Association of circulating metabolites with healthy diet and risk of cardiovascular disease : analysis of two cohort studies

1 Scientific RepoRTS | (2018) 8:8620 | DOI:10.1038/s41598-018-26441-1 www.nature.com/scientificreports Association of circulating metabolites with healthy diet and risk of cardiovascular disease: analysis of two cohort studies Tasnime Akbaraly 1,2,3,17,18, Peter Würtz4, Archana Singh-Manoux2,5, Martin J. Shipley2, Rita Haapakoski2, Maili Lehto2, Catherine Desrumaux1,18,17, Mika Kähönen6, Terho Lehtimäki7, Vera Mikkilä8, Aroon Hingorani 9, Steve E. Humphries9, Antti J. Kangas4, Pasi Soininen4,10, Olli Raitakari6,11, Mika Ala-Korpela4,10,12,13,14,15 & Mika Kivimäki2,16 Diet may modify metabolomic profiles towards higher or lower cardiovascular disease (CVD) risk. We aimed to identify metabolite profiles associated with high adherence to dietary recommendations - the Alternative Healthy Eating Index (AHEI) - and the extent to which metabolites associated with AHEI also predict incident CVD. Relations between AHEI score and 80 circulating lipids and metabolites, quantified by nuclear magnetic resonance metabolomics, were examined using linear regression models in the Whitehall II study (n = 4824, 55.9 ± 6.1 years, 28.0% women) and were replicated in the Cardiovascular Risk in Young Finns Study (n = 1716, 37.7 ± 5.0 years, 56.3% women). We used Cox models to study associations between metabolites and incident CVD over the 15.8-year follow-up in the Whitehall II study. After adjustment for confounders, higher AHEI score (indicating healthier diet) was associated with higher degree of unsaturation of fatty acids (FA) and higher ratios of polyunsaturated FA, omega-3 and docosahexaenoic acid relative to total FA in both Whitehall II and Young Finns studies. A concordance of associations of metabolites with higher AHEI score and lower CVD risk was observed in Whitehall II. Adherence to healthy diet seems to be associated with specific FA that reduce risk of CVD. The benefits of healthy diet are supported by nutritional epidemiological studies on coronary heart diseases1, respiratory diseases2 and healthy old-age phenotypes3. Recent advancements of high-throughput metabolite profiling in large epidemiological studies allow the determination of metabolites predicting the risk for cardiometabolic diseases, providing insights into the molecular mechanisms underlying age-related diseases, such as 1Inserm U 1198, Montpellier, F-34000, France. 2Department of Epidemiology and Public Health, London, University College London, London, United Kingdom. 3Department of Psychiatry & Autism Resources Centre, Hospital and University Research Center of MontpellierCHRU-, Montpellier, F-34000, France. 4Computational Medicine, Faculty of Medicine, University of Oulu and Biocenter Oulu, Oulu, Finland. 5INSERM, U1018, Centre for Research in Epidemiology and Population Health, Hôpital Paul Brousse, Villejuif, France. 6Department of Clinical Physiology, University of Tampere School of Medicine and Tampere University Hospital, Tampere, Finland. 7Department of Clinical Chemistry, Fimlab Laboratories and University of Tampere School of Medicine, Tampere, Finland. 8Research Centre of Applied and Preventive Cardiovascular Medicine, University of Turku, Turku, Finland. 9Centre for Cardiovascular Genetics, British Heart Foundation Laboratories, Institute of Cardiovascular Sciences, University College London, London, United Kingdom. 10NMR Metabolomics Laboratory, School of Pharmacy, University of Eastern Finland, Kuopio, Finland. 11Department of Clinical Physiology and Nuclear Medicine, Turku University Hospital, Turku, Finland. 12Medical Research Council Integrative Epidemiology Unit at the University of Bristol, Bristol, United Kingdom. 13Population Health Science, Bristol Medical School, University of Bristol, Bristol, UK. 14Systems Epidemiology, Baker Heart and Diabetes Institute, Melbourne, VIC, Australia. 15Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Faculty of Medicine, Nursing and Health Sciences, The Alfred Hospital, Monash University, Melbourne, VIC, Australia. 16Clinicum, Faculty of Medicine, University of Helsinki, Helsinki, Finland. 17University Montpellier, Montpellier, F-34000, France. 