Insulin resistance in maturity onset diabetes of the young

Insulin resistance was assessed by euglycaemic clamp studies in matched groups of MODY, classical NIDDM patients and non-diabetic control subjects. The MODY patients metabolised less glucose (4.8 +/- 0.3 mg/Kg/min) than the classical NIDDM patients (7.0 +/- 0.5 mg/Kg/min) at an insulin infusion rate of 1.0 mU/Kg/min (p less than 0.05). At an insulin infusion rate 10 mU/Kg/min the differences between the MODY and the classical NIDDM patients were not significant. At both infusion rates the two diabetic groups metabolised less glucose than the control subjects. The results indicate that despite their younger age, the patients with MODY are more insulin resistant than the patients with classical NIDDM.     

Effects of growth hormone on insulin sensitivity and forearm metabolism in normal man

To elucidate the short-term actions of growth hormone on insulin sensitivity and forearm metabolism, we have studied six normal male subjects receiving a 6-h hyperinsulinaemic euglycemic clamp with and without a concomitant 4-h growth hormone infusion. When infused, serum growth hormone rose to 25 +/- 4 mU/l and during administration of insulin serum insulin increased by 11 +/- 1 mU/l. During euglycemic clamp, administration of growth hormone decreased forearm glucose uptake after 180 min and onward (240 min 0.216 +/- 0.031 vs 0.530 +/- 0.090 mg/100 ml/min, p less than 0.05). Glucose infusion rate (240 min 2.83 +/- 0.24 vs 4.35 +/- 0.28 mg.kg-1.min-1, p less than 0.05) and glucose disposal rate (240 min 3.57 +/- 0.17 vs 4.00 +/- 0.15 mg.kg-1.min-1, p less than 0.05) also decreased. Growth hormone persistently increased hepatic glucose production after 120 min. After 210 min, all circulating lipid intermediates increased slightly. The decrease in forearm glucose uptake and glucose infusion rate and the increase in hepatic glucose production was observed before there was any detectable increase in circulating levels and forearm uptake of lipid intermediates. These data suggest that growth hormone induces insensitivity to insulin in liver, muscle and fat after 120, 180 and 210 min respectively. The early effects of growth hormone on glucose metabolism seems independent of changes in the rate of lipolysis.     

Pharmacokinetics and pharmacodynamics of subcutaneously administered U40 and U100 formulations of regular human insulin.

Action profiles of 12 U of regular human insulin (Actrapid HM) administered subcutaneously as a U40 or U100 formulation were studied. Euglycaemic glucose clamps were performed on two separate days in 8 healthy subjects (basal i.v. insulin infusion 0.1 mU/kg/min, plasma glucose 5.0 mmol/l, mean +/- SD age 25 +/- 2 years, BMI 22.7 +/- 1.4 kg/m2). Serum insulin concentrations increased after injection of U40 or U100 from similar baseline values to maximal individual concentrations of 305 +/- 79 vs. 285 +/- 62 pmol/l (NS) after 90 +/- 33 vs. 114 +/- 58 min (NS). Ten, 15, and 20 min post injection insulin concentrations were significantly higher by an average of 30 pmol/l after U40 insulin vs. U100 insulin (p less than 0.05). Glucose infusion rates increased from comparable baseline rates to maximal individual glucose infusion rates of 10.7 +/- 2.4 vs. 10.9 +/- 3.0 mg/kg/min (NS) after 172 +/- 51 vs. 169 +/- (39) min (NS). At the three time points when significantly different serum insulin concentrations occurred soon after insulin injection, glucose infusion rates were not significantly different between U40 and U100. Although small differences in insulin pharmacokinetics were detected early after s.c. insulin injection (U40 was absorbed faster than U100 insulin) the pharmacodynamics of the U40 and U100 formulation of regular human insulin appear to be comparable in healthy subjects.     

