High-fat diet decreases tyrosine hydroxylase mRNA expression irrespective of obesity susceptibility in mice
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 (ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¿ 29%, ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¿ 26% and ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¿ 26%) and obese-resistant mice (ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¿ 21%, ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¿ 24% and ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¿ 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.
This record is in the process of being updated. Please contact us for more information.