Tacrolimus and sirolimus have distinct effects on insulin signaling in male and female rats

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.

New-Onset Diabetes Mellitus after Kidney Transplantation

New-Onset Diabetes Mellitus after Transplantation (NODAT) emerges as a prevalent complication post-kidney transplantation, with its incidence influenced by variations in NODAT definitions and follow-up periods. The condition's pathophysiology is marked by impaired insulin sensitivity and β-cell dysfunction. Significant risk factors encompass age, gender, obesity, and genetics, among others, with the use of post-transplant immunosuppressants intensifying the condition. NODAT's significant impact on patient survival and graft durability underscores the need for its prevention, early detection, and treatment. This review addresses the complexities of managing NODAT, including the challenges posed by various immunosuppressive regimens crucial for transplant success yet harmful to glucose metabolism. It discusses management strategies involving adjustments in immunosuppressive protocols, lifestyle modifications, and pharmacological interventions to minimize diabetes risk while maintaining transplant longevity. The importance of early detection and proactive, personalized intervention strategies to modify NODAT's trajectory is also emphasized, advocating for a shift towards more anticipatory post-transplant care.

The pharmacogenetics of tacrolimus in renal transplant patients: association with tremors, new-onset diabetes and other clinical events

Our study is the first study to investigate the effect of SNPs in CYP3A5, CYP3A4, ABCB1 and POR genes on the incidence of tremors, nephrotoxicity, and diabetes mellitus. A total of 223 renal transplant patients receiving tacrolimus and mycophenolate mofetil (MMF) were recruited. Both adults and children patients participated in the study. Genotyping was performed using PROFLEX-PCR followed by RFLP. MPA and tacrolimus plasma concentrations were measured by immunoassay. The AUC0-12h of MMF was estimated by a Bayesian method. We found a statistically significant association between the CYP3A5*3 and CYP3A4*1B genotypes and the tacrolimus exposure. We found a lower occurrence of nephrotoxicity (p = 0.03), tremor (p = 0.01), and new-onset diabetes (p = 0.002) associated with CYP3A5*1 allele. The CYP3A4*1B allele was significantly associated with a lower occurrence of new-onset diabetes (p = 0.026). The CYP3A5*1 allele was significantly associated with an increased risk of acute and chronic rejection (p = 0.03 and p < 0.001, respectively). Our results support the usefulness of tacrolimus pharmacokinetics in pre-kidney transplant assessments.

Posttransplant Diabetes Mellitus: Recent Developments in Pharmacological Management of Hyperglycemia

CONTEXT

The management of solid-organ transplantation is rapidly evolving, and posttransplant diabetes mellitus (PTDM), which is increasingly common, is a barrier to transplant success, adversely impacting infection rates, allograft survival, cardiovascular disease, quality of life, and overall mortality. Currently, the management of PTDM relies primarily on intensified insulin therapy. However, emerging studies report that several noninsulin glucose-lowering agents are safe and effective in improving metabolic control and enhancing treatment adherence. More importantly, their use in PTDM can potentially transform the long-term management of these complex patients, as some glucose-lowering agents may provide benefits beyond glycemic control. For instance, glucagon-like peptide 1 receptor agonists (GLP-1 RA) and sodium-glucose cotransporter 2 (SGLT-2) inhibitors may offer cardiorenal protection, and pioglitazone may treat nonalcoholic fatty liver disease (NAFLD). This review will focus on the pharmacological management of PTDM and the emerging evidence for noninsulin glucose-lowering agents in this population.

EVIDENCE ACQUISITION

Evidence from observational studies, randomized controlled trials, and meta-analyses.

EVIDENCE SYNTHESIS

PTDM adversely affects the outcomes of infection, organ survival, cardiovascular events, and mortality. Insulin therapy has been the drug of choice but is associated with weight gain and hypoglycemia. In contrast, noninsulin agents appear safe and may provide additional benefits, such as cardiorenal protection with SGLT-2 inhibitors and GLP-1 RA, and cardiometabolic benefits with pioglitazone, in patients undergoing solid-organ transplantation.

CONCLUSIONS

Optimal care of patients with PTDM requires close monitoring and the early involvement of the endocrinologist as part of a multidisciplinary team. Noninsulin glucose-lowering agents will likely play an increasing role as more long-term, controlled studies become available in this setting.

