Reference gene panel for urinary exosome-based molecular diagnostics in patients with kidney disease

BACKGROUND Kidney disease is a severe complication of diabetes that often leads to end-stage renal disease.Early diagnosis is crucial for prevention or delay.However,the current diagnostic methods,with their limitations in detecting the disease in its early stages,underscore the urgency and importance of finding new solutions.miRNAs encapsulated inside urinary exosomes(UEs)have potential as early biomarkers for kidney diseases.The need for reference miRNAs for accurate interpretation currently limits their translational potential.AIM To identify consistently expressing reference miRNAs from UEs of controls and patients with type 2 diabetesmellitus(T2DM)and biopsy-confirmed kidney diseases.METHODS miRNA profiling was performed on UEs from 31 human urine samples using a rigorous and unbiased method.The UEs were isolated from urine samples collected from healthy individuals(n=6),patients with T2DM(n=13),and T2DM patients who also had kidney diseases(including diabetic nephropathy,n=5;membranous nephropathy,n=5;and IgA nephropathy,n=2)through differential ultracentrifugation.After characterizing the UEs,miRNA expression profiling using microarray technology was conducted.RESULTS Microarray data analysis identified 14 miRNAs that were consistently expressed in UEs from 31 human samples,representing various kidney conditions:diabetic controls,diabetic nephropathy,membrane nephropathy,IgA nephropathy,and healthy controls.Through in silico analysis,we determined that 10 of these miRNAs had significant potential to serve as reference genes in UEs.CONCLUSION We identified uniformly expressing UE miRNAs that could serve as reference genes kidney disease biomarkers.

Challenges in predictive modelling of chronic kidney disease:A narrative review

The exponential rise in the burden of chronic kidney disease(CKD)worldwide has put enormous pressure on the economy.Predictive modeling of CKD can ease this burden by predicting the future disease occurrence ahead of its onset.There are various regression methods for predictive modeling based on the distribution of the outcome variable.However,the accuracy of the predictive model depends on how well the model is developed by taking into account the goodness of fit,choice of covariates,handling of covariates measured on a continuous scale,handling of categorical covariates,and number of outcome events per predictor parameter or sample size.Optimal performance of a predictive model on an independent cohort is desired.However,there are several challenges in the predictive modeling of CKD.Disease-specific methodological challenges hinder the development of a predictive model that is cost-effective and universally applicable to predict CKD onset.In this review,we discuss the advantages and challenges of various regression models available for predictive modeling and highlight those best for future CKD prediction.

Liver or kidney:Who has the oar in the gluconeogenesis boat and when?

Gluconeogenesis is an endogenous process of glucose production from noncarbohydrate carbon substrates.Both the liver and kidneys express the key enzymes necessary for endogenous glucose production and its export into circulation.We would be remiss to add that more recently gluconeogenesis has been described in the small intestine,especially under high-protein,lowcarbohydrate diets.The contribution of the liver glucose release,the net glucose flux,towards systemic glucose is already well known.The liver is,in most instances,the primary bulk contributor due to the sheer size of the organ(on average,over 1 kg).The contribution of the kidney(at just over 100 g each)to endogenous glucose production is often under-appreciated,especially on a weight basis.Glucose is released from the liver through the process of glycogenolysis and gluconeogenesis.Renal glucose release is almost exclusively due to gluconeogenesis,which occurs in only a fraction of the cells in that organ(proximal tubule cells).Thus,the efficiency of glucose production from other carbon sources may be superior in the kidney relative to the liver or at least on the level.In both these tissues,gluconeogenesis regulation is under tight hormonal control and depends on the availability of substrates.Liver and renal gluconeogenesis are differentially regulated under various pathological conditions.The impact of one source vs the other changes,based on post-prandial state,acid-base balance,hormonal status,and other less understood factors.Which organ has the oar(is more influential)in driving systemic glucose homeostasis is still inconclusive and likely changes with the daily rhythms of life.We reviewed the literature on the differences in gluconeogenesis regulation between the kidneys and the liver to gain an insight into who drives the systemic glucose levels under various physiological and pathological conditions.

Renal gluconeogenesis in insulin resistance:A culprit for hyperglycemia in diabetes

Renal gluconeogenesis is one of the major pathways for endogenous glucose production.Impairment in this process may contribute to hyperglycemia in cases with insulin resistance and diabetes.We reviewed pertinent studies to elucidate the role of renal gluconeogenesis regulation in insulin resistance and diabetes.A consensus on the suppressive effect of insulin on kidney gluconeogenesis has started to build up.Insulin-resistant models exhibit reduced insulin receptor(IR)expression and/or post-receptor signaling in their kidney tissue.Reduced IR expression or post-receptor signaling can cause impairment in insulin’s action on kidneys,which may increase renal gluconeogenesis in the state of insulin resistance.It is now established that the kidney contributes up to 20%of all glucose production via gluconeogenesis in the post-absorptive phase.However,the rate of renal glucose release excessively increases in diabetes.The rise in renal glucose release in diabetes may contribute to fasting hyperglycemia and increased postprandial glucose levels.Enhanced glucose release by the kidneys and renal expression of the gluconeogenic-enzyme in diabetic rodents and humans further point towards the significance of renal gluconeogenesis.Overall,the available literature suggests that impairment in renal gluconeogenesis in an insulinresistant state may contribute to hyperglycemia in type 2 diabetes.

Insulin receptors in the kidneys in health and disease

Insulin is an important hormone that affects various metabolic processes,including kidney function.Impairment in insulin's action leads to insulin resistance in the target tissue.Besides defects in post-receptor insulin signaling,impairment at the receptor level could significantly affect insulin sensitivity of the target tissue.The kidney is a known target of insulin;however,whether the kidney develops "insulin resistance" is debatable.Regulation of the insulin receptor(IR) expression and its function is very well studied in major metabolic tissues like liver,skeletal muscles,and adipose tissue.The physiological relevance of IRs in the kidney has recently begun to be clarified.The credit goes to studies that showed a wide distribution of IR throughout the nephron segments and their reduced expression in the insulin resistance state.Moreover,altered renal and systemic metabolism observed in mice with targeted deletion of the IR from various epithelial cells of the kidney has strengthened this proposition.In this review,we recapitulate the crucial findings from literature that have expanded our knowledge regarding the significance of the renal IR in normal-and insulin-resistance states.