Glucose transport, phosphorylation, and utilization in isolated porcine pancreatic islets

Porcine islets have been proposed as a donor source for human transplantation, mainly because of both structural and biological similarities of porcine and human insulin. However, the in vitro function of these islets is poorly characterized. In the present study, we first examined insulin release in response to glucose in static incubation experiments. Increasing glucose concentrations up to 8.3 mmol/L stimulated insulin release; however, this elevation was only twofold, and a paradoxical decline was observed at glucose concentrations higher than 8.3 mmol/L. In cultured porcine islets, a greater insulin secretion may be elicited by agents that increase intracellular cyclic adenosine monophosphate (cAMP) levels. To investigate the possible reasons for the porcine islet low response to glucose in vitro, we then evaluated in parallel experiments glucose transport, phosphorylation, and utilization. Glucose transport studies (using 3-O-methyl glucose uptake at 15 degrees C for 15 seconds) indicated the presence of both a high-affinity (Km, 1.2 +/- 0.6 mmol/L) and a low-affinity (Km, 11.8 +/- 1.9 nmol/L, n = 5) component. Glucose phosphorylation, evaluated by measuring the rate of glucose-6-phosphate formation in a fluorimetric assay, indicated that glucokinase activity had a maximum (Vmax) of 7.97 +/- 0.94 nmol/microgram DNA/h and a Km of 8.3 +/- 0.9 mmol/L (mean +/- SE, n = 8).(ABSTRACT TRUNCATED AT 250 WORDS)

Intraperitoneal insulin absorption after long-term intraperitoneal insulin therapy

OBJECTIVE

To evaluate insulin absorption through the peritoneal membrane after long-term intraperitoneal insulin therapy using an implanted programmable device.

RESEARCH DESIGN AND METHODS

Seven insulin-dependent diabetes mellitus (IDDM) patients implanted with a programmable pump were studied after 3 and 30 months of intraperitoneal insulin therapy. A 20-min square wave infusion of 15 IU of insulin was administered in the peritoneal space, and plasma glucose and plasma free insulin levels were monitored for 180 min. Hypoglycemia was prevented by intravenous glucose infusion.

RESULTS

After 30 months of intraperitoneal insulin therapy, plasma free insulin profiles following the administration of insulin in the peritoneal space were similar to those observed at the beginning of this mode of therapy.

CONCLUSIONS

In IDDM patients, intraperitoneal insulin absorption does not change after long-term intraperitoneal insulin therapy using an implanted device.

The continuous low dose insulin and glucose infusion test: a simplified and accurate method for the evaluation of insulin sensitivity and insulin secretion in population studies

In this study we investigated a simple nonlabor-intensive method to evaluate insulin sensitivity and beta-cell function which is suitable for application in population studies. The method is a refinement of the modified Harano test and consists of a continuous low dose insulin (25 mU/kg.h) and glucose (4 mg/kg.min) infusion test (LDIGIT) lasting 150 min. Insulin sensitivity was evaluated as the MCR of glucose divided by the steady state serum insulin level achieved at the end of the test. Insulin secretion was expressed as the incremental area for C-peptide concentration during the first 15 min of the test. We compared the indices of insulin sensitivity and insulin secretion yielded by LDIGIT with those derived from the euglycemic clamp and the hyperglycemic clamp, respectively. Fifty-four subjects underwent a LDIGIT (33 with normal glucose tolerance and 21 with impaired glucose tolerance); of the 54, 19 were submitted to a euglycemic clamp, 18 to a hyperglycemic clamp, and 10 to a modified Harano test (insulin infusion, 50 mU/kg.h; glucose infusion, 6 mg/kg.min). LDIGIT overcame the drawbacks associated with the modified Harano test because it resulted in more stable final glucose levels and prevented the occurrence of hypoglycemic episodes. No significant differences were found between the insulin sensitivity index (ISI) of the LDIGIT and that of the euglycemic clamp for each group of subjects. Moreover, there was a strong correlation between the ISI determined by LDIGIT and the ISI determined by clamp (r = 0.90; P < 0.0001), and the best regression line was not different from the identity line, suggesting that the two indices are equivalent. The index of insulin secretion provided by LDIGIT correlated well with that of the hyperglycemic clamp (r = 0.82; P < 0.001) and was significantly higher in overweight subjects than in normal weight subjects. In conclusion, LDIGIT is a simple and accurate method to assess insulin sensitivity and secretion. It can be useful in population studies and in situations when more complex techniques are not feasible.

