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)     

Metabolic studies in lipoatrophic diabetes: mechanism of hyperglycemia and evidence of resistance to insulin of lipid metabolism

We determined in 5 control subjects and in one patient with total congenital lipoatrophy (LA) the effect of insulin infusion on glucose flux and some aspects of lipid metabolism. In the post-absorptive state LA had moderate hyperglycemia (9.2 versus 3.80 +/- 0.07 mmol.l-1) and hyperinsulinemia (19 vs 12 +/- 3 mU.l-1) and a massive increase in glucose production (7.51 mg.kg.-1.min-1) and disappearance (7.40 mg.kg-1.min-1) rates (control subjects: 2.29 +/- 0.14 mg.kg-1 min-1). Raising peripheral insulin levels to 28 +/- 3 mU.l-1 suppressed endogenous glucose production in the control subjects whereas in LA significant (2.01 mg.kg-1.min-1) production persisted even when peripheral insulinemia was raised to 58 mU.l-1. Insulin infusion in control subjects increased progressively glucose utilization to a final value of 15.7 +/- 0.7 mg.kg-1.min-1 (corresponding plasma insulin: 482 +/- 44 mU.l-1). Insulin infusion in LA initially lowered glucose level near to normal values and exogenous glucose was infused for an insulin infusion rate of 10 mU.kg-1.min-1; at this insulin infusion rate glucose utilization rate (6.52 mg.kg-1.min-1) was decreased relative to control subjects in spite of higher insulin levels (750 mU.l-1). NEFA, glycerol and ketone bodies (KB) levels were decreased to undetectable levels by insulin infusion in the normal subjects whereas NEFA and glycerol were decreased only in part and KB were not modified in LA. In addition glycerol and KB appearance rates determined in LA were not suppressed by insulin infusion as expected.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lack of effects of angiotensin-converting enzyme (ACE)-inhibitors on glucose metabolism in type 1 diabetes

To evaluate the impact of ACE-inhibitors on insulin-mediated glucose uptake, glucose-induced glucose uptake, and hepatic glucose production, a sequential glucose clamp was performed in eight normotensive Type 1 diabetic patients after 3 weeks of enalapril therapy 20 mg day-1 and during control conditions. The experiments were carried out in random order. Mean arterial blood pressure was significantly reduced during ACE-inhibition (95 +/- 3 (+/- SE) vs 84 +/- 3 mmHg; p less than 0.02), while blood glucose control as assessed by HbA1c was unaltered (7.9 +/- 0.5 vs 7.6 +/- 0.5%). The night prior to the study normoglycaemia was maintained by a Biostator. A two-step hyperinsulinaemic euglycaemic clamp (insulin infusion rate 0.3 and 0.8 mU kg-1 min-1) was followed by a hyperinsulinaemic and hyperglycaemic clamp (insulin infusion rate 0.8 mU kg-1 min-1, plasma glucose 11 mmol l-1). Insulin concentrations were comparable with and without enalapril treatment. During the hyperinsulinaemic clamps isotopically determined glucose disposal was unchanged (low dose 2.5 +/- 0.3, high dose 4.3 +/- 0.7 vs 2.6 +/- 0.3 and 4.3 +/- 0.7 mg kg-1 min-1, enalapril vs control). Glucose-induced glucose disposal (9.2 +/- 1.2 vs 9.1 +/- 1.2 mg kg-1 min-1) was also similar, as were non-protein respiratory exchange ratios (indirect calorimetry). Glucose production was not changed by enalapril. In conclusion, treatment with enalapril has no significant effect on glucose metabolism in Type 1 diabetes.     

