Comparison of a Luminescent Oxygen Channeling Immunoassay and an ELISA for detecting Insulin Aspart in human serum

Predicting human half-life for insulin analogs: An inter-drug approach

An inter-drug approach, applying pharmacokinetic information for insulin analogs in different animal species, rat, dog and pig, performed better compared to allometric scaling for human translation of intra-venous half-life and only required data from a single animal species for reliable predictions. Average fold error (AFE) between 1.2-1.7 were determined for all species and for multispecies allometric scaling AFE was 1.9. A slightly larger prediction error for human half-life was determined from in vitro human insulin receptor affinity data (AFE on 2.3-2.6). The requirements for the inter-drug approach were shown to be a span of at least 2 orders of magnitude in half-life for the included drugs and a shared clearance mechanism. The insulin analogs in this study were the five fatty acid protracted analogs: Insulin degludec, insulin icodec, insulin 320, insulin 338 and insulin 362, as well as the non-acylated analog insulin aspart.

Toward once-monthly insulin therapy via synergy in two pharmacokinetic protractors: Fc-conjugation and fatty acid acylation

Pharmacokinetic properties and duration of therapeutic action of a pharmaceutical agent can be significantly extended through the combination of two distinct strategies aimed at increasing plasma half-life: fatty acid acylation and Fc-conjugation. Using insulin as a case study, we demonstrate that a doubly protracted insulin analog produces a substantial prolongation of pharmacodynamic effect to lower blood glucose in STZ-treated mice when compared to the Fc-only counterparts. This enhancement is further corroborated by direct pharmacokinetic measurements in rat and dog models, demonstrating the potential for once-monthly insulin therapy. The results suggest that this approach might have broad application across a diverse spectrum of peptide- and protein-based therapeutics.

Quantification of pharmacokinetic profiles of a recombinant canine PD-1 fusion protein by validated sandwich ELISA method

Tumors are becoming a serious threat to the quality of life of human and dogs. Studies have shown that tumors have caused more than half of the deaths in older dogs. Similar to human, dogs will develop various and highly heterogeneous tumors, but there are currently no viable therapies for them. In human, immunotherapy has been used widely and considered as an effective treatment for tumors by immune checkpoint targets, which are also expressed on canine tumors, suggesting that immunotherapy may be a potential treatment for canine tumors. In this work, we developed a sandwich ELISA method to detect the concentration of recombinant canine PD-1 fusion protein in canine serum and investigated pharmacokinetics in canines after intravenous infusion administration. After being validated, the ELISA method showed an excellent linear relationship in 25.00–3,200.00 ng/ml in serum, and the R² was more than 0.99 with four-parameter fitting. The precision and accuracy of intra-assay and inter-assay at the five different concentrations met the requirements of quantitative analysis. At the same time, no hook effect was observed at the concentration above ULOQ, and the stability was good under different predicted conditions with accuracy > 80%. The pharmacokinetic study in dogs has shown that the recombinant canine PD-1 fusion protein exhibited a typical biphasic PK profile after intravenous infusion administration, and the linear pharmacokinetic properties were observed between 1.00 and 12.00 mg/kg. Meanwhile, the T_1/2 after intravenous infusion administration with non-compartmental analysis was about 5.79 days.

In vitro and in vivo characterization of insulin vesicles by electron microscopy

Insulin is the main hypoglycemic hormone, promoting the absorption and storage of glucose and inhibiting its production. It is a hexamer composed of six insulin macromolecules and a Zn2+ and clustered in insulin vesicles of pancreatic β cell. Most current research has focused on the in vivo imaging of whole cells while there are few detailed studies on structure of insulin vesicles. The precise content of Zn2+ in vesicles is not clear, and the aggregation state and location of insulin in insulin vesicles is not fully characterized, which hinders a thorough understanding of insulin secretion process and diseases caused by blood sugar regulation. Here, we performed electron microscopy (EM) studies on both whole cells (in vivo) and extracted isolated insulin vesicles by supercentrifugation (in vitro) to explore the location and distribution of insulin vesicles in pancreatic β cells. Meanwhile, we analyzed the content of Zn2+ and Ca2+ through EM imaging and energy dispersive spectroscopy (EDS) mapping, and the content of Zn2+ was found to be proportional to the size of insulin vesicles. In addition, by taking advantage of TEM tomography, the three-dimensional structure of insulin vesicle was obtained by acquisition projections in different angles of insulin vesicle. This study provides a promising way to quantitative analysis of intracellular insulin, which may be of great significance to the study of diabetes and other blood sugar diseases.

