Sirolimus Modifies Cholesterol Homeostasis in Hepatic Cells: A Potential Molecular Mechanism for Sirolimus-Associated Dyslipidemia

Effects of CYP3A5 Genetic Polymorphisms on the Weight-adjusted through Concentration of Sirolimus in Renal Transplant Recipients: A Systematic Review and Meta-analysis

BACKGROUND

Sirolimus, one of the immunosuppressive drugs administered to renal transplant recipients, is metabolized by cytochrome P450 (CYP) 3A5. Accordingly, CYP3A5 polymorphism is a genetic factor affecting sirolimus pharmacokinetics (PK). Therefore, we conducted a systematic review and meta-analysis on the association between sirolimus PK and CYP3A5*3 polymorphism.

METHODS

We searched for studies published up to 13 June 2024 from PubMed, Embase, Cochrane Library, and Web of Science. We reviewed studies on the relationship between CYP3A5*3 polymorphism and weightadjusted trough concentration/dose (C0 /D) ratio and dosage of sirolimus in renal transplant recipients, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We evaluated mean differences (MDs) and 95% confidence intervals (CIs).

RESULTS

A total of seven studies were included. The weight-adjusted C0 /D ratio of sirolimus was significantly higher in patients with the CYP3A5*3/*3 rather than CYP3A5*1/*1 or CYP3A5*1/*3 genotype (MD 95.27 ng/mL per mg/kg; 95% CI: 58.06, 132.47; I2 = 74%; p < 0.00001). Also, the weight-adjusted dosage of sirolimus was significantly lower in patients with the CYP3A5*3/*3 rather than CYP3A5*1/*1 or CYP3A5*1/*3 genotype (MD -2.60 × 10-3 mg/kg; 95% CI: -4.52, -0.69; I2 = 44%; p = 0.008).

CONCLUSION

Our meta-analysis showed a significant effect for the CYP3A5*3 genotype on weight-adjusted C0 /D ratio and dosage of sirolimus in adult renal transplant recipients.

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.

Inhibition of mTOR improves malnutrition induced hepatic metabolic dysfunction

Severe malnutrition accounts for half-a-million deaths annually in children under the age of five. Despite improved WHO guidelines, inpatient mortality remains high and is associated with metabolic dysfunction. Previous studies suggest a correlation between hepatic metabolic dysfunction and impaired autophagy. We aimed to determine the role of mTORC1 inhibition in a murine model of malnutrition-induced hepatic dysfunction. Wild type weanling C57/B6 mice were fed a 18 or 1% protein diet for two weeks. A third low-protein group received daily rapamycin injections, an mTORC1 inhibitor. Hepatic metabolic function was assessed by histology, immunofluorescence, gene expression, metabolomics and protein levels. Low protein-fed mice manifested characteristics of severe malnutrition, including weight loss, hypoalbuminemia, hypoglycemia, hepatic steatosis and cholestasis. Low protein-fed mice had fewer mitochondria and showed signs of impaired mitochondrial function. Rapamycin prevented hepatic steatosis, restored ATP levels and fasted plasma glucose levels compared to untreated mice. This correlated with increased content of LC3-II, and decreased content mitochondrial damage marker, PINK1. We demonstrate that hepatic steatosis and disturbed mitochondrial function in a murine model of severe malnutrition can be partially prevented through inhibition of mTORC1. These findings suggest that stimulation of autophagy could be a novel approach to improve metabolic function in severely malnourished children.

Post-Transplantation Diabetes Mellitus

Solid organ transplantation (SOT) is an established therapeutic option for chronic disease resulting from end-stage organ dysfunction. Long-term use of immunosuppression is associated with post-transplantation diabetes mellitus (PTDM), placing patients at increased risk of infections, cardiovascular disease and mortality. The incidence rates for PTDM have varied from 10 to 40% between different studies. Diagnostic criteria have evolved over the years, as a greater understating of PTDM has been reached. There are differences in pathophysiology and clinical course of type 2 diabetes and PTDM. Hence, managing this condition can be a challenge for a diabetes physician, as there are several factors to consider when tailoring therapy for post-transplant patients to achieve better glycaemic as well as long-term transplant outcomes. This article is a detailed review of PTDM, examining the pathogenesis, diagnostic criteria and management in light of the current evidence. The therapeutic options are discussed in the context of their safety and potential drug-drug interactions with immunosuppressive agents.

