Monophosphate-activated Protein Kinase Research Articles

Targeting FGF21 in cardiovascular and metabolic diseases: from mechanism to medicine.

Cardiovascular and metabolic disease (CVMD) is becoming increasingly prevalent in developed and developing countries with high morbidity and mortality. In recent years, fibroblast growth factor 21 (FGF21) has attracted intensive research interest due to its purported role as a potential biomarker and critical player in CVMDs, including atherosclerosis, coronary artery disease, myocardial infarction, hypoxia/reoxygenation injury, heart failure, type 2 diabetes, obesity, and nonalcoholic steatohepatitis. This review summarizes the recent developments in investigating the role of FGF21 in CVMDs and explores the mechanism whereby FGF21 regulates the development of CVMDs. Novel molecular targets and related pathways of FGF21 (adenosine 5'-monophosphate-activated protein kinase, silent information regulator 1, autophagy-related molecules, and gut microbiota-related molecules) are highlighted in this review. Considering the poor pharmacokinetics and biophysical properties of native FGF21, the development of new generations of FGF21-based drugs has tremendous therapeutic potential. Related preclinical and clinical studies are also summarized in this review to foster clinical translation. Thus, our review provides a timely and insightful overview of the physiology, biomarker potential, molecular targets, and therapeutic potential of FGF21 in CVMDs.

Metformin and Its Immune-Mediated Effects in Various Diseases.

Metformin has been a long-standing prescribed drug for treatment of type 2 diabetes (T2D) and its beneficial effects on virus infection, autoimmune diseases, aging and cancers are also recognized. Metformin modulates the differentiation and activation of various immune-mediated cells such as CD4+ and CD+8 T cells. The activation of adenosine 5'-monophosphate-activated protein kinase (AMPK) and mammalian target of rapamycin complex 1 (mTORC1) pathway may be involved in this process. Recent studies using Extracellular Flux Analyzer demonstrated that metformin alters the activities of glycolysis, oxidative phosphorylation (OXPHOS), lipid oxidation, and glutaminolysis, which tightly link to the modulation of cytokine production in CD4+ and CD+8 T cells in various disease states, such as virus infection, autoimmune diseases, aging and cancers.

Hypoglycemic effect of electroacupuncture at "Tianshu" (ST 25) combined with metformin on rats with type 2 diabetes mellitus based on AMPK

To observe the hypoglycemic effect of electroacupuncture (EA) at "Tianshu" (ST 25) combined with metformin on rats with type 2 diabetes mellitus (T2DM) as well as its effect on expression of adenosine monophosphate activated protein kinase (AMPK) in liver and pancreas. Thirty-six male SD rats were randomly divided into a blank group (6 rats) and a model establishing group (30 rats). The rats in the model establishing group were fed with high-fat diet and treated with intraperitoneal injection of low-dose streptozotocin (STZ) to establish T2DM model. The rats with successful model establishment were randomly divided into a model group, a control group, a metformin group, an EA group and a combination group, 6 rats in each group. The rats in the EA group were treated with EA at "Tianshu" (ST 25), dense-disperse wave, 2 Hz/15 Hz in frequency and 2 mA in current intensity, 20 min each time. The rats in the metformin group were treated with intragastric administration of metformin (190 mg/kg) dissolved in 0.9% sodium chloride solution (2 mL/kg). The rats in the combination group were treated with EA at "Tianshu" (ST 25) and intragastric administration of metformin. The rats in the control group were treated with intragastric administration of 0.9% sodium chloride solution with the same dose. All the treatments were given once a day for 5 weeks. After the intervention, the body mass and random blood glucose were detected; the serum insulin level was detected by ELISA; the expression of AMPK and phosphorylated adenosine monophosphate activated protein kinase (p-AMPK) in liver and pancreas was detected by Western blot method; the expression of protein gene product 9.5 (PGP9.5) was detected by immunofluorescence. ①Compared with the blank group, the body mass in the model group was decreased (P<0.05); compared with the model group, the body mass in the EA group and the combination group was decreased (P<0.05); the body mass in the EA group and the combination group was lower than the metformin group (P<0.05). Compared with the blank group, the random blood glucose in the model group was increased (P<0.01); compared with the model group, the random blood glucose in the metformin group, the EA group and the combination group was decreased (P<0.01). The random blood glucose in the combination group was lower than the metformin group and the EA group (P<0.05). ②Compared with the blank group, the insulin level in the model group was decreased (P<0.05); compared with the model group, the insulin level in the metformin group, the EA group and the combination group was all increased (P<0.05). The insulin level in the combination group was higher than the metformin group and the EA group (P<0.05). ③Compared with the blank group, the protein expression of AMPK and p-AMPK in liver tissue was decreased (P<0.05), and the protein expression of AMPK and p-AMPK in pancreatic tissue was increased (P<0.05) in the model group. Compared with the model group, the protein expression of AMPK and p-AMPK in liver tissue in the metformin group, the EA group and the combination group was increased (P<0.05, P<0.01); the protein expression of AMPK in pancreatic tissue in the metformin group was increased (P<0.05); the protein expression of AMPK in pancreatic tissue in the EA group and the combination group was decreased (P<0.05); the protein expression of p-AMPK in pancreatic tissue in the metformin group, the EA group and the combination group was decreased (P<0.05). The protein expression of AMPK and p-AMPK in liver tissue in the combination group was higher than that in the metformin group and the EA group (P<0.05); the protein expression of AMPK in pancreatic tissue in the EA group and the combination group was less than that in the metformin group (P<0.05), and the expression of p-AMPK protein in pancreatic tissue in the combination group was less than that in the metformin group and the EA group (P<0.05). ④Compared with the blank group, the expression of PGP9.5 in pancreatic tissue in the model group was increased (P<0.01); compared with the model group, the expression of PGP9.5 in pancreatic tissue in the metformin group, the EA group and the combination group was decreased (P<0.05, P<0.01). The expression of PGP9.5 in pancreatic tissue in the EA group was lower than the metformin group and the combination group (P<0.05). Electroacupuncture at "Tianshu" (ST 25) could promote the effect of metformin on activating AMPK in liver tissue of T2DM rats, improve the negative effect of metformin on AMPK in pancreatic tissue, and enhance the hypoglycemic effect of metformin. The mechanism may be related to the inhibition of pancreatic intrinsic nervous system.

