First direct assay for intact human proinsulin

We describe a sensitive two-site sandwich enzyme-linked immunosorbent assay for the measurement of intact human proinsulin in 100 microL of serum or plasma. The assay is based on the use of two monoclonal antibodies specific for epitopes at the C-peptide/insulin A chain junction and at the insulin B chain/C-peptide junction, respectively. Cross-reactivities with insulin, C-peptide, and the four proinsulin conversion intermediates were negligible. The detection limit in buffer was 0.2 pmol/L (3 standard deviations from zero). The working range was 0.2-100 pmol/L. The mean intra- and interassay coefficients of variation were 2.4% and 8.9%, respectively. The mean recovery of added proinsulin was 103%. Dilution curves of 40 serum samples are parallel to the proinsulin calibration curve. Proinsulin concentrations in 20 fasting healthy subjects were all above the limit of detection: median (range), 2.7 pmol/L (1.1-6.9 pmol/L). Six fasting non-insulin-dependent diabetes mellitus and five insulinoma patients had proinsulin concentrations significantly higher than healthy subjects: median (range), 7.7 pmol/L (3.2-18 pmol/L) and 153 pmol/L (98-320 pmol/L), respectively.     

Pharmacoeconomic model of enoxaparin versus heparin for prevention of deep vein thrombosis after total hip replacement

Non-diabetic first degree relatives of non-insulin-dependent diabetic (NIDDM) families are at increased risk of developing diabetes mellitus, and have been studied to identify early metabolic abnormalities. Hormone concentrations measured by specific enzyme immunoassays were assessed in non-diabetic relatives of North European extraction, and control subjects with no family history of diabetes were matched for age, sex and ethnicity. A 75-g oral glucose tolerance test was conducted and those with newly diagnosed NIDDM were excluded. Basal insulin resistance was determined by homeostasis model assessment (HOMA), and hepatic insulin clearance by C-peptide:insulin molar ratio. Relatives (n = 150) were heavier (BMI: p < 0.0001) than the control subjects (n = 152), and had an increased prevalence of impaired glucose tolerance (15 vs 3%, p < 0.01). The relatives had increased fasting proinsulin levels and decreased C-peptide levels following the glucose load, while insulin levels were increased at all time points. To examine whether the differences in hormone levels were secondary to the differences in glucose tolerance and adiposity, we studied 100 normal glucose tolerant relatives and control subjects pair-matched for age, sex, waist-hip ratio and BMI. The differences in proinsulin levels were no longer apparent. However, the relatives remained more insulin resistant, and had decreased C-peptide levels and C-peptide:insulin ratios at all time points. In conclusion, we have identified several metabolic abnormalities in the normal glucose tolerant relatives, and propose that the decreased hepatic insulin clearance helps to maintain normoglycaemia in the face of combined insulin resistance and decreased insulin secretion.     

Circulating proinsulin levels in insulin-dependent diabetic patients after whole pancreas-kidney transplantation

Disproportional hyperproinsulinemia is a sensitive marker for beta-cell dysfunction. The objective of this study was to assess the proinsulin profile in persons with insulin-dependent diabetes mellitus (IDDM) after pancreas-kidney transplantation. We determined serum insulin, C-peptide, and proinsulin concentrations during an oral glucose challenge in five pancreas-kidney transplant recipients, nine nondiabetic kidney transplant recipients, and 17 normal subjects. Basal proinsulin concentrations were significantly increased in pancreas-kidney recipients (geometric mean [+/-1 SE range], 6.0 [5.5 to 6.4] pmol/L) and kidney recipients (6.4 [5.4 to 7.5] pmol/L) compared with the normal subjects (2.8 [2.5 to 3.2] pmol/L). Integrated proinsulin concentrations during the oral glucose load were also higher in pancreas-kidney recipients (1.4 [1.1 to 1.8] nmol/L x min) and kidney recipients (1.5 [1.2 to 2.0] nmol/L x min) versus normal subjects (0.8 [0.7 to 0.9] nmol/L x min). There was no difference in basal or integrated proinsulin concentrations between the two transplant groups. Even after adjustment for the glomerular filtration rate (GFR), basal and incremental proinsulin concentrations continued to be higher in the transplant groups than in the normal subjects. Proinsulin to C-peptide molar ratios both before and after the glucose load were similar in the three groups. From these findings, we conclude that pancreas-kidney transplantation provokes proportional hyperproinsulinemia, which is closely associated with its reduced clearance in the kidneys.     