Diabetic Kidney Disease in Post-Transplant Diabetes Mellitus: Causes, Treatment and Outcomes

Kidney transplant recipients are a unique subgroup of chronic kidney disease patients due to their single functioning kidney, immunosuppressive agent usage, and long-term complications related to transplantation. Post-transplant diabetes mellitus (PTDM) has a significant adverse effect on renal outcomes in particular. As transplantations enable people to live longer, cardiovascular morbidity and mortality become more prevalent, and PTDM is a key risk factor for these complications. Although PTDM results from similar risk factors to those of type 2 diabetes, the conditions differ in their pathophysiology and clinical features. Transplantation itself is a risk factor for diabetes due to chronic exposure to immunosuppressive agents. Considering current evidence, this article describes the risk factors, pathogenesis, diagnostic criteria, prevention strategies, and management of PTDM. The therapeutic options are discussed regarding their safety and potential drug-drug interactions with immunosuppressive agents.

Glucagon-like peptide-1 receptor agonists and sodium-glucose cotransporter 2 inhibitors for diabetes after solid organ transplantation

Post-transplant diabetes mellitus (PTDM) is a common complication of solid organ transplantation and a major cause of increased morbidity and mortality. Additionally, solid organ transplant patients may have pre-existent type 2 diabetes mellitus (T2DM). While insulin is the treatment of choice for hyperglycemia in the first weeks after transplantation, there is no preferred first line agent for long-term management of PTDM or pre-existent T2DM. Glucagon-like peptide-1 receptor agonists (GLP-1RA) and sodium-glucose cotransporter 2 (SGLT2) inhibitors improve glycemic control, lower body weight, and blood pressure, are recommended after lifestyle and metformin as initial therapy for diabetic patients with cardiovascular or kidney comorbidities regarding their cardiorenal benefits. Furthermore, the mechanisms of action of GLP-1RA may counteract some of the driving forces for PTDM, as calcineurin-induced β cell toxicity as per preclinical data, and improve obesity. However, their use in the treatment of PTDM is currently limited by a paucity of data. Retrospective observational and small exploratory studies suggest that GLP-1RA effectively improve glycemic control and induce weight loss in patients with PTDM without interacting with commonly used immunosuppressive agents, although randomized-controlled clinical trials are required to confirm their safety and efficacy. In this narrative review, we evaluate the risk factors and pathogenesis of PTDM and compare the potential roles of GLP-1RA and SGLT2 inhibitors in PTDM prevention and management as well as in pre-existent T2DM, and providing a roadmap for evidence generation on newer antidiabetic drugs for solid organ transplantation.

Diabetes and Cardiovascular Risk in Renal Transplant Patients

End-stage kidney disease (ESKD) is a main public health problem, the prevalence of which is continuously increasing worldwide. Due to adverse effects of renal replacement therapies, kidney transplantation seems to be the optimal form of therapy with significantly improved survival, quality of life and diminished overall costs compared with dialysis. However, post-transplant patients frequently suffer from post-transplant diabetes mellitus (PTDM) which an important risk factor for cardiovascular and cardiovascular-related deaths after transplantation. The management of post-transplant diabetes resembles that of diabetes in the general population as it is based on strict glycemic control as well as screening and treatment of common complications. Lifestyle interventions accompanied by the tailoring of immunosuppressive regimen may be of key importance to mitigate PTDM-associated complications in kidney transplant patients. More transplant-specific approach can include the exchange of tacrolimus with an alternative immunosuppressant (cyclosporine or mammalian target of rapamycin (mTOR) inhibitor), the decrease or cessation of corticosteroid therapy and caution in the prescribing of diuretics since they are independently connected with post-transplant diabetes. Early identification of high-risk patients for cardiovascular diseases enables timely introduction of appropriate therapeutic strategy and results in higher survival rates for patients with a transplanted kidney.