Expert opinion on the metabolic complications of mTOR inhibitors

Using mTOR inhibitors (mTORi) as anticancer drugs led to hyperglycemia (12-50%) and hyperlipidemia (7-73%) in phase-III trials. These high rates require adapted treatment in cancer patients. Before initiating mTORi treatment, lipid profile screening should be systematic, with fasting glucose assay in non-diabetic patients and HbA_1C in diabetic patients. After initiation, lipid profile monitoring should be systematic, with fasting glucose assay in non-diabetic patients, every 2 weeks for the first month and then monthly. The HbA_1C target is≤8%, before and after treatment initiation in known diabetic patients and in case of onset of diabetes under mTORi. LDL-cholesterol targets should be adapted to general health status and cardiovascular and oncologic prognosis. If treatment is indicated, pravastatin should be prescribed in first line; atorvastatin and simvastatin are contraindicated. Fenofibrate should be prescribed for hypertriglyceridemia>5g/l resisting dietary measures adapted to oncologic status. In non-controllable hypertriglyceridemia exceeding 10g/l, mTORi treatment should be interrupted and specialist opinion should be sought.

Shunts, channels and lipoprotein endosomal traffic: a new model of cholesterol homeostasis in the hepatocyte

The liver directs cholesterol metabolism in the organism. All the major fluxes of cholesterol within the body involve the liver: dietary cholesterol is directed to the liver; cholesterol from peripheral cells goes to the liver; the liver is a major site of cholesterol synthesis for the organism; cholesterol is secreted from the liver within the bile, within apoB lipoproteins and translocated to nascent HDL. The conventional model of cholesterol homeostasis posits that cholesterol from any source enters a common, rapidly exchangeable pool within the cell, which is in equilibrium with a regulatory pool. Increased influx of cholesterol leads rapidly to decreased synthesis of cholesterol. This model was developed based on in vitro studies in the fibroblast and validated only for LDL particles. The challenges the liver must meet in vivo to achieve cholesterol homeostasis are far more complex. Our model posits that the cholesterol derived from three different lipoproteins endosomes has three different fates: LDL-derived cholesterol is largely recycled within VLDL with most of the cholesterol shunted through the hepatocyte without entering the exchangeable pool of cholesterol; high density lipoprotein-derived CE is transcytosed into bile; and chylomicron remnant-derived cholesterol primarily enters the regulatory pool within the hepatocyte. These endosomal channels represent distinct physiological pathways and hepatic homeostasis represents the net result of the outcomes of these distinct channels. Our model takes into account the distinct physiological challenges the hepatocyte must meet, underlie the pathophysiology of many of the apoB dyslipoproteinemias and account for the sustained effectiveness of therapeutic agents such as statins.

Everolimus treatment among patients with tuberous sclerosis affects serum lipid profile

BACKGROUND

The purpose of the study was to evaluate lipid homeostasis before and after treatment of everolimus, the mammalian target of the rapamycin (mTOR) inhibitor, among patients with tuberous sclerosis complex (TSC).

METHODS

The study group consisted of 15 patients with a diagnosis of subependymal giant cell astrocytoma (SEGA) related to TSC. The following lipid parameters were determined: total serum cholesterol (TCh), low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), total serum triglyceride (TG) concentration at baseline, then after three and 12 months of observation. The values were compared with those of age-matched healthy controls.

RESULTS

In the study group TCh, LDL and HDL levels at baseline were significantly higher than in the control group. TCh and LDL levels were positively correlated with baseline SDS-BMI in TSC patients. Everolimus treatment resulted in significant increases of TCh (from 192.04±40.51mg/dl to 210.74±51.12mg/dl and to 216.69±45.43mg/dl; p=0.0273) and LDL (from 113.21±38.72mg/dl to 133.88±50.71mg/dl and to 141.58±40.67mg/dl; p=0.0006) after three and 12 months respectively. The differences between the TCh and LDL levels at baseline and after 12 months of therapy were negatively correlated with baseline SDS-BMI. The observed increase of BMI after 12 months was correlated with increases in TCh and LDL levels.

CONCLUSIONS

Patients with TSC have disrupted lipid homeostasis before and during treatment with everolimus, which might be partially connected to the mTOR-dependent nutritional status of the patients. There is a need to develop strategies for children with TSC treated with everolimus, who experience hyperlipidemia.

