Rates of obesity and associated diseases continue to grow worldwide. More than ever before, the development of novel therapeutic approaches to reduce fat mass in obese individuals is necessary. One such approach is through remodeling white fat metabolism so it functions more like the energy-consuming brown fat.
By Rolando B. Ceddia
Adipose tissue can be classified as white and brown. The most abundant is white fat, which is specialized to store excess dietary calories. Conversely, brown fat is made up of fat cells (adipocytes) that are equipped to burn calories and produce heat, which helps to maintain body temperature in cold conditions.
Adult humans have relatively small amounts of brown fat, which limits the capacity of this tissue to consume calories. However, it has been recently discovered that white adipocytes can acquire some features of brown fat and turn into “beige adipocytes”. This process is known as “browning” of the white adipose tissue (WAT). Beige adipocytes have been shown to burn calories instead of storing them, similarly to the brown fat. Thus, if browning of the WAT is induced, then this could enhance the organism’s capacity to burn calories and ultimately reduce fat mass.
A hallmark characteristic of beige adipocytes is the presence of the uncoupling protein 1 (UCP1), the protein responsible for heat production and enhancement of fat burning in brown fat. Current research is focusing on determining whether beige adipocytes elevate energy consumption essentially by increased UCP1 activity or also through other mechanisms.
Futile cyles of spent energy
In a review article published in a special issue of Hormone Molecular Biology and Clinical Investigation, the metabolic features of white, beige, and brown adipocytes are characterized. The authors demonstrate that beige adipocytes spend energy mainly by the activation of “futile cycles”. These futile cycles increase various metabolic pathways in beige adipocytes that prevent fat storage and also consume glucose. Thus, beige adipocytes can increase their calorie-consuming capacity; however, they do so in a manner that does not depend as much on UCP1-mediated heat production as in typical brown fat cells.
Browing – a new approach for obesity?
Browning of the WAT is a promising therapeutic approach for obesity and its associated diseases. As the WAT accounts for a greater proportion of total body weight compared to brown fat, enhancing caloric consumption in the WAT could greatly increase the individual’s capacity and ability to dissipate excess energy.
Recent research has shown that specifically targeting and altering the metabolism of WAT can reduce weight gain and improve glucose tolerance and could be used in the treatment of diseases such as obesity and type II diabetes.
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