AMPK as a Therapeutic Target for Treating Metabolic Diseases

Polyphenol-rich Trapa quadrispinosa pericarp extract ameliorates high-fat diet induced non-alcoholic fatty liver disease by regulating lipid metabolism and insulin resistance in mice

In China, Trapa quadrispinosa (also called water caltrop) has long been used as a function food and folk medicine to treat diabetes mellitus for years. In the present study, the extract of T. quadrispinosa pericarp (TQPE) which mainly contains hydrolysable tannins was prepared to investigate the potential therapeutic action in non-alcoholic fatty liver disease (NAFLD) mice induced by high fat-diet (HFD). After the administration of TQPE (15, 30 mg/kg/day) for 8 weeks, the increased weight of body and liver were significantly suppressed. TQPE also ameliorated liver lipid deposition and reduced lipids parameters of blood in mice. Moreover, TQPE attenuated oxidative stress and showed a hepatoprotective effect in mice. TQPE was also found to decrease the value of homeostatic model assessment for insulin resistance. In addition, TQPE administration increased the phosphorylation of AMP-activated protein kinase (AMPK) and Acetyl-CoA carboxylase (ACC) and inhibited sterol regulatory element-binding protein (SREBP) in the liver tissue. Meanwhile, TQPE elevated insulin receptor substrate-1 (IRs-1) and protein kinase B (Akt) phosphorylation. These results reflected that, as a nature product, TQPE is a potential agent for suppressing the process of NAFLD via regulation of the AMPK/SREBP/ACC and IRs-1/Akt pathways.

Adenylate Kinase: A Ubiquitous Enzyme Correlated with Medical Conditions

Adenylate kinase is a small, usually monomeric, enzyme found in every living thing due to its crucial role in energetic metabolism. This paper outlines the most relevant data about adenylate kinases isoforms, and the connection between dysregulation or mutation of human adenylate kinase and medical conditions. The following datadases were consulted: National Centre for Biotechnology Information, Protein Data Bank, and Mouse Genomic Informatics. The SmartBLAST tool, EMBOSS Needle Program, and Clustal Omega Program were used to analyze the best protein match, and to perform pairwise sequence alignment and multiple sequence alignment. Human adenylate kinase genes are located on different chromosomes, six of them being on the chromosomes 1 and 9. The adenylate kinases' intracellular localization and organ distribution explain their dysregulation in many diseases. The cytosolic isoenzyme 1 and the mitochondrial isoenzyme 2 are the main adenylate kinases that are integrated in the vast network of inflammatory modulators. The cytosolic isoenzyme 5 is correlated with limbic encephalitis and Leu673Pro mutation of the isoenzyme 7 leads to primary male infertility due to impairment of the ciliary function. The impairment of the mitochondrial isoenzymes 2 and 4 is demonstrated in neuroblastoma or glioma. The adenylate kinases are disease modifier that can assess the risk of diseases where oxidative stress plays a crucial role in pathogenesis like metabolic syndrome or neurodegenerative diseases. Because adenylate kinases has ATP as substrate, they are integrated in the global network of energetic process of any organism therefore are valid target for new pharmaceutical compounds.

Palmitoylethanolamide counteracts hepatic metabolic inflexibility modulating mitochondrial function and efficiency in diet-induced obese mice

Peroxisome proliferator-activated receptor (PPAR)-α activation controls hepatic lipid homeostasis, stimulating fatty acid oxidation, and adapting the metabolic response to lipid overload and storage. Here, we investigate the effect of palmitoylethanolamide (PEA), an endogenous PPAR-α ligand, in counteracting hepatic metabolic inflexibility and mitochondrial dysfunction induced by high-fat diet (HFD) in mice. Long-term PEA administration (30 mg/kg/die per os) in HFD mice limited hepatic lipid accumulation, increased energy expenditure, and markedly reduced insulin resistance. In isolated liver mitochondria, we have demonstrated PEA capability to modulate mitochondrial oxidative capacity and energy efficiency, leading to the reduction of intracellular lipid accumulation and oxidative stress. Moreover, we have evaluated the effect of PEA on mitochondrial bioenergetics of palmitate-challenged HepG2 cells, using Seahorse analyzer. In vitro data showed that PEA recovered mitochondrial dysfunction and reduced lipid accumulation in insulin-resistant HepG2 cells, increasing fatty acid oxidation. Mechanistic studies showed that PEA effect on lipid metabolism was limited by AMP-activated protein kinase (AMPK) inhibition, providing evidence for a pivotal role of AMPK in PEA-induced adaptive metabolic setting. All these findings identify PEA as a modulator of hepatic lipid and glucose homeostasis, limiting metabolic inflexibility induced by nutrient overload.

Qingkailing injection ameliorates cerebral ischemia-reperfusion injury and modulates the AMPK/NLRP3 Inflammasome Signalling pathway

Background

Cerebral ischemia is the second-leading cause of death and the main cause of permanent adult disabilities worldwide. Qingkailing (QKL) injection, a patented Chinese medicine approved by the China Food and Drug Administration, has been widely used in clinical practice to treat cerebral ischemia in China. The NOD-like receptor pyrin 3 (NLRP3) inflammasome is activated in cerebral ischemia and thus, is an effective therapeutic target. AMP-activated protein kinase (AMPK) is an important regulator inhibiting NLRP3 inflammasome activation.

Methods

We investigated the potential of QKL injection to provide neuroprotection after cerebral ischemia in a rat model of middle cerebral artery occlusion (MCAO). Adult male Sprague-Dawley rats (210–230 g) were randomly divided into three groups which consist of sham, MCAO and 3 ml/kg QKL. Rats in the QKL group received intraperitoneal injections of 3 ml/kg QKL, while rats in other groups were given saline in the same volumes. After 90 min ischemia and 24 h reperfusion, neurological function, laser speckle imaging, brain infarction, brain water content and brain blood barrier permeability were examined and cell apoptosis at prefrontal cortex were evaluated 24 h after MCAO, and western blot and real-time quantitative polymerase chain reaction was also researched, respectively.

Results

Intraperitoneal administration of QKL alleviated neurological deficiencies, cerebral infarction, blood-brain barrier permeability, brain oedema and brain cell apoptosis after MCAO induction. QKL decreased pro-inflammatory cytokines, TNF-α, IL-6 and IL-1β, and increased anti-inflammatory cytokines, IL-4 and IL-10. Furthermore, QKL activated phosphorylated AMPK, decreased oxidative stress and decreased NLRP3 inflammasome activation.

Conclusions

QKL relieved cerebral ischemia reperfusion injury and suppressed the inflammatory response by inhibiting AMPK-mediated activation of the NLRP3 inflammasome. These results suggest that QKL might have potential in treating brain inflammatory response and attenuating the cerebral ischemia-reperfusion injury.

Apple Polyphenol Extract Alleviates High-Fat-Diet-Induced Hepatic Steatosis in Male C57BL/6 Mice by Targeting LKB1/AMPK Pathway

To explore the role of apple polyphenol extract (APE) in ameliorating hepatic steatosis and the potential mechanisms involved, we conducted this study. Thirty-three male C57BL/6 mice were randomly divided into three groups: high-fat diet (HFD) with aseptic water ig. (CON), HFD with 125 or 500 mg/(kg·bw·day) APE ig., namely 100 or 400 mg/(kg·bw·day) apple polyphenols (LAP or HAP) for 12 weeks. Compared with the CON group, the APE treatment significantly decreased the body weight gain and increased the ratio of serum albumin/globulin. High dose of APE treatment significantly decreased the liver weight, reduced the hepatic contents of triglyceride and cholesterol, and improved the histopathological features of hepatic steatosis, accompanied by significantly upregulated protein expressions of LKB1, phosphorylated-AMPK, phosphorylated-ACC, and SIRT1, downregulated mTOR, p70 s6k, and HMGCR in the liver, increased mRNA expressions of Ampk and Cyp27a1, and reduced expressions of Srebp-1c, Fas, and Hmgcr. Our data provided new evidence supporting the preventive role of 500 mg/(kg·bw·day) APE treatment in the HFD-induced hepatic steatosis in C57BL/6 mice via the LKB1/AMPK pathway.

The relevance of AMP-activated protein kinase in insulin-secreting β cells: a potential target for improving β cell function?

AMP-activated protein kinase (AMPK) is present in different kinds of metabolically active cells. AMPK is an important intracellular energy sensor and plays a relevant role in whole-body energy homeostasis. AMPK is activated, among others, in response to glucose deprivation, caloric restriction and increased physical activity. Upon activation, AMPK affects metabolic pathways leading to increased formation of ATP and simultaneously reducing ATP-consuming processes. AMPK is also expressed in pancreatic β cells and is largely regulated by glucose, which is the main physiological stimulator of insulin secretion. Results of in vitro studies clearly show that glucose-induced insulin release is associated with a concomitant inhibition of AMPK in β cells. However, pharmacological activation of AMPK significantly potentiates the insulin-secretory response of β cells to glucose and to some other stimuli. This effect is primarily due to increased intracellular calcium concentrations. AMPK is also involved in the regulation of gene expression and may protect β cells against glucolipotoxic conditions. It was shown that in pancreatic islets of humans with type 2 diabetes, AMPK is downregulated. Moreover, studies with animal models demonstrated impaired link between glucose and AMPK activity in pancreatic islet cells. These data suggest that AMPK may be a target for compounds improving the functionality of β cells. However, more studies are required to better elucidate the relevance of AMPK in the (patho)physiology of the insulin-secreting cells.

