**3. Omega-3 fatty acids and CHD**

*New Insights into Metabolic Syndrome*

acids (R-TFA) in RBC membranes were associated with the lower risk for SCD during a median of 10 years of follow-up (**Figure 3**) and that three *trans* isomers of C18:2n6 (IP-TFA) were not related to fatal cardiovascular outcomes [30]. Total TFA levels in LURIC patients (mean 0.96%) were much lower than those in US cohorts in the 1990s [31]. According to the TRANSFAIR study, a cross-sectional investigation in eight countries in Europe, TFA intake is below 1%E and 79% of TFA intake was derived from milk and ruminant fat in Germany [32]. Some prospective cohort studies showed that R-TFA were associated with the lower risk for incident diabetes. In the Cardiovascular Health Study, a prospective cohort study comprising elder US adults from 1989 to 1990 from Medicare eligibility lists, plasma phospholipid FA were measured in 3736 adults in 1992 [33]. Higher *trans*-palmitoleate levels were associated with slightly lower adiposity and, independently, with higher HDL-C levels (1.9% across quintiles; P = 0.040), lower triglyceride levels (−19.0%; P < 0.001), a lower total cholesterol/HDL-C ratio (−4.7%; P < 0.001), lower C-reactive protein levels (−13.8%; P < 0.05), and lower insulin resistance (−16.7%, P < 0.001). *Trans*-palmitoleate was also associated with a substantially lower incidence of diabetes, with multivariate hazard ratios of 0.41 (95% CI, 0.27 to 0.64) and 0.38 (CI, 0.24 to 0.62) in quintiles 4 and 5 versus quintile 1 (P for trend <0.001) [33]. In the Multi-Ethnic Study of Atherosclerosis (MESA), a cohort of white, black, Hispanic, and Chinese Americans, plasma phospholipid FA and metabolic risk factors were measured in 2000–2002 in 2281 participants free of baseline diabetes [34]. They prospectively assessed the risk of new-onset diabetes (205 cases) from baseline to 2005–2007 [34]. Circulating *trans-*palmitoleate is associated with higher LDL-C but also with lower triglycerides, fasting insulin, blood pressure, and incident diabetes [34]. Large genome-wide association studies have not identified any significant genetic determinants of circulating palmitelaidic acid (C16:1 n7t) levels

*Adjusted survival curves for sudden cardiac death. Tertiles of palmtelaidic acid (C16:1n7t) were balanced for body mass index, LDL-C, HDL-C. log-Triglyceride, log-fibrinogen, smoking, hypertension, diabetes, lipid-lowering therapy, and estimated glomerular filtration rate by inverse variance weighting. The inset shows the same data on a truncated y axis. Hazard ratios (95% confidence interval) for the second and third tertile compared with the first tertile were 0.82 (0.61–1.12) and 0.67 (0.48–0.93), respectively. The p-value of the* 

**160**

**Figure 3.**

*robust score test was 0.043. Reproduced from [30].*

Numerous studies have demonstrated that omega-3 PUFA protect against CVD, and the ratios of serum levels of EPA and DHA to AA, omega-6 PUFA have been recognized as promising risk markers for CHD [2, 36]. Our case-control study showed that the ACS patients had significantly higher levels of saturated FA, mainly myristic and palmitic acids, and MUFA, mainly oleic acid, and lower levels of omega-3 PUFA, mainly EPA and DHA, and AA, omega-6 PUFA (**Figure 4**) [17]. The Japanese dietary style has markedly changed from the 1960s, and fish to meat ratios in food consumption are decreasing in the younger generation, while the ratios in the Western countries stayed the same or slightly increased [37]. The age profile of the fish/meat >1.0 was ≥40 years in 2000, ≥50 years in 2005 and 2010, and ≥ 60 years in 2015 in Japan. The EPA plus DHA to AA ratios were significantly lower in ACS patients and were further lower in ACS patients <60 years old (**Figure 4**) [17].

PUFA levels depend on dietary intake, bioavailability, and PUFA metabolism. In the biosynthesis of long chain PUFA from precursor PUFA, the crucial enzymes include elongase and desaturase (**Figure 5**) [38, 39]. Delta-5 desaturase (D5D) and

#### **Figure 4.**

*The comparison of trans fatty acids (TFA) between control and ACS patients. Left panel: comparison in whole subjects and Right panel: comparison separated by age. Data are expressed as mean ± standard error (SE), and the error bar represents SE. The number of subjects is 49 (<60 years 24; ≥60 years 25) in control and 67 (<60 years 25; ≥60 years 42) in ACS. (A) \*p < 0.05, \*\*p < 0.01 \*p < 0.001 vs. control. (B) \*p < 0.05, \*\*p < 0.01 \*p < 0.001 vs. control<60y; †P < 0.05, ††p < 0.01 †††p < 0.001 vs. ACS < 60y; #P < 0.05, ##p < 0.01 vs. control ≥60 years. Figure was made by Ref. [17].*

