Relationship of serum fatty acid composition and desaturase activity to C-reactive protein in Japanese men and women
Introduction
Several experimental [1], [2] and prospective epidemiological studies [3], [4] have shown a relationship between C-reactive protein (CRP), a sensitive marker for low-grade inflammation, and atherosclerotic disease. Atherosclerosis, the major underlying cause of cardiovascular disease, is a dynamic process in which an inflammation plays an important role in the initiation and/or progression of atherosclerotic lesions [1], [2].
Dietary fatty acids may be among the important underlying factors of low-grade inflammation [5]. The fatty acid composition of serum cholesteryl esters can be used as a quantitative biomarker of fatty acid intake [6]. A number of studies have examined the association between serum cholesteryl esters fatty acid composition and CRP concentration in Western populations [7], [8], [9], [10], [11]. CRP concentrations have been positively associated with saturated fatty acids such as stearic acid [11] and monounsaturated fatty acids such as palmitoleic acid [10], [11] and oleic acid [10], but inversely associated with polyunsaturated fatty acids such as n-3 polyunsaturated fatty acids [7], alpha-linolenic acid [8], [9], eicosapentaenoic acid [8] and linoleic acid [7].
Fatty acid composition can also be altered through endogenous fatty acid desaturation by a series of desaturation plus elongation reactions, which are particularly active in the liver and to a lesser extent in other tissues [12], [13]. Desaturases are involved in the endogenous synthesis of polyunsaturated fatty acids and are widely expressed in human tissues, with the highest levels in liver [14], [15]. The delta – 9, 6, and 5 desaturases (D9D, D6D, D5D) introduce a double bond at specific positions on long-chain fatty acids [12]: D9D synthesizes mainly palmitoleic and oleic acid from palmitic and stearic acid, respectively; D6D catalyzes the conversion of linoleic acid to gamma-linolenic acid, which is elongated to dihomo-gamma-linolenic acid and then desaturated to arachidonic acid by D5D; and D5D and D6D also promote the conversion of alpha-linolenic acid into eicosapentaenoic acid. Recently, two studies in a Swedish population reported an association between increased CRP concentration and high D9D [11], high D6D [10], [11], and low D5D [10].
To date, however, no study has investigated the relationship of fatty acid composition and fatty acid desaturases to CRP concentrations in Asian populations, which have a different habitual dietary fatty acid intake from western populations. For example, the mean intake of fish (71 g/d) and eicosapentaenoic acid plus docosahexaenoic acid (0.46% of energy intake) among the Japanese population is much higher than that among Western populations (32 g/d and 0.07% of energy intake, respectively) [16], [17]. Thus, we considered that an investigation in a Japanese population might provide useful information about the role of these fatty acids at higher intake levels.
Here, we assessed the relationship of serum fatty acids and of enzymes involved in endogenous fatty acid desaturation to serum CRP concentrations in Japanese men and women, on the hypothesis that a higher intake of saturated fatty acids and lower intake of polyunsaturated fatty acids, as well as higher estimates of D9D and D6D and lower estimates of that of D5D and elongase, would be associated with increased serum CRP concentrations.
Section snippets
Study design
A cross-sectional survey was conducted among municipal employees of two offices in northeastern Kyushu, Japan, at the time of their periodic health examination, in July and November 2006, as described elsewhere [18]. All full-time employees were invited to participate in the study except those on long sick leave or maternity leave. Demographic, lifestyle, anthropometric, and biochemical measurements at the two offices were conducted using the same survey protocol.
Subjects
Of 601 eligible employees, 547
Results
The mean age of subjects was 44.1 for men and 40.6 for women. There were sex differences in anthropometric and lifestyle characteristics (Table 1). Men were more likely to smoke or drink or do physical exercise and had a higher mean BMI and serum CRP concentration than women.
Regarding the bivariate relationship of serum CRP concentration to anthropometric and lifestyle characteristics, serum CRP concentrations were significantly increased as BMI increased in both men and women (p < 0.05) and as
Discussion
In this study in a Japanese working population, we found that mean CRP concentration increased with an increasing proportion of palmitic acid and a decreasing proportion of alpha-linolenic acid in men, and with an increasing proportion of dihomo-gamma-linolenic acid in both sexes. To our knowledge, this is the first study to investigate the relation of CRP concentration to serum fatty acids and the estimated activities of enzymes involved in endogenous fatty acid synthesis in an Asian
Conflicts of interest
The authors declared no conflict of interest.
Acknowledgments
The authors would like to thank the study subjects for their cooperation and participation. The authors also thank Tamami Hatano, Yasumi Kimura, and Akihiro Tanaka (Kyushu University); Mio Ozawa (Fukuoka Women's University); and Akiko Hayashi and Kie Nagao (National Center for Global Health and Medicine, Japan) for their help in data collection. This study was supported by a Grant-in-Aid for Scientific Research (C) (18590601) and (B) (21390213) from the Japan Society for the Promotion of Science
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