二十二碳六烯酸神经保护作用的研究进展

二十二碳六烯酸(简称DHA)是一种n-3长链多不饱和脂肪酸,主要来源于深海鱼油和藻类。在人体除脂肪组织外,DHA主要存在于大脑,对神经系统有重要作用,有潜在的临床应用价值。以下从DHA对神经递质通路、突触传递和信号转导等方面的影响进行综述,为DHA在临床的应用研究提供参考。     

A double-blind dose-finding pilot study of docosahexaenoic acid (DHA) for major depressive disorder

We examined the antidepressant efficacy and dose-response pattern of the n-3 docosahexaenoic acid (DHA). Thirty-five depressed adult outpatients (46% women; mean age 42+/-14 years) with a 17-item Hamilton-Depression Scale (HAM-D-17) score of >/=18 were randomized into one of three double-blind dosing arms for 12 weeks. Group A (n=14): 1 g/day of oral DHA; Group B (n=11): 2 g/day; and Group C (n=10): 4 g/day. We measured HAM-D-17 scores, plasma DHA, eicosapentaenoic acid (EPA), and n-6/n-3 ratio. Completer response rates (>/=50% decrease in HAM-D-17 score) were 83% for Group A, 40% for Group B, and 0% for Group C; Groups A and B had significant decreases in HAM-D-17 scores (p<0.05). For completers and intent-to-treat subjects, plasma DHA increased significantly (p<0.05), EPA had little change (p>0.05), and n-6/n-3 decreased significantly (p<0.05). DHA may be effective for depression at lower doses.     

Safety of docosahexaenoic acid (DHA) administered as DHA ethyl ester in a 9-month toxicity study in dogs

DHA Ethyl Ester (DHA-EE) is a 90% concentrated ethyl ester of docosahexaenoic acid manufactured from the microalgal oil. The objective of the 9-month study was to evaluate safety of DHA-EE administered to beagle dogs at dose levels 150, 1000 and 2000 mg/kg bw/day by oral gavage and to determine reversibility of any findings after a 2-month recovery period. DHA-EE was well tolerated at all doses. There were observations of dry flaky skin with occasional reddened areas at doses ≥1000 mg/kg bw/day. These findings lacked any microscopic correlate and were no longer present after the recovery period. There were no toxicologically relevant findings in body weights, body weight gains, food consumption, ophthalmological examinations, and ECG measurements. Test article-related changes in hematology parameters were limited to decreases in reticulocyte count in the high-dose males and considered non-adverse. In clinical chemistry parameters, dose-related decreases in cholesterol and triglycerides levels were observed at all doses in males and females and attributed to the known lipid-lowering effects of DHA. There were no effects on other clinical chemistry, urinalysis or coagulation parameters. There were no abnormal histopathology findings attributed to test article. The No-Observable-Adverse-Effect Level of DHA-EE was established at 2000 mg/kg bw/day for both genders.     

Co-delivery of paclitaxel (PTX) and docosahexaenoic acid (DHA) by targeting lipid nanoemulsions for cancer therapy

Breast cancer is one of the most common types of cancer in female patients with high morbidity and mortality. Multi-drug chemotherapy has significant advantages in the treatment of malignant tumors, especially in reducing drug toxicity, increasing drug sensitivity and reducing drug resistance. The objective of this research is to fabricate lipid nanoemulsions (LNs) for the co-delivery of PTX and docosahexaenoic acid (DHA) with folic acid (FA) decorating (PTX/DHA-FA-LNs), and investigate the anti-tumor activity of the PTX/DHA-FA-LNs against breast cancer both in vitro and in vivo. PTX/DHA-FA-LNs showed a steady release of PTX and DHA from the drug delivery system (DDS) without any burst effect. Furthermore, the PTX/DHA-FA-LNs exhibited a dose-dependent cytotoxicity and a higher rate of apoptosis as compared with the other groups in MCF-7 cells. The cellular uptake study revealed that this LNs were more readily uptaken by MCF-7 cells and M2 macrophages in vitro. Additionally, the targeted effect of PTX/DHA-FA-LNs was aided by FA receptor-mediated endocytosis, and its cytotoxicity was proportional to the cellular uptake efficiency. The anti-tumor efficiency results showed that PTX/DHA-FA-LNs significant inhibited tumor volume growth, prolonged survival time, and reduced toxicity when compared with the other groups. These results indicated that DHA increases the sensitivity of tumor cells and tumor-associated macrophages (ATM2) to PTX, and synergistic effects of folate modification in breast cancer treatment, thus PTX/DHA-FA-LNs may be a promising nanocarrier for breast cancer treatment.     