Resistance to insulin suppression of plasma free fatty acids in liver cirrhosis

Insulin action on carbohydrate metabolism is known to be reduced in liver cirrhosis. However, little is known about the effect of insulin on free fatty acid (FFA) metabolism in these patients. To investigate this aspect we performed a two-step insulin euglycemic clamp in 11 cirrhotic patients and 6 controls. Insulin was infused at 0.25 mU/Kg min from 0 to 100 min and at 1 mU/Kg from 100 to 200 min. The FFA lowering capacity of insulin was studied during the first step; the glucose metabolizing capacity (M) was evaluated during the second step. In the cirrhotic patients, the M value was lower than in controls (3.91 +/- 0.48 vs 7.75 +/- 1.09 mg/kg/min, respectively). During the low insulin infusion, FFA and glycerol plasma levels were decreased in both groups. However, the ability of insulin to suppress plasma FFA and glycerol was lower in cirrhotics than in controls. In fact, at 100 min, FFA were 50% of basal values in cirrhotics and 20% in controls (p less than 0.01), while glycerol plasma levels decreased to 70% of basal values in patients and to 56% in controls. The slope of the linear regression obtained between Ln-FFA concentrations vs time was significantly less in cirrhotic patients than in controls (p less than 0.001). In addition, a positive correlation was found between the M value (r = 0.70; p less than 0.01) and the slope of the Ln-FFA in each patient. These findings suggest that in cirrhotic patients the effects of insulin on both FFA and glucose metabolism are reduced.     

Insulin sensitivity and metabolic clearance rate of insulin in familial multiple lipomatosis

Intolerance to glucose in certain kinds of lipomatosis is well documented. This article describes a euglucaemic hyperinsulinaemic clamp study of alterations in glucose and/or insulin metabolism in four members of a single family with familial multiple lipomatosis. Fifteen normal subjects were studied as controls. The four patients exhibited no alteration in tolerance to orally administered glucose. When a Biostator Glucose-Controlled Insulin Infusion System (GCIIS) was used to clamp glycaemia at 4.44 mmol/L with successive insulin infusion rates of (a) 0.5 (b) 1.0 or (c) 5.0 mU/kg/min, there was no difference between patients and controls as regards the value of M, the rate of glucose infusion, but the concentrations of immunoreactive insulin recorded during the last 40 minutes of each phase of the clamp were greater in patients than in controls (45 +/- 2 vs 27 +/- 2 uU/mL (p less than 0.01), 83 +/- 2 vs 60 +/- 5 uU/mL (p less than 0.05) and 537 +/- 48 vs 377 +/- 25 uU/mL (p less than 0.05) for insulin infusion rates (a), (b) and (c) respectively), and the ratio M/IRI was consequently smaller for patients than controls (1.92 +/- 0.41 vs 3.06 +/- 0.19 (p less than 0.05) for an insulin infusion rate of 5 mU/kg/min). The metabolic clearance rate of insulin was likewise slower in patients than controls (p less than 0.01). It is concluded that the four patients studied (all members of the same family) have sub-normal sensitivity to insulin secondary to a sub-normal metabolic clearance rate for insulin.     

Does overnight normalization of plasma glucose by insulin infusion affect assessment of glucose metabolism in Type 2 diabetes?

AIMS: In order to perform euglycaemic clamp studies in Type 2 diabetic patients, plasma glucose must be reduced to normal levels. This can be done either (i) acutely during the clamp study using high-dose insulin infusion, or (ii) slowly overnight preceding the clamp study using a low-dose insulin infusion. We assessed whether the choice of either of these methods to obtain euglycaemia biases subsequent assessment of glucose metabolism and insulin action. METHODS: We studied seven obese Type 2 diabetic patients twice: once with (+ ON) and once without (- ON) prior overnight insulin infusion. Glucose turnover rates were quantified by adjusted primed-constant 3-3H-glucose infusions, and insulin action was assessed in 4-h euglycaemic, hyperinsulinaemic (40 mU m-2 min-1) clamp studies using labelled glucose infusates (Hot-GINF). RESULTS: Basal plasma glucose levels (mean +/- sd) were 5.5 +/- 0.5 and 10.7 +/- 2.9 mmol/l in the + ON and - ON studies, respectively, and were clamped at -5.5 mmol/l. Basal rates of glucose production (GP) were similar in the + ON and - ON studies, 83 +/- 13 vs. 85 +/- 14 mg m-2 min-1 (NS), whereas basal rates of glucose disappearance (Rd) were lower in the + ON than in the - ON study, 84 +/- 8 vs. 91 +/- 11 mg m-2 min-1 (P = 0.02). During insulin infusion in the clamp period, rates of GP, 23 +/- 11 vs. 25 +/- 10 mg m-2 min-1, as well as rates of Rd, 133 +/- 32 vs. 139 +/- 37 mg m-2 min-1, were similar in the + ON and - ON studies, respectively (NS). CONCLUSIONS: Apart from basal rates of Rd, assessment of glucose turnover rates in euglycaemic clamp studies of Type 2 diabetic patients is not dependent on the method by which plasma glucose levels are lowered.     

