AMP activated protein kinase: a next generation target for total metabolic control

Tanshinone IIA: a Chinese herbal ingredient for the treatment of atherosclerosis

Tanshinone IIA (Tan IIA) is a fat-soluble compound extracted from Salvia miltiorrhiza, which has a protective effect against atherosclerosis (AS). Tan IIA can inhibit oxidative stress and inflammatory damage of vascular endothelial cells (VECs) and improve endothelial cell dysfunction. Tan IIA also has a good protective effect on vascular smooth muscle cells (VSMCs). It can reduce vascular stenosis by inhibiting the proliferation and migration of vascular smooth muscle cells (VSMCs), and improve the stability of the fibrous cap of atherosclerotic plaque by inhibiting apoptosis and inflammation of VSMCs. In addition, Tan IIA inhibits the inflammatory response of macrophages and the formation of foam cells in atherosclerotic plaques. In summary, Tan IIA improves AS through a complex pathway. We propose to further study the specific molecular targets of Tan IIA using systems biology methods, so as to fundamentally elucidate the mechanism of Tan IIA. It is worth mentioning that there is a lack of high-quality evidence-based medical data on Tan IIA treatment of AS. We recommend that a randomized controlled clinical trial be conducted to evaluate the exact efficacy of Tan IIA in improving AS. Finally, sodium tanshinone IIA sulfonate (STS) can cause adverse drug reactions in some patients, which needs our attention.

A combination of metformin and insulin improve cardiovascular and cerebrovascular risk factors in individuals with type 1 diabetes mellitus

BACKGROUND

This study aims to further clarify whether the addition of metformin to insulin treatment improve cardiovascular and cerebrovascular risk factors in individuals with T1DM.

METHODS

Electronic databases were searched for randomized controlled trials in which the efficacy and safety of metformin were compared with those of a placebo for risk factors of cardiovascular and cerebrovascular disease among individuals with T1DM, and a meta-analysis was conducted.

RESULTS

Thirteen cardiovascular studies were identified. In the metformin group, mean carotid intimal media thickness was significantly reduced by 0.03 mm, ascending aortic pulse wave velocity by 6.3 m/s, descending aortic wall shear stress by 1.77 dyn/cm² (P = 0.02), insulin daily dose by 0.05 U/kg/d, body weight by 2.27 kg, fat-free mass by 1.32 kg, body mass index by 0.58 kg/m², hip circumference by 0.29 m, and low-density lipoprotein by 0.16 mmol/L, all above are P < 0.05. In the metformin group, flow-mediated dilation was increased by 1.29 %, glucose infusion rate/insulin by 18.22 mg/(kg⋅min)/μIU/μL, and waist-to-hip ratio by 0.02, all above are P < 0.00001. The metformin group showed no differences in blood pressure, reactive hyperemia index, waist circumference, triglyceride, total cholesterol, high-density lipoprotein cholesterol, or body mass index Z score. For cerebrovascular studies were identified. But none of them had a risk factor assessment.

CONCLUSIONS

Metformin can ameliorate cardiovascular and cerebrovascular risk factors through non-hypoglycemic multiple pathways in individuals with T1DM.

Dammarane-type triterpenoids from Gynostemma compressum X. X. Chen & D. R. Liang (Cucurbitaceae) and their AMPK activation effect in 3T3-L1 cells

Bioassay-guided fractionation of the 80% ethanol extract of Gynostemma compressum X. X. Chen & D. R. Liang (Cucurbitaceae) resulted in the isolation and identification of eight undescribed triterpenoids, gycomol VN1, gycomol VN2, and gycomosides VN1-6 from the bioactive n-butanol fraction. The structures of these compounds were elucidated by one- and two-dimensional nuclear magnetic resonance spectroscopy, high-resolution electrospray ionisation mass spectrometry, and chemical methods. All isolated compounds were evaluated for their 5'-adenosine monophosphate-activated protein kinase (AMPK) and acetyl-coenzyme A carboxylase (ACC) activation effects on 3T3-L1 cells. Importantly, gycomol VN2, gycomoside VN1, and gycomosides VN3-5 activated the phosphorylation of AMPK and its downstream substrate ACC in 3T3-L1 cells at a dose of 10 μM. These effects imply that the activation of AMPK and ACC by active compounds from G. compressum has considerable potential for the prevention of obesity and its related disorders by activating AMPK signaling pathways.

AMPK-mediated glutaminolysis maintains coelomocytes redox homeostasis in Vibrio splendidus-challenged Apostichopus japonicus

Glutaminolysis has been proved to play an irreplaceable role in vertebrate immunity, including effects on cytokine production, bacterial killing, and redox homeostasis maintenance. Our previous metabolomics analysis indicated that glutaminolysis metabolic substrates glutamine (Gln) and metabolites glutamate (Glu) were significantly lower in Skin ulceration syndrome (SUS)-diseased Apostichopus japonicus. To further delineate the role of glutaminolysis, we assayed the levels of Gln and Glu. We found that their contents in coelomocytes were decreased, accompanied by an increase in glutathione (GSH) in pathogen-challenged Apostichopus japonicus. Consistently, the mRNA transcripts of three key genes in glutaminolysis (AjASCT2, AjGOT, and AjGCS) were significantly induced. Moreover, the increased MDA and NADPH/NADP ⁺ levels in response to pathogen infection indicated that oxidative stress occurs during the immune response. The metabolic regulator AMPKβ could regulate glutaminolysis in vertebrates by inducing cells to take up extracellular Gln. To explore the underlying regulatory mechanism behind glutaminolysis that occurred in coelomocytes, the full-length cDNA of AMPKβ was identified from A. japonicus (designated as AjAMPKβ). AjAMPKβ expression was significantly induced in the coelomocytes after pathogen challenge, which was consistent with the expression of key genes of glutaminolysis. A functional assay indicated that AjAMPKβ silencing by siRNA transfection could increase the levels of Gln and Glu and depress the production of GSH. Moreover, the expression of glutaminolysis-related genes was significantly inhibited, and the reduction of redox homeostasis indexes (MDA and NADPH/NADP⁺) was also observed. Contrastingly, AjAMPKβ overexpression promoted redox homeostasis balance. Intracellular ROS is mostly responsible for breaking redox homeostasis and leading to oxidative stress, contributing to cell fate changes in immune cells. Exogenous Gln and GSH treatments could significantly reduce ROS level while the AjAMPKβ silencing induced the level of ROS and accelerated the necrosis rate. All these results collectively revealed that AjAMPKβ could modulate cellular redox homeostasis by affecting the glutaminolysis in A. japonicus.

Beneficial Activities of Alisma orientale Extract in a Western Diet-Induced Murine Non-Alcoholic Steatohepatitis and Related Fibrosis Model via Regulation of the Hepatic Adiponectin and Farnesoid X Receptor Pathways

The hepatic adiponectin and farnesoid X receptor (FXR) signaling pathways play multiple roles in modulating lipid and glucose metabolism, reducing hepatic inflammation and fibrosis, and altering various metabolic targets for the management of non-alcoholic fatty liver disease (NAFLD). Alisma orientale (AO, Ze xie in Chinese and Taeksa in Korean) is an herbal plant whose tubers are enriched with triterpenoids, which have been reported to exhibit various bioactive properties associated with NAFLD. Here, the present study provides a preclinical evaluation of the biological functions and related signaling pathways of AO extract for the treatment of NAFLD in a Western diet (WD)-induced mouse model. The findings showed that AO extract significantly reversed serum markers (liver function, lipid profile, and glucose) and improved histological features in the liver sections of mice fed WD for 52 weeks. In addition, it also reduced hepatic expression of fibrogenic markers in liver tissue and decreased the extent of collagen-positive areas, as well as inhibited F4/80 macrophage aggregation and inflammatory cytokine secretion. The activation of adiponectin and FXR expression in hepatic tissue may be a major mechanistic signaling cascade supporting the promising role of AO in NAFLD pharmacotherapy. Collectively, our results demonstrated that AO extract improves non-alcoholic steatohepatitis (NASH) resolution, particularly with respect to NASH-related fibrosis, along with the regulation of liver enzymes, postprandial hyperglycemia, hyperlipidemia, and weight loss, probably through the modulation of the hepatic adiponectin and FXR pathways.

