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.

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.

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.

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.

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.