What is Leptin?
Leptin is a hormone produced by fat cells for the purpose of regulating fat storage in the body.
It is known as the “satiety hormone” because among its many functions, it reduces appetite and triggers the burning of fat deposits.
Leptin was discovered in 1994, and since then scientists have established that this protein has anti-obesity and anti-diabetic properties.
Studies in animals have shown that long-term leptin replacement therapy can correct type 1 and type 2 diabetes as it improves glycaemic control, insulin sensitivity as well as plasma triglycerides.
These encouraging results have spurred hope that indeed leptin therapy could be a potential treatment for diabetes.
What is the connection between leptin and diabetes?
Blood sugar basics
When a person eats any type of food, insulin levels in the body rise. If the food had lots of refined carbohydrates and simple sugars, insulin will be raised to even higher levels and within a short time.
As you may already be aware, insulin is the hormone that regulates blood sugar in the body. It does this by basically transporting this blood sugar to areas in the body where it is needed.
Blood sugar is the fuel for the body, much in the same way gasoline is to a car. So following a meal, insulin will be busy acting as a taxi to ensure that cells that need this “fuel” have adequate supplies.
This is why exercise is very important for the body because it means more cells will require the glucose, especially the muscle cells.
In healthy individuals, insulin will deposit a whopping 60% of blood sugar at the liver so that it is converted to glycogen for storage.
Link between insulin and leptin
Now as a person is eating, insulin will ensure that some of the blood sugar also reaches the adipose or fatty tissue which is mostly made up of fatty cells.
These cells then become active and they in turn produce the hormone leptin which enters the blood stream and starts travelling up to the brain.
As you eat more food, more insulin is made, and more leptin is produced.
Leptin’s functions are the opposite of the “hunger hormone” ghrelin. Once the leptin levels in the blood get high enough, it is a signal to the brain that you are full.
The high amounts of leptin will also “tell” the pancreas to cease the beta cell production of insulin because no more blood sugar is required.
As long as the amount of food consumed matches the physical activity level of a person, blood sugar will always have a place to go; insulin will be rising and falling in a controlled fashion, and so does leptin.
The Communication Problem
When there is too much blood sugar in the body, and yet the cells don’t need it any more, insulin will induce the production of triglycerides, which may end up becoming stored fat.
This is how people gain weight. Unfortunately, as the levels of triglycerides increase in the blood, they interfere with the manner in which leptin travels to the brain.
The brain does not receive a full signal in due time, so the person will most likely end up eating more than is necessary, a problem called leptin resistance.
This will encourage formation of even more triglycerides, increasing the possibility of a person gaining more weight. At this point, eating less and exercising can improve the situation.
However, if this problem persists, the levels of blood sugar in the body will keep rising, insulin resistance will worsen, leptin resistance will also worsen, blood pressure will go up, cholesterol levels will increase and triglyceride levels will go up too.
Eventually, type 2 diabetes sets in, along with the possibility of other serious conditions occurring such as heart and kidney disease. This is how leptin and diabetes are related.
As mentioned at the beginning of the article, studies have shown that leptin treatment can reverse hyperglycemia (high blood sugar) in animal models of poorly regulated type 1 (T1D) and type 2 (T2D) diabetes.
The researchers discovered that fasted rats that had poorly controlled T1D and T2D diabetes had lower levels of plasma insulin and leptin.
They were also found to have high levels of plasma corticosterone which is a stress hormone that raises the amounts of blood glucose.
In the T1D rats, they found out that stabilizing plasma leptin levels through a leptin infusion caused a significant drop in plasma glucose concentrations, perhaps as a result of the liver slowing down in converting lactate and amino acids into glucose.
Apparently, leptin achieved this by inhibiting a vital neuroendocrine pathway called the hypothalamic-pituitary-adrenal axis.
This axis consists of 3 major glands which regulate many important body processes, including metabolism, fat storage and reactions to stress.
This is why leptin therapy offers great potential in reducing and reversing uncontrolled high blood sugar in patients with type 1 and type 2 diabetes.