Abstract
Background
While plasma palmitoleic acid has been positively associated with blood pressure, inflammation, and insulin resistance, its association with heart failure has not been investigated. We assessed whether plasma phospholipid cis palmitoleic acid was associated with heart failure risk.
Methods and Results
This ancillary study of the Physicians’ Health Study used a risk set sampling method to select 788 matched pairs. For each case of incident heart failure, we randomly selected a control among subjects that were free of heart failure and alive at the time of index case diagnosis and matched on age, year of birth, race, and time of blood collection. Plasma phospholipid fatty acids were measured using gas chromatography. Heart failure was ascertained using annual follow-up questionnaire and validated in a subsample. In a multivariable conditional logistic regression, odds ratios (95% CI) for heart failure were 1.0 (ref), 1.06 (0.75-1.48), 1.20 (0.85-1.68), and 1.58 (1.11-2.25) across consecutive quartiles of cis palmitoleic acid (p for trend 0.009). Each standard deviation increase in plasma cis palmitoleic acid was associated with 17% higher odds of heart failure (95% CI: 2% to 33%) in a multivariable model. In a secondary analysis, each standard deviation increase of log-stearoyl-coA desaturase activity (16:1n-7/16:0 ratio) was positively associated with the risk of heart failure [OR: 1.14 (95% CI: 1.00-1.29)] whereas oleic acid and cis-vaccenic acid concentrations were not related to heart failure risk.
Conclusions
Our data showed a positive association between plasma phospholipid cis-palmitoleic acid and heart failure risk in male physicians.
Keywords: heart failure, epidemiology, fatty acids, cis-palmitoleic acids, risk factors
Owing in part to a better survival after myocardial infarction and rising prevalence of obesity, diabetes, and hypertension, heart failure (HF) burden and costs are still on the rise in the US1-5. Despite state-of-the art management of symptomatic HF, its mortality remains extremely high with fewer than 50% of patients surviving beyond five years after the onset. Hence, it remains critical to identify novel risk factors and biomarkers that could lead to novel treatment approaches, primary prevention, and risk stratification. Human body can use excess carbohydrate to synthesize fatty acids via de novo lipogenesis (DNL) pathway6. Fatty acids in the DNL or lipid synthese (LS) including palmitic acid (16:0), cis-palmitoleic acid (16:1n-7), oleic acid (18:1n-9), and cis-vaccenic acid (18:1n-7), etc, have been reported to influence risk factors for HF, such as adiposity7-9, hypertension10, diabetes11,12, inflammation7,13, and cardiovascular mortality14,15. Other reports found no relation between plasma palmitoleic acids and CHD16,17 or diabetes7. In animal experiments, a mixture of fatty acids including palmitoleic acid, stearic acid, and palmitic acid was shown to induce cardiac growth and increased left ventricular mass18, suggesting that specific fatty acids from the DNL might influence the development of HF. However, limited data are available in humans on the effects of plasma phospholipids cis-palmitoleic acid and other fatty acids in the DNL on the risk of HF. Data from the ARIC study19 reported no association between total phospholipid palmitic acid (cis and trans combined) and incident HF. Since trans palmitoleic acid is derived from naturally occurring dairy/ruminant trans fatty acids20 and its consumption has not been associated with a higher risk of cardiovascular diseases21, it is possible that the results from the ARIC study were influenced by a neutral effects of trans palmitoleic acid on HF. The current ancillary study sought to examine the association between phospholipid cis palmitoleic acid and HF risk among US male physicians. Because stearoyl coA desaturase drives the desaturation of palmitic acid (16:0) to palmitoleic acid (16:1n7), we hypothesized that stearoyl coA desaturase activity would be positively associated with HF risk. Thus, in a secondary analysis, we assessed the relation of stearoyl coA desaturase activity as well as other fatty acids in the DNL with HF risk.
Methods
Study population
Participants in this ancillary study analyses are members of the Physicians Health Study (PHS) I who provided baseline (1982) blood samples. The PHS I is a completed randomized, double blind, placebo-controlled trial designed to study low-dose aspirin and beta-carotene for the primary prevention of cardiovascular disease and cancer22,23. Current analyses used a prospective nested case-control design to select subjects. For each case of HF, we randomly selected a control among participants who were alive and free of HF at the time of diagnosis of the index case. Each control was matched on age at randomization (within 1 year), race (white vs. non-white), year of birth (within 1 year), and time of blood collection (within 288 days). A total of 788 incident HF with matching controls were used for the current study. Each participant signed an informed consent and the Institutional review Board at Brigham and Women’s Hospital approved the study protocol.
