Solanum anguivi Lam. fruit preparations counteract the negative effects of a high-sugar diet on the glucose metabolism in Drosophila melanogaster.

Solanum anguivi Lam. fruits (SALF) are traditionally consumed as a remedy for type 2 diabetes mellitus (T2DM). However, data regarding the potential anti-diabetic effect of SALF and its underlying mechanisms are scarce. As the fruit fly's energy metabolism has been suggested to be comparable with mammals including the secretion of insulin-like peptides, we fed Drosophila melanogaster a high-sugar diet (HSD) to induce a T2DM-like phenotype and subsequently exposed them to a HSD supplemented with SALF. Following, flies were analyzed for various biomarkers in relation to energy metabolism. The HSD-induced glucose levels were significantly down-regulated in flies exposed to a HSD supplemented with SALF. In addition, flies exposed to SALF-supplemented HSD exhibited a better survival in comparison to HSD-fed counterparts. Other parameters of the energy metabolism such as triglyceride levels, weights, and fitness were not affected by SALF supplementation. This was also true for the expression levels of the insulin-like-peptides 3 and 6 as well as for spargel, the Drosophila homolog of PPARγ-co-activator 1α, a central player in mitochondrial biogenesis. Overall, the present study shows that SALF significantly lowered the HSD-induced glucose levels and increased the survival while the biomarkers of the energy metabolism were not affected.

Solanum anguivi Lam. Fruits: Their Potential Effects on Type 2 Diabetes Mellitus.

Type 2 diabetes mellitus (T2DM) is a complex metabolic disorder of glucose homeostasis associated with a status of insulin resistance, impaired insulin signaling, ß-cell dysfunction, impaired glucose and lipid metabolism, sub-clinical inflammation, and increased oxidative stress. Consuming fruits and vegetables rich in phytochemicals with potential antidiabetic effects may prevent T2DM and/or support a conservative T2DM treatment while being safer and more affordable for people from low-income countries. Solanum anguivi Lam. fruits (SALF) have been suggested to exhibit antidiabetic properties, potentially due to the presence of various phytochemicals, including saponins, phenolics, alkaloids, ascorbic acid, and flavonoids. For the saponin fraction, antidiabetic effects have already been reported. However, it remains unclear whether this is also true for the other phytochemicals present in SALF. This review article covers information on glucose homeostasis, T2DM pathogenesis, and also the potential antidiabetic effects of phytochemicals present in SALF, including their potential mechanisms of action.

Saccharin Supplementation Inhibits Bacterial Growth and Reduces Experimental Colitis in Mice.

Non-caloric artificial sweeteners are frequently discussed as components of the "Western diet", negatively modulating intestinal homeostasis. Since the artificial sweetener saccharin is known to depict bacteriostatic and microbiome-modulating properties, we hypothesized oral saccharin intake to influence intestinal inflammation and aimed at delineating its effect on acute and chronic colitis activity in mice. In vitro, different bacterial strains were grown in the presence or absence of saccharin. Mice were supplemented with saccharin before or after induction of acute or chronic colitis using dextran sodium sulfate (DSS) and the extent of colitis was assessed. Ex vivo, intestinal inflammation, fecal bacterial load and composition were studied by immunohistochemistry analyses, quantitative PCR, 16 S RNA PCR or next generation sequencing in samples collected from analyzed mice. In vitro, saccharin inhibited bacterial growth in a species-dependent manner. In vivo, oral saccharin intake reduced fecal bacterial load and altered microbiome composition, while the intestinal barrier was not obviously affected. Of note, DSS-induced colitis activity was significantly improved in mice after therapeutic or prophylactic treatment with saccharin. Together, this study demonstrates that oral saccharin intake decreases intestinal bacteria count and hence encompasses the capacity to reduce acute and chronic colitis activity in mice.

Lithocholic Acid Improves the Survival of Drosophila Melanogaster.

