Journal of Investigative Medicine

Clinical investigators often find the thought of writing the statistical analysis plan daunting. Early collaboration between the clinical investigator and statistician can improve the study design and validity of the results by developing the statistical methodology that specifically addresses the research hypothesis. With the clinical investigator, a statistician often writes the statistical methods section that includes sample size and power analyses, randomization and blinding procedures, interim analysis, and data monitoring plans, in addition to the statistical analysis plan. To make this process less mysterious, we describe how the statistical methods section is developed in collaboration with a statistician.

Fragile X-associated tremor/ataxia syndrome is a late adult onset neurodegenerative disorder that affects individuals who carry a premutation CGG repeat expansion (55-200 CGG repeats) in the 5′ untranslated portion of the fragile X mental retardation 1 (FMR1) gene. Affected individuals display cognitive decline, progressive intention tremor, gait ataxia, neuropathy, psychiatric symptoms, and parkinsonism; the severity of both clinical and neuropathological phenotypes is positively correlated with the extent of the CGG expansion. Overexpression of the expanded CGG repeat messenger RNA results in a direct gain-of-function cellular toxicity that is believed to form the pathogenic basis for fragile X-associated tremor/ataxia syndrome. This mechanism is entirely different from the mechanism giving rise to fragile X syndrome, which is due to transcriptional silencing and consequent loss of FMR1 protein. Much of the research in the field has focused on understanding the link between the pathogenic FMR1 messenger RNA and the potential proteins that interact with it.

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder caused by a CGG repeat expansion in the premutation range (55-200) in the fragile X mental retardation 1 gene. Onset is typically in the early seventh decade, and men are principally affected. The major signs are cerebellar gait ataxia, intention tremor, frontal executive dysfunction, and global brain atrophy. Other frequent findings are parkinsonism (mild), peripheral neuropathy, psychiatric symptoms (depression, anxiety, and agitation), and autonomic dysfunction. The clinical presentation is heterogeneous, with individuals presenting with varied dominating signs, such as tremor, dementia, or neuropathy. Magnetic resonance imaging shows atrophy and patchy white matter lesions in the cerebral hemispheres and middle cerebellar peduncles. The latter has been designated the middle cerebellar peduncle sign, which occurs in about 60% of affected men, and is relatively specific for FXTAS. Affected females generally have less severe disease, less cognitive decline, and some symptoms different from that of men, for example, muscle pain. Management of FXTAS is complex and includes assessment of the patient's neurological and medical deficits, treatment of symptoms, and provision of relevant referrals, especially genetic counseling. Treatment is empirical, based on anecdotal experience and on knowledge of what works for symptoms of other disorders that also exist in FXTAS. Presently, the disorder is underrecognized because the first published report was only in 2001 and because the presentation is variable and mainly consists of a combination of signs common in the elderly. However, accurate diagnosis is critical for the patient and for the family because they need education regarding their genetic and health risks.

Integrin-mediated cell-extracellular matrix interaction plays key roles in tissue morphogenesis and integrity. The Lin11-Isl-1-Mec-3 (LIM) domain-only particularly interesting cysteine- and histidine-rich (PINCH) protein functions as an adaptor essential for the assembly and function of the focal adhesion complex that links integrin signaling to the cytoskeleton and other intracellular signaling pathways and regulates diverse cellular processes such as cell adhesion, migration, growth, differentiation, and survival. Recent biochemical and genetic studies have greatly advanced our knowledge surrounding the molecular interactions and functions of each component of the focal adhesion complex and revealed a requirement for PINCH in early embryogenesis, in morphogenesis of the neural crest and cardiac outflow, and in myocardial growth and remodeling. In this review article, we will provide an overview of the current knowledge of the molecular interactions of PINCH with other components of focal adhesions, highlighting recent discoveries of the in vivo role of PINCH and discuss its potential implication for human heart disease.