Measurement of plasma phospholipids fatty acids
The fatty acid profile was measured in plasma using the method previously described by Cao et al24. For the extraction of plasma phospholipid fatty acids, 0.3 mL of plasma is mixed with 0.7 volume of 0.9% saline. Lipids are extracted from plasma with a mixture of chloroform:methanol (2:1, v/v), and cholesterol, triglycerides and phospholipid subclasses are separated on a silica thin-layer chromatography plate in a solvent mixture of petroleum ether, diethyl ether, and glacial acetic acid (80:20:1, v/v/v). The band of phospholipids is harvested for the formation of methyl esters. Fatty acid methyl esters are prepared with 1.5 mL of 14% boron trifluoride in methanol, incubated at 80°C for 90 minutes, and extracted with petroleum ether. The final product is dissolved in heptane and injected onto a capillary Varian CP7420 100-m column with a Hewlett Packard 5890 gas chromatograph (GC) equipped with a HP6890A autosampler. The GC is configured for a single capillary column with a flame ionization detector and interfaced with HP chemstation software. Adequate separation of fatty acid methylesters is obtained over a 80-min period with an initial temperature of 190°C for 25 minutes. The temperature is increased to 240°C at a rate of 2°C/min and held for 5 minutes. Fatty acid methylesters from 14:0 through 24:1n-9 are separated, identified and expressed as percent of total fatty acids. The following coefficients of variations were obtained on 30 blind duplicates: linoleic acid = 1.7%; alpha linolenic acid = 3.0%; arachidonic acid = 3.2%; eicosapentaenoic acid = 5.1%; docosapentaenoic acid = 3.8%; docosahexaenoic acid= 4.9%; 16:0=1.1%; 16:1n7cis = 1.8%; 18:0=3.5%; and 18:1n7 = 2.9%.
Ascertainment of incident HF in the PHS
We used annual follow-up questionnaires to ascertain cardiovascular endpoints including HF in the PHS. A detailed description of the validation of self-reported HF in the PHS has been previously published25. Briefly, two independent physicians reviewed medical records on a subsample of participants that reported a diagnosis of HF on a follow-up questionnaire. The positive predictive value of self-reported HF using medical records review was 91% and agreement between the 2 reviewers was excellent (kappa=92%).
Other variables
All relevant covariates were assessed at baseline (1982) to be consistent with the time of blood collection and exposure assessment. Demographic information was obtained through self-reports. At baseline, each subject provided information on exercise, smoking (never, former, and current smoker), and alcohol intake (rarely/never, 1-3 per month, 1 per week, 2-4/week, 5-6/week, daily, and 2+/day). Self-reported baseline weight and height were used to compute body mass index (weight in kilograms divided by height in meter squared). Information on comorbidity including diabetes, atrial fibrillation, hypercholesterolemia, valvular heart disease, coronary heart disease, and hypertension was collected at baseline and through follow-up questionnaires. In the PHS I, a food frequency questionnaire was administered between 1999 and 2000. Nutrients were derived using food composition databases from Harvard University supplemented by manufacturers’ information. Validity of such food frequency questionnaire has been reported elsewhere26.
Statistical analyses
Using the distribution of plasma phospholipids cis palmitoleic acid in the control series (n=788), we created quartiles of cis palmitoleic acid. Means and percentages of baseline characteristics of the study participants are presented according to quartiles of cis palmitoleic acid. We used conditional logistic regression to estimate the relative risk of HF using the lowest quartile of cis palmitoleic acid as the reference category. The initial model adjusted for matching variables (race, age, time of blood collection, and year of birth); a second model also controlled for body mass index, prevalent hypertension, coronary artery disease, atrial fibrillation, diabetes, and plasma phospholipids 18:0 and marine omega-3 fatty acids (20:5n-3, 22:5n-3, and 22:6n-3). A final model also controlled for vigorous physical activity (at least once per week vs. <1 per week), smoking (never, former, and current smokers), and alcohol consumption (rarely/never, <1, 1-6, and 7+ drinks/week). To obtain a p value for linear trend, we used quartile of cis palmitoleic acid as ordinal variable in the regression model. We repeated above analyses using cis palmitoleic acid as a continuous variable and estimated relative risk of HF associated with one standard deviation (0.1467% of total plasma phospholipids fatty acids in the control series) increase of cis palmitoleic acid. In secondary analyses, we evaluated the association between steaoryl-coA activity, defined as a ratio of product–to-substrate (16:1n-7/16:0 and 18:1n-9/18:0)8,14, and the risk of HF. In addition, we explored relations of cis-vaccenic acid (18:1n-7 and cis-oleic acid (18:1n-9) with HF risk using analytical approach outlined for cis palmitoleic acid. Lastly, we used total protein and carbohydrate estimates from a food questionnaire to explore their influence on the observed association and repeated main analyses for HF with and without prior coronary artery disease (myocardial infarction, coronary bypass or angioplasty). All analyses were performed using SAS (SAS version 9.3, NC) and the alpha level was set at 0.05. All p values were 2-sided.
