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  • 1
    ISSN: 1432-0428
    Keywords: Insulin ; free insulin assay ; insulin antibodies ; radioimmunoassay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Plasma insulin concentrations of insulin-treated diabetic patients must be measured after removal of insulin antibodies, usually by precipitation with polyethylene glycol (PEG). Details of the procedure vary between laboratories; commonly, frozen plasma is thawed and incubated at 37 °C to restore a presumed equilibrium between free and antibody bound insulin before extraction. The present study was designed to investigate methodological factors that could affect the measured free insulin concentration. In normal subjects PEG extraction of globulins did not disturb measurement of insulin concentrations, whether carried out after incubation for 2 h at 37 °C, or storage at -20 °C, in either order. Freezing or incubation of PEG extracts of plasma from insulin-treated patients also failed to disturb the measured concentrations of free insulin. When plasma from patients was incubated for 2 h after storage, a marked scatter (51–272%) of measured results occurred when compared to bedside extraction. This problem was not overcome by buffering with HEPES or storage at a lower temperature (-40 °C). Incubation at 0 °C also severely disturbed the apparent concentrations. Incubation of plasma before extraction and freezing also disturbed the measured result, a problem not corrected by maintaining near physiological pH. Total insulin concentrations measured on acid extracts were not disturbed by any of these manoeuvres. The temperature of centrifugation of blood at the time of venepuncture did not influence the result. Furthermore, when insulin concentrations were rising or falling similar percentage changes were seen over a 30-min incubation of plasma before extraction on the day of venepuncture, suggesting that equilibrium between free and bound insulin is maintained in vivo. We suggest that, for accurate estimation of free insulin concentrations in insulin-treated diabetic patients, immediate centrifugation of blood and extraction of insulin antibodies is mandatory.
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  • 2
    ISSN: 1432-0428
    Keywords: Type 1 (insulin-dependent) diabetes mellitus ; insulin antibodies ; insulin absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The influence of moderate and low insulin antibody levels on insulin absorption and plasma free insulin profiles is uncertain. Two groups of six C-peptide negative diabetic patients, one with low (3.8±0.8 μ/l) and one with moderate (16.4±2.0 μg/l) serum insulin antibody levels, were studied. Subjects were given 0.3 U/kg neutral human or acid bovine soluble insulin subcutaneously in random order before breakfast on separate days. Moderate antibody levels significantly blunted the rise in plasma free insulin that followed injection of the human and bovine insulins (p〈0.05). The rise in blood glucose after breakfast was significantly greater in patients with moderate antibody levels (p〈0.05) and more marked following the bovine than the human insulin (p〈0.05). Plasma free insulin, blood glucose and 3-hydroxybutyrate profiles suggest that acid bovine soluble insulin has a significantly more protracted action than neutral human insulin.
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  • 3
    ISSN: 1432-0428
    Keywords: C-peptide ; insulin secretion ; C-peptide pharmacokinetics ; insulin dose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary An understanding of the metabolic abnormalities rising from inappropriate insulin delivery in diabetic patients demands a knowledge of 24-h and basal insulin secretion rates in normal man. We have used biosynthetic human C-peptide to determine its kinetic parameters in 10 normal subjects and applied these to measurements of plasma concentrations in the same subjects to determine pancreatic secretion rate. Metabolic clearance rate measured by stepped primed infusion of biosynthetic human C-peptide at rates of 10, 19 and 26nmol/h was 4.7±0.7 (±SD) ml·kg−1·min−1, and was independent of infusion rate. Fractional clearance (T1/2, 26±3 min) and distribution volume (0.178±0.039 l/kg) were calculated from the decline in concentration after cessation of the highest rate infusion. Basal insulin secretion calculated from the C-peptide metabolic clearance rate and plasma concentrations for the period 02.00 to 07.00 hours was 1.3±0.4U/h. Over 24h total insulin secretion on a standard high carbohydrate diet was 63±15 U, calculated from the area under the C-peptide concentration curve. Basal insulin secretion, therefore, accounted for 50±8% of total insulin secretion. Although only 5.6±1.1% of C-peptide was detected in 24-h urine collections, urinary C-peptide excretion was significantly related to 24-h C-peptide secretion (r=0.74,p〈0.02).
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  • 4
    ISSN: 1432-0428
    Keywords: Intraperitoneal insulin ; plasma insulin ; insulin-dependent diabetes ; intermediary metabolities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The intraperitoneal route may offer more physiological insulin delivery through absorption of a proportion of the dose into the portal circulation. We have compared 1-h square-wave and bolus supplemental infusions of a fixed dose of 10 U of intraperitoneal insulin in 6 C-peptide negative insulin-dependent diabetic patients eating a standard breakfast and compared the insulin, glucose and metabolite responses with those of non-diabetic control subjects. Blood glucose profiles were similar on the two experimental days and although the peak glucose levels were not different from normal they were delayed by 30 min (p〈0.05). Basal free insulin levels were elevated in diabetic patients (square-wave 19.6±2.3, bolus 18.7±1.9mU/l) compared to controls (7.3±1.0mU/l, p〈 0.02) and rose more rapidly after bolus injection than infusion. Peak insulin concentration was achieved at 33±4 min after bolus, 90±13 min after infusion (p〈0.02) and 39±5 min in normal control subjects. The shape of the profile of free insulin concentration was similar after bolus injection and in the controls, but after square-wave infusion the return to baseline was delayed (p〈 0.05). Fasting intermediary metabolite concentrations were normal on both study days in the patients, but serum cortisol levels were significantly elevated and glucagon concentrations low. Metabolite responses to the meal were not significantly different from normal after bolus injection but increases in lactate and glycerol were seen at some time points between 60 and 180 min after infusion. Glucagon levels remained low after square-wave infusion. We conclude that bolus injection of the breakfast insulin supplement gives a more optimal profile of insulin delivery for patients on intraperitoneal insulin.
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  • 5
    ISSN: 1432-0428
    Keywords: Human insulin ; insulin activity ; insulin pharmacokinetics ; glucose clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The activity of semi-synthetic human insulin has been compared with porcine insulin in normal man using an euglycaemic glucose clamp at two different insulin infusion rates. In a two hour infusion insulin levels plateaued for both types of insulin at 44–48 mU/l (infusion rate 0.05 U kg body weight-1 h-1) and 22–24 mU/l (0.02 U kg-1 h-1), giving identical metabolic clearance rates. The glucose delivery required to maintain euglycaemia in the second hour of insulin infusion was 13.9±2.1 g (mean±SEM) and 14.7±1.5 g (NS) at the lower dose for porcine and human insulins respectively, and 27.1±2.5 and 28.0±2.9 g (NS) at the higher dose. The potency ratio for human, compared with porcine, insulin was 1.06 ±0.12. No differences were seen in the time of onset of action of the insulins, serum half-life or distribution space. The responses of blood lactate, pyruvate, alanine, glycerol and 3-hydroxybutyrate were identical. No untoward reactions occurred. The activity and disposal of this semi-synthetic human insulin are indistinguishable from porcine insulin in normal euglycaemic man.
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  • 6
    ISSN: 1432-0428
    Keywords: Insulin ; insulin antibody ; immunogenicity ; immune response genes ; haemocyanin ; HLA ; DR7 ; C2 ; C4 ; factor B ; Gm ; C-peptide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Seventy-nine patients were observed prospectively during their initial period of treatment with conventional bovine insulins. Insulin antibody levels 6 months after starting insulin therapy did not correlate with age, gender or β cell function at onset of treatment. Patients who required soluble insulin in addition to isophane insulin developed higher levels of insulin antibody. Patients bearing the HLA-B8, DR3 and C4AQO alleles had lower levels of insulin antibody, whereas those bearing DR7 produced significantly higher levels. Other alleles at the C4A, C4B, C2, factor B or Gm loci did not appear to have a significant effect on insulin antibody production. The hyporesponsiveness of B8/DR3/C4AQO-positive individuals probably reflects a non-specific abnormality of immunity whereas the enhanced responsiveness of those positive for DR7 suggests the presence of a specific immune response gene for insulin
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  • 7
    ISSN: 0009-8981
    Keywords: Blood analysis ; Gonadotrophin ; Immunoassay ; Monoclonal antibody ; Pituitary ; Quality control ; Test interference
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0009-8981
    Keywords: External quality assessment ; Growth hormone ; Immunoradiometric assay ; Quality control ; Radioimmunoassay
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0009-8981
    Keywords: External quality assessment ; Growth hormone ; Immunoradiometric assay ; Quality control ; Radioimmunoassay
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
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