Oleanolic Acid Exerts a Neuroprotective Effect Against Microglial Cell Activation by Modulating Cytokine Release and Antioxidant Defense Systems

Microglia respond to adverse stimuli in order to restore brain homeostasis and, upon activation, they release a number of inflammatory mediators. Chronic microglial overactivation is related to neuroinflammation in Alzheimer's disease. In this work, we show that oleanolic acid (OA), a natural triterpene present in food and medicinal plants, attenuates the activation of BV2 microglial cells induced by lipopolysaccharide (LPS). Cell pretreatment with OA inhibited the release of IL-1β, IL-6, TNF-α, and NO, which was associated with the downregulation of the expression of genes encoding for these cytokines and inducible nitric oxide synthase (iNOS), and the reinforcement of the endogenous antioxidant cell defense. These findings advocate considering OA as a novel neuroprotective agent to inhibit oxidative stress and inflammatory response in activated microglia associated with Alzheimer's disease.

Poria cocus Wolf Extract Ameliorates Hepatic Steatosis through Regulation of Lipid Metabolism, Inhibition of ER Stress, and Activation of Autophagy via AMPK Activation

Poria cocos Wolf (PCW) is an edible, pharmaceutical mushroom with remarkable biological properties including anti-tumor, anti-inflammation, anti-oxidation, anti-ageing, and anti-diabetic effects. In the current study, we investigated the effects of PCW extract on hepatic steatosis under in vitro and in vivo conditions, and elucidated the underlying mechanisms. In this study, a mixture of HepG2 cells treated with free fatty acid (FFA)—palmitic and oleic acid—and high-fat diet (HFD)-fed obese mice were used; in this background, the triglyceride (TG) levels in HepG2 cells and mice liver were measured, and the expression levels of genes associated with lipogenesis, fatty acid oxidation, endoplasmic reticulum (ER) stress, and autophagy were determined. Treatment of HepG2 cells with FFA enhanced intracellular TG levels in HepG2 cells, but co-treatment with PCW significantly attenuated the TG levels. Notably, PCW significantly enhanced the phosphorylation of AMP-activated protein kinase (AMPK), acetyl-CoA carboxylase (ACC), and sterol regulatory element-binding protein-1c (SREBP-1c) in FFA-treated HepG2 cells. PCW downregulated the expression of lipogenesis-related genes, but upregulated the expression of genes associated with fatty acid oxidation. Further, PCW inhibited FFA-induced expression of ER stress markers and induced autophagy proteins. However, inhibition of AMPK significantly attenuated the beneficial effects of PCW in HepG2 cells. Moreover, PCW efficiently decreased HFD-induced hepatic TG accumulation in vivo and increased the phosphorylation of hepatic AMPK. Three compounds present in PCW including poricoic acid, pachymic acid, and ergosterol, significantly decreased FFA-induced increase in intracellular TG levels, consistent with increased AMPK phosphorylation, suggesting that poricoic acid, pachymic acid, and ergosterol are responsible for PCW-mediated amelioration of hepatic steatosis. Taken together, these results demonstrated that PCW ameliorates hepatic steatosis through the regulation of lipid metabolism, inhibition of ER stress, and activation of autophagy in an AMPK-dependent manner. This suggested that PCW can be potentially used for the treatment of hepatic steatosis.

Differences in Serum Amino Acid Phenotypes Among Patients with Diabetic Nephropathy, Hypertensive Nephropathy, and Chronic Nephritis

Background

We assessed levels of circulating amino acids in different etiologies of chronic kidney disease (CKD) and the association of amino acids with risk factors of CKD progression.

Material/Methods

High-performance liquid chromatography-based analysis was used to determine amino acid profiles in patients with diabetic nephropathy (DN, n=20), hypertensive nephropathy (HN, n=26), and chronic nephritis (CN, n=33), and in healthy controls (HC, n=25).

Results

All 3 types of CKD patients displayed decreased serum levels of serine, glycine, GABA, and tryptophan compared with healthy controls. Moreover, serine and tryptophan were positively correlated with glucose in DN cohorts. Total cholesterol was positively correlated with tryptophan levels in the DN cohort and negatively correlated with serine levels in the CN cohort. In the HN cohort, glycine was negatively correlated with triglyceride levels, and systolic blood pressure (SBP) was negatively correlated with GABA levels.

Conclusions

Patients with different etiologies of CKD have significantly different amino acids profiles, and this indicates specific supplementary nutritional needs in CKD patients.

Macrophages in inflammation, repair and regeneration

Tissue injury triggers a complex series of cellular responses, starting from inflammation activated by tissue and cell damage and proceeding to healing. By clearing cell debris, activating and resolving inflammation and promoting fibrosis, macrophages play key roles in most, if not all, phases of the response to injury. Recent studies of the mechanisms underlying the initial inflammation and later tissue regeneration and repair revealed that macrophages bridge these processes in part by supporting and activating stem/progenitor cells, clearing damaged tissue, remodeling extracellular matrix to prepare scaffolding for regeneration and promoting angiogenesis. However, macrophages also have a central role in the development of pathology induced by failed resolution (e.g. chronic inflammation) and excessive scarring. In this review, we summarize the activities of macrophages in inflammation and healing in response to acute injury in tissues with differing regenerative capacities. While macrophages lead similar processes in response to tissue injury in these tissues, their priorities and the consequences of their activities differ among tissues. Moreover, the magnitude, nature and duration of injury also greatly affect cellular responses and healing processes. In particular, continuous injury and/or failed resolution of inflammation leads to chronic ailments in which macrophage activities may become detrimental.

Dietary β-Cryptoxanthin Inhibits High-Refined Carbohydrate Diet-Induced Fatty Liver via Differential Protective Mechanisms Depending on Carotenoid Cleavage Enzymes in Male Mice

BACKGROUND

β-Cryptoxanthin (BCX), a provitamin A carotenoid shown to protect against nonalcoholic fatty liver disease (NAFLD), can be cleaved by β-carotene-15,15'-oxygenase (BCO1) to generate vitamin A, and by β-carotene-9',10'-oxygenase (BCO2) to produce bioactive apo-carotenoids. BCO1/BCO2 polymorphisms have been associated with variations in plasma carotenoid amounts in both humans and animals.

OBJECTIVES

We investigated whether BCX feeding inhibits high refined-carbohydrate diet (HRCD)-induced NAFLD, dependent or independent of BCO1/BCO2.

METHODS

Six-week-old male wild-type (WT) and BCO1-/-/BCO2-/- double knockout (DKO) mice were randomly fed HRCD (66.5% of energy from carbohydrate) with or without BCX (10 mg/kg diet) for 24 wk. Pathological and biochemical variables were analyzed in the liver and mesenteric adipose tissues (MATs). Data were analyzed by 2-factor ANOVA.

RESULTS

Compared to their respective HRCD controls, BCX reduced hepatic steatosis severity by 33‒43% and hepatic total cholesterol by 43‒70% in both WT and DKO mice (P < 0.01). Hepatic concentrations of BCX, but not retinol and retinyl palmitate, were 33-fold higher in DKO mice than in WT mice (P < 0.001). BCX feeding increased the hepatic fatty acid oxidation protein peroxisome proliferator-activated receptor-α, and the cholesterol efflux gene ATP-binding cassette transporter5, and suppressed the lipogenesis gene acetyl-CoA carboxylase 1 (Acc1) in the MAT of WT mice but not DKO mice (P < 0.05). BCX feeding decreased the hepatic lipogenesis proteins ACC and stearoyl-CoA desaturase-1 (3-fold and 5-fold) and the cholesterol synthesis genes 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase and HMG-CoA synthase 1 (2.7-fold and 1.8-fold) and increased the cholesterol catabolism gene cholesterol 7α-hydroxylase (1.9-fold) in the DKO but not WT mice (P < 0.05). BCX feeding increased hepatic protein sirtuin1 (2.5-fold) and AMP-activated protein kinase (9-fold) and decreased hepatic farnesoid X receptor protein (80%) and the inflammatory cytokine gene Il6 (6-fold) in the MAT of DKO mice but not WT mice (P < 0.05).

CONCLUSION

BCX feeding mitigates HRCD-induced NAFLD in both WT and DKO mice through different mechanisms in the liver-MAT axis, depending on the presence or absence of BCO1/BCO2.