Cordycepin Enhances SIRT1 Expression and Maintains Stemness of Human Mesenchymal Stem Cells.

Mesenchymal stem cells (MSCs) have been employed for therapeutic applications of various degenerative diseases. However, the major concern is MSC aging during the in vitro cultivation. Thus, the approach to delay MSC aging was examined in this research by focusing on the expression of Sirtuin 1 (SIRT1), a key anti-aging marker. Cordycepin, a bioactive compound derived from Cordyceps militaris, was used to up-regulate SIRT1 and maintain stemness of MSCs. Upon treatment with cordycepin, MSCs were investigated for cell viability, doubling time, key gene/protein expression, galactosidase-associated senescence assay, relative telomere length, and telomerase expression. Cordycepin significantly increased the expression of SIRT1 in MSCs by activating the adenosine monophosphate activated protein kinase (AMPK)-SIRT1 signalling pathway. Moreover, cordycepin maintained the stemness of MSCs by deacetylating SRY-box transcription factor 2 (SOX2) via SIRT1, and cordycepin delayed cellular senescence and aging of MSCs by enhancing autophagy, inhibiting the activity of senescence-associated-galactosidase, maintaining proliferation rate, and increasing telomere activity. Cordycepin could be used to increase SIRT1 expression in MSCs for anti-aging applications.

Loss of Mature Lamin A/C Triggers a Shift in Intracellular Metabolic Homeostasis via AMPKα Activation

The roles of lamin A/C in adipocyte differentiation and skeletal muscle lipid metabolism are associated with familial partial lipodystrophy of Dunnigan (FPLD). We confirmed that LMNA knockdown (KD) in mouse adipose-derived mesenchymal stem cells (AD-MSCs) prevented adipocyte maturation. Importantly, in in vitro experiments, we discovered a significant increase in phosphorylated lamin A/C levels at serine 22 or 392 sites (pLamin A/C-S22/392) accompanying increased lipid synthesis in a liver cell line (7701 cells) and two hepatocellular carcinoma (HCC) cell lines (HepG2 and MHCC97-H cells). Moreover, HCC cells did not survive after LMNA knockout (KO) or even KD. Evidently, the functions of lamin A/C differ between the liver and adipose tissue. To date, the mechanism of hepatocyte lipid metabolism mediated by nuclear lamin A/C remains unclear. Our in-depth study aimed to identify the molecular connection between lamin A/C and pLamin A/C, hepatic lipid metabolism and liver cancer. Gain- and loss-of-function experiments were performed to investigate functional changes and the related molecular pathways in 7701 cells. Adenosine 5' monophosphate-activated protein kinase α (AMPKα) was activated when abnormalities in functional lamin A/C were observed following lamin A/C depletion or farnesyltransferase inhibitor (FTI) treatment. Active AMPKα directly phosphorylated acetyl-CoA-carboxylase 1 (ACC1) and subsequently inhibited lipid synthesis but induced glycolysis in both HCC cells and normal cells. According to the mass spectrometry analysis, lamin A/C potentially regulated AMPKα activation through its chaperone proteins, ATPase or ADP/ATP transporter 2. Lonafarnib (an FTI) combined with low-glucose conditions significantly decreased the proliferation of the two HCC cell lines more efficiently than lonafarnib alone by inhibiting glycolysis or the maturation of prelamin A.

