Adipocytes, also called lipocytes or fat cells are the energy storage sites in the body. In the light of a growing obesity pandemic and increasing health issues due to weight, it is essential to understand the composition, functions and development of adipocytes and adipose tissues. Here is everything you need to know about adipocytes.
What are Adipocytes?
In simple terms, adipocytes are fat cells that are important for storing energy, performing endocrine functions and use as fuel for the body. They play an important role in the metabolism and homeostasis in the body. They perform many important functions for the body which is why it is important for us to know about the constitution, development and importance of these adipocytes. Adipocytes are generally divided into two different classes. The first one is white adipocytes which are known to store energy in the form of a single lipid drop and are responsible for carrying out important endocrinal functions. The second type is brown adipocytes which also store energy but this energy is divided into multiple lipid drops that are smaller in size and ate specifically used as body fuel or generating body heat which is also known as thermo genesis.
White Adipocytes
The first kind of adipocytes is the white adipocytes. These fat cells are the most abundantly present in the human body. They have a capacity to store energy and have the ability to expand. They also send signals to the brain and other tissues to influence and control feeding behaviour and the process of metabolic homeostasis. These white adipocytes are adapted to store excess nutrients but they also have a tipping point or a limit after which the essential functions start declining and this situation can lead to problems such as obesity, metabolic diseases or even Type 2 Diabetes.
Brown Adipocytes
Brown adipocytes can often be fascinating as these fat cells are present only in mammals. The main function that these brown adipocytes perform is to generate body heat through a process called thermo genesis. The possession of brown fat cells by human bodies has been drawing attention of several nutritionists and therapists to study chances of over nutrition. Active brown adipocyte cells also consume large quantities of different nutrients at the same time such as glucose, amino acids and lipids; and can engage in both anabolic as well as catabolic metabolism simultaneously.
What is an Adipose Tissue?
An adipose tissue, also known as fatty tissue, is a connective tissue that comprises of smaller fat cells, or adipocytes, which are specially adapted to generate and store large drops of fat within a structured network of fibres. The fat which is stored in these adipose tissues is usually derived from dietary fats or from the fat produced in the body. Adipose tissues are found in different parts of the body such as in the intestines and their membranes, deposits in between muscles, around the heart and it is also present in the bone marrow, where it generates a yellow colour in adults, which is called the yellow marrow.
There are two different types of adipose tissues present in mammals, namely White Adipose Tissue and Brown Adipose tissue. White Adipose, like the white adipocyte fat cells, are the most commonly found in human body. It provides the body with the necessary insulation, stores energy for using it in times of starvation or excessive exertion, and also acts as protective pads between organs. These tissues are also responsible for carrying out the process of lipolysis, which happens when hormones bind themselves to adipose cells and further catalyze the hydrolysis of triacylglycerol, in an event of requirement of energy by tissues or muscles. This tissue also plays an important role in providing many vital hormones which in turn aid in the processes like metabolism and other endocrinal system functions. Hormones such as adiponectin, leptin and resistin, which are produced by white adipose tissues generally help in the process of energy metabolism, whereas hormones like plasminogen helps in the prevention of dissolution of blood clots.
Brown adipose tissues on the other hand are more commonly found in new born animals and are responsible for generating heat. Unlike white adipose tissues, the brown adipose actually consumes energy instead of generating it. In case of humans, the presence of brown adipose tissues in the body keeps on decreasing as the person grows in age. However, in animals, especially in those that hibernate such as grizzly bears and black bears, the brown adipose tissue is also present in adult bodies and plays a pivotal role in their survival. This tissue derives its red colour and its heat generating properties from the mitochondria found in these fat cells. In hibernating species, the body experiences a drop in temperature and a decrease in the pace of metabolism when the animal stays dormant during the winter time. In this situation, the brown adipose tissues and cells generate heat in the body by consuming energy to keep the body warm and enable them to be able to emerge from their dormancy period easily, without disturbing important bodily functions that had earlier slowed down during hibernation.
However, the functions and distribution of these tissues are not just different in animals and humans. It also depends on difference in sex. Men usually tend to have more fat accumulated around their waist, while in women; fat generally accumulates more around the hips than the waist. These adipose cells and tissues also play an important role in regulating body fat during the process of weight loss or weight gain. According to a study, a 10 per cent loss in body weight results in the decrease of adipocyte cells by 16 per cent. There is also a change in the metabolism of fatty acids in the body when one works out or tries out a new diet program that alters the size and composition of these adipocyte cells. Metabolic processes are generally deregulated in people who are obese or lose a lot of weight too fast and in response to activities that cause a loss or gain in weight, there is a change in adipose tissues and subsequently, adipocyte cells.