Blood fatty acids understanding the relevance of different tissue fractions and interpreting circulating concentrations.

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1 Blood fatty acids understanding the relevance of different tissue fractions and interpreting circulating concentrations Leanne Hodson

2 Fatty acid composition as a biomarker of intake Complements dietary assessment Not error free but are objective biochemical measure that has the potential to be more precise than dietary assessment alone Assess dietary intake in relation to disease risk Compare dietary intakes within and between populations Monitor change or assess compliance to dietary intake over time

3 Classes of fatty acids Saturated fatty acids 14:0; 15:0; 16:0; 17:0; 18:0 Monounsaturated fatty acids 16:1 n-7; 18:1 n-9 Polyunsaturated fatty acids n-6: 18:2 n-6; 20:4 n-6 n-3: 18:3 n-3; 20:5 n-3; 22:5 n-3; 22:6 n-3

Non-esterified fatty acids Phospholipids - total phospholipids - sphingomyelin - phosphatidylcholine -

4 What lipid pools have been measured? Whole blood Monocytes Neutrophils Erythrocytes Platelets Plasma Plasma Triglyceride Cholesteryl Ester Non-esterified fatty acids Phospholipids - total phospholipids - sphingomyelin - phosphatidylcholine - phosphatidylserine - phosphatidylinositol - phosphatidylethanolamine Buccal cells Muscle Skin Adipose Tissue Subcutaneous: gluteal, arm, abdominal Intra-abdominal: omental, visceral, perirenal, mesenteric

5 Fatty acid composition: Adipose Tissue (mol%) Food % 16:1 n-7 (g/100g fatty acids) Chocolate 0.6 % Butter / Olive oil 1.4 % Lard 2.5 % Beef (rump steak) 3 % Trout/Tuna 9 %/4.2 % Macadamia nuts 19% Hodson L et al Prog Lipid Res (2008)

6 What does the fatty acid composition of plasma nonesterified fatty acids (NEFA) represent? Plasma NEFA composition (mol%) Adipose tissue has a slightly lower proportion of 16:0 but higher 18:1 n-9 than plasma NEFA. Both fractions have low abundance (<1 mol%) of long chain n-3 and n-6 polyunsaturated fatty acids. Similar abundance of 18:2 n-6. Plasma NEFA has a higher proportion of 18:0. Hodson L et al Prog Lipid Res (2008)

7 Efflux of NEFA from adipose tissue depots Efflux (µmol/min/100g tissue) = veno arterio difference of whole blood NEFA x blood flow Frayn KN et al Clin Sci (1989); McQuaid SE et al Obesity (2010)

03 885±120 µmol/min/100g tissue The fatty acid composition of plasma NEFA will potentially be influenced to a greater

8 Fasting efflux of NEFA from adipose tissue depots Efflux (µmol/min/100g tissue) = veno arterio difference of whole blood NEFA x blood flow 1190±196 µmol/min/100g tissue P< ±90 µmol/min/100g tissue 1495±249 µmol/min/100g tissue P= ±120 µmol/min/100g tissue The fatty acid composition of plasma NEFA will potentially be influenced to a greater extent by upper- rather than lower body adipose tissue composition. NEFA, non-esterified fatty acids Hodson L et al; unpublished data

9 Does the fatty acid composition of plasma NEFA reflect adipose tissue fatty acid composition? r s = 0.48 (P<0.05) r s = 0.23 (P=NS) r s = 0.73 (P<0.05) Hodson et al Prog Lipid Res (2008)

10 Fatty acid composition: Plasma Triglycerides Hodson et al Prog Lipid Res (2008)

(mol%) 50 40 30 20 10 Meal 0 h 4 h 6 h VLDL-TG 0 Hodson et al AJP

11 Triglyceride rich lipoproteins (TRL) Fatty acid composition (mol%) Meal 4 h 6 h Chylomicron-TG Fatty acid composition (mol%) Meal 0 h 4 h 6 h VLDL-TG 0 Hodson et al AJP (2010) C14:0 C16:0 C16:1 C18:0 C18:1 C18:2 0 C14:0 C16:0 C16:1 C18:0 C18:1 C18:2

12 Plasma cholesteryl ester fatty acids (mol%) Plasma phospholipid fatty acids (mol%) Proportion (%) of major PL classes in plasma that contribute to total PL Lipoprotein composition Esterified cholesterol (% by wt) VLDL 14 LDL 40 HDL 16 Hodson et al Prog Lipid Res (2008) PL species Sphingomyelin Phosphatidylcholine Phosphatidylethanolamine 2-4 Phosphatidylserine 2 Phosphatidylinositol 0

13 Erythrocyte total phospholipids Platelet total phospholipids Compared to other lipid fractions plasma, erythrocyte and platelet total phospholipids: have similar or higher amounts of 18:0 compared to 18:1 n-9 have higher proportions of fatty acids with 20 carbons or more Proportion (%) of major PL classes in blood lipid fractions compared to other lipid fractions that contribute to total PL Whole blood: the pool is comprised of plasma (54% by volume) PL species Erythrocytes Platelets and various types of circulating cells (46% by volume). The Sphingomyelin contribution by cells other than erythrocytes is very small. Phosphatidylcholine Phosphatidylethanolamine Phosphatidylserine Phosphatidylinositol Hodson et al Prog Lipid Res (2008)

14 Plasma total fatty acids: what are you measuring? % by weight VLDL LDL HDL Triglyceride Phospholipid Cholesterol (free & esterified) Esterified cholesterol Hodson et al Prog Lipid Res (2008)

