Glucagon-like peptide 1 improves the ability of the beta-cell to sense and respond to glucose in subjects with impaired glucose tolerance

Impaired glucose tolerance (IGT) and NIDDM are both associated with an impaired ability of the beta-cell to sense and respond to small changes in plasma glucose concentrations. The aim of this study was to establish if glucagon-like peptide 1 (GLP-1), a natural enteric peptide and potent insulin secretagogue, improves this defect. Two weight-matched groups, one with eight subjects having IGT (2-h glucose, 10.1 +/- 0.3 mmol/l) and another with seven subjects with diet-treated NIDDM (2-h glucose, 14.5 +/- 0.9 mmol/l), were studied on two occasions during a 12-h oscillatory glucose infusion, a sensitive test of the ability of the beta-cell to sense and respond to glucose. Glucose was infused with a mean rate of 4 mg x kg(-1) x min(-1), amplitude 33% above and below the mean rate, and periodicity of 144 min, with infusion of saline or GLP-1 at 0.4 pmol x kg(-1) x min(-1) for 12 h. Mean glucose levels were significantly lower in both groups during the GLP-1 infusion compared with during saline infusion: 9.2 +/- 0.4 vs. 6.4 +/- 0.1 mmol/l in the IGT subjects (P < 0.0004) and 14.6 +/- 1.0 vs. 9.3 +/- 0.7 mmol/l in NIDDM subjects (P < 0.0002). Despite this significant reduction in plasma glucose concentration, insulin secretion rates (ISRs) increased significantly in IGT subjects (513.3 +/- 77.6 vs. 583.1 +/- 100.7 pmol/min; P < 0.03), with a trend toward increasing in NIDDM subjects (561.7 +/- 122.16 vs. 642.8 +/- 128 pmol/min; P = 0.1). These results were compatible with enhanced insulin secretion in the presence of GLP-1. Spectral power was used as a measure of the ability of the beta-cell to secrete insulin in response to small changes in the plasma glucose concentration during the oscillatory infusion. Spectral power for ISR increased from 2.1 +/- 0.9 during saline infusion to 7.4 +/- 1.3 during GLP-1 infusion in IGT subjects (P < 0.004), but was unchanged in NIDDM subjects (1.0 +/- 0.4 to 1.5 +/- 0.6; P = 0.3). We concluded that low dosage GLP-1 improves the ability of the beta-cell to secrete insulin in both IGT and NIDDM subjects, but that the ability to sense and respond to subtle changes in plasma glucose is improved in IGT subjects, with only a variable response in NIDDM subjects. Beta-cell dysfunction was improved by GLP-1 infusion, suggesting that early GLP-1 therapy may preserve beta-cell function in subjects with IGT or mild NIDDM.     

Forearm nitric oxide balance, vascular relaxation, and glucose metabolism in NIDDM patients

Endothelium-dependent and -independent vascular responses were assessed in 10 NIDDM patients and 6 normal subjects with no evidence of atherosclerotic disease. Changes in forearm blood flow and arteriovenous (AV) serum nitrite/nitrate (NO2-/NO3-) concentrations were measured in response to intra-arterial infusion of acetylcholine (ACh) (7.5, 15, 30 microg/min, endothelium-dependent response) and sodium nitroprusside (SNP) (0.3, 3, 10 microg/min, endothelium-independent response). Insulin sensitivity (determined by minimal model intravenous glucose tolerance test) was lower in NIDDM patients (0.82 +/- 0.20 vs. 2.97 +/- 0.29 10(4) min x microU(-1) x ml(-1); P < 0.01). Baseline forearm blood flow (4.8 +/- 0.3 vs. 4.4 +/- 0.3 ml x 100 ml(-1) tissue x min(-1); NS), mean blood pressure (100 +/- 4 vs. 92 +/- 4 mmHg; NS), and vascular resistance (21 +/- 1 vs. 21 +/- 1 units; NS), as well as their increments during ACh and SNP, infusion were similar in both groups. No difference existed in baseline NO2-/NO3- concentrations (4.09 +/- 0.33 [NIDDM patients] vs. 5.00 +/- 0.48 micromol/l [control subjects]; NS), their forearm net balance (0.31 +/- 0.08 [NIDDM patients] vs. 0.26 +/- 0.08 micromol/l x 100 ml(-1) tissue x min(-1); NS), and baseline forearm glucose uptake. During ACh infusion, both NO2- and NO3- concentrations and net balance significantly increased in both groups, whereas glucose uptake increased only in control subjects. When data from NIDDM and control groups were pooled together, a correlation was found between the forearm AV NO2- and NO3- differences and blood flow (r = 0.494, P = 0.024). On the contrary, no correlation was evident between NO2- and NO3- concentrations or net balance and insulin sensitivity. In summary, 1) no difference existed in basal and ACh-stimulated NO generation and endothelium-dependent relaxation between uncomplicated NIDDM patients and control subjects; 2) in both NIDDM and control groups, forearm NO2- and NO3- net balance following ACh stimulation was related to changes in the forearm blood flow; and 3) ACh-induced increase in forearm blood flow was associated with an increase in glucose uptake only in control subjects but not in NIDDM patients. In conclusion, our results argue against a role of impaired NO generation and blood flow regulation in determining the insulin resistance of uncomplicated NIDDM patients; rather, it supports an independent insulin regulation of hemodynamic and metabolic effects.     

