[11C]palmitate kinetics across the splanchnic bed in arterial, portal and hepatic venous plasma during fasting and euglycemic hyperinsulinemia

Guiducci, Letizia; Järvisalo, Mikko; Kiss, Jan; Någren, Kjell; Viljanen, Antti; Naum, Alexandru G.; Gastaldelli, Amalia; Savunen, Timo; Knuuti, Juhani; Salvadori, Piero A.; Ferrannini, Ele; Nuutila, Pirjo; Iozzo, Patricia

doi:10.1016/j.nucmedbio.2006.02.003

« Previous Next »Nuclear Medicine and Biology
Volume 33, Issue 4 , Pages 521-528, May 2006

[¹¹C]palmitate kinetics across the splanchnic bed in arterial, portal and hepatic venous plasma during fasting and euglycemic hyperinsulinemia

Letizia Guiducci
- SSSUP Medical Sciences Branch, Pisa 56100, Italy
- Turku PET Centre, University of Turku, Turku 20520, Finland
- PET Centre, Institute of Clinical Physiology, CNR National Research Council, 56100 Pisa, Italy
Mikko Järvisalo
- Turku PET Centre, University of Turku, Turku 20520, Finland
Jan Kiss
- Turku PET Centre, University of Turku, Turku 20520, Finland
- Department of Surgery, University of Turku, Turku 20520, Finland
Kjell Någren
- Turku PET Centre, University of Turku, Turku 20520, Finland
Antti Viljanen
- Turku PET Centre, University of Turku, Turku 20520, Finland
Alexandru G. Naum
- Turku PET Centre, University of Turku, Turku 20520, Finland
Amalia Gastaldelli
- PET Centre, Institute of Clinical Physiology, CNR National Research Council, 56100 Pisa, Italy
Timo Savunen
- Department of Surgery, University of Turku, Turku 20520, Finland
Juhani Knuuti
- Turku PET Centre, University of Turku, Turku 20520, Finland
Piero A. Salvadori
- PET Centre, Institute of Clinical Physiology, CNR National Research Council, 56100 Pisa, Italy
Ele Ferrannini
- PET Centre, Institute of Clinical Physiology, CNR National Research Council, 56100 Pisa, Italy
- Department of Internal Medicine, University of Pisa School of Medicine, Pisa 56100, Italy
Pirjo Nuutila
- Turku PET Centre, University of Turku, Turku 20520, Finland
- Department of Medicine, University of Turku, Turku 20520, Finland
Patricia Iozzo
- Turku PET Centre, University of Turku, Turku 20520, Finland
- PET Centre, Institute of Clinical Physiology, CNR National Research Council, 56100 Pisa, Italy
- Corresponding author. Institute of Clinical Physiology, CNR National Research Council, 56100 Pisa, Italy.

Received 25 October 2005; received in revised form 10 January 2006; accepted 1 February 2006. published online 02 May 2006.

Abstract

Purpose

The liver is fundamental in regulating lipid metabolism, and it supplies fatty acids (FA) to the rest of the body in the form of triglycerides (TG); the time-related relevance of this process is incompletely defined. The aim of the study was to investigate the appearance of labeled TG in the hepatic vascular bed after [¹¹C]palmitate injection during fasting and insulin stimulation.

Methods

Plasma [¹¹C]palmitate kinetics in arterial, portal and hepatic venous lipid fractions was studied in eight anesthetized pigs during fasting or euglycemic hyperinsulinemia. Plasma analyses were conducted at 10 and 40 min after tracer injection. Corresponding liver positron emission tomography (PET) images were acquired for the semiquantitative determination of hepatic FA uptake.

Results

At 10 min, plasma levels of unchanged [¹¹C]palmitate were lower in hyperinsulinemic than in fasting experiments in the artery and in the portal vein (P≤.03), suggesting faster clearance. Levels of unmetabolized [¹¹C]palmitate did not differ between portal and arterial plasma. In the fasting state, a tendency to a positive arterial and portal vs. hepatic venous gradient was observed, indicative of net hepatic [¹¹C]palmitate extraction. Labeled TG were already detectable at 10 min (fasting vs. hyperinsulinemia, ns) and were higher in fasting than in hyperinsulinemic animals at 40 min (92±1% and 82±6% of arterial plasma radioactivity). Higher proportions of labeled TG were recovered in portal vein plasma, suggesting release by the gut. The portal and the arterial–portal vs. hepatic venous TG gradient tended to be positive. Accordingly, hepatic FA uptake was higher, but declined more rapidly during fasting than during hyperinsulinemia.

Conclusion

The study indicates that the redistribution of [¹¹C]palmitate between different lipid pools occurs within the short time interval of most PET experiments and is strongly influenced by insulin. Labeled TG constitute an additional [¹¹C]palmitate source in the modeling of PET data.

Keywords: Palmitate, Insulin, Positron emission tomography, Hepatic, Triglyceride