Chronic rapamycin treatment causes glucose intolerance and hyperlipidemia by upregulating hepatic gluconeogenesis and impairing lipid deposition in adipose tissue

Systematic transcriptomics analysis of calorie restriction and rapamycin unveils their synergistic interaction in prolonging cellular lifespan

Aging is a multifaceted biological process marked by the decline in both mitotic and postmitotic cellular function, often central to the development of age-related diseases. In the pursuit of slowing or even reversing the aging process, a prominent strategy of significant interest is calorie restriction (CR), also known as dietary restriction, and the potential influence of a drug called rapamycin (RM). Both CR and RM have demonstrated the capacity to extend healthspan and lifespan across a diverse array of species, including yeast, worms, flies, and mice. Nevertheless, their individual and combined effects on mitotic and postmitotic cells, as well as their comparative analysis, remain areas that demand a thorough investigation. In this study, we employ RNA-sequencing methodologies to comprehensively analyze the impact of CR, RM, and their combination (CR + RM) on gene expression in yeast cells. Our analysis uncovers distinctive, overlapping, and even contrasting patterns of gene regulation, illuminating the unique and shared effects of CR and RM. Furthermore, the transcriptional synergistic interaction of CR + RM is validated in extending the lifespan of both yeast and human cells.

Rubicon siRNA-encapsulated liver-targeting nanoliposome is a promising therapeutic for non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a prevalent metabolic liver disorder worldwide, and effective therapeutic strategies for its treatment remains limited. In this article, we introduced Glipo-siRubi, a hepatocytes-targeting RNA interference (RNAi) nanoliposome for suppression of Rubicon expression, aiming to achieve precise regulation of autophagy in NAFLD. Autophagy activation induced by Rubicon suppression resulted in reduced endoplasmic reticulum stress and intracellular lipid accumulation in vitro. Moreover, Glipo-siRubi administration exhibited remarkable therapeutic efficacy, characterized by decreased liver lipid accumulation, ameliorated histopathology and improved insulin sensitivity in mice with western diet, indicating its notable potential against NAFLD. By inducing autophagy activation, the hepatocytes-targeting Glipo-siRubi provided a promising method for NAFLD treatment, addressing the limitations of current approaches. Our study highlighted the significance of Rubicon-specific suppression in NAFLD treatment, offering a specific, safe, and efficient approach to mitigate NAFLD.

Rapamycin does not compromise physical performance or muscle hypertrophy after PoWeR while intermittent rapamycin alleviates glucose disruptions by frequent rapamycin

An increasing number of physically active adults are taking the mTOR inhibitor rapamycin off label with the goal of extending healthspan. However, frequent rapamycin dosing disrupts metabolic health during sedentary conditions and abates the anabolic response to exercise. Intermittent once weekly rapamycin dosing minimizes many negative metabolic side effects of frequent rapamycin in sedentary mice. However, it remains unknown how different rapamycin dosing schedules impact metabolic, physical, and skeletal muscle adaptations to voluntary exercise training. Therefore, we tested the hypothesis that intermittent rapamycin (2mg/kg; 1x/week) would avoid detrimental effects on adaptations to 8 weeks of progressive weighted wheel running (PoWeR) in adult female mice (5-month-old) by evading the sustained inhibitory effects on mTOR signaling by more frequent dosing schedules (2mg/kg; 3x/week). Frequent but not intermittent rapamycin suppressed skeletal muscle mTORC1 signaling in PoWeR trained mice. PoWeR improved maximal exercise capacity, absolute grip strength, and myofiber hypertrophy with no differences between vehicle or rapamycin treated mice. Conversely, frequent and intermittent rapamycin treated mice had impaired glucose tolerance and insulin sensitivity compared to vehicle treated mice after PoWeR; however, intermittent rapamycin reduced the impact on glucose intolerance versus frequent rapamycin. Collectively, these data in adult female mice suggest that 1) rapamycin is largely compatible with the physical and skeletal muscle benefits of PoWeR and 2) the detrimental effects of rapamycin on body composition and glucose metabolism in the context of voluntary exercise may be reduced by intermittent dosing.

Side Effects of Immunosuppressant Drugs After Liver Transplant

Liver transplantation (LT) is the standard of care for both end-stage liver failure and hepatocellular carcinoma (HCC). Side effects of the main used immunosuppressive drugs have a noteworthy impact on the long-term outcome of LT recipients. Consequently, to achieve a balance between optimal immunosuppression and minimal side effects is a cornerstone of the post-LT period. Today, there are no validated markers for overimmunosuppression and underimmunosuppression, only a few drugs have therapeutic drug monitoring, and immunosuppression regimens vary from center to center and from country to country. Currently, there are many drugs with different efficacy and safety profiles. Using different agents permits a decrease in the dosage and minimizes the toxicities. A small subset of recipients achieves immunotolerance with the chance to stop immunosuppressive therapy. This article focuses on the side effects of immunosuppressive drugs, which significantly impact long-term outcomes for LT recipients. The primary aim is to highlight the balance between achieving effective immunosuppression and minimizing adverse effects, emphasizing the role of personalized therapeutic strategies. Moreover, this review evaluates the mechanisms of action and specific complications associated with immunosuppressive agents. Finally, special attention is given to strategies for reducing immunosuppressive burdens, improving patient quality of life, and identifying immunotolerant individuals.

Autophagy and the peroxisome proliferator-activated receptor signaling pathway: A molecular ballet in lipid metabolism and homeostasis

Lipids, which are indispensable for cellular architecture and energy storage, predominantly consist of triglycerides (TGs), phospholipids, cholesterol, and their derivatives. These hydrophobic entities are housed within dynamic lipid droplets (LDs), which expand and contract in response to nutrient availability. Historically perceived as a cellular waste disposal mechanism, autophagy has now been recognized as a crucial regulator of metabolism. Within this framework, lipophagy, the selective degradation of LDs, plays a fundamental role in maintaining lipid homeostasis. Dysregulated lipid metabolism and autophagy are frequently associated with metabolic disorders such as obesity and atherosclerosis. In this context, peroxisome proliferator-activated receptors (PPARs), particularly PPAR-γ, serve as intracellular lipid sensors and master regulators of gene expression. Their regulatory influence extends to both autophagy and lipid metabolism, indicating a complex interplay between these processes. This review explores the hypothesis that PPARs may directly modulate autophagy within the realm of lipid metabolism, thereby contributing to the pathogenesis of metabolic diseases. By elucidating the underlying molecular mechanisms, we aim to provide a comprehensive understanding of the intricate regulatory network that connects PPARs, autophagy, and lipid homeostasis. The crosstalk between PPARs and other signaling pathways underscores the complexity of their regulatory functions and the potential for therapeutic interventions targeting these pathways. The intricate relationships among PPARs, autophagy, and lipid metabolism represent a pivotal area of research with significant implications for understanding and treating metabolic disorders.

Dietary Restriction and Lipid Metabolism: Unveiling Pathways to Extended Healthspan

Dietary restriction (DR) has been reported to be a significant intervention that influences lipid metabolism and potentially modulates the aging process in a wide range of organisms. Lipid metabolism plays a pivotal role in the regulation of aging and longevity. In this review, we summarize studies on the significant role of lipid metabolism in aging in relation to DR. As a potent intervention to slow down aging, DR has demonstrated promising effects on lipid metabolism, influencing the aging processes across various species. The current review focuses on the relationships among DR-related molecular signaling proteins such as the sirtuins, signaling pathways such as the target of rapamycin and the insulin/insulin-like growth factor (IGF)-1, lipid metabolism, and aging. Furthermore, the review presents research results on diet-associated changes in cell membrane lipids and alterations in lipid metabolism caused by commensal bacteria, highlighting the importance of lipid metabolism in aging. Overall, the review explores the interplay between diet, lipid metabolism, and aging, while presenting untapped areas for further understanding of the aging process.

