2,4-Decadienal downregulates TNF-alpha gene expression in THP-1 human macrophages

Trans, trans-2,4-decadienal, a lipid peroxidation product, aggravates insulin resistance in obese mice by promoting adipose inflammation

Peroxidation of polyunsaturated fatty acids results in the creation of numerous α, β-unsaturated aldehydes, many of which are complicated by the development of diabetes. Trans, trans-2,4-decadienal (DDE) is a dietary α, β-unsaturated aldehyde that is commonly found in food and the environment. However, it is unknown whether DDE exposure has some negative effects on glucose homeostasis and insulin sensitivity. This study investigated the biological effects of long-term DDE exposure in normal chow diet (NCD)-fed non-obese mice and high-fat diet (HFD)-fed obese mice. Results showed that oral administration of DDE for 14 weeks did not cause severe toxicity in NCD-fed non-obese mice but had significant adverse effects in HFD-fed obese mice. It was found that DDE exposure caused significant increases in LDL and ALT levels and aggravated glucose intolerance and insulin resistance in obese mice. Moreover, DDE robustly accumulated in adipose tissue and promoted the impairment of the insulin signaling pathway in the adipose tissue of obese mice while not affecting the skeletal muscle or liver. Mechanistically, DDE aggravated adipose tissue inflammation by promoting M1 macrophage accumulation and increasing proinflammatory cytokines in the adipocytes of obese mice, thus leading to impaired systemic insulin resistance. These findings provide crucial insights into the potential health impacts of long-term DDE exposure.

Impaired Detoxification of Trans, Trans-2,4-Decadienal, an Oxidation Product from Omega-6 Fatty Acids, Alters Insulin Signaling, Gluconeogenesis and Promotes Microvascular Disease

Omega-6 fatty acids are the primary polyunsaturated fatty acids in most Western diets, while their role in diabetes remains controversial. Exposure of omega-6 fatty acids to an oxidative environment results in the generation of a highly reactive carbonyl species known as trans, trans-2,4-decadienal (tt-DDE). The timely and efficient detoxification of this metabolite, which has actions comparable to other reactive carbonyl species, such as 4-hydroxynonenal, acrolein, acetaldehyde, and methylglyoxal, is essential for disease prevention. However, the detoxification mechanism for tt-DDE remains elusive. In this study, the enzyme Aldh9a1b is identified as having a key role in the detoxification of tt-DDE. Loss of Aldh9a1b increased tt-DDE levels and resulted in an abnormal retinal vasculature and glucose intolerance in aldh9a1b-/- zebrafish. Transcriptomic and metabolomic analyses revealed that tt-DDE and aldh9a1b deficiency in larval and adult zebrafish induced insulin resistance and impaired glucose homeostasis. Moreover, alterations in hyaloid vasculature is induced by aldh9a1b knockout or by tt-DDE treatment can be rescued by the insulin receptor sensitizers metformin and rosiglitazone. Collectively, these results demonstrated that tt-DDE is the substrate of Aldh9a1b which causes microvascular damage and impaired glucose metabolism through insulin resistance.

trans,trans-2,4-Decadienal induces endothelial cell injury by impairing mitochondrial function and autophagic flux

This study investigated the toxic effects of trans,trans-2,4-decadienal (tt-DDE) on vascular endothelial cells as well as the underlying mechanisms involved. Human umbilical vascular endothelial cells (HUVECs) were treated with different concentrations of tt-DDE for 24 h, and cell viability, colony formation ability, apoptosis, mitochondrial function and autophagy pathway were determined. The results showed that tt-DDE dose-dependently inhibited cell viability and colony formation, and increased lactate dehydrogenase (LDH) release and apoptosis in HUVECs. Besides, tt-DDE exposure induced extensive mitochondrial damage, as evidenced by the decreased mitochondrial DNA copy number, ATP synthesis, and mitochondrial membrane potential, and increased mitochondrial reactive oxygen species (ROS) production and cytochrome c release from mitochondria. tt-DDE also induced mitochondrial fragmentation and fission by increasing DNM1L protein expression and DNM1L mitochondrial translocation. Additionally, tt-DDE treatment resulted in the blockage of autophagic flux and accumulation of autophagosomes in endothelial cells. Further investigation revealed that the inhibition of autophagy by 3-methyladenine aggravated tt-DDE-induced mitochondrial dysfunction and cell injury. However, scavenging of ROS by N-acetyl-l-cysteine (NAC) significantly prevented tt-DDE-induced mitochondrial damage, autophagy dysfunction, and cell injury. These data indicated that tt-DDE induced endothelial cell injury through impairing mitochondrial function and autophagic flux.

