Study: A New Milestone in Brown Fat Research
17 April 2014 --- The first MRI scan to show ‘brown fat’ in a living adult could prove to be an essential step towards a new wave of therapies to aid the fight against diabetes and obesity, a study shows. Researchers from Warwick Medical School and University Hospitals Coventry and Warwickshire NHS Trust used a magnetic resonance imaging (MRI) based method to identify and confirm the presence of brown adipose tissue in a living adult.
The report’s author, Dr Thomas Barber, from the Department of Metabolic and Vascular Health at Warwick Medical School, told NutritionInsight that brown fat is fundamentally different from what most of us think of fat (white fat). “White fat stores energy whereas brown fat burns energy and releases it as heat,” he said. “Brown fat is abundant in small mammals like rats and mice, and is thought to be important for temperature regulation. We have known for decades that human neonates have brown fat, but only relatively recently have we known that some human adults also have active brown fat.”
“We don’t know how many of us actually have brown fat,” he continued. “Active brown fat shows up on a PET CT scan, but when inactive, it doesn’t show up. Our proof of concept study using MRI holds the potential to address this very question, as this shows anatomy rather than tissue activity, and so will show up brown fat whether active or inactive,” he explained. “Statistically, someone is most likely to have active brown fat if they are young, lean and female. We don’t fully understand why there are associations of brown fat activity with age, BMI and sex.”
Brown fat has become a hot topic for scientists due its ability to use energy and burn calories, helping to keep weight in check. Understanding the brown fat tissue and how it can be used to such ends is of growing interest in the search to help people suffering from obesity or at a high risk of developing diabetes.
Barber explained, “This is an exciting area of study that requires further research and discovery. The potential is there for us to develop safe and effective ways of activating this brown fat to promote weight loss and increase energy expenditure – but we need more data to be able to get to that point. This particular proof of concept is key, as it allows us to pursue MRI techniques in future assessments and gather this required information.”
The study, published in The Journal of Clinical Endocrinology and Metabolism, outlines the benefits of using MRI scans over the existing method of positron emission tomography (PET). Whilst PET does show brown fat activity, it is subject to a number of limitations including the challenge of signal variability from a changing environmental temperature.
Unlike the PET data which only displays activity, the MRI can show brown fat content whether active or not – providing a detailed insight into where it can be found in the adult body. This information could prove vital in the creation of future therapies that seek to activate deposits of brown fat.
Dr Barber added, “The MRI allows us to distinguish between the brown fat, and the more well-known white fat that people associate with weight gain, due to the different water to fat ratio of the two tissue types. We can use the scans to highlight what we term ‘regions of interest’ that can help us to build a picture of where the brown fat is located.”
Barber also told NutritionInsight that brown fat differs from white fat in that it is packed full of mitochondria, the power-house of the cell. “The mitochondria in brown fat are specialized, in that instead of using chemical energy to generate ATP, they release this chemical energy as heat through a process called uncoupled oxidative phosphorylation. The main purpose of white fat, in contrast, is to store chemical energy as fat. Over the last 15 years though, there has been much research so show cross-talk between the brain and white fat.”
Brown fat is not something that one would want to get rid of, explained Barber. “It doesn’t contribute to fat mass in any meaningful way in human adults, as there is overwhelmingly more white fat than brown, and white fat is what actually stores energy and accounts for obesity. Activating brown fat though does represent a novel and exciting means of facilitating weight loss in the future, and there is a lot of interest in this field currently.
“Regarding white fat, both exercise and diet would be important for weight loss (ie. reduction of white fat). When thinking about brown fat, it is likely that future therapeutic strategies would be focused on augmenting brown fat reserves rather than reducing them, because of the potential therapeutic benefit of brown fat activity (in terms of weight loss).”
With the proof of concept now completed, the next step is to further validate this technique across a larger group of adults.
The team includes Dr Barber, Professor Charles Hutchinson, Dr Terence Jones, Dr Narendra Reddy and Dr Sarah Wayte.
Dr Barber works at the Human Metabolism Research Unit at UHCW. The unit has benefitted from substantial investment through the Science City Research Alliance programme.
The Science City Research Alliance (SCRA) is a large scale, long-term research programme between the University of Birmingham and the University of Warwick.
By Sonya Hook