SCOPE: Primary bile acids are produced in the liver, whereas secondary bile acids, such as lithocholic acid (LCA), are generated by gut bacteria from primary bile acids that escape the ileal absorption. Besides their well-known function as detergents in lipid digestion, bile acids are important signaling molecules mediating effects on the host's metabolism. METHODS AND RESULTS: Fruit flies (Drosophila melanogaster) are supplemented with 50 µmol L-1 LCA either for 30 days or throughout their lifetime. LCA supplementation results in a significant induction of the mean (+12 days), median (+10 days), and maximum lifespan (+ 11 days) in comparison to untreated control flies. This lifespan extension is accompanied by an induction of spargel (srl), the fly homolog of mammalian PPAR-γ co-activator 1α (PGC1α). In wild-type flies, the administration of antibiotics abrogates both the LCA-mediated lifespan induction as well as the upregulation of srl. CONCLUSION: It is shown that the secondary bile acid LCA significantly induces the mean, the median, and the maximum survival in D. melanogaster. Our data suggest that besides an upregulation of the PGC1α-homolog srl, unidentified alterations in the structure or metabolism of the gut microbiota contribute to the longevity effect mediated by LCA.

Dietary Resveratrol Does Not Affect Life Span, Body Composition, Stress Response, and Longevity-Related Gene Expression in Drosophila melanogaster.

In this study, we tested the effect of the stilbene resveratrol on life span, body composition, locomotor activity, stress response, and the expression of genes encoding proteins centrally involved in ageing pathways in the model organism Drosophila melanogaster. Male and female w1118 D. melanogaster were fed diets based on sucrose, corn meal, and yeast. Flies either received a control diet or a diet supplemented with 500 µmol/L resveratrol. Dietary resveratrol did not affect mean, median, and maximal life span of male and female flies. Furthermore, body composition remained largely unchanged following the resveratrol supplementation. Locomotor activity, as determined by the climbing index, was not significantly different between control and resveratrol-supplemented flies. Resveratrol-fed flies did not exhibit an improved stress response towards hydrogen peroxide as compared to controls. Resveratrol did not change mRNA steady levels of antioxidant (catalase, glutathione-S-transferase, NADH dehydrogenase, glutathione peroxidase, superoxide dismutase 2) and longevity-related genes, including sirtuin 2, spargel, and I'm Not Dead Yet. Collectively, present data suggest that resveratrol does not affect life span, body composition, locomotor activity, stress response, and longevity-associated gene expression in w1118 D. melanogaster.

Metabolic Activity of Radish Sprouts Derived Isothiocyanates in Drosophila melanogaster.

We used Drosophila melanogaster as a model system to study the absorption, metabolism and potential health benefits of plant bioactives derived from radish sprouts (Raphanus sativus cv. Rambo), a Brassicaceae species rich in glucosinolates and other phytochemicals. Flies were subjected to a diet supplemented with lyophilized radish sprouts (10.6 g/L) for 10 days, containing high amounts of glucoraphenin and glucoraphasatin, which can be hydrolyzed by myrosinase to the isothiocyanates sulforaphene and raphasatin, respectively. We demonstrate that Drosophila melanogaster takes up and metabolizes isothiocyanates from radish sprouts through the detection of the metabolite sulforaphane-cysteine in fly homogenates. Moreover, we report a decrease in the glucose content of flies, an upregulation of spargel expression, the Drosophila homolog of the mammalian PPARγ-coactivator 1 α, as well as the inhibition of α-amylase and α-glucosidase in vitro. Overall, we show that the consumption of radish sprouts affects energy metabolism in Drosophila melanogaster which is reflected by lower glucose levels and an increased expression of spargel, a central player in mitochondrial biogenesis. These processes are often affected in chronic diseases associated with aging, including type II diabetes mellitus.

Chemical Characterization, Free Radical Scavenging, and Cellular Antioxidant and Anti-Inflammatory Properties of a Stilbenoid-Rich Root Extract of Vitis vinifera.