Hyperaminoacidemia from interrupted glucagon signaling increases pancreatic acinar cell proliferation and size via mTORC1 and YAP pathways

Increased blood amino acid levels (hyperaminoacidemia) stimulate pancreas expansion by unclear mechanisms. Here, by genetic and pharmacological disruption of glucagon receptor (GCGR) in mice and zebrafish, we found that the ensuing hyperaminoacidemia promotes pancreatic acinar cell proliferation and cell hypertrophy, which can be mitigated by a low protein diet in mice. In addition to mammalian target of rapamycin complex 1 (mTORC1) signaling, acinar cell proliferation required slc38a5, the most highly expressed amino acid transporter gene in both species. Transcriptomics data revealed the activation signature of yes-associated protein (YAP) in acinar cells of mice with hyperaminoacidemia, consistent with the observed increase in YAP-expressing acinar cells. Yap1 activation also occurred in acinar cells in gcgr-/- zebrafish, which was reversed by rapamycin. Knocking down yap1 in gcgr-/- zebrafish decreased mTORC1 activity and acinar cell proliferation and hypertrophy. Thus, the study discovered a previously unrecognized role of the YAP/Taz pathway in hyperaminoacidemia-induced acinar cell hypertrophy and hyperplasia.

Anti-aging properties of the aminosterols of the dogfish shark

The development of anti-aging drugs is challenged by both the apparent complexity of the physiological mechanisms involved in aging and the likelihood that many of these mechanisms remain unknown. As a consequence, the development of anti-aging compounds based on the rational targeting of specific pathways has fallen short of the goal. To date, the most impressive compound is rapamycin, a natural bacterial product initially identified as an antifungal, and only subsequently discovered to have anti-aging properties. In this review, we focus on two aminosterols from the dogfish shark, Squalus acanthias, that we discovered initially as broad-spectrum anti-microbial agents. This review is the first to gather together published studies conducted both in vitro and in numerous vertebrate species to demonstrate that these compounds target aging pathways at the cellular level and provide benefits in multiple aging-associated conditions in relevant animal models and in humans. The dogfish aminosterols should be recognized as potential anti-aging drugs.

Physiological and Pathological Role of mTOR Signaling in Astrocytes

The mammalian target of rapamycin (mTOR) signaling pathway is one of the key regulators of cellular energy metabolism. It senses diverse alterations in the extracellular environment such as availability of nutrients and growth factors, and mediates the corresponding intracellular response. In the brain, astrocytes crucially contribute to energy and neurotransmitter metabolism, and numerous other functions. However, the relevance of physiological, astrocytic mTOR signaling in maintaining brain homeostasis and function is not well understood. Pathophysiological mTOR signaling is involved in manifold diseases in the central nervous system and most of the knowledge about astrocytic mTOR signaling has been derived from observations on these disorders. Dysregulation of the mTOR signaling pathway impairs important functions of astrocytes including neurotransmitter uptake and -signaling as well as energy metabolism. Some of these alterations could trigger neuropathological conditions such as epilepsy. This review focuses on how mTOR signaling regulates properties of astrocytes, and how these signaling events might contribute to the physiological function of the brain.

Rapamycin administration causes a decrease in muscle contractile function and systemic glucose intolerance concomitant with reduced skeletal muscle Rictor, the mTORC2 component, expression independent of energy intake in young rats

Emerging evidence suggests the potential of rapamycin, an antibiotic from Streptomyces hygroscopicus that functions as a mechanistic target of rapamycin (mTOR) inhibitor, as a mimetic of caloric restriction (CR) for maintaining skeletal muscle health. Several studies showed that rapamycin administration (RAP) reduced appetite and energy intake. However, the physiological and molecular differences between RAP and CR in skeletal muscle are not fully understood. Here we observed the effects of 4 weeks of RAP administration and CR corresponding to the reduction in energy intake produced by RAP administration (PF, paired feeding) on fast glycolytic and slow oxidative muscle in young adult rats. We found that 4 weeks of RAP demonstrated low fast-glycolytic muscle mass with smaller type I and IIb/x myofiber size independent of the energy intake. In addition, PF improved the contractile function of the plantar flexor muscle, whereas RAP did not improve its function. The suppressing response of mTORC1 signaling to RAP is greater in slow-oxidative muscles than in fast-glycolytic muscles. In addition, systemic glucose tolerance was exacerbated by RAP, with reduced expression of Rictor and hexokinase in skeletal muscle. These observations imply that RAP may have a slight but significant negative impact and it obviously different to CR in young adult skeletal muscle.

Personalized phosphoproteomics of skeletal muscle insulin resistance and exercise links MINDY1 to insulin action

Type 2 diabetes is preceded by a defective insulin response, yet our knowledge of the precise mechanisms is incomplete. Here, we investigate how insulin resistance alters skeletal muscle signaling and how exercise partially counteracts this effect. We measured parallel phenotypes and phosphoproteomes of insulin-resistant (IR) and insulin-sensitive (IS) men as they responded to exercise and insulin (n = 19, 114 biopsies), quantifying over 12,000 phosphopeptides in each biopsy. Insulin resistance involves selective and time-dependent alterations to signaling, including reduced insulin-stimulated mTORC1 and non-canonical signaling responses. Prior exercise promotes insulin sensitivity even in IR individuals by "priming" a portion of insulin signaling prior to insulin infusion. This includes MINDY1 S441, which we show is an AKT substrate. We found that MINDY1 knockdown enhances insulin-stimulated glucose uptake in rat myotubes. This work delineates the signaling alterations in IR skeletal muscle and identifies MINDY1 as a regulator of insulin action.

Role of endothelial Raptor in abnormal arteriogenesis after lower limb ischaemia in type 2 diabetes

AIMS

Proper arteriogenesis after tissue ischaemia is necessary to rebuild stable blood circulation; nevertheless, this process is impaired in type 2 diabetes mellitus (T2DM). Raptor is a scaffold protein and a component of mammalian target of rapamycin complex 1 (mTORC1). However, the role of the endothelial Raptor in arteriogenesis under the conditions of T2DM remains unknown. This study investigated the role of endothelial Raptor in ischaemia-induced arteriogenesis during T2DM.

METHODS AND RESULTS

Although endothelial mTORC1 is hyperactive in T2DM, we observed a marked reduction in the expression of endothelial Raptor in two mouse models and in human vessels. Inducible endothelial-specific Raptor knockout severely exacerbated impaired hindlimb perfusion and arteriogenesis after hindlimb ischaemic injury in 12-week high-fat diet fed mice. Additionally, we found that Raptor deficiency dampened vascular endothelial growth factor receptor 2 (VEGFR2) signalling in endothelial cells (ECs) and inhibited VEGF-induced cell migration and tube formation in a PTP1B-dependent manner. Furthermore, mass spectrometry analysis indicated that Raptor interacts with neuropilin 1 (NRP1), the co-receptor of VEGFR2, and mediates VEGFR2 trafficking by facilitating the interaction between NRP1 and Synectin. Finally, we found that EC-specific overexpression of the Raptor mutant (loss of mTOR binding) reversed impaired hindlimb perfusion and arteriogenesis induced by endothelial Raptor knockout in high-fat diet fed mice.

CONCLUSION

Collectively, our study demonstrated the crucial role of endothelial Raptor in promoting ischaemia-induced arteriogenesis in T2DM by mediating VEGFR2 signalling. Thus, endothelial Raptor is a novel therapeutic target for promoting arteriogenesis and ameliorating perfusion in T2DM.

