Harnessing Brown Adipose Tissue to Fight Obesity?Monday, November 18, 2013
Although obesity is largely a “calories-in” rather than a “calories-out” problem, emerging evidence points to the possibilities of harnessing thermogenic brown adipose tissue to help balance this equation by helping burn more calories.
But this may be more difficult than it sounds.
Readers interested in this issue, may wish to refer to an overview of this topic by Canadian Obesity Network Bootcamper Kanta Chachi and colleagues from the University of Montreal, published in Obesity Reviews.
The paper summarizes talks given by various experts in the field at the 11th Stock Conference in Montreal, October 2012.
This includes an analysis of our current understanding of the developmental origin, cellular properties and molecular distinctions between classical brown and beige/brite adipocytes as well as the central circuitries and neuropeptides involved in the regulation of brown adipocyte thermogenesis.
The presence and metabolic activity of brown adipose tissue and its role in various aspects of human energy metabolism, including diet-induced thermogenesis is also discussed.
As for the potential therapeutic utility of brown adipocytes for treating obesity in humans, it is important to distinguish between t BAT mass and BAT activity – thus therapeutic approaches could focus on either increasing the amount of BAT present or increasing the activity of tissue that is already present.
As the authors point out,
“Even if there is no doubt that BAT can be activated by behavioural or pharmacological means, it is doubtful that BAT activation will be a viable strategy for weight loss. Based on the recent studies reporting enhanced energy expenditure in humans upon stimulation of BAT thermogenesis, it is conceivable that activation of BAT may rather be developed as a strategy for maintenance of weight loss achieved by other therapies. Indeed, BAT activation would counteract the ‘metabolic adaptation’ occurring in response to weight loss.”
“Considering that energy balance is a tightly regulated phenomenon, it is likely that BAT-mediated increase in energy expenditure may activate metabolic adaptations or counter-regulatory mechanisms in the body, which could oppose weight loss, in a similar fashion to what is seen with caloric restriction- or exercise-induced weight loss programmes.
“Whether BAT-mediated weight loss would promote similar metabolic adaptations and counter-regulatory mechanisms – including an increase in food intake remain to be determined. Although BAT thermogenesis is an attractive candidate, we are still in the preliminary stages of utilizing this tissue as a therapy for obesity. It would be important to practice ‘caution in extrapolating indirect histological and thermographic evidence to a major role for BAT in human energy metabolism’”
Chechi K, Nedergaard J, & Richard D (2013). Brown adipose tissue as an anti-obesity tissue in humans. Obesity reviews : an official journal of the International Association for the Study of Obesity PMID: 24165204
Monday, November 18, 2013
Interesting summary. Two notes here:
1. “Considering that energy balance is a tightly regulated phenomenon, it is likely that BAT-mediated increase in energy expenditure may activate metabolic adaptations or counter-regulatory mechanisms”
Yes, energy balance is tightly regulated, and BAT (brown fat) plays a key role in this regulation. Obese patients have defective BAT recruitment resulting in less BAT mass than lean people/healthy levels, causing dysregulation of energy balance (or rather, body fat levels). The result is a higher than healthy body fat setpoint.
2. The effects of increasing BAT in lean animals has been documented for decades: they have no fat to lose, and thus increase their food intake to keep up with the increase in metabolic rate caused by the extra BAT.
Increasing BAT in obese animals/humans (who all have decresed BAT to start with) causes a resetting-lowering of the adipostat, leading to weight/fat loss and long-term maintenance of lower body fat (as long as the BAT is maintained).
Monday, November 18, 2013
Also, a key aspect of BAT/brown fat is that the metabolic effects of increasing/restoring healthy amount of BAT go well beyond “energy expenditure” (thermogenic) effects.
Indeed, brown adipocytes (cells in BAT) secrete factors (some still to be identified) that improve glucose metabolism (anti-diabetic) and improve blood lipid profile. Thus, increasing BAT in obese, insulin-resistant (pre-diabetic) or type 2 diabetic patients will profoundly improve diabetes parameters (in addition to having a long-term impact on obesity/body weight).
Monday, November 18, 2013
This topic interests me greatly because it is still such a mystery.
I find myself wondering if exercises focused on specific locations might cause what used to be termed “spot loss” — if brown fat increase can even be achieved and then act specifically on chosen loci through targeting exercises — and if so if abdominal exercises may be extra healthy for menopausal “apples” like me. Traditional viewpoints are that there is no sch thing as spot loss, and that abs exercises are healthy but no more so for us “apples”. Eexercise can increase brown fat but I have not read if that is only systemic or if the increase in brown fat might be greater in bodily areas getting more exercise.