Hypocaloric high-protein diet improves glucose oxidation and spares lean body mass: comparison to hypocaloric high-carbohydrate diet

The aim of the study was to investigate the effects of two hypocaloric (800-kcal) diets on body weight reduction and composition, insulin sensitivity, and proteolysis in 25 normal glucose-tolerant obese women. The two diets had the following composition: 45% protein, 35% carbohydrate (CHO), and 20% fat (HP diet, 10 subjects), and 60% CHO, 20% protein, and 20% fat (HC diet, 15 subjects); both lasted 21 days. A euglycemic hyperinsulinemic (25 mU/kg/h) clamp lasting 150 minutes combined with indirect calorimetry was performed before and after the diet. Both diets induced a similar decrease in body weight and fat mass (FM), whereas fat-free mass (FFM) decreased only after the HC diet. 3-Methylhistidine (3-CH3-HIS) excretion was reduced by 48% after the HP diet and remained unchanged after the HC diet (P < .05). A significant correlation was found between the changes in FFM and in 3-CH3-HIS excretion after the diet (rs = .50, P < .02). Blood glucose remained unchanged, while insulin decreased in both diets. Free fatty acids (FFA) significantly increased only after the HC diet (P < .05). During the clamp period, glucose disposal and glucose oxidation significantly increased after the HP diet and significantly decreased after the HC diet. Opposite results were found when measuring lipid oxidation. In conclusion, our experience suggests that (1) a hypocaloric diet providing a high percentage of natural protein can improve insulin sensitivity; and (2) conversely, a hypocaloric high-polysaccharide-CHO diet decreases insulin sensitivity and is unable to spare muscle tissue.

Analgesic effect of intranasal and intramuscular salmon calcitonin in post-menopausal osteoporosis: a double-blind, double-placebo study

Different types of calcitonin (porcine, human, salmon) are used in the management of bone diseases characterized by a high bone turnover, such as post-menopausal osteoporosis and Paget's disease; recently, salmon calcitonin has become clinically available as an intranasal (i.n.) spray. An analgesic effect has also been described for calcitonins, both in experimental animals and humans, but only a few studies in humans were placebo controlled. The aim of this study was to compare the analgesic efficacy of i.n. and intramuscular (i.m.) salmon calcitonin (sCT) and of placebo in women affected by painful post-menopausal osteoporosis, in a double-blind, double-placebo trial. Twenty-eight women were randomly allocated to one of the following treatments: 1) i.n. sCT 200 U/day plus i.m. placebo; 2) i.n. placebo plus i.m. sCT 100 U/day; and 3) i.n. and i.m. placebo. Each treatment lasted four weeks, and the pain score was evaluated weekly by means of a visual analogic scale (VAS). Twenty-four women completed the trial; with i.n. sCT, the pain score decreased significantly by the second week of treatment (p < 0.05); with i.m. sCT and with placebo, the pain score decreased significantly only by the fourth week (p < 0.05), so that the final pain scores obtained with the three treatments were not different. We conclude that i.n. sCT was probably more rapid, but not more effective than i.m. sCT or placebo in decreasing pain in post-menopausal osteoporosis.

