Autophagy contributes to retardation of cardiac growth in diabetic rats. Lab Anim Res. 2012;28:99-107. [PMID: 22787483 PMCID: PMC3389845 DOI: 10.5625/lar.2012.28.2.99]

Cornerstone Cellular Pathways for Metabolic Disorders and Diabetes Mellitus: Non-Coding RNAs, Wnt Signaling, and AMPK

Metabolic disorders and diabetes (DM) impact more than five hundred million individuals throughout the world and are insidious in onset, chronic in nature, and yield significant disability and death. Current therapies that address nutritional status, weight management, and pharmacological options may delay disability but cannot alter disease course or functional organ loss, such as dementia and degeneration of systemic bodily functions. Underlying these challenges are the onset of aging disorders associated with increased lifespan, telomere dysfunction, and oxidative stress generation that lead to multi-system dysfunction. These significant hurdles point to the urgent need to address underlying disease mechanisms with innovative applications. New treatment strategies involve non-coding RNA pathways with microRNAs (miRNAs) and circular ribonucleic acids (circRNAs), Wnt signaling, and Wnt1 inducible signaling pathway protein 1 (WISP1) that are dependent upon programmed cell death pathways, cellular metabolic pathways with AMP-activated protein kinase (AMPK) and nicotinamide, and growth factor applications. Non-coding RNAs, Wnt signaling, and AMPK are cornerstone mechanisms for overseeing complex metabolic pathways that offer innovative treatment avenues for metabolic disease and DM but will necessitate continued appreciation of the ability of each of these cellular mechanisms to independently and in unison influence clinical outcome.

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.

The effects of acarbose treatment on cardiovascular risk factors in impaired glucose tolerance and diabetic patients: a systematic review and dose-response meta-analysis of randomized clinical trials

Acarbose (ACB) seems to be an effective drug in the management of cardiovascular risk factors. However, no previous meta-analysis of randomized controlled trials (RCTs) has been done to evaluate the effects of ACB on cardiovascular risk factors on impaired glucose tolerance (IGT), type 2 diabetes mellitus (T2D), and type 1 diabetes mellitus (T1D). We comprehensively searched electronic databases including Scopus, Web of Science, and PubMed for RCTs for related keywords up to September 2022. A random-effects model was used to estimate the weighted mean difference (WMD) and 95% confidence interval (CI). The pooled analysis demonstrated that ACB treatment had a significant effect on fasting blood glucose (FBG) (WMD = -3.55 mg/dL; 95%CI: -6.29, -0.81; p = 0.011), fasting insulin (WMD = -6.73 pmoL/L; 95%CI: -10.37, -3.10; p < 0.001), HbA1c [WMD = -0.32%; 95%CI: -0.45, -0.20; p < 0.001], body weight (WMD = -1.25 kg; 95%CI: -1.79, -0.75; p < 0.001), body mass index (BMI) (WMD = -0.64 kg/m2; 95%CI: -0.92, -0.37; p < 0.001), tumor necrosis factor-alpha (TNF-α) (WMD = -2.70 pg/mL, 95%CI: -5.25, -0.16; p = 0.037), leptin (WMD = -1.58 ng/mL; 95%CI: -2.82, -0.35; p = 0.012), alanine transaminase (ALT) (WMD = 0.71 U/L; 95%CI: -0.31, 1.85; p = 0.164), triglyceride (TG) (WMD = -13.89 mg/dL; 95%CI: -20.69, -7.09; p < 0.001), total cholesterol (TC) (WMD = -2.26 mg/dL; 95%CI: -4.18, -0.34; p = 0.021), systolic blood pressure (SBP) (WMD = -1.29 mmHg; 95%CI: -2.44, -0.15; p = 0.027), and diastolic blood pressure (DBP) (WMD = 0.02 mmHg; 95%CI: -0.41, 0.45; p = 0.925) in an intervention group, compared with a placebo group. The non-linear dose-response analysis showed that ACB reduces the TC in trial duration by >50 weeks, and 180 mg/day is more effective for the decrement of CRP. ACB can improve lipid profiles, glycemic indices, anthropometric indices, and inflammatory markers in T2D, T1D, and IGT patients.