AMPK signaling mediates synphilin-1-induced hyperphagia and obesity in Drosophila

Expression of synphilin-1 in neurons induces hyperphagia and obesity in a Drosophila model. However, the molecular pathways underlying synphilin-1-linked obesity remain unclear. Here, Drosophila models and genetic tools were used to study the synphilin-1-linked pathways in energy balance by combining molecular biology and pharmacological approaches. We found that expression of human synphilin-1 in flies increased AMP-activated kinase (AMPK) phosphorylation at Thr172 compared with that in non-transgenic flies. Knockdown of AMPK reduced AMPK phosphorylation and food intake in non-transgenic flies, and further suppressed synphilin-1-induced AMPK phosphorylation, hyperphagia, fat storage and body weight gain in transgenic flies. Expression of constitutively activated AMPK significantly increased food intake and body weight gain in non-transgenic flies, but it did not alter food intake in the synphilin-1 transgenic flies. In contrast, expression of dominant-negative AMPK reduced food intake in both non-transgenic and synphilin-1 transgenic flies. Treatment with STO-609 also suppressed synphilin-1-induced AMPK phosphorylation, hyperphagia and body weight gain. These results demonstrate that the AMPK signaling pathway plays a critical role in synphilin-1-induced hyperphagia and obesity. These findings provide new insights into the mechanisms of synphilin-1-controlled energy homeostasis.

The Role of Metformin in Ovarian Cancer: Does Metformin Increase Survival in Ovarian Neoplasm?

The role of metformin in ovarian cancer (OC) remains a topic of research and open discussion. Because OC has a high mortality rate for various reasons, finding a solution is vital. Although metformin has demonstrated a high level of evidence in preventing and increasing survival in other cancers, its role in OC is still not proven. This review highlights the function of metformin as an antineoplastic agent in OC and its effect on overall survival, progress-free survival, and recurrence-free survival. We conducted a literature search in the PubMed database using the medical subject heading keywords, ovarian neoplasm and metformin. The search yielded 94 articles, of which 86 remained after including only English language articles. Finally, 50 articles published between 1997 and 2020 were reviewed. We recommend more randomized controlled trials in the future to determine the safety and efficacy of metformin in OC.

Experimental Evidence of the Benefits of Acupuncture for Alzheimer's Disease: An Updated Review

As the global population ages, the prevalence of Alzheimer's disease (AD), the most common form of dementia, is also increasing. At present, there are no widely recognized drugs able to ameliorate the cognitive dysfunction caused by AD. The failure of several promising clinical trials in recent years has highlighted the urgent need for novel strategies to both prevent and treat AD. Notably, a growing body of literature supports the efficacy of acupuncture for AD. In this review, we summarize the previously reported mechanisms of acupuncture's beneficial effects in AD, including the ability of acupuncture to modulate Aβ metabolism, tau phosphorylation, neurotransmitters, neurogenesis, synapse and neuron function, autophagy, neuronal apoptosis, neuroinflammation, cerebral glucose metabolism, and brain responses. Taken together, these findings suggest that acupuncture provides therapeutic effects for AD.

The effect of eleutherococcus senticosus on metabolism-associated protein expression in 3T3-L1 and C2C12 cells

[Purpose]

In vivo studies have demonstrated the ergogenic benefits of eleutherococcus senticosus (ES) supplementation. ES has been observed to enhance endurance capacity, improve cardiovascular function, and alter metabolic functions (e.g., increased fat utilization); however, the exact mechanisms involved remain unknown. We aimed to determine whether ES could effectively induce fat loss and improve muscle metabolic profiles through increases in lipolysis- and lipid metabolism-associated protein expression in 3T3-L1 adipocytes and C2C12 skeletal muscle cells, respectively, to uncover the direct effects of ES on adipocytes and skeletal muscle cells.

[Methods]

Different doses of ES extracts (0.2, 0.5, and 1.0 mg/mL) were added to cells (0.2 ES, 0.5 ES, and 1.0 ES, respectively) for 72 h and compared to the vehicle control (control).

[Results]

The intracellular triacylglycerol (TG) content significantly decreased (p < 0.05 for 0.2 ES, p < 0.01 for 0.5 ES and 1.0 ES) in 3T3-L1 cells. Adipose triglyceride lipase, which is involved in active lipolysis, was significantly higher in the 1.0 ES group than in the control group (p < 0.01) of 3T3-L1 adipocytes. In C2C12 cells, the mitochondrial protein voltage-dependent anion channel (VDAC) was significantly increased in the 1.0 ES group (p < 0.01). Furthermore, we found that 1.0 ES activated both 5' AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC) in skeletal muscle cells (p < 0.01).

[Conclusion]

These findings suggest that ES extracts decreased TG content, presumably by increasing lipase in adipocytes and metabolism-associated protein expression as well as mitochondrial biogenesis in muscle cells. These effects may corroborate previous in vivo findings regarding the ergogenic effects of ES supplementation.

Irradiation of carotid baroreceptor with low-intensity pulsed ultrasound exerts different metabolic protection in perirenal, epididymal white adipose tissue and interscapular brown adipose tissue of obese rats

This study was designed to clarify whether the irradiation of carotid baroreceptor (CB) with low-intensity pulsed ultrasound (LIPUS) protects against obesity by rebalancing the autonomic nervous system (ANS). Obesity was induced using a high-fat diet (HFD) for 8 weeks in Sprague-Dawley rats. Irradiation with LIPUS was daily (20 minutes a day) applied to the right CB. In our study, LIPUS significantly ameliorated metabolic disorders in obese rats. LIPUS partly restored norepinephrine (NE) and acetylcholine (ACH) levels in the perirenal white adipose tissue (PWAT), epididymal white adipose tissue (EWAT), interscapular brown adipose tissue (IBAT), and plasma of obese rats. LIPUS partially rectified the dysregulated AMP-activated protein kinase (AMPK)/peroxisome proliferator-activated receptor (PPAR) α/ɣ pathway in the PWAT, EWAT, and IBAT of obese rats. PPARγ and PPARγ target genes respond more sensitively to HFD and LIPUS in PWAT and EWAT than in IBAT. NE, ACH, uncoupling protein-1, phosphorylated AMPK, PPARα, and PPARα target genes respond more sensitively to HFD and LIPUS in IBAT than in PWAT and EWAT. Conclusion: LIPUS irradiation of CB exerts different metabolic protection in PWAT, EWAT, and IBAT by rebalancing the ANS and rectifying the AMPK/PPARα/ɣ pathway in obese rats.

