Effects of collagen peptides from skate (Raja kenojei) skin on improvements of the insulin signaling pathway via attenuation of oxidative stress and inflammation.

It has been well established that hepatic insulin signaling is significantly affected by the antioxidative status of the liver. In this study, we first confirmed that skate skin collagen peptide (SSCP) administration has dose-dependent positive effects on the change in the glucose level as evidenced by oral glucose tolerance tests. Therefore, the beneficial effects of SSCP-showing antioxidative and anti-inflammatory activities-on insulin resistance were examined in high-fat diet (HFD)-fed mice. C57BL/6J mice orally received SSCP at doses of 100, 200, and 300 mg per kg bw per day along with a HFD for 8 weeks (n = 9 per group). Water was given to the HFD- or chow diet-only group as a vehicle. Compared with the HFD group, the final body weight was reduced in all the SSCP-treated groups in a dose-dependent manner. The hepatic protein expression levels of the phosphorylated insulin receptor substrate, phosphorylated phosphatidylinositol 3-kinase, and phosphorylated protein kinase B were increased in the SSCP-treated groups, which led to reduced plasma insulin and HOMA-IR levels (P < 0.05). The hepatic protein expression levels of nuclear factor erythroid 2-related factor 2-mediated antioxidant enzymes were increased in the SSCP-treated groups, whereas those of nuclear factor kappa B-regulated inflammatory enzymes and mediators were decreased (P < 0.05). These effects were dose-dependent. It is apparent that SSCP might enhance insulin sensitivity by increasing the antioxidative status and suppressing the inflammatory response in the liver.

Anti-Obesity Effects of Collagen Peptide Derived from Skate (Raja kenojei) Skin Through Regulation of Lipid Metabolism.

This study investigated the anti-obesity effects of collagen peptide derived from skate skin on lipid metabolism in high-fat diet (HFD)-fed mice. All C57BL6/J male mice were fed a HFD with 60% kcal fat except for mice in the normal group which were fed a chow diet. The collagen-fed groups received collagen peptide (1050 Da) orally (100, 200, or 300 mg/kg body weight per day) by gavage, whereas the normal and control groups were given water (n = 9 per group). The body weight gain and visceral adipose tissue weight were lower in the collagen-fed groups than in the control group (p < 0.05). Plasma and hepatic lipid levels were significantly reduced by downregulating the hepatic protein expression levels for fatty acid synthesis (sterol regulatory element binding protein-1 (SREBP-1), fatty acid synthase (FAS), and acetyl-CoA carboxylase (ACC)) and cholesterol synthesis (SREBP-2 and 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR)) and upregulating those for ß-oxidation (peroxisome proliferator-activated receptor alpha (PPAR-α) and carnitine palmitoyltransferase 1 (CPT1)) and synthesis of bile acid (cytochrome P450 family 7 subfamily A member 1 (CYP7A1)) (p < 0.05). In the collagen-fed groups, the hepatic protein expression level of phosphorylated 5' adenosine monophosphate-activated protein kinase (p-AMPK) and plasma adiponectin levels were higher, and the leptin level was lower (p < 0.05). Histological analysis revealed that collagen treatment suppressed hepatic lipid accumulation and reduced the lipid droplet size in the adipose tissue. These effects were increased in a dose-dependent manner. The findings indicated that skate collagen peptide has anti-obesity effects through suppression of fat accumulation and regulation of lipid metabolism.

Bioactive Compounds of Kimchi Inhibit Apoptosis by Attenuating Endoplasmic Reticulum Stress in the Brain of Amyloid ß-Injected Mice.