15 Effect of lipid profiles on plasma total fatty acid composition Group Subjects Age (y) BMI (kg/m 2 ) TG (mmol/l) NEFA (mmol/l) HDL-C (mmol/l) LDL-C (mmol/l) 1 8M 6F M 3F M 7F M Group 1 = young, healthy Group 2 = Familial combined hyperlipidaemia Group 3 = Type 2 diabetes Group 4 = Controls Quebec Cardiovascular Study Hodson et al Prog Lipid Res (2008) Abbreviations: M, males; F, females; BMI, body mass index; TG, triglyceride; NEFA, non-esterified fatty acids; HDL-C, high density lipoprotein cholesterol; LDL-C, low density lipoprotein cholesterol

16 Effect of lipid profiles on plasma total fatty acid composition Group 16:0 16:1 n-7 18:0 18:1n-9 18:2n-6 20:4n-6 20:5n-3 22:6n The variability in the individual fatty acids is: Long-chain (> 20 carbons) > 18 and 16 carbon unsaturated fatty acids > saturated fatty acids. Group 1 = young, healthy Group Alternative 2 = Familial interpretation: combined variability hyperlipidaemia in fatty acid composition relatively low given Group differences 3 = Type in lipoprotein 2 diabetes concentrations between groups. Group However: 4 = as Controls many studies Quebec report Cardiovascular small differences Study in fatty acid composition across groups, not taking lipoprotein concentrations into account could lead to erroneous differences! Hodson et al Prog Lipid Res (2008)

17 Different lipid fractions reflect dietary fat intakes over different periods Adipose tissue: Considered to be best long-term marker of dietary fatty acid intake due to the long half-life Calculated half-life of fatty acids 1-1.5y (Beyen et al 1980) Stable isotopes half-life of fatty acids 6-9 mth (Strawford et al 2004) Erythrocytes: Considered to be a superior long term marker compared to plasma Suggested to represent previous months of dietary fat intake due to halflife (~90 d) Plasma/Serum: Triglyceride fatty acid composition represents the previous day(s) fatty acid intake Phospholipids and cholesteryl ester fatty acid composition represent previous weeks to months of dietary intake

18 How rapidly do blood fatty acids change? SAFA Grp 1 2 1/2 wk Plasma triglyceride Plasma total phospholipids Plasma cholesteryl esters Platelet phosphatidylcholine Erythrocyte phosphatidylcholine n-6 PUFA /2 wk Skeaff et al J Nutr (2006)

19 15:0 (mol%) 18:2 n-6 (mol%) Temporal change in blood lipid fatty acids Plasma PL * Plasma CE Plasma PL * Erythrocyte PC * Plasma PL * Plasma CE * Skeaff et al J Nutr (2006) * significantly different (P < 0.01) from day 0; Data presented as mean (SD)

20 How rapidly do blood fatty acids change? Grp 1 SAFA 8 wk SAFA wk n-6 PUFA n-6 PUFA Grp 2 Hodson et al J Nutr (2014) 8 wk Plasma triglyceride Plasma phospholipids Plasma cholesteryl esters Plasma non-esterified fatty acids Erythrocyte phospholipids Erythrocyte phosphatidylcholine Buccal cell phospholipids Adipose tissue triglyceride (week 0 and 8) wk

21 Temporal change in blood lipid fatty acids 18:2n-6 18:2n-6 18:2n-6 If you have a (large) change in fatty acid composition of one blood lipid fraction you Adipose tissue Erythrocyte PC also tend to have (large) Buccal Cell Phospholipids 15:0 changes in other 15:0 15:0 fractions. Hodson et al J Nutr (2014)

22 Factors to consider: expression of data Relative: total of all fatty acids are summed to 100% values are individual fatty acids are not independent Reported as: % total fatty acids weight % (g/100g fatty acids) mol %: molecular percentage the number of molecules of the individual fatty acid as a percentage of the total number of fatty acid molecules (mol / 100 mol total fatty acids) Absolute: values of individual fatty acids independent of each other however if individuals have high circulating lipid concentrations this may obscure the fatty acid concentrations Reported as: mg/l or µmol/l

23 Factors to consider: other things Collection fasting, fed, standardisation of biopsy site etc Blood sample processing: plasma can be processed quicker than serum. Storage samples should ideally be stored at -80 C (particularly if being batched up) as changes occur in fatty acid composition when stored -20 C. Analytical reproducibility not often reported! In-house quality controls and quality insurance procedures should be in put in place. If making comparisons between groups other factors that may influence fatty acid composition such as exercise, sex, smoking, age should be considered.

24 What to measure? It depends on the question! Information about long-term intakes adipose tissue Information about recent intakes plasma phospholipids (or plasma CE) No additional information is gained by measuring erythrocytes! (analysis is more labour intensive )

25 The volunteers OxLip Group and CRU Thank you! Murray Skeaff Keith Frayn Fredrik Karpe Sandy Humphreys Camilla Pramfalk Catriona McNeil Charlotte Green Marje Gilbert Camilla Pramfalk Louise Dennis Rachel Craven-Todd Jane Cheeseman Sue Beatty Barbara Fielding

27 (mol%) Fatty acid composition: Adipose Tissue Abdominal Gluteal * * * * Pinnick K et al Diabetes (2012)

The art of tracing dietary fat in humans. Leanne Hodson

The art of tracing dietary fat in humans Leanne Hodson Dietary fat Other lipoproteins: IDL, LDL, HDL Hodson and Fielding linical Lipidology (2010) Relationship between blood & dietary fatty acids Typically: