Negatively charged gold atoms in subnanometric particles: experimental evidence from an X-ray photoelectron spectroscopy study

The results of an X-ray Photoelectron Spectroscopy study conducted on a series of gold nanoparticles recently reported by us, stabilized by monodentate, bidentate, tridentate and tetradentate thiolate calix[n]arene ligands, are presented here. By virtue of the different denticity of the ligands, the nuclearity of the resulting particles can be tuned down to the subnanometric range. From the present XPS results, a clear correlation among the experimental binding energy of single Au 4f peak components and the specific Au state of charge is proposed, where the smaller (i.e., nanometer) fraction of the series selectively shows negatively charged Au atoms. Our findings are relevant for the open discussion of a specific role played by negatively charged Au atoms in catalytic reactions, especially at low temperatures.

Selective assembling of calixarenes and pseudorotaxanes on Si(100) and polycrystalline copper

We report the first compared study of the anchoring mode of calix[6]arene derivatives and pseudorotaxanes on Si(100) and polycrystalline Cu. Calixarenes have been chosen for their flexibility as linkers, being, i.a., efficient building blocks for the constructing of molecular devices based on pseudorotaxanes and rotaxanes. A covalent functionalization on Si or Cu surfaces requires the molecules to be differently modified: thiol (-SH) or C double bond C terminations are respectively suitable for Cu or H-Si(100). Anchoring on Cu was reached by dipping a clean substrate in a calix[6]arene-SH solution, while a wet-chemistry recipe was followed for Si(100), combined with an extra-mild photochemical activation via visible light. Molecular adhesion onto either surfaces has been demonstrated by the presence of XPS signals from specific elements in the molecules: calix[6]arene designed for H-Si were derivatized with NO2 groups on the upper rim of the calix, while the S atom was used as the molecular identifier on Cu. A further extension is represented by the anchoring reaction of rotaxanes on Si(100) and Cu surfaces. A pseudorotaxane species was first formed in solution by reacting a calix[6]arene "wheel," bearing three N-phenylureido groups on the upper rim, with viologen (4,4'-bipyridinium) containing axle. The resulting species has then been anchored on either Cu and Si via its distinct termination of the axle. This two-step reaction has produced a threaded pseudorotaxane covalently bound to either surfaces, as shown by XPS results. These species are ready to respond to external stimuli. We also cross-checked the two different anchoring groups for their reactivity on Cu and Si surfaces. No molecular uptake was observed when two solutions, containing calixarenes with the anchoring arms intended either for Si or Cu surfaces, were exchanged.

Planar coupling to high-Q lithium niobate disk resonators

We demonstrate optical coupling to high-Q lithium niobate disks from an integrated lithium niobate waveguide. The waveguides are made by proton exchange in X-cut lithium niobate substrate. The disks with diameter of 4.7 mm and thickness of 1 mm are made from commercial Z-cut lithium niobate wafers by polishing the edges into a spheroidal profile. Both resonance linewidth and cavity ringdown measurements were performed to calculate the Q factor of the resonator, which is in excess of 10(8). Planar coupling represents the most promising technique for practical applications of whispering gallery mode resonators.

Beta cell function during rapamycin monotherapy in long-term type 1 diabetes

AIMS/HYPOTHESIS

Type 1 diabetes is considered non-reversible at end-stage disease when there is no measurable insulin production. However, there are indications that insulin-producing beta cells could be present or return if autoimmunity could be controlled. We therefore sought to determine whether immunosuppression therapy can reinstate beta cell function in patients with long-term type 1 diabetes.

METHODS

We examined pancreatic beta cell function in 22 patients with long-term type 1 diabetes (median disease duration 27 years), who had been receiving rapamycin monotherapy (0.1 mg/kg; target trough levels 8-10 ng/ml; 26-314 days) as pre-conditioning for islet transplantation. As control, beta cell function was measured in 14 patients (median disease duration 17 years) who were waiting for an islet transplant without rapamycin pre-conditioning.