Akt and ERK/Nrf2 activation by PUFA oxidation-derived aldehydes upregulates FABP4 expression in human macrophages

OBJECTIVE

In macrophages, adipocyte fatty acid-binding protein (FABP4) coordinates key events in oxidized LDL-induced foam cell formation, such as cholesterol trafficking and inflammatory responses. Nrf2 is a redox-sensitive transcription factor with antioxidant and anti-inflammatory properties. We investigated the involvement of the Nrf2 signaling pathway in FABP4-upregulation in response to aldehydes that are derived from polyunsaturated fatty acid (PUFA) oxidation.

METHODS AND RESULTS

Using RT-PCR and western blotting, we found that the aldehyde 2,4-decadienal (2,4-DDE) produced a marked increase in FABP4 mRNA and protein levels. 2,4-DDE acts at the transcriptional level of FABP4 by promoting mRNA synthesis and prolonging the half-life of the de novo synthesized mRNA. 2,4-DDE consistently enhanced nuclear translocation of phosphorylated Nrf2, which was mediated by the activation of the Akt and ERK signaling pathways. A chromatin immunoprecipitation assay showed the in vivo binding of activated Nrf2 to a newly identified ARE site in the human FABP4 promoter.

CONCLUSIONS

We propose an Akt and ERK/Nrf2-dependent FABP4 upregulation pathway in response to PUFA oxidation end-products in human macrophages. These results open a new avenue for putative therapeutic targets addressed to control atherogenesis.

The influence of bioactive oxylipins from marine diatoms on invertebrate reproduction and development

Diatoms are one of the main primary producers in aquatic ecosystems and occupy a vital link in the transfer of photosynthetically-fixed carbon through aquatic food webs. Diatoms produce an array of biologically-active metabolites, many of which have been attributed as a form of chemical defence and may offer potential as candidate marine drugs. Of considerable interest are molecules belonging to the oxylipin family which are broadly disruptive to reproductive and developmental processes. The range of reproductive impacts includes; oocyte maturation; sperm motility; fertilization; embryogenesis and larval competence. Much of the observed bioactivity may be ascribed to disruption of intracellular calcium signalling, induction of cytoskeletal instability and promotion of apoptotic pathways. From an ecological perspective, the primary interest in diatom-oxylipins is in relation to the potential impact on energy flow in planktonic systems whereby the reproductive success of copepods (the main grazers of diatoms) is compromised. Much data exists providing evidence for and against diatom reproductive effects; however detailed knowledge of the physiological and molecular processes involved remains poor. This paper provides a review of the current state of knowledge of the mechanistic impacts of diatom-oxylipins on marine invertebrate reproduction and development.

The apolipoprotein A5 gene -1131T-->C polymorphism affects vitamin E plasma concentrations in type 2 diabetic patients

BACKGROUND

Variations of the apolipoprotein A5 (APOA5) gene are strongly associated with hypertriglyceridemia. Vitamin E is transported in triglyceride (TG)-rich lipoproteins and therefore could also be modulated by apoAV. Patients with type 2 diabetes have a tendency towards high TG values and increased oxidative stress.

