Dash A, Simmers MB, Deering TG, Berry DJ, Feaver RE, Hastings NE, Pruett TL, LeCluyse EL, Blackman BR, Wamhoff BR. Hemodynamic flow improves rat hepatocyte morphology, function, and metabolic activity in vitro. Am J Physiol Cell Physiol 304: C1053-C1063, 2013. First published March 13. 2013 doi:10.1152/ajpcell.00331.2012.-In vitro primary hepatocyte systems typically elicit drug induction and toxicity responses at concentrations much higher than corresponding in vivo or clinical plasma Cmax levels, contributing to poor in vitro-in vivo correlations. This may be partly due to the absence of physiological parameters that maintain metabolic phenotype in vivo. We hypothesized that restoring hemodynamics and media transport would improve hepatocyte architecture and metabolic function in vitro compared with nonflow cultures. Rat hepatocytes were cultured for 2 wk either in nonflow collagen gel sandwiches with 48-h media changes or under controlled hemodynamics mimicking sinusoidal circulation within a perfused Transwell device. Phenotypic, functional, and metabolic parameters were assessed at multiple times. Hepatocytes in the devices exhibited polarized morphology, retention of differentiation markers [E-cadherin and hepatocyte nuclear factor-4␣ (HNF-4␣)], the canalicular transporter [multidrug-resistant protein-2 (Mrp-2)], and significantly higher levels of liver function compared with nonflow cultures over 2 wk (albumin ϳ4-fold and urea ϳ5-fold). Gene expression of cytochrome P450 (CYP) enzymes was significantly higher (fold increase over nonflow: CYP1A1: 53.5 Ϯ 10.3; CYP1A2: 64.0 Ϯ 15.1; CYP2B1: 15.2 Ϯ 2.9; CYP2B2: 2.7 Ϯ 0.8; CYP3A2: 4.0 Ϯ 1.4) and translated to significantly higher basal enzyme activity (device vs. nonflow: CYP1A: 6.26 Ϯ 2.41 vs. 0.42 Ϯ 0.015; CYP1B: 3.47 Ϯ 1.66 vs. 0.4 Ϯ 0.09; CYP3A: 11.65 Ϯ 4.70 vs. 2.43 Ϯ 0.56) while retaining inducibility by 3-methylcholanthrene and dexamethasone (fold increase over DMSO: CYP1A ϭ 27.33 and CYP3A ϭ 4.94). These responses were observed at concentrations closer to plasma levels documented in vivo in rats. The retention of in vivo-like hepatocyte phenotype and metabolic function coupled with drug response at more physiological concentrations emphasizes the importance of restoring in vivo physiological transport parameters in vitro.hemodynamics; hepatocyte; metabolism; organotype; phenotype HEPATOTOXICITY AND BIOAVAILABILITY issues comprise over 60% of drug failures during clinical trials (45) and are a major cause of postmarketing withdrawal (23), pointing to the need to develop more efficient and predictive preclinical test systems. Simple cellular and subcellular assays used to screen compound libraries offer the advantage of higher throughput but are often unable to capture complex biological effects that may require a physiological context for drug interactions with cells. Primary in vitro hepatocyte models widely used to study liver disease, drug metabolism, and toxicity are extensively reviewed in the literature (16,42). The ability to test the metabolic f...

Thiazolidinediones alter cell energy metabolism. They are used to treat or are being considered for the treatment of disorders that feature mitochondrial impairment. Their mitochondrial effects, however, have not been comprehensively studied under long-term exposure conditions. We used the human neuronlike NT2 cell line to directly assess the long-term effects of a thiazolidinedione drug, pioglitazone, on mitochondria. At micromolar concentrations, pioglitazone increased mitochondrial DNA (mtDNA) content, levels of mtDNA and nuclear-encoded electron transport chain subunit proteins, increased oxygen consumption, and elevated complex I and complex IV V max activities. Pioglitazone treatment was also associated with increased cytoplasmic but reduced mitochondrial peroxide levels. Our data suggest that pioglitazone induces mitochondrial biogenesis and show that pioglitazone reduces mitochondrial oxidative stress in a neuron-like cell line. For these reasons pioglitazone may prove useful in the treatment of mitochondriopathies.

Background-Butyrate, a short chain fatty acid produced by bacterial fermentation, is a major fuel source for the colonocyte. In vitro work has shown that ulcerative colitis may be characterised by a metabolic defect in colonocyte butyrate oxidation. Aims-To investigate the rate of metabolism of rectally administered butyrate in patients with quiescent colitis. Methods-[1- 13C]-butyrate enemas were administered to 11 patients with long standing quiescent ulcerative colitis and to 10 control patients. The rate of production of 13 CO 2 in exhaled breath over four hours was measured by isotope ratio mass spectrometry combined with indirect calorimetry in order to measure CO 2 production. This allowed calculation of the patients' resting energy expenditure and respiratory quotient. Results-Over a four hour period, 325 (SEM 21) µmol 13 CO 2 was recovered in breath samples from the colitis group compared with 322 (17) µmol from the control group (NS). The respiratory quotient of the colitic group was significantly lower than that of the control group. Conclusion-There was no diVerence in the rate of metabolism of butyrate between the two groups. It is unlikely that there is a primary metabolic defect of butyrate metabolism in patients with quiescent ulcerative colitis. (Gut 2000;46:73-77) Keywords: ulcerative colitis; in vivo butyrate metabolism Short chain fatty acids (SCFAs) are produced in the human large bowel by fermentation of non-starch polysaccharides (dietary fibre) by the colonic bacteria.1 Acetate, propionate, and butyrate are the major SCFAs produced by this process and much interest has focused on the importance of butyrate in cell metabolism. Butyrate is the major fuel source for the colonic epithelium (colonocyte) 2 and is necessary for salt and water absorption by the colonic mucosa.3 A lack of butyrate can result in inflammation, as seen in diversion colitis. This has been satisfactorily treated in one study by increasing luminal butyrate levels via enema administration.

Cytochrome oxidase (COX) activity varies between individuals and low activities associate with Alzheimer's disease. Whether genetic heterogeneity influences function of this multimeric enzyme is unknown. To explore this we sequenced three mitochondrial DNA (mtDNA) and ten nuclear COX subunit genes from at least 50 individuals. 20% had non-synonymous mtDNA COX gene polymorphisms, 12% had a COX4I1 non-synonymous G to A transition, and other genes rarely contained non-synonymous polymorphisms. Frequent untranslated region (UTR) polymorphisms were seen in COX6A1, COX6B1, COX6C, and COX7A1; heterogeneity in a COX7A1 5' UTR Sp1 site was extensive. Synonymous polymorphisms were common and less frequent in the more conserved COX1 than the less conserved COX3, suggesting at least in mtDNA synonymous polymorphisms experience selection pressure and are not functionally silent. Compound gene variations occurred within individuals. To test whether variations could have functional consequences, we studied the COX4I1 G to A transition and an AGCCCC deletion in the COX7A1 5' UTR Sp1 site. Cells expressing the COX4I1 polymorphism had reduced COX Vmax activity. In reporter construct-transduced cells where green fluorescent protein expression depended on the COX7A1 Sp1 site, AGCCCC deletion reduced fluorescence. Our findings indicate COX subunit gene heterogeneity is pervasive and may mediate COX functional variation.

The firefly luciferase (Luc)