Dietary stilbenoids are receiving increasing attention due to their potential health benefits. However, most studies concerning the bioactivity of stilbenoids were conducted with pure compounds, for example, resveratrol. The aim of this study was to characterize a complex root extract of Vitis vinifera in terms of its free radical scavenging and cellular antioxidant and anti-inflammatory properties. HPLC-ESI-MS/MS analyses of the root extract of Vitis vinifera identified seven stilbenoids including two monomeric (resveratrol and piceatannol), two dimeric (trans-ɛ-viniferin and ampelopsin A), one trimeric (miyabenol C), and two tetrameric (r-2-viniferin = vitisin A and r-viniferin = vitisin B) compounds which may mediate its biological activity. Electron spin resonance and spin trapping experiments indicate that the root extract scavenged 2,2-diphenyl-1-picrylhydrazyl, hydroxyl, galvinoxyl, and superoxide free radicals. On a cellular level it was observed that the root extract of Vitis vinifera protects against hydrogen peroxide-induced DNA damage and induces Nrf2 and its target genes heme oxygenase-1 and γ-glutamylcysteine synthetase. Furthermore, the root extract could induce the antiatherogenic hepatic enzyme paraoxonase 1 and downregulate proinflammatory gene expression (interleukin 1ß, inducible nitric oxide synthase) in macrophages. Collectively our data suggest that the root extract of Vitis vinifera exhibits free radical scavenging as well as cellular antioxidant and anti-inflammatory properties.

The phytoestrogen prunetin affects body composition and improves fitness and lifespan in male Drosophila melanogaster.

Dietary isoflavones, a group of secondary plant compounds that exhibit phytoestrogenic properties, are primarily found in soy. Prunetin, a representative isoflavone, was recently found to affect cell signaling in cultured cells; however, in vivo effects remain elusive. In this study, the model organism Drosophila melanogaster was used to investigate the effects of prunetin in vivo with respect to lifespan, locomotion, body composition, metabolism, and gut health. Adult flies were chronically administered a prunetin-supplemented diet. Prunetin improved median survival by 3 d, and climbing activity increased by 54% in males. In comparison with the females, male flies exhibited lower climbing activity, which was reversed by prunetin intake. Furthermore, prunetin-fed males exhibited increased expression of the longevity gene Sirtuin 1 (Sir2) (22%), as well as elevated AMPK activation (51%) and triglyceride levels (29%), whereas glucose levels decreased (36%). As females are long-lived compared with their male counterparts and exhibit higher triglyceride levels, prunetin apparently "feminizes" male flies via its estrogenicity. We conclude that the lifespan-prolonging effects of prunetin in the male fruit fly depend on changes in AMPK-regulated energy homeostasis via male "feminization." Collectively, we identified prunetin as a plant bioactive compound capable of improving health status and survival in male D. melanogaster.

Epigallocatechin gallate affects glucose metabolism and increases fitness and lifespan in Drosophila melanogaster.

In this study, we tested whether a standardized epigallocatechin-3-gallate (EGCG) rich green tea extract (comprising > 90% EGCG) affects fitness and lifespan as well as parameters of glucose metabolism and energy homeostasis in the fruit fly, Drosophila melanogaster. Following the application of the green tea extract a significant increase in the mean lifespan (+ 3.3 days) and the 50% survival (+ 4.3 days) as well as improved fitness was detected. These effects went along an increased expression of Spargel, the homolog of mammalian PGC1α, which has been reported to affect lifespan in flies. Intriguingly, in flies, treatment with the green tea extract decreased glucose concentrations, which were accompanied by an inhibition of α-amylase and α-glucosidase activity. Computational docking analysis proved the potential of EGCG to dock into the substrate binding pocket of α-amylase and to a greater extent into α-glucosidase. Furthermore, we demonstrate that EGCG downregulates insulin-like peptide 5 and phosphoenolpyruvate carboxykinase, major regulators of glucose metabolism, as well as the Drosophila homolog of leptin, unpaired 2. We propose that a decrease in glucose metabolism in connection with an upregulated expression of Spargel contribute to the better fitness and the extended lifespan in EGCG-treated flies.

Myrosinase-treated glucoerucin is a potent inducer of the Nrf2 target gene heme oxygenase 1--studies in cultured HT-29 cells and mice.

In this study, the effect of myrosinase-treated glucoerucin (GER+MYR), which releases the isothiocyanate (ITC) erucin, on heme oxygenase 1 (HO-1) gene expression and Nrf2 signaling was investigated in vitro in cultured cells and in vivo in mice. Treatment of HT-29 cells with GER+MYR resulted in a significant increase in the mRNA and protein levels of nuclear Nrf2 and HO-1. GER+MYR was more potent at enhancing the nuclear Nrf2 levels than were the following myrosinase-treated glucosinolates: sinigrin, glucoraphanin and gluconasturtiin, which are the precursors of allyl-ITC, R-sulforaphane and 2-phenylethyl ITC, respectively. GER+MYR also significantly induced HO-1 gene expression in the mouse intestinal mucosae and liver but not in the brain. Mechanistic studies suggest that GER+MYR induces Nrf2 via ERK1/2-, p38- and JNK-dependent signal transduction pathways. The GER+MYR-mediated increase in HO-1 expression is primarily attributable to p38 signaling.

