Dietary curcumin supplementation attenuates 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity in C57BL mice.

Studies in vivo and in vitro suggest that curcumin is a neuroprotective agent. Experiments were conducted to determine whether dietary supplementation with curcumin has neuroprotective effects in a mouse model of Parkinson's disease (PD). Treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) significantly induced the loss of dopaminergic cells in the substantia nigra and deletion of dopamine in the striatum, which was attenuated by long-term (7 weeks) dietary supplementation with curcumin at a concentration of 0.5% or 2.0% (w/w). Although curcumin did not prevent the MPTP-induced apoptosis of neuroblasts in the subventricular zone (SVZ), it promoted the regeneration of neuroblasts in the anterior part of the SVZ (SVZa) at 3 days after MPTP treatment. Furthermore, curcumin enhanced the MPTP-induced activation of microglia and astrocytes in the striatum and increased the expression of glial cell line-derived neurotrophic factor (GDNF) and transforming growth factor-ß1 (TGFß1) in the striatum and SVZ. GDNF and TGFß1 are thought to play an important role in protecting neurons from injury in the central and peripheral nervous systems. These results suggest that long-term administration of curcumin blocks the neurotoxicity of MPTP in the nigrostriatal dopaminergic system of the mouse and that the neuroprotective effect might be correlated with the increased expression of GDNF and TGFß1. Curcumin may be effective in preventing or slowing the progression of PD.

A single consumption of curry improved postprandial endothelial function in healthy male subjects: a randomized, controlled crossover trial.

BACKGROUND: Curry, one of the most popular foods in Japan, contains spices that are rich in potentially antioxidative compounds, such as curcumin and eugenol. Oxidative stress is thought to impair endothelial function associated with atherosclerosis, a leading cause of cardiovascular events. The aim of this study was to determine whether a single consumption of curry meal would improve endothelial function in healthy men. METHODS: Fourteen healthy male subjects (BMI 23.7 ± 2.7 kg/m2; age 45 ± 9 years) were given a single serving of curry meal or spice-free control meal (180 g of curry or control and 200 g of cooked rice; approximately 500 kcal in total) in a randomized, controlled crossover design. Before and 1 hr after the consumption, fasting and postprandial flow-mediated vasodilation (FMD) responses and other parameters were measured. RESULTS: The consumption of the control meal decreased FMD from 5.8 ± 2.4% to 5.1 ± 2.3% (P = 0.039). On the other hand, the consumption of the curry meal increased FMD from 5.2 ± 2.5% to 6.6 ± 2.0% (P = 0.001), and the postprandial FMD after the curry meal was higher than that after the control meal (P = 0.002). Presence of spices in the curry did not alter significantly the systemic and forearm hemodynamics, or any biochemical parameters including oxidative stress markers measured. CONCLUSIONS: These findings suggest that the consumption of curry ameliorates postprandial endothelial function in healthy male subjects and may be beneficial for improving cardiovascular health. TRIAL REGISTRATION: UMIN Clinical Trials Registry 000012012.

Yamogenin in fenugreek inhibits lipid accumulation through the suppression of gene expression in fatty acid synthesis in hepatocytes.

Yamogenin is a diastereomer of diosgenin, which we have identified as the compound responsible for the anti-hyperlipidemic effect of fenugreek. Here, we examined the effects of yamogenin on the accumulation of triacylglyceride (TG) in hepatocytes, because yamogenin is also contained in fenugreek. It was demonstrated that yamogenin also inhibited TG accumulation in HepG2 hepatocytes and suppressed the mRNA expression of fatty acid synthesis-related genes such as fatty acid synthase and sterol response element-binding protein-1c. Indeed, yamogenin also antagonized the activation of the liver X receptor (LXR) in luciferase ligand assay similar to diosgenin. However, yamogenin could not exert such effects in the presence of T0901713, a potent agonist of LXR. These findings indicate that the effects of yamogenin on TG accumulation would be weaker than those of diosgenin, suggesting that the structural difference between yamogenin and diosgenin would be important for the inhibition of LXR activation.

Chronic intake of onion extract containing quercetin improved postprandial endothelial dysfunction in healthy men.

BACKGROUND: Epidemiologic studies have shown that dietary flavonoids reduce the risk of cardiovascular events. Onion is rich in quercetin, a strong antioxidant flavonoid. In some in vitro studies, quercetin improved endothelial function associated with atherosclerosis, a leading cause of cardiovascular events. OBJECTIVE: The aim of this study was to determine whether chronic onion extract intake would improve postprandial endothelial dysfunction induced by an oral maltose load in healthy men. METHODS: Healthy men (44±10 years, n=23) received 4.3 g of onion extract (containing 51 mg of quercetin) once a day for 30 days. Before and after the chronic onion extract intake, fasting and postprandial flow-mediated vasodilation (FMD) responses were measured. RESULTS: Maltose loading significantly decreased FMD both before and after chronic onion extract intake (p=0.000037 and p=0.0035, respectively). The chronic onion extract intake did not significantly affect fasting FMD (p=0.069) but improved the postprandial FMD significantly from 5.1%±2.2% to 6.7%±2.6% (p=0.00015). The chronic onion extract intake did not alter systemic and forearm hemodynamics. CONCLUSION: These findings suggest that chronic onion extract intake ameliorates postprandial endothelial dysfunction in healthy men and may be beneficial for improving cardiovascular health.

