Yeni Lim

Onion peel extracts ameliorate hyperglycemia and insulin resistance in high fat diet/streptozotocin-induced diabetic rats

BackgroundQuercetin derivatives in onions have been regarded as the most important flavonoids to improve diabetic status in cells and animal models. The present study was aimed to examine the hypoglycemic and insulin-sensitizing capacity of onion peel extract (OPE) containing high quercetin in high fat diet/streptozotocin-induced diabetic rats and to elucidate the mechanism of its insulin-sensitizing effect.MethodsMale Sprague-Dawley rats were fed the AIN-93G diet modified to contain 41.2% fat and intraperitoneally injected with a single dose of streptozotocin (40 mg/kg body weight). One week after injection, the rats with fasting blood glucose levels above 126 mg/dL were randomly divided into 4 groups to treat with high fat diet containing 0 (diabetic control), 0.5, or 1% of OPE or 0.1% quercetin (quercetin equivalent to 1% of OPE) for 8 weeks. To investigate the mechanism for the effects of OPE, we examined biochemical parameters (insulin sensitivity and oxidative stresses) and protein and gene expressions (pro-inflammatory cytokines and receptors).ResultsCompared to the diabetic control, hypoglycemic and insulin-sensitizing capability of 1% OPE were demonstrated by significant improvement of glucose tolerance as expressed in incremental area under the curve (P = 0.0148). The insulin-sensitizing effect of OPE was further supported by increased glycogen levels in liver and skeletal muscle (P < 0.0001 and P = 0.0089, respectively). Quantitative RT-PCR analysis showed increased expression of insulin receptor (P = 0.0408) and GLUT4 (P = 0.0346) in muscle tissues. The oxidative stress, as assessed by superoxide dismutase activity and malondialdehyde formation, plasma free fatty acids, and hepatic protein expressions of IL-6 were significantly reduced by 1% OPE administration (P = 0.0393, 0.0237, 0.0148 and 0.0025, respectively).ConclusionOPE might improve glucose response and insulin resistance associated with type 2 diabetes by alleviating metabolic dysregulation of free fatty acids, suppressing oxidative stress, up-regulating glucose uptake at peripheral tissues, and/or down-regulating inflammatory gene expression in liver. Moreover, in most cases, OPE showed greater potency than pure quercetin equivalent. These findings provide a basis for the use of onion peel to improve insulin insensitivity in type 2 diabetes.

Selected Phytochemicals and Culinary Plant Extracts Inhibit Fructose Uptake in Caco-2 Cells.

This study compared the ability of nine culinary plant extracts containing a wide array of phytochemicals to inhibit fructose uptake and then explored the involvement of intestinal fructose transporters and phytochemicals for selected samples. The chemical signature was characterized by high performance liquid chromatography with mass spectrometry. Inhibition of [14C]-fructose uptake was tested by using human intestinal Caco-2 cells. Then, the relative contribution of the two apical-facing intestinal fructose transporters, GLUT2 and GLUT5, and the signature components for fructose uptake inhibition was confirmed in naive, phloretin-treated and forskolin-treated Caco-2 cells. HPLC/MS analysis of the chemical signature revealed that guava leaf contained quercetin and catechin, and turmeric contained curcumin, bisdemethoxycurcumin and dimethoxycurcumin. Similar inhibition of fructose uptake (by ~50%) was observed with guava leaf and turmeric in Caco-2 cells, but with a higher contribution of GLUT2 for turmeric and that of GLUT5 for guava leaf. The data suggested that, in turmeric, demethoxycurcumin specifically contributed to GLUT2-mediated fructose uptake inhibition, and curcumin did the same to GLUT5-mediated fructose uptake inhibition, but GLUT2 inhibition was more potent. By contrast, in guava leaf, catechin specifically contributed to GLUT5-mediated fructose uptake inhibition, and quercetin affected both GLUT5- and GLUT2-mediated fructose uptake inhibition, resulting in the higher contribution of GLUT5. These results suggest that demethoxycurcumin is an important contributor to GLUT2-mediated fructose uptake inhibition for turmeric extract, and catechin is the same to GLUT5-mediated fructose uptake inhibition for guava leaf extract. Quercetin, curcumin and bisdemethoxycurcumin contributed to both GLUT5- and GLUT2-mediated fructose uptake inhibition, but the contribution to GLUT5 inhibition was higher than the contribution to GLUT2 inhibition.

