Defective expression of cytochrome P450 proteins in the liver of the genetically obese Zucker rat

Drug-disease interaction: Clinical consequences of inflammation on drugs action and disposition

Inflammation is a culprit in many conditions affecting millions of people worldwide. A plethora of studies has revealed that inflammation and inflammatory mediators such as cytokines and chemokines are associated with altered expression and activity of various proteins such as those involved in drug metabolism, specifically cytochrome P450 enzymes (CYPs). Emphasis of most available reports is on the inflammation-induced downregulation of CYPs, subsequently an increase in their substrate concentrations, and the link between the condition and the inflammatory mediators such as interleukin-6 and tumor necrosis factor alpha. However, reports also suggest that inflammation influences expression and/or activity of other proteins such as those involved in the drug-receptor interaction. These multifaced involvements render the clinical consequence of the inflammation unexpected. Such changes are shown in many inflammatory conditions including rheumatoid arthritis, Crohn's disease, acute respiratory illnesses as well as natural processes such as aging, among others. For example, some commonly used cardiovascular drugs lose their efficacy when patients get afflicted with inflammatory conditions such as rheumatoid arthritis and Crohn's disease. Interestingly, this is despite increased concentration subsequent to reduced clearance. The observation is attributed to a simultaneous reduction in the expression of target receptor proteins such as the calcium and potassium channel and β-adrenergic receptor as well as the metabolic enzymes. This narrative review summarizes the current understanding and clinical implications of the inflammatory effects on both CYPs and drug-receptor target proteins.

Obesity Decreases Hepatic 25-Hydroxylase Activity Causing Low Serum 25-Hydroxyvitamin D

Normal vitamin D homeostasis is critical for optimal health; nevertheless, vitamin D deficiency is a worldwide public health problem. Vitamin D insufficiency is most commonly due to inadequate cutaneous synthesis of cholecalciferol and/or insufficient intake of vitamin D, but can also arise as a consequence of pathological states such as obesity. Serum concentrations of 25(OH)D (calcidiol) are low in obesity, and fail to increase appropriately after vitamin D supplementation. Although sequestration of vitamin D in adipose tissues or dilution of ingested or cutaneously synthesized vitamin D in the large fat mass of obese patients has been proposed to explain these findings, here we investigate the alternative mechanism that reduced capacity to convert parent vitamin D to 25(OH)D due to decreased expression of CYP2R1, the principal hepatic vitamin D 25-hydroxylase. To test this hypothesis, we isolated livers from female mice of 6 to 24 weeks of age, weaned onto either a normal chow diet or a high-fat diet, and determined the abundance of Cyp2r1 mRNA using digital droplet-quantitative PCR. We observed a significant (p < 0.001) decrease in Cyp2r1 mRNA in the liver of high-fat diet-fed mice relative to lean-chow-fed female mice. Moreover, there was a significant (p < 0.01) relationship between levels of Cyp2r1 mRNA and serum 25(OH)D concentrations as well as between Cyp2R1 mRNA and the ratio of circulating 25(OH)D3 to cholecalciferol (p < 0.0001). Using linear regression we determined a curve with 25(OH)D3/cholecalciferol versus normalized Cyp2R1 mRNA abundance with an R2 value of 0.85. Finally, we performed ex vivo activity assays of isolated livers and found that obese mice generated significantly less 25(OH)D3 than lean mice (p < 0.05). Our findings indicate that expression of CYP2R1 is reduced in obesity and accounts in part for the decreased circulating 25(OH)D. © 2019 American Society for Bone and Mineral Research.

Sea ice-associated decline in body condition leads to increased concentrations of lipophilic pollutants in polar bears (Ursus maritimus) from Svalbard, Norway

