AMP-activated Protein Kinase Α1 Research Articles

Puerariae Lobatae radix flavonoids and puerarin alleviate alcoholic liver injury in zebrafish by regulating alcohol and lipid metabolism

Exessive drinking is commonly associated with a wide spectrum of liver injuries. The term alcoholic liver disease (ALD) is generally used to refer to this spectrum of hepatic abnormalities, and the term hepatic steatosis denotes early lesions. Puerariae Lobatae Radix (PLR) is a common traditional Chinese medicine and has been widely used as an efficient treatment for alcohol-induced damage. Flavonoids are the principal components of PLR that could potentially be responsible for the activation of alcohol metabolism and lipid-lowering effects. However, little is known about the mechanisms underlying their activity against alcoholic injury. In this study, PLR flavonoids (PLF) were obtained by microwave extraction. A 2% ethanol solution was used to establish a model of alcoholic fatty liver disease by exposure of zebrafish larvae for 32 h, and then the zebrafish were administered PLF and puerarin. The results showed that PLF and puerarin significantly decreased lipid accumulation and the levels of total cholesterol and triglycerides in zebrafish larvae. Moreover, PLF and puerarin downregulated the expression of genes related to alcohol and lipid metabolism (CYP2y3, CYP3a65, ADH8a, ADH8b, HMGCRB, and FASN), endoplasmic reticulum stress, and DNA damage (CHOP, EDEM1, GADD45αa, and ATF6) and reduced levels of inflammatory factors (IL-1β, TNF-α) in zebrafish larvae. PLF and puerarin increased the phosphorylation of AMP-activated protein kinase-α (AMPKα) and decreased the total protein level of ACC1. The findings suggested that PLF and puerarin alleviated alcohol-induced hepatic steatosis in zebrafish larvae by regulating alcohol and lipid metabolism, which was closely related to the regulation of the AMPKα-ACC signaling pathway. In conclusion, the study provided a possible therapeutic drug for ALD treatment.

AMP-activated protein kinase (AMPK) signaling in GnRH neurons links energy status and reproduction

BackgroundReproduction is tightly coupled to body energy and metabolic status. GnRH neurons, master elements and final output pathway for the brain control of reproduction, directly or indirectly receive and integrate multiple metabolic cues to regulate reproductive function. Yet, the molecular underpinnings of such phenomenon remain largely unfolded. AMP-activated protein kinase (AMPK), the fundamental cellular sensor that becomes activated in conditions of energy deficit, has been recently shown to participate in the control of Kiss1 neurons, essential gatekeepers of the reproductive axis, by driving an inhibitory valence in situations of energy scarcity at puberty. However, the contribution of AMPK signaling specifically in GnRH neurons to the metabolic control of reproduction remains unknown. MethodsDouble immunohistochemistry (IHC) was applied to evaluate expression of active (phosphorylated) AMPK in GnRH neurons and a novel mouse line, named GAMKO, with conditional ablation of the AMPK α1 subunit in GnRH neurons, was generated. GAMKO mice of both sexes were subjected to reproductive characterization, with attention to puberty and gonadotropic responses to kisspeptin and metabolic stress. ResultsA vast majority (>95%) of GnRH neurons co-expressed pAMPK. Female (but not male) GAMKO mice displayed earlier puberty onset and exaggerated LH (as surrogate marker of GnRH) responses to kisspeptin-10 at the prepubertal age. In adulthood, GAMKO females retained increased LH responsiveness to kisspeptin and showed partial resilience to the inhibitory effects of conditions of negative energy balance on the gonadotropic axis. The modulatory role of AMPK in GnRH neurons required preserved ovarian function, since the differences in LH pulsatility detected between GAMKO and control mice subjected to fasting were abolished in ovariectomized animals. ConclusionsAltogether, our data document a sex-biased, physiological role of AMPK signaling in GnRH neurons, as molecular conduit of the inhibitory actions of conditions of energy deficit on the female reproductive axis.

