Matti Marklund

ω-3 Polyunsaturated Fatty Acid Biomarkers and Coronary Heart Disease: Pooling Project of 19 Cohort Studies.

IMPORTANCE The role of ω-3 polyunsaturated fatty acids for primary prevention of coronary heart disease (CHD) remains controversial. Most prior longitudinal studies evaluated self-reported consumption rather than biomarkers. OBJECTIVE To evaluate biomarkers of seafood-derived eicosapentaenoic acid (EPA; 20:5ω-3), docosapentaenoic acid (DPA; 22:5ω-3), and docosahexaenoic acid (DHA; 22:6ω-3) and plant-derived α-linolenic acid (ALA; 18:3ω-3) for incident CHD. DATA SOURCES A global consortium of 19 studies identified by November 2014. STUDY SELECTION Available prospective (cohort, nested case-control) or retrospective studies with circulating or tissue ω-3 biomarkers and ascertained CHD. DATA EXTRACTION AND SYNTHESIS Each study conducted standardized, individual-level analysis using harmonized models, exposures, outcomes, and covariates. Findings were centrally pooled using random-effects meta-analysis. Heterogeneity was examined by age, sex, race, diabetes, statins, aspirin, ω-6 levels, and FADS desaturase genes. MAIN OUTCOMES AND MEASURES Incident total CHD, fatal CHD, and nonfatal myocardial infarction (MI). RESULTS The 19 studies comprised 16 countries, 45 637 unique individuals, and 7973 total CHD, 2781 fatal CHD, and 7157 nonfatal MI events, with ω-3 measures in total plasma, phospholipids, cholesterol esters, and adipose tissue. Median age at baseline was 59 years (range, 18-97 years), and 28 660 (62.8%) were male. In continuous (per 1-SD increase) multivariable-adjusted analyses, the ω-3 biomarkers ALA, DPA, and DHA were associated with a lower risk of fatal CHD, with relative risks (RRs) of 0.91 (95% CI, 0.84-0.98) for ALA, 0.90 (95% CI, 0.85-0.96) for DPA, and 0.90 (95% CI, 0.84-0.96) for DHA. Although DPA was associated with a lower risk of total CHD (RR, 0.94; 95% CI, 0.90-0.99), ALA (RR, 1.00; 95% CI, 0.95-1.05), EPA (RR, 0.94; 95% CI, 0.87-1.02), and DHA (RR, 0.95; 95% CI, 0.91-1.00) were not. Significant associations with nonfatal MI were not evident. Associations appeared generally stronger in phospholipids and total plasma. Restricted cubic splines did not identify evidence of nonlinearity in dose responses. CONCLUSIONS AND RELEVANCE On the basis of available studies of free-living populations globally, biomarker concentrations of seafood and plant-derived ω-3 fatty acids are associated with a modestly lower incidence of fatal CHD.

Omega-6 fatty acid biomarkers and incident type 2 diabetes: Pooled analysis of individual-level data for 39 740 adults from 20 prospective cohort studies

