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.
Taku Uemura, T., Hirai, S., Mizoguchi, N., et al. (2010) Diosgenin present in fenugreek improves glucose metabolism by promoting adipocyte differentiation and inhibiting inflammation in adipose tissues. Molecular Nutrition & Food Research. DOI: 10.1002/mnfr.200900609

Induction of antiproliferative effect by diosgenin through activation of p53, release of apoptosis-inducing factor (AIF) and modulation of caspase-3 activity in different human cancer cells.
The plant steroid, diosgenin, altered cell cycle distribution and induced apoptosis in the human osteosarcoma 1547 cell line. The objective of this study was to investigate if the antiproliferative effect of diosgenin was similar for different human cancer cell lines such as laryngocarcinoma HEp-2 and melanoma M4Beu cells. Moreover, this work essentially focused on the mitochondrial pathway. We found that diosgenin had an important and similar antiproliferative effect on different types of cancer cells. In addition, our new results show that diosgenin-induced apoptosis is caspase-3 dependent with a fall of mitochondrial membrane potential, nuclear localization of AIF and poly (ADP-ribose) polymerase cleavage. Diosgenin treatment also induces p53 activation and cell cycle arrest in the different cell lines studied.
Corbiere C, Liagre B, Terro F & Beneytout J-L. Cell Research (2004) 14, 188196. doi:10.1038/sj.cr.7290219

Diosgenin, a naturally occurring steroid, suppresses fatty acid synthase expression in HER2-overexpressing breast cancer cells through modulating Akt, mTOR and JNK phosphorylation
Fatty acid synthase (FAS) expression is markedly elevated in HER2-overexpressing breast cancer cells. In this study, diosgenin, a plant-derived steroid, was found to be effective in suppressing FAS expression in HER2-overexpressing breast cancer cells. Diosgenin preferentially inhibited proliferation and induced apoptosis in HER2-overexpressing cancer cells. Furthermore, diosgenin inhibited the phosphorylation of Akt and mTOR, and enhanced phosphorylation of JNK. The use of pharmacological inhibitors revealed that the modulation of Akt, mTOR and JNK phosphorylation was required for diosgenin-induced FAS suppression. Finally, we showed that diosgenin could enhance paclitaxel-induced cytotoxicity in HER2-overexpressing cancer cells. These results suggested that diosgenin has the potential to advance as chemopreventive or chemotherapeutic agent for cancers that overexpress HER2.
Chiang C-T, Way T-D, Tsai S-J, & Lin J-K. FEBS letters. 2007, vol. 581, no30, Pp. 5735-42

Diosgenin, a Steroid Saponin of Trigonella foenum graecum (Fenugreek), Inhibits Azoxymethane-Induced Aberrant Crypt Foci Formation in F344 Rats and Induces Apoptosis in HT-29 Human Colon Cancer Cells

To explore the anticancer potential of diosgenin in human colon cancer cells, we conducted several in vitro experiments. We examined the cytotoxic effects of 0 to 100 μmol/L diosgenin (24-hour treatment) on HT-29 cells using the MTT cytotoxicity assay. A dose-dependent MTT reduction (or color change from yellow to purple) was observed in diosgenin-treated cells. On 24-hour exposure to diosgenin, MTT activity reduced by ≥50% was achieved at the higher concentrations (i.e., ≥80 μmol/L). However, compared with the control, 20 to 60 μmol/L diosgenin reduced the MTT activity only by ∼5% to 30%. Next, we examined dose-dependent and time-dependent effects of diosgenin on the proliferation of HT-29 cells using the trypan blue dye exclusion method. Diosgenin caused a significant time-dependent and dose-dependent decrease in the proliferation of HT-29 cells. Twenty-four-hour exposure to diosgenin (20 to 100 μmol/L) inhibited cell proliferation compared with untreated cell growth (taken as 0%). This inhibition was 21%, 68%, 82%, and 100% for 20, 40, 60, and 80 μmol/L diosgenin, respectively.
Results from the in vitro experiments indicated that diosgenin inhibits cell growth and induces apoptosis in the HT-29 human colon cancer cell line in a dose-dependent manner. Furthermore, diosgenin induced apoptosis in HT-29 cells at least in part by inhibition of bcl-2 and by induction of caspase-3 protein expression. On the basis of these findings, the fenugreek constituent diosgenin seems to have potential as a novel colon cancer preventive agent.
Raju J, Patlolla JMR, Swamy MV, & Rao CV. Cancer Epidemiol Biomarkers Prev August 2004 13; 1392

Electrochemical Study of Breast Cancer Cells MCF-7 and Its Application in Evaluating the Effect of Diosgenin
The electrochemical behavior of breast cancer cells was studied on a graphite electrode by cyclic voltammetry (CV) and potentiometric stripping analysis (PSA). In both cases, only one oxidative peak at approximately +0.75 V was observed. The peak area in PSA was used to study the growth of the cells and the effect of diosgenin on MCF-7 cells. The results showed that diosgenin can effectively inhibit the viability and proliferation of the breast cancer cells.
Li J, Liu X, Guo M, Liu Y, Liu S & Yao S. Analytical Sciences. Vol. 21 (2005) , No. 5 p.561. doi:10.2116/analsci.21.561