Results
The mean age (SD) was 58.7 (8.0) years (range 40 to 82) among 1576 study participants. In the control series, mean plasma concentration of cis palmitoleic acid was 0.32% of total plasma phospholipids (range 0.04 to 2.22%). Compared to individuals in the lowest quartile, those with higher concentration of cis palmitoleic acid had a higher prevalence of hypertension and atrial fibrillation, consumed less alcohol, smoked more cigarettes, had higher concentration of marine omega-3 fatty acids and stearoyl-coA desaturase activity, and were more likely to exercise vigorously (Table 1). Cis palmitoleic acids was weakly associated with total, trans, omega-3, and other major fatty acids (Supplemental Table I). Compared to controls, cases had higher body mass index, were less likely to exercise vigorously, were more likely to be current smoker, and had a higher prevalence of diabetes, hypertension, atrial fibrillation, and coronary heart disease (Table 2). In a conditional logistic regression model adjusting for matching factors, odds ratios (95% CI) for HF were 1.0 (ref), 1.05 (0.78-1.41), 1.23 (0.91-1.66), and 1.51 (1.12-2.03) across consecutive quartiles of plasma phospholipid cis-palmitoeic acid (p trend 0.003, Table 3). Additional adjustment for body mass index, prevalent hypertension, atrial fibrillation, diabetes, coronary heart disease, plasma phospholipid 18:0, 20:5n-3, 22:5n-3, 22:6n-3, smoking, alcohol intake, and exercise had minimal influence on the results (p for trend 0.009, Table 2). Each standard deviation increase of cis-palmitoleic acid was associated with a 17% higher risk of heart failure (95% CI: 2% to 33%), Table 2. Additional adjustment for plasma phospholipid total saturated and trans fatty acids had minimal affect on the association [odds ratio: 1.45 (95% CI: 1.02-2.79) comparing the highest to the lowest quartile and p for trend 0.03)]. The positive association of cis-palmitoleic acid with HF was restricted to HF without antecedent coronary disease (myocardial infarction or coronary bypass/angioplasty) with multivariable adjusted odds ratios of 1.0 (ref), 1.07 (0.71-1.62), 1.20 (0.80-1.82), and 1.56 (1.02-2.39), p for trend 0.03. Corresponding values for HF with antecedent coronary disease were 1.0 (ref), 0.91 (0.44-1.91), 0.84 (0.44-2.03), and 1.32 (0.62-2.79), p trend 0.45.
Table 1.
Characteristics of 1576 male physicians according to quartiles of plasma phospholipid palmitoleic acid
| Characteristics | Quartiles of plasma phospholipid palmitoleic acid (% of total fatty acids) | |||
|---|---|---|---|---|
| Q1 (low) [0.039-0.227] N=364 |
Q2 [0.228-0.280] N=376 |
Q3 [0.281-0.359] N=394 |
Q4 (high) [0.360-2.217] N=442 |
|
| Age (y) | 58.4±8.1 | 58.2±8.0 | 59.1±8.1 | 59.1±7.9 |
| Body mass index (kg/m2) | 24.8±2.7 | 25.1±2.8 | 25.2±2.9 | 25.6±3.2 |
| Plasma cis 16:1 n-7† | 0.19±0.03 | 0.25±0.02 | 0.32±0.02 | 0.50±0.16 |
| Plasma DHA† | 3.15±1.04 | 3.03±0.89 | 3.13±1.00 | 2.91±0.94 |
| Plasma DPA† | 0.80±0.20 | 0.85±0.30 | 0.84±0.20 | 0.87±0.24 |
| Plasma EPA† | 0.70±0.38 | 0.70±0.34 | 0.78±0.58 | 0.84±0.37 |
| Linoleic acid† | 22.3±2.8 | 22.0±2.8 | 21.6±2.6 | 20.2±2.5 |
| Plasma 16:0† | 24.9±1.5 | 25.1±1.3 | 25.4±1.4 | 26.4±1.4 |
| Plasma 18:0† | 14.3±1.2 | 14.0±1.1 | 13.9±1.2 | 13.5±1.3 |
| Steaoryl-coA desaturase activity | ||||
| Ratio 16:1n-7/16:0 | 0.008±0.001 | 0.010±0.001 | 0.013±0.001 | 0.019±0.006 |
| Ratio 18:1n-9/18:0 | 0.52±0.10 | 0.55±0.08 | 0.56±0.08 | 0.64±0.11 |
| Prevalent diabetes (%) | 6.0 | 4.5 | 5.3 | 6.3 |
| Prevalent CHD (%)‡ | 16.2 | 13.6 | 17.0 | 14.3 |
| Atrial fibrillation (%) | 3.6 | 2.9 | 4.3 | 4.8 |
| Hypertension (%) | 27.3 | 25.7 | 35.5 | 35.2 |
| Current smoking (%) | 10.4 | 12.2 | 8.4 | 13.6 |
| Never smokers (%) | 52.5 | 43.4 | 48.6 | 37.6 |
| Current drinkers (%) | 80.1 | 84.8 | 79.1 | 90.9 |
| Vigorous exercise (%) | 70.2 | 75.1 | 75.4 | 73.6 |
Data are presented as means ± standard deviation or percentages. Few participants had missing data on hypertension (n=10), smoking (n=2), alcohol use (n=6), and physical activity (n=10).
Plasma phospholipid fatty acids expressed as percentage of total plasma phospholipids
CHD: coronary heart disease
Table 2.
Characteristics of cases and controls
| Characteristics | Cases (N=788) | Controls (n=788) |
|---|---|---|
| Age at randomization (y) | 58.9±8.0 | 58.8±8.0 |
| Age at blood collection (y) | 58.7±8.0 | 58.7±8.1 |
| Year of birth | 1923.6±8.0 | 1923.6±8.0 |
| Year of blood collection | 1982.2±0.4 | 1982.1±0.3 |
| Body mass index (kg/m2) | 25.8±3.2 | 24.6±2.5 |
| Plasma cis 16:1 n-7† | 0.33±0.15 | 0.32±0.15 |
| Plasma DHA† | 3.03±0.95 | 3.07±0.99 |
| Plasma DPA† | 0.83±0.24 | 0.85±0.24 |
| Plasma EPA† | 0.75±0.46 | 0.76±0.41 |
| Linoleic acid† | 21.3±2.8 | 21.6±2.8 |
| Plasma 16:0† | 25.6±1.6 | 25.4±1.5 |
| Plasma 18:0† | 14.0±1.2 | 13.8±1.2 |
| Steaoryl-coA desaturase activity | ||
| Ratio 16:1n-7/16:0 | 0.013±0.005 | 0.012±0.005 |
| Ratio 18:1n-9/18:0 | 0.57±0.11 | 0.57±0.11 |
| Race (% white) | 95.8 | 95.8 |
| Prevalent diabetes (%) | 7.9 | 3.3 |
| Prevalent CHD (%)‡ | 21.7 | 8.8 |
| Atrial fibrillation (%) | 5.5 | 2.4 |
| Hypertension (%) | 37.6 | 24.8 |
| Current smoking (%) | 13.6 | 8.9 |
| Never smokers (%) | 41.0 | 49.4 |
| Current drinkers (%) | 82.9 | 85.1 |
| Vigorous exercise (%) | 71.4 | 75.8 |
Data are presented as means ± standard deviation or percentages. Few participants had missing data on hypertension (n=10), race (n=52), smoking (n=2), alcohol use (n=6), and physical activity (n=10).