BACKGROUND The metabolic effects of omega-6 polyunsaturated fatty acids (PUFAs) remain contentious, and little evidence is available regarding their potential role in primary prevention of type 2 diabetes. We aimed to assess the associations of linoleic acid and arachidonic acid biomarkers with incident type 2 diabetes. METHODS We did a pooled analysis of new, harmonised, individual-level analyses for the biomarkers linoleic acid and its metabolite arachidonic acid and incident type 2 diabetes. We analysed data from 20 prospective cohort studies from ten countries (Iceland, the Netherlands, the USA, Taiwan, the UK, Germany, Finland, Australia, Sweden, and France), with biomarkers sampled between 1970 and 2010. Participants included in the analyses were aged 18 years or older and had data available for linoleic acid and arachidonic acid biomarkers at baseline. We excluded participants with type 2 diabetes at baseline. The main outcome was the association between omega-6 PUFA biomarkers and incident type 2 diabetes. We assessed the relative risk of type 2 diabetes prospectively for each cohort and lipid compartment separately using a prespecified analytic plan for exposures, covariates, effect modifiers, and analysis, and the findings were then pooled using inverse-variance weighted meta-analysis. FINDINGS Participants were 39 740 adults, aged (range of cohort means) 49-76 years with a BMI (range of cohort means) of 23·3-28·4 kg/m2, who did not have type 2 diabetes at baseline. During a follow-up of 366 073 person-years, we identified 4347 cases of incident type 2 diabetes. In multivariable-adjusted pooled analyses, higher proportions of linoleic acid biomarkers as percentages of total fatty acid were associated with a lower risk of type 2 diabetes overall (risk ratio [RR] per interquintile range 0·65, 95% CI 0·60-0·72, p<0·0001; I2=53·9%, pheterogeneity=0·002). The associations between linoleic acid biomarkers and type 2 diabetes were generally similar in different lipid compartments, including phospholipids, plasma, cholesterol esters, and adipose tissue. Levels of arachidonic acid biomarker were not significantly associated with type 2 diabetes risk overall (RR per interquintile range 0·96, 95% CI 0·88-1·05; p=0·38; I2=63·0%, pheterogeneity<0·0001). The associations between linoleic acid and arachidonic acid biomarkers and the risk of type 2 diabetes were not significantly modified by any prespecified potential sources of heterogeneity (ie, age, BMI, sex, race, aspirin use, omega-3 PUFA levels, or variants of the FADS gene; all pheterogeneity≥0·13). INTERPRETATION Findings suggest that linoleic acid has long-term benefits for the prevention of type 2 diabetes and that arachidonic acid is not harmful. FUNDING Funders are shown in the appendix.

Polyunsaturated Fat Intake Estimated by Circulating Biomarkers and Risk of Cardiovascular Disease and All-Cause Mortality in a Population-Based Cohort of 60-Year-Old Men and Women

Background— High intake of polyunsaturated fatty acids (PUFAs) may reduce the risk of cardiovascular disease (CVD) and mortality. Large, prospective studies including both sexes and circulating PUFAs as dietary biomarkers are needed. We investigated sex-specific associations of the major dietary PUFAs, eicosapentaenoic acid, docohexaenoic acid, linoleic acid, and &agr;-linolenic acid, with incident CVD and all-cause mortality in a population-based cohort. Methods and Results— PUFAs in serum cholesterol esters were measured at baseline in 60-year-old Swedish women (n=2193) and men (n=2039). With the use of national registers, 484 incident CVD events (294 men and 190 women) and 456 all-cause deaths (265 men and 191 women) were identified during follow-up (median, 14.5 years) in individuals without prior CVD at baseline. Associations of PUFAs with CVD and mortality were evaluated with Cox proportional hazard models. In multivariable-adjusted models, 1-SD increases in eicosapentaenoic acid and docohexaenoic acid were associated with lower risk of incident CVD among women (hazard ratio [HR], 0.79 [95% confidence interval (CI), 0.64–0.97] and 0.74 [95% CI, 0.61–0.89], respectively). &agr;-Linolenic acid was associated with moderately increased CVD risk in women (HR, 1.16; 95% CI, 1.02–1.32). Inverse associations with all-cause mortality were observed for eicosapentaenoic acid and docohexaenoic acid among all participants (HR, 0.81 [95% CI, 0.72–0.91] and 0.80 [95% CI, 0.72–0.89], respectively) and for linoleic acid in men (HR, 0.73; 95% CI, 0.64–0.83). Conclusions— Serum linoleic acid and very-long-chain n-3 PUFAs, partly reflecting vegetable oil and fish intake, respectively, were inversely associated with all-cause mortality. Inverse associations of eicosapentaenoic acid and docohexaenoic acid with incident CVD were observed only in women.

