Risk factors for post-transplant diabetes mellitus in renal transplant: Role of genetic variability in the CYP450-mediated arachidonic acid metabolism

Inhibiting arachidonic acid generation mitigates aging-induced hyperinsulinemia and insulin resistance in mice

BACKGROUND

Aging-related type 2 diabetes (T2DM) is characterized by hyperinsulinemia, insulin resistance, and β-cell dysfunction. However, the underlying molecular mechanisms remain to be unclear.

METHODS

We conducted non-targeted metabolomics to compare human serum samples from young adults (YA), elderly adults (EA), and elderly adults with diabetes (EA + DM) of Chinese population. Adult mice and aged mice were intragastrically administered with varespladib every day for two weeks and metabolic characteristics were monitored. Serum levels of arachidonic acid, insulin, and C-peptide, as well as serum activity of secretory phospholipase A2 (sPLA2) were detected in mice. Mouse islet perfusion assays were used to assess insulin secretion ability. Phosphorylated AKT levels were measured to evaluate insulin sensitivities of peripheral tissues in mice.

RESULTS

Non-targeted metabolomics analysis of human serum samples revealed differential metabolic signatures among the YA, EA, and EA + DM groups. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed significant enhancement of arachidonic acid metabolism and glycerophospholipid metabolism in the EA group compared with the YA group. Further analysis identified two metabolic fluxes that favored the accumulation of arachidonic acid in the elderly. Increased levels of arachidonic acid were also confirmed in aged mice with hyperinsulinemia and insulin resistance, together with subsequent glucose intolerance. Conversely, inhibiting the generation of arachidonic acid with varespladib, an inhibitor of sPLA2, reduced aging-associated diabetes by improving hyperinsulinemia and hepatic insulin resistance in aged mice but not in adult mice. Islet perfusion assays also showed that varespladib treatment suppressed the enhanced insulin secretion observed in aged islets.

CONCLUSIONS

Collectively, our findings uncover that arachidonic acid serves as a metabolic hub in Chinese elderly population. Our results also suggest that arachidonic acid plays a fundamental role in regulating β-cell function during aging and point to a novel therapy for aging-associated diabetes.

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.

The frequency of cytochrome 4F2 rs2108622 genetic variant and its effects on the lipid profile and complications of type II diabetes among a sample of patients in Jordan: A pilot study

BACKGROUND

Cytochrome 4F2 (CYP4F2) is a major arachidonic acid-metabolizing enzyme which produces 20-Hydroxyeicosatetraenoic acid (20-HETE). It is found that 20-HETE is involved in the pathophysiology of many diseases, including diabetes mellitus. The genetic variants of CYP4F2 can affect its enzymatic activity as well as the 20-HETE production.

AIMS

Our aim with this paper was to find out the genotype frequency of CYP4F2 rs2108622 C>T, the major functional variant in the CYP4F2 gene, among a sample of type II diabetes (TIIDM) and its effects on diabetes complications and lipid profile.

METHODS

The CYP4F2 rs2108622 variant was genotyped among 90 healthy volunteers and 90 TIIDM patients that attending the University of Jordan Hospital, using the DNA Sanger sequencing method. The data of lipid profile and diabetes complications were obtained from the electronic records available in the hospital.

RESULTS

We found that the frequency of CYP4F2 rs2108622C>T variant is significantly (P = 0.02) lower among TIIDM patients in comparison to healthy subjects using both co-dominant and dominant genotyping models. In addition, the CYP4F2 rs2108622 T/T genotype was significantly (P = 0.02) more frequent among TIIDM patients with retinopathy complications (OR=4.36, CI: 1.32-14.37). Lastly, the CYP4F2 rs2108622C>T variant was not associated (P > 0.05) with the glycaemic and lipid profile of patients.

CONCLUSIONS

It can be concluded from this study that the frequency of CYP4F2 rs2108622 T/T genotype is lower among TIIDM, but this genotype is associated with an increased risk of retinopathy complications in patients of Jordanian origin. Further studies with a larger sample size are needed to validate the findings of this study.