Adipose tissue mTORC2 regulates ChREBP-driven de novo lipogenesis and hepatic glucose metabolism

Adipose tissue de novo lipogenesis (DNL) positively influences insulin sensitivity, is reduced in obesity, and predicts insulin resistance. Therefore, elucidating mechanisms controlling adipose tissue DNL could lead to therapies for type 2 diabetes. Here, we report that mechanistic target of rapamycin complex 2 (mTORC2) functions in white adipose tissue (WAT) to control expression of the lipogenic transcription factor ChREBPβ. Conditionally deleting the essential mTORC2 subunit Rictor in mature adipocytes decreases ChREBPβ expression, which reduces DNL in WAT, and impairs hepatic insulin sensitivity. Mechanistically, Rictor/mTORC2 promotes ChREBPβ expression in part by controlling glucose uptake, but without impairing pan-AKT signalling. High-fat diet also rapidly decreases adipose tissue ChREBPβ expression and insulin sensitivity in wild-type mice, and does not further exacerbate insulin resistance in adipose tissue Rictor knockout mice, implicating adipose tissue DNL as an early target in diet-induced insulin resistance. These data suggest mTORC2 functions in WAT as part of an extra-hepatic nutrient-sensing mechanism to control glucose homeostasis.

The kinase mTOR controls anabolic metabolism. Here, the authors create fat-specific mTORC2 knockout mice using the Adiponectin-Cre driver and show mTORC2 signalling is important for systemic metabolic homeostasis by controlling adipocyte de novo lipogenesis and glucose uptake.

Dysregulation of the Low-Density Lipoprotein Receptor Pathway Is Involved in Lipid Disorder-Mediated Organ Injury

The low-density lipoprotein receptor (LDLR) pathway is a negative feedback system that plays important roles in the regulation of plasma and intracellular cholesterol homeostasis. To maintain a cholesterol homeostasis, LDLR expression is tightly regulated by sterol regulatory element-binding protein-2 (SREBP-2) and SREBP cleavage-activating protein (SCAP) in transcriptional level and by proprotein convertase subtilisin/kexin type 9 (PCSK9) in posttranscriptional level. The dysregulation of LDLR expression results in abnormal lipid accumulation in cells and tissues, such as vascular smooth muscle cells, hepatic cells, renal mesangial cells, renal tubular cells and podocytes. It has been demonstrated that inflammation, renin-angiotensin system (RAS) activation, and hyperglycemia induce the disruption of LDLR pathway, which might contribute to lipid disorder-mediated organ injury (atherosclerosis, non-alcoholic fatty liver disease, kidney fibrosis, etc). The mammalian target of rapamycin (mTOR) pathway is a critical mediator in the disruption of LDLR pathway caused by pathogenic factors. The mTOR complex1 activation upregulates LDLR expression at the transcriptional and posttranscriptional levels, consequently resulting in lipid deposition. This paper mainly reviews the mechanisms for the dysregulation of LDLR pathway and its roles in lipid disorder-mediated organ injury under various pathogenic conditions. Understanding these mechanisms leading to the abnormality of LDLR expression contributes to find potential new drug targets in lipid disorder-mediated diseases.

Inflammatory stress exacerbates lipid accumulation and podocyte injuries in diabetic nephropathy

AIMS

Diabetic nephropathy (DN) is a chronic inflammatory disease that is accompanied by different degrees of lipid disorders. The present study was conducted to determine whether inflammatory stress exacerbates lipid accumulation in podocytes and to investigate its underlying mechanisms in DN using in vitro and in vivo studies.

METHODS

We used IL-1β stimulation in podocytes in vitro and casein injections in db/db mice in vivo to induce inflammatory stress. The plasma levels of serum inflammatory cytokines were determined using an enzyme-linked immunosorbent assay. The renal pathology was evaluated using pathological staining and electron microscopy. Intracellular lipid accumulation was evaluated by Oil Red O staining and a cholesterol quantitative assay. The gene and protein expression levels of extracellular matrix proteins, biomarkers of podocyte injury, and molecules involved in the LDLr pathway were evaluated using immunofluorescence staining, real-time PCR, and western blot analysis.

RESULTS

Increased plasma levels of inflammatory cytokines in the casein-injected db/db mice indicated a successful induction of the inflamed DN model. The kidney morphological changes, podocyte injury, and epithelial mesenchymal transition (EMT) were more significant in casein-injected db/db mice. Moreover, inflammation increased the lipid droplet accumulation in the kidneys of db/db mice, which resulted from the increased protein expression levels of LDLr, sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP), and SREBP-2 in the kidneys of db/db mice. The in vitro studies further demonstrated that inflammation increased the lipid accumulation in the podocytes and induced podocyte EMT, which were correlated with inflammation-mediated increases in the expression levels of LDLr, SCAP, and SREBP-2, and increased translocation of the SCAP/SREBP-2 complex from the endoplasmic reticulum to the Golgi in the podocytes.

