Managing biological variation data: modern approaches for study design and clinical application

For more than one half-century, variability observed in clinical test result measurements has been ascribed to three major independent factors: (i) pre-analytical variation, occurring at sample collection and processing steps; (ii) analytical variation of the test method for which measurements are taken, and; (iii) biological variation (BV). Appreciation of this last source of variability is the major goal of this review article. Several recent advances have been made to generate, collate, and utilize BV data of biomarker tests within the clinical laboratory setting. Consideration of both prospective and retrospective study designs will be addressed. The prospective/direct study design will be described in accordance with recent recommendations discussed in the framework of a newly-developed system of checklist items. Potential value of retrospective/indirect study design, modeled on data mining from cohort studies or pathology laboratory information systems (LIS), offers an alternative approach to obtain BV estimates for clinical biomarkers. Moreover, updates to BV databases have made these data more current and widely accessible. Principal aims of this review are to provide the clinical laboratory scientist with a historical framework of BV concepts, to highlight useful applications of BV data within the clinical laboratory environment, and to discuss key terms and concepts related to statistical treatment of BV data.

Transplant Options for Patients With Diabetes and Advanced Kidney Disease: A Review

Optimal glycemic control in kidney transplant recipients with diabetes is associated with improved morbidity and better patient and allograft survival. Transplant options for patients with diabetes requiring insulin therapy and chronic kidney disease who are suitable candidates for kidney transplantation should include consideration of β-cell replacement therapy: pancreas or islet transplantation. International variation related to national regulatory policies exists in offering one or both options to suitable candidates and is further affected by pancreas/islet allocation policies and transplant waiting list dynamics. The selection of appropriate candidates depends on patient age, coexistent morbidities, the timing of referral to the transplant center (predialysis versus on dialysis) and availability of living kidney donors. Therefore, early referral (estimated glomerular filtration rate < 30 mL/min/1.73 m²) is of the utmost importance to ensure adequate time for informed decision making and thorough pretransplant evaluation. Obesity, cardiovascular disease, peripheral vascular disease, smoking, and frailty are some of the conditions that need to be addressed before acceptance on the transplant list, and ideally before dialysis becoming imminent. This review offers insights into selection of pancreas/islet transplant candidates by transplant centers and an update on posttransplant outcomes, which may have practice implications for referring nephrologists.

Clinical Outcomes of Double-Screw Fixation with Autologous Bone Grafting for Unstable Scaphoid Delayed or Nonunions with Cavitary Bone Loss

Objective  This study reports on the clinical outcomes of double screw fixation with autologous cancellous bone grafting and early active range of motion for delayed and nonunited scaphoid waist fractures with cavitary segmental bone loss. Patients and Methods  Twenty-one consecutive patients underwent fixation using two 2.2 mm antegrade headless compression screws with autologous distal radius cancellous bone graft. Postoperatively, patients were allowed early active motion with a resting splint until union was achieved. Patients were reviewed radiologically and clinically to assess for fracture union, complications, residual pain, wrist function, and return to work and recreational activities. Results  All but one patient was male, and the mean age was 23 years (range, 15-38 years). The average time from initial injury was 16 months (range, 3-144 months). Nineteen of 21 (90.5%) patients achieved union at a mean of 2.8 months (range, 1.4-9.2 months). Of the patients who failed, one underwent revision surgery with vascularized bone grafting at 10.6 months. The other patient refused further intervention as he was asymptomatic. Conclusion  Double-screw fixation with bone grafting and early active range of motion is a safe and effective technique for management of delayed and nonunited unstable scaphoid fractures with cavitary bone loss. This potentially allows for earlier return to function, without compromise to union rates. Level of Evidence  This is a Level IV, retrospective case series study.

The effects of kisspeptin on β-cell function, serum metabolites and appetite in humans

AIMS

To investigate the effect of kisspeptin on glucose-stimulated insulin secretion and appetite in humans.

MATERIALS AND METHODS

In 15 healthy men (age: 25.2 ± 1.1 years; BMI: 22.3 ± 0.5 kg m-2 ), we compared the effects of 1 nmol kg-1 h-1 kisspeptin versus vehicle administration on glucose-stimulated insulin secretion, metabolites, gut hormones, appetite and food intake. In addition, we assessed the effect of kisspeptin on glucose-stimulated insulin secretion in vitro in human pancreatic islets and a human β-cell line (EndoC-βH1 cells).

RESULTS

Kisspeptin administration to healthy men enhanced insulin secretion following an intravenous glucose load, and modulated serum metabolites. In keeping with this, kisspeptin increased glucose-stimulated insulin secretion from human islets and a human pancreatic cell line in vitro. In addition, kisspeptin administration did not alter gut hormones, appetite or food intake in healthy men.

CONCLUSIONS

Collectively, these data demonstrate for the first time a beneficial role for kisspeptin in insulin secretion in humans in vivo. This has important implications for our understanding of the links between reproduction and metabolism in humans, as well as for the ongoing translational development of kisspeptin-based therapies for reproductive and potentially metabolic conditions.

Comparison of Clostripain and Neutral Protease as Supplementary Enzymes for Human Islet Isolation

Although human islet transplantation has been established as valid and safe treatment for patients with type 1 diabetes, the utilization rates of human pancreases for clinical islet transplantation are still limited and substantially determined by the quality and composition of collagenase blends. While function and integrity of collagenase has been extensively investigated, information is still lacking about the most suitable supplementary neutral proteases. The present study compared islet isolation outcome after pancreas digestion by means of collagenase used alone or supplemented with either neutral protease (NP), clostripain (CP), or both proteases. Decent amounts of islet equivalents (IEQ) were isolated using collagenase alone (3090 ± 550 IEQ/g), or in combination with NP (2340 ± 450 IEQ/g) or CP (2740 ± 280 IEQ/g). Nevertheless, the proportion of undigested tissue was higher after using collagenase alone (21.1 ± 1.1%, P < 0.05) compared with addition of NP (13.3 ± 2.2%) or CP plus NP (13.7 ± 2.6%). Likewise, the percentage of embedded islets was highest using collagenase only (13 ± 2%) and lowest adding NP plus CP (4 ± 1%, P < 0.01). The latter combination resulted in lowest post-culture overall survival (42.7 ± 3.9%), while highest survival was observed after supplementation with CP (74.5 ± 4.8%, P < 0.01). An insulin response toward glucose challenge was present in all experimental groups, but the stimulation index was significantly decreased using collagenase plus NP (2.0 ± 0.12) compared with supplementation with CP (3.16 ± 0.4, P < 0.001). This study demonstrates for the first time that it is possible to isolate significant numbers of human islets combining collagenase only with CP. The supplementation with CP is an effective means to substantially reduce NP activity, which significantly decreases survival and viability after culture. This will facilitate the manufacturing of enzyme blends with less harmful characteristics.

Defining outcomes for β-cell replacement therapy in the treatment of diabetes: a consensus report on the Igls criteria from the IPITA/EPITA opinion leaders workshop

β-cell replacement therapy, available currently as pancreas or islet transplantation, has developed without a clear definition of graft functional and clinical outcomes. The International Pancreas & Islet Transplant Association (IPITA) and European Pancreas & Islet Transplantation Association (EPITA) held a workshop to develop consensus for an IPITA/EPITA Statement on the definition of function and failure of current and future forms of β-cell replacement therapy. There was consensus that β-cell replacement therapy could be considered as a treatment for β-cell failure, regardless of etiology and without requiring undetectable C-peptide, accompanied by glycemic instability with either problematic hypoglycemia or hyperglycemia. Glycemic control should be assessed at a minimum by glycated hemoglobin (HbA_1c ) and the occurrence of severe hypoglycemia. Optimal β-cell graft function is defined by near-normal glycemic control [HbA_1c  ≤ 6.5% (48 mmol/mol)] without severe hypoglycemia or requirement for insulin or other antihyperglycemic therapy, and with an increase over pretransplant measurement of C-peptide. Good β-cell graft function requires HbA_1c  < 7.0% (53 mmol/mol) without severe hypoglycemia and with a significant (>50%) reduction in insulin requirements and restoration of clinically significant C-peptide production. Marginal β-cell graft function is defined by failure to achieve HbA_1c  < 7.0% (53 mmol/mol), the occurrence of any severe hypoglycemia, or less than 50% reduction in insulin requirements when there is restoration of clinically significant C-peptide production documented by improvement in hypoglycemia awareness/severity, or glycemic variability/lability. A failed β-cell graft is defined by the absence of any evidence for clinically significant C-peptide production. Optimal and good functional outcomes are considered successful clinical outcomes.