18EPHE, Paris, France. Correspondence and requests for materials should be addressed to T.A. (email: tasnime.akbaraly@ inserm.fr) Received: 29 November 2017 Accepted: 2 May 2018 Published: xx xx xxxx OPEN www.nature.com/scientificreports/ 2 Scientific RepoRTS | (2018) 8:8620 | DOI:10.1038/s41598-018-26441-1 cardiovascular diseases (CVD)4. It has been hypothesized that metabolites are very responsive to dietary exposure as diet is an important source of metabolite variation and also induces metabolic response. Few studies have examined the association between overall diet and metabolites and a majority of investigations assessed metabolites via mass spectrometry methods. In the EPIC-Potsdam cohort study of 2380 adults, for example, dietary patterns were derived through reduced rank regression methods to explain the maximum variations of metabolites5 and a weak association between habitual diet and serum metabolites was observed. In a subsample of 1977 participants of the ARIC study, amongst the 336 metabolites assessed, dietary pattern “sugar-rich food and beverages” was associated with 7 unsaturated long-chain fatty acids, five 2-hydroxybutyrate– related metabolites, two sex steroids, five γ-glutamyl dipeptides, and four metabolites in other pathways6 and in the Women’s Health Initiative study, Prudent dietary pattern was associated with 85 metabolites (mostly lipids)7. Another study, carried out on 502 participants from the Prostate, Lung Colorectal and Ovarian Cancer Screening Trial, examined the correlations between 412 metabolites, food groups and the Healthy Eating Index score8. The authors reported that 39 metabolites were associated with 13 dietary groups and concluded that the metabolomic approach might be useful in identifying biomarkers reflecting the effect of nutrition intakes on human metabolism. In agreement with this, results from a study assessing lipoprotein particle subclasses profile via Nuclear Magnetic Resonance (NMR) in 663 adults showed associations between specific dietary patterns (“fish” and “junked food” pattern) and lipoprotein subclasses9. Identifying robust associations between dietary habits and metabolites may offer the possibility to better understand pathways by which overall diet mediates protection against chronic diseases, such asCVD, but none of these studies examined this issue. In this study, we sought to identify metabolites associated with adherence to a healthy diet and to determine the extent to which these metabolites are also related to reduced risk of CVD. To do so, we assessed adherence to dietary guidelines in a large cohort of British middle-aged men and women from the Whitehall II study10 using the Alternative Healthy Eating Index (AHEI) – a dietary index whose high scores have been shown to be associated with reduced risk of CVD morbidity11 and mortality12. We examined associations of healthy diet with metabolites quantified using a serum NMR metabolomics and replicated the results in an independent cohort, the Cardiovascular Risk in Young Finns Study13. We then determined the extent to which metabolites associated with AHEI were also associated with the risk of developing CVD over 15.8 years of follow-up in the Whitehall II study. Results Participant characteristics. A total of 4824 participants from the Whitehall II study were included in the discovery analysis. Characteristics are described in Table1. Mean concentration of the 80 metabolites are detailed in Supplementary Material-Table A. The mean (±SD) score of AHEI was 50.7 ± 9.8 points. Compared to the 3034 participants who attended the 1997/99 examination but were not included in the present analysis, those included were more likely to be men, white, with high socio-economic status, to practice physical activity and to Characteristics Whitehall II Young Finns Study N% or mean (SD) N mean ± SD or ρ* Sex Men 3483 72.2 966 56.3 Women 1341 27.8 750 43.7 Age, years 4824 55.9 (6.1) 1716 37.7 (5.0) Ethnicity White 4541 93.9 1716 1716 (100.0) South Asian 183 3.9 / / Black 100 2.2 / / Smoking habits Non 2490 52.1 886 51.6 Former 1864 39.1 421 24.5 Current 470 8.9 409 23.8 Physical activity MET unit /hours/week 4824 15.6 (14.8) 1716 19.6 (21.5) Total score in AHEI, points 4824 50.7 (9.8) 1716 46.3 (8.0) Total energy intake, kcal/day 4824 2233 (683) 1716 2392 (800) Prevalent type 2 diabetes No 4528 93.9 1665 97.0 Yes 296 6.1 51 3.0 Systolic blood pressure, mmHg 4824 123.1 (16.5) 1716 120.3 (14.3) Diastolic blood pressure, mmHg 4824 77.4 (10.5) 1714 75.4 (11.4) Use of antihypertensive treatment No 4 229 87.4 1604 93.5 Yes 607 12.6 112 6.5 Triglycerides, mmol/L 4823 1.35 (0.86) 1714 1.38 (0.90) HDL-cholesterol, mmol/L 4298 1.46 (0.39) 1708 1.34 (0.32) Use of lipids lowering drugs No 4669 96.9 1686 98.2 Yes 155 3.1 30 1.7 Body mass index, kg/m² 4175 26.0 (3.9) 1695 25.8 (4.7) Table 1. Characteristics of Whitehall II participants and Young Finns Study participants. www.nature.com/scientificreports/ 3 Scientific RepoRTS | (2018) 8:8620 | DOI:10.1038/s41598-018-26441-1 report higher total energy intake. Participants included were also less likely to be smoker, to use antihypertensive or lipids lowering drugs and showed lower concentrations of triglycerides and lower diastolic blood pressure. No significant difference in AHEI score was observed (Supplementary MaterialTable B). Regarding participants included in the Young Finns Study (replication