Synphilin-1 Interacts with AMPK and Increases AMPK Phosphorylation

A role for the cytoplasmic protein synphilin-1 in regulating energy balance has been demonstrated recently. Expression of synphilin-1 increases ATP levels in cultured cells. However, the mechanism by which synphilin-1 alters cellular energy status is unknown. Here, we used cell models and biochemical approaches to investigate the cellular functions of synphilin-1 on the AMP-activated protein kinase (AMPK) signaling pathway, which may affect energy balance. Overexpression of synphilin-1 increased AMPK phosphorylation (activation). Moreover, synphilin-1 interacted with AMPK by co-immunoprecipitation and GST (glutathione S-transferase) pull-down assays. Knockdown of synphilin-1 reduced AMPK phosphorylation. Overexpression of synphilin-1 also altered AMPK downstream signaling, i.e., a decrease in acetyl CoA carboxylase (ACC) phosphorylation, and an increase in p70S6K phosphorylation. Treatment of compound C (an AMPK inhibitor) reduced synphilin-1 binding with AMPK. In addition, compound C diminished synphilin-1-induced AMPK phosphorylation, and the increase in cellular ATP (adenosine triphosphate) levels. Our results demonstrated that synphilin-1 couples with AMPK, and they exert mutual effects on each other to regulate cellular energy status. These findings not only identify novel cellular actions of synphilin-1, but also provide new insights into the roles of synphilin-1 in regulating energy currency, ATP.

M3 muscarinic receptor activation reduces hepatocyte lipid accumulation via CaMKKβ/AMPK pathway

Previously, we reported that hepatic muscarinic receptors modulate both acute and chronic liver injury, however, the role of muscarinic receptors in fatty liver disease is unclear. We observed in patients who underwent weight loss surgery, a decrease in hepatic expression of M3 muscarinic receptors (M3R). We also observed that fat loading of hepatocytes, increased M3R expression. Based on these observations, we tested the hypothesis that M3R regulate hepatocyte lipid accumulation. Incubation of AML12 hepatocytes with 1 mM oleic acid resulted in lipid accumulation that was significantly reduced by co-treatment with a muscarinic agonist (pilocarpine or carbachol), an effect blocked by atropine (a muscarinic antagonist). Similar treatment of Hepa 1-6 cells, a mouse hepatoblastoma cell line, showed comparable results. In both, control and fat-loaded AML12 cells, pilocarpine induced time-dependent AMPKα phosphorylation and significantly up-regulated lipolytic genes (ACOX1, CPT1, and PPARα). Compound C, a selective and reversible AMPK inhibitor, significantly blunted pilocarpine-mediated reduction of lipid accumulation and pilocarpine-mediated up-regulation of lipolytic genes. BAPTA-AM, a calcium chelator, and STO-609, a calcium/calmodulin-dependent protein kinase kinase inhibitor, attenuated agonist-induced AMPKα phosphorylation. Finally, M3R siRNA attenuated agonist-induced AMPKα phosphorylation as well as agonist-mediated reduction of hepatocyte steatosis. In conclusion, this proof-of-concept study demonstrates that M3R has protective effects against hepatocyte lipid accumulation by activating AMPK pathway and is a potential therapeutic target for non-alcoholic fatty liver disease.

AdipoRon prevents myostatin-induced upregulation of fatty acid synthesis and downregulation of insulin activity in a mouse hepatocyte line

Liver diseases such as non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are characterized by excess hepatic accumulation of lipid droplets and triglycerides which are associated with defective insulin action. Myostatin (Mstn) and adiponectin, secreted by muscle cells and adipocytes, respectively, play important roles in regulating insulin signaling and energy metabolism. The mechanisms underlying the actions of Mstn and adiponectin remain largely unknown. Moreover, the interactions between Mstn and adiponectin in regulating gene expression critical for fatty acid metabolism and insulin action in hepatocytes have not been investigated. The effects of Mstn and AdipoRon, a synthetic adiponectin receptor agonist that is orally active, alone or in combination, on hepatic gene expression and function was investigated. While Mstn increased fatty acid (FA) accumulation and desensitized cellular responses to insulin, AdipoRon protected against Mstn-induced defects in hepatic gene expression and function. In addition, these effects of Mstn were associated with reduced AMPK and PPARα activities which were reversed by AdipoRon. Finally, AdipoRon was able to prevent Mstn-induced activation of the Smad2/3 pathway. These data suggest crosstalk between Mstn-induced Smad2/3 and adiponectin-induced AMPK/PPARα pathways, which may play important roles in the regulation of hepatic gene expression critical for FA metabolism and insulin signaling. In addition, the data suggest that AdipoRon, as an adiponectin receptor agonist, may serve a therapeutic role to reduce the hepatic contribution to the disorders of fat metabolism and insulin action.

Rice Hull Extract (RHE) Suppresses Adiposity in High-Fat Diet-Induced Obese Mice and Inhibits Differentiation of 3T3-L1 Preadipocytes

Obesity is one of major health challenges in the industrial world. Although rice hull has been reported to show various bioactivities, no studies have evaluated its anti-obesity effect. We hope to demonstrate the anti-obesity effect of rice hull extract (RHE) and the underlying mechanism in high-fat diet (HFD)-induced obese mice and 3T3-L1 preadipocytes. Serum lipid profiles were determined by enzymatic methods. Histological analysis of liver and epididymis fat tissues was carried out with hematoxylin and eosin stain. The mRNA expression of adipogenic markers was analyzed with qRT-PCR and western blotting. Oral administration of RHE reduced body weight gain and fat accumulation in HFD-fed mice. RHE also reduced lipid accumulation by inhibiting the mRNA expression of adipogenic-related genes in HFD-fed obese mice and differentiated preadipocytes. The downregulation of adipogenesis by RHE was mediated through the phosphorylation of AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC). In addition, RHE induced the phosphorylation of c-Jun N-terminal kinases (JNK) and extracellular-signal-regulated kinases (ERK) in liver and epididymis adipose tissues of HFD-fed obese mice. Taken together, these findings indicate that RHE could inhibit the differentiation of adipose cell and prevent HFD-induced obesity, suggesting its potential in the prevention of obesity and metabolic syndrome and related-disorders.

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.

Adiponectin as a novel biomarker for liver fibrosis

Adiponectin is known to play primary roles in the regulation of systemic glucose homeostasis and lipid metabolism. Interestingly, emerging evidence indicates beneficial effects of adiponectin on liver fibrosis; however, the exact mechanisms of this action remain unclear. Herein, we aimed to summarize the recent findings regarding the role of adiponectin in liver fibrogenesis and update the current comprehensive knowledge regarding usefulness of adiponectin-based treatments in liver fibrosis. Adiponectin has been demonstrated to have an anti-fibrotic action in the liver by blocking the activation of hepatic stellate cell-mediated adenosine monophosphate-activated protein kinase and peroxisome proliferator-activated receptor-alpha pathways, which in turn diminish the expression of pro-fibrotic genes. In addition, hyperadiponectinemia was noted in patients with various chronic liver diseases (CLDs)-related liver fibrosis. An increase in circulating adiponectin levels was also found to be associated with the development of liver fibrosis, indicating a role of adiponectin as a non-invasive biomarker for predicting the progression of liver fibrosis. It is therefore reasonable to speculate that adiponectin may be developed as a new therapeutic candidate for the treatment of liver fibrosis. Nonetheless, future observations are still necessary to fully elucidate the extent of the effects of adiponectin on liver fibrotic outcomes, in order to modify adiponectin as an anti-fibrotic therapy that would speed up fibrosis reversal in patients with CLD.