A beverage of Asiatic plantain extracts alleviated postprandial oxidative stress in overweight hyperlipidemic subjects challenged with a high-fat meal: a preliminary study

There is emerging interest in the potential of the phenolic compounds of Asiatic plantain (Plantago asiatica L.) to attenuate in vitro and in vivo oxidative stress. We hypothesized that a single administration of Asiatic plantain beverage may exert protective effects against postprandial oxidative stress. This preliminary study was designed to compare the ability of different doses of Asiatic plantain beverage to mitigate the postprandial effects of a high-fat meal on the oxidation of lipids and DNA in overweight hyperlipidemic subjects. In a randomized, double-blind, placebo-controlled parallel design (n = 10/group), 40 subjects were administered a single high-fat meal with either a placebo or 1 of 3 Asiatic plantain extract beverages (low, intermediate, or high dose). Blood samples were obtained at fasting and 60, 120, 240, and 360 minutes (total of 5 samples) after intervention. The data showed a tendency for plasma free fatty acid levels to decrease in response to high-dose Asiatic plantain at all time points. Plasma oxidized low-density lipoprotein levels were significantly reduced with high-dose Asiatic plantain at 120 minutes (P = .0251 vs placebo). A comet assay revealed that DNA damage in lymphocytes was significantly decreased by Asiatic plantain at 360 minutes (P = .0225 vs placebo). There were no treatment differences in triglyceride or malondialdehyde levels. The maximum suppression was achieved with a high dose (20 g Asiatic plantain extract/80 mL). These results suggest that by protecting low-density lipoprotein and DNA, an Asiatic plantain beverage may be useful to enhance antioxidant.

Daily Nutritional Dose Supplementation with Antioxidant Nutrients and Phytochemicals Improves DNA and LDL Stability: A Double-Blind, Randomized, and Placebo-Controlled Trial

Reactive oxygen species are important risk factors for age-related diseases, but they also act as signaling factors for endogenous antioxidative defense. The hypothesis that a multi-micronutrient supplement with nutritional doses of antioxidant nutrients and phytochemicals (MP) may provide protection against oxidative damage and maintain the endogenous antioxidant defense capacity was assessed in subjects with a habitually low intake of fruits and vegetables. In a randomized, placebo-controlled, and parallel designed trial, 89 eligible subjects were assigned to either placebo or MP for eight weeks. Eighty subjects have completed the protocol and included for the analysis. MP treatment was superior at increasing serum folate (p < 0.0001) and resistance to DNA damage (p = 0.006, tail intensity; p = 0.030, tail moment by comet assay), and LDL oxidation (p = 0.009) compared with the placebo. Moreover, the endogenous oxidative defense capacity was not weakened after MP supplementation, as determined by the levels of glutathione peroxidase (p = 0.442), catalase (p = 0.686), and superoxide dismutase (p = 0.804). The serum folate level was negatively correlated with DNA damage (r = −0.376, p = 0.001 for tail density; r = −0.329, p = 0.003 for tail moment), but no correlation was found with LDL oxidation (r = −0.123, p = 0.275). These results suggest that MP use in healthy subjects with habitually low dietary fruit and vegetable intake may be beneficial in providing resistance to oxidative damage to DNA and LDL without suppressing the endogenous defense mechanisms.

Acanthopanax divaricatus var. chiisanensis reduces blood pressure via the endothelial nitric oxide synthase pathway in the spontaneously hypertensive rat model