Proton transfer in a reaction catalyzed by onion lachrymatory factor synthase.

We produced a single deuterated lachrymatory factor (propanthial S-oxide, m/z = 91) in a model reaction system comprising purified alliinase, lachrymatory factor synthase (LFS), and (E)-(+)-S-(1-propenyl)-L-cysteine sulfoxide ((E)-PRENCSO) in D(2)O. Onion LFS reacted with the degraded products of (E)-PRENCSO by alliinase, but not with those of (Z)-PRENCSO. These findings indicate that onion LFS is an (E)-1-propenylsulfenic acid isomerase.

Identification of amino acid residues essential for onion lachrymatory factor synthase activity.

Lachrymatory factor synthase (LFS), an enzyme essential for the synthesis of the onion lachrymatory factor (propanethial S-oxide), was identified in 2002. This was the first reported enzyme involved in the production of thioaldehyde S-oxides via an intra-molecular H(+) substitution reaction, and we therefore attempted to identify the catalytic amino acid residues of LFS as the first step in elucidating the unique catalytic reaction mechanism of this enzyme. A comparison of the LFS cDNA sequences among lachrymatory Allium plants, a deletion analysis and site-directed mutagenesis enabled us to identify two amino acids (Arg71 and Glu88) that were indispensable to the LFS activity. Homology modeling was performed for LFS/23-169 on the basis of the template structure of a pyrabactin resistance 1-like protein (PYL) which had been selected from a BLASTP search on SWISS-MODEL against LFS/23-169. We identified in the modeled structure of LFS a pocket corresponding to the ligand-binding site in PYL, and Arg71 and Glu88 were located in this pocket.

Fenugreek with reduced bitterness prevents diet-induced metabolic disorders in rats.

BACKGROUND: Various therapeutic effects of fenugreek (Trigonella foenum-graecum L.) on metabolic disorders have been reported. However, the bitterness of fenugreek makes it hard for humans to eat sufficient doses of it for achieving therapeutic effects. Fenugreek contains bitter saponins such as protodioscin. Fenugreek with reduced bitterness (FRB) is prepared by treating fenugreek with beta-glucosidase. This study has been undertaken to evaluate the effects of FRB on metabolic disorders in rats. METHODS: Forty Sprague-Dawley rats were fed with high-fat high-sucrose (HFS) diet for 12 week to induce mild glucose and lipid disorders. Afterwards, the rats were divided into 5 groups. In the experiment 1, each group (n = 8) was fed with HFS, or HFS containing 2.4% fenugreek, or HFS containing 1.2%, 2.4% and 4.8% FRB, respectively, for 12 week. In the experiment 2, we examined the effects of lower doses of FRB (0.12%, 0.24% and 1.2%) under the same protocol (n = 7 in each groups). RESULTS: In the experiment 1, FRB dose-dependently reduced food intake, body weight gain, epididymal white adipose tissue (EWAT) and soleus muscle weight. FRB also lowered plasma and hepatic lipid levels and increased fecal lipid levels, both dose-dependently. The Plasma total cholesterol levels (mmol/L) in the three FRB and Ctrl groups were 1.58 ± 0.09, 1.45 ± 0.05*, 1.29 ± 0.07* and 2.00 ± 0.18, respectively (*; P < 0.05 vs. Ctrl). The Hepatic total cholesterol levels (mmol/g liver) were 0.116 ± 0.011, 0.112 ± 0.006, 0.099 ± 0.007* and 0.144 ± 0.012, respectively (*; P < 0.05 vs. Ctrl). The calculated homeostasis model assessment as an index of insulin resistance (HOMA-IR) indicated 0.52 ± 0.04*, 0.47 ± 0.06*, 0.45 ± 0.05* and 1.10 ± 0.16, respectively (*; P < 0.05 vs. Ctrl). None of the FRB groups showed any adverse effect on the liver, kidney or hematological functions. In the experiment 2, no significant difference of food intake was observed, while the 1.2% FRB group alone showed nearly the same effects on glucose and lipid metabolism as in the experiment 1. CONCLUSIONS: Thus we have demonstrated that FRB (1.2 ~ 4.8%) prevents diet-induced metabolic disorders such as insulin resistance, dyslipidemia and fatty liver.

