Ghrelin
hormone is a brain-gut
peptide hormone with
two main physiological actions:
growth hormone secretagogue activity and food
intake inducer. Ghrelin is produced in the gut
and triggers the brain to promote eating. Although its production is prevalently gastric, ghrelin is
widely expressed in several tissues, where it might therefore act as a paracrine
or autocrine factor. Ghrelin is much more than a
simple growth hormone secretagogue. Ghrelin has other activities including stimulation of pituitary hormones
secretion, modulation of food intake and control of energy metabolism,
regulation of gastric and pancreatic activity, and cardiovascular and
hemodynamic activities. In addition, modulation of cartilage and bone
homeostasis, sleep and behavioral influences, and modulation of the immune
system, as well as effects on cell proliferation, are other relevant actions of ghrelin. Thus, ghrelin peptide appears to be an important component of an integrated
multifaceted regulatory system.
Ghrelin levels increase before
meals and decrease after meals.
Ghrelin is a 28 amino acid peptide mainly produced by a subset of stomach cells and also by the hypothalamus, the pituitary, and other tissues. It exerts wide physiological actions throughout the body, including growth hormone secretion, appetite and food intake, gastric secretion and gastrointestinal motility, glucose homeostasis, cardiovascular functions, anti-inflammatory functions, reproductive functions, and bone formation.
Hunger hormone, increasing appetite
Ghrelin is the only known orexigenic (a substance that increases
appetite) hormone. It is involved in mealtime hunger and meal
initiation. Circulating ghrelin levels decrease with feeding and increase
before meals, achieving concentrations sufficient to stimulate hunger and
food intake. Before eating, surges occur before every meal on
various fixed feeding schedules and also among individuals initiating
meals voluntarily without time- or food-related cues.
Ghrelin is thought to be the counterpart of the hormone leptin,
produced by fat tissue. Leptin induces satiation when present at high
levels. Sleep deprivation increases morning plasma concentrations of this
hunger-promoting hormone.
Q. I read the article but please let me know which product
will stimulate my appetite best.
A. Besides marijuana, I am not aware of any potent natural appetite
stimulant.
Where is it found?
Ghrelin, the appetite stimulating hormone, has been identified from
a number of different species including humans, rat, pig, mouse, gerbil,
eel, goldfish, bullfrog and chicken. A peptide with ghrelin-like activity
has also been found in certain plants.
Protein in diet suppresses
ghrelin
Diets high in protein are a good way to keep hunger in check. Protein in
the diet is effective at keeping ghrelin in check, while carbohydrates and
fats don't work that well. Suppression of ghrelin is a way to lose
appetite. Fats suppress ghrelin quite poorly. Proteins suppress ghrelin
quite well. Carbohydrates suprress ghrelin well at first, but levels
rebound later, rising to an even higher level. Carbohydrates eventually
make people even hungrier than before they had eaten.
Ghrelin makes you feel good
Tests on rats show that the appetite hormone ghrelin acts on
pleasure receptors in the brain. In mice and rats it triggers the
same neurons as delicious food, sexual experience, and many recreational
drugs; that is, neurons that provide the sensation of pleasure and the
expectation of reward. "These neurons produce dopamine and are located in
a region of the brain known as the ventral tegmental area (VTA). Horvath's
team found that ghrelin, itself only discovered in the last decade, acts
on a molecular structure on brain cells called the ghrelin receptor growth
hormone secretagogue 1 receptor or GHSR for short. When ghrelin is infused
into this area of the rats' brains, they eat as hungrily as they did after
being kept hungry overnight.
Glucomannan supplement and
ghrelin
Immediate and long-term effects of
glucomannan on total
ghrelin and leptin in type 2 diabetes mellitus.
Diabetes Res Clin Pract. 2009. Chearskul S, Kriengsinyos W, Kooptiwut S,
Sangurai S, Onreabroi S.
Department of Physiology, Faculty of Medicine Siriraj Hospital, Mahidol
University, Bangkok 10700, Thailand.
Effects of glucomannan as a supplementary treatment in type 2 diabetes mellitus
were investigated by measuring ghrelin, leptin and insulin responses to OGTT.
