Effects of cyclosporine and sirolimus on insulin-stimulated glucose transport and glucose tolerance in a rat model

Enhanced detection of ligand-PPARγ binding based on surface plasmon resonance through complexation with SRC1- or NCOR2-related polypeptide

A previous study reported the use of a biosensing technique based on surface plasmon resonance (SPR) for the ligand binding detection of peroxisome proliferator activator receptor gamma (PPARγ). This detection was designed based on the structural properties of PPARγ. Because of cross-linked protein inactivation and the low molecular weight of conventional ligands, direct ligand binding detection based on SPR has low stability and repeatability. In this study, we report an indirect response methodology based on SPR technology in which anti-His CM5 chip binds fresh PPARγ every cycle, resulting in more stable detection. We developed a remarkable improvement in ligand-protein binding detectability in vitro by introducing two coregulator-related polypeptides into this system. In parallel, a systematic indirect response methodology can reflect the interaction relationship between ligands and proteins to some extent by detecting the changes in SA-SRC1 and GST-NCOR2 binding to PPARγ. Rosiglitazone, a PPARγ agonist with strong affinity, is a potent insulin-sensitizing agent. Some ligands may be competitively exerted at the same sites of PPARγ (binding rosiglitazone). We demonstrated using indirect response methodology that selective PPARγ modulator (SPPARM) candidates of PPARγ can be found by competing for the binding of the rosiglitazone site on PPARγ, although they may have no effect on polypeptides and PPARγ binding.

Urinary Concentration Defect and Renal Glycosuria in Cyclosporine-treated Rats

Background

Methods

Results

Conclusion

Therapeutic Use of mTOR Inhibitors in Renal Diseases: Advances, Drawbacks, and Challenges

The mammalian (or mechanistic) target of rapamycin (mTOR) pathway has a key role in the regulation of a variety of biological processes pivotal for cellular life, aging, and death. Impaired activity of mTOR complexes (mTORC1/mTORC2), particularly mTORC1 overactivation, has been implicated in a plethora of age-related disorders, including human renal diseases. Since the discovery of rapamycin (or sirolimus), more than four decades ago, advances in our understanding of how mTOR participates in renal physiological and pathological mechanisms have grown exponentially, due to both preclinical studies in animal models with genetic modification of some mTOR components as well as due to evidence coming from the clinical experience. The main clinical indication of rapamycin is as immunosuppressive therapy for the prevention of allograft rejection, namely, in renal transplantation. However, considering the central participation of mTOR in the pathogenesis of other renal disorders, the use of rapamycin and its analogs meanwhile developed (rapalogues) everolimus and temsirolimus has been viewed as a promising pharmacological strategy. This article critically reviews the use of mTOR inhibitors in renal diseases. Firstly, we briefly overview the mTOR components and signaling as well as the pharmacological armamentarium targeting the mTOR pathway currently available or in the research and development stages. Thereafter, we revisit the mTOR pathway in renal physiology to conclude with the advances, drawbacks, and challenges regarding the use of mTOR inhibitors, in a translational perspective, in four classes of renal diseases: kidney transplantation, polycystic kidney diseases, renal carcinomas, and diabetic nephropathy.

Calcineurin is an important factor involved in glucose uptake in human adipocytes

Calcineurin inhibitors are used in immunosuppressive therapy applied after transplantation, but they are associated with major metabolic side effects including the development of new onset diabetes. Previously, we have shown that the calcineurin inhibiting drugs tacrolimus and cyclosporin A reduce adipocyte and myocyte glucose uptakes by reducing the amount of glucose transporter type 4 (GLUT4) at the cell surface, due to an increased internalization rate. However, this happens without alteration in total protein and phosphorylation levels of key proteins involved in insulin signalling or in the total amount of GLUT4. The present study evaluates possible pathways involved in the altered internalization of GLUT4 and consequent reduction of glucose uptake provoked by calcineurin inhibitors in human subcutaneous adipose tissue. Short- and long-term treatments with tacrolimus, cyclosporin A or another CNI deltamethrin (herbicide) decreased basal and insulin-dependent glucose uptake in adipocytes, without any additive effects observed when added together. However, no tacrolimus effects were observed on glucose uptake when gene transcription and protein translation were inhibited. Investigation of genes potentially involved in GLUT4 trafficking showed only a small effect on ARHGEF11 gene expression (p < 0.05). In conlusion, the specific inhibition of calcineurin, but not that of protein phosphatases, decreases glucose uptake in human subcutaneous adipocytes, suggesting that calcineurin is an important regulator of glucose transport. This inhibitory effect is mediated via gene transcription or protein translation; however, expression of genes potentially involved in GLUT4 trafficking and endocytosis appears not to be involved in these effects.

