Mammalian target of rapamycin signaling in diabetic cardiovascular disease

Interactive Effects of Empagliflozin and Hyperglycemia on Urinary Amino Acids in Individuals With Type 1 Diabetes

Optimizing energy use in the kidney is critical for normal kidney function. Here, we investigate the effect of hyperglycemia and sodium-glucose cotransporter 2 (SGLT2) inhibition on urinary amino acid excretion in individuals with type 1 diabetes (T1D). The open-label ATIRMA trial assessed the impact of 8 weeks of 25 mg empagliflozin orally once per day in 40 normotensive normoalbuminuric young adults with T1D. A consecutive 2-day assessment of clamped euglycemia and hyperglycemia was evaluated at baseline and posttreatment visits. Principal component analysis was performed on urinary amino acids grouped into representative metabolic pathways using MetaboAnalyst. At baseline, acute hyperglycemia was associated with changes in 25 of the 33 urinary amino acids or their metabolites. The most significant amino acid metabolites affected by acute hyperglycemia were 3-hydroxykynurenine, serotonin, glycyl-histidine, and nicotinic acid. The changes in amino acid metabolites were reflected by the induction of four biosynthetic pathways: aminoacyl-tRNA; valine, leucine, and isoleucine; arginine; and phenylalanine, tyrosine, and tryptophan. In acute hyperglycemia, empagliflozin significantly attenuated the increases in aminoacyl-tRNA biosynthesis and valine, leucine, and isoleucine biosynthesis. Our findings using amino acid metabolomics indicate that hyperglycemia stimulates biosynthetic pathways in T1D. SGLT2 inhibition may attenuate the increase in biosynthetic pathways to optimize kidney energy metabolism.

ARTICLE HIGHLIGHTS

Resistin secreted by porcine alveolar macrophages leads to endothelial cell dysfunction during Haemophilus parasuis infection

Haemophilus parasuis (H. parasuis) causes exudative inflammation, implying endothelial dysfunction during pathogen infection. However, so far, the molecular mechanism of endothelial dysfunction caused by H. parasuis has not been clarified. By using the transwell-based cell co-culture system, we demonstrate that knocking out resistin in porcine alveolar macrophages (PAMs) dramatically attenuated endothelial monolayer damage caused by H. parasuis. The resistin secreted by PAMs inhibited the expression of the tight junction proteins claudin-5 and occludin rather than the adherens junction protein VE-cadherin in co-cultured porcine aortic endothelial cells (PAECs). Furthermore, we demonstrate that resistin regulated claudin-5 and occludin expression and monolayer PAEC permeability in an LKB1/AMPK/mTOR pathway-dependent manner. Additionally, we reveal that the outer membrane lipoprotein gene lppA in H. parasuis induced resistin expression in PAMs, as deleting lppA reduced resistin expression in H. parasuis-infected PAMs, causing a significant change in LKB1/AMPK/mTOR pathway activity in co-cultured PAECs, thereby restoring tight junction protein levels and endothelial monolayer permeability. Thus, we postulate that the H. parasuis lppA gene enhances resistin production in PAMs, disrupting tight junctions in PAECs and causing endothelial barrier dysfunction. These findings elucidate the pathogenic mechanism of exudative inflammation caused by H. parasuis for the first time and provide a more profound angle of acute exudative inflammation caused by bacteria.

The impact of aging and oxidative stress in metabolic and nervous system disorders: programmed cell death and molecular signal transduction crosstalk

Life expectancy is increasing throughout the world and coincides with a rise in non-communicable diseases (NCDs), especially for metabolic disease that includes diabetes mellitus (DM) and neurodegenerative disorders. The debilitating effects of metabolic disorders influence the entire body and significantly affect the nervous system impacting greater than one billion people with disability in the peripheral nervous system as well as with cognitive loss, now the seventh leading cause of death worldwide. Metabolic disorders, such as DM, and neurologic disease remain a significant challenge for the treatment and care of individuals since present therapies may limit symptoms but do not halt overall disease progression. These clinical challenges to address the interplay between metabolic and neurodegenerative disorders warrant innovative strategies that can focus upon the underlying mechanisms of aging-related disorders, oxidative stress, cell senescence, and cell death. Programmed cell death pathways that involve autophagy, apoptosis, ferroptosis, and pyroptosis can play a critical role in metabolic and neurodegenerative disorders and oversee processes that include insulin resistance, β-cell function, mitochondrial integrity, reactive oxygen species release, and inflammatory cell activation. The silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), AMP activated protein kinase (AMPK), and Wnt1 inducible signaling pathway protein 1 (WISP1) are novel targets that can oversee programmed cell death pathways tied to β-nicotinamide adenine dinucleotide (NAD+), nicotinamide, apolipoprotein E (APOE), severe acute respiratory syndrome (SARS-CoV-2) exposure with coronavirus disease 2019 (COVID-19), and trophic factors, such as erythropoietin (EPO). The pathways of programmed cell death, SIRT1, AMPK, and WISP1 offer exciting prospects for maintaining metabolic homeostasis and nervous system function that can be compromised during aging-related disorders and lead to cognitive impairment, but these pathways have dual roles in determining the ultimate fate of cells and organ systems that warrant thoughtful insight into complex autofeedback mechanisms.

Conserved chamber-specific polyploidy maintains heart function in Drosophila

Developmentally programmed polyploidy (whole-genome duplication) of cardiomyocytes is common across evolution. Functions of such polyploidy are essentially unknown. Here, in both Drosophila larvae and human organ donors, we reveal distinct polyploidy levels in cardiac organ chambers. In Drosophila, differential growth and cell cycle signal sensitivity leads the heart chamber to reach a higher ploidy/cell size relative to the aorta chamber. Cardiac ploidy-reduced animals exhibit reduced heart chamber size, stroke volume and cardiac output, and acceleration of circulating hemocytes. These Drosophila phenotypes mimic human cardiomyopathies. Our results identify productive and likely conserved roles for polyploidy in cardiac chambers and suggest that precise ploidy levels sculpt many developing tissues. These findings of productive cardiomyocyte polyploidy impact efforts to block developmental polyploidy to improve heart injury recovery.

Innovative therapeutic strategies for cardiovascular disease

As a significant non-communicable disease, cardiovascular disease is the leading cause of death for both men and women, comprises almost twenty percent of deaths in most racial and ethnic groups, can affect greater than twenty-five million individuals worldwide over the age of twenty, and impacts global economies with far-reaching financial challenges. Multiple factors can affect the onset of cardiovascular disease that include high serum cholesterol levels, elevated blood pressure, tobacco consumption and secondhand smoke exposure, poor nutrition, physical inactivity, obesity, and concurrent diabetes mellitus. Yet, addressing any of these factors cannot completely eliminate the onset or progression of cardiovascular disorders. Novel strategies are necessary to target underlying cardiovascular disease mechanisms. The silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), a histone deacetylase, can limit cardiovascular injury, assist with stem cell development, oversee metabolic homeostasis through nicotinamide adenine dinucleotide (NAD+) pathways, foster trophic factor protection, and control cell senescence through the modulation of telomere function. Intimately tied to SIRT1 pathways are mammalian forkhead transcription factors (FoxOs) which can modulate cardiac disease to reduce oxidative stress, repair microcirculation disturbances, and reduce atherogenesis through pathways of autophagy, apoptosis, and ferroptosis. AMP activated protein kinase (AMPK) also is critical among these pathways for the oversight of cardiac cellular metabolism, insulin sensitivity, mitochondrial function, inflammation, and the susceptibility to viral infections such as severe acute respiratory syndrome coronavirus that can impact cardiovascular disease. Yet, the relationship among these pathways is both intricate and complex and requires detailed insight to successfully translate these pathways into clinical care for cardiovascular disorders.

Cellular Metabolism: A Fundamental Component of Degeneration in the Nervous System

It is estimated that, at minimum, 500 million individuals suffer from cellular metabolic dysfunction, such as diabetes mellitus (DM), throughout the world. Even more concerning is the knowledge that metabolic disease is intimately tied to neurodegenerative disorders, affecting both the central and peripheral nervous systems as well as leading to dementia, the seventh leading cause of death. New and innovative therapeutic strategies that address cellular metabolism, apoptosis, autophagy, and pyroptosis, the mechanistic target of rapamycin (mTOR), AMP activated protein kinase (AMPK), growth factor signaling with erythropoietin (EPO), and risk factors such as the apolipoprotein E (APOE-ε4) gene and coronavirus disease 2019 (COVID-19) can offer valuable insights for the clinical care and treatment of neurodegenerative disorders impacted by cellular metabolic disease. Critical insight into and modulation of these complex pathways are required since mTOR signaling pathways, such as AMPK activation, can improve memory retention in Alzheimer's disease (AD) and DM, promote healthy aging, facilitate clearance of β-amyloid (Aß) and tau in the brain, and control inflammation, but also may lead to cognitive loss and long-COVID syndrome through mechanisms that can include oxidative stress, mitochondrial dysfunction, cytokine release, and APOE-ε4 if pathways such as autophagy and other mechanisms of programmed cell death are left unchecked.

mTOR (Mammalian Target of Rapamycin): Hitting the Bull's Eye for Enhancing Neurogenesis After Cerebral Ischemia?