Targeting a mTOR/autophagy axis: a double-edged sword of rapamycin in spontaneous miscarriage

Immune dysfunction is a primary culprit behind spontaneous miscarriage (SM). To address this, immunosuppressive agents have emerged as a novel class of tocolytic drugs, modulating the maternal immune system's tolerance towards the embryo. Rapamycin (PubChem CID:5284616), a dual-purpose compound, functions as an immunosuppressive agent and triggers autophagy by targeting the mTOR pathway. Its efficacy in treating SM has garnered significant research interest in recent times. Autophagy, the cellular process of self-degradation and recycling, plays a pivotal role in numerous health conditions. Research indicates that autophagy is integral to endometrial decidualization, trophoblast invasion, and the proper functioning of decidual immune cells during a healthy pregnancy. Yet, in cases of SM, there is a dysregulation of the mTOR/autophagy axis in decidual stromal cells or immune cells at the maternal-fetal interface. Both in vitro and in vivo studies have highlighted the potential benefits of low-dose rapamycin in managing SM. However, given mTOR's critical role in energy metabolism, inhibiting it could potentially harm the pregnancy. Moreover, while low-dose rapamycin has been deemed safe for treating recurrent implant failure, its potential teratogenic effects remain uncertain due to insufficient data. In summary, rapamycin represents a double-edged sword in the treatment of SM, balancing its impact on autophagy and immune regulation. Further investigation is warranted to fully understand its implications.

[A Case of Successful Treatment of Severe Hyperlipidemia After Heart Transplantation With Inclisiran]

The prognosis after heart transplantation continues to improve. Therefore, the prevention of chronic post-transplant sequelae, such as chronic kidney disease, allograft vasculopathy, and malignancies is becoming increasingly important. Everolimus, an inhibitor of the mammalian target of rapamycin (mTOR), is increasingly used for immunosuppression after heart transplantation. However, everolimus may cause a characteristic complex of adverse effects, including dyslipidemia. Currently there are no guidelines for the long-term screening and treatment of dyslipidemia in heart transplant recipients treated with everolimus. This article presents a clinical case of hypercholesterolemia that developed after the start of the everolimus treatment in a heart recipient. The patient was a 39-year-old man who underwent orthotopic heart transplantation for ischemic cardiomyopathy in 2012 (at the age of 27). In 2019, the patient's immunosuppressive therapy was converted from mycophenolate mofetil to everolimus due to the development of cardiac allograft vasculopathy. The change in the immunosuppressive therapy was associated with increases in total cholesterol and low-density lipoprotein cholesterol, which were not reversed with a combined lipid-lowering therapy (maximum doses of rosuvastatin, ezetimibe, fenofibrate). A decrease in lipid levels was achieved with a blocker of hepatic proprotein convertase subtilisin/kexin type 9 synthesis at the level of microribonucleic acid (inclisiran). This case demonstrates the difficulties in correcting dyslipidemia in patients with cardiac allograft, since the treatment with the immunosuppressant everolimus worsens existing dyslipidemia. However, the combination lipid-lowering therapy, that affects various elements of the pathogenesis (specifically, the combined inhibition of hydroxymethylglutaryl-CoA reductase with a statin, cholesterol absorption from the small intestine with ezetimibe, and PCSK9 messenger RNA with inclisiran), provides an effective control of blood lipids and minimizing the adverse effects of immunosuppressive therapy, such as cardiac allograft vasculopathy.

High glucose-induced downregulation of PTEN-Long is sufficient for proximal tubular cell injury in diabetic kidney disease

During the progression of diabetic kidney disease, proximal tubular epithelial cells respond to high glucose to induce hypertrophy and matrix expansion leading to renal fibrosis. Recently, a non-canonical PTEN has been shown to be translated from an upstream initiation codon CUG (leucine) to produce a longer protein called PTEN-Long (PTEN-L). Interestingly, the extended sequence present in PTEN-L contains cell secretion/penetration signal. Role of this non-canonical PTEN-L in diabetic renal tubular injury is not known. We show that high glucose decreases expression of PTEN-L. As a mechanism of its function, we find that reduced PTEN-L activates Akt-2, which phosphorylates and inactivate tuberin and PRAS40, resulting in activation of mTORC1 in tubular cells. Antibacterial agent acriflavine and antiviral agent ATA regulate translation from CUG codon. Acriflavine and ATA, respectively, decreased and increased expression of PTEN-L to altering Akt-2 and mTORC1 activation in the absence of change in expression of canonical PTEN. Consequently, acriflavine and ATA modulated high glucose-induced tubular cell hypertrophy and lamininγ1 expression. Importantly, expression of PTEN-L inhibited high glucose-stimulated Akt/mTORC1 activity to abrogate these processes. Since PTEN-L contains secretion/penetration signals, addition of conditioned medium containing PTEN-L blocked Akt-2/mTORC1 activity. Notably, in renal cortex of diabetic mice, we found reduced PTEN-L concomitant with Akt-2/mTORC1 activation, leading to renal hypertrophy and lamininγ1 expression. These results present first evidence for involvement of PTEN-L in diabetic kidney disease.

Integrating network pharmacology and experimental validation reveals therapeutic effects of D-mannose on NAFLD through mTOR suppression

Non-alcoholic fatty liver disease (NAFLD), a chronic liver condition and metabolic disorder, has emerged as a significant health issue worldwide. D-mannose, a natural monosaccharide widely existing in plants and animals, has demonstrated metabolic regulatory properties. However, the effect and mechanism by which D-mannose may counteract NAFLD have not been studied. In this study, network pharmacology followed by molecular docking analysis was utilized to identify potential targets of mannose against NAFLD, and the leptin receptor-deficient, genetically obese db/db mice was employed as an animal model of NAFLD to validate the regulation of D-mannose on core targets. As a result, 67 targets of mannose are predicted associated with NAFLD, which are surprisingly centered on the mechanistic target of rapamycin (mTOR). Further analyses suggest that mTOR signaling is functionally enriched in potential targets of mannose treating NAFLD, and that mannose putatively binds to mTOR as a core mechanism. Expectedly, repeated oral gavage of supraphysiological D-mannose ameliorates liver steatosis of db/db mice, which is based on suppression of hepatic mTOR signaling. Moreover, daily D-mannose administration reduced hepatic expression of lipogenic regulatory genes in counteracting NAFLD. Together, these findings reveal D-mannose as an effective and potential NAFLD therapeutic through mTOR suppression, which holds translational promise.

mTORC1 in energy expenditure: consequences for obesity

In eukaryotic cells, the mammalian target of rapamycin complex 1 (sometimes referred to as the mechanistic target of rapamycin complex 1; mTORC1) orchestrates cellular metabolism in response to environmental energy availability. As a result, at the organismal level, mTORC1 signalling regulates the intake, storage and use of energy by acting as a hub for the actions of nutrients and hormones, such as leptin and insulin, in different cell types. It is therefore unsurprising that deregulated mTORC1 signalling is associated with obesity. Strategies that increase energy expenditure offer therapeutic promise for the treatment of obesity. Here we review current evidence illustrating the critical role of mTORC1 signalling in the regulation of energy expenditure and adaptive thermogenesis through its various effects in neuronal circuits, adipose tissue and skeletal muscle. Understanding how mTORC1 signalling in one organ and cell type affects responses in other organs and cell types could be key to developing better, safer treatments targeting this pathway in obesity.

Licochalcone A alleviates abnormal glucolipid metabolism and restores energy homeostasis in diet-induced diabetic mice

Licochalcone A (LCA) is a bioactive chalcone compound identified in licorice. This study aimed to investigate the effects of LCA on glucolipid metabolism and energy homeostasis, as well as the underlying mechanisms. Blood glucose levels, oral glucose tolerance, serum parameters, and histopathology were examined in high-fat-high-glucose diet (HFD)-induced diabetic mice, with metformin as a positive control. Additionally, changes in key markers related to glucolipid metabolism and mitochondrial function were analyzed to comprehensively assess LCA's effects on metabolism. The results showed that LCA alleviated metabolic abnormalities in HFD-induced diabetic mice, which were manifested by suppression of lipogenesis, promotion of lipolysis, reduction of hepatic steatosis, increase in hepatic glycogenesis, and decrease in gluconeogenesis. In addition, LCA restored energy homeostasis by promoting mitochondrial biogenesis, enhancing mitophagy, and reducing adenosine triphosphate production. Mechanistically, the metabolic benefits of LCA were associated with the downregulation of mammalian target of rapamycin complex 1 and activation of adenosine monophosphate-activated protein kinase, the two central regulators of metabolism. This study demonstrates that LCA can alleviate abnormal glucolipid metabolism and restore energy balance in diet-induced diabetic mice, highlighting its therapeutical potential for the treatment of diabetes.

