The Durk Pearson & Sandy Shaw®
Life Extension NewsTM
Volume 11 No. 5 • September 2008


Another Dogma Bites the Dust! Adult Humans Do Have Brown Fat

It has long been believed that, although human infants do have brown adipose (fat) tissue (BAT), adult humans do not. As the authors of a recent paper1 note, “The alleged absence of brown adipose tissue . . . precludes that alterations in amount and activity of brown adipose tissue could be an explanatory contributory factor for obesity in humans, in contrast to what seems to be the case in rodents.” The authors report that since 2002, brown adipose tissue was discovered serendipitously and most curiously in humans.

The discovery was at first considered a nuisance! Scientists had developed a way to identify tissues that were taking up unusually large amounts of glucose, such as tumors, which rely on glycolytic production of energy (ATP) and, hence, require large supplies of glucose. The new methodology required both fluorodeoxyglucose positron emission tomography (FDG PET) and computer tomography (CT). But because brown adipose tissue takes up much more glucose than normal tissue under cool conditions, such as during the testing procedures, which activate the BAT, the “spots” of the BAT that showed up were seen as a “disturbing complication” in the effort to identify tumors. As the authors of the paper explain, “. . . experimental efforts in nuclear medicine have concentrated on how to eliminate the problem of brown fat uptake. Accordingly, all data concerning FDG uptake in brown adipose tissue have been published in journals addressing nuclear medicine scientists, i.e., journals not normally studied by physiologists.”1

The sites of the adult BAT are consistent with the location of BAT in human infants. The neck depots (supraclavicular and neck) constitute the two largest and most often occurring depots in man; then there is a pattern of small depots located along the spinal cord as a paravertebral depot, also in the mediastinum, particularly in the para-aortic area, and around the heart, particularly the apex. Then there is an infradiaphragmatic depot, particularly in the perirenal area. (See paper for diagram showing depot locations.)

The tissue has been examined for evidence that it is indeed BAT. “The one identifying characteristic of brown adipose tissue is the presence of UCP1 [uncoupling protein 1] in the tissue.”1 Several studies are cited that have shown the presence of functional characteristics indicating the presence of UCP1 as well as UCP1 protein or UCP1 mRNA in these depots. Moreover, the activity of the purported BAT is induced by acute exposure to cold. It has been found that if patients are kept warm during the hour from injection of FDG to PET imaging, FDG uptake into the BAT is fully suppressed.1

The bottom line is that BAT exists in adult humans, and therefore BAT thermogenesis is a potentially useful method of weight control in humans by increasing energy expenditure.

Reference

  1. Nedergaard et al. Unexpected evidence for active brown adipose tissue in adult humans. Am J Physiol Endocrinol Metab 293:E444-52 (2007).

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