• Journal of Yeungnam Medical Science
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• 제29권2호
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• pp.77-82
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• 2012

AMP-activated protein kinase (AMPK) is an important cellular fuel sensor. Its activation requires phosphorylation at Thr-172, which resides in the activation loop of the ${\alpha}1$ and ${\alpha}2$ subunits. Several AMPK upstream kinases are capable of phosphorylating AMPK at Thr-172, including LKB1 and CaMKK${\beta}$ ($Ca^{2+}$/calmodulin-dependent protein kinase kinase${\beta}$). AMPK has been implicated in the regulation of physiological signals, such as in the inhibition of cholesterol fatty acid, and protein synthesis, and enhancement of glucose uptake and blood flow. AMPK activation also exhibits several salutary effects on the vascular function and improves vascular abnormalities. AMPK is modulated by numerous hormones and cytokines that regulate the energy balance in the whole body. These hormone and cytokines include leptin, adiponectin, ghrelin, and even thyroid hormones. Moreover, AMPK is activated by several drugs and xenobiotics. Some of these are in being clinically used to treat type 2 diabetes (e.g., metformin and thiazolidinediones), hypertension (e.g., nifedipine and losartan), and impaired blood flow (e.g., aspirin, statins, and cilostazol). I reviewed the precise mechanisms of the AMPK activation pathway and AMPK-modulating drugs.

• IMMUNE NETWORK
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• 제14권5호
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• pp.241-248
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• 2014

It is debatable whether AMP-activated protein kinase (AMPK) activation is involved in anti-apoptotic or pro-apoptotic signaling. AICAR treatment increases AMPK-${\alpha}1$ phosphorylation, decreases intracellular reactive oxygen species (ROS) levels, and significantly increases Annexin V-positive cells, DNA laddering, and caspase activity in human myeloid cell. AMPK activation is therefore implicated in apoptosis. However, AMPK-${\alpha}1$-knockdown THP-1 cells are more sensitive to apoptosis than control THP-1 cells are, suggesting that the apoptosis is AMPK-independent. Low doses of AICAR induce cell proliferation, whereas high doses of AICAR suppress cell proliferation. Moreover, these effects are significantly correlated with the downregulation of intracellular ROS, strongly suggesting that AICAR-induced apoptosis is critically associated with the inhibition of NADPH oxidase by AICAR. Collectively, our results demonstrate that in AICAR-induced apoptosis, intracellular ROS levels are far more relevant than AMPK activation.

• 약학회지
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• 제47권1호
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• pp.31-36
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• 2003

To investigate the effect of protein kinase on melanin production via cAMP-dependent pathway, we measured the melanin amount and tyrosinase activity in B16 melanoma cells stimulated by alpha-melanocyte stimulating hormone (MSH), forskolin and 8-Br-cAMP. MSH, forskolin and 8-Br-cAMP significantly increased both melanin production and tyrosinase activity in B16 cells. Melanin production and tyrosinase activity by MSH are significantly inhibited by cyclic AMP-dependent protein kinase inhibitor (KT5720) and protein kinase C down-regulation treated with PMA. Bisindolmaleimide (1$\mu$M), protein kinase C inhibitor, significantly inhibited melanin production and tyrosinase activity stimulated by MSH, forskolin and 8-Br-cAMP with the following order of potency: MSH＞forskolin＞8-Br-cAMP. Tyrosine kinase inhibitor, genistein and DHC, significantly inhibited both, but the inhibitory effect was more potent in 8-Br-cAMP-stimulated B16 cells than MSH-stimulated cells. NFkB inhibitor (parthenolide) significantly inhibited melanin production and tyrosinase activity. Neither melanin production nor tyrosinase activity induced by MSH, forskolin and 8-Br-cAMP were affected by KN-62 (calmodulin-dependent protein kinase II inhibitor), PD098059 (mitogen-activated protein kinase inhibitor, MAPKK) and worthmannin (phosphatidylinositol 3-kinase inhibitor). These results suggest that both protein kinase C and tyrosine kinase are involved in melanin production by cyclic AMP-dependent pathway and NFkB pathway may play an important role in cyclic AMP-dependent melanin production in B16 melanoma cells.

• Nutrition Research and Practice
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• 제7권1호
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• pp.15-21
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• 2013

Leaf of Sasa borealis, a species of bamboo, has been reported to exhibit anti-hyperglycemic effect. However, its antidiabetic mechanism is not fully understood. In this study, we examined whether an extract of S. borealis activates AMP-activated protein kinase (AMPK) and exerts anti-hyperglycemic effects. Treatment with the S. borealis extract increased insulin signaling and phosphorylation of AMPK and stimulated the expression of its downstream targets, including $PPAR{\alpha}$, ACO, and CPT-1 in C2C12 cells and $PPAR{\alpha}$ in HepG2 cells. However, inhibition of AMPK activation attenuated insulin signaling and prevented the stimulation of AMPK target genes. The S. borealis extract increased glucose uptake in C2C12 cells and suppressed expression of the gluconeogenic gene, PEPCK in HepG2 cells. The extract significantly reduced blood glucose and triglyceride levels in STZ-induced diabetic mice. The extract enhanced AMPK phosphorylation and increased Glut-4 expression in the skeletal muscle of the mice. These findings demonstrated that the S. borealis extract exerts its anti-hyperglycemic effect through activation of AMPK and enhancement of insulin signaling.