Long-term efficacy of a self-retaining intraurethral catheter for the treatment of prostatic obstruction

The aim of the present study was to estimate insulin secretion, insulin sensitivity (SI), and glucose effectiveness at basal insulin (SG) in subjects with bulimia nervosa. Eight bulimic patients and eight age-, body mass index-, and sex-matched healthy control subjects without a family history of diabetes were studied. The subjects all had normal glucose tolerance. They underwent a modified frequently sampled intravenous glucose tolerance test; glucose (300 mg/kg body weight) was administered, and insulin (4 mU/kg body weight/min) was infused from 20 to 25 minutes after administration of glucose. SI and SG were estimated by Bergman's minimal model method. Basal insulin (27 +/- 3 v 45 +/- 3 pmol/L) was significantly lower in bulimic patients than in normal controls (P < .05), but basal glucose was similar between the two groups (4.5 +/- 0.1 v 4.9 +/- 0.1 mmol/L, P > .05). The glucose disappearance rate (KG) and acute insulin response to glucose estimated by the intravenous glucose tolerance test (AIR(glucose)) were similar between the two groups (KG, 1.35 +/- 0.29 v 2.20 +/- 0.21 min(-1), P > .05; AIR(glucose), 2,920 +/- 547 v 2,368 +/- 367 pmol/L x min, P > .05). No significant difference was observed in SI between the two groups (1.34 +/- 0.18 v 1.25 +/- 0.20 x 10(-4) x min(-1) x pmol/L(-1), P > .05). On the other hand, glucose effectiveness at basal (SG) and zero (GEZI) insulin was significantly diminished in comparison to normal controls (SG, 0.011 +/- 0.002 v 0.024 +/- 0.002 min(-1), P < .01; GEZI, 0.008 +/- 0.002 v 0.017 +/- 0.003 min(-1), P < .01). Thus, bulimic patients with normal glucose tolerance without a family history of diabetes were characterized by normal insulin secretion, normal SI, and reduced SG and GEZI.     

Effect of glibenclamide on insulin release at moderate and high blood glucose levels in normal man

Insulin release occurs in two phases; sulphonylurea derivatives may have different potencies in stimulating first- and second-phase insulin release. We studied the effect of glibenclamide on insulin secretion at submaximally and maximally stimulating blood glucose levels with a primed hyperglycaemic glucose clamp. Twelve healthy male subjects, age (mean +/- SEM) 22.5 +/- 0.5 years, body mass index (BMI) 21.7 +/- 0.6 kgm-2, were studied in a randomized, double-blind study design. Glibenclamide 10 mg or placebo was taken before a 4-h hyperglycaemic clamp (blood glucose 8 mmol L-1 during the first 2 h and 32 mmol L-1 during the next 2 h). During hyperglycaemic clamp at 8 mmol L-1, the areas under the delta insulin curve (AUC delta insulin, mean +/- SEM) from 0 to 10 min (first phase) were not different: 1007 +/- 235 vs. 1059 +/- 261 pmol L-1 x 10 min (with and without glibenclamide, P = 0.81). However, glibenclamide led to a significantly larger increase in AUC delta insulin from 30 to 120 min (second phase): 16087 +/- 4489 vs. 7107 +/- 1533 pmol L-1 x 90 min (with and without glibenclamide respectively, P < 0.03). The same was true for AUC delta C-peptide no difference from 0 to 10 min but a significantly higher AUC delta C-peptide from 30 to 120 min on the glibenclamide day (P < 0.01). The M/I ratio (mean glucose infusion rate divided by mean plasma insulin concentration) from 60 to 120 min, a measure of insulin sensitivity, did not change: 0.26 +/- 0.05 vs. 0.22 +/- 0.03 mumol kg-1 min-1 pmol L-1 (with and without glibenclamide, P = 0.64). During hyperglycaemic clamp at 32 mmol L-1, the AUC delta insulin from 120 to 130 min (first phase) was not different on both study days: 2411 +/- 640 vs. 3193 +/- 866 pmol L-1 x 10 min (with and without glibenclamide, P = 0.29). AUC delta insulin from 150 to 240 min (second phase) also showed no difference: 59623 +/- 8735 vs. 77389 +/- 15161 pmol L-1 x 90 min (with and without glibenclamide, P = 0.24). AUC delta C-peptide from 120 to 130 min and from 150 to 240 min were slightly lower on the glibenclamide study day (both P < 0.04). The M/I ratio from 180 to 240 min did not change: 0.24 +/- 0.04 vs. 0.30 +/- 0.07 mumol kg-1 min-1 pmol L-1 (with and without glibenclamide, P = 0.25). In conclusion, glibenclamide increases second-phase insulin secretion only at a submaximally stimulating blood glucose level without enhancement of first-phase insulin release and has no additive effect on insulin secretion at maximally stimulating blood glucose levels. Glibenclamide did not change insulin sensitivity in this acute experiment.     