In this study, we investigated the antihypertensive effects of Acanthopanax divaricatus var. chiisanensis extract (AE) and its active compound, acanthoside D (AD), on arterial blood pressure (BP) in vivo and endothelial function in vitro. We hypothesized that AE has antihypertensive effects, which is attributed to enhancement of endothelial function via the improvement of nitric oxide synthesis or the angiotensin II (Ang II) response. Spontaneously hypertensive rats (SHRs) and Wistar-Kyoto rats (WKYs) were randomly divided into 7 groups and then fed the following diets for 14 weeks: WKY fed a normal diet (WN); SHR fed a normal diet (SN); SHR fed a high-cholesterol (HC) diet (SH); SHR fed a HC diet with AE of 150, 300, 600 mg/kg body weight (SH-L, SH-M, SH-H); and SHR fed an HC diet with AD of 600 μg/kg body weight (SH-D). Blood pressure was significantly reduced in the SH-H compared with the SH from week 10 until week 14; BP was also significantly decreased in the SHR fed a HC diet with AE of 300 at week 14. Aortic wall thickness showed a tendency to decrease by AE and AD treatment. The SH-H showed increased endothelial nitric oxide synthase (eNOS) expression in the intima and media, compared with the SH. Furthermore, a significant increase in intracellular nitric oxide production was induced by AE and AD treatment in human umbilical vein endothelial cells. A significant increase of phospho-eNOS was found with a high dose of AE in human umbilical vein endothelial cells but not with AD. These results suggest that AE can regulate BP and improve endothelial function via eNOS-dependent vasodilation.

Platycodi radix beverage ameliorates postprandial lipemia response through lipid clearance of triglyceride-rich lipoprotein: A randomized controlled study in healthy subjects with a high-fat load

BACKGROUND/OBJECTIVES Elevation of postprandial lipemia characterized by a rise in triglyceride (TG)-rich lipoproteins can increase the risk of atherogenesis. The objective of this study was to investigate postprandial lipemia response to a single dietary fat/sugar load test and monitor beneficial changes induced by the consumption of Platycodi radix (AP) beverage in healthy subjects. SUBJECTS/METHODS A total of 52 subjects were randomly assigned to either placebo or AP beverage group with a high-fat shake in a randomized controlled crossover trial. Postprandial blood was collected at 0, 1, 2, 4, and 6 h and analyzed for TG and lipoprotein lipase mass. Inhibition of pancreatic lipase was determined in vitro. RESULTS AP inhibited pancreatic lipase activity in vitro (IC50 = 5 mg/mL). Compared to placebo beverage, AP beverage consumption with a high-fat shake induced significant increase of plasma lipoprotein lipase mass (P = 0.0111, β estimate = 4.2948) with significant reduction in very low-density lipoprotein (VLDL) TG concentration (P = 0.038, β estimate = −52.69) at 6 h. Based on significant correlation between high-fat dietary scores MEDFICTS and postprandial TG responses in VLDL (P = 0.0395, r = 0.2127), subgroup analysis revealed that 6 h-postprandial VLDL TG response was significantly decreased by AP consumption in subjects with MEDFICTS ≥ 40 (P = 0.0291, β estimate = −7214). CONCLUSIONS AP beverage might have potential to alleviate postprandial lipemia through inhibiting pancreatic lipase activity and elevating lipoprotein lipase mass. Subgroup analysis revealed that subjects with high-fat dietary pattern could be classified as responders to AP beverage among all subjects.

Soybean-Hop Alleviates Estrogen Deficiency-Related Bone Loss and Metabolic Dysfunction in Ovariectomized Rats Fed a High-Fat Diet

Soybeans and hops have been traditionally used as a natural estrogen replacement therapy and their major active ingredients, isoflavones and prenylflavanones, are known to have estrogenic/antiestrogenic effects depending on the target organ. However, their potential benefits are still subject to controversies. The present study investigated the dual effect of soy isoflavones plus hop prenylflavanones (Soy-Hop) on bone loss and metabolic dysfunction under estrogen deficient condition. Rats were sham-operated (n = 10) or ovariectomized (OVX; n = 40) and then fed a high-fat diet (HFD) to develop hyperlipidemia in OVX rats within the experimental period of 8 weeks. The OVX/HFD rats were assigned to four groups to receive different doses of Soy-Hop (0, 30, 100, and 300 mg/kg) by oral gavage for 8 weeks. High-dose Soy-Hop significantly suppressed OVX/HFD-induced increases in food intake, body weight gain, fat mass, and circulating levels of leptin, adiponectin, LDL-cholesterol, total cholesterol, triglycerides, glucose, and insulin. High-dose Soy-Hop also attenuated OVX/HFD-induced elevation of osteocalcin, alkaline phosphatase, and CTX in plasma and RANKL/OPG gene expression ratio in femur. These findings were confirmed visually by confocal analysis of GLUT4 translocation in soleus muscle cells and micro-computed tomography scanning of the distal femoral epiphysis, respectively. These results suggest that Soy-Hop may have potential to ameliorate estrogen deficiency-related alterations in both metabolism and bone quality, at least in part, by hormonal factors secreted by adipocytes.