Metformin improves peripheral but not hepatic insulin action in obese patients with type II diabetes

Nine obese patients with Type II diabetes mellitus were examined in a double-blind cross-over study. Metformin 0.5 g trice daily or placebo were given for 4 weeks. At the end of each period fasting and day-time postprandial values of plasma glucose, insulin, C-peptide and lactate were determined, and in vivo insulin action was assessed using the euglycemic clamp in combination with [3-3H]glucose tracer technique. Metformin treatment significantly reduced mean day-time plasma glucose levels (10.2 +/- 1.2 vs 11.4 +/- 1.2 mmol/l, P less than 0.01) without enhancing mean day-time plasma insulin (43 +/- 4 vs 50 +/- 7 mU/l, NS) or C-peptide levels (1.26 +/- 0.12 vs 1.38 +/- 0.18 nmol/l, NS). Fasting plasma lactate was unchanged (1.57 +/- 0.16 vs 1.44 +/- 0.11 mmol/l, NS), whereas mean day-time plasma lactate concentrations were slightly increased (1.78 +/- 0.11 vs 1.38 +/- 0.11 mmol/l, P less than 0.01). The clamp study revealed that metformin treatment was associated with an enhanced insulin-mediated glucose utilization (370 +/- 38 vs 313 +/- 33 mg.m-2.min-1, P less than 0.01), whereas insulin-mediated suppression of hepatic glucose production was unchanged. Also basal glucose clearance was improved (61.0 +/- 5.8 vs 50.6 +/- 2.8 ml.m-2.min-1, P less than 0.05), whereas basal hepatic glucose production was unchanged (81 +/- 6 vs 77 +/- 4 mg.m-2.min-1, NS). Conclusions: 1) Metformin treatment in obese Type II diabetic patients reduces hyperglycemia without changing the insulin secretion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Suppression of insulin secretion by falling plasma glucose levels is impaired in type 2 diabetes

The ability of Type 2 diabetic patients to suppress islet B-cell secretion in response to falling plasma glucose levels has been studied with two different protocols. (1) Five diet-treated diabetic patients and 6 normal subjects were studied after the termination of a hyperglycaemic clamp at 15 mmol l-1 for 150 min, with the plasma glucose levels then being allowed to fall and the glucose clamp re-established at 10 mmol l-1. The plasma insulin levels fell in normal subjects from 178 +/- 141 (+/- SD) mU l-1 at the end of the 15 mmol l-1 clamp to 147 +/- 97 mU l-1 (p less than 0.02) 20 min later, whereas in diabetic patients there was no significant change from 61 +/- 41 to 56 +/- 35 mU l-1, respectively (NS). (2) The second study was performed to assess the turn-off of islet B-cell secretion with diabetic patients and normal subjects starting at comparable plasma insulin levels. Twelve diet-treated diabetic patients and 11 normal subjects were given a continuous low-dose glucose infusion for 60 min at a rate of 5 mg kg-1 ideal body weight min-1, after which the infusion was turned off and the plasma glucose level allowed to fall.(ABSTRACT TRUNCATED AT 250 WORDS)     

Long-term stability of low insulin responses to glucose in non-diabetic subjects.

We investigated the stability of the insulin response to glucose in healthy subjects by making retrospective comparisons of insulin responses after two 60 min glucose infusion tests performed many years apart. The subjects (N = 49) were divided into two lower and two higher quartiles as assessed by the incremental 0-10 min insulin area during the initial glucose infusion test. Ages were initially 32.3 +/- 2.8 years in lower quartiles and 26.6 +/- 1.1 in higher quartiles and body mass indexes 21.6 +/- 0.6 kg/m2 and 21.8 +/- 0.5, respectively. The interval between the first and second glucose infusion tests was 8.1 +/- 2.8 years for lower quartiles and 10.4 +/- 1.3 for higher quartiles. In lower quartiles, the 0-10 min insulin area at first testing was 157.1 +/- 15.9 mU/l x 10 min and at follow-up 202.2 +/- 26.6 (+29%, NS). In higher quartiles, the insulin area decreased from 654.8 +/- 70.6 mU/l x 10 min at first testing to 489.8 +/- 53.6 at follow-up (-25%, p less than 0.05). The 0-60 min glucose area did not change significantly between glucose infusion tests in lower quartiles (+5%), but did increase by 12% (p less than 0.005) in higher quartiles. Only one subject of the lowest quartile at first testing changed to higher quartiles at follow-up. Predictable "regression toward the mean" at follow-up was moderate, hence the individual insulin response to glucose was relatively stable with time. This finding is compatible with the hypothesis that genetic factors are of major importance for the insulin response to glucose.     

The effect of intraperitoneal insulin delivery on carbohydrate metabolism in type 1 (insulin-dependent) diabetic patients.