Acute changes in plasma non-esterified fatty acid concentration do not change hepatic glucose production in people with type 2 diabetes

The effect of changes in plasma non-esterified fatty acid concentration (NEFA) on plasma glucose concentration, hepatic glucose production (Ra), and glucose disposal (Rd) rates was determined in 14 patients with Type 2 diabetes. Seven patients had relatively mild fasting hyperglycaemia (less than 10.0 mmol l-1), whereas the remaining seven had relatively severe fasting hyperglycaemia (greater than 14.0 mmol l-1). Each patient was infused from 2000 to 0800 h with 3-3H-glucose on two occasions, with or without neutral fat emulsion and heparin (mild hyperglycaemia group), or with or without nicotinic acid (severe hyperglycaemia group). Plasma NEFA concentration increased from 0.33 +/- 0.06 (+/- SE) to 4.78 +/- 0.42 mmol l-1 in response to the lipid and heparin infusion, but plasma glucose concentration (7.8 +/- 0.7 vs 7.4 +/- 0.8 mmol l-1), Ra (0.44 +/- 0.02 vs 0.46 +/- 0.02 mmol m-2 min-1), and Rd (0.42 +/- 0.02 vs 0.46 +/- 0.02 mmol m-2 min-1) were unchanged. Nicotinic acid decreased plasma NEFA concentration from 0.54 +/- 0.15 to 0.23 +/- 0.08 mmol l-1, but plasma glucose (15.0 +/- 1.0 vs 15.5 +/- 1.4 mmol l-1), Ra (0.74 +/- 0.07 vs 0.68 +/- 0.07 mmol m-2 min-1), and Rd (0.73 +/- 0.07 vs 0.68 +/- 0.07 mmol m-2 min-1) were unchanged. The results indicate that acute changes in plasma NEFA concentration did not lead to any change in overnight glucose production or disposal rates.     

Peripheral and hepatic resistance to insulin and hepatic resistance to glucagon in uraemic subjects. Studies at physiologic and supraphysiologic hormone levels

To characterize endogenous glucose production in uraemia, nondialyzed uraemic patients and controls were exposed to two major modulating hormones, insulin and glucagon. Nineteen uraemic and 15 healthy subjects underwent either a 2-step (insulin infusion rates: 0.45 and 1.0 mU.kg-1.min-1) or a 3-step (insulin infusion rates: 0.1, 0.2 and 0.3 mU.kg-1.min-1) sequential euglycaemic insulin clamp. Average steady state serum insulin concentrations were almost identical during all five infusion rates in uraemic patients (16, 22, 26, 31 and 66 mU/l) and controls (15, 19, 24, 33 and 68 mU/l). At all steps, insulin infusion was accompanied by significantly lower glucose disposal rates [( 3(-3)H]glucose) in uraemic patients compared with controls (P less than 0.05 or less). Moreover, the restraining potency of insulin on endogenous glucose production was much more prominent in healthy than in uraemic subjects at the lowest three infusion rates (0.6 +/- 1.0 versus 1.4 +/- 0.3 (mean +/- 1 SD), -0.3 +/- 0.7 versus 0.7 +/- 0.3, and -1.1 +/- 0.7 versus 0.2 +/- 0.6 mg.kg-1.min-1; P less than 0.05, P less than 0.01 and P less than 0.01, respectively), implying a shift to the right of the dose-response curve in uraemia. In contrast, basal values were comparable (2.4 +/- 0.3 versus 2.2 +/- 0.6 mg.kg-1.min-1) as the difference vanished at higher infusion rates, i.e. peripheral insulinaemia above approximately equal to 30 mU/l. Another 7 uraemic patients and 7 controls were infused with glucagon at constant rates of 4 or 6 ng.kg-1.min-1, respectively, for 210 min concomitant with somatostatin (125 micrograms/h) and tritiated glucose. The ability of glucagon to elevate plasma glucose was markedly attenuated in uraemic patients compared with controls during the initial 60 min of glucagon exposure. This difference was entirely due to diminished hepatic glucose production (3.5 +/- 0.8 versus 4.8 +/- 1.0 mg.kg-1.min-1; P less than 0.05). In conclusion, in addition to insulin resistance in peripheral tissues, uraemia is also associated with hepatic insulin resistance. Furthermore, glucagon challenge implies impaired early endogenous glucose release in uraemia suggesting a superimposed hepatic resistance to glucagon.     

