Ghrelin is mostly known as the hunger hormone, but it has many more
functions than this alone.
Ghrelin is a peptide hormone primarily produced by the stomach. Ghrelin
is secreted by the stomach when it is empty and increases your appetite,
sending a message to your brain that you need to eat. This message is sent
through your bloodstream or signals via the vagus nerve to your brain.
It has been said that too much ghrelin makes your body crave fatty and
sugary foods. In saying this, Dr. Mauro Di Pasquale, mentions a study where low
carb, high fat intake reduced ghrelin levels, and as such decreased appetite
and fat formation. He says that this is one of the ways that the body limits
fat formation on a high fat diet.
Things that can increase ghrelin levels include:
· Lack of sleep
· Fasting
· Chronic stress
Ghrelin signaling increases food intake, fat storage, and reduces
thermogenesis and reduces energy expenditure. So, you want to control ghrelin
levels as much as possible if on a fat loss diet or even to maintain your
current body weight.
How can you control ghrelin levels? Get enough sleep, ensure optimal
amounts of protein, increase muscle mass, avoid excess sugar, eat regular meals
/ don’t fast for too long, and use refeed meals strategically. Refeed meals
will ensure you aren’t low calorie for too long and will help increase leptin
levels.
The major biological functions of
ghrelin include:
· the secretion of growth hormone,
· the stimulation of appetite and food intake,
· the modulation of gastric acid secretion and
motility,
· and the modulation of the endocrine and exocrine
pancreatic secretions.
Ghrelin also exerts wide physiological actions throughout the body
including: inflammatory functions, glucose homeostasis, reproductive functions,
cardiovascular function, and bone formation.
The clinical applications of
ghrelin have been investigated in both eating disorders and muscle wasting
conditions, including obesity, anorexia, cachexia, and sarcopenia (muscle
wasting due to aging).
“Ghrelin can indirectly increase
muscle mass by increasing food intake and activating the GH/Insulin-like growth
factor-1 (IGF-1) axis in cachexic mice”.
Ghrelin has multiple beneficial
effects on cardiovascular functions, thereby improving cardiovascular disease
risk. Ghrelin improves the survival prognosis of myocardial infarction by
reducing sympathetic nerve activity. “Overall, ghrelin treatment may reduce
cardiac sympathetic nerve activity (CSNA) inflammation and oxidative stress in
the heart, and induce angiogenesis. More studies are needed to further assess
whether ghrelin is beneficial for treating heart diseases.” They are looking
into the usefulness of ghrelin analogues to find out more about any potential benefits.
Ghrelin exerts many
anti-inflammatory actions in inflammatory bowel disease, pancreatitis, sepsis,
arthritis, and diabetic nephropathy.
“Several synthetic ghrelin
mimetics are being pursued in clinical trials for diverse indications. Three
compounds are currently in development. Macimorelin is in clinical trials for
the diagnosis of GH deficiency. A second compound, anamorelin, is in
clinical trials for the treatment of cancer cachexia. A third compound,
relamorelin (also known as RM-131) is currently in phase II clinical trials and
is being developed for treatment of diabetic gastroparesis and other
gastrointestinal (GI) disorders.”
A concern with ghrelin though is
its link to cancer development and progression. “Ghrelin and GHS-R have been
detected in many endocrine and non-endocrine tumors (21, 22),
suggesting that the ghrelin/GHS-R axis might be associated with tumor growth
and progression. In pituitary tumors, ghrelin mRNA is detected in
non-functional adenomas, GH- and gonadotropin-producing adenomas and
prolactinomas, with highest GHS-R expression detected in the GH-producing
adenomas”. It has also been linked with breast cancer as well.
References:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3863518/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5819073/
Amino acids and
proteins for the athlete – Dr. Mauro Di Pasquale
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