2-[2-(4-(trifluoromethyl)phenylamino)thiazol-4-yl]acetic acid (Activator-3) is a potent activator of AMPK

AMPK is considered as a potential high value target for metabolic disorders. Here, we present the molecular modeling, in vitro and in vivo characterization of Activator-3, 2-[2-(4-(trifluoromethyl)phenylamino)thiazol-4-yl]acetic acid, an AMP mimetic and a potent pan-AMPK activator. Activator-3 and AMP likely share common activation mode for AMPK activation. Activator-3 enhanced AMPK phosphorylation by upstream kinase LKB1 and protected AMPK complex against dephosphorylation by PP2C. Molecular modeling analyses followed by in vitro mutant AMPK enzyme assays demonstrate that Activator-3 interacts with R70 and R152 of the CBS1 domain on AMPK γ subunit near AMP binding site. Activator-3 and C2, a recently described AMPK mimetic, bind differently in the γ subunit of AMPK. Activator-3 unlike C2 does not show cooperativity of AMPK activity in the presence of physiological concentration of ATP (2 mM). Activator-3 displays good pharmacokinetic profile in rat blood plasma with minimal brain penetration property. Oral treatment of High Sucrose Diet (HSD) fed diabetic rats with 10 mg/kg dose of Activator-3 once in a day for 30 days significantly enhanced glucose utilization, improved lipid profiles and reduced body weight, demonstrating that Activator-3 is a potent AMPK activator that can alleviate the negative metabolic impact of high sucrose diet in rat model.

Adiponectin Signaling Pathways in Liver Diseases

In the liver, adiponectin regulates both glucose and lipid metabolism and exerts an insulin-sensitizing effect. The binding of adiponectin with its specific receptors induces the activation of a proper signaling cascade that becomes altered in liver pathologies. This review describes the different signaling pathways in healthy and diseased hepatocytes, also highlighting the beneficial role of adiponectin in autophagy activation and hepatic regeneration.

Central insulin dysregulation and energy dyshomeostasis in two mouse models of Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder worldwide. While the causes of AD are not known, several risk factors have been identified. Among these, type two diabetes (T2D), a chronic metabolic disease, is one of the most prevalent risk factors for AD. Insulin resistance, which is associated with T2D, is defined as diminished or absent insulin signaling and is reflected by peripheral blood hyperglycemia and impaired glucose clearance. In this study, we used complementary approaches to probe for peripheral insulin resistance, central nervous system (CNS) insulin sensitivity and energy homeostasis in Tg2576 and 3xTg-AD mice, two widely used animal models of AD. We report that CNS insulin signaling abnormalities are evident months before peripheral insulin resistance. In addition, we find that brain energy metabolism is differentially altered in both mouse models, with 3xTg-AD mice showing more extensive changes. Collectively, our data suggest that early AD may reflect engagement of different signaling networks that influence CNS metabolism, which in turn may alter peripheral insulin signaling.

Metformin activation of AMPK suppresses AGE-induced inflammatory response in hNSCs

A growing body of evidence suggests type 2 diabetes mellitus (T2DM) is linked to neurodegenerative diseases such as Alzheimer's disease (AD). Although the precise mechanisms remain unclear, T2DM may exacerbate neurodegenerative processes. AMP-activated protein kinase (AMPK) signaling is an evolutionary preserved pathway that is important during homeostatic energy biogenesis responses at both the cellular and whole-body levels. Metformin, a ubiquitously prescribed anti-diabetic drug, exerts its effects by AMPK activation. However, while the roles of AMPK as a metabolic mediator are generally well understood, its performance in neuroprotection and neurodegeneration are not yet well defined. Given hyperglycemia is accompanied by an accelerated rate of advanced glycosylation end product (AGE) formation, which is associated with the pathogenesis of diabetic neuronal impairment and, inflammatory response, clarification of the role of AMPK signaling in these processes is needed. Therefore, we tested the hypothesis that metformin, an AMPK activator, protects against diabetic AGE induced neuronal impairment in human neural stem cells (hNSCs). In the present study, hNSCs exposed to AGE had significantly reduced cell viability, which correlated with elevated inflammatory cytokine expression, such as IL-1α, IL-1β, IL-2, IL-6, IL-12 and TNF-α. Co-treatment with metformin significantly abrogated the AGE-mediated effects in hNSCs. In addition, metformin rescued the transcript and protein expression levels of acetyl-CoA carboxylase (ACC) and inhibitory kappa B kinase (IKK) in AGE-treated hNSCs. NF-κB is a transcription factor with a key role in the expression of a variety of genes involved in inflammatory responses, and metformin did prevent the AGE-mediated increase in NF-κB mRNA and protein levels in the hNSCs exposed to AGE. Indeed, co-treatment with metformin significantly restored inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) levels in AGE-treated hNSCs. These findings extend our understanding of the central role of AMPK in AGE induced inflammatory responses, which increase the risk of neurodegeneration in diabetic patients.

Metformin activation of AMPK-dependent pathways is neuroprotective in human neural stem cells against Amyloid-beta-induced mitochondrial dysfunction

Alzheimer's disease (AD) is the general consequence of dementia and is diagnostic neuropathology by the cumulation of amyloid-beta (Aβ) protein aggregates, which are thought to promote mitochondrial dysfunction processes leading to neurodegeneration. AMP-activated protein kinase (AMPK), a critical regulator of energy homeostasis and a major player in lipid and glucose metabolism, is potentially implied in the mitochondrial deficiency of AD. Metformin, one of the widespread used anti- metabolic disease drugs, use its actions in part by stimulation of AMPK. While the mechanisms of AD are well established, the neuronal roles for AMPK in AD are still not well understood. In the present study, human neural stem cells (hNSCs) exposed to Aβ had significantly reduced cell viability, which correlated with decreased AMPK, neuroprotective genes (Bcl-2 and CREB) and mitochondria associated genes (PGC1α, NRF-1 and Tfam) expressions, as well as increased activation of caspase 3/9 activity and cytosolic cytochrome c. Co-treatment with metformin distinct abolished the Aβ-caused actions in hNSCs. Metformin also significantly rescued hNSCs from Aβ-mediated mitochondrial deficiency (lower D-loop level, mitochondrial mass, maximal respiratory function, COX activity, and mitochondrial membrane potential). Importantly, co-treatment with metformin significantly restored fragmented mitochondria to almost normal morphology in the hNSCs with Aβ. These findings extend our understanding of the central role of AMPK in Aβ-related neuronal impairment. Thus, a better understanding of AMPK might assist in both the recognition of its critical effects and the implementation of new therapeutic strategies in the treatment of AD.

Anti-Obesity Effects of Spiramycin In Vitro and In Vivo

The effects of spiramycin on adipogenesis and high fat diet (HFD)-induced obesity were investigated. Potential mechanisms contributing to these effects were elucidated. The inhibitory effect of spiramycin on adipocyte differentiation was assessed using 3T3-L1 preadipocyte cells, in which several parameters involved in AMPK signal pathways and lipid metabolism were examined. To further investigate the pharmacological effects of spiramycin in vivo, we examined several obesity-related parameters in HFD-induced obese mice. Spiramycin significantly inhibited preadipocyte differentiation by attenuating intracellular lipid accumulation. Spiramycin also reduced the expression of adipogenic master regulators (PPARγ, C/EBPα, and SREBP1c) and their downstream target genes (FAS, aP2, and GLUT4) in 3T3-L1 cells. In addition, AMPK phosphorylation was increased by spiramycin treatment in 3T3-L1 cells during early differentiation. Notably, HFD-induced obese mice administered spiramycin showed substantial decreases in body weight gain, serum leptin levels, adipose tissue mass, and hepatic lipid accumulation. Moreover, the decreased levels of GPT and GOT in the serum indicated that spiramycin attenuated hepatic injury caused by HFD. Taken together, these results demonstrate for the first time that spiramycin effectively attenuates HFD-induced obesity and hepatic steatosis by inhibiting adipogenesis.

