Reversible Adsorption of Soluble Hexameric Insulin onto the Surface of Insulin Crystals Cocrystallized with Protamine: An Electrostatic Interaction

Mixing pharmaceutical preparations of soluble neutral regular insulin solution (NRI) and neutral protamine Hagedorn (NPH) crystalline insulin suspension leads to a reduction in the measurable amount of soluble insulin in the formulation supernatant. However in spite of the loss in soluble insulin, the time-actions of these components have been shown, in clinical trials, to be unaffected. The interaction between these different physical forms of insulin has been studied using reversed-phase HPLC, isothermal titrating calorimetry, and Doppler electrophoretic light scattering analysis. Sorbent surface and solution perturbation studies revealed that the NRI adsorbs to the surface of the NPH crystal with an equilibrium constant ranging from 10⁴ M^–1 to 10⁷ M^–!, depending on the protamine concentration, pH, ionic strength, and temperature. This adsorption behavior suggests that the binding is mediated by electrostatic interactions arising between the positively-charged NPH crystal and the negatively-charged NRI hexamer. Doppler electrophoretic light scattering results, used to probe the pH-dependent surface charge of NPH and soluble insulin hexamer, support the conclusion that electrostatic interactions mediate the adsorption process. Adsorption studies under physiological conditions indicate that the elevated temperature and ionic strength, in a subcutaneous depot, are sufficient to lead to the dissociation of the NRI/NPH complex that exists in these NPH mixture formulations.     

Vascular endothelial growth factor in the CSF of elderly patients with ventriculomegaly: Variability,periodicity and levels in drainage responders and non-responders

Objectives

The aim of this study was to examine lumbar CSF-VEGF levels from elderly patients with ventriculomegaly to evaluate the possible circadian or periodic concentration profile and relevance to the prediction of drainage response.

Methods

Lumbar CSF samples were collected in 1-h interval over 35 h from 22 patients with ventriculomegaly. CSF-VEGF levels were measured to elucidate the possible circadian or periodic concentration profiles. These VEGF levels were evaluated for correlations with clinical response to CSF drainage, ventricle size and other clinical information.

Results

The 35-h CSF-VEGF levels demonstrated a periodic concentration pattern with significant episodic fluctuation with 3–5 h intervals. CSF-VEGF levels in non-responder group in which patients did not show clinical improvement with CSF drainage were significantly higher than these in responder group.

Conclusion

VEGF variation in hydrocephalus patients suggests its possible pathophysiological role in hydrocephalus. The periodic concentration pattern of CSF-VEGF must be considered when choosing the most appropriate time for sample collection or clinical manipulation. Increased VEGF level in patients who showed no improvement with CSF drainage suggests that a possible greater ischemic or vascular injury may play a role in these patients. Pending further studies, these results suggest that high VEGF levels have a potential application in predicting non-responder patients with CSF drainage and so reducing the morbidity and cost of drainage and shunting in these patients.     

Molecular karyotyping in patients with mental retardation using 100K single-nucleotide polymorphism arrays

Background

Using array techniques, it was recently shown that about 10% of patients with mental retardation of unknown origin harbour cryptic chromosomal aneusomies. However, data analysis is currently not standardised and little is known about its sensitivity and specificity.

Methods

We have developed an electronic data analysis tool for gene‐mapping SNP arrays, a software tool that we call Copy Number Variation Finder (CNVF). Using CNVF, we analysed 104 unselected patients with mental retardation of unknown origin with a genechip mapping 100K SNP array and established an optimised set of analysis parameters.

Results

We detected deletions as small as 20 kb when covered by at least three single‐nucleotide polymorphisms (SNPs) and duplications as small as 150 kb when covered by at least six SNPs, with only one false‐positive signal in six patients. In 9.1% of patients, we detected apparently disease‐causing or de novo aberrations ranging in size from 0.4 to 14 Mb. Morphological anomalies in patients with de novo aberrations were equal to that of unselected patients when measured with de Vries score.

Conclusion

Our standardised CNVF data analysis tool is easy to use and has high sensitivity and specificity. As some genomic regions are covered more densely than others, the genome‐wide resolution of the 100K array is about 400–500 kb for deletions and 900–1000 kb for duplications. The detection rate of about 10% of de novo aberrations is independent of selection of patients for particular features. The incidental finding in two patients of heterozygosity for the 250 kb recurrent deletion at the NPH1 locus, associated with autosomal recessive juvenile nephronophthisis, which was inherited from a healthy parent, highlights the fact that inherited aberrations might be disease‐related even though not causal for mental retardation.     