Global climate changes are magnified in the Arctic and are having an especially dramatic effect on the spatial and temporal distribution and the thickness traits of sea ice. Decline of Arctic sea ice may lead to qualitative and/or quantitative changes in diet and reduced body condition (i.e. adipose tissue stores) of ice-associated apex predators such as polar bears (Ursus maritimus). This may further affect their tissue concentrations of lipophilic pollutants. We determined how variations in adipose tissue stores associated to both breeding status and spatial changes in sea ice conditions and diet influence concentrations and biotransformation of lipophilic persistent organic pollutants (POPs). We collected 112 blood and fat samples from female polar bears (Ursus maritimus) of different breeding status (alone, with cubs of the year, or with yearlings) during two seasons (April and September) in 2012 and 2013 at three locations of Svalbard, Norway, with contrasted sea ice conditions. We inferred diet from nitrogen and carbon stable isotope ratios in red blood cells and fatty acid composition in adipose tissue. Relative to diet, body condition, which was negatively related to sea ice extent at both temporal and spatial scales, was the most important predictor for concentrations of POPs in plasma and fat, whereas diet showed a minor influence. Additionally, fatter females were more efficient at biotransforming PCBs than were leaner ones. Breeding status influenced the concentrations of less lipophilic compounds such as β-hexachlorocyclohexane, which were lower in females with yearlings, probably due to excretion into milk and subsequent offloading to young. In conclusion, our results indicate that declining sea ice indirectly leads to increased concentrations of lipophilic pollutants in polar bears mediated through reduced feeding opportunities and declining body condition rather than changes in diet composition.

Comparison of tacrolimus and cyclosporin A in CYP3A5 expressing Chinese de novo kidney transplant recipients: a 2-year prospective study

AIMS

To assess the efficacy and safety of tacrolimus and cyclosporin A (CsA)-based immunosuppressive regimens in Chinese de novo kidney transplant recipients who are CYP3A5 expressers.

METHODS

The CYP3A5 (6986 A>G, rs776746) polymorphism of eligible patients was determined before transplantation. De novo kidney transplant recipients enrolled in this study were assigned to tacrolimus (Tac group) or CsA (CsA group) based therapy. The follow-up period was 2 years. The incidence of acute rejection, patient and graft survival rates, renal allograft function and post-transplant complications were compared. The intra-individual variability (IIV) of Tac and CsA blood concentrations was analysed. Medication costs were also compared. The analysis was conducted on the intention-to-treat principle.

RESULTS

A total of 72 CYP3A5 expressers were enrolled, with 36 patients in each group. AR incidence was higher in the Tac group (11.1% vs. 5.6%), but there was no significant difference (p > 0.05). The 2-year patient and graft survival was comparable, and renal function was comparable in the two groups. Notably, the Tac group presented a significantly higher incidence of BK viremia (22.2% vs. 5.6%, p < 0.05) and BK viruria (38.9% vs. 16.7%, p < 0.05) than the CsA group. The CsA IIV at 1 and 3 months post-transplant was significantly lower than the Tac IIV (p < 0.05). The medical costs of both immunosuppressive drugs and management of complications was significantly lower in the CsA group.

CONCLUSIONS

Cyclosporin A-based maintenance therapy is safe for Chinese de novo kidney transplant recipients who are CYP3A5 expressers. CsA significantly reduced medication costs and decreased BKV infection, suggesting that it is more beneficial for this specific population.

High-fat diets rich in saturated fat protect against azoxymethane/dextran sulfate sodium-induced colon cancer

High-fat-diet (HFD) consumption is associated with colon cancer risk. However, little is known about how the lipid composition of a HFD can influence prooncogenic processes. We examined the effects of three HFDs differing in the percentage of total calories from saturated fat (SF) (6, 12, and 24% of total caloric intake), but identical in total fat (40%), and a commercially available Western diet (26 and 41% saturated and total fat, respectively) on colon cancer development using the azoxymethane (AOM)/dextran sulfate sodium (DSS) murine model. A second dose-response experiment was performed using diets supplemented with the saturated-fatty-acid (SFA)-rich coconut oil. In experiment 1, we found an inverse association between SF content and tumor burden. Furthermore, increased SF content was associated with reduced inflammation, increased apoptosis, and decreased proliferation. The second dose-response experiment was performed to test whether this effect may be attributed to the SF content of the diets. Consistent with the initial experiment, we found that high SF content was protective, at least in male mice; there was a decrease in mortality in mice consuming the highest concentration of SFAs. To explore a potential mechanism for these findings, we examined colonic mucin 2 (Muc2) protein content and found that the HFDs with the highest SF content had the greatest concentration of Muc2. Our data suggest that high dietary SF is protective in the AOM/DSS model of colon cancer, which may be due, at least in part, to the ability of SF to maintain intestinal barrier integrity through increased colonic Muc2.

Role of high-fat diet in regulation of gene expression of drug metabolizing enzymes and transporters

AIM

Our aim is to investigate the molecular mechanism of regulation of gene expression of drug metabolizing enzymes (DMEs) and transporters in diet-induced obesity.