Proprotein Convertase Subtilisin/Kexin Type 9 Inhibitors Use for Atherogenic Dyslipidemia in Solid Organ Transplant Patients

Dyslipidemia is a widespread risk factor in solid organ transplant patients, due to many reasons, such as the use of immunosuppressive drugs, with a consequent increase in cardiovascular diseases in this population. PCSK9 is an enzyme mainly known for its role in altering LDL levels, consequently increasing cardiovascular risk. Monoclonal antibody PCSK9 inhibitors demonstrated remarkable efficacy in the general population in reducing LDL cholesterol levels and preventing cardiovascular disease. In transplant patients, these drugs are still poorly used, despite having comparable efficacy to the general population and giving fewer drug interactions with immunosuppressants. Furthermore, there is enough evidence that PCSK9 also plays a role in other pathways, such as inflammation, which is particularly dangerous for graft survival. In this review, the current evidence on the function of PCSK9 and the use of its inhibitors will be discussed, particularly in transplant patients, in which they may provide additional benefits.

Caloric restriction reduces the pro-inflammatory eicosanoid 20- hydroxyeicosatetraenoic acid to protect from acute kidney injury

Acute kidney injury is a frequent complication in the clinical setting and associated with significant morbidity and mortality. Preconditioning with short-term caloric restriction is highly protective against kidney injury in rodent ischemia reperfusion injury models. However, the underlying mechanisms are unknown hampering clinical translation. Here, we examined the molecular basis of caloric restriction-mediated protection to elucidate the principles of kidney stress resistance. Analysis of an RNAseq dataset after caloric restriction identified Cyp4a12a, a cytochrome exclusively expressed in male mice, to be strongly downregulated after caloric restriction. Kidney ischemia reperfusion injury robustly induced acute kidney injury in male mice and this damage could be markedly attenuated by pretreatment with caloric restriction. In females, damage was significantly less pronounced and preconditioning with caloric restriction had only little effect. Tissue concentrations of the metabolic product of Cyp4a12a, 20-hydroxyeicosatetraenoic acid (20-HETE), were found to be significantly reduced by caloric restriction. Conversely, intraperitoneal supplementation of 20-HETE in preconditioned males partly abrogated the protective potential of caloric restriction. Interestingly, this effect was accompanied by a partial reversal of caloric restriction-induced changes in protein but not RNA expression pointing towards inflammation, endoplasmic reticulum stress and lipid metabolism. Thus, our findings provide an insight into the mechanisms underlying kidney protection by caloric restriction. Hence, understanding the mediators of preconditioning is an important pre-requisite for moving towards translation to the clinical setting.

Genetics Variants in the Epoxygenase Pathway of Arachidonic Metabolism Are Associated with Eicosanoids Levels and the Risk of Diabetic Nephropathy

Genes in the epoxygenase pathway of arachidonic acid metabolism leading to vasoactive eicosanoids, mainly 20-hydroxyeicosatetraenoic (20-HETE) and epoxyeicosatrienoic (EETs) acids, have been related to glucose-induced renal damage in preclinical reports. We genotyped 1088 diabetic kidney disease (DKD) patients and controls for seven polymorphisms in five genes (CYP2C8, CYP2J2, CYP4F2, CYP4A11, and EPHX2) along this metabolic route and evaluated their effect on DKD risk, clinical outcomes, and the plasma/urine levels of eicosanoids measured by LC/MS/MS and immunoenzymatic assays. The CYP4F2 433M variant allele was associated with lower incidence of DKD (OR = 0.65 (0.48-0.90), p = 0.008), whilst the CYP2C8*3/*3 genotype was related to increased risk (OR = 3.21 (1.05-9.87), p = 0.036). Patients carrying the 433M allele also showed lower eGFR [median and interquartile range vs. wildtype carriers: 30.8 (19.8) and 33.0 (23.2) mL/min/1.73 m², p = 0.037). Finally, the 433VM/MM variant genotypes were associated with lower urinary levels of 20-HETE compared with 433VV (3.14 (0.86) vs. 8.45 (3.69) ng/mg Creatinine, p = 0.024). Our results indicate that the CYP4F2 V433M polymorphism, by decreasing 20-HETE levels, may play an important role in DKD.