Persistence of counter-regulatory abnormalities in insulin-dependent diabetes mellitus after pancreas transplantation

Conventional insulin therapy does not correct the counter-regulatory abnormalities of insulin-dependent diabetes mellitus. Pancreas transplantation is an alternative therapy that restores the endogenous insulin secretion in diabetes. In this study, the effects of segmental pancreas transplantation on counter-regulation to mild hypoglycaemia were evaluated. Glucose kinetics and the counter-regulatory hormonal responses were assessed in eight insulin-dependent diabetics with end-stage renal failure who had received pancreas and kidney transplantation 1 year previously, seven diabetic uraemic subjects (candidates for combined transplantation), five patients with chronic uveitis on immunosuppressive therapy comparable to pancreas recipients and 10 normal subjects. Insulin (0.3 mU kg-1 min-1) was infused for 2 h to induce mild hypoglycaemia (plasma glucose 3.2-3.5 mmol l-1) and exogenous glucose was infused as required to prevent any glucose decrease below 3.1 mmol l-1. After transplantation, two of eight recipients had hypoglycaemic episodes reported in their medical records. During the study, hepatic glucose production was rapidly suppressed in the controls and in the patients on immunosuppression (-80 +/- 7 and -54 +/- 7%, P < 0.001 vs. basal), and rebounded to the baseline values within 1 h (-3 +/- 1 and -6 +/- 2%, P = NS vs. basal). The transplant recipients had similar suppression in the first hour (-88 +/- 8%, P < 0.001 vs. basal), but the suppression persisted in the second hour (-69 +/- 11%, P < 0.001 vs. basal) indicating a lack of glucose counter-regulatory response.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunocytochemical detection and characterization of intrahepatic human pancreatic islets after combined liver-islet allotransplantation

The unique availability of an explanted liver-islet allograft, removed for primary nonfunction of the liver, led us to evaluate distribution and phenotype of exocrine and endocrine components of the pancreatic graft. Immunocytochemistry was used to map patterns of gene products for islet hormones, proprotein processing enzymes, panneuroendocrine markers, and pancreatic exocrine markers. When compared with age-matched control pancreases, insulin-, glucagon-, somatostatin-, and pancreatic polypeptide-producing cells were similarly represented and distributed within the grafted islet. We also demonstrate that the intrahepatic transplanted islets retained the enzyme machinery able to process the hormone precursors into bioactive fragments. In the clinical setting, this resulted in an immediate functioning of the graft and insulin-independence of the patient one month after transplantation. The purity in islets, as assessed by immunocytochemistry with antibodies to tissue constituents of endocrine and exocrine lineages, was around 40%. Despite the massive intraportal presence of pancreatic acinar tissue, no signs or symptoms attributable to ectopic hypersecretion of exocrine enzymes occurred. In fact, when tested with antibodies to such enzymes, low levels of immunoreactivity were observed in the grafted acinar cells.

Hyperinsulinemia decreases second-phase but not first-phase arginine-induced insulin release in humans

The aim of this study was to investigate the effect of hyperinsulinemia on the first and second phase of arginine-induced insulin release in humans. Seven healthy subjects underwent three studies (lasting 360 min): a control study using saline infusion and two euglycemic clamps using a low-dose (0.33 mU.kg-1.min-1) and a high-dose (1.20 mU.kg-1.min-1) insulin infusion. After a 3-h equilibration period, arginine (25 g) was infused for 30 min, and insulin and C-peptide responses to arginine were followed for 180 min. At the end of the equilibration period, before arginine administration, steady-state insulin levels were (means +/- SE) 60.0 +/- 2.4, 165.6 +/- 1.8, and 455.4 +/- 7.8 pmol/l during saline, low-dose, and high-dose insulin infusions, respectively. The time course of insulin release during the arginine test was calculated from C-peptide concentrations by using C-peptide kinetic modeling and deconvolution. In particular, first-phase and second-phase insulin response was obtained by integrating the time course of the insulin release during either the first 5 min or the following 40 min of the arginine test, respectively. Whereas first-phase insulin release was independent of any effect induced by either insulin infusion, second-phase insulin release was reduced in a similar degree by both insulin infusion doses. First phase was 75.5 +/- 10.1, 73.7 +/- 12.8, and 73.4 +/- 10.3 pmol/kg, whereas second phase was 266.1 +/- 46.0, 143.1 +/- 33.5, and 133.0 +/- 30.2 pmol/kg for saline, low-dose, and high-dose insulin infusions, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence that apolipoprotein(a) phenotype is a risk factor for coronary artery disease in men < 55 years of age

