Pathogenesis of NASH and Promising Natural Products.

Nonalcoholic steatohepatitis (NASH) is a common clinical condition that can lead to advanced liver diseases. The mechanism of the diaease progression, which is lacking effective therapy, remains obsure. Therefore, there is a need to understand the pathogenic mechanisms responsible for disease development and progression in order to develop innovative therapies. To accomplish this goal, experimental animal models that recapitulate the human disease are necessary. Currently, an increasing number of studies have focused on natural constituents from medicinal plants which have been emerged as a new hope for NASH. This review summarized the pathogenesis of NASH, animal models commonly used, and the promising targets for therapeutics. We also reviewed the natural constituents as potential NASH therapeutic agents.

Activation of SIK1 by phanginin A inhibits hepatic gluconeogenesis by increasing PDE4 activity and suppressing the cAMP signaling pathway.

OBJECTIVE: Salt-induced kinase 1 (SIK1) acts as a key modulator in many physiological processes. However, the effects of SIK1 on gluconeogenesis and the underlying mechanisms have not been fully elucidated. In this study, we found that a natural compound phanginin A could activate SIK1 and further inhibit gluconeogenesis. The mechanisms by which phanginin A activates SIK1 and inhibits gluconeogenesis were explored in primary mouse hepatocytes, and the effects of phanginin A on glucose homeostasis were investigated in ob/ob mice. METHODS: The effects of phanginin A on gluconeogenesis and SIK1 phosphorylation were examined in primary mouse hepatocytes. Pan-SIK inhibitor and siRNA-mediated knockdown were used to elucidate the involvement of SIK1 activation in phanginin A-reduced gluconeogenesis. LKB1 knockdown was used to explore how phanginin A activated SIK1. SIK1 overexpression was used to evaluate its effect on gluconeogenesis, PDE4 activity, and the cAMP pathway. The acute and chronic effects of phanginin A on metabolic abnormalities were observed in ob/ob mice. RESULTS: Phanginin A significantly increased SIK1 phosphorylation through LKB1 and further suppressed gluconeogenesis by increasing PDE4 activity and inhibiting the cAMP/PKA/CREB pathway in primary mouse hepatocytes, and this effect was blocked by pan-SIK inhibitor HG-9-91-01 or siRNA-mediated knockdown of SIK1. Overexpression of SIK1 in hepatocytes increased PDE4 activity, reduced cAMP accumulation, and thereby inhibited gluconeogenesis. Acute treatment with phanginin A reduced gluconeogenesis in vivo, accompanied by increased SIK1 phosphorylation and PDE4 activity in the liver. Long-term treatment of phanginin A profoundly reduced blood glucose levels and improved glucose tolerance and dyslipidemia in ob/ob mice. CONCLUSION: We discovered an unrecognized effect of phanginin A in suppressing hepatic gluconeogenesis and revealed a novel mechanism that activation of SIK1 by phanginin A could inhibit gluconeogenesis by increasing PDE4 activity and suppressing the cAMP/PKA/CREB pathway in the liver. We also highlighted the potential value of phanginin A as a lead compound for treating type 2 diabetes.

16-nor Limonoids from Harrisonia perforata as promising selective 11ß-HSD1 inhibitors.

Two new 16-nor limonoids, harperspinoids A and B (1 and 2), with a unique 7/5/5/6/5 ring system, have been isolated from the plant Harrisonia perforate together with a known one, Harperforin G (3). Their structures were elucidated by NMR spectroscopy, X-ray diffraction analysis and computational modelling. Compound 1 exists as polymorphic crystals. Conformations of 1 in solution were further discussed based on the computational results. These compounds exhibited notable inhibitory activity against the 11ß-HSD1 enzyme. Compound 3 had potencies for the inhibition of human 11ß-HSD1 with high selectivity against 11ß-HSD2 (IC50 0.58 µM, SI > 174). Molecular docking and quantitative structure-activity relationship studies revealed a mixed regulatory mechanism.

Hupehenols A-E, selective 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) inhibitors from Viburnum hupehense.

