Browning of Adipocytes: A Potential Therapeutic Approach to Obesity

Abstract

The increasing prevalence of overweight and obesity suggests that current strategies based on diet, exercise, and pharmacological knowledge are not sufficient to tackle this epidemic. Obesity results from a high caloric intake and energy storage, the latter by white adipose tissue (WAT), and when neither are counterbalanced by an equally high energy expenditure. As a matter of fact, current research is focused on developing new strategies to increase energy expenditure. Against this background, brown adipose tissue (BAT), whose importance has recently been re-evaluated via the use of modern positron emission techniques (PET), is receiving a great deal of attention from research institutions worldwide, as its main function is to dissipate energy in the form of heat via a process called thermogenesis. A substantial reduction in BAT occurs during normal growth in humans and hence it is not easily exploitable. In recent years, scientific research has made great strides and investigated strategies that focus on expanding BAT and activating the existing BAT. The present review summarizes current knowledge about the various molecules that can be used to promote white-to-brown adipose tissue conversion and energy expenditure in order to assess the potential role of thermogenic nutraceuticals. This includes tools that could represent, in the future, a valid weapon against the obesity epidemic.

Keywords: brown adipose tissue; browning; obesity; thermogenesis; thermogenic nutraceuticals.

Figure 1

Overview of the main characteristics of white, brown, and beige adipocytes.

Figure 2

Molecular mechanisms involved in WAT browning and BAT activation mediated by thermogenic nutraceuticals. Each group of nutraceuticals, through different pathways, induces the expression of thermogenic genes (PPARγ, PRDM16, PGC1α, SIRT-1, CIDEA) leading to mitochondrial biogenesis and to the increase in UCP1 in white and brown adipocytes, which is responsible for the browning of WAT and enhancement of thermogenesis in BAT. TRP agonists, via the stimulation of adrenergic receptors, not only are crucial for the initiation of thermogenic pathways and beige differentiation, but also promote lipolysis. Polyunsaturated fatty acids and polyphenols, in addition, play an anti-inflammatory role in WAT.