Vitexin alleviates non-alcoholic fatty liver disease by activating AMPK in high fat diet fed mice

Non-alcoholic fatty liver disease (NAFLD) is a most common liver disorder characterized by accumulation of fat in the liver and currently there is no approved treatment for it. Obesity and diabetes being leading cause of NAFLD, compounds having anti-obesity activity and potential to reduce insulin resistance are considered suitable candidate for NAFLD treatment. In this study, we checked effect of vitexin, a naturally occurring flavonoid, on high fat diet (HFD) induced NAFLD in C57BL/6J mice. In presence of vitexin, significant reduction in body and liver weight, triglyceride and cholesterol content in serum and liver was observed. Serum Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST) levels were reduced significantly by vitexin which were elevated in HFD group whereas serum lipase activity remained unchanged. Vitexin suppressed de novo lipogenesis by downregulating expression of Peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer-binding protein-α (C/EBP-α), sterol regulatory element-binding protein-1c (SREBP-1c), Fatty acid synthase (FAS) and Acetyl-CoA Carboxylase (ACC). Additionally, it also enhanced fatty acid oxidation and lipolysis by upregulating Peroxisome proliferator-activated receptor α (PPAR-α), carnitine palmitoyltransferase-1a (CPT-1a) and Adipose triglyceride lipase (ATGL). Inhibition of lipogenesis and activation of lipolysis and fatty acid oxidation by vitexin was found to be mediated by activation of AMP-activated protein kinase (AMPK). Vitexin also improved insulin signalling by activating insulin receptor substrate-1 (IRS-1) and its downstream target AKT. AMPK activation of vitexin was possibly through binding of vitexin to leptin receptor (LepR) which was confirmed by molecular docking studies and by observed enhanced expression of LepR. Thus, we propose that vitexin alleviates NAFLD by activating AMPK possibly by binding to LepR.

Zeaxanthin promotes mitochondrial biogenesis and adipocyte browning via AMPKα1 activation

Zeaxanthin (ZEA), a type of oxygenated carotenoid with strong antioxidant activity, has previously been found to exhibit an anti-lipogenesis effect. In the present study, we investigated the effect of ZEA on brown-like adipocyte formation and mitochondrial biogenesis in 3T3-L1 adipocytes. Brown adipocyte-specific markers, mitochondrial biogenesis and oxidative stress, and the involvement of AMP-activated protein kinase (AMPK) α1 were assessed. ZEA treated adipocytes demonstrated a brown-like pattern, with upregulated expression of uncoupling protein 1 (UCP1) and other brown adipocyte markers. In addition, ZEA intervention induced a dramatic increase in mitochondrial DNA (mtDNA) content and in the mRNA levels of genes associated with mitochondrial biogenesis. Furthermore, ZEA attenuated mitochondrial oxidative damage caused by lipid peroxidation in adipocytes, significantly improved the mitochondrial membrane potential (MMP), and scavenged intracellular reactive oxygen species (ROS) and mitochondrial superoxide. Finally, we concluded that AMPKα1 mediated the ZEA-caused inhibition of lipid accumulation and promotion of brown and beige adipocyte-biomarker expression, as the positive effects of ZEA were diminished by Prkaa1 (AMPKα1) knockdown. These findings demonstrated that ZEA promoted the expression of brown and beige adipogenesis markers and mitochondrial biogenesis, which involved AMPKα1 activation, thus contributing to the anti-obesity effects of ZEA.

AMPK promotes induction of the tumor suppressor FLCN through activation of TFEB independently of mTOR

AMPK is a central regulator of energy homeostasis. AMPK not only elicits acute metabolic responses but also promotes metabolic reprogramming and adaptations in the long-term through regulation of specific transcription factors and coactivators. We performed a whole-genome transcriptome profiling in wild-type (WT) and AMPK-deficient mouse embryonic fibroblasts (MEFs) and primary hepatocytes that had been treated with 2 distinct classes of small-molecule AMPK activators. We identified unique compound-dependent gene expression signatures and several AMPK-regulated genes, including folliculin (Flcn), which encodes the tumor suppressor FLCN. Bioinformatics analysis highlighted the lysosomal pathway and the associated transcription factor EB (TFEB) as a key transcriptional mediator responsible for AMPK responses. AMPK-induced Flcn expression was abolished in MEFs lacking TFEB and transcription factor E3, 2 transcription factors with partially redundant function; additionally, the promoter activity of Flcn was profoundly reduced when its putative TFEB-binding site was mutated. The AMPK-TFEB-FLCN axis is conserved across species; swimming exercise in WT zebrafish induced Flcn expression in muscle, which was significantly reduced in AMPK-deficient zebrafish. Mechanistically, we have found that AMPK promotes dephosphorylation and nuclear localization of TFEB independently of mammalian target of rapamycin activity. Collectively, we identified the novel AMPK-TFEB-FLCN axis, which may function as a key cascade for cellular and metabolic adaptations.—Collodet, C., Foretz, M., Deak, M., Bultot, L., Metairon, S., Viollet, B., Lefebvre, G., Raymond, F., Parisi, A., Civiletto, G., Gut, P., Descombes, P., Sakamoto, K. AMPK promotes induction of the tumor suppressor FLCN through activation of TFEB independently of mTOR.

A influência do exercício físico na captação de glicose independente de insulina

O diabetes melito é uma desordem metabólica de múltipla etiologia, que se caracteriza por hiperglicemia crônica decorrente de defeitos na secreção e/ou ação da insulina e captação reduzida de glicose nos tecidos periféricos, resultando em resistência à insulina. A partir disso, este artigo aborda aspectos fisiopatológicos do diabetes melito tipo 2 (DM2), tendo como objetivo elucidar as vias de sinalização da insulina no tecido muscular esquelético e como a captação de glicose pode ser prejudicada em um indivíduo resistente à insulina, apontando a prática de exercício físico como recurso não farmacológico e/ou terapia adjacente para a melhora da sensibilidade à insulina e captação de glicose no tecido muscular esquelético. Para tal, foi realizada uma pesquisa de revisão da literatura de materiais já publicados sobre o tema e uma análise qualitativa. A sinalização da proteína quinase ativada por adenosina monofosfato (AMPK), mediada pelo exercício físico pode otimizar a captação de glicose no músculo independente de insulina. Assim, o exercício físico serve como recurso não farmacológico e/ou terapia adjacente para restaurar a sensibilidade da via de sinalização receptor de insulina/substrato do receptor de insulina/fosfatidilinositol-3-quinase/Akt e aumento da atividade da proteína quinase ativada de AMP, para translocação e exocitose de transportadores de glicose tipo 4 (GLUT-4) independente de insulina.

Effect of Konjac Mannan Oligosaccharides on Glucose Homeostasis via the Improvement of Insulin and Leptin Resistance In Vitro and In Vivo

Functional oligosaccharides, particularly konjac mannan oligosaccharides (KMOS), can regulate glucose metabolism. However, the molecular mechanisms involved in the hypoglycemic effect of KMOS remain largely unknown. Here, the effect of KMOS supplementation on glucose homeostasis was evaluated in both high-fat diet (HFD)-fed C57BL/6J mice and high-glucosamine-induced HepG2 cells. KMOS supplementation remarkably ameliorated the fasting blood glucose, glucose tolerance, and insulin tolerance of HFD-fed mice. Abnormalities of triglyceride and glycogen metabolism in the liver induced by the HFD were reversed by KMOS supplementation. The insulin signaling pathway was activated by KMOS, with stimulation of GLUT2 membrane translocation and glucose uptake in HepG2 cells via the AMPK pathway. Moreover, KMOS suppressed p-mTOR expression and stimulated the GSK-3β/CREB pathway via the AMPK pathway. KMOS significantly upregulated leptin receptor expression and downregulated PTP1B and SOCS3 levels in the liver and brain, with a decreased serum leptin concentration. Phosphorylation of JAK2 and STAT3 in the liver was activated by KMOS supplementation, while the expressions of Sirt1, Tfam, and Pgc1-α in the brain were elevated. Conclusively, KMOS attenuated HFD-induced glucose metabolism dysfunction through the regulation of insulin resistance and leptin resistance. This finding indicates that KMOS have potential value as an anti-hyperglycemic dietary supplement.

Protectin DX ameliorates palmitate-induced hepatic insulin resistance through AMPK/SIRT1-mediated modulation of fetuin-A and SeP expression

The role as well as the molecular mechanisms of protectin DX (PDX) in the prevention of hepatic insulin resistance, a hallmark of type 2 diabetes, remains unknown. Therefore, the present study was designed to explore the direct impact of PDX on insulin resistance and to investigate the expression of fetuin-A and selenoprotein P (SeP), hepatokines that are involved in insulin signalling, in hepatocytes. Human serum levels of PDX as well as fetuin-A and SeP were determined by high-performance liquid chromatography (HPLC). Human primary hepatocytes were treated with palmitate and PDX. NF-κB phosphorylation as well as expression of insulin signalling associated genes and hepatokines were determined by Western blotting analysis. FOXO1 binding levels were measured by quantitative real-time PCR. Selected genes from candidate pathways were evaluated by small interfering (si) RNA-mediated gene suppression. Serum PDX levels were significantly (P < 0.05) downregulated, whereas serum fetuin-A and SeP levels were increased (P < 0.05) in obese subjects compared with healthy subjects. In in vitro experiments, PDX treatment increased AMP-activated protein kinase (AMPK) phosphorylation and SIRT1 expression and attenuated palmitate-induced fetuin-A and SeP expression and insulin resistance in hepatocytes. AMPK or SIRT1 siRNA mitigated the suppressive effects of PDX on palmitate-induced fetuin-A through NF-κB and SeP expression linked to FOXO1 and insulin resistance. Recombinant fetuin-A and SeP reversed the suppressive effects of fetuin-A and SeP expression on palmitate-mediated impairment of insulin signalling. The current finding provides novel insight into the underlying mechanism linking hepatokines to the pathogenesis of hepatic insulin resistance.