Five selective 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) competitive inhibitors, hupehenols A-E (1-5), were isolated from Viburnum hupehense. The structure elucidation indicated that compounds 1-5 are new 20,21,22,23,24,25,26,27-octanordammarane triterpenoids. Their structures were established on the basis of NMR spectroscopic and mass spectrometric analysis. Hupehenols A-E (1-5) showed inhibition against human 11ß-HSD1, with hupehenols B (2) and E (5) having IC50 values of 15.3 and 34.0 nM, respectively. Moreover, hupehenols C (3) and D (4) are highly selective inhibitors of human 11ß-HSD1 when compared to murine 11ß-HSD1.

Lithocarpic acids O-S, five homo-cycloartane derivatives from the cupules of Lithocarpus polystachyus.

Chemical investigation of the cupules of Lithocarpus polystachyus resulted in the identification of four 3,4-seco-homo-cycloartane and one homo-cycloartane derivatives named lithocarpic acids O-S. Their structures were determined based on extensive 1D/2D NMR, IR, MS spectroscopic analyses and chemical methods. Lithocarpic acid O (1) exhibited inhibitory activities on mouse and human isozymes of 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) with IC50 values of 0.49 and 1.1 µM, respectively.

Lithocarpic Acids A-N, 3,4-seco-Cycloartane Derivatives from the Cupules of Lithocarpus polystachyus.

Fourteen new 3,4-seco-cycloartane-type triterpenes, lithocarpic acids A-N (1-14), together with one known compound, coccinetane E (15), were identified from the cupules of Lithocarpus polystachyus. The structures of 1-14 were determined by spectroscopic data analysis and chemical methods, and the absolute configurations of 1 and 4 were defined unequivocally by X-ray crystallography using Cu Kα radiation. Compounds 1-15 are the first examples of 3,4-seco-cycloartane derivatives isolated from the genus Lithocarpus. Among them, compounds 1 and 2, 9 and 10, and 11 and 12 were found to be three pairs of C-24 epimers, while compounds 7 and 8 represent the first examples of 3,4-seco-norcycloartane-type triterpenes. Compound 1, as the major component of the plant extract, showed potent antibacterial activity against Micrococcus luteus and Bacillus subtilis, with MIC values of 3.1 and 6.3 µg/mL, respectively, as well as inhibitory activity against human and mouse 11ß-hydroxysteroid dehydrogenase type 1, with IC50 values of 1.9 and 0.24 µM, respectively.

Ingol-type diterpenes from Euphorbia antiquorum with mouse 11ß-hydroxysteroid dehydrogenase type 1 inhibition activity.

Eighteen new ingol-type diterpenes, euphorantins A-R (1-18), along with four known analogues (19-22), were isolated from the aerial parts of Euphorbia antiquorum. Compounds 1-3 are the first examples of C-17-oxygenated ingol-type diterpenes, and compounds 16-18 represent a rare class of 2,3-di-epimers of ingols. Diterpenes 1, 14, and 22 exhibited inhibitory activities against mouse 11ß-HSD1 with IC50 values of 12.0, 6.4, and 0.41 µM, respectively.

Downregulation of the Werner syndrome protein induces a metabolic shift that compromises redox homeostasis and limits proliferation of cancer cells.

The Werner syndrome protein (WRN) is a nuclear protein required for cell growth and proliferation. Loss-of-function mutations in the Werner syndrome gene are associated with the premature onset of age-related diseases. How loss of WRN limits cell proliferation and induces replicative senescence is poorly understood. Here, we show that WRN depletion leads to a striking metabolic shift that coordinately weakens the pathways that generate reducing equivalents for detoxification of reactive oxygen species and increases mitochondrial respiration. In cancer cells, this metabolic shift counteracts the Warburg effect, a defining characteristic of many malignant cells, resulting in altered redox balance and accumulation of oxidative DNA damage that inhibits cell proliferation and induces a senescence-like phenotype. Consistent with these findings, supplementation with antioxidant rescues at least in part cell proliferation and decreases senescence in WRN-knockdown cancer cells. These results demonstrate that WRN plays a critical role in cancer cell proliferation by contributing to the Warburg effect and preventing metabolic stress.

Guanidine alkaloids from Plumbago zeylanica.

Eleven new guanidine alkaloids, plumbagines A-G (2-8) and plumbagosides A-D (9-12), as well as two known analogues (1, 13), were isolated from the aerial parts of Plumbago zeylanica. Their structures were elucidated by spectroscopic analyses including 1D and 2D NMR, MS, IR, and CD methods. The absolute configuration of 1 was determined by single-crystal X-ray diffraction of its derivative (1a).