Crystal anisotropy explains structure-mechanics impact on tableting performance of flufenamic acid polymorphs

Anisotropic features with other crystallographic properties like d-spacing, and attachment energy (E_att) can predict material performance during the secondary pharmaceutical processing. A newly developed state-of-the-art compression cell lodged in a powder X-ray diffractometer was used to measure anisotropic Young's moduli (YM) of flufenamic acid (FFA) polymorphs in this study. Methodology is based on the generation of a single crystal deformation in this cell, which reflects as a change in the d-spacing in the PXRD pattern. Anisotropic YM was calculated from such information gathered along different FFA planes. Measured FFA crystallographic molecular features were concatenated to understand macroscopic compaction (Heckel and Shapirao's parameters) and tableting performance. Block shaped crystals of FFA form I, and III after initial characterization with SEM, DSC, PXRD, and FTIR were compressed normal to X, Y, and Z-planes, identified from calculated PXRD pattern using the reported single crystal structure. YM of X and Y planes of form I was significantly higher than corresponding planes of form III. Z plane of form III showed significantly higher YM than that for form I. Low YM of form III can be attributed to its large d-spacing regardless of their high E_att than form I, as well as orientation of supramolecular acid dimer (OH⋯O) homosynthon chains in the FFA planes. FFA form I stiffness was further confirmed with lower densification and higher yield pressure of deformation than form III. Clearly, form III exhibited better compressibility, compactibility, and tableting performance than form I due to favorable molecular and macroscopic features. Thus, developed anisotropic measurement approach can be used to distinguish material performance in the early development stage of the pharmaceutical processes.

GLP-1 suppresses glucagon secretion in human pancreatic alpha-cells by inhibition of P/Q-type Ca2+ channels

Glucagon is the body's main hyperglycemic hormone, and its secretion is dysregulated in type 2 diabetes mellitus (T2DM). The incretin hormone glucagon-like peptide-1 (GLP-1) is released from the gut and is used in T2DM therapy. Uniquely, it both stimulates insulin and inhibits glucagon secretion and thereby lowers plasma glucose levels. In this study, we have investigated the action of GLP-1 on glucagon release from human pancreatic islets. Immunocytochemistry revealed that only <0.5% of the α-cells possess detectable GLP-1R immunoreactivity. Despite this, GLP-1 inhibited glucagon secretion by 50-70%. This was due to a direct effect on α-cells, rather than paracrine signaling, because the inhibition was not reversed by the insulin receptor antagonist S961 or the somatostatin receptor-2 antagonist CYN154806. The inhibitory effect of GLP-1 on glucagon secretion was prevented by the PKA-inhibitor Rp-cAMPS and mimicked by the adenylate cyclase activator forskolin. Electrophysiological measurements revealed that GLP-1 decreased action potential height and depolarized interspike membrane potential. Mathematical modeling suggests both effects could result from inhibition of P/Q-type Ca2+ channels. In agreement with this, GLP-1 and ω-agatoxin (a blocker of P/Q-type channels) inhibited glucagon secretion in islets depolarized by 70 mmol/L [K+ ]o , and these effects were not additive. Intracellular application of cAMP inhibited depolarization-evoked exocytosis in individual α-cells by a PKA-dependent (Rp-cAMPS-sensitive) mechanism. We propose that inhibition of glucagon secretion by GLP-1 involves activation of the few GLP-1 receptors present in the α-cell membrane. The resulting small elevation of cAMP leads to PKA-dependent inhibition of P/Q-type Ca2+ channels and suppression of glucagon exocytosis.

Targeting GLP-1 receptor trafficking to improve agonist efficacy

Glucagon-like peptide-1 receptor (GLP-1R) activation promotes insulin secretion from pancreatic beta cells, causes weight loss, and is an important pharmacological target in type 2 diabetes (T2D). Like other G protein-coupled receptors, the GLP-1R undergoes agonist-mediated endocytosis, but the functional and therapeutic consequences of modulating GLP-1R endocytic trafficking have not been clearly defined. Here, we investigate a series of biased GLP-1R agonists with variable propensities for GLP-1R internalization and recycling. Compared to a panel of FDA-approved GLP-1 mimetics, compounds that retain GLP-1R at the plasma membrane produce greater long-term insulin release, which is dependent on a reduction in β-arrestin recruitment and faster agonist dissociation rates. Such molecules elicit glycemic benefits in mice without concomitant increases in signs of nausea, a common side effect of GLP-1 therapies. Our study identifies a set of agents with specific GLP-1R trafficking profiles and the potential for greater efficacy and tolerability as T2D treatments.

Glucagon-like peptide-1 receptor (GLP-1R) promotes insulin secretion from pancreatic beta cells and undergoes agonist-mediated endocytosis. Here, authors study GLP-1R endocytosis caused by different agonists and show that a longer plasma membrane retention time of GLP-1R results in greater long-term insulin release.

A Targeted RNAi Screen Identifies Endocytic Trafficking Factors That Control GLP-1 Receptor Signaling in Pancreatic β-Cells

The glucagon-like peptide 1 (GLP-1) receptor (GLP-1R) is a key target for type 2 diabetes (T2D) treatment. Because endocytic trafficking of agonist-bound receptors is one of the most important routes for regulation of receptor signaling, a better understanding of this process may facilitate the development of new T2D therapeutic strategies. Here, we screened 29 proteins with known functions in G protein-coupled receptor trafficking for their role in GLP-1R potentiation of insulin secretion in pancreatic β-cells. We identify five (clathrin, dynamin1, AP2, sorting nexins [SNX] SNX27, and SNX1) that increase and four (huntingtin-interacting protein 1 [HIP1], HIP14, GASP-1, and Nedd4) that decrease insulin secretion from murine insulinoma MIN6B1 cells in response to the GLP-1 analog exendin-4. The roles of HIP1 and the endosomal SNX1 and SNX27 were further characterized in mouse and human β-cell lines and human islets. While HIP1 was required for the coupling of cell surface GLP-1R activation with clathrin-dependent endocytosis, the SNXs were found to control the balance between GLP-1R plasma membrane recycling and lysosomal degradation and, in doing so, determine the overall β-cell incretin responses. We thus identify key modulators of GLP-1R trafficking and signaling that might provide novel targets to enhance insulin secretion in T2D.

Acyclovir chemical kinetics with the discovery and identification of newly reported degradants and degradation pathways involving formaldehyde as a degradant and reactant intermediate

The purpose of this research was to determine acyclovir (ACV) acidic degradation kinetics which is relevant to gastric retentive device product design. A stability-indicating method revealed two unknown degradation products which have been identified by mass spectrometry as ACV and guanine formaldehyde adducts. In addition to the formation of these adducts, a proposed degradation scheme identifies the formation of methyl acetal ethylene glycol, formaldehyde, ethylene glycol, and guanine as additional ACV degradation products. pH-rate profiles were explained by using a rate law which assumed acid-catalyzed hydrolysis of protonated and unprotonated ACV. The predicted and observed rate constants were in good agreement. Data-driven excipient selection recommendations were based on the chemical kinetic study results, degradation scheme, and pH-rate profiles. The average activation energy for the degradation reaction was determined to be 31.3±1.6kcal/mol. The predicted ACV t_90% at 37°C and pH 1.2 was calculated to be 7.2days. As a first approximation, this suggests that ACV gastric retentive devices designed to deliver drug for 7days should have acceptable drug product stability in the stomach.