Rapamycin negatively impacts insulin signaling, glucose uptake and uncoupling protein-1 in brown adipocytes

New onset diabetes after transplantation (NODAT) is a metabolic disorder that affects 40% of patients on immunosuppressive agent (IA) treatment, such as rapamycin (also known as sirolimus). IAs negatively modulate insulin action in peripheral tissues including skeletal muscle, liver and white fat. However, the effects of IAs on insulin sensitivity and thermogenesis in brown adipose tissue (BAT) have not been investigated. We have analyzed the impact of rapamycin on insulin signaling, thermogenic gene-expression and mitochondrial respiration in BAT. Treatment of brown adipocytes with rapamycin for 16h significantly decreased insulin receptor substrate 1 (IRS1) protein expression and insulin-mediated protein kinase B (Akt) phosphorylation. Consequently, both insulin-induced glucose transporter 4 (GLUT4) translocation to the plasma membrane and glucose uptake were decreased. Early activation of the N-terminal Janus activated kinase (JNK) was also observed, thereby increasing IRS1 Ser 307 phosphorylation. These effects of rapamycin on insulin signaling in brown adipocytes were partly prevented by a JNK inhibitor. In vivo treatment of rats with rapamycin for three weeks abolished insulin-mediated Akt phosphorylation in BAT. Rapamycin also inhibited norepinephrine (NE)-induced lipolysis, the expression of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) and uncoupling protein (UCP)-1 in brown adipocytes. Importantly, basal mitochondrial respiration, proton leak and maximal respiratory capacity were significantly decreased in brown adipocytes treated with rapamycin. In conclusion, we demonstrate, for the first time the important role of brown adipocytes as target cells of rapamycin, suggesting that insulin resistance in BAT might play a major role in NODAT development.

Branched-chain amino acids in metabolic signalling and insulin resistance

Branched-chain amino acids (BCAAs) are important nutrient signals that have direct and indirect effects. Frequently, BCAAs have been reported to mediate antiobesity effects, especially in rodent models. However, circulating levels of BCAAs tend to be increased in individuals with obesity and are associated with worse metabolic health and future insulin resistance or type 2 diabetes mellitus (T2DM). A hypothesized mechanism linking increased levels of BCAAs and T2DM involves leucine-mediated activation of the mammalian target of rapamycin complex 1 (mTORC1), which results in uncoupling of insulin signalling at an early stage. A BCAA dysmetabolism model proposes that the accumulation of mitotoxic metabolites (and not BCAAs per se) promotes β-cell mitochondrial dysfunction, stress signalling and apoptosis associated with T2DM. Alternatively, insulin resistance might promote aminoacidaemia by increasing the protein degradation that insulin normally suppresses, and/or by eliciting an impairment of efficient BCAA oxidative metabolism in some tissues. Whether and how impaired BCAA metabolism might occur in obesity is discussed in this Review. Research on the role of individual and model-dependent differences in BCAA metabolism is needed, as several genes (BCKDHA, PPM1K, IVD and KLF15) have been designated as candidate genes for obesity and/or T2DM in humans, and distinct phenotypes of tissue-specific branched chain ketoacid dehydrogenase complex activity have been detected in animal models of obesity and T2DM.

The impact of cytomegalovirus infection on new-onset diabetes mellitus after kidney transplantation: a review on current findings

CONTEXT

New onset diabetes mellitus after transplantation (NODAT) increases the risk of cardiovascular disease, rate of infections, graft rejection and graft loss as well as decreases patient and graft survival rates. There is a controversy surrounding the impact of cytomegalovirus (CMV) infection in the development of NODAT. This meta-analysis aims to identify the role of CMV infection leading to the development of NODAT in kidney recipient patients.