Diosgenin, the main aglycon of fenugreek, inhibits LXRα activity in HepG2 cells and decreases plasma and hepatic triglycerides in obese diabetic mice.

Trigonella foenum-graecum (fenugreek) can ameliorate dyslipidemia, but the detailed mechanism is unclear. In this study, we examined the effects of fenugreek on hepatic lipid metabolism, particularly lipogenesis, which is enhanced in obesity and diabetes, in diabetic obese KK-Ay mice. KK-Ay mice were fed a control high-fat diet (HFD; 60% of energy as fat) (C group) or an HFD containing 0.5% or 2% fenugreek (0.5F and 2.0F groups, respectively) for 4 wk. Hepatic and plasma TG and mRNA expression levels of lipogenic genes were lower in the 2.0F group at 4 wk (P < 0.05), but not in the 0.5F group, than in the C group. The hydrolyzed saponin fraction, but not the saponin fraction per se, in fenugreek inhibited the accumulation of TG in HepG2 cells. We fractionated the hydrolyzed saponin into 15 fractions by HPLC and examined the effect of these fractions on TG accumulation in HepG2 cells. Fraction 11 inhibited TG accumulation in HepG2 cells and we determined by liquid chromatography tandem MS that the active substance contained in fraction 11 is diosgenin. Diosgenin (5 and 10 µmol/L) inhibited the accumulation of TG and the expression of lipogenic genes in HepG2 cells. Moreover, diosgenin inhibited the transactivation of liver-X-receptor-α, as measured using a luciferase assay system and by gel mobility shift assay. These findings suggest that fenugreek ameliorates dyslipidemia by decreasing the hepatic lipid content in diabetic mice and that its effect is mediated by diosgenin. Fenugreek, which contains diosgenin, may be useful for the management of diabetes-related hepatic dyslipidemias.

An Efficient Purification Method for Quantitative Determinations of Protodioscin, Dioscin and Diosgenin in Plasma of Fenugreek-Fed Mice.

An efficient purification method for simultaneous recovery of polar saponins, protodioscin (PD) and dioscin (DC), and non-polar aglycon, diosgenin (DG), from plasma of mice fed diets containing seed flours of fenugreek (Trigonella foenum-graecum) was established for subsequent quantitative analysis by LC-ESI-MS/MS. Mice plasma samples were first deproteinated by addition of acetonitrile, and the supernatant was applied to a carbon-based solid phase extraction tube. After successive washing with methanol and 35% chroloform/methanol (v/v), PD, DC and DG were eluted simultaneously with 80% chroloform/methanol (v/v). The eluate was evaporated to dryness, and re-dissolved in 80% methanol (v/v). The filtered sample was analyzed with an LC-ESI-MS/MS system. After the purification procedure, recovery rates between 89.3 to 117.4% were obtained without notable ion suppression or enhancement. The use of internal standards was therefore not necessary. The utility of the method was demonstrated by analyzing plasma of mice from a fenugreek feeding study.

Dill seed extract improves abnormalities in lipid metabolism through peroxisome proliferator-activated receptor-α (PPAR-α) activation in diabetic obese mice.

Dill, a small annual herb, is widely used as a flavoring agent in dishes including salads. It has been demonstrated that dill extract and its essential oil show hypolipidemic effects in rats. However, the mechanism of these effects has not been elucidated yet. We found that dill seed extract (DSE) activated peroxisome proliferator-activated receptor-α (PPAR-α), an indispensable regulator for hepatic lipid metabolism, by luciferase assay. Thus, we performed DSE feeding experiments using diabetic obese model KK-Ay mice to examine the effects of DSE on PPAR-α activation in vivo. A 4-week feeding of DSE contained in a high-fat diet decreased plasma triacylglyceride and glucose levels and increased the mRNA expression levels of fatty acid oxidation-related genes in the liver. In addition, the DSE feeding as well as bezafibrate (a PPAR-α potent agonist) feeding increased oxygen consumption rate and rectal temperature. These results indicate that DSE suppresses high-fat diet-induced hyperlipidemia through hepatic PPAR-α activation.

Structure and bioactivity of thiosulfinates resulting from suppression of lachrymatory factor synthase in onion.

