Palmitoleic acid is elevated in fatty liver disease and reflects hepatic lipogenesis.

Abstract

BACKGROUND:

Biochemical evidence has linked the coordinate control of fatty acid (FA) synthesis with the activity of stearoyl-CoA desaturase-1 (SCD1). The ratio of 16:1n-7 to 16:0 [SCD1₁₆] in plasma triacylglycerol FA has been used as an index to reflect liver SCD1₁₆ activity and has been proposed as a biomarker of FA synthesis, although this use has not been validated by comparison with isotopically measured de novo lipogenesis (DNL(Meas)).

OBJECTIVE:

We investigated plasma lipid 16:1n-7 and FA indexes of elongation and desaturation in relation to lipogenesis.

DESIGN:

In this cross-sectional investigation of metabolism, 24 overweight adults, who were likely to have elevated DNL, consumed D2O for 10 d and had liver fat (LF) measured by magnetic resonance spectroscopy. Very-low-density lipoprotein (VLDL)-triacylglycerols and plasma free FA [nonesterified fatty acids (NEFAs)] were analyzed by using gas chromatography for the FA composition (molar percentage) and gas chromatography-mass spectrometry and gas chromatography-combustion isotope ratio mass spectrometry for deuterium enrichment.

RESULTS:

In all subjects, VLDL-triacylglycerol 16:1n-7 was significantly (P < 0.01) related to DNL(Meas) (r = 0.56), liver fat (r = 0.53), and adipose insulin resistance (r = 0.56); similar positive relations were shown with the SCD1₁₆ index, and the pattern in NEFAs echoed that of VLDL-triacylglycerols. Compared with subjects with low LF (3.1 ± 2.7%; n = 11), subjects with high LF (18.4 ± 3.6%; n = 13) exhibited a 45% higher VLDL-triacylglycerol 16:1n-7 molar percentage (P < 0.01), 16% of subjects had lower 18:2n-6 (P = 0.01), and 27% of subjects had higher DNL as assessed by using a published DNL index (ratio of 16:0 to 18:2n-6; P = 0.03), which was isotopically confirmed by DNL(Meas) (increased 2.5-fold; P < 0.01). Compared with 16:0 in the diet, the low amount of dietary 16:1n-7 in VLDL-triacylglycerols corresponded to a stronger signal of elevated DNL.

CONCLUSION:

The current data provide support for the use of the VLDL-triacylglycerol 16:1n-7 molar percentage as a biomarker for elevated liver fat when isotope use is not feasible; however, larger-scale confirmatory studies are needed.

• Authors: Joseph J Lee, Jennifer E Lambert, Yelena Hovhannisyan, Maria A Ramos-Roman, Justin R Trombold, David A Wagner, Elizabeth J Parks
• Journal: The American journal of clinical nutrition (Am J Clin Nutr) Vol. 101 Issue 1 Pg. 34-43 (Jan 2015) ISSN: 1938-3207 [Electronic] United States
• PMID: 25527748 (Publication Type: Clinical Trial, Journal Article, Research Support, N.I.H., Extramural)
• Copyright: © 2015 American Society for Nutrition.

Chemical References

• Biomarkers
• Fatty Acids, Monounsaturated
• Fatty Acids, Nonesterified
• Lipoproteins, VLDL
• Triglycerides
• very low density lipoprotein triglyceride
• palmitoleic acid
• Palmitic Acid
• SCD1 protein, human
• Stearoyl-CoA Desaturase
• Deuterium Oxide

Topics

• Adiposity
• Adult
• Algorithms
• Biomarkers (blood, metabolism)
• Body Mass Index
• Cross-Sectional Studies
• Deuterium Oxide (metabolism)
• Diet, Fat-Restricted
• Fatty Acids, Monounsaturated (blood, metabolism)
• Fatty Acids, Nonesterified (blood)
• Female
• Humans
• Insulin Resistance
• Lipogenesis
• Lipoproteins, VLDL (blood, metabolism)
• Liver (enzymology, metabolism)
• Male
• Non-alcoholic Fatty Liver Disease (blood, diet therapy, etiology, metabolism)
• Overweight (physiopathology)
• Palmitic Acid (blood, metabolism)
• Stearoyl-CoA Desaturase (metabolism)
• Triglycerides (blood, metabolism)
• Up-Regulation