cohort), the latter were younger and showed lower means of AHEI compared to participants included in Whitehall II study (Table1). Association between AHEI score and metabolites in the Whitehall II study. Results of the associations between AHEI z-score and 80 metabolites in Whitehall II study are shown in Fig.1, (estimates and p values are available in Supplementary Material-Table C). Good adherence to healthy dietary recommendations, as assessed by higher AHEI score, was associated with lower circulating concentrations of specific amino acids (isoleucine, leucine and phenylalanine) and of metabolites related to gluconeogenesis (mainly glycerol) as well as lower chronic inflammation (assessed by glycoprotein acetyls) after accounting for Bonferroni correction for 80 tests. Adherence to healthy diet was also associated with a smaller average size of VLDL particles and larger average size of HDL particles. Regarding lipids in different lipoproteins subclasses, participants with higher AHEI score showed lower concentration of lipids in VLDL, IDL and LDL particles (from large to small) and with lipids in small HDL particles. AHEI score was also inversely associated with concentrations of cholesterol in VLDL, cholesterol not contained in HDL nor LDL (remnant cholesterol) and with free cholesterol. Higher AHEI score was associated with lower triglycerides concentrations in all lipid subfractions and lower circulating sphingomyelins. The strongest associations between metabolites and AHEI score were observed for fatty acid measures, especially for monounsaturated and conjugated linoleic acids for which linear regression coefficients were three times higher than for other metabolites on average (Supplementary Material-Table B). Regarding fatty acids, high AHEI score was associated with lower concentrations of saturated and monounsaturated fatty acids. Conversely, participants with higher AHEI score displayed higher concentrations of polyunsaturated fatty acids, including Figure 1. Age-, sexand energy intake-adjusted associations between AHEI z-score and metabolites in Whitehall II study. Results are expressed as regression coefficients accompanied with their 95% confidence interval for one standard deviation increment in AHEI diet score. To facilitate comparison, metabolites were square root transformed and standardized to z-scores (mean = 0, SD = 1). P ≥ 0.0006; P < 0.0006. www.nature.com/scientificreports/ 4 Scientific RepoRTS | (2018) 8:8620 | DOI:10.1038/s41598-018-26441-1 omega-3 (docosahexaenoic acid especially) and omega-6 (linoleic acids) but lower concentrations of conjugated linoleic acids. Analyses for ratios of each fatty acids category relative to total fatty acid concentrations confirmed the association between AHEI score and fatty acids and tended to display even stronger associations. All analyses were repeated by replacing AHEI by AHEI 2010 and similar trends were observed. Results are detailed in Supplementary Material-Table D. The metabolites associations were only modestly attenuated (30.7% on average) after further adjustment for ethnicity, physical activity, smoking habits and cardiovascular risk factors (including type 2 diabetes, diastolic and systolic blood pressure, use of antihypertensive drugs and use of lipid-lowering drugs). All but one remained statistically significant (Table2). An additional model in which body mass index (BMI) was added as covariate was performed. Analyses, carried out on the 4175 participants with available data on BMI, showed similar results (Supplementary Material-Table E). Because both dietary changes and a modification of circulating metabolites are expected in participants with prevalent CVD, cancer or longstanding illness, we performed sensitivity analyses to assess the extent by which the AHEI-metabolites associations reported here might be explained by these diseases. Analyses repeated after excluding participants (1) reporting history of cardiovascular diseases (2) with a diagnosis of cancer and (3) reporting a longstanding illness indicate that the associations reported were not explained by these chronic diseases (Supplemental Material-Table F). Replication analysis in the Young Finns study. Analyses of the associations between the 41 metabolites (those significantly associated with AHEI score in multivariate model performed in Whitehall II study) and AHEI z-score were repeated in the Young Finns Study whose sample effective was about the third of the Whitehall II effective. Mean concentration of these 41 metabolites in Young Finns are listed in Supplemental Material-Table G. The replication analyses and meta-analyses, displayed in Table2 and Supplementary Material-Table H respectively and illustrated in Fig.2 showed that 38 of the 41 diet-metabolites associations were directionally concordant. The only deviating