RESULTS

Fasting C-peptide increased from <0.03 nmol/l (0.0066 nmol/l, interquartile range [IQR] 0.0003-0.023) at baseline to 0.039 nmol/l (IQR 0.0066-0.096) at end of rapamycin monotherapy (p < 0.005). In 12 patients, fasting C-peptide increased to >0.076 nmol/l (C-peptide responders). Exogenous insulin requirement decreased from 0.64 U/kg daily (IQR 0.56-0.72) to 0.57 U/kg (IQR 0.45-0.70; p = 0.01), but this reduction was significant only in the 12C-peptide-responsive patients. Rapamycin monotherapy was also associated with a decrease in insulin antibody titre (median decrease 110 to 35.9 U/ml; p < 0.001) and fasting serum proinsulin (median decrease 0.51 to 0.28 pmol/l; p = 0.001). All variables remained unchanged in the 14 control patients.

CONCLUSIONS/INTERPRETATION

Therapies to reinstate beta cell function may be applicable to patients with long-term C-peptide-negative type 1 diabetes.

TRIAL REGISTRATION

ClinicalTrial.gov NCT01060605.

Improved function of circulating angiogenic cells is evident in type 1 diabetic islet-transplanted patients

Circulating angiogenic cells (CACs) are vascular-committed bone marrow-derived cells that are dysfunctional in type 1 diabetes (T1D). Here we studied whether restoration of normoglycemia following islet transplantation is associated with better CAC function. We carried out a cross-sectional study of 18 T1D patients, 14 insulin-independent islet-transplanted patients (ITA) and 14 healthy controls (C) evaluating in vivo and in vitro CACs viability and function. We found that the percentage of CACs in vivo did not differ among the three groups while the number of CAC colonies obtained from T1D, but not from ITA, was reduced compared to C (C = 7.3 ± 1.9, T1D = 0.9 ± 0.4 and ITA = 4.7 ± 1.9; p < 0.05 T1D vs. all). In vitro CAC migration/differentiation were similar, while in vivo an improved angiogenic ability of ITA compared to T1D was shown (capillary density: C = 93.5 ± 22.1, T1D = 19.2 ± 2.8 and ITA = 44.0 ± 10.5, p < 0.05 T1D vs. all). Increased apoptosis and lesser IL-8 secretion were evident in CACs obtained from T1D compared to C and ITA. in vitro addition of anti-hIL-8 reduced the number of colonies obtained from C. Finally, T1D, but not ITA, had a lower endothelial-dependent dilatation (EDD) compared with C. These data suggest that CAC function is altered in T1D and may be improved after islet transplantation.

Liver focal fatty changes at ultrasound after islet transplantation: an early sign of altered graft function?

AIMS

Few longitudinal imaging studies of liver-engrafted islets after islet transplantation are available for islet-transplant-alone (ITA) and islet-after-kidney (IAK) transplanted patients. Particularly controversial is the link between islet function and the appearance of islet-induced liver focal fatty changes. Aims of this study were to assess liver focal fatty changes at ultrasound after islet transplantation and their relationship with islet function.

METHODS

The timing of first ultrasound detection of liver focal fatty changes and the prevalence and duration of these changes were assessed in 30 IAK transplanted patients, in five ITA patients and, retrospectively, in full-, partial- and no-function groups, according to islet function evaluated 1 year after transplantation. Patients with persistent ultrasound detected liver focal fatty changes underwent liver biopsy. Ultrasound positive and negative patients with functioning islets were compared for islet-function and C-peptide-levels during the follow-up. Variations of cholesterol/triglycerides and other metabolic parameters were also recorded at 1 year.

RESULTS

Liver focal fatty changes at ultrasound were found in 12 patients (10/30 IAK, 2/5 ITA). First detection was at 6 months in eight cases and at 12 months in four cases. Liver ultrasound changes were of more than 1 year duration in eight cases. Steatosis was found histologically in 8/8 patients. At 12 months, liver ultrasound changes were detected to a greater extent in patients with partial islet function (10/12, eight IAK, two ITA) compared with patients with full islet function. C-peptide-levels were significantly lower in ultrasound-positive than in ultrasound-negative patients. At 18 months, ultrasound- positive patients were more prone to worsening of their function (9/12) compared with ultrasound-negative patients (3/18). No statistically significant differences of cholesterol/triglycerides levels were found in either the total number of patients or the IAK and ITA patients.

CONCLUSIONS

Liver focal fatty changes at ultrasound (steatosis) after islet transplantation in IAK and ITA patients may represent an early sign of altered graft function.