Molecular Engineering of Efficacious Mono-Valent Ultra-Long Acting Two-Chain Insulin-Fc Conjugates

Here, we describe molecular engineering of monovalent ultra-long acting two-chain insulin-Fc conjugates. Insulin-Fc conjugates were synthesized using trifunctional linkers with one amino reactive group for reaction with a lysine residue of insulin and two thiol reactive groups used for re-bridging of a disulfide bond within the Fc molecule. The ultra-long pharmacokinetic profile of the insulin-Fc conjugates was the result of concertedly slowing insulin receptor-mediated clearance by (1) introduction of amino acid substitutions that lowered the insulin receptor affinity and (2) conjugating insulin to the Fc element. Fc conjugation leads to recycling by the neonatal Fc receptor and increase in the molecular size, both contributing to the ultra-long pharmacokinetic and pharmacodynamic profiles.

Optimization of pig models for translation of subcutaneous pharmacokinetics of therapeutic proteins: Liraglutide, insulin aspart and insulin detemir

Prediction of human pharmacokinetics (PK) from data obtained in animal studies is essential in drug development. Here, we present a thorough examination of how to achieve good pharmacokinetic data from the pig model for translational purposes by using single-species allometric scaling for selected therapeutic proteins: liraglutide, insulin aspart and insulin detemir. The predictions were based on non-compartmental analysis of intravenous and subcutaneous PK data obtained from two injection regions (neck, thigh) in two pig breeds, domestic pig and Göttingen Minipig, that were compared with PK parameters reported in humans. The effects of pig breed, injection site and injection depth (insulin aspart only) on the PK of these proteins were also assessed. Results show that the prediction error for human PK was within two-fold for most PK parameters in both pig breeds. Furthermore, pig breed significantly influenced the plasma half-life and mean absorption time (MAT), both being longer in Göttingen Minipigs compared to domestic pigs (P <0.01). In both breeds, thigh vs neck dosing was associated with a higher dose-normalized maximum plasma concentration and area under the curve as well as shorter MAT and plasma half-life (P <0.01). Finally, more superficial injections resulted in faster absorption, higher C_max/dose and bioavailability of insulin aspart (P <0.05, 3.0 vs 5.0 mm injection depth). In conclusion, pig breed and injection region affected the PK of liraglutide, insulin aspart and insulin detemir and reliable predictions of human PK were demonstrated when applying single-species allometric scaling with the pig as a pre-clinical animal model.

Molecular Engineering of Insulin Icodec, the First Acylated Insulin Analog for Once-Weekly Administration in Humans

Here, we describe the molecular engineering of insulin icodec to achieve a plasma half-life of 196 h in humans, suitable for once-weekly subcutaneously administration. Insulin icodec is based on re-engineering of the ultra-long oral basal insulin OI338 with a plasma half-life of 70 h in humans. This systematic re-engineering was accomplished by (1) further increasing the albumin binding by changing the fatty diacid from a 1,18-octadecanedioic acid (C18) to a 1,20-icosanedioic acid (C20) and (2) further reducing the insulin receptor affinity by the B16Tyr → His substitution. Insulin icodec was selected by screening for long intravenous plasma half-life in dogs while ensuring glucose-lowering potency following subcutaneous administration in rats. The ensuing structure-activity relationship resulted in insulin icodec. In phase-2 clinical trial, once-weekly insulin icodec provided safe and efficacious glycemic control comparable to once-daily insulin glargine in type 2 diabetes patients. The structure-activity relationship study leading to insulin icodec is presented here.

Oxytocin in bovine saliva: validation of two assays and changes in parturition and at weaning

BACKGROUND

The possible use of oxytocin in saliva as an indicator of positive emotions in bovine species has been poorly investigated. In the present study, two new assays (one using a monoclonal antibody and the other using a polyclonal antibody) for the measurement of oxytocin in bovine saliva were developed and validated. Also, the changes in oxytocin in saliva were explored in two different situations. One was around parturition, and for this purpose, saliva samples from 13 cows were collected at three different times: 7 days before the parturition, the day of parturition and 7 days after the parturition. The second situation was weaning and grouping of calves, and for this purpose, saliva from 25 calves was collected at three different times: 1 day before weaning, 2 days after weaning or milk withdrawal and 4 days after grouping calves.