AMPK upregulates KCa2.3 channels and ameliorates endothelial dysfunction in diet-induced obese mice

The opening of endothelial small-conductance calcium-activated potassium channels (KCa2.3) is essential for endothelium-dependent hyperpolarization (EDH), which predominantly occurs in small resistance arteries. Adenosine monophosphate-activated protein kinase (AMPK), an important metabolic regulator, has been implicated in regulating endothelial nitric oxide synthase activity. However, it was unclear whether AMPK regulated endothelial KCa2.3-mediated EDH-type vasodilation. Using bioinformatics analysis and myograph system, we investigated the regulation by AMPK of KCa2.3 in human umbilical vein endothelial cells (HUVECs) or mouse second-order mesenteric resistance arteries. In HUVECs, AMPK activation either by activators (AICAR, A769662 and MK-8722) or expression of the constitutively active form of AMPK significantly upregulated KCa2.3 expression. Such effects were abolished by AMPK inhibitor (compound C) or AMPK α1-/α2-siRNA, extracellular-signal-regulated-kinase 5 (ERK5) inhibitor (ERK5-IN-1), and specific siRNA to myocyte-enhancer factor 2 (MEF2) or krüppel-like factor 2/4 (KLF2/4). KCa2.3 expression was significantly reduced in mesenteric resistance arteries in AMPKα2 knockout mice when compared with littermate control mice. Furthermore, in high-fat diet fed mice, 2-week treatment with AICAR restored endothelial KCa2.3 expression in mesenteric resistance arteries with improved endothelial dysfunction. Our results demonstrate that activation of AMPK upregulates KCa2.3 channel expression through the ERK5–MEF2–KLF2/4 signaling pathway in vascular endothelium, which contributes to benefits through KCa2.3-mediated EDH-type vasodilation in mesenteric resistance arteries.

Activation of AMP-activated protein kinase signaling pathway ameliorates steatosis in laying hen hepatocytes

The fatty liver hemorrhage syndrome in laying hens is a disease of lipid metabolism disorders. Importantly, energy sensor AMP-activated protein kinase (AMPK) plays an essential role in homeostasis regulation of liver lipid. The current research aims to investigate the relationship between AMPK signaling pathway and lipid metabolism in laying hen hepatocytes and explore the underlying mechanisms. The steatotic hepatocytes model of laying hen was established and treated with AMPK agonist AICAR and inhibitor compound C. The results showed that the levels of triglyceride, total cholesterol, and low-density lipoprotein cholesterol significantly declined while high-density lipoprotein cholesterol level increased in the AICAR-treated steatosis group compared with the steatosis group. Furthermore, the mRNA levels of liver kinase B1 and AMP-activated protein kinase α1 declined significantly in the steatosis group compared with those in the normal group. However, AMPK activation significantly upregulated the mRNA levels of peroxisome proliferator-activated receptor α and carnitine palmitoyl transferase-1 while downregulated the mRNA levels of acetyl CoA carboxylase, fatty acid synthase, 3-hydroxy-3-methyl glutaryl coenzyme A reductase, Sn-glycerol-3-phosphate acyltransferase, and hepatocyte nuclear factor 4α. These results suggest that activated AMPK signaling pathway increases fatty acid oxidation and reduces lipid synthesis in laying hen hepatocytes, thereby ameliorating liver steatosis.

Lipid deposition in abalone Haliotis discus hannai affected by dietary lipid levels through AMPKα2/PPARα and JNK/mTOR/SREBP-1c pathway

A 100-day feeding trial was conducted to investigate the effects of dietary lipid on growth performance and lipid deposition as well as the regulation mechanism in abalone Haliotis discus hannai Ino. Abalones (initial weight: 10.98 ± 0.05 g) were fed with graded levels of dietary lipid (1.57%, 2.34%, 3.17%, 3.82%, 4.63%, 5.56%, 6.17% and 6.72%). Results showed that weight gain rate (WGR) and increment in shell length of abalone were highest in 3.82% dietary lipid level. Based on the quadratic regression analysis for WGR, the optimal dietary lipid level for abalone was estimated to be 3.87%. Concentrations of the total triacylglycerol, low-density lipoprotein cholesterol and non-esterified fatty acids in serum as well as lipid contents in hepatopancreas and muscle were positively related to dietary lipid levels. Compared to the group with 3.82% of dietary lipid, higher (6.72%) and lower (1.57%) dietary lipid down regulated the expression of genes involved in fatty acids transport and lipolysis in hepatopancreas and muscle, which might be related to AMP-activated protein kinase α2 (AMPKα2)/peroxisome proliferator-activated receptor α (PPARα) signaling. Higher dietary lipid (6.72%) down regulated, while lower dietary lipid (1.57%) up-regulated the expressions of genes involved in de-novo lipogenesis in hepatopancreas. Both higher (6.72%) and lower (1.57%) dietary lipid down regulated these genes' expression in muscle. It was found that c-Jun N-terminal kinases (JNK)/mammalian target of rapamycin (mTOR)/sterol regulatory element-binding protein 1c (SREBP-1c) signaling participate in the regulation of de-novo lipogenesis. In conclusion, lipid deposition in abalone was affected by dietary lipid levels through AMPKα2/PPARα and JNK/mTOR/SREBP-1c pathway.

