Essay on "Adipose Cells"

Essay 5 pages (1574 words) Sources: 10 Style: Harvard

[EXCERPT] . . . .

Adipose Cells

The medical and the biological sciences have always been fascinated with the study of cells, and for a good reason since within them one can find many clues to the development of the human body. Adipose cells have become quite "popular," especially for medical and clinical researchers, their popularity not necessarily being a positive one since a breakdown within the adipose system can lead to obesity, eating disorders, diabetes and heart failure.

Adipose tissue represents one of the most complex, highly active and essential parts of the metabolism and also a critical endocrine organ. "Adipose tissue is a highly specialized connective tissue found in two forms: white and brown. Both of these forms serve to insulate and cushion the body, but they each have specialized function as well." Brown adipose tissue, named like this due to its color, is more vascularized and its main property is to serve as a heat source in the body. As the organism age, the brown adipose tissue is gradually replaced by white adipose tissue, whose role is to supply energy for the well functioning of the body (Gomillion & Burg 2006, p. 6053).

Adipocytes alongside tissue matrix, nerves, stromal vascular cells and immune cells create the lucrative components of this integrated unit. Beside its important endocrine function, adipose tissue responds to the signals received from the hormonal and nervous systems; the secretion factors include: "leptin, other cytokines, adiponectin, complement components, plasminogen activator inhibitor-1, proteins of the renin-angiotensin system, and resistin." Another important role of adipose cells is in the regulation of the metabolism of sex steroids and glucocorticoids, but the major part of the endocrine purpose of adipose tissue is emphasized by the adverse metabolic consequences of both adipose tissue excess and deficiency (Kershaw & Flier 2004).

Moving on, it is important to analyze shortly but concisely the structure of a white adipose cell, in order to better understand how it functions in relation to the multitude of working networks within each organism.

Almost 60 to 85% of the weight of white adipose tissue is lipid, from which 90 to 99% is triglyceride. Fatty acids, diglyceride, cholesterol, phospholipid and small particles of cholesterol ester and monoglyceride are also present. In this intricate part of any living organism there are six fatty acids that make up 90% of the total: myristic, plamitic, palmitoleic, stearic, oleic and linoleic. Based on every individual's diet these components can vary in percentage and thus in their role. The residual mass of white adipose tissue is made up of 5 to 30% water and 2 to 3% protein. While white adipose tissue is not as vascularized as the brown one, each adipocyte is in contact with at least one capillary, which will supply the metabolism with enough blood, every action taking place in the thin rim of cytoplasm around the lipid droplet. Again, the blood flow varies based upon body weight and nutritional state (long periods of fasting or dieting present an increased flow) (Albright & Stern 1998).

There are various conditions related to these functions of the adipose cells, and researchers around the world have tried to come up with reasons and explanations why these cells seize to work normally. One of the most common conditions is obesity, which viewed broadly would make one think it's related to bad eating habits, lack of fitness activities or perhaps an hormonal imbalance; taken on a microscopically point-of-view, many answers lay in the adipose cells and the many theories developed from their role and structure. The following section discusses obesity and the other disorders closely associated to the irregular growth and distribution of adipose cells.

Wellen and Hotamisligil (2003 p. 1785) state that, obesity and the associated metabolic pathologies affect over 50% of the adult population, and that "these conditions are associated with a chronic inflammatory response characterized by abnormal cytokine production, increased acute-phase reactants, and activation of inflammatory signaling pathways." During the process of the disease there are many factors that trigger the inflammatory response and they reside mostly in the adipose tissue, but critical questions like metabolic deregulations, and the underlying molecular mechanisms remain unanswered.

Other scientists have announced that the answer to so many obesity problems could be found in the adipose tissue cellularity and the ability to calculate fat cell number and weight. These conclusions were then confirmed by the experiments of Sims et al., which demonstrated that adipose mass increase is directly connected to an increase in fat cell weight. This increase was also shown to be more rapid and more lasting in subjects with a higher number of fat cells (Bosello & al. 1980). These types of discoveries are indeed groundbreaking and can lead to better cures and ideas for people with treatment-resistant obesity -- recently, these types of reluctant genes are more and more present, due to either genetic malfunctions or the disproportion of white fat cells.

So based on the recent findings, the size of the adipose depot in man and animals is proportionally dependent with the number and size of its constituent cells. Therefore, in the course of a lifetime of an individual, the concluding result achieved by any other organ in the body will be modified by factors that exert their effect on cell division and/or cellular enlargement. "It has been demonstrated in other organ systems that the degree to which either of these mechanisms is modulated by nutritional factors depends in part on the age of the animal. The earlier in life that they exert their influence, the greater the likelihood that permanent alterations in body and organ size will occur." Though this theory has strong scientific roots, there are few studies about comparative cellular growth, so little is known about the factors that determine the number of adipose cells (Knittle & Hirsch 1968, p. 2091).

Obesity is not just a simple eating disorder. Linked to its physical and pathological characteristic, another one has a strong influence on how the sickness evolves: the psychological feature. The way others perceive us is, unfortunately, in today's society, connected to the way we look, and unflattering external remarks can gravely alter the treatment an individual is undertaking to take care of his/her disorder. Alongside a well-planned diet and fitness programme, a clear and motivated mind and a rational self-image are crucial elements in treating not only eating disorders, but any other illness.

Greenberg & Obin (2006) discuss 4 major themes that lead to obesity:

1. Adipocytes are decisive for being healthy and represent a "storage" for free fatty acids (FFAs).

2. Adipocytes release hormones that, in slim individuals at least, modulate and distribute body fat mass proportionally.

3. If a person gains weight and the adipocytes enlarge, these hormones sustain the enlargement process, macrophages accumulate in the adipose tissue, and so the inflammation ensues.

4. The regulators of FFA storage and oxidation in adipocytes and the periphery are critical regulators of metabolic homeostasis. (http://www.ajcn.org/content/83/2/461S.full)

In conclusion, the two researchers show that adipocytes don't simply act as a reservoir for fat but have an important say in the way endocrine processes follow in the body. Their metabolic purpose transforms as they increase with growing obesity, thus there is a clear interplay between cell inflammation and obesity. These intracellular mechanisms by which these factors affect energy intake, utilization, and metabolism are being better understood, and therapies are being developed to solve the cell enlargement.

Obesity has been named the disease of the century, widespread across the globe and continuously generating new victims.

The new WHO report tackles the problem of how to prevent excessive overweight and how to treat the different degrees of overweight and obesity. The BMI limit of 18.5 to 24.9 kg/m2 was a compromise, since in the United States higher levels of BMI were accepted as normal, due to the appreciation… READ MORE

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