Geroprotector drugs and exercise: friends or foes on healthy longevity?

Physical activity and several pharmacological approaches individually combat age-associated conditions and extend healthy longevity in model systems. It is tantalizing to extrapolate that combining geroprotector drugs with exercise could extend healthy longevity beyond any individual treatment. However, the current dogma suggests that taking leading geroprotector drugs on the same day as exercise may limit several health benefits. Here, we review leading candidate geroprotector drugs and their interactions with exercise and highlight salient gaps in knowledge that need to be addressed to identify if geroprotector drugs can have a harmonious relationship with exercise.

Obesity under the moonlight of c-MYC

The moonlighting protein c-Myc is a master regulator of multiple biological processes including cell proliferation, differentiation, angiogenesis, apoptosis and metabolism. It is constitutively and aberrantly expressed in more than 70% of human cancers. Overwhelming evidence suggests that c-Myc dysregulation is involved in several inflammatory, autoimmune, metabolic and other non-cancerous diseases. In this review, we addressed the role of c-Myc in obesity. Obesity is a systemic disease, accompanied by multi-organ dysfunction apart from white adipose tissue (WAT), such as the liver, the pancreas, and the intestine. c-Myc plays a big diversity of functions regulating cellular proliferation, the maturation of progenitor cells, fatty acids (FAs) metabolism, and extracellular matrix (ECM) remodeling. Moreover, c-Myc drives the expression of a wide range of metabolic genes, modulates the inflammatory response, induces insulin resistance (IR), and contributes to the regulation of intestinal dysbiosis. Altogether, c-Myc is an interesting diagnostic tool and/or therapeutic target in order to mitigate obesity and its consequences.

Genetic variations in a Sestrin2/Sestrin3/mTOR Axis and development of new-onset diabetes after kidney transplantation

BACKGROUND

Genetic variations in Sestrin2/Sestrin3/ mTOR axis may cause obesity-associated metabolic syndrome, including lipid accumulation and insulin resistance thereby increasing individual's risk of diabetes. In this study, we explored the association between single nucleotide polymorphisms (SNPs) of these genes and new onset diabetes after transplantation in Hispanic renal transplant recipients (RTRs).

METHODS

Nine potential functional polymorphisms in Sestrin2, Sestrin3 and mTOR genes were genotyped using the Taqman qPCR method in this study. We compared 160 Hispanic RTRs with no evidence of pre-existing diabetes, who developed new onset diabetes after transplantation (NODAT) with 152 controls with no history of diabetes. The logistic proportional hazard model was used to examine risks for NODAT. Nongenetic and genetic characteristics were included in the multivariate risk model.

RESULTS

Significant associations were observed between NODAT and mTOR TT (rs2295080 OR = 1.79, 95% CI =1.14-2.82, p = 0.01), Sestrin2 AA (rs580800, OR = 0.42, 95% CI =0.27-0.67, p = 0.002), and Sestrin3 AA (rs684856, OR = 0.45, 95% CI = 0.27-0.75, p = 0.001). Sestrin2 AA (rs580800), Sestrin3 AA (rs684856) and mTOR TT (rs2295080) remained significantly associated with NODAT after adjusting for acute rejection and sirolimus use. No interactions observed between the mTOR rs2295080 and Sestrin3 rs684856 and risk of NODAT (mTOR rs2295080 and Sestrin3 rs684856, p = 0.123 and mTOR rs2295080 and Sestrin2 rs580800, p = 0.167). Of the nongenetic factors, use of sirolimus and older age were associated with an increased risk for NODAT.

CONCLUSION

Polymorphisms in the Sestrin2/Sestrin3/ mTOR gene may confer certain protection/predisposition for NODAT.

Case report: Severe asymptomatic hypertriglyceridemia associated with long-term low-dose rapamycin administration in a healthy middle-aged Labrador retriever

Rapamycin is an mTOR inhibitor that has been shown to extend the lifespan of laboratory model organisms. In humans, rapamycin is used at higher doses as an immunosuppressive medication to prevent organ rejection. Numerous adverse effects are seen with rapamycin treatment in humans, with one of the most common being dysregulation of lipid metabolism. In humans, this often manifests as mild to moderate serum lipid elevations, with a small subset developing extreme triglyceride elevations. This case report describes an eight-year-old, castrated male, clinically healthy Labrador retriever who developed severe hypertriglyceridemia associated with low-dose rapamycin administration over a six-month period. During this time, the dog was asymptomatic and displayed no other clinical abnormalities, aside from a progressive lipemia. Within 15 days of discontinuing rapamycin treatment, and with no targeted lipemic intervention, the dog's lipemia and hypertriglyceridemia completely resolved.

Leflunomide alleviates obesity via activation of the TAK1-AMPK pathway and induction of lipophagy

Lipophagy is a subset of selective autophagy that specifically degrades lipid droplets and plays an important role in obesity. Leflunomide treatment in rheumatoid arthritis (RA) patients has been associated with weight loss and decreased blood glucose levels, which cannot be attributed to its known side effects. Our prior studies showed that A77 1726, the active metabolite of leflunomide, acts as an inhibitor of S6K1 to sensitize the insulin receptor and control hyperglycemia. Whether the anti-obesity effect of leflunomide is mediated by targeting S6K1 and its underlying mechanisms remain unclear. Here, we report that A77 1726 induced LC3 lipidation and increased the formation of autophagosomes and lipoautolysosomes in 3T3-L1 adipocytes by activating TGF-β-activated kinase 1 (TAK1), AMP-activated kinase (AMPK), and Unc-51 like autophagy-activated kinase 1 (ULK1). A77 1726 reduced the content of lipid droplets in 3T3-L1 adipocytes, which was blocked by bafilomycin or by beclin-1 knockdown. Similar observations were made in murine adipocytes differentiated from S6K1-/- embryonic fibroblasts (MEFs). Leflunomide treatment restricted bodyweight gains in ob/ob mice and reduced the visceral fat deposit and the size of adipocytes. Leflunomide treatment induced autophagy in adipose and liver tissues and reduced hepatic lipid contents. Consistently, S6K1 knockout increased the levels of LC3 lipidation in the liver, muscle, and fat of S6K-/- mice. Leflunomide treatment and S6K1 deficiency both induced TAK1, AMPK, and ULK1 phosphorylation in these tissues. These observations collectively suggest that leflunomide controls obesity in part by activating AMPK and inducing lipophagy. Our study provides insights into the mechanisms of leflunomide-mediated anti-obesity activity.

mTORC1 and SGLT2 Inhibitors-A Therapeutic Perspective for Diabetic Cardiomyopathy

Diabetic cardiomyopathy is a critical diabetes-mediated co-morbidity characterized by cardiac dysfunction and heart failure, without predisposing hypertensive or atherosclerotic conditions. Metabolic insulin resistance, promoting hyperglycemia and hyperlipidemia, is the primary cause of diabetes-related disorders, but ambiguous tissue-specific insulin sensitivity has shed light on the importance of identifying a unified target paradigm for both the glycemic and non-glycemic context of type 2 diabetes (T2D). Several studies have indicated hyperactivation of the mammalian target of rapamycin (mTOR), specifically complex 1 (mTORC1), as a critical mediator of T2D pathophysiology by promoting insulin resistance, hyperlipidemia, inflammation, vasoconstriction, and stress. Moreover, mTORC1 inhibitors like rapamycin and their analogs have shown significant benefits in diabetes and related cardiac dysfunction. Recently, FDA-approved anti-hyperglycemic sodium-glucose co-transporter 2 inhibitors (SGLT2is) have gained therapeutic popularity for T2D and diabetic cardiomyopathy, even acknowledging the absence of SGLT2 channels in the heart. Recent studies have proposed SGLT2-independent drug mechanisms to ascertain their cardioprotective benefits by regulating sodium homeostasis and mimicking energy deprivation. In this review, we systematically discuss the role of mTORC1 as a unified, eminent target to treat T2D-mediated cardiac dysfunction and scrutinize whether SGLT2is can target mTORC1 signaling to benefit patients with diabetic cardiomyopathy. Further studies are warranted to establish the underlying cardioprotective mechanisms of SGLT2is under diabetic conditions, with selective inhibition of cardiac mTORC1 but the concomitant activation of mTORC2 (mTOR complex 2) signaling.

