• Journal of Ginseng Research
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• v.46 no.3
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• pp.444-453
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• 2022

Background: Compound K (CK) is among the protopanaxadiol (PPD)-type ginsenoside group, which produces multiple pharmacological effects. Herein, we examined the effects of CK on muscle atrophy under hyperlipidemic conditions along with its pro-myogenic effects. Further, the molecular pathways underlying the effects of CK on skeletal muscle have been justified. Methods: C2C12 myotubes were treated with palmitate and CK. C2C12 myoblasts were differentiated using CK for 4-5 days. For the in vivo experiments, CK was administered to mice fed on a high-fat diet for 8 weeks. The protein expression levels were analyzed using western blotting analysis. Target protein suppression was performed using small interfering (si) RNA transfection. Histological examination was performed using Jenner-Giemsa and H&E staining techniques. Results: CK treatment attenuated ER stress markers, such as eIF2a phosphorylation and CHOP expression and impaired myotube formation in palmitate-treated C2C12 myotubes and skeletal muscle of mice fed on HFD. CK treatment augmented AMPK along with autophagy markers in skeletal muscle cells in vitro and in vivo experiments. AMPK siRNA or 3-MA, an autophagy inhibitor, abrogated the impacts of CK in C2C12 myotubes. CK treatment augmented p38 and Akt phosphorylation, leading to an enhancement of C2C12 myogenesis. However, AMPK siRNA abolished the effects of CK in C2C12 myoblasts. Conclusion: These findings denote that CK prevents lipid-induced skeletal muscle apoptosis via AMPK/autophagy-mediated attenuation of ER stress and induction of myoblast differentiation. Therefore, we may suggest the use of CK as a potential therapeutic approach for treating muscle-wasting conditions associated with obesity.

• Molecules and Cells
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• v.39 no.3
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• pp.195-203
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• 2016

Copper is an essential element required for a variety of functions exerted by cuproproteins. An alteration of the copper level is associated with multiple pathological conditions including chronic ischemia, atherosclerosis and cancers. Therefore, copper homeostasis, maintained by a combination of two copper ions ($Cu^+$ and $Cu^{2+}$), is critical for health. However, less is known about which of the two copper ions is more toxic or functional in endothelial cells. Cubic-shaped $Cu_2O$ and CuO crystals were prepared to test the role of the two different ions, $Cu^+$ and $Cu^{2+}$, respectively. The $Cu_2O$ crystal was found to have an effect on cell death in endothelial cells whereas CuO had no effect. The $Cu_2O$ crystals appeared to induce p62 degradation, LC3 processing and an elevation of LC3 puncta, important processes for autophagy, but had no effect on apoptosis and necrosis. $Cu_2O$ crystals promote endothelial cell death via autophagy, elevate the level of reactive oxygen species such as superoxide and nitric oxide, and subsequently activate AMP-activated protein kinase (AMPK) through superoxide rather than nitric oxide. Consistently, the AMPK inhibitor Compound C was found to inhibit $Cu_2O$-induced AMPK activation, p62 degradation, and LC3 processing. This study provides insight on the pathophysiologic function of $Cu^+$ ions in the vascular system, where $Cu^+$ induces autophagy while $Cu^{2+}$ has no detected effect.

• Biomolecules & Therapeutics
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• v.27 no.2
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• pp.178-184
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• 2019