Dietary isoleucine affects muscle fatty acid and amino acid profiles through regulating lipid metabolism and autophagy in hybrid catfish (Pelteobagrus vachelli ♀× Leiocassis longirostris ♂).

The present study explored the impacts of Ile on muscle fatty acid and amino acid profiles, lipid metabolism, and autophagy in hybrid catfish. Seven isonitrogenous (387.8g/kg protein) semi-purified diets were formulated to contain 5.0 (control), 7.5, 10.0, 12.5, 15.0, 17.5, and 20.0g Ile/kg diet respectively. The fish (initial weight of 33.11±0.09g) were randomly assigned to 7 groups for a 56-day trial. Each group has 3 replicates with 30 fish per replicate, fed at 08:00 and 18:00 each day. Results showed that muscle protein and lipid, C14:0, C18:0, C22:0, C14:1, C18:1n-9, polyunsaturated fatty acid (PUFA), Arg, Ile, Ala, Cys, Gly, Tyr, essential amino acid (EAA), and total amino acid (TAA) contents and flavor amino acid (FAA)/TAA in muscle had positive linear and/or quadratic responses to dietary Ile levels (P<0.05). Fatty acid synthase (FAS), stearoyl-CoA desaturase (SCD), acetyl-CoA carboxylase (ACC), and lipoprotein lipase (LPL) activities had positive linear and/or quadratic responses, but carnitine palmitoyl transferase 1 (CPT1) activity had a negative response with increasing dietary Ile levels (P<0.05). The mRNA expressions of FAS, SCD, ACC, LPL, fatty acid binding protein 4 (FABP4), FATP1, sterol response element-binding protein 1c (SREBP-1c), sequestosome 1 (SQSTM1), and adenosine 5'-monophosphate-activated protein kinase (AMPK) had positive linear and/or quadratic responses to dietary Ile levels (P<0.05). The mRNA expressions of hormone-sensitive lipase (HSL), CPT1, peroxisome proliferator-activated receptor α (PPARα), PPARγ, uncoordinated 51-like kinase 1 (ULK1), beclin1 (Becn1), autophagy-related protein 9α (Atg9α), Atg4b, Atg7, autophagy marker light chain 3B (LC3B), and SQSTM1 in muscle had negative linear and/or quadratic responses to dietary Ile levels (P<0.05). The p-AMPK and ULK1 protein levels, and p-AMPK/AMPK were decreased by 12.5g Ile/kg in the diet (P<0.05). Finally, SQSTM1 protein level had the opposite effect (P<0.05). The above results indicate that dietary Ile improves fish muscle fatty acid and amino acid profiles potentially via respectively regulating lipid metabolism and autophagy. The Ile requirement of hybrid catfish (33 to 72g) were estimated to be 12.63, 13.77, 13.75, 11.45, 10.50, 12.53 and 12.21g/kg diet based on the regression analysis of protein, lipid, SFA, PUFA, FAA, EAA, and TAA muscle contents, respectively.

Roles of Ghrelin and Leptin in Body Mass Regulation under Food Restriction Based on the AMPK Pathway in the Red-Backed Vole, Eothenomys miletus, from Kunming and Dali Regions.

The phenotype plasticity of animals' physiological characteristics is an important survival strategy to cope with environmental changes, especially the change in climate factors. Small mammals that inhabit seasonally changing environments often face the stress of food shortage in winter. This study measured and compared the thermogenic characteristics and related physiological indicators in the adenosine-5'-monophosphate-activated protein kinase (AMPK) pathway in Eothenomys miletus between Kunming (KM, n = 18) and Dali (DL, n = 18) under food restriction and refeeding. The results showed that food restriction and the region have significant effects on body mass, the resting metabolic rate (RMR), hypothalamic neuropeptide gene expression, ghrelin levels in the stomach and serum, serum leptin level and the activity of AMPK, and malonyl CoA and carnitine palmitoyltransferase 1 (CPT-1) activity. Food restriction reduced the body mass, the gene expression of neuropeptide proopiomelanocortin (POMC), cocaine- and amphetamine-regulated transcription peptide (CART), and leptin level. However, the ghrelin concentration and AMPK activity increased. After refeeding, there was no difference in these physiological indexes between the food restriction and control groups. Moreover, the physiological indicators also showed regional differences, such as the body mass, POMC and CART gene expression, ghrelin concentration in the stomach and serum, and AMPK activity in DL changed more significantly. All these results showed that food restriction reduces energy metabolism in E. miletus. After refeeding, most of the relevant physiological indicators can return to the control level, indicating that E. miletus has strong phenotypic plasticity. Ghrelin, leptin, and the AMPK pathway play an important role in the energy metabolism of E. miletus under food restriction. Moreover, regional differences in physiological indicators under food restriction may be related to the different temperatures or food resources in different regions.

