Ghrelin; The "Hunger Hormone" Paradox

Ghrelin; The “Hunger Hormone” Paradox

Ghrelin concentrations in blood are reduced in obese humans compared to lean control subjects, but whether this is cause or effect is not defined. Patients with anorexia nervosa have higher than normal plasma ghrelin levels, which decrease if weight gain occurs.

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Ghrelin

Ghrelin is synthesized as a preprohormone, then proteolytically processed to yield a 28-amino acid peptide.

The predominant source of circulating ghrelin is the gastrointestinal tract, primarily from the stomach

Physiologic Effects of Ghrelin

two major biologic activites

Stimulation of growth hormone secretion:

Regulation of energy balance: In both rodents and humans, ghrelin functions to increase hunger though its action on hypothalamic feeding centers.

Ghrelin also appears to suppress fat utilization in adipose tissue, which is somewhat paradoxical considering that growth hormone has the opposite effect. Overall, ghrelin seems to be one of several hormonal signals that communicates the state of energy balance in the body to the brain.

ghrelin include stimulating gastric emptying

Blood concentrations of ghrelin are lowest shortly after consumption of a meal, then rise during the fast just prior to the next meal.

immunization of rats against ghrelin resulted in decreased weight gain and adiposity relative control rats

a comprehensive understanding of, for example, short term control of secretion from the stomach, is lacking.

Ghrelin concentrations in blood are reduced in obese humans compared to lean control subjects, but whether this is cause or effect is not defined. Patients with anorexia nervosa have higher than normal plasma ghrelin levels, which decrease if weight gain occurs.

Prader-Willi syndrome is another disorder relevant to ghrelin science. Affected patients develop extreme obesity associated with uncontrollable and voracious appetite. The plasma ghrelin levels are exceptionally high in comparison to patients similarly obese due to other causes. Prader-Willi syndrome is clearly a complex disease with many defects; it may be that excessive ghrelin production contributes to the appetite and obesity components. Read more at www.vivo.colostate.edu

 

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