Ischemic stroke remains a leading cause of morbidity and disability around the world. The sequelae of serious neurological damage are irreversible due to body's own limited repair capacity. However, endogenous neurogenesis induced by cerebral ischemia plays a critical role in the repair and regeneration of impaired neural cells after ischemic brain injury. mTOR (mammalian target of rapamycin) kinase has been suggested to regulate neural stem cells ability to self-renew and differentiate into proliferative daughter cells, thus leading to improved cell growth, proliferation, and survival. In this review, we summarized the current evidence to support that mTOR signaling pathways may enhance neurogenesis, angiogenesis, and synaptic plasticity following cerebral ischemia, which could highlight the potential of mTOR to be a viable therapeutic target for the treatment of ischemic brain injury.

Hyperglycemic conditions induce rapid cell dysfunction-promoting transcriptional alterations in human aortic endothelial cells

Hyperglycemia is a major risk factor in the development of diabetic complications and promotes vascular complications through dysregulation of endothelial cell function. Various mechanisms have been proposed for endothelial cell dysregulation but the early transcriptomic alterations of endothelial cells under hyperglycemic conditions are not well documented. Here we use deep time-series RNA-seq profiling of human aortic endothelial cells (HAECs) following exposure to normal (NG) and high glucose (HG) conditions over a time course from baseline to 24 h to identify the early and transient transcriptomic changes, alteration of molecular networks, and their temporal dynamics. The analysis revealed that the most significant pathway activation/inhibition events take place in the 1- to 4-h transition and identified distinct clusters of genes that underlie a cascade of coordinated transcriptional events unique to HG conditions. Temporal co-expression and causal network analysis implicate the activation of type 2 diabetes (T2D) and growth factor signalling pathways including STAT3 and NF-κB. These results document HAEC transcriptional changes induced by hyperglycemic conditions and provide basic insight into the rapid molecular alterations that promote endothelial cell dysfunction.

Peripheral tissular analysis of rapamycin's effect as a neuroprotective agent in vivo

Rapamycin is the best-characterized autophagy inducer, which is related to its antiaging and neuroprotective effects. Although rapamycin is an FDA-approved drug for human use in organ transplantation and cancer therapy, its administration as an antiaging and neuroprotective agent is still controversial because of its immunosuppressive and reported side effects. Therefore, it is critical to determine whether the dose that exerts a neuroprotective effect, 35 times lower than that used as an immunosuppressant agent, harms peripheral organs. We validated the rapamycin neuroprotective dosage in a Parkinson's disease (PD) model induced with paraquat. C57BL/6 J mice were treated with intraperitoneal (IP) rapamycin (1 mg/kg) three times per week, followed by paraquat (10 mg/kg) twice per week for 6 weeks, along with rapamycin on alternate days. Rapamycin significantly decreased dopaminergic neuronal loss induced by paraquat. Since rapamycin's neuroprotective effect in a PD model was observed at 7 weeks of treatment; we evaluated its effect on the liver, kidney, pancreas, and spleen. In addition, we prolonged treatment with rapamycin for 14 weeks. Tissue sections were subjected to histochemical, immunodetection, and morphometric analysis. Chronic rapamycin administration does not affect bodyweight, survival, and liver or kidney morphology. Although the pancreas tissular architecture and cellular distribution in Langerhans islets are modified, they may be reversible. The spleen B lymphocyte and macrophage populations were decreased. Notably, the lymphocyte T population was not affected. Therefore, chronic administration of a rapamycin neuroprotective dose does not produce significant tissular alterations. Our findings support the therapeutic potential of rapamycin as a neuroprotective agent.

Evolution of drug-eluting coronary stents: a back-and-forth journey from the bench-to-bedside

Coronary stents have revolutionized the treatment of coronary artery disease. Compared with balloon angioplasty, bare-metal stents effectively prevented abrupt vessel closure but were limited by in-stent restenosis due to smooth muscle cell proliferation and neointimal hyperplasia. The first-generation drug-eluting stent (DES), with its antiproliferative drug coating, offered substantial advantages over bare-metal stents as it mitigated the risk of in-stent restenosis. Nonetheless, they had several design limitations that increased the risk of late stent thrombosis. Significant advances in stent design, including thinner struts, enhanced polymers' formulation, and more potent antiproliferative agents, have led to the introduction of new-generation DES with a superior safety profile. Cardiologists have over 20 different DES types to choose from, each with its unique features and characteristics. This review highlights the evolution of stent design and summarizes the clinical data on the different stent types. We conclude by discussing the clinical implications of stent design in high-risk subsets of patients.

Erythropoietin and Bacillus Calmette-Guérin Vaccination Mitigate 3-Nitropropionic Acid-Induced Huntington-like Disease in Rats by Modulating the PI3K/Akt/mTOR/P70S6K Pathway and Enhancing the Autophagy

Oxidative stress and mitochondrial dysfunction are among the mechanisms expected to explain the pathogenesis of Huntington's disease. Erythropoietin (EPO) and the Bacillus Calmette-Guérin (BCG) vaccine have neuroprotective effects against neurodegenerative diseases; however, the full mechanisms of their action are currently unclear. Here, for the first time, we investigated the neuroprotective effect of BCG vaccination in Huntington-like disease induced by 3-nitropropionic acid (3-NP) and its combination with EPO. Male Wistar rats were randomized into five groups: saline-treated control; 3-NP group (20 mg/kg/day, i.p.) for 7 days; EPO-treated group (5000 IU/kg/day, i.p.) for 14 days after 3-NP administration; live BCG vaccine prophylactic group (5000 cfu/g, i.p.) 10 days prior to 3-NP administration; and live BCG vaccine (5000 cfu/g, i.p.) 10 days before 3-NP administration, followed by EPO treatment (5000 IU/kg/day, i.p.) for 14 days. In a histopathological examination, striatum neurodegeneration was evidenced in the 3-NP injected rats. Administration of 3-NP elevated the levels of p-PI3K, p-Akt, p-mTOR, p-P70S6K, BAX, malondialdehyde, nitric oxide, and cytochrome oxidase while reduced the levels of BCL-2, superoxide dismutase, reduced glutathione, and the autophagy marker microtubule-associated protein light chain 3 in the striatum. EPO and BCG ameliorated the biochemical, histopathological, and behavioral derangements induced by 3-NP, with prominent neuroprotection observed in rats administered the BCG prophylactic combined with EPO treatment. These results highlight the role played by EPO and BCG in the management of 3-NP-induced Huntington-like disease by inhibiting the PI3K/Akt/mTOR/P70S6K pathway and enhancing the autophagy.

PROTACs technology for treatment of Alzheimer's disease: Advances and perspectives

Neurodegenerative diseases (NDs) are characteristic with progression of neuron degeneration, resulting in dysfunction of cognition and mobility. Many neurodegenerative diseases are because of proteinopathies that results from unusual protein accumulations and aggregations. The aggregation of misfolded proteins like β-amyloid, α-synuclein, tau, and polyglutamates are hallmarked in Alzheimer's disease (AD), which are undruggable targets, and usually do not respond to conventional small-molecule agents. Therefore, developing novel technology and strategy for reducing the levels of protein aggregates would be critical for treatment of AD. Recently, the emerging proteolysis targeting chimeras (PRPTACs) technology has been significantly considered for artificial and selective degradation of aberrant target proteins. These engineered bifunctional molecules engage target proteins to be degraded by either the cellular degradation machinery in the ubiquitin-proteasome system (UPS) or via the autophagy-lysosome degradation pathway. Although the application of PROTACs technology is preferable than oligonucleotide and antibodies for treatment of NDs, many limitations such as their pharmacokinetic properties, tissue distribution and cell permeabilities, still need to be corrected. Herein, we review the recent advances in PROTACs technology with their limitation for pharmaceutical targeting of aberrant proteins involved in Alzheimer's diseases. We also review therapeutic potential of dysregulated signaling such as PI3K/AKT/mTOR axis for the management of AD.