Disproportionately elevated proinsulin levels precede the onset of insulin-dependent diabetes mellitus in siblings with low first phase insulin responses. The Childhood Diabetes in Finland Study Group

The objective of this study was to test whether levels of proinsulin immunoreactivity (PIM) relative to those of insulin immunoreactivity (IRI) or C-peptide are changed and related to subclinical beta-cell dysfunction in siblings of insulin-dependent diabetes mellitus (IDDM) patients. Twenty-three siblings, previously found positive for islet cell antibodies and/or insulin autoantibodies, were divided into 2 groups according to their first phase insulin response (FPIR) to i.v. glucose tolerance tests (IVGTTs) sequentially performed during an observation period of 2 yr. Eleven siblings had diminished FPIR on at least 1 occasion (group 1), whereas 12 siblings had a normal FPIR on all occasions studied (group 2). All underwent a further IVGTT (0.5 g glucose/kg BW), and serum samples were taken at 0, 1, 3, 6, 10, 20, 30, 40, 50, and 60 min. The 2 groups had comparable median age, female/male ratio, weight, height, fasting blood glucose, immunoreactive insulin, C-peptide, and insulin autoantibodies levels, but group 1 had significantly higher islet cell antibodies levels. Fasting median PIM/IRI and PIM/C-peptide ratios were 2- to 3-fold higher in group 1 [10.5% (range, 1.8-93.8%) vs. 5.2% (range, 1.9-14.3%) and 3.3% (range, 0.4-23.1%) vs. 1.3% (range, 0.7-2.6%; P < 0.05]. Fasting PIM/C-peptide ratios correlated inversely with FPIRs (rs = -0.68; P < 0.01). During glucose stimulation, maximal responses of IRI and C-peptide were 4-fold lower in group 1, and the time of maximal responses of IRI and C-peptide occurred later in group 1 than in group 2. In contrast, no difference in maximal responses of PIM was found, but the time of maximal responses of PIM occurred later in group 1. Nine of 11 siblings in group 1 presented with IDDM 1-28 months after the test, compared to none in group 2. In group 1 a paradoxical inhibitory response of PIM was observed during the first 6 min of the IVGTT. These data indicate that fasting PIM/IRI and/or PIM/C-peptide ratio reflects subclinical beta-cell dysfunction in prediabetic subjects with evidence of immunological beta-cell assault and suggests that an elevated ratio may be an additional marker for later development of IDDM.     

The Ala/Val98 polymorphism of the hepatocyte nuclear factor-1alpha gene contributes to the interindividual variation in serum C-peptide response during an oral glucose tolerance test: evidence from studies of 231 glucose-tolerant first degree relatives of type 2 diabetic probands

The third form of maturity-onset diabetes of the young is caused by mutations in the hepatocyte nuclear factor-1alpha gene. Recently, we demonstrated an association between a prevalent polymorphism at codon 98, Ala/Val98, of this gene and a 20% decreased insulin release during an oral glucose tolerance test (OGTT) in middle-aged glucose-tolerant Danish Caucasian subjects. The major objective of the present study was to replicate this finding among glucose-tolerant first degree relatives of type 2 diabetic patients of the same ethnic origin. All participants, 231 glucose-tolerant offspring of 62 type 2 diabetic probands, underwent an OGTT with measurements of plasma glucose, serum insulin, and serum C peptide during the test. Thirty-three heterozygous carriers of the Ala/Val variant were identified, whereas no subjects had the variant in its homozygous form. Ala/Val carriers had a 20% reduction in serum C peptide at 30 min during the OGTT (1225+/-636 vs. 1507+/-624 pmol/L; P=0.02) compared to wild-type carriers. No significant differences in serum insulin levels during the OGTT were observed between carriers of the variant and Ala/Ala homozygotes. In conclusion, among Danish glucose-tolerant first degree relatives of type 2 diabetic patients the Ala/Val98 polymorphism of the hepatocyte nuclear factor-1alpha gene is associated with a decreased serum C-peptide secretion during an OGTT. This finding confirms our previously reported observation of the functional importance of the variant to insulin secretion during an OGTT among middle-aged healthy subjects.     

