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Browsing by Author "Pagliassotti, Michael, advisor"

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    Novel therapies for NAFLD
    (Colorado State University. Libraries, 2011) Nivala, Angela Marie, author; Pagliassotti, Michael, advisor; Vivanco, Jorge, committee member; Frye, Melinda, committee member; Vanamala, Jairam, committee member
    Background/Aims Non Alcoholic Fatty Liver Disease (NAFLD) is a chronic liver disease often associated with metabolic disorders like type 2 diabetes, cardiovascular disease, obesity, and metabolic syndrome. It is characterized by hepatic fat accumulation (steatosis) that is at or above 5% of liver weight in the absence of excessive alcohol consumption (< 20 g/day). Current treatment for NAFLD focuses on reducing body weight and improving insulin action. The intent of this thesis was to identify therapies that targeted the liver. In the first aim, we examined whether secretions from plant roots contained compounds that restricted lipid accumulation or improved insulin action. The second aim examined whether taurine could prevent characteristic features of disease progression. Specifically, we hypothesized that (1) onion root exudates will prevent or reduce lipid accumulation and improve insulin signaling and (2) taurine will prevent or reduce endoplasmic reticulum (ER) stress, oxidative stress and liver injury. Methods To examine these hypotheses, liver cells and dietary models of NAFLD were employed. Analyses focused on hepatic triglycerides, insulin signaling, ER stress, oxidative stress and inflammation using basic biochemical methods such as western blotting, Real Time PCR, immunohistochemistry and enzyme-linked assays. Results Onion root exudates prevented fatty acid-mediated lipid accumulation and enhanced insulin signaling in H4IIE liver cells. Onion root exudates reduced plasma glucose, free fatty acids (FFA), and improved insulin action in rats fed a high fat diet. Taurine mitigated palmitate-mediated caspase-3 activity, cell death, ER stress, and oxidative stress in H4IIE liver cells and primary hepatocytes. In rats fed a high sucrose diet, taurine supplementation significantly reduced hepatic lipid accumulation, liver injury, inflammation, plasma triglycerides and insulin levels. The high sucrose diet resulted in an induction of multiple components of the unfolded protein response (UPR) in the liver consistent with ER stress which was ameliorated by taurine supplementation. Treatment of mice with the ER stress inducing agent tunicamycin resulted in liver injury, UPR induction and hepatic lipid accumulation, and this was significantly ameliorated by supplementation with taurine. Conclusion Both onion root exudates and taurine reduced metabolic abnormalities associated with NAFLD. Onion root exudates appear to exert this effect through reduced lipid accumulation and enhanced insulin sensitivity in the liver, while taurine reduced hepatic steatosis, ER stress, oxidative stress and liver injury. Overall, onion root exudates and taurine show promise as novel therapies for the treatment of NAFLD.
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    The effects of moderate exercise on measures of postprandial lipemia
    (Colorado State University. Libraries, 2009) Cox-York, Kimberly Ann, author; Horton, Tracy J., advisor; Pagliassotti, Michael, advisor
    Background. Elevated triglycerides (TG) and small lipid particle size are risk factors for cardiovascular disease (CVD), which are typically assessed after an overnight fast. Most individuals spend the day in the postprandial (PP) state, however, which might be more reflective of CVD risk. A single exercise bout has been shown to decrease PP TGs in response to a single, high-fat meal. The current study assessed the effect of a single bout of morning exercise on PP lipids over an entire day with 3 mixed meals of a typical macronutrient composition (34% fat, 15% protein, 51% CHO). Methods. 26 normal weight (NW) subjects and 18 subjects with metabolic syndrome (MetS) were studied. After an overnight fast, subjects exercised (treadmill walking, 60%VO2peak) or rested for 60 min then consumed breakfast, lunch, and dinner, contributing 25%, 35% and 40% of daily energy intake respectively. Fasting blood samples were collected before exercise or rest and continued throughout the day and were analyzed for PP lipids, glucose and insulin. A subset of the plasma samples were separated into triglyceride-rich lipoprotein (TRL) subfractions in which TG and cholesterol were measured. Apolipoprotein (apo) B-100 and B-48 proteins were measured in the medium-sized subfraction (TRL2) to assess particle origin, size and composition. Postprandial responses were analyzed via ANOVA (SPSS 16.0). Results. Overall, exercise had no effect on PPTG. With exercise, total apoB IAUC decreased 20% in the whole group, and total cholesterol IAUC decreased 30% in the NW group. MetS subjects maintained significantly higher TG than NW subjects over the day (p<0.001). PPTG in MetS women declined mid-day, and remained low for the rest of the study day. In MetS men, however, PPTG rose consistently from breakfast, and then leveled out post-lunch and remained high. TRL particle size (TG:apoB ratio) was 30% lower in MetS women than MetS men. TRL2 apoB-100 and B-48 were twice as high in MetS as in NW subjects, resulting in significantly smaller particles in the MetS group (p=0.01). Conclusions. Although exercise did not have a significant effect on PPTG, there were other potentially cardio-protective effects on apoB and cholesterol levels.