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.

The Metabolic Basis for Nervous System Dysfunction in Alzheimer's Disease, Parkinson's Disease, and Huntington's Disease

Disorders of metabolism affect multiple systems throughout the body but may have the greatest impact on both central and peripheral nervous systems. Currently available treatments and behavior changes for disorders that include diabetes mellitus (DM) and nervous system diseases are limited and cannot reverse the disease burden. Greater access to healthcare and a longer lifespan have led to an increased prevalence of metabolic and neurodegenerative disorders. In light of these challenges, innovative studies into the underlying disease pathways offer new treatment perspectives for Alzheimer's Disease, Parkinson's Disease, and Huntington's Disease. Metabolic disorders are intimately tied to neurodegenerative diseases and can lead to debilitating outcomes, such as multi-nervous system disease, susceptibility to viral pathogens, and long-term cognitive disability. Novel strategies that can robustly address metabolic disease and neurodegenerative disorders involve a careful consideration of cellular metabolism, programmed cell death pathways, the mechanistic target of rapamycin (mTOR) and its associated pathways of mTOR Complex 1 (mTORC1), mTOR Complex 2 (mTORC2), AMP-activated protein kinase (AMPK), growth factor signaling, and underlying risk factors such as the apolipoprotein E (APOE-ε4) gene. Yet, these complex pathways necessitate comprehensive understanding to achieve clinical outcomes that target disease susceptibility, onset, and progression.

Nicotinamide as a Foundation for Treating Neurodegenerative Disease and Metabolic Disorders

Neurodegenerative disorders impact more than one billion individuals worldwide and are intimately tied to metabolic disease that can affect another nine hundred individuals throughout the globe. Nicotinamide is a critical agent that may offer fruitful prospects for neurodegenerative diseases and metabolic disorders, such as diabetes mellitus. Nicotinamide protects against multiple toxic environments that include reactive oxygen species exposure, anoxia, excitotoxicity, ethanolinduced neuronal injury, amyloid (Aß) toxicity, age-related vascular disease, mitochondrial dysfunction, insulin resistance, excess lactate production, and loss of glucose homeostasis with pancreatic β-cell dysfunction. However, nicotinamide offers cellular protection in a specific concentration range, with dosing outside of this range leading to detrimental effects. The underlying biological pathways of nicotinamide that involve the silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), the mechanistic target of rapamycin (mTOR), AMP activated protein kinase (AMPK), and mammalian forkhead transcription factors (FoxOs) may offer insight for the clinical translation of nicotinamide into a safe and efficacious therapy through the modulation of oxidative stress, apoptosis, and autophagy. Nicotinamide is a highly promising target for the development of innovative strategies for neurodegenerative disorders and metabolic disease, but the benefits of this foundation depend greatly on gaining a further understanding of nicotinamide's complex biology.

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.

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.

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.

High-glucose induces cardiac myocytes apoptosis through Foxo1 /GRK2 signaling pathway

High glucose-induced cardiac myocytes apoptosis has been well demonstrated, but the mechanism remains unknown. In this study, we found that exposure of cardiac H9c2 cells to high glucose promoted Foxo1 and GRK2 expression, and induced autophagy. Further investigation showed that high glucose simultaneously increased the expression of cytoplasmic and nuclear Foxo1. Inhibition of Foxo1 reduced GRK2 expression and blocked autophagy, enhancing high glucose-induced apoptosis. GRK2 knockdown did not significantly affect Foxo1 expression and autophagy, but attenuated high glucose-induced apoptosis. Intriguingly, GRK2 knockdown reduced ROS generation. NAC treatment not only reduced the levels of cytoplasmic and nuclear Foxo1, but also inhibited GRK2 expression and autophagy, remarkably reducing high glucose-induced apoptosis. Inhibition of autophagy did not notably affect the expression of Foxo1 and GRK2, but enlarged high glucose-induced apoptosis. ChIP assay and Luciferase reporter assay confirmed that Foxo1 positively regulated GRK2 transcription. These results suggested that Foxo1 was involved in glucose-induced apoptosis by regulating GRK2 expression and autophagy.

