The American Journal of Gastroenterology is published by Nature Publishing Group (NPG) on behalf of the American College of Gastroenterology (ACG). Ranked the #1 clinical journal covering gastroenterology and hepatology*, The American Journal of Gastroenterology (AJG) provides practical and professional support for clinicians dealing with the gastroenterological disorders seen most often in patients. Published with practicing clinicians in mind, the journal aims to be easily accessible, organizing its content by topic, both online and in print. www.amjgastro.com, *2007 Journal Citation Report (Thomson Reuters, 2008)

Context: Increased abdominal fat has been linked to insulin resistance and increased cardiovascular risk. Because many patients with polycystic ovary syndrome (PCOS) present abdominal obesity, it may be the cause of insulin resistance in this disorder. Setting: Fat quantity and distribution were evaluated by dual x-ray absorptiometry at the Departments of Clinical Medicine at the University of Palermo and the University of Naples, Italy. Patients: A total of 110 patients with PCOS and 112 weight-matched controls were studied. Anthropometric data, blood glucose, serum insulin, and testosterone were evaluated. Total, trunk, and central abdominal fat quantity were measured by total-body dual x-ray absorptiometry. Results: Compared with weight-matched controls, patients with PCOS had similar quantity of total and trunk fat but higher quantity of central abdominal fat. This difference was not observed when comparing obese PCOS and obese controls but depended on differences between overweight and normoweight patients and controls. All obese subjects, independently of having PCOS or not, had increased central abdominal fat. The same parameter was increased in 71% of overweight PCOS, 50% of overweight controls, and 30% of normoweight PCOS patients. PCOS patients with increased central abdominal fat had significantly higher (P < 0.01) insulin levels and significantly reduced (P < 0.01) insulin sensitivity than controls with similar quantities of central abdominal fat. Overweight PCOS patients with normal abdominal fat had significantly higher (P < 0.05) insulin levels and significantly reduced (P < 0.05) insulin sensitivity than overweight controls with normal abdominal fat. Conclusions: Most obese subjects, independent of being affected by PCOS, have an abdominal form of obesity. However, abdominal fat excess may not be the only determinant of insulin resistance in PCOS.

Human rickettsial diseases comprise a variety of clinical entities caused by microorganisms belonging to the generaRickettsia,Orientia,Ehrlichia, andAnaplasma. These microorganisms are characterized by a strictly intracellular location which has, for long, impaired their detailed study. In this paper, the critical steps taken by these microorganisms to play their pathogenic roles are discussed in detail on the basis of recent advances in our understanding of molecularRickettsia-host interactions, preferential target cells, virulence mechanisms, three-dimensional structures of bacteria effector proteins, upstream signalling pathways and signal transduction systems, and modulation of gene expression. The roles of innate and adaptive immune responses are discussed, and potential new targets for therapies to block host-pathogen interactions and pathogen virulence mechanisms are considered.