Self-assembled hydrogel nanoparticle of cholesterol-bearing pullulan as a carrier of protein drugs: complexation and stabilization of insulin

The effects of the acute insulin response to glucose (AIRg), insulin sensitivity (SI), and glucose effectiveness at zero insulin (GEZI) on intravenous glucose tolerance were studied in 94 non elderly healthy subjects with a wide range of body mass index (BMI). Conrad's coefficient of glucose assimilation (KG) was calculated between 10 and 19 minutes of an intravenous glucose tolerance test. Both SI and GEZI were estimated using Bergman's minimal model. AIRg was calculated as the area under the insulin curve above basal between 0 and 10 minutes, and the suprabasal insulin effect was determined by the product of SI x AIRg. Stepwise multiple regression showed that the combined effect of SI x AIRg and GEZI explained 67% of the KG index variance. Division of the sample into tertiles according to KG shows that subjects with the lowest KG (KG < 1.32 min[-1]) had the lowest AIRg (2,832 +/- 1,362 v 6,510 +/- 4,410 [pmol x L(-1)] min, P = .0005), the lowest GEZI (0.092 +/- 0.06 v 0.179 +/- 0.09 min(-1), P = .0004), and the lowest SI x AIRg (0.014 +/- 0.008 v 0.022 +/- 0.01 min(-1), P = .00001), and were the oldest (41 +/- 10 v 31 +/- 10 years, P = .002) compared with subjects with the highest KG (KG > 1.8 min[-1]). However, no differences in SI (4.86 +/- 4.6 v 6.5 +/- 3.7 min(-1) [pmol x L(-1)],(-1) NS) or BMI (29.6 +/- 5.0 v 26.6 +/- 5.9 kg x m(-2), NS) were observed. These results did not vary when lean and obese subjects were analyzed separately. Age correlated significantly only with SI x AIRg. In conclusion, although the main factors that determine intravenous glucose tolerance are the suprabasal insulin effect and GEZI, worsening of the KG index depends on inadequate insulin secretion for the degree of insulin sensitivity and lower non-insulin-mediated glucose uptake. Age seems to be another factor in the worsening of intravenous glucose tolerance through a lower suprabasal insulin effect.     

Hyperamylinemia is associated with hyperinsulinemia in the glucose-tolerant, insulin-resistant offspring of two Mexican-American non-insulin-dependent diabetic parents

Several investigations have presented evidence that amylin inhibits insulin secretion and induces insulin resistance both in vitro and in vivo. However, basal and postmeal amylin concentrations proved similar in non-insulin-dependent diabetes mellitus (NIDDM) patients and controls. Since hyperglycemia may alter both amylin and insulin secretion, we examined basal and glucose-stimulated amylin secretion in eight glucose-tolerant, insulin-resistant Mexican-American subjects with both parents affected with NIDDM (offspring) and correlated the findings with the insulin sensitivity data acquired by an insulin clamp. Eight offspring and eight Mexican-Americans without any family history of diabetes (controls) underwent measurement of fat free mass (3H2O dilution method), 180-minutes, 75-g oral glucose tolerance test (OGTT), and 40-mU/m2, 180-minute euglycemic insulin clamp associated with 3H-glucose infusion and indirect calorimetry. Fasting amylin was significantly increased in offspring versus controls (11.5 +/- 1.4 v 7.0 +/- 0.8 pmol/L, P < .05). After glucose ingestion, both total (3,073 +/- 257 v 1,870 +/- 202 pmol.L-1.min-1, P < .01) and incremental (1,075 +/- 170 v 518 +/- 124 pmol.L-1.min-1, P < .05) areas under the curve (AUCs) of amylin concentration were significantly greater in offspring. The amylin to insulin molar ratio was similar in offspring and controls at all time points. Basal and postglucose insulin and C-peptide concentrations were significantly increased in the offspring. No correlation was found between fasting amylin, postglucose amylin AUC or IAUC, and any measured parameter of glucose metabolism during a euglycemic-hyperinsulinemic clamp (total glucose disposal, 7.21 +/- 0.73 v 11.03 +/- 0.54, P < .001; nonoxidative glucose disposal, 3.17 +/- 0.59 v 6.33 +/- 0.56, P < .002; glucose oxidation, 4.05 +/- 0.46 v 4.71 +/- 0.21, P = NS; hepatic glucose production, 0.29 +/- 0.16 v 0.01 +/- 0.11, P = NS; all mg.min-1.kg-1 fat-free mass, offspring v controls). In conclusion, these data do not support a causal role for amylin in the genesis of insulin resistance in NIDDM.     

NIDDM in the elderly

OBJECTIVE: We conducted this study to assess the metabolic alterations in elderly patients with NIDDM. RESEARCH DESIGN AND METHODS: Healthy, lean (n = 15; age, 73 +/- 1 years; BMI, 23.8 +/- 0.5 kg/m2), and obese (n = 10; age, 71 +/- 1 years; BMI, 28.9 +/- 1.2 kg/m2) control subjects and lean (n = 10; age, 75 +/- 2 years; BMI, 24.0 +/- 0.5 kg/m2) and obese (n = 23; age, 73 +/- 1 years; BMI, 29.9 +/- 0.7 kg/m2) NIDDM patients underwent a 3-h glucose tolerance test, a 2-h hyperglycemic glucose clamp study, and a 3-h euglycemic glucose clamp study with tritiated glucose methodology to measure glucose production and disposal rates. RESULTS: Waist-to-hip ratio (WHR) was greater in both lean and obese NIDDM patients than in control subjects. Insulin responses during the oral glucose tolerance test were similar in obese subjects (control subjects: 417 +/- 64 pmol/l; NIDDM patients: 392 +/- 47 pmol/l) but were reduced in lean NIDDM patients (control subjects: 374 +/- 34 pmol/l; NIDDM patients: 217 +/- 20 pmol/l, P < 0.01). Lean and obese NIDDM patients had absent first-phase insulin responses during the hyperglycemic clamp. Second-phase insulin responses were reduced in lean (P < 0.01 vs. control subjects by analysis of variance) but not obese NIDDM patients. Hepatic glucose output was not increased in lean or obese NIDDM patients. Steady-state (150-180 min) glucose disposal rates were 16% less in lean NIDDM patients (control subjects: 8.93 +/- 0.37 mg.kg LBM (lean body mass)-1.min-1; NIDDM patients: 7.50 +/- 0.28 mg.kg LBM-1.min-1, P < 0.05) and 37% less in obese NIDDM patients (control subjects: 8.17 +/- 0.38 mg.kg LBM-1.min-1; NIDDM patients: 5.03 +/- 0.36 mg.kg LBM-1.min-1, P < 0.001). CONCLUSIONS: Lean elderly NIDDM patients have a profound impairment in glucose-induced insulin release but mild resistance to insulin-mediated glucose disposal. Obese elderly NIDDM patients have adequate circulating insulin, but marked resistance to insulin-mediated glucose disposal. Hepatic glucose output is not increased in elderly NIDDM patients.     

