Dietary fat content and fiber type modulate hind gut microbial community and metabolic markers in the pig.

Obesity leads to changes in the gut microbial community which contribute to the metabolic dysregulation in obesity. Dietary fat and fiber affect the caloric density of foods. The impact of dietary fat content and fiber type on the microbial community in the hind gut is unknown. Effect of dietary fat level and fiber type on hindgut microbiota and volatile fatty acid (VFA) profiles was investigated. Expression of metabolic marker genes in the gut, adipose tissue and liver was determined. A 2 × 2 experiment was conducted in pigs fed at two dietary fat levels (5% or 17.5% swine grease) and two fiber types (4% inulin, fermentable fructo-oligosaccharide or 4% solka floc, non-fermentable cellulose). High fat diets (HFD) resulted in a higher (P<0.05) total body weight gain, feed efficiency and back fat accumulation than the low fat diet. Feeding of inulin, but not solka floc, attenuated (P<0.05) the HFD-induced higher body weight gain and fat mass accumulation. Inulin feeding tended to lead to higher total VFA production in the cecum and resulted in a higher (P<0.05) expression of acyl coA oxidase (ACO), a marker of peroxisomal ß-oxidation. Inulin feeding also resulted in lower expression of sterol regulatory element binding protein 1c (SREBP-1c), a marker of lipid anabolism. Bacteria community structure characterized by DGGE analysis of PCR amplified 16S rRNA gene fragments showed that inulin feeding resulted in greater bacterial population richness than solka floc feeding. Cluster analysis of pairwise Dice similarity comparisons of the DGGE profiles showed grouping by fiber type but not the level of dietary fat. Canonical correspondence analysis (CCA) of PCR- DGGE profiles showed that inulin feeding negatively correlated with back fat thickness. This study suggests a strong interplay between dietary fat level and fiber type in determining susceptibility to obesity.

Metabolic markers in Ossabaw pigs fed high fat diets enriched in regular or low α-linolenic acid soy oil.

BACKGROUND: Soy oil is a major vegetable oil consumed in the US. A recently developed soybean variety produces oil with a lower concentration of α-linolenic acid, hence a higher (n-6)/(n-3) ratio, than regular soy oil. The study was conducted to determine the metabolic impact of the low α-linolenic acid containing soy oil. METHODS: Ossabaw pigs were fed diets supplemented with either 13% regular soybean oil (SBO), or 13% of the low α-linolenic soybean oil (LLO) or a control diet (CON) without extra oil supplementation, for 8 weeks. RESULTS: Serum and adipose tissue α-linolenic acid concentration was higher in pigs fed the SBO diet than those on the CON and LLO diets. In the serum, the concentration of saturated fatty acids (SFA) was lower in the LLO group than in CON and SBO groups polyunsaturated fatty acid (PUFA) concentration was higher in the LLO group compared to CON and SBO groups. Glucose, insulin, triglycerides and LDL-cholesterol were higher in pigs fed the SBO diet than those fed the CON and LLO diets. HDL-cholesterol was lower in pigs on the SBO diet than those on the CON and LLO diets. Pigs fed SBO and LLO diets had lower CRP concentration than those on the CON diet. Adipose tissue expression of Interleukin 6 (IL-6) was higher in the SBO and LLO diets than the CON. Expression of ECM genes, COLVIA and fibronectin, was significantly reduced in the SBO diet relative to the CON and LLO diets whereas expression of inflammation-related genes, cluster of differentiation 68 (CD68) and monocyte chemoattractant protein 1 (MCP-1), was not different across treatments. CONCLUSIONS: Results suggest that lowering the content of α-linolenic acid in the context of a high fat diet could lead to mitigation of development of hyperinsulinemia and dyslipidemia without significant effects on adipose tissue inflammation.

The effect of lipid supplements on ruminal bacteria in continuous culture fermenters varies with the fatty acid composition.

A single flow continuous culture fermenter system was used in this study to investigate the influence of dietary lipid supplements varying in their fatty acid content on the DNA concentration of selected rumen bacteria. Four continuous culture fermenters were used in a 4 × 4 Latin square design with four periods of 10 d each. Treatment diets were fed at 45 g/d (DM basis) in three equal portions during the day. The diets were: 1) control (CON), 2) control with animal fat source (SAT), 3) control with soybean oil (SBO), and 4) control with fish oil (FO). Lipid supplements were added at 3% of diet DM. The concentrations of total volatile fatty acids and acetate were not affected (P>0.05) by lipid supplements. Concentrations of propionate, iso-butyrate, valerate and iso-valerate were highest (P<0.05) with the FO diet compared with the other treatment diets. The concentration of til C18:l (vaccenic acid, VA) in effluents increased (P<0.05) with SBO and FO diets and was highest with the SBO diet. The concentrations of C18:0 in effluents were lowest (P<0.05) for the FO diet compared with the other treatment diets. Concentrations of DNA for Anaerovibrio lipolytica, and Butyrivibrio proteoclasticus in fermenters were similar (P>0.05) for all diets. The DNA concentrations of Butyrivibrio fibrisolvens and Ruminococcus albus in fermenters were lowest (P<0.05) with the FO diet but were similar (P>0.05) among the other treatment diets. Selenomonas ruminantium DNA concentration in fermenters was highest (P<0.05) with the FO diet. In conclusion, SBO had no effect on bacterial DNA concentrations tested in this study and the VA accumulation in the rumen observed on the FO diet may be due in part to FO influence on B. fibrisolvens, R. albus, and S. ruminantium.