A Dietary Biomarker Approach Captures Compliance and Cardiometabolic Effects of a Healthy Nordic Diet in Individuals with Metabolic Syndrome

Assessment of compliance with dietary interventions is necessary to understand the observed magnitude of the health effects of the diet per se. To avoid reporting bias, different dietary biomarkers (DBs) could be used instead of self-reported data. However, few studies investigated a combination of DBs to assess compliance and its influence on cardiometabolic risk factors. The objectives of this study were to use a combination of DBs to assess compliance and to investigate how a healthy Nordic diet (ND) influences cardiometabolic risk factors in participants with high apparent compliance compared with the whole study population. From a recently conducted isocaloric randomized trial, SYSDIET (Systems Biology in Controlled Dietary Interventions and Cohort Studies), in 166 individuals with metabolic syndrome, several DBs were assessed to reflect different key components of the ND: canola oil (serum phospholipid α-linolenic acid), fatty fish [eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)], vegetables (plasma β-carotene), and whole grains (plasma alkylresorcinols). High-fat dairy intake (expectedly low in the ND) was reflected by serum pentadecanoic acid. All participants with biomarker data (n = 154) were included in the analyses. Biomarkers were combined by using a biomarker rank score (DB score) and principal component analysis (PCA). The DB score was then used to assess compliance. During the intervention, median concentrations of alkylresorcinols, α-linolenic acid, EPA, and DHA were >25% higher in the ND individuals than in the controls (P < 0.05), whereas median concentrations of pentadecanoic acid were 14% higher in controls (P < 0.05). Median DB score was 57% higher in the ND than in controls (P < 0.001) during the intervention, and participants were ranked similarly by DB score and PCA score. Overall, estimates of group difference in cardiometabolic effects generally appeared to be greater among compliant participants than in the whole study population (e.g., estimates of treatment effects on blood pressure and lipoproteins were ∼1.5- to 2-fold greater in the most compliant participants), suggesting that poor compliance attenuated the dietary effects. With adequate consideration of their limitations, DB combinations (e.g., DB score) could be useful for assessing compliance in intervention studies investigating cardiometabolic effects of healthy dietary patterns. The study was registered at clinicaltrials.gov as NCT00992641.

Plasma alkylresorcinols, biomarkers of whole-grain wheat and rye intake, and risk of type 2 diabetes in Scandinavian men and women

BACKGROUND Studies that use dietary biomarkers to investigate the association between whole-grain intake and the risk of developing type 2 diabetes (T2D) are lacking. OBJECTIVE We examined the association between plasma total alkylresorcinols and the alkylresorcinol C17:0-to-C21:0 ratio, biomarkers of whole-grain wheat and rye intake and relative whole-grain rye over whole-grain wheat intake, respectively, and the risk of T2D among Scandinavian men and women. DESIGN A nested case-control study was established within the Northern Sweden Health and Disease Study and the Danish Diet, Cancer and Health cohort. Alkylresorcinol concentrations and the ratios of C17:0 to C21:0 were determined in plasma samples from 931 case-control pairs. ORs for T2D were calculated for plasma total alkylresorcinol concentration or C17:0-to-C21:0 ratio in quartiles with the use of conditional logistic regression that was adjusted for potential confounders. Additional analyses with whole-grain wheat and rye intake estimated from food-frequency questionnaires (FFQs) as exposures were also performed. RESULTS The plasma total alkylresorcinol concentration was not associated with T2D risk (OR: 1.34; 95% CI: 0.95, 1.88) for the highest compared with the lowest quartiles in multivariable adjusted models. However, the C17:0-to-C21:0 ratio was associated with a lower diabetes risk (OR: 0.54; 95% CI: 0.37, 0.78). Analyses with whole-grain intake estimated from FFQs yielded similar results. CONCLUSIONS Total whole-grain wheat and rye intake, reflected by alkylresorcinols in plasma, was not associated with a lower risk of T2D in a population with high whole-grain intake. In contrast, the proportion of whole-grain rye to whole-grain wheat intake, indicated by the plasma C17:0-to-C21:0 ratio, was inversely associated with T2D. This suggests that whole-grain intake dominated by rye may be favorable for T2D prevention.