RESULTS

In cows, oxytocin concentrations showed an increase on the day of parturition with both assays, while in calves, oxytocin concentrations showed a decrease 4 days after the grouping.

CONCLUSIONS

The assays validated in this report could be used for the measurement of oxytocin in bovine saliva and detect changes in this analyte that can occur in different physiological or productive situations such as parturition and weaning.

Food intake rather than blood glucose levels affects the pharmacokinetic profile of insulin aspart in pigs

In humans, food intake and glucose infusion have been reported to increase subcutaneous blood flow. Since local blood flow influences the rate of insulin absorption from the subcutaneous tissue, we hypothesised that an increase in blood glucose levels-occurring as the result of glucose infusion or food intake-could modulate the pharmacokinetic properties of subcutaneously administered insulin. The pharmacokinetic profile of insulin aspart was assessed in 29 domestic pigs that were examined in a fed and fasted state or included in hyperinsulinaemic clamp studies of 4 vs. 10 mmol/L glucose prior to subcutaneous (30 nmol) or intravenous (0.1 nmol/kg) insulin administration. Results showed that food intake compared to fasting accelerated absorption and decreased clearance of insulin aspart (P < 0.05). Furthermore, higher c-peptide but also glucagon levels were observed in fed compared to fasted pigs (P < 0.05). The pharmacokinetic profile of insulin aspart did not differ between pigs clamped at 4 vs. 10 mmol/L glucose. Hence, food intake rather than blood glucose levels within normal range modulates the pharmacokinetic properties of insulin aspart upon subcutaneous and intravenous administration in pigs.

Molecular engineering of safe and efficacious oral basal insulin

Recently, the clinical proof of concept for the first ultra-long oral insulin was reported, showing efficacy and safety similar to subcutaneously administered insulin glargine. Here, we report the molecular engineering as well as biological and pharmacological properties of these insulin analogues. Molecules were designed to have ultra-long pharmacokinetic profile to minimize variability in plasma exposure. Elimination plasma half-life of ~20 h in dogs and ~70 h in man is achieved by a strong albumin binding, and by lowering the insulin receptor affinity 500-fold to slow down receptor mediated clearance. These insulin analogues still stimulate efficient glucose disposal in rats, pigs and dogs during constant intravenous infusion and euglycemic clamp conditions. The albumin binding facilitates initial high plasma exposure with a concomitant delay in distribution to peripheral tissues. This slow appearance in the periphery mediates an early transient hepato-centric insulin action and blunts hypoglycaemia in dogs in response to overdosing.

Measurement of cortisol, cortisone and 11β-hydroxysteroid dehydrogenase type 2 activity in hair of sows during different phases of the reproductive cycle

Two sensitive assays based on AlphaLISA technology were developed and validated for the measurement of cortisol and cortisone in hair of pigs, that also enabled estimation of 11β-hydroxysteroid dehydrogenase type 2 activity. These assays were applied to hair samples from sows (n = 32) collected at 5 days before, and at 23 and 59 after farrowing, in reproductive cycles in two different periods: spring-summer (n = 16) and winter-spring (n = 16). The assays were precise (imprecision <12%) and accurate (recovery range, 80-115%) for cortisol and cortisone determination. Hair cortisone concentrations and the cortisone/cortisol ratio (an estimate of 11β-hydroxysteroid dehydrogenase isoenzyme type 2 activity) increased after farrowing more than cortisol, being these changes of higher magnitude during periods of higher atmospheric temperature. The measurement of hair cortisone concentrations and estimations of the activity of the 11β-hydroxysteroid dehydrogenase isoenzyme type 2, measured by the assays developed in this study, are complementary biomarkers to hair cortisol, and can increase at periods associated with stress, such as farrowing and lactation, especially at high atmospheric temperatures. .

