Studies of a Simplified Plasma Insulin Immunoassay Using Cellulose Powder

Zaharko, Daniel S.; Beck, Lyle V.

doi:10.2337/diab.17.7.444

Cited by 138 publications

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“…Plasma glucose levels were measured at 5-min intervals using the glucose oxidase method (Beckman Instruments, Fullerton, CA) and maintained at basal levels with a variable infusion of 20% glucose, which was adjusted according to a computerized algorithm. Samples were obtained at 10-min intervals during the clamp for subsequent measurement of plasma insulin levels by radioimmunoassay (18).…”

Section: Hyperinsulinemic-euglycemic Glucose Clampmentioning

confidence: 99%

Limited Value of the Homeostasis Model Assessment to Predict Insulin Resistance in Older Men With Impaired Glucose Tolerance

Ferrara

Goldberg

2001

Diabetes Care

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A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances. Limited Value of the Homeostasis Model Assessment to Predict Insulin Resistance in Older Men With Impaired Glucose Tolerance O R I G I N A L A R T I C L EOBJECTIVE -Insulin resistance (IR) in older individuals is associated with risk factors for coronary artery disease. The glucose clamp measures IR directly, but the homeostasis model assessment (HOMA) of IR, referred to here as HOMA-IR, is based on fasting glucose and insulin and is less invasive and labor intensive. This method requires validation in the elderly. RESEARCH DESIGN AND METHODS -We assessed the validity of HOMA-IR as an index of IR by comparing it to glucose infusion rates (GIRs) measured by a glucose clamp (600 pmol и m Ϫ2 и min Ϫ1 ) in 45 obese men (61 ± 8 years of age, mean ± SD) with normal glucose tolerance (NGT) (n = 21) or impaired glucose tolerance (IGT) (n = 24). We also evaluated relationships between body composition, exercise capacity, and IR.RESULTS -Subjects with NGT had lower BMI (28 ± 3 vs. 31 ± 3 kg/m 2 ), waist circumference (97 ± 9 vs. 105 ± 9 cm), waist-to-hip ratio (WHR) (0.93 ± 0.06 vs. 0.97 ± 0.05), and percent body fat (25 ± 6 vs. 30 ± 6) than subjects with IGT. Subjects with NGT also had lower areas above basal during the 2-h oral glucose tolerance test for glucose (274 ± 95 vs. 419 ± 124 mmol и min/l) and insulin (38,142 ± 18,206 vs. 58,383 ± 34,408 pmol и min/l) and lower HOMA-IR values (2.2 ± 0.8 vs. 4.2 ± 2.6) than subjects with IGT. GIR (µmol и kg -1 FFM и min -1 ) was higher in subjects with NGT than in subjects with IGT (53 ± 11 vs. 43 ± 14). HOMA-IR correlated with GIR in subjects with NGT (r = Ϫ0.59), but not in subjects with IGT (r = Ϫ0.13). GIR correlated with VO 2max in subjects with NGT (r = 0.58) and IGT (r = 0.42), but with WHR only in subjects with NGT (r = Ϫ0.53). HOMA-IR correlated with VO 2max (r = Ϫ0.57) and waist circumference (r = 0.54) in subjects with NGT, but with percent body fat in subjects with IGT (r = 0.54).CONCLUSIONS -These findings indicate that HOMA-IR should not be used as an index of IR in older individuals who may be at risk for IGT, and suggest that lifestyle changes that increase VO 2max and decrease body fat may reduce IR in older people.