Long-term Stability of a Compounded Suspension of Torsemide (5 mg/mL) for Oral Administration

Background

Torsemide use for congestive heart failure (CHF) has been reported, but prescription frequency is unknown. Commercially available tablet sizes in North America limit dosing precision, indicating a need to evaluate its strength and stability in suspension.

Objectives

To determine the frequency of torsemide prescriptions and to determine a beyond use date (BUD) of a compounded suspension of torsemide for oral administration stored under 2 temperature conditions for 90 days.

Animals

No animals used.

Methods

Pharmacy records were retrospectively reviewed for torsemide and furosemide prescriptions from 2008 to 2015 at 2 veterinary referral centers. After preliminary strength testing, compounded torsemide suspension (5 mg/mL) for oral administration was prepared using torsemide tablets suspended in OraPlus:OraSweet 1:1, buffered to a pH of 8.3 and stored at refrigeration (2–8°C) and room temperature (20–25°C) in 2 oz amber plastic bottles. Samples were analyzed by reverse phase high‐performance liquid chromatography (RP‐HPLC) on days 0, 14, 30, 60, and 90.

Results

Prescriptions for torsemide increased from 2008 to 2015. Analysis of the torsemide 5 mg/mL suspension for oral administration at each time point met United States Pharmacopeia (USP) requirements for torsemide content of 90–110% of label claim. The average strength at 90 days decreased to 92 ± 3% at 2–8°C and 95 ± 2% at 20–25°C. Stability testing did not detect unknown impurities.

Conclusions

Increasing torsemide use warrants availability of a validated and stable compounded formulation. Our results support the assignment of a 90‐day BUD for torsemide 5 mg/mL suspension for oral administration compounded in OraPlus:Sweet 1:1 buffered to a pH of 8.3.

Y-site Incompatibility Between Premix Concentrations of Vancomycin and Piperacillin-Tazobactam: Do Current Compatibility Testing Methodologies Tell the Whole Story?

Background: Published literature has demonstrated commercially available premix vancomycin (5 mg/mL) and piperacillin-tazobactam (67.5 mg/mL) as physically compatible via simulated Y-site methodology. Compatibility via actual Y-site infusion has yet to be established. Objective: To assess and compare the compatibility of commercially available premix concentrations of vancomycin and piperacillin-tazobactam via simulated and actual Y-site evaluation. Methods: Vancomycin and piperacillin-tazobactam were tested using simulated and actual Y-site infusion methodologies. Simulated Y-site compatibility was performed using previously published methods via visual inspection, turbidity evaluation, and pH evaluation. Evaluation occurred immediately, 60 minutes, 120 minutes, and 240 minutes following mixing for each mixture and control. Mixtures were considered physically incompatible if there was visual evidence of precipitation or haze, an absorbance value was greater than 0.01 A, or an absolute change of 1.0 pH unit occurred. Actual Y-site infusion was simulated to mirror antibiotic infusion in the clinical setting by nursing personnel using smart pumps and intravenous tubing. Results: No evidence of physical incompatibility was observed during simulated Y-site testing via visual inspection, turbidity assessment, and pH evaluation. Conversely, physical incompatibility was observed to the unaided eye within 2 minutes during actual Y-site infusion. Conclusions: Despite observed compatibility between vancomycin and piperacillin-tazobactam via simulated Y-site testing, visual evidence of physical incompatibility was observed during actual Y-site infusion. This poses a potential compromise to patient safety if these antibiotics are administered simultaneously in the clinical setting. Actual Y-site testing should be performed prior to clinical adoption of compatibility studies that are based solely on simulated methodologies.

The Effect of UW Solution and Its Components on the Collagenase Digestion of Human and Porcine Pancreas

University of Wisconsin (UW) solution is used extensively as a cold storage solution during the procurement and transport of the pancreas prior to islet isolation. However, it has been observed that UW inhibits the collagenase digestion phase of human but not porcine islet isolation, resulting in poor islet yields and islets of poor viability. The aim of this study was, therefore, to confirm this species difference and to determine which components of UW are responsible for the inhibition in the human. In the initial experiment, blocks of human and porcine pancreas (n = 7) were incubated in test tubes containing collagenase at a concentration of 4 mg/mL at 37°C dissolved in 4 mL of either Hanks' solution or UW. Every 5 min the tubes were manually shaken and the degree of tissue dissociation scored on a scale of + and +++. Our results confirm the inhibition of collagenase digestion in the human but not the pig. Using the same methodology, we then investigated the components of UW that were causing the observed inhibition in the human pancreas (n = 7). This time the collagenase was dissolved in individual or combinations of UW components. Using Hank's as a control, the results were then expressed as a median ratio. The components found to be most inhibitory were magnesium, the Na+/K+ ratio, hydroxyethyl starch (HES), and adenosine. Allopurinol in combination with either lactobionate or glutathione was markedly inhibitory (i.e., median ratio 1.8 and 1.9, respectively). The most inhibitory solution tested was a combination of the three components raffinose, glutathione, and lactobionate (median ratio 2.1). This combination was almost as inhibitory as UW itself (median ratio 2.7). These findings are essential for the development of effective cold-storage solutions for the human pancreas that do not inhibit the subsequent collagenase digestion phase of islet isolation.

SIV-specific CD8 T cells with perforin granules located exclusively within cell membranes correlate with the maturation of SIVmac239Δnef vaccine induced protection

Vaccination with live-attenuated SIVmac239Δnef protects most animals challenged with a pathogenic SIV. In this model, there is a maturation of protection which occurs between 5 and 20 weeks post-vaccination. We previously showed that this maturation of protection did not correlate with distribution or density of SIV-specific CD8 T cells in lymphoid or genital tissues. In this study, we investigated whether the maturation of protection correlated with levels of the effector protein perforin in SIV-specific CD8 T cells in lymphoid or vaginal tissues. Using in situ tetramer staining with MHC tetramers combined with immunohistochemistry, and quantitative image analysis, we quantified perforin levels in SIV-specific CD8 T cells; Perforin negative cells are characterized as central memory T cells (TCM), perforin low cells are effector memory (TEM), and perforin high/med are effector T cells (TEFF). We also quantified a unique population of SIV-specific CD8 T cells with perforin localized exclusively within the cell membrane, which are likely to be a subset of TEM. From 5 to 20 weeks post-infection, we found increase in perforin negative and decrease in perforin high tetramer binding CD8 T cells. We also found an increase in SIV-specific CD8 T cells expressing low levels of perforin located exclusively in the cell membrane that correlated with the maturation of protection. These findings indicate that the maturation of protection induced by SIVmac239Δnef vaccine correlates with a shift from a primary response dominated by effector CD8 T cells, to a memory response, which includes an increase in SIV-specific CD8 T cells with perforin located exclusively in the cell membrane. These findings help inform the development of a successful HIV vaccine.

