Evaluation of a 3-item screening tool to identify men with benign prostatic enlargement/obstruction in a primary care cohort.

BACKGROUND: Benign prostatic hyperplasia (BPH), a progressive condition and common cause of lower urinary tract symptoms (LUTS), is underdiagnosed in primary care, impacting patient outcomes. Here, we evaluate the utility of a BPH screening tool in general practice, to identify men confirmed to have BPH after urologist assessment of diagnostic test results. METHODS: A 3-item questionnaire was developed to discriminate between LUTS due to BPH versus other conditions and was translated and validated cross-culturally. Its utility was assessed in a cohort study (FDC116114/NCT02757963) conducted in 47 centers across France, Germany, Italy, Russia, and Spain. The study enrolled men ≥50 years of age presenting to general practice clinics with a score of ≥3 on the BPH screening tool or ≥8 on the International Prostate Symptom Score (IPSS). In total, 561 men completed the study. The primary endpoint was the proportion of patients with a urologist-confirmed BPH diagnosis among those with a positive result on the BPH screening tool (score ≥3) and serum prostate specific antigen (PSA) ≥2 ng/mL. RESULTS: The primary endpoint was fulfilled; 88.3% (95% CI: 84.9, 91.2) of patients had urologist-confirmed BPH diagnoses among those with positive results on the BPH screening tool and serum PSA≥2 ng/mL, similar to the proportion seen with IPSS≥8 and serum PSA≥2 ng/mL (87.7%; 95% CI: 84.6, 90.4). CONCLUSIONS: The BPH screening tool, in conjunction with serum PSA, demonstrated adequate predictive value by allowing general practitioners to quickly screen men presenting with different medical conditions but identified as having urological symptoms.

A Diagnostic Approach for Rodent Progressive Cardiomyopathy and Like Lesions in Toxicology Studies up to 28 Days in the Sprague Dawley Rat (Part 2 of 2).

To test the diagnostic approach described in part 1 of this article, 2 exercises were completed by pathologists from multiple companies/agencies. Pathologist's examination of whole slide image (WSI) heart sections from rats using personal diagnostic approaches (exercise #1) corroborated conclusions from study #1. Using the diagnostic approach described in part 1, these pathologists examined the same WSI heart sections (exercise #2) to determine whether that approach increased consistency of diagnosis of rodent progressive cardiomyopathy (PCM) lesions. In exercise #2, there was improved consistency of categorization of small borderline morphologies and mild lesions, but a decrement in consistency of categorizing minimal lesions. Exercises 1 and 2 suggest the described diagnostic approach is representative of that in use by the majority of toxicologic pathologists across companies/agencies and that application by all may improve diagnostic consistency of PCM/like lesions. Additionally, a criterion of approximately 5% heart section involvement is suggested for separating mild from moderate or greater severity. While evidence is not absolute, until further investigation shows otherwise, microscopic changes resembling PCM, but located in the epicardial and subepicardial region of the right ventricle, may be considered as part of the spectrum of PCM.

A Diagnostic Approach for Rodent Progressive Cardiomyopathy and Like Lesions in Toxicology Studies up to 28 Days in the Sprague Dawley Rat (Part 1 of 2).

Spontaneous rodent progressive cardiomyopathy (PCM) in the Sprague Dawley rat may confound identification and/or interpretation of potential test article (TA)-related cardiotoxicity. Pathologists apply diagnostic term(s) and thresholds for diagnosing and assigning severity grades for PCM and/or PCM-like (PCM/like) lesions consistently within a study, which is necessary to identify and interpret TA-related findings. Due to differences in training and/or experiences, diagnostic terms and thresholds may vary between pathologists. Harmonized terminology and thresholds across studies will generate better historical control data, will likely enhance interpretation of study data, and may further enhance our understanding of the spontaneous change. An assessment of the diagnostic approaches of a group of 37 pathologists identified an approach that is relatively easily applied; and if adopted, it could enhance diagnostic consistency across studies. This approach uses the single "slash" term "necrosis/inflammatory cell infiltrate (NICI)" as the diagnosis for the spectrum of lesions seen in younger rats, uses no threshold for diagnosis (e.g., diagnose all lesions clearly identifiable as PCM/like), and uses aggregate lesion size of approximately ≥45% of the field of view (FOV) using a 10×/22 eyepiece and the 40× objective or approximately ≥100% of the FOV using the 60× objective as the criterion separating minimal from mild severities.