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Section: Hyperinsulinemic-euglycemic Glucose Clampmentioning

confidence: 99%

Limited Value of the Homeostasis Model Assessment to Predict Insulin Resistance in Older Men With Impaired Glucose Tolerance

Ferrara

Goldberg

2001

Diabetes Care

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“…Insulin was measured by radioimmune assay, as described previously. 43 Briefly, this assay uses antisera raised to intact insulin in rabbits and iodinated insulin as tracer and has an inter-and intra-assay CV of 8% and 6%, respectively. Glucose and insulin were measured 3 times serially (15 minutes after insertion of intravenous line), with blood draw 5 minutes apart on each subject and the mean of the 3 samples is reported.…”

Section: Lipid and Hormone Determinationsmentioning

confidence: 99%

A Hepatic Lipase Gene Promoter Polymorphism Attenuates the Increase in Hepatic Lipase Activity With Increasing Intra-abdominal Fat in Women

Carr

Hokanson

Deeb

et al. 1999

ATVB

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Abstract-High hepatic lipase (HL) activity is associated with an atherogenic lipoprotein profile of small, dense LDL particles and lower HDL 2 -C. Intra-abdominal fat (IAF) is positively associated with HL activity. A hepatic lipase gene (LIPC) promoter variant (G3 A Ϫ250 ) is associated with lower HL activity, higher HDL 2 -C, and less dense LDL particles.To determine whether the LIPC promoter polymorphism acts independently of IAF to regulate HL, 57 healthy, premenopausal women were studied. The LIPC promoter A allele was associated with significantly lower HL activity (GA/AAϭ104Ϯ34 versus GGϭ145Ϯ57 nmoles ⅐ mL Ϫ1 ⅐ min Ϫ1 , Pϭ0.009 lipolytic enzyme that is a serine hydrolase. It appears to act not only in hydrolysis of triglyceride (TG) and phospholipid in HDL and LDL 1,2 but also as a ligand directing lipoproteins to hepatic cell surface receptors. 3-5 HL is secreted by hepatocytes and anchored to the liver sinusoidal surface by heparin sulfate proteoglycans. 6 The HL gene (LIPC) spans 35 kb of DNA, maps to chromosome 15q21, and is composed of nine exons and eight introns. 7,8 HL plays a role in the metabolic processing of both HDL and LDL. HL acts to convert large, buoyant HDL 2 to small, dense HDL 3 by modulating the phospholipid content of the particle. 9,10 By functioning as a ligand between the lipoprotein and cell surface receptors, HL has been shown to play a role in increased clearance of HDL particles 11,12 and remnant lipoproteins. 13 HL also catalyzes the hydrolysis of triglyceride and phospholipid in large, buoyant LDL forming small, dense more atherogenic LDL particles. 14 Increased risk of premature coronary artery disease (CAD) has been shown to be associated with the presence of small, dense LDL particles. [15][16][17][18][19] Similarly, low HDL-C is another major risk factor for CAD. 20,21 It appears that gender differences in HDL-C levels may account, in part, for the temporal separation in CAD risk between men and women. 20 HDL-C metabolism is modulated by both environmental and genetic factors that combine to account for the significant interindividual variation in HDL-C levels and hence CAD risk. Sedentary lifestyle, 22 tobacco usage, 23 and obesity 24 are all associated with lower HDL-C levels. Forty to sixty percent of the variation in HDL levels appear to be genetic, 25 and Cohen et al have demonstrated genetic linkage between the hepatic lipase promoter (LIPC) locus and HDL-C levels that account for approximately 25% of the interindividual variation in plasma HDL-C levels. 26 HL activity appears to be influenced by several different factors including intra-abdominal fat (IAF), 27 ethnic background, 28,29 sex-steroid hormones, 30 -32 and LIPC genotype. 28,29 Four polymorphisms have now been identified in the 5Ј flanking region of the LIPC gene; a G to A substitution at position Ϫ250, C to T at Ϫ514, T to C at Ϫ710, and A to G at Ϫ763, which appear to be in complete linkage disequilibrium in white populations. 33 The allele frequency of the substitution ranges from 0.15 33 to 0.21 29 ...

