What is Leptin?
Thank goodness for fat mice. If it wasn’t for an observant Scientist, the link between Obesity, Diabetes & Leptin may have never been discovered. (1)
At a Glance
What is Leptin?
Leptin is a protein hormone that plays a critical role in the regulation of energy in the body. Leptin acts on specific cell receptors in the hypothalamus portion of the brain that helps to regulate your hunger, thirst, food intake and metabolism. Modern science has now proven that it is the absence of functional Leptin, or its receptors, in the hypothalamus region of the brain, that leads to increased food intake as well as reduced energy expenditure. (2)
The above gif shows an image of the human skull with the brain inside. Where you can see that little red dot is the location of the hypothalamus, the portion of the brain that helps to regulate your hunger.
Images are generated by Life Science Databases(LSDB). – from Anatomography, website maintained by Life Science Databases(LSDB).You can get this image through URL below. 次のアドレスからこのファイルで使用している画像を取得できますURL., CC BY-SA 2.1 jp, https://commons.wikimedia.org/w/index.php?curid=7848292
How Was Leptin Discovered?
The year was 1994 and a molecular geneticist name Jeffrey Friedman wanted to discover just how one single gene could have such a huge effect on an animal’s body weight and desire to eat.
Freidman had learned of a strain of mice discovered in 1950, that not only weighed three times more than their counterparts, but had insatiable appetites. The Jackson Laboratory, located in Sacramento California USA, named this strain of mice obese or ob for short.
In the 1980’s, when Friedman first began his research, he was using a then new method called positional cloning. Positional cloning is a laboratory technique used to locate the position of a particular gene along the chromosome that correlates with a specific disease. It is a technique that is particularly useful when little or no information is available about the biochemical basis of the disease you are researching.
It took eight long years, but finally in 1994 Freidman had cloned the ob gene in mice and its homolog in humans. Freidman had discovered that the LEP gene provides instructions for producing the hormone called Leptin. (4)
Then in 1995, after purifying the gene product, Freidman called the hormone Leptin. He chose the title Leptin from the Greek word “Leptos” meaning thin in reference to the fact that the normal allele of the ob gene keeps you thin. (3)
Other names for the LEP gene include (2)
- LEP_HUMAN
- LEPD
- leptin (murine obesity homolog)
- leptin (obesity homolog, mouse)
- OB
- obese protein
- obese, mouse, homolog of
- obesity factor
- OBS
The above names are interchangeable but refer to the same thing ie the LEP gene.
If you are interested you can read this very interesting interview with Jeffrey Friedman about what lead him to discover Leptin here.
The above image is an ideogram of the human chromosome. The chromosome outlined by the red box is Chromosome 7. It is here that Leptin is coded for by the ob gene.
The above image is a closer look at the Human Chromosome 7. What you are looking at is a horizontal version of the previous ideogram above this one. Where you can see the yellow arrow pointing (the white area) is the q32.1 position on Chromosome 7 ie 7q32.1. This is the location of the LEP gene in which a genetic mutation can cause a Leptin deficiency, leading to an absence of Leptin and excessive hunger.
What Does Leptin do in the Body?
As we learned previously, the hormone leptin is controlled by the hypothalamus region of the brain. The primary function of Leptin, is to regulate the amount of adipose tissue present in your body. This is done by mediating our hunger, and how we use the food we ingest to produce, use and conserve energy in order to ensure our survival.
A few of the secondary functions of leptin are:
- modulate energy expenditure within many bodily functions
- during pregnancy leptin aids in the modulation between the metabolisms of both the mother and child
- leptin is an activator of immune cells
- during puberty leptin aids with growth factors for advancement in development from adolescences into adulthood
The major role of Leptin in the body is to regulate your hunger.
Where is Leptin Produced?
Leptin is primarily produced by white adipose cells and secondly enterocyte cells in the small intestine. Other locations in the body where Leptin may also be produced are brown adipose tissue (BAT), the ovaries in women, skeletal muscle, the fundic glands in the stomach, the placenta in pregnant females, bone marrow, the pituitary gland and the liver.
Your fat cells are the primary producers of Leptin.
How Does Leptin Work?
Leptin attaches (binds) to and activates a protein called the leptin receptor, fitting into the receptor like a key into a lock. The leptin receptor protein is found on the surface of cells in many organs and tissues of the body including a part of the brain called the hypothalamus. The hypothalamus controls hunger and thirst as well as other functions such as sleep, moods, and body temperature. It also regulates the release of many hormones that have functions throughout the body. In the hypothalamus, the binding of leptin to its receptor triggers a series of chemical signals that affect hunger and help produce a feeling of fullness (satiety).
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