Insulin-mediated glucose disposal in type 1 (insulin-dependent) diabetic subjects treated by continuous subcutaneous or intraperitoneal insulin fusion

In order to determine if intraperitoneal insulin infusion could improve the insulin resistance of type 1 diabetic patients we have used the englycaemic insulin clamp technique in order to study the effects of insulin on glucose disposal in four C peptide negative type 1 diabetic patients treated by continuous subcutaneous or intraperitoneal insulin infusion and in five control subjects. Compared to control subjects, the diabetic patients treated by subcutaneous insulin infusion had a decreased maximal capacity of glucose utilization (diabetics: 12.6 +/- 0.3 mg.kg-1.min-1; controls: 15.7 +/- 0.7 mg/kg-1.min-1, p less than 0.01) and a trend towards higher half-maximally effective insulin concentrations (diabetics: 70 +/- 11 mU/l-1, controls: 48 +/- 4 mU/l-1). Treatment of the diabetic patients by intraperitoneal insulin infusion for 2 months decreased their mean peripheral free insulin levels (during subcutaneous infusion: 23.5 +/- 2.2 mU/l-1; during intraperitoneal infusion: 18.4 +/- 1.4 mU/l-1, p less than 0.05). However, mean daily insulin requirements were not decreased (during subcutaneous infusion: 0.59 +/- 0.05 U/kg-1.day-1; during intraperitoneal infusion: 0.57 +/- 0.03 U/kg-1.min-1). Moreover, the diabetic patients had a consistently lower maximal capacity of glucose utilization (12.6 +/- 0.7 mg kg-1.min-1) than control subjects (p less than 0.01) without modification of the half-maximally effective insulin concentration (62 +/- 10 mU.l-1). In conclusion, the only benefit of intraperitoneal insulin infusion was a reduction of peripheral free insulin levels; this decrease of peripheral insulinaemia was not associated with an improvement in the insulin resistance of diabetic patients.     

Insulin supplement in type 2 diabetic patients with secondary failure to oral agents ameliorates hepatic and peripheral insulin sensitivity but not insulin secretion

In order to investigate the mechanism of amelioration of metabolic abnormalities with supplementary doses of insulin, islet B-cell function and insulin sensitivity were measured in 10 patients with Type 2 diabetes in secondary failure to oral agents. A small dose of ultralente insulin (0.26 +/- 0.07 U kg-ideal-body-weight-1) was added in the morning before breakfast. After 3 months insulin therapy and progressive improvement of metabolic control (HbA1 from 10.5 +/- 0.4 to 9.0 +/- 0.3% at the end of insulin treatment, p less than 0.001), basal C-peptide and incremental area during an oral glucose tolerance test were unchanged. In vivo peripheral insulin sensitivity (euglycaemic clamp with insulin infusion of 40, 160, and 600 mU m-2 min-1, respectively) was significantly improved (glucose requirement: to 4.7 +/- 1.0 from 3.0 +/- 0.6 mg kg-1 min-1, p less than 0.05 at first insulin level; to 10.8 +/- 0.5 from 9.3 +/- 0.7 mg kg-1 min-1, p less than 0.01 at second level; to 13.3 +/- 0.6 from 11.8 +/- 0.8 mg kg-1 min-1, p less than 0.025 at third level). Basal hepatic glucose production was also significantly reduced (from 4.3 +/- 0.4 to 3.3 +/- 0.3 mg kg-1 min-1, p less than 0.05), and residual glucose production further suppressed after insulin supplement (from 1.1 +/- 0.4 to 0.3 +/- 0.2 mg kg-1 min-1 after 120 min at 100 mU l-1 plasma insulin, p less than 0.05). Specific insulin binding to mononuclear leucocytes was unchanged (from 3.1 +/- 0.3 to 3.5 +/- 0.3%, NS).     

Impaired glucose tolerance in obesity is associated with insensitivity to insulin in multiple aspects of metabolism as assessed by a low dose incremental insulin infusion technique.