二十二碳六烯酸(DHA)复合物对胃腺癌细胞内H-Ras和p16 mRNA含量的影响

目的研究DHA复合物抗肿瘤作用机理。方法用RT-PCR法研究DHA复合物对胃腺癌细胞内H-Ras和p16mRNA含量的影响。结果与阴性对照组相比,DHA复合物使胃腺癌细胞内H-RasmRNA含量明显降低(P<0.05),p16mRNA含量明显增加(P<0.05).结论DHA复合物能显著降低H-Ras癌基因的转录,并能显著增加p16押癌基因的转录,从而抑制肿瘤细胞的增殖。     

The induction of apoptosis in pre-malignant keratinocytes by omega-3 polyunsaturated fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) is inhibited by albumin

The long chain omega-3 polyunsaturated fatty acids (PUFA) have been reported to exert anti-cancer effects. At this study we tested the effect of the omega-3 PUFA, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), on pre-malignant keratinocytes growth in the well-characterised human pre-malignant epidermal cell line, HaCaT and attempted to identify a PUFA serum antagonist. Both EPA and DHA inhibited HaCaT growth and induced apoptosis. At the 10% (v/v) foetal bovine serum (FBS) medium, limited growth inhibition (3–20% for 50 μM DHA and EPA respectively) and negligible apoptosis were observed with PUFA use. However, at 3% (v/v) FBS medium, 30–50 μM of PUFA caused impressive levels of growth inhibition (82–83% for 50 μM DHA and EPA respectively) and increase of apoptosis (8–19% increase in 72 h). None of the numerous serum growth factors present in FBS or the antioxidant n-tert-butyl-α-phenylnitrone could inhibit the PUFA-induced cytotoxicity. In contrast, bovine and human albumin (0.1–0.3%, w/v) significantly antagonized the growth inhibitory and apoptosis-inducing effects of PUFA. In conclusion, we have shown for the first time that omega-3 PUFA inhibit the growth and induce apoptosis of pre-malignant keratinocytes and identified albumin as a major antagonistic factor in serum that could limit their effectiveness at pharmacologically-achievable doses.     

Comparison of the inhibitory effects of docosahexaenoic acid (DHA) on U46619- and phenylephrine-induced contractions in guinea-pig aorta

Inhibitory effects of docosahexaenoic acid (DHA) on the muscle contractions induced by U46619, a thromboxane A2 (TXA2) mimetic, and phenylephrine were compared in guinea-pig aorta. In de-endothelialized guinea-pig aortic ring preparations, DHA at 10 microM strongly inhibited a sustained contraction produced by U46619 (3-100 nM) whereas it did not exhibit an appreciable effect on phenylephrine (3-10 microM)-induced contraction. The present findings indicate that DHA inhibits more selectively TXA2 receptor (TP receptor)-mediated vascular contraction than alpha-adrenoceptor-mediated response. Selective inhibition by DHA of TP receptor-mediated contraction of blood vessels seems underlie in part the mechanisms by which this polyunsaturated fatty acid exerts its circulatory-protective effects.     

Inhibitory effect of docosahexaenoic acid (DHA) on the intestinal metabolism of midazolam: in vitro and in vivo studies in rats

The aim of this study was to evaluate the effects of docosahexaenoic acid (DHA) on the intestinal cytochrome P450 isoenzyme (CYP3A) and P-glycoprotein (P-gp) functions using midazolam and rhodamine-123 as specific substrates of CYP3A and P-gp, respectively. Perfused everted intestinal segments from rats were employed to determine the effects of DHA on midazolam metabolism and rhodamine-123 transport. In addition, the effects of DHA on in vitro midazolam metabolism in rat intestinal microsomes and on midazolam bioavailability in rats were examined. The intestinal extraction ratio (ER G) of midazolam was determined to be 0.43 and decreased significantly to 0.12, 0.07, and 0.06 in the presence of 50, 100, and 200 microM DHA, respectively, in a concentration-dependent manner. The results from an in vitro study using rat intestinal microsomes demonstrated that DHA competitively inhibited the intestinal CYP3A activity with Ki of 15.7 and 27.1 microM for the formations of 1'-OH midazolam and 4-OH midazolam, respectively. Moreover, the oral administration of DHA (100mg/kg) increased the AUC infinity, Cmax, and oral bioavailability (F) of midazolam by about 50% in rats, without affecting the T 1/2, V dss/F, or CL tot/F. In contrast, DHA did not change the serosal-to-mucosal transport of rhodamine-123 in the perfused everted intestine and oral administration of DHA (100mg/kg) had no influence on the pharmacokinetics of intravenously administered midazolam in rats, thus suggesting that DHA has little effect on the intestinal P-gp activity and hepatic clearance of midazolam. This study provided the first direct evidence to show that DHA has an inhibitory effect on the intestinal pre-systemic metabolism of a CYP3A substrate and that DHA has little, if any, effect on the P-gp activity in the gut.     

