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Published on: November 4, 2011
Decreased intake of sucrose solutions in orexin knockout mice
Eiko Matsuo1, Ayako Mochizuki, Kiyomi Nakayama
1Department of Oral Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
Abstract:
Orexins are synthesized by lateral hypothalamic neurons and are suggested to be implicated in feeding behavior. Recent studies have shown that intracerebroventricular administration of orexin-A increases intake of sweet-tasting solution. Effects of suppressing the orexin system on consumption of sweet-tasting solution and sensory processing with sweet taste inputs, however, have yet to be examined. We examined the effects of orexin deficiency on sucrose solution intake, locomotor activity, and preference for sweet solution using male orexin knockout (OxKO) and littermate wild-type (WT) mice. In the dark and over 24-h periods, OxKO mice showed significantly less sucrose intake and lower locomotor activity than WT mice without alteration in food intake whereas preferences for 100 mM sucrose were not different between the genotypes. Moreover, sucrose intake of OxKO mice was significantly less than sucrose intake of a subgroup of WT mice with similar locomotor activity compared to that of OxKO mice. These results suggest that factors other than the lower energy expenditure due to lower locomotor activity are likely responsible for the decreased sucrose intake of OxKO mice. Orexin deficiency may lower the satiety threshold resulting in reduced sucrose intake, without altering food intake.
Insights
Orexin deficiency in mice significantly reduced sweet solution intake and activity levels. This suggests orexin may influence satiety, not just energy expenditure, impacting feeding behavior.
Area of Science:
- Neuroscience
- Behavioral Endocrinology
- Metabolic Research
Background:
- Orexins, neuropeptides from the lateral hypothalamus, are linked to feeding behaviors.
- Previous studies indicate orexin-A administration boosts sweet solution intake.
- The impact of orexin system suppression on sweet taste consumption remains unexplored.
Purpose of the Study:
- To investigate the role of orexin deficiency in regulating sweet (sucrose) solution intake.
- To assess the effects of orexin deficiency on locomotor activity and sweet preference.
- To determine if reduced activity or other factors contribute to altered sucrose consumption.
Main Methods:
- Utilized male orexin knockout (OxKO) and wild-type (WT) littermate mice.
- Measured sucrose solution intake, food intake, locomotor activity, and sweet preference over 24-hour periods.
- Compared OxKO mice to WT mice and a subgroup of WT mice with matched activity levels.
Main Results:
- OxKO mice exhibited significantly lower sucrose intake and locomotor activity compared to WT mice.
- No significant differences in overall food intake or preference for 100 mM sucrose were observed between genotypes.
- Reduced sucrose intake in OxKO mice persisted even when compared to WT mice with similar activity levels.
Conclusions:
- Orexin deficiency decreases sucrose intake independently of reduced locomotor activity or overall food consumption.
- The findings suggest orexin deficiency may lower the satiety threshold, leading to reduced intake of palatable solutions.
- Orexin's role extends beyond energy expenditure to modulating appetite and taste-related feeding behaviors.