Hypothetical protein FoDbp40 influences the growth and virulence of Fusarium oxysporum by regulating the expression of isocitrate lyase.

Fungal growth is closely related to virulence. Finding the key genes and pathways that regulate growth can help elucidate the regulatory mechanisms of fungal growth and virulence in efforts to locate new drug targets. Fusarium oxysporum is an important plant pathogen and human opportunistic pathogen that has research value in agricultural and medicinal fields. A mutant of F. oxysporum with reduced growth was obtained by Agrobacterium tumefaciens-mediated transformation, the transferred DNA (T-DNA) interrupted gene in this mutant coded a hypothetical protein that we named FoDbp40. FoDbp40 has an unknown function, but we chose to explore its possible functions as it may play a role in fungal growth regulatory mechanisms. Results showed that F. oxysporum growth and virulence decreased after FoDbp40 deletion. FOXG_05529 (NCBI Gene ID, isocitrate lyase, ICL) was identified as a key gene that involved in the reduced growth of this mutant. Deletion of FoDbp40 results in a decrease of more than 80% in ICL expression and activity, succinate level, and energy level, plus a decrease in phosphorylated mammalian target of rapamycin level and an increase in phosphorylated 5'-adenosine monophosphate activated protein kinase level. In summary, our study found that the FoDbp40 regulates the expression of ICL at a transcriptional level and affects energy levels and downstream related pathways, thereby regulating the growth and virulence of F. oxysporum.

Cathelicidin LL-37 Activates Human Keratinocyte Autophagy through the P2X₇, Mechanistic Target of Rapamycin, and MAPK Pathways

Human cathelicidin LL-37 is a multifunctional antimicrobial peptide that exhibits antimicrobial and immunomodulatory activities. LL-37 regulates skin barrier function and was recently reported to activate autophagy in macrophages. Because autophagy deficiency is associated with skin diseases characterized by a dysfunctional epidermal barrier, we hypothesized that LL-37 might regulate the skin barrier through autophagy modulation. We showed that LL-37 activated autophagy in human keratinocytes and three-dimensional skin equivalent models as indicated by increases in LC3 puncta formation, decreases in p62, and autophagosome and autolysosome formation. LL-37‒induced autophagy was suppressed by P2X7 receptor, adenosine monophosphate‒activated protein kinase, and unc-51-like kinase 1 inhibitors, suggesting that the P2X7, adenosine monophosphate‒activated protein kinase, and unc-51-like kinase 1 pathways are involved. Moreover, LL-37 enhanced the phosphorylation of adenosine monophosphate‒activated protein kinase and unc-51-like kinase 1. In addition, LL-37‒mediated autophagy involves the mechanistic target of rapamycin and MAPK pathways. Interestingly, the LL-37‒induced distribution of tight junction proteins and improvement in the tight junction barrier were inhibited in autophagy-deficient keratinocytes and keratinocytes and skin models treated with autophagy inhibitors, indicating that the LL-37‒mediated tight junction barrier is associated with autophagy activation. Collectively, these findings suggest that LL-37 is a potential therapeutic target for skin diseases characterized by dysfunctional autophagy and skin barriers.

Fecal Bacterial Community and Metagenome Function in Asians with Type 2 Diabetes, According to Enterotypes.