MAIN METHODS

Adult male CD1 mice were fed diets containing 60% kcal fat (HFD) or 10% kcal fat (LFD) for 14 weeks. RNA levels of hepatic DMEs, transporters and their regulatory nuclear receptors (NRs) were analyzed by real-time PCR. Activation of cell-signaling components (JNK and NF-κΒ) and pro-inflammatory cytokines (IL-1β, IL-6 and TNFα) were measured in the liver. Finally, the pharmacodynamics of drugs metabolized by DMEs was measured to determine the clinical relevance of our findings.

KEY FINDINGS

RNA levels of the hepatic phase I (Cyp3a11, Cyp2b10, Cyp2a4) and phase II (Ugt1a1, Sult1a1, Sultn) enzymes were reduced ~30-60% in HFD compared to LFD mice. RNA levels of Cyp2e1, Cyp1a2 and the drug transporters, multidrug resistance proteins, (Mrp)2, Mrp3 and multidrug resistant gene (Mdr)1b were unaltered in HFD mice. Gene expression of the NRs, PXR and CAR and nuclear protein levels of RXRα was reduced in HFD mice. Cytokines, JNK and NF-κΒ were induced in HFD mice. Thus reduction in hepatic gene expression in obesity may be modulated by cross-talk between NRs and inflammation-induced cell-signaling. Sleep time of Midazolam (Cyp3a substrate) was prolonged in HFD mice, while Zoxazolamine (Cyp1a2 and Cyp2e1 substrate)-induced sleep time was unaltered.

SIGNIFICANCE

This study demonstrates that gene-specific reductions in DMEs can affect specific drugs metabolized by these enzymes, thus providing a rationale to monitor the effectiveness of drug therapy in obese individuals.

Attenuation of high cholesterol-induced oxidative stress in rabbit liver by thymoquinone

BACKGROUND/AIMS

This study examines the modifying effects of thymoquinone (TQ), an agent with antioxidant and hypolipidemic properties, on reactive oxygen species, antioxidant activity, and steatosis in livers of hyperlipidemic rabbit.

METHODS

Oxidative stress was induced in New Zealand White rabbit by a high-cholesterol diet for 8 weeks. Four groups of six animals each were divided into a control group; a high cholesterol group (received 1% cholesterol diet); a high cholesterol/low TQ group (received 1% cholesterol diet plus TQ 10 mg/kg/day), and a high cholesterol/high TQ (20 mg/kg/day) group. Blood samples were taken at the end of the study and examined for fasting serum glucose, insulin, and aminotransaminases. Hepatic tissue samples were examined for malondialdehyde, protein carbonyls, antioxidant enzymes, and steatosis.

RESULTS

There was severe hepatic steatosis and elevated serum alanine aminotransferase in the high cholesterol group (group II) but not in the high cholesterol and low or high TQ groups (groups III, IV). The hepatic reactive oxygen species activity in the high cholesterol group was significantly higher while the antioxidant enzymes were lower (P<0.05) when compared with the control (group I) or either of the high cholesterol and TQ groups.

CONCLUSION

TQ attenuates hepatic oxidative stress in fatty liver injury induced by high-cholesterol diet in rabbits.

Impact of obesity on oral contraceptive pharmacokinetics and hypothalamic-pituitary-ovarian activity

BACKGROUND

This study was conducted to determine whether increased body mass index (BMI) affects oral contraceptive (OC) pharmacokinetics and suppression of hypothalamic-pituitary-ovarian (HPO) axis activity.

STUDY DESIGN

Ovulatory reproductive-age women with normal weight (BMI <25 kg/m(2); n=10) and with obesity (BMI >30 kg/m(2); n=10) received OCs for two cycles (prospective cohort). Subjects were admitted for two 48-h inpatient stays at the beginning and end of the hormone-free interval. Ethinyl estradiol and levonorgestrel (LNG) levels were evaluated during both inpatient stays. Gonadotropin pulsatility (follicle-stimulating hormone and luteinizing hormone) was measured during the second inpatient stay. Estradiol (E(2)) and progesterone (P) were measured daily during inpatient stays and twice per week in Cycle 2.