Docosahexaenoic acid (DHA) attenuated paraquat induced lung damage in mice

Context: Accumulating evidences have proposed the critical roles of oxidative stress in the etiology of lung injury caused by paraquat (PQ). Docosahexaenoic acid (DHA) is an essential n-3 polyunsaturated fatty acid (PUFA), which has been proved to possess prominent antioxidative and anti-inflammatory effects. Objective: The aim of this study was to evaluate effects of DHA against acute lung injury (ALI) induced by PQ in mice. Materials and methods: Male Kunming mice were randomly divided into three groups: control group, PQ group, and PQ+DHA group (n = 24). The mice of PQ+DHA group received 500 mg/kg bodyweight DHA by gavage daily for consecutive 14 days. On day 8, the mice in PQ and PQ+DHA groups received a single oral dose of 50 mg/kg bodyweight PQ. All the mice were sacrificed on day 15. The myeloperoxidase (MPO) activities, levels of the malondialdehyde (MDA) and glutathione (GSH), and the 4-hydroxynonenal (4-HNE) and MDA modified proteins of lung were investigated. Results: DHA treatment significantly increased the survival rate of mice treated with PQ. Pulmonary MPO activities and MDA contents were elevated in the mice of the PQ group, while the GSH level was reduced. Furthermore, levels of 4-HNE and MDA modified protein in lungs of the PQ group mice were significantly increased. All the above changes were significantly inhibited by DHA pretreatment. Morphological examination revealed that DHA effectively attenuated the hyperemia, edema of ALI induced by PQ. Conclusion: These results demonstrated that DHA could effectively attenuate PQ-induced ALI in mice probably via its antioxidant activity.     

Health effects of oleic acid and long chain omega-3 fatty acids (EPA and DHA) enriched milks. A review of intervention studies

Substitution of dietary saturated fat by oleic acid and/or polyunsaturated fatty acids (PUFA) has been described to reduce the cardiovascular risk by reducing blood lipids, mainly cholesterol. Additional benefits have been described for long chain omega-3 PUFA (eicosapentaenoic acid—EPA and docosahexaenoic acid—DHA) from fish oils. In recent years, food technology has been used to produce dairy drinks with a reduced content of saturated fat in favour of those fatty acids, most of them claiming cardiovascular benefits. This review summarises all the scientific evidence regarding the effects of milks enriched with long chain omega-3 PUFA (EPA + DHA) and/or oleic acid on cardiovascular health. Nine controlled intervention studies with enriched milks have reported effects on healthy volunteers, subjects with increased risk factors and cardiovascular patients. The main effects observed were reductions of blood lipids, mainly cholesterol, LDL-cholesterol and triglycerides.     

Docosahexaenoic acid (DHA) inhibits saquinavir metabolism in-vitro and enhances its bioavailability in rats

This study investigated the effect of docosahexaenoic acid (DHA) on the metabolism of saquinavir by cytochrome P450 3A (CYP3A) in-vitro using rat liver microsomes and in-vivo using rats. DHA showed a concentration-dependent inhibition of in-vitro saquinavir metabolism with Km, Vmax and Ki values of 2.21 microM, 0.054 micromol h(-1) (mg protein)(-1) and 149.6 microM, respectively. After oral co-administration with 250 microg kg(-1) DHA, the bioavailability of saquinavir significantly increased approximately 4 fold (P < 0.01) without affecting the elimination half-life, as compared with the control. In contrast, oral administration of DHA did not affect the kinetic parameters of saquinavir administered intravenously. These results suggest that the inhibitory effect of DHA on saquinavir metabolism predominantly takes place in the gut and imply that DHA impairs the function of enteric, but not of hepatic, CYP3A. The pharmacokinetic interaction occurred only when DHA was taken simultaneously with oral administration of saquinavir. These results considered together with the lack of time-dependent saquinavir metabolism inactivation effects in-vitro, imply that the inhibitory effect of DHA is primarily reversible. It is concluded that DHA inhibited saquinavir metabolism in-vitro and enhanced the oral bioavailability of saquinavir in rats.     

