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  • insulin secretion  (5)
  • non-esterified fatty acid  (3)
  • Indirect two-site immunoradiometric assay  (2)
  • 1
    ISSN: 1432-0428
    Schlagwort(e): Indirect two-site immunoradiometric assay ; human proinsulin ; insulin ; C-peptide ; diabetes ; insulinoma
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary An indirect two-site immunoradiometric assay is described for the measurement of human proinsulin in plasma. Polyethylene tubes coated with purified guinea-pig antibodies to insulin were used to extract proinsulin and insulin from plasma. Rabbit antibody to human C peptide was then added to react with the C-peptide moiety of the bound proinsulin. The uptake of this antibody was measured by the subsequent binding of125I-sheep antibody to rabbit IgG. The binding of radioactivity to the tubes was a function of the proinsulin concentration in the sample. The sensitivity of the assay was 0.006 pmol/ml. Only 200 μl of plasma was required in the assay and the125I-labelled antibody was produced from readily available reagents. The polyethylene tubes remained stable for at least 5 months after coating. The mean fasting proinsulin level was 0.009 pmol/ml in sixteen normal subjects and 0.025 pmol/ml in twelve maturity onset diabetics. Oral glucose produced an 8 fold increase in proinsulin concentration but a decline in the plasma proinsulin/insulin molar ratio. Four patients with insulinoma had extremely elevated proinsulin levels and proinsulin/insulin ratios.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Diabetologia 21 (1981), S. 224-229 
    ISSN: 1432-0428
    Schlagwort(e): Islet cell tumour ; B cell ; insulin secretion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Investigation of the subcellular and molecular components of insulin secretion has been made difficult by the small quantities of material available. The recent development of a transplantable rat islet cell tumour of high insulin content and state of differentiation suggested a system more amenable to analysis. To validate the tumour as a model of secretion we have studied its release of insulin. In acute experiments in vitro immunoreactive insulin release was increased by leucine, glucagon, theophylline and dibutyryl cyclic AMP, though not by glucose. Leucine (20mmol/l) plus theophylline (5 mmol/l) caused an abrupt, sustained and rapidly reversible stimulation of two- to fivefold. The response was inhibited by antagonists of cellular oxidative phosphorylation (cyanide, 2,4-dinitrophenol, antimycin A), calcium flux (EGTA, verapamil, Mg2+), calmodulin (trifluoperazine), microtubules (vinblastine, colchicine) and by adrenaline and somatostatin. These findings suggest that the tumour secretes insulin by an exocytotic mechanism similar to that of normal islet tissue.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Diabetologia 37 (1994), S. 592-596 
    ISSN: 1432-0428
    Schlagwort(e): NIDDM ; insulin secretion ; fetal growth ; programming
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Recent studies suggest that NIDDM is linked with reduced fetal and infant growth. Observations on malnourished infants and studies of experimental animals exposed to protein energy or protein deficiency in fetal or early neonatal life suggest that the basis of this link could lie in the detrimental effects of poor early nutrition on the development of the beta cells of the islets of Langerhans. To test this hypothesis we have measured insulin secretion following an IVGTT in a sample of 82 normoglycaemic and 23 glucose intolerant subjects who were born in Preston, England, and whose birthweight and body size had been recorded at birth. The subjects with impaired glucose tolerance had lower first phase insulin secretion than the normoglycaemic subjects (mean plasma insulin concentrations 3 min after intravenous glucose 416 vs 564 pmol/l, p=0.04). Insulin secretion was higher in men than women (601 vs 457 pmol/l, P=0.02) and correlated with fasting insulin level (p=0.04). However, there was no relationship between insulin secretion and the measurements of prenatal growth in either the normoglycaemic or glucose intolerant subjects. These results argue against a major role for defective insulin secretion as a cause of glucose intolerance in adults who were growth retarded in pre-natal life.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1432-0428
    Schlagwort(e): Proinsulin ; insulin ; insulin secretion ; non-insulin-dependent diabetes mellitus ; epidemiology ; follow-up study
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Insulin resistance and impaired insulin secretion are thought to be the primary defects in the pathogenesis of non-insulin-dependent diabetes mellitus (NIDDM). Disproportionately increased proinsulin relative to insulin levels are suggested to be an early indicator of a failing pancreas. We examined the relationship of fasting specific insulin, proinsulin, and 32, 33 split proinsulin concentrations, and the proinsulin: insulin ratio to the risk of developing NIDDM 3.5 years later in 65–74-year-old non-diabetic Finnish subjects participating in a populationbased study (n=892) on diabetes and heart disease. Altogether 69 subjects developed NIDDM over a 3.5-year follow-up (cases). The cases were compared to randomly-selected gender-matched control subjects (n=69) and control subjects matched for gender, glucose tolerance status (normal or impaired), and body mass index (n=69). There were no differences in insulin concentrations between cases and random or matched control subjects [median and interquartile range; 123 (77–154), 108 (74–143), 118 (83–145) pmol/l, p=0.271]. Random control subjects had lower proinsulin and 32,33 split proinsulin concentrations and split proinsulin: insulin ratios compared to cases [5.7 (3.8–9.0) vs 7.3 (4.8–10.0) pmol/l, p=0.005; 7.3 (4.5–13.0) vs 10.4 (7.1–18.0) pmol/l, p=0.002; 0.073 (0.057–0.110) vs 0.097 (0.060–0.135), p=0.003]. Matched control subjects had lower proinsulin concentrations and proinsulin: insulin ratios compared to cases [5.9 (4.0–7.7) vs 7.3 (4.8–10.0) pmol/l, p=0.019; 0.048 (0.035–0.071) vs 0.064 (0.045–0.100), p=0.008]. When cases were compared to matched control subjects a 1 SD increase in baseline proinsulin: insulin ratio was associated with a 1.37-fold risk (p=0.020) of developing diabetes. Moreover, this association was independent of fasting glucose concentration at baseline. Thus, in elderly prediabetic subjects disproportionately increased proinsulin concentration, an indicator of defective insulin secretion, is associated with conversion to diabetes over a short time period.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1432-0428
    Schlagwort(e): Keywords Proinsulin ; insulin ; insulin secretion ; insulin resistance.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Aims/hypothesis. Proinsulin concentrations are increased relative to insulin concentrations in subjects with Type II (non-insulin-dependent) diabetes mellitus. This could be secondary to hyperglycaemia or insulin resistance or due to a defect in insulin secretion. Methods. We investigated the association between fasting insulin, intact proinsulin and the intact proinsulin: insulin ratio with insulin sensitivity, estimated by a frequently sampled intravenous glucose tolerance test and the minimal model and with acute insulin response (AIR) in 182 newly diagnosed Type II diabetic subjects aged 40 to 69 years. None of the subjects was receiving hypoglycaemic medication. Results. Insulin sensitivity correlated inversely with fasting insulin (r s = –0.42) and intact proinsulin (r s = –0.32) (p 〈 0.001). The intact proinsulin:insulin ratio was not correlated with insulin sensitivity. AIR correlated positively with intact proinsulin (r s = 0.23) and inversely with the intact proinsulin:insulin ratio (r s = –0.29, p 〈 0.001). Fasting glucose correlated positively with intact proinsulin (r s = 0.34) and the intact proinsulin:insulin ratio (r s = 0.24, p 〈 0.001). The intact proinsulin:insulin ratio increased by decreasing AIR (quartiles of AIR from high to low: 7.8, 8.2, 9.7 and 12.1 %, p 〈 0.001). This association was independent of age, sex, ethnicity, body mass index, fasting glucose, and insulin sensitivity. Conclusion/interpretation. Insulin resistance (low insulin sensitivity) was not related to the intact proinsulin:insulin ratio in subjects with Type II diabetes. In contrast, both low AIR and high fasting glucose concentrations were associated with a disproportionate increase in proinsulin concentration. These results suggest that increased intact proinsulin:insulin ratio is a marker of a defect in insulin secretion in Type II diabetic subjects. [Diabetologia (1999) 42: 1060–1066]
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Diabetologia 17 (1979), S. 235-242 
    ISSN: 1432-0428
    Schlagwort(e): Indirect two-site immunoradiometric assay ; rat proinsulin ; mouse proinsulin ; islets ; proinsulin/insulin ratio