In silico network pharmacology and in vivo analysis of berberine-related mechanisms against type 2 diabetes mellitus and its complications

ETHNOPHARMACOLOGICAL RELEVANCE

Berberine (BBR), extracted from the traditional medicinal plant Coptis chinensis Franch., has been widely used for the treatment of type 2 diabetes mellitus (T2DM) and its complications.

AIM OF THE STUDY

To determine the potential pharmacological mechanisms underlying BBR therapeutic effect on T2DM and its complications by in silico network pharmacology and experimental in vivo validation.

MATERIALS AND METHODS

A predictive network depicting the relationship between BBR and T2DM was designed based on information collected from several databases, namely STITCH, CHEMBL, PharmMapper, TTD, Drugbank, and PharmGKB. Identified overlapping targets related to both BBR and T2DM were crossed with information on biological processes (BPs) and molecular/signaling pathways using the DAVID platform and Cytoscape software. Three candidate targets identified with the BBR-T2DM network (RXRA, KCNQ1 and NR3C1) were evaluated in the C57BL/6J mouse model of T2DM. The mice were treated with BBR or metformin for 10 weeks. Weight, fasting blood glucose (FBG), oral glucose tolerance, and expression levels of the three targets were evaluated.

RESULTS

A total of 31 targets of BBR that were also related to T2DM were identified, of which 14 had already been reported in previous studies. Furthermore, these 31 overlapping targets were enriched in 21 related BPs and 18 pathways involved in T2DM treatment. The identified BP-target-pathway network revealed the underlying mechanisms of BBR antidiabetic activity were mediated by core targets such as RXRA, KCNQ1, and NR3C1. In vivo experiments further confirmed that treatment with BBR significantly reduced weight and FBG and alleviated insulin resistance in T2DM mice. Moreover, BBR treatment promoted RXRA expression, whereas it reduced KCNQ1 and NR3C1 expression in the liver.

CONCLUSION

Using network pharmacology and a T2DM mouse model, this study revealed that BBR can effectively prevent T2DM symptoms through vital targets and multiple signaling pathways. Network pharmacology provides an efficient, time-saving approach for therapeutic research and the development of new drugs.

20-HETE interferes with insulin signaling and contributes to obesity-driven insulin resistance

20-HETE, a metabolite of arachidonic acid produced by Cytochrome P450 (CYP) 4A/4 F, has been implicated in the development of obesity-associated complications such as diabetes and insulin resistance. In this study, we examined whether the acute elevation of 20-HETE levels contributes to the development of diet-driven hyperglycemia and insulin resistance. We employed a conditional transgenic mouse model to overexpress Cyp4a12 (Cyp4a12tg), a murine 20-HETE synthase, together with high fat diet (HFD) feeding. Mice in which Cyp4a12 was induced by doxycycline (DOX) at the onset of HFD feeding gained weight at a greater rate and extent than corresponding DOX-untreated Cyp4a12 mice. Cyp4a12tg mice fed HFD + DOX displayed hyperglycemia and impaired glucose metabolism while corresponding HFD-fed Cyp4a12tg mice (no DOX) did not. Importantly, administration of a 20-HETE antagonist, 20-SOLA, to Cyp4a12tg mice fed HFD + DOX significantly attenuated weight gain and prevented the development of hyperglycemia and impaired glucose metabolism. Levels of insulin receptor (IR) phosphorylation at Tyrosine 972 and insulin receptor substrate-1 (IRS1) phosphorylation at serine 307 were markedly decreased and increased, respectively, in liver, skeletal muscle and adipose tissues from Cyp4a12tg mice fed HFD + DOX; 20-SOLA prevented the IR and IRS1 inactivation, suggesting that 20-HETE interferes with insulin signaling. Additional studies in 3T3-1 differentiated adipocytes confirmed that 20-HETE impairs insulin signaling and that its effect may require activation of its receptor GPR75. Taken together, these results provide strong evidence that 20-HETE interferes with insulin function and contributed to diet-driven insulin resistance.