Multiplexed Luminescence Oxygen Channeling Immunoassay Based on Dual-Functional Barcodes with a Host-Guest Structure: A Facile and Robust Suspension Array Platform

The development of a powerful immunoassay platform with capacities of both simplicity and high multiplexing is promising for disease diagnosis. To meet this urgent need, for the first time, a multiplexed luminescent oxygen channeling immunoassay (multi-LOCI) platform by implementation of LOCI with suspension array technology is reported. As the microcarrier of the platform, a unique dual-functional barcode with a host-guest structure composed of a quantum dot host bead (QDH) and LOCI acceptor beads (ABs) is designed, in which QDH provides function of high coding capacity while ABs facilitate the LOCI function. The analytes bridge QDH@ABs and LOCI donor beads (DBs) into a close proximity, forming a QDH@ABs-DBs "host-guest-satellite" superstructure that generates both barcode signal from QDH and LOCI signal induced by singlet oxygen channeling between ABs and DBs. Through imaging-based decoding, different barcodes are automatically distinguished and colocalized with LOCI signals. Importantly, the assay achieves simultaneous detection of multiple analytes within one reaction, simply by following a "mix-and-measure" protocol without the need for tedious washing steps. Furthermore, the multi-LOCI platform is validated for real sample measurements. With the advantages of robustness, simplicity, and high multiplexing, the platform holds great potential for the development of point-of-care diagnostics.

Insulin Treatment Attenuates Small Nerve Fiber Damage in Rat Model of Type 2 Diabetes

INTRODUCTION

Current clinical guidelines for management of diabetic peripheral neuropathy (DPN) emphasize good glycemic control. However, this has limited effect on prevention of DPN in type 2 diabetic (T2D) patients. This study investigates the effect of insulin treatment on development of DPN in a rat model of T2D to assess the underlying causes leading to DPN.

METHODS

Twelve-week-old male Sprague-Dawley rats were allocated to a normal chow diet or a 45% kcal high-fat diet. After eight weeks, the high-fat fed animals received a mild dose of streptozotocin to induce hyperglycemia. Four weeks after diabetes induction, the diabetic animals were allocated into three treatment groups receiving either no insulin or insulin-releasing implants in a high or low dose. During the 12-week treatment period, blood glucose and body weight were monitored weekly, whereas Hargreaves' test was performed four, eight, and 12 weeks after treatment initiation. At study termination, several blood parameters, body composition, and neuropathy endpoints were assessed.

RESULTS

Insulin treatment lowered blood glucose in a dose-dependent manner. In addition, both doses of insulin lowered lipids and increased body fat percentage. High-dose insulin treatment attenuated small nerve fiber damage assessed by Hargreaves' test and intraepidermal nerve fiber density compared to untreated diabetes and low-dose insulin; however, neuropathy was not completely prevented by tight glycemic control. Linear regression analysis revealed that glycemic status, circulating lipids, and sciatic nerve sorbitol level were all negatively associated with the small nerve fiber damage observed.

CONCLUSION

In summary, our data suggest that high-dose insulin treatment attenuates small nerve fiber damage. Furthermore, data also indicate that both poor glycemic control and dyslipidemia are associated with disease progression. Consequently, this rat model of T2D seems to fit well with progression of DPN in humans and could be a relevant preclinical model to use in relation to research investigating treatment opportunities for DPN.

Peripherally delivered hepatopreferential insulin analog insulin-406 mimics the hypoglycaemia-sparing effect of portal vein human insulin infusion in dogs

AIMS

We previously quantified the hypoglycaemia-sparing effect of portal vs peripheral human insulin delivery. The current investigation aimed to determine whether a bioequivalent peripheral vein infusion of a hepatopreferential insulin analog, insulin-406, could similarly protect against hypoglycaemia.

MATERIALS AND METHODS

Dogs received human insulin infusions into either the hepatic portal vein (PoHI, n = 7) or a peripheral vein (PeHI, n = 7) for 180 minutes at four-fold the basal secretion rate (6.6 pmol/kg/min) in a previous study. Insulin-406 (Pe406, n = 7) was peripherally infused at 6.0 pmol/kg/min, a rate determined to decrease plasma glucose by the same amount as with PoHI infusion during the first 60 minutes. Glucagon was fixed at basal concentrations, mimicking the diminished α-cell response seen in type 1 diabetes.