• Journal of Cancer Prevention
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• 제21권3호
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• pp.135-143
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• 2016

Background: Fraxetin (7,8-dihydroxy-6-methoxy coumarin), a coumarin derivative, has been reported to possess antioxidative, anti-inflammatory and neuroprotective effects. A number of recent observations suggest that the induction of heme oxygenase-1 (HO-1) inhibits inflammation and tumorigenesis. In the present study, we determined the effect of fraxetin on HO-1 expression in HaCaT human keratinocytes and investigated its underlying molecular mechanisms. Methods: Reverse transcriptase-PCR and Western blot analysis were performed to detect HO-1 mRNA and protein expression, respectively. Cell viability was measured by the MTS test. The induction of intracellular reactive oxygen species (ROS) by fraxetin was evaluated by 2′,7′-dichlorofluorescin diacetate staining. Results: Fraxetin upregulated mRNA and protein expression of HO-1. Incubation with fraxetin induced the localization of nuclear factor-erythroid-2-related factor-2 (Nrf2) in the nucleus and increased the antioxidant response element-reporter gene activity. Fraxetin also induced the phosphorylation of Akt and AMP-activated protein kinase $(AMPK){\alpha}$ and diminished the expression of phosphatase and tensin homolog, a negative regulator of Akt. Pharmacological inhibition of Akt and $AMPK{\alpha}$ abrogated fraxetin-induced expression of HO-1 and nuclear localization of Nrf2. Furthermore, fraxetin generated ROS in a concentration-dependent manner. Conclusions: Fraxetin induces HO-1 expression through activation of Akt/Nrf2 or $AMPK{\alpha}/Nrf2$ pathway in HaCaT cells.

• Tuberculosis and Respiratory Diseases
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• 제78권1호
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• pp.8-17
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• 2015

Background: AMP-activated protein kinase (AMPK) not only functions as an intracellular energy sensor and regulator, but is also a general sensor of oxidative stress. Furthermore, there is recent evidence that it participates in limiting acute inflammatory reactions, apoptosis and cellular senescence. Thus, it may oppose the development of chronic obstructive pulmonary disease. Methods: To investigate the role of AMPK in cigarette smoke-induced lung inflammation and emphysema we first compared cigarette smoking and polyinosinic-polycytidylic acid [poly(I:C)]-induced lung inflammation and emphysema in $AMPK{\alpha}1$-deficient ($AMPK{\alpha}1$-HT) mice and wild-type mice of the same genetic background. We then investigated the role of AMPK in the induction of interleukin-8 (IL-8) by cigarette smoke extract (CSE) in A549 cells. Results: Cigarette smoking and poly(I:C)-induced lung inflammation and emphysema were elevated in $AMPK{\alpha}1$-HT compared to wild-type mice. CSE increased AMPK activation in a CSE concentration- and time-dependent manner. 5-Aminoimidazole-4-carboxamide-1-${\beta}$-4-ribofuranoside (AICAR), an AMPK activator, decreased CSE-induced IL-8 production while Compound C, an AMPK inhibitor, increased it, as did pretreatment with an $AMPK{\alpha}1$-specific small interfering RNA. Conclusion: $AMPK{\alpha}1$-deficient mice have increased susceptibility to lung inflammation and emphysema when exposed to cigarette smoke, and AMPK appears to reduce lung inflammation and emphysema by lowering IL-8 production.

• 한방비만학회지
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• 제14권2호
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• pp.55-62
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• 2014

Objective: The prevalence of metabolic syndrome and type 2 diabetes is increasing worldwide. Mitochondrial dysfunction is known to be involved in insulin resistance and obesity, researches have been increasing highly. Astragali Radix extract (ARE) or its main components have been shown to perform comparably to insulin by significantly reducing blood glucose levels in animal models however, the influence on mitochondrial dysfunction are not well understood. Methods: ARE (0.2, 0.5 and 1.0 mg/ml) or metformin (2.5 mM) were treated in C2C12 after 6 day-differentiation. The expressions of adenosine monophosphate (AMP)-activated protein kinase (AMPK) and phosphorylation AMPK, peroxisome proliferators-activated receptror ${\gamma}$ coactivator $1{\alpha}$ ($PGC1{\alpha}$), nuclear respiratory factors 1 (NRF1), mitochondrial transcription factor (Tfam) and myosin heavy chain were detected with western blotting or polymerase chain reaction analysis. The morphological changes were also investigated. Results: ARE dose dependently increased phosphorylation of AMPK and respectively activated mRNA expressions of $PGC1{\alpha}$, NRF1 and Tfam which are mitochondrial biogenesis regulators. Furthermore, there were some morphologic differences of differentiated cells between ARE treatment and control. Conclusions: This study suggests that ARE has the potential to increase muscle mitochondrial function by activating AMPK and $PGC1{\alpha}$.