CONCLUSION

Inflammation induced lipid accumulation and the EMT of podocytes through the dysregulation of the LDLr pathway, which contributed to podocyte injury and accelerated the progression of DN.

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.

Activation of mTORC1 disrupted LDL receptor pathway: a potential new mechanism for the progression of non-alcoholic fatty liver disease

Our previous studies demonstrated that inflammation exacerbates the progression of non-alcoholic fatty liver disease (NAFLD) by disrupting cholesterol homeostasis. This study aimed to investigate the role of mammalian target of rapamycin complex 1 (mTORC1) in NAFLD under conditions of inflammation. Chronic inflammation was induced by using subcutaneous injections of 10% casein in apolipoprotein E knockout (ApoE KO) mice in vivo and interleukin-1β stimulation of the HepG2 hepatoblastoma cell line in vitro. Results demonstrated that inflammation increased lipid accumulation in HepG2 cells and in livers of apolipoprotein E knockout mice. These effects were correlated with an increase in low density lipoprotein receptor (LDLR) gene transcription, which was mediated through the up-regulation of sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP), SREBP-2, and through enhanced translocation of the SCAP/SREBP-2 complex from endoplasmic reticulum (ER) to Golgi. In addition, our data indicated that inflammation down-regulated the expression of proprotein convertase subtilisin kexin 9 (PCSK9) and prevented the degradation of LDLR protein via posttranscriptional mechanisms. Further analysis showed that inflammation increased the protein phosphorylation of mTOR, eukaryotic initiation factor 4E-binding protein 1, and p70 S6 kinase. Interestingly, blocking mTORC1 activity inhibited the translocation of SCAP/SREBP-2 complex from the ER to the Golgi and decreased the expression of LDLR, SCAP, and SREBP-2. These effects were accompanied by an increase in the expression of PCSK9 and accelerated LDLR degradation. Our findings demonstrated that increased mTORC1 activity exacerbated the progression of NAFLD by disrupting LDLR expression via transcriptional and posttranscriptional mechanisms.

mTOR inhibitors and dyslipidemia in transplant recipients: a cause for concern?

Post-transplant dyslipidemia is exacerbated by mammalian target of rapamycin (mTOR) inhibitors. Early clinical trials of mTOR inhibitors used fixed dosing with no concomitant reduction in calcineurin inhibitor (CNI) exposure, leading to concerns when consistent and marked dyslipidemia was observed. With use of modern concentration-controlled mTOR inhibitor regimens within CNI-free or reduced-exposure CNI regimens, however, the dyslipidemic effect persists but is less pronounced. Typically, total cholesterol levels are at the upper end of normal, or indicate borderline risk, in kidney and liver transplant recipients, and are lower in heart transplant patients under near-universal statin therapy. Of note, it is possible that mTOR inhibitors may offer a cardioprotective effect. Experimental evidence for delayed progression of atherosclerosis is consistent with evidence from heart transplantation that coronary artery intimal thickening and the incidence of cardiac allograft vasculopathy are reduced with everolimus versus cyclosporine therapy. Preliminary data also indicate that mTOR inhibitors may improve arterial stiffness, a predictor of cardiovascular events, and may reduce ventricular remodeling and decrease left ventricular mass through an anti-fibrotic effect. Post-transplant dyslipidemia under mTOR inhibitor therapy should be monitored and managed closely, but unless unresponsive to therapy should not be regarded as a barrier to its use.