Evaluation of Pepsinogen I as a Biomarker of Drug-induced Gastric Mucosal Injury in Cynomolgus Monkeys.

Gastric mucosal injury is frequently observed in nonclinical studies of nonhuman primates. Because microscopic evaluation of stomach is generally a terminal procedure, our objective was to determine whether serum pepsinogen I (PG I) could serve as a noninvasive biomarker for detection of gastric mucosal injury in monkey. Serum PG I was measured using a commercial human immunoassay in cynomolgus monkeys ( n = 166) prior to dosing and/or terminally in 11 studies of up to 1 month duration. Mean ( SD) PG I values (ug/L) for monkeys with ( n = 59) and without ( n = 100) gastric mucosal degeneration were 101 (215) and 28 (12.6), respectively. For monkeys with baseline and terminal PG I data, mean ( SD) fold change (ratio of terminal to baseline PG I) for monkeys with ( n = 57) and without ( n = 76) glandular degeneration were 4.1 (11.3) and 1 (0.28). Receiver operating characteristic area under the curve (AUC) data demonstrated moderate diagnostic accuracy for serum PG I for glandular degeneration, AUC ( SE) 0.789 (0.04), with improved diagnostic accuracy as a fold change of baseline, AUC ( SE) 0.816 (0.04), consistent with the large interindividual but low intraindividual variability of serum PG I values in control monkeys. These data demonstrate that serum PG I is a useful biomarker of drug-induced gastric mucosal injury in the cynomolgus monkey.

Acute Alpha-Naphthylisothiocyanate-induced Liver Toxicity in Germfree and Conventional Male Rats.

Differences in the responses of conventional and germfree male Sprague-Dawley rats to acute injury induced by alpha-naphthylisothiocyanate (ANIT), a well-characterized biliary epithelial toxicant, were evaluated. Conventional and germfree rats were dosed once orally with 50 mg/kg of ANIT or corn oil alone and serially sacrificed daily for the next 3 days. Germfree rats treated with ANIT tended to have greater increases in virtually all liver and biliary-related analytes compared with conventional rats treated with ANIT; however, significant differences were found only in a few of these analytes including increased bile acids on day 3, total bilirubin on day 4, glutamate dehydrogenase (GLDH) on day 3, and reduced paraoxonase 1 (PON1) on days 2 and 3. Histologic differences between the conventional and germfree rats were modest, but most pronounced on day 2 (24-hr post dosing). Based on subjective scoring, biliary necrosis, neutrophilic cholangitis, and portal tract edema were more severe in germfree rats at 24 hr post dosing compared with conventional rats. Biliary epithelial replication did not differ between treated groups, however. Overall, germfree rats had a modestly greater level of biliary tract injury based on subjective histologic scoring and clinical chemistry measurements following an acute exposure to the well-characterized biliary toxin, ANIT; however, the difference between the ANIT-treated germfree and conventional groups was modest and most evident only within the first day following exposure. These findings suggest that the microbiome did not significantly affect ANIT-induced acute biliary tract injury in the conditions of this study.

Lapatinib Plasma and Tumor Concentrations and Effects on HER Receptor Phosphorylation in Tumor.