Alterations in glucose metabolism in the elderly patient with diabetes

OBJECTIVE: To determine the alterations in glucose metabolism in elderly patients with NIDDM. RESEARCH DESIGN AND METHODS: We studied 9 healthy elderly control subjects (73 +/- 1 yr of age; body mass index 25.7 +/- 0.4 kg/m2) and 9 untreated elderly NIDDM patients (72 +/- 2 yr of age; BMI 25.9 +/- 0.5 kg/m2). Each subject underwent a 3-h oral glucose tolerance test (40 g/m2); a 2-h hyperglycemic glucose clamp study (glucose 5.4 mM above basal); and a 4-h euglycemic insulin clamp (40 mM.m2.min-1). Tritiated glucose methodology was used to measure glucose production and disposal rates during the euglycemic clamp. RESULTS: Patients with NIDDM had a higher fasting glucose (9.3 +/- 0.3 vs. 5.1 +/- 0.1 mM in control subjects vs. NIDDM patients, respectively, P < 0.001) and a greater area under the curve for glucose during the OGTT (16.0 +/- 0.6 vs. 6.7 +/- 0.3 mM in control subjects vs. NIDDM patients, respectively, P < 0.01) than the healthy control subjects. During the hyperglycemic clamp, patients with NIDDM had an absent first-phase insulin response (112 +/- 6 vs. 250 +/- 31 pM in control subjects vs. NIDDM patients, respectively, P < 0.01), and a blunted second-phase insulin response (159 +/- 11 vs. 337 +/- 46 pM in control subjects vs. NIDDM patients, respectively, P < 0.01). Before the euglycemic clamp, fasting insulin (99 +/- 5 vs. 111 +/- 10 pM in control subjects vs. NIDDM patients, respectively) and hepatic glucose production (11.8 +/- 0.7 vs. 11.5 +/- 0.5 mumol.kg-1-min-1 in control subjects vs. NIDDM patients, respectively) were similar. Steady-state (180-240 min) glucose disposal rates during the euglycemic clamp were slightly, but not significantly, higher in the normal control subjects (36.5 +/- 1.1 vs. 33.1 +/- 1.9 mumol.kg-1-min-1 in control subjects vs. NIDDM patients, respectively, NS). CONCLUSIONS: We conclude that NIDDM in nonobese elderly subjects is characterized by a marked impairment in insulin release. This may be attributable to the toxic effects of chronic hyperglycemia on the beta-cell. When compared with age-matched control subjects, the NIDDM patients showed no increase in fasting insulin or hepatic glucose production, and insulin resistance was mild.     

Mechanism of the diabetogenic action of cyclosporin A

To investigate the mechanism of diabetogenic action of cyclosporin A (CsA), 7 male Wistar albino rats received 10 mg/kg/day of the drug for 4 weeks (CsA). The results were compared with controls (C); blood CsA levels measured weekly remained stable throughout the experiment (mean +/- SEM) (X = 2657.9+/-155.1 ng/ml). Intravenous glucose load (0.75 g/kg) performed after 2 weeks of CsA therapy showed glucose intolerance in treated animals as evaluated by the glucose area under the curve (CsA = 409.2+/-17.8 vs. C = 313.3+/-12.6 umol x ml(-1) x min(-1)) (p < 0.05) with insulin levels being similar in the two groups (CsA = 8603.9+/-1645.5 vs. C = 9571.9+/-828.5 pmol x ml(-1) x min(-1)). After 4 weeks of CsA administration, glucose intolerance was maintained (CsA = 398.6+/-35.6 vs. C = 301.7+/-23.0 umol x ml(-1) x min(-1)) (p < 0.05) associated with a significant decrease in insulin secretion (CsA = 4404.9+/-2392.0 vs. C = 10075.9+/-2861.0 pmol x ml(-1) x min(-1) (p < 0.05). These results suggest that CsA induced a state of insulin resistance preceding the failure of insulin secretion. After 4 weeks, the pancreatic insulin content was also decreased (CsA = 0.7+/-0.1 vs. C = 1.4+/-0.5 mU/mg) (p < 0.05). Maximal insulin binding to isolated adipocytes was not affected by CsA (CsA = 7.4+/-2.6 vs. C = 6.4+/-2.0%), although glucose transport and oxidation decreased after CsA treatment (p < 0.05). In conclusion, glucose intolerance induced by CsA in Wistar albino rats is due to decreased insulin production and impaired insulin action by a post-binding mechanism.     