SIRT-3 Modulation by Resveratrol Improves Mitochondrial Oxidative Phosphorylation in Diabetic Heart through Deacetylation of TFAM

Background and Purpose: Mitochondrial dysfunction remains the crucial cause for many heart diseases including diabetic cardiomyopathy (DCM). Sirtuin-3 (SIRT-3) is a protein deacetylase localized in the mitochondria and regulates mitochondrial function. Being a noteworthy mitochondrial protein deacetylase enzyme, the role of SIRT-3 in DCM is yet to be explored. Experimental Approach: Diabetes mellitus (Type-I, T1DM) was induced using streptozotocin (STZ, 50 mg/kg) in male Sprague Dawley (SD) rats. Rats with >200 mg/dL blood glucose levels were then divided randomly into two groups, DIA and DIA + RESV, where vehicle and resveratrol (25 mg/kg/day) were administered orally in both groups, respectively. Cardiac oxidative stress, fibrosis, and mitochondrial parameters were evaluated. H9c2 cells were transfected with SIRT-3 siRNA and shRNA, and ORF plasmid for silencing and overexpression, respectively. Key Results: After eight weeks, diabetic rat heart showed reduced cardiac cell size, increased oxidative stress and reduction of the activities of enzymes involved in mitochondrial oxidative phosphorylation (OXPHOS). There was reduced expression and activity of SIRT-3 and mitochondrial transcription factor (TFAM) in diabetic heart. Reduced SIRT-3 expression is also correlated with increased acetylation, decreased mitochondrial DNA (mtDNA) binding activity of TFAM, and reduced transcription of mitochondrial DNA encoded genes. Administration of resveratrol prevented the decrease in SIRT-3 and TFAM activity, which was corresponding to the reduced acetylation status of TFAM. Silencing SIRT-3 using siRNA in H9C2 cells showed increased acetylation of TFAM. Conclusion and Implications: Together our data shows that resveratrol activates SIRT-3, regulates the acetylation status of TFAM and preserves the mitochondrial function along with cellular size in diabetic rat heart.

Proanthocyanidins against Oxidative Stress: From Molecular Mechanisms to Clinical Applications

Proanthocyanidins (PCs) are naturally occurring polyphenolic compounds abundant in many vegetables, plant skins (rind/bark), seeds, flowers, fruits, and nuts. Numerous in vitro and in vivo studies have demonstrated myriad effects potentially beneficial to human health, such as antioxidation, anti-inflammation, immunomodulation, DNA repair, and antitumor activity. Accumulation of prooxidants such as reactive oxygen species (ROS) exceeding cellular antioxidant capacity results in oxidative stress (OS), which can damage macromolecules (DNA, lipids, and proteins), organelles (membranes and mitochondria), and whole tissues. OS is implicated in the pathogenesis and exacerbation of many cardiovascular, neurodegenerative, dermatological, and metabolic diseases, both through direct molecular damage and secondary activation of stress-associated signaling pathways. PCs are promising natural agents to safely prevent acute damage and control chronic diseases at relatively low cost. In this review, we summarize the molecules and signaling pathways involved in OS and the corresponding therapeutic mechanisms of PCs.

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.

Myocardial stress and autophagy: mechanisms and potential therapies

Autophagy is a ubiquitous cellular catabolic process responsive to energy stress. Research over the past decade has revealed that cardiomyocyte autophagy is a prominent homeostatic pathway, important in adaptation to altered myocardial metabolic demand. The cellular machinery of autophagy involves targeted direction of macromolecules and organelles for lysosomal degradation. Activation of autophagy has been identified as cardioprotective in some settings (that is, ischaemia and ischaemic preconditioning). In other situations, sustained autophagy has been linked with cardiopathology (for example, sustained pressure overload and heart failure). Perturbation of autophagy in diabetic cardiomyopathy has also been observed and is associated with both adaptive and maladaptive responses to stress. Emerging research findings indicate that various forms of selective autophagy operate in parallel to manage various types of catabolic cellular cargo including mitochondria, large proteins, glycogen, and stored lipids. In this Review, induction of autophagy associated with cardiac benefit or detriment is considered. The various static and dynamic approaches used to measure autophagy are critiqued, and current inconsistencies in the understanding of autophagy regulation in the heart are highlighted. The prospects for pharmacological intervention to achieve therapeutic manipulation of autophagic processes are also discussed.

