Research targets biologic profile of obesity


Condition plays major role in health care maintenance, cost

New Orleans, LA Obesity has reached epidemic proportions in America due to a number of factors including increased technology and the rise in consumption of prepared and preserved foods. Finding a solution has been a major challenge for researchers, but according to two studies presented today at Digestive Disease Week in New Orleans, significant progress has been made in finding the underlying characteristics of obesity. Digestive Disease Week (DDW) is the largest international gathering of physicians, researchers and academics in the fields of gastroenterology, hepatology, endoscopy and gastrointestinal surgery.

"Obesity is one of the most serious risk factors for some of the leading causes of death in Americans today, such as heart disease," said Barbara Bass, M.D., of the University of Maryland School of Medicine. "Finding its basic biological conditions may offer scientists better tools with which to fight this chronic condition."

Exaggerated Gastric Accommodation in Patients with Obesity (Abstract 105214*)
Overeating is one of the primary causes of obesity. For patients suffering from morbid obesity, new research suggests that exaggerated gastric accommodation to meals may be to blame for the continued struggle against weight loss, according to researchers from the Union Hospital of Tongji Medical College in China.

The results of the study showed that obese patients eat more during meals than people at a healthy weight before experiencing a feeling of fullness, due to an increased minimal distending pressure and an exaggerated gastric accommodation. The mean value of minimal distending pressure, reflecting intra-abdominal pressure, was significantly elevated in obese patients, as compared with the healthy controls, as was the postprandial (after a meal) increase in gastric volume. No significant difference was noted in gastric compliance between the two.

"We believe this could help explain some of the biological challenges for the morbidly obese to losing weight through conventional methods such as calorie counting," said Xiaohua Hou, M.D., lead author of the study. "Weight loss approaches in this population need to be addressed differently to achieve successful results and surgery may often be a necessity to correct the problem."

The study consisted of 10 obese patients [average body mass index (BMI): 33.4 +/- 3.8 kg/m2, average age: 32.8 +/- 10.5, three males and seven females] and 11 healthy volunteers [average BMI: 22.1 +/- 1.6 kg/m2, average age: 28.0 +/- 13.3, four males and seven females]. Researchers monitored minimal distending pressure (MDP, the lowest pressure at which respiration motion is present in the barostat reading), gastric compliance and gastric accommodation using an electronic barostat, which monitors the volume of air in the stomach. Gastric volume was measured after a liquid meal of 300kcal.

Gene Expression Profiles Associated with Obesity (Abstract 106979*)
According to previous studies, phenotypic expression of obesity is influenced by both environmental and genetic factors. In this study, researchers from the Center for Liver Diseases at Inova Fairfax Hospital and George Mason University noted significant differentiation of gene expression in obese patients undergoing bariatric surgery.

Gene expression data comparing obese patients to lean controls revealed a number of genes with more than a two-fold increased altered expression. In particular, obese patients showed significant up-regulation of genes related to energy expenditure pathways as compared to controls.

"In patients with morbid obesity, differential expression of genes related to energy expenditure in the fat tissue is important to note, as this may explain a host of related factors contributing to obesity for this patient population," said Zobair Younossi, M.D., MPH, lead investigator of the study. "The exact contribution of these genes to the development of obesity is currently being studied to offer additional insight on the underlying mechanisms of the disease."

To confirm these results, snap-frozen intra-abdominal adipose (fat) tissues from morbidly obese patients and lean controls were used for RNA extraction. Upon analysis, gene expression profiles of obese patients were compared to the lean control samples, with and without gender separation. Genes with statistically significant up- or down-regulation of more than two-fold were considered for further inspection. Of 120 patients enrolled, gene expression data was available for 33 obese patients and six lean controls. Baseline demographic data for the obese patients were: average age 44.1 +/- 10.6 years, 88 percent female, 82 percent Caucasian, 15 percent type 2 diabetes, and body mass index 43.87 +/- 8.01.

Source: Eurekalert & others

Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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