Verifying Identities of Plant-Based Multivitamins Using Phytochemical Fingerprinting in Combination with Multiple Bioassays

Sales of multivitamins have been growing rapidly and the concept of natural multivitamin, plant-based multivitamin, or both has been introduced in the market, leading consumers to anticipate additional health benefits from phytochemicals that accompany the vitamins. However, the lack of labeling requirements might lead to fraudulent claims. Therefore, the objective of this study was to develop a strategy to verify identity of plant-based multivitamins. Phytochemical fingerprinting was used to discriminate identities. In addition, multiple bioassays were performed to determine total antioxidant capacity. A statistical computation model was then used to measure contributions of phytochemicals and vitamins to antioxidant activities. Fifteen multivitamins were purchased from the local markets in Seoul, Korea and classified into three groups according to the number of plant ingredients. Pearson correlation analysis among antioxidant capacities, amount phenols, and number of plant ingredients revealed that ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picryhydrazyl (DPPH) assay results had the highest correlation with total phenol content. This suggests that FRAP and DPPH assays are useful for characterizing plant-derived multivitamins. Furthermore, net effect linear regression analysis confirmed that the contribution of phytochemicals to total antioxidant capacities was always relatively higher than that of vitamins. Taken together, the results suggest that phytochemical fingerprinting in combination with multiple bioassays could be used as a strategy to determine whether plant-derived multivitamins could provide additional health benefits beyond their nutritional value.

A combination of Korean mistletoe extract and resistance exercise retarded the decline in muscle mass and strength in the elderly: A randomized controlled trial

Abstract Given the increased concerns about the degenerative decline in the physical performance of the elderly, there is a need for developing effective strategies to suppress the age‐related loss of skeletal muscle mass and functional capacity through a lifestyle intervention. This randomized controlled trial examined whether a combination of Korean mistletoe extract (KME) supplement and exercise affected muscle mass, muscle function, and targeted molecular expressions. Sixty‐seven subjects aged 55–75 years were assigned to placebo, low‐dose (1 g/d), or high‐dose (2 g/d) of KME for 12 weeks. The body composition was significantly changed in the high‐dose group during the intervention period as determined by skeletal muscle mass (P = 0.040), fat free mass (P = 0.042), soft lean mass (P = 0.023), skeletal muscle index (P = 0.041), fat‐free mass index (P = 0.030), percent body fat (P = 0.044), and fat mass to lean mass ratio (P = 0.030). Knee strength was measured by Cybex, demonstrating a significant effect in the KME groups compared to the placebo group (P = 0.026 for peak torque and P = 0.057 for set total work), which was more pronounced after adjusting for age, gender, protein, and energy intake (P = 0.009 for peak torque and P = 0.033 for set total work). The dynamic balance ability was remarkably improved in the high‐dose group over a 12‐week period as determined by Timed “Up and Go” (P = 0.005 for fast walk test and P = 0.024 for ordinary walk test). Consistent with these results, RT‐PCR, multiplex analyses, and immunocytofluorescence staining revealed that a high‐dose KME supplementation was effective for suppressing intracellular pathways related to muscle protein degradation, but stimulating those related to myogenesis. In particular, significant differences were found in atrogin‐1 mRNA (P = 0.002 at a single administration and P = 0.001 at a 12‐week administration), myogenin mRNA (P < 0.0001 at a single administration and P = 0.040 at a 12‐week administration), and insulin growth factor 1 receptor phosphorylation (P = 0.002 at a 12‐week administration). These results suggest that KME supplementation together with resistance exercise may be useful in suppressing the age‐related loss of muscle mass and strength in the elderly. Graphical abstract Figure. No Caption available. HighlightsWe tested impact of KME on declines in muscle mass and strength in the elderly.Muscle mass, knee strength, and balance ability improved with KME supplementation.IGF1R, atrogin‐1, and myogenin were involved in the modulating effect of KME.