Contribution of very low-density lipoprotein triglyceride fatty acids to postabsorptive free fatty acid flux in obese humans

Nikki C. Bush; Jessica M. Triay; Nicola W. Gathaiya; Kazanna C. Hames; Michael D. Jensen

doi:10.1016/j.metabol.2013.09.008

Contribution of very low-density lipoprotein triglyceride fatty acids to postabsorptive free fatty acid flux in obese humans

Nikki C. Bush, Jessica M. Triay, Nicola W. Gathaiya, Kazanna C. Hames, Michael D. Jensen

Endocrinology, Diabetes, Metabolism, and Nutrition

Research output: Contribution to journal › Article › peer-review

12 Scopus citations

Abstract

Objective In the fasting state, plasma free fatty acids (FFA) are thought to derive almost exclusively from adipose tissue lipolysis. However, there are mixed reports as to whether the spillover of fatty acids (FA) from very low-density lipoprotein triglyceride (VLDL-TG) hydrolysis contributes significantly to the plasma FFA pool. Because substantial VLDL-TG fatty acid spillover into the plasma FFA pool would profoundly impact the interpretation of isotope dilution measures of FFA flux, we investigated the contribution of VLDL-TG spillover to plasma FFA appearance. Materials/Methods Eighteen obese adults (15 women) participated in these studies. Each volunteer received a primed, continuous infusion of their own ex-vivo labeled ([1- ¹⁴C]triolein) VLDL-TG and a continuous infusion of [U- ¹³C]oleate (8 nmol·kg fat free mass^{- 1}· min^{- 1}) to measure VLDL-TG and FFA rate of appearance (Ra), respectively. The presence of ¹⁴C-oleate in the plasma FFA-oleate pool was used to calculate the contribution of spillover from VLDL-TG-oleate to the plasma FFA-oleate Ra. Results The spillover rate of VLDL-TG-oleate into plasma FFA-oleate was 6 ± 2 μmol/min (7% ± 2% of [ ¹⁴C]oleate from VLDL-TG) and FFA-oleate flux was 240 ± 61 μmol/min. Thus, only 3% ± 1% of total plasma FFA-oleate appearance could be accounted for by VLDL-TG spillover. Conclusion The contribution of VLDL-TG spillover to the total plasma FFA pool is negligible and will not materially affect the interpretation of FFA flux measures as an index of adipose tissue lipolysis.

Original language	English (US)
Pages (from-to)	137-140
Number of pages	4
Journal	Metabolism: Clinical and Experimental
Volume	63
Issue number	1
DOIs	https://doi.org/10.1016/j.metabol.2013.09.008
State	Published - Jan 2014

Keywords

Hypertriglyceridemia
Isotope dilution
[C]triolein
[U-C]oleate

ASJC Scopus subject areas

Endocrinology, Diabetes and Metabolism
Endocrinology

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10.1016/j.metabol.2013.09.008

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title = "Contribution of very low-density lipoprotein triglyceride fatty acids to postabsorptive free fatty acid flux in obese humans",

abstract = "Objective In the fasting state, plasma free fatty acids (FFA) are thought to derive almost exclusively from adipose tissue lipolysis. However, there are mixed reports as to whether the spillover of fatty acids (FA) from very low-density lipoprotein triglyceride (VLDL-TG) hydrolysis contributes significantly to the plasma FFA pool. Because substantial VLDL-TG fatty acid spillover into the plasma FFA pool would profoundly impact the interpretation of isotope dilution measures of FFA flux, we investigated the contribution of VLDL-TG spillover to plasma FFA appearance. Materials/Methods Eighteen obese adults (15 women) participated in these studies. Each volunteer received a primed, continuous infusion of their own ex-vivo labeled ([1- 14C]triolein) VLDL-TG and a continuous infusion of [U- 13C]oleate (8 nmol·kg fat free mass- 1· min- 1) to measure VLDL-TG and FFA rate of appearance (Ra), respectively. The presence of 14C-oleate in the plasma FFA-oleate pool was used to calculate the contribution of spillover from VLDL-TG-oleate to the plasma FFA-oleate Ra. Results The spillover rate of VLDL-TG-oleate into plasma FFA-oleate was 6 ± 2 μmol/min (7% ± 2% of [ 14C]oleate from VLDL-TG) and FFA-oleate flux was 240 ± 61 μmol/min. Thus, only 3% ± 1% of total plasma FFA-oleate appearance could be accounted for by VLDL-TG spillover. Conclusion The contribution of VLDL-TG spillover to the total plasma FFA pool is negligible and will not materially affect the interpretation of FFA flux measures as an index of adipose tissue lipolysis.",

keywords = "Hypertriglyceridemia, Isotope dilution, [C]triolein, [U-C]oleate",

author = "Bush, {Nikki C.} and Triay, {Jessica M.} and Gathaiya, {Nicola W.} and Hames, {Kazanna C.} and Jensen, {Michael D.}",

