Abstract
BackgroundPrevious studies showed that plasma n-3 polyunsaturated fatty acid (PUFA) was negatively associated with plasma homocysteine (Hcy).ObjectiveWe investigated the regulatory effect of n-3 PUFA on mRNA expression of the critical genes encoding the enzymes involved in Hcy metabolism.MethodsHepG2 cells were treated with docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), alpha-linolenic acid (ALA) respectively for 48 h. The cells were collected and total RNA was isolated. The mRNA expression levels of the genes were determined by using Real Time-PCR.ResultsCompared with controls, the mRNA expression levels of 5-methyltetrahydrofolate reductase (MTHFR) were significantly increased in the DHA group (p < 0.05) and ALA group (p < 0.05); Significantly down-regulated mRNA expression of methionine adenosyltransferase (MAT) was observed with the treatments compared with the controls; the level of MAT expression was significant lower in the DHA group than the ALA group (p < 0.05); Cystathionine-γ-lyase (CSE) expression was significantly increased in the DHA (p < 0.05) and EPA groups (p < 0.05) compared with control. No significant changes were shown in mRNA expression levels of S-adenosylhomocysteine hydrolases (SAHH), cystathionine β-synthase (CBS), and 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR).ConclusionsOur results suggest that DHA up-regulates CSE and MTHFR mRNA expression and down-regulates MAT mRNA expression involved in Hcy metabolism.
Highlights
Previous studies showed that plasma n-3 polyunsaturated fatty acid (PUFA) was negatively associated with plasma homocysteine (Hcy)
Our results suggest that docosahexaenoic acid (DHA) up-regulates CSE and methyltetrahydrofolate reductase (MTHFR) mRNA expression and down-regulates methionine adenosyltransferase (MAT) mRNA expression involved in Hcy metabolism
The phospholipids fatty acid composition of cell membrane of HepG2 cell after the treatment of n-3 PUFA When compared with the control group, the concentration of 22:6n-3, 20:5n-3, 18:3n-3 were significantly increased in the three treated groups respectively (p < 0.05); the level of n-3 PUFA was significantly elevated in the three groups (p < 0.05) (Table 2)
Summary
Previous studies showed that plasma n-3 polyunsaturated fatty acid (PUFA) was negatively associated with plasma homocysteine (Hcy). Homocysteine (Hcy) is a thiol-containing amino acid derived from methionine metabolism [2]. Methionine is converted to Sadenosylmethionine (SAM) via methionine adenosyltransferase (MAT), which is the only methyl-donating pathway in humans [3]. Hcy can be degraded through two enzymatic pathways: transsulfuration and remethylation (Figure 1) [1]. Hcy can be converted back to methionine in the remethylation pathway via 5-methyltetrahydrofolate reductase (MTHFR) and methionine synthase (MS) using cofactors such as vitamin B12 and folic acid [4]. Hcy is condensed with serine to form cystathionine via vitamin B6 dependent cystathionine b-synthase (CBS), subsequently, cystathionine is converted to cysteine, a-ketosuccinic acid, taurine, and hydrogen sulfide (H2S) via vitamin B6 dependent cystathionine-g-lyase (CSE) [5]
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