Comparison of the effects on glucose and lipid metabolism of equipotent doses of insulin detemir and NPH insulin with a 16-h euglycaemic clamp

Aims/hypothesis The association of insulin detemir with non-esterified fatty acid binding sites on albumin may limit its transfer from the circulation into the extravascular extracellular space in adipose tissue and muscle, due to the capillary endothelial cell barrier. In the liver, the open sinusoids may expose hepatocytes to insulin detemir, enabling it to have a greater effect in the liver than in peripheral tissues.Methods We investigated the effects of equipotent doses of insulin detemir and NPH insulin on hepatic glucose rate of appearance (R_a), peripheral glucose rate of disposal (R_d) and glycerol R_a (a measure of lipolysis) using stable isotope techniques. We also investigated the effects of these insulins on NEFA concentrations in seven healthy volunteers during a 16-h euglycaemic clamp. A higher dose of insulin detemir was also studied.Results There was no difference in the glucose infusion profile between insulin detemir and NPH. Insulin detemir had a greater effect on mean suppression of glucose R_a (mean difference 0.24 mg kg^–1 min^–1; CI 0.09–0.39; p<0.01), and minimum glucose R_a, with minimum low dose detemir –0.10±0.15 mg·kg^–1·min^–1 and minimum NPH 0.17±0.10 mg·kg^–1·min^–1 (p<0.02). However, it had a lesser effect on mean suppression of NEFA concentrations (mean difference –0.10 mmol/l; CI –0.03 to –0.17; ANOVA, p<0.02) than NPH. The effect of insulin detemir on glucose R_d and glycerol R_a was not different from NPH. Following high-dose detemir, total glucose infused and maximum glucose R_d were higher (p<0.02, p<0.03) and plasma NEFA concentrations lower (p<0.01) than with low-dose determir.Conclusions/interpretation This study suggests that insulin detemir, when compared to NPH insulin, has a greater effect on the liver than on peripheral tissues and thus has the potential to restore the physiological insulin gradient.     

An economic assessment of analogue basal–bolus insulin versus human basal–bolus insulin in subjects with type 1 diabetes in the UK

ABSTRACT

Background: A recent study demonstrated that treatment of type 1 diabetes with an analogue basal–bolus insulin regimen was associated with improved glycaemic control (HbA_1c –0.22% points, p < 0.001), reduced risk of hypo­glycaemic events (–21%, p = 0.036) and reduction in body mass index (–0.30?kg/m², p < 0.001) compared to a human basal–bolus regimen after 18 weeks.

Methods: A published and validated computer simulation model was used to project long-term economic and clinical outcomes in a simulated cohort of type 1 diabetes patients treated with either insulin detemir plus insulin aspart (analogue) or Neutral Protamine Hagedorn plus human soluble insulin (human), in a UK setting. Probabilities of complications and HbA_1c-dependent adjustments were derived from major clinical and epidemiological studies. Complication and treatment costs were projected over patient lifetimes from a National Health Service perspective. Costs and clinical benefits were discounted at 3.5% annually.

Results: Quality-adjusted life expectancy (QALE) was 0.66 quality-adjusted life years (QALY) higher in the analogue insulin versus the human insulin group (mean ± SD) (7.65 ± 0.09 versus 6.99 ± 0.08). Direct lifetime costs were £1654 greater with analogue versus human insulin treatment (£40?876 ± 1119 versus £39?222 ± 1141), producing an incremental cost effectiveness ratio (ICER) of £2500 per QALY gained. Sensitivity analyses showed the results were robust under a range of plausible scenarios.

Conclusions: Treatment with analogue insulin was associated with a decreased incidence of long-term complications and improved QALE, but slightly higher treatment costs compared to human insulin therapy. Analogue insulin treatment had an ICER within the range generally considered to represent good value for money in the UK.     