Disappearing subdural hematomas in children

Serum glucose and plasma C-peptide response to i.v. glucagon administration was evaluated in 24 healthy dogs, 12 dogs with untreated diabetes mellitus, 30 dogs with insulin-treated diabetes mellitus, and 8 dogs with naturally acquired hyperadrenocorticism. Serum insulin response also was evaluated in all dogs, except 20 insulin-treated diabetic dogs. Blood samples for serum glucose, serum insulin, and plasma C-peptide determinations were collected immediately before and 5, 10, 20, 30, and (for healthy dogs) 60 minutes after i.v. administration of 1 mg glucagon per dog. In healthy dogs, the patterns of glucagon-stimulated changes in plasma C-peptide and serum insulin concentrations were identical, with single peaks in plasma C-peptide and serum insulin concentrations observed approximately 15 minutes after i.v. glucagon administration. Mean plasma C-peptide and serum insulin concentrations in untreated diabetic dogs, and mean plasma C-peptide concentration in insulin-treated diabetic dogs did not increase significantly after i.v. glucagon administration. The validity of serum insulin concentration results was questionable in 10 insulin-treated diabetic dogs, possibly because of anti-insulin antibody interference with the insulin radioimmunoassay. Plasma C-peptide and serum insulin concentrations were significantly increased (P < .001) at all blood sampling times after glucagon administration in dogs with hyperadrenocorticism, compared with healthy dogs, and untreated and insulin-treated diabetic dogs. Five-minute C-peptide increment, C-peptide peak response, total C-peptide secretion, and, for untreated diabetic dogs, insulin peak response and total insulin secretion were significantly lower (P < .00l) in diabetic dogs, compared with healthy dogs, whereas these same parameters were significantly increased (P < .01) in dogs with hyperadrenocorticism, compared with healthy dogs, and untreated and insulin-treated diabetic dogs. Although not statistically significant, there was a trend for higher plasma C-peptide concentrations in untreated diabetic dogs compared with insulin-treated diabetic dogs during the glucagon stimulation test. Baseline C-peptide concentrations also were significantly higher (P < .05) in diabetic dogs treated with insulin for less than 6 months, compared with diabetic dogs treated for longer than 1 year. Finally, 7 of 42 diabetic dogs had baseline plasma C-peptide concentrations greater than 2 SD (ie, > 0.29 pmol/mL) above the normal mean plasma C-peptide concentration; values that were significantly higher, compared with the results in healthy dogs (P < .001) and with the other 35 diabetic dogs (P < .001). In summary, measurement of plasma C-peptide concentration during glucagon stimulation testing allowed differentiation among healthy dogs, dogs with impaired beta-cell function (ie, diabetes mellitus), and dogs with increased beta-cell responsiveness to glucagon (ie, insulin resistance). Plasma C-peptide concentrations during glucagon stimulation testing were variable in diabetic dogs and may represent dogs with type-1 and type-2 diabetes or, more likely, differences in severity of beta-cell loss in dogs with type-1 diabetes.     

Metformin reduces systemic methylglyoxal levels in type 2 diabetes

Methylglyoxal (MG) is a reactive alpha-dicarbonyl that is thought to contribute to diabetic complications either as a direct toxin or as a precursor for advanced glycation end products. It is produced primarily from triose phosphates and is detoxified to D-lactate (DL) by the glyoxalase pathway. Because guanidino compounds can block dicarbonyl groups, we have investigated the effects of the diamino biguanide compound metformin and of hyperglycemia on MG and its detoxification products in type 2 diabetes. MG and DL were measured by high-performance liquid chromatography in plasma from 57 subjects with type 2 diabetes. Of these subjects, 27 were treated with diet, sulfonylureas, or insulin (nonmetformin), and 30 were treated with metformin; 28 normal control subjects were also studied. Glycemic control was determined by HbA1c. MG was significantly elevated in diabetic subjects versus the normal control subjects (189.3 +/- 38.7 vs. 123.0 +/- 37 nmol/l, P = 0.0001). MG levels were significantly reduced by high-dosage (1,500-2,500 mg/day) metformin (158.4 +/- 44.2 nmol/l) compared with nonmetformin (189.3 +/- 38.7 nmol/l, P = 0.03) or low-dosage (< or = 1,000 mg/day) metformin (210.98 +/- 51.0 nmol/l, P = 0.001), even though the groups had similar glycemic control. Conversely, DL levels were significantly elevated in both the low- and high-dosage metformin groups relative to the nonmetformin group (13.8 +/- 7.7 and 13.4 +/- 4.6 vs. 10.4 +/- 3.9 micromol/l, P = 0.03 and 0.06, respectively). MG correlated with rising HbA1c levels (R = 0.4, P = 0.03, slope = 13.2) in the nonmetformin subjects but showed no increase with worsening glycemic control in the high-dosage metformin group (R = 0.0004, P = 0.99, slope = 0.02). In conclusion, MG is elevated in diabetes and relates to glycemic control. Metformin reduces MG in a dose-dependent fashion and minimizes the effect of worsening glycemic control on MG levels. To the extent that elevated MG levels lead to their development, metformin treatment may protect against diabetic complications by mechanisms independent of its antihyperglycemic effect.     