RESULTS

BMI was greater in the obese compared to the normal-BMI group [37.3 kg/m(2) (SD, 6.0) vs. 21.9 kg/m(2) (SD, 1.6); p<.05]. The LNG half-life was significantly longer in the obese group (52.1+/-29.4 vs. 25.6+/-9.3 h, p<.05), which correlated with a lower maximum LNG concentration on Cycle 2, Day 1 [1.9 ng/mL (SD, 0.5) vs. 2.5 ng/mL (SD, 0.7)] and a longer time to reach steady state (10 vs. 5 days) in obese women. There were no significant differences in volume of distribution between groups. LH pulse parameters did not differ statistically between groups but trended toward greater HPO activity in the obese group. Additionally, more obese (6/10 vs. 3/10 normal BMI, p>.05) women exhibited E(2) levels consistent with development of a dominant follicle and P levels consistent with ovulation (2/10 vs. 1/10) during Cycle 2.

CONCLUSIONS

Compared to women with normal BMI, obese women exhibit differences in OC pharmacokinetics that are associated with greater HPO activity.

A rabbit model of pediatric nonalcoholic steatohepatitis: the role of adiponectin

AIM

To create a rabbit model of pediatric nonalcoholic steatohepatitis (NASH) and to evaluate the role of adiponectin in the process.

METHODS

Thirty-two specific pathogen-free male New Zealand rabbits were divided randomly into three groups: (1) the normal control group (n = 10) was fed with standard diet for 12 wk; (2) the model group A (n = 11); and (3) model group B (n = 11) were fed with a high-fat diet (standard diet + 10% lard + 2% cholesterol) for 8 and 12 wk, respectively. Hepatic histological changes were observed and biochemical parameters as well as serum levels of adiponectin, interleukin (IL)-6, IL-10 and tumor necrosis factor (TNF)-alpha were measured.

RESULTS

Typical histological hepatic lesions of NASH were observed in both model groups described as liver steatosis, liver inflammatory infiltration, cytologic ballooning, perisinusoidal fibrosis and overall fibrosis. Compared with the normal control group, there were significant increases in model groups A and B in weight gain (1097.2 +/- 72.3, 1360.5 +/- 107.6 vs 928.0 +/- 58.1, P < 0.05, P < 0.01), liver weight (93.81 +/- 6.64, 104.6 +/- 4.42 vs 54.4 +/- 1.71, P < 0.01), Lg (ALT) (1.9 +/- 0.29, 1.84 +/- 0.28 vs 1.60 +/- 0.17, P < 0.01), and Lg (TG) (1.03 +/- 0.24, 1.16 +/- 0.33 vs 0.00 +/- 0.16, P < 0.01). Weight gain was much more in model group B than in model group A (1360.5 +/- 107.6 vs 1097.2 +/- 72.3, P < 0.05). But, there was no significant difference between the two groups concerning the other indexes. Pro-inflammatory cytokines (IL-6 and TNF-alpha) increased in model group B compared with that of control and model group A (IL-6: 1.86 +/- 0.21 vs 1.41 +/- 0.33, 1.38 +/- 0.42, P < 0.01; TNF-alpha: 1.18 +/- 0.07 vs 0.66 +/- 0.08, 0.86 +/- 0.43, P < 0.01, P < 0.05), whereas serum adiponectin and IL-10 decreased in model groups compared with that in the control (adiponectin: A: 21.87 +/- 4.84 and B: 21.48 +/- 4.60 vs 27.36 +/- 7.29, P < 0.05. IL-10: A: 1.72 +/- 0.38 and B: 1.83 +/- 0.39 vs 2.26 +/- 0.24, P < 0.01). Lg (TC) and the degree of liver fatty infiltration was an independent determinant of serum adiponectin level analyzed by stepwise multiple regressions, resulting in 29.4% of variances.

CONCLUSION

This rabbit model produces the key features of pediatric NASH and may provide a realistic model for future studies. Adiponectin level partially reflects the severity of liver steatosis, but not the degree of liver inflammation.

Sterol regulatory element binding protein 1 interacts with pregnane X receptor and constitutive androstane receptor and represses their target genes

OBJECTIVE

Sterol regulatory element binding protein 1 (SREBP-1) is a lipogenic transcription factor of the basic helix-loop-helix family. SREBP-1 binds to sterol regulatory elements (SREs) in the promoter of lipogenic genes and induces fatty acid and triglyceride synthesis. Decreased drug clearance has been observed in obese and other dyslipidemic rodents as well as in diabetic, obese or overfed rodents. A hallmark of these conditions is increased expression of SREBP-1 in the liver. We therefore searched for a possible link between regulation of cytochromes P450 (CYPs) and SREBP-1.

