Rapamycin induces glucose intolerance in mice by reducing islet mass, insulin content, and insulin sensitivity. J Mol Med (Berl). 2012;90:575-585. [PMID: 22105852 DOI: 10.1007/s00109-011-0834-3]

Drug-induced hyperglycemia and diabetes

BACKGROUND

Drug-induced hyperglycemia and diabetes have negative and potentially serious health consequences but can often be unnoticed.

METHODS

We reviewed the literature searching Medline database for articles addressing drug-induced hyperglycemia and diabetes up to January 31, 2023. We also selected drugs that could induce hyperglycemia or diabetes according official data from drug information databases Thériaque and Micromedex. For each selected drug or pharmacotherapeutic class, the mechanisms of action potentially involved were investigated. For drugs considered to be at risk of hyperglycemia or diabetes, disproportionality analyses were performed using data from the international pharmacovigilance database VigiBase. In order to detect new pharmacovigilance signals, additional disproportionality analyses were carried out for drug classes with more than 100 cases reported in VigiBase, but not found in the literature or official documents.

RESULTS

The main drug classes found to cause hyperglycemia are glucocorticoids, HMG-coA reductase inhibitors, thiazide diuretics, beta-blockers, antipsychotics, fluoroquinolones, antiretrovirals, antineoplastic agents and immunosuppressants. The main mechanisms involved are alterations in insulin secretion and sensitivity, direct cytotoxic effects on pancreatic cells and increases in glucose production. Pharmacovigilance signal were found for a majority of drugs or pharmacological classes identified as being at risk of diabetes or hyperglycemia. We identified new pharmacovigilance signals with drugs not known to be at risk according to the literature or official data: phosphodiesterase type 5 inhibitors, endothelin receptor antagonists, sodium oxybate, biphosphonates including alendronic acid, digoxin, sartans, linosipril, diltiazem, verapamil, and darbepoetin alpha. Further studies will be needed to confirm these signals.

CONCLUSIONS

The risks of induced hyperglycemia vary from one drug to another, and the underlying mechanisms are multiple and potentially complex. Clinicians need to be vigilant when using at-risk drugs in order to detect and manage these adverse drug reactions. However, it is to emphasize that the benefits of appropriately prescribed treatments most often outweigh their metabolic risks.

A mixed blessing for liver transplantation patients - Rapamycin

BACKGROUND

Liver transplantation (LT) is an effective treatment option for end-stage liver disease. Mammalian target of rapamycin (mTOR) inhibitors, such as rapamycin, are widely used post LT.

DATA SOURCES

In this review, we focused on the anti-cancer activities and metabolic side effects of rapamycin after LT. The literature available on PubMed for the period of January 1999-September 2022 was reviewed. The key words were rapamycin, sirolimus, liver transplantation, hepatocellular carcinoma, diabetes, and lipid metabolism disorder.

RESULTS

Rapamycin has shown excellent effects and is safer than other immunosuppressive regimens. It has exhibited excellent anti-cancer activity and has the potential in preventing hepatocellular carcinoma (HCC) recurrence post LT. Rapamycin is closely related to two long-term complications after LT, diabetes and lipid metabolism disorders.

CONCLUSIONS

Rapamycin prevents HCC recurrence post LT in some patients, but it also induces metabolic disorders. Reasonable use of rapamycin benefits the liver recipients.

The effect of high-intensity interval training (HIIT) on protein expression in Flexor Hallucis Longus (FHL) and soleus (SOL) in rats with type 2 diabetes

Purpose

In people with diabetes, one of the problems for patients is muscle wasting and inhibition of the protein synthesis pathway. This study aimed to evaluate the effects of HIIT on protein expression in two skeletal muscles, flexor hallucis longus (FHL) and soleus (SOL) in rats with type 2 diabetes mellitus (T2DM).

Materials and methods

Diabetes initially was induced by streptozotocin (STZ) and nicotinamide. Rats with type 2 diabetes were randomly and equally divided into control (n = 6) and HIIT groups (n = 6). After 8 weeks of training, the content of total and phosphorylated proteins of serine/threonine-protein kinases (AKT1), mammalian target of rapamycin (mTOR), P70 ribosomal protein S6 kinase 1 (P70S6K1), and 4E (eIF4E)-binding protein 1 (4E-BP1) in FHL and SOL muscles were measured by Western blotting. While body weight and blood glucose were also controlled.

Results

In the HIIT training group, compared to the control group, a significant increase in the content of AKT1 (0.003) and mTOR (0.001) proteins was observed in the FHL muscle. Also, after 8 weeks of HIIT training, protein 4E-BP1 (0.001) was increased in SOL muscle. However, there was no significant change in other proteins in FHL and SOL muscle.

Conclusions

In rats with type 2 diabetes appear to HIIT leading to more protein expression of fast-twitch muscles than slow-twitch muscles. thus likely HIIT exercises can be an important approach to increase protein synthesis and prevent muscle atrophy in people with type 2 diabetes.

Congenital hyperinsulinism: recent updates on molecular mechanisms, diagnosis and management

Congenital hyperinsulinism (CHI) is a rare disease characterized by an unregulated insulin release, leading to hypoglycaemia. It is the most frequent cause of persistent and severe hypoglycaemia in the neonatal period and early childhood. Mutations in 16 different key genes (ABCC8, KCNJ11, GLUD1, GCK, HADH, SLC16A1, UCP2, HNF4A, HNF1A, HK1, KCNQ1, CACNA1D, FOXA2, EIF2S3, PGM1 and PMM2) that are involved in regulating the insulin secretion from pancreatic β-cells have been described to be responsible for the underlying molecular mechanisms of CHI. CHI can also be associated with specific syndromes and can be secondary to intrauterine growth restriction (IUGR), maternal diabetes, birth asphyxia, etc. It is important to diagnose and promptly initiate appropriate management as untreated hypoglycaemia can be associated with significant neurodisability. CHI can be histopathologically classified into diffuse, focal and atypical forms. Advances in molecular genetics, imaging techniques (18F-fluoro-l-dihydroxyphenylalanine positron emission tomography/computed tomography scanning), novel medical therapies and surgical advances (laparoscopic pancreatectomy) have changed the management and improved the outcome of patients with CHI. This review article provides an overview of the background, clinical presentation, diagnosis, molecular genetics and therapy for children with different forms of CHI.

The effect of spermidine on autoimmunity and beta cell function in NOD mice

Spermidine is a natural polyamine which was shown to prolong lifespan of organisms and to improve cardiac and cognitive function. Spermidine was also reported to reduce inflammation and modulate T-cells. Autophagy is one of the mechanisms that spermidine exerts its effect. Autophagy is vital for β-cell homeostasis and autophagy deficiency was reported to lead to exacerbated diabetes in mice. The effect of spermidine in type 1 diabetes pathogenesis remains to be elucidated. Therefore, we examined the effect of spermidine treatment in non-obese diabetic (NOD) mice, a mouse model for type 1 diabetes. NOD mice were given untreated or spermidine-treated water ad libitum from 4 weeks of age until diabetes onset or 35 weeks of age. We found that treatment with 10 mM spermidine led to higher diabetes incidence in NOD mice despite unchanged pancreatic insulitis. Spermidine modulated tissue polyamine levels and elevated signs of autophagy in pancreas. Spermidine led to increased proportion of pro-inflammatory T-cells in pancreatic lymph nodes (pLN) in diabetic mice. Spermidine elevated the proportion of regulatory T-cells in early onset mice, whereas it reduced the proportion of regulatory T-cells in late onset mice. In summary spermidine treatment led to higher diabetes incidence and elevated proportion of T-cells in pLN.

Hyperinsulinism

Congenital or monogenic hyperinsulinism (HI) is a group of rare genetic disorders characterized by dysregulated insulin secretion and is the most common cause of persistent hypoglycemia in children. Knowledge of normal glucose homeostasis allows for a better understanding of the underlying pathophysiology of hyperinsulinemic hypoglycemia, facilitating timely diagnosis and management. The goal of management is to prevent cerebral insults secondary to hypoglycemia, which can result in poor neurologic outcomes and intellectual disability. Responsiveness to diazoxide, the first-line pharmacologic therapy for persistent hypoglycemia, is also the first step to distinguishing the different genotypic causes of monogenic hyperinsulinism. Early genetic testing becomes necessary when monogenic HI is strongly considered. Knowledge of specific gene mutations allows the determination of a clinical prognosis and definite therapeutic options, such as identifying those with focal forms of hyperinsulinism, who may attain a complete cure through surgical removal of specific affected parts of the pancreas. However, the lack of identifiable cause in a considerable number of patients identified with HI suggests there may be other genetic loci that are yet to be discovered. Furthermore, continued research is needed to explore new forms of therapy, particularly in severe, diazoxide-nonresponsive cases.