RESULTS

Glucose dropped quickly with PeHI infusion, reaching 41 ± 3 mg/dL at 60 minutes, but more slowly with PoHI and Pe406 infusion (67 ± 2 and 72 ± 4 mg/dL, respectively; P < 0.01 vs PeHI for both). The hypoglycaemic nadir (c. 40 mg/dL) occurred at 60 minutes with PeHI infusion vs 120 minutes with PoHI and Pe406 infusion. ΔAUC_epinephrine during the 180-minute insulin infusion period was two-fold higher with PeHI infusion compared with PoHI and Pe406 infusion. Glucose production (mg/kg/min) was least suppressed with PeHI infusion (Δ = 0.79 ± 0.33) and equally suppressed with PoHI and Pe406 infusion (Δ = 1.16 ± 0.21 and 1.18 ± 0.17, respectively; P = NS). Peak glucose utilization (mg/kg/min) was highest with PeHI infusion (4.94 ± 0.17) and less with PoHI and Pe406 infusion (3.58 ± 0.58 and 3.26 ± 0.08, respectively; P < 0.05 vs Pe for both).

CONCLUSIONS

Peripheral infusion of hepatopreferential insulin can achieve a metabolic profile that closely mimics portal insulin delivery, which reduces the risk of hypoglycaemia compared with peripheral insulin infusion.

Delayed insulin absorption correlates with alterations in subcutaneous depot kinetics in rats with diet-induced obesity

OBJECTIVE

Obesity is associated with delayed insulin absorption upon subcutaneous (s.c.) dosing in humans. The aim of this study was to investigate whether alterations in depot structure and kinetics of the s.c. injection depot contribute to this delay.

METHODS

Rats fed a high-fat diet (HFD) and low-fat diet (LFD) were included in a series of insulin pharmacokinetic and imaging studies. Injection depots were visualized with micro X-ray computed tomography imaging upon s.c. administration of insulin aspart mixed with the contrast agent iomeprol, and insulin aspart exposure was measured by means of luminescent oxygen channelling immunoassay.

RESULTS

Body weight and fat mass were increased in rats fed an HFD vs. LFD (p < 0.05), whereas the lean mass was not. The HFD group exhibited delayed insulin absorption from the s.c. tissue (p < 0.001). This delay was associated with smaller injection depots upon s.c. dosing (p < 0.05) and correlated with a slower depot disappearance from the s.c. tissue (p < 0.05) compared with the LFD group. Depot disappearance from the s.c. tissue was inversely correlated with body fat mass (p < 0.05).

CONCLUSIONS

Alterations in s.c. injection depot structure and kinetics may play a role in the obesity-associated delay in insulin absorption.

Targeting insulin to the liver corrects defects in glucose metabolism caused by peripheral insulin delivery

Peripheral hyperinsulinemia resulting from subcutaneous insulin injection is associated with metabolic defects which include abnormal glucose metabolism. The first aim of this study was to quantify the impairments in liver and muscle glucose metabolism that occur when insulin is delivered via a peripheral vein compared to when it is given through its endogenous secretory route (the hepatic portal vein) in overnight fasted conscious dogs. The second aim was to determine if peripheral delivery of a hepato-preferential insulin analog could restore the physiologic response to insulin that occurs under meal feeding conditions. This study is the first to show that hepatic glucose uptake correlates with insulin's direct effects on the liver under hyperinsulinemic-hyperglycemic conditions. In addition, glucose uptake was equally divided between the liver and muscle when insulin was infused into the portal vein, but when it was delivered into a peripheral vein the percentage of glucose taken up by muscle was 4-times greater than that going to the liver, with liver glucose uptake being less than half of normal. These defects could not be corrected by adjusting the dose of peripheral insulin. On the other hand, hepatic and non-hepatic glucose metabolism could be fully normalized by a hepato-preferential insulin analog.

Elucidating the Mechanism of Absorption of Fast-Acting Insulin Aspart: The Role of Niacinamide

Purpose

Fast-acting insulin aspart (faster aspart) is a novel formulation of insulin aspart containing two additional excipients: niacinamide, to increase early absorption, and L-arginine, to optimize stability. The aim of this study was to evaluate the impact of niacinamide on insulin aspart absorption and to investigate the mechanism of action underlying the accelerated absorption.

Methods

The impact of niacinamide was assessed in pharmacokinetic analyses in pigs and humans, small angle X-ray scattering experiments, trans-endothelial transport assays, vascular tension measurements, and subcutaneous blood flow imaging.

Results

Niacinamide increased the rate of early insulin aspart absorption in pigs, and pharmacokinetic modelling revealed this effect to be most pronounced up to ~30–40 min after injection in humans. Niacinamide increased the relative monomer fraction of insulin aspart by ~35%, and the apparent permeability of insulin aspart across an endothelial cell barrier by ~27%. Niacinamide also induced a concentration-dependent vasorelaxation of porcine arteries, and increased skin perfusion in pigs.