Cardiomyopathy is a heart muscle disease caused by decreased contractility of the ventricles leading to heart failure and premature death. Multiple conditions like ischemic heart disease (atherosclerosis), hypertension, diabetes, viral infection, alcohol abuse, obesity and genetic mutations can lead to cardiomyopathy. Single gene mutations in sarcomeric proteins, Z-disk-associated proteins, membrane/associated proteins, intermediate filaments, calcium cycle proteins as well as in modifier genes have been linked to cardiomyopathy. Clinical practice guidelines have been formulated by the American Heart Association and the Heart Failure Association of America on how to genetically evaluate patients with cardiomyopathy. To illustrate the concept that alterations in genes cause cardiovascular disease, this review will focus on two membrane-associated proteins, vinculin and talin. We will discuss the general function of vinculin/metavinulin as well as talin1 and talin2, with emphasis on what is understood about their role in the cardiac myocyte and in whole heart.

How the myocardium undergoes geometric, structural, and molecular alterations that result in an end phenotype as might be seen in patients with dilated cardiomyopathy or after myocardial infarction is still poorly understood. Structural modification of the left ventricle, which occurs during these pathological states, results from long-term changes in loading conditions and is commonly referred to as “remodeling.” Remodeling may occur from increased wall stress in the face of hypertensive heart disease, valvular disease, or, perhaps most dramatically, after permanent coronary occlusion. A fundamental derangement of myocyte function is the most common perception for the basis of remodeling, but the role of cells in the heart other than the muscle cell must, of course, be considered. Although studies of the myocyte have been extensive, cardiac fibroblasts have been studied less than myocytes. The fibroblast has a broad range of functions in the myocardium ranging from elaboration and remodeling of the extracellular matrix to communication of a range of signals within the heart, including electrical, chemical, and mechanical ones. Integrins are cell surface receptors that are instrumental in mediating cell-matrix interactions in all cells of the organism, including all types within the myocardium. This review will focus on the role of integrins and related proteins in the remodeling process, with a particular emphasis on the cardiac fibroblast. We will illustrate this function by drawing on 2 unique mouse models with perturbation of proteins linked to integrin function.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a primary heart muscle disorder characterized by the early occurrence of serious tachyarrhythmias often out of proportion to the extent of structural changes and contractile derangement. Approximately 40% of patients with ARVC have one or more mutations in genes encoding proteins in desmosomes, intercellular adhesion junctions which, in cardiac myocytes, reside within intercalated disks. Some desmosomal proteins fulfill roles both as structural proteins in cell-cell adhesion junctions and as nuclear signaling molecules. It has been proposed that mutations in desmosomal proteins implicated in ARVC may perturb the normal balance of protein in junctions and the cytosol which, in turn, could promote dysregulated gene expression circumventing the normal controls of Wnt signaling pathways. This review highlights recent advances in understanding the pathogenesis of ARVC and presents evidence, suggesting that the disease is caused by a combination of altered cellular biomechanical behavior and altered signaling.

Acute lung injury (ALI) and its most severe form the acute respiratory distress syndrome occur in patients who have a predisposing severe inflammatory insult to the lung. Most often ALI is due to sepsis from bacterial infection, but ALI can occur with any infection and with noninfectious insults such as severe trauma, acute pancreatitis, aspiration, and near-drowning. After any of these insults, the interindividual risk of progression to ALI and the risk of death remain difficult to predict. Our inability to predict an individual's susceptibility to acute lung injury has long suggested that genetic factors influence ALI risk. There is substantial evidence for heritable predispositions to severe infections and an emerging body of literature implicating genetic factors in ALI pathogenesis. A paradigm is emerging that the genetic risk for ALI can be best understood in terms of factors that control 3 overlapping stages of ALI pathogenesis: risk for the acquisition of a predisposing condition (such as a severe pneumonia), risk for progression to lung injury during systemic inflammatory states (such as severe sepsis), and risk for failure of endogenous mechanisms to resolve the lung injury. The evidence supporting this paradigm is herein reviewed, along with potential treatment strategies that could be directed by knowledge of specific genetic factors in an individual patient.

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) represent a spectrum of diseases that are commonly encountered in the intensive care unit and are associated with high mortality. Although significant advances have been made with respect to the ventilatory management of patients with ALI/ARDS with proven beneficial effects on outcomes, pharmacologic therapies remain nonexistent. Because the cardinal feature of ALI/ARDS is an increase in lung vascular permeability, often precipitated by an exuberant inflammatory response with subsequent endothelial barrier disruption, strategies aimed at promoting endothelial barrier function could serve as novel therapies in this setting. We have identified several promising agonists in this regard including sphingosine 1-phosphate, activated protein C, and statins, a class of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors. These agonists all have in common the ability to directly mediate endothelial cell signaling and induce characteristic actin cytoskeletal rearrangement leading to endothelial cell barrier protection. Our in vitro findings have been extended to animal models of ALI/ARDS and suggest that effective pharmacologic therapies for patients with ALI/ARDS may soon be available.

