Adaptation and maladaptation of heart and skeletal muscle to different diets in a rodent model of human obesity

Obesity and diabetes are metabolic disorders associated with fatty acid availability in excess of the tissues' capacity for fatty acid oxidation. This mismatch is implicated in the pathogenesis of cardiac contractile dysfunction and also in skeletal muscle insulin resistance. My dissertation will present work to test the overall hypothesis that "western" and high fat diets differentially affect cardiac and skeletal muscle fatty acid oxidation, the expression of fatty acid responsive genes, and cardiac contractile function. Wistar rats were fed a low fat, "western," or high fat (10%, 45%, or 60% calories from fat, respectively) diet for acute (1 day to 1 week), short (4 to 8 weeks), intermediate (16 to 24 weeks), or long (32 to 48 weeks) term. With high fat diet, cardiac oleate oxidation increased at all time points investigated. In contrast, with western diet cardiac oleate oxidation increased in the acute, short and intermediate term, but not in the long term. Consistent with a maladaptation of fatty acid oxidation, cardiac power (measured ex vivo) decreased with long term western diet only. In contrast to the heart, soleus muscle oleate oxidation increased only in the acute and short term with either western or high fat feeding. Transcript analysis revealed that several fatty acid responsive genes, including pyruvate dehydrogenase kinase 4, uncoupling protein 3, mitochondrial thioesterase 1, and cytosolic thioesterase 1 increased in heart and soleus muscle to a greater extent with high fat diet, versus western diet, feeding. In conclusion, the data implicate inadequate induction of a cassette of fatty acid responsive genes in both the heart and skeletal muscle by western diet resulting in impaired activation of fatty acid oxidation, and the development of cardiac dysfunction. ^

The role of CD1d in adipogenesis

Atherosclerosis-associated coronary heart disease is the number one cause of death in the western society, and often triggered by metabolic disorders, such as hyperlipidemia, hypertension, obesity, and diabetes. The CD1 molecules are a group of evolutionarily conservative transmembrane proteins that have recently emerged as novel lipid-binding and transporting molecules. The current study was aimed at illustrating the role of CD1d in regulation of lipid metabolism and adipogenesis. In stably transfected smooth muscle cells where CD1d is overexpressed via a pCMV promoter, high levels of binding of the oxysterol 7-ketocholesterol was found. Adipogenic treatment induces the cells to transdifferentiate into an adipocyte-like morphology. This adipocyte morphology of CD1d transfected SMCs strongly resembles that of the pre-adipocytes 3T3-L1 cells grown in the same adipogenic media. Adipogenic treatment of CD1d transfected 3T3-L1 cells led to an increased accumulation of lipids compared to mock transfected cells. Induction of adipogenic gene expression and activation, such as PPARγ and lipoprotein lipase (LPL), was achieved in adipogenically treated smooth muscle cells as well as 3T3-L1 cells with overexpression of CD1d. For determination of the role of CD1d in regulation of adipogenesis, a CD1d transgenic mouse strain was created using the CD1d-smooth muscle promoter construct. Compared to wild type control mice matched in age and sex, the transgenic mice show an age-dependent increase in abdominal and visceral fat tissue. Histopathological examination demonstrated marked enlargement of adipocytes in the transgenic fat tissue which otherwise remained a normal fat tissue structure. Immunohistochemical analysis of CD1d expression in the fat tissue revealed much stronger membrane CD1d immunostaining in the transgenic tissue than the wild type fat tissue. Under normal chow diets, CD1d-transgenic mice also developed fatty livers. In conclusion, CD1d serves as a regulator of lipid metabolism, which may transducer signals from oxysterols to induce expression of genes important in lipogenesis. These experimental results point to a novel mechanism by which CD1d mediates lipid metabolism in adipose tissue and contributes to the development of obesity. ^

Epidemiological trends of influenza A positive patients hospitalized at St. Luke's Episcopal Hospital, Houston, Texas September, 2009--January, 2010

This study was a descriptive analysis of 437 influenza A positive inpatients and outpatients during the five month period between September, 2009 and January, 2010. The objective of the study was to describe the epidemiological trends of the total influenza A positive population and more specifically the clinical features of patients hospitalized with influenza A at St. Luke's Episcopal Hospital in Houston, Texas from September 2009 through January 2010. Eligible cases were included if they tested positive for influenza A test using the rapid antigen test and/or rRT-PCR. Hospitalized cases were included based on the laboratory confirmation of influenza A as well as hospital admission for at least 24 hours. Data was collected from medical record abstraction and included patient demographics, clinical history and history of chronic disease. Clinical findings in the differential diagnosis that led to laboratory-confirmation of influenza A as well as course of treatment during the hospital admission were summarized. Finally, co-morbid conditions charted during the hospital visit were reviewed and evaluated for associations with influenza A complications. During the study period, forty-eight patients were included in the study of which 27 tested positive for the H1N1 subtype. Females were more likely to be hospitalized than men. The median age of all patients admitted to St. Luke's Episcopal Hospital with influenza A was 42. The distribution for admitted cases was 15 White, 15 Black, and 18 Hispanic. Patients with co-morbid disease constituted 81% of the admissions for Influenza A. The presence of an underlying medical condition remains a risk factor for both seasonal and H1N1 influenza. Although respiratory conditions such as asthma and COPD are commonly associated with complications of seasonal influenza, patients with metabolic disorders such as kidney disease and/or diabetes were admitted more frequently (58%) during the study period. The patients in the study also of a much younger age than the age that is usually associated with complications of influenza infection, i.e. no patients greater than 65 years of age were admitted with a diagnosis of influenza A. Lower infection rates among elderly populations were similarly reported in other studies of influenza during the same time period. Older patient populations may benefit from antibodies to previous H1N1 strains that have circulated during the twentieth century, whereas younger age groups lack these exposures.^