The emerging role of docosahexaenoic acid in neuroinflammation

Epidemiological studies have linked fish consumption to lower rates of neurological diseases. Fish contains high levels of omega-3 polyunsaturated fatty acids (n-3 PUFA), and several lines of evidence suggest that the n-3 PUFA docosahexaenoic acid (DHA; 22:6n-3) acts in the brain via anti-apoptotic and neurotrophic pathways. In addition, DHA may act through anti-neuroinflammatory pathways, as DHA possesses anti-inflammatory properties in the periphery. Evidence from animal models has indicated that DHA and its derivatives (resolvin D1 and protectin D1) attenuate colitis, peritonitis and ischemic stroke. n-3 PUFA deprivation in rats decreases brain levels of DHA and increases markers of the brain arachidonic acid (20:4n-6) cascade, a proinflammatory pathway. Thus, chronic low intake of n-3 PUFA may predispose the brain to weak anti-inflammatory, as well as strong proinflammatory signals. Neurological disorders, including Alzheimer's disease, Parkinson's disease and major depression, display a neuroinflammatory component. n-3 PUFA supplementation, as well as drugs targeting brain PUFA metabolism, are promising candidates in the prevention and treatment of neurological disorders.     

Docosahexaenoic acid (DHA) ameliorates paraquat-induced pulmonary fibrosis in rats possibly through up-regulation of Smad 7 and SnoN

Paraquat (PQ) poisoning has caused a large number of human fatalities due to the progressive and irreversible pulmonary fibrosis. Docosahexaenoic acid (DHA) is well-recognized as important modulators of multiple biological pathways that affect health and disease. A line of studies have shown that DHA supplementation is associated with the alleviation of some tissue fibrosis. In the current study, pulmonary fibrosis of rats was produced by a single oral dose of 50 mg/kg bw PQ treatment. Daily 500 mg/kg bw DHA supplementation was provided 7 days before PQ treatment and lasted for consecutive 35 days. DHA was found to ameliorate the pulmonary fibrotic alterations induced by PQ, which was evidenced by significant reduction of histological changes, hydroxyproline content and level of the transforming growth factor-β₁ (TGF-β₁) mRNA. Furthermore, the protein levels of Smad 7 and SnoN in the DHA supplemented rats were significantly increased compared with those in the rats of the PQ group. These results suggested that DHA ameliorated pulmonary fibrosis induced by PQ might be attributed to its enhancement of Smad 7 and SnoN expression.     

Coronary flow reactions to arachidonic acid are inhibited by docosahexaenoic acid

Arachidonic acid (AA) administered to isolated perfused rat hearts produced coronary vasoconstriction followed by vasodilatation due to biotransformation of AA into vasoactive metabolites. The formation of these metabolites may be blocked with ibuprofen or fenclorac. Slow infusions of docosahexaenoic acid (DHx) resulted in an inhibition of the coronary responses to AA. These results indicate that DHx behaves as a modulator of coronary responses elicited by AA metabolites.     

Role of docosahexaenoic acid in modulating methylmercury-induced neurotoxicity.

The effect of docosahexaenoic acid (DHA) in modulating methylmercury (MeHg)-induced neurotoxicity was investigated in C6-glial and B35-neuronal cell lines. Gas chromatography measurements indicated increased DHA content in both the cell lines after 24 h supplementation. Mitochondrial activity evaluated by 3-(4, 5-dimethylthiazol-2-yl)-2, 5 diphenyltetrazolium bromide (MTT) reduction indicated that 10 microM MeHg treatment for 50 min led to a significant (p < 0.001) and similar decrease in MTT activity in both the cell lines. However, DHA pretreatment led to more pronounced depletion (p < 0.05) in the MTT activity in C6 cells as compared to B35 cells. The depletion of glutathione (GSH) content measured with the fluorescent indicator monochlorobimane was more apparent (p < 0.001) in C6 cells treated with DHA and MeHg. The amount of reactive oxygen species (ROS) detected with the fluorescent indicator -- chloromethyl derivative of dichloro dihydro fluorescein diacetate (CMH(2)DCFDA) -- indicated a fourfold increase in C6 cells (p < 0.001) as compared to twofold increase in B35 cells (p < 0.001) upon DHA and MeHg exposure. However, the cell-associated MeHg measurement using (14)C-labeled MeHg indicated a decrease (p < 0.05) in MeHg accumulation upon DHA exposure in both the cell lines. These findings provide experimental evidence that although pretreatment with DHA reduces cell-associated MeHg, it causes an increased ROS (p < 0.001) and GSH depletion (p < 0.05) in C6 cells.     