Whereas the importance of plasma lipoprotein(a) [Lp(a)] levels as a risk factor for premature coronary artery disease (CAD) is certain, it is not clear if the apolipoprotein(a) [apo(a)] phenotype plays an additional and independent role. To investigate the possible effect of apo(a) phenotype on premature CAD (in patients < 55 years of age), plasma Lp(a) concentrations, the apo(a) phenotypes, and their relation with many recognized CAD risk factors were examined in 96 non-diabetic male patients with angiographically defined CAD and in 83 age-matched male control subjects with no angiographic evidence of CAD. Results demonstrate that patients with premature CAD are characterized by higher Lp(a) levels (24 +/- 21 vs 17 +/- 15 mg/dl, p < 0.01) and a higher frequency of S2 phenotype (32% vs 15%, p < 0.01). Patients with an S2 phenotype exhibited significantly higher plasma Lp(a) concentrations than control subjects with the same isoform (37 +/- 22 vs 22 +/- 17 mg/dl, p < 0.05). A significant correlation was found between apo B and Lp(a) levels in patients with an S2 phenotype. In addition, patients had a low frequency of S1 and S4, and a high frequency of double-band phenotypes of apo(a). Multivariate analysis did not demonstrate an independent role for apo(a) phenotype as a risk factor for premature CAD. In conclusion, CAD patients < 55 years of age have a very different pattern of apo(a) phenotypes than subjects with no angiographic evidence of CAD; this study confirms the hypothesis that apo(a) phenotype may play an additional role in the etiology of premature CAD.

Fast gas chromatographic-mass spectrometric method for the evaluation of plasma fatty acid turnover using [1-13C]palmitate

Turnover of plasma free fatty acids (FFAs) can be determined from the palmitate enrichment of plasma after administration of analogues labeled with stable isotopes. We studied the conditions to measure both the concentration and the 13C enrichment of plasma palmitate by gas chromatography-mass spectrometry (GC-MS) using crude extracts. The method used plasma extraction after addition of heptadecanoic acid as internal standard and methylation with diazomethane. Subsequently the samples were analyzed by GC-MS. Plasma palmitate levels determined with this simplified method did not differ statistically from those obtained by a more "classical" procedure using FFA separation from other plasma lipids. Palmitic acid turnover rates (Ra) were evaluated in the steady-state period, in two normal subjects after 90 min infusion with [1-13C]palmitate bound to human albumin. The rate of appearance (Ra) was found to be 0.92 and 1.08 mmol kg-1 min-1, which is in good agreement with the turnover rate previously reported for normal subjects. Sample preparation and GC-MS analysis by the proposed procedure are simple and rapid and thus the method appears to be particularly useful in clinical studies where numerous samples have to be analyzed.

Clinical reliability of multi-drug intracavernous vasoactive pharmacotherapy for diabetic impotence

The aim of this study was to assess the effectiveness and safety of intracavernous injections of a four-drug vasoactive mixture in diabetic patients with organic impotence. A group of 60 diabetic patients with either pure neurogenic, pure vasculogenic or mixed neurovasculogenic impotence were treated with intracavernous injections of a combination of 12.1 mg/ml papaverine hydrochloride, 1.01 mg/ml phentolamine mesylate, 10.1 micrograms/ml prostaglandin E1 and 0.15 mg/ml atropine sulphate ('full-dose' mixture). A mixture of the same drugs but at one-third concentrations ('reduced-dose' mixture) was also used. The mean (+/- SEM) volumes of the full-dose and reduced-dose mixtures used were 0.21 +/- 0.03 ml and 0.31 +/- 0.02 ml, respectively. All the patients were able to sustain a rigid erection at the end of the titration phase of the study. At a mean follow-up of 18 months, 48 patients (80%) were successfully using the mixture, 6 patients (10%) were using the mixture at a dose lower than the initial dose and 6 patients (10%) had dropped out from the injection therapy. No major complications were seen. The association of multiple vasoactive drugs which use different mechanisms of action, thus exerting a pharmacological synergism, is an effective and safe procedure in intracavernous pharmacotherapy for diabetic patients with organic impotence.