Statistical Optimization of Evaporative Light Scattering Detection for Molten Sucrose Octaacetate and Comparison With Ultraviolet Diode Array Detection Validation Parameters Using Tandem HPLC Ultraviolet Diode Array Detection/Evaporative Light Scattering Detection-Specific Stability-Indicating Method

A sucrose octaacetate (SOA) gradient HPLC evaporative light scattering detection (ELSD) and low-wavelength UV-diode array detection (UV-DAD)-specific stability-indicating method development and validation comparison is reported. A central composite response surface design and multicriteria optimization was used to maximize molten SOA area-under-the-curve response and signal-to-noise ratio. The ELSD data were also analyzed using multivariate principal component analysis, analysis of variance, and standard least squares effects modeling. The method suitability and validation parameters of both methods were compared. To the authors' knowledge, this is the first report that validates an ELSD method using a molten analyte. SOA exhibited a low molar absorptivity of 439 absorption units/cm/M in water at 210 nm requiring low-wavelength UV-DAD detection. The low-wavelength UV-DAD method provided substantially better intraday and interday precision, intraday and interday goodness-of-fit, detection limit, and quantitation limit than ELSD. ELSD exhibited a 60-fold greater area-under-the-curve response, better resolution, and 58% more theoretical plates. On balance, the UV-DAD method was chosen for SOA chemical kinetic studies. This study illustrates that ELSD may not always be the best alternative to gradient HPLC low-wavelength UV detection.

Pancreatic L-Glutamine Administration Protects Pig Islets From Cold Ischemic Injury and Increases Resistance Toward Inflammatory Mediators

The isolation and transplantation of porcine islets represent a future option for the treatment of type 1 diabetic patients. Stringent product release criteria and limited availability of transgenic and specific pathogen-free pigs will essentially require processing of explanted pig pancreata in specialized, possibly remote isolation facilities, whereby pancreata are exposed to cold ischemia due to prolonged tissue transit time. In the present study we investigated whether pancreas oxygenation can be efficiently combined with an antioxidant strategy utilizing intraductal L-glutamine administration. Pig pancreata were intraductally perfused after retrieval and after cold storage in oxygen-precharged perfluorohexyloctane utilizing University of Wisconsin solution supplemented with (n = 16) or without (n = 14) 5 mmol/L L-glutamine. After isolation purified islets were subjected to extensive quality assessment. Islet recovery postpurification was significantly higher in glutamine-treated pancreata (77.0 ± 3.3% vs. 60.3 ± 6.0%, p < 0.05). Glutamine administration increased intraislet content of reduced glutathione (117.8 ± 16.5 vs. 15.9 ± 2.8 ng/ng protein, p < 0.001) associated with increased islet recovery after culture (65.8 ± 12.1% vs. 40.3 ± 11.7%, p < 0.05), enhanced glucose stimulation index (1.82 ± 0.16 vs. 1.38 ± 0.10, p < 0.05), and improved posttransplant function in diabetic nude mice (p < 0.05). Furthermore, intraductally administered glutamine increased pig islet resistance toward reactive oxygen species, nitric oxide, and high-dose proinflammatory cytokines. The present study demonstrates that quality and function of pig islets exposed to warm and cold ischemia can significantly be improved using intraductal l-glutamine administration. As the efficiency of the intraductal route may be inferior compared to intravascular administration further studies should aim on assessment of l-glutamine as supplement for pancreas perfusion during organ procurement.

In Vitro Assessment of Human Islet Vulnerability to Instant Blood-Mediated Inflammatory Reaction (IBMIR) and Its Use to Demonstrate a Beneficial Effect of Tissue Culture

Culture of human pancreatic islets is now routinely carried out prior to clinical islet allotransplantation, using conditions that have been developed empirically. One of the major causes of early islet destruction after transplantation is the process termed instant blood-mediated inflammatory reaction (IBMIR). The aim of this study was to develop in vitro methods to investigate IBMIR and apply them to the culture conditions used routinely in our human islet isolation laboratory. Freshly isolated or precultured (24 h, 48 h) human islets were incubated in either ABO-compatible allogeneic human blood or Hank's buffered salt solution (HBSS) for 1 h at 37°C. Tissue factor (TF) expression and leukocyte migration were assessed by light microscopy. TF was also quantified by ELISA. To assess β-cell function, glucose-stimulated insulin secretion (GSIS) assay was carried out. The extent of islet β-cell damage was quantified using a proinsulin assay. Islets cultured for 24 h had higher GSIS when compared to freshly isolated or 48-h precultured islets. Freshly isolated islets had significantly higher TF content than 24-h and 48-h precultured islets. Incubation of freshly isolated human islets in allogeneic human blood released 6.5-fold higher level of proinsulin in comparison to freshly isolated human islets in HBSS. The high level of proinsulin released was significantly attenuated when precultured islets (24 h or 48 h) were exposed to fresh blood. Histological examination of fresh islets in blood clot showed that some islets were fragmented, showing signs of extraislet insulin leakage and extensive neutrophil infiltration and necrosis. These features were markedly reduced when the islets were cultured for 24 h. These results suggest that our standard 24-h islet culture is markedly beneficial in attenuating IBMIR, as evidenced by increased GSIS, lower content of TF, decrease islet fragmentation, and proinsulin release.

ADCY5 couples glucose to insulin secretion in human islets

Single nucleotide polymorphisms (SNPs) within the ADCY5 gene, encoding adenylate cyclase 5, are associated with elevated fasting glucose and increased type 2 diabetes (T2D) risk. Despite this, the mechanisms underlying the effects of these polymorphic variants at the level of pancreatic β-cells remain unclear. Here, we show firstly that ADCY5 mRNA expression in islets is lowered by the possession of risk alleles at rs11708067. Next, we demonstrate that ADCY5 is indispensable for coupling glucose, but not GLP-1, to insulin secretion in human islets. Assessed by in situ imaging of recombinant probes, ADCY5 silencing impaired glucose-induced cAMP increases and blocked glucose metabolism toward ATP at concentrations of the sugar >8 mmol/L. However, calcium transient generation and functional connectivity between individual human β-cells were sharply inhibited at all glucose concentrations tested, implying additional, metabolism-independent roles for ADCY5. In contrast, calcium rises were unaffected in ADCY5-depleted islets exposed to GLP-1. Alterations in β-cell ADCY5 expression and impaired glucose signaling thus provide a likely route through which ADCY5 gene polymorphisms influence fasting glucose levels and T2D risk, while exerting more minor effects on incretin action.

Incretin-modulated beta cell energetics in intact islets of Langerhans

Incretins such as glucagon-like peptide 1 (GLP-1) are released from the gut and potentiate insulin release in a glucose-dependent manner. Although this action is generally believed to hinge on cAMP and protein kinase A signaling, up-regulated beta cell intermediary metabolism may also play a role in incretin-stimulated insulin secretion. By employing recombinant probes to image ATP dynamically in situ within intact mouse and human islets, we sought to clarify the role of GLP-1-modulated energetics in beta cell function. Using these techniques, we show that GLP-1 engages a metabolically coupled subnetwork of beta cells to increase cytosolic ATP levels, an action independent of prevailing energy status. We further demonstrate that the effects of GLP-1 are accompanied by alterations in the mitochondrial inner membrane potential and, at elevated glucose concentration, depend upon GLP-1 receptor-directed calcium influx through voltage-dependent calcium channels. Lastly, and highlighting critical species differences, beta cells within mouse but not human islets respond coordinately to incretin stimulation. Together, these findings suggest that GLP-1 alters beta cell intermediary metabolism to influence ATP dynamics in a species-specific manner, and this may contribute to divergent regulation of the incretin-axis in rodents and man.

Microbial community structure across a wastewater-impacted riparian buffer zone in the southeastern coastal plain

Riparian buffer zones are important for both natural and developed ecosystems throughout the world because of their ability to retain nutrients, prevent soil erosion, protect aquatic environments from excessive sedimentation, and filter pollutants. Despite their importance, the microbial community structures of riparian buffer zones remains poorly defined. Our objectives for this study were twofold: first, to characterize the microbial populations found in riparian buffer zone soils; and second, to determine if microbial community structure could be linked to denitrification enzyme activity (DEA). To achieve these objectives, we investigated the microbial populations of a riparian buffer zone located downslope of a pasture irrigated with swine lagoon effluent, utilizing DNA sequencing of the 16S rDNA, DEA, and quantitative PCR (qPCR) of the denitrification genes nirK, nirS, and nosZ. Clone libraries of the 16S rDNA gene were generated from each of twelve sites across the riparian buffer with a total of 986 partial sequences grouped into 654 operational taxonomic units (OTUs). The Proteobacteria were the dominant group (49.8% of all OTUs), with the Acidobacteria also well represented (19.57% of all OTUs). Analysis of qPCR results identified spatial relationships between soil series, site location, and gene abundance, which could be used to infer both incomplete and total DEA rates.

