In addition, differences at the phylogenetic order level in both dominant and minor bacterial orders were determined Y-27632 msds in the cecal contents. Previous data in humans and rodents have shown that >90% of the microbiota in a normal distal gut is represented by the Bacteroidetes and Firmicutes phyla (21). Among the Bacteroidetes, the Bacteroides class and Bacteroidales order dominate, and, among the Firmicutes, the Clostridia class and Clostridiales order dominate; moreover, members of these phyla have been shown to be influenced by high-fat feeding or obesity (3, 28, 38�C39). An increase in the ��-proteobacteria class, in which belong the order Enterobacteriales and the family Enterobacteriaceae, has also been reported on a HF diet (21).

Host inflammation has also been shown to promote the growth of aerotolerant bacteria such as Enterobacteriaceae (30). Therefore Bacteroidales, Clostridiales, and Enterobacteriales were chosen for the current study. The data showed that consumption of a HF diet induces changes in gut microbiota, but it is the development of inflammation in response to these changes that is associated with the appearance of hyperphagia and an obese phenotype. MATERIALS AND METHODS Animals. Male Sprague-Dawley rats (initial body wt = 262 �� 2 g) were single-housed in a temperature-controlled room with a 12:12-h light-dark cycle and fed either a low-fat diet (LF; Research Diets 12450B) or a HF diet (Research Diets 12451) for 8 or 12 wk. The diets provided 3.85 kcal/g of energy for the LF 70% carbohydrate, 20% protein, 10% fat [saturated fatty acids (SAT), 25.

1%; monounsaturated fatty acids (MUFA), 34.7%; polyunsaturated fatty acids (PUFA), 40.2%] and 4.73 kcal/g of energy for the HF [35% carbohydrate, 20% protein, 45% fat (SAT, 36.3%; MUFA, 45.3%; PUFA, 18.5%)]. Body weight and food intake were recorded daily. Animals were killed after 8 wk (n = 17; LF n = 6, HF = 11) or 12 wk (n Batimastat = 13; LF n = 5, HF = 8). An additional group of rats (n = 12; LF n = 4, HF = 8) were fed diets for 12 wk, and body weight was recorded weekly. All experiments were performed in accordance with protocols reviewed and approved by the Institutional Animal Care and Use Committee, University of California Davis. Measurement of gut permeability in vivo. After 10 wk on the diet, rats were fasted for 6 h and gavaged with 4,000 kDa FITC-labeled dextran diluted in saline (Sigma-Aldrich, St. Louis, MO) (500 mg/kg, 125 mg/ml). After 1 h, blood (500 ��l) was collected from the tail vein and centrifuged (10,000 rpm for 3 min at 4��C), and FITC-dextran concentration in plasma was determined by spectrophotometry (excitation wavelength 485 nm; emission wavelength 535 nm; SpectraMax M2; Molecular Devices, Sunnyvale, CA). Tissue collection.