Plasma phospholipid fatty acids expressed as percentage of total plasma phospholipids.
CHD: coronary heart disease
Table 3.
Odds ratios for heart failure by quartiles or per standard deviation increase of plasma phospholipid palmitoleic fatty acids in the Physicians’ Health Study
| Cis 16 :1n-7 quartiles [Range] | Cases | Odds ratio (95% CI) for heart failure
|
||
|---|---|---|---|---|
| Model 1* | Model 2† | Model 3‡ | ||
| Q1 (low) [0.039-0.227] | 169 | 1.0 | 1.0 | 1.0 |
| Q2 [0.228-0.280] | 177 | 1.05 (0.78-1.41) | 1.10 (0.79-1.53) | 1.06 (0.75-1.48) |
| Q3 [0.281-0.359] | 197 | 1.23 (0.91-1.66) | 1.20 (0.86-1.68) | 1.20 (0.85-1.68) |
| Q4(high) [0.360-2.217] | 245 | 1.51 (1.12-2.03) | 1.52 (1.08-2.14) | 1.58 (1.11-2.25) |
| P for trend | 0.003 | 0.014 | 0.009 | |
| Per SD (0.1467%) increase of plasma cis 16:1n-7 | 1.13 (1.02-1.26) | 1.13 (1.00-1.28) | 1.17 (1.02-1.33) | |
Model 1 adjusted for matching variables; SD=standard deviation
Model 2 adjusted for matching variables plus body mass index, prevalent hypertension, coronary disease, atrial fibrillation, and diabetes, plasma phospholipid 18:0 and marine omega-3 fatty acids (EPA. DHA, and DPA)
Model 3 adjusted for variables in model 2 plus smoking (never, former, current smokers), vigorous physical activity (at least weekly vs. less frequent), and alcohol consumption (rarely/never, <1, 1-6, and 7+ drinks per week).
In secondary analyses, we examine the relation of steaoryl-coA desaturase activity and other fatty acids in the DNL [cis-oleic acid (18:1n-9) and cis-vaccenic acid (18:1n7)] with the risk of HF and found a positive association with 16:1n-7/16:0 ratio, but not with any of the other biomarkers examined (Table 4). Each standard deviation of log-transformed ratio of 16:1n-7/16:0 was associated with an odds ratio of 1.14 (95% CI: 1.00-1.29), Table 3.
Table 4.
Odds ratios for heart failure per standard deviation increase of stearoyl-coA desaturase activity, plasma phospholipid oleic acid, and cis-vaccenic acid in the Physicians’ Health Study
| One standard deviation (SD) increase of | Odds ratio (95% CI) for heart failure
|
||
|---|---|---|---|
| Model 1* | Model 2† | Model 3‡ | |
| Cis vaccenic acid (18:1n-7) [SD= 0.208] | 0.88 (0.79-0.97) | 1.02 (0.91-1.15) | 1.03 (0.91-1.17) |
| Cis Oleic acid (18:1 n-9) [SD= 1.06] | 1.09 (0.98-1.21) | 1.10 (0.97-1.25) | 1.11 (0.97-1.26) |
| Stearoyl-coA desaturase activity | |||
| Estimated by 16:1n-7-to-16:0 ratio [SD= 0.358]* | 1.13 (1.01-1.25) | 1.11 (0.99-1.26) | 1.14 (1.00-1.29) |
| Estimated by 18:1n-9-to-18:0 ratio [SD= 0.178]* | 1.02 (0.92-1.13) | 1.04 (0.91-1.19) | 1.04 (0.90-1.20) |
Model 1 adjusted for matching variables; SD=standard deviation; log-transformed ratio of product-to-substrate to estimate stearoyl-coA desaturase activity
Model 2 adjusted for matching variables plus body mass index, prevalent hypertension, coronary disease, atrial fibrillation, and diabetes, plasma phospholipid 18:0 and marine omega-3 fatty acids (EPA. DHA, and DPA)
Model 3 adjusted for variables in model 2 plus smoking (never, former, current smokers), vigorous physical activity (at least weekly vs. less frequent), and alcohol consumption (rarely/never, <1, 1-6, and 7+ drinks per week). Stearoyl-coA desaturase activity (16:1n-7/16:0) was also adjusted for 18:0 and 18:1n-9/18:0 was also adjusted for 16:0.