Preliminary characterization of glial-secreted factors responsible for the induction of high electrical resistances across endothelial monolayers in a blood-brain barrier model

Low levels of sex hormone-binding globulin (SHBG) are considered to be an indirect index of hyperinsulinemia, predicting the later onset of diabetes mellitus type 2. In the insulin resistance state and in the presence of an increased pancreatic beta-cell demand (e.g. obesity) both absolute and relative increases in proinsulin secretion occur. In the present study we investigated the correlation between SHBG and pancreatic beta-cell secretion in men with different body compositions. Eighteen young men (30.0 +/- 2.4 years) with normal glucose tolerance and body mass indexes (BMI) ranging from 22.6 to 43.2 kg/m2 were submitted to an oral glucose tolerance test (75 g) and baseline and 120-min blood samples were used to determine insulin, proinsulin and C-peptide by specific immunoassays. Baseline SHBG values were significantly correlated with baseline insulin (r = -0.58, P < 0.05), proinsulin (r = -0.47, P < 0.05), C-peptide (r = -0.55, P < 0.05) and also with proinsulin at 120 min after glucose load (r = -0.58, P < 0.05). Stepwise regression analysis revealed that proinsulin values at 120 min were the strongest predictor of SHBG (r = -0.58, P < 0.05). When subjects were divided into obese (BMI > 28 kg/m2, N = 8) and nonobese (BMI < or = 25 kg/m2, N = 10) groups, significantly lower levels of SHBG were found in the obese subjects. The obese group had significantly higher baseline proinsulin, C-peptide and 120-min proinsulin and insulin levels. For the first time using a specific assay for insulin determination, a strong inverse correlation between insulinemia and SHBG levels was confirmed. The finding of a strong negative correlation between SHBG levels and pancreatic beta-cell secretion, mainly for the 120-min post-glucose load proinsulin levels, reinforces the concept that low SHBG levels are a suitable marker of increased pancreatic beta-cell demand.     

Biological activity of C-peptide on the skin microcirculation in patients with insulin-dependent diabetes mellitus

19 insulin-dependent diabetes mellitus (IDDM) patients participated in a randomized double-blind crossover investigation to investigate the impact of human C-peptide on skin microvascular blood flow. The investigation was also carried out with 10 healthy volunteers. Blood pressure, heart rate, blood sugar, and C-peptide levels were monitored during a 60-min intravenous infusion period of C-peptide (8 pmol kg-1 min-1) or saline solution (154 mmol liter-1 NaCl), and 30 min after stopping the infusion. During the same time period, capillary blood cell velocity (CBV), laser Doppler flux (LDF), and skin temperature were assessed in the feet. In the verum arm, C-peptide levels increased after starting infusion to reach a maximum of 2.3+/-0.2 nmol liter-1 after 45 min, but remained below 0. 15 nmol liter-1 during the saline treatment. Baseline CBV was lower in diabetic patients compared with healthy subjects (147+/-3.6 vs. 162+/-4.2 micron s-1; P < 0.01). During C-peptide administration, CBV in IDDM patients increased progressively from 147+/-3.6 to 167+/-3.7 micron s-1; P < 0.001), whereas no significant change occurred during saline infusion or in healthy subjects. In contrast to the CBV measurements, the investigation of LDF, skin temperature, blood pressure, heart rate, or blood sugar did not demonstrate any significant change during the study. Replacement of human C-peptide in IDDM patients leads to a redistribution in skin microvascular blood flow levels comparable to levels in healthy subjects by increasing the nutritive CBV relative to subpapillary arteriovenous shunt flow.     

Reduced beta-adrenergic sensitivity in patients with type 1 diabetes and hypoglycemia unawareness

OBJECTIVE: We tested the hypothesis that impaired tissue sensitivity to catecholamines contributes to hypoglycemia unawareness in subjects with type 1 diabetes. RESEARCH DESIGN AND METHODS: A total of 21 subjects with type 1 diabetes underwent a standardized insulin infusion protocol to produce a stepwise decrease in plasma glucose to 45-min plateaus of 4.3, 3.6, 3.0, and 2.3 mmol/l. Glycemic thresholds, maximum responses for adrenergic and neuroglycopenic symptoms, and counterregulatory hormones were determined. Patients were classified as hypoglycemia unaware if the initiation of adrenergic symptoms occurred at a plasma glucose level 2 SD below that of nondiabetic volunteers. beta-Adrenergic sensitivity was measured as the dose of isoproterenol required to produce an increment in heart rate of 25 beats per minute above baseline (I25) in resting subjects. RESULTS: Subjects with type 1 diabetes and hypoglycemia unawareness experienced the onset of adrenergic symptoms at a lower plasma glucose level than did those with awareness (2.5+/-0.1 vs. 3.7+/-0.1 mmol/l, P < 0.001), whereas neuroglycopenic symptoms occurred at similar glucose levels (2.7+/-0.2 vs. 2.8+/- 0.1 mmol/l). The plasma glucose levels for counterregulatory hormone secretion (epinephrine 2.9+/-0.2 vs. 4.1+/-0.2 mmol/l; norepinephrine 2.7+/-0.1 vs. 3.2+/-0.2 mmol/l; cortisol 2.5+/-0.2 vs. 3.3+/-0.2 mmol/l, P < 0.01) were also lower in subjects with unawareness. The maximal epinephrine (1,954+/-486 vs. 5,332+/- 1,059 pmol/l, P < 0.01), norepinephrine (0.73 +/- 0.14 vs. 1.47+/-0.21 nmol/l, P = 0.04), and cortisol (276+/-110 vs. 579+/-83 nmol/l, P < 0.01) responses were reduced in the unaware group. I25 was greater in unaware subjects than in subjects without unawareness (1.5+/-0.3 vs. 0.8+/-0.2 microg), where I25 was not different from that of controls (0.8 +/-0.2 microg). CONCLUSIONS: We conclude that subjects with type 1 diabetes and hypoglycemia unawareness have reduced beta-adrenergic sensitivity, which may contribute to their impaired adrenergic warning symptoms during hypoglycemia.     