Effects of Different Exercise Interventions on Cardiac Function in Rats With Myocardial Infarction

High-intensity interval training (HIIT) and aerobic training (AT) both improve cardiac function; however, their effects on cardiac function after myocardial infarction (MI) and the molecular mechanisms are unclear. In this study, HIIT, AT and sedentary (SED) interventions were performed for 4 weeks to compare the effects on cardiac function after MI and explore a more suitable approach for clinical application and the potential mechanisms. Twenty-four (24) male rats were randomly divided into a control group (CON), MI-sedentary group (MI-SED), MI-aerobic training group (MI-AT), and MI-high-intensity interval training group (MI-HIIT). After 4 weeks of intervention the exercise capacity, heart rate (HR), left ventricular end-diastolic diameter (LVEDD), left ventricular end systolic diameter (LVESD), left ventricular ejection fraction (LVEF), AMP-activated protein kinase α1 (AMPKα1), cardiomyocyte morphology, and cardiac mitochondria were assessed. After intervention: 1) exercise capacity in the MI-AT (49.08±3.141 m; p<0.001) and MI-HIIT (51.70±7.572m; p<0.001) groups was significantly more increased than the MI-SED group; there was no significant difference between the MI-AT and MI-HIIT group (p=0.33). 2) LVEDD and LVESD in the MI-SED (p<0.01) and MI-HIIT (p<0.01) groups was significantly more increased than the CON group; the MI-AT group showed no significant difference in LVEDD and LVESD compared with the CON group; LVEF in the MI-AT (53.47±7.913%; p=0.03) and MI-HIIT (56.20±7.224%; p=0.006) groups was significantly more increased than the MI-SED group, and there was no statistical difference between the MI-AT and MI-HIIT groups. 3) AMPKα1 expression was significantly increased in the MI-AT (1.15±0.264; p=0.001) and MI-HIIT (1.04±0.238; p=0.003) groups and decreased in the MI-SED group (0.71±0.257; p<0.001) when compared with the CON group. 4) The MI-SED group exhibited sarcoplasmic dissolution and fibrous hyperplasia in the myocardium, cardiac mitochondrial damage and reduced mitochondrial numbers; the MI-HIIT group displayed swollen and vacuolated cardiac mitochondria with disrupted cristae; the MI-AT and MI-HIIT groups had significantly increased cardiac mitochondrial numbers than the MI-SED group; there was no statistical difference between the MI-AT and MI-HIIT groups. Aerobic training and HIIT for 4 weeks had similar cardioprotection and were superior to SED intervention. Both AT and HIIT improved cardiac function and exercise capacity by upregulating AMPKα1 expression. However, 4 weeks of intervention resulted in left ventricular dilation and cardiac myocardial mitochondrial injury in the MI-HIIT group.

Icariin ameliorates endothelial dysfunction in type 1 diabetic rats by suppressing ER stress viathe PPARα/Sirt1/AMPKα pathway.