#### **Figure 5.**

*The omega-3 and omega-6 FA metabolism. ALA,* α*-linolenic acid; ARA, arachidonic acid; DGLA, dihomo*γ*-linolenic acid; DHA, docosahexaenoic acid; DPA, docosapentaenoic acid; EPA, eicosapentaenoic acid; GLA,*  γ*-linolenic acid; LA, linoleic acid. Reproduced Ref. [38].*

delta-6 desaturase (D6D) are two key enzymes in the synthesis of long-chain PUFA and are encoded by fatty acid desaturase 1 (FADS1) and FADS2 genes, respectively [39]. Previous studies have reported that the FADS1 gene polymorphism (less function) was associated with an increased CHD risk [40, 41]. D5D is involved in one step in the conversion of linoleic acid (LA, 18:2 *n*-6) and alpha-linoleneic acid (ALA, 18:3 *n*-3) to AA (20:4 *n*-6) and EPA (20:5 *n*-3), respectively, as the sole enzymatic source of endogenous AA and EPA. EPA and DHA are strongly influenced by the dietary intake of pre-formed PUFA, and, while human can readily retroconvert DHA to EPA, the elongation of ALA to EPA and DHA is minimal [38, 42]. However, contrary results have also been very recently reported [43]. The activities of D5D cannot be measured directly; generally, they are conventionally estimated from the ratio of AA to dihomo-gamma linolenic acid (DGLA, 20:3 *n*-6) [39, 44–46].

In our cross-sectional study with ACS patients alone, PUFA and various lipid markers such as small dense LDL cholesterol (sdLDL-C), malondialdehydemodified LDL (MDA-LDL), and remnant lipoprotein cholesterol (RL-C) were assessed in 436 men with the first episode of ACS not take any lipid-lowering drugs [47]. Approximately 70% of ACS patients had low EPA/AA (<0.41) or DHA/AA (<0.93) according to the median levels in Japanese general population [48]. Serum levels of LDL-C, apolipoprotein B (apoB), and RL-C were significantly higher in the low EPA/AA or DHA/AA groups, while those of triglycerides and MDA-LDL were significantly higher in the low EPA/AA group alone. Thus, low EPA/AA is associated with more atherogenic lipid biomarkers than low DHA/AA. Patients without any reperfusion at the culprit coronary artery on the initial CAG had significantly lower EPA levels and similar DHA and AA levels compared with the others. The levels of LDL-C, non-HDL-C, triglycerides, sdLDL-C, RL-C, MDA-LDL, and apoB decreased progressively and those of EPA, DHA, and HDL-C increased as D5D increased (**Figure 6**). While large buoyant LDL-C (lbLDL-C) estimated by subtracting the sdLDL-C concentration from the LDL-C concentration, and apoA-1 did not differ among quartiles of D5D. Previous prospective case-control studies

**163**

**Figure 6.**

*Significance of Trans Fatty Acids and Omega-3 Fatty Acids in Japanese Men with Coronary…*

*Comparisons of various lipid biomarkers between the quartiles of D5D estimated by AA/DGLA. Data are expressed as means ± standard deviation, or median (25% and 75% quartiles) (triglyceride and or RL-C). Abbreviations are presented in the main text. Kruskal-Wallis tests and analysis of variance (ANOVA) with Tukey's honest significant difference test was used to identify the differences between the groups. Q1: AA/ DGLA < 4.03; Q2: 4.04 ≤ AA/ DGLA < 5.07; Q3: 5.08 ≤AA/ DGLA < 6.29; Q4: AA/DGLA ≥ 6.29. \*p < 0.05 vs. Q1, §p < 0.05 vs. Q2, †p < 0.05 vs. Q3 using Tukey-–Kramer post-hoc test. Figure is made by Ref. [47].*

*DOI: http://dx.doi.org/10.5772/intechopen.93357*

*Significance of Trans Fatty Acids and Omega-3 Fatty Acids in Japanese Men with Coronary… DOI: http://dx.doi.org/10.5772/intechopen.93357*

#### **Figure 6.**

*New Insights into Metabolic Syndrome*

delta-6 desaturase (D6D) are two key enzymes in the synthesis of long-chain PUFA and are encoded by fatty acid desaturase 1 (FADS1) and FADS2 genes, respectively [39]. Previous studies have reported that the FADS1 gene polymorphism (less function) was associated with an increased CHD risk [40, 41]. D5D is involved in one step in the conversion of linoleic acid (LA, 18:2 *n*-6) and alpha-linoleneic acid (ALA, 18:3 *n*-3) to AA (20:4 *n*-6) and EPA (20:5 *n*-3), respectively, as the sole enzymatic source of endogenous AA and EPA. EPA and DHA are strongly influenced by the dietary intake of pre-formed PUFA, and, while human can readily retroconvert DHA to EPA, the elongation of ALA to EPA and DHA is minimal [38, 42]. However, contrary results have also been very recently reported [43]. The activities of D5D cannot be measured directly; generally, they are conventionally estimated from the

