Introduction:
Calcitonin is a hormone secreted from the C cells of the thyroid gland. It has a major role in regulating calcium levels in the blood. Researchers have found that calcitonin has a protective effect against cardiovascular disease.
What Is Calcitonin?
Calcitonin is a hormone that regulates blood calcium levels. Hormones are chemical substances that help in the functioning of various body activities. Researchers have not found an answer regarding the varying calcitonin levels, as they do not affect any of the functions in the body.
Functions of calcitonin include
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It stops the activity of the osteoclasts. Osteoclasts are cells that have the action of breaking down the bone. Calcitonin helps stop the activity of bone breakdown and helps stop the release of calcium into the blood.
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It helps decrease calcium reabsorption in the kidney, releasing calcium into the blood. This causes lowered blood calcium levels.
What Is a Calcitonin Gene-Related Peptide?
Calcitonin gene-related peptide (CGRP) belongs to the calcitonin family. It was first introduced in 1982 by Amar et al. It is produced and stored by the nervous system. It is made up of 37 amino acids produced by the splicing of the calcitonin gene (CALCA). There are two types of CGRP present in humans.
They are
- CGRP alpha (CGRP I).
- CGRP beta (CGRP II).
CGRP is primarily synthesized in the dorsal root ganglion, stored in large vesicles of the sensory nerve terminals, and released along with the substance P.
Following neuronal depolarization, calcium-dependent mechanisms help in exocytosis. This helped with the release of CGRP. Their release is linked to the activation of sensory fibers through electrical stimulation or by activation of transient receptor potential ( TRP) channels.
According to a study, transient receptor potential ankyrin 1 (TRPA 1) and transient receptor potential vanilloid 1 (TRPV 1) are channels coexpressed in CGRP-positive fibers. These channels increase the release of CGRP by increasing intracellular calcium levels. These are also responsible for neurogenic vasodilation. It is found in the central and peripheral sensory nervous systems and other brain areas. A study has demonstrated that CGRP is also found in the smooth muscles of the heart and its vasculature.
Functions:
Functions of CGRP include
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It can act as a vasodilator.
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Helps in the transmission of nociception (a process that occurs in both the central and peripheral nervous systems, which helps identify the pain stimulus and help in triggering the defensive mechanism).
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It acts on the cardiovascular system as a chronotrope (affects the heart rate).
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It has a role in ingestion by acting on the autonomic nervous system (ANS).
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It has a role in controlling migraine.
What Are the Effects of CGRP?
CGRP has a role in pain and has effects on the cardiovascular system.
Effects of CGRP as a Vasodilator:
When CGRP is given intravenously, it causes a decrease in blood pressure due to its vasodilator effect. It also has a positive chronotropic effect on humans. It also affects other organ systems due to increased blood flow. CGRP acts directly on the coronary vasculature and affects heart rate and blood pressure.
Effects of CGRP on Cardiovascular Functions:
CGRP has effects on the cardiovascular system.
Hypertension:
This is a condition in which the pressure in the blood vessels is found to be high.
Despite having a vasodilatory effect, CGRP is found more in the plasma of hypertensive patients. Studies have found that exogenous CGRP reduces blood pressure. Another study showed the protective action of CGRP on the pathophysiology and onset of hypertension.
One more study showed that when an individual with hypertension was treated with angiotensin-converting enzyme inhibitors, they increased the density of CGRP innervation and expression. This concept says that CGRP interacts with RAAS to regulate blood pressure.
Another study conducted showed that when there is a loss of CGRP, it may lead to hypertension. It was found that CGRP interacts with other vasoactive mediators to bring about changes. It was found that noradrenaline can influence CGRP release, and the reverse is also possible. This indicates the ability of CGRP to regulate vascular resistance.
A study showed that blocking CGRP nerve transmission by CGRP8-37 showed increased vasoconstriction. This also suggests that exogenous CGRP can inhibit the action of noradrenergic-induced vasoconstriction. Hence, these studies show that CGRP can inhibit the sympathetic nervous system.
These findings suggest that CGRP interacts with many pro-hypertensive systems to counterbalance the diseases associated with the cardiovascular system.
Ischemia:
It is a condition where there is an inadequate supply of blood to the organ or part of the organ. Ischemia is usually seen in the heart. In the case of ischemia, CGRP is produced in response to reduced blood flow. This helps protect against reperfusion injuries. A study has shown increased CGRP expression in plasma in acute myocardial infarction.
Studies had understood that CGRP plays a main role in preconditioning and protection, as they found that when the introduction of CGRP8-37 and TRP V1 antagonists was done, they observed the loss of protection action against ischemia.
Heart Failure:
This condition occurs when the heart fails to pump as much blood as possible. The heart contains CGRP nerves in the coronary arteries, ventricular muscles, and conduction system. Hence, CGRP has an important role in regulating the functions of the heart. The vasodilator effect of CGRP helps decrease afterload and improve heart function.
Another study showed that CGRP increased calcium currents by stimulating adenylyl cyclase. This led to positive inotropy but was not seen in ventricular myocytes. Since CGRP affects the sympathetic nervous system, this also helps protect against heart failure.
Recently, CGRP antagonists and antibodies were used to treat migraine. It was found that there were no side effects related to the cardiovascular system.
Conclusion:
The calcitonin gene-regulating peptide has protective effects on the cardiovascular system. Its effects are seen in pathological conditions such as hypertension, heart failure, and ischemia. CGRP belongs to the calcitonin family. Hence, it becomes important to know about calcitonin, CGRP, and its effects on the cardiovascular system. Knowing this helps you seek the help of a healthcare provider early. Early diagnosis helps in getting effective treatment. This, in turn, helps achieve a good quality of life.