Conclusion

Niacinamide mediates the acceleration of initial insulin aspart absorption, and the mechanism of action appears to be multifaceted. Niacinamide increases the initial abundance of insulin aspart monomers and transport of insulin aspart after subcutaneous administration, and also mediates a transient, local vasodilatory effect.

Electronic supplementary material

The online version of this article (10.1007/s11095-019-2578-7) contains supplementary material, which is available to authorized users.

A light-initiated chemiluminescent assay for rapid quantitation of allergen-specific IgG4 in clinical samples

BACKGROUND

An increase in allergen-specific IgG₄ (sIgG₄), which serves as a blocking antibody, is associated with acquisition of immune tolerance after immunotherapy. In this study, we developed a rapid, sensitive, and homogeneous immunoassay based on the light-initiated chemiluminescent assay (LICA) technology for quantifying allergen sIgG₄ in serum samples.

METHODS

Allergen sIgG₄ was measured in vitro by incubating the sample with biotinylated allergens and chemiluminescent beads coated with anti-human IgG₄ antibody, followed by the addition of streptavidin-coated sensitizer beads. Multiple tests were performed to optimize the working conditions of the LICA and evaluate its performance.

RESULTS

We established the optimal concentration of biotinylated allergens (250 ng/mL), the optimal dilution range (1:8 for Gal d 1, Gal d 2 sIgG₄ and 1:4 for Gal d 3, Gal d 4 sIgG₄), and the optimal incubation time (20 min for Gal d 1, Gal d 2 sIgG₄ and 40 min for Gal d 3, Gal d 4 sIgG₄). The lower limit of quantification (LLOQ) was 0.261 ng/mL. The coefficient variation (CV) of the LICA was <10%. The assay was unaffected by general interfering substances at physiological concentrations. It exhibited excellent accuracy to detect allergen-sIgG₄ in human serum. Additionally, we demonstrated that the levels of Gal d 1, Gal d 2, and Gal d 3-sIgG₄ were significantly higher in the egg allergy group (p < .05), but no differences were found between the groups for Gal d 4-sIgG₄.

CONCLUSIONS

The LICA demonstrated satisfactory performance and can be used for quantifying allergen sIgG₄ in clinical practice.

Dietary normalization from a fat, fructose and cholesterol-rich diet to chow limits the amount of myocardial collagen in a Göttingen Minipig model of obesity

Background

Dietary interventions have been shown to attenuate some of the myocardial pathological alterations associated with obesity. This study evaluated the effect of dietary normalization from a fat/fructose/cholesterol-rich diet to chow on left ventricular (LV) myocardial fibrosis, fat infiltration and hypertrophy but also the specific influence of obesity, plasma lipids and glucose metabolism markers on heart morphology in a Göttingen Minipig model of obesity.

Methods

Forty castrated male Göttingen Minipigs were assigned to three groups fed either standard minipig chow (SD, n = 8) for 13 months, fat/fructose/cholesterol-rich diet (FFC, n = 16) for 13 months or fat/fructose/cholesterol-rich diet for 7 months and then changed to standard minipig chow for the remaining 6 months (FFC/SD, n = 16). Body weight, body fat percentage, plasma lipids and glucose metabolism markers were evaluated in all three groups after 6–7 months (prior to diet adjustment for FFC/SD) and again before termination. Further, biochemical quantification of myocardial collagen and triglyceride content, semi-quantitative histological evaluation of fibrosis and fat infiltration and quantitative histological analysis of collagen and cardiomyocyte diameter were performed and heart weight was obtained after termination. Group differences were evaluated using Kruskal-Wallis test and Fisher’s exact test for categorical variables. Pearson correlation analysis was performed to test for correlations between myocardial changes and selected explanatory variables. For non-parametric response variables, a Spearman correlation analysis was applied.

Results

Myocardial collagen content quantified biochemically was significantly lower in FFC/SD compared to FFC (P = 0.02). Furthermore, dietary normalization from a fat/fructose/cholesterol-rich diet to chow caused stagnation of body weight and body fat percentage, normalized intravenous glucose tolerance index (K_G) and plasma lipid levels.

