Wednesday, June 18, 2014

4th Canadian Obesity student Meeting (COSM 2014)

Uwaterloo_sealOver the next three days, I will be in Waterloo, Ontario, attending the 4th biennial Canadian Obesity Student Meeting (COSM 2014), a rather unique capacity building event organised by the Canadian Obesity Network’s Students and New Professionals (CON-SNP).

CON-SNP consist of an extensive network within CON, comprising of over 1000 trainees organised in about 30 chapters at universities and colleges across Canada.

Students and trainees in this network come from a wide range of backgrounds and span faculties and research interests as diverse as molecular genetics and public health, kinesiology and bariatric surgery, education and marketing, or energy metabolism and ingestive behaviour.

Over the past eight years, since the 1st COSM was hosted by laval university in Quebec, these meetings have been attended by over 600 students, most presenting their original research work, often for the first time to an audience of peers.

Indeed, it is the peer-led nature of this meeting that makes it so unique. COSM is entirely organised by CON-SNP – the students select the site, book the venues, review the abstracts, design the program, chair the sessions, and lead the discussions.

Although a few senior faculty are invited, they are largely observers, at best participating in discussions and giving the odd plenary lecture. But 85% of the program is delivered by the trainees themselves.

Apart from the sheer pleasure of sharing in the excitement of the participants, it has been particularly rewarding to follow the careers of many of the trainees who attended the first COSMs – many now themselves hold faculty positions and have trainees of their own.

As my readers are well aware, I regularly attend professional meetings around the world – none match the excitement and intensity of COSM.

I look forward to another succesful meeting as we continue to build the next generation of Canadian obesity researchers, health professionals and policy makers.

You can follow live tweets from this meeting at #COSM2014

@DrSharma
Waterloo, Ontario

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Wednesday, May 7, 2014

The Colour Of Fat

Brown Fat Cells in White Fat Tissue

Brown Fat Cells in White Fat Tissue

As a regular reader you will be well aware that body fat is not body fat. Much depends on its exact location, but also on the cellular structure and biological function of the different types of fat depots.

This is the subject of a paper by Brian Owens, a science editor from New Brunswick, Canada, published in the recent Nature Outlook supplement on Obesity.

Although, the predominant form of fat tissue in humans is white fat (which, is in fact yellow), we also have other types of fat cells that are either brown or beige.

While the primary function of white fat cells is to store fat, brown(ish) fat cells specialize in burning it.

This may lead us to believe that brown fat cells are the “good guys” whereas white fat cells are the “bad guys” but this could not be further from the truth.

As Owens explains (quoting Patrick Seale), the white fat cells actually play a key role in keeping us safe from the ill-effects of excess fat by safely sequestering it away:

“Healthy white fat protects the body by providing a ‘safe home’ for lipids, which can be toxic to other tissues such as muscle or the liver. So these fat cells hold on to the lipids until the energy they are storing is needed, when they release them into the blood.”

Thus, white fat actually plays an important role in protecting us from metabolic disease. This is most evident in people who genetically (or in the case of anti-retroviral treatment) lack sufficient white fat cells. These folks end up depositing their excess fat in those other tissues (e.g. liver, pancreas, muscle, etc), thereby causing exactly the same metabolic problems that are commonly associated with obesity.

So why do some people with excess white fat develop these problems?

Here Owens quotes Philipp Scherer, who explains that cell size may have something to do with this:

“Problems arise when white fat cells store too much lipid. They begin expanding and proliferating rapidly in a process that resembles the growth of a solid tumour….The blood supply cannot keep up with this expansion, and the cells begin to suffer from lack of oxygen. This hypoxia attracts the protein HIF-1α, which in fat tissue stimulates the extracellular matrix surrounding the cells, leading to fibrosis. The huge, oxygen-starved fat cells do not have enough room to expand and get squeezed to death, releasing their lipid cargo. As the cells start to die, macrophages swarm to the fat depots to try and clean up the mess by carrying away the lipid droplets. The problem is that the macrophages cannot clear up the lipids fast enough, and so they begin to spill over into other tissues, such as the liver and pancreas.”