The role of gut microbes has been suggested in type 2 diabetes (T2DM) risk. However, their results remain controversial. We hypothesized that Asians with T2DM had different fecal bacterial compositions, co-abundance networks, and metagenome functions compared to healthy individuals, according to enterotypes. This hypothesis was examined using the combined gut microbiota data from human fecal samples from previous studies. The human fecal bacterial FASTA/Q files from 36 different T2DM studies in Asians were combined (healthy, n = 3378; T2DM, n = 551), and operational taxonomic units (OTUs) and their counts were obtained using qiime2 tools. In the machine learning approaches, fecal bacteria rich in T2DM were found. They were separated into two enterotypes, Lachnospiraceae (ET-L) and Prevotellaceae (ET-P). The Shannon and Chao1 indices, representing α-diversity, were significantly lower in the T2DM group compared to the healthy group in ET-L (p &lt; 0.05) but not in ET-P. In the Shapley additive explanations analysis of ET-L, Escherichia fergusonii, Collinsella aerofaciens, Streptococcus vestibularis, and Bifidobacterium longum were higher (p &lt; 0.001), while Phocaeicola vulgatus, Bacteroides uniformis, and Faecalibacterium prausnitzii were lower in the T2DM group than in the healthy group (p &lt; 0.00005). In ET-P, Escherichia fergusonii, Megasphaera elsdenii, and Oscillibacter valericigenes were higher, and Bacteroides koreensis and Faecalibacterium prausnitzii were lower in the T2DM group than in the healthy group. In ET-L and ET-P, bacteria in the healthy and T2DM groups positively interacted with each other within each group (p &lt; 0.0001) but negatively interacted between the T2DM and healthy groups in the network analysis (p &lt; 0.0001). In the metagenome functions of the fecal bacteria, the gluconeogenesis, glycolysis, and amino acid metabolism pathways were higher, whereas insulin signaling and adenosine 5' monophosphate-activated protein kinase (AMPK) signaling pathways were lower in the T2DM group than in the healthy group for both enterotypes (p &lt; 0.00005). In conclusion, Asians with T2DM exhibited gut dysbiosis, potentially linked to intestinal permeability and the enteric vagus nervous system.

Prostaglandin EP3 receptor activation is antinociceptive in sensory neurons via PI3Kγ, AMPK and GRK2.

Prostaglandin E2 is considered a major mediator of inflammatory pain, by acting on neuronal Gs protein-coupled EP2 and EP4 receptors. However, the neuronal EP3 receptor, colocalized with EP2 and EP4 receptor, is Gi protein-coupled and antagonizes the pronociceptive prostaglandin E2 effect. Here, we investigated the cellular signalling mechanisms by which the EP3 receptor reduces EP2 and EP4 receptor-evoked pronociceptive effects in sensory neurons. Experiments were performed on isolated and cultured dorsal root ganglion (DRG) neurons from wild type, phosphoinositide 3-kinase γ (PI3Kγ)-/- , and PI3Kγkinase dead (KD)/KD mice. For subtype-specific stimulations, we used specific EP2, EP3, and EP4 receptor agonists from ONO Pharmaceuticals. As a functional readout, we recorded TTX-resistant sodium currents in patch-clamp experiments. Western blots were used to investigate the activation of intracellular signalling pathways. EP4 receptor internalization was measured using immunocytochemistry. Different pathways mediate the inhibition of EP2 and EP4 receptor-dependent pronociceptive effects by EP3 receptor stimulation. Inhibition of EP2 receptor-evoked pronociceptive effect critically depends on the kinase-independent function of the signalling protein PI3Kγ, and adenosine monophosphate activated protein kinase (AMPK) is involved. By contrast, inhibition of EP4 receptor-evoked pronociceptive effect is independent on PI3Kγ and mediated through activation of G protein-coupled receptor kinase 2 (GRK2), which enhances the internalization of the EP4 receptor after ligand binding. Activation of neuronal PI3Kγ, AMPK, and GRK2 by EP3 receptor activation limits cAMP-dependent pain generation by prostaglandin E2 . These new insights hold the potential for a novel approach in pain therapy.

Identification of novel benzimidazole derivatives as highly potent AMPK activators with anti-diabetic profiles

Diabetes is a global healthcare problem that affects more than 400 million people worldwide. Treatment for type 1 and 2 diabetes is expected by targeting adenosine monophosphate activated protein kinase, AMPK, a well-known master regulator of glucose. Many pharmaceutical companies have tried to identify AMPK activators but few direct AMPK activators with high potency for the β2-AMPK isoform, which is important for glucose homeostasis, have been found. In addition, their chemical structure is limited to benzimidazole or indole derivatives bearing an aromatic substituent at the C5 position of the core structure. We describe herein our efforts to identify novel benzimidazole derivatives that directly activate the β2-AMPK isoform. Our newly designed activator 14d bearing a 1-amino indanyl moiety at the C5 position of the core exhibited high in vitro potency and good pharmacokinetic profiles. A single oral dosing of 14d showed dose-dependent activation of AMPK and blood-glucose-lowering effects was observed in a diabetic animal model. In addition, chronic AMPK activation with 14d led to dose-dependent reduction in HbA1c of the animal model.