To determine whether Impaired Glucose Tolerance gives rise to additional defects in insulin action in lipid and ketone metabolism, thirty-two obese subjects were studied by low-dose incremental insulin infusion. Sixteen had Impaired Glucose Tolerance and 16 had normal glucose tolerance. Body mass index was 36.9-80.9 kg m-2 and was similar in each group. In patients with Impaired Glucose Tolerance, plasma insulin was higher in the fasted state (logarithmic mean 14.5 (9.8-21.6) (-SD(-)+SD) vs 9.6 (6.4-14.5) mU l-1, p less than 0.01) and during the infusion (p less than 0.001). The metabolic clearance rate for insulin at the highest infusion rate was lower (14.2 +/- 0.8 (+/- SE) vs 18.9 +/- 2.1 ml kg-1 min-1, p less than 0.05) in these subjects. Basal hepatic glucose production was higher in subjects with Impaired Glucose Tolerance (6.3 +/- 0.4 vs 4.5 +/- 0.6 mol kg-1 min-1, p less than 0.02) and remained elevated during infusion (p less than 0.01). Glucose disposal per unit circulating insulin at the maximal infusion rate was approximately half in subjects with Impaired Glucose Tolerance (0.022 +/- 0.010 vs 0.047 +/- 0.017 ml kg-1 min-1 mU-1 l, p less than 0.01). When simultaneous insulin and metabolite concentrations during the infusion are plotted as dose-response relationships, a difference in relative sensitivity to insulin in Impaired Glucose Tolerance over subjects with normal glucose tolerance is suggested for non-esterified fatty acids 0.72 (95% CI 0.62-0.84) and glycerol 1.85 (1.37-2.49).(ABSTRACT TRUNCATED AT 250 WORDS)     

Hepatic response to insulin in control of glucose kinetics in the neonatal lamb

Imprecise control of neonatal glucose homeostasis may be partially due to decreased hepatic response to insulin. In prior kinetic studies the effect of that response could not be determined because the hormonal effects of insulin could not be separated from those of glucagon. Somatostatin (SRIF) suppresses secretion of both and has been used to differentiate the hormonal effects. Eighteen term lambs (age 4.2 +/- 0.3 days and birth weight 4.0 +/- 0.2 kg (M +/- SEM] were infused with 0.9% NaCl at 0.06 mL.kg-1 min-1 plus 100 microCi/kg D[6-3H] glucose by prime plus constant infusion. Ra (production) and Rd (utilization) were measured during infusion of SRIF or SRIF plus replacement insulin (0.2 mU.kg-1 min-1). There was a rise in pl. glucose (98 +/- 10 to 119 +/- 10 mg/dL (P less than .0001)); a fall (46.2%) in pl insulin [13 +/- 2 to 7 +/- 1 microU/mL (P less than .0004); a rise in Ra (7.8 +/- 1.5 to 13.2 +/- 4.1 mg.kg-1 min-1 P less than .047); and a rise in Rd (7.7 +/- 1.4 to 11.3 +/- 3.0 mg.kg-1 min-1 (P less than .047)) in SRIF treated animals compared to nontreated controls. There was no change in plasma glucagon (454 +/- 182 to 255 +/- 141 pg/mL) in SRIF treated animals compared to nontreated controls. All perturbations were eliminated when SRIF plus replacement insulin produced control insulin levels. Insulin suppression in the neonatal period resulted in glucagon being unopposed which produced an elevated rate of glucose production and elevated plasma glucose concentration.     

Insulin resistance in alloxan-diabetic dogs: Evidence for reversal following insulin therapy