Inflammatory stress increases hepatic CD36 translational efficiency via activation of the mTOR signalling pathway

Inflammatory stress is an independent risk factor for the development of non-alcoholic fatty liver disease (NAFLD). Although CD36 is known to facilitate long-chain fatty acid uptake and contributes to NAFLD progression, the mechanisms that link inflammatory stress to hepatic CD36 expression and steatosis remain unclear. As the mammalian target of rapamycin (mTOR) signalling pathway is involved in CD36 translational activation, this study was undertaken to investigate whether inflammatory stress enhances hepatic CD36 expression via mTOR signalling pathway and the underlying mechanisms. To induce inflammatory stress, we used tumour necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) stimulation of the human hepatoblastoma HepG2 cells in vitro and casein injection in C57BL/6J mice in vivo. The data showed that inflammatory stress increased hepatic CD36 protein levels but had no effect on mRNA expression. A protein degradation assay revealed that CD36 protein stability was not different between HepG2 cells treated with or without TNF-α or IL-6. A polysomal analysis indicated that CD36 translational efficiency was significantly increased by inflammatory stress. Additionally, inflammatory stress enhanced the phosphorylation of mTOR and its downstream translational regulators including p70S6K, 4E-BP1 and eIF4E. Rapamycin, an mTOR-specific inhibitor, reduced the phosphorylation of mTOR signalling pathway and decreased the CD36 translational efficiency and protein level even under inflammatory stress resulting in the alleviation of inflammatory stress-induced hepatic lipid accumulation. This study demonstrates that the activation of the mTOR signalling pathway increases hepatic CD36 translational efficiency, resulting in increased CD36 protein expression under inflammatory stress.

Rapamycin and dietary restriction induce metabolically distinctive changes in mouse liver

Dietary restriction (DR) is the gold standard intervention used to delay aging, and much recent research has focused on the identification of possible DR mimetics. Energy sensing pathways, including insulin/IGF1 signaling, sirtuins, and mammalian Target of Rapamycin (mTOR), have been proposed as pathways involved in the antiaging actions of DR, and compounds that affect these pathways have been suggested to act as DR mimetics, including metformin (insulin/IGF1 signaling), resveratrol (sirtuins), and rapamycin (mTOR). Rapamycin is a promising DR mimetic because it significantly increases both health span and life span in mice. Unfortunately, rapamycin also leads to some negative effects, foremost among which is the induction of insulin resistance, potentially limiting its translation into humans. To begin clarifying the mechanism(s) involved in insulin resistance induced by rapamycin, we compared several aspects of liver metabolism in mice treated with DR or rapamycin for 6 months. Our data suggest that although both DR and rapamycin inhibit lipogenesis, activate lipolysis, and increased serum levels of nonesterified fatty acids, only DR further activates β-oxidation of the fatty acids leading to the production of ketone bodies.

Automated Structure-Activity Relationship Mining: Connecting Chemical Structure to Biological Profiles

Understanding the structure-activity relationships (SARs) of small molecules is important for developing probes and novel therapeutic agents in chemical biology and drug discovery. Increasingly, multiplexed small-molecule profiling assays allow simultaneous measurement of many biological response parameters for the same compound (e.g., expression levels for many genes or binding constants against many proteins). Although such methods promise to capture SARs with high granularity, few computational methods are available to support SAR analyses of high-dimensional compound activity profiles. Many of these methods are not generally applicable or reduce the activity space to scalar summary statistics before establishing SARs. In this article, we present a versatile computational method that automatically extracts interpretable SAR rules from high-dimensional profiling data. The rules connect chemical structural features of compounds to patterns in their biological activity profiles. We applied our method to data from novel cell-based gene-expression and imaging assays collected on more than 30,000 small molecules. Based on the rules identified for this data set, we prioritized groups of compounds for further study, including a novel set of putative histone deacetylase inhibitors.

Combined treatment of rapamycin and dietary restriction has a larger effect on the transcriptome and metabolome of liver

Rapamycin (Rapa) and dietary restriction (DR) have consistently been shown to increase lifespan. To investigate whether Rapa and DR affect similar pathways in mice, we compared the effects of feeding mice ad libitum (AL), Rapa, DR, or a combination of Rapa and DR (Rapa + DR) on the transcriptome and metabolome of the liver. The principal component analysis shows that Rapa and DR are distinct groups. Over 2500 genes are significantly changed with either Rapa or DR when compared with mice fed AL; more than 80% are unique to DR or Rapa. A similar observation was made when genes were grouped into pathways; two-thirds of the pathways were uniquely changed by DR or Rapa. The metabolome shows an even greater difference between Rapa and DR; no metabolites in Rapa-treated mice were changed significantly from AL mice, whereas 173 metabolites were changed in the DR mice. Interestingly, the number of genes significantly changed by Rapa + DR when compared with AL is twice as large as the number of genes significantly altered by either DR or Rapa alone. In summary, the global effects of DR or Rapa on the liver are quite different and a combination of Rapa and DR results in alterations in a large number of genes and metabolites that are not significantly changed by either manipulation alone, suggesting that a combination of DR and Rapa would be more effective in extending longevity than either treatment alone.