Patients with type 1 diabetes are usually given insulin subcutaneously, but this does not mimic the physiological route of pancreatic insulin release, which may be better achieved with intraperitoneal insulin. Five C-peptide negative type 1 diabetic patients were studied on two occasions, once with intravenous (IV) and once with intraperitoneal (IP) insulin. Normoglycaemia was maintained from 1700 h with variable insulin infusion, and glucose turnover and recycling assessed from 0600 to 0800 h. A 4-h hyperinsulinaemic (25 mU kg-1 h-1) euglycaemic clamp was then performed, with IP or IV insulin delivery. During the night similar insulin infusion rates were needed to achieve equal blood glucose concentrations. Glucose turnover was identical (IV: 2.4 +/- 0.2 vs IP: 2.3 +/- 0.1 mg kg-1 min-1) (+/- SE) with glucose/carbon recycling 8.8 +/- 4.7 and 12.8 +/- 2.9% (NS). Blood lactate, pyruvate and alanine concentrations were significantly higher with IP than IV insulin (P less than 0.05). During the clamp, insulin concentration was 28 +/- 3 mU/l with IV insulin and 15 +/- 1 mU/l with IP insulin (P less than 0.05) and glucose requirement 2.0 +/- 0.5 and 0.8 +/- 0.3 mg kg-1 min-1, respectively (P less than 0.05). Glucose carbon recycling was higher with IP insulin (P less than 0.05). We conclude that: (1) in type 1 (insulin-dependent) diabetic patients hepatic glucose production could be normalized with both routes of insulin administration, and (2) at the same insulin infusion rate, the relative peripheral hypoinsulinaemia with IP route is sufficient to increase the rate of release of gluconeogenic precursors, or decrease their hepatic uptake.     

Evidence for peripheral impaired glucose handling in patients with connective tissue diseases

Sixteen patients suffering from rheumatoid arthritis (RA) (n = 8), systemic lupus erythematosus (SLE) (n = 5), and systemic sclerosis (SSc) (n = 3), and 10 healthy subjects matched for age, sex, and body mass index, were submitted to an intravenous (IV) glucose tolerance test (GTT) (0.33 g/kg of body weight in 3 minutes) and to a euglycemic hyperinsulinemic glucose clamp to study insulin response and action. In the euglycemic clamp, along with the two insulin infusion rates (0.5 mU/kg.min from 0 to 120 minutes and 1 mU/kg.min from 121 to 240 minutes), a primed (20 microCi) continuous (0.2 microCi/min) infusion of 3H-glucose allowed determination of glucose kinetics. Our data show that patients versus controls have (1) a significant increase in basal plasma insulin levels (87.2 +/- 14.8 v 41.3 +/- 6.0 pmol/L, P less than .05); (2) similar glucose-induced acute insulin response; and (3) a lower glucose disappearance rate (Rd), glucose metabolic clearance rate (gMCR), and glucose infusion rate (GIR) when the lowest insulin infusion rate was delivered. These differences disappeared when the insulin infusion rate was doubled. Furthermore, basal plasma insulin levels and glucose disappearance rate significantly correlated with the main inflammatory indices of each disease studied. We conclude that in our patients impaired glucose handling is mainly due to peripheral insulin resistance.     

Insulin sensitivity in newly diagnosed type 1 diabetics after ketoacidosis and after three months of insulin therapy

Tissue sensitivity to insulin (euglycemic insulin clamp technique), hepatic glucose production (3-[3H]glucose infusion) and insulin binding to erythrocyte receptors were studied in 14 newly diagnosed type 1 diabetic patients after the disappearance of ketosis and after 3 months of insulin therapy. The control group consisted of 14 normal subjects. During the two insulin clamp studies, plasma glucose in the diabetic patients was maintained at 5.0 +/- 0.04 (SEM) mmol/liter and 4.9 +/- 0.05 mmol/liter, with corresponding steady state free insulin levels of 90 +/- 4 mU/liter, and 67 +/- 6 mU/liter (P less than 0.02) during the first and second study, respectively. The decline in free insulin levels was due to the development of insulin antibodies during insulin therapy (10 +/- 0.1% vs. 18 +/- 2%, P less than 0.001, serum insulin-binding capacity during the first and second study, respectively). In the normal subjects, steady state plasma glucose and insulin levels were 4.9 +/- 0.1 mmol/liter and 89 +/- 4 mU/liter, respectively. The rate of glucose metabolism (M) in the diabetic patients during the first study (5.13 +/- 0.65 mg/kg X min) was 35% lower than that in the normal subjects (7.94 +/- 0.50 mg/kg X min, P less than 0.005). After 3 months of insulin therapy, M increased by 35% to 6.92 +/- 0.58 mg/kg X min, which was comparable to that in the normal subjects. To compensate for the difference in plasma free insulin levels, we calculated an index for insulin sensitivity by dividing M by the ambient insulin concentration (I). During the 3 months of insulin therapy, M/I rose 2-fold to 11.63 +/- 1.10 mg/kg X min per mU insulin/liter X 100, which was similar to that in normal subjects (9.16 +/- 0.67 mg/kg X min per mU insulin/liter X 100). Five diabetic patients had a partial clinical remission, as determined by normal fasting C-peptide levels. In these patients, insulin sensitivity was 35-50% greater than in those who failed to have a remission (P less than 0.05). Basal hepatic glucose production in the diabetic patients during the first study (2.78 +/- 0.14 mg/kg X min) was 56% higher than in the normal subjects (1.78 +/- 0.04 mg/kg X min, P less than 0.001), and remained unchanged during insulin therapy. During the hyperinsulinemia induced by the clamp, hepatic glucose production was totally suppressed in both the diabetic and control subjects.(ABSTRACT TRUNCATED AT 400 WORDS)     