Development of a 3-Dimensional Back Contour Imaging System for Monitoring Scoliosis Progression in Children

STUDY DESIGN

Control study.

OBJECTIVES

To present a new surface topography system capable of taking 3-dimensional (3D) spine measurements, to establish baseline values for the measured parameters in a typically developing population, and to determine the intra-rater and inter-rater reproducibility of these parameters.

SUMMARY OF BACKGROUND DATA

Cumulative exposure to radiation from diagnostic radiographs increases patient risk for cancer development. There is a need for noninvasive and non-radiographic tools to accurately and reproducibly measure spine deformity and track scoliosis progression.

METHODS

We measured 10 typically developing subjects with the new Milwaukee Topography System, which is composed of 2 electromagnetic markers, an electronic processing unit, a handheld laser scanner, a software package, and a desktop computer. Two investigators separately scanned the same subjects multiple times, yielding a total of 4 scans per subject per investigator. We measured 17 3D back parameters in each scan. We performed a multivariate analysis of variances to test the hypothesis of no difference for all variables, measured intra-rater and inter-investigator reliability with intra-class correlation (ICC) coefficients, and calculated mean values.

RESULTS

There were highly reproducible ICC values between investigators for 6 parameters (ICC > 0.75), moderate ICC values for 8 parameters (0.75 > ICC > 0.4), and poor ICC values for 3 parameters (ICC < 0.4), all at p < .05. Intra-investigator ICCs were moderate to excellent for almost all parameters.

CONCLUSIONS

The Milwaukee Topography System can be used to monitor and measure 3D back contours in children. The 3D back parameters values measured in the typically developing population can be considered baseline values that can be compared with parameters measured in children with idiopathic scoliosis.

Insights into the molecular mechanism for type 2 diabetes susceptibility at the KCNQ1 locus from temporal changes in imprinting status in human islets

The molecular basis of type 2 diabetes predisposition at most established susceptibility loci remains poorly understood. KCNQ1 maps within the 11p15.5 imprinted domain, a region with an established role in congenital growth phenotypes. Variants intronic to KCNQ1 influence diabetes susceptibility when maternally inherited. By use of quantitative PCR and pyrosequencing of human adult islet and fetal pancreas samples, we investigated the imprinting status of regional transcripts and aimed to determine whether type 2 diabetes risk alleles influence regional DNA methylation and gene expression. The results demonstrate that gene expression patterns differ by developmental stage. CDKN1C showed monoallelic expression in both adult and fetal tissue, whereas PHLDA2, SLC22A18, and SLC22A18AS were biallelically expressed in both tissues. Temporal changes in imprinting were observed for KCNQ1 and KCNQ1OT1, with monoallelic expression in fetal tissues and biallelic expression in adult samples. Genotype at the type 2 diabetes risk variant rs2237895 influenced methylation levels of regulatory sequence in fetal pancreas but without demonstrable effects on gene expression. We demonstrate that CDKN1C, KCNQ1, and KCNQ1OT1 are most likely to mediate diabetes susceptibility at the KCNQ1 locus and identify temporal differences in imprinting status and methylation effects, suggesting that diabetes risk effects may be mediated in early development.

The miRNA profile of human pancreatic islets and beta-cells and relationship to type 2 diabetes pathogenesis

Recent advances in the understanding of the genetics of type 2 diabetes (T2D) susceptibility have focused attention on the regulation of transcriptional activity within the pancreatic beta-cell. MicroRNAs (miRNAs) represent an important component of regulatory control, and have proven roles in the development of human disease and control of glucose homeostasis. We set out to establish the miRNA profile of human pancreatic islets and of enriched beta-cell populations, and to explore their potential involvement in T2D susceptibility. We used Illumina small RNA sequencing to profile the miRNA fraction in three preparations each of primary human islets and of enriched beta-cells generated by fluorescence-activated cell sorting. In total, 366 miRNAs were found to be expressed (i.e. >100 cumulative reads) in islets and 346 in beta-cells; of the total of 384 unique miRNAs, 328 were shared. A comparison of the islet-cell miRNA profile with those of 15 other human tissues identified 40 miRNAs predominantly expressed (i.e. >50% of all reads seen across the tissues) in islets. Several highly-expressed islet miRNAs, such as miR-375, have established roles in the regulation of islet function, but others (e.g. miR-27b-3p, miR-192-5p) have not previously been described in the context of islet biology. As a first step towards exploring the role of islet-expressed miRNAs and their predicted mRNA targets in T2D pathogenesis, we looked at published T2D association signals across these sites. We found evidence that predicted mRNA targets of islet-expressed miRNAs were globally enriched for signals of T2D association (p-values <0.01, q-values <0.1). At six loci with genome-wide evidence for T2D association (AP3S2, KCNK16, NOTCH2, SCL30A8, VPS26A, and WFS1) predicted mRNA target sites for islet-expressed miRNAs overlapped potentially causal variants. In conclusion, we have described the miRNA profile of human islets and beta-cells and provide evidence linking islet miRNAs to T2D pathogenesis.

SSTR2 is the functionally dominant somatostatin receptor in human pancreatic β- and α-cells

Somatostatin-14 (SST) inhibits insulin and glucagon secretion by activating G protein-coupled somatostatin receptors (SSTRs), of which five isoforms exist (SSTR1-5). In mice, the effects on pancreatic β-cells are mediated by SSTR5, whereas α-cells express SSTR2. In both cell types, SSTR activation results in membrane hyperpolarization and suppression of exocytosis. Here, we examined the mechanisms by which SST inhibits secretion from human β- and α-cells and the SSTR isoforms mediating these effects. Quantitative PCR revealed high expression of SSTR2, with lower levels of SSTR1, SSTR3, and SSTR5, in human islets. Immunohistochemistry showed expression of SSTR2 in both β- and α-cells. SST application hyperpolarized human β-cells and inhibited action potential firing. The membrane hyperpolarization was unaffected by tolbutamide but antagonized by tertiapin-Q, a blocker of G protein-gated inwardly rectifying K⁺ channels (GIRK). The effect of SST was mimicked by an SSTR2-selective agonist, whereas a SSTR5 agonist was marginally effective. SST strongly (>70%) reduced depolarization-evoked exocytosis in both β- and α-cells. A slightly weaker inhibition was observed in both cell types after SSTR2 activation. SSTR3- and SSTR1-selective agonists moderately reduced the exocytotic responses in β- and α-cells, respectively, whereas SSTR4- and SSTR5-specific agonists were ineffective. SST also reduced voltage-gated P/Q-type Ca²⁺ currents in β-cells, but normalization of Ca²⁺ influx to control levels by prolonged depolarizations only partially restored exocytosis. We conclude that SST inhibits secretion from both human β- and α-cells by activating GIRK and suppressing electrical activity, reducing P/Q-type Ca²⁺ currents, and directly inhibiting exocytosis. These effects are mediated predominantly by SSTR2 in both cell types.