METHODS

We examined the impact of genetic APOA5 variation (-1131T-->C) on vitamin E and oxidative status in 169 non-smoker type 2 diabetic patients. Plasma samples were analyzed for lipids, lipoproteins, vitamin E, oxidized low-density lipoprotein (oxLDL), lipoperoxides, autoantibodies against oxLDL and diene formation of LDL.

RESULTS

Vitamin E concentrations were higher in TC carriers compared with TT carriers (45.48+/-8.20 micromol/L vs. 40.32+/-10.47 micromol/L; p=0.02). The prevalence of the TC genotype was 2.6-fold higher among individuals with high vitamin E concentrations (p=0.02). The APOA5 polymorphism did not determine any differences in oxidative status. Fasting TG concentration was a significant 21% higher in carriers of the TC genotype (p=0.04) due to higher TG concentrations in very-low-density lipoprotein (VLDL) and high-density lipoprotein.

CONCLUSIONS

The APOA5-1131T-->C polymorphism is associated with both higher vitamin E concentrations and higher VLDL-TGs in diabetic patients.

Oxidized to non-oxidized lipoprotein ratios are associated with arteriosclerosis and the metabolic syndrome in diabetic patients

BACKGROUND AND AIM

Type 2 diabetic patients have a greater prevalence of the metabolic syndrome, oxidative stress and accelerated atherosclerosis, compared to non-diabetics. We examined the association between biomarkers of lipid peroxidation and the presence of atherosclerosis and the metabolic syndrome in diabetic patients.

METHODS AND RESULTS

We studied oxidized LDL (OxLDL), OxLDL/LDL, OxLDL/HDL, lipoperoxides, autoantibodies against OxLDL (OxLDL-Ab), diene formation of LDL (lag phase), vitamin E, vitamin E/cholesterol and PON1 polymorphisms (-108C>T, 55T>A, and 192A>G) in 166 non-smoking type 2 diabetic patients, 119 fulfilling the criteria for the metabolic syndrome, 73 with atherosclerosis and 93 without atherosclerosis. Patients with macrovascular disease had higher values of OxLDL/LDL (11%; P=0.016), OxLDL/HDL (18%; P=0.024) and OxLDL-Ab (12%; P=0.046). OxLDL/LDL and OxLDL/HDL were correlated with the number of components of the metabolic syndrome (P<0.001). PON1 polymorphisms were not associated to LDL oxidation markers, only PON1 (-108TT) was weakly associated with higher OxLDL-Ab concentrations (22%; P=0.040) in patients with atherosclerosis.

CONCLUSION

OxLDL/LDL, OxLDL/HDL and OxLDL-Ab are the most useful clinical parameters of lipoprotein oxidation for discriminating the presence of macrovascular disease in diabetic patients. The presence of the metabolic syndrome in these patients is also associated with an increase in the oxidized lipoprotein ratios.

Investigation of volatile biomarkers in liver cancer blood using solid-phase microextraction and gas chromatography/mass spectrometry

Solid-phase microextraction (SPME) followed by gas chromatography/mass spectrometry (GC/MS) was used for the detection of liver cancer volatile biomarkers. Headspace SPME conditions (fiber coating, extraction temperature and extraction time) and desorption conditions were optimized and applied to the determination of volatiles in human blood. Between the liver cancer group (n = 19) and the normal group (n = 18), positive rates of 19 volatile compounds among the total of 47 detected were found to be different with statistical significance (p < 0.05, chi-squared test). We suggested hexanal, 1-octen-3-ol and octane, of the 19 compounds, as biomarkers of liver cancer with clinical diagnostic value. The sensitivity and specificity of 94.7% and 100% for hexanal, 84.2% and 100% for 1-octen-3-ol, and 89.5% and 100% for octane were obtained, respectively, after the cutoff values had been properly established. These results show that SPME-GC/MS is a simple, rapid and sensitive method for the investigation of volatile disease markers in human blood.