Polymorphisms in vasoactive eicosanoid genes of kidney donors affect biopsy scores and clinical outcomes in renal transplantation

Cytochrome P450 (CYP) enzymes metabolize arachidonic acid to vasoactive eicosanoids such as epoxyeicosatrienoic acids (EETs) and 20-Hydroxyeicosatetraenoic acid (20-HETE), whilst soluble epoxide hydrolase, encoded by the EPHX2 gene, is in charge of EETs degradation. We aimed to analyze the influence of common, functional polymorphisms in four genes of the donor on the renal biopsy scores independently assigned by pathologists. Additionally, we examined whether this score or the presence of these SNPs were independent risk factors of clinical outcomes in the first year after grafting. A cohort of 119 recipients and their corresponding 85 deceased donors were included in the study. Donors were genotyped for the CYP4F2 V433M, CYP2C8*3, CYP2J2*7, EPHX2 3’UTR A>G, EPHX2 K55R and EPHX2 R287Q polymorphisms. The association of the donors’ SNPs with the biopsy scores and clinical outcomes was retrospectively evaluated by multivariate regression analysis. The CYP2C8*3 polymorphism in the donor was significantly associated with higher scores assigned to pretransplant biopsies [OR = 3.35 (1.03–10.93), p = 0.045]. In turn, higher scores were related to an increased risk of acute rejection [OR = 5.28 (1.32–21.13), p = 0.019] and worse glomerular filtration rate (eGFR) (45.68±16.05 vs. 53.04±16.93 ml/min in patients whose grafts had lower scores, p = 0.010) one year after transplant. Patients whose donors carried the CYP4F2 433M variant showed lower eGFR values (48.96±16.89 vs. 55.94±18.62 ml/min in non-carriers, p = 0.038) and higher risk of acute rejection [OR = 6.18 (1.03–37.21), p = 0.047]. The CYP2J2*7 SNP in the donor was associated with elevated risk of delayed graft function [OR = 25.68 (1.52–43.53), p = 0.025]. Our results taken together suggest that donor genetic variability may be used as a predictor of tissue damage in the graft as well as to predict clinical outcomes and graft function in the recipient.

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.

Variability in the leptin receptor gene and other risk factors for post-transplant diabetes mellitus in renal transplant recipients

Aim: Post-transplant diabetes mellitus (PTDM) is one of the main complications after kidney transplantation. It is known that leptin plays an important role in glucose metabolism and mutations in the leptin receptor gene (LEPR) are responsible for different complications in renal transplant recipients. We aimed to analyse the association of polymorphisms in LEPR with the development of PTDM in these patients. Methods: A total of 315 renal transplant recipients were genotyped for the Lys109Arg, Gln223Arg and Lys656Asn polymorphisms. The impact of these genetic variables together with other clinical and demographic parameters on PTDM risk was evaluated in a multivariate regression analysis. Results: The 223Arg variant showed a significant association with PTDM risk [OR = 3.26 (1.35-7.85), p = 0.009] after correcting for multiple testing. Carriers of this variant also showed higher BMI values (26.95 ± 4.23) than non-carriers (25.67 ± 4.43, p = 0.025). In addition, it was BMI at transplant and not the BMI increment in the first year after grafting that was associated with PTDM (p > 0.00001). Haplotype analyses did not reveal significant associations. Conclusions: Our result show, for the first time to our knowledge, that genetic variability in the LEPR may contribute significantly to the risk for PTDM in renal transplant recipients. KEY MESSAGES The LEPR Gln223Arg polymorphism significantly contributes to the development of PTDM in renal transplant recipients. The effect of the 223Arg variant on PTDM is strongly modulated by the age of the recipient. The 223Arg variant in the leptin receptor is related to higher BMI in renal transplant recipients.

