This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.ABSTRACTHYPOTHESISIn a group of young adult males who increase their fractionalcalcium absorption by >5% after 3 weeks of consuming 8 g/d of Synergy 1, there will be a significant increase in the level of the oral isotope in blood between 7 and 26 hours after oral dosing (Barger-Lux, Heaney and Recker, Calcif Tissue Int 1989;44:308-311) reflecting a significant increase in colonic phase calcium absorption.
SPECIFIC AIMS To determine the likely mechanism of increased mineral absorption by insulin-type fructans by kinetic analysis using calcium stable isotopes.BACKGROUND AND SIGNIFICANCEThere is only one study looking at the time course of calcium absorption to determine the colonic component. This study (Barger-Lux, 1989), from Dr. Heaney's group at Creighton University, showed clearly that calcium absorption via the colonic component occurs after 7 hrs. from oral ingestion and is >99% complete by 23 hours after oral dosing (virtually complete at 23 hrs). Therefore, we will measure to 26 hours to provide a margin and reach the time used by Dr. Heaney to achieve 99.8% completion. Because the mouth-cecum transfer time is much shorter in young people than in elderly, it is likely that this will provide a substantial margin. The 48-hour sample will represent a backup for assessment of total maximal absorption.Because of the very large number of samples and costs associated with the stable isotopes and the analysis, we will need to identify responders to Synergy 1 before analyzing the kinetic data or performing a follow-up kinetic study. This is feasible as it is possible to determine responders from the urine absorption method within a few days after the study. From our previous data, as noted below (Abrams 2005, Griffin 2002; Halloway, under review), we expect that about 50-70% of screened adults or adolescents will respond to Synerty 1 by increasing their calcium absorption by >5% (this is substantially greater than the random variability in duplicate study calcium absorption measurements). The reason for this lack of response in some cases is uncertain, but very likely relates both to intrinsic calcium absorptive capacity and also the natural gut transit time and GI flora. This issue is not being addressed in this study. Rather we will identify the responders to evaluate the mechanisms of their response.
Showing the most recent 10 out of 459 publications