Glucomannan enhanced prandial ghrelin reduction when given before glucose load
and impeded the rise of fasting ghrelin after 4-week supplement. Ghrelin-induced
feeding may be attenuated by glucomannan.
Improved appetite
In a small study of frail older women with unexplained weight loss, infusion of
ghrelin led to improvement in appetite and was well tolerated. The study,
conducted at the University of Pennsylvania School of Medicine in Philadelphia,
involved five women aged 70 or older who had lost more than 5 percent of their
body weight without intending to do so, and who met at least two other clinical
criteria for frailty, and five healthy control women. The study findings were
presented at The Endocrine Society's annual meeting in Washington, D.C. in June
2009. Each woman received two three-hour infusions, one week apart, of ghrelin
or inactive solution (saline). Overall, women consumed 51 percent more calories
after receiving the ghrelin infusion than after the saline. With ghrelin, the
women ate more carbohydrates and protein, but the same amount of fat, Dr. Anne
Cappola and colleagues reported.
Research
In the future, the application of compounds targeting the ghrelin
pathway could involve the use of pharmacotherapies of ghrelin agonists,
antagonists or inverse agonists, neutralisation of ghrelin by vaccines and
spiegelmers, desacyl ghrelin analogues.
J Psychiatr Res. 2013. Ghrelin suppresses nocturnal secretion of luteinizing hormone (LH) and thyroid stimulating hormone (TSH) in patients with major depression. Major depression is associated with various endocrine disturbances. Apart from the well-known hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, also the function of the hypothalamic-pituitary-gonadal (HPG) axis and of the hypothalamic-pituitary-thyroid (HPT) axis may be altered compared to healthy subjects. The orexigenic hormone ghrelin is involved in mood regulation and may have antidepressant effects. In addition, it has been shown to suppress secretion of luteinizing hormone (LH) and thyroid stimulating hormone (TSH) in healthy subjects. Ghrelin suppressed nocturnal secretion of LH and TSH in patients with major depression. However, these effects were weaker than previously shown in healthy subjects.
Effect of a high-protein breakfast on the postprandial ghrelin
response
American Journal of Clinical Nutrition
2006.
The most satiating macronutrient appears to be dietary protein. Few
studies have investigated the effects of dietary protein on ghrelin
secretion in humans. This study was designed to investigate whether a
high-protein (HP) breakfast is more satiating than a high-carbohydrate
breakfast (HC) through suppression of postprandial ghrelin concentrations
or through other physiologic processes. Fifteen healthy men were studied in
a single-blind, crossover design. Blood samples and subjective measures of
satiety were assessed frequently for 3 h after the consumption of 2
isocaloric breakfasts that differed in their protein and carbohydrate
content (58% of energy from protein and 14% of energy from
carbohydrate compared with19.3% of energy from protein and 47% of energy
from carbohydrate). Conclusions: The HP breakfast decreased postprandial ghrelin concentrations more strongly over time than did the HC breakfast.
High associations between ghrelin and glucose-dependent insulinotropic
polypeptide and glucagon suggest that stimulation of these peptides may
mediate the postprandial ghrelin response. The HP breakfast also reduced
gastric emptying, probably through increased secretion of cholecystokinin
and glucagon-like peptide 1.
Additional gut hormones
Food intake and bodyweight are regulated by the brainstem, hypothalamus
and reward circuits. These centers integrate cognitive inputs with humoral
and neuronal signals of nutritional status. Gut hormones and enzymes
include pancreatic polypeptide, peptide YY, amylin, glucagon-like
peptide-1, oxyntomodulin, cholecystokinin and ghrelin.
Questions
My brother 49 years old started to get a dialysis on May 5,2007.
Since than he lost almost half of his weight ( from 85 kg to 47 kg). After
each session of this dialysis he could not eat for a day, even he did, he
eat like a baby. To top it up, during his dialysis, his usually weight
lost is in the range of 0.5-3 kg. In the July 2005 issue of the Journal of
the American Society of Nephrology, I learned that hormone ghrelin might
help to boost food intake. I talked to his doctor about it, he said that
he never heard about it and doesn’t have any desire to do any
investigation.
I am not aware of ghrelin hormone being available as a
prescription drug. Would Marinol be helpful to increase
appetite? I am not sure.