A combined subchronic (90-day) toxicity and neurotoxicity study of a single-cell source of docosahexaenoic acid triglyceride (DHASCO oil).

Docosahexaenoic acid (DHA), a 22-carbon long-chain polyunsaturated fatty acid of the omega-3 family, is a major structural component of neural membranes and is a particularly important nutrient during infant development. New safe and well-defined sources of DHA are required for infant formula fortification and dietary supplementation. DHASCO oil is an algal-derived triglyceride containing 40-50% DHA. Previous studies have shown that DHASCO oil is neither mutagenic nor toxic in acute or 28-day subchronic tests. To further establish the safety of this oil, a 90-day subchronic toxicity study in rats which included haematology, clinical chemistry, pathology and ophthalmologic, neurobehavioural and neuropathological assessments, using doses of 0.5 and 1.25g/kg body weight/day was performed. There were no treatment-related adverse effects in any of the parameters measured at either dose. Based on these results, the no-adverse-effect level (NOAEL) for DHASCO oil under the conditions of this study corresponds to the highest dose level. The DHA in the DHASCO oil was bioavailable, resulting in significant elevations in the levels of this fatty acid in liver, heart and brain after 90 days of administration. In conclusion, this 90-day subchronic toxicity study provides additional evidence that DHASCO oil is a safe and bioavailable source of dietary DHA.     

Eicosapentaenoic acid and docosahexaenoic acid modulate mitogen-activated protein kinase activity in endothelium

Omega-3 polyunsaturated fatty acids (PUFA) regulate inflammation and immunoreaction partially via affecting endothelial functions. However, the intracellular signaling mechanisms for inhibiting endothelial activation by omega-3 PUFA remain unclear. We investigated the effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on mitogen-activated protein kinases (MAPK) of endothelium. We analyzed the expression of extracellular signal-related kinases (ERK1/2), Jun amino-terminal kinases (JNK), and p38 mRNA by real-time RT-PCR and the kinases activity by western blotting in tumor necrosis factor-alpha (TNF-alpha)-activated human umbilical vein endothelial cells (HUVEC). We observed that EPA or DHA alone significantly reduced the TNF-alpha-induced activation of p38 and JNK kinases at a concentration of 20 microM, but EPA is a more potent inhibitor than DHA. In contrast, both EPA and DHA significantly counteracted the TNF-alpha-mediated deactivation of ERK1/2 kinases. Meanwhile, both EPA and DHA significantly attenuated the TNF-alpha-induced expression of p38 and ERK1/2 mRNA, and DHA but not EPA also reduced the TNF-alpha-induced JNK mRNA expression. We present data show that both EPA and DHA alone diminish activation of p38 and JNK kinases, while maintaining the activation of ERK1/2 kinases of TNF-alpha-stimulated HUVEC. This may contribute to the inhibiting effects of omega-3 PUFA on endothelial activation by proinflammatory stimuli.     

Mechanism of improvement of spatial cognition with dietary docosahexaenoic acid

We estimated the effects of dietary administration of docosahexaenoic acid (DHA, 22:6n-3) on rat spatial cognition using young male Wistar rats. Chronic administration of DHA to rats increased the hippocampal levels of DHA. Six weeks after the start of the administration, the rats were for 5 weeks trained to acquire a reward at the end of each of 4 arms of an 8-arm radial maze. The retention test interposed with a delayed task (20-min interval after the first 2 free choices) was then given to each rat to determine spatial working memory retention. On completion of the test, the Fos expression in the hippocampus was examined immunohistochemically. DHA administration reduced the number of working memory errors after the 20-min interval in the retention test. The number of Fos-positive neurons in the CA1 hippocampus demonstrated a statistically significant negative correlation with the number of working memory errors, suggesting that the DHA-induced improvement in spatial cognition is associated with increased Fos expression in the CA1 hippocampus.     

二十二碳六烯酸与二甲氨基乙醇复方制剂的临床研究

目的研究二十二碳六烯酸与二甲氨基乙醇复方制剂 (胶丸 )对脑功能障碍和高脂血症患者的临床效果。方法实验组口服该复方制剂 ,对照组脑功能障碍患者口服安慰剂 ,高脂血症患者口服月见草油胶丸 ,进行对比。结果供试胶丸能增强和改善脑功能 ,提高智力 ,调节血脂。结论供试胶丸适用于脑功能障碍综合征和高脂血症