Betanin--a food colorant with biological activity.

Betalains are water-soluble nitrogen-containing pigments that are subdivided in red-violet betacyanins and yellow-orange betaxanthins. Due to glycosylation and acylation betalains exhibit a huge structural diversity. Betanin (betanidin-5-O-ß-glucoside) is the most common betacyanin in the plant kingdom. According to the regulation on food additives betanin is permitted quantum satis as a natural red food colorant (E162). Moreover, betanin is used as colorant in cosmetics and pharmaceuticals. Recently, potential health benefits of betalains and betalain-rich foods (e.g. red beet, Opuntia sp.) have been discussed. Betanin is a scavenger of reactive oxygen species and exhibits gene-regulatory activity partly via nuclear factor (erythroid-derived 2)-like 2-(Nrf2) dependent signaling pathways. Betanin may induce phase II enzymes and antioxidant defense mechanisms. Furthermore, betanin possibly prevents LDL oxidation and DNA damage. Potential blood pressure lowering effects of red beet seem to be mainly mediated by dietary nitrate rather than by betanin per se.

Dietary alpha-tocopherol affects tissue vitamin e and malondialdehyde levels but does not change antioxidant enzymes and fatty acid composition in farmed Atlantic salmon (Salmo salar L.).

In this study the effect of increasing dietary alpha tocopherol on vitamin E tissue concentrations, lipid peroxidation (malondialdehyde), antioxidant enzymes, and fatty acid composition has been investigated in farmed Atlantic salmon. To this end fish (initial body weight ~ 193 g, n = 70 per group) were fed diets based on fish oil (27.5 %), fish meal (15.0 %), wheat gluten (20.6 %), and soy protein concentrate (24.0 %) for 14 weeks. Diets were supplemented with 0 (negative control), 150, and 400 mg/kg vitamin E as all-rac alpha-tocopheryl acetate. Dietary vitamin E did not affect feed conversion efficiency ratio but significantly (p < 0.05) increased alpha-tocopherol concentrations in salmon plasma, liver, and fillet (n = 8 per group each). The increase in fillet alpha-tocopherol was accompanied by a considerable decrease (p < 0.01) in malondialdehyde concentrations at the higher supplementation level. Furthermore, we observed an antagonistic interaction between alpha- and gamma-tocopherol in plasma at the highest supplementation level, since high dietary alpha-tocopherol reduced plasma gamma-tocopherol concentrations. Liver antioxidant enzymes, including glutathione peroxidase and superoxide dismutase, remained largely unchanged in response to dietary alpha-tocopherol. Dietary alpha-tocopherol did not affect eicosapentaenoic acid and docosahexaenoic acid concentrations in salmon fillet. Present data suggest that alpha-tocopherol supplementations beyond dietary recommendations may further improve flesh quality and nutritional value of Atlantic salmon fillet as far as malondialdehyde and vitamin E concentrations are concerned.

Effect of quercetin on inflammatory gene expression in mice liver in vivo - role of redox factor 1, miRNA-122 and miRNA-125b.

The anti-inflammatory properties of the flavonol quercetin have been intensively investigated using in vitro cell systems and are to a great extent reflected by changes in the expression of inflammatory markers. However, information relating to the degree at which quercetin affects inflammatory gene expression in vivo is limited. Recently, micro RNAs (miRNAs) have been identified as powerful post-transcriptional gene regulators. The effect of quercetin on miRNA regulation in vivo is largely unknown. Laboratory mice were fed for six weeks with control or quercetin enriched high fat diets and biomarkers of inflammation as well as hepatic levels of miRNAs previously involved in inflammation (miR-125b) and lipid metabolism (miR-122) were determined. We found lower mRNA steady state levels of the inflammatory genes interleukin 6, C-reactive protein, monocyte chemoattractant protein 1, and acyloxyacyl hydrolase in quercetin fed mice. In addition we found evidence for an involvement of redox factor 1, a modulator of nuclear factor κB signalling, on the attenuation of inflammatory gene expression mediated by dietary quercetin. Furthermore, the results demonstrate that hepatic miR-122 and miR-125b concentrations were increased by dietary quercetin supplementation and may therefore contribute to the gene-regulatory activity of quercetin in vivo.

