Triglycerides produced in the livers of fasting rabbits are predominantly stored as opposed to secreted into the plasma

Demidmaa Tuvdendorj, Xiao Jun Zhang, David L. Chinkes, Lijian Wang, Zhanpin Wu, Noe A. Rodriguez, David Herndon, Robert R. Wolfe

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Objective The liver plays a central role in regulating fat metabolism; however, it is not clear how the liver distributes the synthesized triglycerides (TGs) to storage and to the plasma. Materials and methods We have measured the relative distribution of TGs produced in the liver to storage and the plasma by means of U-13C16-palmitate infusion in anesthetized rabbits after an overnight fast. Results The fractional synthesis rates of TGs stored in the liver and secreted into the plasma were not significantly different (stored vs. secreted: 31.9 ± 0.8 vs. 27.7 ± 2.6% h- 1, p > 0.05). However, the absolute synthesis rates of hepatic stored and secreted TGs were 543 ± 158 and 27 ± 7 nmol kg- 1 min- 1 respectively, indicating that in fasting rabbits the TGs produced in the liver were predominately stored (92 ± 3%) rather than secreted (8 ± 3%) into the plasma. This large difference was mainly due to the larger pool size of the hepatic TGs which was 21 ± 9-fold that of plasma TGs. Plasma free fatty acids (FFAs) contributed 47 ± 1% of the FA precursor for hepatic TG synthesis, and the remaining 53 ± 1% was derived from hepatic lipid breakdown and possibly plasma TGs depending on the activity of hepatic lipase. Plasma palmitate concentration significantly correlated with hepatic palmitoyl-CoA and TG synthesis. Conclusion In rabbits, after an overnight fast, the absolute synthesis rate of hepatic stored TGs was significantly higher than that of secreted due to the larger pool size of hepatic TGs. The net synthesis rate of TG was approximately half the absolute rate. Plasma FFA is a major determinant of hepatic TG synthesis, and therefore hepatic TG storage.

Original languageEnglish (US)
Pages (from-to)580-587
Number of pages8
JournalMetabolism: Clinical and Experimental
Volume64
Issue number5
DOIs
StatePublished - May 1 2015

Fingerprint

Fasting
Triglycerides
Rabbits
Liver
Palmitates
Nonesterified Fatty Acids
Palmitoyl Coenzyme A
Lipase
Fats
Lipids

Keywords

  • Mass spectrometry
  • Rabbit liver
  • Stable isotopes
  • Triglyceride synthesis
  • Very low density lipoprotein

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Triglycerides produced in the livers of fasting rabbits are predominantly stored as opposed to secreted into the plasma. / Tuvdendorj, Demidmaa; Zhang, Xiao Jun; Chinkes, David L.; Wang, Lijian; Wu, Zhanpin; Rodriguez, Noe A.; Herndon, David; Wolfe, Robert R.

In: Metabolism: Clinical and Experimental, Vol. 64, No. 5, 01.05.2015, p. 580-587.

Research output: Contribution to journalArticle

Tuvdendorj, Demidmaa ; Zhang, Xiao Jun ; Chinkes, David L. ; Wang, Lijian ; Wu, Zhanpin ; Rodriguez, Noe A. ; Herndon, David ; Wolfe, Robert R. / Triglycerides produced in the livers of fasting rabbits are predominantly stored as opposed to secreted into the plasma. In: Metabolism: Clinical and Experimental. 2015 ; Vol. 64, No. 5. pp. 580-587.
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abstract = "Objective The liver plays a central role in regulating fat metabolism; however, it is not clear how the liver distributes the synthesized triglycerides (TGs) to storage and to the plasma. Materials and methods We have measured the relative distribution of TGs produced in the liver to storage and the plasma by means of U-13C16-palmitate infusion in anesthetized rabbits after an overnight fast. Results The fractional synthesis rates of TGs stored in the liver and secreted into the plasma were not significantly different (stored vs. secreted: 31.9 ± 0.8 vs. 27.7 ± 2.6{\%} h- 1, p > 0.05). However, the absolute synthesis rates of hepatic stored and secreted TGs were 543 ± 158 and 27 ± 7 nmol kg- 1 min- 1 respectively, indicating that in fasting rabbits the TGs produced in the liver were predominately stored (92 ± 3{\%}) rather than secreted (8 ± 3{\%}) into the plasma. This large difference was mainly due to the larger pool size of the hepatic TGs which was 21 ± 9-fold that of plasma TGs. Plasma free fatty acids (FFAs) contributed 47 ± 1{\%} of the FA precursor for hepatic TG synthesis, and the remaining 53 ± 1{\%} was derived from hepatic lipid breakdown and possibly plasma TGs depending on the activity of hepatic lipase. Plasma palmitate concentration significantly correlated with hepatic palmitoyl-CoA and TG synthesis. Conclusion In rabbits, after an overnight fast, the absolute synthesis rate of hepatic stored TGs was significantly higher than that of secreted due to the larger pool size of hepatic TGs. The net synthesis rate of TG was approximately half the absolute rate. Plasma FFA is a major determinant of hepatic TG synthesis, and therefore hepatic TG storage.",
keywords = "Mass spectrometry, Rabbit liver, Stable isotopes, Triglyceride synthesis, Very low density lipoprotein",
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T1 - Triglycerides produced in the livers of fasting rabbits are predominantly stored as opposed to secreted into the plasma

