Possible Role of the Hypothalamic Melanocortin System to Induce Satiety by High Protein/low Carbohydrate Diets

The percentage of American adults, aged 20 years and older, who are overweight or obese continues to increase. High protein diets have been successful as weight reduction strategies, in part, because subjects report feeling more satiated and subsequently eat less. These diets are also reported to improve other clinical markers associated with obesity and metabolic syndrome such as insulin sensitivity, blood lipid profiles and waist circumference. The goal of the present research was to first characterize neuropeptide expression in the mediobasal hypothalamus (MBH) in animals fed large amounts of dietary protein. The neuropeptides profiled were those previously demonstrated to affect feeding behavior, either by reducing or inducing food intake. Results from this first study lead to our hypothesis that the greater satiety when a high protein/low carbohydrate diet is consumed is influenced, in part, by an increase in the activity of the melanocortin system, specifically the neuropeptide alpha-melanocyte stimulating hormone (alphaMSH) within the MBH. We then evaluated some characteristics of high protein diets that might induce these changes in neuropeptides. Soy protein was more effective than casein in reducing food intake, though no clear association between plasma amino acid levels and food intake were apparent. Finally, we sought to establish a causal association between increased melanocortin activity in the MBH and the reduction in food intake of high protein diets by evaluating the affects of a competitive MC4 receptor agonist (MTII) or antagonist (SHU9119). The effects of the agents were greater in the control diet and antagonism of the receptor returned the food intake of the high protein diet to the level of standard protein diet, while the agonist induced the same degree of decreased food intake of standard protein diet observed in the high protein diet fed animals. Together, these results support increased activity of the melanocortin system mediating the enhanced satiety experienced by those eating high protein/low carbohydrate diets.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Nutritional Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Guest, Dolores Doane

Contributors dc:contributor

• Kelly A. Tappenden
• J. Lee Beverly

• Health Sciences, Nutrition

Language dc:language

eng

Identifier

(MiAaPQ)AAI3362800

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/84962