Cold Plasma Treatment Increases Bioactive Metabolites in Oat (Avena sativa L.) Sprouts and Enhances In Vitro Osteogenic Activity of their Extracts

Cold plasma treatment has been studied to enhance the germination, growth, and bioactive phytochemical production in crops. Here, we aimed to investigate the effects of cold plasma treatment on the growth, bioactive metabolite production, and protein expression related to the physiological and osteogenic activities of oat sprouts. Oat seeds were soaked for 12 h, and then exposed to plasma for 6 min/day for 3 days after sowing. Plasma exposure did not significantly change the growth of oat sprouts; however, increased the content of bioactive metabolites. A single exposure for 6 min on the first day (T-1) increased the content of free amino acids (39.4%), γ-aminobutyric acid (53%), and avenacoside B (23%) compared to the control. Hexacosanol content was the highest in T-3 (6 min exposure on each day for 3 days), 28% higher than that in the control. Oat sprout extracts induced the phosphorylation of adenosine 5′-monophosphate-activated protein kinase and osteoblast differentiation was enhanced by increasing the alkaline phosphatase (ALP) activity; all these effects were induced by plasma treatment. Avenacoside B content was positively correlated with ALP activity (r = 0.911, p < 0.1). These results suggest that plasma treatment has the potential to improve the value of oat sprouts and that it may be used in food fortification to enhance nutritional value for promoting human health.

Fermented Psidium guajava leaves regulate the gut microbiota and improve metabolic alterations in diabetic mice

The phenolic extract from fermented Psidium guajava leaves (PFGL) helps to improve diabetes; however, its hypoglycemic and hypolipidemic mechanisms remain unclear. In this study, gut microbiota modulation and glucose-lipid metabolism was investigated. The results showed that dietary supplement of PFGL enriched in quercetin glucosides significantly improved serum glucose-lipid profiles as well as insulin resistance in diabetic mice. The gut microbiota of diabetic mice was modulated by PFGL (200 mg/kg), causing an abundance of Bacteroidetes, Prevotellaceae, and Alistipes and a reduced the presence of Firmicutes and Streptococcus. Increased levels of short-chain fatty acids (SCFA) activated G protein-coupled receptor signaling that induced peptide YY release to promote insulin secretion. Diabetes-induced serum metabolite disorders that are involved in glycerophospholipid metabolism and tryptophan metabolism were restored by PFGL. The protein expression of metabolic enzymes including phospho-adenosine 5’-monophosphate-activated protein kinase, fatty acid synthase, acyl-coenzyme A oxidase, and diacylglycerol aeyltransferase 2 were also regulated to promote glucose-lipid metabolism. In particular, gut microbiota enriched with Alistipes genera and SCFA metabolic regulation were closely correlated with diabetes-related indicators. These findings provide a theoretical support for the development and application of PFGL for the treatment of diabetes.

Natural activators of AMPK signaling: potential role in the management of type-2 diabetes.

Adenosine 5'-monophosphate-activated protein kinase (AMPK) is an evolutionarily conserved serine/threonine kinase involved in the homeostasis of cellular energy. AMPK has developed as an appealing clinical target for the diagnosis of multiple metabolic diseases such as diabetes mellitus, obesity, inflammation, and cancer. Genetic and pharmacological studies indicate that AMPK is needed in response to glucose deficiency, dietary restriction, and increased physical activity for preserving glucose homeostasis. After activation, AMPK influences metabolic mechanisms contributing to enhanced ATP production, thus growing processes that absorb ATP simultaneously. In this review, several natural products have been discussed which enhance the sensitivity of AMPK and alleviate sub complications or different pathways by which such AMPK triggers can be addressed. AMPK Natural products as potential AMPK activators can be developed as alternate pharmacological intervention to reverse metabolic disorders including type 2 diabetes.

ERK Inhibition Increases RANKL-Induced Osteoclast Differentiation in RAW 264.7 Cells by Stimulating AMPK Activation and RANK Expression and Inhibiting Anti-Osteoclastogenic Factor Expression.

