Ancient Critters Made Human Hormone System What It Is Today

I bet you weren’t expecting to read about sea cucumbers when clicking on a hormone blog, did you? Surprise! That is what this article is all about...sort of. We’ll be exploring the ancient origins of our endocrine system and its evolutionary history, which just so happens to be traced back to sea cucumbers. Neat, huh? Let’s begin on our journey through time…

Proteins Essential for Reproduction, Metabolism, and Immunity Traced Back to Sea Cucumbers

We love to study evolution and understand how we got to where we are today in terms of our genetics, our technology, our cultural history, etc. Scientists from the Marine Science and Technology College in China decided to pursue a study investigating the evolutionary history of our endocrine (hormone) system.

They found that a critical set of proteins that aid in hormone regulation and are necessary for many essential functions in humans and other vertebrates have origins that can be traced back to more primitive creatures: sea cucumbers. Who would have thought?

The group of proteins that they focused on is part of a system called the kisspeptin system. The kisspeptin system controls hormones released by the human body's three main endocrine glands: the hypothalamus, the pituitary gland, and the sex organs of both men (testicles) and women (ovaries). These three endocrine glands regulate significant processes, including reproduction, the immune system, metabolism, and more. Let’s delve into these organs a bit further…

The Basics of the Endocrine System

The endocrine, or hormone system, is a collection of glands or organs that produce hormones. Besides the three previously mentioned, other glands are involved, including the thyroid gland and adrenal glands. The word endocrine is derived from the Greek words “endo,” which means “within,” and “crinis” which means to secrete. A gland selectively uptakes materials from the blood, processes them, and secretes a finished biochemical product (hormone, protein, enzyme) for use in other body areas. Our endocrine system is so important because it acts on almost every organ and cell in our bodies.

Each type of hormone, such as growth hormone or estrogen, circulates through the bloodstream to targeted organs and tissues. Once the hormone reaches its destination, it will begin a chain reaction within the cell, such as the production of sperm or the breakdown of fat for energy use. Hormones are what keep our bodies running efficiently or running at all.

Hypothalamus: The hypothalamus is a small section in the brain's center with the central role of keeping the body and/or endocrine system in homeostasis (or balance) as much as possible. Quite the job!

The hypothalamus is the connector between the endocrine system and the nervous system. Because of this connection, it plays a part in body temperature, appetite/hunger, emotions, sleep, blood pressure, the balance of bodily fluids, etc.

As different parts of the body send signals to the brain, they tell the hypothalamus about any unbalanced factors that need to be fixed. For example, if the internal temperature is too high, the hypothalamus tells the body to start sweating.

Pituitary Gland: The pituitary gland sits underneath the brain, at the base of the skull in a bony hollow, connected to the hypothalamus, and is considered the “master gland.” Even though it is the “master gland,” which regulates several vital functions and controls the activity of other glands, it is only the size of a pea. The anterior portion is connected to the brain by blood vessels, and the posterior portion is actually a part of the brain and secretes hormones directly into the bloodstream.

Most of the time, the hypothalamus acts on the pituitary gland first and stimulates it to release the hormones that the body needs, but not with every hormone.

The pituitary gland secretes a variety of hormones, including prolactin (which induces milk production in the breasts), growth hormone (which regulates growth, metabolism, and body composition), luteinizing hormone (LH), and follicle-stimulating hormone (FSH – for sex hormone production and other activities in the sex organs) and thyroid-stimulating hormone (stimulates the thyroid gland to secrete thyroid hormones).

Sex Organs – The sex organs comprise the testicles in men and the ovaries in women. They both can secrete their hormones, such as testosterone and estrogen. The secretion of these hormones stimulates processes such as puberty, egg maturation, and sperm production.

Evolutionary Origins of Kisspeptin Proteins

Now that you know more about the endocrine system and the central trio composing the kisspeptin system (hypothalamus, pituitary gland, and sex organs), we can delve into their evolutionary origins.

Lead author, Tianming Wang, stated, “The origins of these proteins have previously been traced to straightforward creatures with spinal cords, but it hadn’t been traced back any further. This raises an important question: does the kisspeptin system have an ancient evolutionary origin, or did it first emerge in animals with spinal cords?”

Wang and his team wanted to answer this question. To do so, they looked for kisspeptin system genes in the sea cucumber. Sea cucumbers are straightforward creatures that have no spinal cord. The scientists could identify equivalents of the kisspeptin genes in the squishy little creatures.

Next on the scientist’s agenda was administering kisspeptin-like cucumber proteins into mammal cells to see what would happen. This caused the mammal cells to secrete calcium, similar to how human versions of the protein would behave.

These sea cucumber proteins were able to interact with receptors in human cells as well. This finding suggests that not much has changed in these proteins over years of evolution.

The scientist’s final phase of experiments consisted of activating or blocking the signaling system in sea cucumbers. By blocking these proteins from being produced, it became clear that they are critical for such vital functions as reproduction and metabolism in sea cucumbers.

Endocrine System Predates Evolution of Spinal Cord

The senior author of the study, Naiming Zhou, says that their experiments suggest that the kisspeptin system actually predates the evolution of the spinal cord in animals and would also be present in other animals that are closely related to the sea cucumber.

Zhou states, “Our findings indicate the existence of a kisspeptin signaling system in a very simple organism lacking a spinal cord. They provide new evidence to support the ancient evolutionary origin of the physiological functions in vertebrates controlled by the kisspeptin system.”

There you have it, folks. Our hormones and endocrine system can be traced back to primitive sea creatures. Fascinating, indeed. Continue to follow our blog for more exciting and up-to-date hormone news!

Reference

Science Magazine

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