Altered insulin secretory responses to glucose in diabetic and nondiabetic subjects with mutations in the diabetes susceptibility gene MODY3 on chromosome 12

One form of maturity-onset diabetes of the young (MODY) results from mutations in a gene, designated MODY3, located on chromosome 12 in band q24. The present study was undertaken to define the interactions between glucose and insulin secretion rate (ISR) in subjects with mutations in MODY3. Of the 13 MODY3 subjects, six subjects with normal fasting glucose and glycosylated hemoglobin and seven overtly diabetic subjects were studied as were six nondiabetic control subjects. Each subject received graded intravenous glucose infusions on two occasions separated by a 42-h continuous intravenous glucose infusion designed to prime the beta-cell to secrete more insulin in response to glucose. ISRs were derived by deconvolution of peripheral C-peptide levels. Basal glucose levels were higher and insulin levels were lower in MODY3 subjects with diabetes compared with nondiabetic subjects or with normal healthy control subjects. In response to the graded glucose infusion, ISRs were significantly lower in the diabetic subjects over a broad range of glucose concentrations. ISRs in the nondiabetic MODY3 subjects were not significantly different from those of the control subjects at plasma glucose levels <8 mmol/l. As glucose rose above this level, however, the increase in insulin secretion in these subjects was significantly reduced. Administration of glucose by intravenous infusion for 42 h resulted in a significant increase in the amount of insulin secreted over the 5-9 mmol/l glucose concentration range in the control subjects and nondiabetic MODY3 subjects (by 38 and 35%, respectively), but no significant change was observed in the diabetic MODY3 subjects. In conclusion, in nondiabetic MODY3 subjects insulin secretion demonstrates a diminished ability to respond when blood glucose exceeds 8 mmol/l. The priming effect of glucose on insulin secretion is preserved. Thus, beta-cell dysfunction is present before the onset of overt hyperglycemia in this form of MODY. The defect in insulin secretion in the nondiabetic MODY3 subjects differs from that reported previously in nondiabetic MODY1 or mildly diabetic MODY2 subjects.     

Acute lowering of plasma fatty acids lowers basal insulin secretion in diabetic and nondiabetic subjects

The objective of this study was to determine whether basal plasma free fatty acid (FFA) concentrations affect basal insulin secretion rates (ISRs). Effects of FFA levels on basal ISRs were evaluated by lowering basal plasma FFA levels with nicotinic acid (NA) (100-150 mg p.o., q 30 min x 4 h) in type 2 diabetic patients and in normal volunteers. Lowering of FFAs (from approximately 600 to approximately 100 micromol/l) lowered ISRs in type 2 diabetic patients during isoglycemic clamping (from 139 to 101 pmol/min; -23%; P < 0.02) and euglycemic clamping (from 99 to 63 pmol/min; -36%; P < 0.03) and in normal subjects during euglycemic clamping (from 127 to 96 pmol/min; -25%; P < 0.03). In addition, peripheral insulin concentrations decreased by approximately 30% in diabetic and nondiabetic subjects. NA had no direct effect on ISRs; that is, NA did not change ISRs when plasma FFAs were prevented from decreasing with a lipid/heparin infusion. We concluded that 1) basal plasma FFAs exerted physiologically important, long-lasting effects supporting 25-33% of basal insulin secretion in nondiabetic and diabetic subjects; 2) basal plasma FFAs were responsible for some of the hyperinsulinemia in normoglycemic obese subjects; and 3) NA had no direct effect on insulin secretion.     