Hepatic glucose production and peripheral glucose utilization were measured basally and during infusion of insulin (25 and 40 m U X kg-1 X h-1) in normal dogs and in insulin-deficient diabetic dogs, before and after a 10-14 day period of insulin treatment. Basal hepatic glucose production was significantly raised in the diabetic dogs (21.4 +/- 2.5 mumol X kg-1. min-1; p less than 0.005) compared with normal dogs (11.9 +/- 2.5 mumol X kg-1 X min-1) and fell by 20% in diabetic dogs following insulin treatment (17.4 +/- 3.0 mumol X kg-1 X min-1). However, in all groups, hepatic glucose production suppressed equally well during the low dose insulin infusions, suggesting that the raised hepatic glucose production of diabetes is due to insulin deficiency and not hepatic insulin resistance. In addition, a marked defect of glucose utilization was found in the diabetic dogs (25 +/- 5 mumol X kg-1 X min-1; p less than 0.001) compared with normal dogs (99 +/- 15 mumol X kg-1 X min-1) during matched hyperinsulinaemia and hyperglycaemia. This defect of glucose utilization, as defined by euglycaemic insulin dose-response curves employing insulin infusion rates between 40-600 mU X kg-1 X h-1, demonstrated a marked reduction of glucose disposal in diabetic dogs. The severity of the insulin resistance closely paralleled the degree of hyperglycaemia. In contrast, following 10-14 days of insulin treatment, an improvement of glucose disposal was seen in all diabetic dogs. It is concluded that insulin deficiency leads to (a) increased hepatic glucose production, and (b) the development of marked peripheral insulin resistance, which is reversed by insulin treatment.     

Insulin action and hepatic glucose cycling in essential hypertension.

Peripheral insulin resistance is a feature of essential hypertension, but there is little information about hepatic insulin sensitivity. To investigate peripheral and hepatic insulin sensitivity and activity of the hepatic glucose/glucose 6-phosphate (G/G6P) substrate cycle in essential hypertension, euglycemic glucose clamps were performed in eight untreated patients and eight matched controls at insulin infusion rates of 0.2 and 1.0 mU.kg-1.min-1. A simultaneous infusion of (2(3)H)- and (6(3)H)glucose, combined with a selective detritiation procedure, was used to determine glucose turnover, the difference being G/G6P cycle activity. Endogenous hepatic glucose production (EGP) determined with (6(3)H)glucose was similar in hypertensive and control groups in the postabsorptive state (11.0 +/- 0.3 v 10.9 +/- 0.3 mumol.kg-1.min-1) and with the 0.2 mU insulin infusion (4.9 +/- 0.5 v 4.0 +/- 0.8 mumol.kg-1.min-1). With the 1.0 mU insulin infusion, glucose disappearance determined with (6(3)H)glucose was lower in the hypertensive group (21.8 +/- 2.4 v 29.9 +/- 2.4 mumol.kg-1.min-1, P less than .001). G/G6P cycle activity was similar both in the postabsorptive state (2.2 +/- 0.4 v 2.7 +/- 0.4 mumol.kg-1.min-1) and during insulin infusion (0.2 mU, 2.5 +/- 0.3 v 2.9 +/- 0.4; 1.0 mU, 4.7 +/- 0.3 v 5.3 +/- 1.1 mumol.kg-1.min-1 for hypertensive and control groups, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Alpha-adrenergic agonists stimulate neonatal glucose production less than beta-adrenergic agonists in the lamb

Epinephrine, a catecholamine with both alpha (alpha)- and beta (beta)-adrenergic agonist effects, may produce clinical hyperglycemia in the adult by increasing glucose production and decreasing glucose clearance. However, the relative contribution of alpha v beta adrenergic agonists in control of neonatal glucose kinetics has not been defined. Twenty-three term lambs (weighing 4.4 +/- 0.2 kg, mean +/- SEM, and aged 3.8 +/- 0.4 days) were infused with 0.9% NaCl at 0.6 mL.kg-1 min-1 + 100 microCi/kg D[6-3H]-glucose by prime plus constant infusion for 210 minutes. Ra (rate of production) was measured during infusion of variable doses of epinephrine with or without variable doses of propranolol, a competitive beta-adrenergic antagonist to isolate the alpha-adrenergic agonist effects. All basal kinetic data were comparable. Under conditions of epinephrine infusion, the plasma glucose concentration increased from 95 +/- 10 mg/dL to 129 +/- 18 mg/dL (50 ng.kg-1 min-1 epinephrine; P less than .0001) and from 85 +/- 6 mg/dL to 253 +/- 8 mg/dL (500 ng.kg-1 min-1 epinephrine; P less than .00001) compared with controls (96 +/- 7 mg/dL to 95 +/- 8 mg/dL). When epinephrine and propranolol were infused simultaneously, plasma glucose concentration increased from 95 +/- 10 mg/dL to 122 +/- 12 mg/dL (50 ng.kg-1 min-1 epinephrine + 1.1 micrograms.kg-1 min-1; P less than .0001) and from 78 +/- 9 mg/dL to 134 +/- 12 mg/dL (500 ng.kg-1 min-1 epinephrine + 11 micrograms.kg-1 min-1; P less than .0001) compared with controls (no epinephrine, no propranolol).(ABSTRACT TRUNCATED AT 250 WORDS)     