Discussion
In the current study, we demonstrated a positive association between plasma phospholipids cis palmitoleic acid and stearoyl-coA desaturase activity and the risk of HF in US male physicians, after adjustment for major risk factors for HF and determinants of DNL including alcohol intake. In contrast, phospholipids concentrations of cis-vaccenic acid and oleic acid were not associated with HF risk.
To the best of our knowledge, this is the first large study to demonstrate a positive association between plasma phospholipids cis palmitoleic acid and the risk of HF in a large cohort. In a cross-sectional study, HF patients were shown to have higher plasma levels of 16:1n-7 compared with controls (1.88 vs. 1.40 % weight of total fatty acids, p<0.001)27. In the Atherosclerosis Risk in Community (ARIC) study19, the highest quintile of plasma phospholipid palmitoleic acids was associated with 67% higher risk of incident HF compared with the lowest quintile after controlling for age and sex (RR= 1.67 (95% CI: 1.10-2.52). However, adjustment for body mass index, systolic blood pressure, antihypertensive medication, lipids, diabetes, smoking, alcohol consumption, energy intakes, education, and physical activity attenuated the association [i.e., RR=1.10 (95% CI: 0.70-1.73) when comparing extreme quintile]. The difference between our findings and ARIC data merits some comments. First, we examined cis-isoform of plasma phospholipids palmitoleic acid whereas ARIC19 data reported findings of cis and trans 16:1n-7. Trans-(16:1n-7) is a biomarker of dairy intake, which may exert favorable effect on HF risk factors including diabetes28. The average age in our study was about 5 years higher than in the ARIC (54 y for men and 53 y for women in ARIC vs ~59 y in PHS) but ARIC had fewer HF events (n=197) than PHS (n=788). It is possible that the ARIC study had limited statistical power to detect small effect of 16:1n-7. Lastly, the fact that our study consisted of highly educated male healthcare professionals with a higher prevalence of healthful lifestyle factors (low prevalence of smoking, comorbidity, and obesity, high prevalence of physical activity, etc,) than the general population in ARIC could partially account for the difference in the results.
In our secondary analysis, we observed a positive association between plasma cis palmitoleic acid and HF without antecedent coronary heart disease and no relation between cis palmitoleic acid and HF with antecedent coronary events. This suggests that cis palmitoleic acid might not influence the risk of HF via adverse effects on coronary heart disease. However, such a hypothesis is not consistent with our previous work showing a higher risk of coronary heart disease with higher concentrations of red blood cell cis palmitoleic acid15. It is also possible that the discrepancy between HF and coronary disease outcomes when related to cis palmitoleic acid might be partially explained by our inability to correctly classify HF with and without antecedent coronary events.
Our findings of a positive association between stearoyl-coA desaturase activity (16:1n-7/16:0 ratio) and HF is contrary to the ARIC report19, which did not show an association [p for trend across quintile 0.68 and RR=1.06 (95% CI: 0.66-1.69) comparing the fifth to the first quintile of 16:1n-7/16:0 ratio]. We examined for the first time the relation of cis-vaccenic acid (18:1n-7) with HF risk and found no association. This is contrary to our hypothesis of an inverse relation between 18:1n-7 and HF risk owing to the conversion of plasma 16:1n-7 to 18:1n-7 via elongase activity in the DNL pathway. A lack of such an association could be due to the relatively small proportions of both cis-vaccenic and cis-palmitoleic acids to total phospholipids with a median [IQR] of 0.28% [0.23-0.36] of total plasma phospholipid fatty acids for 18:1n-7 and 1.42% [1.30-1.54] for 16:1n-7 among controls.
Biologic mechanisms
What possible biologic mechanisms could help establish a causal relation between cis-palmitoleic acids and HF risk? Animal experiments have shown that python heart grows in mass by 40% after ingestion of a large meal29,30; such physiologic changes are accompanied by an increase in plasma free fatty acids18. Infusion of fasted pythons with a mixture of myristic, palmitic, and palmitoleic acids was as effective as feeding itself in cardiac hypertrophy18. Furthermore, treatment of mice with a similar mixture of fatty acids led to increased left ventricular mass as well as increased cardiomyocyte cross-sectional area18. Although these animal results may not be transferable to humans, they suggest that fatty acids in the DNL (i.e. palmitoleic acid) could modulate left ventricular geometry and contribute to the development of HF. Palmitoleic acid may increase the risk of HF via hypertension. Zheng et al.10 reported an increased prevalent hypertension per interquartile increment of cholesterol ester 16:1n-7 [OR=1.31 (95% CI: 1.18-1.44)] as well as increased incident hypertension before adjustment for baseline blood pressure [OR=1.26 (95% CI: 1.11-1.42]. However, our data did not support a major role of baseline hypertension on the association of cis palmitoleic acid with HF, as there was no meaningful difference in regression models with and without adjustment of hypertension (data not shown). Lastly, heightened inflammation could be a potential mechanism by which 16:1n-7 increases the risk of HF as Petersson et al13 reported a positively correlated between serum cholesteryl ester levels of 16:1n-7 and C-reactive protein in men. In mice, palmitoleic acid down-regulated mRNA expression of pro-inflammatory genes (TNFα and resistin) in white adipose tissue and lipogenic genes (i.e., FAS or SCD-1) in the liver31.