Endocrine side effects of anti-cancer drugs: effects of anti-cancer targeted therapies on lipid and glucose metabolism

During the past years, targeted therapies for cancer have been developed using drugs that have significant metabolic consequences. Among them, the mammalian target of rapamycin (mTOR) inhibitors and, to a much lesser extent, the tyrosine kinase inhibitors (TKIs) are involved. mTOR plays a key role in the regulation of cell growth as well as lipid and glucose metabolism. Treatment with mTOR inhibitors is associated with a significant increase in plasma triglycerides and LDL cholesterol. mTOR inhibitors seem to increase plasma triglycerides by reducing the activity of the lipoprotein lipase which is in charge of the catabolism of triglyceride-rich lipoproteins. The increase in LDL cholesterol observed with mTOR inhibitors seems to be due to a decrease in LDL catabolism secondary to a reduction of LDL receptor expression. In addition, treatment with mTOR inhibitors is associated with a high incidence of hyperglycemia, ranging from 13 to 50% in the clinical trials. The mechanisms responsible for hyperglycemia with new onset diabetes are not clear, but are likely due to the combination of impaired insulin secretion and insulin resistance. TKIs do not induce hyperlipidemia but alter glucose homeostasis. Treatment with TKIs may be associated either with hyperglycemia or hypoglycemia. The molecular mechanism by which TKIs control glucose homeostasis remains unknown. Owing to the metabolic consequences of these agents used as targeted anti-cancer therapies, a specific and personalized follow-up of blood glucose and lipids is recommended when using mTOR inhibitors and of blood glucose when using TKIs.

Obesity, metabolic syndrome and diabetes mellitus after renal transplantation: prevention and treatment

The prevalence of the metabolic syndrome in dialysis patients is high and further increases after transplantation due to weight gain and the detrimental metabolic effects of immunosuppressive drugs. Corticosteroids cause insulin resistance, hyperlipidemia, abnormal glucose metabolism and arterial hypertension. The calcineurin inhibitor tacrolimus is diabetogenic by inhibiting insulin secretion, whereas cyclosporine causes hypertension and increases cholesterol levels. Mtor antagonists are responsible for hyperlipidemia and abnormal glucose metabolism by mechanisms that also implicate insulin resistance. The metabolic syndrome in transplant recipients has numerous detrimental effects such as increasing the risk of new onset diabetes, cardiovascular disease events and patient death. In addition, it has also been linked with accelerated loss of graft function, proteinuria and ultimately graft loss. Prevention and management of the metabolic syndrome are based on increasing physical activity, promotion of weight loss and control of cardiovascular risk factors. Bariatric surgery before or after renal transplantation in patients with body mass index >35 kg/m(2) is an option but its long term effects on graft and patient survival have not been investigated. Steroid withdrawal and replacement of tacrolimus with cyclosporine facilitate control of diabetes, whereas replacement of cyclosporine and mtor antagonists can improve hyperlipidemia. The new costimulation inhibitor belatacept has potent immunosuppressive properties without metabolic adverse effects and will be an important component of immunosuppressive regimens with better metabolic risk profile. Medical treatment of cardiovascular risk factors has to take potential drug interactions with immunosuppressive medication and drug accumulation due to renal insufficiency into account.

Associations of ABCB1 and IL-10 genetic polymorphisms with sirolimus-induced dyslipidemia in renal transplant recipients

BACKGROUND

Hyperlipidemia is a common adverse effect of sirolimus (SRL). We previously showed significant associations of ABCB1 3435C>T and IL-10 -1082G>A with log-transformed SRL dose-adjusted weighted-normalized trough. We further examined to see whether these polymorphisms were also associated with SRL-induced dyslipidemia.

METHODS

Genotyping was performed for ABCB1 1236C>T, 2677 G>T/A, and 3435C>T; CYP3A4 -392A>G; CYP3A5 6986A>G and 14690G>A; IL-10 -1082G>A; TNF -308G>A; and ApoE ε2, ε3, and ε4 alleles. The longitudinal changes of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and triglyceride (TG) levels after SRL treatment before statin therapy were analyzed by a linear mixed-effects model, with adjustments for selected covariates for each lipid.