Global Epidemiology, Health Outcomes, and Treatment Options for Patients With Type 2 Diabetes and Kidney Failure

The burden of type 2 diabetes and related complications has steadily increased over the last few decades and is one of the foremost global public health threats in the 21st century. Diabetes is one of the leading causes of chronic kidney disease and kidney failure and is an important contributor to the cardiovascular morbidity and mortality in this population. In addition, up to one in three patients who have received kidney transplants develop post-transplant diabetes, but the management of this common complication continues to pose a significant challenge for clinicians. In this review, we will describe the global prevalence and temporal trend of kidney failure attributed to diabetes mellitus in both developing and developed countries. We will examine the survival differences between treated kidney failure patients with and without type 2 diabetes, focusing on the survival differences in those on maintenance dialysis or have received kidney transplants. With the increased availability of novel hypoglycemic agents, we will address the potential impacts of these novel agents in patients with diabetes and kidney failure and in those who have developed post-transplant diabetes.

Mammalian/mechanistic target of rapamycin (mTOR) complexes in neurodegeneration

Novel targets to arrest neurodegeneration in several dementing conditions involving misfolded protein accumulations may be found in the diverse signaling pathways of the Mammalian/mechanistic target of rapamycin (mTOR). As a nutrient sensor, mTOR has important homeostatic functions to regulate energy metabolism and support neuronal growth and plasticity. However, in Alzheimer's disease (AD), mTOR alternately plays important pathogenic roles by inhibiting both insulin signaling and autophagic removal of β-amyloid (Aβ) and phospho-tau (ptau) aggregates. It also plays a role in the cerebrovascular dysfunction of AD. mTOR is a serine/threonine kinase residing at the core in either of two multiprotein complexes termed mTORC1 and mTORC2. Recent data suggest that their balanced actions also have implications for Parkinson's disease (PD) and Huntington's disease (HD), Frontotemporal dementia (FTD) and Amyotrophic Lateral Sclerosis (ALS). Beyond rapamycin; an mTOR inhibitor, there are rapalogs having greater tolerability and micro delivery modes, that hold promise in arresting these age dependent conditions.

Low-Dose IL-2 Therapy in Autoimmune and Rheumatic Diseases

Regulatory T cells (Treg) are crucial for the maintenance of peripheral tolerance and for the control of ongoing inflammation and autoimmunity. The cytokine interleukin-2 (IL-2) is essentially required for the growth and survival of Treg in the peripheral lymphatic tissues and thus plays a vital role in the biology of Treg. Most autoimmune and rheumatic diseases exhibit disturbances in Treg biology either at a numerical or functional level resulting in an imbalance between protective and pathogenic immune cells. In addition, in some autoimmune diseases, a relative deficiency of IL-2 develops during disease pathogenesis leading to a disturbance of Treg homeostasis, which further amplifies the vicious cycle of tolerance breach and chronic inflammation. Low-dose IL-2 therapy aims either to compensate for this IL-2 deficiency to restore a physiological state or to strengthen the Treg population in order to be more effective in counter-regulating inflammation while avoiding global immunosuppression. Here we highlight key findings and summarize recent advances in the clinical translation of low-dose IL-2 therapy for the treatment of autoimmune and rheumatic diseases.

Sirolimus Therapy and Follow-up in a Patient with Severe Congenital Hyperinsulinism Following Subtotal Pancreatectomy

Congenital hyperinsulinism (CHI) is the most common cause of severe, persistent hypoglycemia in neonates and infants. If the patient does not respond to medical treatment the currently available treatment is subtotal pancreatectomy, but some patients still experience severe hypoglycemia after surgery. Sirolimus, a mammalian target of rapamycin inhibitor has recently been reported to be effective in the treatment of insulinoma and CHI patients. Here we report a patient with CHI who had prolonged hypoglycemia after subtotal pancreatectomy. The patient had a heterozygous mutation in ABCC8 but was unresponsive to an optimal dose of diazoxide (15 mg/ kg/day) and octreotide (30 μg/kg/day). The patient subsequently had subtotal pancreatectomy but severe and persistent hypoglycemia continued post-operatively. Sirolimus was commenced. There was a remarkable improvement in glycemic control without major adverse events, although he required a small dose of octreotide to maintain euglycemia. Sirolimus therapy was discontinued when the patient was 15 months old. At the time of this report, at an age of three years and eight months, the patient continues to maintain good glycemic control. This report suggests that sirolimus may be an effective treatment option in patients with CHI resistant to established medical therapy or failure of ubtotal pancreatectomy. However, the long-term safety requires study in larger groups of very young patients.

An Overview of Hypoglycemia in Children Including a Comprehensive Practical Diagnostic Flowchart for Clinical Use

Hypoglycemia is the result of defects/impairment in glucose homeostasis. The main etiological causes are metabolic and/or endocrine and/or other congenital disorders. Despite hypoglycemia is one of the most common emergencies in neonatal age and childhood, no consensus on the definition and diagnostic work-up exists yet. Aims of this review are to present the current age-related definitions of hypoglycemia in neonatal-pediatric age, to offer a concise and practical overview of its main causes and management and to discuss the current diagnostic-therapeutic approaches. Since a systematic and prompt approach to diagnosis and therapy is essential to prevent hypoglycemic brain injury and long-term neurological complications in children, a comprehensive diagnostic flowchart is also proposed.

pre-existing diabetes and PTDM in kidney transplant recipients: how to handle immunosuppression

INTRODUCTION

Preexisting diabetes (PD) and post-transplant diabetes mellitus (PTDM) are common and severe comorbidities posttransplantation. The immunosuppressive regimens are modifiable risk factors.

AREAS COVERED

We reviewed Pubmed and Cochrane database and we summarize the mechanisms and impacts of available immunosuppressive treatments on the risk of PD and PTDM. We also assess the possible management of these drugs to improve glycemic parameters while considering risks inherent in transplantation.

EXPERT OPINION

PD i) increases the risk of sepsis, ii) is an independent risk factor for infection-related mortality, and iii) increases acute rejection risk. Regarding PTDM development i) immunosuppressive strategies without corticosteroids significantly reduce the risk but the price may be a higher incidence of rejection; ii) minimization or rapid withdrawal of steroids are two valuable approaches; iii) the diabetogenic role of calcineurin inhibitors(CNIs) is also well-described and is more important for tacrolimus than for cyclosporine. Reducing tacrolimus-exposure may improve glycemic parameters but also has a higher risk of rejection. PTDM risk is higher in patients that receive sirolimus compared to mycophenolate mofetil. Finally, conversion from CNIs to belatacept may offer the best benefits to PTDM-recipients in terms of glycemic parameters, graft and patient-outcomes.

Is Rapamycin a Dietary Restriction Mimetic?

Since the initial suggestion that rapamycin, an inhibitor of target of rapamycin (TOR) nutrient signaling, increased lifespan comparable to dietary restriction, investigators have viewed rapamycin as a potential dietary restriction mimetic. Both dietary restriction and rapamycin increase lifespan across a wide range of evolutionarily diverse species (including yeast, Caenorhabditis elegans, Drosophila, and mice) as well as reducing pathology and improving physiological functions that decline with age in mice. The purpose of this article is to review the research comparing the effect of dietary restriction and rapamycin in mice. The current data show that dietary restriction and rapamycin have different effects on many pathways and molecular processes. In addition, these interventions affect the lifespan of many genetically manipulated mouse models differently. In other words, while dietary restriction and rapamycin may have similar effects on some pathways and processes; overall, they affect many pathways/processes quite differently. Therefore, rapamycin is likely not a true dietary restriction mimetic. Rather dietary restriction and rapamycin appear to be increasing lifespan and retarding aging largely through different mechanisms/pathways, suggesting that a combination of dietary restriction and rapamycin will have a greater effect on lifespan than either manipulation alone.