SHP-1 phosphatase acts as a coactivator of PCK1 transcription to control gluconeogenesis

We previously reported that the protein-tyrosine phosphatase SHP-1 (PTPN6) negatively regulates insulin signaling, but its impact on hepatic glucose metabolism and systemic glucose control remains poorly understood. Here, we use co-immunoprecipitation assays, chromatin immunoprecipitation sequencing, in silico methods, and gluconeogenesis assay, and found a new mechanism whereby SHP-1 acts as a coactivator for transcription of the phosphoenolpyruvate carboxykinase 1 (PCK1) gene to increase liver gluconeogenesis. SHP-1 is recruited to the regulatory regions of the PCK1 gene and interacts with RNA polymerase II. The recruitment of SHP-1 to chromatin is dependent on its association with the transcription factor signal transducer and activator of transcription 5 (STAT5). Loss of SHP-1 as well as STAT5 decrease RNA polymerase II recruitment to the PCK1 promoter and consequently PCK1 mRNA levels leading to blunted gluconeogenesis. This work highlights a novel nuclear role of SHP-1 as a key transcriptional regulator of hepatic gluconeogenesis adding a new mechanism to the repertoire of SHP-1 functions in metabolic control.

Anlotinib affects systemic lipid metabolism and induces lipid accumulation in human lung cancer cells

BACKGROUND

Anlotinib has demonstrated encouraging clinical outcomes in the treatment of lung cancer, soft tissue sarcoma and thyroid carcinoma. Several clinical studies have shown a relationship between anlotinib treatment and the occurrence of hyperlipidemia. The fundamental mechanisms, however, are still largely unclear. Here, the effect of anlotinib on lipid metabolism in an animal model and human cancer cells was evaluated and the role of lipid metabolism in the antitumor efficacy of anlotinib was investigated.

METHODS

The C57BL/6 J mouse model as well as A549 and H460 human lung cancer cell lines were used to examine the impact of anlotinib on lipid metabolism both in vivo and in vitro. Levels of triglycerides, high-density lipoprotein, low-density lipoprotein (LDL), and total cholesterol in serum or cell samples were determined using assay kits. The expression levels of crucial genes and proteins involved in lipid metabolism were measured by quantitative RT-PCR and Western blotting. Furthermore, exogenous LDL and knockdown of low-density lipoprotein receptor (LDLR) were used in H460 cells to investigate the relevance of lipid metabolism in the anticancer efficacy of anlotinib.

RESULTS

Anlotinib caused hyperlipidemia in C57BL/6 J mice, possibly by downregulating hepatic LDLR-mediated uptake of LDL cholesterol. AMP-activated protein kinase and mammalian target of rapamycin inhibition may also be involved. Additionally, anlotinib enhanced sterol response element binding protein 1/2 nuclear accumulation as well as upregulated LDLR expression in A549 and H460 cells, which may be attributable to intracellular lipid accumulation. Knockdown of LDLR reduced intracellular cholesterol content, but interestingly, anlotinib significantly improved intracellular cholesterol accumulation in LDLR-knockdown cells. Both exogenous LDL and LDLR knockdown decreased the sensitivity of cells to anlotinib.

CONCLUSIONS

Anlotinib modulates host lipid metabolism through multiple pathways. Anlotinib also exerts a significant impact on lipid metabolism in cancer cells by regulating key transcription factors and metabolic enzymes. In addition, these findings suggest lipid metabolism is implicated in anlotinib sensitivity.

mTOR Signaling Pathway in Bone Diseases Associated with Hyperglycemia

The interplay between bone and glucose metabolism has highlighted hyperglycemia as a potential risk factor for bone diseases. With the increasing prevalence of diabetes mellitus worldwide and its subsequent socioeconomic burden, there is a pressing need to develop a better understanding of the molecular mechanisms involved in hyperglycemia-mediated bone metabolism. The mammalian target of rapamycin (mTOR) is a serine/threonine protein kinase that senses extracellular and intracellular signals to regulate numerous biological processes, including cell growth, proliferation, and differentiation. As mounting evidence suggests the involvement of mTOR in diabetic bone disease, we provide a comprehensive review of its effects on bone diseases associated with hyperglycemia. This review summarizes key findings from basic and clinical studies regarding mTOR's roles in regulating bone formation, bone resorption, inflammatory responses, and bone vascularity in hyperglycemia. It also provides valuable insights into future research directions aimed at developing mTOR-targeted therapies for combating diabetic bone diseases.

A masked, placebo-controlled, randomized clinical trial evaluating safety and the effect on cardiac function of low-dose rapamycin in 17 healthy client-owned dogs

Introduction

Geroscience studies of low-dose rapamycin in laboratory species have identified numerous benefits, including reversing age-related cardiac dysfunction. Cardiovascular benefits have been observed in dogs with 10 weeks of treatment, raising questions about possible benefits and adverse effects of long-term use of low-dose rapamycin. The objectives of this study were to assess the impact of 6 months of low-dose rapamycin on echocardiographic indices of cardiac function in healthy dogs and to document the occurrence of adverse events.

Methods

Seventeen client-owned dogs aged 6-10 years, weighing 18-36 kg, and without significant systemic disease were included in a prospective, randomized, placebo-controlled, masked clinical trial. Low-dose rapamycin (0.025 mg/kg) or placebo was administered three times per week for 6 months. Baseline, 6-month, and 12-month evaluation included physical examination, cardiology examination, and clinicopathology. Three-month evaluation included physical examination and clinicopathology. Owners completed online questionnaires every 2 weeks.

Results

There were no statistically significant differences in echocardiographic parameters between rapamycin and placebo groups at 6 or 12 months. No clinically significant adverse events occurred. In 26.8% of the bi-weekly surveys owners whose dogs received rapamycin reported perceived positive changes in behavior or health, compared to 8.1% in the placebo group (p = 0.04).

Discussion

While no clinically significant change in cardiac function was observed in dogs treated with low-dose rapamycin, the drug was well-tolerated with no significant adverse events.

mTOR-inhibitors and post-transplant diabetes mellitus: a link still debated in kidney transplantation

The mammalian target of rapamycin inhibitors (mTOR-Is, Sirolimus, and Everolimus) are immunosuppressive drugs widely employed in kidney transplantation. Their main mechanism of action includes the inhibition of a serine/threonine kinase with a pivotal role in cellular metabolism and in various eukaryotic biological functions (including proteins and lipids synthesis, autophagy, cell survival, cytoskeleton organization, lipogenesis, and gluconeogenesis). Moreover, as well described, the inhibition of the mTOR pathway may also contribute to the development of the post-transplant diabetes mellitus (PTDM), a major clinical complication that may dramatically impact allograft survival (by accelerating the development of the chronic allograft damage) and increase the risk of severe systemic comorbidities. Several factors may contribute to this condition, but the reduction of the beta-cell mass, the impairment of the insulin secretion and resistance, and the induction of glucose intolerance may play a pivotal role. However, although the results of several in vitro and in animal models, the real impact of mTOR-Is on PTDM is still debated and the entire biological machinery is poorly recognized. Therefore, to better elucidate the impact of the mTOR-Is on the risk of PTDM in kidney transplant recipients and to potentially uncover future research topics (particularly for the clinical translational research), we decided to review the available literature evidence regarding this important clinical association. In our opinion, based on the published reports, we cannot draw any conclusion and PTDM remains a challenge. However, also in this case, the administration of the lowest possible dose of mTOR-I should also be recommended.

