Structural identification and combination mechanism of iron (II)-chelating Atlantic salmon (Salmo salar L.) skin active peptides.

In order to utilize salmon skin for high value, and investigate the structural identification and combination mechanism of iron (II)-chelating peptides systemically, Atlantic salmon (Salmo salar L.) skin, a by-product of Atlantic salmon processing, was treated by two-step enzymatic hydrolysis to obtain salmon skin active peptides (SSAP). Then they reacted with iron (II) to obtain iron (II)-chelating salmon skin active peptides (SSAP-Fe) with a high iron (II) chelating ability of 98.84%. The results of Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD) spectroscopy, 8-anilino-1-naphthalenesulfonic acid ammonium salt hydrate (ANS) combined fluorescence measurement, isothermal titration calorimetry (ITC) and full wavelength ultraviolet (UV) scanning showed that the structural characteristics of SSAP changed before and after chelating iron (II). Reverse phase high performance liquid chromatography (RP-HPLC) and mass spectrometry were used to identify and quantify the peptides in SSAP-Fe. Four peptide sequences (STEGGG, GIIKYGDDFMH, PGQPGIGYDGPAGPPGPPGPPGAP and QNQRESWTTCRSQSSLPDG) were identified. The content of PGQPGIGYDGPAGPPGPPGPPGAP was the highest, at 25.17 µg/mg. The pharmacokinetic and pharmacodynamic properties of these four peptides were also investigated, and the results indicated that they have satisfactory predicted ADMET properties. Molecular docking technology was used to analyze the binding sites between iron (II) and SSAP, and it was found that PGQPGIGYDGPAGPPGPPGPPGAP had the lowest predicted binding energy with iron (II) and the most stable predicted binding energy with iron (II). This results showed that the stability of SSAP-Fe were closely related to the number of covalent bonds and the types of amino acids. This study revealed the structure and combination mechanism of SSAP-Fe, and indicated that SSAP-Fe prepared by chelation may be used as a Fe supplement that can be applied in functional foods or ingredients.

A unique inflammation-related mechanism by which high-fat diets induce depression-like behaviors in mice.

BACKGROUND: High-fat diet (HFD) consumption is an important reason for promoting depression, but the mechanism is unclear. The present study aims to explore the relationship between metabolic disturbance and HFD-induced depression-like behaviors. METHODS: Depression models were established by HFD consumption and chronic unpredictable mild stress (CUMS) in mice. Enzyme-linked immunosorbent assay, western blotting, real-time polymerase chain reaction, gas chromatography and metabolomic analysis were undertaken to investigate the 5-hydroxytryptamine (5-HT) system, neuroinflammation and to identify altered lipid metabolic pathways. RESULTS: Depression-like behaviors, impaired 5-HT neurotransmission and disordered lipid metabolism were observed upon HFD consumption. Despite a similar reduction of high-density lipoprotein cholesterol in CUMS and HFD group, high levels of body low-density lipoprotein cholesterol in the HFD group could help distinguish HFD from CUMS. Levels of interleukin (IL)-1ß, IL-6, tumor necrosis factor (TNF)-α and inflammation-related metabolites were increased in HFD mice, so a link between depression and inflammation was postulated. Different metabolites were enriched in the two groups. The linoleic acid (LA) metabolic pathway and expression of fatty acid desaturase (FADS)1 and FADS2 (key enzymes in LA metabolic pathway) were enhanced significantly in HFD mice compared with the control group. LIMITATIONS: Causality analyses for HFD and inflammation-related features were not undertaken. CONCLUSIONS: HFD-induced depression-like behaviors was characterized by more severely disordered metabolism of lipids (especially in the LA metabolic pathway) and increased levels of inflammatory mediators, which might be the reasons for the disturbance of serotonergic system in hippocampus.

Effects of topical application of different molecular weight marine fish skin collagen oligopeptides on UVB-induced photoaging rat skin.