A diet rich in olive oil phenolics reduces oxidative stress in the heart of SAMP8 mice by induction of Nrf2-dependent gene expression.

A Mediterranean diet rich in olive oil has been associated with health benefits in humans. It is unclear if and to what extent olive oil phenolics may mediate these health benefits. In this study, we fed senescence-accelerated mouse-prone 8 (SAMP8, n=11 per group) semisynthetic diets with 10% olive oil containing either high (HP) or low amounts of olive oil phenolics (LP) for 4.5 months. Mice consuming the HP diet had significantly lower concentrations of the oxidative damage markers thiobarbituric acid-reactive substances and protein carbonyls in the heart, whereas proteasomal activity was similar in both groups. Nrf2-dependent gene expression may be impaired during the aging process. Therefore, we measured Nrf2 and its target genes glutathione-S-transferase (GST), γ-glutamyl cysteine synthetase (γ-GCS), nicotinamide adenine dinucleotide phosphate [NAD(P)H]:quinone oxidoreductase (NQO1), and paraoxonase-2 (PON2) in the hearts of these mice. Nrf2 as well as GST, γ-GCS, NQO1, and PON2 mRNA levels were significantly higher in heart tissue of the HP as compared to the LP group. The HP-fed mice had significantly higher PON1 activity in serum compared to those receiving the LP diet. Furthermore, HP feeding increased relative SIRT1 mRNA levels. Additional mechanistic cell culture experiments were performed, and they suggest that the olive oil phenolic hydroxytyrosol present in the HP oil may be responsible for the induction of Nrf2-dependent gene expression and the increase in PON activity. In conclusion, a diet rich in olive oil phenolics may prevent oxidative stress in the heart of SAMP8 mice by modulating Nrf2-dependent gene expression.

Ascorbic acid partly antagonizes resveratrol mediated heme oxygenase-1 but not paraoxonase-1 induction in cultured hepatocytes - role of the redox-regulated transcription factor Nrf2.

BACKGROUND: Both resveratrol and vitamin C (ascorbic acid) are frequently used in complementary and alternative medicine. However, little is known about the underlying mechanisms for potential health benefits of resveratrol and its interactions with ascorbic acid. METHODS: The antioxidant enzymes heme oxygenase-1 and paraoxonase-1 were analysed for their mRNA and protein levels in HUH7 liver cells treated with 10 and 25 µmol/l resveratrol in the absence and presence of 100 and 1000 µmol/l ascorbic acid. Additionally the transactivation of the transcription factor Nrf2 and paraoxonase-1 were determined by reporter gene assays. RESULTS: Here, we demonstrate that resveratrol induces the antioxidant enzymes heme oxygenase-1 and paraoxonase-1 in cultured hepatocytes. Heme oxygenase-1 induction by resveratrol was accompanied by an increase in Nrf2 transactivation. Resveratrol mediated Nrf2 transactivation as well as heme oxygenase-1 induction were partly antagonized by 1000 µmol/l ascorbic acid. CONCLUSIONS: Unlike heme oxygenase-1 (which is highly regulated by Nrf2) paraoxonase-1 (which exhibits fewer ARE/Nrf2 binding sites in its promoter) induction by resveratrol was not counteracted by ascorbic acid. Addition of resveratrol to the cell culture medium produced relatively low levels of hydrogen peroxide which may be a positive hormetic redox-signal for Nrf2 dependent gene expression thereby driving heme oxygenase-1 induction. However, high concentrations of ascorbic acid manifold increased hydrogen peroxide production in the cell culture medium which may be a stress signal thereby disrupting the Nrf2 signalling pathway.

Effect of dietary quercetin on brain quercetin levels and the expression of antioxidant and Alzheimer's disease relevant genes in mice.

