Effect of high-fat feeding on expression of genes controlling availability of dopamine in mouse hypothalamus.

Objective: Hypothalamic centers integrate external signals of nutrient availability and energy status and initiate responses to maintain homeostasis. Quantifying changes in hypothalamic gene expression in the presence of nutrient excess may identify novel responsive elements.

Methods: Affymetrix Mouse Genome 430 2.0 oligonucleotide microarrays containing 45 102 probe sets were used to interrogate differential expression of genes in dietary-induced obesity model C57BL6 inbred mice fed a high-fat (35% fat; n=8) or standard (4% fat; n=6) diet from 3 to 15 wk of age. Ontologies of regulated genes were examined and expression of selected genes was validated by quantitative real-time polymerase chain reaction.

Results: One thousand two hundred twelve unique gene transcripts showed altered expression on the microarrays. Gene ontology analysis revealed changes in neuropeptide genes responding to leptin, Pomc, Cart, Npy, and Agrp, compatible with a homeostatic response to high-fat intake, although mean weight increased 2.3-fold compared with standard fed mice (P<0.001). Neurotransmitter system ontologies revealed upregulation of five genes controlling availability of dopamine. Changes in Th tyrosine hydroxylase (2.1-fold) and Slc18a2 solute carrier family 18 (vesicular monoamine), member 2 (4.4-fold) controlling synthesis and release, and Slc6a3 solute carrier family 6 (neurotransmitter transporter, dopamine), member 3 (4.8-fold), Snca alpha-synuclein (1.3-fold), and Maoa monoamine oxidase (1.9-fold) limiting availability were confirmed by quantitative real-time polymerase chain reaction.

Conclusion: Expression of five genes involved in availability of dopamine was increased after a high-fat diet. Failure to reduce dopamine availability sufficiently, to counter the feeding reward effect, could contribute to diet-induced obesity in these mice.