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“…Insulin and glucagon were measured in the incubation media by radioimmunoassay. 16 ' 17 Statistical analysis was performed using Newman-Keul's multiple comparison procedure. 18 The naturally occurring peptides leucine-and methionine-enkephalin, D-ala 2 -leucine-, and D-phe 4 -leucine-enkephalin analogues were generously provided by Dr. Richard J. Miller of the University of Chicago.…”

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confidence: 99%

Disparate Effects of Enkephalin and Morphine upon Insulin and Glucagon Secretion by Islet Cell Cultures

1980

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SUMMARYInsulin and glucagon release from monolayer pancreatic islet cell cultures were inhibited in a dose-response fashion by various enkephalins. Morphine, however, stimulated insulin and glucagon release. Both effects were blocked by naloxone, while naloxone alone had no effect. In isolated and denervated islet cells, opiates directly influence secretion from islet cells. DIABETES 29:84-86, January 1980. E ndogenous opiates (endorphins and enkephalins) are widely distributed in the nervous system and gastrointestinal tract of animals, including man. They have been shown to affect rates of neuronal transmission and the secretion of several pituitary hormones (ADH, prolactin, growth hormone, and gonadotrophins).1 " 3 By immunocytochemical techniques, endorphin-like substances have been demonstrated in the A-cells of the islets of Langerhans of the rat, 4 and morphine and B-endorphin have been reported to enhance insulin and glucagon release from the isolated perfused dog pancreas. 5Since islets are richly enervated by sympathetic, parasympathetic, and peptidergic systems, opiates might alter islet secretion indirectly by modulating these neuronal influences or directly by interacting with receptors on the islet secretory cells. We have used pancreatic islet cell monolayer cultures, an isolated and denervated islet cell system, to determine if opiates have a direct effect on islet cells and if all opiates act in a similar fashion. MATERIALS AND METHODSPancreatic monolayer cultures were established according to previously described techniques.6 " 8 These cultures have been shown by immunocytochemistry to contain cells that stain for insulin, glucagon, somatostatin (SRIF), gastric inhibitory polypeptide, secretin, gastrin, and pancreatic polypeptide.9 " 15 Experiments were performed on the fourth day of culture. Experimental incubation medium was Eagle's minimal essential medium supplemented with nonessential amino acids, Earle's salts, and 0.5% (v/v) heat-inactivated fetal bovine serum. All dishes were preincubated for 2 h in 5.5 mM glucose. This was followed by a 1-h incubation during which secretagogues plus varying concentrations of opiate were added to experimental cultures and compared with control cultures with segretagogues alone. Insulin and glucagon were measured in the incubation media by radioimmunoassay. 16 ' 17 Statistical analysis was performed using Newman-Keul's multiple comparison procedure. 18 The naturally occurring peptides leucine-and methionine-enkephalin, D-ala 2 -leucine-, and D-phe 4 -leucine-enkephalin analogues were generously provided by Dr. Richard J. Miller of the University of Chicago. RESULTSWith glucose 16.5 mM, the naturally occurring opiates leucine-enkephalin (LEK) and methionine-enkephalin (MEK) produced, over a concentration range of 0.02 to 2.0 /Jvi, a dose-related suppression of both insulin and glucagon release (Figure 1). D-ala 2 -leucine-enkephalin (DLE) is an enkephalin analogue that has been reported to resist metabolic degradation.1 Over the same concentration range, ...

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Studies of a Simplified Plasma Insulin Immunoassay Using Cellulose Powder

Cited by 138 publications

References 0 publications

Limited Value of the Homeostasis Model Assessment to Predict Insulin Resistance in Older Men With Impaired Glucose Tolerance

Limited Value of the Homeostasis Model Assessment to Predict Insulin Resistance in Older Men With Impaired Glucose Tolerance

A Hepatic Lipase Gene Promoter Polymorphism Attenuates the Increase in Hepatic Lipase Activity With Increasing Intra-abdominal Fat in Women

Disparate Effects of Enkephalin and Morphine upon Insulin and Glucagon Secretion by Islet Cell Cultures

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