The Challenges of Treating Patients with Breast Cancer and Obesity

Obesity is defined as a body mass index (BMI) of 30 kg/m2 or more and is associated with worse outcomes in patients with breast cancer, resulting in an increased incidence of breast cancer, recurrence, and death. The incidence of obesity is increasing, with almost half of all individuals in the United States classified as obese. Patients with obesity present with unique pharmacokinetics and physiology and are at increased risk of developing diabetes mellitus and cardiovascular disease, which leads to specific challenges when treating these patients. The aim of this review is to summarize the impact of obesity on the efficacy and toxicity of systemic therapies used for breast cancer patients, describe the molecular mechanisms through which obesity can affect systemic therapies, outline the existing American Society of Clinical Oncology (ASCO) guidelines for treating patients with cancer and obesity, and highlight additional clinical considerations for treating patients with obesity and breast cancer. We conclude that further research on the biological mechanisms underlying the obesity-breast cancer link may offer new treatment strategies, and clinicals trials that focus on the treatment and outcomes of patients with obesity and all stages of breast cancer are needed to inform future treatment guidelines.

mTORC1 inhibition uncouples lipolysis and thermogenesis in white adipose tissue to contribute to alcoholic liver disease

BACKGROUND

Adipose tissue thermogenic activities use fatty acids from lipolysis for heat generation. Therefore, a tight coupling between lipolysis and thermogenesis is physiologically imperative in maintaining not only body temperature but also lipids homeostasis. Adipose tissue dysfunction contributes to alcoholic liver disease (ALD). Here, studies were conducted to examine how alcohol intake affects adipose tissue thermogenic activities and whether altered adipose tissue thermogenesis contributes to ALD.

METHODS

Both the Lieber-DeCarli and the NIAAA mouse models of ALD were used. Denervation surgery in epididymal fat pads was performed. CL316,243, a selective β3-adrenoceptor agonist, SR59230A, a selective β3 adrenoceptor (ADRB3) antagonist, and rapamycin, a selective mechanistic target of rapamycin complex 1 (mTORC1) inhibitor, were administrated through i.p. injection. Adipocyte-specific Prdm16 knockout mice were subjected to alcohol-containing diet chronically.

RESULTS

Chronic alcohol consumption, which enhances adipose tissue lipolysis, inhibits thermogenic activities of beige adipocytes in inguinal white adipose tissue (WAT), leading to an uncoupling status between lipolysis and thermogenesis in WAT at both basal and ADRB3 stimulation states. CL316,243 administration exacerbates liver pathologies of ALD. Alcohol intake inhibits mTORC1 activities in WAT. In mice, mTORC1 inhibition by rapamycin inhibits the thermogenesis of iWAT, whereas enhancing WAT lipolysis. Further investigations using adipocyte-specific Prdm16 knockout mice revealed that functional deficiency of beige adipocytes aggravates liver pathologies of ALD, suggesting that the inhibitory effect of alcohol on WAT browning/thermogenesis contributes to ALD pathogenesis.

CONCLUSION

Chronic alcohol consumption induces an "uncoupling status" between lipolysis and browning/thermogenesis in WAT by inhibiting mTORC1 activation. Diminished WAT browning/thermogenesis, concomitant with enhanced lipolysis, contributes to ALD pathogenesis.

Effect of sirolimus on insulin dynamics in horses

BACKGROUND

Sirolimus, a mechanistic target of rapamycin inhibitor, suppresses insulin production in other species and has therapeutic potential for hyperinsulinemia in horses.

HYPOTHESIS/OBJECTIVE

Determine the pharmacokinetics (PKs) of sirolimus and evaluate its effect on insulin dynamics in healthy and insulin dysregulation (ID) horses.

ANIMALS

Eight Standardbred geldings.

METHODS

A PK study was performed followed by a placebo-controlled, randomized, crossover study. Blood sirolimus concentrations were measured by liquid chromatography-mass-spectrometry. PK indices were estimated by fitting a 2-compartment model using nonlinear least squares regression. An oral glucose test (OGT) was conducted before and 4, 24, 72, and 144 hours after administration of sirolimus or placebo. Effects of time, treatment and animal on blood glucose and insulin concentrations were analyzed using mixed-effects linear regression. Sirolimus was then administered to 4 horses with dexamethasone-induced ID and an OGT was performed at baseline, after ID induction and after 7 days of treatment.

RESULTS

Median (range) maximum sirolimus concentration was 277.0 (247.5-316.06) ng/mL at 5 (5-10) min and half-life was 3552 (3248-4767) min. Mean (range) oral bioavailability was 9.5 (6.8-12.4)%. Sirolimus had a significant effect on insulin concentration 24 hours after a single dose: median (interquartile range) insulin at 60 min (5.0 [3.7-7.0] μIU/mL) was 37 (-5 to 54)% less than placebo (8.7 [5.8-13.7] μIU/mL, P = .03); and at 120 min (10.2 [8.4-12.2] μIU/mL) was 28 (-15 to 53)% less than placebo (14.9 [8.4-24.8] μIU/mL, P = .02). There was minimal effect on glucose concentration. Insulin responses decreased toward baseline in ID horses after 7 days of treatment.

CONCLUSION AND CLINICAL IMPORTANCE

Sirolimus decreased the insulinemic response to glucose and warrants further investigation.

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.

Effect of Sirolimus/Metformin Co-Treatment on Hyperglycemia and Cellular Respiration in BALB/c Mice

Sirolimus (SRL) is widely used as an immunosuppressant to prevent graft rejection, despite the risk of impairing glucose metabolism. Metformin (MET) can reduce the detrimental effects of SRL in many patients, including diabetes and renal transplant recipients. Limited in vivo studies have reported on SRL and MET therapy, particularly in relation to cellular bioenergetics, glucose metabolism, and insulin resistance. Herein, we investigated the efficacy of SRL and MET co-treatment in BALB/c mice over 4 weeks. Balb/c mice (4-6 weeks old) were divided into four groups and injected intraperitoneally (i.p.) with water (control, CTRL), MET (200 µg/g), SRL (5 µg/g), or MET (200 µg/g) +SRL (5 µg/g) over a period of one month. We evaluated the body weight, food consumption rate, random blood glucose (BG), insulin levels, serum biochemistry parameters (ALT, Albumin, BUN, Creatinine), and histomorphology in all groups using standardized techniques and assays. All drug-treated groups showed a statistically significant decrease in weight gain compared to the CTRL group, despite normal food intake. Treatment with SRL caused elevated BG and insulin levels, which were restored with SRL + MET combination. Serum biochemical parameters were within the normal range in all the studied groups. SRL+ MET co-treatment decreased liver cellular respiration and increased cellular ATP levels in the liver. In the pancreas, co-treatment resulted in increased cellular respiration and decreased cellular ATP levels. Liver and pancreatic histology were unchanged in all groups. This study showed that co-treatment of SRL with MET alleviates hyperglycemia induced by SRL without any deleterious effects. These results provide initial insights into the potential use of SRL + MET therapy in various settings.