Parkinson's disease is a neurodegenerative disease characterized by the progressive loss of dopaminergic neurons within the substantia nigra pars compacta. In the present study, we investigated whether ${\beta}-Lapachone$ (${\beta}-LAP$), a natural naphthoquinone compound isolated from the lapacho tree (Tabebuia avellanedae), elicits neuroprotective effects in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease mouse model. ${\beta}-LAP$ reduced the tyrosine hydroxylase (TH)-immunoreactive fiber loss induced by MPTP in the dorsolateral striatum, and alleviated motor dysfunction as determined by the rotarod test. In addition, ${\beta}-LAP$ protected against MPTP-induced loss of TH positive neurons, and upregulated B-cell lymphoma 2 protein (Bcl-2) expression in the substantia nigra. Based on previous reports on the neuroprotective role of nuclear factor-E2-related factor-2 (Nrf2) in neurodegenerative diseases, we investigated whether ${\beta}-LAP$ induces upregulation of the Nrf2-hemeoxygenae-1 (HO-1) signaling pathway molecules in MPTP-injected mouse brains. Western blot and immunohistochemical analyses indicated that ${\beta}-LAP$ increased HO-1 expression in glial fibrillary acidic protein-positive astrocytes. Moreover, ${\beta}-LAP$ increased the nuclear translocation and DNA binding activity of Nrf2, and the phosphorylation of upstream adenosine monophosphate-activated protein kinase (AMPK). ${\beta}-LAP$ also increased the localization of p-AMPK and Nrf2 in astrocytes. Collectively, our data suggest that ${\beta}-LAP$ exerts neuroprotective effect in MPTP-injected mice by upregulating the p-AMPK/Nrf2/HO-1 signaling pathways in astrocytes.

• Natural Product Sciences
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• v.23 no.1
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• pp.21-28
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• 2017

In our program to search for new AMP-activated protein kinase (AMPK) activators from plants that exert potential anticancer property, we found that an EtOAc extract of Myristica fragrans (nutmeg) activated AMPK enzyme in human breast cancer MCF-7 cells. Two major diarylbutane-type lignans, macelignan and meso-dihydroguaiaretic acid (MDGA), were isolated as active principles from this extract. Treatment of breast cancer cells with two compounds induced cellular apoptosis, evidenced by cleavage of poly-(ADP-ribose) polymerase (PARP) and Ser 15 phosphorylation of p53. Moreover, macelignan and MDGA significantly inhibited the colony formation of MCF-7 breast cancer cells on soft agar. Intraperitoneal injection of macelignan and MDGA (20 mg/kg) suppressed the tumor growth of 4T1 mammary cancer cells. These results indicate that the chemopreventive effects of two major diarylbutane-type lignans from Myristica fragrans (nutmeg) may be associated with induction of apoptosis presumably through AMPK activation.

• Molecular & Cellular Toxicology
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• v.4 no.3
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• pp.224-229
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• 2008

Eucommia ulmoides (Duchung) is commonly used for treatment of diabetes in Korean traditional medicine. However, the exact mechanism of its anti-diabetic effect has not yet been fully elucidated. In this study, the effect of E. ulmoides extract on glucose uptake was investigated in L6 rat skeletal muscle cells. E. ulmoides extract stimulated the activity of phosphatidylinositol (PI) 3-kinase that is a major regulatory molecule in glucose uptake pathway. Protein kinase B (PKB) and protein kinase C-${\xi}$ (PKC-${\xi}$), downstream mediators of PI 3-kinase, were also activated by E. ulmoides extract. We assessed the activity of AMP-activated protein kinase (AMPK), another regulatory molecule in glucose uptake pathway. Phosphorylation level of AMPK did not change with treatment of E. ulmoides extract. Phosphorylations of p38 mitogen activated protein kinase (p38 MAPK) and acetyl-CoA carboxylase (ACC), downstream mediators of AMPK, were not significantly different. Taken together, our results suggest that E. ulmoides may stimulate glucose uptake through PI 3-kinase but not AMPK in L6 skeletal muscle cells.