Bone absorption is necessary for the maintenance of bone homeostasis. An osteoclast (OC) is a monocyte-macrophage lineage cell that absorbs bone tissue. Extracellular signal-regulated kinases (ERKs) are known to play important roles in regulating OC growth and differentiation. In this study, we examined specific downstream signal pathways affected by ERK inhibition during OC differentiation. Our results showed that the ERK inhibitors PD98059 and U0126 increased receptor activator of NF-κB ligand (RANKL)-induced OC differentiation in RAW 264.7 cells, implying a negative role in OC differentiation. This is supported by the effect of ERK2-specific small interfering RNA on increasing OC differentiation. In contrast to our findings regarding the RAW 264.7 cells, the ERK inhibitors attenuated the differentiation of bone marrow-derived cells into OCs. The ERK inhibitors significantly increased the phosphorylation of adenosine 5'-monophosphate-activated protein kinase (AMPK) but not the activation of p38 MAPK, Lyn, and mTOR. In addition, while the ERK inhibition increased the expression of the RANKL receptor RANK, it decreased the expression of negative mediators of OC differentiation, such as interferon regulatory factor-8, B-cell lymphoma 6, and interferon-γ. These dichotomous effects of ERK inhibition suggest that while ERKs may play positive roles in bone marrow-derived cells, ERKs may also play negative regulatory roles in RAW 264.7 cells. These data provide important information for drug development utilizing ERK inhibitors in OC-related disease treatment.

Lycium barbarum polysaccharides regulate AMPK/Sirt autophagy pathway to delay D-gal-induced premature ovarian failure

This study aims to explore the molecular mechanism of Lycium barbarum polysaccharides(LBP) in alleviating premature ovarian failure(POF) in mice via the 5'-adenosine monophosphate activated protein kinase(AMPK)/silent information regulator 1(Sirt1) signaling pathway. The POF mouse model was established by D-galactose(D-gal) injection at the back. Six groups were set up, including a normal control group, a model group, a LBP group, a 3-MA(autophagy inhibitor 3-methyladenine) group, an AMPK inhibitor group, and a LBPAMPK inhibitor group, with 15 mice in each group. After 28 continuous days of administration, enzyme-linked immunosorbent assay(ELISA) was employed to determine the levels of sex hormones [estradiol(E_2), luteinizing hormone(LH), and follicle-stimulating hormone(FSH)] in serum. The ovarian mass coefficient was measured. Senescence-associated β-Galactosidase(SA-β-Gal) staining and hematoxylin-eosin(HE) staining were performed for observing the state of ovarian senescence and the morphological changes of the ovary. Immunohistochemical method was used to measure the expression of the autophagy marker LC3-Ⅱ in ovarian tissue. Western blot was employed to measure the expression levels of the senescence marker p16~(INK4 a), autophagy markers(LC3-Ⅱ and Beclin-1), the autophagy substrate p62, lysosome-associated membrane protein 2(LAMP2), and the proteins in the AMPK/Sirt1 pathway and mammalian target of rapamycin complex 1(mTORC1)/UNC-51-like kinase 1 Ser757 site(Ulk1 Ser757) pathway. Compared with the normal control group, the modeling of POF decreased the ovarian granulosa cells and follicles, led to the ovarian aging and severe sex hormone secretion disorders, weakened ovarian autophagy activity, and down-regulated the expression of proteins in the AMPK/Sirt1 pathway(P&lt;0.05). Compared with the model group, the treatment with LBP increased ovarian granulosa cells and follicles, alleviated aging and sex hormone disorders, increased autophagy activity, and activated the AMPK/Sirt1 pathway(P&lt;0.05). Both 3-MA and AMPK inhibitor can inhibit autophagy and aggravate ovarian damage and aging in mice. AMPK inhibitor can partially attenuate the role of LBP in promoting autophagy activation and alleviating aging and ovarian tissue damage(P&lt;0.05). LBP can alleviate the symptoms of POF induced by D-gal by promoting the activation of AMPK/Sirt1 pathway.

Piperine attenuates hepatic steatosis and insulin resistance in high-fat diet-induced obesity in Sprague-Dawley rats

Substantial evidence suggests that pepper consumption is associated with a reduced risk of obesity-related complications. However, whether piperine, the main component of pepper, improves obesity-induced hepatic lipid accumulation and insulin resistance and the action mechanism of piperine still remain unclear. We hypothesized that piperine attenuates high-fat diet (HFD)-induced obesity and improves the related metabolic complications in HFD-induced obese rats. Adult Sprague-Dawley (SD) male rats were fed a control diet (CON) or an HFD for 16 weeks. Obese rats were divided into 4 groups: HFD and HFD with daily gavage of piperine 2.7 mg/kg body weight (PIP-Low), 13.5 mg/kg body weight (PIP-Medium), and 27 mg/kg body weight (PIP-High) for another 8 weeks. Rats were euthanized after an 8-hour fast, and the liver, heart, kidney, and white adipose tissue were collected and stored at –80 °C. Piperine administration significantly reduced weight gain, plasma insulin, and glucose concentration. For oral piperine at a dose of 27 mg/kg body weight, body weight significantly decreased by 5.7% compared with that in the HFD group. Additionally, oral piperine administration considerably reduced serum triglyceride concentration. Furthermore, piperine administration reversed the HFD-induced downregulation of adenosine 5′-monophosphate-activated protein kinase (AMPK) signaling molecules and increased the plasma levels of adiponectin and the messenger RNA expression of the adiponectin receptor; additionally, it increased the phosphorylation of phosphatidylinositol-3 kinase (PI3K) and protein kinase B. Overall, oral piperine administration reversed HFD-induced liver lipid accumulation and insulin resistance, possibly via the inactivation of adiponectin-AMPK and PI3K-Akt signaling. These findings imply that piperine could serve as an effective agent for healthy weight loss.