Rapamycin Reduced Ischemic Brain Damage in Diabetic Animals Is Associated with Suppressions of mTOR and ERK1/2 Signaling

The objectives of the present study are to investigate the activation of mTOR and ERK1/2 signaling after cerebral ischemia in diabetic rats and to examine the neuroprotective effects of rapamycin. Ten minutes transient global cerebral ischemia was induced in straptozotocin-induced diabetic hyperglycemic rats and non-diabetic, euglycemic rats. Brain samples were harvested after 16 h of reperfusion. Rapamycin or vehicle was injected 1 month prior to the induction of ischemia. The results showed that diabetes increased ischemic neuronal cell death and associated with elevations of p-P70S6K and Ras/ERK1/2 and suppression of p-AMPKα. Rapamycin ameliorated diabetes-enhanced ischemic brain damage and suppressed phosphorylation of P70S6K and ERK1/2. It is concluded that diabetes activates mTOR and ERK1/2 signaling pathways in rats subjected to transient cerebral ischemia and inhibition of mTOR by rapamycin reduces ischemic brain damage and suppresses the mTOR and ERK1/2 signaling in diabetic settings.

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.

New Insights for Oxidative Stress and Diabetes Mellitus

The release of reactive oxygen species (ROS) and the generation of oxidative stress are considered critical factors for the pathogenesis of diabetes mellitus (DM), a disorder that is growing in prevalence and results in significant economic loss. New therapeutic directions that address the detrimental effects of oxidative stress may be especially warranted to develop effective care for the millions of individuals that currently suffer from DM. The mechanistic target of rapamycin (mTOR), silent mating type information regulation 2 homolog 1 (S. cerevisiae) (SIRT1), and Wnt1 inducible signaling pathway protein 1 (WISP1) are especially justified to be considered treatment targets for DM since these pathways can address the complex relationship between stem cells, trophic factors, impaired glucose tolerance, programmed cell death pathways of apoptosis and autophagy, tissue remodeling, cellular energy homeostasis, and vascular biology that greatly impact the biology and disease progression of DM. The translation and development of these pathways into viable therapies will require detailed understanding of their proliferative nature to maximize clinical efficacy and limit adverse effects that have the potential to lead to unintended consequences.

Novel applications of trophic factors, Wnt and WISP for neuronal repair and regeneration in metabolic disease

Diabetes mellitus affects almost 350 million individuals throughout the globe resulting in significant morbidity and mortality. Of further concern is the growing population of individuals that remain undiagnosed but are susceptible to the detrimental outcomes of this disorder. Diabetes mellitus leads to multiple complications in the central and peripheral nervous systems that include cognitive impairment, retinal disease, neuropsychiatric disease, cerebral ischemia, and peripheral nerve degeneration. Although multiple strategies are being considered, novel targeting of trophic factors, Wnt signaling, Wnt1 inducible signaling pathway protein 1, and stem cell tissue regeneration are considered to be exciting prospects to overcome the cellular mechanisms that lead to neuronal injury in diabetes mellitus involving oxidative stress, apoptosis, and autophagy. Pathways that involve insulin-like growth factor-1, fibroblast growth factor, epidermal growth factor, and erythropoietin can govern glucose homeostasis and are intimately tied to Wnt signaling that involves Wnt1 and Wnt1 inducible signaling pathway protein 1 (CCN4) to foster control over stem cell proliferation, wound repair, cognitive decline, β-cell proliferation, vascular regeneration, and programmed cell death. Ultimately, cellular metabolism through Wnt signaling is driven by primary metabolic pathways of the mechanistic target of rapamycin and AMP activated protein kinase. These pathways offer precise biological control of cellular metabolism, but are exquisitely sensitive to the different components of Wnt signaling. As a result, unexpected clinical outcomes can ensue and therefore demand careful translation of the mechanisms that govern neural repair and regeneration in diabetes mellitus.