RESULTS

Under the dominant genetic model, ABCB1 3435C>T was associated with TC (P=0.0001) and LDL-C (P<0.0001) values after SRL administration. Mean TC and LDL-C levels were 26.9 and 24.9 mg/dL higher, respectively, in ABCB1 3435T carriers than 3435CC homozygotes at an average SRL trough concentration of 4 ng/mL without concomitant medication. ABCB1 1236C>T under the recessive model and IL-10 -1082G>A under the dominant model were associated with log-transformed TG values (P=0.0051 and 0.0436, respectively). Mean TG value was 25.1% higher in ABCB1 1236TT homozygotes compared with ABCB1 1236C carriers and was 12.4% higher in IL-10 -1082AA homozygotes than -1082G carriers.

CONCLUSIONS

ABCB1 polymorphisms were found to be associated with lipid responses to SRL treatment, confirming the role of ABCB1 gene in SRL pharmacokinetics and pharmacodynamics. Further studies are necessary to define the role of ABCB1 and IL-10 polymorphisms on SRL-induced dyslipidemia in renal transplantation.

Lipid metabolism and oxidative stress in children after liver transplantation treated with sirolimus

Lipid disturbances are one of the most frequent side effects of SRL; however, clinical consequences are not known. The aim of the study was to evaluate the risk of AS in children after LTx treated with SRL. In 17 children with median age 13.2 yr (1.9-17.9) who received SRL on average for 4.1 yr (s.d. ± 2.9) we measured and compared with age-matched healthy control group (n = 45) lipid parameters and markers of AS: ADMA, oxyLDL, GSH, GPx, TC, TG, HDL cholesterol, LDL cholesterol, VLDL cholesterol, ApoAI, ApoB, ApoE, lipoprotein (a) (Lp(a)). We found no major differences in cholesterol, cholesterol in lipoprotein fractions and TG concentrations between patients receiving SRL and the control group. ApoE was markedly increased in the study group (19.1 g/L [±1.8]) when compared to controls (9.8 [±3.9]). ApoA1 was decreased in the study group: 1.30 g/L (±0.2) vs. 1.45 (±0.25), p = 0.04. ApoB and Lpa concentrations were similar in both groups. There were differences in oxidative stress markers: GSH 743 (±66.2) mol/mL vs. 780 (±48.2), p = 0.02 and GPx 32.8 (±5.5) U/gHb vs. 34.3(±2.6), p = 0.01. Markers of AS: ADMA did not differ between groups and oxidized LDLc was significantly lower in SRL group: 190 mU/mL (±113) vs. 237 (±107) in control, p < 0.05. SRL does not significantly disturb lipid metabolism and oxidative status in children after LTx.

Regulation of the SREBP transcription factors by mTORC1

In recent years several reports have linked mTORC1 (mammalian target of rapamycin complex 1) to lipogenesis via the SREBPs (sterol-regulatory-element-binding proteins). SREBPs regulate the expression of genes encoding enzymes required for fatty acid and cholesterol biosynthesis. Lipid metabolism is perturbed in some diseases and SREBP target genes, such as FASN (fatty acid synthase), have been shown to be up-regulated in some cancers. We have previously shown that mTORC1 plays a role in SREBP activation and Akt/PKB (protein kinase B)-dependent de novo lipogenesis. Our findings suggest that mTORC1 plays a crucial role in the activation of SREBP and that the activation of lipid biosynthesis through the induction of SREBP could be part of a regulatory pathway that co-ordinates protein and lipid biosynthesis during cell growth. In the present paper, we discuss the increasing amount of data supporting the potential mechanisms of mTORC1-dependent activation of SREBP as well as the implications of this signalling pathway in cancer.

Acute cholecystitis in a patient with metastatic renal cell carcinoma treated with everolimus

Everolimus (RAD001) is an orally administered inhibitor of the mammalian target of rapamycin (mTOR), a therapeutic target for metastatic renal cell carcinoma. A 58-year-old woman was treated with everolimus as a third-line therapy for metastatic clear-cell renal carcinoma. She was given oral everolimus 10 mg once daily. During the fourth week of her first cycle, the patient was admitted to our hospital because of an acute-onset, right upper quadrant pain associated with nausea and vomiting. She was diagnosed with acute cholecystitis, which was treated with broad-spectrum antibiotics, and everolimus therapy was discontinued. A follow-up computed tomography scan of the abdomen revealed a complete resolution of gallbladder changes. Our patient did not have major risk factors for developing a cholecystitis except for a relative immunosuppressed state secondary to her advanced renal cancer. The Naranjo adverse drug reaction probability scale score for this event was 5, indicating a probable association of the event with everolimus. Because the use of everolimus is expanding in clinical practice, we want to alert the oncology community about this uncommon and life-threatening complication in patients receiving everolimus or another agent with antiangiogenic activity. To our best knowledge, only one case of an acute cholangitis associated with everolimus in a metastatic renal cell carcinoma has been reported. We report herein the first case of a metastatic renal cell carcinoma developed everolimus-associated cholecystitis that was completely reversed after drug withdrawal.