Diabetic Complications: An Update on Pathobiology and Therapeutic Strategies

Despite the advent of novel therapies which manage and control diabetes well, the increased risk of morbidity and mortality in diabetic subjects is associated with the devastating secondary complications it produces. Long-standing diabetes majorly drives cellular and molecular alterations, which eventually damage both small and large blood vessels. The complications are prevalent both in type I and type II diabetic subjects. The microvascular complications include diabetic neuropathy, diabetic nephropathy, diabetic retinopathy, while the macrovascular complications include diabetic heart disease and stroke. The current therapeutic strategy alleviates the complications to some extent but does not cure or prevent them. Also, the recent clinical trial outcomes in this field are disappointing. Success in the drug discovery of diabetic complications may be achieved by a better understanding of the underlying pathophysiology and by recognising the crucial factors contributing to the development and progression of the disease. In this review, we discuss the well-studied cellular mechanisms leading to the development and progression of diabetic complications. In addition, we also highlight the various therapeutic paradigms currently in clinical practice.

Glucose Variability: How Does It Work?

A growing body of evidence points to the role of glucose variability (GV) in the development of the microvascular and macrovascular complications of diabetes. In this review, we summarize data on GV-induced biochemical, cellular and molecular events involved in the pathogenesis of diabetic complications. Current data indicate that the deteriorating effect of GV on target organs can be realized through oxidative stress, glycation, chronic low-grade inflammation, endothelial dysfunction, platelet activation, impaired angiogenesis and renal fibrosis. The effects of GV on oxidative stress, inflammation, endothelial dysfunction and hypercoagulability could be aggravated by hypoglycemia, associated with high GV. Oscillating hyperglycemia contributes to beta cell dysfunction, which leads to a further increase in GV and completes the vicious circle. In cells, the GV-induced cytotoxic effect includes mitochondrial dysfunction, endoplasmic reticulum stress and disturbances in autophagic flux, which are accompanied by reduced viability, activation of apoptosis and abnormalities in cell proliferation. These effects are realized through the up- and down-regulation of a large number of genes and the activity of signaling pathways such as PI3K/Akt, NF-κB, MAPK (ERK), JNK and TGF-β/Smad. Epigenetic modifications mediate the postponed effects of glucose fluctuations. The multiple deteriorative effects of GV provide further support for considering it as a therapeutic target in diabetes.

Specific amino acid supplementation rescues the heart from lipid overload-induced insulin resistance and contractile dysfunction by targeting the endosomal mTOR-v-ATPase axis

Objective

The diabetic heart is characterized by extensive lipid accumulation which often leads to cardiac contractile dysfunction. The underlying mechanism involves a pivotal role for vacuolar-type H⁺-ATPase (v-ATPase, functioning as endosomal/lysosomal proton pump). Specifically, lipid oversupply to the heart causes disassembly of v-ATPase and endosomal deacidification. Endosomes are storage compartments for lipid transporter CD36. However, upon endosomal deacidification, CD36 is expelled to translocate to the sarcolemma, thereby inducing myocardial lipid accumulation, insulin resistance, and contractile dysfunction. Hence, the v-ATPase assembly may be a suitable target for ameliorating diabetic cardiomyopathy. Another function of v-ATPase involves the binding of anabolic master-regulator mTORC1 to endosomes, a prerequisite for the activation of mTORC1 by amino acids (AAs). We examined whether the relationship between v-ATPase and mTORC1 also operates reciprocally; specifically, whether AA induces v-ATPase reassembly in a mTORC1-dependent manner to prevent excess lipids from entering and damaging the heart.

Methods

Lipid overexposed rodent/human cardiomyocytes and high-fat diet-fed rats were treated with a specific cocktail of AAs (lysine/leucine/arginine). Then, v-ATPase assembly status/activity, cell surface CD36 content, myocellular lipid uptake/accumulation, insulin sensitivity, and contractile function were measured. To elucidate underlying mechanisms, specific gene knockdown was employed, followed by subcellular fractionation, and coimmunoprecipitation.

Results

In lipid-overexposed cardiomyocytes, lysine/leucine/arginine reinternalized CD36 to the endosomes, prevented/reversed lipid accumulation, preserved/restored insulin sensitivity, and contractile function. These beneficial AA actions required the mTORC1–v-ATPase axis, adaptor protein Ragulator, and endosomal/lysosomal AA transporter SLC38A9, indicating an endosome-centric inside-out AA sensing mechanism. In high-fat diet-fed rats, lysine/leucine/arginine had similar beneficial actions at the myocellular level as in vitro in lipid-overexposed cardiomyocytes and partially reversed cardiac hypertrophy.

Conclusion

Specific AAs acting through v-ATPase reassembly reduce cardiac lipid uptake raising the possibility for treatment in situations of lipid overload and associated insulin resistance.

• High physiological concentrations of specific AAs (K/L/R) activate v-ATPase.

• The KLR mix activates v-ATPase by mutually dependent activation of mTORC1.

• KLR-induced v-ATPase activation enables endosomes to retain lipid transporter CD36.

• KLR mends lipid-induced insulin resistance and cardiomyocytic contractile dysfunction.

• KLR reverses v-ATPase disassembly and cardiac hypertrophy in high-fat diet-fed rats.

Short- and long-term effects of rapamycin on ischemic damage and apoptotic changes in torsion of rat testes

Rapamycin has antioxidant defense mechanisms and immune suppressive effects. To detect the short- and long-term effects of rapamycin on ischemic damage and apoptotic changes in torsion of rat testes, mature male albino Wistar rats (n = 48) were included in the study as control, sham, early torsion-detorsion (T/D), early rapamycin treatment, early rapamycin control, late T/D, late rapamycin treatment, and late rapamycin control. The right testis was rotated 720° in a clockwise direction during 4 h in operation groups. Rapamycin was administered orally three times: 30 min before detorsion and 24 and 48 h after detorsion. The animals were killed on the third day in early groups and on the tenth day in late groups after detorsion. Statistically significant differences among all groups were detected for SOD and TBARS, mean seminiferous tubule diameter (MSTD) and Cosentino's histologic score (CHS), caspase 3, bax, average number of apoptotic cells per tubule (ANPCT), and percentage of apoptotic tubule (PAT) values. ANPCT values ​​were 10% lower in the rapamycin treatment groups compared with the untreated T/D groups, and the PAT values ​​were also approximately 1.3 times lower. Although short-term usage of rapamycin may reduce to the tubular injury caused by I/R conversely to apoptosis in the testicular tissue after testicular torsion, rapamycin may have the potential to increase the long-term apoptosis with/without testicular torsion and a subsequent regression in fertility.

FKBPL is associated with metabolic parameters and is a novel determinant of cardiovascular disease

Type 2 diabetes (T2D) is associated with increased risk of cardiovascular disease (CVD). As disturbed angiogenesis and endothelial dysfunction are strongly implicated in T2D and CVD, we aimed to investigate the association between a novel anti-angiogenic protein, FK506-binding protein like (FKBPL), and these diseases. Plasma FKBPL was quantified by ELISA cross-sectionally in 353 adults, consisting of 234 T2D and 119 non-diabetic subjects with/without CVD, matched for age, BMI and gender. FKBPL levels were higher in T2D (adjusted mean: 2.03 ng/ml ± 0.90 SD) vs. non-diabetic subjects (adjusted mean: 1.79 ng/ml ± 0.89 SD, p = 0.02), but only after adjustment for CVD status. In T2D, FKBPL was negatively correlated with fasting blood glucose, HbA1c and diastolic blood pressure (DBP), and positively correlated with age, known diabetes duration, waist/hip ratio, urinary albumin/creatinine ratio (ACR) and fasting C-peptide. FKBPL plasma concentrations were increased in the presence of CVD, but only in the non-diabetic group (CVD: 2.02 ng/ml ± 0.75 SD vs. no CVD: 1.68 ng/ml ± 0.79 SD, p = 0.02). In non-diabetic subjects, FKBPL was positively correlated with an established biomarker for CVD, B-type Natriuretic Peptide (BNP), and echocardiographic parameters of diastolic dysfunction. FKBPL was a determinant of CVD in the non-diabetic group in addition to age, gender, total-cholesterol and systolic blood pressure (SBP). FKBPL may be a useful anti-angiogenic biomarker in CVD in the absence of diabetes and could represent a novel CVD mechanism.