Why do sexes differ in lifespan extension? Sex-specific pathways of aging and underlying mechanisms for dimorphic responses

Males and females typically have different lifespans and frequently differ in their responses to anti-aging interventions. These sex-specific responses are documented in mice and Drosophila species, in addition to other organisms where interventions have been tested. While the prevalence of sex-specific responses to anti-aging interventions is now recognised, the underlying causes remain poorly understood. This review first summarises the main pathways and interventions that lead to sex-specific lifespan responses, including the growth-hormone/insulin-like growth factor 1 (GH-IGF1) axis, mechanistic target of rapamycin (mTOR) signalling, and nutritional and pharmacological interventions. After summarising current evidence, several different potential causes for sex-specific responses are discussed. These include sex-differences in xenobiotic metabolism, differing disease susceptibility, sex-specific hormone production and chromosomes, and the relative importance of different signalling pathways in the control of male and female life-history. Understanding why sex-differences in lifespan-extension occur should provide a greater understanding of the mechanisms that regulate the aging process in each sex, and will be crucial for understanding the full implications of these treatments if they are translated to humans.

Review of Newer Antidiabetic Agents for Diabetes Management in Kidney Transplant Recipients

OBJECTIVE

This systematic review describes the efficacy, safety, and drug interactions of dipeptidyl peptidase-4 (DPP-4) inhibitors, glucagon-like peptide-1 receptor agonists (GLP-1 RAs), and sodium-glucose transport protein 2 (SGLT2) inhibitors in kidney transplant recipients (KTRs).

DATA SOURCES

Articles were identified by English-language MEDLINE search, published prior to May 2020, using the terms kidney transplant, OR PTDM, OR NODAT, AND metformin, OR DPP4, OR GLP1, OR SGLT2.

STUDY SELECTION AND DATA EXTRACTION

All selected studies were included if the study population was composed of adult KTRs who were diagnosed with either impaired glucose tolerance, diabetes mellitus (DM), new-onset diabetes after transplant (NODAT), or posttransplantation diabetes mellitus (PTDM).

DATA SYNTHESIS

In KTRs, there is evidence for safety with DPP-4 inhibitors, GLP-1 RAs, and SGLT2 inhibitors. However, urinary tract infections and a slight initial decrease in renal function may limit use of SGLT2 inhibitors. As compared with the nontransplant type 2 DM population, SGLT2 inhibitors are not as efficacious in KTRs.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

This review provides an overview of the current literature on newer antidiabetic agents, addressing efficacy, safety, and drug interactions to help guide clinical decision-making for their use in KTRs.

CONCLUSION

Newer antidiabetic agents have been recommended by the American Diabetes Association for potential cardiovascular, renal, and hypoglycemic benefits. Particular agents, such as DPP-4 inhibitors and GLP-1 RAs may play a role in correcting PTDM-related defects. Clinicians need to take into account both patient-specific and drug-specific characteristics when initiating these agents in KTRs.

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.

FXR activation alleviates tacrolimus-induced post-transplant diabetes mellitus by regulating renal gluconeogenesis and glucose uptake

BACKGROUND

Tacrolimus (FK506)-induced diabetes mellitus is one of the most important factors of post-transplant diabetes mellitus (PTDM). However, the detailed mechanisms underlying PTDM are still unclear. Farnesoid X receptor (FXR) regulates glycolipid metabolism. The objective of this study was to explore whether FXR is involved in the development of tacrolimus-induced diabetes mellitus.

METHODS

After C57BL/6J mice were treated with tacrolimus (FK506) for 3 months, the fasting blood glucose levels, body weights, renal morphological alterations, and mRNA expression levels of phosphoenolpyruvate carboxykinase (PEPCK) and glucose transporter 2 (GLUT2) among the control group, the FK506 group and the FK506 + GW4064 (a FXR agonist) group (n = 7) were measured. The intracellular location of peroxisome proliferator activated receptor γ coactivator-1α (PGC1α) and forkhead box O1 (FOXO1) was detected by immunofluorescence. Human renal cortex proximal tubule epithelial cells (HK-2) were treated with 15 μM FK506 or 4 μM FXR agonist (GW4064) for 24, 48 and 72 h, and the expression levels of FXR, gluconeogenesis and glucose uptake, representing the enzymes PEPCK and GLUT2, were detected with real-time PCR and western blot analyses. Finally, the mRNA levels of PEPCK and GLUT2 in HK-2 cells were measured after FXR was upregulated.

RESULTS

FK506 significantly inhibited the mRNA and protein levels of FXR at 48 h and 72 h in HK-2 cells (P < 0.05). Meanwhile, FK506 promoted gluconeogenesis and inhibited glucose uptake in HK-2 cells (P < 0.05). However, overexpression of FXR in transfected HK-2 cell lines significantly inhibited gluconeogenesis and promoted glucose uptake (P < 0.05). The FXR agonist GW4064 significantly decreased the fasting blood glucose in mice challenged with FK506 for 3 months (P < 0.05), inhibited gluconeogenesis (P < 0.05) and significantly promoted glucose uptake (P < 0.05). Immunofluorescence staining and western blot analyses further revealed that FXR activation may affect the translocation of PGC1α and FOXO1 from the nucleus to the cytoplasm.