Resveratrol ameliorates lipid accumulation in HepG2 cells, associated with down-regulation of lipin1 expression

The pathogenesis of alcoholic fatty liver (AFL) disease is associated with the excessive accumulation of lipids in hepatocytes as well as oxidative stress. Resveratrol (RES), a dietary polyphenol found in red wine and grapes, has been shown to protect against AFL disease. However, the precise mechanisms that lead to this protective effect remain elusive. In this study, we used HepG2 cells to investigate the effects of RES on lipid metabolism and the mechanisms underlying these effects. HepG2 cells were cultured with oleic acid and alcohol for 48 h to induce excessive lipid accumulation. Oil red O staining showed that administration of oleic acid and alcohol induced more lipid accumulation than was observed in the control group, and that RES (15, 45, or 135 μmol/L) treatment reduced intracellular lipid droplets. RES treatment also significantly attenuated hepatic steatosis and lowered levels of intracellular triglycerides (TG). Western blot analysis showed that RES enhanced the phosphorylation of AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC) and down-regulated the expression of sterol regulatory element-binding protein 1c (SREBP-1c) and lipin1. However, compound C, an AMPK inhibitor, reversed these effects of RES. In conclusion, RES reduced lipid accumulation and protected HepG2 cells. This effect may be associated with the down-regulation of SREBP-1c and lipin1 expression, increased levels of phosphorylated AMPK and ACC, and the activation of AMPK–lipin1 signaling.

Electroacupuncture improves cognitive deficits associated with AMPK activation in SAMP8 mice

Perturbations of brain energy metabolism are involved in Alzheimer's disease (AD). Adenosine monophosphate-activated kinase (AMPK) is a master energy sensor that monitors the levels of key energy metabolites. Electroacupuncture (EA) has demonstrated therapeutic potential for the treatment of AD. The effects of EA on cognitive functions and the changes of AMPK and its phosphorylated form (p-AMPK) expression were investigated in senescence-accelerated mouse prone 8 (SAMP8) mice. Cognitive function of SAMP8 mice was assessed using Morris water maze test after EA treatment. Then mice were sacrificed for immunohistochemistry and western blot analysis. EA stimulation significantly alleviated memory impairment of AD mice, and increased the levels of p-AMPK in the hippocampus. These results suggest that EA improved cognitive function associated with AMPK activation, AMPK may be a molecular target of EA in treating AD.

Euphorbiasteroid, a component of Euphorbia lathyris L., inhibits adipogenesis of 3T3-L1 cells via activation of AMP-activated protein kinase

The purpose of this study is to investigate the effects of euphorbiasteroid, a component of Euphorbia lathyris L., on adipogenesis of 3T3-L1 pre-adipocytes and its underlying mechanisms. Euphorbiasteroid decreased differentiation of 3T3-L1 cells via reduction of intracellular triglyceride (TG) accumulation at concentrations of 25 and 50 μM. In addition, euphorbiasteroid altered the key regulator proteins of adipogenesis in the early stage of adipocyte differentiation by increasing the phosphorylation of AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase. Subsequently, levels of adipogenic proteins, including fatty acid synthase, peroxisome proliferator-activated receptor-γ and CCAAT/enhancer-binding protein α, were decreased by euphorbiasteroid treatment at the late stage of adipocyte differentiation. The anti-adipogenic effect of euphorbiasteroid may be derived from inhibition of early stage of adipocyte differentiation. Taken together, euphorbiasteroid inhibits adipogenesis of 3T3-L1 cells through activation of the AMPK pathway. Therefore, euphorbiasteroid and its source plant, E. lathyris L., could possibly be one of the fascinating anti-obesity agent.

Cardioprotective effect of epigallocatechin-3-gallate against myocardial infarction in hypercholesterolemic rats

Cardiovascular diseases are closely associated with a high-cholesterol or high-fat diet. The aim of the present study was to investigate the cadioprotective effect of epigallocatechin-3-gallate (EGCG) in high-fat diet-fed rats, with special emphasis on myocardial infarction. A high-fat diet was administered to male Wistar rats for 45 days and the rats of the treatment group were administered EGCG via intraperitoneal injection for the last 15 days. The serum lipid profile, antioxidant enzyme activity, lipid peroxidation, lipid metabolic proteins and cardiac tissue markers were assessed. The myocardium and aorta were also histopathologically examined. The high-fat diet-fed rats were found to be hypercholesterolemic or exhibited abnormal values in the selected parameters. However, these abnormalities were reversed to near-normal values in the rats administered EGCG. Similarly, the enzymatic antioxidant activity and non-enzymatic antioxidant levels were improved with EGCG treatment in high-fat diet-fed rats. In addition, EGCG activated sirtuin 1, endothelial nitric oxide synthase and AMP-activated protein kinase α, which suggests that its protective effect is mediated through the stimulation of lipid metabolism. The histopathological examination further revealed that EGCG significantly prevented the development of tissue abnormalities and improved the morphology of myocardial tissue. Taken together, our results suggested that EGCG plays a significant role in the protection of the cardiovascular system against the high-fat diet. This is a preliminary study, emphasizing on the cardioprotective properties of EGCG. We are currently analyzing the molecular mechanism underlying the protective effects of EGCG.

Ethanol extract of Cirsium japonicum attenuates hepatic lipid accumulation via AMPK activation in human HepG2 cells

One of the most common causes of chronic liver disease, nonalcoholic fatty liver disease (NAFLD), is strongly associated with obesity and dysregulated insulin action in the liver. However, there are no pharmacological agents currently established for the treatment of NAFLD. A flowering plant in the Asteraceae family, Cirsium japonicum (CJ), exhibits a variety of pharmacological and antioxidative properties that promote hepatoprotection. In the present study, CJ ethanol extract was shown to reduce hepatic triglyceride (TG) and cholesterol accumulation. CJ significantly increased AMP-activated protein kinase (AMPK) phosphorylation in HepG2 hepatocytes and downregulated the level of the target genes, acetyl-CoA carboxylase and fatty acid synthase. In addition, CJ upregulated the expression of carnitine palmitoyltransferase-1, which is involved in fatty acid oxidation. The results of the present study indicated that the positive effects of CJ extract on high-fat diet-induced hepatic TG accumulation were mediated via the AMPK signaling pathway, indicating a potential target for the preventative treatment of NAFLD.

Sodium tanshinone IIA silate inhibits high glucose-induced vascular smooth muscle cell proliferation and migration through activation of AMP-activated protein kinase

The proliferation of vascular smooth muscle cells may perform a crucial role in the pathogenesis of diabetic vascular disease. AMPK additionally exerts several salutary effects on vascular function and improves vascular abnormalities. The current study sought to determine whether sodium tanshinone IIA silate (STS) has an inhibitory effect on vascular smooth muscle cell (VSMC) proliferation and migration under high glucose conditions mimicking diabetes without dyslipidemia, and establish the underlying mechanism. In this study, STS promoted the phosphorylation of AMP-activated protein kinase (AMPK) at T172 in VSMCs. VSMC proliferation was enhanced under high glucose (25 mM glucose, HG) versus normal glucose conditions (5.5 mM glucose, NG), and this increase was inhibited significantly by STS treatment. We utilized western blotting analysis to evaluate the effects of STS on cell-cycle regulatory proteins and found that STS increased the expression of p53 and the Cdk inhibitor, p21, subsequent decreased the expression of cell cycle-associated protein, cyclin D1. We further observed that STS arrested cell cycle progression at the G0/G1 phase. Additionally, expression and enzymatic activity of MMP-2, translocation of NF-κB, as well as VSMC migration were suppressed in the presence of STS. Notably, Compound C (CC), a specific inhibitor of AMPK, as well as AMPK siRNA blocked STS-mediated inhibition of VSMC proliferation and migration. We further evaluated its potential for activating AMPK in aortas in animal models of type 2 diabetes and found that Oral administration of STS for 10 days resulted in activation of AMPK in aortas from ob/ob or db/db mice. In conclusion, STS inhibits high glucose-induced VSMC proliferation and migration, possibly through AMPK activation. The growth suppression effect may be attributable to activation of AMPK-p53-p21 signaling, and the inhibitory effect on migration to the AMPK/NF-κB signaling axis.