Quality of isolated pig islets is improved using perfluorohexyloctane for pancreas storage in a split lobe model

Pancreas transportation between donor center and islet production facility is frequently associated with prolonged ischemia impairing islet isolation and transplantation outcomes. It is foreseeable that shipment of pig pancreases from distant centralized biosecure breeding facilities to institutes that have a long-term experience in porcine islet isolation is essentially required in future clinical islet xenotransplantation. Previously, we demonstrated that perfluorohexyloctan (F6H8) is significantly more efficient to protect rat and human pancreata from ischemically induced damage compared to perfluorodecalin (PFD). To evaluate the effect of F6H8 on long-term stored pig pancreases in a prospective study, we utilized the split lobe model to minimize donor variability. Retrieved pancreases were dissected into the connecting and splenic lobe, intraductally flushed with UW solution and immersed alternately in either preoxygenated F6H8 or PFD for 8-10 h. Prior to pancreas digestion, the intrapancreatic pO2 and the ratio of ATP-to-inorganic phosphate was compared utilizing 31P-NMR spectroscopy. Isolated islets were cultured for 2-3 days at 37°C and subjected to quality assessment. Pancreatic lobes stored in preoxygenated F6H8 had a significantly higher intrapancreatic pO2 compared to pancreata in oxygen-precharged PFD (10.11 ± 3.87 vs. 1.64 ± 1.13 mmHg, p < 0.05). This correlated with a higher ATP-to-inorganic phosphate ratio (0.30 ± 0.04 vs. 0.14 ± 0.01). No effect was observed concerning yield and purity of freshly isolated islets. Nevertheless, a significantly improved glucose-stimulated insulin response, increased viability and postculture survival (57.2 ± 5.7 vs. 39.3 ± 6.4%, p < 0.01) was measured in islets isolated from F6H8-preserved pancreata. The present data suggest that F6H8 does not increase islet yield but improves quality of pig islets isolated after prolonged cold ischemia.

Human β cell transcriptome analysis uncovers lncRNAs that are tissue-specific, dynamically regulated, and abnormally expressed in type 2 diabetes

A significant portion of the genome is transcribed as long noncoding RNAs (lncRNAs), several of which are known to control gene expression. The repertoire and regulation of lncRNAs in disease-relevant tissues, however, has not been systematically explored. We report a comprehensive strand-specific transcriptome map of human pancreatic islets and β cells, and uncover >1100 intergenic and antisense islet-cell lncRNA genes. We find islet lncRNAs that are dynamically regulated and show that they are an integral component of the β cell differentiation and maturation program. We sequenced the mouse islet transcriptome and identify lncRNA orthologs that are regulated like their human counterparts. Depletion of HI-LNC25, a β cell-specific lncRNA, downregulated GLIS3 mRNA, thus exemplifying a gene regulatory function of islet lncRNAs. Finally, selected islet lncRNAs were dysregulated in type 2 diabetes or mapped to genetic loci underlying diabetes susceptibility. These findings reveal a new class of islet-cell genes relevant to β cell programming and diabetes pathophysiology.

SUMO-1: Ubiquitin gains weight

The highly conserved ubiquitin polypeptide functions by covalently modifying other proteins. This modification has a well-established role in facilitating substrate degradation by the proteasome and can regulate some proteins by ways other than targeting them to the proteasome. It has now emerged that proteins bearing only distant similarity to ubiquitin can also be attached to specific proteins. The consequences of most of these modifications are not yet understood. However, two recent papers on one ubiquitin-like protein, SUMO-1, demonstrate a role in targeting a protein crucial for nucleocytoplasmic trafficking to the nuclear pore complex. These and other recent findings suggest a much wider influence of the 'ubiquitin system' on cell biology and raise intriguing regulatory and mechanistic questions.

Choosing staff members reduces time in mechanical restraint due to self-injurious behaviour and requesting restraint

BACKGROUND

Using mechanical restraints to protect a person who engaged in dangerous self-injury was decreased by manipulation of an establishing operation involving the client choosing the staff person who would work with her.

MATERIALS AND METHODS

The client was a 28-year-old woman diagnosed with autism, bipolar disorder, static cerebral encephalopathy, moderate intellectual disabilities, hypotonia and musculoskeletal deformities. She had a history of biting herself and further bites could produce irreversible nerve damage. Mechanical restraints were applied when she bit, tried to bite herself or asked for them.

RESULTS

When she was allowed to choose staff members, the use of mechanical restraint decreased.

CONCLUSION

Reducing the time spent in mechanical restraint by giving the client a choice of staff members who would work with her demonstrates that such a choice may be an establishing operation. The usefulness of cumulative records and scatterplots to evaluate changes in the occurrence of self-injurious behaviour (SIB) and associated mechanical restraint is shown as are the advantages of using alternating treatment designs to assess the effectiveness of treatment conditions for someone who exhibits long-term cyclic behaviour.

Membrane potential-dependent inactivation of voltage-gated ion channels in alpha-cells inhibits glucagon secretion from human islets

OBJECTIVE

To document the properties of the voltage-gated ion channels in human pancreatic alpha-cells and their role in glucagon release.

RESEARCH DESIGN AND METHODS

Glucagon release was measured from intact islets. [Ca(2+)](i) was recorded in cells showing spontaneous activity at 1 mmol/l glucose. Membrane currents and potential were measured by whole-cell patch-clamping in isolated alpha-cells identified by immunocytochemistry.

RESULT

Glucose inhibited glucagon secretion from human islets; maximal inhibition was observed at 6 mmol/l glucose. Glucagon secretion at 1 mmol/l glucose was inhibited by insulin but not by ZnCl(2). Glucose remained inhibitory in the presence of ZnCl(2) and after blockade of type-2 somatostatin receptors. Human alpha-cells are electrically active at 1 mmol/l glucose. Inhibition of K(ATP)-channels with tolbutamide depolarized alpha-cells by 10 mV and reduced the action potential amplitude. Human alpha-cells contain heteropodatoxin-sensitive A-type K(+)-channels, stromatoxin-sensitive delayed rectifying K(+)-channels, tetrodotoxin-sensitive Na(+)-currents, and low-threshold T-type, isradipine-sensitive L-type, and omega-agatoxin-sensitive P/Q-type Ca(2+)-channels. Glucagon secretion at 1 mmol/l glucose was inhibited by 40-70% by tetrodotoxin, heteropodatoxin-2, stromatoxin, omega-agatoxin, and isradipine. The [Ca(2+)](i) oscillations depend principally on Ca(2+)-influx via L-type Ca(2+)-channels. Capacitance measurements revealed a rapid (<50 ms) component of exocytosis. Exocytosis was negligible at voltages below -20 mV and peaked at 0 mV. Blocking P/Q-type Ca(2+)-currents abolished depolarization-evoked exocytosis.

CONCLUSIONS

Human alpha-cells are electrically excitable, and blockade of any ion channel involved in action potential depolarization or repolarization results in inhibition of glucagon secretion. We propose that voltage-dependent inactivation of these channels underlies the inhibition of glucagon secretion by tolbutamide and glucose.

Gamma-aminobutyric acid (GABA) is an autocrine excitatory transmitter in human pancreatic beta-cells

OBJECTIVE

Paracrine signaling via gamma-aminobutyric acid (GABA) and GABA(A) receptors (GABA(A)Rs) has been documented in rodent islets. Here we have studied the importance of GABAergic signaling in human pancreatic islets.

RESEARCH DESIGN AND METHODS

Expression of GABA(A)Rs in islet cells was investigated by quantitative PCR, immunohistochemistry, and patch-clamp experiments. Hormone release was measured from intact islets. GABA release was monitored by whole-cell patch-clamp measurements after adenoviral expression of alpha(1)beta(1) GABA(A)R subunits. The subcellular localization of GABA was explored by electron microscopy. The effects of GABA on electrical activity were determined by perforated patch whole-cell recordings.