Diosgenin induces cell cycle arrest and apoptosis in human leukemia K562 cells with the disruption of Ca 2+ homeostasis
Diosgenin is a steroidal sapogenin with estrogenic and antitumor properties. In order to elucidate the mechanism of its antiproliferative activity, we investigated its effects on the cell cycle and apoptosis in human chronic myelogenous leukemia K562 cells.
Cell viability was assessed via an MTT assay. Apoptosis was investigated in terms of nuclear morphology, DNA fragmentation, and phosphatidylserine externalization. Cell cycle analysis was performed via PI staining and flow cytometry (FCM). Western blotting and immunofluorescence methods were used to determine the levels of p53, cell cycle-related proteins and Bcl-2 family members. FCM was also used to estimate the changes in mitochondrial membrane potential (MMP), intracellular Ca2+ concentration and reactive oxygen species (ROS) generation.
Cell cycle analysis showed that diosgenin caused G2/M arrest independently of p53. The levels of cyclin B1 and p21Cip1/Waf1 were decreased, whereas cdc2 levels were increased. Subsequent apoptosis was demonstrated with the dramatic activation of caspase-3. A dramatic decline in intracellular Ca2+ concentration was observed as an initiating event in the process of cell cycle arrest and apoptosis, which was followed by the hyperpolarization and depolarization of MMP. Generation of ROS was observed in the progression of apoptosis. The antiapoptotic Bcl-2 and Bcl-xL proteins were downregulated, whereas the proapoptotic Bax was upregulated.
Diosgenin inhibits K562 cell proliferation via cell cycle G2/M arrest and apoptosis, with disruption of Ca2+ homeostasis and mitochondrial dysfunction playing vital roles.
Liu M-J, Wang Z, Ju Y, Wong RN-S & Wu Q-Y. Cancer Chemotherapy and Pharmacology. (2005) Volume 55, Number 1, 79-90, DOI: 10.1007/s00280-004-0849-3

Diosgenin targets Akt-mediated prosurvival signaling in human breast cancer cells

In recent years, Akt signaling has gained recognition for its functional role in more aggressive, therapy-resistant malignancies. As it is frequently constitutively active in cancer cells, several drugs are being investigated for their ability to inhibit Akt signaling. The purpose of this study is to determine effect of diosgenin (fenugreek), a dietary compound on Akt signaling and its downstream targets on estrogen receptor positive (ER+) and estrogen receptor negative (ER-) breast cancer (BCa) cells. Diosgenin inhibits pAkt expression and Akt kinase activity without affecting PI3 kinase levels, resulting in the inhibition of its downstream targets, NF-κB, Bcl-2, survivin and XIAP. The Raf/MEK/ERK pathway, another functional downstream target of Akt, was inhibited by diosgenin in ER+ but not in ER- BCa cells. Additionally, we found that diosgenin caused G1 cell cycle arrest by downregulating cyclin D1, cdk-2 and cdk-4 expression in both ER+ and ER- BCa cells resulting in the inhibition of cell proliferation and induction of apoptosis.
Interestingly, no significant toxicity was seen in the normal breast epithelial cells (MCF-10A) following treatment with diosgenin. Additionally, in vivo tumor studies indicate diosgenin significantly inhibits tumor growth in both MCF-7 and MDA-231 xenografts in nude mice. Thus, these results suggest that diosgenin might prove to be a potential chemotherapeutic agent for the treatment of BCa.
Srinivasan S, Koduru S, Kumar R, Venguswamy G, Kyprianou N & Damodaran C. International Journal of Cancer. Volume 125, Issue 4, pages 961967, 15 August 2009. DOI: 10.1002/ijc.24419

Protodioscin isolated from fenugreek (Trigonella foenumgraecum L.) induces cell death and morphological change indicative of apoptosis in leukemic cell line H-60, but not in gastric cancer cell line KATO III.

Protodioscin (PD) was purified from fenugreek (Trigonella foenumgraecum L.) and identified by Mass, and 1H- and 13C-NMR. The effects of PD on cell viability in human leukemia HL-60 and human stomach cancer KATO III cells were investigated. PD displayed strong growth inhibitory effect against HL-60 cells, but weak growth inhibitory effect on KATO III cells. Morphological change showing apoptotic bodies was observed in the HL-60 cells treated with PD, but not in KATO III cells treated with PD. Flow cytometric analysis showed that the hypodiploid nuclei of HL-60 cells were increased to 75.2, 96.3, and 100% after a 3-day treatment with 2.5, 5, and 10 microM PD, respectively. The fragmentation by PD of DNA to oligonucleosomal-sized fragments, that is a characteristic of apoptosis, was observed to be both concentration- and time-dependent in the HL-60 cells. These findings suggest that growth inhibition by PD of HL-60 cells results from the induction of apoptosis by this compound in HL-60 cells.
Hibasami H, Moteki H, Ishikawa K, Katsuzaki H, Imai K, Yoshioka K, Ishii Y, Komiya T. Int J Mol Med. 2003 Jan;11(1):23-6.
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