Dysregulation of metabolic flexibility: The impact of mTOR on autophagy in neurodegenerative disease

Non-communicable diseases (NCDs) that involve neurodegenerative disorders and metabolic disease impact over 400 million individuals globally. Interestingly, metabolic disorders, such as diabetes mellitus, are significant risk factors for the development of neurodegenerative diseases. Given that current therapies for these NCDs address symptomatic care, new avenues of discovery are required to offer treatments that affect disease progression. Innovative strategies that fill this void involve the mechanistic target of rapamycin (mTOR) and its associated pathways of mTOR complex 1 (mTORC1), mTOR complex 2 (mTORC2), AMP activated protein kinase (AMPK), trophic factors that include erythropoietin (EPO), and the programmed cell death pathways of autophagy and apoptosis. These pathways are intriguing in their potential to provide effective care for metabolic and neurodegenerative disorders. Yet, future work is necessary to fully comprehend the entire breadth of the mTOR pathways that can effectively and safely translate treatments to clinical medicine without the development of unexpected clinical disabilities.

The Association between the Plasma Sugar and Lipid Profile with the Gene Expression of the Regulatory Protein of mTOR (Raptor) in Patients with Rheumatoid Arthritis

BACKGROUND

Rheumatoid arthritis (RA) is an autoinflammatory and self-perpetuating disease with both articular and extra-articular manifestations, such as cardiovascular complications, which are the leading cause of mortality and morbidity in RA patients. Impaired sugar and lipid metabolism are considered as the critical risk factors for cardiovascular disease (CVD). Regarding the regulatory function of Raptor in the immunometabolism, in this study, we evaluated the association between plasma sugar and lipid profiles with the gene expression of Raptor and the cytokine tumor necrosis factor-α (TNF-α), as an inflammatory mediator, in peripheral blood leukocyte of RA patients.

MATERIAL AND METHODS

Thirty-five RA patients who received combinational disease modified anti-rheumatoid drugs (DMARD) regimen and thirty healthy subjects enrolled in this study. The gene expression of Raptor was assessed by the real-time PCR method, and the Plasma levels of glucose and lipids, as well as TNF-α, were obtained using Hitachi device and enzyme-linked immunosorbent assay (ELISA) technique, respectively.

RESULTS

The gene expression of Raptor was reduced significantly in RA patients compared to the healthy subjects (p = .001). The plasma level of HDL was significantly higher in RA patients than the control group (p = .001), while the plasma level of LDL was reduced significantly in these patients (p = .001).

CONCLUSION

In our study, the reduced gene expression of Raptor may contribute to the impaired immunometabolism in RA patients, which is independent of plasma sugar and lipid profile.

New Insights for nicotinamide: Metabolic disease, autophagy, and mTOR

Metabolic disorders, such as diabetes mellitus (DM), are increasingly becoming significant risk factors for the health of the global population and consume substantial portions of the gross domestic product of all nations. Although conventional therapies that include early diagnosis, nutritional modification of diet, and pharmacological treatments may limit disease progression, tight serum glucose control cannot prevent the onset of future disease complications. With these concerns, novel strategies for the treatment of metabolic disorders that involve the vitamin nicotinamide, the mechanistic target of rapamycin (mTOR), mTOR Complex 1 (mTORC1), mTOR Complex 2 (mTORC2), AMP activated protein kinase (AMPK), and the cellular pathways of autophagy and apoptosis offer exceptional promise to provide new avenues of treatment. Oversight of these pathways can promote cellular energy homeostasis, maintain mitochondrial function, improve glucose utilization, and preserve pancreatic beta-cell function. Yet, the interplay among mTOR, AMPK, and autophagy pathways can be complex and affect desired clinical outcomes, necessitating further investigations to provide efficacious treatment strategies for metabolic dysfunction and DM.

Association of WISP1/CCN4 with Risk of Overweight and Gestational Diabetes Mellitus in Chinese Pregnant Women

BACKGROUND

Obese women with gestational diabetes mellitus (GDM) have a higher risk of adverse outcomes than women with obesity or GDM alone. Our study is aimed at investigating the discriminatory power of circulatory Wnt1-inducible signaling pathway protein-1 (WISP1), a novel adipocytokine, on the copresence of prepregnancy overweight/obesity and GDM and at clarifying the relationship between the WISP1 level and clinical cardiometabolic parameters.

METHODS

A total of 313 participants were screened from a multicenter prospective prebirth cohort: Born in Shenyang Cohort Study (BISCS). Subjects were examined with a 2 × 2 factorial design for body mass index (BMI) ≥ 24 and GDM. Between 24 and 28 weeks of pregnancy, follow-up individuals underwent an OGTT and blood sampling for cardiometabolic characterization.

RESULTS

We observed that the WISP1 levels were elevated in prepregnancy overweight/obesity patients with GDM, compared with nonoverweight subjects with normal blood glucose (3.45 ± 0.89 vs. 2.91 ± 0.75 ng/mL). Multilogistic regression analyses after adjustments for potential confounding factors revealed that WISP1 was a strong and independent risk factor for prepregnancy overweight/obesity with GDM (all ORs > 1). In addition, the results of the ROC analysis indicated that WISP1 exhibited the capability to identify individuals with prepregnancy overweight/obesity and GDM (all AUC > 0.5). Finally, univariate and multivariate linear regression showed that WISP1 level was positively and independently correlated with fasting blood glucose, systolic blood pressure, and aspartate aminotransferase and was negatively correlated with HDL-C and complement C1q.

CONCLUSIONS

WISP1 may be critical for the prediction, diagnosis, and therapeutic strategies against obesity and GDM in pregnant women.

Nicotinamide: Oversight of Metabolic Dysfunction Through SIRT1, mTOR, and Clock Genes

Metabolic disorders that include diabetes mellitus present significant challenges for maintaining the welfare of the global population. Metabolic diseases impact all systems of the body and despite current therapies that offer some protection through tight serum glucose control, ultimately such treatments cannot block the progression of disability and death realized with metabolic disorders. As a result, novel therapeutic avenues are critical for further development to address these concerns. An innovative strategy involves the vitamin nicotinamide and the pathways associated with the silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), the mechanistic target of rapamycin (mTOR), mTOR Complex 1 (mTORC1), mTOR Complex 2 (mTORC2), AMP activated protein kinase (AMPK), and clock genes. Nicotinamide maintains an intimate relationship with these pathways to oversee metabolic disease and improve glucose utilization, limit mitochondrial dysfunction, block oxidative stress, potentially function as antiviral therapy, and foster cellular survival through mechanisms involving autophagy. However, the pathways of nicotinamide, SIRT1, mTOR, AMPK, and clock genes are complex and involve feedback pathways as well as trophic factors such as erythropoietin that require a careful balance to ensure metabolic homeostasis. Future work is warranted to gain additional insight into these vital pathways that can oversee both normal metabolic physiology and metabolic disease.

Cognitive impairment with diabetes mellitus and metabolic disease: innovative insights with the mechanistic target of rapamycin and circadian clock gene pathways

Introduction: Dementia is the 7th leading cause of death that imposes a significant financial and service burden on the global population. Presently, only symptomatic care exists for cognitive loss, such as Alzheimer's disease.Areas covered: Given the advancing age of the global population, it becomes imperative to develop innovative therapeutic strategies for cognitive loss. New studies provide insight to the association of cognitive loss with metabolic disorders, such as diabetes mellitus.Expert opinion: Diabetes mellitus is increasing in incidence throughout the world and affects 350 million individuals. Treatment strategies identifying novel pathways that oversee metabolic and neurodegenerative disorders offer exciting prospects to treat dementia. The mechanistic target of rapamycin (mTOR) and circadian clock gene pathways that include AMP activated protein kinase (AMPK), Wnt1 inducible signaling pathway protein 1 (WISP1), erythropoietin (EPO), and silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1) provide novel strategies to treat cognitive loss that has its basis in metabolic cellular dysfunction. However, these pathways are complex and require precise regulation to maximize treatment efficacy and minimize any potential clinical disability. Further investigations hold great promise to treat both the onset and progression of cognitive loss that is associated with metabolic disease.

