title: Altered sympathetic activity during development of diet-induced obesity in rat.
abstract: Sprague-Dawley rats developed diet-induced obesity (DIO) after 3 mo on a high-fat, high-sucrose diet (DIO diet), with associated increases in total body and interscapular brown adipose tissue (IBAT) lipid content. After 7 days on the DIO diet, rats had increased levels of tyrosine hydroxylase (TH; 34%), norepinephrine (NE; 34%), and NE turnover (94%; estimated by alpha-methyl-p-tyrosine inhibition of TH) in their IBAT compared with chow-fed controls. After 3 mo on the DIO diet, NE levels and/or turnover were reduced by 27-50% in aortas, hearts, and pancreata in obese rats. While IBAT NE turnover was normal, TH inhibition failed to increase the lipid content of IBAT in obese rats as it did in controls, suggesting a postsynaptic defect in basal NE-stimulated lipolysis in this thermogenically active tissue. When obese rats were switched from the DIO diet to rat chow for 3 days, NE levels remained depressed in their hearts (25%) and aortas (14%) but were increased by 36-45% in IBAT, pancreata, and white adipose tissue. NE turnover rates and/or constants were increased by 37-110% in hearts, aortas, pancreata, and IBAT of these obese rats while there were increased IBAT TH (20%) and dopamine-beta-hydroxylase (87%) activities compared with chow-fed controls. Therefore, sympathetic activity varied markedly as a function of both dietary composition and relative body weight during the development of DIO.
mesh_terms: D000273:Adipose Tissue / Q000503:physiopathology; D002001:Adipose Tissue, Brown / Q000503:physiopathology; D000818:Animals; D001823:Body Composition; D001835:Body Weight; D004040:Dietary Carbohydrates; D002149:Energy Intake; D004837:Epinephrine / Q000378:metabolism; D007700:Kinetics; D008297:Male; D009638:Norepinephrine / Q000378:metabolism; D009765:Obesity / Q000503:physiopathology*; D009928:Organ Specificity; D051381:Rats; D011919:Rats, Inbred Strains; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D004040:Dietary Carbohydrates; D014446:Tyrosine 3-Monooxygenase; D009638:Norepinephrine; D004837:Epinephrine