Pirenzepine decreases basal and stimulated GH secretion in patients with type 2 (non-insulin-dependent) diabetes mellitus

Growth hormone (GH) hypersecretion has been described in diabetes mellitus and seems to be involved in the pathogenesis of diabetes complications. As pirenzepine (PZ), a cholinergic muscarinic antagonist, is able to inhibit GH hypersecretion in insulin-dependent diabetes mellitus (IDDM), we investigated whether PZ is also able to inhibit spontaneous and stimulated GH-release in non-insulin-dependent diabetes mellitus (NIDDM). Ten non-obese well-controlled patients with NIDDM underwent in random order the following three double-blind one week treatments: placebo (PL), PZ at low dose (PL in the morning plus PZ 50 mg at 22 h) or high dose (PZ 50 mg at 8 h plus 100 mg at 22 h). Pirenzepine administration significantly (p < 0.05) decreased nocturnal GH release after both low and high dose (AUC, PL vs PZ: 107.3 +/- 26.5 vs 48.3 +/- 10.5 and 57.6 +/- 9.6 micrograms/L/h, respectively). The GH response to arginine infusion was significantly inhibited by PZ at high dose (AUC, 147.1 +/- 48.8 vs 444.7 +/- 194.3 micrograms/L/h, p < 0.01), but not at low dose. Glucose, insulin, glucagon and somatostatin responses to arginine infusion were not changed by pirenzepine treatment. In conclusion, the muscarinic blockade by PZ is able to inhibit the spontaneous and stimulated GH secretion also in NIDDM without affecting insulin secretion.

Heterogeneous IgG subclass distribution of islet cell antibodies

Islet cell antibodies (ICA)-IgG are the serological marker of type 1 diabetes, an organ-specific autoimmune disease. A proportion of patients also have thyro-gastric autoimmunity, implying a broader humoral autoreactivity in these cases. In order to determine whether this is also reflected within islet cell antibodies (ICA) we examined the ICA-IgG subclass distribution in type 1 diabetic patients with or without associated thyro-gastric autoantibodies. ICA-IgG subclasses were detected by two-step indirect immunofluorescence, using monoclonal antibodies against the four IgG subclasses, in sera from 51 patients with type 1 diabetes and detectable ICA; 31 had no other antibodies (group 1) and 20 had at least one associated thyroid and/or gastric autoantibody (group 2). Our results show that ICA are polyclonal and invariably IgG1. In 48% of patients with type 1 diabetes without associated thyro-gastric autoantibodies, ICA were restricted to IgG1 only. Conversely, only 10% of those with thyro-gastric antibodies had ICA-IgG1 only (P < 0.02), and a larger ICA-IgG subclass recruitment was observed in these patients (P = 0.002). These findings provide evidence of heterogeneity within ICA at the IgG subclass level, with a broader clonal recruitment within this specificity in individuals displaying features of multiple organ autoimmunity. These results support the hypothesis of heterogeneity within the pathogenetic process leading to type 1 diabetes.

Normalization of lipoprotein composition by intraperitoneal insulin in IDDM. Role of increased hepatic lipase activity

OBJECTIVE

To characterize the effects of intraperitoneal insulin pump therapy on lipoprotein composition and lipolytic enzyme activity in patients with insulin-dependent diabetes mellitus (IDDM).