Bouchardatine analogue alleviates non-alcoholic hepatic fatty liver disease/non-alcoholic steatohepatitis in high-fat fed mice by inhibiting ATP synthase activity

BACKGROUND AND PURPOSE

Non-alcoholic hepatic fatty liver disease (NAFLD) is a manifestation of the metabolic syndrome in the liver and non-alcoholic steatohepatitis (NASH) represents its advanced stage. R17 derived from bouchardatine, shows benefits in the metabolic syndrome, but has not been tested in the liver. The present study examined the pharmacological effects of R17 in a model of NAFLD/NASH and its mode of action.

EXPERIMENTAL APPROACH

The effects of R17 were examined in mice fed a high-fat (HF) diet to induce the pathological characteristics of NAFLD/NASH and in cultures of HuH7 cells. We used histological and immunohistochemical techniques along with western blotting and siRNA. Generation of ROS and apoptosis were measured.

KEY RESULTS

Administration of R17 (20 mg·kg^-1 , i.p. every other day) for 5 weeks reversed HF-induced hepatic triglyceride content, inflammation (inflammatory cytokines and macrophage numbers), injury (hepatocyte ballooning and apoptosis, plasma levels of alanine aminotransferase and aspartate aminotransferase), and fibrogenesis (collagen deposition and mRNA expression of fibrosis markers). In cultured cells, R17 reduced cell steatosis from both lipogenesis and fatty acid influx. The attenuated inflammation and cell injury were associated with inhibition of both endoplasmic reticulum (ER) stress and oxidative stress. Notably, R17 activated the liver kinase B1-AMP-activated protein kinase (AMPK) pathway by inhibiting activity of ATP synthase, rather than direct stimulation of AMPK.

CONCLUSION AND IMPLICATIONS

R17 has therapeutic potential for NAFLD/NASH. Its mode of action involves the elimination of ER and oxidative stresses, possibly via activating the LKB1-AMPK axis by inhibiting the activity of ATP synthase.

Humulus japonicus stimulates thermogenesis and ameliorates oxidative stress in mouse adipocytes

An aqueous extract of Humulus japonicus (AH) has been documented to ameliorate hypertension and non-alcoholic fatty liver disease (NAFLD). Here, we investigated the effects of an aqueous extract of AH on thermogenesis and palmitate-induced oxidative stress in adipocytes. To verify the effect of AH on browning, we measured the expression levels of specific markers in 3T3-L1 adipocytes using qPCR and Western blotting, respectively. To assess the role of oxidative stress, cells were stained with DCFDA and observed by fluorescence microscopy. AH increased the expression of brown adipose tissue-specific markers. Additionally, it induced fatty acid oxidation and lipolysis and suppressed both lipogenic markers and lipid accumulation. Furthermore, AH ameliorated hydrogen peroxide-induced oxidative stress. Enhanced expression of these markers contributed to fat browning, fatty acid oxidation and lipolysis of 3T3-L1 adipocytes via the AMP-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor delta (PPARδ) signaling pathways. Moreover, AMPK and PPARδ resulting in protective effects of AH against oxidative stress. In sum, AH could promote the browning, lipolysis and thermogenesis in 3T3-L1 adipocytes and would suppress the hydrogen peroxide-induced oxidative stress and lipogenesis during differentiation. We therefore suggest that AH could be used as a potential candidate for treating obesity and related metabolic disorders.

AMP-activated protein kinase complexes containing the β2 regulatory subunit are up-regulated during and contribute to adipogenesis

AMP-activated protein kinase (AMPK) is a heterotrimer of α-catalytic and β- and γ-regulatory subunits that acts to regulate cellular and whole-body nutrient metabolism. The key role of AMPK in sensing energy status has led to significant interest in AMPK as a therapeutic target for dysfunctional metabolism in type 2 diabetes, insulin resistance and obesity. Despite the actions of AMPK in the liver and skeletal muscle being extensively studied, the role of AMPK in adipose tissue and adipocytes remains less well characterised. Small molecules that selectively influence AMPK heterotrimers containing specific AMPKβ subunit isoforms have been developed, including MT47-100, which selectively inhibits complexes containing AMPKβ2. AMPKβ1 and AMPKβ2 are the principal AMPKβ subunit isoforms in rodent liver and skeletal muscle, respectively, yet the contribution of specific AMPKβ isoforms to adipose tissue function, however, remains largely unknown. This study therefore sought to determine the contribution of AMPKβ subunit isoforms to adipocyte biology, focussing on adipogenesis. AMPKβ2 was the principal AMPKβ isoform in 3T3-L1 adipocytes, isolated rodent adipocytes and human subcutaneous adipose tissue, as assessed by the contribution to total cellular AMPK activity. Down-regulation of AMPKβ2 with siRNA inhibited lipid accumulation, cellular adiponectin levels and adiponectin secretion during 3T3-L1 adipogenesis, whereas down-regulation of AMPKβ1 had no effect. Incubation of 3T3-L1 cells with MT47-100 selectively inhibited AMPK complexes containing AMPKβ2 whilst simultaneously inhibiting cellular lipid accumulation as well as cellular levels and secretion of adiponectin. Taken together, these data indicate that increased expression of AMPKβ2 is an important feature of efficient adipogenesis.

The Impact of Ethinyl Estradiol on Metformin Action on Prolactin Levels in Women with Hyperprolactinemia

Background Metformin reduced prolactin levels only in women with hyperprolactinemia.

Objective The purpose of this case-control study was to compare metformin action on lactoctrope function between women receiving oral contraceptive pills and women not using hormonal contraception.

Methods The study included two groups of matched women with elevated prolactin levels and new-onset prediabetes or diabetes. The first group consisted of 20 women using oral contraceptive pills for at least 12 months before entering the study, while the second group included 20 patients not using any hormonal contraception. Over the whole study period, all women were treated with metformin (1.7–3 g daily). Circulating levels of glucose, insulin, prolactin, thyrotropin, free thyroid hormones, adrenocorticotropic hormone, gonadotropins and insulin-like growth factor-1 were measured at the beginning and at the end of the study (16 weeks later).

Results Thirty-eight patients completed the study. Metformin reduced plasma glucose levels and improved insulin sensitivity but the latter effect was stronger in women receiving oral contraceptive pills than in women not using any contraception. Although metformin treatment decreased plasma prolactin levels in both study groups, this effect was stronger in women taking oral contraceptive pills. Only in this group of women, metformin increased plasma luteinizing hormone levels. The changes in plasma prolactin correlated with their baseline insulin sensitivity and the effect of metformin on insulin sensitivity. Metformin did not affect plasma levels of thyrotropin, free thyroxine, free triiodothyronine, follicle-stimulating hormone, adrenocorticotropic hormone and insulin-like growth factor-1.

Conclusions The obtained results suggest that the effect of metformin on overactive lactotropes depends on estrogen levels.

Mitochondria-Mediated Pathogenesis and Therapeutics for Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) has become a worldwide epidemic over the last decade. Remarkable progress has been made in understanding the pathogenesis of NAFLD and, subsequently, in developing medications to treat this disease. Although the mechanisms of NAFLD are complex and multifactorial, accumulating and emerging evidence indicates that mitochondria play a critical role in the pathogenesis and progression of NAFLD. Pharmacologic therapies acting on mitochondria may therefore pave the way to novel strategies for the prevention and protection against NAFLD. This review focuses on new insights into the role of hepatic mitochondrial dysfunction in NAFLD, and summarizes recent studies on mitochondria-centric therapies for NAFLD utilizing new medications or repurposing of currently available drugs. Although some studies presented may feature controversial results or are still in lack of clinical verification, it is undoubted that medications that may spare the mitochondria from multiple levels of damage are highly promising, and have begun to be used with some degree of success.