RESULTS

PCR analysis detected relatively high levels of the mRNAs encoding GABA(A)R alpha(2), beta(3,) gamma(2), and pi subunits in human islets. Patch-clamp experiments revealed expression of GABA(A)R Cl(-) channels in 52% of beta-cells (current density 9 pA/pF), 91% of delta-cells (current density 148 pA/pF), and 6% of alpha-cells (current density 2 pA/pF). Expression of GABA(A)R subunits in islet cells was confirmed by immunohistochemistry. beta-Cells secreted GABA both by glucose-dependent exocytosis of insulin-containing granules and by a glucose-independent mechanism. The GABA(A)R antagonist SR95531 inhibited insulin secretion elicited by 6 mmol/l glucose. Application of GABA depolarized beta-cells and stimulated action potential firing in beta-cells exposed to glucose.

CONCLUSIONS

Signaling via GABA and GABA(A)R constitutes an autocrine positive feedback loop in human beta-cells. The presence of GABA(A)R in non-beta-cells suggests that GABA may also be involved in the regulation of somatostatin and glucagon secretion.

Somatostatin release, electrical activity, membrane currents and exocytosis in human pancreatic delta cells

AIMS/HYPOTHESIS

The aim of this study was to characterise electrical activity, ion channels, exocytosis and somatostatin release in human delta cells/pancreatic islets.

METHODS

Glucose-stimulated somatostatin release was measured from intact human islets. Membrane potential, currents and changes in membrane capacitance (reflecting exocytosis) were recorded from individual human delta cells identified by immunocytochemistry.

RESULTS

Somatostatin secretion from human islets was stimulated by glucose and tolbutamide and inhibited by diazoxide. Human delta cells generated bursting or sporadic electrical activity, which was enhanced by tolbutamide but unaffected by glucose. Delta cells contained a tolbutamide-insensitive, Ba(2+)-sensitive inwardly rectifying K(+) current and two types of voltage-gated K(+) currents, sensitive to tetraethylammonium/stromatoxin (delayed rectifying, Kv2.1/2.2) and 4-aminopyridine (A current). Voltage-gated tetrodotoxin (TTX)-sensitive Na(+) currents contributed to the action potential upstroke but TTX had no effect on somatostatin release. Delta cells are equipped with Ca(2+) channels blocked by isradipine (L), omega-agatoxin (P/Q) and NNC 55-0396 (T). Blockade of any of these channels interferes with delta cell electrical activity and abolishes glucose-stimulated somatostatin release. Capacitance measurements revealed a slow component of depolarisation-evoked exocytosis sensitive to omega-agatoxin.

CONCLUSIONS/INTERPRETATION

Action potential firing in delta cells is modulated by ATP-sensitive K(+)-channel activity. The membrane potential is stabilised by Ba(2+)-sensitive inwardly rectifying K(+) channels. Voltage-gated L- and T-type Ca(2+) channels are required for electrical activity, whereas Na(+) currents and P/Q-type Ca(2+) channels contribute to (but are not necessary for) the upstroke of the action potential. Action potential repolarisation is mediated by A-type and Kv2.1/2.2 K(+) channels. Exocytosis is tightly linked to Ca(2+)-influx via P/Q-type Ca(2+) channels. Glucose stimulation of somatostatin secretion involves both K(ATP) channel-dependent and -independent processes.

CXCL13-CXCR5 interactions support prostate cancer cell migration and invasion in a PI3K p110-, SRC- and FAK-dependent fashion (98.5)

We have previously shown that CXCR5 is significantly expressed by the prostate cancer (PCa) tissue than compared to high grade prostatic intraepithelial neoplasia and benign prostatic hyperplasia. We have also demonstrated PCa cell lines significantly express functional CXCR5, which promote cell invasion, migration, and active matrix metalloproteinase expression. In the present study, we elucidate the molecular mechanisms of PCa cell migration and invasion mediated by CXCL13-CXCR5. Using phospho-specific antibody microarray and Western blot analyses, we have delineated the pathways involved in CXCL13-CXCR5 signaling by PCa cell lines. For the first time, we show Gα, Gβ, and Gγ protein isoforms are differentially expressed by normal prostatic epithelial cell lines (PrEC and RWPE-1) versus PCa cell lines (PC3, DU145, LNCaP, and C4-2b). We also illustrate LNCaP cells express PI3K-p110α, -p110β, and -p110δ, while PC3 cells express PI3K-p110α, -p110β, -p110γ, and DOCK2. Migration and invasion assays revealed that both PC3 and LNCaP cell lines invade and migrate toward CXCL13 in a PI3K-dependent fashion. Src-FAK were required for this CXCL13-mediated migration and invasion. PC3 cells were capable of exploiting both PI3K-p110α/β /γ- and PI3K-p110γ-integrin β3-mediated events for migration and invasion, while LNCaP cells were only able to use PI3K-p110α/β /δ-dependent mechanisms for progression. In conclusion, the diversity of G protein and PI3K p110 isoforms along with Src- and FAK-signaling dictate the potential of PCa cell lines to migrate and invade in response to CXCL13.

Exocytotic properties of human pancreatic beta-cells

Pancreatic beta-cells secrete insulin in response to elevated blood glucose via Ca(2+)-dependent fusion of secretory granules with the plasma membrane (regulated exocytosis). While exocytosis has been extensively investigated in rodent beta-cells, studies on human beta-cells are scarce. We have characterized the exocytotic properties of human beta-cells by insulin release measurements, carbon fiber amperometry, and capacitance measurements using the patch-clamp technique. Voltage-clamp depolarizations evoked capacitance increases in single beta-cells in a time- and voltage-dependent manner. The capacitance responses as well as insulin release from intact islets were strongly amplified by elevation of intracellular cAMP levels. Exocytosis was more dependent on Ca(2+) influx through P/Q-type than L-type Ca(2+) channels, reflecting the relative contribution of these channels to the total Ca(2+) current. Exocytosis (as monitored by capacitance or amperometric measurements) decreased during repetitive stimulation as a result of inactivation of Ca(2+) channels as well as depletion of a readily releasable pool of granules. These results reveal both similarities and differences between human and rodent beta-cells.

Voltage-gated ion channels in human pancreatic beta-cells: electrophysiological characterization and role in insulin secretion

OBJECTIVE

To characterize the voltage-gated ion channels in human beta-cells from nondiabetic donors and their role in glucose-stimulated insulin release.

RESEARCH DESIGN AND METHODS

Insulin release was measured from intact islets. Whole-cell patch-clamp experiments and measurements of cell capacitance were performed on isolated beta-cells. The ion channel complement was determined by quantitative PCR.

RESULTS

Human beta-cells express two types of voltage-gated K(+) currents that flow through delayed rectifying (K(V)2.1/2.2) and large-conductance Ca(2+)-activated K(+) (BK) channels. Blockade of BK channels (using iberiotoxin) increased action potential amplitude and enhanced insulin secretion by 70%, whereas inhibition of K(V)2.1/2.2 (with stromatoxin) was without stimulatory effect on electrical activity and secretion. Voltage-gated tetrodotoxin (TTX)-sensitive Na(+) currents (Na(V)1.6/1.7) contribute to the upstroke of action potentials. Inhibition of Na(+) currents with TTX reduced glucose-stimulated (6-20 mmol/l) insulin secretion by 55-70%. Human beta-cells are equipped with L- (Ca(V)1.3), P/Q- (Ca(V)2.1), and T- (Ca(V)3.2), but not N- or R-type Ca(2+) channels. Blockade of L-type channels abolished glucose-stimulated insulin release, while inhibition of T- and P/Q-type Ca(2+) channels reduced glucose-induced (6 mmol/l) secretion by 60-70%. Membrane potential recordings suggest that L- and T-type Ca(2+) channels participate in action potential generation. Blockade of P/Q-type Ca(2+) channels suppressed exocytosis (measured as an increase in cell capacitance) by >80%, whereas inhibition of L-type Ca(2+) channels only had a minor effect.