Assessment of the Mixing Efficiency of Neutral Protamine Hagedorn Cartridges

Reliable application of neutral protamine Hagedorn (NPH) insulin requires previous resuspension of the suspension by tipping over the cartridge 20 times. This procedure is considered annoying by patients. The goal of this investigation was to assess the efficiency of the mixing procedure when performed less frequently than recommended. Neutral protamine Hagedorn insulin cartridges from five different manufacturers (sanofi-aventis, Lilly, Berlin-Chemie, B. Braun, and Novo Nordisk) were emptied with doses of 28 IU in the morning and the evening over 5 days. While the first dose was obtained after a regular resuspension procedure (20× tipping over), the consecutive doses were obtained after 3, 6, 10, or 20 mixing procedures (12 cartridges per experimental series, two doses/day). Insulin concentrations of doses 1, 2, 6, and 10 were determined by high-pressure liquid chromatography. Between dosing, cartridges were stored at room temperature in a horizontal position. Comparable insulin concentrations were seen in the first correctly prepared doses. Pronounced and substantial deviations from the selected dose were observed with most of the cartridges, in particular when resuspending only 3 and 6 times. Mean absolute percentage deviations when tipping 3 times and maximally observed overdoses were: Insuman basal: 1.1 ± 1.0%/4 IU, Humulin N: 2.6 ± 3.4%/19 IU, Berlinsulin H basal: 4.4 ± 6.0%/26 IU, Insulin B. Braun basal: 10.4 ± 8.9%/38 IU, and Protaphane: 4.7 ± 4.1%/19 IU (all p < 0.05 vs Insuman basal). Only one cartridge with three metal mixing bullets (sanofi-aventis) was resuspended efficiently with only a few mixing procedures. All other cartridges with fewer bullets were shown to deliver potentially harmful doses if used for treatment when the mixing procedure was less frequent than demanded in the instructions for use.     

A Clinicopathological Study of Idiopathic Normal Pressure Hydrocephalus

Background : Since Hakim and Adams introduced the clinical entity of normal pressure hydrocephalus (NPH) in 1965, postmortem studies of idiopathic NPH have been few in number. Several autopsy cases reported with clinically probable "idiopathic NPH" were diagnosed with Alzheimer's disease (AD) or Binswanger's disease (BD) neuropathologically. Therefore, the neuropathological study of pathologically confirmed idiopathic NPH remains to be completed both quantitatively and qualitatively.
Methods : Out of 239 autopsy cases in Fukushimura Hospital, 13 patients had been diagnosed clinically as having NPH. After excluding seven cases diagnosed neuropathologically with other diseases or secondary NPH, we investigated the clinicopathological findings of six patients with idiopathic NPH.
Results : Four patients presented with the complete classic triad consisting of progressive dementia, gait disturbance, and urinary incontinence. All cases exhibited progressive ventricular enlargement with periventricular lucency by computed tomography images. We found (1) diffuse marked dilatation of the lateral ventricles of unknown etiology, and (2) the changes of ependymal cells and subependymal tissue around the callosocaudate angle. Furthermore, no complications were suspected neuropathologically in all cases, such as AD, BD, or Lewy body disease.
Conclusion : We experienced six autopsy cases with pathologically confirmed idiopathic NPH. They had two pathological features of NPH but no other pathological disorders that might cause NPH. Several "idiopathic NPH" cases reported previously have been diagnosed neuropathologically with other disorders. However, the presented cases could be clearly distinguished from such "idiopathic NPH." Therefore, our cases should be defined as idiopathic NPH neuropathologically. By accumulating more cases and investigating further we hope to elucidate the pathogenesis and further develop treatment for idiopathic NPH.     

Upper extremity motor measures of Tap Test response in Normal Pressure Hydrocephalus

Objective

The Tap Test (TT) is a commonly used method for predicting shunt responsiveness in patients with Normal Pressure Hydrocephalus (NPH). The present study investigates whether measures of upper extremity motor function are useful for assessing response to spinal fluid drainage.

Methods

42 subjects undergoing evaluations for idiopathic NPH (iNPH) participated in this study. A standardized gait evaluation, a neuropsychological battery, and objective tests of upper extremity motor functions were administered. A Neurologist skilled in NPH assessment independently rated patients as TT Responders (n = 26) or Non-Responders (n = 16) based on clinical impression of change 2–4 h after 40–50 cm³ drainage of spinal fluid by lumbar puncture (LP). In the subset of subjects who underwent shunt placement, operative outcome was also evaluated.