measures are branched amino acids, glycerol and size of HDL particle. Of the 41 metabolites assessed, AHEI score was significantly associated with two fatty acids and 5 fatty acids ratio (Fig.2 and Supplementary Table H) confirming the strong associations between good adherence to healthy diet and higher concentrations of omega-3 and docosahexaenoic acid, higher ratios of all polyunsaturated fatty acids ratio (including omega-3, omega-6) and lower ratios of saturated and monounsaturated fatty acids relative to total fatty acids. Regarding the other metabolites, even if the direction of most of associations was similar as observed in Whitehall II, the associations were weaker and did not reach statistical significance in the Young Finns study with much smaller sample size than in Whitehall II. Metabolites associated with AHEI and predicting cardiovascular disease. We assessed the extent to which each of the 41 metabolites associated with diet score also predicted CVD events. Of the 5481 Whitehall II participants, 697 developed CVD over the 15.8 years of follow-up. Results are presented in Table3. Metabolites found to significantly predict CVD risk consisted of amino acids, glycoprotein acetyls, size of lipoprotein particule size, total lipids in lipoproteins (except those in IDL and in small HDL), total cholesterol in VLDL particles and triglycerides. Amongst fatty acids, significant association were found for saturated fatty acids and monounsaturated fatty acids. Degree of unsaturation was inversely associated with CVD risk. When ratio of fatty acids categories relative to total fatty acids concentration was considered, significant associations were observed for monoand poly-unsaturated fatty acids, omega-3 and docosahexaenoic acid, with higher ratio of monounsaturated fatty acids increasing the risk of CVD risk, and higher ratio of polyunsaturated fatty acids, omega-3 and docosahexaenoic acid decreasing CVD risk. Other fatty acids ratios were not found significantly associated with CVD risk. Figure3 illustrates whether metabolites associated with poor adherence to healthy dietary guidelines were also related to higher CVD risk. Of the 41 diet-metabolites and metabolites-CVD risk associations assessed, only 5 were directionally discordant and concerned polyunsaturated fatty acids, omega 6 and linoleic acids whose higher blood concentrations were associated with higher CVD risk but without reaching statistical significance. Discordance in terms of direction of association was also observed for total lipids in small HDL and sphingomyelin (Fig.3). Discussion The present study based on metabolic profiling analyses identified and replicated metabolites associated with the adherence to dietary recommendations provided by the Alternative Healthy Eating Index after taking into account potential confounders and multiple testing in two population-based studies - the Whitehall II and the Cardiovascular Risk in Young Finns. A key finding of these analyses concerns the metabolic profiles of fatty acids associated with diet score. Furthermore, our study highlights the concordance between metabolites profile associated with low adherence to healthy diet and the metabolites profile associated with 15.8-year risk of CVD in Whitehall II participants by showing that an increased risk of CVD onset was associated with high levels of saturated and monounsaturated fatty acidsand a decreased risk of CVD was associated with a higher ratio of polyunsaturated fatty acids, omega-3 and docosahexaenoic acid relative to total fatty acids concentrations (Fig.4). Our metabolic profiling analyses identified 41 metabolites associated with the adherence to healthy diet. The strongest associations between metabolites and AHEI score were observed for fatty acid measures. We reported a robust and positive association between AHEI scores and degree of unsaturation of fatty acids, ratio and concentrations of polyunsaturated fatty acids including omega-3 (docosahexaenoic acid in particular, brought by fatty fish intake but also oil supplements), omega-6 (linoleic acids found in nuts, fatty seeds and their derived vegetable oil). Conversely, a negative association was found between AHEI scores and ratio (and concentrations) of saturated (found in dairy products, fatty products, processed food and fatty meat intakes) and monounsaturated fatty www.nature.com/scientificreports/ 5 Scientific RepoRTS | (2018) 8:8620 | DOI:10.1038/s41598-018-26441-1 Multivariable-adjusted Model* Whitehall II (N = 4699) Young Finns Study (N = 1625) Beta 95% CI p Beta 95% CI p Amino Acids Isoleucine −0.044 −0.072 to −0.017 0.002 0.011 −0.034 to 0.056 0.64 Leucine −0.061 −0.088 to −0.034 1*10−50.010 −0.035 to 0.055 0.65 Phenylalanine −0.074 −0.104 to −0.044 1*10−6−0.038 −0.090 to 0.014 0.15 Glycolysis related metabolites Glycerol −0.044 −0.074 to −0.014 0.004 −0.009 −0.060 to 0.042 0.73 Inflammation Glycoprotein acetyls −0.035 −0.064 to −0.006 0.02 −0.012 −0.063 to 0.039 0.64 Size of lipoprotein particles (Mean diameters) VLDL particle size −0.048 −0.076 to −0.019 0.0009 −0.003 −0.051 to 0.046 0.91 HDL particle size 0.033 0.006 to 0.061 0.02 −0.005 −0.051 to 0.040 0.82 Total lipid concentrations in lipoprotein subclasses Total lipids in chylomicrons and extremely large VLDL −0.073 −0.102 to −0.044 8*10−7−0.033 −0.082 to 0.016 0.19 Total lipids in very large VLDL −0.061 −0.089 to −0.032 4*10−5−0.022 −0.070 to 0.027 0.38 Total lipids in large VLDL −0.049 −0.078 to −0.021 0.0007 −0.006 −0.054 to 0.042 0.81 Total lipids in medium VLDL −0.036 −0.067 to −0.008 0.01 0.001 −0.048 to 0.048 0.99 Total lipids in small VLDL −0.019 −0.048 to 0.010 0.21 0.017 −0.031 to 0.065 0.49 Total lipids in IDL −0.039 −0.069 to −0.010 0.01 −0.032 −0.084 to 0.021 0.24 Total lipids in large LDL −0.045 −0.075 to −0.015 0.003 −0.032 −0.084 to 0.021 0.24 Total lipids in medium LDL −0.044 −0.074 to −0.014 0.004 −0.028 −0.080 to 0.024 0.29 Total lipids in small LDL −0.039 −0.069 to −0.009 0.01 −0.028 −0.080 to 0.023 0.28 Total lipids in small HDL −0.054 −0.083 to −0.024 0.0003 0.001 −0.052 to 0.054 0.96 Cholesterol Cholesterol in VLDL −0.036 −0.065 to −0.006 0.02 −0.006 −0.055 to 0.043 0.81 Remnant cholesterol (non−HDL, non−LDL −cholesterol) −0.041 −0.071 to −0.011 0.007 −0.021 −0.072 to 0.029 0.41 Free cholesterol −0.055 −0.084 to −0.026 0.0002 −0.035 −0.089 to 0.018 0.19 Glycerides and other Phospholipids Serum total TG −0.034 −0.063 to −0.005 0.02 −0.002 −0.050 to 0.047 0.95 TG in VLDL −0.031 −0.061 to −0.003 0.04 0.001 −0.046 to 0.049 0.95 TG in LDL −0.031 −0.060 to −0.002 0.04 −0.012 −0.064 to 0.041 0.66 TG in HDL −0.060 −0.090 to −0.031 5*10−5−0.017 −0.070 to 0.036 0.53 Sphingomyelins −0.081 −0.110 to −0.053 2*10−8−0.022 −0.074 to 0.031 0.42 Fatty Acids (FA) Saturated FA −0.056 −0.086 to −0.027 0.0002 −0.029 −0.080 to 0.022 0.27 Monounsaturated FA −0.069 −0.098 to −0.040 2*10−6−0.022 −0.072 to 0.028 0.39 Polyunsaturated FA 0.076 0.047 to 0.106 4*10−70.028 −0.025 to 0.080 0.30 Omega-3 FA 0.140 0.111 to 0.169 1*10−20 0.097 0.045 to 0.149 0.0003 docosahexaenoic acid 0.176 0.147 to 0.205 1*10−32 0.096 0.044 to 0.149 0.0003 Omega-6 FA 0.054 0.024 to 0.083 0.0004 0.009 −0.043 to 0.062 0.72 linoleic acid 0.076 0.046 to 0.105 6*10−70.004 −0.049 to 0.056 0.89 Conjugated linoleic acid −0.198 −0.227 to −0.169 2*10−40 NA NA Fatty acids ratios, relative to total fatty acids Estimated degree of unsaturation 0.210 0.183 to 0.238 1*10−48 0.116 0.066 to 0.166 5*10−6 Ratio of saturated FA to total FA (%) −0.164 −0.194 to −0.134 4*10−27 −0.089 −0.141 to −0.037 0.0008 Ratio of monounsaturated FA to total FA (%) −0.124 −0.152 to −0.095 2*10−17 −0.034 −0.082 to 0.015 0.17 Ratio of polyunsaturated FA to total FA (%) 0.194 0.162 to 0.219 2*10−41 0.082 0.033 to 0.131 0.0011 Ratio of omega-3 FA to total FA (%) 0.190 0.162 to 0.219 1*10−37 0.142 0.091 to 0.193 5*10−8 Ratio of docosahexaenoic acid to total FA (%) 0.220 0.192 to 0.249 9*10−52 0.139 0.090 to 0.189 4*10−8 Ratio of omega-6 FA to total FA (%) 0.137 0.109 to 0.166 6*10−21 0.044 −0.006 to 0.094 0.08 Ratio of linoleic acid to total FA (%) 0.145 0.116 to 0.174 1*10−22 0.029 −0.022 to 0.080 0.26 Ratio of conjugated linoleic acid to total FA (%) −0.226 −0.255 to −0.197 7*10−52 NA NA / Table 2. Results of multivariable adjusted linear regression models of the association between AHEI z-score and the 42 selected metabolites in the Whitehall II study and in YoungFinns Study. *Multivariable adjusted model: adjusted for age, sex, total energy intake, ethnicity, smoking habits, physical activity, type 2 diabetes, diastolic and systolic blood pressure, use of antihypertensive drugs and use of lipid-lowering drugs. Results were expressed as linear regression coefficients accompanied with their 95% confidence interval. Analyses were carried out on participants for which all metabolites measurement were available. www.nature.com/scientificreports/ 6 Scientific RepoRTS | (2018) 8:8620 | DOI:10.1038/s41598-018-26441-1 acids(affected by vegetable oils, lean meat but also produced endogenously by the desaturation of dietary saturated fatty acids4,14) and conjugated linoleic acids (found in ruminant meat and dairy products15). This fatty acids pattern associated with AHEI score was directionally concordant with fatty acids pattern (except for omega-6) associated with incident CVD in Whitehall II study. Our results are also concordant with previous findings from observational studies suggesting associations of higher levels of omega-316 and linoleic acid17 with lower coronary heart disease events and an increased disease risk in relation to high levels of monounsaturated fatty acids4,18. The strong association