CONCLUSIONS

Voltage-gated T-type and L-type Ca(2+) channels as well as Na(+) channels participate in glucose-stimulated electrical activity and insulin secretion. Ca(2+)-activated BK channels are required for rapid membrane repolarization. Exocytosis of insulin-containing granules is principally triggered by Ca(2+) influx through P/Q-type Ca(2+) channels.

Preparing and probing atomic number states with an atom interferometer

We describe the controlled loading and measurement of number-squeezed states and Poisson states of atoms in individual sites of a double well optical lattice. These states are input to an atom interferometer that is realized by symmetrically splitting individual lattice sites into double wells, allowing atoms in individual sites to evolve independently. The two paths then interfere, creating a matter-wave double-slit diffraction pattern. The time evolution of the double-slit diffraction pattern is used to measure the number statistics of the input state. The flexibility of our double well lattice provides a means to detect the presence of empty lattice sites, an important and so far unmeasured factor in determining the purity of a Mott state.

The male obese Wistar diabetic fatty rat is a new model of extreme insulin resistance

The male obese Wistar Diabetic Fatty (WDF) rat is a genetic model of obesity and non-insulin dependent diabetes (NIDDM). The obese Zucker rat shares the same gene for obesity on a different genetic background but is not diabetic. This study evaluated the degree of insulin resistance in both obese strains by examining the binding and post binding effects of muscle insulin receptors in obese rats exhibiting hyperinsulinemia and/or hyperglycemia. Insulin receptor binding and affinity and tyrosine kinase activity were measured in skeletal muscle from male WDF fa/fa (obese) and Fa/? (lean) and Zucker fa/fa (obese) and Fa/Fa (homozygous lean) rats. Rats were fed a high sucrose (68% of total Kcal) or Purina stock diet for 14 weeks. At 27 weeks of age, adipose depots were removed for adipose cellularity analysis and the biceps femoris muscle was removed for measurement of insulin binding and insulin-stimulated receptor kinase activity. Plasma glucose (13.9 vs. 8.4 mM) and insulin levels (14,754 vs. 7440 pmol/L) were significantly higher in WDF obese than in Zucker obese rats. Insulin receptor number and affinity and TK activity were unaffected by diet. Insulin receptor number was significantly reduced in obese WDF rats ( 2.778 +/- 0.617 pmol/mg protein), compared to obese Zucker rats (4.441 +/- 0.913 pmol/mg potein). Both obese strains exhibited down regulation of the insulin receptor compared to their lean controls. Maximal tyrosine kinase (TK) activity was significantly reduced in obese WDF rats (505 +/- 82 fmol/min/mg protein) compared to obese Zucker rats (1907 +/- 610 fmol/min/mg protein). Only obese WDF rats displayed a decrease in TK activity per receptor. These observations establish the obese WDF rat as an excellent model for exploring mechanisms of extreme insulin resistance, particularly post-receptor tyrosine kinase-associated defects, in non-insulin dependent diabetes.

Use of glycated hemoglobin to assess Glycemic control in Wistar diabetic fatty rats and Zucker fatty rats

The Wistar Diabetic Fatty rat (WDF fafa) is a congenic strain of the Wistar Kyoto rat. Studies using blood glucose reveal that only fatty male (not female) WDF rats spontaneously develop hyperglycemia when fed a stock diet. Blood glucose values have not provided consistent results for evaluation of glycemic status in fatty male WDF rats. Zucker fatty (fafa) rats, while sharing the fa gene and the development of hyperinsulinemia and hyperlipemia, do not spontaneously become hyperglycemic. In order to examine strain differences and the effects of age on long-term average glycemic status in WDF and Zucker rats, glycated hemoglobin (GHb) was analyzed. Glycated hemoglobin was measured in male lean and obese WDF and Zucker rats at 2, 3, 6, and 12 months of age. Nonfasted plasma glucose was measured in male lean and obese WDF rats at 2, 3, 6, and 12 months of age and in lean and obese Zucker rats at 3, 6, and 12 months of age. Plasma insulin was measured in lean and obese WDF and Zucker rats at 3, 6, and 12 months of age. Obese WDF rats had significantly elevated GHb compared to lean controls at 3, 6, and 12 months of age. Glycated hemoglobin was substantially above the normal range (3.8-6.5%) at 3 months of age (14.1%). Glycated hemoglobin significantly declined in the obese WDF rats between 6 and 12 months of age. Nonfasted plasma glucose was significantly elevated in the obese WDF rats at 3 months (14.1 +/- 2.1 mM/L) and 6 months of age (16.2 +/- 2.3 mM/L) compared to lean controls. At 12 months of age there was no difference in plasma glucose between obese and lean WDF rats. Obese and lean Zucker rats had similar levels of GHb and plasma glucose at all ages. In conclusion, GHb provides more integrated data for classifying disease status of WDF rats and evaluation of potential long-term complications associated with hyperglycemia.

2-Cyano-4-fluoro-1-thiovalylpyrrolidine analogues as potent inhibitors of DPP-IV

We report the synthesis and biological activity of a series of 2-cyano-4-fluoro-1-thiovalylpyrrolidine inhibitors of DPP-IV. Within this series, compound 19 provided a potent, selective, and orally active DPP-IV inhibitor which demonstrated a very long duration of action in both rat and dog.

The contribution of proficiency testing to improving laboratory performance and ensuring quality patient care

The idea of comparing laboratories' test results against one another predated federal regulations by decades (1) and was initially used as an educational tool. The introduction of federal regulations altered the proficiency testing (PT) environment (2,3) and today there is concern that the regulatory requirements do not address extraneous factors that may adversely affect a laboratory's PT performance (6). This article aims to address these concerns and hopes to convince the reader that while the scope of PT has expanded beyond its original intent as an educational tool for the laboratory, PT can still function in that capacity. Improvements in laboratory performance and laboratory medicine as a whole continue to be supported by proficiency testing for numerous reasons. Several mistakes laboratories have made in the past are addressed and suggestions for improvement are given. Laboratory managers who take proactive steps to ensure quality patient test results should experience fewer PT failures, and in turn can focus more attention on the educational benefits that participating in PT can offer.

Non-uniform distribution of mitochondria in pancreatic acinar cells

The distribution of mitochondria in pancreatic acinar cells was investigated using confocal fluorescence microscopy and transmission electron microscopy (EM). Acinar cells were studied either after enzymatic isolation or in small segments of undisassociated pancreatic tissue. Loading of isolated acinar cells with Mito Tracker Green or Red, a fluorescence mitochondrial probe, showed that mitochondria are predominantly situated in the perigranular, subplasmalemmal and perinuclear regions. Subsequent applications of EM fixatives induced a leak of the fluorescent indicator to the cytosol but did not change the distribution of mitochondria. EM was then performed on isolated acinar cells and on acinar cells of pancreatic tissue segments. The intracellular distribution of mitochondria was quantified by calculating the percentage of the cross-sectional area that was occupied by mitochondria. In isolated acinar cells the highest density of mitochondria was seen in the perigranular region, where mitochondria occupied 25.69+/-1.58% of the area, then the subplasmalemmal region with 12.61+/-0.77% and the perinuclear region with 9.07+/-0.97% ( n=26). Similar results were obtained from acinar cells of pancreatic tissue segments: the perigranular 22.9+/-1.95%, subplasmalemmal 12.45+/-0.78% and perinuclear regions 9.07+/-0.97% ( n=26). The outer mitochondrial membranes were frequently positioned close to membranes of the ER, which followed the outer contour of mitochondria. Mitochondria were never found in direct contact with the nuclear envelope: there were usually layers of ER between the mitochondrial and nuclear membranes. Subplasmalemmal mitochondria were found in a very close proximity to the plasma membrane with no ER layers between the mitochondrial and the corresponding plasma membranes. We conclude that in pancreatic acinar cells mitochondria are preferentially distributed to perigranular, subplasmalemmal and perinuclear regions and this distribution is not affected by isolation or fixation procedures.