In normal onion (Allium cepa), trans-S-1-propenyl-L-cysteine sulfoxide is transformed via 1-propenesulfenic acid into propanethial S-oxide, a lachrymatory factor, through successive reactions catalyzed by alliinase and lachrymatory factor synthase (LFS). A recent report showed that suppression of the LFS activity caused a dramatic increase in thiosulfinates previously reported as "zwiebelane isomers". After purification by recycle high-performance liquid chromatography and subsequent analyses, we established the planar structure of the putative "zwiebelane isomers" as S-3,4-dimethyl-5-hydroxythiolane-2-yl 1-propenethiosulfinate, in which two of the three molecules of 1-propenesulfenic acid involved in the formation gave the thiolane backbone, and the third molecule gave the thiosulfinate structure. Of at least three stereoisomers observed, one in the (2'R,3'R,4'R,5'R)-configuration was collected as an isolated fraction, and the other isomers were collected as a combined fraction because spontaneous tautomerization prevented further purification. Both fractions showed inhibitory activities against cyclooxygenase-1 and α-glucosidase in vitro.

Using synthesized onion lachrymatory factor to measure age-related decreases in reflex-tear secretion and ocular-surface sensation.

PURPOSE: To use synthesized onion lachrymatory factor (SOLF) to investigate age-related changes in reflex-tear secretion and ocular-surface sensation. METHODS: We separated 91 healthy volunteers into four groups: groups A, age 20-29 years; B, 30-39; C, 40-49; and D, older than 50 years. We exposed one eye of each subject to SOLF and measured the elapsed time until the subject's limit of irritation tolerance (TLI) was reached and an increase in the tear meniscus radius (DeltaR). After the SOLF stimulus, corneal sensitivity was examined by Cochet-Bonnet esthesiometry (CB), and reflex-tear secretion was examined by the Schirmer I-test (ST). RESULTS: TLI was significantly shorter in group A than in the other groups (P < 0.0001), and the groups B and D also differed significantly from each other (P = 0.0013). The increase in DeltaR was significantly greater in group A than in group C (P = 0.0306) or D (P < 0.0001), and groups B (P = 0.0002) and C (P = 0.0308) also differed significantly from group D. There were no significant intergroup differences in the CB and ST results. CONCLUSIONS: An age-related decrease in reflex-tear secretion and ocular-surface sensation was revealed by the SOLF test but could not be detected by either CB or the ST.

Diosgenin attenuates inflammatory changes in the interaction between adipocytes and macrophages.

Obese adipose tissues are characterized by the enhanced infiltration of macrophages. It is considered that the paracrine loop involving monocyte chemoattractant protein-1, tumor necrosis factor-alpha, and the free fatty acid between adipocytes and macrophages establishes a vicious cycle that aggravates inflammatory changes and insulin resistance in obese adipose tissues. Diosgenin, a saponin aglycon found in a variety of plants, has anti-inflammatory properties. In the present study, we examined the effect of diosgenin on the inflammatory changes in the interaction between adipocytes and macrophages. A coculture of 3T3-L1 adipocytes and RAW 264 macrophages markedly enhanced the production of tumor necrosis factor-alpha, monocyte chemoattractant protein-1, and nitric oxide compared with the sum of their single cultures; however, treatment with diosgenin inhibited the production of these proinflammatory mediators. Diosgenin also suppressed the inflammation in RAW 264 macrophages that was induced by the conditioned medium derived from 3T3-L1 adipocytes. Furthermore, diosgenin inhibited the conditioned medium-induced degradation of inhibitor kappaB and the phosphorylation of c-jun N-terminal kinase in macrophages. These results indicate that diosgenin exhibits anti-inflammatory properties in the interaction of adipocytes and macrophages by inhibiting the inflammatory signals in macrophages. Diosgenin may be useful for ameliorating the inflammatory changes in obese adipose tissues.

Diosgenin present in fenugreek improves glucose metabolism by promoting adipocyte differentiation and inhibiting inflammation in adipose tissues.

In obesity, adipocyte hypertrophy and chronic inflammation in adipose tissues cause insulin resistance and type-2 diabetes. Trigonella foenum-graecum (fenugreek) can ameliorate hyperglycemia and diabetes. However, the effects of fenugreek on adipocyte size and inflammation in adipose tissues have not been demonstrated. In this study, we determined the effects of fenugreek on adipocyte size and inflammation in adipose tissues in diabetic obese KK-Ay mice, and identified the active substance in fenugreek. Treatment of KK-Ay mice with a high fat diet supplemented with 2% fenugreek ameliorated diabetes. Moreover, fenugreek miniaturized the adipocytes and increased the mRNA expression levels of differentiation-related genes in adipose tissues. Fenugreek also inhibited macrophage infiltration into adipose tissues and decreased the mRNA expression levels of inflammatory genes. In addition, we identified diosgenin, a major aglycone of saponins in fenugreek to promote adipocyte differentiation and to inhibit expressions of several molecular candidates associated with inflammation in 3T3-L1 cells. These results suggest that fenugreek ameliorated diabetes by promoting adipocyte differentiation and inhibiting inflammation in adipose tissues, and its effects are mediated by diosgenin. Fenugreek containing diosgenin may be useful for ameliorating the glucose metabolic disorder associated with obesity.