Glucose metabolism in quinine-treated patients with uncomplicated falciparum malaria

To investigate host and drug effects on glucose metabolism in acute falciparum malaria, 10 previously untreated, fasting Thai males with uncomplicated infections were given a 2-h intravenous glucose infusion (5 mg/kg ideal body weight min) with an infusion of quinine dihydrochloride (10 mg/kg body weight) during the second hour. Eight patients were restudied in convalescence. Fasting plasma glucose (mean +/- SD) and insulin (geometric mean (-SD to + SD] were higher during acute illness (5.5 +/- 1.0 mmol/l and 6.2 (5.0-7.7) mU/l) than in convalescence (4.2 +/- 0.25 mmol/l and 3.7 (2.1-6.7) mU/l; P less than 0.001 and P = 0.058 respectively). After 1 h, both plasma glucose (9.3 +/- 1.4 vs 7.5 +/- 0.8 mmol/l, P less than 0.001) and insulin (21.2 (13.8-32.5) vs 15.2 (11.2-20.8) mU/l, P = 0.089) remained higher during acute illness; mathematical model (CIGMA) assessment of these values indicated lower tissue insulin sensitivity on admission (97% (71-134] than in convalescence (139% (109-178), P less than 0.025) but normal beta-cell function on both occasions. Two-hour plasma glucose (9.5 +/- 2.0 mmol/l) and insulin (81.8 (51.5-129.9) mU/l) concentrations during acute illness were also significantly higher than in convalescence (7.2 +/- 1.2 mmol/l and 40.1 (23.5-68.4) mU/l, P less than or equal to 0.025) despite similar end-infusion free plasma quinine concentrations (P greater than 0.5). Basal plasma free fatty acid concentrations were increased in acute illness (0.68 +/- 0.24 vs 0.21 +/- 0.12 mmol/l, P less than 0.001) but fell to low levels at 2 h in both studies. These data suggest tissue insulin resistance and augmented quinine-stimulated insulin secretion in acute falciparum malaria, factors which are likely to influence the clinical situation in which malaria-associated hypoglycaemia occurs.     

The use of the hypoglycaemic clamp in the assessment of pituitary function

OBJECTIVE: The standard dynamic test used to diagnose hypopituitarism is the insulin tolerance test (ITT), in which insulin-induced secretion of ACTH, GH and cortisol is measured. However, because of differences in insulin sensitivity some patients fail achieve sufficient hypoglycaemia to assess pituitary function and colleagues experience severe hypoglycaemia and are at risk for cardiac dysrhythmia, seizure or coma. This risk may be particularly pertinent in the evaluation of older adults. We hypothesized that the hypoglycaemic clamp may be useful in assessing pituitary function in some patients. PATIENTS AND MEASUREMENTS: Twenty-one normal subjects (14 old [50-76 years] and 7 young [18-36 years]) and 7 hypopituitary subjects were studied. A clamp study was performed in which insulin infusion was given at 2 mU/kg/min and increased to 4 mU/kg/min if the target glucose concentration was not reached after 40 min. Dextrose was infused as needed to clamp the plasma glucose concentration at 2.2 mmol/l for 30 min. On a separate day, 7 young controls also underwent an ITT in which 0.15 U/kg insulin was administered as a bolus intravenous injection at time 0. In both studies, baseline values were taken at - 10, - 5 and 0 min. Samples were then collected every 5 min for plasma glucose and every 10 min for insulin, ACTH, cortisol and GH. RESULTS: ACTH and GH secretion during each test were similar in younger controls (P = NS) but cortisol secretion was lower during ITT (P < 0.01 vs. clamp). Hypopituitary subjects had significantly less ACTH, cortisol and GH secretion than controls of all ages (P < 0.001 for all). Peak GH secretion was significantly lower in the old controls than in young controls (22 +/- 12 vs. 48 +/- 26 mU/l, respectively; P < 0.01) but significantly higher than the hypopituitary subjects (2 +/- 2 mu/l; P < 0.001). CONCLUSION: These data demonstrate that the hypoglycaemic clamp can be used in the assessment of pituitary function and suggest that this technique may be particularly beneficial in the evaluation of GH deficiency in older adults who may not tolerate the ITT.     