Rapamycin for longevity: opinion article

From the dawn of civilization, humanity has dreamed of immortality. So why didn't the discovery of the anti-aging properties of mTOR inhibitors change the world forever? I will discuss several reasons, including fear of the actual and fictional side effects of rapamycin, everolimus and other clinically-approved drugs, arguing that no real side effects preclude their use as anti-aging drugs today. Furthermore, the alternative to the reversible (and avoidable) side effects of rapamycin/everolimus are the irreversible (and inevitable) effects of aging: cancer, stroke, infarction, blindness and premature death. I will also discuss why it is more dangerous not to use anti-aging drugs than to use them and how rapamycin-based drug combinations have already been implemented for potential life extension in humans. If you read this article from the very beginning to its end, you may realize that the time is now.

Molecular Targeting of Immunosuppressants Using a Bifunctional Elastin-Like Polypeptide

Elastin-Like Polypeptides (ELP) are environmentally responsive protein polymers which are easy to engineer and biocompatible, making them ideal candidates as drug carriers. Our team has recently utilized ELPs fused to FKBP12 to carry Rapamycin (Rapa), a potent immunosuppressant. Through high affinity binding to Rapa, FKBP carriers can yield beneficial therapeutic effects and reduce the off-site toxicity of Rapa. Since ICAM-1 is significantly elevated at sites of inflammation in diverse diseases, we hypothesized that a molecularly targeted ELP carrier capable of binding ICAM-1 might have advantageous properties. Here we report on the design, characterization, pharmacokinetics, and biodistribution of a new ICAM-1-targeted ELP Rapa carrier (IBPAF) and its preliminary characterization in a murine model exhibiting elevated ICAM-1. Lacrimal glands (LG) of male NOD mice, a disease model recapitulating the autoimmune dacryoadenitis seen in Sjögren's Syndrome patients, were analyzed to confirm that ICAM-1 was significantly elevated in the LG relative to control male BALB/c mice (3.5-fold, p < 0.05, n = 6). In vitro studies showed that IBPAF had significantly higher binding to TNF-α-stimulated bEnd.3 cells which overexpress surface ICAM-1, relative to nontargeted control ELP (AF)(4.0-fold, p < 0.05). A pharmacokinetics study in male NOD mice showed no significant differences between AF and IBPAF for plasma half-life, clearance, and volume of distribution. However, both constructs maintained a higher level of Rapa in systemic circulation compared to free Rapa. Interestingly, in the male NOD mouse, the accumulation of IBPAF was significantly higher in homogenized LG extracts compared to AF at 2 h (8.6 ± 6.6% versus 1.3 ± 1.3%, respectively, n = 5, p < 0.05). This accumulation was transient with no differences detected at 8 or 24 h. This study describes the first ICAM-1 targeted protein-polymer carrier for Rapa that specifically binds to ICAM-1 in vitro and accumulates in ICAM-1 overexpressing tissue in vivo, which may be useful for molecular targeting in diverse inflammatory diseases where ICAM-1 is elevated.

Fasting and rapamycin: diabetes versus benevolent glucose intolerance

Rapamycin (Sirolimus) slows aging, extends life span, and prevents age-related diseases, including diabetic complications such as retinopathy. Puzzlingly, rapamycin can induce insulin sensitivity, but may also induce insulin resistance or glucose intolerance without insulin resistance. This mirrors the effect of fasting and very low calorie diets, which improve insulin sensitivity and reverse type 2 diabetes, but also can cause a form of glucose intolerance known as benevolent pseudo-diabetes. There is no indication that starvation (benevolent) pseudo-diabetes is detrimental. By contrast, it is associated with better health and life extension. In transplant patients, a weak association between rapamycin/everolimus use and hyperglycemia is mostly due to a drug interaction with calcineurin inhibitors. When it occurs in cancer patients, the hyperglycemia is mild and reversible. No hyperglycemic effects of rapamycin/everolimus have been detected in healthy people. For antiaging purposes, rapamycin/everolimus can be administrated intermittently (e.g., once a week) in combination with intermittent carbohydrate restriction, physical exercise, and metformin.

Metformin reduces glucose intolerance caused by rapamycin treatment in genetically heterogeneous female mice

The use of rapamycin to extend lifespan and delay age-related disease in mice is well-established despite its potential to impair glucose metabolism which is driven partially due to increased hepatic gluconeogenesis. We tested whether a combination therapeutic approach using rapamycin and metformin could diminish some of the known metabolic defects caused by rapamycin treatment in mice. In genetically heterogeneous HET3 mice, we found that chronic administration of encapsulated rapamycin by diet caused a measurable defect in glucose metabolism in both male and female mice as early as 1 month after treatment. In female mice, this defect was alleviated over time by simultaneous treatment with metformin, also by diet, such that females treated with both drugs where indistinguishable from control mice during glucose tolerance tests. While rapamycin-mediated glucose intolerance was unaffected by metformin in males, we found metformin prevented rapamycin-mediated reduction in insulin and leptin concentrations following 9 months of co-treatment. Recently, the Interventions Testing Program showed that mice treated with metformin and rapamycin live at least as long as those treated with rapamycin alone. Together, our data provide compelling evidence that the pro-longevity effects of rapamycin can be uncoupled from its detrimental effects on metabolism through combined therapeutic approaches.

Hyperinsulinaemic hypoglycaemia-an overview of a complex clinical condition

Hyperinsulinaemic hypoglycaemia (HH) is a major cause of hypoglycaemia in the neonatal period, infancy and childhood. It is caused by unsuppressed insulin secretion in the setting of hypoglycaemia and carries a high risk of significant neurological sequelae, such as cognitive impairment. Genetic mutations have been implicated in the pathogenesis of the condition. Other causes include intra-uterine growth retardation, perinatal asphyxia, maternal diabetes mellitus and syndromes, such as Beckwith-Wiedemann. Based on the aetiology, the clinical presentation can range from absence of symptoms to the typical adrenergic symptoms and coma and even death. The diagnosis is based on biochemical findings and the gold-standard imaging technique is 18F-DOPA PET/CT scanning. Treatment options involve medications, such as diazoxide, nifedipine, glucagon and octreotide, as well as surgery. Novel treatment, such as long-acting octreotide, lanreotide and sirolimus, may be used as an alternative to pancreatectomy. Potential future medical treatments include exendin, a GLP-1 receptor antagonist, and glucagon infusion via a pump.Conclusion: Advances in the fields of genetic testing, imaging techniques and medical treatment are beginning to provide novel insights into earlier detection, less invasive treatment approaches and fewer complications associated with the complex entity of hyperinsulinaemic hypoglycaemia. What is Known: • HH is caused by dysregulated insulin release from the β cell due to genetic mutations and carries a risk for complications, such as neurocognitive impairment. 18F-DOPA PET/CT scanning is presented as the gold-standard imaging technique currently in children with hyperinsulinaemic hypoglycaemia. • Clinical presentation is heterogeneous and treatment options include medical therapy and pancreatectomy. What is New: • 18F-DOPA PET/CT is indicated in suspected focal CHI due to paternal transmitted mutations in ABCC8 or KCNJ11. • Novel treatment options have been introduced, such as long-acting octreotide, lanreotide, sirolimus and selective nonpeptide somatostatin receptor subtype 5 (SSTR5) agonists. Future medical treatments include exendin, a GLP-1 antagonist, and glucagon infusion via a pump. However, all these options are off-label at present.

Off-Label Use of Sirolimus and Everolimus in a Pediatric Center: A Case Series and Review of the Literature

BACKGROUND

It has been 15 years since sirolimus, an mTOR inhibitor, received Food and Drug Administration approval to prevent acute rejection in kidney transplantation, and 8 years since its analog everolimus acquired the same status. Since then, these drugs have become more and more utilized and their immunosuppressive and antiproliferative properties have been tested in a great variety of clinical conditions, often achieving excellent results. Despite such positive evidence, the on-label indications for these rapalogs are still very restrictive, especially in children.