Highly specific radioimmunoassay for human insulin based on immune exclusion of all insulin precursors

We describe a rapid and simple insulin RIA in which proinsulin and conversion intermediates do not interfere. Three monoclonal antibodies (S1, S2, and S53) were selected for their specificity (directed, respectively, against the B10 region, the junction between A chain and C-peptide, and the junction between B chain and C-peptide), their affinity constant (approximately 10(10) L/mol), and their interactive properties in mixture. S2 and S53 were able to bind simultaneously to the same proinsulin molecule, whereas neither could bind simultaneously with S1. Preincubation of serum samples with an excess of S2 resulted in capture of proinsulin and conversion intermediates modified at the junction between B chain and C-peptide into immune complexes that no longer reacted with S1. Similarly, preincubation with S53 prevented proinsulin and conversion intermediates modified at the junction between A chain and C-peptide from reacting with S1. Preincubation with an excess of both S2 and S53 left insulin as the sole reactant with S1. Thus, separation of insulin precursors from insulin by mutually exclusive antibodies is feasible, and on the basis of this new principle, a highly specific RIA for insulin was designed. The detection limit was 11 pmol/L, and the inter- and intraassay coefficients of variation were 11% and 5%, respectively. The potential of the assay for use in clinical studies was verified by application to serum samples from control subjects and patients with diabetes or insulinoma.     

Novel D-ring analogues of podophyllotoxin as potent anti-cancer agents

Insulin is one of the hormonal regulators of leptin synthesis and participates in adipose tissue maintenance. The present study was undertaken to clarify the association of endogenous insulin secretion and mode of therapy with body fat and serum leptin levels in diabetic subjects. We measured the fasting serum C-peptide level, as an estimate of endogenous insulin secretion, and the serum leptin level in 176 Japanese diabetic subjects (79 men and 97 women; age, 55.9+/-14.3 years; body mass index [BMI], 23.8+/-4.1 kg/m2 [mean+/-SD]). Thirty-one subjects were treated with diet therapy alone, 66 with sulfonylurea (SU), and 79 with insulin (including 29 with type I diabetes mellitus). Body fat was analyzed by the impedance method. Serum leptin levels significantly correlated with the BMI and body fat and were higher in women, mainly because of their greater body fat. Serum C-peptide concentrations positively correlated with body fat and serum leptin in subjects treated with diet and SU. In insulin-treated type II diabetic subjects, both serum C-peptide and the daily insulin dose were weakly associated with body fat and serum leptin. In those subjects, despite a lower percent body fat and body fat mass, serum leptin concentrations (10.3+/-8.4 ng/mL) were comparable to the levels in subjects treated with diet (8.8+/-8.5 ng/mL). When compared within the same BMI and body fat groups (BMI 20 to 25 and > 25 kg/m2) including the control subjects matched for age and sex, serum leptin levels were higher in insulin-treated type II diabetic subjects versus the control subjects and diabetic patients treated with diet or SU. Stepwise regression analysis for all of the diabetic subjects showed that both the serum C-peptide level and exogenous insulin administration, as well as the BMI, gender, and age, were determinants of the serum leptin level. In conclusion, endogenous insulin secretion is closely associated with body fat and serum leptin in diabetic subjects treated with diet therapy and SU. In Japanese insulin-treated type II diabetic subjects, both endogenous and exogenous insulin are associated with body fat and serum leptin, which is maintained at levels comparable to or somewhat higher than the levels in control subjects and diabetic patients treated without insulin.     

The heart of anorexic adolescents]

The study of diabetic neuropathy has been primarily in Europids, despite the high prevalence of diabetes in other populations. We set out to ascertain the prevalence of diabetic neuropathy and its risk factors in the island nation of Mauritius. Population surveys were carried out in 1987 and 1992 in Mauritius to establish the prevalence of Type 2 diabetes. In the second survey, vibration perception threshold (VPT) was also measured at the great toe in 847 subjects with diabetes, 204 subjects with impaired glucose tolerance and 127 subjects with normal glucose tolerance. Neuropathy was defined as levels of VPT exceeding the mean plus 2 standard deviations defined separately for three age groups of Mauritian non-diabetic subjects. Risk factors for neuropathy were identified cross sectionally from the 1992 data, and longitudinally from the 1987 data. Neuropathy was detected in 8.3% of the 847 diabetic subjects (12.7%) of those with known diabetes, and 3.6% of those with newly diagnosed diabetes). Logistic regression identified diabetes duration (odds ratio [95% CI]; 1.08 [1.04-1.13] per year, P=0.0002), treatment with insulin or oral hypoglycaemic agents (2.63 [1.36-5.09], P=0.004) and greater height (1.36 [1.19-1.57] per 5 cm, P < 0.001) as risk factors for neuropathy, in the cross sectional analysis. In the longitudinal analysis, diabetes duration (1.11 [1.05-1.18] per year, P=0.001), fasting glucose (1.12 [1.03-1.22] per mmol/l, P=0.01) and height (1.23 [1.03-1.45] per 5 cm, P=0.02) were associated with neuropathy. A lower 2-h plasma insulin was also associated with neuropathy in the longitudinal analysis. The prevalence of diabetic neuropathy in Mauritius is the lowest reported for any population, but the risk factors associated with it are similar to those previously found.     