CONCLUSIONS

FXR activation may mitigate tacrolimus-induced diabetes mellitus by regulating gluconeogenesis as well as glucose uptake of renal cortex proximal tubule epithelial cells in a PGC1α/FOXO1-dependent manner, which may be a potential therapeutic strategy for the prevention and treatment of PTDM.

3D Bioprinting of Functional Islets of Langerhans in an Alginate/Methylcellulose Hydrogel Blend

Transplantation of pancreatic islets is a promising strategy to alleviate the unstable blood-glucose control that some patients with diabetes type 1 exhibit and has seen many advances over the years. Protection of transplanted islets from the immune system can be accomplished by encapsulation within a hydrogel, the most investigated of which is alginate. In this study, islet encapsulation is combined with 3D extrusion bioprinting, an additive manufacturing method which enables the fabrication of 3D structures with a precise geometry to produce macroporous hydrogel constructs with embedded islets. Using a plottable hydrogel blend consisting of clinically approved ultrapure alginate and methylcellulose (Alg/MC) enables encapsulating pancreatic islets in macroporous 3D hydrogel constructs of defined geometry while retaining their viability, morphology, and functionality. Diffusion of glucose and insulin in the Alg/MC hydrogel is comparable to diffusion in plain alginate; the embedded islets continuously produce insulin and glucagon throughout the observation and still react to glucose stimulation albeit to a lesser degree than control islets.

Post-transplant diabetes mellitus in patients with solid organ transplants

Solid organ transplantation (SOT) is a life-saving procedure and an established treatment for patients with end-stage organ failure. However, transplantation is also accompanied by associated cardiovascular risk factors, of which post-transplant diabetes mellitus (PTDM) is one of the most important. PTDM develops in 10-20% of patients with kidney transplants and in 20-40% of patients who have undergone other SOT. PTDM increases mortality, which is best documented in patients who have received kidney and heart transplants. PTDM results from predisposing factors (similar to type 2 diabetes mellitus) but also as a result of specific post-transplant risk factors. Although PTDM has many characteristics in common with type 2 diabetes mellitus, the prevention and treatment of the two disorders are often different. Over the past 20 years, the lifespan of patients who have undergone SOT has increased, and PTDM becomes more common over the lifespan of these patients. Accordingly, PTDM becomes an important condition not only to be aware of but also to treat. This Review presents the current knowledge on PTDM in patients receiving kidney, heart, liver and lung transplants. This information is not only for transplant health providers but also for endocrinologists and others who will meet these patients in their clinics.

The effects of addition of coenzyme Q10 to metformin on sirolimus-induced diabetes mellitus

BACKGROUND/AIMS

This study was performed to determine whether adding coenzyme Q10 (CoQ10) to metformin (MET) has a beneficial effect as a treatment for sirolimus (SRL)-induced diabetes mellitus (DM).

METHODS

DM was induced in rats by daily treatment with SRL (0.3 mg/kg, subcutaneous) for 28 days, and animals were treated with CoQ10 (20 mg/kg, oral) and MET (250 mg/kg, oral) alone or in combination for the latter 14 days of SRL treatment. The effects of CoQ10 and MET on SRL-induced DM were assessed with the intraperitoneal glucose tolerance test (IPGTT) and by determining plasma insulin concentration and the homeostatic model assessment of insulin resistance (HOMA-R) index. We also evaluated the effect of CoQ10 on pancreatic islet size, apoptosis, oxidative stress, and mitochondria morphology.

RESULTS

IPGTT revealed overt DM in SRL-treated rats. The addition of CoQ10 to MET further improved hyperglycemia, decreased HOMA-R index, and increased plasma insulin concentration compared with the SRL group than MET alone therapy. While SRL treatment induced smaller islets with decreased insulin staining intensity, the combination of CoQ10 and MET significantly improved insulin staining intensity, which was accompanied by a reduction in oxidative stress and apoptosis. In addition, co-treatment of CoQ10 and MET significantly increased the levels of antiperoxidative enzymes in the pancreas islet cells compared with MET. At the subcellular level, addition of CoQ10 to MET improved the average mitochondrial area and insulin granule number.

