Gut Microbiota as a Hidden Risk Factor in Adult Obesity

Abstract

Obesity has become one of the most important medical and public health problems of this era. It was described as the “new world syndrome”, and it had been called the disease of the twenty first century. It was defined as a medical condition in which excess body fat has accumulated to the extent that it may have a negative effect on health leading to reduced life expectancy and/or increased health problems. People are considered obese when their body mass index (BMI), a measurement obtained by dividing a person’s weight by the square of person’s height, (exceeds 30 kg/m2). As obesity is a complex condition influenced by many factors as Genetic, endocrinal and environmental factors, recent evidence suggests that gut microbiota is one of the new environmental risk factors of obesity by causing weight gain and altered energy metabolism that accompanies the obese state. Gut microbiota which is an assortment of microorganisms inhabiting the length and width of mammalian GIT and dominated by bacteria as Bacteroides and Bifidobacterium, also have different profile associated with human obesity, as low abundance of Lactobacilli and high abundance of E-coli. Some studies showed that microbiota in obese subjects has an elevated proportion of Lactobacilli and reduced population of Bacteroides, while other studies linked the Enterobacteriaceae and specifically E-coli to overweight and obesity, but the discrimination between lean and obese gut microbiota is improved when the taxonomic depth of the analysis is increased. Some studies showed that Lactobacillus Paracasei and Lactobacillus Plantarum was significantly associated with lean status and Lactobacillus Reuteri was found more frequently in obese subjects. Different mechanisms linked gut microbiota to obesity such as ileal inflammation that decrease intestinal alkaline phosphatase activity which is an enzyme that detoxifies the bacterial component known to cause inflammation and increase innate immune system activation in the luminal walls. Another mechanism by which the gut microbiota affects body weight is by increasing energy harvesting from dietary fibers by breaking down indigestible polysaccharides to short chain fatty acids that may be a contribution factor in the obese state. Other mechanisms linking gut microbiota to obese status by inhibition of production of fasting induced adipocyte factor (FIAF) leading to stimulation of Lipoprotein Lipase thereby promoting the dissociation of fatty acids from triglycerides for increas uptake into tissues. Unfortunately the role of gut microbiota in energy expenditure in humans is not known, and only limited information is known from animal models. The aim of this study was to assess the count and variability of gut microbiota profile (with special consideration to Lactobacilli, E.coli and staph.aureus) in relation to body mass index and their association with obesity. This study was a case control study which was conducted on a total number of one hundred individuals divided into four random groups according to BMI (weight/(height)2) in the central microbiology laboratory in collaboration with obesity outpatient clinic in Ain Shams University Hospitals over a study period from September, 2013 to February, 2014. Data was collected regarding gender, age, clinical history and laboratory investigations as (blood sugar and hormonal profile liver, kidney function tests and lipid profile) with exclusion of patient <18 years old, history of colon cancer, inflammatory bowel disease, acute or chronic diarrhea in previous 4 weeks , antibiotic, prebiotic and probiotic administration of a period less than 1 month before taking faecal sample, familial obesity, patients with associated co-morbidities as (DM, hypertension), and patients with dyslipidemia, hormonal or endocrinal disturbance, also anthropometric measurements was done as regards weight, height, body mass index, waist circumference, hip circumference and (waist/hip circumference ratio). Fresh stool samples were collected and conventional stool culture, with manual quantitative viable bacterial count (VBC) (CFu/mL) was performed regarding (E.coli and Lactobacilli). As regards the stool culture technique, the quadrant technique was performed which was indicated for samples with neumerous colony forming unit as stool or sputum (rich in microflora) for well separation and enumeration of colonies. As regards manual quantitative method it was a preferred method for quantitative population analysis of pure and mixed cultures which relies on plating serial dilutions and subsequent counting of colony forming units. In recent years a range of alternative costly methods as quantitative PCR and fluorescent labeling or genome probing with microarrays, but these methods measure all cells even nonviable cells and may require the use of special equipment or extensive protocol development. The total number of 100 participants that were included in this study; (26%) were males, (74%) were females, their ages ranged from (19-54) years with mean (32.760+9.058). The studied groups were divided into Obese group (29%) with BMI >30, which were subdivided into obese group 40>BMI>30 and morbidly obese group 50<BMI>40, overweight group (23%) with 30> BMI>25, average weight group (26%) with 25> BMI >19, and underweight (22%) with BMI <19.