycemia on progression in the early phase of NAFLD in mice.

METHODS

Male ddY mice were fed a choline-deficient, l-amino acid-defined, high-fat diet (CDAHFD) consisting of 60% of kcal from fat and 0.1% methionine by weight. Hyperglycemic condition was induced by streptozotocin (STZ) treatment. The assessment of liver function used serum AST and ALT levels, and histological analysis. Hepatic tumour necrosis factor (TNF)-α mRNA levels was estimated by qRT-PCR.

KEY FINDINGS

During the 3-42 days that the mice were fed CDAHFD, the livers gradually caused accumulation of fat, and infiltration of inflammation cells gradually increased. Serum AST and ALT levels and significantly increased after being fed CDAHFD for 3 days and were exacerbated by the STZ-induced hyperglycemic condition. In addition, hepatic TNF-α mRNA also significantly increased. These phenomena reversed by insulin administration.

CONCLUSIONS

The results showed that progression in the early phase of NAFLD may be exacerbated by hyperglycemia-induced exacerbation of inflammation.

Biphasic regulation of P-glycoprotein function and expression by NO donors in Caco-2 cells

AIM

To investigate the effects of nitric oxide (NO) donors on the function and expression of P-glycoprotein (P-gp) in Caco-2 cells.

METHODS

Caco-2 cells were exposed to NO donors for designated times. P-gp function and expression were assessed using Rhodamine123 uptake assay and Western blotting, respectively. Intracellular reactive oxygen species (iROS) and intracellular reactive nitrogen species (iRNS) levels were measured using ROS and RNS assay kits, respectively.

RESULTS

Exposure of Caco-2 cells to 0.1 or 2 mmol/L of sodium nitroprusside (SNP) affected the function and expression of P-gp in concentration- and time-dependent manners. A short-term (4 h) exposure reduced P-gp function and expression accompanied with significantly increased levels of iROS and iRNS. In contrast, a long-term (24 h) exposure stimulated the P-gp function and expression. The stimulatory effects of 2 mmol/L SNP was less profound as compared to those caused by 0.1 mmol/L SNP. The other NO donors SIN-1 and SNAP showed similar effects. Neither the NO scavenger PTIO (2 mmol/L) nor soluble guanylate cyclase inhibitor ODQ (50 μmol/L) reversed the SNP-induced alteration of P-gp function. On the other hand, free radical scavengers ascorbate, glutathione and uric acid (2 mmol/L for each), PKC inhibitor chelerythrine (5 μmol/L), PI3K/Akt inhibitor wortmannin (1 μmol/L) and p38 MAPK inhibitor SB203580 (10 μmol/L) reversed the upregulation of P-gp function by the long-term exposure to SNP, but these agents had no effect on the impaired P-gp function following the short-term exposure to SNP.

CONCLUSION

NO donors time-dependently regulate P-gp function and expression in Caco-2 cells: short-term exposure impairs P-gp function and expression, whereas long-term exposure stimulates P-gp function and expression. The regulation occurs via a NO-independent mechanism.

[Altered intestinal P-glycoprotein expression levels affect pharmacodynamics under diabetic condition]

P-glycoprotein (P-gp), one of the important drug-efflux pumps, is known to affect pharmacokinetics and pharmacodynamics of P-gp substrate drugs. We have previously reported that intestinal P-gp expression levels are transiently decreased in streptozotocin (STZ)-induced type 1 diabetic mouse model. Herein, we examined the analgesic effects of orally administered morphine and its pharmacokinetic properties under diabetic conditions, specifically focusing on the involvement of intestinal P-gp in a type 1 diabetic mouse model. Type 1 diabetes was induced in male ddY mice by an i.p. injection of STZ (230 mg/kg). We assessed the oral morphine analgesia using the tail-flick test. Serum and brain morphine content were determined on a HPLC-ECD system. Intestinal P-gp expression levels were significantly decreased on day 9 after STZ administration. On the other hands, oral morphine analgesia, and serum and brain morphine content were significantly increased on day 9 after STZ administration. The decrease in the intestinal P-gp expression levels were suppressed by aminoguanidine, a specific iNOS inhibitor. Interestingly, the increase in the analgesic effect of morphine, as well as serum and brain morphine content, was suppressed by aminoguanidine. Conversely, there was no change in the analgesic effect obtained with subcutaneous morphine in STZ-treated mice. In conclusions, our findings suggest that the oral morphine analgesia is dependent on intestinal P-gp expression, and that may be one of the problems against obtaining stable pharmacological effects of morphine in diabetic patients.