METHODS

We combined gene expression analysis, lipid analysis, effects of high levels of SREBP-1 in hepatocyte cultures to characterize the effects and protein interaction and chromatin immunoprecipitation assays to define the underlying mechanism. Finally, mice were fed a diet enriched in cholesterol to demonstrate the relevance of our data in vivo. By analyzing gene expression and lipids in cholesterol-fed mice or transfection of recombinant SREBP-1 in hepatocyte cultures the effect on CYPs was characterized. By use of protein interaction assays and chromatin immunoprecipitation the underlying mechanism was defined.

RESULTS

We observed that SREBP-1 represses drug-mediated induction of hepatic CYPs, mainly members of the 2B and the 3A subfamilies. These drugs induce transcription of CYPs and other drug metabolizing enzymes via activation of the nuclear receptors pregnane X receptor (PXR) and constitutive androstane receptor (CAR). Here we report that the activation of SREBP-1 by insulin or cholesterol in mouse liver and primary human hepatocytes inhibits the transcriptional effects in PXR and CAR. Our results suggest that SREBP-1 functions as a non-DNA binding inhibitor and blocks the interaction of PXR and CAR with cofactors such as steroid receptor coactivator 1. Consequently, mRNA induction of CYPs by drugs and other xenochemicals is impaired.

CONCLUSION

We conclude that PXR and CAR respond to lipid accumulation by direct interaction with SREBP-1 and show that drug metabolism and lipid metabolism are interconnected within a complex network of transcriptional regulators.

Methionine deficiency and hepatic injury in a dietary steatohepatitis model

Methionine (Meth) is an essential amino acid involved in DNA methylation and glutathione biosynthesis. We examined the effect of Meth on the development of steatohepatitis. Rats were fed (five weeks) amino acid-based Meth-choline-sufficient (A-MCS) or total deficient (MCD) diets and gavaged daily (two weeks) with vehicle (B-vehicle/MCD), or Meth replacement (C-Meth/MCD). To assess the effect of short-term deficiency, after three weeks one MCS group was fed a deficient diet (D-MCS/MCD). Animals fed the deficient diet for two weeks lost (29%) weight and after five weeks weighed one third as much as those on the sufficient diet, and also developed anemia (P < 0.01). Hepatic transaminases progressively increased from two to five weeks (P < 0.01), leading to severe hepatic pathology. Meth administration normalized hematocrit, improved weight (P < 0.05), and suppressed abnormal enzymes activities (P < 0.01). Meth administration improved blood and hepatic glutathione (GSH), S-adenosylmethionine (SAMe), and hepatic lesions (P < 0.01). The deficient diet significantly upregulated proinflammatory and fibrotic genes, which was ameliorated by Meth administration. These data support a pivotal role for methionine in the pathogenesis of the dietary model of Meth-choline-deficient (MCD) steatohepatitis (NASH).

Long term highly saturated fat diet does not induce NASH in Wistar rats

BACKGROUND

Understanding of nonalcoholic steatohepatitis (NASH) is hampered by the lack of a suitable model. Our aim was to investigate whether long term high saturated-fat feeding would induce NASH in rats.

METHODS

21 day-old rats fed high fat diets for 14 weeks, with either coconut oil or butter, and were compared with rats feeding a standard diet or a methionine choline-deficient (MCD) diet, a non physiological model of NASH.

RESULTS

MCDD fed rats rapidly lost weight and showed NASH features. Rats fed coconut (86% of saturated fatty acid) or butter (51% of saturated fatty acid) had an increased caloric intake (+143% and +30%). At the end of the study period, total lipid ingestion in term of percentage of energy intake was higher in both coconut (45%) and butter (42%) groups than in the standard (7%) diet group. No change in body mass was observed as compared with standard rats at the end of the experiment. However, high fat fed rats were fattier with enlarged white and brown adipose tissue (BAT) depots, but they showed no liver steatosis and no difference in triglyceride content in hepatocytes, as compared with standard rats. Absence of hepatic lipid accumulation with high fat diets was not related to a higher lipid oxidation by isolated hepatocytes (unchanged ketogenesis and oxygen consumption) or hepatic mitochondrial respiration but was rather associated with a rise in BAT uncoupling protein UCP1 (+25-28% vs standard).

CONCLUSION

Long term high saturated fat feeding led to increased "peripheral" fat storage and BAT thermogenesis but did not induce hepatic steatosis and NASH.