• 한방비만학회지
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• 제16권2호
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• pp.109-115
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• 2016

Objectives: The all anti-obesity drugs currently approved by the US Food and Drug Administration work by reducing energy intake. In fact, no approved drug targets energy expenditure. In Korean medicine, it is known to Qi or Yang invigorating therapy could increase energy metabolism. Aconitum carmichaeli Debx (ACD) is a Yang invigorating herb, often used for treat obesity in Korean medicine. In the present study, the authors investigated the regulatory effects of ACD in energy metabolism and mitochondrial biogenesis in C2C12 skeletal muscle cells. Methods: The water extract of ACD (0.2, 0.5 and 1.0 mg/ml) were treated in differentiated C2C12 cells. The protein or mRNA levels of target genes were analyzed and mitochondrial mass were investigated. Results: ACD activated the expressions of peroxisome proliferator-activated receptor gamma coactivator 1-alpha ($PGC-1{\alpha}$), nuclear respiratory factor 1 and TFAM and increased mitochondrial mass. ACD also increased adenosin monophosphate-activated protein kinase (AMPK), and acetyl-CoA carboxylase. Conclusions: This study suggests that ACD has the potential to increase energy metabolism and mitochondrial biogenesis by activating AMPK and $PGC1{\alpha}$.

• 대한수의학회지
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• 제39권6호
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• pp.1073-1080
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• 1999

Previous studies suggested that the inhibition of thyroxine ($T_4$) release by ${\alpha}_1$-adrenoceptor and muscarinic receptor stimulation results in activated protein kinase C (PKC) from mouse and guinea pig thyroids. In the present study, the effect of carbachol, methoxamine, phorbol myristate acetate (PMA), and R59022 on the release of $T_4$ from the mouse, rat, and guinea pig thyroids was compared to clarify the role of PKC in the regulation of the release of $T_4$. The thyroids were incubated in the medium containing the test agents, samples of the medium were assayed for $T_4$ by EIA kits. Forskolin, an adenylate cyclase activator, chlorophenylthio-cAMP sodium, a membrane permeable analog of cAMP, and isobutyl-methylxanthine, a phosphodiesterase inhibitor, like TSH (thyroid stimulating hormone), enhaced the release of $T_4$ from the mouse, rat, and guinea pig thyroids. Methoxamine, an ${\alpha}_1$-adrenoceptor agonist, inhibited the TSH-stimulated release of $T_4$ in mouse, but not rat and guinea pig thyroids. In contrast, carbachol, a muscarinic receptor agonist, inhibited the release of $T_4$ in guinea pig, but not mouse and rat thyroids. These inhibition were reversed by prazosin, an ${\alpha}_1$-adrenoceptor antagonist or atropine, a muscarinic antagonist or $M_1$- and $M_3$-muscarinic antagonists, in mouse or guinea pig thyroids. In addition, staurosporine, a PKC inhibitor, reversed methoxamine or carbachol inhibition of TSH stimulation. Furthermore, PMA, a PKC activator, and R59022, a diacylglycerol (DAG) kinase inhibitor, inhibited the TSH-stimulated release of $T_4$ in mouse, rat, and guinea pig thyroids. These inhibition were blocked by staurosporine. These findings suggest that the activation of receptor or DAG inhibits TSH-stimulated $T_4$ release through a PKC-dependent mechanism in thyroid gland.

• 생명과학회지
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• 제32권7호
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• pp.542-549
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• 2022

Polymethoxyflavones (PMFs)는 주로 감귤류에서 발견되는 플라보노이드로 다양한 생리활성을 나타낸다고 알려져 있다. 본 연구에서는 제주재래귤인 진귤(Citrus sunki Hort. ex Tanaka)에서 PMFs를 다량 함유하는 분획물(PMFs-rich fraction, PRF)을 획득하는 방법을 확립하여 3T3-L1 세포에서 지방대사에 미치는 영향을 분석하였다. PRF는 3T3-L1 전구지방세포의 지방생성(lipogenesis)을 농도 의존적으로 억제하였다. PRF는 peroxisome proliferator-activated receptor 𝛾 (PPAR𝛾)와 CCAAT/enhancer binding protein 𝛼 (CEBP𝛼) 발현을 억제함으로써 fatty acid synthase (FAS), adipocyte fatty-acid-binding protein 2 (aP2)의 발현을 억제하여 지방생성을 억제함을 확인할 수 있었다. 성숙한 3T3-L1 지방세포에 PRF를 처리하면, cAMP 의존성 protein kinase A (PKA)/sterol regulatory element-binding protein 1 (HSL)의 활성화가 일어나 지방분해(lipogenesis)는 촉진됨을 확인할 수 있었다. 그리고 PRF는 AMP-activated protein kinase (AMPK)/acetyl-CoA carboxylase (ACC)의 인산화를 증가시켜 지방산화를 촉진할 수 있음을 확인하였다. 이 연구결과는 진귤 잎 유래 PRF는 3T3-L1 전구지방세포의 분화를 억제하고 성숙한 지방세포에서 지방분해 및 지방산 산화를 촉진하는 활성을 나타내어 항비만 소재로서의 활용가능성을 제시하였다.