This study investigated the inhibitory effects of kimchi bioactive compounds against endoplasmic reticulum (ER) stress-induced apoptosis in amyloid beta (Aß)-injected mice. Mice received a single intracerebroventricular injection of Aß25-35, except for the normal group. Mice were subjected to oral administration of 10 mg of capsaicin, 50 mg of 3-(4'-hydroxyl-3',5'-dimethoxyphenyl)propionic acid (HDMPPA), 50 mg of quercetin, 50 mg of ascorbic acid, or 200 mg of kimchi methanol extract (KME) per kilogram of body weight for 2 weeks ( n = 7 per group). In the in vitro blood-brain barrier (BBB) permeability test, all bioactive compounds penetrated the BBB except ascorbic acid. The protein expression level of APP, BACE, and p-Tau elevated by Aß injection was decreased by kimchi bioactive compounds ( P < 0.05). Quercetin, HDMPPA, and KME decreased oxidative stress, as indicated by ROS and TBARS levels ( P < 0.05). The protein expression level of ER stress markers GRP78, p-PERK, p-eIF2α, XBP1, and CHOP and the proapoptotic molecules Bax, p-JNK, and cleaved caspases-3 and -9 decreased ( P < 0.05). In contrast, the protein expression level of antiapoptotic molecules Bcl2 and cIAP increased ( P < 0.05). These results were supported by histological analysis.

Comparison of the Effects of Nonfermented and Fermented Panax ginseng Root Against Hypertriglycemia in High-Fat Diet-Fed Mice.

Panax ginseng (P. ginseng C.A. Meyer, Araliaceae) is used as a therapeutic agent for various diseases. P. ginseng saponins, known as ginsenosides, are the main bioactive compounds responsible for its pharmacological activities. In this work, we have developed a new method of P. ginseng root processing termed solid-state fermentation and examined its effects compared with nonfermented P. ginseng. Mice were fed a high-fat diet (HFD) to induce hyperlipidemia and then received 100 mg·kg bw-1·day-1 of fermented or nonfermented P. ginseng orally for 3 weeks. We assessed the activities of lipogenic pathways and lipid levels in the liver and plasma. The administration of either nonfermented or fermented P. ginseng improved hepatic lipid transfer protein profiles. Nonfermented P. ginseng exhibited significant effects on the regulation of lipid synthesis and oxidation. However, apolipoprotein A4 (apoA4) expression was increased by the administration of fermented P. ginseng. When ginsenosides were analyzed by high-performance liquid chromatography (HPLC), the amounts of the ginsenosides, Rg2, Rc, Rh1(S), Rh1(R), and Rd, were increased by fermentation, with Rd becoming a major constituent of fermented P. ginseng. These findings imply that nonfermented P. ginseng improves hypertriglycemia in HFD-fed mice through regulation of the hepatic lipogenic pathway. In contrast, the effects of fermented P. ginseng were mediated through increased apoA4, leading to decreased triglycerides. The HPLC profiles of ginsenosides suggest that the compositional changes in P. ginseng caused by fermentation processing could be useful in the development of novel triglyceride-lowering therapies.

Hypolipidemic and Antidiabetic Effects of Functional Rice Cookies in High-Fat Diet-Fed ICR Mice and db/db Mice.

We have previously reported the lipid-lowering effects of a Korean rice cookie called dasik (RCD) in comparison with a western style cookie. In this study, Schisandra chinensis (Turcz.) Baill. (Chinese magnolia vine) fruit-supplemented RCD (SRCD) was added to a diet, and the hypolipidemic and antidiabetic effects of different diets were examined by using the ICR and db/db mouse models, respectively. ICR mice were fed the AIN-76 diet, or high-fat diet (HFD), or the RCD- or SRCD-supplemented HFD (10%, w/w) for 9 weeks (n = 7 per group). Compared with the RCD group, plasma and hepatic triglyceride and cholesterol concentrations were decreased in the SRCD group. Hepatic expressions for fatty acid and cholesterol synthesis were downregulated, whereas those for beta-oxidation and cholesterol export were upregulated (P < .05). The antidiabetic effects of SRCD were tested in db/db mice for 10 weeks (n = 7 per group). Glucose tolerance was improved in the SRCD group through the regulation of gluconeogenic enzymes and biomarkers related to the insulin signaling pathway (P < .05). In addition, SRCD increased the expression levels of antioxidative enzymes, and decreased those of inflammatory cytokines (P < .05). Moreover, oxidative stress, leptin, and insulin levels were lower in the SRCD group than in the other groups (P < .05). In conclusion, the lipid-lowering and antidiabetic effects of SRCD were greater than those of RCD with respect to the suppression of lipid synthesis, oxidative stress, and inflammation and the improvement of glucose metabolism.