Discovery of urinary biomarkers of whole grain rye intake in free‐living subjects using nontargeted LC‐MS metabolite profiling

SCOPE Whole grain (WG) intake is associated with decreased risk of developing colorectal cancer, type 2 diabetes, and cardiovascular disease and its comorbidities. However, the role of specific grains is unclear. Moreover, intake of specific WG is challenging to measure accurately with traditional dietary assessment methods. Our aim was to use nontargeted metabolite profiling to discover specific urinary biomarkers for WG rye to objectively reflect intake under free-living conditions. METHODS AND RESULTS WG rye intake was estimated by weighed food records, and 24 h urine collections were analyzed by LC-MS. Multivariate modeling was undertaken by repeated double cross-validated partial least squares regression against reported WG rye intake, which correlated well with multivariate prediction estimates (r = 0.67-0.80, p < 0.001), but not with intakes of WG wheat or oats. Hydroxyhydroxyphenyl acetamide sulfate, 3,5-dihydroxyphenylpropionic acid sulfate, caffeic acid sulfate, and hydroxyphenyl acetamide sulfate were among the 20 features that had the greatest potential as intake biomarkers of WG. In addition, three compounds exhibited MS/MS fragmentation of carnitine structures. CONCLUSION With this nontargeted approach, we confirmed the specificity of alkylresorcinol metabolites as biomarkers for WG rye intake, but also discovered other compounds that should be evaluated as putative biomarkers in future studies.

Role of a prudent breakfast in improving cardiometabolic risk factors in subjects with hypercholesterolemia : a randomized controlled trial

BACKGROUND & AIMS It is unclear whether advising a prudent breakfast alone is sufficient to improve blood lipids and cardiometabolic risk factors in overweight hypercholesterolemic subjects. The aim of this study was to investigate whether a prudent low-fat breakfast (PB) rich in dietary fiber lowers low-density lipoprotein cholesterol (LDL-C) and other cardiometabolic risk factors in subjects with elevated LDL-cholesterol levels. METHODS In a parallel, controlled, 12-week study, 79 healthy overweight subjects (all regular breakfast eaters) were randomly allocated to a group that received a PB based on Nordic foods provided ad libitum or a control group that consumed their usual breakfast. The primary outcome was plasma LDL-C. Secondary outcomes were other blood lipids, body weight, sagittal abdominal diameter (SAD), glucose tolerance, insulin sensitivity and inflammation markers (C-reactive protein [CRP] and tumor necrosis factor receptor-2 [TNF-R2]), and blood pressure. The PB was in accordance with national and Nordic nutrition recommendations and included oat bran porridge with low-fat milk or yogurt, bilberry or lingonberry jam, whole grain bread, low-fat spread, poultry or fatty fish, and fruit. RESULTS No differences were found in LDL-C, other blood lipids, body weight, or glucose metabolism, but SAD, plasma CRP, and TNF-R2 decreased more during PB compared with controls (p < 0.05). In the overall diet, PB increased dietary fiber and β-glucan compared with controls (p < 0.05). CONCLUSIONS Advising a prudent breakfast for 3 months did not influence blood lipids, body weight, or glucose metabolism but reduced markers of visceral fat and inflammation. The trial was registered in the Current Controlled Trials database (http://www.controlled-trials.com); International Standard Randomized Controlled Trial Number (ISRCTN): 84550872.

Milk fat biomarkers and cardiometabolic disease

Purpose of review Dairy is a major food group with potential impact on cardiometabolic health. Self-reported dairy intake has limitations that can partly be avoided by using biomarkers. This review aims to summarize the evidence of odd-chain saturated fatty acids (OCFAs), that is, pentadecanoic acid (C15 : 0) and heptadecanoic acid (17 : 0), as biomarkers of dairy fat intake. In addition, the associations of OCFA biomarkers with cardiometabolic disease will be overviewed. Recent findings Adipose tissue 15 : 0 is the preferred biomarker but also circulating 15 : 0, and to a weaker extent 17 : 0, reflects both habitual and changes in dairy intake. Whereas results from studies assessing cardiovascular outcomes are inconsistent, OCFA biomarkers are overall associated with lower diabetes risk. Residual confounding should however be considered until interventional data and mechanisms are available. Although OCFA biomarkers mainly reflect dairy fat intake, recently proposed endogenous synthesis and metabolism do motivate further research. Summary Taking into account the study population diet and limitations of OCFA biomarkers, both adipose and circulating levels of 15 : 0, in particular, are useful for estimating total dairy fat intake. OCFA biomarkers are overall not linked to cardiovascular disease risk, but a possible beneficial role of dairy foods in diabetes prevention warrant further study.