Combination of Capsaicin and Capsiate Induces Browning in 3T3-L1 White Adipocytes via Activation of the Peroxisome Proliferator-Activated Receptor γ/β3-Adrenergic Receptor Signaling Pathways

This study investigated the effects and molecular mechanism of a combination of capsaicin and capsiate on promoting lipid metabolism and inducing browning in 3T3-L1 white adipocytes. The combination significantly suppressed lipid accumulation in adipocytes ( p = 0.019) and robustly improved lipid metabolic profiles, including decreased triacylglycerol (0.6703 ± 0.0385 versus 0.2849 ± 0.0188 mmol/g of protein; p < 0.001), total cholesterol (0.1282 ± 0.0241 versus 0.0651 ± 0.0178 mmol/g of protein; p = 0.003), and low-density lipoprotein cholesterol (0.0021 ± 0.0017 versus 0.0005 ± 0.0002 mmol/g of protein; p = 0.024) and increased high-density lipoprotein cholesterol (0.0162 ± 0.0141 versus 0.1002 ± 0.0167 mmol/g of protein; p = 0.012). Furthermore, this combination markedly upgraded the protein levels of cluster of differentiation 36 ( p = 0.007) and adipose triglyceride lipase ( p = 0.013) and phosphorylation of hormone-sensitive lipase at Ser660, Ser565, and Ser563 ( p < 0.001, p = 0.027, and p = 0.002, respectively), indicating increases of fatty acid transport and lipolysis. The levels of lipid metabolism regulators, phosphorylation of adenosine-monophosphate-activated protein kinases α and β ( p = 0.011, and p < 0.001, respectively), sirtuin 1 ( p = 0.004), and vanilloid transient receptor subtype I ( p = 0.014) were also increased by the combination. Moreover, the combination greatly activated the browning program in adipocytes, as demonstrated by increases in beige-specific gene and protein. Further research found that the protein levels of peroxisome proliferator-activated receptor γ (PPARγ; p = 0.001) and β₃-adrenergic receptor (β₃-AR; p = 0.026) were elevated by the combination, and most of the beige-specific markers were abolished by pretreatment of antagonists of PPARγ or β₃-AR. In conclusion, these results indicated that a combination of capsaicin and capsiate could induce browning in white adipocytes via activation of the PPARγ/β₃-AR signaling pathway, and this combination might be worth investigating as a potential cure for obesity.

Irbesartan Ameliorates Lipid Deposition by Enhancing Autophagy via PKC/AMPK/ULK1 Axis in Free Fatty Acid Induced Hepatocytes

Irbesartan has shown significant therapeutic effects in hypertensive patients with non-alcoholic fatty liver disease (NAFLD). To determine the underlying mechanisms of its action, we established an in vitro model of NAFLD by treating human and mouse hepatocytes with free fatty acids (FFAs) and angiotensin (Ang) II. Irbesartan significantly reversed AngII/FFA-induced lipid deposition and mitochondrial dysfunction by restoring ATP production and the mitochondrial membrane potential (MMP), and decreasing the levels of reactive oxygen species (ROS) and inflammatory markers. In addition, irbesartan also increased the autophagy flux, in terms of increased numbers of autolysosomes and autophagosomes, and the upregulation and mitochondrial localization of the autophagic proteins Atg5 and LC3BII/I. Activation of protein kinase C (PKC) and inhibition of the autophagic flux exacerbated mitochondrial dysfunction in the steatotic hepatocytes. Furthermore, AngII upregulated PKC which inhibited AMPK phosphorylation via direct interaction with the AngII receptor AT1-R. Irbesartan inhibited PKC and activated AMPK and its downstream effector ULK1, thereby inducing autophagy, decreasing lipid deposition, and restoring mitochondrial function. Taken together, irbesartan triggers autophagy via the PKC/AMPK/ULK1 axis to ameliorate the pathological changes in the steatotic hepatocytes.

Carotid baroreceptor stimulation in obese rats affects white and brown adipose tissues differently in metabolic protection

The sympathetic nervous system (SNS) regulates the functions of white adipose tissue (WAT) and brown adipose tissue (BAT) tightly. Carotid baroreceptor stimulation (CBS) efficiently inhibits SNS activation. We hypothesized that CBS would protect against obesity. We administered CBS to obese rats and measured sympathetic and AMP-activated protein kinase (AMPK)/ PPAR pathway responses as well as changes in perirenal WAT (PWAT), epididymal WAT (EWAT), and interscapular BAT (IBAT). CBS alleviated obesity-related metabolic changes, improving insulin resistance; reducing adipocyte hypertrophy, body weight, and adipose tissue weights; and decreasing norepinephrine but increasing acetylcholine in plasma, PWAT, EWAT, and IBAT. CBS also downregulated fatty acid translocase (CD36), fatty acid transport protein (FATP), phosphorylated and total hormone sensitive lipase, phosphorylated and total protein kinase A, and PPARγ in obese rats. Simultaneously, CBS upregulated phosphorylated adipose triglyceride lipase, phosphorylated and total AMPK, and PPARα in PWAT, EWAT, and IBAT. However, BAT and WAT responses differed; although many responses were more sensitive in IBAT, responses of CD36, FATP, and PPARγ were more sensitive in PWAT and EWAT. Overall, CBS decreased chronically activated SNS and ameliorated obesity-related metabolic disorders by regulating the AMPK/PPARα/γ pathway.

All-Trans-Retinoic Acid Suppresses Neointimal Hyperplasia and Inhibits Vascular Smooth Muscle Cell Proliferation and Migration via Activation of AMPK Signaling Pathway

The proliferation and migration of vascular smooth muscle cells (VSMC) is extensively involved in pathogenesis of neointimal hyperplasia. All-trans-retinoic acid (ATRA) is a natural metabolite of vitamin A. Here, we investigated the involvement of AMP-activated protein kinase (AMPK) in the anti-neointimal hyperplasia effects of ATRA. We found that treatment with ATRA significantly reduced neointimal hyperplasia in the left common carotid artery ligation mouse model. ATRA reduced the proliferation and migration of VSMC, A7r5 and HASMC cell lines. Our results also demonstrated that ATRA altered the expression of proliferation-related proteins, including CyclinD1, CyclinD3, CyclinA2, CDK2, CDK4, and CDK6 in VSMC. ATRA dose-dependently enhanced the phosphorylation level of AMPKα (Thr172) in the left common carotid artery of experimental mice. Also, the phosphorylation level of AMPKα in A7r5 and HASMC was significantly increased. In addition, ATRA dose-dependently reduced the phosphorylation levels of mTOR and mTOR target proteins p70 S6 kinase (p70S6K) and 4E-binding protein 1 (4EBP1) in A7r5 and HASMC. Notably, the inhibition of AMPKα by AMPK inhibitor (compound C) negated the protective effect of ATRA on VSMC proliferation in A7r5. Also, knockdown of AMPKα by siRNA partly abolished the anti-proliferative and anti-migratory effects of ATRA in HASMC. Molecular docking analysis showed that ATRA could dock to the agonist binding site of AMPK, and the binding energy between AMPK and ATRA was -7.91 kcal/mol. Molecular dynamics simulations showed that the binding of AMPK-ATRA was stable. These data demonstrated that ATRA might inhibit neointimal hyperplasia and suppress VSMC proliferation and migration by direct activation of AMPK and inhibition of mTOR signaling.

Aspalathin, a natural product with the potential to reverse hepatic insulin resistance by improving energy metabolism and mitochondrial respiration

Aspalathin is a rooibos flavonoid with established blood glucose lowering properties, however, its efficacy to moderate complications associated with hepatic insulin resistance is unknown. To study such effects, C3A liver cells exposed to palmitate were used as a model of hepatic insulin resistance. These hepatocytes displayed impaired substrate metabolism, including reduced glucose transport and free fatty acid uptake. These defects included impaired insulin signaling, evident through reduced phosphatidylinositol-4,5-bisphosphate 3-kinase/ protein kinase B (PI3K/AKT) protein expression, and mitochondrial dysfunction, depicted by a lower mitochondrial respiration rate. Aspalathin was able to ameliorate these defects by correcting altered substrate metabolism, improving insulin signaling and mitochondrial bioenergetics. Activation of 5'-adenosine monophosphate-activated protein kinase (AMPK) may be a plausible mechanism by which aspalathin increases hepatic energy expenditure. Overall, these results encourage further studies assessing the potential use of aspalathin as a nutraceutical to improve hepatocellular energy expenditure, and reverse metabolic disease-associated complications.

Amelioration of obesity-related biomarkers by Lactobacillus sakei CJLS03 in a high-fat diet-induced obese murine model

Recent progresses in clinical diagnostic analyses have demonstrated the decisive influence of host gut microbiota on the status of metabolic disorders. Short chain fatty acids (SCFAs) produced by gut microbiota, in particular, are considered as a key biomarker, both of communication between gut microbiota and the host, and of impact on host metabolic homeostasis. Microbiota modulation and concomitant anti-obesity effects of probiotics have been reported by different researchers. However, the underlying modulatory functions of probiotics on gut microbiota towards host metabolic homeostasis are still not fully understood. In this study, the impact of Lactobacillus sakei CJLS03 (isolated from Korean kimchi) on obesity-related biomarkers was investigated using a diet-induced obese mouse model. Body weight increase, SCFAs, the gut microbiota and various obesity-associated biomarkers were significantly and beneficially influenced by L. sakei CJLS03 administration compared to the control groups. Analytical data on faecal samples support the role of the colonic microbial population in SCFA production. The composition of the latter may be influenced by modulation of the distal gastro-intestinal microbiota by putative probiotics such as L. sakei CJLS03.

BMP and mTOR signaling in heterotopic ossification: Does their crosstalk provide therapeutic opportunities?