• Biomolecules & Therapeutics
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• v.24 no.6
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• pp.581-588
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• 2016

Lonchocarpine is a phenylpropanoid compound isolated from Abrus precatorius that has anti-bacterial, anti-inflammatory, antiproliferative, and antiepileptic activities. In the present study, we investigated the antioxidant effects of lonchocarpine in brain glial cells and analyzed its molecular mechanisms. We found that lonchocarpine suppressed reactive oxygen species (ROS) production and cell death in hydrogen peroxide-treated primary astrocytes. In addition, lonchocarpine increased the expression of anti-oxidant enzymes, such as heme oxygenase-1 (HO-1), NAD(P)H:quinone oxidoreductase 1 (NQO1), and manganese superoxide dismutase (MnSOD), which are all under the control of Nrf2/antioxidant response element (ARE) signaling. Further, mechanistic studies showed that lonchocarpine increases the nuclear translocation and DNA binding of Nrf2 to ARE as well as ARE-mediated transcriptional activities. Moreover, lonchocarpine increased the phosphorylation of AMP-activated protein kinase (AMPK) and three types of mitogen-activated protein kinases (MAPKs). By treating astrocytes with each signaling pathway-specific inhibitor, AMPK, c-jun N-terminal protein kinase (JNK), and p38 MAPK were identified to be involved in lonchocarpine-induced HO-1 expression and ARE-mediated transcriptional activities. Therefore, lonchocarpine may be a potential therapeutic agent for neurode-generative diseases that are associated with oxidative stress.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2023.04a
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• pp.46-46
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• 2023

It has been reported that Rosa acicularis has anti-obesity activity by inhibiting the digestive lipase activity. However, there is a lack of clear in vitro studies regarding the anti-obesity activity of Rosa acicularis. Therefore, in this study, we aimed to verify the anti-obesity activity of Rosa acicularis leaves (RAL) and elucidate its mechanism of action in 3T3-L1 preadipocytes. RAL dose-dependently inhibited the accumulation of lipid droplets and triacylglycerol. RAL had no effect on cell proliferation and survival in undifferentiated 3T3-L1 cells, but it inhibited cell proliferation in differentiating 3T3-L1 cells. RAL increased ATGL, p-HSL, and HSL, and decreased perilipin-1 in differentiating 3T3-L1 cells. In addition, RAL reduced lipid droplet accumulation and increased free glycerol content in differentiated 3T3-L1 cells. RAL increased ATGL and HSL in differentiated 3T3-L1 cells. Also, RAL increased p-AMPK, PPARγ, UCP-1, and PGC-1α in differentiating 3T3-L1 cells. AMPK inhibition by Compound C attenuated RAL-mediated increase of ATGL, HSL, PPARγ, and UCP-1 in 3T3-L1 cells. Taken together, it is thought that RAL may inhibit lipid accumulation through lipolysis and thermogenesis via the activation of AMPK in adipocytes.

• Journal of Life Science
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• v.19 no.5
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• pp.644-651
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• 2009

The objective of this study was to identify EXE (1 hr a day at 21 m/min for 5 day/wk, at 0 % grade for 6 wk) on myocardium glucose metabolic phenotypic proteins (AMPK-PGC-1${\alpha}$-GLUT-4) and HSP-60 protein expression after ischemia/reperfusion injury (IRI) in STZ-induced rats. EXE was performed using STZ-induced diabetic rats on a rodent treadmill (28 m/min, 1 hr/day, 5 day/wk for 6 wk). The results of this study suggest that i) serum insulin level was not changed among groups (p>l0.05). ii) the LVDP level increased significantly in the STZ-EXE-IRI group compared to the STZ-IRI group at 60 min (p<0.01), 70 min (p<0.05) and 80 min (p<0.05) after reperfusion, respectively, and iii) AMPK phosphorylation (p<0.01), PGC-1${\alpha}$ protein (p<0.001), GLUT-4 protein (p<0.001) and HSP-60 protein expressions (p<0.05) increased significantly in the STZ-EXE-IRI group compared to the STZ-IRI group. In conclusion, the findings of the present study reveal that EXE may provide therapeutic value to insulin dependent diabetic patients with peripheral insulin resistance and myocardium injury by improving glucose metabolic proteins (AMPK-PGC-1${\alpha}$-GLUT-4) and heat shock protein-60 (HSP-60), along with increasing LVDP levels and decreasing glucose levels. Therefore, EXE protects the STZ-induced diabetic myocardium injury against ischemia/ reperfusion injury.

