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Role of fat amount and type in ameliorating diet-induced obesity: insights at the level of hypothalamic arcuate nucleus leptin receptor, neuropeptide Y and pro-opiomelanocortin mRNA expression

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Aims: 

Dietary fatty acid profile, independent of caloric percent of fat, is a major regulator of body adiposity. This study examined the effects of dietary fat amount and types on fat storage and hypothalamic gene expression in the mouse model of chronic diet-induced obesity. Methods: 

The dietary interventions were in twofold: (1) the obesity was induced by a 13-week obesogenic fat diet compared with a low-fat (LF) diet, and (2) the reversibility was tested by using high n-3 polyunsaturated fat (PUFA) and LF diets. Fifty-four C57Bl/6 mice were fed a high-fat (59% in kcal) diet for 13 weeks and then classified as diet-induced obese (DIO) or diet-resistant (DR) mice according to upper and lower tertiles of body weight gain. The DIO mice were then subdivided into three groups for a 6-week secondary dietary intervention. Two of the groups were switched to either a high n-3 PUFA (DIO-n3) or a low-fat (10% in kcal, DIO-LF) diet, whereas the third (controls) and DR mice continued on the initial high-fat diet. Food efficiency was calculated as weekly body weight gain per gram of food intake. Results: 

After switching the DIO mice to the n-3 PUFA or LF diet, their body weights were reduced to the level of the DR and LF mice. The food efficiencies were, from the highest to lowest, in the order: DIO > LF > DR >  DIO-LF > DIO-n3. Using quantitative in situ hybridization, we found that the DIO mice had higher levels of leptin receptor (LR, +290%, p < 0.005) and neuropeptide Y (NPY, +25%, p < 0.05) mRNA expression in the hypothalamic arcuate nucleus (Arc) than the DR mice, whereas the level of pro-opiomelanocortin (POMC) mRNA expression was significantly reduced (−45%, p < 0.01). All effects that were essentially returned to DR levels by the change to the n-3 PUFA diet and, with the exception of a failure to normalize Arc NPY mRNA levels, by the change to LF diet. Conclusions: 

Taken together, the present results show that both change in level and quality of dietary fat can potently alter hypothalamic neuropeptide expression and result in effective amelioration of diet-induced obesity. Interestingly, the n-3 PUFA diet when fed to already obese mice produced a pattern of hypothalamic gene expression similar to that in obesity resistant (DR) mice. It remains to be determined if the effects of n-3 fatty acids on brain neuropeptide gene expression are direct or indirect.
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Keywords: leptin receptor; mRNA expression; n-3 polyunsaturated fat; neuropeptide Y; obesity; pro-opiomelanocortin

Document Type: Research Article

Affiliations: Molecular Neurobiology Laboratory, Smart Food Center, Department of Biomedical Science, University of Wollongong, Australia

Publication date: 01 January 2004

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