mTOR: Driving apoptosis and autophagy for neurocardiac complications of diabetes mellitus

The World Health Organization estimates that diabetes mellitus (DM) will become the seventh leading cause of death during the next two decades. DM affects approximately 350 million individuals worldwide and additional millions that remain undiagnosed are estimated to suffer from the complications of DM. Although the complications of DM can be seen throughout the body, the nervous, cardiac, and vascular systems can be significantly affected and lead to disorders that include cognitive loss, stroke, atherosclerosis, cardiac failure, and endothelial stem cell impairment. At the cellular level, oxidative stress is a significant determinant of cell fate during DM and leads to endoplasmic reticulum stress, mitochondrial dysfunction, apoptosis, and autophagy. Multiple strategies are being developed to combat the complications of DM, but it is the mechanistic target of rapamycin (mTOR) that is gaining interest in drug development circles especially for protective therapies that involve cytokines and growth factors such as erythropoietin. The pathways of mTOR linked to mTOR complex 1, mTOR complex 2, AMP activated protein kinase, and the hamartin (tuberous sclerosis 1)/tuberin (tuberous sclerosis 2) complex can ultimately influence neuronal, cardiac, and vascular cell survival during oxidant stress in DM through a fine interplay between apoptosis and autophagy. Further understanding of these mTOR regulated pathways should foster novel strategies for the complications of DM that impact millions of individuals with death and disability.

Myocardial autophagic energy stress responses--macroautophagy, mitophagy, and glycophagy

An understanding of the role of autophagic processes in the management of cardiac metabolic stress responses is advancing rapidly and progressing beyond a conceptualization of the autophagosome as a simple cell recycling depot. The importance of autophagy dysregulation in diabetic cardiomyopathy and in ischemic heart disease - both conditions comprising the majority of cardiac disease burden - has now become apparent. New findings have revealed that specific autophagic processes may operate in the cardiomyocyte, specialized for selective recognition and management of mitochondria and glycogen particles in addition to protein macromolecular structures. Thus mitophagy, glycophagy, and macroautophagy regulatory pathways have become the focus of intensive experimental effort, and delineating the signaling pathways involved in these processes offers potential for targeted therapeutic intervention. Chronically elevated macroautophagic activity in the diabetic myocardium is generally observed in association with structural and functional cardiomyopathy; yet there are also numerous reports of detrimental effect of autophagy suppression in diabetes. Autophagy induction has been identified as a key component of protective mechanisms that can be recruited to support the ischemic heart, but in this setting benefit may be mitigated by adverse downstream autophagic consequences. Recent report of glycophagy upregulation in diabetic cardiomyopathy opens up a novel area of investigation. Similarly, a role for glycogen management in ischemia protection through glycophagy initiation is an exciting prospect under investigation.

FoxO Transcription Factors and Regenerative Pathways in Diabetes Mellitus

Mammalian forkhead transcription factors of the O class (FoxO) are exciting targets under consideration for the development of new clinical entities to treat metabolic disorders and diabetes mellitus (DM). DM, a disorder that currently affects greater than 350 million individuals globally, can become a devastating disease that leads to cellular injury through oxidative stress pathways and affects multiple systems of the body. FoxO proteins can regulate insulin signaling, gluconeogenesis, insulin resistance, immune cell migration, and cell senescence. FoxO proteins also control cell fate through oxidative stress and pathways of autophagy and apoptosis that either lead to tissue regeneration or cell demise. Furthermore, FoxO signaling can be dependent upon signal transduction pathways that include silent mating type information regulation 2 homolog 1 (S. cerevisiae) (SIRT1), Wnt, and Wnt1 inducible signaling pathway protein 1 (WISP1). Cellular metabolic pathways driven by FoxO proteins are complex, can lead to variable clinical outcomes, and require in-depth analysis of the epigenetic and post-translation protein modifications that drive FoxO protein activation and degradation.