Results

TT Responders improved significantly more than TT Non-Responders in Upper Extremity Coordination/Speed tasks (p < .001). The groups did not differ on other neuropsychological measures post-LP. A possible association was observed between pre- and post-TT changes in Upper Extremity Coordination/Speed and post-shunt improvement. Among Upper Extremity Coordination/Speed measures, Line Tracing displayed the greatest sensitivity (76%) to change post-LP.

Conclusions

Our data suggest that measures of upper extremity motor functions may be useful as measures of Tap Test response in patients with iNPH. These upper extremity motor tasks can be rapidly administered (<5 min) in clinical practice and may provide an additional dimension beyond gait and cognition for evaluating response to LP.     

Evaluating the cost-effectiveness of therapy conversion to insulin detemir in patients with type 2 diabetes in Germany: a modelling study of long-term clinical and cost outcomes

OBJECTIVES: To evaluate the long-term cost-effectiveness of transferring type 2 diabetes patients to an insulin detemir regimen after failure to achieve adequate control with oral antidiabetic agents (OADs) alone, or in combination with neutral protamine hagedorn (NPH) insulin, or with insulin glargine in Germany. METHODS: A computer simulation model of diabetes was used to make long-term projections of future clinical outcomes and direct medical costs based on findings from a German subanalysis of the PREDICTIVE trial. The study analysed the impact of converting patients failing their current treatments to an insulin detemir regimen. Therapy conversion to insulin detemir +/- OADs was associated with a significant reduction in glycosylated haemoglobin (HbA(1)c) compared with OADs alone, NPH insulin +/- OADs, and insulin glargine +/- OADs. Across all three groups, hypoglycaemia rates decreased by 80% and patients lost an average of 0.9 kg of body weight during treatment with insulin detemir +/- OADs. RESULTS: Therapy conversion to insulin detemir +/- OADs was projected to improve life expectancy by 0.28 years compared with OADs alone, and by 0.13 years compared with the NPH and glargine regimens. Transfer to insulin detemir was associated with improvements in quality-adjusted life expectancy of 0.21 quality-adjusted life years (QALYs) over OADs alone, 0.28 QALYs over NPH +/- OADs, and 0.29 QALYs over glargine +/- OADs. Insulin detemir was associated with savings over patient lifetimes due to reduced diabetes-related complications in all three comparisons. CONCLUSIONS: Therapy conversion to insulin detemir +/- OADs in type 2 diabetes patients failing OADs alone, NPH or insulin glargine regimens was associated with improvements in life expectancy, quality-adjusted life expectancy and cost savings in all three scenarios evaluated.     

Measurement of peak CSF flow velocity at cerebral aqueduct, before and after lumbar CSF drainage, by use of phase-contrast MRI: utility in the management of idiopathic normal pressure hydrocephalus

OBJECTIVE: Since it was first described, normal pressure hydrocephalus (NPH) and its treatment by means of cerebrospinal fluid (CSF) shunting have been the focus of much investigation. Whatever be the cause of NPH, it has been hypothesized that in this disease there occurs decreased arterial expansion and an increased brain expansion leading to increased transmantle pressure. We cannot measure the latter, but fortunately the effect of these changes (increased peak flow velocity through the aqueduct) can be quantified with cine phase-contrast magnetic resonance imaging (MRI). This investigation was thus undertaken to characterize and measure CSF peak flow velocity at the level of the aqueduct, before and after lumbar CSF drainage, by means of a phase-contrast cine MRI and determine its role in selecting cases for shunt surgery. PATIENTS AND METHODS: 37 patients with clinically suspected NPH were included in the study. Changes in the hyperdynamic peak CSF flow velocity with 50 ml lumbar CSF drainage (mimicking shunt) were evaluated in them for considering shunt surgery. RESULTS: 14 out of 15 patients who were recommended for shunt surgery, based on changes peak flow velocity after lumbar CSF drainage, improved after shunt surgery. None of the cases which were not recommended for shunt surgery, based on changes in CSF peak flow velocity after lumbar CSF drainage, improved after shunt surgery (2 out of 22 cases). CONCLUSION: The study concluded that the phase-contrast MR imaging, done before and after CSF drainage, is a sensitive method to support the clinical diagnosis of normal pressure hydrocephalus, selecting patients of NPH who are likely to benefit from shunt surgery, and to select patients of NPH who are not likely to benefit from shunt surgery.