Changes in the expression of cytochromes P450 and nuclear receptors in the liver of genetically diabetic db/db mice

Physiological and pathophysiological conditions often affect the expression of drug metabolizing enzymes such as cytochromes P450 (P450s). Diabetes is one such factor and it is of great interest to understand its effects on drug metabolism, since diabetic patients generally have increased need for pharmacotherapy. We have recently reported the coordinated reduction of CYP2B1/2 and their transcriptional regulator constitutive androstane receptor (CAR), a member of the nuclear receptor superfamily, in the liver of genetically obese/diabetic Zucker fatty rats (Xiong, H., Yoshinari, K., et al., Drug Metab. Dispos., 30, 918-923, 2002). In this study, we investigated the expression of P450s and liver-enriched nuclear receptors in the liver of genetically diabetic db/db mice. Surprisingly, both CYP2B10 and CAR levels were increased in db/db mice. CYP4A expression was also increased at both mRNA and protein levels in db/db mice, while those of peroxisome proliferator-activated receptor alpha, a key regulator for the transcriptional activation of CYP4As, were comparable to those in age-matched C57BL/6 mice. Our results demonstrate that db/db mice and Zucker fatty rats exhibit different expression profiles of P450s and nuclear receptors despite their similar characteristics for obesity and diabetes resulting from a defect in the leptin signaling pathway.

Obesity-induced increase of CYP2E1 activity and its effect on disposition kinetics of chlorzoxazone in Zucker rats

This study was designed to investigate the induction of CYP2E1 in obese Zucker rats and its effect on the disposition kinetics of chlorzoxazone (CZX). CZX 20mg/kg was administered to three groups of rats: normal Zucker rats fed a normal diet (ND), normal Zucker rats fed a high-fat diet (HF), and genetically obese Zucker rats fed a normal diet (OB). The values of the area under the plasma concentration-time curve from 0 to infinity (AUC(infinity)) of CZX were in the order of ND>HF>OB rats. The AUC(infinity) values of total 6-hydroxychlorzoxazone (6OHCZX-T), which is considered to be a CYP2E1 metabolic marker, were in the opposite order. The values of the AUC(infinity) ratio (6OHCZX-T/CZX) in ND, HF and OB rats were approximately 0.2, 0.3 and 0.4, respectively. The CZX concentration in fat was much higher than the concentrations in plasma, liver and kidney in all groups. Induction of CYP2E1 protein was greater in both liver and fat of OB rats than in those of HF rats. Microsomal activity of CYP2E1 in liver and fat was also in the order of OB>HF>NM rats. These results suggest that CYP2E1 may be induced in liver and fat of obese patients, thereby potentially altering the disposition kinetics of not only CZX, but also other lipophilic drugs metabolized by CYP2E1.

Hepatic CYP3A Expression is Attenuated in Obese Mice Fed a High-Fat Diet

PURPOSE

Changes in physiological, pathophysiological, and/or nutritional conditions often alter the expression of drug-metabolizing enzymes. In this study, we investigated obesity-induced changes in hepatic cytochrome P450 (P450) levels using nutritionally obese mice.

METHODS

To induce obesity, mice were fed a high-fat diet or treated with gold thioglucose, which impairs ventromedial hypothalamus. Total RNAs and microsomal and nuclear proteins were prepared from the liver of these mice, and mRNA and protein levels of P450s and transcription factors were determined.

RESULTS

Among P450s examined, the constitutive expression of CYP3As was drastically reduced at both mRNA and protein levels by nutrition-induced obesity. One-week administration of a high-fat diet also reduced hepatic CYP3As. However, changes in nuclear receptors involved in the transcriptional regulation of CYP3A genes were not correlated with that of CYP3As. Obese mice induced by gold thioglucose exhibited a different expression profile of hepatic P450s with no significant change in CYP3As.

CONCLUSION

High-fat diet-induced changes in energy metabolism, which eventually result in obesity, modulate the hepatic expression profile of P450s, particularly CYP3As. Alternatively, the accumulation of a certain component in a high-fat diet may directly attenuate the CYP3A expression, suggesting a clinically important drug-diet interaction.