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary An indirect two-site immunoradiometric assay for rat and mouse proinsulin using a rabbit antibody to synthetic rat C-peptide has been developed. The sensitivity of the assay is 0.006 pmol/ml. Proinsulin was 4.95% of the total proinsulin and insulin in extracts of rat pancreas and 5.45% in extracts of isolated rat islets. The mean fasting rat insulin and proinsulin concentrations were 0.13±0.09 pmol/ml (n=5) and 0.008±0.002 pmol/ml (n=5) respectively. The mean fasting mouse proinsulin concentration was 0.019±0.006 pmol/ml (n=8). In rats intravenous glucose produced a biphasic insulin response but proinsulin rose progressively to 0.021±0.011 pmol/ml at 45 min. In mouse oral glucose increased the proinsulin concentration to 0.13 pmol/ ml at 30 min. Proinsulin release from isolated rat islets was studied during intermittent or continuous high glucose (20 mmol/l) stimulation in static incubation. Significant increases in proinsulin release were only observed 90 min after initial exposure to high glucose whether glucose stimulation was continuous or intermittent. Both in vivo and in vitro glucose stimulation led initially to a fall in the proinsulin/ insulin molar ratio but later upon prolonged stimulation this progessively increased to above the basal value.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1432-0428
    Schlagwort(e): Non-insulin-dependent diabetes mellitus ; impaired glucose tolerance ; hypertriglyceridaemia ; hyperinsulinaemia ; non-esterified fatty acid
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Although plasma insulin and triglyceride concentrations are positively correlated in many studies, the relationships between insulin resistance, insulin secretion and hypertriglyceridaemia remain unclear. To study these associations, subjects between the ages of 40 and 64 were randomly selected from a general practice register and invited to attend for a standard oral glucose tolerance test for measurement of insulin, triglyceride and non-esterified fatty acid concentrations. The study comprised 1122 subjects who were not previously known to have diabetes and who completed the test. Using the World Health Organisation criteria, 51 subjects were classified to have non-insulin-dependent diabetes mellitus, 188 had impaired glucose tolerance and 883 subjects had normal glucose tolerance. Triglyceride concentrations in subjects with glucose intolerance were elevated compared to those in control subjects, even after adjustment for age, obesity and gender (p〈0.001 for subjects with diabetes and p〈0.01 for those with impaired glucose tolerance compared to normal subjects). In separate multiple regression analyses for males and females, the most important determinants of the plasma triglyceride concentration were the area under the non-esterified fatty acid suppression curve (p〈0.001 in both genders) and the waist-hip ratio (p〈0.001 for men and 〈0.01 for women). The fasting insulin concentration was independently associated with triglyceride concentration in women only (p〈0.01). The most important determinant of the area under the non-esterified fatty acid suppression curve in men was the 30-min insulin increment, a measure of insulin secretion, (p〈0.001) whereas for women age (p〈0.001) and the body mass index (p〈0.01) were the most important.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1432-0428
    Schlagwort(e): Key words Proinsulin ; insulin ; insulin secretion ; non-insulin-dependent diabetes mellitus ; epidemiology ; follow-up study.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Insulin resistance and impaired insulin secretion are thought to be the primary defects in the pathogenesis of non-insulin-dependent diabetes mellitus (NIDDM). Disproportionately increased proinsulin relative to insulin levels are suggested to be an early indicator of a failing pancreas. We examined the relationship of fasting specific insulin, proinsulin, and 32, 33 split proinsulin concentrations, and the proinsulin: insulin ratio to the risk of developing NIDDM 3.5 years later in 65–74-year-old non-diabetic Finnish subjects participating in a population-based study (n = 892) on diabetes and heart disease. Altogether 69 subjects developed NIDDM over a 3.5-year follow-up (cases). The cases were compared to randomly-selected gender-matched control subjects (n = 69) and control subjects matched for gender, glucose tolerance status (normal or impaired), and body mass index (n = 69). There were no differences in insulin concentrations between cases and random or matched control subjects [median and interquartile range; 123 (77–154), 108 (74–143), 118 (83–145) pmol/l, p = 0.271]. Random control subjects had lower proinsulin and 32,33 split proinsulin concentrations and split proinsulin: insulin ratios compared to cases [5.7 (3.8–9.0) vs 7.3 (4.8–10.0) pmol/l, p = 0.005; 7.3 (4.5–13.0) vs 10.4 (7.1–18.0) pmol/l, p = 0.002; 0.073 (0.057–0.110) vs 0.097 (0.060–0.135), p = 0.003]. Matched control subjects had lower proinsulin concentrations and proinsulin: insulin ratios compared to cases [5.9 (4.0–7.7) vs 7.3 (4.8–10.0) pmol/l, p = 0.019; 0.048 (0.035–0.071) vs 0.064 (0.045–0.100), p = 0.008]. When cases were compared to matched control subjects a 1 SD increase in baseline proinsulin: insulin ratio was associated with a 1.37-fold risk (p = 0.020) of developing diabetes. Moreover, this association was independent of fasting glucose concentration at baseline. Thus, in elderly prediabetic subjects disproportionately increased proinsulin concentration, an indicator of defective insulin secretion, is associated with conversion to diabetes over a short time period. [Diabetologia (1995) 38: 1176–1182]
    Materialart: Digitale Medien
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  • 9
    ISSN: 1432-0428
    Schlagwort(e): Key words Hypertriglyceridaemia ; non-esterified fatty acid ; ischaemic heart disease ; smoking.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary To investigate causes of increased triglyceride concentrations in subjects with normal glucose tolerance (determined by oral glucose tolerance testing using World Health Organization criteria) 883 healthy subjects (389 men and 494 women) between 40 and 65 years of age were studied. Subjects were divided by gender into four groups according to 120-min glucose concentrations. Individuals in the highest quartile of glucose concentration had the highest mean triglyceride concentrations (p 〈 0.0001) and highest mean non-esterified fatty acid (NEFA) concentrations (p 〈 0.0001). There was also a clustering of cardiovascular risk factors normally associated with the insulin resistance syndrome in subjects in this group. Regression analysis showed that the most important determinants of triglyceride levels were smoking (men p = 0.001, women p = 0.005), waist:hip ratio (men p = 0.01, women p 〈 0.001) and NEFA suppression (men p = 0.02, women p = 0.005). NEFAs suppressed 16.7 % in women compared to 2.4 % in men during the first 30 min of the oral glucose tolerance test (p 〈 0.001). These results show that a clustering of cardiovascular risk factors associated with decreased NEFA suppression occurs in a sub-group of subjects with normal glucose tolerance and that the pattern of NEFA suppression differs between men and women. [Diabetologia (1995) 38: 1358–1366]
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    ISSN: 1432-0428
    Schlagwort(e): Hypertriglyceridaemia ; non-esterified fatty acid ; ischaemic heart disease ; smoking
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary To investigate causes of increased triglyceride concentrations in subjects with normal glucose tolerance (determined by oral glucose tolerance testing using World Health Organization criteria) 883 healthy subjects (389 men and 494 women) between 40 and 65 years of age were studied. Subjects were divided by gender into four groups according to 120-min glucose concentrations. Individuals in the highest quartile of glucose concentration had the highest mean triglyceride concentrations (p〈0.0001) and highest mean non-esterified fatty acid (NEFA) concentrations (p〈0.0001). There was also a clustering of cardiovascular risk factors normally associated with the insulin resistance syndrome in subjects in this group. Regression analysis showed that the most important determinants of triglyceride levels were smoking (men p=0.001, women p=0.005), waist:hip ratio (men p=0.01, women p〈0.001) and NEFA suppression (men p=0.02, women p=0.005). NEFAs suppressed 16.7% in women compared to 2.4% in men during the first 30 min of the oral glucose tolerance test (p〈0.001). These results show that a clustering of cardiovascular risk factors associated with decreased NEFA suppression occurs in a sub-group of subjects with normal glucose tolerance and that the pattern of NEFA suppression differs between men and women.
    Materialart: Digitale Medien
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