Lipid+Analysis+Lecture+John+Newman

Lipid+Analysis+Lecture+John+Newman - Quantitative Analysis...

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Quantitative Analysis of Dietary Lipids John W. Newman USDA, ARS, WHNRC UC Davis Dept Nutrition Oct 2009
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Dietary Lipids: Key Sources of Energy Biochemical Building Blocks & Substrates Regulators/Effectors of Plasma Lipids
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Lipids have diverse structures and properties Triglycerides (TG) Phospholipids (PL) Sterols: Cholesterol Ester (CE) Sphingomeylin (SM) Free Fatty Acids (FFA) From Wenk. 2005. Nature. 4 :504-610.
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Estimating Dietary Lipid To estimate the lipid-derived energy of a diet, the ether-extractable mass is generally used. Good isolation of neutral lipids. Low yield of phospholipids Within 10% of more exhaustive techniques. Triglycerides (TG) Cholesterol Ester (CE)
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The Dietary Fatty Acid Composition is Important: Animals Need Plants Without linoleate (18:2n6) and alpha-linolenate (18:3n3) mammals cannot biosynthesize very long-chain PUFAs
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Dietary Oil Composition The fatty acid composition of dietary oils can vary greatly.
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Dietary Fatty Acids Influence Plasma Cholesterol and Vascular Risk Saturated fatty acids increase LDL Cholesterol 12:0 > 14:0 >> 16:0 >> 18:0 Increase plasma LDL-Chol and decrease LDL turnover MUFAs and PUFAs reduce LDL Cholesterol MUFAs and n6-PUFAs stimulate peripheral LDL uptake n3-PUFAs increase reverse cholesterol transport, reduce hepatic lipogenesis and increase LpL activity Mechanisms by which Dietary Fatty Acids Modulate Plasma Lipids1 Maria Luz Fernandez2 and Kristy L. West. J. Nutr. 135: 2075–2078, 2005.
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Food Frequency Questionnaires are one means  of estimating dietary intake of lipids.
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How do we quantify these components? Extraction – S eparation of target analytes from matrix Separation – Fine resolution of “target signals” Detection – Use of physical-chemical properties to generate a measurable signal Quantification – Transformation of signal to a value Quality Assessment – Evaluation of measurement error
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Accuracy Accuracy and Precision Accurate and precise measurement of chemical components within a matrix Accuracy and precision describe the degree of error associated with measurements. The Goal is to Generate Quality Data
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Extraction Crude separation of target analytes from the bulk matrix & many interferences Liquid vs. Solid Phase extraction
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Separation Fine resolution of the target signal from interferences.
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