Assessment of insulin sensitivity and secretion with the labelled intravenous glucose tolerance test: improved modelling analysis

A new modelling analysis was developed to assess insulin sensitivity with a tracer-modified intravenous glucose tolerance test (IVGTT). IVGTTs were performed in 5 normal (NGT) and 7 non-insulin-dependent diabetic (NIDDM) subjects. A 300 mg/kg glucose bolus containing [6,6-(2)H2]glucose was given at time 0. After 20 min, insulin was infused for 5 min (NGT, 0.03; NIDDM, 0.05 U/kg). Concentrations of tracer, glucose, insulin and C-peptide were measured for 240 min. A circulatory model for glucose kinetics was used. Glucose clearance was assumed to depend linearly on plasma insulin concentration delayed. Model parameters were: basal glucose clearance (Cl(b)), glucose clearance at 600 pmol/l insulin concentration (Cl600), basal glucose production (Pb), basal insulin sensitivity index (BSI = Cl(b)/basal insulin concentration); incremental insulin sensitivity index (ISI = slope of the relationship between insulin concentration and glucose clearance). Insulin secretion was calculated by deconvolution of C-peptide data. Indices of basal pancreatic sensitivity (PSIb) and first (PSI1) and second-phase (PSI2) sensitivity were calculated by normalizing insulin secretion to the prevailing glucose levels. Diabetic subjects were found to be insulin resistant (BSI: 2.3 +/- 0.6 vs 0.76 +/- 0.18 ml x min(-1) x m(-2) x pmol/l(-1), p < 0.02; ISI: 0.40 +/- 0.06 vs 0.13 +/- 0.05 ml x min(-1) x m(-2) x pmol/l(-1), p < 0.02; Cl600: 333 +/- 47 vs 137 +/- 26 ml x min(-1) x m(-2), p < 0.01; NGT vs NIDDM). Pb was not elevated in NIDDM (588 +/- 169 vs 606 +/- 123 micromol x min(-1) x m(-2), NGT vs NIDDM). Hepatic insulin resistance was however present as basal glucose and insulin were higher. PSI1 was impaired in NIDDM (67 +/- 15 vs 12 +/- 7 pmol x min x m(-2) x mmol/l(-1), p < 0.02; NGT vs NIDDM). In NGT and in a subset of NIDDM subjects (n = 4), PSIb was inversely correlated with BSI (r = 0.95, p < 0.0001, log transformation). This suggests the existence of a compensatory mechanism that increases pancreatic sensitivity in the presence of insulin resistance, which is normal in some NIDDM subjects and impaired in others. In conclusion, using a simple test the present analysis provides a rich set of parameters characterizing glucose metabolism and insulin secretion, agrees with the literature, and provides some new information on the relationship between insulin sensitivity and secretion.     

Effect of continuous subcutaneous insulin infusion with lispro on hepatic responsiveness to glucagon in type 1 diabetes

OBJECTIVE: People with type 1 diabetes frequently develop a blunted counterregulatory hormone response to hypoglycemia coupled with a decreased hepatic response to glucagon, and consequently, they have an increased risk of severe hypoglycemia. We have evaluated the effect of insulin lispro (Humalog) versus regular human insulin (Humulin R) on the hepatic glucose production (HGP) response to glucagon in type 1 diabetic patients on intensive insulin therapy with continuous subcutaneous insulin infusion (CSII). RESEARCH DESIGN AND METHODS: Ten subjects on CSII were treated for 3 months with lispro and 3 months with regular insulin in a double-blind randomized crossover study After 3 months of treatment with each insulin, hepatic sensitivity to glucagon was measured in each subject. The test consisted of a 4-h simultaneous infusion of somatostatin (450 microg/h) to suppress endogenous glucagon, regular insulin (0.15 mU x kg(-1) x min(-1)), glucose at a variable rate to maintain plasma glucose near 5 mmol/l, and D-[6,6-2H2]glucose to measure HGP During the last 2 h, glucagon was infused at 1.5 ng x kg(-1) x min(-1). Eight nondiabetic people served as control subjects. RESULTS: During the glucagon infusion period, free plasma insulin levels in the diabetic subjects were 71.7+/-1.6 vs. 74.8+/-0.5 pmol/l after lispro and regular insulin treatment, with plasma glucagon levels of 88.3+/-1.8 and 83.7+/-1.5 ng/l for insulin:glucagon ratios of 2.8 and 3.0. respectively (NS). However, plasma glucose increased to 9.2+/-1.1 mmo/l after lispro insulin compared with 7.1+/-0.9 mmol/l after regular insulin (P < 0.01), and the rise in HGP was 5.7 +/-2.8 micromol x kg(-1) x min(-1) after lispro insulin versus 3.1+/-2.9 micromol x kg(-1) x min(-1) after regular insulin treatment (P=0.02). In the control subjects, HGP increased by 10.7+/-4.2 micromol x kg(-1) x min(-1) under glucagon infusion. CONCLUSIONS: Insulin lispro treatment by CSII was associated with a heightened response in HGP to glucagon compared with regular human insulin. This suggests that insulin lispro increases the sensitivity of the liver to glucagon and could potentially decrease the risk of severe hypoglycemia.     