found between fatty acids and diet in the Whitehall II and Young Finns studies and the fact that similar metabolic profile of fatty acids was associated with incident CVD suggest that these specific fatty acids are potential molecular mediators between unhealthy diet and increased CVD risk. Even if recent randomized trials19,20 did not indicate a beneficial impact of replacing dietary saturated fatty acids with polyunsaturated ones on CVD risk, our work suggests that the better understanding of the mechanisms underlying the variability of these fatty acids may be helpful in explaining how overall diet might be linked to CVD development. We identified detailed lipid profiles associated with a good adherence to AHEI recommendations. Using NMR spectroscopy, we were able to determine the lipoprotein subclasses distribution as well as their lipid composition. We found that participants with high score in AHEI had a lipid profile characterized by lower concentrations of lipids in chylomicrons and extremely large, very large and large VLDL, as well as small HDL compared to participants with low score in AHEI. Higher amounts of lipids packaged into chylomicrons may reflect higher ingestion of lipids through the diet and postprandial lipidemia, an established risk factor for CVD21,22. Since chylomicrons and VLDL are competitive substrates for triglyceride hydrolysis by lipoprotein lipase in adipose and muscle tissues, higher amounts of circulating chylomicrons are usually associated with predominance of oversized VLDL particles. This specific metabolic profile of lipids in participants with low AHEI scores has also been linked to an increased risk of artherosclerosis and premature CVD23–25. The predominance of large VLDL has also been linked to metabolically unhealthy individuals, regardless of BMIand metabolic health definition21. Even if the NMR metabolomics platform featured here is not designed for novel biomarker discovery and includes less metabolites than mass spectrometry-based platforms, the panel of biomarkers covers a wide range of potential relevant biomarkers for diet-CVD associations, including amino acids, glycolysis related metabolites, inflammation, lipids and cholesterol, glycerides and other phospholipids, and fatty acids. The possibility to quantify these measures robustly in a single experiment26 is important to determine their relative importance for diet and CVD risk. In contrast to other NMR methodologies of advanced lipoprotein profiling27, the platform used in this study provides quantification of many fatty-acid measures, some abundant proteins, and a broad range of low-molecular-weight metabolites together with very detailed lipoprotein subclasses profiling28. This simultaneous quantification of circulating biomarkers across multiple pathways provide a very detailed picture of a person’s metabolic state27; we found that in particular fatty acids and lipids components metabolites play a role in both overall unhealthy diet and incidence of CVD events. Beyond the lipid and fatty acids components, we showed that amino acid components – phenylalanine, leucine and isoleucine - were also associated with both lower AHEI score and increased incident CVD risk. These amino acids have previously been associated with higher risks of developing type 2 diabetes29–31. Branched-chain and aromatic amino acid are affected by intakes of animal (pork, beef, chicken, eggs and dairy products) and plant (soy beans, rice, corn, wheat) protein32. However, our analyses did not allow to assess the associations of these amino acids in the diet-CVD association according to their plant or animal origins. Further analyses to examine this question would be relevant in a context where beneficial effects of plant protein on cardiometabolic diseases has been reported33. Our study has both strengths and limitations. First, the assessment of dietary intake using a semi-quantitative food frequency questionnaire covered only specific foods and is recognized to be less precise than dietary assessment by the food diary method. However, in a large sample size cohort study, the use of food frequency questionnaires is particularly adapted and a commonly used method. Second, we assessed healthy diet through using the AHEI score which is a summary measure of the degree to which an individual’s diet conforms to the serving recommendations of the US Department of Agriculture Food Guide Pyramid and the US Dietary Guidelines for Americans11. By being based on a set of specific and limited food groups, AHEI does not cover all aspects of “healthy” diet and may not be adapted to dietary habits in all populations. However, high scores on this index have been shown to be associated with reduced risk of CVD11, and type 2 diabetes34. The use of AHEI in the present analyses is particularly relevant, as