I bet you werent 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. Actually, well 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? Lets 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 key set of proteins that aid in hormone regulation and are necessary for many, many essential functions in humans as well as 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 are part of a system called the kisspeptin system. The kisspeptin system controls hormones that are released by the three main endocrine glands of the human body: the hypothalamus, the pituitary gland and the sex organs of both men (testicles) and women (ovaries). These three endocrine glands regulate major processes including reproduction, the immune system, metabolism and more. Lets 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. There are other glands involved besides the three previously mentioned, 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. Basically, a gland selectively uptakes materials from the blood, processes them and secretes a finished biochemical product (hormone, protein, enzyme) for use in other areas of the body. 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. Basically, hormones is what keeps our bodies running efficiently, or running at all, really.
Hypothalamus: The hypothalamus is a small section in the center of the brain with the main role of keeping the body and/or endocrine system in homeostasis (or balance) as much as possible. Quite the job!
The hypothalamus is basically the connector between the endocrine system and the nervous system. Because of this connection, it plays a part in functions such as body temperature, appetite/hunger, emotions, sleep, blood pressure, balance of bodily fluids, etc. As different parts of the body send signals to the brain, they are telling 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 actually 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, 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 (induces milk production in the breasts), growth hormone (regulates growth, metabolism and body composition), leuteinizing hormone (LH) and follicle-stimulating hormone (FSH for sex hormone production and other activities in the sex organs) and thyroid stimulating hormone (stimulates thyroid gland to secrete thyroid hormones).
Sex Organs The sex organs are comprised of the testicles in men and the ovaries in women. They both are able to secrete their own 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 a bit more about the endocrine system and the major trio composing the kisspeptin system (hypothalamus, pituitary gland and sex organs) we can delve into the evolutionary origins of them.
Lead author, Tianming Wang, stated, The origins of these proteins have previously been traced to very simple creatures with spinal cords, but it hadnt 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 very simple creatures that have no spinal cord. The scientists actually were able to identify equivalents of the kisspeptin genes in the squishy little creatures.
Next on the scientists agenda was to administer kisspeptin-like cucumber proteins into mammal cells to see what would happen. This caused the mammal cells to secrete calcium, which is 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 the course of years of evolution.
The scientists 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 important functions as reproduction and metabolism in the 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 that are controlled by the kisspeptin system.
There you have it, folks. Our hormones and endocrine system can be traced all the way back to primitive sea creatures. Fascinating, indeed. Continue to follow our blog for more interesting and up-to-date hormone news!