AIMS

The aims of this study were to describe our center's experience with sirolimus and everolimus in managing rare pediatric conditions for which mTOR inhibitors have been reported as a therapeutic option, although without conclusive approval from regulatory agencies, and to evaluate safety and tolerability of the treatment at the prescribed doses.

METHODS

All the subjects who received off-label sirolimus or everolimus at the Pediatric Department of the IRCCS Burlo Garofolo in the last 13 years were included. For each disease found in our case series, we reviewed the current scientific literature.

RESULTS

Off-label treatment with rapalogs was prescribed in 16 children (11 males, 5 females, median age of 9.5 years, range 1-16 years). Seven had immunologic disorders: four autoimmune lymphoproliferative syndrome (ALPS), one multicentric Castleman disease (mCD), one activated PI3K delta kinase syndrome (APDS), and one immunodysregulation with polyendocrinopathy enteropathy X-linked (IPEX). Eight had proliferative disorders or vascular anomalies: one cystic lymphangioma, two Bannayan-Riley-Ruvalcaba syndrome (BRRS), one blue rubber bleb nevus syndrome (BRBNS), two tuberous sclerosis complex (TSC), and one low-flow mixed arterial and venous malformation. One case had congenital hyperinsulinism (CHI). The average dosage administered was 1 mg/m² for sirolimus and 7 mg/m² for everolimus. We experienced a good measurable clinical improvement in 14 patients. Nobody experienced serious adverse events (SAEs). The therapy was interrupted in two cases, for lack of efficacy and poor tolerance in one case and for occurrence of bacterial pneumonia in the other one. A review of the literature identified 101 published reports that met our inclusion criteria.

CONCLUSIONS

Although use of mTOR inhibitors has been considered to be complicated, our experience shows that, using low dosages, it is possible to obtain relevant clinical improvements, with a good profile of safety and tolerability.

Mammalian Target of Rapamycin at the Crossroad Between Alzheimer's Disease and Diabetes

Accumulating evidence suggests that Alzheimer's disease may manifest as a metabolic disorder with pathology and/or dysfunction in numerous tissues. Adults with Alzheimer's disease suffer with significantly more comorbidities than demographically matched Medicare beneficiaries (Zhao et al, BMC Health Serv Res 8:108, 2008b). Reciprocally, comorbid health conditions increase the risk of developing Alzheimer's disease (Haaksma et al, PLoS One 12(5):e0177044, 2017). Type 2 diabetes mellitus is especially notable as the disease shares many overlapping pathologies observed in patients with Alzheimer's disease, including hyperglycemia, hyperinsulinemia, insulin resistance, glucose intolerance, dyslipidemia, inflammation, and cognitive dysfunction, as described in Chap. 8 of this book (Yoshitake et al, Neurology 45(6):1161-1168, 1995; Leibson et al, Am J Epidemiol 145(4):301-308, 1997; Ott et al, Neurology 53(9):1937-1942, 1999; Voisin et al, Rev Med Interne 24(Suppl 3):288s-291s, 2003; Janson et al. Diabetes 53(2):474-481, 2004; Ristow M, J Mol Med (Berl) 82(8):510-529, 2004; Whitmer et al, BMJ 330(7504):1360, 2005, Curr Alzheimer Res 4(2):103-109, 2007; Ohara et al, Neurology 77(12):1126-1134, 2011). Although nondiabetic older adults also experience age-related cognitive decline, diabetes is uniquely associated with a twofold increased risk of Alzheimer's disease, as described in Chap. 2 of this book (Yoshitake et al, Neurology 45(6):1161-1168, 1995; Leibson et al, Am J Epidemiol 145(4):301-308, 1997; Ott et al. Neurology 53(9):1937-1942, 1999; Ohara et al, Neurology 77(12):1126-1134, 2011). Good glycemic control has been shown to improve cognitive status (Cukierman-et al, Diabetes Care 32(2):221-226, 2009), and the use of insulin sensitizers is correlated with a lower rate of cognitive decline in older adults (Morris JK, Burns JM, Curr Neurol Neurosci Rep 12(5):520-527, 2012). At the molecular level, the mechanistic/mammalian target of rapamycin (mTOR) plays a key role in maintaining energy homeostasis. Nutrient availability and cellular stress information, both extracellular and intracellular, are integrated and transduced through mTOR signaling pathways. Aberrant regulation of mTOR occurs in the brains of patients with Alzheimer's disease and in numerous tissues of individuals with type 2 diabetes (Mannaa et al, J Mol Med (Berl) 91(10):1167-1175, 2013). Moreover, modulating mTOR activity with a pharmacological inhibitor, rapamycin, provides wide-ranging health benefits, including healthy life span extension in numerous model organisms (Vellai et al, Nature 426(6967):620, 2003; Jia et al, Development 131(16):3897-3906, 2004; Kapahi et al, Curr Biol 14(10):885-890, 2004; Kaeberlein et al, Science 310(5751):1193-1196, 2005; Powers et al, Genes Dev 20(2):174-184, 2006; Harrison et al, Nature 460(7253):392-395, 2009; Selman et al, Science 326(5949):140-144, 2009; Sharp ZD, Strong R, J Gerontol A Biol Sci Med Sci 65(6):580-589, 2010), which underscores its importance to overall organismal health and longevity. In this chapter, we discuss the physiological role of mTOR signaling and the consequences of mTOR dysregulation in the brain and peripheral tissues, with emphasis on its relevance to the development of Alzheimer's disease and link to type 2 diabetes.

Chronic oral rapamycin decreases adiposity, hepatic triglycerides and insulin resistance in male mice fed a diet high in sucrose and saturated fat

NEW FINDINGS

What is the central question of this study? Whether chronic oral rapamycin promotes beneficial effects on glucose/lipid metabolism and energy balance when administered to mice with an obesogenic diet rich in saturated fat and sucrose has not been explored. What is the main finding and its importance? Chronic oral rapamycin reduces body weight and fat gain, improves insulin sensitivity and reduces hepatic steatosis when administered to mice with a high-fat, high-sucrose diet. In addition, we make the new observation that there appear to be tissue-specific effects of rapamycin. Although rapamycin appears to impart its effects mainly on visceral adipose tissue, its effects on insulin sensitivity are mediated by subcutaneous adipose tissue.

ABSTRACT

Excess adiposity is commonly associated with insulin resistance, which can increase the risk of cardiovascular disease. However, the exact molecular mechanisms by which obesity results in insulin resistance are yet to be understood clearly. The intracellular nutrient-sensing protein, mechanistic target of rapamycin (mTOR), is a crucial signalling component in the development of obesity-associated insulin resistance. Given that increased tissue activation of mTOR complex-1 (mTORC1) occurs in obesity, diabetes and ageing, we hypothesized that pharmacological inhibition of mTORC1 would improve metabolic dysregulation in diet-induced obesity. We administered continuous rapamycin, a specific mTORC1 inhibitor, orally to C57BL/6J mice concurrently with a high-fat, high-sucrose (HFHS) diet for 20 weeks. The control group received placebo microcapsules. Rapamycin-treated mice showed significantly reduced weight gain and adiposity (33.6 ± 4.9 versus 40.4 ± 3.0% body fat, P < 0.001, n = 8 mice per group), despite increased or equivalent food intake compared with the placebo group. The rapamycin-fed mice also demonstrated reduced plasma glucose (252 ± 57 versus 297 ± 67 mg dl^-1 , P < 0.001) and improved insulin sensitivity during insulin and glucose tolerance testing. Rapamycin-treated mice also had lower plasma triglycerides (48 ± 13 versus 67 ± 11 mg/dL, P < 0.01) and hepatic triglyceride content (89 ± 15 versus 110 ± 19 mg/g liver, P < 0.05) compared with the placebo group. A moderately low dose of rapamycin decreased adiposity and improved the metabolic profile in a model of diet-induced obesity. These data suggest that low-grade chronic mTORC1 inhibition might be a potential strategy for anti-obesity therapies.

mTORC Inhibitors as Broad-Spectrum Therapeutics for Age-Related Diseases

Chronological age represents the greatest risk factor for many life-threatening diseases, including neurodegeneration, cancer, and cardiovascular disease; ageing also increases susceptibility to infectious disease. Current efforts to tackle individual diseases may have little impact on the overall healthspan of older individuals, who would still be vulnerable to other age-related pathologies. However, recent progress in ageing research has highlighted the accumulation of senescent cells with chronological age as a probable underlying cause of pathological ageing. Cellular senescence is an essentially irreversible proliferation arrest mechanism that has important roles in development, wound healing, and preventing cancer, but it may limit tissue function and cause widespread inflammation with age. The serine/threonine kinase mTOR (mechanistic target of rapamycin) is a regulatory nexus that is heavily implicated in both ageing and senescence. Excitingly, a growing body of research has highlighted rapamycin and other mTOR inhibitors as promising treatments for a broad spectrum of age-related pathologies, including neurodegeneration, cancer, immunosenescence, osteoporosis, rheumatoid arthritis, age-related blindness, diabetic nephropathy, muscular dystrophy, and cardiovascular disease. In this review, we assess the use of mTOR inhibitors to treat age-related pathologies, discuss possible molecular mechanisms of action where evidence is available, and consider strategies to minimize undesirable side effects. We also emphasize the urgent need for reliable, non-invasive biomarkers of senescence and biological ageing to better monitor the efficacy of any healthy ageing therapy.

