Posts Tagged ‘gut hormones’

Research

September 26th, 2009

                                                                                                                                                                                                                                                                              

Research is fundamental to understanding, preventing and treating obesity. And yet research reports are often not accepted by the public or policy-makers. One reason is that almost every adult is their own self-study of weight control. A study might have the most precise protocol, a powerful sample size and control for a variety of factors but if it does not comport with what “I” experience, I am not likely to believe it. But research itself in obesity is not without its difficulties. Many studies are ‘underpowered”, i.e. they have too few subjects to draw a conclusion from. That is why many preliminary studies do not pan out in larger tests. Also, in many cases, especially in drug trials, researchers try to remove “confounders” from the test subjects so they can see if there is an effect of the drug. That means that many patients who are sick, smoke, take other drugs, etc. are excluded from the trial. When the drug, for example, gets used by a more ‘real-world’ sample, the effects sometimes vanish. Studies that rely on self-reported weights or dietary recall or physical activity diaries are sometimes less reliable than studies where a more objective measurement is needed. Self-reported weight and height — Rowland 52 (6): 1125 — American Journal of Clinical Nutrition and COMPARISON OF SELF-REPORTED AND MEASURED HEIGHT AND WEIGHT — PALTA et al. 115 (2): 223 — American Journal of Epidemiology

There also may be a bias from the funding source (See Conflict of Interest in Medical Research, Education, and Practice – Institute of Medicine, Relationship between funding source and conclusion…[PLoS Med. 2007] – PubMed Result, Scope and impact of financial conflicts of interes…[JAMA. 2003 Jan 22-29] – PubMed Result) or a selection of participants which may skew the results one way or another. Currently, there is a lot of concern about ghost written scientific articles. Ghostwriting Widespread in Medical Journals, Study Says – NYTimes.com

What’s a reader to do? The first is to read skeptically. The second is to go to several different papers or research articles. If different authors appear to agree upon key points, chances are that they are on to something. Remember, extraordinary claims require extraordinary evidence. Research is a communications process among researchers and it should be thought of as a dialogue to which we can all listen.

Many readers may find useful this site, The Little Handbook of Statistical Practice. It is a handy guide to understanding some of the statistical issues involved…like association is not causation.

Research is key. If you are interested in furthering research, you should look into participating in a clinical research activity. To see what clinical trials are underway in obesity research, see www.ClinicalTrials.gov/Search of: Open Studies | “Obesity” – List Results – ClinicalTrials.gov

A major NIH initiative is support for Obesity and Nutrition Research Centers. In addition to the research they carry out, these centers are critical training facilities for new investigators exploring obesity. Most have their own websites which can provide additional, valuable information. Their sites may provide you with helpful information. Also included are their annual reports.