PURPOSE: The paradigm shift in cancer treatment from cytotoxic drugs to tumor targeted therapies poses new challenges, including optimization of dose and schedule based on a biologically effective dose, rather than the historical maximum tolerated dose. Optimal dosing is currently determined using concentrations of tyrosine kinase inhibitors in plasma as a surrogate for tumor concentrations. To examine this plasma-tumor relationship, we explored the association between lapatinib levels in tumor and plasma in mice and humans, and those effects on phosphorylation of human epidermal growth factor receptors (HER) in human tumors. EXPERIMENTAL DESIGN: Mice bearing BT474 HER2+ human breast cancer xenografts were dosed once or twice daily (BID) with lapatinib. Drug concentrations were measured in blood, tumor, liver, and kidney. In a randomized phase I clinical trial, 28 treatment-naïve female patients with early stage HER2+ breast cancer received lapatinib 1000 or 1500 mg once daily (QD) or 500 mg BID before evaluating steady-state lapatinib levels in plasma and tumor. RESULTS: In mice, lapatinib levels were 4-fold higher in tumor than blood with a 4-fold longer half-life. Tumor concentrations exceeded the in vitro IC90 (~ 900 nM or 500 ng/mL) for inhibition of HER2 phosphorylation throughout the 12-hour dosing interval. In patients, tumor levels were 6- and 10-fold higher with QD and BID dosing, respectively, compared to plasma trough levels. The relationship between tumor and plasma concentration was complex, indicating multiple determinants. HER receptor phosphorylation varied depending upon lapatinib tumor concentrations, suggestive of changes in the repertoire of HER homo- and heterodimers. CONCLUSION: Plasma lapatinib concentrations underestimated tumor drug levels, suggesting that optimal dosing should be focused on the site of action to avoid to inappropriate dose escalation. Larger clinical trials are required to determine optimal dose and schedule to achieve tumor concentrations that maximally inhibit HER receptors. CLINICAL TRIAL REGISTRATION: NCT00359190.

Cardiolipin profiles as a potential biomarker of mitochondrial health in diet-induced obese mice subjected to exercise, diet-restriction and ephedrine treatment.

Cardiolipin (CL) is crucial for mitochondrial energy metabolism and structural integrity. Alterations in CL quantity or CL species have been associated with mitochondrial dysfunction in several pathological conditions and diseases, including mitochondrial dysfunction-related compound attrition and post-market withdrawal of promising drugs. Here we report alterations in the CL profiles in conjunction with morphology of soleus muscle (SM) and brown adipose tissue (BAT) in diet-induced obese (DIO) mice, subjected to ephedrine treatment (EPH: 200 mg kg(-1) day(-1) orally), treadmill exercise (EX: 10 meters per min, 1 h per day), or dietary restriction (DR: 25% less of mean food consumed by the EX group) for 7 days. Mice from the DR and EPH groups had a significant decrease in percent body weight and reduced fat mass compared with DIO controls. Morphologic alterations in the BAT included brown adipocytes with reduced cytoplasmic lipid droplets and increased cytoplasmic eosinophilia in the EX, DR and EPH groups. Increased cytoplasmic eosinophilia in the BAT was ultrastructurally manifested by increased mitochondrial cristae, fenestration of mitochondrial cristae, increased electron density of mitochondrial matrix, and increased complexity of shape and elongation of mitochondria. Mitochondrial ultrastructural alterations in the SM of the EX and DR groups included increased mitochondrial cristae, cup-shaped mitochondria and mitochondrial degeneration. All four CL species (tri-linoleoyl-mono-docosahexaenoyl, tetralinoleoyl, tri-linoleoyl-mono-oleoyl, and di-linoleoyl-di-oleoyl) were increased in the BAT of the DR and EPH groups and in the SM of the EPH and EX groups. In conclusion, cardiolipin profiling supported standard methods for assessing mitochondrial biogenesis and health, and may serve as a potential marker of mitochondrial dysfunction in preclinical toxicity studies.

Lack of association of ABCB4 insertion mutation with gallbladder mucoceles in dogs.