Rofecoxib decreases renal injury in obese Zucker rats

The present study tested the hypothesis that altered vascular regulation of arachidonic acid enzymes in obese Zucker rats contributes to renal damage. Protein expression of CYP450 (cytochrome P450) and COX (cyclo-oxygenase) enzymes in renal microvessels was studied in obese and lean Zucker rats at 20–21 weeks of age. Body weight and blood glucose averaged 649±13 g and 142±10 mg/dl in obese Zucker rats compared with 437±10 g and 111±5 mg/dl in age-matched lean Zucker rats. Renal microvascular CYP4A and COX-2 protein levels were increased and CYP2C protein levels decreased in obese Zucker rats. TX (thromboxane) B2 excretion was 2-fold higher and PG (prostaglandin) E2 excretion significantly lower in obese Zucker rats. Additional studies investigated the ability of the COX-2 inhibitor, rofecoxib, to slow the progression of renal injury in obese Zucker rats. Rofecoxib treatment decreased urinary PGF2α and 8-isoprostane levels in obese Zucker rats. Renal microvessel mRNA expression of pro-inflammatory chemokines was decreased in COX-2-inhibitor-treated obese Zucker rats. Urinary albumin excretion, an index of kidney damage, averaged 95±11 mg/day in vehicle-treated and 9±1 mg/day in rofecoxib-treated obese Zucker rats. Glomerulosclerosis, characterized by mesangial expansion, tubulo-interstitial fibrosis and extracellular matrix accumulation, was prominent in obese Zucker rats compared with a lack of damage in age-matched lean Zucker rats and rofecoxib-treated obese Zucker rats. These results suggest that altered vascular arachidonic acid enzymes contribute to the renal damage, and that COX-2 inhibition decreases glomerular injury in obese Zucker rats.

Altered kidney CYP2C and cyclooxygenase-2 levels are associated with obesity-related albuminuria

OBJECTIVE

To determine cytochrome P450 (CYP450) and cyclooxygenase (COX) expression and metabolite regulation and renal damage in the early stages of obesity-related hypertension and diabetes.

RESEARCH METHODS AND PROCEDURES

Obese and lean Zucker rats at 10 to 12 weeks of age were studied. Blood pressure was measured in the conscious state using radiotelemetry. Blood glucose levels and body weight were measured periodically. Protein expression of CYP450 and COX enzymes in the kidney cortex, renal microvessels, and glomeruli was studied. The levels of CYP450 and COX metabolites in urine were measured, and urinary albumin excretion, an indicator of kidney damage, was measured.

RESULTS

Body weight and blood glucose averaged 432 +/- 20 grams and 105 +/- 5 mg/dl, respectively, in obese Zucker rats as compared with 320 +/- 8 grams and 91 +/- 5 mg/dl, respectively, in age-matched 10- to 12-week-old lean Zucker rats. Renal microvascular CYP4A and COX-2 protein levels were increased 2.3- and 17.0-fold, respectively, in obese Zucker rats. The protein expression of CYP2C11 and CYP2C23 was decreased 2.0-fold in renal microvessels isolated from obese Zucker rats when compared with lean Zucker rats. The urinary excretion rate of thromboxane B(2) was increased significantly in obese Zucker as compared with lean Zucker rats (22.0 +/- 1.8 vs. 13.4 +/- 1.0 ng/d). Urinary albumin excretion, an index of kidney damage, was increased in the obese Zucker rat at this early age.

DISCUSSION

These results suggest that increased CYP4A and COX-2 protein levels and decreased CYP2C11 and CYP2C23 protein levels occur in association with microalbuminuria during the onset of obesity-related hypertension and type 2 diabetes.

Cytochrome P450 1A2 (CYP1A2) activity and risk factors for breast cancer: a cross-sectional study

INTRODUCTION

Breast cancer risk may be determined by various genetic, metabolic, and lifestyle factors that alter sex hormone metabolism. Cytochrome P450 1A2 (CYP1A2) is responsible for the metabolism of estrogens and many exogenous compounds, including caffeine.

METHODS

In a cross-sectional study of 146 premenopausal and 149 postmenopausal women, we examined the relationships between CYP1A2 activity and known or suspected risk factors for breast cancer. Blood levels of sex hormones, lipids, and growth factors were measured. In vivo CYP1A2 activity was assessed by measuring caffeine metabolites in urine. Stepwise and maximum R regression analyses were used to identify covariates related to CYP1A2 activity after adjustment for ethnicity.

RESULTS

In both menopausal groups CYP1A2 activity was positively related to smoking and levels of sex hormone binding globulin. In premenopausal women, CYP1A2 activity was also positively related to insulin levels, caffeine intake, age, and plasma triglyceride levels, and negatively related with total cholesterol levels and body mass index. In postmenopausal women CYP1A2 activity was positively associated with insulin-like growth factor-1, and negatively associated with plasma triglyceride, high-density lipoprotein cholesterol, and age at menarche.