Conclusion

Dietary normalization led to lower LV collagen content in obese Göttingen Minipigs. Despite gross obesity and significant deteriorations in glucose and lipid metabolism, only mild myocardial changes were found in this model of obesity and therefore further model optimization is warranted in order to induce more severe myocardial changes before dietary or pharmacological interventions.

Interaction between exogenous insulin, endogenous insulin, and glucose in type 2 diabetes patients

BACKGROUND

Little is known about the influence of exogenous insulin and actual glucose levels on the release of endogenous insulin in insulin-treated type 2 diabetes mellitus (T2DM) patients. This study investigated the interaction among serum endogenous insulin (s-EI), serum exogenous insulin aspart (s-IAsp), and blood glucose levels in an experimental short-term crossover design.

STUDY DESIGN AND METHODS

Eight T2DM patients (63.52 years old; range, 49-69 years; mean body mass index, 28.8±3.8 kg/m(2)) were randomized to treatment with individual fixed doses of insulin aspart (0.5-1.5 IU/h) as a continuous subcutaneous insulin infusion (CSII) during a 10-h period on two occasions with different duration of hyperglycemia: (1) transient hyperglycemia for 2 h (visit TH) and (2) continuous hyperglycemia for 12 h (visit CH).

RESULTS

During steady state the variances of plasma glucose (p-glucose), s-IAsp, and s-EI were equal within visit TH and within visit CH, but variances were significantly higher during visit CH compared with visit TH. The s-IAsp reached lower levels at visit CH compared with visit TH (test for slope=1, P=0.005). The s-EI depended on p-glucose in a nonlinear fashion during the first 100 min of both visits when s-IAsp was undetectable (adjusted R(2)=0.9). A complex but statistically significant interaction among s-IAsp, s-EI, p-glucose, and patients was observed during measurable s-IAsp levels (adjusted R(2)=0.70).

CONCLUSIONS

Endogenous and exogenous insulin showed higher variation during continuous hyperglycemia. Significantly lower levels of exogenous insulin were observed following CSII during continuous hyperglycemia compared with transient hyperglycemia. Endogenous insulin levels could in a complex way be explained by an individual interaction among p-glucose and serum exogenous insulin, if present.

HtrA3 as an early marker for preeclampsia: specific monoclonal antibodies and sensitive high-throughput assays for serum screening

Mammalian HtrA3 (high temperature requirement A3) is a serine protease of the HtrA family. It has two isoforms [long (HtrA3-L) and short (HtrA3-S)] and is important for placental development and cancer progression. Recently, HtrA3 was identified as a potential diagnostic marker for early detection of preeclampsia, a life-threatening pregnancy-specific disorder. Currently there are no high-throughput assays available to detect HtrA3 in human serum. In this study we generated and fully tested a panel of five HtrA3 mouse monoclonal antibodies (mAbs). Three mAbs recognised both HtrA3-L and HtrA3-S and the other two detected HtrA3-L only. All five mAbs were highly specific to HtrA3 and applicable in western blotting and immunohistochemical analysis of endogenous HtrA3 proteins in the mouse and human tissues. Amplified luminescent proximity homogeneous assays-linked immunosorbent assays (AlphaLISAs), were developed to detect HtrA3 isoforms in picomolar levels in serum. The HtrA3 AlphaLISA detected significantly higher serum levels of HtrA3 in women at 13-14 weeks of gestation who subsequently developed preeclampsia compared to gestational-age matched controls. These HtrA3 mAbs are valuable for the development of immunoassays and characterisation of HtrA3 isoform-specific biology. The newly developed HtrA3 AlphaLISA assays are suitable for large scale screening of human serum.

Pharmacokinetics and pharmacodynamics of different modes of insulin pump delivery. A randomized, controlled study comparing subcutaneous and intravenous administration of insulin aspart

AIMS

To study the pharmacokinetics and pharmacodynamics of three different modes of insulin infusion delivered by means of an insulin pump: subcutaneous bolus insulin injection once an hour, continuous subcutaneous insulin infusion and continuous intravenous insulin infusion.

METHODS

In random order, ten patients with Type 1 diabetes mellitus received insulin aspart with subcutaneous bolus insulin injection, continuous subcutaneous insulin infusion and continuous intravenous insulin infusion. The insulin aspart doses were individualized.

