Publication Date

2012

Document Type

Thesis

Committee Members

James Lucot (Committee Member), Mariana Morris (Advisor), Mariana Morris (Other), Roberta Pohlman (Committee Member)

Degree Name

Master of Science (MS)

Abstract

Consumption of high levels of fructose produces glucose intolerance, sympathetic nervous system activation, and renal dysfunction. A diet high in fructose may play a role in the worldwide epidemic of obesity and diabetes. The aim of this study was to test the hypothesis that time (light/dark) limited access to fructose influences body fat, metabolic function, and adipose tissue catecholaminergic activity in mice. Male C57BL/6 mice were given standard chow and assigned to one of three groups: Control (n=10, water 24h); FL (n=11, 10% fructose solution during 12h light period); and FD (n=10, 10% fructose solution during 12h dark period). Metabolic parameters measured were body fat (BF, Echo-MRI), adipocyte cell size, and glucose tolerance as well as plasma glucose, adiponectin, insulin, leptin, triglycerides, and cholesterol. Catecholamine levels were measured directly in white adipose tissue (WAT) using high performance liquid chromatography (HPLC) with electrochemical detection. Immunochemistry was used for examining tyrosine hydroxylase (TH) staining in WAT and brainstem. Mice given fructose during the light phase (inactive period for mice) showed evidence for a diabetic like symptoms with prominent changes in adipose tissue fat. Results showed: 1) enhanced increase in BF and increased size of adipocytes in FL; 2) increased plasma insulin and leptin in FL without changes in glucose or glucose tolerance; 3) no change in cholesterol or triglycerides; 4) measurable amounts of norepinephrine (NE), epinephrine (EPI) in WAT without difference among groups; 5) enhanced staining for TH in WAT and brainstem locus coeruleus. The changes in adiposity occurred even though caloric intake was not different among groups. In conclusion, results document that restriction of fructose access to the light period produced pathological effects on metabolic function along with catecholaminergic activation in WAT and brainstem. These data may have clinical implications since the timing of intake may be important in the control of adiposity and the development of metabolic syndrome.

Page Count

56

Department or Program

Department of Pharmacology and Toxicology

Year Degree Awarded

2012

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