CONCLUSION

These results suggest that CYP1A2 activity is correlated with hormones, blood lipids, and lifestyle factors associated with breast cancer risk, although some of the observed associations were contrary to hypothesized directions and suggest that increased CYP1A2 function may be associated with increased risk for breast cancer.

Model of nonalcoholic steatohepatitis

BACKGROUND

Obesity and diabetes are frequently associated with nonalcoholic steatohepatitis (NASH), but studies have been hampered by the absence of a suitable experimental model.

OBJECTIVE

Our objective was to create a rat model of NASH.

DESIGN

Sprague-Dawley rats were fed a high-fat, liquid diet (71% of energy from fat, 11% from carbohydrates, 18% from protein) or the standard Lieber-DeCarli diet (35% of energy from fat, 47% from carbohydrates, 18% from protein). The diets were given ad libitum or as two-thirds of the amount consumed ad libitum.

RESULTS

Rats fed the high-fat diet ad libitum for 3 wk developed panlobular steatosis, whereas those fed the standard diet had few fat droplets. Accordingly, total lipid concentrations with the high-fat and standard diets were 129.9 +/- 9.1 ( +/- SEM) and 66.7 +/- 4.6 mg/g liver, respectively (P < 0.001). The high-fat diet caused abnormal mitochondria and mononuclear inflammation, which were accompanied by increased hepatic tumor necrosis factor alpha (TNF-alpha; P < 0.001), TNF-alpha messenger RNA (mRNA) (P < 0.001), collagen type 1, and alpha1(I) procollagen mRNA (P < 0.001). In addition, these rats had increased cytochrome P4502E1 (CYP2E1) mRNA (P < 0.001), which was accompanied by CYP2E1 induction (P < 0.001) and oxidative stress with increased 4-hydroxynonenal (P < 0.001). Plasma insulin was elevated, which reflected insulin resistance, a NASH pathogenic factor. Rats fed a restricted high-fat diet developed only mild steatosis with attenuated biochemical changes, whereas those given a restricted standard diet had normal livers.

CONCLUSION

This rat model reproduces the key features of human NASH and provides a realistic experimental model for elucidating its treatment.

Constitutive and inducible expression of hepatic CYP2E1 in leptin-deficient ob/ob mice

In this study we have analyzed the inducible as well as constitutive hepatic expression of Cyp2e1 in a genetic model of obesity and non-insulin dependent (type II) diabetes, the leptin-deficient ob/ob mouse. In obese mice, Cyp2e1 levels were decreased compared to lean littermates. Treatment with leptin increased hepatic Cyp2e1 in obese mice to the levels observed in lean animals, but failed to alter Cyp2e1 expression in lean animals. As expected, leptin also reduced food intake in treated mice compared to saline-treated controls. In obese mice pair-fed the reduced amount of food, there was a significant increase in Cyp2e1 mRNA but no increase in Cyp2e1 protein or enzyme activity. Fasting and administration of acetone and 4-methylpyrazole increased Cyp2e1 mRNA as well as protein and activity in both obese and lean mice. The present data indicate that while Cyp2e1 is still inducible in obese mice by xenobiotics and fasting, full constitutive expression of Cyp2e1 requires leptin to be present. This effect of leptin appears to be at least partly independent of the hypothalamic control of food intake.

Altered expression of hepatic CYP2E1 and CYP4A in obese, diabetic ob/ob mice, and fa/fa Zucker rats

Hepatic levels of the cytochrome P450 (CYP) proteins 2E1 and 4A are often increased in obesity, diabetes and fasting. In such states of nutritional imbalance, CYPs 2E1 and 4A may play a more significant role in fatty acid oxidation. In order to more fully characterize the regulation of CYP2E1 and CYP4A in obesity and obesity-related (type II) diabetes, we analyzed the hepatic expression of CYP2E1 and CYP4A in ob/ob mice which are leptin deficient, and fa/fa Zucker rats which have defective leptin receptor function. CYP2E1 protein and mRNA were either unchanged or reduced in both models. Conversely, expression of murine Cyp4a10 and 4a14 in the obese mice, and 4A2 in the male fatty Zucker rat, were greatly increased. The levels of other CYP4As were either unchanged or reduced. These results show that CYP2E1 is not inevitably increased by obesity and diabetes and indicate differential regulation of CYP4A subfamily genes in rodent models. Further, they implicate leptin receptor signaling as a factor that may modulate expression of CYP gene products involved in fatty acid oxidation.