The etiology of canine gallbladder mucocele (GBM) has not yet been identified. However, several studies have linked GBM in dogs to particular breeds (Shetland Sheepdogs are commonly implicated), concurrent endocrine disease (hyperadrenocorticism and/or hypothyroidism), and a mutation in the canine ABCB4 gene (ABCB4 1583_1584G), particularly in Shetland Sheepdogs. The current study assessed ABCB4 1583_1584G, in a wider sample of dogs with GBM compared with age and breed-matched controls. ABCB4 1583_1584G was identified in 4 of 8 Shetland Sheepdogs and 13 of 28 other breeds with GBM. ABCB4 1583_1584G was also detected in 9 of 12 Shetland Sheepdogs and 23 of 37 other breeds that did not have GBM. No statistically significant association existed between ABCB4 1583_1584G and the presence of GBM for all dogs combined or for Shetland Sheepdogs alone. In contrast to previously reported findings, the current study did not identify a strong association between ABCB4 1583_1584G and GBM in Shetland Sheepdogs or other breeds.

Gene expression analysis and urinary biomarker assays reveal activation of tubulointerstitial injury pathways in a rodent model of chronic proteinuria (Doxorubicin nephropathy).

BACKGROUND: Tubular atrophy and interstitial fibrosis are well-recognized sequelae of chronic proteinuria; however, little is known regarding the molecular pathways activated within tubulointerstitium in chronic proteinuric nephropathies. METHODS: To investigate the molecular mechanisms of proteinuria-associated tubulointerstitial (TI) disease, doxorubicin nephropathy was induced in rats. Progression of disease was monitored with weekly urinary biomarker assays. Because histopathology revealed multifocal TI injury, immunodirected laser capture microdissection was used to identify and isolate injured proximal tubules, as indicated by kidney injury molecule-1 immunolabeling. Adjacent interstitial cells were harvested separately. Gene expression microarray, manual annotation of gene lists, and Gene Set Enrichment Analysis were performed. A subset of the regulated transcripts was validated by quantitative PCR and immunohistochemistry. RESULTS: Severe proteinuria preceded tubular injury biomarkers by 1 week. Histology revealed multifocal, mild TI damage at 3 weeks, which progressed in severity at 5 weeks. Affymetrix microarray analysis revealed tissue-specific regulation of gene expression. Manual annotation of gene lists, gene set enrichment analysis, and urinary biomarker assays revealed similarities to pathways activated in direct TI injuries. This suggests commonalities amongst the molecular mechanisms of TI injury secondary to proteinuria, ischemia-reperfusion, and nephrotoxicity. © 2013 S. Karger AG, Basel.

Spontaneous cardiomyopathy in young Sprague-Dawley rats: evaluation of biological and environmental variability.

Cardiovascular safety signals in nonclinical studies remain among the main reasons for drug attrition during pharmaceutical research and development. Drug-induced changes can be functional and/or associated with morphological alterations in the normal heart histology. It is therefore crucial to understand the normal variations in histology to discriminate test article-related changes from background lesions. Rodent progressive cardiomyopathy is probably the most commonly encountered change in control animals of nonclinical toxicity studies. A multisite study mimicking standard short-term toxicity studies using young male Sprague-Dawley rats was performed to better characterize this finding. Using an enhanced sectioning method for this research study, it was observed that the incidence of background cardiomyopathy was 100%. The vast majority of the microscopic findings were inflammatory in nature, with associated necrotic changes (defined as necrosis/inflammatory cell infiltrate) and these changes were mainly located in the myocardium of the mid region of the ventricles (the left side being predominantly affected). The monitored environmental factors in this study (multiple facilities, study duration, handling) did not have an effect on the incidence or severity of the spontaneous cardiomyopathy. In addition, cardiac-specific serum troponin levels were measured and were within the published control range.

Responses of brown adipose tissue to diet-induced obesity, exercise, dietary restriction and ephedrine treatment.