Heterotopic ossification (HO) refers to the pathological formation of ectopic bone in soft tissues, it occurs following severe trauma or in patients with a rare genetic disorder known as fibrodysplasia ossificans progressiva. The pathological process of HO formation is a two-step mechanism: inflammation and destruction of connective tissues, followed by bone formation. The latter is further subdivided into three stages: fibroproliferation/angiogenesis, chondrogenesis, and osteogenesis. Currently, therapeutic options for HO are limited. New potential therapeutics will most likely arise from a more detailed understanding of the signaling pathways implicated in each stage of ectopic bone formation and molecular targets that may be effective at both the early and late stages of HO. Bone morphogenetic protein (BMP) signaling is believed to play a key role in the overall HO process. Recently, the mammalian target of rapamycin (mTOR) signaling pathway has received attention as a critical pathway for chondrogenesis, osteogenesis, and HO. Inhibition of mTOR signaling has been shown to block trauma-induced and genetic HO. Intriguingly, recent studies have revealed crosstalk between mTOR and BMP signaling. Moreover, mTOR has emerged as a factor involved in the early hypoxic and inflammatory stages of HO. We will summarize the current knowledge of the roles of mTOR and BMP signaling in HO, with a particular focus on the crosstalk between mTOR and BMP signaling. We also discuss the activation of AMP activated protein kinase (AMPK) by the most widely used drug for type 2 diabetes, metformin, which exerts a dual negative regulatory effect on mTOR and BMP signaling, suggesting that metformin is a promising drug treatment for HO. The discovery of an mTOR-BMP signaling network may be a potential molecular mechanism of HO and may represent a novel therapeutic target for the pharmacological control of HO.

AMPK activating and anti adipogenic potential of Hibiscus rosa sinensis flower in 3T3-L1 cells

ETHNOPHARMACOLOGICAL RELEVANCE

The flowers of Hibiscus rosa sinensis has array of pharmacological actions. They are used in preparation of herbal decoction and teas, which have been used traditionally to reduce body weight and for its effect on metabolic syndrome.

AIM OF THE STUDY

To investigate the anti adipogenic efficacy of major fraction from ethyl acetate extract of the Hibiscus rosa sinensis flower at 25 and 50 µg/mL (HRF 25 and 50 µg/mL) in 3T3-L1 cells and delineate its possible mechanism of action.

MATERIALS AND METHODS

Pre adipocyte 3T3-L1 cells were differentiated in the presence and absence of HRF 25 and 50 µg/mL, their lipid accumulation was measured qualitatively by Oil red O staining and quantitatively by triglyceride estimation. Effect on adipolysis was determined, adipogenic and its regulatory gene and protein expression were studied and effect of HRF 25 and 50 µg/mL on AMPK was confirmed in the presence of dorsomorphin.

RESULTS

Treatment with HRF 25 and 50 µg/mL activated AMP-activated protein kinase (AMPK) and was found to alleviate triglyceride accumulation significantly (p < 0.001) by 1.6 and 2.3 times respectively in pre adipocytes during differentiation. HRF 25 and 50 µg/mL also nonsignificantly reduced lipolysis which releases free fatty acids, a major contributing factor for insulin resistance. Activation of AMPK by phosphorylation has led to reduced gene and protein expression of adipogenic factors Peroxisome proliferator- activated receptor gamma (PPAR-γ), CCAT/enhancer binding protein alpha (C/EBPα), Sterol regulatory element- binding protein-1c (SREBP-1c) and their targets Fatty acid binding protein 4 (FABP4), Fatty acid synthase (FAS), Perilipin and enhanced Adiponectin expression. Treatment with HRF 25 and 50 µg/mL also resulted in inactivation of Acetyl-CoA carboxylase (ACC) by enhancing ACC phosphorylation, which reduced the levels of malonyl-CoA an allosteric inhibitor of carnitine palmitoyl transferase 1 (CPT1). Enhanced CPT1 levels causes induction of fatty acid β- oxidation. Effects of HRF were nullified in the presence of AMPK antagonist dorsomorphin.

CONCLUSION

In summary, HRF treatments reduced adipogenesis, enhanced factors regulating fatty acid oxidation and this is mediated by AMPK activation. The results conclusively showed anti-obesity potential of HRF and it might be helpful in treatment of associated complications.

Serum from Jiao-Tai-Wan treated rats increases glucose consumption by 3T3-L1 adipocytes through AMPK pathway signaling

Type 2 diabetes (T2DM) is characterized by hyperglycemia resulting from insulin resistance. Jiao-Tai-Wan (JTW), a traditional Chinese medicine consisting of a 10:1 formulation of Rhizoma Coptidis (RC) and Cortex Cinnamomi (cinnamon) was shown to have hypoglycemic efficacy in a type 2 diabetic mouse model. Here we investigated whether glucose consumption by insulin-resistant adipocytes could be modulated by serum from JTW-treated rats, and if so, through what mechanism. JTW-medicated serum was prepared from rats following oral administration of JTW decoction twice a day for 4 days. Fully differentiated 3T3-L1 adipocytes – rendered insulin resistance by dexamethasone treatment – were cultured in medium containing JTW-medicated rat serum. JTW-medicated serum treatment increased glucose uptake, up-regulated levels of phosphorylated adenosine 5′-monophoshate-activated protein kinase (p-AMPK), and stimulated expression and translocation of glucose transporter 4 (GLUT4). JTW-medicated serum induced significantly greater up-regulation of p-AMPK and GLUT4 than either RC or cinnamon-medicated serum. JTW-medicated serum induced effects on 3T3-L1 adipocytes could be partially inhibited by treatment with the AMPK inhibitor compound C. In conclusion, JTW-medicated serum increased glucose consumption by IR adipocytes partially through the activation of the AMPK pathway, and JTW was more effective on glucose consumption than either RC or cinnamon alone.

Genetic deletion of soluble 5'-nucleotidase II reduces body weight gain and insulin resistance induced by a high-fat diet

We previously investigated whether inhibition of AMP-metabolizing enzymes could enhance AMP-activated protein kinase (AMPK) activation in skeletal muscle for the treatment of type 2 diabetes. Soluble 5'-nucleotidase II (NT5C2) hydrolyzes IMP and its inhibition could potentially lead to a rise in AMP to activate AMPK. In the present study, we investigated effects of NT5C2 deletion in mice fed a normal-chow diet (NCD) or a high-fat diet (HFD). On a NCD, NT5C2 deletion did not result in any striking metabolic phenotype. On a HFD however, NT5C2 knockout (NT5C2^-/-) mice displayed reduced body/fat weight gain, improved glucose tolerance, reduced plasma insulin, triglyceride and uric acid levels compared with wild-type (WT) mice. There was a tendency towards smaller and fewer adipocytes in epididymal fat from NT5C2^-/- mice compared to WT mice, consistent with a reduction in triglyceride content. Differences in fat mass under HFD could not be explained by changes in mRNA expression profiles of epididymal fat from WT versus NT5C2^-/- mice. However, rates of lipolysis tended to increase in epididymal fat pads from NT5C2^-/- versus WT mice, which might explain reduced fat mass. In incubated skeletal muscles, insulin-stimulated glucose uptake and associated signalling were enhanced in NT5C2^-/- versus WT mice on HFD, which might contribute towards improved glycemic control. In summary, NT5C2 deletion in mice protects against HFD-induced weight gain, adiposity, insulin resistance and associated hyperglycemia.

Chronic treatment with the modified Longdan Xiegan Tang attenuates olanzapine-induced fatty liver in rats by regulating hepatic de novo lipogenesis and fatty acid beta-oxidation-associated gene expression mediated by SREBP-1c, PPAR-alpha and AMPK-alpha

ETHNOPHARMACOLOGICAL RELEVANCE

The modified Longdan Xiegan Tang (mLXT) has been used clinically for various neuropsychiatric disorders and liver diseases. The use of antipsychotics is associated with nonalcoholic fatty liver disease.

AIM OF THE STUDY

To investigate the effect and underlying mechanisms of mLXT on antipsychotic-induced fatty liver.

MATERIALS AND METHODS

The representative active components in the formula were identified and quantified by a HPLC method. Fatty liver in male rats was induced by olanzapine (5 mg/kg) (p.o., × 8 weeks), and the rats were co-treated with mLXT extract (50 and 500 mg/kg). Blood and liver variables were determined enzymatically or histologically. Gene/protein expression was analyzed by real-time PCR and Western blot.

RESULTS

Treatment of rats with mLXT decreased olanzapine-induced increases in hepatic triglyceride content, cell vacuolar degeneration and Oil Red O-stained area, accompanied by suppression of olanzapine-stimulated hepatic mRNA and/or protein overexpression of sterol regulatory element-binding protein (SREBP)-1c, and its downstream lipogenic enzymes for de novo lipogenesis. Besides, mLXT also activated hepatic expression of peroxisome proliferator-activated receptor-alpha and its target genes associated with fatty acid beta-oxidation, phosphorylated Thr¹⁷² in AMP-activated protein kinase (AMPK)-alpha (the upstream enzyme of SREBP-1c and PPAR-alpha), and its ratio to total AMPK-alpha.

CONCLUSIONS

The present results suggest that chronic treatment with mLXT ameliorates olanzapine-induced fatty liver by regulating hepatic de novo lipogenesis- and fatty acid beta-oxidation-associated gene expression mediated by SREBP-1c and PPAR-alpha, respectively, through activation of AMPK-alpha. Our findings provide the evidence that supports clinical use of the formula for antipsychotic medication-induced fatty liver.

