Effect of thyroid hormone binding proteins on insulin receptor binding of B1-thyronine-insulin analogues

Certain thyronine-insulin analogues, which form non-covalent complexes with plasma proteins, have been shown to act preferentially in the liver. We hypothesized that this property may be dependent on the ability of the analogue to bind to the insulin receptor without prior dissociation from the binding protein. NaB1-L-thyroxyl-insulin, NaB1-3,3',5'-triiodothyronine-insulin, NaB1-D-thyroxyl-insulin and NaB1-L-thyroxyl-aminolauroyl-insulin were compared with insulin for their capacity to inhibit the binding of [125I]TyrA14-insulin to rat liver plasma membrane in albumin-free buffer. Effective doses at 50% maximum inhibition of binding (ED50) were calculated with and without addition of the thyroid hormone binding proteins transthyretin, thyroxine binding globulin and human serum albumin. The binding of thyronine-insulin analogues to insulin receptors was inhibited in a dose-dependent manner by the addition of thyroid hormone binding proteins at concentrations in the physiological range. Complexes of thyronine-insulin analogues with thyroid hormone binding proteins exhibit impaired insulin receptor binding affinities compared with those of the analogues in their free form. Hepatoselectivity in vivo may not depend on binding of the intact complexes to hepatocytes. These results have implications for the physiological role of hormone binding proteins and the in vivo properties of other insulin analogues which bind to plasma proteins.

Continuous intraperitoneal insulin infusion in patients with 'brittle' diabetes: favourable effects on glycaemic control and hospital stay

AIMS

To evaluate the effects of continuous intraperitoneal insulin infusion (CIPII) using implantable pumps on glycaemic control and duration of hospital stay in poorly controlled 'brittle' Dutch diabetes patients, and to assess their current quality of life.

METHODS

Thirty-three patients were included. Glycaemic control was retrospectively assessed with HbA(1c) levels acquired before implantation, 1 year later and at long-term follow up of 58 months. Duration of hospital stay the year before and the year following first implantation was extracted from hospital records. Determinants of long-term glycaemic response were sought. Self-report questionnaires were administered at 58 months follow-up only, to assess current psychopathology and quality of life.

RESULTS

Mean HbA(1c) decreased from 10.0 +/- 2.3% to 9.0 +/- 1.8% (P = 0.039) 1 year after implantation and stabilized at 9.0 +/- 1.6% (P = 0.023) during long-term follow-up. Median number of hospital days in the 20 patients suffering from hospital admission before implantation decreased from 45 the year before implantation to 13 the year after (P = 0.005). Patients with a higher baseline HbA(1c) showed a larger long-term response (P < 0.001). Relatively low levels for quality of life were found, as well as a higher than expected number of patients with psychiatric symptoms.

CONCLUSIONS

CIPII proved effective in complex patients with a history of poor control and hospital admission. Despite a substantial long-term improvement in glycaemic control and diminished hospital stay, normal levels of glycaemic control and quality of life were not attained.

The narrow therapeutic window of glycated hemoglobin and assay variability

Glycated hemoglobin is measured by a variety of assays, each of which has a unique normal level. Our purpose is to show that among the different assays available in the United States, using the same patient's blood sample, assay results may vary widely and may more or less easily achieve a glycated hemoglobin value within the normal range. The following assays were compared using the same patient's blood sample for each pair of assays: glycohemoglobin affinity assay (GHB Reader; Isolab, Akron, OH) versus gel electrophoresis assay (n = 76); Isolab versus ion capture assay (IMX; Abbott Laboratories, Irving, TX) (n = 57); monoclonal antibody assay (DCA2000; Bayer Diagnostics, Pittsburgh, PA) versus IMX (n = 100); and high-performance liquid chromatography (HPLC) assay (Bio-Rad Variant A1c; Bio-Rad Laboratories, Richmond, CA) versus IMX assay (n = 55). Our analyses indicate that a relative ranking can be established for the ease of achieving a normal glycated hemoglobin level. The ranking indicates that the most stringent or difficult assays for achieving a normal level are the Isolab and DCA2000 assays. The intermediate assays are the IMX and Bio-Rad Variant, and the easiest method for achieving a normal value is the gel electrophoresis assay. Our results indicate that various glycated hemoglobin assays vary widely and are associated with more or less difficulty for an individual patient to achieve a glycated hemoglobin level within the normal range. These results are especially significant with respect to (1) the clinically narrow therapeutic window of glycated hemoglobin values in type 1 diabetes to avoid rapidly advancing severe hypoglycemia rates and chronic microvascular complication rates, and (2) the glycated hemoglobin threshold for rapidly advancing macrovascular disease in both type 1 and type 2 patients.