Chain Length of Dietary Alkylresorcinols Affects Their In Vivo Elimination Kinetics in Rats

Two phenolic acids, 3,5-dihydroxybenzoic acid (DHBA) and 3-(3,5-dihydroxyphenyl)- propanoic acid (DHPPA), are the major metabolites of cereal alkylresorcinols (ARs). Like their precursors, AR metabolites have been suggested as biomarkers for intake of whole-grain wheat and rye and as such could aid the understanding of diet-disease associations. This study estimated and compared pharmacokinetic parameters of ARs and their metabolites in rats and investigated differences in metabolite formation after ingestion of different AR homologs. Rats were i.v. infused for 30 min with 2, 12, or 23 μmol/kg DHBA or DHPPA or orally given the same amounts of the AR homologs, C17:0 and C25:0. Repeated plasma samples, obtained from rats for 6 h (i.v.) or 36 h (oral), were simultaneously analyzed for ARs and their metabolites by GC-mass spectrometry. Pharmacokinetic parameters were estimated by population-based compartmental modeling and noncompartmental calculation. A 1-compartment model best described C25:0 pharmacokinetics, whereas C17:0 and AR metabolites best fitted 2-compartment models. Combined models for simultaneous prediction of AR and metabolite concentration were more complex, with less reliable estimates of pharmacokinetic parameters. Although the AUC of C17:0 was lower than that of C25:0 (P < 0.05), the total amount and composition of AR metabolites did not differ between rats given C17:0 or C25:0. The elimination half-life of ARs and their metabolites increased with length of the side chain (P-trend < 0.001) and ranged from 1.2 h (DHBA) to 8.8 h (C25:0). The formation of AR metabolites was slower than their elimination, indicating that the rate of AR metabolism and not excretion of DHBA and DHPPA determines their plasma concentrations in rats.

Serum Fatty Acids, Desaturase Activities and Abdominal Obesity - A Population-Based Study of 60-Year Old Men and Women

Abdominal obesity is a key contributor of metabolic disease. Recent trials suggest that dietary fat quality affects abdominal fat content, where palmitic acid and linoleic acid influence abdominal obesity differently, while effects of n-3 polyunsaturated fatty acids are less studied. Also, fatty acid desaturation may be altered in abdominal obesity. We aimed to investigate cross-sectional associations of serum fatty acids and desaturases with abdominal obesity prevalence in a population-based cohort study. Serum cholesteryl ester fatty acids composition was measured by gas chromatography in 60-year old men (n = 1883) and women (n = 2015). Cross-sectional associations of fatty acids with abdominal obesity prevalence and anthropometric measures (e.g., sagittal abdominal diameter) were evaluated in multivariable-adjusted logistic and linear regression models, respectively. Similar models were employed to investigate relations between desaturase activities (estimated by fatty acid ratios) and abdominal obesity. In logistic regression analyses, palmitic acid, stearoyl-CoA-desaturase and Δ6-desaturase indices were associated with abdominal obesity; multivariable-adjusted odds ratios (95% confidence intervals) for highest versus lowest quartiles were 1.45 (1.19–1.76), 4.06 (3.27–5.05), and 3.07 (2.51–3.75), respectively. Linoleic acid, α-linolenic acid, docohexaenoic acid, and Δ5-desaturase were inversely associated with abdominal obesity; multivariable-adjusted odds ratios (95% confidence intervals): 0.39 (0.32–0.48), 0.74 (0.61–0.89), 0.76 (0.62–0.93), and 0.40 (0.33–0.49), respectively. Eicosapentaenoic acid was not associated with abdominal obesity. Similar results were obtained from linear regression models evaluating associations with different anthropometric measures. Sex-specific and linear associations were mainly observed for n3-polyunsaturated fatty acids, while associations of the other exposures were generally non-linear and similar across sexes. In accordance with findings from short-term trials, abdominal obesity was more common among individuals with relatively high proportions of palmitic acid, whilst the contrary was true for linoleic acid. Further trials should examine the potential role of linoleic acid and its main dietary source, vegetable oils, in abdominal obesity prevention.