Aldose reductase regulates hyperglycemia-induced HUVEC death via SIRT1/AMPK-α1/mTOR pathway

Although hyperglycemia-mediated death and dysfunction of endothelial cells have been reported to be a major cause of diabetes associated vascular complications, the mechanisms through which hyperglycemia cause endothelial dysfunction is not well understood. We have recently demonstrated that aldose reductase (AR, AKR1B1) is an obligatory mediator of oxidative and inflammatory signals induced by growth factors, cytokines and hyperglycemia. However, the molecular mechanisms by which AR regulates hyperglycemia-induced endothelial dysfunction is not well known. In this study, we have investigated the mechanism(s) by which AR regulates hyperglycemia-induced endothelial dysfunction. Incubation of human umbilical vein endothelial cells (HUVECs) with high glucose (HG) decreased the cell viability and inhibition of AR prevented it. Further, AR inhibition prevented the HG-induced ROS generation and expression of BCL-2, BAX and activation of Caspase-3 in HUVECs. AR inhibition also prevented the adhesion of THP-1 monocytes on HUVECs, expression of iNOS and eNOS and adhesion molecules ICAM-1 and VCAM-1 in HG-treated HUVECs. Further, AR inhibition restored the HG-induced depletion of SIRT1 in HUVECs and increased the phosphorylation of AMPKα1 along-with a decrease in phosphorylation of mTOR in HG-treated HUVECs. Fidarestat decreased SIRT1 expression in HUVECs pre-treated with specific SIRT1 inhibitor but not with the AMPKα1 inhibitor. Similarly, knockdown of AR in HUVECs by siRNA prevented the HG-induced HUVECs cell death, THP-1 monocyte adhesion and SIRT1 depletion. Furthermore, fidarestat regulated the phosphorylation of AMPKα1 and mTOR, and expression of SIRT1 in STZ-induced diabetic mice heart and aorta tissues. Collectively, our data suggest that AR regulates hyperglycemia-induced endothelial death and dysfunction by altering the ROS/SIRT1/AMPKα1/mTOR pathway.

Ginkgo Biloba Leaf Extract Attenuates Atherosclerosis in Streptozotocin-Induced Diabetic ApoE-/- Mice by Inhibiting Endoplasmic Reticulum Stress via Restoration of Autophagy through the mTOR Signaling Pathway

Background

There is a crosstalk between endoplasmic reticulum stress (ERS) and autophagy, and autophagy could attenuate endoplasmic reticulum stress-mediated apoptosis. Ginkgo biloba leaf extract (GBE) exerts vascular protection functions. The purpose of the present study is to investigate the role of autophagy in diabetic atherosclerosis (AS) and the effect of GBE on autophagy and ERS.

Methods

Network pharmacology was utilized to predict the targets and pathways of the active chemical compounds of Gingko biloba leaf to attenuate AS. ApoE^−/− mice were rendered diabetic by intraperitoneal ingestion with streptozotocin combined with a high-fat diet. The diabetic mice were divided into five groups: model group, atorvastatin group, rapamycin group, and low- and high-dose GBE groups. Serum and tissue markers of autophagy or ERS markers, including the protein expression, were examined.

Results

The mammalian target of rapamycin (mTOR) and NF-κB signaling pathways were targeted by the active chemical compounds of GBE to attenuate AS predicted by network pharmacology. GBE reduced the plaque area/lumen area and the plaque lipid deposition area/intimal area and inhibited the expressions of CD68, MMP2, and MMP9. Rapamycin and GBE inhibited the expression of mTOR and SQSTM1/p62 which increased in the aorta of diabetic mice. In addition, GBE reduced the expression of ERS markers in diabetic mice. GBE reduced the serum lipid metabolism levels, blood glucose, and inflammatory cytokines.

Conclusion

Impaired autophagy and overactive endoplasmic reticulum stress contributed to diabetic atherosclerosis. mTOR inhibitor rapamycin and GBE attenuated diabetic atherosclerosis by inhibiting ERS via restoration of autophagy through inhibition of mTOR.

Emerging Role of mTOR Signaling-Related miRNAs in Cardiovascular Diseases

Mechanistic/mammalian target of rapamycin (mTOR), an atypical serine/threonine kinase of the phosphoinositide 3-kinase- (PI3K-) related kinase family, elicits a vital role in diverse cellular processes, including cellular growth, proliferation, survival, protein synthesis, autophagy, and metabolism. In the cardiovascular system, the mTOR signaling pathway integrates both intracellular and extracellular signals and serves as a central regulator of both physiological and pathological processes. MicroRNAs (miRs), a class of short noncoding RNA, are an emerging intricate posttranscriptional modulator of critical gene expression for the development and maintenance of homeostasis across a wide array of tissues, including the cardiovascular system. Over the last decade, numerous studies have revealed an interplay between miRNAs and the mTOR signaling circuit in the different cardiovascular pathophysiology, like myocardial infarction, hypertrophy, fibrosis, heart failure, arrhythmia, inflammation, and atherosclerosis. In this review, we provide a comprehensive state of the current knowledge regarding the mechanisms of interactions between the mTOR signaling pathway and miRs. We have also highlighted the latest advances on mTOR-targeted therapy in clinical trials and the new perspective therapeutic strategies with mTOR-targeting miRs in cardiovascular diseases.

Negative feedback loop of autophagy and endoplasmic reticulum stress in rapamycin protection against renal ischemia-reperfusion injury during initial reperfusion phase

Rapamycin, an immunosuppressant, is widely used in patients with kidney transplant. However, the therapeutic effects of rapamycin remain controversial. Additionally, previous studies have revealed deleterious effects of rapamycin predominantly when administered for ≥24 h. Few studies, however, have focused on the short-term effects of rapamycin administered only during the initial reperfusion phase. As such, we designed this study to explore the potential effects and mechanisms of rapamycin under a specific therapeutic regimen in which rapamycin is mixed in the perfusate during the initial reperfusion phase (within 24 h). Interestingly, we found that rapamycin maintained renal function and attenuated ischemia-reperfusion (I/R)-induced apoptosis in vivo and in vitro during the initial reperfusion phase, especially at 8 h after reperfusion. Simultaneously, rapamycin activated autophagy and inhibited endoplasmic reticulum (ER) stress and 3 pathways of unfolding protein response: ATF6, PERK, and IRE1α. Interestingly, we further found that the protective effects of rapamycin were suppressed when autophagy was inhibited by chloroquine and 3-methyladenine or when ER stress was induced by thapsigargin. Moreover, in terms of the regulatory effects of rapamycin, a negative-feedback loop between autophagy and ER stress occurred, with autophagy inhibiting ER stress and increased ER stress promoting autophagy during the initial reperfusion phase of renal I/R injury. Our study provides evidence that immediate reperfusion with rapamycin during the initial reperfusion phase repairs renal function and reduces apoptosis via activating autophagy, which could further inhibit ER stress. These results suggest a novel treatment modality for application during the initial reperfusion phase of renal I/R injury caused by kidney transplantation.-Li, X., Zhu, G., Gou, X., He, W., Yin, H., Yang, X., Li, J. Negative feedback loop of autophagy and endoplasmic reticulum stress in rapamycin protection against renal ischemia-reperfusion injury during initial reperfusion phase.

Moving to the Rhythm with Clock (Circadian) Genes, Autophagy, mTOR, and SIRT1 in Degenerative Disease and Cancer

BACKGROUND

The mammalian circadian clock and its associated clock genes are increasingly been recognized as critical components for a number of physiological and disease processes that extend beyond hormone release, thermal regulation, and sleep-wake cycles. New evidence suggests that clinical behavior disruptions that involve prolonged shift work and even space travel may negatively impact circadian rhythm and lead to multi-system disease.

METHODS

In light of the significant role circadian rhythm can hold over the body's normal physiology as well as disease processes, we examined and discussed the impact circadian rhythm and clock genes hold over lifespan, neurodegenerative disorders, and tumorigenesis.

RESULTS

In experimental models, lifespan is significantly reduced with the introduction of arrhythmic mutants and leads to an increase in oxidative stress exposure. Interestingly, patients with Alzheimer's disease and Parkinson's disease may suffer disease onset or progression as a result of alterations in the DNA methylation of clock genes as well as prolonged pharmacological treatment for these disorders that may lead to impairment of circadian rhythm function. Tumorigenesis also can occur with the loss of a maintained circadian rhythm and lead to an increased risk for nasopharyngeal carcinoma, breast cancer, and metastatic colorectal cancer. Interestingly, the circadian clock system relies upon the regulation of the critical pathways of autophagy, the mechanistic target of rapamycin (mTOR), AMP activated protein kinase (AMPK), and silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1) as well as proliferative mechanisms that involve the wingless pathway of Wnt/β-catenin pathway to foster cell survival during injury and block tumor cell growth.

CONCLUSION

Future targeting of the pathways of autophagy, mTOR, SIRT1, and Wnt that control mammalian circadian rhythm may hold the key for the development of novel and effective therapies against aging- related disorders, neurodegenerative disease, and tumorigenesis.