*The omega-3 and omega-6 FA metabolism. ALA,* α*-linolenic acid; ARA, arachidonic acid; DGLA, dihomo*γ*-linolenic acid; DHA, docosahexaenoic acid; DPA, docosapentaenoic acid; EPA, eicosapentaenoic acid; GLA,* 

ratio of AA to dihomo-gamma linolenic acid (DGLA, 20:3 *n*-6) [39, 44–46].

markers such as small dense LDL cholesterol (sdLDL-C), malondialdehydemodified LDL (MDA-LDL), and remnant lipoprotein cholesterol (RL-C) were assessed in 436 men with the first episode of ACS not take any lipid-lowering drugs [47]. Approximately 70% of ACS patients had low EPA/AA (<0.41) or DHA/AA (<0.93) according to the median levels in Japanese general population [48]. Serum levels of LDL-C, apolipoprotein B (apoB), and RL-C were significantly higher in the low EPA/AA or DHA/AA groups, while those of triglycerides and MDA-LDL were significantly higher in the low EPA/AA group alone. Thus, low EPA/AA is associated with more atherogenic lipid biomarkers than low DHA/AA. Patients without any reperfusion at the culprit coronary artery on the initial CAG had significantly lower EPA levels and similar DHA and AA levels compared with the others. The levels of LDL-C, non-HDL-C, triglycerides, sdLDL-C, RL-C, MDA-LDL, and apoB decreased progressively and those of EPA, DHA, and HDL-C increased as D5D increased (**Figure 6**). While large buoyant LDL-C (lbLDL-C) estimated by subtracting the sdLDL-C concentration from the LDL-C concentration, and apoA-1 did not differ among quartiles of D5D. Previous prospective case-control studies

In our cross-sectional study with ACS patients alone, PUFA and various lipid

**162**

**Figure 5.**

γ*-linolenic acid; LA, linoleic acid. Reproduced Ref. [38].*

*Comparisons of various lipid biomarkers between the quartiles of D5D estimated by AA/DGLA. Data are expressed as means ± standard deviation, or median (25% and 75% quartiles) (triglyceride and or RL-C). Abbreviations are presented in the main text. Kruskal-Wallis tests and analysis of variance (ANOVA) with Tukey's honest significant difference test was used to identify the differences between the groups. Q1: AA/ DGLA < 4.03; Q2: 4.04 ≤ AA/ DGLA < 5.07; Q3: 5.08 ≤AA/ DGLA < 6.29; Q4: AA/DGLA ≥ 6.29. \*p < 0.05 vs. Q1, §p < 0.05 vs. Q2, †p < 0.05 vs. Q3 using Tukey-–Kramer post-hoc test. Figure is made by Ref. [47].*

reported that low D5D predict the development of type 2 diabetes [49–51] and the risk of CVD [39]. In a Swedish population-based prospective cohort study of 2009 50-year old men, D5D was reported to have an inverse correlation with CVD mortality over a follow-up of 30 years [52]. The association of lower D5D with accumulation of atherogenic sdLDL, MDA-LDL, and RL-C in our study may provide the association between lower D5D and atherosclerotic CVD.

Previous studies reported that statins, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, have differential effects on the activities of D5D, D6D, and elongase, and any statins increased AA [53]. It is suggested that EPA/AA may better reflect the residual risk for CHD following statin treatment than DHA / AA. Some previous cross-sectional studies have demonstrated that EPA/AA but not DHA/AA was significantly associated with ACS [54, 55]. A cohort study of CHD patients underwent nonemergency percutaneous coronary intervention (PCI) found that lower EPA/AA (but not lower DHA/AA) was significantly associated with the incidence of major adverse cardiac events [56]. Our study showed that the EPA/AA is a superior risk marker than DHA/AA in terms of correlation with atherogenic lipid profiles in ACS patients.