RESEARCH DESIGN AND METHODS

Ten IDDM patients were studied 3 times: when receiving conventional subcutaneous insulin therapy and at 3 and 9 months from the initiation of intraperitoneal insulin regimen. Ten nondiabetic subjects matched for age, sex, and body weight were studied as controls. Levels of cholesterol, triglycerides, apolipoprotein A-I (apoA-I) and B (apoB) were measured in total plasma and lipoprotein fractions (very-low-density lipoprotein [VLDL], intermediate-density lipoprotein [IDL], low-density lipoprotein [LDL], and high-density lipoprotein [HDL]: HDL2 and HDL3). Postheparin plasma lipoprotein lipase and hepatic lipase activities were determined by an immunochemical method.

RESULTS

IDDM patients showed higher levels of HDL3 and lower levels of HDL2 particles during intraperitoneal insulin therapy in comparison with subcutaneous insulin therapy. Both cholesterol and apoA-I significantly increased in HDL3 and decreased in HDL2 during intraperitoneal treatment. Plasma total cholesterol significantly decreased in the diabetic patients at 3 months of intraperitoneal insulin therapy compared with both subcutaneous insulin regimen and control subjects. IDL triglyceride concentrations during intraperitoneal treatment were significantly lower than those seen with subcutaneous therapy. Furthermore, triglyceride:apoB ratio in VLDL and cholesterol:apoB ratio in LDL significantly decreased in IDDM patients treated by intraperitoneal insulin. A significant increase in the activity of hepatic lipase with intraperitoneal insulin therapy by 9 months compared with subcutaneous insulin therapy has been shown.

CONCLUSIONS

The increased activity of hepatic lipase after intraperitoneal insulin administration in IDDM patients appears to be one of the main determinants of lipoprotein changes observed, resulting in the normalization of lipoprotein composition during this mode of therapy. The normal inverse relationship between VLDL triglycerides and HDL cholesterol, which was not present in IDDM patients with subcutaneous therapy, was restored with intraperitoneal insulin regimen.

Metabolic effects of graded glucagon infusions in man: inhibition of glucagon, insulin, and somatostatin response to arginine

Insulin inhibits its own release (autofeedback), and growth hormone (GH) inhibits the GH response to a variety of stimuli. The aim of this study was to evaluate whether glucagon (G) can modify pancreatic G (IRG) release in humans. Seven healthy men received intravenous (i.v.) arginine (30 g in 30 minutes) 240 minutes after the beginning of a 0.9% NaCI saline infusion and a 2.5-, 4.0-, and 8.0-ng/kg.min-1 porcine G infusion, with each infusion lasting 360 minutes. All G infusions yielded stable and dose-related plasma IRG levels, and the 4.0- and 8.0-ng/kg.min-1 G infusions decreased plasma free fatty acids (FFA) and blood glycerol and beta-OH-butyrate levels and elicited insulin (IRI) release, and the 8.0-ng/kg.min-1 G infusion elicited GH release and increased blood glucose (BG) levels; somatostatin (SRIF) levels were not affected by G infusions. At 240 minutes, plasma IRG levels were higher during G infusion than during saline infusion, whereas serum IRI and BG levels had returned to preinfusion levels. At this point, G infusions decreased the integrated (240 to 300 minutes) IRG, IRI, BG, and SRIF responses, but not the GH response to arginine. These data indicate that prolonged G infusions decrease the IRG response to arginine; in addition, G decreases plasma FFA levels, and higher G doses stimulate IRI release and exert a self-limited hyperglycemic effect. The fact that the IRI response to arginine was decreased by G could be due to a refractoriness of beta cells to subsequent stimuli; the decreased SRIF response to arginine is likely due to G itself or to a decrease of plasma FFA levels.