Role of AMPK in Diabetic Cardiovascular Complications: An Overview

Macrovascular complications of diabetes like cardiovascular diseases appear to be one of the leading causes of mortality. Current therapies aimed at counteracting the adverse effects of diabetes on cardiovascular system are found to be inadequate. Hence, there is a growing need in search of novel targets. Adenosine Monophosphate Activated Protein Kinase (AMPK) is one such promising target, as a plethora of evidences pointing to its cardioprotective role in pathological milieu like cardiac hypertrophy, atherosclerosis and heart failure. AMPK is a serine-threonine kinase, which gets activated in response to a cellular depriving energy status. It orchestrates cellular metabolic response to energy demand and is, therefore, often referred to as "metabolic master switch" of the cell. In this review, we provide an overview of patho-mechanisms of diabetic cardiovascular disease; highlighting the role of AMPK in the regulation of this condition, followed by a description of extrinsic modulators of AMPK as potential therapeutic tools.

Beneficial Effects of Resveratrol-Mediated Inhibition of the mTOR Pathway in Spinal Cord Injury

Spinal cord injury (SCI) causes a high rate of morbidity and disability. The clinical features of SCI are divided into acute, subacute, and chronic phases according to its pathophysiological events. The mammalian target of rapamycin (mTOR) signaling pathway plays an important role in cell death and inflammation in the acute phase and neuroregeneration in the subacute/chronic phases at different times. Resveratrol has the potential of regulating cell growth, proliferation, metabolism, and angiogenesis through the mTOR signaling pathway. Herein, we explicate the role of resveratrol in the repair of SCI through the inhibition of the mTOR signaling pathway. The inhibition of the mTOR pathway by resveratrol has the potential of serving as a neuronal restorative mechanism following SCI.

Warming Up to New Possibilities with the Capsaicin Receptor TRPV1: mTOR, AMPK, and Erythropoietin

BACKGROUND

Transient receptor potential (TRP) channels are a superfamily of ion channels termed after the trp gene in Drosophila that are diverse in structure and control a wide range of biological functions including cell development and growth, thermal regulation, and vascular physiology. Of significant interest is the transient receptor potential cation channel subfamily V member 1 (TRPV1) receptor, also known as the capsaicin receptor and the vanilloid receptor 1, that is a non-selective cation channel sensitive to a host of external stimuli including capsaicin and camphor, venoms, acid/basic pH changes, and temperature.

METHODS

Given the multiple modalities that TRPV1 receptors impact in the body, we examined and discussed the role of these receptors in vasomotor control, metabolic disorders, cellular injury, oxidative stress, apoptosis, autophagy, and neurodegenerative disorders and their overlap with other signal transduction pathways that impact trophic factors.

RESULTS

Surprisingly, TRPV1 receptors do not rely entirely upon calcium signaling to affect cellular biology, but also have a close relationship with the mechanistic target of rapamycin (mTOR), AMP activated protein kinase (AMPK), and protein kinase B (Akt) that have roles in pain sensitivity, stem cell development, cellular survival, and cellular metabolism. These pathways with TRPV1 converge in the signaling of growth factors with recent work highlighting a relationship with erythropoietin (EPO). Angiogenesis and endothelial tube formation controlled by EPO requires, in part, the activation of TRPV1 receptors in conjunction with Akt and AMPK pathways.

CONCLUSION

TRPV1 receptors could prove to become vital to target disorders of vascular origin and neurodegeneration. Broader and currently unrealized implementations for both EPO and TRPV1 receptors can be envisioned for for the development of novel therapeutic strategies in multiple systems of the body.

The mechanistic target of rapamycin (mTOR) and the silent mating-type information regulation 2 homolog 1 (SIRT1): oversight for neurodegenerative disorders

As a result of the advancing age of the global population and the progressive increase in lifespan, neurodegenerative disorders continue to increase in incidence throughout the world. New strategies for neurodegenerative disorders involve the novel pathways of the mechanistic target of rapamycin (mTOR) and the silent mating-type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1) that can modulate pathways of apoptosis and autophagy. The pathways of mTOR and SIRT1 are closely integrated. mTOR forms the complexes mTOR Complex 1 and mTOR Complex 2 and can impact multiple neurodegenerative disorders that include Alzheimer's disease, Huntington's disease, and Parkinson's disease. SIRT1 can control stem cell proliferation, block neuronal injury through limiting programmed cell death, drive vascular cell survival, and control clinical disorders that include dementia and retinopathy. It is important to recognize that oversight of programmed cell death by mTOR and SIRT1 requires a fine degree of precision to prevent the progression of neurodegenerative disorders. Additional investigations and insights into these pathways should offer effective and safe treatments for neurodegenerative disorders.

Leucine reduces the proliferation of MC3T3-E1 cells through DNA damage and cell senescence

Leucine (Leu) is an essential branched-chain amino acid, present in dairy products, which has been investigated for its important role in cell signaling. The effects of Leu on several kinds of cells have been studied, altough little is known on its action upon bone cells and cell proliferation. Thus, the aim of this study is to investigate the effects of Leu supplementation on the proliferation of pre-osteoblasts from MC3T3-E1 lineage. MC3T3-E1 cells were kept in Alpha medium supplemented with 10% fetal bovine serum and 1% antibiotic-antimitotic. Cells were treated during 48h by adding 50μM of Leu, which corresponds to a 12.5% increase of the amino acid in the culture medium. The evaluation of viability and proliferation of cultured cells was performed using Trypan Blue dye. In order to identify the mechanisms related to the decreased cellular proliferation, assays were performed to assess cytotoxicity, apotosis, oxidative stress, inflammation, autophagy, senescence and DNA damage. Results showed that Leu supplementation decreased cell proliferation by 40% through mechanisms not related to cell necrosis, apoptosis, oxidative stress, autophagy or inhibition of the mTORC1 pathway. On the other hand, Leu supplementation caused DNA damage. In conclusion, Leu caused a negative impact on bone cell proliferation by inducing cell senescence through DNA damage.

Functional analyses of major cancer-related signaling pathways in Alzheimer's disease etiology

Alzheimer's disease (AD) is an aging-related neurodegenerative disease and accounts for majority of human dementia. The hyper-phosphorylated tau-mediated intracellular neurofibrillary tangle and amyloid β-mediated extracellular senile plaque are characterized as major pathological lesions of AD. Different from the dysregulated growth control and ample genetic mutations associated with human cancers, AD displays damage and death of brain neurons in the absence of genomic alterations. Although various biological processes predominately governing tumorigenesis such as inflammation, metabolic alteration, oxidative stress and insulin resistance have been associated with AD genesis, the mechanistic connection of these biological processes and signaling pathways including mTOR, MAPK, SIRT, HIF, and the FOXO pathway controlling aging and the pathological lesions of AD are not well recapitulated. Hence, we performed a thorough review by summarizing the physiological roles of these key cancer-related signaling pathways in AD pathogenesis, comprising of the crosstalk of these pathways with neurofibrillary tangle and senile plaque formation to impact AD phenotypes. Importantly, the pharmaceutical investigations of anti-aging and AD relevant medications have also been highlighted. In summary, in this review, we discuss the potential role that cancer-related signaling pathways may play in governing the pathogenesis of AD, as well as their potential as future targeted strategies to delay or prevent aging-related diseases and combating AD.

Erythropoietin and mTOR: A "One-Two Punch" for Aging-Related Disorders Accompanied by Enhanced Life Expectancy

Life expectancy continues to increase throughout the world, but is accompanied by a rise in the incidence of non-communicable diseases. As a result, the benefits of an increased lifespan can be limited by aging-related disorders that necessitate new directives for the development of effective and safe treatment modalities. With this objective, the mechanistic target of rapamycin (mTOR), a 289-kDa serine/threonine protein, and its related pathways of mTOR Complex 1 (mTORC1), mTOR Complex 2 (mTORC2), proline rich Akt substrate 40 kDa (PRAS40), AMP activated protein kinase (AMPK), Wnt signaling, and silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), have generated significant excitement for furthering novel therapies applicable to multiple systems of the body. Yet, the biological and clinical outcome of these pathways can be complex especially with oversight of cell death mechanisms that involve apoptosis and autophagy. Growth factors, and in particular erythropoietin (EPO), are one avenue under consideration to implement control over cell death pathways since EPO can offer potential treatment for multiple disease entities and is intimately dependent upon mTOR signaling. In experimental and clinical studies, EPO appears to have significant efficacy in treating several disorders including those involving the developing brain. However, in mature populations that are affected by aging-related disorders, the direction for the use of EPO to treat clinical disease is less clear that may be dependent upon a number of factors including the understanding of mTOR signaling. Continued focus upon the regulatory elements that control EPO and mTOR signaling could generate critical insights for targeting a broad range of clinical maladies.

