A Dynamic Mass Redistribution Assay for the Human Sweet Taste Receptor Uncovers G-Protein Dependent Biased Ligands.

The sweet taste receptor is rather unique, recognizing a diverse repertoire of natural or synthetic ligands, with a surprisingly large structural diversity, and with potencies stretching over more than six orders of magnitude. Yet, it is not clear if different cell-based assays can faithfully report the relative potencies and efficacies of these molecules. Indeed, up to now, sweet taste receptor agonists have been almost exclusively characterized using cell-based assays developed with overexpressed and promiscuous G proteins. This non-physiological coupling has allowed the quantification of receptor activity via phospholipase C activation and calcium mobilization measurements in heterologous cells on a FLIPR system, for example. Here, we developed a novel assay for the human sweet taste receptor where endogenous G proteins and signaling pathways are recruited by the activated receptor. The effects of several sweet taste receptor agonists and other types of modulators were recorded by measuring changes in dynamic mass redistribution (DMR) using an Epic® reader. Potency and efficacy values obtained in the DMR assay were compared to those results obtained with the classical FLIPR assay. Results demonstrate that for some ligands, the two assay systems provide similar information. However, a clear bias for the FLIPR assay was observed for one third of the agonists evaluated, suggesting that the use of non-physiological coupling may influence the potency and efficacy of sweet taste receptor ligands. Replacing the promiscuous G protein with a chimeric G protein containing the C-terminal tail 25 residues of the physiologically relevant G protein subunit Gαgustducin reduced or abrogated bias.

Making sense of glucose sensors in end-stage kidney disease: A review.

Diabetes mellitus remains the leading cause of end-stage kidney disease worldwide. Inadequate glucose monitoring has been identified as one of the gaps in care for hemodialysis patients with diabetes, and lack of reliable methods to assess glycemia has contributed to uncertainty regarding the benefit of glycemic control in these individuals. Hemoglobin A1c, the standard metric to evaluate glycemic control, is inaccurate in patients with kidney failure, and does not capture the full range of glucose values for patients with diabetes. Recent advances in continuous glucose monitoring have established this technology as the new gold standard for glucose management in diabetes. Glucose fluctuations are uniquely challenging in patients dependent on intermittent hemodialysis, and lead to clinically significant glycemic variability. This review evaluates continuous glucose monitoring technology, its validity in the setting of kidney failure, and interpretation of glucose monitoring results for the nephrologist. Continuous glucose monitoring targets for patients on dialysis have yet to be established. While continuous glucose monitoring provides a more complete picture of the glycemic profile than hemoglobin A1c and can mitigate high-risk hypoglycemia and hyperglycemia in the context of the hemodialysis procedure itself, whether the technology can improve clinical outcomes merits further investigation.

Genetic factors associated with favourable pollinator traits in the wheat cultivar Piko.

Hybrid breeding in wheat has the potential to boost yields. An efficient hybrid seed production system requires elite pollinators; however, such germplasm is limited among modern cultivars. Piko, a winter wheat (Triticum aestivum L.) cultivar, has been identified as a superior pollinator and has been used in Europe. Piko has favourable pollinator traits for anther extrusion, anther length, pollen mass and hybrid seed set. However, the genetic factors responsible for Piko's favourable traits are largely unknown. Here, we report on the genetic analysis of a Piko-derived F2 mapping population. We confirmed that Piko's Rht-D1a allele for tall stature is associated with large anthers and high anther extrusion. However, Rht-D1 was not found to be associated with anther filament length, confirmed by near isogenic lines. Piko's photoperiod sensitive Ppd-B1b allele shows an association with increased spike length, more spikelets and spike architecture traits, while the insensitive Ppd-B1a allele is linked with high anther extrusion and larger anthers. We identified an anther extrusion quantitative trait locus (QTL) on chromosome 6A that showed significantly biased transmission of the favourable Piko allele amongst F2 progenies. The Piko allele is completely absent in the distal 6AS region and the central 6A region revealed a significantly lower ratio (<8%) of F2 with homozygous Piko alleles. Our study provided further evidence for the effects of Rht-D1 and Ppd-B1 loci on multiple pollinator traits and a novel anther extrusion QTL that exhibits segregation distortion.

ATTENTION: Workforce shortages as a barrier to optimal dialysis.

Providing optimal end-stage kidney disease (ESKD) management requires an adequately trained and sufficiently staffed workforce, including doctors, nurses, and patient care technicians (PCTs). The growing need for ESKD services for a surging population of dialysis-dependent patients has made obvious a workforce crisis affecting nephrology. For a multitude of reasons, the physician workforce supply available to provide dialysis care has failed to expand commensurate with patients need in recent years. Of most importance, fewer US trainees are choosing to enter nephrology, and fewer international medical graduates are available to fill training program rosters. Equally important but less frequently cited are occupational shortages of trained dialysis nurses and PCTs. This article brings attention to this complex workforce shortage and addresses the limited information available regarding how it might constitute a barrier to optimal dialysis care.