Icariin (ICA), as a flavonoid glycoside, is associated with the improvement of vascular complications in diabetes. However, its protective mechanisms remain to be well-established. Here, we testedthe hypothesis that ICA attenuates vascular endothelial dysfunction by inhibiting endoplasmic reticulum (ER) stress in type 1 diabetes. In streptozotocin-induced diabetic rats, ICA positively affected acetylcholine-induced vasodilation and phenylephrine-induced vasoconstriction in aortas. ICA treatment significantly attenuated ER stress in diabetic rats and high-glucose induced human umbilical vein endothelial cells. Incubation with ICA in vitro attenuated vascular reactivity in diabetic rats, which was blocked by the ER stress inducer, and peroxisome proliferator-activated receptor α (PPARα), sirtuin1 (Sirt1), or AMP-activated protein kinase-α (AMPKα) inhibitors. Western blot showed that ICA activated the PPARα/Sirt1/AMPKα pathway, which contributed to reducing ER stress and activating endothelial nitric oxide synthase in vivo and vitro. Our results implicate that ICA normalizes ER stress to attenuate endothelial dysfunction by the regulation of the PPARα/Sirt1/AMPKα pathway.

Systemic inhibition of miR-451 increases fibrotic signaling and diminishes autophagic response to exacerbate renal damage in Tallyho/Jng mice.

miRNAs provide fine tuning of gene expression via inhibition of translation. miR-451 has a modulatory role in cell cycling via downregulation of mechanistic target of rapamycin. We aimed to test whether chronic systemic inhibition of miR-451 would enhance renal fibrosis (associated with deranged autophagy). Adult TallyHo/Jng mice (obese insulin resistant) were randomized to two treatment groups to receive either miR-451 inhibition [via a locked nucleic acid construct] or a similar scrambled locked nucleic acid control for 8 wk. All mice were fed a high-fat diet (60% kcal from fat) ad libitum and humanely euthanized after 12 wk. Kidneys and blood were collected for analysis. Renal expression of miR-451 was sixfold lower in inhibitor-treated mice compared with control mice. miR-451 inhibition increased kidney weight and collagen and glycogen deposition. Blood chemistry revealed significantly higher Na+ and anion gap (relative metabolic acidosis) in inhibitor-treated mice. Western blot analysis and immunohistochemistry of the kidney revealed that the inhibitor increased markers of renal injury and fibrosis, e.g., kidney injury molecule 1, neutrophil gelatinase-associated lipocalin, transforming growth factor-β, 14-3-3 protein-ζ, mechanistic target of rapamycin, AMP-activated protein kinase-α, calcium-binding protein 39, matrix metallopeptidase-9, and the autophagy receptor sequestosome 1. In contrast, the inhibitor reduced the epithelial cell integrity marker collagen type IV and the autophagy markers microtubule-associated protein 1A/1B light chain 3B and beclin-1. Taken together, these results support a protective role for miR-451 in reducing renal fibrosis by enhancing autophagy in obese mice.

Skeletal muscle AMPK is not activated during 2h of moderate intensity exercise at ∼65% in endurance trained men.

Key points AMP‐activated protein kinase (AMPK) is considered a major regulator of skeletal muscle metabolism during exercise.However, we previously showed that, although AMPK activity increases by 8–10‐fold during ∼120 min of exercise at ∼65% V˙O2peak in untrained individuals, there is no increase in these individuals after only 10 days of exercise training (longitudinal study).In a cross‐sectional study, we show that there is also a lack of activation of skeletal muscle AMPK during 120 min of cycling exercise at 65% V˙O2peak in endurance‐trained individuals.These findings indicate that AMPK is not an important regulator of exercise metabolism during 120 min of exercise at 65% V˙O2peak in endurance trained men.It is important that more energy is directed towards examining other potential regulators of exercise metabolism. AMP‐activated protein kinase (AMPK) is considered a major regulator of skeletal muscle metabolism during exercise. Indeed, AMPK is activated during exercise and activation of AMPK by 5‐aminoimidazole‐4‐carboxyamide‐ribonucleoside (AICAR) increases skeletal muscle glucose uptake and fat oxidation. However, we have previously shown that, although AMPK activity increases by 8–10‐fold during ∼120 min of exercise at ∼65% V˙O2peak in untrained individuals, there is no increase in these individuals after only 10 days of exercise training (longitudinal study). In a cross‐sectional study, we examined whether there is also a lack of activation of skeletal muscle AMPK during 120 min of cycling exercise at 65% V˙O2peak in endurance‐trained individuals. Eleven untrained (UT; V˙O2peak = 37.9 ± 5.6 ml.kg−1 min−1) and seven endurance trained (ET; V˙O2peak = 61.8 ± 2.2 ml.kg−1 min−1) males completed 120 min of cycling exercise at 66 ± 4% V˙O2peak (UT: 100 ± 21 W; ET: 190 ± 15 W). Muscle biopsies were obtained at rest and following 30 and 120 min of exercise. Muscle glycogen was significantly (P < 0.05) higher before exercise in ET and decreased similarly during exercise in the ET and UT individuals. Exercise significantly increased calculated skeletal muscle free AMP content and more so in the UT individuals. Exercise significantly (P < 0.05) increased skeletal muscle AMPK α2 activity (4‐fold), AMPK αThr172 phosphorylation (2‐fold) and ACCβ Ser222 phosphorylation (2‐fold) in the UT individuals but not in the ET individuals. These findings indicate that AMPK is not an important regulator of exercise metabolism during 120 min of exercise at 65% V˙O2peak in endurance trained men.

