GPAT1 Deficiency in Mice Modulates NASH Progression in a Model-Dependent Manner.

BACKGROUND & AIMS: Nonalcoholic fatty liver disease (NAFLD), and its more severe form, nonalcoholic steatohepatitis (NASH), is the leading cause for liver failure and liver cancer. Although the etiology is likely multifactorial, genes involved in regulating lipid metabolism are enriched in human NAFLD genome-wide association studies (GWAS), pointing to dysregulated lipid metabolism as a major pathogenic factor. Glycerol-3-phosphate acyltransferase 1 (GPAT1), encoded by GPAM, converts acyl-CoAs and glycerol-3-phosphate into lysophosphatidic acid and has been shown to regulate lipid accumulation in the liver. However, its role in mediating the progression from NAFLD to NASH has not been explored. METHODS: GPAT1-deficient mice were generated and challenged with diets inducing hepatic steatosis and NASH. Effects of GPAT1 deficiency on lipid and systemic metabolic end points were evaluated. RESULTS: Ablating GPAT1 globally or specifically in mouse hepatocytes reduced hepatic steatosis in the context of diet-induced or genetic obesity. Interestingly, blunting of progression from NAFLD to NASH in global GPAT1 knockout (KO) mice was model dependent. GPAT1 KO mice were protected from choline deficient, amino acid defined high-fat diet-induced NASH development, but not from the high fat, high carbohydrate, and high cholesterol diet-induced NASH. CONCLUSIONS: Our preclinical data support the notion that lipid metabolism pathways regulated by GPAT1 in hepatocytes play an essential role in NASH progression, albeit in a model-dependent manner.

Antibody modeling assessment.

A blinded study to assess the state of the art in three-dimensional structure modeling of the variable region (Fv) of antibodies was conducted. Nine unpublished high-resolution x-ray Fab crystal structures covering a wide range of antigen-binding site conformations were used as benchmark to compare Fv models generated by four structure prediction methodologies. The methodologies included two homology modeling strategies independently developed by CCG (Chemical Computer Group) and Accerlys Inc, and two fully automated antibody modeling servers: PIGS (Prediction of ImmunoGlobulin Structure), based on the canonical structure model, and Rosetta Antibody Modeling, based on homology modeling and Rosetta structure prediction methodology. The benchmark structure sequences were submitted to Accelrys and CCG and a set of models for each of the nine antibody structures were generated. PIGS and Rosetta models were obtained using the default parameters of the servers. In most cases, we found good agreement between the models and x-ray structures. The average rmsd (root mean square deviation) values calculated over the backbone atoms between the models and structures were fairly consistent, around 1.2 Å. Average rmsd values of the framework and hypervariable loops with canonical structures (L1, L2, L3, H1, and H2) were close to 1.0 Å. H3 prediction yielded rmsd values around 3.0 Å for most of the models. Quality assessment of the models and the relative strengths and weaknesses of the methods are discussed. We hope this initiative will serve as a model of scientific partnership and look forward to future antibody modeling assessments.

Traumatic noncombat-related hand injuries in U.S. troops in the combat zone.

BACKGROUND: The epidemiology of traumatic, nonbattle, Combat Zone hand injuries has not been well explored. METHODS: This was a retrospective chart review of Emergency Department visits occurring at the Ibn Sina Hospital in Baghdad Iraq. RESULTS: During the 24-month period from May 2007 to June 2009, 7,520 patients were seen at the Ibn Sina Hospital Emergency Department. Three hundred thirty-one cases met the inclusion criteria. Seventy-four cases were found to have required near-term evacuation from area of operation. CONCLUSIONS: Traumatic, nonbattle hand injuries are common and appear to be a significant problem in the Combat Zone. Injuries occurring because of the closure of vehicle doors, hatches, and turrets make up a large portion of these injuries and represent an optimal area of intervention for possible injury mitigation.

Structure-based charge calculations for predicting isoelectric point, viscosity, clearance, and profiling antibody therapeutics.

The effect of hydrophobicity on antibody aggregation is well understood, and it has been shown that charge calculations can be useful for high-concentration viscosity and pharmacokinetic (PK) clearance predictions. In this work, structure-based charge descriptors are evaluated for their predictive performance on recently published antibody pI, viscosity, and clearance data. From this, we devised four rules for therapeutic antibody profiling which address developability issues arising from hydrophobicity and charged-based solution behavior, PK, and the ability to enrich for those that are approved by the U.S. Food and Drug Administration. Differences in strategy for optimizing the solution behavior of human IgG1 antibodies versus the IgG2 and IgG4 isotypes and the impact of pH alterations in formulation are discussed.

Acetyl-CoA Carboxylase Inhibition Improves Multiple Dimensions of NASH Pathogenesis in Model Systems.

BACKGROUND & AIMS: Disordered metabolism, steatosis, hepatic inflammation, and fibrosis contribute to the pathogenesis of nonalcoholic steatohepatitis (NASH). Acetyl-CoA carboxylase (ACC) catalyzes the first committed step in de novo lipogenesis (DNL) and modulates mitochondrial fatty acid oxidation. Increased hepatic DNL flux and reduced fatty acid oxidation are hypothesized to contribute to steatosis. Some proinflammatory cells also show increased dependency on DNL, suggesting that ACC may regulate aspects of the inflammatory response in NASH. PF-05221304 is an orally bioavailable, liver-directed ACC1/2 inhibitor. The present studies sought to evaluate the effects of PF-05221304 on NASH pathogenic factors in experimental model systems. METHODS: The effects of PF-05221304 on lipid metabolism, steatosis, inflammation, and fibrogenesis were investigated in both primary human-derived in vitro systems and in vivo rodent models. RESULTS: PF-05221304 inhibited DNL, stimulated fatty acid oxidation, and reduced triglyceride accumulation in primary human hepatocytes, and reduced DNL and steatosis in Western diet-fed rats in vivo, showing the potential to reduce hepatic lipid accumulation and potentially lipotoxicity. PF-05221304 blocked polarization of human T cells to proinflammatory but not anti-inflammatory T cells, and suppressed activation of primary human stellate cells to myofibroblasts in vitro, showing direct effects on inflammation and fibrogenesis. Consistent with these observations, PF-05221304 also reduced markers of inflammation and fibrosis in the diethylnitrosamine chemical-induced liver injury model and the choline-deficient, high-fat-fed rat model. CONCLUSIONS: The liver-directed dual ACC1/ACC2 inhibitor directly improved multiple nonalcoholic fatty liver disease/NASH pathogenic factors including steatosis, inflammation, and fibrosis in both human-derived in vitro systems and rat models.

De novo lipogenesis is essential for platelet production in humans.

Acetyl-CoA carboxylase (ACC) catalyses the first step of de novo lipogenesis (DNL). Pharmacologic inhibition of ACC has been of interest for therapeutic intervention in a wide range of diseases. We demonstrate here that ACC and DNL are essential for platelet production in humans and monkeys, but in not rodents or dogs. During clinical evaluation of a systemically distributed ACC inhibitor, unexpected dose-dependent reductions in platelet count were observed. While platelet count reductions were not observed in rat and dog toxicology studies, subsequent studies in cynomolgus monkeys recapitulated these platelet count reductions with a similar concentration response to that in humans. These studies, along with ex vivo human megakaryocyte maturation studies, demonstrate that platelet lowering is a consequence of DNL inhibition likely to result in impaired megakaryocyte demarcation membrane formation. These observations demonstrate that while DNL is a minor quantitative contributor to global lipid balance in humans, DNL is essential to specific lipid pools of physiological importance.