Transient p53 inhibition sensitizes aged white adipose tissue for beige adipocyte recruitment by blocking mitophagy

Aging of white adipose tissue (WAT) is associated with reduced insulin sensitivity, which contributes to whole-body glucose intolerance. WAT aging in mice impairs cold-induced beige adipocyte recruitment (beiging), which has been attributed to the senescence of adipose progenitor cells. Tumor suppressor p53 has also been implicated in WAT aging. However, whether p53-related cellular aging in mature white adipocytes is causative of age-impaired WAT beiging remains unknown. It is also unclear whether transient p53 inhibition can rescue WAT beiging. Herein, we report that p53 increased in adipose tissues of 28-wk-old (aged) mice with impaired beiging capability. Cold exposure decreased p53 in beiging WAT of young mice but not in aged mice. In aged mice, inducible p53 ablation in differentiated adipocytes restored cold-induced WAT beiging and augmented whole-body energy expenditure and insulin sensitivity. Transient pharmacological inhibition of p53 led to the same beneficial effects. Mechanistically, cold exposure repressed autophagy in beiging WAT of young mice yet increased autophagy in aged WAT. p53-ablation reduced microtubule-associated protein light chain 3-mediated mitochondria clearance (mitophagy) and hence facilitated the increase of mitochondria during beiging. These findings suggest that p53-induced mitophagy in aged white adipocytes impedes WAT beiging and may be therapeutically targeted to improve insulin sensitivity in aged WAT.-Fu, W., Liu, Y., Sun, C., Yin, H. Transient p53 inhibition sensitizes aged white adipose tissue for beige adipocyte recruitment by blocking mitophagy.

A small molecule inhibitor of Rheb selectively targets mTORC1 signaling

The small G-protein Rheb activates the mechanistic target of rapamycin complex 1 (mTORC1) in response to growth factor signals. mTORC1 is a master regulator of cellular growth and metabolism; aberrant mTORC1 signaling is associated with fibrotic, metabolic, and neurodegenerative diseases, cancers, and rare disorders. Point mutations in the Rheb switch II domain impair its ability to activate mTORC1. Here, we report the discovery of a small molecule (NR1) that binds Rheb in the switch II domain and selectively blocks mTORC1 signaling. NR1 potently inhibits mTORC1 driven phosphorylation of ribosomal protein S6 kinase beta-1 (S6K1) but does not inhibit phosphorylation of AKT or ERK. In contrast to rapamycin, NR1 does not cause inhibition of mTORC2 upon prolonged treatment. Furthermore, NR1 potently and selectively inhibits mTORC1 in mouse kidney and muscle in vivo. The data presented herein suggest that pharmacological inhibition of Rheb is an effective approach for selective inhibition of mTORC1 with therapeutic potential.

Cardioprotective effects of dietary rapamycin on adult female C57BLKS/J-Leprdb mice

Rapamycin (RAPA), an inhibitor of mTORC signaling, has been shown to extend life span in mice and other organisms. Recently, animal and human studies have suggested that inhibition of mTORC signaling can alleviate or prevent the development of cardiomyopathy. In view of this, we used a murine model of type 2 diabetes (T2D), BKS-Lepr^db , to determine whether RAPA treatment can mitigate the development of T2D-induced cardiomyopathy in adult mice. Female BKS-Lepr^db mice fed diet supplemented with RAPA from 11 to 27 weeks of age showed reduced weight gain and significant reductions of fat and lean mass compared with untreated mice. No differences in plasma glucose or insulin levels were observed between groups; however, RAPA-treated mice were more insulin sensitive (P < 0.01) than untreated mice. Urine albumin/creatinine ratio was lower in RAPA-treated mice, suggesting reduced diabetic nephropathy and improved kidney function. Echocardiography showed significantly reduced left ventricular wall thickness in mice treated with RAPA compared with untreated mice (P = 0.02) that was consistent with reduced heart weight/tibia length ratios, reduced myocyte size and cardiac fibrosis measured by histomorphology, and reduced mRNA expression of Col1a1, a marker for cardiomyopathy. Our results suggest that inhibition of mTORC signaling is a plausible strategy for ameliorating complications of obesity and T2D, including cardiomyopathy.

Congenital Hyperinsulinism: Diagnosis and Treatment Update

Pancreatic β-cells are finely tuned to secrete insulin so that plasma glucose levels are maintained within a narrow physiological range (3.5-5.5 mmol/L). Hyperinsulinaemic hypoglycaemia (HH) is the inappropriate secretion of insulin in the presence of low plasma glucose levels and leads to severe and persistent hypoglycaemia in neonates and children. Mutations in 12 different key genes (ABCC8, KCNJ11, GLUD1, GCK, HADH, SLC16A1, UCP2, HNF4A, HNF1A, HK1, PGM1 and PMM2) that are involved in the regulation of insulin secretion from pancreatic β-cells have been described to be responsible for the underlying molecular mechanisms leading to congenital HH. In HH due to the inhibitory effect of insulin on lipolysis and ketogenesis there is suppressed ketone body formation in the presence of hypoglycaemia thus leading to increased risk of hypoglycaemic brain injury. Therefore, a prompt diagnosis and immediate management of HH is essential to avoid hypoglycaemic brain injury and long-term neurological complications in children. Advances in molecular genetics, imaging techniques (18F-DOPA positron emission tomography/computed tomography scanning), medical therapy and surgical advances (laparoscopic and open pancreatectomy) have changed the management and improved the outcome of patients with HH. This review article provides an overview to the background, clinical presentation, diagnosis, molecular genetics and therapy in children with different forms of HH.

Sirolimus induces depletion of intracellular calcium stores and mitochondrial dysfunction in pancreatic beta cells

Sirolimus (rapamycin) is an immunosuppressive drug used in transplantation. One of its major side effects is the increased risk of diabetes mellitus; however, the exact mechanisms underlying such association have not been elucidated. Here we show that sirolimus impairs glucose-stimulated insulin secretion both in human and murine pancreatic islets and in clonal β cells in a dose- and time-dependent manner. Importantly, we demonstrate that sirolimus markedly depletes calcium (Ca²⁺) content in the endoplasmic reticulum and significantly decreases glucose-stimulated mitochondrial Ca²⁺ uptake. Crucially, the reduced mitochondrial Ca²⁺ uptake is mirrored by a significant impairment in mitochondrial respiration. Taken together, our findings indicate that sirolimus causes depletion of intracellular Ca²⁺ stores and alters mitochondrial fitness, eventually leading to decreased insulin release. Our results provide a novel molecular mechanism underlying the increased incidence of diabetes mellitus in patients treated with this drug.

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.

Mex3a expression and survival analysis of bladder urothelial carcinoma

Objective

Bladder urothelial carcinoma is a common tumor in humans and a multifactorial disease. The gene mex3a is associated with tumor formation and may promote cell proliferation and migration. Therefore, this study aimed to determine the relationship between mex3a and bladder urothelial carcinoma.

Methods

The clinical and RNA sequencing expression data in patients with bladder urothelial carcinoma were downloaded from the The Cancer Genome Atlas data portal. A total of 412 bladder urothelial carcinoma samples were available in the database, for which the clinical information was acquired, of which 412 are RNA sequencing samples with a total of 19 paired samples. Univariate and multivariate Cox analyses and univariate logistic regression analysis were conducted using the software SPSS version 22.0 and P<0.05 was considered statistically significant.