Programming apoptosis and autophagy with novel approaches for diabetes mellitus

According to the World Health Organization, diabetes mellitus (DM) in the year 2030 will be ranked the seventh leading cause of death in the world. DM impacts all systems of the body with oxidant stress controlling cell fate through endoplasmic reticulum stress, mitochondrial dysfunction, alterations in uncoupling proteins, and the induction of apoptosis and autophagy. Multiple treatment approaches are being entertained for DM with Wnt1 inducible signaling pathway protein 1 (WISP1), mechanistic target of rapamycin (mTOR), and silent mating type information regulation 2 homolog) 1 (S. cerevisiae) (SIRT1) generating significant interest as target pathways that can address maintenance of glucose homeostasis as well as prevention of cellular pathology by controlling insulin resistance, stem cell proliferation, and the programmed cell death pathways of apoptosis and autophagy. WISP1, mTOR, and SIRT1 can rely upon similar pathways such as AMP activated protein kinase as well as govern cellular metabolism through cytokines such as EPO and oral hypoglycemics such as metformin. Yet, these pathways require precise biological control to exclude potentially detrimental clinical outcomes. Further elucidation of the ability to translate the roles of WISP1, mTOR, and SIRT1 into effective clinical avenues offers compelling prospects for new therapies against DM that can benefit hundreds of millions of individuals throughout the globe.

Acetylated FoxO1 mediates high-glucose induced autophagy in H9c2 cardiomyoblasts: regulation by a polyphenol -(-)-epigallocatechin-3-gallate

OBJECTIVE

FoxO1 acts as a pivotal transcription factor in insulin signaling. However, in hyperglycemia induced cardiac complications, whether FoxO1 is involved remains unclear. The goal of this study was to delineate the potential role of FoxO1 under high-glucose condition.

MATERIALS/METHODS

We investigated insulin resistance and reactive oxygen species (ROS) generation in H9c2 cardiomyoblasts after high-glucose exposure. A series of autophagy biomarkers were measured and further confirmed by LC3 turnover assay. Using gene silencing and overexpression experiments we dissected the molecular mechanisms of FoxO1 regulated autophagy. We also tested the protective effect of (-)-epigallocatechin-3-gallate (EGCG, a green tea-derived polyphenol) in high-glucose treated H9c2 cardiomyoblasts.

RESULTS

High-glucose elicited elevated ROS, autophagy and FoxO1 abundance in cultured H9c2 cardiomyoblasts. Specifically, high-glucose significantly augmented the acetylated FoxO1 in cytosol. In line, compared with 3A-FoxO1 (majorly localized in nuclei with a strong transcriptional activity), overexpression of WT-FoxO1 led to more intense elevated autophagy with enhanced acetylation of FoxO1. In addition, FoxO1 RNAi brought down autophagy induced by high-glucose. Intriguingly, EGCG successfully reversed ROS, autophagy and acetylated FoxO1 in high-glucose treated H9c2 cells.

CONCLUSION

Our findings suggest that FoxO1, especially the acetylated form, regulates high-glucose induced autophagy in H9c2 cardiomyoblasts, which can be prevented by EGCG via a possible ROS-FoxO1 pathway.

Oleifolioside B-mediated autophagy promotes apoptosis in A549 human non-small cell lung cancer cells

The biochemical mechanisms of cell death by oleifolioside B (OB), a cycloartane-type triterpene glycoside isolated from Dendropanax morbifera Leveille, were investigated in A549 human lung carcinoma cells. Our data indicated that exposure to OB led to caspase activation and typical features of apoptosis; however, apoptotic cell death was not prevented by z-VAD-fmk, a pan-caspase inhibitor, demonstrating that OB-induced apoptosis was independent of caspase activation. Subsequently, we found that OB increased autophagy, as indicated by an increase in monodansylcadaverine fluorescent dye-labeled autophagosome formation and in the levels of the autophagic form of microtubule-associated protein 1 light chain 3 and Atg3, an autophagy-specific gene, which is associated with inhibiting phospho-nuclear factor erythroid 2-related factor 2 (Nrf2) expression. However, pretreatment with bafilomycin A1, an autophagy inhibitor, attenuated OB-induced apoptosis and dephosphorylation of Nrf2. The data suggest that OB-induced autophagy functions as a death mechanism in A549 cells and OB has potential as a novel anticancer agent capable of targeting apoptotic and autophagic cell death and the Nrf2 signaling pathway.