Transport of paraquat by isolated renal proximal tubular segments from rabbits

In order to evaluate somatostatin (SRIH) secretion in uremia, plasma SRIH concentrations were determined in basal conditions and after an oral glucose tolerance test (OGTT) in 14 non-dialysed patients with chronic renal failure (CRF), seven of whom had normal glucose tolerance (NGT) and seven impaired glucose tolerance (IGT). Plasma insulin, C-peptide and glucagon and blood glucose concentrations were also evaluated. The results were compared with those obtained in a group of age- and sex-matched normal subjects. In CRF patients, plasma SRIH fasting values (8.6 +/- 0.6 and 7.8 +/- 0.6 pmol/L in NGT and IGT patients, respectively) were comparable to those recorded in controls (7.7 +/- 0.5 pmol/L). SRIH response to OGTT, evaluated as area under curves (AUC) above basal, was similar in both groups of CRF patients (412.9 +/- 84.5 and 415.6 +/- 51.9 pmol/L per min), and significantly lower than in controls (660.1 +/- 58.5 pmol/L per min). Data indicate that chronic uremia induces a loss of SRIH secretory cell responsiveness to glucose. A possible effect of impaired SRIH secretion on glucose metabolism in CRF is discussed.     

Neural network subtyping of depression

OBJECTIVE: To examine the mechanisms by which weight loss improves glycemic control in overweight subjects with NIDDM, particularly the relationships between energy restriction, improvement in insulin sensitivity, and regional and overall adipose tissue loss. RESEARCH DESIGN AND METHODS: Hyperinsulinemic glucose clamps were performed in 20 subjects (BMI = 32.0 +/- 0.5 [SEM] kg/m2, age = 48.4 +/- 2.7 years) with normal glucose tolerance (NGT) (n = 10) or mild NIDDM (n = 10) before and on the 4th (d4) and 28th (d28) days of a reduced-energy (1,100 +/- 250 [SD] kcal/day) formula diet. Body composition changes were assessed by dual energy x-ray absorptiometry and insulin secretory changes were measured by insulin response to intravenous glucose before and after weight loss. RESULTS: In both groups, energy restriction (d4) reduced fasting plasma glucose (FPG) (delta FPG: NGT = -0.4 +/- 0.2 mmol/l and NIDDM = -1.1 +/- 0.03 mmol/l, P = 0.002), which was independently related to reduced carbohydrate intake (partial r = 0.64, P = 0.003). There was a marked d4 increase in percent of insulin suppression of hepatic glucose output (HGO) in both groups (delta HGO suppression: NGT = 28 +/- 15% and NIDDM = 32 +/- 8%, P = 0.002). By d28, with 6.3 +/- 0.4 kg weight loss, FPG was further reduced (d4 vs. d28) in NIDDM only (P = 0.05), and insulin sensitivity increased in both groups (P = 0.02). Only loss of abdominal fat related to improvements in FPG (r = 0.51, P = 0.03) and insulin sensitivity after weight loss (r = 0.48, P = 0.05). In contrast to insulin action, there were only small changes in insulin secretion. CONCLUSIONS: Both energy restriction and weight loss have beneficial effects on insulin action and glycemic control in obesity and mild NIDDM. The effect of energy restriction is related to changes in individual macronutrients, whereas weight loss effects relate to changes in abdominal fat.     

Tinnitus after head injury: evidence from otoacoustic emissions

The ability of portal vein insulin to control hepatic glucose production (HGP) is debated. The aim of the present study was to determine, therefore, if the liver can respond to a selective decrease in portal vein insulin. Isotopic ([3H]glucose) and arteriovenous difference methods were used to measure HGP in conscious overnight fasted dogs. A pancreatic clamp (somatostatin plus basal portal insulin and glucagon) was used to control the endocrine pancreas. A 40-min control period was followed by a 180-min test period. During the latter, the portal vein insulin level was selectively decreased while the arterial insulin level was not changed. This was accomplished by stopping the portal insulin infusion and giving insulin peripherally at half the basal portal rate (PID, n=5). In a control group (n=5), the portal insulin infusion was not changed and glucose was infused to match the hyperglycemia that occurred in the PID group. A selective decrease of 120 pmol/l in portal vein insulin was achieved (basal, 150+/-36 to last 30 min, 30+/-12 pmol/l) in the absence of a change in the arterial insulin level (basal, 30+/-3 to last 30 min, 36+/-4 pmol/l). Neither arterial nor portal insulin levels changed in the control group (30+/-6 and 126+/-30 pmol/l, respectively). In response to the selective decrease in portal vein insulin, net hepatic glucose output (NHGO) increased significantly, from 8+/-1 (basal) to 30+/-6 and 14+/-2 micromol x kg(-1) x min(-1) by 15 min and the last 30 min (P < 0.05) of the experimental period, respectively. Arterial plasma glucose increased from 5.9+/-0.2 (basal) to 10.5+/-0.4 micromol/l (last 30 min). Three-carbon gluconeogenic precursor uptake fell from 11.2+/-2.9 (basal) to 5.9+/-0.7 micromol x kg(-1) x min(-1) (last 30 min), and thus a change in gluconeogenesis could not account for any of the increase in NHGO. With matched hyperglycemia (basal, 5.5+/-0.3 to last 30 min, 10.5+/-0.8 micromol/l) but no change in insulin, NHGO decreased from 12+/-1 (basal) to 0 (-1+/-6 micromol x kg(-1) x min(-1), last 30 min, P < 0.05) and hepatic gluconeogenic precursor uptake did not change (basal, 8.0+/-1.7 to last 30 min, 8.9+/-2.2 micromol x kg[-1] x min[-1]). Thus, the liver responds rapidly to a selective decrease in portal vein insulin by markedly increasing HGP as a result of increased glycogenolysis. These studies indicate that after an overnight fast, basal HGP (glycogenolysis) is highly sensitive to the hepatic sinusoidal insulin level.     