Results

The results of the independent t-test of 19 paired samples indicated that the expression level of mex3a was significantly higher in tumor tissues compared with adjacent normal tissues. Mex3a expression as a categorical dependent variable was not associated with overall survival, and the overall survival of bladder urothelial carcinoma was associated with the group of age, cancer status, lymphatic vascular invasion, pathological stage, pathological size, and pathological lymph metastasis. The multivariable Cox model adjusted for the group of mex3a expression level, age, gender, tumor status, and pathological stage showed that only the age and cancer status groups were associated with the overall survival.

Conclusion

Mex3a expression was not a poor prognostic factor of bladder urothelial carcinoma. Moreover, the expression levels of mex3a in the papillary type of bladder urothelial carcinoma were higher than those of the non-papillary type.

Identification of hMex-3A and its effect on human bladder cancer cell proliferation

In this study, hMex-3A was selected from TCGA database as a research object to observe the effects of small interfering RNA (siRNA) targeting hMex-3A on the biological activities of human bladder cancer and explore its mechanism for the first time. In this study, there were 2 groups including negative control group and hMex-3A-siRNA-transfected cells group for 5637 and T24 cell lines, respectively. After bladder cancer cells were transfected with the interference RNA sequence, proliferation of transfected cells were assessed by Celigo Cell Counting, and apoptosis were detected by flow cytometry. The knockdown rate of hMex-3A was 74% in 5637 cells and 68% in T24 cells after RNA interference. In addition, Celigo Cell Counting indicated that cell viability was significantly lower in hMex-3A-siRNA-transfected cells group (2196/well) than in negative control group (6777/well) (P < 0.05), but T24 cells did not show statistical significance between hMex-3A-siRNA-transfected cells group (5799/well) and negative control group (7899/well) (P >0.05). Flow cytometer showed that apoptosis was the highest and cells were significantly blocked after cells were transfected in hMex-3A-siRNA-transfected cells group in 5 days later (P < 0.05). Mex-3A protein was detected in bladder carcinoma sections with a mean staining intensity of 7.06±2.60. Mex-3A protein expression was significantly higher in cancerous tissue than in para-cancerous tissue (P <0.05). Our study suggested that siRNA targeting hMex-3A could markedly inhibit cell proliferation and promote apoptosis in 5637 cells. These might have significant implications to bladder carcinogenesis and serve as a potential target for the treatment of bladder cancer.

Moderate lifelong overexpression of tuberous sclerosis complex 1 (TSC1) improves health and survival in mice

The tuberous sclerosis complex 1/2 (TSC1/2) is an endogenous regulator of the mechanistic target of rapamycin (mTOR). While mTOR has been shown to play an important role in health and aging, the role of TSC1/2 in aging has not been fully investigated. In the current study, a constitutive TSC1 transgenic (Tsc1^tg) mouse model was generated and characterized. mTORC1 signaling was reduced in majority of the tissues, except the brain. In contrast, mTORC2 signaling was enhanced in Tsc1^tg mice. Tsc1^tg mice are more tolerant to exhaustive exercises and less susceptible to isoproterenol-induced cardiac hypertrophy at both young and advanced ages. Tsc1^tg mice have less fibrosis and inflammation in aged as well as isoproterenol-challenged heart than age-matched wild type mice. The female Tsc1^tg mice exhibit a higher fat to lean mass ratio at advanced ages than age-matched wild type mice. More importantly, the lifespan increased significantly in female Tsc1^tg mice, but not in male Tsc1^tg mice. Collectively, our data demonstrated that moderate increase of TSC1 expression can enhance overall health, particularly cardiovascular health, and improve survival in a gender-specific manner.

Sirolimus therapy in a child with partially diazoxide-responsive hyperinsulinaemic hypoglycaemia

Hyperinsulinaemic hypoglycaemia (HH), which causes persistent neonatal hypoglycaemia, can result in neurological damage and it’s management is challenging. Diazoxide is the first-line treatment, albeit not all patients will fully respond to it, as episodes of hypoglycaemia may persist and it entails unpleasant adverse effects. Sirolimus, an mTOR inhibitor, has reportedly been successful in treating children with severe diffuse HH, thus obviating the need for pancreatectomy. We report a girl with HH, with a novel heterozygous ABCC8 gene missense mutation (c.4154A>T/ p.Lys1385Thr), who was initially responsive to diazoxide therapy. After 11 months of diazoxide treatment, she developed intermittent, unpredictable breakthrough episodes of hypoglycaemia, in addition to generalized hypertrichosis and weight gain from enforced feeding to avoid hypoglycaemia. Sirolimus, which was commenced at 15 months of age, gradually replaced diazoxide, with significant reduction and abolition of hypoglycaemia. The hypertrichosis resolved and there was less weight gain given the reduced need for enforced feeding. Sirolimus, which was administered over the next 15 months, was well tolerated with no significant side effects and was gradually weaned off. After stopping sirolimus, apart from hypoglycaemia developing during an episode of severe viral gastroenteritis, the capillary glucose concentrations were maintained >3.5 mmol/L, even after a 10 h fast. Sirolimus may have a role in the treatment of partially diazoxide-responsive forms of HH who experience breakthrough hypoglycaemia, but the long-term safety and efficacy of sirolimus are not established.

Facile mechanical shaking method is an improved isolation approach for islet preparation and transplantation

Successful islet isolation is crucial for islet transplantation and cell treatment for type 1 diabetes. Current isolation methods are able to obtain 500-1,000 islets per rat, which results in a waste of ≥50% of total islets. In the present study, a facile mechanical shaking method for improving islet yield (up to 1,500 per rat) was developed and summarized, which was demonstrated to be more effective than the existing well-established stationary method. The present results showed that isolated islets have a maximum yield of 1,326±152 when shaking for 15 min for the fully-cannulated pancreas. For both fully-cannulated and half-cannulated pancreas in the presence of rat DNAse inhibitor, the optimal shaking time was amended to 20 min with a further increased yield of 1,344±134 and 1,286±124 islets, respectively. Furthermore, the majority of the isolated islets were morphologically intact with a well-defined surface and almost no central necrotic zone, which suggested that the condition of islets obtained via the mechanical shaking method was consistent with the stationary method. Islet size distribution was also calculated and it was demonstrated that islets from the stationary method exhibited the same size distribution as the non-cannulated group, which had more larger islets than the fully-cannulated and half-cannulated groups isolated via the shaking method. In addition, the results of glucose challenge showed that the refraction index of each group was >2.5, which indicated the well-preserved function of isolated islets. Furthermore, the transplanted islets exhibited a therapeutic effect after 1 day of transplantation; however, they failed to control blood glucose levels after ~7 days of transplantation. In conclusion, these results demonstrated that the facile mechanical shaking method may markedly improve the yield of rat islet isolation, and in vitro and in vivo investigation demonstrated the well-preserved function of isolated islets in the control of blood glucose. Therefore, the facile mechanical shaking method may be an alternative improved procedure to obtain higher islet yield for islet preparation and transplantation in the treatment of type 1 diabetes.

mTORC1 pathway mediates beta cell compensatory proliferation in 60 % partial-pancreatectomy mice

Beta cell replication is the major component for maintenance of beta cell mass in adult rodents; however, little is known about what is the earliest signals that initiate rodent beta cell proliferation. The mTORC1 pathway integrates signals from growth factors and nutrients and regulates cell growth and survival. Here, we used normoglycemic 60 % partial-pancreatectomy (60 % Px) mouse model to determine whether mTORC1 pathway was required for compensatory beta cell proliferation. C57BL/6 J male mice were subjected to 60 % Px or sham operation, and subsequently treated with either rapamycin or vehicle for 7 days. Metabolic profile, pancreatic beta cell mass, and proliferation were examined, and expression levels of cell cycle regulators were determined. Beta cell proliferation was increased by 2.5-fold, and mTORC1 signaling was activated in islets post-Px. Rapamycin treatment impaired glucose tolerance and glucose stimulating insulin secretion in 60 % Px mice, but did not affect their insulin sensitivity in peripheral tissue. Rapamycin inhibited mTORC1 activity in beta cells, suppressed compensatory beta cell proliferation and growth, and reduced beta cell mass and insulin content in 60 % Px mice. Px caused an increase of the cyclin D2 at protein level and promoted cyclin D2 nuclear localization in an mTOR-dependent manner. Disrupting mTORC1 signaling suppressed cell proliferation and simultaneously diminished cyclin D2 protein abundance in RINm5F cells. Our data demonstrated that mTORC1 plays an essential role in beta cell adaption to significant beta cell mass loss in 60 % Px model and in early compensatory beta cell proliferation via cyclin D2 pathway.