Said the glucose sensor to the insulin pump: can glycemic control be improved in hospitalized ESRD patients with diabetes mellitus?

Although control of chronic glycemia in the population with diabetes and end-stage renal disease (ESRD) has been extensively studied in recent years, the unique problems of short-term glycemic management in acutely ill patients undergoing dialysis have received little attention. Bally et al. evaluated the role of a "closed-loop" (glucose sensor/algorithm tablet device/insulin pump) system in a cohort of hospitalized patients with type 2 diabetes receiving hemodialysis. Compared with usual care, the intervention group had superior glycemic control without increased hypoglycemic events. Additional studies are warranted.

The Glycemic Indices in Dialysis Evaluation (GIDE) study: Comparative measures of glycemic control in diabetic dialysis patients.

The validity of hemoglobin A1c (HgbA1c) is undergoing increasing scrutiny in the advanced CKD/ESRD (chronic kidney disease/end-stage renal disease) population, where it appears to be discordant from other glycemic indices. In the Glycemic Indices in Dialysis Evaluation (GIDE) Study, we sought to assess correlation of HgbA1c with casual glucose, glycated albumin, and serum fructosamine in a large group of diabetic patients on dialysis. From 26 dialysis facilities in the United States, 1758 diabetic patients (hemodialysis = 1476, peritoneal dialysis = 282) were enrolled in the first quarter of 2013. The distributions of HgbA1c and the other glycemic indices were analyzed. Intra-patient coefficients of variation and correlations among the four glycemic indices were determined. Patients with low HgbA1c values were both on higher erythropoietin (ESA) doses and more anemic. Serum glucose exhibited the highest intra-patient variability over a 3-month period; variability was modest among the other glycemic indices, and least with HgbA1c. Statistical analyses inclusive of all glycemic markers indicated modest to strong correlations. HgbA1c was more likely to be in the target range than glycated albumin or serum fructosamine, suggesting factors which may or may not be directly related to glycemic control, including anemia, ESA management, and iron administration, in interpreting HgbA1c values. These initial results from the GIDE Study clarify laboratory correlations among glycemic indices and add to concerns about reliance on HgbA1c in patients with diabetes and advanced kidney disease.

A pair of homoeolog ClpP5 genes underlies a virescent yellow-like mutant and its modifier in maize.

Gene-background interaction is a commonly observed phenomenon in many species, but the molecular mechanisms of such an interaction is less well understood. Here we report the cloning of a maize mutant gene and its modifier. A recessive mutant with a virescent yellow-like (vyl) phenotype was identified in an ethyl methanesulfonate-mutagenized population derived from the maize inbred line B73. Homozygous mutant maize plants exhibited a yellow leaf phenotype after emergence but gradually recovered and became indistinguishable from wild-type plants after approximately 2 weeks. Taking the positional cloning approach, the Chr.9_ClpP5 gene, one of the proteolytic subunits of the chloroplast Clp protease complex, was identified and validated as the candidate gene for vyl. When introgressed by backcross into the maize inbred line PH09B, the mutant phenotype of vyl lasted much longer in the greenhouse and was lethal in the field, implying the presence of a modifier(s) for vyl. A major modifier locus was identified on chromosome 1, and a paralogous ClpP5 gene was isolated and confirmed as the candidate for the vyl-modifier. Expression of Chr.1_ClpP5 is induced significantly in B73 by the vyl mutation, while the expression of Chr.1_ClpP5 in PH09B is not responsive to the vyl mutation. Moreover, expression and sequence analysis suggests that the PH09B Chr.1_ClpP5 allele is functionally weaker than the B73 allele. We propose that functional redundancy between duplicated paralogous genes is the molecular mechanism for the interaction between vyl and its modifier.

Glycemic management in ESRD and earlier stages of CKD.

The management of hyperglycemia in patients with kidney failure is complex, and the goals and methods regarding glycemic control in chronic kidney disease (CKD) are not clearly defined. Although aggressive glycemic control seems to be advantageous in early diabetic nephropathy, outcome data supporting tight glycemic control in patients with advanced CKD (including end-stage renal disease [ESRD]) are lacking. Challenges in the management of such patients include therapeutic inertia, monitoring difficulties, and the complexity of available treatments. In this article, we review the alterations in glucose homeostasis that occur in kidney failure, current views on the value of glycemic control and issues with its determination, and more recent approaches to monitor or measure glycemic control. Hypoglycemia and treatment options for patients with diabetes and ESRD or earlier stages of CKD also are addressed, discussing the insulin and noninsulin agents that currently are available, along with their indications and contraindications. The article provides information to help clinicians in decision making in order to provide individualized glycemic goals and appropriate therapy for patients with ESRD or earlier stages of CKD.

Principles of separation: indications and therapeutic targets for plasma exchange.