  1. University of Alabama Nutrition & Obesity Research Center | Nutrition & Obesity Research Center Annual report at http://www2.niddk.nih.gov/NR/rdonlyres/E6AE7940-23AC-402E-BCAC-D4F11A9213B0/0/Alabama.pdf
  2. University of Colorado at Denver and Health Science Center. No website. Annual report at http://www2.niddk.nih.gov/NR/rdonlyres/061BCC83-261E-4B39-95CC-226C97B03ED2/0/Colorado.pdf
  3. Pennington Biomedical Research Center PBRC – Nutrition Obesity Research Center. Annual report at: http://www2.niddk.nih.gov/NR/rdonlyres/841B5FA5-7AC1-4DDB-AD3F-300B94468560/0/Pennington.pdf
  4. University of Maryland, http://medschool.umaryland.edu/cnru/index.asp. Annual report at http://www2.niddk.nih.gov/NR/rdonlyres/BF6E7D31-948E-450A-AFF5-B863FF427B24/0/Maryland.pdf
  5. Boston, MA  Boston Obesity Nutrition Research Center Annual report at: http://www2.niddk.nih.gov/NR/rdonlyres/83F114DD-E707-4623-BA20-BCE02C33ADF6/0/Boston.pdf
  6. Harvard,MA,  no website. Annual report at: http://www2.niddk.nih.gov/NR/rdonlyres/9AFA2465-42C0-40CB-87DB-35813E80A978/0/Harvard.pdf
  7. University of Minnesota. Minnesota Obesity Center | College of Food, Agricultural and Natural Resource Sciences | University of Minnesota Annual Report at http://www2.niddk.nih.gov/NR/rdonlyres/78A3842A-030C-45F7-856E-5C27BE202C15/0/Minnesota.pdf
  8. Washington University, Missouri http://www2.niddk.nih.gov/NR/rdonlyres/BB5BBA2D-AA63-4B73-99D6-56741BB220B3/0/WashingtonUniversity.pdf
  9. Columbia/Cornell, New York, NY http://www.nyorc.org/favicon.ico Annual Report at: http://www2.niddk.nih.gov/NR/rdonlyres/28E027FF-5212-4F15-960B-4E5C84FF952A/0/NewYork.pdf
  10. University of North Carolina at Chapel Hill. No website. Annual report at: http://www2.niddk.nih.gov/NR/rdonlyres/8836D29C-0AF8-4C6A-914E-9D12828A1A82/0/NorthCarolina.pdf
  11. University of Pittsburgh. No web site. Annual Report at: http://www2.niddk.nih.gov/NR/rdonlyres/C8B65B24-EE7A-495C-B441-05EAD3372283/0/Pittsburgh.pdf
  12. University of Washington. http://depts.washington.edu/favicon.ico. Annual Report at: http://www2.niddk.nih.gov/NR/rdonlyres/739D3F88-98FE-4733-9D31-6BB81A1DA915/0/Washington.pdf

 

New Studies , updated October 16, 2009

Obesity driven GERD drives up health care visits Trends in Gastroesophageal Reflux Disease as Measu…[Dig Dis Sci. 2009] – PubMed Result

Psychiatrists survey on attitudes to obese patients Psychiatrists’ perceptions and practices in treati…[Acad Psychiatry. 2009 Sep-Oct] – PubMed Result

More evidence for role of FTO gene in obesity via loss of control and selecting diet high in fat The FTO gene rs9939609 obesity-risk allele and los…[Am J Clin Nutr. 2009] – PubMed Result

AHRQ summarizes evidence on breast-feeding, finds reduced risk of obesity, type 2 diabetes A Summary of the Agency for Healthcare Research an…[Breastfeed Med. 2009] – PubMed Result

Weight loss after bariatric surgery may be explained by changes in gut hormones controlling appetite. The Gut Hormone Response Following Roux-en-Y Gastr…[Obes Surg. 2009] – PubMed Result

Brain and Gut

September 26th, 2009

Frequently, when persons with obesity are depicted in the media, they are headless forms (butts and guts I call the pictures) for we think of obesity in terms of body fat accumulation. But obesity really starts in the brain with multiple signals coming from the gut. Adipose tissue itself generates hormones such as leptin and adiponectin; the GI tract generates ghrelin which signals the brain to initiate feeding . Other products which may stimulate feeding or signal time to stop feeding include leptin, insulin neuropeptide Y among others. Parts of the brain involved are the hypothalamus, the dorsal vagal complex and the reward system.

Researchers now appreciate that food acquisition, preparation, and intake are the result of a several physical signals by which the body communicates to the brain that it is hungry and needs to start feeding or full and needs to stop. MD

Brain

So, just how does the body regulate its weight? The body needs to get its weight just right. Too little nourishment and the body becomes ill and cannot reproduce. Too much also a problem. Look at the precision needed. If one ate the recommended 2,200 calories per day (and a lot eat a lot more) they would consumer 792,000 calories in a year. If they are just 1% more calories, they would add 2 pounds per year or 20 pounds over a decade of life. That’s just an extra 22 calories a day – about half a lower fat Oreo cookie. 100 extra calories a day – about 2/3 of 1 ounce of potato chips – can result in a 5-pound weight gain a year. To keep within these narrow boundaries of health body weight, our bodies have evolved a sophisticated, redundant system to gauge its body weight and when to feed and when to stop feeding.