Myocardial glucose uptake in patients with NIDDM and stable coronary artery disease

Whole body insulin resistance characterizes patients with NIDDM, but it is not known whether insulin also has impaired ability to stimulate myocardial glucose uptake (MGU) in these patients. This study was designed to evaluate MGU as measured by 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) and positron emission tomography (PET) in patients with NIDDM and stable coronary artery disease (CAD) under standardized metabolic conditions. Eight patients with NIDDM, 11 nondiabetic patients with CAD, and 9 healthy control subjects were enrolled in the study. MGU was quantitated in the normal myocardial regions with [18F]FDG and PET and the whole body glucose disposal by glucose-insulin clamp technique (serum insulin, -430 pmol/l). Plasma glucose and serum insulin concentrations were comparable in all groups during PET studies. The whole body glucose uptake was 45% lower in NIDDM patients (22 +/- 9 micromol x min(-1) X kg(-1) body wt [mean +/- SD]), compared with healthy control subjects (40 +/- 17 micromol x min(-1) x kg(-1) body wt, P < 0.05). In CAD patients, whole body glucose uptake was 30 +/- 9 micromol x min(-1) x kg(-1) body wt (NS between the other groups). MGU was similar in the normal segments in all three groups (69 +/- 28 micromol x min(-1) x 100 g(-1) in NIDDM patients, 72 +/- 17 micromol x min(-1) x 100 g(-1) in CAD patients, and 76 +/- 10 micromol x min(-1) x 100 g(-1) in healthy control subjects, NS). No correlation was found between whole body glucose uptake and MGU. As studied by [18F]FDG PET under stable normoglycemic hyperinsulinemic conditions, MGU is not reduced in patients with NIDDM and CAD in spite of peripheral insulin resistance. These findings suggest that there is no significant defect in MGU in patients with NIDDM.     

Influence of reduced glutathione infusion on glucose metabolism in patients with non-insulin-dependent diabetes mellitus

To evaluate the relationship between oxidative stress and glucose metabolism, insulin sensitivity and intraerythrocytic reduced glutathione (GSH)/oxidized glutathione (GSSG) ratio were measured in 10 non-insulin-dependent diabetes mellitus (NIDDM) patients and 10 healthy subjects before and after the intravenous administration of GSH. In particular, after baseline insulin sensitivity was assessed by a 2-hour euglycemic hyperinsulinemic clamp, either glutathione (1.35 g x m2 x min(-1)) or placebo (saline) were infused over a period of 1 hour. The same protocol was repeated at a 1-week interval, in cross-over, according to a randomized, single-blind design. In healthy subjects, baseline intraerythrocytic GSH/GSSG ratio (P < .0005) and total glucose uptake (P < .005) were significantly higher than in NIDDM patients. In the same subjects, GSH infusion significantly increased total glucose uptake (from 37.1 +/- 6.7 micromol kg(-1) x min(-1) to 39.5 +/- 7.7 micromol x kg(-1) x min(-1), P < .05), whereas saline infusion was completely ineffective. In addition, the mean intraerythrocytic GSH/GSSG ratio significantly increased after GSH infusion (from 21.0 +/- 0.9 to 24.7 +/- 1.3, P < .05). Similar findings were found in diabetic patients, in whom GSH infusion significantly increased both total glucose uptake (from 25.3 +/- 9.0 micromol x kg(-1) x min(-1) to 31.4 +/- 10.0 micromol x kg(-1) x min(-1), P < .001) and intraerythrocytic GSH/GSSG ratio (from 14.8 +/- 4.1 to 21.7 +/- 6.7, P < .01). Pooling diabetic patients and controls, significant correlations were found between intraerythrocytic GSH/GSSG ratio and total glucose uptake (r = .425, P < .05), as well as between increments of the same variables after GSH infusion (r = .518, P < .05). In conclusion, our data support the hypothesis that abnormal intracellular GSH redox status plays an important role in reducing insulin sensitivity in NIDDM patients. Accordingly, intravenous GSH infusion significantly increased both intraerythrocytic GSH/GSSG ratio and total glucose uptake in the same patients.     