Cancer metabolism: New insights into classic characteristics

Initial studies of cancer metabolism in the early 1920s found that cancer cells were phenotypically characterized by aerobic glycolysis, in that these cells favor glucose uptake and lactate production, even in the presence of oxygen. This property, called the Warburg effect, is considered a hallmark of cancer. The mechanism by which these cells acquire aerobic glycolysis has been uncovered. Acidic extracellular fluid, secreted by cancer cells, induces a malignant phenotype, including invasion and metastasis. Cancer cells survival depends on a critical balance of redox status, which is regulated by amino acid metabolism. Glutamine is extremely important for oxidative phosphorylation and redox regulation. Cells highly dependent on glutamine and that cannot survive with glutamine are called glutamine-addicted cells. Metabolic reprogramming has been observed in cancer stem cells, which have the property of self-renewal and are resistant to chemotherapy and radiotherapy. These findings suggest that studies of cancer metabolism can reveal methods of preventing cancer recurrence and metastasis.

Rhodiola crenulata Attenuates High Glucose Induced Endothelial Dysfunction in Human Umbilical Vein Endothelial Cells

Rhodiola crenulata root extract (RCE), a traditional Chinese medicine, has been shown to regulate glucose and lipid metabolism via the AMPK pathway in high glucose (HG) conditions. However, the effect of RCE on HG-induced endothelial dysfunction remains unclear. The present study was designed to examine the effects and mechanisms of RCE against hyperglycemic insult in endothelial cells. Human umbilical vein endothelial cells (HUVECs) were pretreated with or without RCE and then exposed to 33[Formula: see text]mM HG medium. The cell viability, nitrite production, oxidative stress markers, and vasoactive factors, as well as the mechanisms underlying RCE action, were then investigated. We found that RCE significantly improved cell death, nitric oxide (NO) defects, and oxidative stress in HG conditions. In addition, RCE significantly decreased the HG-induced vasoactive markers, including endothelin-1 (ET-1), fibronectin, and vascular endothelial growth factor (VEGF). However, the RCE-restored AMPK-Akt-eNOS-NO axis and cell viability were abolished by the presence of an AMPK inhibitor. These findings suggested that the protective effects of RCE were associated with the AMPK-Akt-eNOS-NO signaling pathway. In conclusion, we showed that RCE protected endothelial cells from hyperglycemic insult and demonstrated its potential for use as a treatment for endothelial dysfunction in diabetes mellitus.

The Molecular Mechanism of Glucagon-Like Peptide-1 Therapy in Alzheimer's Disease, Based on a Mechanistic Target of Rapamycin Pathway

The mechanistic target of rapamycin (mTOR) is an important molecule that connects aging, lifespan, energy balance, glucose and lipid metabolism, and neurodegeneration. Rapamycin exerts effects in numerous biological activities via its target protein, playing a key role in energy balance, regulation of autophagy, extension of lifespan, immunosuppression, and protection against neurodegeneration. There are many similar pathophysiological processes and molecular pathways between Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM), and pharmacologic agents used to treat T2DM, including glucagon-like peptide-1 (GLP-1) analogs, seem to be beneficial for AD. mTOR mediates the effects of GLP-1 analogs in the treatment of T2DM; hence, I hypothesize that mTOR is a key molecule for mediating the protective effects of GLP-1 for AD.

Folic acid inhibits dedifferentiation of PDGF-BB-induced vascular smooth muscle cells by suppressing mTOR/P70S6K signaling

OBJECTIVE

Folic acid (FA) supplementation reduces the risk of atherosclerosis and stroke. Phenotypic change from differentiated to dedifferentiated vascular smooth muscle cells (VSMCs) plays an important role in atherosclerosis development; however, the exact mechanisms remain unknown. This study aimed to assess whether FA through mammalian target of rapamycin (mTOR)/P70S6K signaling inhibits platelet derived growth factor (PDGF-BB) induced VSMC dedifferentiation.

METHODS

VSMCs from primary cultures were identified by morphological observation and α-smooth muscle actin (α-SM-actin, α-SMA) immunocytochemistry. Then, VSMCs were induced by PDGF-BB and treated with varying FA concentrations. Rapamycin and MHY-1485 were used to inhibit or activate the mTOR/P70S6K pathway, respectively. Next, MTT, Transwell, and wound healing assays were employed to assess proliferation and migration of VSMCs. In addition, Western blotting was used to evaluate protein levels of α-SMA, calponin, osteopontin, mTOR, p-mTOR, P70S6K and p-P70S6K in VSMCs.

RESULTS

VSMCs showed phenotypic alteration from differentiated to dedifferentiated cells in response to PDGF-BB. MTT, Transwell and wound healing assays showed that FA markedly inhibited proliferation and migration in PDGF-BB-induced VSMCs, in a time and concentration-dependent manner. FA treatment increased the expression levels of the contractile phenotype marker proteins α-SMA and calponin compared with VSMCs stimulated by PDGF-BB alone. Furthermore, FA significantly suppressed mTOR and P70S6K phosphorylation compared with PDGF-BB alone. Similar to FA, downregulation of mTOR signaling by rapamycin inhibited VSMC dedifferentiation. In contrast, upregulation of mTOR signaling by MHY-1485 reversed the FA-induced inhibition of VSMC dedifferentiation.

CONCLUSION

Folic acid inhibits dedifferentiation of PDGF-BB-induced VSMCs by suppressing mTOR/P70S6K signaling.

Target acquired: Selective autophagy in cardiometabolic disease

The accumulation of damaged or excess proteins and organelles is a defining feature of metabolic disease in nearly every tissue. Thus, a central challenge in maintaining metabolic homeostasis is the identification, sequestration, and degradation of these cellular components, including protein aggregates, mitochondria, peroxisomes, inflammasomes, and lipid droplets. A primary route through which this challenge is met is selective autophagy, the targeting of specific cellular cargo for autophagic compartmentalization and lysosomal degradation. In addition to its roles in degradation, selective autophagy is emerging as an integral component of inflammatory and metabolic signaling cascades. In this Review, we focus on emerging evidence and key questions about the role of selective autophagy in the cell biology and pathophysiology of metabolic diseases such as obesity, diabetes, atherosclerosis, and steatohepatitis. Essential players in these processes are the selective autophagy receptors, defined broadly as adapter proteins that both recognize cargo and target it to the autophagosome. Additional domains within these receptors may allow integration of information about autophagic flux with critical regulators of cellular metabolism and inflammation. Details regarding the precise receptors involved, such as p62 and NBR1, and their predominant interacting partners are just beginning to be defined. Overall, we anticipate that the continued study of selective autophagy will prove to be informative in understanding the pathogenesis of metabolic diseases and to provide previously unrecognized therapeutic targets.

Harnessing the Power of SIRT1 and Non-coding RNAs in Vascular Disease

Noncommunicable diseases (NCDs) contribute to a significant amount of disability and death in the world. Of these disorders, vascular disease is ranked high, falls within the five leading causes of death, and impacts multiple other disease entities such as those of the cardiac system, nervous system, and metabolic disease. Targeting the silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1) pathway and the modulation of micro ribonucleic acids (miRNAs) may hold great promise for the development of novel strategies for the treatment of vascular disease since each of these pathways are highly relevant to cardiac and nervous system disorders as well as to metabolic dysfunction. SIRT1 is vital in determining the course of stem cell development and the survival, metabolism, and life span of differentiated cells that are overseen by both autophagy and apoptosis. SIRT1 interfaces with a number of pathways that involve forkhead transcription factors, mechanistic of rapamycin (mTOR), AMP activated protein kinase (AMPK) and Wnt1 inducible signaling pathway protein 1 (WISP1) such that the level of activity of SIRT1 can become a critical determinant for biological and clinical outcomes. The essential fine control of SIRT1 is directly tied to the world of non-coding RNAs that ultimately oversee SIRT1 activity to either extend or end cellular survival. Future studies that can further elucidate the crosstalk between SIRT1 and non-coding RNAs should serve well our ability to harness the power of SIRT1 and non-coding RNAs for the treatment of vascular disorders.