High-fat diet-induced obesity and insulin resistance in CYP4a14-/- mice is mediated by 20-HETE

20-Hydroxyeicosatetraenoic acid (20-HETE) has been shown to positively correlate with body mass index, hyperglycemia, and plasma insulin levels. This study seeks to identify a causal relationship between 20-HETE and obesity-driven insulin resistance. Cyp4a14-/- male mice, a model of 20-HETE overproduction, were fed a regular or high-fat diet (HFD) for 15 wk. 20-SOLA [2,5,8,11,14,17-hexaoxanonadecan-19-yl 20-hydroxyeicosa-6( Z),15( Z)-dienoate], a 20-HETE antagonist, was administered from week 0 or week 7 of HFD. HFD-fed mice gained significant weight (16.7 ± 3.2 vs. 3.8 ± 0.35 g, P < 0.05) and developed hyperglycemia (157 ± 3 vs. 121 ± 7 mg/dl, P < 0.05) and hyperinsulinemia (2.3 ± 0.4 vs. 0.5 ± 0.1 ng/ml, P < 0.05) compared with regular diet-fed mice. 20-SOLA attenuated HFD-induced weight gain (9.4 ± 1 vs. 16.7 ± 3 g, P < 0.05) and normalized the hyperglycemia (157 ± 7 vs. 102 ± 5 mg/dl, P < 0.05) and hyperinsulinemia (1.1 ± 0.1 vs. 2.3 ± 0.4 ng/ml, P < 0.05). The impaired glucose homeostasis and insulin resistance in HFD-fed mice evidenced by reduced insulin and glucose tolerance were also ameliorated by 20-SOLA. Circulatory and adipose tissue 20-HETE levels significantly increased in HFD-fed mice correlating with impaired insulin signaling, including reduction in insulin receptor tyrosine (Y972) phosphorylation and increased serine (S307) phosphorylation of the insulin receptor substrate-1 (IRS-1). 20-SOLA treatments prevented changes in insulin signaling. These findings indicate that 20-HETE contributes to HFD-induced obesity, insulin resistance, and impaired insulin signaling.

Genetic risk factors for post-transplantation diabetes mellitus in Chinese Han renal allograft recipients treated with tacrolimus

BACKGROUND

Post-transplantation diabetes mellitus (PTDM) is a serious metabolic complication after kidney transplantation. The aim of this study was to explore the association of clinical variables and five selected single nucleotide polymorphisms (SNPs) with PTDM in Chinese Han renal allograft recipients taking tacrolimus (TAC).

METHODS

A total of 129 non-diabetic, primary, Chinese Han renal allograft recipients treated with TAC were enrolled. Five SNPs (CYP3A5 rs776741, rs776746, rs15524, CYP24A1 rs2296241, and PPARG rs1801282) were genotyped and analyzed.

RESULTS

Among 129 recipients, 17 (13.2%) developed PTDM. Both univariate and multivariate analysis demonstrated that age over 50 years old and CYP24A1 rs2296241 A allele were independently correlated with the development of PTDM, while no significant differences was observed in TAC pharmacokinetics and CYP3A5, PPARG polymorphisms between two groups.

CONCLUSIONS

Patients with advanced age and CYP24A1 rs2296241 A allele had an increased risk of PTDM after kidney transplantation.

Polymorphisms in genes involved in vasoactive eicosanoid synthesis affect cardiovascular risk in renal transplant recipients

OBJECTIVE

Arachidonic acid metabolism by cytochrome P450 (CYP) epoxygenases leads to epoxyeicosatrienoic acids (EETs), which are eicosanoids with vasodilator and anti-inflammatory properties. We aim to determine whether genetic variability in these routes may contribute to cardiovascular (CV) risk in renal transplant recipients.

METHODS

In a cohort of 355 patients, we determined the presence of two polymorphisms, CYP2C8*3 and CYP2J2*7, known to affect eicosanoid levels. Associations with CV mortality, CV event-free long-term survival and graft survival were retrospectively investigated by logistic regression models.

RESULTS

CYP2J2*7 showed a statistical trend towards higher CV mortality (p = .06) and lower cardiac or cerebral event-free long-term survival (p = .05), whilst CYP2C8*3 displayed a significant inverse association with the risk of CV event (hazard ratio [HR] = 0.34 [0.15-0.78], p = .01). The association of CYP2J2*7 with CV mortality became significant when the analysis was restrained to 316 patients without a history of CV events prior to transplantation (HR = 15.72 [2.83-91.94], p = .005). In this subgroup of patients both single nucleotide polymorphisms (SNPs) were significantly associated with event-free survival. HR values were 5.44 (1.60-18.51), p = .007 and 0.26 (0.09-0.75), p = .012 for CYP2J2*7 and CYP2C8*3, respectively.

