Published paper #1-Brown Adipose Tissue as a Regulator of Energy Expenditure and Body Fat in Humans

Saito M. 23 FEB 2013, ‘Brown Adipose Tissue as a Regulator of Energy Expenditure and Body Fat in Humans’ Accessed 12th April 2013  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3579148/

gladden-willis-human-infant-multilocular-or-brown-fat-a-special-type-of-adipose-tissue-concerned

Brown Adipose Tissue, (BAT), was one of the topics suggested to us my Mr Matthew, for our published paper review, but I chose this particular topic because during the semester I learnt a lot BAT. In my second year course Animal Physiology we learnt how animals such as mice use BAT to maintain their body temperature, when placed in cold environments; we also did a lab using a real live mouse to demonstrate how they react to varying temperatures. Quite interesting I must say! Anyways, onto this paper.

Brown Adipose tissue is known as a major site in the body where non shivering thermogenesis occurs during cold exposure, hence controlling energy use and body fat. The study states that BAT had been recently discovered in humans, and has a potential to be used for decreasing body fat in humans. There are two main types of adipose tissue, white adipose tissue (WAT) and brown adipose tissue (BAT).  WAT is used mainly for energy storage and BAT for energy use.  BAT was discovered in human using fluorodeoxyglucose (FDG)-positron emission tomography (PET), together with computed tomography (CT).

The inner membrane of the mitochondria of BAT contains a protein known as unique uncoupling protein 1 (UCP1), which acts to uncouple oxidative phosphorylation from ATP synthesis, releasing heat energy, thereby ensuring thermogenesis. The primary substrates for this process are fatty acids from triglycerides and circulating free fatty acids and lipoproteins.

The existence of metabolically active BAT in adult humans was confirmed by using FDG-PET/CT studies.

In humans, the fact that the metabolic activity of BAT is increased after cold exposure suggests a contribution of BAT to cold-induced thermogenesis, thereby regulating whole body energy expenditure. In humans studies have shown an inverse relationship between the presence of BAT and indices of measuring obesity such as body mass index (BMI). It was observed in past studies that BAT prevalence is lower in patients with a higher BMI. Age also influences adiposity, since cold activated BAT is more than 50% in younger subjects and decreases with age.

Since it has been observed that BAT can be used to prevent body fat accumulation, attempts has been made to activate this process. The most effective stimulus discovered in both mice experimental studies and humans for activating BAT was exposure to colder temperatures. In humans a cold stimulus is received by transient receptor potential channels (TRP).  Chemical activation of these receptors (TRPM8 and TRPA1), would mimic the effects of cold exposure. These receptors may be activated by common food ingredients such as menthol, found in mint, mustard and Wasabi. Also mentioned is capsaicin, found in chilli pepper, which can act as a agonists for TRPV1. All these substances can act to mimic the effect of thermogenesis without having to decrease the external environmental temperature.

Also BAT may be relevant in improving insulin sensitivity and enhanced glucose utilization in cold acclimated animals, hence BAT maybe useful for not only treating obesity but also other obesity related diseases.

This concept of using BAT as an energy and body fat regulator in humans is an interesting concept that can be further enhanced by more research into how it can be used to increase metabolism and aid in preventing obesity.

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