It is not clear whether palmitoleic acid may influence the risk of HF via its effects on coronary heart disease or diabetes. In a nested-case-control study, total plasma phospholipid 16:1n-7 was not associated with coronary heart disease in men (OR: 1.08 (95% CI: 00.77-1.57) per standard deviation of 16:1n-7)17. Administration of palmitoleic acid in mice was associated with enhanced whole-body glucose disposal and improved insulin sensitivity31,32. In humans, some28,33 but not other7 investigators have reported insulin-sensitizing effects of palmitoleic acid. Our group has reported a positive association between red blood cell cis palmitoleic acid and the risk of coronary heart disease15. Additional studies are needed to elucidate biologic mechanisms lending support to a causal relation between cis palmitoleic acid and HF risk. The absence of an association between cis vaccenic acid and HF suggests that if our findings are confirmed in future studies, pharmacological interventions targeting elongase activity (to metabolize cis palmitoleic acid (16:1n-7) to cis vaccenic acid (18:1n-7) might be of interest to mitigate such a risk. Our working hypothesis is that a positive association between stearoyl-coA desaturase activity and HF is due to conversion of a neutral palmitic acid (16:0) to a detrimental cis palmitoleic acid (16:1n7).
Strengths and limitations
The large number of participants, 22+ years of follow up, and the standardized methods of comorbidity ascertainment and measurement of plasma phospholipids fatty acids are major strengths of this study. In addition, we were able to minimize confounding by age, race, time of blood collection, and birth cohort effect through matching between cases and control series. Lastly, our findings remained robust upon additional adjustment for alcohol (and perhaps estimates of carbohydrate and protein intake), factors that influence DNL. On the other hand, the fact that all participants were male physicians, most of whom were Caucasians, limits generalization of current findings to the general population, other ethnic groups, and women. Furthermore, we did not have data to allow us to further classify HF based on etiology or left ventricular systolic function (systolic or diastolic HF). HF diagnosis was primarily self-reported by participants who were physicians and despite a 91% positive predictive value of self-reported HF against validation via medical record review in a subsample, we cannot completely exclude HF misclassification (over- or under-reporting). Such misclassification, if present, is more likely to be non-differential with respect to plasma fatty acids assays and would likely have led to an underestimation of the true effect. The lack of nutrients at baseline precluded a full adjustment for other dietary determinants of cis palmitoleic acid including carbohydrate and protein consumption. In a secondary analysis, we controlled for total proteins and carbohydrates collected about 17 years after cis palmitoleic assessment and observed similar findings. Of note is that we cannot assume that dietary patterns remained constant over 17 years of follow up; further, some participants were deceased or had missing data on nutrients and these limitations could have led to inadequate adjustment. Lastly, this ancillary study could not support the cost of plasma fatty acid measurement on all PHS subjects. Nonetheless, the use of risk-set technique to randomly select control subjects makes our findings generalizable to the entire PHS I population.
In summary, our data showed a positive association between plasma phospholipid cis palmitoleic acid and steaoryl-coA desaturase (16:1n-7/16:0 ratio) and the risk of HF in US male physicians. Avoidance of diet that favors DNL (i.e., diet with excess carbohydrate, protein, and alcohol) could be recommended to minimize high plasma cis palmitoleic acids if our findings were confirmed in other studies.
Supplementary Material
Short Commentary.
De novo lipogenesis (endogenous production of fatty acids including palmitoleic acid) may influence blood pressure, inflammation, insulin resistance, and coronary disease. However, it is unknown whether fatty acids generated by the de novo lipogenesis influence the risk of heart failure. Furthermore, the association of key enzymes involved in the de novo lipogenesis with heart failure risk has not been investigated. Using a nested case-control design, we studied 788 incident heart failure cases and 788 matched controls from the Physicians’ Health Study. Each case of heart failure was matched to its control on age, year of birth, race, and time of blood collection. Plasma phospholipid fatty acids were measured using gas chromatography. Heart failure was ascertained using annual follow-up questionnaire and validated in a subsample. In a multivariable conditional logistic regression, odds ratios (95% CI) for heart failure were 1.0 (ref), 1.06 (0.75-1.48), 1.20 (0.85-1.68), and 1.58 (1.11-2.25) across consecutive quartiles of cis palmitoleic acid (p for trend 0.009). This association was restricted to heart failure without antecedent coronary heart disease. In a secondary analysis, each standard deviation increase of log-stearoyl-coA desaturase activity was associated with a 14% higher risk of heart failure (95% CI: 1.00-1.29)]. In contrast, oleic acid and cis-vaccenic acids were not associated with heart failure risk. If confirmed in other studies, our study might provide a novel pharmacological target to lower the risk of heart failure caused by a heightened endogenous fatty acid production.
Acknowledgments
Dr Djoussé has full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. We are indebted to the participants in the PHS for their outstanding commitment and cooperation and to the entire PHS staff for their expert and unfailing assistance.
Sources of Funding
This ancillary study was funded by grants R01HL092946 and HL092946S1 (Dr Djousse) from the National Heart, Lung, and Blood Institute and the Office of Dietary Supplement, Bethesda, MD. The Physicians’ Health Study is supported by grants CA-34944, CA-40360, and CA-097193 from the National Cancer Institute and grants HL-26490 and HL-34595 from the National Heart, Lung, and Blood Institute, Bethesda, MD.
Role of the sponsor: The funding agencies did not have any role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript.
Footnotes
Disclosures
None.