CONCLUSIONS

Our results show, for the first time to our knowledge, that two SNPs in CYP2C8 and CYP2J2, which synthesize EETs, may modify CV outcomes in renal transplant recipients, a population that is already at a high risk of suffering these events.

Distribution of CYP2C8 and CYP2C9 amino acid substitution alleles in South Indian diabetes patients: A genotypic and computational protein phenotype study

The CYP2C8 and CYP2C9 are two major isoforms of the cytochrome P450 enzyme family, which is involved in drug response, detoxification, and disease development. This study describes the differential distribution of amino acid substitution variants of CYP2C8 (*2-I269F & *3-R139K) and CYP2C9 (*2-C144R & *3-L359A) genes in 234 type 2 diabetes mellitus (T2DM) patients and 218 healthy controls from Andhra Pradesh, South India. Single locus genotype analysis has revealed that homozygous recessive genotypes of 2C8*2-TT (P ≤ .03), 2C9*2-TT (P ≤ .02), and heterozygous 2C9*3-AC (P ≤ .006) are seen to be increasingly present in the case group, indicating a significant level of their association with diabetes in Andhra population. The statistical significance of these recessive genotypes has persisted even under their corresponding allelic forms (P ≤ .01). Genotype association results were further examined by computational protein structure and stability analysis to assess the deleteriousness of the amino acid changes. The mutant CYP 2C8 and 2C9 (both *2 and *3) proteins showed structural drifts at both amino acid residue (range 0.43Å-0.77Å), and polypeptide chain levels (range 0.68Å-1.81Å) compared to their wild-type counterparts. Furthermore, the free energy value differences (range -0.915 to -1.38 Kcal/mol) between mutant and native protein structures suggests the deleterious and destabilizing potential of amino acid substitution polymorphisms of CYP genes. The present study confirms the variable distribution of CYP2C8 (*2 and *3) and CYP2C9 (*2 and *3) allelic polymorphisms among South Indian diabetic populations and further warrants the serious attention of CYP gene family, as a putative locus for disease risk assessment and therapy.

Effect of Cytochrome P450 Metabolites of Arachidonic Acid in Nephrology

Thirty-five years ago, a third pathway for the metabolism of arachidonic acid by cytochrome P450 enzymes emerged. Subsequent work revealed that 20-hydroxyeicosatetraenoic and epoxyeicosatrienoic acids formed by these pathways have essential roles in the regulation of renal tubular and vascular function. Sequence variants in the genes that produce 20-hydroxyeicosatetraenoic acid are associated with hypertension in humans, whereas the evidence supporting a role for variants in the genes that alter levels of epoxyeicosatrienoic acids is less convincing. Studies in animal models suggest that changes in the production of cytochrome P450 eicosanoids alter BP. However, the mechanisms involved remain controversial, especially for 20-hydroxyeicosatetraenoic acid, which has both vasoconstrictive and natriuretic actions. Epoxyeicosatrienoic acids are vasodilators with anti-inflammatory properties that oppose the development of hypertension and CKD; 20-hydroxyeicosatetraenoic acid levels are elevated after renal ischemia and may protect against injury. Levels of this eicosanoid are also elevated in polycystic kidney disease and may contribute to cyst formation. Our review summarizes the emerging evidence that cytochrome P450 eicosanoids have a role in the pathogenesis of hypertension, polycystic kidney disease, AKI, and CKD.

Genetic factors in pathogenesis of diabetes mellitus after kidney transplantation

Posttransplant diabetes mellitus (PTDM) is one of the major metabolic complications after transplantation of solid organs including the kidney. This type of diabetes mellitus affects allograft survival, cardiovascular complications and overall patient survival. The modifiable risk factors that contribute to PTDM include obesity, some viral infections (eg, hepatitis C virus, cytomegalovirus) and especially immunosuppressive drugs including corticosteroids, tacrolimus, cyclosporine and sirolimus. Currently, predisposing genetic factors have been considered important in PTDM development. The commonly evaluated genetic determinants include genes encoding transcription factors, cytokines, chemokines, adipokines, ionic channels, glucose transporters, cytochrome P450 enzymes and other enzymes metabolizing drugs, drug transporters. Unfortunately, the results of studies are inconclusive and differ between populations. There is a need for large genome-wide association study to identify the genetic risk factors associated with PTDM development.