The aim of the present feeding trial was to investigate the effect of the dietary flavonol quercetin on brain quercetin concentration and the expression of antioxidant and Alzheimer's disease relevant genes in mouse brain. Laboratory mice were fed control and quercetin-enriched diets (2 mg/g diet) for 6 weeks. Dietary quercetin supplementation significantly increased the levels of quercetin and its methylated metabolite isorhamnetin in plasma and brain. However, quercetin and isorhamnetin levels in the brain were manifold lower as compared to the plasma. Both mRNA and activity levels of alpha- and beta-secretase in cortex remained unchanged by the dietary quercetin supplementation. Furthermore dietary quercetin did not affect brain mRNA levels of neprilysin, heme oxygenase-1 and gamma-glutamylcysteine synthetase. Taken together, a short term dietary treatment with quercetin increased quercetin and isorhamnetin levels in the brain but had no effect on mRNA levels of antioxidant and Alzheimer's disease relevant genes in mouse brain.

Effect of dietary genistein on Phase II and antioxidant enzymes in rat liver.

Isoflavones are thought to be biologically active components in soy that play a role in the prevention of chronic diseases including cancer. How isoflavones may mediate their beneficial effects has not yet been fully established. Potential mechanisms of cellular action of isoflavones may include their ability to modulate gene expression and the activity levels of enzymes involved in antioxidant defence and the metabolism of xenobiotics including NAD(P)H (Nicotinamide-adenine-dinucleotide-phosphate) quinone oxidoreductase 1 (NQO1) and glutathione S-transferase (GST). Although there is increasing evidence from cell culture studies that genistein, the major isoflavone present in soy, may regulate the expression of genes encoding for phase II and antioxidant enzymes, little is known about its effect in vivo. Feeding rats over 3 weeks with semisynthetic diets enriched with genistein (2 g/kg) significantly increased both the hepatic mRNA and activity levels of NQO1. The total GST activity did not change in response to dietary genistein supplementation, whereas the mRNA levels of individual GST isoenzymes were differentially modulated. The hepatic mRNA level of Gsta2 (class alpha 2) was significantly increased whereas the mRNA levels of Gstm2 (class mu 2) and Gstp1 (class pi 1) were significantly lowered due to genistein supplementation. The protein level of Nrf2 (Nuclear factor E2-related factor 2), a transcription factor involved in the regulation of phase II enzymes, was not altered by dietary genistein. Furthermore, genistein did not affect the hepatic enzyme activity of the antioxidant enzymes catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD) or liver lipid peroxidation and glutathione levels. The induction of NQO1 may be one mechanism by which dietary genistein improves the capacity of the liver to detoxify carcinogens.

Quercetin reduces systolic blood pressure and plasma oxidised low-density lipoprotein concentrations in overweight subjects with a high-cardiovascular disease risk phenotype: a double-blinded, placebo-controlled cross-over study.

Regular consumption of flavonoids may reduce the risk for CVD. However, the effects of individual flavonoids, for example, quercetin, remain unclear. The present study was undertaken to examine the effects of quercetin supplementation on blood pressure, lipid metabolism, markers of oxidative stress, inflammation, and body composition in an at-risk population of ninety-three overweight or obese subjects aged 25-65 years with metabolic syndrome traits. Subjects were randomised to receive 150 mg quercetin/d in a double-blinded, placebo-controlled cross-over trial with 6-week treatment periods separated by a 5-week washout period. Mean fasting plasma quercetin concentrations increased from 71 to 269 nmol/l (P < 0.001) during quercetin treatment. In contrast to placebo, quercetin decreased systolic blood pressure (SBP) by 2.6 mmHg (P < 0.01) in the entire study group, by 2.9 mmHg (P < 0.01) in the subgroup of hypertensive subjects and by 3.7 mmHg (P < 0.001) in the subgroup of younger adults aged 25-50 years. Quercetin decreased serum HDL-cholesterol concentrations (P < 0.001), while total cholesterol, TAG and the LDL:HDL-cholesterol and TAG:HDL-cholesterol ratios were unaltered. Quercetin significantly decreased plasma concentrations of atherogenic oxidised LDL, but did not affect TNF-alpha and C-reactive protein when compared with placebo. Quercetin supplementation had no effects on nutritional status. Blood parameters of liver and kidney function, haematology and serum electrolytes did not reveal any adverse effects of quercetin. In conclusion, quercetin reduced SBP and plasma oxidised LDL concentrations in overweight subjects with a high-CVD risk phenotype. Our findings provide further evidence that quercetin may provide protection against CVD.