Recovery of (13)CO2 during rest and exercise after [1-(13)C]acetate, [2-(13)C]acetate, and NaH(13)CO3 infusions.

نویسندگان

  • J K Trimmer
  • G A Casazza
  • M A Horning
  • G A Brooks
چکیده

For estimating the oxidation rates (Rox) of glucose and other substrates by use of (13)C-labeled tracers, we obtained correction factors to account for label dilution in endogenous bicarbonate pools and TCA cycle exchange reactions. Fractional recoveries of (13)C label in respiratory gases were determined during 225 min of rest and 90 min of leg cycle ergometry at 45 and 65% peak oxygen uptake (VO(2 peak)) after continuous infusions of [1-(13)C]acetate, [2-(13)C]acetate, or NaH(13)CO(3). In parallel trials, [6,6-(2)H]glucose and [1-(13)C]glucose were given. Experiments were conducted after an overnight fast with exercise commencing 12 h after the last meal. During the transition from rest to exercise, CO(2) production increased (P < 0.05) in an intensity-dependent manner. Significant differences were observed in the fractional recoveries of (13)C label as (13)CO(2) at rest (NaH(13)CO(3), 77.5 +/- 2.8%; [1-(13)C]acetate, 49.8 +/- 2.4%; [2-(13)C]acetate, 26.1 +/- 1.4%). During exercise, fractional recoveries of (13)C label from [1-(13)C]acetate, [2-(13)C]acetate, and NaH(13)CO(3) were increased compared with rest. Magnitudes of label recoveries during both exercise intensities were tracer specific (NaH(13)CO(3), 93%; [1-(13)C]acetate, 80%; [2-(13)C]acetate, 65%). Use of an acetate-derived correction factor for estimating glucose oxidation resulted in Rox values in excess (P < 0.05) of glucose rate of disappearance during hard exercise. We conclude that, after an overnight fast: 1) recovery of (13)C label as (13)CO(2) from [(13)C]acetate is decreased compared with bicarbonate; 2) the position of (13)C acetate label affects carbon dilution estimations; 3) recovery of (13)C label increases in the transition from rest to exercise in an isotope-dependent manner; and 4) application of an acetate correction factor in glucose oxidation measurements results in oxidation rates in excess of glucose disappearance during exercise at 65% of VO(2 peak). Therefore, bicarbonate, not acetate, correction factors are advocated for estimating glucose oxidation from carbon tracers in exercising men.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Recovery of labeled CO2 from acetate in severely burned children.

The purpose of this study was to determine the fractional recovery rate of labeled CO(2) in the breath of severely burned children. This information is needed to perform tracer studies of substrate oxidation using carbon-labeled fatty acids. Nine children, ages 4-14 yr with massive burns participated in the study. All experiments were performed 7 days post burn after an overnight fast. A primed...

متن کامل

Determinants of the acetate recovery factor: implications for estimation of [13C]substrate oxidation.

When using (13)C or (14)C tracers to study substrate metabolism, an acetate correction factor should be applied to correct for loss of label in the exchange pathways of the tricarboxylic acid cycle. We have shown recently that the [(13)C]acetate recovery factor has a high inter-individual variability and should therefore be determined in every subject. In the present study we examined the facto...

متن کامل

Phytogenic biosynthesis and emission of methyl acetate.

Acetylation of plant metabolites fundamentally changes their volatility, solubility and activity as semiochemicals. Here we present a new technique termed dynamic (13) C-pulse chasing to track the fate of C1-3 carbon atoms of pyruvate into the biosynthesis and emission of methyl acetate (MA) and CO2 . (13) C-labelling of MA and CO2 branch emissions respond within minutes to changes in (13) C-po...

متن کامل

Colonic fermentation of inulin increases whole-body acetate turnover in dogs.

Metabolism of acetate from colonic fermentation was investigated in dogs. Beagle dogs (n = 9) were fed a control diet for 17 d followed by a 3% inulin-enriched diet (from chicory) for 4 and 21 d. On 3 occasions, the dogs were administered simultaneously infusions of [1-(13)C]acetate i.v. and [1,2-(13)C(2)]acetate intrarectally. Peripheral acetate concentration and turnover did not change over t...

متن کامل

Pathway of propionate oxidation by a syntrophic culture of Smithella propionica and Methanospirillum hungatei.

The pathway of propionate conversion in a syntrophic coculture of Smithella propionica and Methanospirillum hungatei JF1 was investigated by (13)C-NMR spectroscopy. Cocultures produced acetate and butyrate from propionate. [3-(13)C]propionate was converted to [2-(13)C]acetate, with no [1-(13)C]acetate formed. Butyrate from [3-(13)C]propionate was labeled at the C2 and C4 positions in a ratio of...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:
  • American journal of physiology. Endocrinology and metabolism

دوره 281 4  شماره 

صفحات  -

تاریخ انتشار 2001