CONCLUSION

Addition of CoQ10 to MET has a beneficial effect on SRL-induced DM compared to MET alone.

Post-Liver Transplantation Diabetes Mellitus: A Review of Relevance and Approach to Treatment

Post-liver transplantation diabetes mellitus (PLTDM) develops in up to 30% of liver transplant recipients and is associated with increased risk of mortality and multiple morbid outcomes. PLTDM is a multicausal disorder, but the main risk factor is the use of immunosuppressive agents of the calcineurin inhibitor (CNI) family (tacrolimus and cyclosporine). Additional factors, such as pre-transplant overweight, nonalcoholic steatohepatitis and hepatitis C virus infection, may further increase risk of developing PLTDM. A diagnosis of PLTDM should be established only after doses of CNI and steroids are stable and the post-operative stress has been overcome. The predominant defect induced by CNI is insulin secretory dysfunction. Plasma glucose control must start immediately after the transplant procedure in order to improve long-term results for both patient and transplant. Among the better known antidiabetics, metformin and DPP-4 inhibitors have a particularly benign profile in the PLTDM context and are the preferred oral agents for long-term management. Insulin therapy is also an effective approach that addresses the prevailing pathophysiological defect of the disorder. There is still insufficient evidence about the impact of newer families of antidiabetics (GLP-1 agonists, SGLT-2 inhibitors) on PLTDM. In this review, we summarize current knowledge on the epidemiology, pathogenesis, course of disease and medical management of PLTDM.

Sex differences in lifespan extension with acarbose and 17-α estradiol: gonadal hormones underlie male-specific improvements in glucose tolerance and mTORC2 signaling

Interventions that extend lifespan in mice can show substantial sexual dimorphism. Here, we show that male‐specific lifespan extension with two pharmacological treatments, acarbose (ACA) and 17‐α estradiol (17aE2), is associated, in males only, with increased insulin sensitivity and improved glucose tolerance. Females, which show either smaller (ACA) or no lifespan extension (17aE2), do not derive these metabolic benefits from drug treatment. We find that these male‐specific metabolic improvements are associated with enhanced hepatic mTORC2 signaling, increased Akt activity, and phosphorylation of FOXO1a – changes that might promote metabolic health and survival in males. By manipulating sex hormone levels through gonadectomy, we show that sex‐specific changes in these metabolic pathways are modulated, in opposite directions, by both male and female gonadal hormones: Castrated males show fewer metabolic responses to drug treatment than intact males, and only those that are also observed in intact females, while ovariectomized females show some responses similar to those seen in intact males. Our results demonstrate that sex‐specific metabolic benefits occur concordantly with sexual dimorphism in lifespan extension. These sex‐specific effects can be influenced by the presence of both male and female gonadal hormones, suggesting that gonadally derived hormones from both sexes may contribute to sexual dimorphism in responses to interventions that extend mouse lifespan.

Effects of metformin on hyperglycemia in an experimental model of tacrolimus- and sirolimus-induced diabetic rats

BACKGROUND/AIMS

Metformin (MET) is a first-line drug for type 2 diabetes mellitus (DM); its effect on new-onset diabetes after transplantation caused by immunosuppressant therapy is unclear. We compared the effects of MET on DM caused by tacrolimus (TAC) or sirolimus (SRL).

METHODS

DM was induced by injection of TAC (1.5 mg/kg) or SRL (0.3 mg/kg) for 2 weeks in rats, and MET (200 mg/kg) was injected for 2 more weeks. The effects of MET on DM caused by TAC or SRL were evaluated using an intraperitoneal glucose tolerance test (IPGTT) and by measuring plasma insulin concentration, islet size, and glucose-stimulated insulin secretion (GSIS). The effects of MET on the expression of adenosine monophosphate-activated protein kinase (AMPK), a pharmacological target of MET, were compared between TAC- and SRL-treated islets.

RESULTS

IPGTT showed that both TAC and SRL induced hyperglycemia and reduced plasma insulin concentration compared with vehicle. These changes were reversed by addition of MET to SRL but not to TAC. Pancreatic islet cell size was decreased by TAC but not by SRL, but addition of MET did not affect pancreatic islet cell size in either group. MET significantly increased GSIS in SRL- but not in TAC-treated rats. AMPK expression was not affected by TAC but was significantly decreased in SRL-treated islets. Addition of MET restored AMPK expression in SRL-treated islets but not in TAC-treated islets.