Antipsychotics Promote Metabolic Disorders Disrupting Cellular Lipid Metabolism and Trafficking

Antipsychotics frequently cause obesity and related metabolic disorders that current psychopharmacological/endocrinological theories do not explain consistently. An integrative/alternative theory implies metabolic alterations happening at the cellular level. Many observations in vitro and in vivo, and pivotal observations in humans, point towards chemical properties of antipsychotics, independent of receptor binding characteristics. Being amphiphilic weak bases, antipsychotics can disrupt lysosomal function, affecting cholesterol trafficking; moreover, by chemical mimicry, antipsychotics can inhibit cholesterol biosynthesis. These two molecular adverse effects may trigger a cascade of transcriptional and biochemical events, ultimately reducing available cholesterol while increasing cholesterol precursors and fatty acids. The macroscopic manifestation of these molecular alterations includes decreased high-density lipoprotein and increased very low-density lipoprotein and triglycerides that may translate into obesity and related metabolic disorders.

Bempedoic acid: effects on lipoprotein metabolism and atherosclerosis

PURPOSE OF REVIEW

Bempedoic acid has emerged as a potent inhibitor of ATP-citrate lyase (ACLY), a target for the reduction of LDL cholesterol (LDL-C). We review the impact of bempedoic acid treatment on lipoprotein metabolism and atherosclerosis in preclinical models and patients with hypercholesterolemia.

RECENT FINDINGS

The liver-specific activation of bempedoic acid inhibits ACLY, a key enzyme linking glucose catabolism to lipogenesis by catalyzing the formation of acetyl-CoA from mitochondrial-derived citrate for de novo synthesis of fatty acids and cholesterol. Adenosine monophosphate-activated protein kinase activation by bempedoic acid is not required for its lipid-regulating effects in vivo. Mendelian randomization of large human study cohorts has validated ACLY inhibition as a target for LDL-C lowering and atheroprotection. In rodents, bempedoic acid decreases plasma cholesterol and triglycerides, and prevents hepatic steatosis. In apolipoprotein E-deficient (Apoe) mice, LDL receptor-deficient (Ldlr) mice and LDLR-deficient miniature pigs, bempedoic acid reduces LDL-C and attenuates atherosclerosis. LDLR expression and activity are increased in primary human hepatocytes and in Apoe mouse liver treated with bempedoic acid suggesting a mechanism for LDL-C lowering, although additional pathways are likely involved. Phase 2 and 3 clinical trials revealed that bempedoic acid effectively lowers LDL-C as monotherapy, combined with ezetimibe, added to statin therapy and in statin-intolerant hypercholesterolemic patients. Treatment does not affect plasma concentrations of triglyceride or other lipoproteins.

SUMMARY

The LDL-C-lowering and attenuated atherosclerosis in animal models and reduced LDL-C in hypercholesterolemic patients has validated ACLY inhibition as a therapeutic strategy. Positive results from phase 3 long-term cardiovascular outcome trials in high-risk patients are required for bempedoic acid to be approved for prevention of atherosclerosis.

Genetic Liver-Specific AMPK Activation Protects against Diet-Induced Obesity and NAFLD

The AMP-activated protein kinase (AMPK) is a highly conserved master regulator of metabolism, whose activation has been proposed to be therapeutically beneficial for the treatment of several metabolic diseases, including nonalcoholic fatty liver disease (NAFLD). NAFLD, characterized by excessive accumulation of hepatic lipids, is the most common chronic liver disease and a major risk factor for development of nonalcoholic steatohepatitis, type 2 diabetes, and other metabolic conditions. To assess the therapeutic potential of AMPK activation, we have generated a genetically engineered mouse model, termed iAMPKCA, where AMPK can be inducibly activated in vivo in mice in a spatially and temporally restricted manner. Using this model, we show that liver-specific AMPK activation reprograms lipid metabolism, reduces liver steatosis, decreases expression of inflammation and fibrosis genes, and leads to significant therapeutic benefits in the context of diet-induced obesity. These findings further support AMPK as a target for the prevention and treatment of NAFLD.

Effects of Royal jelly on metabolic variables in diabetes mellitus: A systematic review

Diabetes mellitus is one of the most common endocrine disorders in the world. This systematic review was conducted with focus on the current knowledge on the effect of royal jelly on metabolic variables in diabetes mellitus. PubMed, Scopus, Embase, ProQuest and Google Scholar databases were searched from inception until June 2018. All clinical trials and animal studies that evaluated the effects of royal jelly on diabetes mellitus, and were published in English-language journals were eligible. Studies that provided insufficient outcomes were excluded. Out of 522 articles found in the search, only twelve articles were eligible for analysis. Seven studies showed a significant reduction in FBS, and one reported HbA1c decrease following royal jelly supplementation. Although royal jelly supplementation resulted in significant reductions in HOM A-I R in three studies, the findings on insulin levels were controversial. In addition, royal jelly substantially improved serum levels of triglycerides, cholesterol, HDL, LDL, VLDL and Apo-A1 in diabetes mellitus. In addition, royal jelly resulted in a decrease oxidative stress indicators and increase antioxidant enzymes levels. In conclusion, royal jelly could improve glycemic status, lipid profiles and oxidative stress in diabetes mellitus. However, exploring the underlying mechanisms warrants further studies.

Ginsenoside Rg2 inhibits adipogenesis in 3T3-L1 preadipocytes and suppresses obesity in high-fat-diet-induced obese mice through the AMPK pathway

Rg2-induced activation of AMPK reduced the expression of adipogenic transcription factors, and regulated the lipogenic and lipolysis genes, thus inhibiting adipogenesis.

Isoquercetin Improves Hepatic Lipid Accumulation by Activating AMPK Pathway and Suppressing TGF-β Signaling on an HFD-Induced Nonalcoholic Fatty Liver Disease Rat Model

Isoquercetin (IQ), a glucoside derivative of quercetin, has been reported to have beneficial effects in nonalcoholic fatty liver disease (NAFLD). In this study, we investigated the potential improvement of IQ in liver lipid accumulation, inflammation, oxidative condition, and activation in Kupffer cells (KCs) on a high-fat diet (HFD) induced NAFLD models. Male Sprague-Dawley (SD) rats were induced by HFD, lipopolysaccharides/free fatty acids (LPS/FFA) induced co-culture cells model between primary hepatocytes and Kupffer cells was used to test the effects and the underlying mechanism of IQ. Molecular docking was performed to predict the potential target of IQ. Significant effects of IQ were found on reduced lipid accumulation, inflammation, and oxidative stress. In addition, AMP-activated protein kinase (AMPK) pathway was activated by IQ, and is plays an important role in lipid regulation. Meanwhile, IQ reversed the increase of activated KCs which caused by lipid overload, and also suppression of Transforming growth factor beta (TGF-β) signaling by TGF-β Recptor-1 and SMAD2/3 signaling. Finally, TGF-βR1 and TGF-βR2 were both found may involve in the mechanism of IQ. IQ can improve hepatic lipid accumulation and decrease inflammation and oxidative stress by its activating AMPK pathway and suppressing TGF-β signaling to alleviate NAFLD.

Hypoglycemic effect of whole grain diet in C57BL/KsJ-db/db mice by activating PI3K/Akt and AMPK pathways

Type II diabetes mellitus (T2DM), characterized by abnormal blood glucose level, is a metabolic disease caused by pancreatic β-cell dysfunction and insulin resistance. Previous studies have reported that whole grain intake alleviated various metabolic syndromes. Here, the hypoglycemic effect of whole grain diet (WGD) on type II diabetes was investigated in C57BL/KsJ-db/db mice. WGD improved the regulation of fasting and postprandial blood glucose levels and reduced weight gain and lipid accumulation. On the molecular level, WGD up-regulated the glucose transporter type 4 and stimulated the insulin receptor substrate 1/phosphoinositide 3-kinase ((PI3K)/Akt) pathway. WGD stimulated the AMP-activated protein kinase (AMPK)/p38/Acetyl-CoA carboxylate pathway related to lipid metabolism and glucose uptake, and down-regulated the pro-inflammatory cytokines, C-reactive protein, interleukin (IL)-6, IL-1β, and tumor necrosis factor-alpha. Taken together, whole grains can be employed as functional food ingredients to alleviate T2DM by enhancing the PI3K/Akt and AMPK pathways.

Dual targeting of Nur77 and AMPKα by isoalantolactone inhibits adipogenesis in vitro and decreases body fat mass in vivo

BACKGROUND

Suppression of adipogenesis has been considered as a potential target for the prevention and treatment of obesity and associated metabolic disorders, and the nuclear receptor 4A1 (NR4A1/Nur77) and AMPKα are known to play important roles during early and intermediate stages of adipogenesis. Therefore, we hypothesized that dual targeting Nur77 and AMPKα would show strong inhibitory effect on adipogenesis.