Sulfonylureas in insulin-dependent (type I) diabetes: evidence for an extrapancreatic effect in vivo

The effect of glibenclamide treatment on insulin-mediated glucose disposal was studied in eight C-peptide-negative type I diabetic patients. The patients were studied twice by the euglycemic insulin clamp technique. One of the two experiments was preceded by glibenclamide treatment at the dose of 5 mg, three times daily for 15 days; half of the patients had the first test before and the second test after sulfonylurea treatment, and vice versa. Insulin was infused for four periods of 2 h each sequentially at 0.5, 1.0, 2.0, and 5.0 mU kg-1 min-1; for each insulin infusion period, the steady state plasma free insulin levels were comparable with or without glibenclamide. The mean +/- SEM plasma glucose concentration was 88 +/- 2 mg/dl in both experiments. The insulin-mediated glucose disposal rate was greater with glibenclamide during the first insulin infusion period (which generated plasma free insulin levels within the physiological range) 2.68 +/- 0.32 mg kg-1 min-1 with glibenclamide vs. 1.97 +/- 0.20 mg kg-1 min-1 without glibenclamide (P less than 0.005). However, glucose disposal rates did not differ in the diabetic patients with or without glibenclamide treatment during the second, third, and fourth insulin infusion periods, which generated plasma free insulin levels in the supraphysiological range. These results provide evidence for an extrapancreatic effect of glibenclamide at low insulin concentrations during euglycemic clamping in patients with insulin-dependent diabetes mellitus. However, this effect was not reflected clinically in either an increased rate of hypoglycemic reactions or decreased insulin needs during the short term period of treatment.     

Effects of hypopituitarism and growth hormone replacement therapy on the production and utilization of glucose in childhood

Glucose metabolism during fasting was investigated in 10 children aged 1.5 month-11.5 yr with deficiency of GH with or without other pituitary hormone deficiencies. After 10-16 h of fasting, mean plasma glucose was 56 +/- 4 (SEM) mg/dl, the result of decreased hepatic production of glucose (3.3 +/- 0.3 mg kg-1 min-1) insufficient to match glucose utilization (3.6 +/- 0.4 mg kg-1 min-1). The diminution of plasma glucose and of glucose production was similar whether ACTH deficiency was present (3.2 +/- mg kg-1 min-1) or not (3.5 +/- 0.6 mg kg-1 min-1). These results indicate that the lack of GH was the primary cause of hypoglycemia. Fasting plasma alanine (212 +/- 41 mumol/liter) and lactate (1222 +/- 136 mumol/liter), the main gluconeogenic substrates, were normal and did not correlate with the decrease of hepatic glucose release. Both plasma FFA (552 +/- 35 microM) and beta-hydroxybutyrate (654 +/- 158 microM) were in the low normal range, and neither correlated with the rate of glucose utilization. hGH replacement therapy resulted in a normalization of fasting plasma glucose concentration (78.5 +/- 6 mg/dl, P less than 0.005) and hepatic glucose production (6.1 +/- 1.2 mg kg-1 min-1). No significant changes occurred in the plasma concentrations of gluconeogenic or lipid substrates. These results, together with the known stimulatory effects of GH on carbohydrate-induced insulin secretion and storage of hepatic glycogen, suggest that the changes in glucose production in untreated and GH treated patients reflect the degree of hepatic glycogen replenishment.     

Hyperglycemia inhibits glucose production in man independent of changes in glucoregulatory hormones.

