title: High-fat diet decreases tyrosine hydroxylase mRNA expression irrespective of obesity susceptibility in mice.
abstract: Tyrosine hydroxylase is the rate-limiting enzyme in the synthesis of dopamine, a key neurotransmitter in the regulation of food intake. This study examined tyrosine hydroxylase mRNA expression in obese mice fed a high-fat diet. After 8 week feeding of high-fat diet mice were classified as diet-induced obese and obese-resistant according to body weight gain. They were then placed on different dietary interventions including a high-fat diet, a low-fat diet and an energy-restricted high-fat diet for six weeks. The control group was fed a low-fat diet. The results revealed that tyrosine hydroxylase mRNA expression was significantly decreased in the ventral tegmental area (VTA), ventromedial hypothalamic nucleus (VMH), and substantia nigra (SN) of the high-fat diet-induced obese (-29%, -26% and -26%) and obese-resistant mice (-21%, -24% and -18%) compared to controls. After switching the diet from high to low-fat diet tyrosine hydroxylase mRNA was increased in the VTA, VMH, and SN of the diet-induced obese mice and in the VMH, and SN of the obese-resistant mice. Energy restriction, even with high-fat feeding, reduced tyrosine hydroxylase mRNA expression in the VTA, VMH, and SN compared to controls. In addition, tyrosine hydroxylase mRNA expression in the VTA, VMH, and SN showed a significant negative correlation with plasma leptin levels. This study suggests that the up- or down-regulation of tyrosine hydroxylase mRNA expression in the VTA, VMH, and SN is mainly due to the intake of macronutrient type rather than body weight.
authors.affiliation: Institute of Biochemistry and Molecular Biology, Lanzhou University, PR China; Centre for Translational Neuroscience, School of Health Sciences, University of Wollongong, NSW2522, Australia.
authors.forename: Yulin
authors.initials: Y
authors.lastname: Li
authors.affiliation: Centre for Translational Neuroscience, School of Health Sciences, University of Wollongong, NSW2522, Australia.
authors.forename: Timothy
authors.initials: T
authors.lastname: South
authors.affiliation: Centre for Translational Neuroscience, School of Health Sciences, University of Wollongong, NSW2522, Australia.
authors.forename: Mei
authors.initials: M
authors.lastname: Han
authors.affiliation: Centre for Translational Neuroscience, School of Health Sciences, University of Wollongong, NSW2522, Australia.
authors.forename: Jiezhong
authors.initials: J
authors.lastname: Chen
authors.affiliation: Institute of Biochemistry and Molecular Biology, Lanzhou University, PR China. Electronic address: wangrui@lzu.edu.cn.
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
authors.affiliation: Centre for Translational Neuroscience, School of Health Sciences, University of Wollongong, NSW2522, Australia. Electronic address: xhuang@uow.edu.au.
authors.forename: Xu-Feng
authors.initials: XF
authors.lastname: Huang
mesh_terms: D052438:Adipocytes, White; D000818:Animals; D001823:Body Composition; D001835:Body Weight / Q000502:physiology; D001921:Brain / Q000378:metabolism*; D004032:Diet; D004041:Dietary Fats / Q000008:administration & dosage*; D015536:Down-Regulation; D002149:Energy Intake; D020022:Genetic Predisposition to Disease; D007328:Insulin / Q000097:blood; D020738:Leptin / Q000097:blood; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009765:Obesity / Q000178:diet therapy / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013378:Substantia Nigra / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics / Q000378:metabolism*; D017557:Ventral Tegmental Area / Q000378:metabolism; D014697:Ventromedial Hypothalamic Nucleus / Q000378:metabolism
chemical_list: D004041:Dietary Fats; D007328:Insulin; D020738:Leptin; D012333:RNA, Messenger; D014446:Tyrosine 3-Monooxygenase