previous findings from the Whitehall II study suggest that adherence to the AHEI may reduce the long-term risk of all-cause and cardiovascular mortality12 and to be related to an almost 2-fold higher odds of reversing the metabolic syndrome35, a condition known to predict cardiovascular morbidity and mortality36. Third, AHEI provides an overall measure of the extent to which a person adheres healthy dietary guidelines in terms of the intake of vegetables, fruits, nuts and soy, white vs red meat, trans-fat, polyunsaturated and saturated fatty acids, multivitamin, alcohol and cereal fiber. Fourth, to counteract the problem of multiple comparisons we applied a stringent Bonferroni correction which reduces the probability of false significant findings but might increase the probability of false negative results, since many of the examined metabolites and lipid components are strongly correlated with one another. Additionally, we adjusted our analyses for correlated measures such as blood pressure that may artificially reduce the associations’ estimates. Fifth, with an epidemiological observational framework, our observations may be partly explained by unmeasured confounders such as gut microbiota which can potentially influence metabolite variability as well as dietary behaviors. However, by carrying out our analyses on a larger sample size population study compared to previous studies on the same topic and by replicating our findings in another cohort study while previous reports were based on single cohort studies, bring strength to the validity of our observations. The NMR platform used has also limitations. The metabolic profile measured through this platform provided fasting steady-state levels of metabolites. The fact that metabolites related to carbohydrate and protein intakes might be less detectable in fasting state than lipids and www.nature.com/scientificreports/ 7 Scientific RepoRTS | (2018) 8:8620 | DOI:10.1038/s41598-018-26441-1 fatty acids might explain why metabolites found to be associated with high quality diet were lipids and fatty acids while significant associations with branched amino acids, metabolites related to glycolysis were scarce and most of them were not confirmed in the replication analyses. Furthermore, as glycolysis related metabolites and some amino-acids, lipids and specific fatty acids are produced endogenously with different rates depending on issues, such as individual’s metabolic state, the NMR metabolite measures reflect both metabolites’ exogeneous intake and their endogenous synthesis; they cannot be viewed as markers of specific dietary intakes. A further limitation is that the NMR platform does not include many metabolites from vegetables, fruits, nuts and soy. Further research examining the association of dietary exposure to a wider range of metabolites is needed. Conclusions Our metabolic profiling study enabled us to identify and replicate a number of metabolites robustly associated with adherence to dietary recommendations provided by the Alternative Healthy Eating Index. A key finding of these analyses concerns the metabolic profiles of fatty acids (higher ratio of polyunsaturated fatty acids, omega-3, omega-6 and lower ratio of saturated, monounsaturated and conjugated fatty acids relative to total fatty acids) associated with AHEI score in Whitehall II Study and in Young Finns Study. Our report also highlights the high overlap in metabolites associated with low adherence to healthy dietary guidelines and those predicting long-term risk of CVD in Whitehall II. By showing that an increased risk of CVD onset was associated with high levels of saturated and monounsaturated fatty acids and a decreased risk of CVD was associated with higher ratio ofpolyunsaturated fatty acids, omega-3 and docosahexaenoic acid relative to total fatty acids concentrations, our findings suggest that these specific fatty acids might be important molecular mediators linking overall unhealthy diet to increased CVD risk. Methods Study samples. Participants of the discovery cohort were drawn from the Whitehall II cohort study10, an on-going prospective cohort study of adults recruited from 20 London-based Civil Service departments in 198510. Of these, 10 308 (6,895 men and 3,413 women, aged 35 to 55) enrolled, a response proportion of 73%. The baseline medical examination (phase 1) took place during 1985/88, and subsequent phases including both clinical examination and self-administrated questionnaire have taken place approximately every 5 years. The Figure 2. Multivariable-adjusted associations between AHEI z-score and metabolites from meta-analysis of the Whitehall II Study and the Young Finns Study (YFS). Whitehall II study; YFS; Metaanalysis. Linear regression models were adjusted for age, sex, total energy intake, ethnicity, smoking habits, physical