Role of AMP-activated protein kinase in cancer therapy

Recent advances in AMP-activated protein kinase (AMPK) as a target in cancer waxed and waned over the past decade of cancer research. AMPK is a cellular energy sensor, present in almost all eukaryotic cells. An elevated AMP/ATP ratio activates the AMPK, which in turn inhibits energy-consuming processes and induces catabolic events that generate ATP to restore the energy homeostasis inside the cell. Several reports have indicated that AMPK regulates several metabolic pathways and may be a potential therapeutic target for the treatment of cancer. Cancer cells have specific metabolic changes that differ from normal cells, and AMPK prevents the deregulated processes in cancer. AMPK may also act to inhibit tumor formation through modulation of cell growth, cell proliferation, autophagy, stress responses, and cell polarity. AMPK has been shown to inhibit mammalian target of rapamycin (mTOR) through tuberous sclerosis complex 2 (TSC2) phosphorylation and phosphatase and tensin homolog (PTEN), considered as central cell growth controller signals in diseases. In response to glucose deprivation, AMPK phosphorylates and activates p53, which induces cell cycle arrest in the G1/S phase of the cell cycle. AMPK has also been reported to block cyclin-dependent kinases through phosphorylation of p27(kip1) , promoting its stabilization and allowing cells to survive metabolic stress via induction of autophagy. Additionally, AMPK induces autophagy by phosphorylation and activation of eEF-2 kinase, and prevents the formation of new proteins. AMPK activators are also used for the treatment of type II diabetes and cancer. This review focuses on AMPK activation and its possible therapeutic role in the treatment of cancer.

Gastrodia elata Ameliorates High-Fructose Diet-Induced Lipid Metabolism and Endothelial Dysfunction

Overconsumption of fructose results in dyslipidemia, hypertension, and impaired glucose tolerance, which have documented correlation with metabolic syndrome. Gastrodia elata, a widely used traditional herbal medicine, was reported with anti-inflammatory and antidiabetes activities. Thus, this study examined whether ethanol extract of Gastrodia elata Blume (EGB) attenuate lipid metabolism and endothelial dysfunction in a high-fructose (HF) diet animal model. Rats were fed the 65% HF diet with/without EGB 100 mg/kg/day for 8 weeks. Treatment with EGB significantly suppressed the increments of epididymal fat weight, blood pressure, plasma triglyceride, total cholesterol levels, and oral glucose tolerance, respectively. In addition, EGB markedly prevented increase of adipocyte size and hepatic accumulation of triglycerides. EGB ameliorated endothelial dysfunction by downregulation of endothelin-1 (ET-1) and adhesion molecules in the aorta. Moreover, EGB significantly recovered the impairment of vasorelaxation to acetylcholine and levels of endothelial nitric oxide synthase (eNOS) expression and induced markedly upregulation of phosphorylation AMP-activated protein kinase (AMPK) α in the liver, muscle, and fat. These results indicate that EGB ameliorates dyslipidemia, hypertension, and insulin resistance as well as impaired vascular endothelial function in HF diet rats. Taken together, EGB may be a beneficial therapeutic approach for metabolic syndrome.

Role of pregnane X receptor in obesity and glucose homeostasis in male mice

Clinical obesity is a complex metabolic disorder affecting one in three adults. Recent reports suggest that pregnane X receptor (PXR), a xenobiotic nuclear receptor important for defense against toxic agents and for eliminating drugs and other xenobiotics, may be involved in obesity. Noting differences in ligand specificities between human and mouse PXRs, the role of PXR in high fat diet (HFD)-induced obesity was examined using male PXR-humanized (hPXR) transgenic and PXR-knock-out (PXR-KO) mice in comparison to wild-type (WT) mice. After 16 weeks on either a control diet or HFD, WT mice showed greater weight gain, whereas PXR-KO mice gained less weight due to their resistance to HFD-induced decreases in adipose tissue peroxisome proliferator-activated receptor α and induction of hepatic carnitine palmitoyltransferase 1, suggesting increased energy metabolism. Interestingly, control-fed PXR-KO mice exhibited hepatomegaly, hyperinsulinemia, and hyperleptinemia but hypoadiponectinemia and lower adiponectin receptor R2 mRNA levels relative to WT mice. Evaluation of these biologic indicators in hPXR mice fed a control diet or HFD revealed further differences between the mouse and human receptors. Importantly, although HFD-fed hPXR mice were resistant to HFD-induced obesity, both PXR-KO and hPXR mice exhibited impaired induction of glucokinase involved in glucose utilization and displayed elevated fasting glucose levels and severely impaired glucose tolerance. Moreover, the basal hepatic levels of the gluconeogenic enzyme phosphoenolpyruvate carboxykinase 1 were increased in hPXR mice compared with WT mice. Altogether, although the mouse PXR promotes HFD-induced obesity, the hPXR mouse carries a genetic predisposition for type 2 diabetes and thus provides a model for exploring the role of human PXR in the metabolic syndrome.

FoxO1 controls lysosomal acid lipase in adipocytes: implication of lipophagy during nutrient restriction and metformin treatment

Finding new molecular pathways and strategies modulating lipolysis in adipocytes is an attractive goal of the current research. Indeed, it is becoming clear that several human age-related pathologies are caused by adipose tissue expansion and altered lipid metabolism. In the present work, we show that transcription factor forkhead homeobox type protein O1 (FoxO1) is upregulated by nutrient restriction (NR) in adipocytes and exerts the transcriptional control of lipid catabolism via the induction of lysosomal acid lipase (Lipa). An increased autophagy and colocalization of lipid droplets (LDs) with lysosomes was observed implying lipophagy in Lipa-mediated LDs degradation. Interestingly, we found that metformin (Metf), a biguanide drug commonly used to treat type-2 diabetes, exerts effects comparable to that of NR. Actually, it was able to elicit FoxO1-dependent Lipa induction as well as LDs degradation through lipophagy. Moreover, we demonstrate that, during NR or Metf treatment, free fatty acids released by Lipa are directed toward AMP-activated protein kinase-mediated mitochondrial oxidation, thus maintaining energetic homeostasis in adipocytes. In conclusion, our data show that lysosomal-mediated lipid catabolism is activated by NR in adipocytes and give further support to the use of Metf as a NR mimetic to combat age-related diseases associated with altered lipid metabolism.

Metformin increases mitochondrial energy formation in L6 muscle cell cultures

A popular hypothesis for the action of metformin, the widely used anti-diabetes drug, is the inhibition of mitochondrial respiration, specifically at complex I. This is consistent with metformin stimulation of glucose uptake by muscle and inhibition of gluconeogenesis by liver. Yet, mitochondrial inhibition is inconsistent with metformin stimulation of fatty acid oxidation in both tissues. In this study, we measured mitochondrial energy production in intact cells adapting an in vivo technique of phosphocreatine (PCr) formation following energy interruption ("PCr recovery") to cell cultures. Metformin increased PCr recovery from either dinitrophenol (DNP) or azide in L6 cells. We found that metformin alone had no effect on cell viability as measured by total ATP concentration, trypan blue exclusion, or 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction. However, treatments with low concentrations of DNP or azide reversibly decreased ATP concentration. Metformin increased 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction during recovery from either agent. Viability measured by trypan blue exclusion indicated that cells were intact under these conditions. We also found that metformin increased free AMP and, to a smaller extent, free ADP concentrations in cells, an action that was duplicated by a structurally unrelated AMP deaminase inhibitor. We conclude that, in intact cells, metformin can lead to a stimulation of energy formation, rather than an inhibition.