CONCLUSIONS

MET has different effects on hyperglycemia caused by TAC and SRL. The discrepancy between these drugs is related to their different mechanisms causing DM.

SFRP2 Is Associated with Increased Adiposity and VEGF Expression

AIMS

The aim of this study was to assess depot-specific expression and secretion of secreted frizzled-related protein 2 (sFRP2) by adipose tissue and its effect on adipocyte biology. We measured serum sFRP2 concentrations in 106 patients in vivo to explore its relationship to fat mass, glycaemia and insulin resistance.

METHODS

Expression of sFRP2 in mouse and human tissues was assessed using polymerase chain reaction and Western blot. Western blot confirmed secretion of sFRP2 by adipose tissue into cell culture medium. Effects of recombinant sFRP2 on lipogenesis and preadipocyte proliferation were measured. Preadipocyte expression of the angiogenic genes vascular endothelial growth factor (VEGF) and nuclear factor of activated T-cells 3 (NFATC3) was measured after recombinant sFRP2 exposure. Complementary clinical studies correlating human serum sFRP2 with age, gender, adiposity and insulin secretion were also performed.

RESULTS

sFRP2 messenger RNA (mRNA) was expressed in mouse and human adipose tissue. In humans, sFRP2 mRNA expression was 4.2-fold higher in omental than subcutaneous adipose. Omental adipose tissue secreted 63% more sFRP2 protein than subcutaneous. Treatment with recombinant sFRP2 did not impact on lipogenesis or preadipocyte proliferation but was associated with increased VEGF mRNA expression. In human subjects, circulating insulin levels positively correlated with serum sFRP2, and levels were higher in patients with abnormal glucose tolerance (34.2ng/ml) compared to controls (29.5ng/ml). A positive correlation between sFRP2 and BMI was also observed.

CONCLUSIONS

Circulating sFRP2 is associated with adipose tissue mass and has a potential role to drive adipose angiogenesis through enhanced VEGF expression.

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.

The Origin of New-Onset Diabetes After Liver Transplantation: Liver, Islets, or Gut? Transplantation. 2016;100:808-813. [PMID: 26910326 DOI: 10.1097/tp.0000000000001111]

New-onset diabetes is a frequent complication after solid organ transplantation. Although a number of common factors are associated with the disease, including recipient age, body mass index, hepatitis C infection, and use of immunosuppressive drugs, new-onset diabetes after liver transplantation (NODALT) has the following unique aspects and thus needs to be considered its own entity. First, a liver graft becomes the patient's primary metabolic regulator after liver transplantation, but this would not be the case for kidney or other grafts. The metabolic states, as well as the genetics of the graft, play crucial roles in the development of NODALT. Second, dysfunction of the islets of Langerhans is common in cirrhotic patients and would be exacerbated by immunosuppressive agents, particularly calcineurin inhibitors. On the other hand, minimized immunosuppressive protocols have been widely advocated in liver transplantation because of liver tolerance (immune privilege). Third and last, through the "gut-liver axis," graft function is closely linked to gut microbiota, which is now considered an important metabolic organ and known to independently influence the host's metabolic homeostasis. Liver transplant recipients present with specific gut microbiota that may be prone to trigger metabolic disorders. In this review, we proposed 3 possible sites for the origin of NODALT, which are liver, islets, and gut, to help elucidate the underlying mechanism of NODALT.

Effects of addition of a dipeptidyl peptidase IV inhibitor to metformin on sirolimus-induced diabetes mellitus