Gain-of-function genetic screen of the kinome reveals BRSK2 as an inhibitor of the NRF2 transcription factor.

Nuclear factor erythroid 2-related factor 2 (NFE2L2, also known as NRF2) is a transcription factor and master regulator of cellular antioxidant response. Aberrantly high NRF2-dependent transcription is recurrent in human cancer, but conversely NRF2 activity diminishes with age and in neurodegenerative and metabolic disorders. Although NRF2-activating drugs are clinically beneficial, NRF2 inhibitors do not yet exist. Here, we describe use of a gain-of-function genetic screen of the kinome to identify new druggable regulators of NRF2 signaling. We found that the under-studied protein kinase brain-specific kinase 2 (BRSK2) and the related BRSK1 kinases suppress NRF2-dependent transcription and NRF2 protein levels in an activity-dependent manner. Integrated phosphoproteomics and RNAseq studies revealed that BRSK2 drives 5'-AMP-activated protein kinase α2 (AMPK) signaling and suppresses the mTOR pathway. As a result, BRSK2 kinase activation suppresses ribosome-RNA complexes, global protein synthesis and NRF2 protein levels. Collectively, our data illuminate the BRSK2 and BRSK1 kinases, in part by functionally connecting them to NRF2 signaling and mTOR. This signaling axis might prove useful for therapeutically targeting NRF2 in human disease.This article has an associated First Person interview with the first author of the paper.

Modulating lipid and glucose metabolism by glycosylated kaempferol rich roasted leaves of Lycium chinense via upregulating adiponectin and AMPK activation in obese mice-induced type 2 diabetes

• Roasted leaves of Lycium chinense (rLF) enhanced glycosylated kaempferol. • rLF decreased leptin and sterol response element-binding protein 1c expression. • rLF upregulated activity of adiponectin and AMP-activated protein kinase α. • It is a potential ingredient to prevent obese-induced type 2 diabetes damages. The aim of the study was to elucidate the protective action of roasted Lycium chinense (rLF) enhanced kaempferol glycosides as bioactive components from obese-induced type 2 diabetes mice by investigating the histopathological, biochemical, and transcriptional analyses in blood, liver, and adipose tissue. The rLF extract significantly decreased the hypertrophy of fat deposition, pancreatic hyperplasia, hyperinsulinemia, hepatocellular steatosis, and nephropathy in a dose dependent manner ( p < 0.01). However, rLF increased the expression of adiponectin while decreased leptin and sterol response element-binding protein 1c (SREBP1c) expression. rLF also upregulated the expression of AMP-activated protein kinase α1 (AMPKα1) and AMPKα2. The results from this study suggested that rLF extract could be an effective ingredient to prevent obese-induced type 2 diabetes damages by enhancing both adiponectin-induced signaling and AMPK activity in the liver.

AMP-activated protein kinase in the grass carp Ctenopharyngodon idellus: Molecular characterization, tissue distribution and mRNA expression in response to overwinter starvation stress.