References
- 1.Rosamond W, Flegal K, Furie K, Go A, Greenlund K, Haase N, Hailpern SM, Ho M, Howard V, Kissela B, Kittner S, Lloyd-Jones D, McDermott M, Meigs J, Moy C, Nichol G, O’Donnell C, Roger V, Sorlie P, Steinberger J, Thom T, Wilson M, Hong Y. Heart disease and stroke statistics--2008 update: a report from the American Heart Association Statistics Committee and Stroke Statistics Subcommittee. Circulation. 2008;117:e25–146. doi: 10.1161/CIRCULATIONAHA.107.187998. [DOI] [PubMed] [Google Scholar]
- 2.Garg R, Packer M, Pitt B, Yusuf S. Heart failure in the 1990s: evolution of a major public health problem in cardiovascular medicine. J Am Coll Cardiol. 1993;22:3A–5A. doi: 10.1016/0735-1097(93)90454-9. [DOI] [PubMed] [Google Scholar]
- 3.Massie BM, Shah NB. Evolving trends in the epidemiologic factors of heart failure: rationale for preventive strategies and comprehensive disease management. Am Heart J. 1997;133:703–712. doi: 10.1016/s0002-8703(97)70173-x. [DOI] [PubMed] [Google Scholar]
- 4.O’Connell JB, Bristow MR. Economic impact of heart failure in the United States: time for a different approach. J Heart Lung Transplant. 1994;13:S107–S112. [PubMed] [Google Scholar]
- 5.Jessup M, Brozena S. Heart failure. N Engl J Med. 2003;348:2007–2018. doi: 10.1056/NEJMra021498. [DOI] [PubMed] [Google Scholar]
- 6.Chong MF, Hodson L, Bickerton AS, Roberts R, Neville M, Karpe F, Frayn KN, Fielding BA. Parallel activation of de novo lipogenesis and stearoyl-CoA desaturase activity after 3 d of high-carbohydrate feeding. Am J Clin Nutr. 2008;87:817–823. doi: 10.1093/ajcn/87.4.817. [DOI] [PubMed] [Google Scholar]
- 7.Mozaffarian D, Cao H, King IB, Lemaitre RN, Song X, Siscovick DS, Hotamisligil GS. Circulating palmitoleic acid and risk of metabolic abnormalities and new-onset diabetes. Am J Clin Nutr. 2010;92:1350–1358. doi: 10.3945/ajcn.110.003970. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Gong J, Campos H, McGarvey S, Wu Z, Goldberg R, Baylin A. Adipose tissue palmitoleic acid and obesity in humans: does it behave as a lipokine? Am J Clin Nutr. 2011;93:186–191. doi: 10.3945/ajcn.110.006502. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Okada T, Furuhashi N, Kuromori Y, Miyashita M, Iwata F, Harada K. Plasma palmitoleic acid content and obesity in children. Am J Clin Nutr. 2005;82:747–750. doi: 10.1093/ajcn/82.4.747. [DOI] [PubMed] [Google Scholar]
- 10.Zheng ZJ, Folsom AR, Ma J, Arnett DK, McGovern PG, Eckfeldt JH. Plasma fatty acid composition and 6-year incidence of hypertension in middle-aged adults: the Atherosclerosis Risk in Communities (ARIC) Study. Am J Epidemiol. 1999;150:492–500. doi: 10.1093/oxfordjournals.aje.a010038. [DOI] [PubMed] [Google Scholar]
- 11.Kroger J, Zietemann V, Enzenbach C, Weikert C, Jansen EH, Doring F, Joost HG, Boeing H, Schulze MB. Erythrocyte membrane phospholipid fatty acids, desaturase activity, and dietary fatty acids in relation to risk of type 2 diabetes in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam Study. Am J Clin Nutr. 2011;93:127–142. doi: 10.3945/ajcn.110.005447. [DOI] [PubMed] [Google Scholar]
- 12.Wang L, Folsom AR, Zheng ZJ, Pankow JS, Eckfeldt JH. Plasma fatty acid composition and incidence of diabetes in middle-aged adults: the Atherosclerosis Risk in Communities (ARIC) Study. Am J Clin Nutr. 2003;78:91–98. doi: 10.1093/ajcn/78.1.91. [DOI] [PubMed] [Google Scholar]
- 13.Petersson H, Basu S, Cederholm T, Riserus U. Serum fatty acid composition and indices of stearoyl-CoA desaturase activity are associated with systemic inflammation: longitudinal analyses in middle-aged men. Br J Nutr. 2008;99:1186–1189. doi: 10.1017/S0007114507871674. [DOI] [PubMed] [Google Scholar]
- 14.Warensjo E, Sundstrom J, Vessby B, Cederholm T, Riserus U. Markers of dietary fat quality and fatty acid desaturation as predictors of total and cardiovascular mortality: a population-based prospective study. Am J Clin Nutr. 2008;88:203–209. doi: 10.1093/ajcn/88.1.203. [DOI] [PubMed] [Google Scholar]
- 15.Djousse L, Matthan NR, Lichtenstein AH, Gaziano JM. Red blood cell membrane concentration of cis-palmitoleic and cis-vaccenic acids and risk of coronary heart disease. Am J Cardiol. 2012;110:539–44. doi: 10.1016/j.amjcard.2012.04.027. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Wang L, Folsom AR, Eckfeldt JH. Plasma fatty acid composition and incidence of coronary heart disease in middle aged adults: the Atherosclerosis Risk in Communities (ARIC) Study. Nutr Metab Cardiovasc Dis. 2003;13:256–266. doi: 10.1016/s0939-4753(03)80029-7. [DOI] [PubMed] [Google Scholar]