Multiple studies have demonstrated that EPA and DHA have different effects on cardiometabolic risk factors [57, 58]. Innes and Calder reviewed 18 randomized controlled trials that compare EPA or DHA (>2 g/day and purity ≥90%) and placebo on cardiometabolic risk factors [57]. The study durations were between 4 and 10 weeks. They reported the following results: (1) both EPA and DHA lowered triglycerides with DHA having a greater triglyceride-lowering effects than EPA; (2) while total cholesterol was largely unchanged by EPA and DHA, DHA increased HDL-C, particularly HDL2 and increased LDL-C and LDL particle size; (3) both EPA and DHA inhibited platelet activity while DHA improved vascular function and lowered heart rate and blood pressure to a greater extent than EPA; and

#### **Figure 7.**

*Relative changes in the expression of specific genes determined by quantitative real-time polymerase chain reaction (Q-PCR) in olive oil, EPA and DHA supplementation groups. Data are expressed as mean ± standard error. Differences within each group were determined by paired t test (\*\*p < 0.01, \*p < 0.05). Brackets indicate differences between two groups as determined with a 2-factor ANOVA with Tukey honestly significant difference correction. CCR6, chemokine (C-C motif) receptor 6; CREB1, cAMP responsive element binding protein 1; HIF1A, hypoxia-inducible factor 1-alpha; HMGB1, high mobility group box 1; IL1RN, interleukin 1 receptor antagonist; IL2RB, interleukin 2 receptor, beta; IRF7, interferon regulatory factor 7; STAT3, signal transducer and activator of transcription. Reproduced from [58].*

**165**

*Significance of Trans Fatty Acids and Omega-3 Fatty Acids in Japanese Men with Coronary…*

(4) the effects of EPA and DHA on inflammatory markers and glycemic control were inconclusive [57]. Tsunoda et al. assessed the effect of a six-week supplementation with either olive oil (6 g/day), EPA (1.8 g/day), or DHA (1.8 g/day) on gene expression in peripheral blood mononuclear cells in healthy men and postmenopausal women [58]. EPA but not DHA or olive oil significantly affected the gene expression in the interferon signaling, receptor recognition of bacteria and viruses, G protein signaling, glycolysis, glycolytic shunting, S-adenosyl-L-methionine biosynthesis, cAMP-mediated signaling, as well as many other individual genes including hypoxia inducible factor 1 (**Figure 7**) [58]. They concluded that the effects of EPA and DHA were mediated by different pathways in human peripheral blood mononuclear cells and that EPA affected cellular immune responses including the interferon signaling

IP-TFA intake (estimated from plasma levels) is low in Japan, and accordingly,

there is a little difference in IP-TFA levels between Japanese ACS patients and healthy controls. However, a certain IP-TFA is associated with the increased risk of CHD even in Japan. Although it is not clear whether R-TFA are cardioprotective or not, the ACS patients, especially middle-aged patients showed significantly lower levels of R-TFA and omega-3 FA. Although average EPA and DHA levels in Japan are much higher than in the United States [59], still higher levels of the marine omega-3 PUFA are associated with the lower cardiovascular disease risk. However, the Japanese dietary style has changed markedly in the younger generation since 1990 [37, 60]. The lack of fish intake and excessive oils and meat and poultry intakes have been recognized in subjects <60 years old in the present Japanese. Decreased biosynthesis of long-chain PUFA and imbalance of omega-3 and omega-6 FA are clearly associated with atherogenic lipid profiles in Japanese ACS patients. Multiple studies have demonstrated that EPA and DHA have different effects on cardiometabolic risk factors. The EPA/AA may be a superior risk marker than DHA/AA in

terms of correlation with atherogenic lipid profiles in clinical practice.

*DOI: http://dx.doi.org/10.5772/intechopen.93357*

pathway [58].

**4. Conclusion**

**Abbreviations**

AA arachidonic acid

apoA1 apolipoprotein A1 apoB apolipoprotein B CAG coronary angiography CHD coronary heart disease CI confidence interval CVD cardiovascular disease

ACS acute coronary syndromes AMI acute myocardial infarction

DGLA dihomo-gamma linolenic acid

DHA docosahexaenoic acid D5D Delta-5 desaturase D6D delta-6 desaturase EPA eicosapentaenoic acid

FADS fatty acid desaturase HDL-C HDL cholesterol

FA Fatty acids

*Significance of Trans Fatty Acids and Omega-3 Fatty Acids in Japanese Men with Coronary… DOI: http://dx.doi.org/10.5772/intechopen.93357*

(4) the effects of EPA and DHA on inflammatory markers and glycemic control were inconclusive [57]. Tsunoda et al. assessed the effect of a six-week supplementation with either olive oil (6 g/day), EPA (1.8 g/day), or DHA (1.8 g/day) on gene expression in peripheral blood mononuclear cells in healthy men and postmenopausal women [58]. EPA but not DHA or olive oil significantly affected the gene expression in the interferon signaling, receptor recognition of bacteria and viruses, G protein signaling, glycolysis, glycolytic shunting, S-adenosyl-L-methionine biosynthesis, cAMP-mediated signaling, as well as many other individual genes including hypoxia inducible factor 1 (**Figure 7**) [58]. They concluded that the effects of EPA and DHA were mediated by different pathways in human peripheral blood mononuclear cells and that EPA affected cellular immune responses including the interferon signaling pathway [58].