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    The role of fatty acids on endoplasmic reticulum proteostasis in non-alcoholic fatty liver disease
    (Colorado State University. Libraries, 2017) Estrada, Andrea Lee, author; Pagliassotti, Michael, advisor; Miller, Benjamin, committee member; Foster, Michelle, committee member; Frye, Melinda, committee member; Gentile, Christopher, committee member
    Non-alcoholic fatty liver disease (NAFLD) is currently a significant health concern in both adults and children. NAFLD is a disease characterized by accumulation of fat in the liver (steatosis) in the absence of chronic alcohol consumption. In some individuals, steatosis progresses to non-alcoholic steatohepatitis (NASH), which is characterized by steatosis, inflammation, apoptosis and fibrosis, and can ultimately lead to end-stage liver disease. The underlying causes of NAFLD are unclear, although recent evidence has implicated the endoplasmic reticulum (ER) in both the development of steatosis and progression to NASH. Disruption of ER homeostasis or "ER stress" has been observed in the livers and adipose tissue of humans with NAFLD and/or obesity. Downstream signaling events that arise from ER stress include lipid biogenesis, insulin resistance, inflammation, fibrosis and apoptosis, all of which are hallmark features of NAFLD and NASH. Elevated circulating free fatty acids are a characteristic feature of humans with NAFLD and are positively correlated with disease severity. Our laboratory has demonstrated that in rodents, selective elevation of circulating free fatty acids induces ER stress in liver and adipose tissue. In addition, ER stress is exacerbated when the composition of fatty acids includes levels of saturated fats comparable to what is encountered in the typical western diet. We, and others, have also demonstrated that saturated fatty acids provoke ER stress in cultured hepatocytes, pancreatic beta cells, and various other cell types. These data have led to the hypothesis that the composition of fatty acids presented to and stored within the liver is an important determinant of ER homeostasis. ER stress is characterized by an accumulation of unfolded proteins within the lumen of the ER. Therefore, the presence of ER stress in NAFLD implies that there is an imbalance between the protein load presented to the ER, and the ability of the ER to process, degrade and/or remove these proteins. The overall aim of this thesis was to examine how saturated fatty acids disrupt ER homeostasis in the liver. We explored in vivo hepatic protein synthesis in response to acute dietary intervention, namely using diets high saturated fat and sucrose, which promote hepatic steatosis and insulin resistance in rats. We utilized the saturated fat, palmitate in controlled delivery to H4IIE liver hepatocytes in order to assess protein synthesis and components of protein degradation. Lastly, we examined the roles of calcium homeostasis and protein palmitoylation in response to palmitate treatment in H4IIE liver hepatocytes. We found that diets high in saturated fat did not affect hepatic protein synthesis in rats. In agreement with this observation, H4IIE hepatocyte treatment with palmitate did not selectively stimulate cellular protein synthesis. Provision of palmitate increased protein ubiquitination, this result was observed independent of proteasome activity or total cellular protein degradation. Lastly, we found that palmitate-induced ER stress was characterized by a reduction in sarcoendoplasmic reticulum ATPase (SERCA) activity. Our data suggest that saturated fatty acid-induced ER stress is mediated via reduced SERCA activity, and subsequent disruption in protein handling.