Digesta passage rates in the rat

The movements of digestion markers in the gut of the rat were investigated and the results of the investigation are reported in two manuscripts. The objective of the first study was to determine the influence of particle size of dietary wheat bran, chosen as a representative insoluble fiber, on the mean retention time (MRT) of digesta in the rat. The study design included a control group to detect the influence of particle size of digestion marker on the observed retention times. Additionally, a comparison was made between bran and the soluble fiber pectin. Both the soluble cobalt EDTA (Co EDTA) and insoluble chromium mordanted bran (CrMB), of two size ranges were administered to 4 groups of rats fed a semi-purified diet supplemented with wheat bran or pectin (10% dilution). Bran size and particulate marker size were large/large, large/small, small/small and pectin/small for the 4 groups. Mean retention times for CrMB were significantly longer in the pectin than the bran supplemented groups. Differences were not significantly different within the bran supplemented group. No significant differences were found between the rate of passage of CrMB and Co EDTA in any group. The second study was designed to identify pooling of markers in the rat gut. A mathematical model was developed as a system of equations which predicted the marker distribution along the gut following dosing. The model assumed that two pools, the stomach and cecum, were kinetically recognizable in the rat. The predicted distribution of CrMB and Co EDTA was compared to in vivo distribution at 4 h intervals by sequential termination and dissection of the animals. The smaller particle bran had a longer MRT in the cecum and a shorter MRT in the proximal colon. Total MRT to the mid-colon was similar in all bran supplemented groups. Pectin fed animals had significantly enlarged gut organs which explained the slower movement of marker in these animals. The cecum was found to delay the transit of marker from the small intestine to the proximal colon as much as 2.1 h. This delay resulted in the gut appearing as a single pool overall and therefore led the model to overpredict the initial rate of appearance of marker distal to the cecum. A streamlined system was developed to digest the fecal samples in preparation for atomic absorption spectroscopy, the method used to quantify digestion marker recovery. The development of the method is discussed and supporting data are presented on the reproducibility and limits of the method

A stable isotope biomarker of marine food intake captures associations between n-3 fatty acid intake and chronic disease risk in a Yup'ik study population, and detects new associations with blood pressure and adiponectin.

The nitrogen isotope ratio (δ(15)N) of RBCs has been proposed as a biomarker of marine food intake in Yup'ik people based on strong associations with RBC eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). However, EPA and DHA derive from marine fats, whereas elevated δ(15)N derives from marine protein, and these dietary components may have different biologic effects. Whether δ(15)N is similarly associated with chronic disease risk factors compared with RBC EPA and DHA is not known. We used covariate-adjusted linear models to describe biomarker associations with chronic disease risk factors in Yup'ik people, first in a smaller (n = 363) cross-sectional study population using RBC EPA, DHA, and δ(15)N, and then in a larger (n = 772) cross-sectional study population using δ(15)N only. In the smaller sample, associations of RBC EPA, DHA, and δ(15)N with obesity and chronic disease risk factors were similar in direction and significance: δ(15)N was positively associated with total, HDL, and LDL cholesterol, apolipoprotein A-I, and insulin-like growth factor binding protein-3 (IGFBP-3), and inversely associated with triglycerides. Based on comparisons between covariate-adjusted β-coefficients, EPA was more strongly associated with circulating lipids and lipoproteins, whereas δ(15)N was more strongly associated with adipokines, the inflammatory marker interleukin-6, and IGFBP-3. In the larger sample there were new findings for this population: δ(15)N was inversely associated with blood pressure and there was a significant association (with inverse linear and positive quadratic terms) with adiponectin. In conclusion, δ(15)N is a valid measure for evaluating associations between EPA and DHA intake and chronic disease risk in Yup'ik people and may be used in larger studies. By measuring δ(15)N, we report beneficial associations of marine food intake with blood pressure and adiponectin, which may contribute to a lower incidence of some chronic diseases in Yup'ik people

Red blood cell δ15N: a novel biomarker of dietary eicosapentaenoic acid and docosahexaenoic acid intake1234

Background: The long-chain omega-3 (n–3) fatty acids derived from fish, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are associated with a reduced risk of cardiovascular disease and other chronic diseases. Study of the associations between EPA and DHA intake and disease requires a valid biomarker of dietary intake; however, the direct measurement of tissue fatty acid concentrations is expensive and time consuming