The four parts of this system are (1) the nervous system which connects the brain, gut and adipose tissue, (2) hormones, including those made by fat cells, (3) neuropeptides which act as messengers and (4) messenger molecules in the immune system called cytokines. These molecules control body weight. The pancreas and adipose tissue make leptin, insulin, adiponectin, visfatin and resistin. The brain makes NPY, melanocortin and cocaine and amphetamine regulated transcript called CART. The stomach makes ghrelin, PYY and CCK.

The process can begin before you eat. Even the sight, smell or thought of food can trigger the “cephalic response.” This can start the production of insulin. Ghrelin increases the desire to eat. PYY can signal an end to feeding. Under stress, the sympathetic nervous system is activiated. This promotes storage of fat, decreases metabolism and promotes insulin resistance. Weight increases and metabolism slows down when this system is activated. The key hormone is insulin which is produced in the pancreas. It is designed to use carbohydrates or store them for later use.

The signals to the brain come from both the central nervous system and the peripheral nervous system Central and peripheral regulation of food intake a…[Obesity (Silver Spring). 2008] – PubMed Result

They appear to converge in the hypothalamus region of the brain.Hypothalamic control of energy balance. [Curr Drug Targets. 2004] – PubMed Result

No fewer than ten possible automatic and largely uncontrollable responses to the modern food environment have been proposed to understand why people can consume more calories than they need without their full awareness or control over their behavior Neurophysiological pathways to obesity: below awar…[Diabetes. 2008] – PubMed Result

Obese individuals appear to respond differently to food visual cues Obese adults have visual attention bias for food c…[Int J Obes (Lond). 2009] – PubMed Result

Obese and overweight persons appear to have lower brain volume Brain structure and obesity. [Hum Brain Mapp. 2009] – PubMed Result

Gut Hormones

Leptin has been identified as one of the most powerful hormones involved in appetite regulation. Appetite control and energy balance regulation in …[Int J Obes (Lond). 2009] – PubMed Result Now, newer techniques like brain imaging can be used to understand the role the brain and central nervous system play in eating behaviours.Leptin regulates striatal regions and human eating…[Science. 2007] – PubMed Result and Neuroimaging and obesity: mapping the brain respon…[Ann N Y Acad Sci. 2002] – PubMed Result

Another class of signaling substances are neuropeptides. Orexin is one of several currently of interest to scientists. Orexin/Hypocretin: a neuropeptide at the interface…[Pharmacol Rev. 2009] – PubMed Result and Orexin neuronal circuitry: role in the regulation …[Front Neuroendocrinol. 2008] – PubMed Result

Chronic stress and obesity: a new view of “comfort…[Proc Natl Acad Sci U S A. 2003] – PubMed Result

Maternal corticotropin-releasing hormone levels du…[Obesity (Silver Spring). 2006] – PubMed Result

The role of gut hormones in the regulation of body…[Mol Cell Endocrinol. 2009] – PubMed Result

Gut hormones: a weight off your mind. [J Neuroendocrinol. 2008] – PubMed Result

Gut hormones and appetite control. [Gastroenterology. 2007] – PubMed Result

Cord blood leptin and adiponectin as predictors of…[Pediatrics. 2009] – PubMed Result

The leptin/adiponectin ratio in mid-infancy correl…[J Pediatr Endocrinol Metab. 2008] – PubMed Result

As research progresses, new theories of evolutionary development are looking at Build-ups in the supply chain of the brain: on the…[Front Neuroenergetics. 2009] – PubMed Result

Ghrelin is a gut hormone which appears to be very significant and is the subject of much research.Lean Mean Fat Reducing “Ghrelin” Machine: Hypothal…[Neuropharmacology. 2009] – PubMed Result

Appetite

Viewing photographs of fattening foods, compared to non-food objects can result in greater activiation in parts of the brain. Activation in brain energy regulation and reward c…[Int J Obes (Lond). 2009] – PubMed Result In one study, obese women had greater brain activity in response to pictures of high fat foods than did non-obese women. Widespread reward-system activation in obese women…[Neuroimage. 2008] – PubMed Result and Effective connectivity of a reward network in obes…[Brain Res Bull. 2009] – PubMed Result

Gut peptides and the regulation of appetite. [Obes Rev. 2006] – PubMed Result