In 1385 adults with primary untreated hyperlipidemia and in a population study of 339 adults (Princeton Follow-up Study [PFS]), we hypothesized that homeostasis model assessment (HOMA) insulin resistance (IR) was a significant explanatory variable for triglycerides (TG) and that IR rose in a stepwise fashion, independent of age, race, sex, and body mass index (BMI), whereas TG categories rose from less than 150 to 150 to 200, to 200 to 500, and to more than 500 mg/dL. A third hypothesis was that TG, BMI, and the ratio of TG to high-density lipoprotein cholesterol (TG/HDL-C) were significant explanatory variables for IR and that IR was inversely associated with HDL-C quintiles and positively associated with non-HDL-C quintiles. By stepwise multiple regression with age, race, sex, BMI, and IR as explanatory variables, in the 1385 patients, positive explanatory variables for TG included BMI (partial R² = 1.3%, P < 0.0001), sex (men higher, partial R² = 1.1%, P = 0.0001), and IR (partial R² = 0.4%, P = 0.012). In the 339 PFS subjects, positive explanatory variables for TG were IR (partial R² = 11.4%, P < 0.0001), race (whites higher, partial R² = 2.1%, P = 0.005), and sex (men higher, partial R² = 1.4%, P = 0.019). After adjusting for age, race, sex, and BMI, in 1385 patients, HOMA IR rose while TG categories rose, with least square means of 2.64 for the TG category less than 150 mg/dL, 3.27 for 150 to 200 mg/dL, 3.85 for 200 to 500 mg/dL, and 4.12 for more than 500 mg/dL. Similarly, in the PFS, while TG categories rose, the least square means of HOMA IR rose, with 1.68 for the TG category less than 150 mg/dL, 2.34 for 150 to 200 mg/dL, and 3.03 for 200 to 500 mg/dL. Body mass index, TG, and TG/HDL-C were significant explanatory variables for IR. Homeostasis model assessment IR is a significant, potentially reversible explanatory variable for TG in patients referred because of hyperlipidemia and in population subjects.

The aim of the present paper was to review recent developments in the management of patients with acute kidney injury or chronic kidney disease occurring secondary to either cancer itself or its therapy, with a focus on infiltration of the renal parenchyma, myeloma, tumor lysis syndrome, glomerular disease, thrombotic microangiopathy, chemotherapy-associated thrombotic microangiopathy, biphosphonate-induced renal diseases, acute kidney injury, and chronic kidney disease after hematopoietic cell transplantation. Further studies are awaited because a better knowledge of renal complications, which frequently occur in patients with oncohematologic diseases, would be conducive to making an early diagnosis and providing prompt therapy.

Allopurinol as an effective inhibitor of the enzyme xanthine oxidase (XO) has been used for several decades for the treatment of patients with gout and hyperuricemia. Because the inhibition of XO limits the formation of radical oxygen species as well as uric acid (UA) production, allopurinol has been used experimentally for the treatment of conditions associated with ischemia and reperfusion (I/R) injury.

Although there have been many ischemic organs treated in the laboratory with allopurinol, the heart has been of particular interest. Therefore, we emphasize our attention to the administration of XO inhibitors such as allopurinol on cardiac I/R as well as cardiac failure. Experimental data also support allopurinol as a possible consideration for biochemical support after acute myocardial infarction.

Anker and associates (Circulation. 2003;107:1991-1997) have observed a direct correlation between uric acid levels and mortality in treated heart failure patients. Anker and associates showed a 100% mortality rate in patients with UA levels 800 μmol/L or less over a period of 3 years. Comparing this to a 27% mortality rate in patients with UA levels 400 μmol/L or less over a period of 10 years, it seems that the suppression of XO activity ameliorates myocardial inefficiency, and poor vascular flow may present innovative contributions to the future treatment of I/R heart failure patients. Our review focuses on the role of allopurinol on ischemic hearts as well as those with added chronic heart failure.