Rapamycin suppresses inflammation and increases the interaction between p65 and IκBα in rapamycin-induced fatty livers

Rapamycin treatment significantly increases lifespan and ameliorates several aging-related diseases in mice, making it a potential anti-aging drug. However, there are several obvious side effects of rapamycin, which may limit the broad applications of this drug. Lipid metabolism disorders such as fatty liver and hyperlipidemia are some of those unwanted side effects. Fatty liver is characterized as ectopic lipid accumulation in livers, which is usually accompanied by increased inflammation levels. Rapamycin is also a well-known anti-inflammation chemical. How rapamycin affects the inflammation level in rapamycin-induced fatty liver remains poorly understood. Here, we show that eight-day rapamycin treatment induced fatty liver and increased liver free fatty acid levels in mice, while the expression levels of inflammatory markers are even lower than those in the control mice. Mechanistically, the upstream of the pro-inflammatory pathway was activated in rapamycin-induced fatty livers, however, there is no increased NFκB nuclear translocation probably because the interaction between p65 and IκBα was enhanced by rapamycin treatment. The lipolysis pathway in the liver is also suppressed by rapamycin. Liver cirrhosis is an adverse consequence of fatty liver, while prolonged rapamycin treatment did not increase liver cirrhosis markers. Our results indicate that although fatty livers are induced by rapamycin, the fatty livers are not accompanied by increased inflammation levels, implying that rapamycin-induced fatty livers might not be as harmful as other types of fatty livers, such as high-fat diet and alcohol-induced fatty livers.

REDD1 promotes obesity-induced metabolic dysfunction via atypical NF-κB activation

Regulated in development and DNA damage response 1 (REDD1) expression is upregulated in response to metabolic imbalance and obesity. However, its role in obesity-associated complications is unclear. Here, we demonstrate that the REDD1-NF-κB axis is crucial for metabolic inflammation and dysregulation. Mice lacking Redd1 in the whole body or adipocytes exhibited restrained diet-induced obesity, inflammation, insulin resistance, and hepatic steatosis. Myeloid Redd1-deficient mice showed similar results, without restrained obesity and hepatic steatosis. Redd1-deficient adipose-derived stem cells lost their potential to differentiate into adipocytes; however, REDD1 overexpression stimulated preadipocyte differentiation and proinflammatory cytokine expression through atypical IKK-independent NF-κB activation by sequestering IκBα from the NF-κB/IκBα complex. REDD1 with mutated Lys^219/220Ala, key amino acid residues for IκBα binding, could not stimulate NF-κB activation, adipogenesis, and inflammation in vitro and prevented obesity-related phenotypes in knock-in mice. The REDD1-atypical NF-κB activation axis is a therapeutic target for obesity, meta-inflammation, and metabolic complications.

Insulin-induced mTOR signaling and gluconeogenesis in renal proximal tubules: A mini-review of current evidence and therapeutic potential

Energy is continuously expended in the body, and gluconeogenesis maintains glucose homeostasis during starvation. Gluconeogenesis occurs in the liver and kidneys. The proximal tubule is the primary location for renal gluconeogenesis, accounting for up to 25% and 60% of endogenous glucose production during fasting and after a meal, respectively. The mechanistic target of rapamycin (mTOR), which exists downstream of the insulin pathway, plays an important role in regulating proximal tubular gluconeogenesis. mTOR is an atypical serine/threonine kinase present in two complexes. mTORC1 phosphorylates substrates that enhance anabolic processes such as mRNA translation and lipid synthesis and catabolic processes such as autophagy. mTORC2 regulates cytoskeletal dynamics and controls ion transport and proliferation via phosphorylation of SGK1. Therefore, mTOR signaling defects have been implicated in various pathological conditions, including cancer, cardiovascular disease, and diabetes. However, concrete elucidations of the associated mechanisms are still unclear. This review provides an overview of mTOR and describes the relationship between mTOR and renal.

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

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

Tissue-restricted inhibition of mTOR using chemical genetics

Mammalian target of rapamycin (mTOR) is a highly conserved eukaryotic protein kinase that coordinates cell growth and metabolism, and plays a critical role in cancer, immunity, and aging. It remains unclear how mTOR signaling in individual tissues contributes to whole-organism processes because mTOR inhibitors, like the natural product rapamycin, are administered systemically and target multiple tissues simultaneously. We developed a chemical-genetic system, termed selecTOR, that restricts the activity of a rapamycin analog to specific cell populations through targeted expression of a mutant FKBP12 protein. This analog has reduced affinity for its obligate binding partner FKBP12, which reduces its ability to inhibit mTOR in wild-type cells and tissues. Expression of the mutant FKBP12, which contains an expanded binding pocket, rescues the activity of this rapamycin analog. Using this system, we show that selective mTOR inhibition can be achieved in Saccharomyces cerevisiae and human cells, and we validate the utility of our system in an intact metazoan model organism by identifying the tissues responsible for a rapamycin-induced developmental delay in Drosophila.

Rapamycin treatment during development extends life span and health span of male mice and Daphnia magna

Development is tightly connected to aging, but whether pharmacologically targeting development can extend life remains unknown. Here, we subjected genetically diverse UMHET3 mice to rapamycin for the first 45 days of life. The mice grew slower and remained smaller than controls for their entire lives. Their reproductive age was delayed without affecting offspring numbers. The treatment was sufficient to extend the median life span by 10%, with the strongest effect in males, and helped to preserve health as measured by frailty index scores, gait speed, and glucose and insulin tolerance tests. Mechanistically, the liver transcriptome and epigenome of treated mice were younger at the completion of treatment. Analogous to mice, rapamycin exposure during development robustly extended the life span of Daphnia magna and reduced its body size. Overall, the results demonstrate that short-term rapamycin treatment during development is a novel longevity intervention that acts by slowing down development and aging, suggesting that aging may be targeted already early in life.

Haematological Drugs Affecting Lipid Metabolism and Vascular Health

Many drugs affect lipid metabolism and have side effects which promote atherosclerosis. The prevalence of cancer-therapy-related cardiovascular (CV) disease is increasing due to development of new drugs and improved survival of patients: cardio-oncology is a new field of interest and research. Moreover, drugs used in transplanted patients frequently have metabolic implications. Increasingly, internists, lipidologists, and angiologists are being consulted by haematologists for side effects on metabolism (especially lipid metabolism) and arterial circulation caused by drugs used in haematology. The purpose of this article is to review the main drugs used in haematology with side effects on lipid metabolism and atherosclerosis, detailing their mechanisms of action and suggesting the most effective therapies.

Modulation of mTOR Signaling in Cardiovascular Disease to Target Acute and Chronic Inflammation

Inflammation is a key component in the pathogenesis of cardiovascular diseases causing a significant burden of morbidity and mortality worldwide. Recent research shows that mammalian target of rapamycin (mTOR) signaling plays an important role in the general and inflammation-driven mechanisms that underpin cardiovascular disease. mTOR kinase acts prominently in signaling pathways that govern essential cellular activities including growth, proliferation, motility, energy consumption, and survival. Since the development of drugs targeting mTOR, there is proven efficacy in terms of survival benefit in cancer and allograft rejection. This review presents current information and concepts of mTOR activity in myocardial infarction and atherosclerosis, two important instances of cardiovascular illness involving acute and chronic inflammation. In experimental models, inhibition of mTOR signaling reduces myocardial infarct size, enhances functional remodeling, and lowers the overall burden of atheroma. Aside from the well-known effects of mTOR inhibition, which are suppression of growth and general metabolic activity, mTOR also impacts on specific leukocyte subpopulations and inflammatory processes. Inflammatory cell abundance is decreased due to lower migratory capacity, decreased production of chemoattractants and cytokines, and attenuated proliferation. In contrast to the generally suppressed growth signals, anti-inflammatory cell types such as regulatory T cells and reparative macrophages are enriched and activated, promoting resolution of inflammation and tissue regeneration. Nonetheless, given its involvement in the control of major cellular pathways and the maintenance of a functional immune response, modification of this system necessitates a balanced and time-limited approach. Overall, this review will focus on the advancements, prospects, and limits of regulating mTOR signaling in cardiovascular disease.

