2012 Annual Report
1a.Objectives (from AD-416):
1. Determine if consumption of fermentable fiber, provided as soluble oligosaccharide at low or high dose or as a mixture of whole grains, results in a shift in fecal microbiota to enrich Bifidobacteria, increase Bifidobacteria to Firmicutes ratio (B/F), and enhance butyrate-producing Clostridial clusters IV and XIa.
2. Determine if B/F ratio and Clostridial clusters IV and XIa are associated with breath hydrogen, butyrate levels in isolated colonocytes, and postprandial GLP-1.
3. Determine if B/F ratio and Clostridial clusters IV and XIa are associated with (a) glucose tolerance,(b) satiety, (c) inflammatory markers.
4. Measure available energy content of the oligosaccharide and the whole grain foods and determine if total energy harvest from controlled diets is related to B/F ratio and Clostridial clusters IV and XIa.
1b.Approach (from AD-416):
Healthy subjects (n=20) will participate in a crossover study with 4 treatment arms: i) control diet with low fiber, ii) low dose (20 g) oligosaccharide added to control diet, iii) high dose (40 g) oligosaccharide added to control diet, and iv) comparison diet with adequate fiber from whole grains. Each treatment will be administered for 3 weeks interspersed with washout periods of 2 weeks. Fecal microbiota will be characterized by sequencing of community 16S rRNA genes. The procedure includes extraction of genomic DNA, amplification of V1 to V3 regions of 16S rRNA genes by PCR, and sequencing using the 454/Roche A sequencing primer kit and Roche 454 GS-FLX Titanium chemistry. Meal challenge protocols will be conducted during the 3rd week of each treatment and fermentation products, glucose control, inflammatory markers and satiety will be assessed. In addition coloncytes will be isolated from fecal samples for the analysis of fermentation products. Measurement of digestible and metabolizable energy will be done by bomb calorimetry and proximate analysis of the controlled treatment diets and coinciding complete urine and fecal collections obtained during the 3rd week of treatment. Biological samples will be archived for future metabolomic analyses using 1H NMR- and mass spec-metabolite profiling, both global & targeted.
This research contributes to objective 2 of the in-house parent project. In FY2012, the human study protocol was written and approved by the University of California-Davis IRB, the diet intervention was developed and nutrient content analyzed, the manual of procedures was written, and new methods needed to support this project were tested and validated, including breath hydrogen analysis, and isolating gut bacterial DNA for genotyping. The human study is progressing as planned with a total of 10 subjects currently enrolled. Recruitment is ongoing with the goal of achieving a full cohort of 20 subjects at the end of FY2012.