Combination of continuous subcutaneous infusion of insulin and octreotide in Type 1 diabetic patients

The effect of 7 day continuous subcutaneous infusion of octreotide (200 microg day(-1)) was evaluated in seven insulin-pump treated Type 1 diabetic patients (age 43+/-1.5 year; BMI 25.1+/-0.7 kg m(-2); HbA(1c) 7.4+/-0.3%). A 24-h metabolic and hormonal profile, and a euglycaemic hyperinsulinaemic clamp (0.25, 0.5, 1.0 mg kg(-1) min(-1)), with [3H]glucose infusion and indirect calorimetry, were performed before and after a 7-day octreotide infusion. Mean 24-h plasma glucose was similar before and after octreotide (9.7+/-0.8 vs. 9.1+/-1.0 mmol l(-1)) but insulin requirement dropped by 45% (49+/-4 vs. 27+/-2 U day(-1); P<0.01). Both 24-h plasma hGH and glucagon were suppressed by octreotide (1.85+/-0.35 vs. 0.52+/-0.04 microg l(-1), and 117+/-23 vs. 102+/-14 ng l(-1), respectively). Glucose utilisation increased after octreotide (insulin 0.5 mU kg(-1) min(-1) clamp 3.09+/-0.23 vs. 4.19+/-0.19 mg kg(-1) min(-1); 1 mU kg(-1) min(-1) clamp 5.64+/-0.61 vs. 7.93+/-0.57 mg kg(-1) min(-1); both P<0.05) and endogenous glucose production was similarly suppressed. Glucose oxidation was not affected by octreotide, while the improvement in glucose storage (insulin 1.0 mU kg(-1) min(-1) clamp 3.89+/-0.60 vs. 5.64+/-0.67 mg kg(-1) min(-1), P<0.05) entirely accounted for the increase in glucose disposal. Endogenous glucose production was more effectively suppressed at the two lower insulin infusion rates (P>0.05). Energy expenditure declined after octreotide. Continuous subcutaneous octreotide infusion suppresses counterregulatory hormones, increases insulin-mediated glucose metabolism by enhancing glucose storage, and reduces energy expenditure. These results support a role for counterregulatory hormones in the genesis of insulin resistance and the catabolic state of Type 1 diabetes.     

Peripheral and hepatic insulin antagonism in hyperthyroidism

Eight hyperthyroid and eight normal subjects underwent 2-h oral glucose tolerance tests (OGTT) and euglycemic clamp studies to assess the presence of peripheral and hepatic insulin antagonism in hyperthyroidism. Although the mean total glucose area during the OGTT was similar in the hyperthyroid patients and normal subjects [16.4 +/- 0.8 (+/- SE) vs. 15.8 +/- 0.7 mmol/L.h], the mean insulin area was significantly elevated in the hyperthyroid group (1413 +/- 136 vs. 1004 +/- 122 pmol/L.h; P less than 0.05). Basal hepatic glucose production was measured during the second hour of a primed [3-3H]glucose infusion. A two-insulin dose euglycemic clamp study with [3-3H]glucose and somatostatin (500 micrograms/h) was carried out during the next 6 h. The insulin infusion rate was 0.05 mU/kg.min during the third, fourth, and fifth hours and 0.60 mU/kg.min during the sixth, seventh, and eighth hours. Hepatic glucose production and glucose utilization were measured during the final 0.5 h of each clamp period. Serum C-peptide concentrations were measured in the initial sample and in the last sample of each clamp period. The mean equilibrium serum insulin concentrations were similar in both groups during the final 0.5 h of the low (90 +/- 8 vs. 79 +/- 6 pmol/L) and high (367 +/- 11 vs. 367 +/- 15 pmol/L) insulin infusion rates. Basal serum C-peptide levels were significantly increased in the hyperthyroid patients (596 +/- 17 vs. 487 +/- 43 pmol/L; P less than 0.05) but were suppressed equally in both groups at the end of both clamp periods. The MCRs of insulin were similar in the hyperthyroid and normal subjects during the low (6.7 +/- 1.1 vs. 5.6 +/- 0.5 mL/kg.min) and high (11.9 +/- 0.4 vs. 12.1 +/- 0.5 mL/kg.mm) insulin infusion rates. Glucose production was significantly increased in the hyperthyroid patients during the basal state (17.6 +/- 0.9 vs. 11.5 +/- 0.5 mumol/kg.min; P less than 0.001) and remained elevated during the final 0.5 h of the low (12.1 +/- 1.1 vs. 5.9 +/- 1.7; P less than 0.01) and high (3.2 +/- 1.2 vs. 0.5 +/- 0.3; P less than 0.05) insulin infusion rates. Peripheral insulin action, assessed by Bergman's sensitivity index, was significantly decreased in the hyperthyroid patients (7.4 +/- 2.2 vs. 15.6 +/- 2.1 L/kg min-1/pmol/L; P less than 0.02). In conclusion, hyperthyroidism is characterized by 1) hyperinsulinemia after oral glucose loading, 2) increased basal hepatic glucose production, 3) impairment of insulin-mediated suppression of hepatic glucose production, and 4) antagonism to insulin-stimulated peripheral glucose utilization.     