METHODS

We screened a herbal medicine-based small molecule library to identify novel natural compounds dual targeting Nur77 and AMPKα, and the antiadipogenic effects and mechanisms of action of a "hit" compound were studied in 3T3-L1 cells. In vivo antiobesity effects of the compound were also investigated in high-fat diet (HFD)-induced obese mice.

RESULTS

We identified isoalantolactone (ISO) as a new NR4A1 inactivator that also activates AMPKα in 3T3-L1 cells. ISO, as expected, inhibited adipogenic differentiation of 3T3-L1 preadipocytes, accompanied by reduced mitotic clonal expansion (MCE) which occurs in the early stage of adipogenesis and decreased expression of genes required for MCE and cell cycle markers including cyclin A, cyclin D1. Furthermore, ISO reduced body weight gain and fat mass (epididymal, subcutaneous, perirenal, and inguinal white adipose tissues) in the high-fat diet-fed C57BL/6 N mice. Serum levels of triglycerides, aspartate transaminase, and alanine transaminase and hepatic steatosis were also significantly improved in the ISO-treated group compared to the high-fat diet control group.

CONCLUSIONS

These results suggest that ISO dual targeting Nur77 and AMPKα during adipogenesis represents a novel class of mechanism-based antiadipogenic agents for treatment of obesity and associated metabolic disorders, including hyperlipidemia and fatty liver.

Host Adaptive Immune Status Regulates Expression of the Schistosome AMP-Activated Protein Kinase

Schistosomes exhibit profound developmental adaptations in response to the immune status of their mammalian host, including significant attenuation of parasite growth, development and reproduction in response to deficits in host adaptive immunity. These observations led us to hypothesize that schistosomes regulate the utilization of energy resources in response to immunological conditions within the host. To test this hypothesis, we identified and characterized the Schistosoma mansoni AMP-activated protein kinase (AMPK), a heterotrimeric enzyme complex that is central to regulating energy metabolism at the cellular and organismal level in eukaryotes. We show that expression of the catalytic α subunit is developmentally regulated during the parasite life cycle, with peak expression occurring in adult worms. However, the protein is present and phosphorylated in all life cycle stages examined, suggesting a need for active regulation of energy resources throughout the life cycle. In contrast, transcription of the AMPK α gene is down-regulated in cercariae and schistosomula, suggesting that the protein in these life cycle stages is pre-synthesized in the sporocyst and that expression must be re-initiated once inside the mammalian host. We also show that schistosome AMPK α activity in adult worms is sensitive to changes in the parasite's environment, suggesting a mechanism by which schistosome metabolism may be responsive to host immune factors. Finally, we show that AMPK α expression is significantly down-regulated in parasites isolated from immunodeficient mice, suggesting that modulation of parasite energy metabolism may contribute to the attenuation of schistosome growth and reproduction in immunodeficient hosts. These findings provide insights into the molecular interactions between schistosomes and their vertebrate hosts and suggest that parasite energy metabolism may represent a novel target for anti-schistosome interventions.

A769662 Inhibits Insulin-Stimulated Akt Activation in Human Macrovascular Endothelial Cells Independent of AMP-Activated Protein Kinase

Protein kinase B (Akt) is a key enzyme in the insulin signalling cascade, required for insulin-stimulated NO production in endothelial cells (ECs). Previous studies have suggested that AMP-activated protein kinase (AMPK) activation stimulates NO synthesis and enhances insulin-stimulated Akt activation, yet these studies have largely used indirect activators of AMPK. The effects of the allosteric AMPK activator A769662 on insulin signalling and endothelial function was therefore examined in cultured human macrovascular ECs. Surprisingly, A769662 inhibited insulin-stimulated NO synthesis and Akt phosphorylation in human ECs from umbilical veins (HUVECs) and aorta (HAECs). In contrast, the AMPK activators compound 991 and AICAR had no substantial inhibitory effect on insulin-stimulated Akt phosphorylation in ECs. Inhibition of AMPK with SBI-0206965 had no effect on the inhibition of insulin-stimulated Akt phosphorylation by A769662, suggesting the inhibitory action of A769662 is AMPK-independent. A769662 decreased IGF1-stimulated Akt phosphorylation yet had no effect on VEGF-stimulated Akt signalling in HUVECs, suggesting that A769662 attenuates early insulin/IGF1 signalling. The effects of A769662 on insulin-stimulated Akt phosphorylation were specific to human ECs, as no effect was observed in the human cancer cell lines HepG2 or HeLa, as well as in mouse embryonic fibroblasts (MEFs). A769662 inhibited insulin-stimulated Erk1/2 phosphorylation in HAECs and MEFs, an effect that was independent of AMPK in MEFs. Therefore, despite being a potent AMPK activator, A769662 has effects unlikely to be mediated by AMPK in human macrovascular ECs that reduce insulin sensitivity and eNOS activation.

Metabolite sensing and signaling in cell metabolism

Metabolite sensing is one of the most fundamental biological processes. During evolution, multilayered mechanisms developed to sense fluctuations in a wide spectrum of metabolites, including nutrients, to coordinate cellular metabolism and biological networks. To date, AMPK and mTOR signaling are among the best-understood metabolite-sensing and signaling pathways. Here, we propose a sensor-transducer-effector model to describe known mechanisms of metabolite sensing and signaling. We define a metabolite sensor by its specificity, dynamicity, and functionality. We group the actions of metabolite sensing into three different modes: metabolite sensor-mediated signaling, metabolite-sensing module, and sensing by conjugating. With these modes of action, we provide a systematic view of how cells sense sugars, lipids, amino acids, and metabolic intermediates. In the future perspective, we suggest a systematic screen of metabolite-sensing macromolecules, high-throughput discovery of biomacromolecule-metabolite interactomes, and functional metabolomics to advance our knowledge of metabolite sensing and signaling. Most importantly, targeting metabolite sensing holds great promise in therapeutic intervention of metabolic diseases and in improving healthy aging.

A simple, three-part model provides a systematic view of how cells sense sugars, lipids, amino acids and metabolic intermediates. Cells quickly and accurately perceive changes in intra- and extracellular molecules such as nutrients to respond to changing environments. Drawing on existing knowledge about AMPK and MTORC1 signaling, Yi-Ping Wang and Qun-Ying Lei at Fudan University in Shanghai propose a model in which three components: a sensor, transducer and effector enable metabolic sensing and signaling to proceed. The sensor detects the metabolite, and, through conjugation, conformational changes or protein–protein interactions, transmits this information to the transducer, which decides the appropriate response. The transducer then issues orders to effector proteins which coordinate the action. The future identification of novel metabolic sensors through systematic screening could lead to new therapeutic interventions for metabolic and age-related diseases.

Involvement of 5'-Activated Protein Kinase (AMPK) in the Effects of Resveratrol on Liver Steatosis

This review focuses on the role of 5′AMP-activated protein kinase (AMPK) in the effects of resveratrol (RSV) and some RSV derivatives on hepatic steatosis. In vitro studies, performed in different hepatic cell models, have demonstrated that RSV is effective in preventing liver TG accumulation by activating AMPK, due to its phosphorylation. These preventive effects have been confirmed in studies conducted in animal models, such as mice and rats, by administering the phenolic compound at the same time as the diet which induces TG accumulation in liver. The literature also includes studies focused on other type of models, such as animals showing alcohol-induced steatosis or even steatosis induced by administering chemical products. In addition to the preventive effects of RSV on hepatic steatosis, other studies have demonstrated that it can alleviate previously developed liver steatosis, thus its role as a therapeutic tool has been proposed. The implication of AMPK in the delipidating effects of RSV in in vivo models has also been demonstrated.

Cilostazol Improves HFD-Induced Hepatic Steatosis by Upregulating Hepatic STAMP2 Expression through AMPK

Nonalcoholic fatty liver disease (NAFLD) is an increasingly studied condition that can progress to end-stage liver disease. Although NAFLD was first described in 1980, a complete understanding of the mechanism and causes of this disease is still lacking. Six-transmembrane protein of prostate 2 (STAMP2) plays a role in integrating inflammatory and nutritional signals with metabolism. Our previous study suggested that STAMP2 may be a suitable target for treating NAFLD. In the current study, we performed a focused drug-screening and found that cilostazol could be a potential STAMP2 enhancer. Thus, we examined whether cilostazol alleviates NAFLD through STAMP2. The in vivo and in vitro pharmacological efficacies of cilostazol on STAMP2 expression and lipid accumulation were analyzed in NAFLD mice induced by high-fat diet (HFD) and in HepG2 cell lines treated by oleic acid (OA), respectively. Cilostazol increased the expression of STAMP2 through transcriptional regulation in vivo and in vitro. Cilostazol also dampened the STAMP2 downregulation caused by the HFD and by OA in vivo and in vitro, respectively. Cilostazol activated AMP-activated protein kinase (AMPK) in vivo and in vitro, and AMPK functions upstream of STAMP2, and reversed downregulation of STAMP2 expression through AMPK in the NAFLD model. Cilostazol ameliorates hepatic steatosis by enhancing hepatic STAMP2 expression through AMPK. Enhancing STAMP2 expression with cilostazol represents a potential therapeutic avenue for treatment of NAFLD.