Improving the procedure for detection of intrahepatic transplanted islets by magnetic resonance imaging

Islet transplantation is an effective therapy for restoring normoglycemia in type-1 diabetes, but long-term islet graft function is achieved only in a minority of cases. Noninvasive magnetic resonance imaging of pancreatic islets is an attractive option for "real-time" monitoring of graft evolution. So far, previous studies have been performed in the absence of a standardized labeling procedure and, besides a feasibility study in patients, the effectiveness and safety of various labeling approaches were tested only with high field magnets (4.7 T). In this study, we addressed: (a) standardization of a labeling procedure for human islets with clinically-approved contrast agent Endorem, (b) safety aspects of labeling related to inflammation and (c) quality of imaging both at 7 T and 1.5 T. We have highlighted that the ratio of Endorem/islet is crucial for reproducible labeling, with a ratio of 2.24 ug/IEQ, allowing successful in vivo imaging both with 1.5 T and 7.0 T magnets up to 143 days after intrahepatic transplant. With this standardized labeling procedure, labeled islets are neither inflamed nor more susceptible to inflammatory insults than unlabeled ones. This report represents an important contribution towards the development of a standardized and safe clinical protocol for the noninvasive imaging of transplanted islets in humans.

Protein and glutamine kinetics during counter-regulatory failure in type 1 diabetes

BACKGROUND AND AIMS

Healthy individuals counteract insulin-induced hypoglycaemia by increasing glutamine utilization but not proteolysis. Glucagon is important to this response because it increases glutamine uptake. In type 1 diabetes (T1DM) glucagon and epinephrine responses to hypoglycaemia are defective. We investigated whether glutamine and amino acid utilization during hypoglycaemia is altered in T1DM with defective counter-regulatory responses.

METHODS AND RESULTS

Eight T1DM patients (duration of diabetes 14+/-4 years and therefore with presumed defective counter-regulatory response) and eight controls (CON) received a 3h hypoglycaemic hyperinsulinaemic (0.65mU/kg per min) clamp coupled to [6,6-(2)H(2)]glucose, [1-(13)C]leucine and [2-(15)N]glutamine to trace the relative kinetics. Post-absorptive plasma glucose and glucose uptake were increased in T1DM (9.09+/-0.99 vs 5.01+/-0.22mmol/l and 19.5+/-0.9 vs 12.6+/-0.8micromol/kg per min, p<0.01). During the clamp T1DM but not CON required exogenous glucose (4.4+/-1.7micromol/kg per min) to maintain the hypoglycaemic plateau because the endogenous glucose production was significantly suppressed (p<0.01). In T1DM the leucine and phenylalanine concentrations were less suppressed from basal (p<0.05) despite a similar insulin suppression of proteolysis (-16+/-2 vs -20+/-4%, p=ns) indicating a defective stimulation of leucine metabolic clearance from basal (+18+/-3% vs +55+/-9%, p<0.01). Glutamine concentration remained unchanged from basal (-7+/-3% vs -35+/-3%, p<0.01) and the clearance of glutamine was markedly defective in T1DM (+6+/-2%) in comparison with controls (+22+/-4%; p=0.02).

CONCLUSIONS

In T1DM, the counter-regulatory failure to hypoglycaemia seems to be associated with a defective glutamine utilization. The failure to clear circulating amino acids, specifically glutamine, during hypoglycaemia may adversely affect gluconeogenesis.

The clinical impact of islet transplantation

Islet cell transplantation has recently emerged as one of the most promising therapeutic approaches to improving glycometabolic control in diabetic patients and, in many cases, achieving insulin independence. Unfortunately, many persistent flaws still prevent islet transplantation from becoming the gold standard treatment for type 1 diabetic patients. We review the state of the art of islet transplantation, outcomes, immunosuppression and--most important--the impact on patients' survival and long-term diabetic complications and eventual alternative options. Finally, we review the many problems in the field and the challenges to islet survival after transplantation. The rate of insulin independence 1 year after islet cell transplantation has significantly improved in recent years (60% at 1 year posttransplantation compared with 15% previously). Recent data indicate that restoration of insulin secretion after islet cell transplantation is associated with an improvement in quality of life, with a reduction in hypoglycemic episodes and potentially with a reduction in long-term diabetic complications. Once clinical islet transplantation has been successfully established, this treatment could even be offered to diabetic patients long before the onset of diabetic complications.