To evaluate the influence of hyperglycemia on hepatic glucose output in the absence of a rise in insulin, glucose was infused for 2 hours into six juvenile-onset diabetics receiving a constant infusion of insulin at a rate of 0.05-0.15 microM kg-1min-1. Prior to the infusion of glucose, insulin administration resulted in stable levels of plasma glucose (76 +/- 8 mg/dl) and glucose output (1.9 +/- 0.1 mg kg-1min-1). The addition of glucose produced a 2-3 fold rise in plasma glucose and a prompt fall in glucose output to 0.2-0.4 mg kg-1min-1, despite the unchanged rate of insulin infusion and the absence of a reduction in plasma glucagon or catecholamines. A similar decline in glucose output was observed when exogenous glucagon (1 ng kg-1-min-1) was added to the glucose infusion. We conclude that in the presence of basal insulin levels hyperglycemia inhibits glucose output independent of a rise in insulin or a fall in anti-insulin hormones.     

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.     

Interaction of lipid and carbohydrate metabolism after infusions of lipids or of lipid lowering agents: lack of a direct relationship between free fatty acid concentrations and glucose disposal.

The present work was planned to study the effects of changes in lipid metabolism irrespective of FFA concentrations (FFA) on the regulation of oxidative and nonoxidative disposal of a glucose infusion during hyperinsulinaemia. Fifteen normal volunteers participated in the 3 protocols, in which 1) Intralipid 2) beta-pyridylcarbinol or 3) isotonic saline were infused during 2 hours. Thereafter, these infusions were discontinued and a two-hour euglycaemic hyperinsulinaemic clamp was performed. All three studies were carried out in combination with indirect calorimetry to measure glucose uptake, and oxidative and nonoxidative glucose disposal (corresponding essentially to glucose storage). Plasma FFA concentrations were 508 +/- 34, 601 +/- 43 and 546 +/- 45 mumol/l in the basal state during the Intralipid, beta-pyridylcarbinol and control protocols. It increased to 960 +/- 71 mumol/l after the Intralipid infusion, fell to 246 +/- 17 mumol/l after the beta-pyridylcarbinol infusion, vs 600 +/- 48 mumol/l in the control. At the end of the glucose-insulin clamp the values were low in the 3 protocols: 263 +/- 17, 233 +/- 19 and 204 +/- 14 mumol/l. Intralipid infusion prior to the clamp protocol induced a suppression of both insulin-mediated glucose uptake (4.91 +/- 0.46 (Intralipid) vs 6.83 +/- 0.63 mg.kg-1.min-1 (saline)) and storage (1.61 +/- 0.34 vs 2.99 +/- 0.53 mg.kg-1.min-1) while beta-pyridylcarbinol infusion induced an increased insulin-mediated glucose uptake (8.58 +/- 0.37 mg.kg-1.min-1) and in glucose storage (4.29 +/- 0.31 mg.kg-1.min-1) (p less than 0.5 vs Intralipid). These changes occurred even though FFA plasma concentrations were similar in the 3 experimental conditions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Decreased response to catecholamines in the newborn: effect on glucose kinetics in the lamb

Epinephrine, a catecholamine with both alpha (alpha) and beta (beta) adrenergic effects, may produce hyperglycemia in adults by increasing glucose production and decreasing glucose clearance. To document the degree of sensitivity and characterize maturation of neonatal glucose control, glucose kinetics were measured in 14 term newborn lambs (weight 4.5 +/- 0.3 kg [mean +/- SEM] and aged 4.1 +/- 0.4 days). Following infusion of 0.9% NaCl at 0.06 mg.kg-1 min-1 plus 100 microCi/kg D[6-3H] glucose by prime plus constant infusion, rate of production (Ra) and glucose clearance were measured during administration of epinephrine. The responses in the newborns were compared with those in six adult sheep. Under conditions of epinephrine infusion, the plasma glucose concentration in the newborn lambs increased to 129 +/- 18 mg/dL (50 ng.kg-1 min-1 epinephrine), P less than .0001, and 253 +/- 8 mg/dL (500 ng.kg-1 min-1 epinephrine), P less than .0001, compared with 95 +/- 8 mg/dL (controls, no epinephrine). Comparable values for Ra were 6.5 +/- 1.6 mg.kg-1 min-1 (50 ng.kg-1 min-1 epinephrine), P = NS, and 18.5 +/- 3.0 mg.kg-1 min-1 (500 ng.kg-1 min-1 epinephrine), P less than .0001, compared with 5.3 +/- 0.5 mg.kg-1 min-1 (controls, no epinephrine).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of metformin on glucose, insulin and lipid metabolism in patients with mild hypertriglyceridaemia and non-insulin dependent diabetes by glucose tolerance test criteria.