Neuroprotective Effects of the Methanol Extract of Kimchi, a Korean Fermented Vegetable Food, Mediated Via Suppression of Endoplasmic Reticulum Stress and Caspase Cascade Pathways in High-Cholesterol Diet-Fed Mice.

Endoplasmic reticulum (ER) stress-related unfolded peptide accumulation is closely associated with the development of neurodegenerative diseases known as protein misfolding disorders. The antioxidative properties of kimchi, a traditional Korean fermented vegetable dish, have been well established. In this study, the neuroprotective effects of the kimchi methanol extract (KME) were examined in high-cholesterol diet (HCD)-fed mice. The animals were fed a HCD, with oral administration of either KME (KME group, 200 mg·kg bw-1·day-1, n = 10) or distilled water (Control group, n = 10) for 8 weeks. Compared with the levels in the control group, the reactive oxygen species, peroxynitrite, and lipid peroxidation levels in the brain were significantly decreased in the KME group (P < .05), whereas the glutathione level was increased (P < .05). In addition, the ER stress biomarkers, phospho-eukaryotic initiation factor 2 subunit α, glucose-regulated protein 78, X-box binding protein 1, inositol-requiring enzyme 1, and C/EBP homologous protein and the nuclear factor-kappaB-mediated inflammation were significantly reduced in the KME group (P < .05). In contrast, the expression levels of antioxidative enzymes regulated by nuclear factor erythroid 2-related factor-2 were elevated (P < .05). The amyloid-beta expression levels of the KME group were lower than that of the control group (P < .05). Moreover, the expression levels of Bcl-2-associated X, and caspases-3 and -9 were downregulated, with a concomitant upregulation of B cell lymphoma 2 (P < .05). Accordingly, KME provide neuronal cell protection via suppressing ER stress and caspase cascade signaling.

Low-Molecular-Weight Oligonol, a Polyphenol Derived from Lychee Fruit, Attenuates Experimental Reflux Esophagitis and HCl/Ethanol-Induced Gastric Ulcer.

Oligonol, a polyphenol derived from lychee fruit, is produced by an oligomerization process that converts high-molecular-weight polyphenol polymers into low-molecular-weight oligomers. Evidence suggests that oligonol exerts its beneficial effects based on antioxidant and anti-inflammatory properties. This study was the first to investigate the antioxidative and anti-inflammatory effects of oligonol on gastroesophageal inflammatory models: surgically induced acute reflux esophagitis (RE) and gastric ulcer (GU) induced by HCl/ethanol. In the in vitro study, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazolin-6-sulfonic acid) (ABTS) radical scavenging assays were performed to determine the antioxidant activity of oligonol. The experimental groups were each composed of normal, vehicle, and oligonol groups. RE rats and GU mice were treated orally with oligonol (100 mg/kg bw) or distilled water as a vehicle (n = 8 for each group). Oligonol exhibited potent free radical-scavenging capacities for DPPH and ABTS radicals, activities that were similar to those of ascorbic acid. The in vivo study revealed that oligonol consumption significantly prevented RE and GU formation and decreased the gross mucosal injury from oxidative stress. Oligonol decreased the reactive oxygen species levels and elevated levels of both inflammatory mediators and cytokines (p-IκB, NF-κBp65, COX-2, iNOS, TNF-α, and IL-1ß) in the RE and GU models. Oligonol had a protective effect against oxidative stress by regulating antioxidant enzyme (superoxide dismutase, catalase, and GPx-1/2) activities in GU mice. Oligonol has potential as a preventive and therapeutic agent for gastroesophageal inflammatory diseases, including RE and GU.