note = "Funding Information: Supported by grants DK40484 , DK45343 , DK50456 and the National Center for Research Resources and the National Center for Advancing Translational Sciences, National Institutes of Health , through Grant Number 1 UL1 RR024150-01 and UL1 TR000135 . N.B. received fellowship funding from the NIH training grant T32-DK07352 and the ADA fellowship grant 7-112-MN-36 . The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH. ",

year = "2014",

month = jan,

doi = "10.1016/j.metabol.2013.09.008",

language = "English (US)",

volume = "63",

pages = "137--140",

journal = "Metabolism: Clinical and Experimental",

issn = "0026-0495",

publisher = "W.B. Saunders Ltd",

number = "1",

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T1 - Contribution of very low-density lipoprotein triglyceride fatty acids to postabsorptive free fatty acid flux in obese humans

AU - Bush, Nikki C.

AU - Triay, Jessica M.

AU - Gathaiya, Nicola W.

AU - Hames, Kazanna C.

AU - Jensen, Michael D.

N1 - Funding Information: Supported by grants DK40484 , DK45343 , DK50456 and the National Center for Research Resources and the National Center for Advancing Translational Sciences, National Institutes of Health , through Grant Number 1 UL1 RR024150-01 and UL1 TR000135 . N.B. received fellowship funding from the NIH training grant T32-DK07352 and the ADA fellowship grant 7-112-MN-36 . The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

PY - 2014/1

Y1 - 2014/1

N2 - Objective In the fasting state, plasma free fatty acids (FFA) are thought to derive almost exclusively from adipose tissue lipolysis. However, there are mixed reports as to whether the spillover of fatty acids (FA) from very low-density lipoprotein triglyceride (VLDL-TG) hydrolysis contributes significantly to the plasma FFA pool. Because substantial VLDL-TG fatty acid spillover into the plasma FFA pool would profoundly impact the interpretation of isotope dilution measures of FFA flux, we investigated the contribution of VLDL-TG spillover to plasma FFA appearance. Materials/Methods Eighteen obese adults (15 women) participated in these studies. Each volunteer received a primed, continuous infusion of their own ex-vivo labeled ([1- 14C]triolein) VLDL-TG and a continuous infusion of [U- 13C]oleate (8 nmol·kg fat free mass- 1· min- 1) to measure VLDL-TG and FFA rate of appearance (Ra), respectively. The presence of 14C-oleate in the plasma FFA-oleate pool was used to calculate the contribution of spillover from VLDL-TG-oleate to the plasma FFA-oleate Ra. Results The spillover rate of VLDL-TG-oleate into plasma FFA-oleate was 6 ± 2 μmol/min (7% ± 2% of [ 14C]oleate from VLDL-TG) and FFA-oleate flux was 240 ± 61 μmol/min. Thus, only 3% ± 1% of total plasma FFA-oleate appearance could be accounted for by VLDL-TG spillover. Conclusion The contribution of VLDL-TG spillover to the total plasma FFA pool is negligible and will not materially affect the interpretation of FFA flux measures as an index of adipose tissue lipolysis.

AB - Objective In the fasting state, plasma free fatty acids (FFA) are thought to derive almost exclusively from adipose tissue lipolysis. However, there are mixed reports as to whether the spillover of fatty acids (FA) from very low-density lipoprotein triglyceride (VLDL-TG) hydrolysis contributes significantly to the plasma FFA pool. Because substantial VLDL-TG fatty acid spillover into the plasma FFA pool would profoundly impact the interpretation of isotope dilution measures of FFA flux, we investigated the contribution of VLDL-TG spillover to plasma FFA appearance. Materials/Methods Eighteen obese adults (15 women) participated in these studies. Each volunteer received a primed, continuous infusion of their own ex-vivo labeled ([1- 14C]triolein) VLDL-TG and a continuous infusion of [U- 13C]oleate (8 nmol·kg fat free mass- 1· min- 1) to measure VLDL-TG and FFA rate of appearance (Ra), respectively. The presence of 14C-oleate in the plasma FFA-oleate pool was used to calculate the contribution of spillover from VLDL-TG-oleate to the plasma FFA-oleate Ra. Results The spillover rate of VLDL-TG-oleate into plasma FFA-oleate was 6 ± 2 μmol/min (7% ± 2% of [ 14C]oleate from VLDL-TG) and FFA-oleate flux was 240 ± 61 μmol/min. Thus, only 3% ± 1% of total plasma FFA-oleate appearance could be accounted for by VLDL-TG spillover. Conclusion The contribution of VLDL-TG spillover to the total plasma FFA pool is negligible and will not materially affect the interpretation of FFA flux measures as an index of adipose tissue lipolysis.

KW - Hypertriglyceridemia

KW - Isotope dilution

KW - [C]triolein

KW - [U-C]oleate

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Contribution of very low-density lipoprotein triglyceride fatty acids to postabsorptive free fatty acid flux in obese humans

Abstract

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