EVIDENCE ACQUISITIONS

We searched several electronic databases, including PubMed, Embase, Medline, Scopus, Trip Database and Google Scholar for studies that completely fulfill our criteria between January 1990 and January 2014 RESULTS: Seven studies with 1389 kidney transplant patients were included in this metaanalysis.The mean age of patients ranged from 42.8 to 48.8 years and males made up 53% to 75% of patients in the cohort studies. The incidence of NODAT varies from 14.3% to 27.1% in these studies. Overall adj OR was 1.94 [exp (0.66)] with a 95% CI of 1.26-2.98 [exp (0.23) and (1.09)]. There was no significant publication bias based on the Begg's and Egger's test (p value = 0.17 and 0.54, respectively).

CONCLUSIONS

Our study showed that CMV infection is a risk factor for increasing incidence of NODAT. Thus, prophylaxis against CMV infection after kidney transplantation is strongly suggested. However, further clinical trials and cohorts are needed to confirm this association.

A case report of improved metabolic control after conversion from everolimus to cyclosporin A: role of adipose tissue mechanisms?

BACKGROUND

New-onset diabetes after transplantation is associated with an increase in risk of graft failure, cardiovascular disease, and mortality. Therefore, it compromises the overall beneficial outcome of organ transplantation.

CASE REPORT

A patient with new-onset diabetes after renal transplantation showed glucose and lipid metabolism improvements after switching immunosuppressant from everolimus to cyclosporin A. A subcutaneous adipose tissue biopsy displayed changes in gene and protein expression that could contribute to the clinical improvement of hyperglycemia and dyslipidemia.

Short and long term in vivo effects of Cyclosporine A and Sirolimus on genes and proteins involved in lipid metabolism in Wistar rats

OBJECTIVE

Cyclosporine A (CsA) and sirolimus (SRL) are immunosuppressive agents (IA) associated with new onset diabetes after transplantation and dyslipidemia. We aim to evaluate the molecular effects of CsA (5mg/kg/day) and SRL (1mg/kg/day) treatment for 3 and 9weeks on lipid metabolism, in Wistar rats.

MATERIALS/METHODS

Lipolysis was evaluated in isolated adipocytes, while triglycerides (TG) and non-esterified fatty acid (NEFA) were measured in serum. Gene and protein expression involved in lipid metabolism was assessed in adipose tissue and liver.

RESULTS

CsA and SRL treatments of rats for 3 and 9weeks increased isoproterenol-stimulated lipolysis by 5-9 fold and 4-6 fold in isolated adipocytes, respectively. While CsA increased adipocyte weight and diameter, as well as NEFA and TG levels in circulation after 9weeks, SRL treatment caused ectopic deposition of TG in the liver after 3weeks. Moreover, ACC1 and FAS protein expression was increased after 3weeks (>100%, p<0.01), while HSL was increased after 9weeks of CsA treatment. On the other hand, SRL decreased the expression of lipogenic genes, including ACC1 (50%, p<0.05), lipin1 (25%, p<0.05), PPAR-γ (42%, p<0.05) and SCD1 (80%, p<0.001) in adipose tissue, after 3weeks of treatment.

CONCLUSION

The effects of both IAs on expression of lipolytic and lipogenic genes suggest that these agents influence lipid metabolism, thus contributing to the dyslipidemia observed during immunosuppressive therapy.

Pathogenesis and management of FK506- and CsA-induced post-transplant diabetes mellitus: Similarities and differences

Tacrolimus (FK506) and cyclosporine (CsA) are clinically commonly used immunosuppressive agents, and both of them belong to calcineurin inhibitors. FK506 is more excellent in anti-rejection therapy. They are similar in pharmacological mechanism, but FK506 is more likely to induce post-transplant diabetes mellitus than CsA. This paper analyzes and compares the similarities and differences in the pathogenesis and management between FK506- and CsA-induced post-transplant diabetes mellitus.