Adenosine monophosphate-activated protein kinase (AMPK) is the main energy sensor in mammals, but limited information is available regarding its role as an energy sensor in nutrient-restricted fish particularly in period of overwinter starvation. The present study aimed to investigate the role of AMPK in the grass carp Ctenopharyngodon idellus through characterization of AMPK full-length cDNAs and the measurement of transcriptional activity in response to overwinter starvation. AMPK is a heterotrimeric serine/threonine kinase that consists of a catalytic alpha (α) subunit complexed with two regulatory subunits, beta (β) and gamma (γ). In our study, we identified nine isoforms of the AMPK family in grass carp and obtained their complete coding sequences (CDS). In the grass carp, the α subunit is encoded by two isoforms (α1 and α2). The β and γ subunits are encoded by three (β1a, β1b, β2) and four isoforms (γ1, γ2a, γ2b, γ3), respectively. AMPK isoforms in grass carp possess structural features similar to mammalian AMPK and exhibit a high degree of homology with other fish and vertebrate AMPK sequences. The mRNA of nine grass carp AMPK isoforms were found to be expressed in a wide range of tissues in vivo, but the abundance of each AMPK mRNA demonstrated a tissue-dependent expression pattern, indicating that they might be key complexes playing the role of energy metabolism sensors during overwinter starvation conditions. Compared to expression levels in control fish (week 0), the expression of various AMPK isoforms significantly increased in the hepatopancreas of fish exposed to 1week or more of overwinter starvation conditions as follows: week 1 (AMPK α1 and AMPK α2), week8 (AMPK β1b and AMPK γ2b), week 12 (AMPK β2 and AMPK γ1), and week 16 (AMPK β1a, AMPK γ2a, and AMPK γ3). Additionally, compared to expression levels in control fish (week 0), the expression of various AMPK isoforms significantly increased in the adipose tissue of fish exposed to 1week or more of overwinter starvation conditions as follows: week 1(AMPK β1a and AMPK β1b), week 4 (AMPK α1, AMPK α2, AMPK γ1, AMPK γ2b and AMPK γ3), and week 8 (AMPK β2 and AMPK γ2a). Further in vitro analysis revealed that the mRNA levels of AMPK isoforms in hepatocytes (AMPK α1, AMPK α2, AMPK β1a, AMPK β1b, AMPK β2, AMPK γ2b and AMPK γ3) and adipocytes (AMPK γ2a, AMPK γ2b and AMPK γ3) changed significantly with in the first 24h of exposure to the overwinter starvation conditions. These findings confirm that nine AMPK subunits are present in grass carp and that all encode proteins with conserved functional domains. The nine AMPK subunits are all regulated at the transcriptional levels to manage excess energy expenditure during overwinter starvation stress.

Berberine Improves Glucose and Lipid Metabolism in HepG2 Cells Through AMPKα1 Activation.

AimThis study is designed to investigate whether or not AMP-activated protein kinase α1 (AMPKα1) is required for natural product berberine (BBR) to improve glucose and lipid metabolism in HepG2 cells.MethodsAMPKα1 knocked-out (KO, AMPKα1-/-) cells were obtained by co-transfection of the CRISPR/Cas9 KO and HDR (homology-directed repair) plasmid into HepG2 cells, as well as subsequent screen with puromycin. The expression levels of target proteins or mRNAs were determined by western blot or real-time RT-PCR, respectively. Cellular AMPK activity, glucose consumption, lactate release, glucose production, and lipid accumulation were determined by kits.ResultsThe results showed that the AMPKα1 gene was successfully KO in HepG2 cells. In AMPKα1-/- cells, the protein expression of AMPKα1 and phosphorylated-AMPKα1 (p-AMPKα1) disappeared, the level of total AMPKα declined to about 45–50% of wild type (p < 0.01), while p-AMPKα level and AMPK activity were reduced to less than 10% of wild type (p < 0.001). BBR increased p-AMPKα1, p-AMPKα, AMPK activity, and stimulated glucose consumption, lactate release, inhibited glucose production in wild type HepG2 cells (p < 0.05 or p < 0.01). BBR also reduced intracellular lipid accumulation and suppressed the expression of lipogenic genes in oleic acid (OA) treated wild type HepG2 cells (p < 0.05 or p < 0.01). In AMPKα1-/- HepG2 cells, the stimulating effects of BBR on p-AMPKα1, p-AMPKα, AMPK activity, and its improving effects on glucose and lipid metabolism were completely abolished.ConclusionOur study proves that AMPKα1 plays a critical role for BBR to improve glucose and lipid metabolism in HepG2 cells. Our results will provide new information to further understand the molecular mechanisms of BBR.