Oncoprotein DJ-1 interacts with mTOR complexes to effect transcription factor Hif1α-dependent expression of collagen I (α2) during renal fibrosis

Proximal tubular epithelial cells respond to transforming growth factor β (TGFβ) to synthesize collagen I (α2) during renal fibrosis. The oncoprotein DJ-1 has previously been shown to promote tumorigenesis and prevent apoptosis of dopaminergic neurons; however, its role in fibrosis signaling is unclear. Here, we show TGFβ-stimulation increased expression of DJ-1, which promoted noncanonical mTORC1 and mTORC2 activities. We show DJ-1 augmented the phosphorylation/activation of PKCβII, a direct substrate of mTORC2. In addition, coimmunoprecipitation experiments revealed association of DJ-1 with Raptor and Rictor, exclusive subunits of mTORC1 and mTORC2, respectively, as well as with mTOR kinase. Interestingly, siRNAs against DJ-1 blocked TGFβ-stimulated expression of collagen I (α2), while expression of DJ-1 increased expression of this protein. In addition, expression of dominant negative PKCβII and siRNAs against PKCβII significantly inhibited TGFβ-induced collagen I (α2) expression. In fact, constitutively active PKCβII abrogated the effect of siRNAs against DJ-1, suggesting a role of PKCβII downstream of this oncoprotein. Moreover, we demonstrate expression of collagen I (α2) stimulated by DJ-1 and its target PKCβII is dependent on the transcription factor hypoxia-inducible factor 1α (Hif1α). Finally, we show in the renal cortex of diabetic rats that increased TGFβ was associated with enhanced expression of DJ-1 and activation of mTOR and PKCβII, concomitant with increased Hif1α and collagen I (α2). Overall, we identified that DJ-1 affects TGFβ-induced expression of collagen I (α2) via an mTOR-, PKCβII-, and Hif1α-dependent mechanism to regulate renal fibrosis.

eIF4A1 Inhibitor Suppresses Hyperactive mTOR-Associated Tumors by Inducing Necroptosis and G2/M Arrest

Aberrantly activated mechanistic target of rapamycin (mTOR) signaling pathway stimulates translation initiation/protein synthesis and eventually causes tumors. Targeting these processes thus holds potential for treating mTOR-associated diseases. We tested the potential of eFT226, a sequence-selective inhibitor of eIF4A-mediated translation, in the treatment of mTOR hyperactive cells caused by the deletion of tuberous sclerosis complex 1/2 (TSC1/2) or phosphatase and TENsin homology (PTEN). eFT226 preferentially inhibited the proliferation of Tsc2- and Pten-deficient cells by inducing necroptosis and G2/M phase arrest. In addition, eFT226 blocked the development of TSC2-deficient tumors. The translation initiation inhibitor is thus a promising regimen for the treatment of hyperactive mTOR-mediated tumors.

Sirolimus or Everolimus Improves Survival After Liver Transplantation for Hepatocellular Carcinoma: A Systematic Review and Meta-Analysis

The effects of mammalian target of rapamycin (mTOR) inhibitors (sirolimus [SRL] and everolimus [EVL]) on survival in liver transplantation (LT) recipients with hepatocellular carcinoma (HCC) remain the subject of intense research. Therefore, we performed this systematic review and meta-analysis to investigate the potential survival benefits of mTOR inhibitors (mTORis). Embase, PubMed, and Cochrane Central Register of Controlled Trials (CENTRAL) were searched for all randomized controlled trials (RCTs) and cohort studies investigating effects of SRL or EVL on LT recipients for HCC. The primary outcomes were 1-, 2-, 3-, and 5-year overall survival (OS), and the secondary outcomes were 1-, 2-, and 3-year recurrence-free survival (RFS) and adverse effects. Pooled relative risks (RRs) with 95% confidence interval (CI) were calculated by a fixed or random effects model with Mantel-Haenszel weighting. Subgroup analyses were performed according to crucial clinical characteristics. We also conducted sensitivity analyses to assess the reliability of our findings. A total of 17 studies were included. OS was improved in both RCTs (1 year: RR, 1.04; 95% CI, 1.00-1.08; 2 years: RR, 1.09; 95% CI, 1.02-1.16; 3 years: RR, 1.13; 95% CI, 1.04-1.24; 5 years: RR, 1.13; 95% CI, 1.02-1.26) and cohort studies (1 year: RR, 1.13; 95% CI, 1.06-1.20; 2 years: RR, 1.24; 95% CI, 1.16-1.32; 3 years: RR, 1.24; 95% CI, 1.15-1.34; 5 years: RR, 1.17; 95% CI, 1.10-1.24), with a lower risk of renal toxicity (RR, 0.75; 95% CI, 0.60 to 0.93). The 1-, 2-, and 3-year RFS were also improved. Current evidence indicates that SRL- or EVL-based immunosuppression improves OS and RFS with a lower risk of renal toxicity compared with mTORi-free immunosuppression. Nevertheless, results must be interpreted with caution.

Targeting mTOR in the Context of Diet and Whole-body Metabolism

The mechanistic target of the rapamycin (mTOR) signaling pathway is the central regulator of cell growth and proliferation by integrating growth factor and nutrient availability. Under healthy physiological conditions, this process is tightly coordinated and essential to maintain whole-body homeostasis. Not surprisingly, dysregulated mTOR signaling underpins several diseases with increasing incidence worldwide, including obesity, diabetes, and cancer. Consequently, there is significant clinical interest in developing therapeutic strategies that effectively target this pathway. The transition of mTOR inhibitors from the bench to bedside, however, has largely been marked with challenges and shortcomings, such as the development of therapy resistance and adverse side effects in patients. In this review, we discuss the current status of first-, second-, and third-generation mTOR inhibitors as a cancer therapy in both preclinical and clinical settings, with a particular emphasis on the mechanisms of drug resistance. We focus especially on the emerging role of diet as an important environmental determinant of therapy response, and posit a conceptual framework that links nutrient availability and whole-body metabolic states such as obesity with many of the previously defined processes that drive resistance to mTOR-targeted therapies. Given the role of mTOR as a central integrator of cell metabolism and function, we propose that modulating nutrient inputs through dietary interventions may influence the signaling dynamics of this pathway and compensatory nodes. In doing so, new opportunities for exploiting diet/drug synergies are highlighted that may unlock the therapeutic potential of mTOR inhibitors as a cancer treatment.

Distinct and additive effects of calorie restriction and rapamycin in aging skeletal muscle

Preserving skeletal muscle function is essential to maintain life quality at high age. Calorie restriction (CR) potently extends health and lifespan, but is largely unachievable in humans, making “CR mimetics” of great interest. CR targets nutrient-sensing pathways centering on mTORC1. The mTORC1 inhibitor, rapamycin, is considered a potential CR mimetic and is proven to counteract age-related muscle loss. Therefore, we tested whether rapamycin acts via similar mechanisms as CR to slow muscle aging. Here we show that long-term CR and rapamycin unexpectedly display distinct gene expression profiles in geriatric mouse skeletal muscle, despite both benefiting aging muscles. Furthermore, CR improves muscle integrity in mice with nutrient-insensitive, sustained muscle mTORC1 activity and rapamycin provides additive benefits to CR in naturally aging mouse muscles. We conclude that rapamycin and CR exert distinct, compounding effects in aging skeletal muscle, thus opening the possibility of parallel interventions to counteract muscle aging.

The anti-aging intervention calorie restriction (CR) is thought to act via the nutrient-sensing multiprotein complex mTORC1. Here the authors show that the mTORC1-inhibitor rapamycin and CR use largely distinct mechanisms to slow mouse muscle aging.