Marked impairment of the effect of hyperglycaemia on glucose uptake and glucose production in insulin-dependent diabetes

The effect of hyperglycaemia per se on glucose utilization and glucose production was evaluated in 12 patients with insulin-dependent diabetes and in 9 non-diabetic control subjects. In diabetic patients normoglycaemia was maintained during the night preceding the study by a variable intravenous insulin infusion. During the study endogenous insulin secretion was suppressed by somatostatin (300 micrograms h-1) and replaced by infusion of insulin (0.2 mU kg-1 min-1). Glucose utilization and hepatic glucose production rates were quantified at two plasma glucose concentrations (6.7 and 16.7 mmol l-1) using the two-step sequential hyperglycaemic clamp technique in combination with 3-3H-glucose tracer infusion. Duration of each step was 120 min. In diabetic patients glucose utilization, at a glucose concentration of 6.7 mmol l-1, was not different from normal (mean +/- SE: 2.9 +/- 0.2 vs 3.6 +/- 0.3 mg kg-1 min-1, 0.05 less than p less than 0.10), but the response to marked hyperglycaemia was significantly reduced (5.4 +/- 0.5 vs 9.4 +/- 1.0 mg kg-1 min-1, p less than 0.01). Hepatic glucose production was also normal at 6.7 mmol l-1 (1.4 +/- 0.1 vs 1.4 +/- 0.1 mg kg-1 min-1, NS), but whereas in control subjects glucose production was suppressed during hyperglycaemia of 16.7 mmol l-1 (0.3 +/- 0.4 mg kg-1 min-1, p less than 0.01), a slight increase was observed in diabetic patients (2.0 +/- 0.2 mg kg-1 min-1, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of insulin immunization on glucose tolerance in normal rats

Normal rats were immunized with insulin and Freund's adjuvant and submitted to an intravenous glucose tolerance test. Plasma glucose and free and total IRI levels were determined and compared to those observed in untreated rats, and in animals injected with the Freund's adjuvant used for the immunization procedure. In six of the 15 insulin injected animals, a significant amount of IRI (more than 100 mU/l) was found to circulate in bound form. In these animals, the fasting plasma glucose concentrations, and glucose disappearance rates were not different from those observed in all the other groups. However, the rise in their free IRI level was delayed, as was the return to basal level: 45 min after glucose injection, the free IRI concentration was still 98 +/- 29 mU/l in the six immunized rats vs 14 +/- 6 mU/l in those treated with Freund's adjuvant (p less than 0.01). Furthermore, the secondary nadir in the plasma glucose concentration observed at 60 min after glucose injection, was lower in the immunized rats (5.4 +/- 0.5 vs 6.8 +/- 0.3 mmol/l, p less than 0.05). It is concluded that in normal animals, IRI binding in proportions similar to those commonly observed in insulin-treated diabetic patients does not alter glucose tolerance but might lead to abnormal insulin kinetics and secondary hypoglycemia. These results might have implications for the use of closed-loop insulin delivery systems in type 1 (insulin-dependent) diabetic patients with insulin antibodies.     

