Hindsight: AT-1 Blockade and Tissue Metabolism
Continuing with our research on the potential function of the adipose tissue renin angiotensin system, in 2006, we published a paper in the American Journal of Physiology (Regul Integr Comp Physiol) where we examined the effect of systemic Angiotensin Type-1 (AT1) receptor blockade on tissue metabolism in obese volunteers. We studied 14 obese men, whe were treated for 10 days with the AT1 receptor blocker irbesartan or with placebo in a double-blind and crossover fashion. At the end of each treatment period, we assessed skeletal muscle and adipose tissue metabolism using the microdialysis technique. We found that treatment with irbesartan slightly attenuated the isoproterenol-induced glycerol response in adipose tissue but there were no discernible effects on interstitial glucose supply or lactate production. We concluded from these (rather unspectacular) findings that AT1 receptor blockade in obese men does not reveal a major tonic ANG II effect on interstitial glucose supply, lipolysis, or glycolysis in skeletal muscle, either at rest or during beta-adrenergic stimulation. The only significant result (if any) was that endogeneous ANG II may slightly increase adipose tissue lipolysis, which could (in theory) promote the redistribution of triglycerides from adipose tissue toward other organs (think ectopic fat). Six years later, while the topic continues to attract some attention, very few of us still believe that the renin-angiotensin system has clinically relevant metabolic effects. I guess nothing ventured, nothing learned. AMS San Antonio, TX
Warding Off Obesity At The Alamo
The next few days, I will be attending the 30th Annual Scientific Meeting of The Obesity Society at the San Antonio Convention Centre, just a few steps from the Alamo. As a Fellow of this organisation and someone, who has sat on well over a handful of TOS committees, attending this conference has become part of an annual rite – one that I certainly enjoy very much. This year, to coincide with the start of this meeting, the Journal of the American Medical Association (JAMA) dedicates a full issue to obesity. Articles include a discussion of government’s role in obesity prevention, a number of viewpoint pieces on obesity drugs, a randomised controlled study on the effect of exercise dose on diabetes risk in children, a survey on the possible role of bisphenol A in obesity, a 20 year analysis of the health benefits of bariatric surgery, a randomised controlled trial of surgery versus conservative treatment for obstructive sleep apnea, and a discussion of differences in diabetes risk by adiposity phenotype – in short, a pot-pourri of current topics of interest – no game changers – but certainly a few thoughtful comments, interesting new data and a general indication of the breadth of epidemiological and clinical research in this field. Certainly an issue of JAMA that all of us working in the field should probably read cover-to-cover (fortunately, most of these articles are available for free download). Historians may recall that in the end the defenders of the Alamo, despite their heroics, ultimately lost the battle (but not the war). Often, the few researchers and practitioners, who have dedicated most of their careers to better understanding and fighting obesity (and the many misconceptions about it), may feel that they too are fighting against impossible odds. Just how much progress will be made remains to be seen – the next few days will at least show if we are headed in the right direction. AMS San Antonio, TX
Does Vitamin D Help Prevent Diabetes?
In the continuing saga of putative metabolic or cardiovascular benefits of this or the other vitamin, the current attention appears to be largely on vitamin D (given that the effects of supplementing other vitamins on these parameters have either been found to be non-existant or even harmful). Much of the rationale for vitamin D is based on the known biological action of this vitamin (in experimental settings) and on the rather widespread suboptimal vitamin D levels found in a substantial proportion of the population (especially in nordic countries like Canada). This said, a new systematic review on the role of vit D on glycemic control by George and colleagues from the University of Dundee, UK, published in Diabetic Medicine, finds little effect of vitamin D (or analogues) on preventing or improving diabetes control. Their review of 15 randomised controlled trials – all of rather moderate quality – showed no significant improvement in fasting glucose, HbA(1c) or insulin resistance in those treated with vitamin D compared with placebo. For patients with diabetes or impaired glucose tolerance, meta-analysis showed a small effect (non-significant) effect on fasting glucose and a small improvement in insulin resistance but no effect on HbA(1c) levels. As the authors also note, due to the rather short duration of these trials, there was insufficient data to draw conclusions regarding micro- or macrovascular events. Furthermore, in the two trials that looked at this issue, there was no reduction in new cases of diabetes in patients treated with vitamin D. Thus, despite the considerable hype about vitamin D in the popular literature, there is currently no evidence that recommending vitamin D supplementation as a means of preventing diabetes or improving glycaemia or insulin resistance in patients with diabetes is warranted. Not that this is likely to stop anyone from still expecting wonders from this vitamin beyond its well-recognised benefits (largely on bone health) in patients who do have severe vitamin D deficiencies. AMS Edmonton, Alberta photo credit: Treasure Tia via photo pin cc George PS, Pearson ER, & Witham MD (2012). Effect of vitamin D supplementation on glycaemic control and insulin resistance: a systematic review and meta-analysis. Diabetic medicine : a journal of the British Diabetic Association, 29 (8) PMID: 22486204 .
What’s Happening in After-School Programs?
This week, the Alberta Centre for Active Living released an environmental scan on participation and opportunities to participate in physical activity in After-school Programs in Alberta. Happily enough, the report finds that 61% of after-school programs offer more than 30 minutes of moderate-to-vigorous physical activity (MVPA) per day, 78% of programs include 30 minutes or more of active play and 79% of after-school program managers identified that it is possible to provide daily moderate-to-vigorous physical activity in Alberta after-school programs. However, the report also identifies important barriers to and ways to further increase participate in after-shool physical activities: • improvements/alterations to indoor space (50%), • physical activity training or workshops for staff (47%), • resource manuals for staff, with lesson plans (42%), and • portable equipment, e.g., balls, pylons, ropes, mats, etc. (41%). The focus group sessions identified the most common barriers to physical activity as space (lack of space or proper space for activity) and a lack of specialized staff training and workshops. The report also notes that most programs plan at least 60 mins of sedentary time. The most common types of sedentary activities included in after-school programs were: • doing crafts (93%), • eating (90%), • reading (87%), • making art (86%) • doing homework (82%). The report has a number of important recommendations for after-school program managers, policy makers and parents. A copy of the report can be downloaded here. AMS Edmonton, Alberta
Inadequate sleep can lead to obesity, study suggests
And there’s a third factor at play, suggested Dr. Arya Sharma, who holds a chair in obesity research at the University of Alberta in Edmonton…“We’ve … known for a long time that people who don’t get enough sleep tend to be less physically active during the day,” Sharma said.
Watch Dr. Sharma in the News!
Listen to Dr. Sharma!