Intermittent Administration of Rapamycin Extends the Life Span of Female C57BL/6J Mice

Inhibition of the mTOR (mechanistic target of rapamycin) signaling pathway by the FDA-approved drug rapamycin promotes life span in numerous model organisms and delays age-related disease in mice. However, the utilization of rapamycin as a therapy for age-related diseases will likely prove challenging due to the serious metabolic and immunological side effects of rapamycin in humans. We recently identified an intermittent rapamycin treatment regimen-2mg/kg administered every 5 days-with a reduced impact on glucose homeostasis and the immune system as compared with chronic treatment; however, the ability of this regimen to extend life span has not been determined. Here, we report for the first time that an intermittent rapamycin treatment regimen starting as late as 20 months of age can extend the life span of female C57BL/6J mice. Our work demonstrates that the anti-aging potential of rapamycin is separable from many of its negative side effects and suggests that carefully designed dosing regimens may permit the safer use of rapamycin and its analogs for the treatment of age-related diseases in humans.

Toxicity of rapamycin and its derivatives to pancreatic islets

The development of islet transplantation has been promoted by the proposal of the Edmonton protocol. Rapamycin, as a recommended immunosuppressive medicine of the Edmonton protocol, has been getting extraordinarily popular. At the same time, derivatives of rapamycin (everolimus, deforolimus, zotarolimus and temsirolimus) have also garnered great interest. While the immunosuppressive and anti-cancer effects of rapalogs were being discussed actively, researchers discovered their cytotoxic effect on pancreatic islets. Whether they could be ideal drugs for anti-rejection after islet transplantation needs further study. This review aims to elucidate the function and application of rapalogs as well as their toxicity to pancreatic islets.

The Mechanistic Target of Rapamycin: The Grand ConducTOR of Metabolism and Aging

Since the discovery that rapamycin, a small molecule inhibitor of the protein kinase mTOR (mechanistic target of rapamycin), can extend the lifespan of model organisms including mice, interest in understanding the physiological role and molecular targets of this pathway has surged. While mTOR was already well known as a regulator of growth and protein translation, it is now clear that mTOR functions as a central coordinator of organismal metabolism in response to both environmental and hormonal signals. This review discusses recent developments in our understanding of how mTOR signaling is regulated by nutrients and the role of the mTOR signaling pathway in key metabolic tissues. Finally, we discuss the molecular basis for the negative metabolic side effects associated with rapamycin treatment, which may serve as barriers to the adoption of rapamycin or similar compounds for the treatment of diseases of aging and metabolism.

Rapamycin: An InhibiTOR of Aging Emerges From the Soil of Easter Island

Rapamycin (sirolimus) is a macrolide immunosuppressant that inhibits the mechanistic target of rapamycin (mTOR) protein kinase and extends lifespan in model organisms including mice. Although rapamycin is an FDA-approved drug for select indications, a diverse set of negative side effects may preclude its wide-scale deployment as an antiaging therapy. mTOR forms two different protein complexes, mTORC1 and mTORC2; the former is acutely sensitive to rapamycin whereas the latter is only chronically sensitive to rapamycin in vivo. Over the past decade, it has become clear that although genetic and pharmacological inhibition of mTORC1 extends lifespan and delays aging, inhibition of mTORC2 has negative effects on mammalian health and longevity and is responsible for many of the negative side effects of rapamycin. In this review, we discuss recent advances in understanding the molecular and physiological effects of rapamycin treatment, and we discuss how the use of alternative rapamycin treatment regimens or rapamycin analogs has the potential to mitigate the deleterious side effects of rapamycin treatment by more specifically targeting mTORC1. Although the side effects of rapamycin are still of significant concern, rapid progress is being made in realizing the revolutionary potential of rapamycin-based therapies for the treatment of diseases of aging.

Inhibition of the Mechanistic Target of Rapamycin (mTOR)-Rapamycin and Beyond

Rapamycin is a Food and Drug Administration (FDA)-approved immunosuppressant and anticancer agent discovered in the soil of Easter Island in the early 1970s. Rapamycin is a potent and selective inhibitor of the mechanistic target of rapamycin (mTOR) protein kinase, which acts as a central integrator of nutrient signaling pathways. During the last decade, genetic and pharmaceutical inhibition of mTOR pathway signaling has been found to promote longevity in yeast, worms, flies, and mice. In this article, we will discuss the molecular biology underlying the effects of rapamycin and its physiological effects, evidence for rapamycin as an antiaging compound, mechanisms by which rapamycin may extend life span, and the potential limitations of rapamycin as an antiaging molecule. Finally, we will discuss possible strategies that may allow us to inhibit mTOR signaling safely while minimizing side effects, and reap the health, social, and economic benefits from slowing the aging process.

Alternative rapamycin treatment regimens mitigate the impact of rapamycin on glucose homeostasis and the immune system

Inhibition of the mechanistic target of rapamycin (mTOR) signaling pathway by the FDA-approved drug rapamycin has been shown to promote lifespan and delay age-related diseases in model organisms including mice. Unfortunately, rapamycin has potentially serious side effects in humans, including glucose intolerance and immunosuppression, which may preclude the long-term prophylactic use of rapamycin as a therapy for age-related diseases. While the beneficial effects of rapamycin are largely mediated by the inhibition of mTOR complex 1 (mTORC1), which is acutely sensitive to rapamycin, many of the negative side effects are mediated by the inhibition of a second mTOR-containing complex, mTORC2, which is much less sensitive to rapamycin. We hypothesized that different rapamycin dosing schedules or the use of FDA-approved rapamycin analogs with different pharmacokinetics might expand the therapeutic window of rapamycin by more specifically targeting mTORC1. Here, we identified an intermittent rapamycin dosing schedule with minimal effects on glucose tolerance, and we find that this schedule has a reduced impact on pyruvate tolerance, fasting glucose and insulin levels, beta cell function, and the immune system compared to daily rapamycin treatment. Further, we find that the FDA-approved rapamycin analogs everolimus and temsirolimus efficiently inhibit mTORC1 while having a reduced impact on glucose and pyruvate tolerance. Our results suggest that many of the negative side effects of rapamycin treatment can be mitigated through intermittent dosing or the use of rapamycin analogs.

Treatment with Tacrolimus and Sirolimus Reveals No Additional Adverse Effects on Human Islets In Vitro Compared to Each Drug Alone but They Are Reduced by Adding Glucocorticoids

Tacrolimus and sirolimus are important immunosuppressive drugs used in human islet transplantation; however, they are linked to detrimental effects on islets and reduction of long-term graft function. Few studies investigate the direct effects of these drugs combined in parallel with single drug exposure. Human islets were treated with or without tacrolimus (30 μg/L), sirolimus (30 μg/L), or a combination thereof for 24 hrs. Islet function as well as apoptosis was assessed by glucose-stimulated insulin secretion (GSIS) and Cell Death ELISA. Proinflammatory cytokines were analysed by qRT-PCR and Bio-Plex. Islets exposed to the combination of sirolimus and tacrolimus were treated with or without methylprednisolone (1000 μg/L) and the expression of the proinflammatory cytokines was investigated. We found the following: (i) No additive reduction in function and viability in islets existed when tacrolimus and sirolimus were combined compared to the single drug. (ii) Increased expression of proinflammatory cytokines mRNA and protein levels in islets took place. (iii) Methylprednisolone significantly decreased the proinflammatory response in islets induced by the drug combination. Although human islets are prone to direct toxic effect of tacrolimus and sirolimus, we found no additive effects of the drug combination. Short-term exposure of glucocorticoids could effectively reduce the proinflammatory response in human islets induced by the combination of tacrolimus and sirolimus.