Drug-induced weight loss in humans has been associated with undesirable side effects not present in weight loss from lifestyle interventions (caloric restriction or exercise). To investigate the mechanistic differences of weight loss by drug-induced and lifestyle interventions, we examined the gene expression (mRNA) in brown adipose tissue (BAT) and conducted histopathologic assessments in diet-induced obese (DIO) mice given ephedrine (18 mg/kg/day orally), treadmill exercise (10 m/min, 1-h/day), and dietary restriction (DR: 26% dietary restriction) for 7 days. Exercise and DR mice lost more body weight than controls and both ephedrine and exercise reduced percent body fat. All treatments reduced BAT and liver lipid accumulation (i.e., cytoplasmic lipids in brown adipocytes and hepatocytes) and increased oxygen consumption (VO2 ml/kg/h) compared with controls. Mitochondrial biogenesis/function-related genes (TFAM, NRF1 and GABPA) were up-regulated in the BAT of all groups. UCP-1 was up-regulated in exercise and ephedrine groups, whereas MFSD2A was up-regulated in ephedrine and DR groups. PGC-1α up-regulation was observed in exercise and DR groups but not in ephedrine group. In all experimental groups, except for ephedrine, fatty acid transport and metabolism genes were up-regulated, but the magnitude of change was higher in the DR group. PRKAA1 was up-regulated in all groups but not significantly in the ephedrine group. ADRß3 was slightly up-regulated in the DR group only, whereas ESRRA remained unchanged in all groups. Although our data suggest a common pathway of BAT activation elicited by ephedrine treatment, exercise or DR, mRNA changes were indicative of additional nutrient-sensing pathways in exercise and DR.

Effects of Kupffer cell depletion on acute alpha-naphthylisothiocyanate-induced liver toxicity in male mice.

Depletion of Kupffer cells, known to modulate chemical-induced hepatocellular injury, has not been studied with regard to biliary epithelial injury. Here, the authors investigated the effect of Kupffer cell depletion by clodronate on the toxicity of alpha-naphthylisothiocyanate (ANIT), known to injure biliary epithelium as well as hepatocytes. Up to 99% depletion of Kupffer cells occurred in ANIT and liposome-encapsulated clodronate-treated mice. The effect of Kupffer cell depletion was most evident one day following ANIT treatment. Histologically, there was a modest increase in neutrophil infiltration of the bile ducts, hepatocytic necrosis, and microvesicular vacuolization in the ANIT and clodronate-treated mice, but differences between other groups did not persist. Clinical pathology analytes related to the biliary or hepatocellular injury were significantly elevated in ANIT and clodronate-treated mice compared to mice given clodronate only. This was also true for mice given ANIT and empty liposomes in the case of the biliary analytes. However, group means were typically higher for the ANIT and clodronate-treated group than others on the first 2 days following ANIT injection. These findings suggest that Kupffer cell reduction increases hepatobiliary damage due to ANIT treatment.

Effect of estrous cycle phase on clinical pathology values in beagle dogs.

BACKGROUND: In dogs, the diestrus phase is considerably longer than in most domestic animals, and is characterized by high circulating progesterone concentrations that may influence clinical pathology values. OBJECTIVE: The objective of this retrospective study was to investigate differences in clinical pathology data in dogs in diestrus compared with data from dogs in all other phases of the estrous cycle. METHODS: Phase of the estrous cycle was determined by histologic evaluation of reproductive tissues from 86 control female Beagles that had participated in 23 toxicity studies. Serum biochemical, hematologic, and urinalysis values from dogs in diestrus were compared with data from dogs in all other estrous cycle phases using a 2-tailed t-test. RESULTS: In Beagles in diestrus (n = 38), serum cholesterol concentrations and eosinophil counts were 35% (P < .0001) and 45.8% (P = .0035) higher, respectively, than for Beagles in all other phases of the estrous cycle (n = 48). Furthermore, Beagles in diestrus had 14% lower AST activity (P = .0011), 1% lower chloride concentration (P = .0224), 7.8% lower hemoglobin concentration (P < .0001), 7.8% lower RBC count (P < .0001), and 7.6% lower hematocrit (P < .0001) compared with female dogs in all other phases of the estrous cycle. Urine values did not differ significantly between groups. CONCLUSIONS: Differences in clinical pathology values between dogs in different phases of the estrous cycle could potentially confound interpretation of data in toxicity studies, which often have small group sizes. Interpretation of clinical pathology data in female dogs should be performed with due consideration given to the phase of the estrous cycle.