4-Hydroxynonenal modifies IgA in rat intestine after lipopolysaccharide injection

The lipid peroxide 4-hydroxynonenal (HNE) was measured in rat intestinal mucosa after lipopolysaccharide (LPS) injection (0.5 mg/kg, ip) by a highly sensitive time-resolved fluoroimmunoassay. HNE was increased, with a small peak at 20 min followed by a sustained elevation at 2-4 h, after injection of LPS. Immunohistochemistry demonstrated enhanced labeling with anti-IgA and anti-HNE antibodies in the plasma cells followed by diffusion of the labeled materials into the submucosal tissue after LPS injection. Immunoprecipitation with anti-IgA antibody and Western blotting with anti-HNE antibody showed that IgA is modified with HNE after LPS injection. The HNE (5 microM-5 mM) modification in vitro reduced the bactericidal activity of IgA and anti-Escherichia coli serum. The HNE modification in vitro also promoted polymerization of IgA as shown by nondenaturing gel electrophoresis. This is the first demonstration of the modification of IgA with HNE in an in vivo model of intestinal inflammation as well as in vitro effects of HNE on bactericidal activity and polymerization of IgA. These findings will help in understanding the involvement of oxidative stress in the IgA-mediated immune response exerted by plasma cells in early intestinal inflammation.

Acute effects of exposure to hexanal vapors in humans

OBJECTIVE

n-Hexanal is a major component in emissions from stored wood pellets. The production and use of wood pellets has increased dramatically. Our aim was to evaluate acute health effects of n-hexanal vapors.

METHODS

Twelve healthy volunteers were exposed to 0, 2, and 10 ppm n-hexanal for 2 hours at rest in a balanced order.

RESULTS

Ratings of discomfort in the eyes and nose, solvent smell, and headache increased significantly with the level of exposure. Frequency of blinking was significantly increased at 10 ppm. No effects on pulmonary function and nasal swelling were detected, except a not-significant tendency to increased nasal obstruction at 10 ppm. No clear effects on plasma inflammatory markers (C-reactive protein and interleukin-6) were observed.

CONCLUSIONS

Two hours of exposure to n-hexanal results in mild irritation at 10 ppm, with no apparent adversity at 2 ppm.

Unsaturated fatty acids and their oxidation products stimulate CD36 gene expression in human macrophages

Fatty acids (FA) have been implicated in the control of expression of several atherosclerosis-related genes. Similarly, the CD36 receptor has recently been shown to play an important role in atherosclerosis and other pathologies. The aim of the present study was to evaluate the direct effect of FA and their oxidation products (aldehydes), on the expression of CD36 in both THP-1 macrophages and human monocyte-derived macrophages (HMDM). The FA tested included the saturated FA (SFA) lauric, myristic, palmitic and stearic acid; the monounsaturated FA oleic acid; and the unsaturated FA (UFA) linoleic, arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Aldehydes used were malondialdehyde (MDA), hexanal, 2,4-decadienal (DDE) and 4-hydroxynonenal (HNE). CD36 expression was measured by RT-PCR, Western blot and immunofluorescence. Incubation of THP-1 macrophages for 24 h with non-cytotoxic concentrations of UFA significantly increased CD36 mRNA expression. By contrast, exposure of THP-1 macrophages to SFA did not affect the levels of CD36 mRNA. Among all UFAs tested, EPA and DHA were the strongest inducers of CD36 mRNA levels, followed by oleic and linoleic acid. Incubation of HMDM with either oleic or linoleic acid significantly increased steady-state CD36 mRNA in a dose-dependent manner. Consistent with the increase of CD36 mRNA expression, incubation of THP-1 macrophages with oleic and linoleic acid for 24 h markedly increased CD36 protein expression. Treatment of THP-1 macrophages with MDA or hexanal for 24 h significantly increased CD36 mRNA expression in a dose dependent manner. In contrast, DDE and HNE significantly decreased this parameter. The data provide evidence for a direct regulatory effect of UFA on CD36 gene expression and support a role for aldehydes in the regulation of CD36 expression by FA.