OBJECTIVE: The objective of this work was to develop a peptide production process of the exact molecular weight propitious to topical application for cosmetics and to investigate the effects of enzymolysis-derived peptide on UVB-induced photoaging rat skin. METHODS: The chum salmon fish skins were hydrolyzed by alkaline protease and neutral protease and spray-dried at different conditions, and three kinds of molecular weight peptide (MFSOP) were obtained. A total of 66 ICR rats (female, 20 ± 1 g) were randomly divided into eleven groups, including the normal, model, and experimental groups. The three kinds of MFSOP were dissolved at different dosages (5‰, 2.5%, and 5%) and then applied on the ICR hairless back skins prior to exposing UVB irradiation of 3000mJ/cm2 to them 4 h later. After 8 weeks, the rats were killed and the hair-shaved skins were tested for skin moisture, hyaluronic acid, hydroxyproline, antioxidant activity, and RNA expression. RESULTS: Three kinds of MFSOP were obtained, with the average molecular weights of 495.16, 1194.00, and 2032.46 Dalton, respectively. The MFSOPs, especially the MFSOP of average molecular weight of 1194.00 Dalton, played an important role in the recovery of the UVB-injured skin tissue in lock in moisture, in antioxidant activity and in promotion in collagen and elastin protein to some extent. CONCLUSION: MFSOPs, especially MFSOP of average molecular weight of 1194.00 Dalton, derived from enzymolysis are potential materials to apply in cosmetics for the UVB9-induced anti-photoaging activity (lock in moisture, antioxidant activity, and promotion in collagen and elastin protein).

Effects of high-fat diet on the formation of depressive-like behavior in mice.

Depression is an important global health issue that is associated with serious physical and mental health consequences. The field of nutritional psychiatry has generated observational and efficacy data supporting a role for healthy dietary patterns in depression. Here, we aim to evaluate the effects of high-fat diet (HFD) consumption on depressive-like behaviors. BALB/c mice were grouped randomly: control, chronic restraint stress (CRS), HFD and CRS + HFD groups. The depressive-like behavior was evaluated using behavioral tests. The serotonin content in murine brain tissue and blood lipid concentrations were detected by ELISA. The fatty acid content in the liver, adipose tissue of epididymis, brain tissue, and serum of mice was determined by gas chromatography (GC). Expression of the fatty acid synthesis pathway-related enzymes at the mRNA level was analyzed by qRT-PCR. The results indicated that a high-fat diet could promote depressive-like behavior. In comparison with regular feeding, concentrations of blood lipids were significantly changed in the HFD group. Correlation analysis implied that high-density lipoprotein cholesterol (HDL-c) and low-density lipoprotein cholesterol (LDL-c) were closely related to depressive-like behavior. Based on fatty acid analysis, the palmitoleic acid, linoleic acid, oleic acid, and arachidonic acid content was remarkably changed in mice with depressive-like behavior. In addition, acetyl-CoA carboxylase (ACC), stearoyl-CoA desaturase-1 (SCD1), fatty acid desaturase 1 (FADS1), and fatty acid desaturase 2 (FADS2) expression, which are involved in de novo fatty acid synthesis, desaturation of fatty acids, and arachidonic acid synthesis, were strengthened in HFD mice with depressive-like behavior. Therefore, we postulated that the disorder of lipid metabolism induced by HFD consumption accelerated the development of depressive-like behavior.

Hypoallergenic mutants of the major oyster allergen Cra g 1 alleviate oyster tropomyosin allergenic potency.

Design of hypoallergen with low IgE reactivity is desirable for allergen-specific immunotherapy. Despite oyster tropomyosin (Cra g 1) is considered as the major allergen, no immunotherapy is available now. In the current research, we generated hypoallergens of Cra g 1 and evaluated their allergenicity. Four hypoallergenic derivatives were constructed by epitope deletion or site-directed mutagenesis on grounds of the identified epitopes. They showed obvious reduction in reactivity towards IgE from oyster-allergic patients and Cra g 1-sensitized BN rats, as well as significant decrease in degranulation and secretion of allergic mediators including histamine, IL-4, IL-6 and TNF-α. In addition, to further investigate the molecular mechanism, we examined the effects of these variants on FcεRI-dependent signalling pathway in IgE-challenged RBL-2H3 cells. We found that the hypoallergenic mutants were able to attenuate FcεRI-mediated signaling cascades in tested cells. These results indicate that the hypoallergenic molecules have ideal characteristics and offer a promising new strategy in clinical immunotherapy for shellfish-allergic subjects.