The effect of metformin treatment was studied in nine patients with mild (fasting plasma glucose concentration less than 7.5 mmol.l-1) non-insulin-dependent diabetes mellitus (NIDDM) and fasting plasma triglyceride (TG) concentration greater than 2.0 mmol.l-1. Individuals were studied before and three months after receiving 2.5 g/day of metformin. Mean hourly plasma glucose concentration from 8 AM to 4 PM (7.5 +/- 0.5 vs 6.5 +/- 0.4 mmol.l-1, p less than 0.001), as well as glycosylated hemoglobin levels (7.0 +/- 0.5 vs 6.2 +/- 0.2%, p less than 0.02) were significantly lower following metformin treatment. The improvement in glycaemic control was not associated with an improvement in insulin stimulated glucose disposal as measured by the glucose clamp technique. Mean hourly day-long concentrations of plasma insulin (519 +/- 81 vs 364 +/- 64 pmol.l-1, p less than 0.001), FFA (502 +/- 45 vs 460 +/- 35 mu mol.l-1, p less than 0.01), and triglyceride (3.60 +/- 0.33 vs 3.02 +/- 0.31 mmol.l-1, p less than 0.001) concentrations were significantly lower following three months of metformin treatment. Finally, fasting plasma TG concentration, very low density lipoprotein (VLDL)-TG, and VLDL-cholesterol concentrations were significantly decreased, while high density lipoprotein (HDL)-cholesterol concentration was significantly increased following metformin therapy. Thus, metformin administration to individuals with NIDDM, who did not have significant fasting hyperglycaemia, led to a decrease in plasma glucose, insulin, FFA, and TG concentration, and an increase in plasma HDL-cholesterol concentration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relationship between glucose oxidation and FFA concentration in septic cancer-bearing patients

Glucose oxidation is inhibited in severely ill patients. The present investigation was designed to study the relationship between glucose tissue uptake, glucose oxidation, and FFA concentration in septic cancer-bearing patients. The influence of glucose infusion alone (3.9 mg x kg-1 x min-1), followed by a euglycemic clamp with the same glucose load, on oxidation of glucose, plasma FFA concentration, and lipid oxidation were measured in eight septic cancer-bearing patients. During infusion of 3.9 mg glucose x kg-1 x min-1 glucose tissue uptake was 4.6 +/- 0.3 mg x kg-1 x min-1, glucose oxidation 0.5 +/- 0.2 mg x kg-1 x min-1, FFA concentration 377 +/- 52 mumol x L-1, and lipid oxidation 2.0 +/- 0.2 mumol x kg-1 x min-1. During the euglycemic clamp glucose tissue uptake was 4.4 +/- 0.3 mg x kg-1 x min-1, glucose oxidation rose to 1.8 mg x kg-1 x min-1 (.001 less than P less than .01), FFA concentration dropped to 202 +/- 23 mumol x L-1 (P less than .001), and lipid oxidation to 1.2 +/- 0.2 mumol x kg-1 x min-1 (.001 less than P less than .01). Nonprotein respiratory quotient rose from 0.73 +/- 0.02 to 0.85 +/- 0.02 (.001 less than P less than .01); 11% +/- 5% of the total amount of glucose taken up by the tissues was oxidized during infusion of glucose alone and increased to 42% +/- 6% during the euglycemic glucose clamp. It is concluded that in septic cancer-bearing patients glucose oxidation is inhibited during infusion of 3.9 mg glucose x kg-1 x min-1, even when expressed as percentage of glucose tissue uptake. With insulin, glucose tissue uptake was not influenced, but glucose oxidation expressed as percentage of glucose tissue uptake was normalized.