Glucagon-like peptide-1 reduces hepatic glucose production indirectly through insulin and glucagon in humans

The effect of glucagon-like peptide-1 (GLP-1) on hepatic glucose production and peripheral glucose utilization was investigated with or without infusion of somatostatin to inhibit insulin and glucagon secretion in 13 healthy, non-diabetic women aged 59 years. After 120 min 3-(3)H-glucose infusion, GLP-1 was added (4.5 pmol kg(-1) bolus + 1.5 pmol kg(-1) min(-1)). Without somatostatin (n = 6), GLP-1 decreased plasma glucose (from 4.8 +/- 0.2 to 4.2 +/- 0.3 mmol L(-1), P = 0.007). Insulin levels were increased (48 +/- 3 vs. 243 +/- 67 pmol L(-1), P = 0.032), as was the insulin to glucagon ratio (P = 0.044). The rate of glucose appearance (Ra) was decreased (P = 0.003) and the metabolic clearance rate of glucose (MCR) was increased during the GLP-1 infusion (P = 0.024 vs. saline). Also, the rate of glucose disappearance (Rd) was reduced during the GLP-1 infusion (P = 0.004). Since Ra was reduced more than Rd, the net glucose flow was negative, which reduced plasma glucose. Somatostatin infusion (500 microg h(-1), n = 7) abolished the effects of GLP-1 on plasma glucose, serum insulin, insulin to glucagon ratio, Ra, Rd, MCR and net glucose flow. The results suggest that GLP-1 reduces plasma glucose levels mainly by reducing hepatic glucose production and increasing the metabolic clearance rate of glucose through indirectly increasing the insulin to glucagon ratio in healthy subjects.     

Regulation of skeletal muscle hexokinase II by insulin in nondiabetic and NIDDM subjects

Impaired muscle glucose phosphorylation to glucose-6-phosphate by hexokinases (HKs)-I and -II may contribute to insulin resistance in NIDDM and obesity. HK-II expression is regulated by insulin. We tested the hypothesis that basal and insulin-stimulated expression of HK-II is decreased in NIDDM and obese subjects. Skeletal muscle HK-I and HK-II activities were measured in seven lean and six obese normal subjects and eight patients with NIDDM before and at 3 and 5 h of a hyperinsulinemic (80 mU x m(-2) x min(-1)) euglycemic clamp. To assess whether changes in HK-II expression seen during a glucose clamp are likely to be physiologically relevant, we also measured HK-I and HK-II activity in 10 lean normal subjects before and after a high-carbohydrate meal. After an overnight fast, total HK, HK-I, and HK-II activities were similar in lean and obese control subjects; but HK-II was lower in NIDDM patients than in lean subjects (1.42 +/- 0.16 [SE] vs. 2.33 +/- 0.24 nmol x min(-1) x mg(-1) molecular weight, P < 0.05) and accounted for a lower proportion of total HK (33 +/- 3 vs. 47 +/- 3%, P < 0.025). HK-II (but not HK-I) activity increased during the clamp in lean and obese subjects by 34 and 36% after 3 h and by 14 and 22% after 5 h of hyperinsulinemia; no increase was found in the NIDDM patients. In the lean subjects, muscle HK-II activity also increased by 15% 4 h after the meal, from 2.47 +/- 0.19 basally to 2.86 +/- 0.28 nmol x min(-1) x mg(-1) protein (P < 0.05). During the clamps, muscle HK-II activity correlated with muscle citrate synthase activity in the normal subjects (r = 0.58, P < 0.05) but not in the NIDDM patients. A weak relationship was noted between muscle HK-II activity and glucose disposal rate at the end of the clamp when all three groups were combined (r = 0.49, P < 0.05). In summary, NIDDM patients have lower muscle HK-II activity basally and do not increase the activity of this enzyme in response to a 5-h insulin stimulus. This defect may contribute to their insulin resistance. In nondiabetic obese subjects, muscle HK-II expression and its regulation by insulin are normal.     

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.     

Localization of Rho GTPase in sea urchin eggs

OBJECTIVE: Previous studies in our laboratory showed that the platelet anti-aggregating effect exerted by insulin, mediated by a nitric oxide (NO)-induced increase of guanosine-3',5'-cyclic monophosphate (cGMP), is lost in the insulin-resistant of obesity and obese NIDDM. It is not clear 1) whether the alterations observed in obese NIDDM patients are attributable to the obesity-related insulin resistance or to diabetes per se and 2) whether insulin-resistant states present a normal or a blunted response to NO. This study has been conducted to investigate 1) the platelet sensitivity to insulin in lean NIDDM and 2) the platelet sensitivity to an NO donor, glyceryl trinitrate (GTN), in obesity and in both lean and obese NIDDM. RESEARCH DESIGN AND METHODS: We determined 1) ADP-induced platelet aggregation and platelet cGMP content in platelet-rich plasma (PRP) obtained from 11 lean NIDDM patients, after a 3-min incubation with insulin (0, 240, 480, 960, 1,920 pmol/l) and 2) ADP-induced platelet aggregation and platelet cGMP content in PRP obtained from 9 obese subjects, 11 lean and 8 obese NIDDM patients, and 18 control subjects, after a 3-min incubation with 0, 20, 40, and 100 mumol/l GTN. RESULTS: Insulin dose-dependently decreased platelet aggregation in lean NIDDM patients (P = 0.0001): with 1,920 pmol/l of insulin, ADP ED50 was 141.5 +/- 6.4% of basal values (P = 0.0001). Furthermore, insulin increased platelet cGMP (P = 0.0001) from 7.5 +/- 0.2 to 21.1 +/- 3.7 pmol/10(9) platelets. These results were similar to those previously described in healthy subjects. GTN reduced platelet aggregation in all the groups (P = 0.0001) at all the concentrations tested (P = 0.0001), but GTN IC50 values were much higher in insulin-resistant patients: 36.3 +/- 5.0 mumol/l in healthy control subjects, 26.0 +/- 6.0 mumol/l in lean NIDDM patients (NS vs. control subjects), 123.6 +/- 24.0 mumol/l in obese subjects (P = 0.0001 vs. control subjects), and 110.1 +/- 19.2 mumol/l in obese NIDDM patients (P = 0.0001 vs. control subjects). GTN dose-dependently increased platelet cGMP in all the groups (P = 0.0001 in control subjects, lean NIDDM patients, and obese subjects; P = 0.04 in obese NIDDM patients). Values reached by obese subjects and obese NIDDM patients, however, were lower than those reached by control subjects (with 100 mumol/l of GTN, P = 0.001 and P = 0.0001, respectively). In healthy control subjects and in obese subjects, the insulin:glucose ratio, used as an indirect measure of insulin sensitivity, was positively correlated to GTN IC50 (r = 0.530, P = 0.008), further suggesting that the sensitivity to NO is reduced in the presence of insulin resistance. CONCLUSIONS: The insulin anti-aggregating effect is preserved in lean NIDDM; platelet sensitivity to GTN in preserved in lean NIDDM but is reduced in the insulin-resistant states of obesity and obese NIDDM. Resistance to nitrates, therefore, could be considered another feature of the insulin-resistance syndrome.     