Rapamycin alleviates oxidative stress-induced damage in rat erythrocytes

An imbalanced cellular redox system promotes the production of reactive oxygen species (ROS) that may lead to oxidative stress-mediated cell death. Erythrocytes are the best-studied model of antioxidant defense mechanism. The present study was undertaken to investigate the effect of the immunosuppressant drug rapamycin, an inducer of autophagy, on redox balance of erythrocytes and blood plasma of oxidatively challenged rats. Male Wistar rats were oxidatively challenged with HgCl2 (5 mg/kg body mass (b.m.)). A significant (p < 0.05) induction in ROS production, plasma membrane redox system (PMRS), intracellular Ca2+ influx, lipid peroxidation (LPO), osmotic fragility, plasma protein carbonyl (PCO) content, and plasma advanced oxidation protein products (AOPP) and simultaneously significant reduction in glutathione (GSH) level and ferric reducing ability of plasma (FRAP) were observed in rats exposed to HgCl2. Furthermore, rapamycin (0.5 mg/kg b.m.) provided significant protection against HgCl2-induced alterations in rat erythrocytes and plasma by reducing ROS production, PMRS activity, intracellular Ca2+ influx, LPO, osmotic fragility, PCO content, and AOPP and also restored the level of antioxidant GSH and FRAP. Our observations provide evidence that rapamycin improves redox status and attenuates oxidative stress in oxidatively challenged rats. Our data also demonstrate that rapamycin is a comparatively safe immunosuppressant drug.

Novel nervous and multi-system regenerative therapeutic strategies for diabetes mellitus with mTOR

Throughout the globe, diabetes mellitus (DM) is increasing in incidence with limited therapies presently available to prevent or resolve the significant complications of this disorder. DM impacts multiple organs and affects all components of the central and peripheral nervous systems that can range from dementia to diabetic neuropathy. The mechanistic target of rapamycin (mTOR) is a promising agent for the development of novel regenerative strategies for the treatment of DM. mTOR and its related signaling pathways impact multiple metabolic parameters that include cellular metabolic homeostasis, insulin resistance, insulin secretion, stem cell proliferation and differentiation, pancreatic β-cell function, and programmed cell death with apoptosis and autophagy. mTOR is central element for the protein complexes mTOR Complex 1 (mTORC1) and mTOR Complex 2 (mTORC2) and is a critical component for a number of signaling pathways that involve phosphoinositide 3-kinase (PI 3-K), protein kinase B (Akt), AMP activated protein kinase (AMPK), silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), Wnt1 inducible signaling pathway protein 1 (WISP1), and growth factors. As a result, mTOR represents an exciting target to offer new clinical avenues for the treatment of DM and the complications of this disease. Future studies directed to elucidate the delicate balance mTOR holds over cellular metabolism and the impact of its broad signaling pathways should foster the translation of these targets into effective clinical regimens for DM.

Targeting PRAS40 for multiple diseases

Proline-rich Akt substrate 40kDa (PRAS40) bridges cell signaling between protein kinase B (Akt) and the mammalian target of rapamycin complex 1 (mTORC1). Both Akt and mTORC1 can phosphorylate PRAS40. As a negative regulator of mTORC1, PRAS40 prevents the binding of mTOR to its substrates. The phosphorylation of PRAS40 results in its dissociation from mTORC1 and enhanced mTOR activation. PRAS40 in conjunction with mTORC1 has been closely associated with programmed cell death and is implicated in diabetes mellitus (DM), cardiovascular diseases, cancer, and neurological diseases. Thus, targeting PRAS40 might hold great promise for innovative therapeutic strategies for these diseases.

Mesoglycan attenuates VSMC proliferation through activation of AMP-activated protein kinase and mTOR

BACKGROUND

Vascular smooth muscle cells (VSMC) proliferation contributes significantly to intimal thickening in atherosclerosis and restenosis diseases. Platelet derived growth factor (PDGF) has been implicated in VSMC proliferation though the activation of multiple growth-promoting signals. Mesoglycan, a natural glycosaminoglycans preparation, is reported to show vascular protective effect. However, the mechanisms by which mesoglycan inhibits proliferation of VSMC are not fully understood. Here, we investigated whether mesoglycan exert therapeutic effect via AMP-activated protein kinase (AMPK) and its underlying mechanism.

METHODS

We cultured VSMC with increasing doses of mesoglycan. AMPK activation was measured by western blot analysis and cell proliferation was measured by flow cytometry.

RESULTS

Mesoglycan dose- and time- dependently increased the phosphorylation of AMPK (Thr(172)) and its upstream target, LKB1 (Ser(428)) and its downstream, ACC (Ser(79)) in VSMCs. Mesoglycan also blocked the PDGF-stimulated cell cycle progression through the G0/G1 arrest. AMPK DNα1, AMPK DNα2 or AMPK siRNA reduced the mesoglycan-mediated inhibition of VSMC proliferation. AMPK signaling activated by mesoglycan regulates mTOR phosphorylation which closely related to cell proliferation.

CONCLUSION

These data suggest that mesoglycan-induced AMPK activation suppress the VSMC proliferation via mTOR-dependent mechanism and mesoglycan may have beneficial effects on vascular proliferative disorders such as atherosclerosis.

A novel AKT inhibitor, AZD5363, inhibits phosphorylation of AKT downstream molecules, and activates phosphorylation of mTOR and SMG-1 dependent on the liver cancer cell type

Due to frequent phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway dysregulation, AKT is typically accepted as a promising anticancer therapeutic target. mTOR, in particular, represents a suitable therapeutic target for hepatocellular carcinoma, whilst suppressor with morphogenetic effect on genitalia family member-1 (SMG-1) is believed to serve a potential tumor suppressor role in human cancer. Despite SMG-1 and mTOR belonging to the same PI3K-related kinase family, the interactions between them are not yet fully understood. In the present study, a novel pyrrolopyrimidine-derived compound, AZD5363, was observed to suppress proliferation in liver cancer Hep-G2 and Huh-7 cells by inhibiting the phosphorylation of downstream molecules in the AKT signal pathway, in a dose- and time-dependent manner. AZD5363 activated the phosphorylation of mTOR, dependent on the liver cancer cell type, as it may have differing effects in various liver cancer cell lines. Additionally, AZD5363 also activated SMG-1 within the same liver cancer cells types, which subsequently activated the phosphorylation of mTOR. In conclusion, the present study indicates that AZD5363 inhibited phosphorylation of AKT downstream molecules, and activated phosphorylation of mTOR and SMG-1, dependent on the liver cancer type.

Regeneration in the nervous system with erythropoietin

Globally, greater than 30 million individuals are afflicted with disorders of the nervous system accompanied by tens of thousands of new cases annually with limited, if any, treatment options. Erythropoietin (EPO) offers an exciting and novel therapeutic strategy to address both acute and chronic neurodegenerative disorders. EPO governs a number of critical protective and regenerative mechanisms that can impact apoptotic and autophagic programmed cell death pathways through protein kinase B (Akt), sirtuins, mammalian forkhead transcription factors, and wingless signaling. Translation of the cytoprotective pathways of EPO into clinically effective treatments for some neurodegenerative disorders has been promising, but additional work is necessary. In particular, development of new treatments with erythropoiesis-stimulating agents such as EPO brings several important challenges that involve detrimental vascular outcomes and tumorigenesis. Future work that can effectively and safely harness the complexity of the signaling pathways of EPO will be vital for the fruitful treatment of disorders of the nervous system.

Targeting molecules to medicine with mTOR, autophagy and neurodegenerative disorders

Neurodegenerative disorders are significantly increasing in incidence as the age of the global population continues to climb with improved life expectancy. At present, more than 30 million individuals throughout the world are impacted by acute and chronic neurodegenerative disorders with limited treatment strategies. The mechanistic target of rapamycin (mTOR), also known as the mammalian target of rapamycin, is a 289 kDa serine/threonine protein kinase that offers exciting possibilities for novel treatment strategies for a host of neurodegenerative diseases that include Alzheimer's disease, Parkinson's disease, Huntington's disease, epilepsy, stroke and trauma. mTOR governs the programmed cell death pathways of apoptosis and autophagy that can determine neuronal stem cell development, precursor cell differentiation, cell senescence, cell survival and ultimate cell fate. Coupled to the cellular biology of mTOR are a number of considerations for the development of novel treatments involving the fine control of mTOR signalling, tumourigenesis, complexity of the apoptosis and autophagy relationship, functional outcome in the nervous system, and the intimately linked pathways of growth factors, phosphoinositide 3-kinase (PI 3-K), protein kinase B (Akt), AMP activated protein kinase (AMPK), silent mating type information regulation two homologue one (Saccharomyces cerevisiae) (SIRT1) and others. Effective clinical translation of the cellular signalling mechanisms of mTOR offers provocative avenues for new drug development in the nervous system tempered only by the need to elucidate further the intricacies of the mTOR pathway.