Vanillic Acid Alleviates Acute Myocardial Hypoxia/Reoxygenation Injury by Inhibiting Oxidative Stress.

Oxidative stress is an important factor of myocardial hypoxia/reoxygenation (H/R) injury. Our research focuses on how to reduce the cardiac toxicity caused by oxidative stress through natural plant extracts. Vanillic acid (VA) is a phenolic compound found in edible plants and rich in the roots of Angelica sinensis. Experimental studies have provided evidence for this compound's effectiveness in cardiovascular diseases; however, its mechanism is still unclear. In this study, molecular mechanisms related to the protective effects of VA were investigated in H9c2 cells in the context of H/R injury. The results showed that pretreatment with VA significantly increased cell viability and decreased the percentage of apoptotic cells, as well as lactate dehydrogenase and creatine phosphokinase activity, in the supernatant, accompanied by reduced levels of reactive oxygen species and reduced caspase-3 activity. VA pretreatment also restored mitochondrial membrane potentials. Moreover, preincubation with VA significantly attenuated mitochondrial permeability transition pore activity. VA administration upregulated adenosine monophosphate-activated protein kinase α2 (AMPKα2) protein expression, and interestingly, pretreatment with AMPKα2-siRNA lentivirus effectively attenuated the cardioprotective effects of VA in response to H/R injury.

Dipeptidyl peptidase-4 inhibition improves endothelial senescence by activating AMPK/SIRT1/Nrf2 signaling pathway

Dipeptidyl peptidase-4 (DPP4) is elevated in numerous cardiovascular pathological processes and DPP4 inhibition is associated with reduced inflammation and oxidative stress. The aim of this study was to examine the role of DPP4 in endothelial senescence. Sprague-Dawley rats (24 months) were orally administrated saxagliptin (10 mg·kg−1·d−1), a DPP4 inhibitor, for 12 weeks in drinking water. Body weight, heart rate, blood glucose, and blood pressure were measured and vascular histological experiments were performed. In vitro studies were performed using H2O2-induced senescent human umbilical vein endothelial cells. Both in vivo and in vitro studies confirmed the elevation of DPP4 in senescent vascular endothelium, and inhibition or knockdown of DPP4 ameliorated endothelial senescence. In addition, DPP4 inhibition or silencing reduced endothelial oxidative stress levels in aging vasculature and senescent endothelial cells. Moreover, DPP4 inhibition or knockdown normalized the expression and phosphorylation of AMP-activated protein kinase-α (AMPKα) and sirtuin 1 (SIRT1) expression. Furthermore, the beneficial effects of DPP4 inhibition or knockdown on endothelial cell senescence were at least partly dependent on SIRT1 and Nrf2 activation. In conclusion, our study demonstrated that DPP4 inhibition or silencing ameliorated endothelial senescence both in vivo and in vitro by regulating AMPK/SIRT1/Nrf2. DPP4 may be a new therapeutic target to combat endothelial senescence.

Metformin limits osteoarthritis development and progression through activation of AMPK signalling

ObjectivesIn this study, we aim to determine the effect of metformin on osteoarthritis (OA) development and progression.MethodsDestabilisation of the medial meniscus (DMM) surgery was performed in 10-week-old wild type and...

Omega-3 and Omega-6 polyunsaturated fatty acids stimulate vascular differentiation of mouse embryonic stem cells.

Polyunsaturated fatty acids (PUFAs) and their metabolites may influence cell fate regulation. Herein, we investigated the effects of linoleic acid (LA) as ω-6 PUFA, eicosapentaenoic acid (EPA) as ω-3 PUFA and palmitic acid (PA) on vasculogenesis of embryonic stem (ES) cells. LA and EPA increased vascular structure formation and protein expression of the endothelial-specific markers fetal liver kinase-1, CD31 as well as VE-cadherin, whereas PA was without effect. LA and EPA increased reactive oxygen species (ROS) and nitric oxide (NO), activated endothelial NO synthase (eNOS) and raised intracellular calcium. The calcium response was inhibited by the intracellular calcium chelator BAPTA, sulfo-N-succinimidyl oleate which is an antagonist of CD36, the scavenger receptor for fatty acid uptake as well as by a CD36 blocking antibody. Prevention of ROS generation by radical scavengers or the NADPH oxidase inhibitor VAS2870 and inhibition of eNOS by L-NAME blunted vasculogenesis. PUFAs stimulated AMP activated protein kinase-α (AMPK-α) as well as peroxisome proliferator-activated receptor-α (PPAR-α). AMPK activation was abolished by calcium chelation as well as inhibition of ROS and NO generation. Moreover, PUFA-induced vasculogenesis was blunted by the PPAR-α inhibitor GW6471. In conclusion, ω-3 and ω-6 PUFAs stimulate vascular differentiation of ES cells via mechanisms involving calcium, ROS and NO, which regulate function of the energy sensors AMPK and PPAR-α and determine the metabolic signature of vascular cell differentiation.