Extracorporeal "blood purification," mainly in the form of hemodialysis has been a major portion of the clinical activity of many nephrologists for the past 5 decades. A possibly older procedure, therapeutic plasma exchange, separates and then removes plasma as a method of removing pathogenic material from the patient. In contrast to hemodialysis, therapeutic plasma exchange preferentially removes biologic substances of high molecular weight such as autoantibodies or alloantibodies, antigen-antibody complexes, and Ig paraproteins. These molecular targets may be cleared through two alternative procedures: centrifugal separation and membrane separation. This review presents operational features of each procedure, with relevance to the nephrologist. Kinetics of removal of these plasma constituents are based on the principles of separation by the apheresis technique and by features specific to each molecular target, including their production and compartmentalization in the body. Molecular targets for common renal conditions requiring therapeutic plasma exchange are also discussed in detail.

High Hemoglobin A1c levels and glycemic variability increase risk of severe hypoglycemia in diabetic hemodialysis patients.

While hyperglycemia is central to the pathogenesis and management of diabetes mellitus, hypoglycemia and glucose variability also contribute to outcomes. We previously reported on the relationship of glycemic control to outcomes in a large population of diabetic end-stage renal disease (ESRD) patients. Recognizing that ESRD is a risk factor for severe hypoglycemia, we have now analyzed the association between glycosylated hemoglobin A1c (HgbA1c) levels and glycemic variability in those with hypoglycemia. This is a retrospective study of patients with diabetes enrolled in a large hemodialysis program. Hypoglycemia was identified from hospital discharge diagnostic codes. Glycemic variability was assessed by the standard deviation of HgbA1c and glucose levels over time. Hypoglycemia as a discharge diagnosis was documented in 4.1% of patients. Higher baseline HgbA1c was associated with greater risk for hypoglycemia hospitalization, a finding confirmed by time-lagged HgbA1c levels drawn a quarter earlier. Higher baseline HgbA1c categories were also associated with greater variability in HgbA1c levels during the analysis period. Similarly, greater glucose variability was associated with higher mean glucose levels by trend analysis. High, not low, HgbA1c levels are associated with greater risk of severe hypoglycemia, which may derive from glucose variability in the setting of treatment for hyperglycemia. High HgbA1c and glycemic variability are associated with increased risk of hypoglycemia in individuals with diabetes and ESRD.

Guidelines on the use of therapeutic apheresis in clinical practice-evidence-based approach from the Writing Committee of the American Society for Apheresis: the sixth special issue.

The American Society for Apheresis (ASFA) JCA Special Issue Writing Committee is charged with reviewing, updating and categorizating indications for therapeutic apheresis. Beginning with the 2007 ASFA Special Issue (Fourth Edition), the committee has incorporated systematic review and evidence-based approach in the grading and categorization of indications. This Sixth Edition of the ASFA Special Issue has further improved the process of using evidence-based medicine in the recommendations by consistently applying the category and GRADE system definitions, but eliminating the "level of evidence" criteria (from the University HealthCare Consortium) utilized in prior editions given redundancy between GRADE and University HealthCare Consortium systems. The general layout and concept of a fact sheet that was utilized in the Fourth and Fifth Editions, has been largely maintained in this edition. Each fact sheet succinctly summarizes the evidence for the use of therapeutic apheresis in a specific disease entity. This article consists of 78 fact sheets (increased from 2010) for therapeutic indications in ASFA categories I through IV, with many diseases categorized having multiple clinical presentations/situations which are individually graded and categorized.

Diabetic kidney disease in elderly individuals.

The treatment of diabetic nephropathy in elderly individuals is based primarily on data from younger age groups. However, the assumption that the same treatment approaches for the younger age groups can be uniformly applied to elderly individuals is likely to be incorrect. The cornerstones of aggressive therapy for diabetic kidney disease in general may have drawbacks in elderly patients. For example, significant risks of tight glycemic control have emerged in recent studies. Excessive decrease of blood pressure to existing targets may be unsafe in elderly individuals. Limited data do indicate that renin-angiotensin blockade may be as effective and no riskier than in middle-aged diabetic kidney patients. Until further studies are carried out, it is prudent to treat the elderly patient with similar approaches as in younger patients, but tempered by the issues reviewed in this article. There is a growing need for the development of clinical guidelines to retool CKD management in the elderly diabetic population using both current and emerging therapies.

Diabetes management in the kidney patient.

Hyperglycemia management in chronic kidney disease (CKD) patients presents difficult challenges, partly due to the complexity involved in treating these patients, and partly due to lack of data supporting benefits of tight glycemic control. While hyperglycemia is central to the pathogenesis and management of diabetes, hypoglycemia and glucose variability also contribute to outcomes. Multiple agents with different mechanisms of action are now available; some can lower glucose levels without the risk of hypoglycemia. This article reviews metabolic changes present in kidney impairment/failure, current views about glycemic goals, and treatment options for the diabetic patient with CKD.