As for brown fat – it has a completely different function, namely to help regulate body temperature by burning off calories to generate heat.

But researchers have discovered yet an additional type of fat cell – one that lies some where between typical white and brown fat. In fact, it seems that most the brown fat in humans is actually beige – these seem to be cells recruited from white fat depots that transform themselves into “brownish” cells with certain stimuli (e.g. cold exposure, physical exercise).

These beige cells may also be important protectors against metabolic disease. The article quotes work by Bruce Spiegelman showing that selectively disabling beige fat in mice by targeting the protein PRDM16, which is found only in these cells, leaving the white and brown fat intact leads to animals with severe metabolic dysfunction — obesity, insulin resistance and fatty livers.

Thus it appears that the loss of the beige fat destroys the protective abilities of subcutaneous white fat – at least in mice.

If nothing else, these studies show that we have yet much to learn about fat cells. In fact, there may be other subtypes of fat cells specific to the different fat depots in the body (of which there are many), that may each have their unique importance and functions.

Whether or not we can harness this new knowledge to find better treatments for obesity remains to be seen – simply destroying fat cells willy-nilly can certainly do more harm than good.

@DrSharma
New York, NY

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Tuesday, March 4, 2014

Can Eating More Fat Make You Leaner?

sharma-obesity-visceral-fat-mriYes, if the excess fat is poly-unsaturated – no, if it is saturated.

At least this was the finding in an overfeeding study conducted by Fredrik Rosqvist and colleagues from the Uppsala University, Sweden, published in DIABETES.

The study with the memorable acronym LIPOGAIN, was a double-blind, parallel-group, randomized trial involving 39 young normal-weight individuals who were overfed muffins either high in saturated fats (palm oil) or in n-6 poly-unsaturated fats (sunflower oil) for seven weeks.

The number of muffins that each subject had to consume were individually adjusted to ensure that each subject increased their body weight by about 1.5 Kg (or 3%). To achieve this, the subjects consumed on average three muffins or about an extra 750 kcals/day.

However, where the excess calories went was quite different.

While the subjects eating saturated fat markedly increased their liver fat and gained almost twice as much visceral fat as those in the poly-unsaturated fat group, the latter experienced a nearly three-fold larger increase in lean tissue than the saturated fat group.

The two diets also had quite different effects on the expression of genes regulating energy dissipation, insulin resistance, body composition and fat cell differentiation in subcutaneous fat tissue.

Thus, the authors conclude that while overeating saturated fat promotes liver and visceral fat storage, the excess energy from poly-unsaturated fat may instead promote the growth of lean tissue.

What I learnt from this study is that there are indeed important differences in how the body handles excess calories depending on where they come from.

In that respect at least, not all calories are equal.

@DrSharma
Edmonton, AB

Fat Jokes Are Not Funny! Help publish this anti-bullying children’s book

ResearchBlogging.orgRosqvist F, Iggman D, Kullberg J, Jonathan Cedernaes J, Johansson HE, Larsson A, Johansson L, Ahlström H, Arner P, Dahlman I, & Risérus U (2014). Overfeeding Polyunsaturated and Saturated Fat Causes Distinct Effects on Liver and Visceral Fat Accumulation in Humans. Diabetes PMID: 24550191

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Monday, November 18, 2013

Harnessing Brown Adipose Tissue to Fight Obesity?

Brown Fat Cells in White Fat Tissue

Brown Fat Cells in White Fat Tissue

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.”

However,

“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.

Thus,

“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’”

@DrSharma
Edmonton, AB

ResearchBlogging.orgChechi 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

 

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Sunday, October 20, 2013

Obesity Weekend Roundup, October 18, 2013

As not everyone may have a chance during the week to read every post, here’s a roundup of last week’s posts:

Have a great Sunday! (or what is left of it)

@DrSharma
Edmonton, AB

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In The News

Diabetics in most need of bariatric surgery, university study finds

Oct. 18, 2013 – Ottawa Citizen: "Encouraging more men to consider bariatric surgery is also important, since it's the best treatment and can stop diabetic patients from needing insulin, said Dr. Arya Sharma, chair in obesity research and management at the University of Alberta." Read article

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