Peritoneal and subcutaneous absorption of insulin in type I diabetic subjects

We and others have shown that in type I diabetes, ip insulin delivery results in lower free insulin levels than sc delivery. The aim of this study was to compare the rate of appearance of insulin in the peripheral circulation during ip and sc insulin administration in type I diabetes, in steady state and nonsteady state. To do this, we determined free insulin levels during ip or sc infusion as well as the impulse response of the insulin system after iv injection of a 6-nmol bolus of insulin. Twelve hours after a constant basal insulin infusion (5.5 +/- 1.4 nmol/h) was started, five C-peptide-negative type I diabetic subjects showed a lower systemic rate of appearance of insulin (expressed as a percentage of the administered dose) with ip than sc administration (27 +/- 6% vs. 40 +/- 10%; P < 0.001). In nonsteady state, when the infusion rate was increased from basal to 15 nmol/h (0-150 min) and subsequently to 42 nmol/h (150-300 min), the percent increase in insulin's systemic rate of appearance was higher with ip than sc infusion (P < 0.05 from 60-150 min; P < 0.01 from 150-300 min), indicating faster absorption. Thus, we conclude that insulin is more rapidly absorbed from the peritoneal cavity than from sc tissue. However, with ip administration, a sizable amount of insulin, once absorbed, is extracted before reaching the peripheral circulation, most likely by the liver. This is indirect evidence that ip insulin delivery results in a portal-peripheral insulin gradient in humans.

Substitution of Leu for Pro-193 in the insulin receptor in a patient with a genetic form of severe insulin resistance

Mutations have been identified in the insulin receptor (IR) gene in patients who are insensitive to insulin action. We studied an extremely insulin resistant patient whose insulin binding to Epstein-Barr virus (EBV) transformed lymphocytes was severely reduced. Transmembrane signalling, evaluated as insulin receptor autophosphorylation, was normal. The patient's IR was immunoprecipitated normally by AbP6, a polyclonal antibody directed to the beta subunit. However, there was an approximately 50% decrease in the affinity of IR immunoprecipitation by a monoclonal antibody (MA-10) directed against the alpha subunit. These observations suggested that there were likely to be a mutation in the patient's insulin receptor that caused misfolding of the IR alpha subunit. Analysis of gene structure by Southern blotting experiments did not reveal any major deletion in the IR gene of the proband. Northern blot analysis showed a normal level of expression of IR gene. We applied denaturing gradient gel electrophoresis (DGGE) as well as direct sequence analysis to study the 22 exons of IR gene amplified by polymerase chain reaction (PCR) using the proband's genomic DNA as a template. We identified a new missense mutation substituting leucine (CTG) for proline (CCG) in homozygous state at codon 193 in exon 3. Both parents are heterozygous for the Leu193 mutation. The Leu193 mutation was not detected in any of 75 normal subjects (150 chromosomes), indicating that it is not a common sequence variant of the insulin receptor. In addition, during the course of screening the patient's DNA with perpendicular DGGE, we identified two previously unreported silent substitutions in exon 9.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of meal ingestion on insulin profiles following intraperitoneal delivery

This study evaluated the effect of meal ingestion on intraperitoneal insulin absorption in type I diabetic patients with an implanted pump for long-term intraperitoneal insulin delivery. On four separate occasions, patients (n = 7) were administered 15 IU insulin as a 20-minute square-wave infusion using their implanted device; hypoglycemia was prevented by intravenous infusion of 10% dextrose at a variable rate. Two studies were performed during fasting conditions (n = 2 fasting tests) and two studies after the administration of an 800-kcal standard meal (n = 2 postprandial tests). An insulin peak of 630 +/- 545.4 pmol/L (mean +/- SD) in fasting tests and 696 +/- 420.5 pmol/L in postprandial tests was reached in the peripheral circulation after 45 +/- 11.7 and 45 +/- 14.7 minutes, respectively, with no significant difference between the two experimental conditions. Areas under the insulin curves were not significantly different in fasting and postprandial tests (51,500 +/- 34,278 v 50,916 +/- 20,558 pmol/L.min-1, respectively; NS). In type I diabetic patients receiving long-term intraperitoneal insulin therapy, the increase in splanchnic blood flow following ingestion of a standard meal does not accelerate the appearance of insulin in the peripheral circulation.