Stereological study of the diabetic heart of male rats

The present study aimed to quantitatively compare the normal and diabetic hearts of rats using stereological methods. Diabetic and control rats received streptozotocin (60 mg/kg) and no treatments, respectively. On the 56^th day, the hearts were removed and their total volume was estimated using isotropic Cavalieri method. The total volume of the connective tissues and vessels, total length and diameter of the vessels, total number of cardiomyocytes nuclei, and the mean volume of the cardiomyocytes were estimated, as well. In comparison to the control animals, 60 and 43% increase was observed in the total volume of the connective tissue and microvessels of the diabetic rats, respectively (P<0.05). The percent of the vessel profiles with the diameter of 2-4 µm was decreased, while the percent of the vessel profiles with the diameter of 4.1-8 µm was increased in the diabetic hearts (P<0.05). No significant difference was found in the vessels with more than 8 µm diameters. The total number of the cardiomyocytes' nuclei and the number-weighted mean volume were respectively decreased by 37 and 64% in the diabetic group (P<0.01). A significant difference was observed between the two groups concerning the left ventricle volume to body weight ratio as an index for ventricular hypertrophy (P<0.05), while no difference was found regarding the right ventricle to body weight ratio. It can be concluded that diabetes can induce structural changes, including loss and/or atrophy of the cardiomyocytes, accompanied with increase in the connective tissue in the rats' hearts.

Oxidant stress and signal transduction in the nervous system with the PI 3-K, Akt, and mTOR cascade

Oxidative stress impacts multiple systems of the body and can lead to some of the most devastating consequences in the nervous system especially during aging. Both acute and chronic neurodegenerative disorders such as diabetes mellitus, cerebral ischemia, trauma, Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and tuberous sclerosis through programmed cell death pathways of apoptosis and autophagy can be the result of oxidant stress. Novel therapeutic avenues that focus upon the phosphoinositide 3-kinase (PI 3-K), Akt (protein kinase B), and the mammalian target of rapamycin (mTOR) cascade and related pathways offer exciting prospects to address the onset and potential reversal of neurodegenerative disorders. Effective clinical translation of these pathways into robust therapeutic strategies requires intimate knowledge of the complexity of these pathways and the ability of this cascade to influence biological outcome that can vary among disorders of the nervous system.

Novel directions for diabetes mellitus drug discovery

INTRODUCTION

Diabetes mellitus impacts almost 200 million individuals worldwide and leads to debilitating complications. New avenues of drug discovery must target the underlying cellular processes of oxidative stress, apoptosis, autophagy, and inflammation that can mediate multi-system pathology during diabetes mellitus.

AREAS COVERED

The authors examine the novel directions for drug discovery that involve: the β-nicotinamide adenine dinucleotide (NAD(+)) precursor nicotinamide, the cytokine erythropoietin, the NAD(+)-dependent protein histone deacetylase SIRT1, the serine/threonine-protein kinase mammalian target of rapamycin (mTOR), and the wingless pathway. Furthermore, the authors present the implications for the targeting of these pathways that oversee gluconeogenic genes, insulin signaling and resistance, fatty acid beta-oxidation, inflammation, and cellular survival.

EXPERT OPINION

Nicotinamide, erythropoietin, and the downstream pathways of SIRT1, mTOR, forkhead transcription factors, and wingless signaling offer exciting prospects for novel directions of drug discovery for the treatment of metabolic disorders. Future investigations must dissect the complex relationship and fine modulation of these pathways for the successful translation of robust reparative and regenerative strategies against diabetes mellitus and the complications of this disorder.

Guinea pig husbandry and medicine

Guinea pigs are hardy, gentle, virtually odor-free rodents. Their adverse, often lethal response to antibiotics requires an appropriate program of nutrition, husbandry, and handling, which are reviewed in this article. A summary of anatomical characteristics, basic biology, and reproductive data is provided. Diseases of practical clinical significance, primarily those of bacterial or nutritional origin, are also reviewed.