It's well and truly time to stop stating that AMPK regulates glucose uptake and fat oxidation during exercise.

None for Perspective.

Metformin Inhibits Tumor Metastasis through Suppressing Hsp90α Secretion in an AMPKα1-PKCγ Dependent Manner.

Metformin has been documented in epidemiological studies to mitigate tumor progression. Previous reports show that metformin inhibits tumor migration in several cell lines, such as MCF-7 and H1299, but the mechanisms whereby metformin exerts its inhibitory effects on tumor metastasis remain largely unknown. The secreted proteins in cancer cell-derived secretome have been reported to play important roles in tumor metastasis, but whether metformin has an effect on tumor secretome remains unclear. Here we show that metformin inhibits tumor metastasis by suppressing Hsp90α (heat shock protein 90α) secretion. Mass spectrometry (MS) analysis and functional validation identify that eHsp90α (extracellular Hsp90α) is one of the most important secreted proteins for metformin to inhibit tumor cells migration, invasion and metastasis both in vitro and in vivo. Moreover, we find that metformin inhibits Hsp90α secretion in an AMPKα1 dependent manner. Our data elucidate that AMPKα1 (AMP-activated protein kinase α1) decreases the phosphorylation level of Hsp90α by inhibiting the kinase activity of PKCγ (protein kinase Cγ), which suppresses the membrane translocation and secretion of Hsp90α. Collectively, our results illuminate that metformin inhibits tumor metastasis by suppressing Hsp90α secretion in an AMPKα1 dependent manner.

Effect of chromium citrate on the mechanism of glucose transport and insulin resistance in Buffalo rat liver cells.

OBJECTIVE:Our published literature indicated that chromium citrate could regulate the glycemic index in alloxaninduced diabetic mice. The present study investigated the mechanism of chromium citrate in insulin resistance (IR) buffalo rat liver (BRL) cells.MATERIALS And METHODS:Chromium citrate was synthesized in our laboratory. BRL cells were purchased from the Chinese Academy of Sciences Cell Bank. The glucose transport and IR affected by chromium citrate in BRL cells were examined. The Thiazolyl Blue Tetrazolium Bromide (MTT) and glucose assay experiments were measured by microplate ELISA reader. The protein kinase B (Akt), glucose transporter-4 (Glut4), and phosphor-AMP-activated protein kinase β1 levels were tested by Western blot, and the mRNA expression of glucose transport proteins (Akt2, Glut4, and AMPactivated protein kinase α2 (AMPKα2)) and insulin sensitivity proteins (insulin receptor substrate1 (IRS-1), phosphatidylinositol 3 kinase (PI3K), and peroxisome proliferator-activated receptor γ (PPARγ)) was measured by reverse transcription–polymerase chain reaction.RESULTS:The results indicated that the glucose absorption level of chromium citrate groups was higher than model group significantly. It demonstrated that chromium citrate could significantly improve glucose absorption in IR BRL cells. The Akt, Glut4, and phosphor-AMPKβ1 levels in chromium citrate groups (at doses of 0.4, 0.2, and 0.1 μg Cr/mL) were markedly improved when compared with the other experiment groups, and chromium citrate could more effectively increase the Akt level than chromium trichloride. In addition, the mRNA expression of Akt2, Glut4, and AMPKα2 in chromium citrate groups was significantly improved when contrasted with model group.CONCLUSION:The consequences illustrated that chromium citrate can affect the IR BRL cells' ameliorating glucose transport and IR.