Dyslipidemia following kidney transplantation: diagnosis and treatment

Lipid abnormalities are a common complication of kidney transplantation, occurring in up to 60% of patients. In fact, impairment of lipid metabolism is often present before renal transplantation due to the uremic state. After transplantation and recovery of renal function, lipid disturbances usually persist but show a different profile due to the various effects of immunosuppressive drugs on lipid metabolism. Actually, steroids, calcineurin inhibitors, and mammalian target of rapamycin inhibitors usually lead to quantitative and qualitative abnormalities of very low-density, low-density, and high-density lipoproteins. As cardiovascular diseases remain the leading cause of death in renal transplant recipients, management of dyslipidemia and other traditional risk factors, such as smoking, arterial hypertension, diabetes mellitus, and obesity, is of great importance to prevent cardiovascular complications and chronic allograft dysfunction. This review addresses the causes of dyslipidemia, the role of immunosuppressive drugs, and current recommendations to manage lipid disorders in renal transplant recipients.

Genomic consequences of cytochrome P450 2C9 overexpression in human hepatoma cells

Cytochrome P450 2C9 (P450 2C9) is one of the most important P450 isoforms in the human liver, as it metabolizes numerous exogenous and endogenous substrates. Moreover, it is inducible by several compounds, such as rifampicin, phenobarbital, and NSAIDs (nonsteroidal anti-inflammatories). The aim of this study was to investigate the global cellular consequences of P450 2C9 overexpression at the transcriptional level using an untargeted approach: pangenomic microarrays. Recombinant adenovirus was used to express P450 2C9 instead of an inducer to prevent a per se effect of inducer or its metabolites. P450 2C9 overexpression induced endoplasmic reticulum (ER) stress and regulated genes implicated in the unfolded protein response (UPR) as heat shock protein (HSP) (we studied particurlarly HSPA5 and HSPB1) and in the endoplasmic reticulum associated degradation (ERAD) system as Sec61 and ubiquitin and proteasome pathways. UPR and ERAD are two mechanisms of adaptative response to ER stress. Moreover, activation of Akt was observed in HepG2 cells that overexpress P450 2C9 and might participate in the cellular adaptive response to stress, thus leading to the activation of cell survival pathways. UPR and ERAD should be caused by accumulation of native and misfolded P450 2C9 protein. Our results indicated that P450 2C9 overexpression did not lead to toxicity but induced an ER stress due to protein overexpression rather than mono-oxygenase activity. The ER stress triggered activation of the adaptative response and of pathways leading to cell survival.

Mammalian target of rapamycin inhibitor dyslipidemia in kidney transplant recipients

The incidence, pathogenesis, consequences and treatment of mammalian target of rapamycin (mTOR) inhibitor dyslipidemia are not well described. We conducted a systematic review of randomized controlled trials reporting cholesterol and triglycerides in mTOR versus non-mTOR inhibitor immunosuppressive treatment regimens in kidney transplant recipients. All but one of 17 trials reported higher levels of cholesterol and triglycerides, or an increased prevalence of treatment with lipid-lowering agents. Approximately 60% of mTOR inhibitor-treated patients received lipid-lowering agents (2-fold higher than controls). There appeared to be little difference between dyslipidemias caused by sirolimus (14 trials) versus everolimus (3 trials). It was difficult to determine the extent to which declines in lipids over time posttransplant were due to lipid-lowering therapy, changes in doses and/or discontinuations of mTOR inhibitors. From the four trials that measured lipoproteins, it appeared that at least some of the increase in total cholesterol with mTOR inhibitors was due to increased low-density lipoprotein cholesterol. What direct or indirect effects mTOR inhibitors have on atherosclerotic cardiovascular disease in kidney transplant patients are unknown. However, in the absence of the necessary clinical trials, dyslipidemia should be managed, as it would be in nontransplant patients at high risk for cardiovascular disease.