Implantable insulin pumps: diagnosis and management of decreased flow rates using radionuclide investigation

The aim of this study was to develop a diagnostic procedure for pumping unit malfunction by radionuclide imaging (RI) and to validate the method by comparing the results with those obtained using more conventional methods. Fifteen radionuclide investigations were performed in 11 patients with intraperitoneal implantable insulin pumps. One mCi of 99 mTc in 1 ml isotonic sodium chloride was injected into the reservoir. The results based on catheter visualization and peritoneal accumulation were compared blindly to the efficacy of alkaline rinses and laparoscopic findings. In all RI stoppage cases except one alkaline rinses failed to restore flow. Where laparoscopy was performed, comparisons were concordant i.e. no outflow from the tip of the catheter. The RI images obtained were reproduced in vitro using a pump under normal flow conditions and complete proximal and distal catheter obstruction. RI is a safe, quick non invasive method which allows the location of the site of pump/catheter malfunction within a one step procedure and the prediction of the efficacy of sodium hydroxide rinses.

Use of an integrated sideport for diagnosis and management of decreased flow rates in a programmable implanted insulin delivery system. Implantable Insulin Pump Trial Study Group

The aim of this study was to develop procedures for the diagnosis and nonsurgical management of decreased insulin flow in an implantable programmable pump for long-term intraperitoneal or intravenous insulin delivery featuring a sideport. Patency of the catheter lumen was tested by measuring the time needed for sideport pressure to decrease by 50% after the injection of 0.1 ml of buffer solution. Pumping unit performances were assessed by measuring the volume of pump pulses after diverting the pump flow at the sideport. A catheter flush with buffer solution through the sideport was effective in clearing 79% of intraperitoneal and 84% of intravenous catheter occlusions. Washing the pumping unit with an alkaline solution after diverting pump flow at the sideport was effective in dissolving insulin aggregates inside the pumping unit and in restoring normal pump flow. These procedures were associated with a 1.3% rate of hypoglycemic episodes.

The application of engineering and technology in the management of diabetes

Diabetes mellitus is a relatively common disorder in which many of the body's systems are affected, resulting in morbidity and mortality. Early diagnosis and good blood glucose control can delay or prevent the onset of these complications. This review illustrates how engineering and technology can help to achieve these goals.

Immunogenicity of intraperitoneal insulin infusion using programmable implantable devices

Intraperitoneal insulin infusion using implantable devices in insulin-dependent diabetic (IDDM) patients is promising since it improves diabetic control and decreases frequency of hypoglycaemia. However, preliminary data show a striking increase in plasma levels of anti-insulin antibodies with this therapy. In order to more precisely evaluate the immunogenicity and its consequences, anti-insulin antibody levels in 62 IDDM patients were assessed every 3 months during a 2-year period following pump implantation. At the same time, diabetes control was evaluated with HbA1c, mean blood glucose levels, standard deviation of the daily blood glucose levels and the frequency of low blood glucose (< 3.58 mmol/l). Factors involved in antibody formation such as age, gender, HLA typing, and complement C4 alleles were also studied. After implantation, anti-insulin antibody levels increased significantly from 3.14% (range 0-26%) to 8.34% (0-49%) after 1 year and remained elevated. Patients were divided into two groups: responders able to show at least one antiinsulin antibody titre higher than 15% and non-responders whose titres were always lower than 6%. None of the factors studied was shown to statistically influence the anti-insulin antibody titres. Non-responders had significantly better metabolic results than the responders. Severe hypoglycaemic episodes decreased dramatically in both groups. Insulin requirements were comparable at time 0 and decreased initially in both groups. They remained low for the non-responders but returned to pre-implantation values for responders. Intraperitoneal insulin infusion led to a high immunogenetic response towards insulin in about half of the patients, leading to only moderately deleterious effects on metabolic control.(ABSTRACT TRUNCATED AT 250 WORDS)