Activation of AMP-Activated Protein Kinase α and Extracelluar Signal-Regulated Kinase Mediates CB-PIC-Induced Apoptosis in Hypoxic SW620 Colorectal Cancer Cells

Here, antitumor mechanism of cinnamaldehyde derivative CB-PIC was elucidated in human SW620 colon cancer cells. CB-PIC significantly exerted cytotoxicity, increased sub-G1 accumulation, and cleaved PARP with apoptotic features, while it enhanced the phosphorylation of AMPK alpha and ACC as well as activated the ERK in hypoxic SW620 cells. Furthermore, CB-PIC suppressed the expression of HIF1 alpha, Akt, and mTOR and activated the AMPK phosphorylation in hypoxic SW620 cells. Conversely, silencing of AMPK α blocked PARP cleavage and ERK activation induced by CB-PIC, while ERK inhibitor PD 98059 attenuated the phosphorylation of AMPK α in hypoxic SW620 cells, implying cross-talk between ERK and AMPK α . Furthermore, cotreatment of CB-PIC and metformin enhanced the inhibition of HIF1 α and Akt/mTOR and the activation of AMPK α and pACC in hypoxic SW620 cells. In addition, CB-PIC suppressed the growth of SW620 cells inoculated in BALB/c athymic nude mice, and immunohistochemistry revealed that CB-PIC treatment attenuated the expression of Ki-67, CD34, and CAIX and increased the expression of pAMPK α in CB-PIC-treated group. Interestingly, CP-PIC showed better antitumor activity in SW620 colon cancer cells under hypoxia than under normoxia, since it may be applied to chemoresistance. Overall, our findings suggest that activation of AMPK α and ERK mediates CB-PIC-induced apoptosis in hypoxic SW620 colon cancer cells.

Protective effect of nectandrin B, a potent AMPK activator on neointima formation: inhibition of Pin1 expression through AMPK activation

BACKGROUND AND PURPOSE

Neointima is considered a critical event in the development of vascular occlusive disease. Nectandrin B from nutmeg functions as a potent AMP-activated protein kinase (AMPK) activators. The present study addressed whether nectandrin B inhibits intimal hyperplasia in guide wire-injured arteries and examined its molecular mechanism.

EXPERIMENTAL APPROACH

Neointima was induced by guide wire injury in mouse femoral arteries. Cell proliferation and mechanism studies were performed in rat vascular smooth muscle cells (VSMC) culture model.

KEY RESULTS

Nectandrin B increased AMPK activity in VSMC. Nectandrin B inhibited the cell proliferation induced by PDGF and DNA synthesis. Moreover, treatment of nectandrin B suppressed neointima formation in femoral artery after guide wire injury. We have recently shown that Pin1 plays a critical role in VSMC proliferation and neointima formation. Nectandrin B potently blocked PDGF-induced Pin1 and cyclin D1 expression and nectandrin B's anti-proliferation effect was diminished in Pin1 overexpressed VSMC. PDGF-induced phosphorylation of ERK and Akt was marginally affected by nectandrin B. However, nectandrin B increased the levels of p53 and its downstream target p21 and, also reversibly decreased the expression of E2F1 and phosphorylated Rb in PDGF-treated VSMC. AMPK inhibition by dominant mutant form of adenovirus rescued nectandrin B-mediated down-regulation of Pin1 and E2F1.

CONCLUSIONS AND IMPLICATIONS

Nectandrin B inhibited VSMC proliferation and neointima formation via inhibition of E2F1-dependent Pin1 gene transcription, which is mediated through the activation of an AMPK/p53-triggered pathway.

Genistein suppresses LPS-induced inflammatory response through inhibiting NF-κB following AMP kinase activation in RAW 264.7 macrophages

Genistein, the major isoflavone in soybean, was recently reported to exert beneficial effects in metabolic disorders and inflammatory diseases. In the present study, we investigated the effects and mechanisms of a dietary concentration of genistein on the inflammatory response in lipopolysaccharide (LPS)-treated RAW 264.7 macrophages. Our results demonstrated that genistein effectively inhibited the LPS-induced overproduction of tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6), as well as LPS-induced nuclear factor kappa B (NF-κB) activation. In addition, the data also showed that genistein prevented LPS-induced decrease in adenosine monophosphate-activated protein kinase (AMPK) phosphorylation. These effects were obviously attenuated by an AMPK inhibitor. Taken together, our results suggest that the dietary concentration of genistein is able to attenuate inflammatory responses via inhibition of NF-κB activation following AMPK stimulation. The data provide direct evidence for the potential application of low concentrations of genistein in the prevention and treatment of inflammatory diseases.

Metabolomic fingerprint reveals that metformin impairs one-carbon metabolism in a manner similar to the antifolate class of chemotherapy drugs

Metabolomic fingerprint of breast cancer cells treated with the antidiabetic drug metformin revealed a significant accumulation of 5-formimino-tetrahydrofolate, one of the tetrahydrofolate forms carrying activated one-carbon units that are essential for the de novo synthesis of purines and pyrimidines. De novo synthesis of glutathione, a folate-dependent pathway interconnected with one-carbon metabolism was concomitantly depleted in response to metformin. End-product reversal studies demonstrated that thymidine alone leads to a significant but incomplete protection from metformin's cytostatic effects. The addition of the substrate hypoxanthine for the purine salvage pathway produces major rightward shifts in metformin's growth inhibition curves. Metformin treatment failed to activate the DNA repair protein ATM kinase and the metabolic tumor suppressor AMPK when thymidine and hypoxanthine were present in the extracellular milieu. Our current findings suggest for the first time that metformin can function as an antifolate chemotherapeutic agent that induces the ATM/AMPK tumor suppressor axis secondarily following the alteration of the carbon flow through the folate-related one-carbon metabolic pathways.

Metformin affects the circadian clock and metabolic rhythms in a tissue-specific manner

Metformin is a commonly-used treatment for type 2 diabetes, whose mechanism of action has been linked, in part, to activation of AMP-activated protein kinase (AMPK). However, little is known regarding its effect on circadian rhythms. Our aim was to evaluate the effect of metformin administration on metabolism, locomotor activity and circadian rhythms. We tested the effect of metformin treatment in the liver and muscle of young lean, healthy mice, as obesity and diabetes disrupt circadian rhythms. Metformin led to increased leptin and decreased glucagon levels. The effect of metformin on liver and muscle metabolism was similar leading to AMPK activation either by liver kinase B1 (LKB1) and/or other kinases in the muscle. AMPK activation resulted in the inhibition of acetyl CoA carboxylase (ACC), the rate limiting enzyme in fatty acid synthesis. Metformin also led to the activation of liver casein kinase I α (CKIα) and muscle CKIε, known modulators of the positive loop of the circadian clock. This effect was mainly of phase advances in the liver and phase delays in the muscle in clock and metabolic genes and/or protein expression. In conclusion, our results demonstrate the differential effects of metformin in the liver and muscle and the critical role the circadian clock has in orchestrating metabolic processes.