Hypoglycemic effects and biochemical mechanisms of Pea oligopeptide on high-fat diet and streptozotocin-induced diabetic mice.

The aim of this study was to evaluate the hypoglycemic effects of Pea oligopeptide on the glycemic and lipidemic status of mice with type 2 diabetes (T2D) induced by a high-fat diet and streptozotocin (STZ). Using HPLC-MS/MS spectra processing, 70 significant peptide (2-3 amino acids) sequences were identified, noting four peptides from Pea oligopeptide with a proline residue at the C-terminus, which might have dipeptidase-IV (DPP-IV) inhibitory activity for the treatment of T2D. After a 4-week administration of Pea oligopeptide and metformin, various blood biochemical indexes and organic histopathologies were detected to aid the discussion regarding potential mechanisms. The results showed a significant reduction in the levels of blood glucose, lipid profiles, and liver fat deposition in diabetic mice. Furthermore, Pea oligopeptide and metformin improved glucose tolerance, promoted glycogen synthesis, and protected the liver and kidney structures in diabetic mice. The results indicated that Pea oligopeptide played an essential role in the hypoglycemic effect in the T2D mice model. Practical applications This paper examined the preliminary hypoglycemic activities of Pea oligopeptide in a high-fat diet and STZ-induced T2D mice. Furthermore, four kinds of dipeptides and tripeptides that might exhibit antidiabetic functions were detected using HPLC-MS/MS. The results provided practical knowledge regarding the hypoglycemic effects of Pea oligopeptide and established the foundation of its structure-function relationships.

Large-scale transport of PM2.5 in the lower troposphere during winter cold surges in China.

A comprehensive investigation using the air quality network and meteorological data of China in 2015 showed that PM2.5 driven by cold surges from the ground level could travel up to 2000 km from northern to southern China within two days. Air pollution is more severe and prominent during the winter in north China due to seasonal variations in energy usage, trade wind movements, and industrial emissions. In February 2015, two cold surges traveling from north China caused a temporary increase in the concentration of PM2.5 in Shanghai. Subsequently, the concentration of PM2.5 in Xiamen increased to a high of 80 µg/m3, which is double the average PM2.5 concentration in Xiamen during the winter. This finding is a new long-range transport mechanism comparing to the well-established mechanism, with long-range transport more likely to occur in the upper troposphere than at lower levels. These observations were validated by results from the back trajectory analysis and the RAMS- CMAQ model. While wind speed was found to be a major facilitator in transporting PM2.5 from Beijing to Xiamen, more investigation is required to understand the complex relationship between wind speed and PM2.5 and how it moderates air quality in Beijing, Shanghai, and Xiamen.

Inhibitory effect of hesperetin on α-glucosidase: Molecular dynamics simulation integrating inhibition kinetics.

The α-glucosidase inhibitor is of interest to researchers due to its association with type-2 diabetes treatment. Hesperetin is a flavonoid with natural antioxidant properties. This paper presents an evaluation on the effects of hesperetin on α-glucosidase via inhibitory kinetics using a Molecular Dynamics (MD) simulation integration method. Due to the antioxidant properties of hesperetin, it reversibly inhibits α-glucosidase in a slope-parabolic mixed-type manner (IC50=0.38±0.05mM; Kslope=0.23±0.01mM), accompanied by tertiary structural changes. Based on computational MD and docking simulations, two hesperetin rings interact with several residues near the active site on the α-glucosidase, such as Lys155, Asn241, Glu304, Pro309, Phe311 and Arg312. This study provides insight into the inhibition of α-glucosidase by binding hesperetin onto active site residues and accompanying structural changes. Hesperetin presents as a potential agent for treating α-glucosidase-associated type-2 diabetes based on its α-glucosidase-inhibiting effect and its potential as a natural antioxidant.