Biomedical imaging and the evolution of medical informatics

BACKGROUND: Data concerning the insulin status in the early phase of NIDDM are controversial. PATIENTS AND METHOD: Since this has therapeutical implications, ten patients were identified with new-onset type 2 diabetes, defined by fasting blood glucose concentrations below 120 mg/dl, no previous history of diabetes and venous blood glucose concentrations at 120 min of an oral glucose tolerance test above 200 mg/dl (x 262 +/- 15 mg/dl) ("diabetic glucose tolerance"). Ten subjects with normal glucose tolerance and no familial history of NIDDM, who were matched for gender, age (n: 56 +/- 2 years, D: 61 +/- 5) and BMI (n: 28 +/- 1, D: 28 +/- 1), served as control group. Serum insulin was measured using a double-antibody sandwich-test (no cross-reaction with proinsulin and C-peptide) at 0, 30 and 120 min of an oGTT. RESULT: In the diabetic group, basal insulin levels were found to be elevated 1.7-fold (n: 7.9 +/- 1.4 uU/ml, D: 13.3 +/- 1.4, p = 0.03), 30 min values were the same in both groups and the 120 min value was 4.6-fold higher in the diabetic group (n: 33.9 +/- 8.7, D: 156.2 +/- 27.4, p = 0.0008). CONCLUSION: Thus, in new-onset diabetes, in the early phase of an oGTT (30 min) both insulin secretion and action are reduced, in the second phase (120 min) severe insulin resistance predominates at maximally stimulated secretion. These findings underline the therapeutical strategy in these patients, to reduce postprandial blood glucose increments and improve insulin resistance by diet and, if necessary, pharmacologically.     

Psychological and socio-medical aspects of HIV/AIDS: a reflection on publications in AIDS care (1989-1995)

Cardiovascular disease is the leading cause of death in non-insulin dependent diabetes mellitus and first degree relatives of such patients are at increased risk of developing diabetes and cardiovascular disease. The aim of the present study was to determine whether lipid abnormalities occur in normoglycaemic relatives of non-insulin dependent diabetic patients. Cholesterol, triglycerides, apolipoprotein A-I and apolipoprotein B concentrations were measured in serum; the lipoprotein fractions very low density, intermediate density, low density and high density lipoprotein were prepared by sequential flotation ultracentrifugation and their composition investigated. The groups were matched for age, sex and blood glucose concentrations although the relatives (n = 126) were more insulin resistant as determined using the homeostasis model assessment method [1.9 (0.8-9.0) vs 1.6 (0.4-4.9) mmol/mU per l (mean [95% confidence intervals]); p < 0.001] and had greater body mass indices [26.6 (4.1) vs 24.8 (3.9) (mean [S.D.]); p = 0.001] than control subjects (n = 126). Relatives had higher serum apolipoprotein B concentrations than control subjects [0.9 (0.3) vs 0.8 (0.3) g/l, p = 0.02) and lower serum apolipoprotein A-I concentrations (1.4 (0.3) vs 1.5 (0.3), p = 0.02). In multivariate linear regression analysis of all subjects log insulin resistance (p = 0.0001), age (p = 0.002) and waist:hip ratio (p = 0.01) were independent predicators of apolipoprotein B concentrations while waist:hip ratio (p < 0.001) and smoking status (p = 0.002) were independent predictors of apolipoprotein A-I concentrations. Lipoprotein composition (measured in a subgroup of 76 control subjects and 88 relatives), serum cholesterol and serum triglyceride concentrations did not differ between the groups. We conclude that atherogenic apolipoprotein abnormalities occur in normoglycaemic relatives of non-insulin dependent diabetic patients.