An initial characterization of N-terminal-proatrial natriuretic peptide in serum of Sprague Dawley rats.

In the clinical setting, natriuretic peptides (NPs) have proven to be reliable noninvasive markers for diagnostic, prognostic, and therapeutic monitoring of heart failure. Given their proven utility in humans, NPs are potential candidates for translational biomarkers during drug development to detect drug-induced hemodynamic stress resulting in cardiac hypertrophy in preclinical species. We evaluated the intra- and interassay precision and the stability of serum N-terminal-proatrial natriuretic peptide (NT-proANP) using a commercially available enzyme-linked immunoassay (EIA). We then measured NT-proANP concentrations in 532 serum samples from 337 male Crl:CD(SD) rats with or without pressure-induced cardiac hypertrophy. Additionally, we established a reference range using samples from control animals across multiple studies. The data demonstrate that the NT-proANP EIA is a robust and reproducible assay for the measurement of NT-proANP. The noninvasive translational utility, minimal sample volume requirement, and the lack of existing hypertrophic biomarkers in the male rat make NT-proANP an excellent candidate for further interrogation as a biomarker of cardiac hypertrophy in preclinical toxicology investigations.

Time course gene expression using laser capture microscopy-extracted bile ducts, but not hepatic parenchyma, reveals acute alpha-naphthylisothiocyanate toxicity.

Acute toxic responses to a 50-mg/kg oral dose of 1-naphthylisothiocyanate (ANIT) were evaluated by microarray analysis of laser capture-microdissected rat biliary epithelium or hepatic parenchyma obtained 2 and 6 hours postdose. Distinct differences in gene expression patterns between biliary epithelium and hepatic parenchyma were noted at the 2-hour postdose time point, where 375 genes were altered in biliary epithelium but only 38 genes were altered in hepatic parenchyma. Endoplasmic reticulum stress genes were uniquely expressed in biliary epithelial cells at 2 hours postdose. By 6 hours postdose, 620 genes were altered in biliary epithelium, but only 32 genes were altered in hepatic parenchyma. In biliary epithelium, expression of genes involved in the unfolded protein response had decreased compared with the 2-hour time point, while expression of genes involved in protein degradation such as proteasome-ubquination pathways and cell death pathways had increased. At this same time, hepatic parenchymal gene expression changed little. Within 6 hours following oral exposure to ANIT, prior to morphologic changes, specific biliary epithelial gene expression changes, indicative of a vigorous unfolded protein response with protein destruction and cell death pathway activation were noted, in contrast to minor changes in the hepatic parenchyma.

Direct inotropic effects of exogenous and endogenous urotensin-II: divergent actions in failing and nonfailing human myocardium.

BACKGROUND: Urotensin-II (U-II) is an endogenous peptide upregulated in failing hearts. To date, insights into the myocardial actions of U-II have been obscured by its potent vasoconstrictor effects and interspecies differences in physiological responses to U-II. METHODS AND RESULTS: We examined the direct effects of exogenous U-II on in vitro contractility in nonfailing and failing human myocardial trabeculae (n=47). Rapid cooling contractures (RCC) were used to examine sarcoplasmic reticulum Ca(2+) load. In nonfailing myocardium, exogenous U-II increased developed force (DF), rates of force generation and decline and RCC amplitude suggesting increased sarcoplasmic reticulum Ca(2+) load. In isolated myocyte suspensions from nonfailing hearts, U-II increased phospholamban phosphorylation. In failing myocardium, exogenous U-II reduced DF and rates of force generation and decline without a significant change in RCC amplitude in trabeculae or a change in phospholamban phosphorylation in myocytes. To examine the effects of endogenous U-II, we administered the peptidic U-II receptor antagonist (UT-A) GSK248451A to isolated trabeculae. UT-A induced a decrease in DF in nonfailing myocardium and an increase in DF in failing myocardium. UT-A increased RCC amplitude slightly in both nonfailing and failing myocardium. During ongoing UT-A, exogenous U-II had little effect on DF and RCC amplitude, confirming effective receptor blockade. CONCLUSIONS: U-II modulates contractility independent of vasoconstriction with opposite effects in failing and nonfailing hearts. Positive inotropic responses to UT-A alone suggests that increased endogenous U-II constrains contractility in failing hearts via an autocrine or paracrine mechanism. These findings support a potential therapeutic role for UT-A in heart failure.