Adenosine monophosphate activated protein kinase contributes to skeletal muscle health through the control of mitochondrial function.

Skeletal muscle is one of the largest organs in the body and the largest protein repository. Mitochondria are the main energy-producing organelles in cells and play an important role in skeletal muscle health and function. They participate in several biological processes related to skeletal muscle metabolism, growth, and regeneration. Adenosine monophosphate-activated protein kinase (AMPK) is a metabolic sensor and regulator of systemic energy balance. AMPK is involved in the control of energy metabolism by regulating many downstream targets. In this review, we propose that AMPK directly controls several facets of mitochondrial function, which in turn controls skeletal muscle metabolism and health. This review is divided into four parts. First, we summarize the properties of AMPK signal transduction and its upstream activators. Second, we discuss the role of mitochondria in myogenesis, muscle atrophy, regeneration post-injury of skeletal muscle cells. Third, we elaborate the effects of AMPK on mitochondrial biogenesis, fusion, fission and mitochondrial autophagy, and discuss how AMPK regulates the metabolism of skeletal muscle by regulating mitochondrial function. Finally, we discuss the effects of AMPK activators on muscle disease status. This review thus represents a foundation for understanding this biological process of mitochondrial dynamics regulated by AMPK in the metabolism of skeletal muscle. A better understanding of the role of AMPK on mitochondrial dynamic is essential to improve mitochondrial function, and hence promote skeletal muscle health and function.

1,25-D3 attenuates cerebral ischemia injury by regulating mitochondrial metabolism via the AMPK/AKT/GSK3β pathway.

The brain injury caused by cerebral ischemia-reperfusion is related to mitochondrial damage. Maintaining the normal function of mitochondria, promoting angiogenesis, protecting neuronal cells, and resisting oxidative stress are the keys to functional recovery after acute ischemic stroke. In this study, we established a middle cerebral artery occlusion (MCAO) model and investigated the effects of 1α,25-dihydroxyvitamin D3 (VitD or 1,25-D3) on mitochondrial function via the adenosine 5'-monophosphate-activated protein kinase (AMPK)/protein kinase B (AKT)/glycogen synthase kinase-3β (GSK-3β) signaling pathway in rats with cerebral ischemia-reperfusion injury. The neurological function and infarct size were measured in each group. Hematoxylin-eosin, neuronal nucleus, and Nissl staining procedures were conducted to observe the morphology and number of the cerebral cortical neurons. Western blotting was then used to analyze p-AMPK, vitamin D receptor (VDR), p-GSK-3β, p-AKT, P53, cytochrome C (CytC), TGF-β, and vascular endothelial growth factor (VEGF) in mitochondria. Immunofluorescence staining was used to observe the expression of CytC and caspase-3. Succinate dehydrogenase, ATPase, reactive oxygen species, and malondialdehyde were detected by kits. RT-qPCR was used to analyze TGF-β, VEGF, P53, and CytC mRNA. The results revealed that the cerebral infarct volume, neurological function score, apoptotic protein P53, CytC, caspase-3, reactive oxygen species, and malondialdehyde were significantly increased in MCAO rats. 1,25-D3 reduced the infarct size and neurological function score, activated VDR, upregulated TGF-β, p-AMPK, p-AKT, p-GSK-3β, VEGF, ATP, and succinate dehydrogenase, and downregulated P53, CytC, caspase-3, reactive oxygen species, and malondialdehyde. As an antagonist of VDRs, pyridoxal-5-phosphate could partially block the neuroprotective effect of 1,25-D3. In conclusion, 1,25-D3 activated AMPK/AKT/GSK-3β signaling and VDRs, inhibited P53, CytC, and caspase-3, increased TGF-β and VEGF, regulated mitochondrial metabolism, reduced neuronal apoptosis, promoted vascular growth, and exerted neuroprotective effects. These findings suggest that this signaling pathway may be an effective target for the treatment of ischemic stroke.