- 17.Simon JA, Hodgkins ML, Browner WS, Neuhaus JM, Bernert JT, Jr, Hulley SB. Serum fatty acids and the risk of coronary heart disease. Am J Epidemiol. 1995;142:469–476. doi: 10.1093/oxfordjournals.aje.a117662. [DOI] [PubMed] [Google Scholar]
- 18.Riquelme CA, Magida JA, Harrison BC, Wall CE, Marr TG, Secor SM, Leinwand LA. Fatty acids identified in the Burmese python promote beneficial cardiac growth. Science. 2011;334:528–531. doi: 10.1126/science.1210558. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Yamagishi K, Nettleton JA, Folsom AR. Plasma fatty acid composition and incident heart failure in middle-aged adults: the Atherosclerosis Risk in Communities (ARIC) Study. Am Heart J. 2008;156:965–974. doi: 10.1016/j.ahj.2008.06.017. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Micha R, King IB, Lemaitre RN, Rimm EB, Sacks F, Song X, Siscovick DS, Mozaffarian D. Food sources of individual plasma phospholipid trans fatty acid isomers: the Cardiovascular Health Study. Am J Clin Nutr. 2010;91:883–893. doi: 10.3945/ajcn.2009.28877. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.Mozaffarian D, Katan MB, Ascherio A, Stampfer MJ, Willett WC. Trans fatty acids and cardiovascular disease. N Engl J Med. 2006;354:1601–1613. doi: 10.1056/NEJMra054035. [DOI] [PubMed] [Google Scholar]
- 22.Findings from the aspirin component of the ongoing Physicians’ Health Study. N Engl J Med. 1988;318:262–264. doi: 10.1056/NEJM198801283180431. [DOI] [PubMed] [Google Scholar]
- 23.Final report on the aspirin component of the ongoing Physicians’ Health Study. Steering Committee of the Physicians’ Health Study Research Group. N Engl J Med. 1989;321:129–135. doi: 10.1056/NEJM198907203210301. [DOI] [PubMed] [Google Scholar]
- 24.Cao J, Schwichtenberg KA, Hanson NQ, Tsai MY. Incorporation and clearance of omega-3 fatty acids in erythrocyte membranes and plasma phospholipids. Clin Chem. 2006;52:2265–2272. doi: 10.1373/clinchem.2006.072322. [DOI] [PubMed] [Google Scholar]
- 25.Djousse L, Driver JA, Gaziano JM. Relation between modifiable lifestyle factors and lifetime risk of heart failure. JAMA. 2009;302:394–400. doi: 10.1001/jama.2009.1062. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 26.Stein AD, Shea S, Basch CE, Contento IR, Zybert P. Consistency of the Willett semiquantitative food frequency questionnaire and 24-hour dietary recalls in estimating nutrient intakes of preschool children. Am J Epidemiol. 1992;135:667–677. doi: 10.1093/oxfordjournals.aje.a116346. [DOI] [PubMed] [Google Scholar]
- 27.Oie E, Ueland T, Dahl CP, Bohov P, Berge C, Yndestad A, Gullestad L, Aukrust P, Berge RK. Fatty acid composition in chronic heart failure: low circulating levels of eicosatetraenoic acid and high levels of vaccenic acid are associated with disease severity and mortality. J Intern Med. 2011;270:263–272. doi: 10.1111/j.1365-2796.2011.02384.x. [DOI] [PubMed] [Google Scholar]
- 28.Mozaffarian D, Cao H, King IB, Lemaitre RN, Song X, Siscovick DS, Hotamisligil GS. Trans-palmitoleic acid, metabolic risk factors, and new-onset diabetes in U.S. adults: a cohort study. Ann Intern Med. 2010;153:790–799. doi: 10.1059/0003-4819-153-12-201012210-00005. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 29.Secor SM, Diamond J. A vertebrate model of extreme physiological regulation. Nature. 1998;395:659–662. doi: 10.1038/27131. [DOI] [PubMed] [Google Scholar]
- 30.Andersen JB, Rourke BC, Caiozzo VJ, Bennett AF, Hicks JW. Physiology: postprandial cardiac hypertrophy in pythons. Nature. 2005;434:37–38. doi: 10.1038/434037a. [DOI] [PubMed] [Google Scholar]
- 31.Yang ZH, Miyahara H, Hatanaka A. Chronic administration of palmitoleic acid reduces insulin resistance and hepatic lipid accumulation in KK-Ay Mice with genetic type 2 diabetes. Lipids Health Dis. 2011;10:120. doi: 10.1186/1476-511X-10-120. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 32.Cao H, Gerhold K, Mayers JR, Wiest MM, Watkins SM, Hotamisligil GS. Identification of a lipokine, a lipid hormone linking adipose tissue to systemic metabolism. Cell. 2008;134:933–944. doi: 10.1016/j.cell.2008.07.048. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 33.Stefan N, Kantartzis K, Celebi N, Staiger H, Machann J, Schick F, Cegan A, Elcnerova M, Schleicher E, Fritsche A, Haring HU. Circulating palmitoleate strongly and independently predicts insulin sensitivity in humans. Diabetes Care. 2010;33:405–407. doi: 10.2337/dc09-0544. [DOI] [PMC free article] [PubMed] [Google Scholar]
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