The guideline for the management of new-onset diabetes after transplantation recommends metformin (MET) as a first-line drug, and addition of a second-line drug is needed to better control of hyperglycemia. We tested the effect of addition of a dipeptidyl peptidase IV (DPP IV) inhibitor to MET on sirolimus (SRL)-induced diabetes mellitus (DM). In animal model of SRL-induced DM, MET treatment improved pancreatic islet function (blood glucose level and insulin secretion) and attenuated oxidative stress and apoptotic cell death. Addition of a DPP IV inhibitor to MET improved these parameters more than MET alone. An in vitro study showed that SRL treatment increased pancreas beta cell death and production of reactive oxygen species (ROS), and pretreatment of ROS inhibitor, or p38MAPK inhibitor effectively decreased SRL-induced islet cell death. Exendin-4 (EXD), a substrate of DPP IV or MET significantly improved cell viability and decreased ROS production compared with SRL treatment, and combined treatment with the 2 drugs improved both parameters. At the subcellular level, impaired mitochondrial respiration by SRL were partially improved by MET or EXD and much improved further after addition of EXD to MET. Our data suggest that addition of a DPP IV inhibitor to MET decreases SRL-induced oxidative stress and improves mitochondrial respiration. This finding provides a rationale for the combined use of a DPP IV inhibitor and MET in treating SRL-induced DM.

Post-Transplant Diabetes Mellitus: Causes, Treatment, and Impact on Outcomes

Post-transplant diabetes mellitus (PTDM) is a frequent consequence of solid organ transplantation. PTDM has been associated with greater mortality and increased infections in different transplant groups using different diagnostic criteria. An international consensus panel recommended a consistent set of guidelines in 2003 based on American Diabetes Association glucose criteria but did not exclude the immediate post-transplant hospitalization when many patients receive large doses of corticosteroids. Greater glucose monitoring during all hospitalizations has revealed significant glucose intolerance in the majority of recipients immediately after transplant. As a result, the international consensus panel reviewed its earlier guidelines and recommended delaying screening and diagnosis of PTDM until the recipient is on stable doses of immunosuppression after discharge from initial transplant hospitalization. The group cautioned that whereas hemoglobin A1C has been adopted as a diagnostic criterion by many, it is not reliable as the sole diabetes screening method during the first year after transplant. Risk factors for PTDM include many of the immunosuppressant medications themselves as well as those for type 2 diabetes. The provider managing diabetes and associated dyslipidemia and hypertension after transplant must be careful of the greater risk for drug-drug interactions and infections with immunosuppressant medications. Treatment goals and therapies must consider the greater risk for fluctuating and reduced kidney function, which can cause hypoglycemia. Research is actively focused on strategies to prevent PTDM, but until strategies are found, it is imperative that immunosuppression regimens are chosen based on their evidence to prolong graft survival, not to avoid PTDM.

New-onset diabetes mellitus after pediatric liver transplantation

In the first five yr after liver transplant, approximately one in 10 pediatric recipients will develop NODAT. Factors associated with higher risk for NODAT have been difficult to identify due to lack of uniformity in reporting and data collection. Limited studies have reported higher risk in those who are at an older age at transplant, those with high-risk ethnic backgrounds, and in those with particular underlying conditions, such as CF and primary sclerosing cholangitis. Immunosuppressive medications, including tacrolimus, cyclosporine A, GC, and sirolimus, have been implicated as contributing to NODAT, to varying degrees. Identifying those at highest risk, appropriately screening, and diagnosing NODAT is critical to initiating timely treatment and avoiding potential complications. In the pediatric population, treatment is limited primarily to insulin, with some consideration for metformin. Children with NODAT should be monitored carefully for complications of DM, including microalbuminuria, hypertension, hyperlipidemia, and retinopathy.

Engineered hair follicle mesenchymal stem cells overexpressing controlled-release insulin reverse hyperglycemia in mice with type L diabetes

Genetically engineered stem cells that overexpress genes encoding therapeutic products can be exploited to correct metabolic disorders by repairing and regenerating diseased organs or restoring their function. Hair follicles are readily accessible and serve as a rich source of autologous stem cells for cell-based gene therapy. Here we isolated mesenchymal stem cells from human hair follicles (HF-MSCs) and engineered them to overexpress the human insulin gene and release human insulin in a time- and dose-dependent manner in response to rapamycin. The engineered HF-MSCs retained their characteristic cell surface markers and retained their potential to differentiate into adipocytes and osteoblasts. When mice with streptozotocin-induced type 1 diabetes were engrafted with these engineered HF-MSCs, these cells expressed and released a dose of human insulin, dramatically reversed hyperglycemia, and significantly reduced death rate. Moreover, the engineered HF-MSCs did not form detectable tumors throughout the 120-day animal tests in our experiment. Our results show that HF-MSCs can be used to safely and efficiently express therapeutic transgenes and therefore show promise for cell-based gene therapy of human disease.