AU - Tuvdendorj, Demidmaa

AU - Zhang, Xiao Jun

AU - Chinkes, David L.

AU - Wang, Lijian

AU - Wu, Zhanpin

AU - Rodriguez, Noe A.

AU - Herndon, David

AU - Wolfe, Robert R.

PY - 2015/5/1

Y1 - 2015/5/1

N2 - Objective The liver plays a central role in regulating fat metabolism; however, it is not clear how the liver distributes the synthesized triglycerides (TGs) to storage and to the plasma. Materials and methods We have measured the relative distribution of TGs produced in the liver to storage and the plasma by means of U-13C16-palmitate infusion in anesthetized rabbits after an overnight fast. Results The fractional synthesis rates of TGs stored in the liver and secreted into the plasma were not significantly different (stored vs. secreted: 31.9 ± 0.8 vs. 27.7 ± 2.6% h- 1, p > 0.05). However, the absolute synthesis rates of hepatic stored and secreted TGs were 543 ± 158 and 27 ± 7 nmol kg- 1 min- 1 respectively, indicating that in fasting rabbits the TGs produced in the liver were predominately stored (92 ± 3%) rather than secreted (8 ± 3%) into the plasma. This large difference was mainly due to the larger pool size of the hepatic TGs which was 21 ± 9-fold that of plasma TGs. Plasma free fatty acids (FFAs) contributed 47 ± 1% of the FA precursor for hepatic TG synthesis, and the remaining 53 ± 1% was derived from hepatic lipid breakdown and possibly plasma TGs depending on the activity of hepatic lipase. Plasma palmitate concentration significantly correlated with hepatic palmitoyl-CoA and TG synthesis. Conclusion In rabbits, after an overnight fast, the absolute synthesis rate of hepatic stored TGs was significantly higher than that of secreted due to the larger pool size of hepatic TGs. The net synthesis rate of TG was approximately half the absolute rate. Plasma FFA is a major determinant of hepatic TG synthesis, and therefore hepatic TG storage.

AB - Objective The liver plays a central role in regulating fat metabolism; however, it is not clear how the liver distributes the synthesized triglycerides (TGs) to storage and to the plasma. Materials and methods We have measured the relative distribution of TGs produced in the liver to storage and the plasma by means of U-13C16-palmitate infusion in anesthetized rabbits after an overnight fast. Results The fractional synthesis rates of TGs stored in the liver and secreted into the plasma were not significantly different (stored vs. secreted: 31.9 ± 0.8 vs. 27.7 ± 2.6% h- 1, p > 0.05). However, the absolute synthesis rates of hepatic stored and secreted TGs were 543 ± 158 and 27 ± 7 nmol kg- 1 min- 1 respectively, indicating that in fasting rabbits the TGs produced in the liver were predominately stored (92 ± 3%) rather than secreted (8 ± 3%) into the plasma. This large difference was mainly due to the larger pool size of the hepatic TGs which was 21 ± 9-fold that of plasma TGs. Plasma free fatty acids (FFAs) contributed 47 ± 1% of the FA precursor for hepatic TG synthesis, and the remaining 53 ± 1% was derived from hepatic lipid breakdown and possibly plasma TGs depending on the activity of hepatic lipase. Plasma palmitate concentration significantly correlated with hepatic palmitoyl-CoA and TG synthesis. Conclusion In rabbits, after an overnight fast, the absolute synthesis rate of hepatic stored TGs was significantly higher than that of secreted due to the larger pool size of hepatic TGs. The net synthesis rate of TG was approximately half the absolute rate. Plasma FFA is a major determinant of hepatic TG synthesis, and therefore hepatic TG storage.

KW - Mass spectrometry

KW - Rabbit liver

KW - Stable isotopes

KW - Triglyceride synthesis

KW - Very low density lipoprotein

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