activity, type 2 diabetes, diastolic and systolic blood pressure, use of antihypertensive drugs and use of lipid-lowering drugs. Results are expressed as linear regression coefficients accompanied with their 95% confidence interval. To facilitate comparison, metabolites were first square root transformed and then standardized to z-scores (mean = 0, SD = 1). www.nature.com/scientificreports/ 8 Scientific RepoRTS | (2018) 8:8620 | DOI:10.1038/s41598-018-26441-1 Association with CVD risk (total N = 5481; N incident cases = 697) Hazard Ratio*95% CI p Amino Acids Isoleucine 1.14 1.06 to 1.24 0.001 Leucine 1.13 1.04 to 1.22 0.003 Phenylalanine 1.14 1.07 to 1.23 0.000 Glycolysis related metabolites Glycerol 1.06 0.98 to 1.14 0.14 Inflammation Glycoprotein acetyls 1.20 1.11 to 1.30 3*10−6 Size of lipoprotein particles (Mean diameters) VLDL particle size 1.12 1.03 to 1.21 0.007 HDL particle size 0.86 0.79 to 0.94 0.0006 Total lipid concentrations in lipoprotein subclasses Total lipids in chylomicrons and extremely large VLDL 1.09 1.01 to 1.18 0.02 Total lipids in very large VLDL 1.09 1.01 to 1.17 0.03 Total lipids in large VLDL 1.12 1.03 to 1.21 0.005 Total lipids in medium VLDL 1.12 1.04 to 1.21 0.004 Total lipids in IDL 1.07 0.99 to 1.16 0.003 Total lipids in large LDL 1.09 1.01 to 1.18 0.01 Total lipids in medium LDL 1.09 1.01 to 1.18 0.08 Total lipids in small LDL 1.08 1.00 to 1.17 0.03 Total lipids in small HDL 0.97 0.90 to 1.05 0.02 Cholesterol Cholesterol in VLDL 1.09 1.01 to 1.18 0.03 Remnant cholesterol (non-HDL, non-LDL -cholesterol) 1.07 0.99 to 1.16 0.07 Free cholesterol 1.04 0.96 to 1.12 0.36 Glycerides and other Phospholipids Serum total TG 1.15 1.07 to 1.24 0.0002 TG in VLDL 1.14 1.05 to 1.23 0.0013 TG in LDL 1.19 1.11 to 1.28 3*10−6 TG in HDL 1.13 1.04 to 1.22 0.0021 Sphingomyelins 0.98 0.90 to 1.06 0.56 Fatty Acids (FA) Saturated FA 1.09 1.01 to 1.18 0.02 Monounsaturated FA 1.12 1.04 to 1.21 0.004 Polyunsaturated FA 1.05 0.97 to 1.13 0.26 Omega-3 FA 0.97 0.90 to 1.05 0.43 docosahexaenoic acid 0.96 0.89 to 1.04 0.33 Omega-6 FA 1.06 0.98 to 1.14 0.14 linoleic acid 1.06 0.98 to 1.14 0.14 Conjugated linoleic acid 1.05 0.97 to 1.13 0.23 Fatty acids ratios, relative to total fatty acids Estimated degree of unsaturation 0.90 0.83 to 0.97 0.009 Ratio of saturated FA to total FA (%) 1.01 0.93 to 1.08 0.90 Ratio of monounsaturated FA to total FA (%) 1.11 1.03 to 1.21 0.007 Ratio of polyunsaturated FA to total FA (%) 0.90 0.84 to 0.97 0.009 Ratio of omega-3 FA to total FA (%) 0.90 0.83 to 0.97 0.008 Ratio of docosahexaenoic acid to total FA (%) 0.90 0.83 to 0.97 0.009 Ratio of omega-6 FA to total FA (%) 0.93 0.87 to 1.01 0.083 Ratio of linoleic acid to total FA (%) 0.96 0.89 to 1.04 0.28 Ratio of conjugated linoleic acid to total FA (%) 1.03 0.95 to 1.11 0.53 Table 3. Association between baseline metabolites and incident cardiovascular disease over 15.8 years of follow-up in the Whitehall II study. *Cox regression models were performed to estimate association between each metabolites and risk of CVD onset over the 16-y of follow-up. Models were adjusted for age, sex, total energy intake, ethnicity, smoking habits, physical activity, type 2 diabetes, diastolic and systolic blood pressure, use of antihypertensive drugs and use of lipid-lowering drugs. www.nature.com/scientificreports/ 9 Scientific RepoRTS | (2018) 8:8620 | DOI:10.1038/s41598-018-26441-1 Figure 3. Comparison of diet-metabolites associations and metabolites-incident CVD risk associations in Whitehall II study. Associations directionally concordant. Associations directionally discordant. On the left hand size: Linear regression models estimating the associations between AHEI z-score and the 41 selected metabolites performed in 4824 participants and adjusted for age, sex, total energy intake, ethnicity, smoking habits, physical activity, type 2 diabetes, diastolic and systolic blood pressure, use of antihypertensive drugs and use of lipid-lowering drugs. Results are expressed as linear regression coefficients accompanied with their 95% confidence interval. To facilitate comparison, metabolites were first square root transformed and then standardized to z-scores (mean = 0, SD = 1). On the right hand size: Cox proportional hazards regression models estimating the association between the selected 41 metabolites and the risk of incident CVD over the 15.8 years of follow-up, performed in 5840 Whitehall II participant, adjusted for age, sex, total energy intake, ethnicity, smoking habits, physical activity, type 2 diabetes, diastolic and systolic blood pressure, use of antihypertensive medication. Results are expressed as Hazard Ratio accompanied with their 95% confidence interval. To facilitate comparison, metabolites were first square root transformed and then standardized to z-scores (mean = 0, SD = 1).