Mimetics of caloric restriction include agonists of lipid-activated nuclear receptors.

The obesity epidemic in industrialized countries is associated with increases in cardiovascular disease (CVD) and certain types of cancer. In animal models, caloric restriction (CR) suppresses these diseases as well as chemical-induced tissue damage. These beneficial effects of CR overlap with those altered by agonists of nuclear receptors (NR) under control of the fasting-responsive transcriptional co-activator, peroxisome proliferator-activated co-activator 1alpha (PGC-1alpha). In a screen for compounds that mimic CR effects in the liver, we found statistically significant overlaps between the CR transcript profile in wild-type mice and the profiles altered by agonists of lipid-activated NR, including peroxisome proliferator-activated receptor alpha (PPARalpha), liver X receptor, and their obligate heterodimer partner, retinoid X receptor. The overlapping genes included those involved in CVD (lipid metabolism and inflammation) and cancer (cell fate). Based on this overlap, we hypothesized that some effects of CR are mediated by PPARalpha. As determined by transcript profiling, 19% of all gene expression changes in wild-type mice were dependent on PPARalpha, including Cyp4a10 and Cyp4a14, involved in fatty acid omega-oxidation, acute phase response genes, and epidermal growth factor receptor but not increases in PGC-1alpha. CR protected the livers of wild-type mice from damage induced by thioacetamide, a liver toxicant and hepatocarcinogen. CR protection was lost in PPARalpha-null mice due to inadequate tissue repair. These results demonstrate that PPARalpha mediates some of the effects of CR and indicate that a pharmacological approach to mimicking many of the beneficial effects of CR may be possible.

Fibrates induce hepatic peroxisome and mitochondrial proliferation without overt evidence of cellular proliferation and oxidative stress in cynomolgus monkeys.

There is little primate risk factor data in the literature evaluating the relationship between proposed mechanisms of PPAR agonist-induced hepatocarcinogenesis at clinically relevant therapeutic exposures. These studies were conducted to characterize the hepatic effects of fenofibrate and ciprofibrate in the cynomolgus monkey. Male cynomolgus monkeys were given fenofibrate (250, 1250 or 2500 mg/kg/day) or ciprofibrate (3, 30, 150 or 400 mg/kg/day) for up to 15 days. The highest doses used were approximately 4 times (fenofibrate) and 9.4 times (ciprofibrate) the human therapeutic exposure for these agents based on AUC (area under the curve). For both compounds, there was a treatment-related increase in liver weight and periportal hepatocellular hypertrophy, which was related to increases in peroxisomes (up to 2.8 times controls) and mitochondria (up to 2.5 times controls). An increase in smooth endoplasmic reticulum probably contributed to the hypertrophy. There was no indication of cell proliferation as determined by the number of mitotic figures and this was confirmed by evaluating cell proliferation by immunohistochemical staining for the Ki-67 antigen. Consistent with the findings by light microscopy, there was no treatment-related effect on the level of mRNA for proteins known to be involved in the control of hepatocyte cell division or apoptosis (e.g. P21, Cyclin D1, PCNA, CDKN1A). Furthermore, there was minimal indication of oxidative stress. Thus, there was no evidence of lipofuscin accumulation, and there was no remarkable increase in the mRNA levels for most proteins known to respond to oxidative stress (e.g. catalase, glutathione peroxidase). A mild induction in the mRNA levels of cellular beta-oxidation and detoxification enzymes (e.g. acyl CoA oxidase, thioredoxin reductase) was observed. Collectively, the data from these studies suggest that the primate responds to PPARalpha agonists in a manner that is different from the rodent suggesting that the primate may be refractory to PPAR-induced hepatocarcinogenesis.