Association of coronary artery calcification with hepatic steatosis in asymptomatic individuals.

OBJECTIVE: To determine the association of coronary artery calcification with hepatic steatosis in asymptomatic volunteers. PATIENTS AND METHODS: The study group comprised 400 asymptomatic volunteers, enrolled from April 1, 2011, to September 30, 2012, without known coronary artery disease who were self-referred for screening noncontrast computed tomography to determine coronary calcium score (CCS). Computed tomographic images were used to determine the presence of hepatic steatosis. An a priori model was created to predict a CCS of 100 Agatston units (AU) or higher on the basis of Framingham risk factors, diabetes mellitus, and metabolic syndrome. Hepatic steatosis was then added to this model. Computation of the odds ratio (OR) for hepatic steatosis predicting a CCS of 100 AU or higher was performed. Finally, the OR for a CCS of 100 AU or higher being associated with hepatic steatosis was calculated. RESULTS: When hepatic steatosis was added to traditional coronary risk factors, it was independently associated with a CCS of 100 AU or higher (OR, 2.85). This was greater than the OR of Framingham factors, diabetes mellitus, or metabolic syndrome. A CCS of 100 AU or higher was independently associated with an increased risk for hepatic steatosis (OR, 2.4). This OR was higher than traditional hepatic steatosis risk factors or metabolic syndrome. CONCLUSION: Hepatic steatosis is a strong independent predictor of a CCS of 100 AU or higher in asymptomatic patients. It is associated with an increased risk of coronary artery disease beyond that expected from traditional coronary risk factors and/or metabolic syndrome. Additional studies are needed to clarify the role of hepatic steatosis as a possible independent risk factor for the development of coronary artery disease.

ATR-p53 restricts homologous recombination in response to replicative stress but does not limit DNA interstrand crosslink repair in lung cancer cells.

Homologous recombination (HR) is required for the restart of collapsed DNA replication forks and error-free repair of DNA double-strand breaks (DSB). However, unscheduled or hyperactive HR may lead to genomic instability and promote cancer development. The cellular factors that restrict HR processes in mammalian cells are only beginning to be elucidated. The tumor suppressor p53 has been implicated in the suppression of HR though it has remained unclear why p53, as the guardian of the genome, would impair an error-free repair process. Here, we show for the first time that p53 downregulates foci formation of the RAD51 recombinase in response to replicative stress in H1299 lung cancer cells in a manner that is independent of its role as a transcription factor. We find that this downregulation of HR is not only completely dependent on the binding site of p53 with replication protein A but also the ATR/ATM serine 15 phosphorylation site. Genetic analysis suggests that ATR but not ATM kinase modulates p53's function in HR. The suppression of HR by p53 can be bypassed under experimental conditions that cause DSB either directly or indirectly, in line with p53's role as a guardian of the genome. As a result, transactivation-inactive p53 does not compromise the resistance of H1299 cells to the interstrand crosslinking agent mitomycin C. Altogether, our data support a model in which p53 plays an anti-recombinogenic role in the ATR-dependent mammalian replication checkpoint but does not impair a cell's ability to use HR for the removal of DSB induced by cytotoxic agents.

Animal models of restricted repetitive behavior in autism.

Restricted, repetitive behavior, along with deficits in social reciprocity and communication, is diagnostic of autism. Animal models relevant to this domain generally fall into three classes: repetitive behavior associated with targeted insults to the CNS; repetitive behavior induced by pharmacological agents; and repetitive behavior associated with restricted environments and experience. The extant literature provides potential models of the repetitive behavioral phenotype in autism rather than attempts to model the etiology or pathophysiology of restricted, repetitive behavior, as these are poorly understood. This review focuses on our work with deer mice which exhibit repetitive behaviors associated with environmental restriction. Repetitive behaviors are the most common category of abnormal behavior observed in confined animals and larger, more complex environments substantially reduce the development and expression of such behavior. Studies with this model, including environmental enrichment effects, suggest alterations in cortical-basal ganglia circuitry in the development and expression of repetitive behavior. Considerably more work needs to be done in this area, particularly in modeling the development of aberrant repetitive behavior. As mutant mouse models continue to proliferate, there should be a number of promising genetic models to pursue.