Paradoxical effect of rapamycin on inflammatory stress-induced insulin resistance in vitro and in vivo

Insulin resistance is closely related to inflammatory stress and the mammalian target of rapamycin/S6 kinase (mTOR/S6K) pathway. The present study investigated whether rapamycin, a specific inhibitor of mTOR, ameliorates inflammatory stress-induced insulin resistance in vitro and in vivo. We used tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) stimulation in HepG2 hepatocytes, C2C12 myoblasts and 3T3-L1 adipocytes and casein injection in C57BL/6J mice to induce inflammatory stress. Our results showed that inflammatory stress impairs insulin signaling by reducing the expression of total IRS-1, p-IRS-1 (tyr632), and p-AKT (ser473); it also activates the mTOR/S6K signaling pathway both in vitro and in vivo. In vitro, rapamycin treatment reversed inflammatory cytokine-stimulated IRS-1 serine phosphorylation, increased insulin signaling to AKT and enhanced glucose utilization. In vivo, rapamycin treatment also ameliorated the impaired insulin signaling induced by inflammatory stress, but it induced pancreatic β-cell apoptosis, reduced pancreatic β-cell function and enhanced hepatic gluconeogenesis, thereby resulting in hyperglycemia and glucose intolerance in casein-injected mice. Our results indicate a paradoxical effect of rapamycin on insulin resistance between the in vitro and in vivo environments under inflammatory stress and provide additional insight into the clinical application of rapamycin.

Rapamycin-induced metabolic defects are reversible in both lean and obese mice

The inhibition of mTOR (mechanistic target of rapamycin) by the macrolide rapamycin has many beneficial effects in mice, including extension of lifespan and reduction or prevention of several age-related diseases. At the same time, chronic rapamycin treatment causes impairments in glucose metabolism including hyperglycemia, glucose intolerance and insulin resistance. It is unknown whether these metabolic effects of rapamycin are permanent or whether they can be alleviated. Here, we confirmed that rapamycin causes glucose intolerance and insulin resistance in both inbred and genetically heterogeneous mice fed either low fat or high fat diets, suggesting that these effects of rapamycin are independent of genetic background. Importantly, we also found that these effects were almost completely lost within a few weeks of cessation of treatment, showing that chronic rapamycin treatment does not induce permanent impairment of glucose metabolism. Somewhat surprisingly, chronic rapamycin also promoted increased accumulation of adipose tissue in high fat fed mice. However, this effect too was lost when rapamycin treatment was ended suggesting that this effect of rapamycin is also not permanent. The reversible nature of rapamycin's alterations of metabolic function suggests that these potentially detrimental side-effects might be managed through alternative dosing strategies or concurrent treatment options.

Sirolimus therapy in a patient with severe hyperinsulinaemic hypoglycaemia due to a compound heterozygous ABCC8 gene mutation

INTRODUCTION

Hyperinsulinaemic hypoglycaemia (HH) is the most common cause of severe and persistent hypoglycaemia in neonates. The treatment of severe diazoxide unresponsive HH involves near total pancreatectomy. Mammalian target of rapamycin (mTOR) is a protein kinase that regulates cellular proliferation. mTOR inhibitors are used in cancer patients and recently found to be effective in the treatment of insulinoma and HH patients.

CASE

A 36 weeks large for gestational age neonate presented with severe hypoglycaemia on day 1 of life. The hypoglycaemia screen confirmed HH and genetic testing revealed compound heterozygous ABCC8 mutation, confirming diffuse disease. He was unresponsive to the maximal dose of diazoxide (15 mg/kg/day), hence needed treatment with higher concentration of intravenous glucose (25 mg/kg/min), intravenous glucagon and subcutaneous octreotide (30 μg/kg/day) infusions to maintain normoglycaemia. Sirolimus, a mTOR inhibitor, was commenced at 9 weeks of age following which he showed a marked improvement in his glycaemic control. After 4 weeks of sirolimus therapy, he was discharged home on subcutaneous octreotide injection (20 μg/kg/day) and oral sirolimus, thereby avoiding the need for a near total pancreatectomy.

CONCLUSION

We report the first case of compound heterozygous ABCC8 mutation causing severe diffuse HH that responded to therapy with a mTOR inhibitor.

Rapamycin ameliorates nephropathy despite elevating hyperglycemia in a polygenic mouse model of type 2 diabetes, NONcNZO10/LtJ

While rapamycin treatment has been reported to have a putatively negative effect on glucose homeostasis in mammals, it has not been tested in polygenic models of type 2 diabetes. One such mouse model, NONcNZO10/LtJ, was treated chronically with rapamycin (14 ppm encapsulated in diet) and monitored for the development of diabetes. As expected, rapamycin treatment accelerated the onset and severity of hyperglycemia. However, development of nephropathy was ameliorated, as both glomerulonephritis and IgG deposition in the subendothelial tuft were markedly reduced. Insulin production and secretion appeared to be inhibited, suppressing the developing hyperinsulinemia present in untreated controls. Rapamycin treatment also reduced body weight gain. Thus, rapamycin reduced some of the complications of diabetes despite elevating hyperglycemia. These results suggest that multiple factors must be evaluated when assessing the benefit vs. hazard of rapamycin treatment in patients that have overt, or are at risk for, type 2 diabetes. Testing of rapamycin in combination with insulin sensitizers is warranted, as such compounds may ameliorate the putative negative effects of rapamycin in the type 2 diabetes environment.

Interleukin 2 in the pathogenesis and therapy of type 1 diabetes

Regulatory T cells (Tregs) play a major role in controlling effector T cells (Teffs) responding to self-antigens, which cause autoimmune diseases. An improper Treg/Teff balance contributes to most autoimmune diseases, including type 1 diabetes (T1D). To restore a proper balance, blocking Teffs with immunosuppressants has been the only option, which was partly effective and too toxic. It now appears that expanding/activating Tregs with low-dose interleukin-2 (IL-2) could provide immunoregulation without immunosuppression. This is particularly interesting in T1D as Tregs from T1D patients are reported as dysfunctional and a relative deficiency in IL-2 production and/or IL-2-mediated signaling could contribute to this phenotype. A clinical study of low-dose IL-2 showed a very good safety profile and good Treg expansion/activation in T1D patients. This opens the way for efficacy trials to test low-dose IL-2 in prevention and treatment of T1D and to establish in which condition restoration of a proper Treg/Teff balance would be beneficial in the field of autoimmune and inflammatory diseases.

Acute rapamycin treatment improved glucose tolerance through inhibition of hepatic gluconeogenesis in rainbow trout (Oncorhynchus mykiss)

Our aim was to investigate the potential role of TOR (target of rapamycin) signaling pathway in the regulation of hepatic glucose metabolism in rainbow trout. Fasted fish were first treated with a single intraperitoneal injection of rapamycin or vehicle and then submitted to a second intraperitoneal administration of glucose 4 h later. Our results revealed that intraperitoneal administration of glucose induced hyperglycemia for both vehicle and rapamycin treatments, which peaked at 2 h. Plasma glucose level in vehicle-treated fish was significantly higher than in rapamycin-treated fish at 8 and 17 h, whereas it remained at the basal level in rapamycin-treated fish. Glucose administration significantly enhanced the phosphorylation of Akt and ribosomal protein S6 kinase (S6K1) in vehicle-treated fish, while rapamycin completely abolished the activation of S6K1 in rapamycin-treated fish, without inhibiting the phosphorylation of Akt on Thr-308 or Ser-473. Despite the lack of significant variation in phosphoenolpyruvate carboxykinase mRNA abundance, mRNA abundance for glucokinase (GK), glucose 6-phosphatase (G6Pase) I and II, and fructose 1,6-bisphosphatase (FBPase) was reduced by rapamycin 17 h after glucose administration. The inhibition effect of rapamycin on GK and FBPase was further substantiated at the activity level. The suppression of GK gene expression and activity by rapamycin provided the first in vivo evidence in fish that glucose regulates hepatic GK gene expression and activity through a TORC1-dependent manner. Unlike in mammals, we observed that acute rapamycin treatment improved glucose tolerance through the inhibition of hepatic gluconeogenesis in rainbow trout.