Model for determination of 13C substrate oxidation rates in humans in the fed state

Abstract

The effect of a test diet of conventional North American foods on breath 13CO2 abundance was determined in 4 healthy males. Subjects consumed a diet containing 41.9% energy as fat and a polyunsaturated:saturated fatty acid ratio of 0.217 for 5 days at a level equal to estimated requirements for total energy. One subject underwent four 5-day feeding periods. Over the feeding period mean change in subjects' body weight was -0.165 +/- 0.64% (means +/- SEM) of initial body weight. On day 5 breath samples were collected hourly from 0745 to 1645 h and analyzed for 13CO2 enrichment relative to the pre-breakfast fasted state (level at 0745 h). Breakfast and lunch were consumed at 0820 and 1300 h respectively. Mean enrichment peaked at 1445 h at 0.00311 atom % excess above fasting level for all subjects and 0.00243 atom % excess for the four repeated trials on one subject. Between subject variation (SEM) in 13CO2 enrichment (0.000618 atom %) was significantly greater than within subject variation (0.000308 atom %). These results indicate that ingestion of normal meals during the breath test period increases breath 13CO2 abundance due to a shift in substrate oxidation. The small within subject variation in repeated 13CO2 enrichment profiles indicates the reliability of 13C breath tests using controlled diets. It is concluded that for tests conducted under identical conditions, an initial background 13CO2 abundance profile determined once for each subject, can be subtracted from the subsequent enrichment profile generated by a labeled test substrate.

Endogenous fat oxidation during medium chain versus long chain triglyceride feeding in healthy women

“…C breath enrichment due to oxidation of labelled fatty acids delivered at the present dose is measurably higher than that due to natural 13 C abundance, 30 making the impact of potential background shifts in 13 C enrichment negligible.…”

The Effect of Energy Intake and Expenditure on the Recovery of 13CO2 in the Parenterally Fed Neonate during a 4-Hour Primed Constant Infusion of NAH13CO3

“…Multiple analyses (n = 10) of an NBS no. 20 standard demonstrated the analytical precision (f 1 SD) of this instrument at 0.00007 APE (8). Results of ''C abundance of both baselines and plateau were calculated as APE over a reference C 0 2 tank standard sample.…”

“…Wong WW, Irving CS, Thomas MR, Malphus EW, Boutton TW, Garza C, epidermal skin potential and skin conductance bioelectric measurements for the clinical purpose of preliminary cystic fibrosis screening. These electrodermal measurements, which are relatively simple to obtain, are sensitive to sweat gland activity in amounts too small to produce surface sweating (3)(4)(5)(6)(7)(8). These microdischarges of sweat transiently alter the standing electric SPL and SCL, producing a SPR and a SPR (see Figs.…”

Stable isotope approaches, applications, and issues related to polyunsaturated fatty acid metabolism studies

“…The carbon-13 breath test is used as a safe and noninvasive research tool for measuring fatty acid oxidation in children and healthy adults. IRMS methods are used to measure changes in the 13 CO 2 / 12 CO 2 ratios of breath samples and can accurately detect small changes if appropriate corrections for variation in the natural 13 C background are made (33). The " 13 CO 2 Breath Test" has been used in many studies to measure factors that affect fatty acid oxidation.…”