Design, synthesis, and structure-activity relationships of 3,4,5-trisubstituted 4,5-dihydro-1,2,4-oxadiazoles as TGR5 agonists.

Given its role in the mediation of energy and glucose homeostasis, the G-protein-coupled bile acid receptor 1 (TGR5) is considered a potential target for the treatment of type 2 diabetes mellitus and other metabolic disorders. By thorough analysis of diverse structures of published TGR5 agonists, a hypothetical ligand-based pharmacophore model was built, and a new class of potent TGR5 agonists, based on the novel 3,4,5-trisubstituted 4,5-dihydro-1,2,4-oxadiazole core, was discovered by rational design. Three distinct synthetic methods for constructing 4,5-dihydro-1,2,4-oxadiazoles and extensive structure-activity relationship studies are reported herein. Compound (R)-54 n, the structure of which was determined by single-crystal X-ray diffraction and quantum chemical solid-state TDDFT-ECD calculations, showed the best potency, with an EC50 value of 1.4 nM toward hTGR5. Its favorable properties in vitro warrant further investigation.

11ß-HSD1 inhibitors from Walsura cochinchinensis.

A search for inhibitors of 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) from Walsura cochinchinensis yielded 10 new limonoids, cochinchinoids A-J (1-10), and two new triterpenoids, 3-epimesendanin S (11) and cochinchinoid K (12). Their structures were assigned on the basis of spectroscopic data, with the absolute configurations of 1 and 12 being established by X-ray diffraction analysis. Of these compounds, cochinchinoid K (12) displayed inhibitory activity against mouse 11ß-HSD1 with an IC50 value of 0.82 µM.

Inhibition of 11b-HSD1 by tetracyclic triterpenoids from Euphorbia kansui.

The roots of Euphorbia kansui are considered an important traditional folk medicine. In this study the ethanol extracts of E. kansui were investigated. A new tetracyclic triterpenoid, euphane-3b,20-dihydroxy-24-ene, in addition to five known triterpenoids with euphane skeletons were isolated. Their structures were elucidated on the basis of physical and spectral techniques (1D-, 2D-NMR and MS, respectively). Furthermore, these compounds 1-6 exhibited strong inhibitory activity against human 11b-hydroxysteroid dehydrogenase type 1 (11b-HSD1), with IC(50) values of 34.86 nM, 1.115 mM, 16.08 nM, 2.815 nM, 26.47 nM, 15.99 nM, and 41.86 nM, respectively. The docking results show that the ring part of compounds can insert into the hydrophobic core of h11b-HSD1 and the alkane chain orientates toward the outside. The results presented herein provide a scientific explanation for the usage of the E. kansui in clinical treatment of diabetes.

Chemical constituents and their bioactivities of "Tongling White Ginger" (Zingiber officinale).

Gingerols and their corresponding dehydration products shogaols were considered as the active principles of ginger, the rhizome of the plant Zingiber officinale, for its antioxidant, anti-inflammatory, and antitumor activities. Ginger (Z. officinale) has been cultivated for thousands of years as a spice and for medicinal purposes in China. Tongling (Anhui province, China) has traditionally been regarded as an ideal cultivation place. "Tongling White Ginger" enjoys a reputation for being one of the top gingers in China for its thin white peel, tender flesh, rich juice, and flavor. In this study, we have isolated and identified two novel gingerdione dimers, bisgingerdiones A (1) and B (2); two new gingerol derivatives, (5R)-5-acetoxy-1,7-bis(4-hydroxy-3-methoxyphenyl)heptan-3-one (3) and methyl (Z)-neral acetal-[6]-gingerdiol (4); and 38 known compounds (5-42) from rhizomes of Zingiber officinale collected from Tongling, China. Their structures were elucidated by means of spectroscopic methods. Compounds 1-4 showed weak cytotoxic and anti-HIV-1 activities. Compounds 6, 8, and 26 showed inhibitory activities against human and mouse 11ß-HSD1 (11ß-hydroxysteroid dehydrogenases) with IC(50) values between 1.09 and 1.30 µM.