Lack of effect of a physiological elevation of plasma non-esterified fatty acid levels on insulin secretion

Elevated plasma non-esterified fatty acid (NEFA) levels in obese subjects may contribute to their higher insulin secretory rates by direct effects on the islet B-cells. This may involve short-term metabolic effects, or long-term effects on islet B-cell mass, which is characteristically increased in obesity. We examined the effects of elevating plasma NEFA levels for 5.5 to 7 h on insulin secretion after an overnight fast and during a 90 min 12 mmol/l hyperglycemic clamp in 9 normal women (40.1 +/- 9.5 years [mean +/- SD]; BMI: 25.2 +/- 3.72 kg/m(2) ). Subjects were studied twice. In one study plasma NEFA levels were increased approximately 2-fold by infusion of 20% Intralipid (60 ml/h) and heparin (900 U/h) for 5.5 h before and throughout the glucose clamp. Elevated NEFA levels were associated with a small increase in fasting plasma glucose (5.0 +/- 0.1 vs 4.7 +/- 0.1 mmol/l, P <0.05) and C-peptide levels (0.54 +/- 0.09 vs 0.41 +/- 0.06 nmol/l, P <0.05). The increase in fasting insulin levels did not, however, reach statistical significance (9.0 +/- 2.5 vs 5.3 +/- 1.4 mU/l, NS). During the glucose clamp, plasma NEFA levels were suppressed to very low levels in the saline control study. Although plasma NEFA levels also fell in the lipid/heparin study, they remained significantly higher than on the control day, and somewhat higher than might be expected postprandially in obese subjects. During the glucose clamps, plasma glucose, insulin, and C-peptide profiles were similar on the two study days. No difference in either first or second phase insulin secretion was observed between the two studies. In conclusion, our findings do not support the idea that the exaggerated insulin secretion in obesity is mediated by short-term effects of plasma NEFA levels on islet B-cell metabolism, independent of plasma glucose levels.     

Glucagon-like peptide-1 (7-37) augments insulin-mediated glucose uptake in elderly patients with diabetes.

BACKGROUND: Glucagon-like peptide-1 (GLP-1) is an intestinal insulinotropic hormone that augments glucose-induced insulin secretion in patients with type 2 diabetes. It has also been proposed that a substantial component of the glucose-lowering effects of GLP-1 occurs because this hormone enhances insulin-mediated glucose disposal. However, interpretations of the studies have been controversial. This study determines the effect of GLP-1 on insulin-mediated glucose disposal in elderly patients with type 2 diabetes. METHODS: Studies were conducted on 8 elderly patients with type 2 diabetes (age range, 76 +/- 1 years; body mass index, 28 +/- 1 kg/m(2)). Each subject underwent two 180-minute euglycemic (insulin infusion rate, 40 mU/m(2)/min) insulin clamps in random order. Glucose production (Ra) and disposal (Rd) rates were measured using tritiated glucose methodology. In one study, glucose and insulin alone were infused. In the other study, a primed-continuous infusion of GLP-1 was administered at a final rate of 1.5 pmol x kg(-1) x min(-1) from 30 to 180 minutes. RESULTS: Glucose values were similar between the control and GLP-1 infusion studies. 120- to 180-minute insulin values appeared to be higher during the GLP-1 infusion study (control, 795 +/- 63 pmol/l; GLP-1, 1140 +/- 275 pmol/l; p = not significant [NS]). The higher insulin values were largely due to 2 subjects who had substantial insulin responses to GLP-1 despite euglycemia and hyperinsulinemia. The 120- to 180-minute insulin values were similar in the other 6 subjects (control, 746 +/- 35 pmol/l; GLP-1, 781 +/- 41 pmol/l; p = NS). Basal (control, 2.08 +/- 0.05 mg/kg/min; GLP-1, 2.13 +/- 0.04 mg/kg/min; p = NS) and 120- to 180-minute (control, 0.50 +/- 0.18 mg/kg/min; GLP-1, 0.45 +/- 0.14 mg/kg/min; p = NS) Ra was similar between studies. The 120- to 180-minute Rd values were higher during the GLP-1 infusion studies (control, 4.73 +/- 0.39 mg/kg/min; GLP-1, 5.52 +/- 0.43 mg/kg/min; p <.01). When the 2 subjects who had significant insulin responses to GLP-1 during the euglycemic clamp were excluded, the 120- to 180-minute Rd values were still higher in the GLP-1 infusion study (control, 5.22 +/- 0.32 mg/kg/min; GLP-1, 6.05 +/- 0.37 mg/kg/min; p <.05). CONCLUSIONS: We conclude that GLP-1 may enhance insulin sensitivity in elderly patients with diabetes.