Antihyperglycaemic activity of 2,4:3,5-dibenzylidene-D-xylose-diethyl dithioacetal in diabetic mice

We have recently generated lipophilic D-xylose derivatives that increase the rate of glucose uptake in cultured skeletal muscle cells in an AMP-activated protein kinase (AMPK)-dependent manner. The derivative 2,4:3,5-dibenzylidene-D-xylose-diethyl dithioacetal (EH-36) stimulated the rate of glucose transport by increasing the abundance of glucose transporter-4 in the plasma membrane of cultured myotubes. The present study aimed at investigating potential antihyperglycaemic effects of EH-36 in animal models of diabetes. Two animal models were treated subcutaneously with EH-36: streptozotocin-induced diabetes in C57BL/6 mice (a model of insulin-deficient type 1 diabetes), and spontaneously diabetic KKAy mice (Kuo Kondo rats carrying the A(y) yellow obese gene; insulin-resistant type 2 diabetes). The in vivo biodistribution of glucose in control and treated mice was followed with the glucose analogue 2-deoxy-2-[(18) F]-D-glucose; the rate of glucose uptake in excised soleus muscles was measured with [(3) H]-2-deoxy-D-glucose. Pharmacokinetic parameters were determined by non-compartmental analysis of the in vivo data. The effective blood EH-36 concentration in treated animals was 2 μM. It reduced significantly the blood glucose levels in both types of diabetic mice and also corrected the typical compensatory hyperinsulinaemia of KKAy mice. EH-36 markedly increased glucose transport in vivo into skeletal muscle and heart, but not to adipose tissue. This stimulatory effect was mediated by Thr(172) -phosphorylation in AMPK. Biochemical tests in treated animals and acute toxicological examinations showed that EH-36 was well tolerated and not toxic to the mice. These findings indicate that EH-36 is a promising prototype molecule for the development of novel antidiabetic drugs.

Extracts of Scutellaria baicalensis reduced body weight and blood triglyceride in db/db Mice

Scutellaria baicalensis has been extensively employed for the clinical treatment of hyperlipidemia, atherosclerosis, hypertension, dysentery, inflammatory diseases, and the common cold. The present study was performed to investigate the anti-obesity and anti-dyslipidemia effect of Scutellaria baicalensis extracts (SBE) in type 2 diabetic db/db mice. Male db/db mice were divided into three groups (n = 5) and orally administrated vehicle (control), SBE 10, and 100 mg/kg body weight/day for 4 weeks everyday. Administration of SBE improves weight gain, hypertriglyceridemia, and hyperinsulinemia in db/db mice. In obese db/db mice, SBE treatment also reduced plasma alanine aminotransferase levels. In the livers of db/db mice, SBE promoted 5' AMP-activated protein kinase activity and restored metabolic process and insulin signaling pathways. Our data demonstrate that SBE exerts potent anti-obesity and anti-hypertriglyceride effects suggesting its useful potential function as adjuvant therapeutic agent for the treatment of weight gain and hypertriglyceridemia.

Anti-Diabetic Effects of a Coptis chinensis Containing New Traditional Chinese Medicine Formula in Type 2 Diabetic Rats

The Chinese formula Tang-Min-Ling (TML), an improved product of the decoction of Dachaihu which has a history of more than 2000 years, has main constituents of Coptis chinensis Franch, Scutellaria baicalensis Georgi, Rheum officinale Baill and Bupleurum chinense DC. A multi-central randomized controlled investigation performed previously by us has showed that TML has positive effects on regulating glycometabolism in type 2 diabetes (T2DM) patients, but the mechanisms remain unclear. Using Otsuka Long-Evans Tokushima Fatty (OLETF) rats as an animal model with rosiglitazone as a positive control, we were able to detect TML's effect on the serum glucose, serum lipid, serum leptin and adiponcetin after oral administration for 12 weeks. We were also able to detect the insulin resistance level by a glucose clamp test and study the mechanisms of TML in improving insulin resistance by detecting skeletal muscle AMP-activated protein kinase (AMPK) and glucose transporter 4 (GLUT4). Results showed that TML significantly reduced the glucose area under a curve of the oral glucose tolerance test, and had a positive effect in regulating serum lipid metabolism. TML treatment also significantly reduced the serum leptin level, but it had no effect on the serum adiponectin level. The AMPK enzymatic activity and GLUT4 expression in Skeletal Muscle were also upregulated in the TML group. The results suggest that the Chinese medicine TML, which contains Coptis chinensis Franch as one of its components, improves glycometabolism and its possible mechanisms may involve in improvement of insulin resistance of OLETF rats.

Simple thermodynamic model of unassisted proton shuttle uncoupling and prediction of activity from calculated speciation, lipophilicity, and molecular geometry

A mechanistic model of uncoupling of oxidative phosphorylation by lipophilic weak acids (i.e. proton shuttles) was developed for the purposes of predicting the relative activity of xenobiotics of widely varying structure and of guiding the design of optimized derivatives. The model is based on thermodynamic premises not formulated elsewhere that allow for the calculation of steady-state conditions and of rate of energy dissipation on the basis of acid-dissociation and permeability behavior, the later estimated from partitioning behavior and geometric considerations. Moreover, permeability of either the neutral or of the ionized species is proposed to be effectively enhanced under conditions of asymmetrical molecular distribution. Finally, special considerations were developed to accommodate multi-protic compounds. The comparison of predicted to measured activity for a diverse testset of 48 compounds of natural origin spanning a wide range of activity yielded a Spearman's rho of 0.90. The model was used to tentatively identify several novel proton shuttles, as well as to elucidate core structures particularly conducive to proton shuttle activity from which optimized derivatives can be designed. Principles of design were formulated and examples of derivatives projected to be active at concentrations on the order of 10(-7)M are proposed. Among these are di-protic compounds predicted to shuttle two protons per cycle iteration and proposed to maximally exploit the proton shuttle mechanism. This work promotes the design of highly active, yet easily-metabolized uncouplers for therapeutic applications, namely the indirect activation of AMP-kinase, as well as for various industrial applications where low persistence is desirable.

Roles of AMP-activated protein kinase in Alzheimer's disease

AMP-activated protein kinase (AMPK), a master regulator of cellular energy homeostasis and a central player in glucose and lipid metabolism, is potentially implicated in the pathogenesis of Alzheimer's disease (AD). AMPK activity decreases in AD brain, indicating decreased mitochondrial biogenesis and function. Emerging evidence demonstrates that AMPK activation is a potential target for improving perturbed brain energy metabolism that is involved in the pathogenesis of AD. The roles of AMPK in the pathogenesis of AD include β-amyloid protein (Aβ) generation and tau phosphorylation. In particular, AMPK may regulate Aβ generation through modulating neuronal cholesterol and sphingomyelin levels and through regulating APP distribution in the lipid rafts. AMPK is activated by phosphorylation of Thr-172 by LKB1 complex in response to increase in the AMP/ATP ratio and by calmodulin-dependent protein kinase kinase-beta in response to elevated Ca(2+) levels, which contributes to regulating Aβ generation. AMPK is a physiological tau kinase and can increase the phosphorylation of tau at Ser-262. AMPK can also directly phosphorylate tau at Thr-231 and Ser-396/404. Furthermore, AMPK activation decreases mTOR signaling activity to facilitate autophagy and promotes lysosomal degradation of Aβ. However, AMPK activation has non-neuroprotective property and may lead to detrimental outcomes, including Aβ generation and tau phosphorylation. Therefore, it is still unclear whether AMPK could serve a potential therapeutic target for AD, and hence, further studies will be needed to clarify the role of AMPK in AD.