Defects in insulin secretion and action in women with a history of gestational diabetes

Gestational diabetes mellitus (GDM) is associated with defects in insulin secretion and insulin action, and women with a history of GDM carry a high risk for the development of non-insulin-dependent diabetes mellitus (NIDDM). Assessment of subjects with a history of GDM who are currently normoglycemic should help elucidate some of the underlying defects in insulin secretion or action in the evolution of NIDDM. We have studied 14 women with normal oral glucose tolerance who had a history of GDM. They were compared with a group of control subjects who were matched for both body mass index (BMI) and waist-to-hip ratio (WHR). All subjects underwent tests for the determination of oral glucose tolerance, ultradian oscillations in insulin secretion during a 28-h glucose infusion, insulin secretion in response to intravenous glucose, glucose disappearance after intravenous glucose (Kg), and insulin sensitivity (SI) as measured by the Bergman minimal model method. The BMI in the post-GDM women was similar to that in the control subjects (24.9 +/- 1.2 vs. 25.4 +/- 1.4 kg/m2, respectively), as was the WHR ratio (0.80 +/- 0.01 vs. 0.76 +/- 0.01, respectively). The post-GDM women were slightly older (35.2 +/- 0.9 vs. 32.1 +/- 1.4 years, P = 0.04). The fasting plasma glucose levels were significantly higher in the post-GDM group than in the control group (4.9 +/- 0.1 vs. 4.4 +/- 0.1 mmol/l, respectively, P < 0.001) and remained higher at each of the subsequent determinations during the oral glucose tolerance test, although none had a result indicative of either diabetes or impaired glucose tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Neonatal de-afferentation of capsaicin-sensitive sensory nerves increases in vivo insulin sensitivity in conscious adult rats

Sensory neuropeptides, released from the peripheral nervous system, might modulate glucose homeostasis by antagonizing insulin action. The effects of de-afferentation of functional small diameter unmyelinated C-fibres (sensory nerves) on in vivo insulin-mediated intracellular glucose metabolism were investigated by using euglycaemic insulin (6 and 18 mU/kg x min) clamps with [3-(3)H]-glucose infusion in 24 adult rats, treated neonatally with either capsaicin (CAP) (50 mg/kg) or vehicle (CON). Following the clamp, skeletal muscle groups, liver and adipose tissue were freeze-clamped. At plasma insulin levels of approximately 90 mU/l, CAP-rats showed a 21% increase in whole body glucose uptake compared with CON (24.4 +/- 1.6 vs 20.1 +/- 0.8 mg/kg min, p < 0.02), which was paralleled by a 20% increase in whole body glycolysis (12.6 +/- 0.8 vs 10.5 +/- 0.5 mg/ kg.min p < 0.05) (concentration of 3H2O in plasma). Whole body skeletal muscle glycogenesis was increased by 80% in CAP-rats (5.7 +/- 0.7 vs 3.1 +/- 0.7 mg/kg x min, p < 0.05) with increased muscle glycogen synthase activity. Whole body (muscle, liver and adipose tissue combined) de novo lipogenesis also was increased in CAP-rats compared with CON (0.69 +/- 0.10 vs 0.44 +/- 0.06 mg/kg x min, p < 0.05) (incorporation of [3-(3)H]-glucose counts into glycogen or fat). Hepatic glucose production was lower in CAP-rats compared with CON (0.6 +/- 0.6 vs 2.1 +/- 0.7 mg/kg x min, p < 0.05). Plasma glucagon, corticosterone, epinephrine and norepinephrine levels were reduced in CAP-rats: 43 +/- 2 compared with 70 +/- 6 pg/ml, 855 +/- 55 compared with 1131 +/- 138 nmol/l, 513 +/- 136 compared with 1048 +/- 164 pmol/l and 928 +/- 142 compared with 1472 +/- 331 pmol/l, respectively, p < 0.05. At plasma insulin levels of approximately 400 mU/l, CAP-rats showed no differences in peripheral and hepatic insulin action compared with CON. We conclude that the removal of endogenous sensory neuropeptides, by de-afferentation of capsaicin-sensitive sensory nerves, increases in vivo insulin sensitivity, but not responsiveness: 1) primarily through an increased sensitivity of skeletal muscle glycogen synthesis to insulin; 2) through a reduction in the levels of counter-regulatory hormones, thereby creating a milieu which favours overall in vivo insulin sensitivity with respect to glucose uptake, glucose production, glycolysis, glycogenesis and lipogenesis.