20-HETE Signals Through G-Protein-Coupled Receptor GPR75 (Gq) to Affect Vascular Function and Trigger Hypertension

RATIONALE

20-Hydroxyeicosatetraenoic acid (20-HETE), one of the principle cytochrome P450 eicosanoids, is a potent vasoactive lipid whose vascular effects include stimulation of smooth muscle contractility, migration, and proliferation, as well as endothelial cell dysfunction and inflammation. Increased levels of 20-HETE in experimental animals and in humans are associated with hypertension, stroke, myocardial infarction, and vascular diseases.

OBJECTIVE

To date, a receptor/binding site for 20-HETE has been implicated based on the use of specific agonists and antagonists. The present study was undertaken to identify a receptor to which 20-HETE binds and through which it activates a signaling cascade that culminates in many of the functional outcomes attributed to 20-HETE in vitro and in vivo.

METHODS AND RESULTS

Using crosslinking analogs, click chemistry, binding assays, and functional assays, we identified G-protein receptor 75 (GPR75), currently an orphan G-protein-coupled receptor (GPCR), as a specific target of 20-HETE. In cultured human endothelial cells, 20-HETE binding to GPR75 stimulated Gα_q/11 protein dissociation and increased inositol phosphate accumulation and GPCR-kinase interacting protein-1-GPR75 binding, which further facilitated the c-Src-mediated transactivation of epidermal growth factor receptor. This results in downstream signaling pathways that induce angiotensin-converting enzyme expression and endothelial dysfunction. Knockdown of GPR75 or GPCR-kinase interacting protein-1 prevented 20-HETE-mediated endothelial growth factor receptor phosphorylation and angiotensin-converting enzyme induction. In vascular smooth muscle cells, GPR75-20-HETE pairing is associated with Gα_q/11- and GPCR-kinase interacting protein-1-mediated protein kinase C-stimulated phosphorylation of MaxiKβ, linking GPR75 activation to 20-HETE-mediated vasoconstriction. GPR75 knockdown in a mouse model of 20-HETE-dependent hypertension prevented blood pressure elevation and 20-HETE-mediated increases in angiotensin-converting enzyme expression, endothelial dysfunction, smooth muscle contractility, and vascular remodeling.

CONCLUSIONS

This is the first report to identify a GPCR target for an eicosanoid of this class. The discovery of 20-HETE-GPR75 pairing presented here provides the molecular basis for the signaling and pathophysiological functions mediated by 20-HETE in hypertension and cardiovascular diseases.

A novel long non-coding RNA CYP4B1-PS1-001 regulates proliferation and fibrosis in diabetic nephropathy

Diabetic nephropathy is an important microvascular complication of diabetes, and the incidence of end-stage renal disease caused by it are rising annually. Long non-coding RNAs (lncRNAs) are widely regarded to associate with the occurrence and development of various diseases; however, the relationship between lncRNAs and diabetic nephropathy remains largely unknown. This work studied the effect of lncRNAs on diabetic nephropathy pathogenesis. LncRNA microarrays were initially used to detect lncRNAs with altered expression in three cases of kidney tissue from db/db mice with diabetic nephropathy. LncRNAs with differential expression (>2-fold) could be considered candidates. Particularly, CYP4B1-PS1-001 was significantly downregulated in response to early diabetic nephropathy in vitro and in vivo, while overexpression of CYP4B1-PS1-001 inhibited proliferation and fibrosis of mesangial cells. Overall, our data indicate the potential role of CYP4B1-PS1-001 in the proliferation and fibrosis of mice mesangial cells as the prominent features during early stage of diabetic nephropathy, which extend the relationship between lncRNAs and diabetic nephropathy, and may provide a potential therapeutic target and molecular biomarker for the disease.