• Biomolecules & Therapeutics
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• v.29 no.6
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• pp.615-629
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• 2021

An active compound, triterpene saponin, astersaponin I (AKNS-2) was isolated from Aster koraiensis Nakai (AKNS) and the autophagy activation and neuroprotective effect was investigated on in vitro and in vivo Parkinson's disease (PD) models. The autophagy-regulating effect of AKNS-2 was monitored by analyzing the expression of autophagy-related protein markers in SH-SY5Y cells using Western blot and fluorescent protein quenching assays. The neuroprotection of AKNS-2 was tested by using a 1-methyl-4-phenyl-2,3-dihydropyridium ion (MPP⁺)-induced in vitro PD model in SH-SY5Y cells and an MPTP-induced in vivo PD model in mice. The compound-treated SH-SY5Y cells not only showed enhanced microtubule-associated protein 1A/1B-light chain 3-II (LC3-II) and decreased sequestosome 1 (p62) expression but also showed increased phosphorylated extracellular signal-regulated kinases (p-Erk), phosphorylated AMP-activated protein kinase (p-AMPK) and phosphorylated unc-51-like kinase (p-ULK) and decreased phosphorylated mammalian target of rapamycin (p-mTOR) expression. AKNS-2-activated autophagy could be inhibited by the Erk inhibitor U0126 and by AMPK siRNA. In the MPP⁺-induced in vitro PD model, AKNS-2 reversed the reduced cell viability and tyrosine hydroxylase (TH) levels and reduced the induced α-synuclein level. In an MPTP-induced in vivo PD model, AKNS-2 improved mice behavioral performance, and it restored dopamine synthesis and TH and α-synuclein expression in mouse brain tissues. Consistently, AKNS-2 also modulated the expressions of autophagy related markers in mouse brain tissue. Thus, AKNS-2 upregulates autophagy by activating the Erk/mTOR and AMPK/mTOR pathways. AKNS-2 exerts its neuroprotective effect through autophagy activation and may serve as a potential candidate for PD therapy.

• Journal of Life Science
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• v.27 no.2
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• pp.155-163
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• 2017

Mori Folium, the leaf of Morus alba, is a traditional medicinal herb that shows various pharmacological activities such as antiinflammatory, antidiabetic, antimelanogenesis, antioxidant, antibacterial, antiallergic, and immunomodulatory activities. However, the mechanisms of their inhibitory effects on adipocyte differentiation and adipogenesis remain poorly understood. In the present study, we investigated the inhibition of adipocyte differentiation and adipogenesis by ethanol extracts of Mori Folium (EEMF) in 3T3-L1 preadipocytes. Treatment with EEMF suppressed the terminal differentiation of 3T3-L1 preadipocytes in a dose-dependent manner, as confirmed by a decrease in the lipid droplet number and lipid content through Oil Red O staining. EEMF significantly reduced the accumulation of cellular triglyceride, which is associated with a significant inhibition of pro-adipogenic transcription factors, including sterol regulatory element-binding protein-1c (SREBP-1c), peroxisome proliferator-activated receptor-${\gamma}$ ($PPAR{\gamma}$), and CCAAT/enhancer-binding proteins ${\alpha}$ ($C/EBP{\alpha}$) and ${\beta}$ ($C/EBP{\beta}$). In addition, EEMF potentially downregulated the expression of adipocyte-specific genes, including adipocyte fatty acid binding protein (aP2) and leptin. Furthermore, EEMF treatment effectively increased the phosphorylation of the AMP-activated protein kinase (AMPK) and acetyl CoA carboxylase (ACC); however, treatment with a potent inhibitor of AMPK, compound C, significantly restored the EEMF-induced inhibition of pro-adipogenic transcription factors and adipocyte-specific genes. These results together indicate that EEMF has preeminent effects on the inhibition of adipogenesis through the AMPK signaling pathway, and further studies will be needed to identify the active compounds in Mori Folium.