RESULTS

  A non-random, sinus-like variation of serum insulin aspart over time was found with subcutaneous bolus insulin injection compared with continuous subcutaneous insulin infusion and continuous intravenous insulin infusion (P<0.0001). Random variation of serum insulin aspart over time was significantly higher with continuous intravenous insulin infusion compared with subcutaneous bolus insulin injection (P=0.023) and continuous subcutaneous insulin infusion (P=0.013). Mean serum insulin aspart did not differ significantly between subcutaneous bolus insulin injection, continuous subcutaneous insulin infusion and continuous intravenous insulin infusion (P=0.17). Thus, absolute bioavailability was near 100% for both subcutaneous bolus insulin injection and continuous subcutaneous insulin infusion. Statistically significant differences were seen in mean plasma glucose and mean glucose infusion rate, with the highest mean plasma glucose and the lowest mean glucose infusion rate with continuous intravenous insulin infusion, suggesting a slightly lower bioefficacy of continuous intravenous insulin infusion compared with subcutaneous bolus insulin injection and continuous subcutaneous insulin infusion.

CONCLUSIONS

Small but statistically significant differences in pharmacokinetics and pharmacodynamics between subcutaneous bolus insulin injection, continuous subcutaneous insulin infusion and continuous intravenous insulin infusion were observed. However, no major clinically relevant differences were found, suggesting that, for a basal subcutaneous insulin aspart pump therapy, relatively infrequent pump stroke frequency may suffice.

Explorative study of pharmacokinetics and pharmacodynamics after change in basal insulin infusion rate

BACKGROUND

The use of insulin pumps is rapidly increasing and new, technologically more advanced pumps are continuously being developed. It is of interest to assess the clinical relevance of the many technical features of these pumps, e.g., the effect on pharmacokinetics and pharmacodynamics with change in infusion rate.

METHOD

The aim of this study was to explore the sequence of pharmacokinetic and pharmacodynamic changes after dose doubling of the basal insulin infusion rate with subcutaneous bolus insulin injections once an hour, continuous subcutaneous insulin infusion, and continuous intravenous insulin infusion. Ten type 1 diabetes mellitus patients were included. The insulin doses were calculated based on the habitual insulin doses. The study was designed as an open-labeled, single-center, randomized, crossover exploratory trial.

RESULTS

Dose doubling of the basal insulin infusion rate with the three different administration protocols did not result in any clinically relevant differences in the time courses of the pharmacokinetic and pharmacodynamic parameters. With all three administration protocols, we observed a time interval of more than 6 hours before a new steady state of insulin was achieved.

CONCLUSIONS

Our results indicate that frequent changes in basal subcutaneous insulin infusion rates are not of significant clinical relevance on a 24-hour basis. Regarding technological features of subcutaneous insulin pumps, no discernable advantages of increasing pump stroke frequency were found. This indicates that pump stroke frequency sophistication might not be of clinical relevance in pumps used for basal subcutaneous insulin infusion.

Pharmacokinetics following continuous subcutaneous insulin infusion of insulin aspart with or without initial subcutaneous bolus

AIM

To evaluate time to steady state insulin concentration (C(ss)) following continuous subcutaneous insulin infusion (CSII) of insulin aspart (IAsp) with or without an initial s.c. bolus.

METHODS

In random order 10 healthy volunteers were given a basal insulin infusion rate (0.5 U/h) for 8 h with or without an initial s.c. bolus (1.4 U). Serum IAsp was measured until 3 h after infusion was stopped.

RESULTS

An overshoot of IAsp was seen before C(ss) was achieved following an initial bolus of insulin as compared to no bolus. The apparent half-life (t((1/2))) with or without bolus did not differ (p = 0.15). Time to steady state (T(ss)) was evaluated in two ways: (1) T(ss) defined as the first point within an interval of C(ss)+/- 2 x CV was 233 vs. 166 min with and without a bolus respectively (p = 0.068). (2) A t-test was performed for each concentration-time point vs. mean C(ss), and the first point with no significance was defined, T(ss). This gave 208 (p = 0.09) and 178 min (p = 0.24) with and without bolus respectively. Mathematical modelling suggests that an ideal mean bolus should be 0.89 U, and that this bolus dose may result in a shorter T(ss).

CONCLUSION

A bolus of 1.4 U resulted in an overshoot of serum IAsp before C(ss) and a longer period before C(ss) is achieved. Mathematical modelling suggests that a mean bolus of 0.89 U would result in a faster achievement of C(ss) compared to no bolus.