Fat cell

FIGURE 24.1 Scanning electron micrograph of an adipose cell (fat cell). Globules of triacylglycerols occupy most of the volume of such cells. (Prof. P. Motta, Dept, of Anatomy, University La Sapienza, Rome/Science Photo Library/Photo Researchers, Inc.)... 

The term adipokine refers to any protein secreted from adipocytes [1]. Collectively, the various adipokines form the adipokinome which together with the lipid moieties secreted from fat cells (e.g. fatty acids, cholesterol, retinol) constitute what can be referred to as the secretome of adipocytes. Most adipokines are also secreted from other cell types in other organs, but one in particular - adiponectin - is considered to be exclusive to adipocytes. 

PPARy is a transcription factor which controls the expression of enzymes and proteins involved in fat and glucose metabolism. More importantly, stimulation of this receptor induces differentiation of preadipocytes to adipose cells. It is believed that the formation of additional, small fat cells lowers free fatty acids and hepatic triglycerides, thereby collecting insulin resistance. 

The cytokine leptin is secreted by adipocytes (fat cells) in proportion to the size of the adipose dq>ot and circulates via the bloodstream to the brain, where it ultimately affects feeding behavior, endocrine systems including reproductive function and, at least in rodents, energy expenditure. The major effect of Lqrtin is on the hy-pothalamous, where it suppresses appetite and hence food intake. Leptin exerts its effects via binding to the leptin receptor in the brain (specifically in the hypothalamus), which activates the JAK-STAT Pathway. 

Figure 2.2 Fat, or adipose, cells store extra energy from food. Adipose cells help insulate the body to keep it warm, cushion and protect the internal organs, and store extra energy for later use. When people consume more energy from food, the extra energy is stored as fat in adipose cells. Years ago, this stored energy could be used to avoid starvation in times of famine. Today, people never use this stored fat because famine does not exist in developed countries. These fat cells continue to accumulate and lead to weight gain and eventually to obesity.

Fats and oils, constituted by acylglycerolipids, represent a major subgroup of lipids. They are the most common class of medium-size molecules produced by living organisms. They are the main constituents of the storage fat cells in plants and animals. They have quite a similar chemical composition, as they are mainly composed of triglycerides, triesters of glycerol with fatty acids (FAs). 

These agents activate PPAR-y a nuclear transcription factor important in fat cell differentiation and fatty acid metabolism. PPAR-yagonists enhance insulin sensitivity in muscle, liver, and fat tissues indirectly. Insulin must be present in significant quantities for these actions to occur. 

Release of active pancreatic enzymes directly causes local or distant tissue damage. Trypsin digests cell membranes and leads to the activation of other pancreatic enzymes. Lipase damages fat cells, producing noxious substances that cause further pancreatic and peripancreatic injury. 

Bone Marrow The soft tissue filling the cavities of bones. Bone marrow exists in two types, yellow and red. Yellow marrow is found in the large cavities of large bones and consists mostly of fat cells and a few primitive blood cells. Red marrow is a hematopoietic tissue and is the site of production of erythrocytes and granular leukocytes. Bone marrow is made up of a framework of connective tissue containing branching fibers with the frame being filled with marrow cells. [NIH]... 

The promotion by insulin of glucose uptake by muscle and fat cells (adipocytes), of glycogen deposition in liver and muscle, and its stimulation of growth soon emerged as the purified hormone became available for study. Although insulin was crystallized by Abel in 1926, its primary structure established by Sanger in 1953 (see Chapter 10),... 

In 1979, Ross et al 22i" measured the ODMR of tyrosine in glucagon and the derivative [12-homoarginine]glucagon to examine the effect of chemical modification of a lysine residue adjacent to Tyr-10 and Tyr-13. The guanidinated analogue had lower potency than glucagon in a fat cell hormone receptor assay. Since the tyrosine ODMR and other spectral properties of the polypeptide, including circular dichroism, were essentially identical, it was... 

During fasting, the decrease in insulin and the increase in epinephrine activate hormone-sensitive lipase in fat cells, allowing fatty acids to be released into the circulation. 

As people become obese they accumulate more fat, but not all fat cells (adipocytes) are equal there are different types of adipose tissue and adipocytes behave differently depending on the location of the fat depot. 

As discussed above, insulin suppresses the breakdown of triglyceride within fat cells in the post-prandial period, preventing release of fatty acids from adipocytes in healthy individuals. Insulin also stimulates triglyceride clearance from triglyceride-rich lipoprotein particles and the esterification of fatty acids to form the intra-adipocyte triglyceride store. 

The dermis contains several types of cells, including fibroblasts, fat cells, macrophages, histiocytes, mast cells, and cells associated with the blood vessels and nerves of the skin. The predominant cell is the fibroblast, which is associated with biosynthesis of the fibrous proteins and ground substances such as hyaluronic acid, chondroitin sulfates, and mucopolysaccharides. 

Cyproheptadine has antianaphylactic activity that is associated with its ability to slow down the release of histamine and other mediators from fat cells. It is mainly used for treating bronchial asthma attacks, allergic bronchitis, rhinitis, and allergic skin reactions as well as in adjuvant therapy for anaphylactic reactions. Synonyms of this drug are periactin and vimicon. 

THC is fat soluble, and it gets stored in your fat cells. Cleaning it out of your lipid tissue is very difficult. Many herbal products claim to clean out your system, yet they do nothing to remove THC byproducts from fat cells. A study was done in Germany in 1993 on 50 of the most common herbs used by people trying to pass the test. All 50 herbs failed to cause a negative. 

Unfortunately, this rumor will not die. Goldenseal is useless yet it s the most common thing for people to use. The only way to extract THC from fat cells is to exercise (5.8). Fat cells secrete fat with THC metabolites at a constant rate, regardless of what herbs you consume. You may be able to temporarily rid THC metabolites from your bloodstream, or dilute your fluids to yield a larger urine/THC ratio, but your bloodstream will continue collecting THC metabolites from fat. Your urine will continue collecting THC metabolites from your bloodstream. 

This is a very new product, untested by a third party. It claims to absorb toxins, however, experts say that absorbing THC metabolites from fat cells is impossible. Here is a copy of the ad from Party Hut Enterprizes ... 

Insulin action increases glucose uptake by individual fat cells (adipocytes), and this accelerates metabolic activity. 

Abdominal or visceral fat cells have a higher rate of fat turnover and are more contributory to disease than fat stores in the buttocks and thighs. 

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