Surgical removal of insulinoma restores glucose recovery from hypoglycaemia but does not normalize insulin action

In the present study we have evaluated the effects of chronic hyperinsulinaemia secondary to insulinoma, on insulin sensitivity and on counter-regulatory responses to hypoglycaemia. We studied six patients (M/F = 3/3; age = 40 +/- years), before and 6-9 months after surgical ablation of the neoplasia, by means of an euglycaemic-hyperinsulinaemic clamp (1 mU kg-1 min-1). Seven normal subjects (M/F = 4/3; age = 38 +/- 6 years) underwent the same experimental study as the control subjects. In insulinoma patients after 100 min of the euglycaemic-hyperinsulinaemic clamp, glycaemia was allowed to drop to a minimum value of 1.9 mmol L-1, and recovery evaluated after interrupting insulin infusion. During the entire study, 3-3H-glucose was infused to determine hepatic glucose production and glucose utilization. Surgical removal of the pancreatic adenoma was followed by a reduction in body weight (BMI = 25.7 +/- 1.9 vs. 23.0 +/- 1.6 kg m-2; P < 0.05), normalization of fasting plasma levels of glucose (2.94 +/- 0.16 vs. 4.83 +/- 0.11 mmol L-1), insulin (162 +/- 24 vs. 48 +/- 12 pmol L-1) and of basal hepatic glucose production (7.6 +/- 0.7 vs. 12.2 +/- 1.11 mumol kg-1 min-1). Before the operation, insulin-mediated glucose disposal was significantly lower than in the controls (30.8 +/- 3.1 vs. 49.1 +/- 3.1 mumol kg-1 min-1). Six to nine months after surgical removal of the adenoma, glucose utilization was unchanged (30.5 +/- 3.3 mumol kg-1 min-1) and still significantly lower than in controls (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of postprandial whole-body proteolysis in insulin-deprived IDDM

Suppression of tissue proteolysis is an important mechanism of postprandial protein anabolism, and it may be mediated by insulin, hyperaminoacidemia, or both. To evaluate whether insulin is essential in the regulation of this process, we have investigated the effect of mixed-meal ingestion on whole-body protein breakdown in insulin-deprived insulin-dependent diabetes mellitus (IDDM) patients and normal control subjects. Endogenous phenylalanine and leucine rate of appearance (Ra) from proteolysis were measured at steady-state conditions using a multiple stable isotope technique before and after the constant administration of a synthetic mixed meal. In the postabsorptive state, the IDDM patients exhibited accelerated intracellular leucine Ra (IDDM, 2.64 +/- 0.19 mumol.min-1.kg-1; control, 2.02 +/- 0.08 mumol.min-1.kg-1; P < 0.05) and plasma phenylalanine Ra (IDDM, 0.73 +/- 0.03 mumol.min-1.kg-1; control, 0.61 +/- 0.04 mumol.min-1.kg-1; P < 0.05). During meal ingestion, endogenous phenylalanine and leucine Ra values were suppressed in both the insulin-deficient IDDM (P < 0.05) and control subjects (P < 0.05). Although postmeal endogenous leucine and phenylalanine Ra values remained greater (P < 0.05) in IDDM, the delta changes from the basal endogenous leucine Ra (IDDM, -0.56 +/- 0.11 mumol.min-1.kg-1; control, -0.56 +/- 0.09 mumol.min-1.kg-1) and phenylalanine Ra (IDDM, -0.13 +/- 0.01 mumol.min-1.kg-1; control, -0.14 +/- 0.02 mumol.min-1.kg-1) were similar in both groups. In the IDDM patients, the postmeal increases from the basal leucine concentration were onefold greater (P < 0.05) than in the control-subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin action and glucose metabolism are improved by gemfibrozil treatment in hypertriglyceridemic patients

The aim of this study was to determine whether gemfibrozil-mediated decrease in very low density lipoprotein triglyceride (VLDL-TG) concentration is accompanied by an improvement in overall glucose metabolism in hypertriglyceridemic patients. We assessed this hypothesis in 7 hypertriglyceridemic without (HTG) and in 11 hypertriglyceridemic with noninsulin-dependent diabetes mellitus (NIDDM-HTG) who followed three-months treatment either with the drug or with placebo. Placebo VLDL-TG concentrations in both HTG (3.82 +/- 0.92 mmol/l (mean +/- S.D.) vs. 3.91 +/- 1.01 mmol/l) and in NIDDM-HTG (6.62 +/- 3.93 mmol/l vs. 6.84 +/- 4.16 mmol/l) were not different from baseline values, whereas gemfibrozil decreased VLDL-TG in both groups (1.84 +/- 0.56 mmol/l, P < 0.001 for HTG, and 1.93 +/- 2.68 mmol/l, P = 0.013 in NIDDM-HTG). In both groups, gemfibrozil treatment was associated with an improvement in fasting plasma glucose levels (from 5.85 +/- 0.92 mmol/l to 4.87 +/- 0.40 mmol/l in HTG, P = 0.001, and from 11.47 +/- 2.92 mmol/l to 9.56 +/- 3.41 mmol/l in NIDDM-HTG, P = 0.042). In NIDDM-HTG, gemfibrozil treatment was associated with a significantly lower 2 h-postprandial plasma glucose level (9.87 +/- 3.63 vs. 13.09 +/- 3.62, P = 0.05). A significant decrease in fasting free fatty acids (FFA) level was observed during gemfibrozil treatment in both groups, whereas in NIDDM-HTG, a significant drop of these substrates was observed in both fasting and postprandial conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of metformin treatment on whole-body and splanchnic amino acid turnover in mild type 2 diabetes

The effects of metformin therapy on whole body and splanchnic amino acid turnover are not known. Therefore, we have studied fasting and postprandial phenylalanine kinetics in type 2 diabetic subjects (non-insulin-dependent diabetes mellitus), previously treated with diet only, both before and after 4 weeks of either metformin (850 mg twice a day) (n = 11) or placebo administration (n = 6). Phenylalanine kinetic was evaluated by means of a multiple isotope technique: tritiated phenylalanine was infused i.v., whereas carbon-labeled phenylalanine was incorporated into a chemically-defined meal. Compared with placebo, metformin administration decreased both fasting (from 162 +/- 17 to 141 +/- 20 mg/dl) and postprandial (from 217 +/- 20 to 164 +/- 20 mg/dl) glucose concentrations (P < 0.05-P < 0.01). Fasting insulin concentrations were unaffected, but postmeal insulin tended to be lower (P < 0.06) after metformin. Compared with the pretreatment period, metformin administration did not change total phenylalanine rate of appearance (fasted state, 0.74 +/- 0.10 vs. 0.71 +/- 0.08 mumol/kg.min; fed state, 0.77 +/- 0.10 vs. 0.75 +/- 0.08 mumol/kg.min, respectively), dietary and endogenous phenylalanine rate of appearance, dietary phenylalanine oxidation, and splanchnic uptake, similar to what was observed in the placebo group. Our data indicate that, at least after a 4-week treatment, metformin does not affect fasting and postprandial protein turnover, as indicated by phenylalanine data, in subjects with mild non-insulin-dependent diabetes mellitus.

Fasting and postprandial phenylalanine and leucine kinetics in liver cirrhosis

To investigate body protein turnover and the pathogenesis of increased concentration of plasma phenylalanine in liver cirrhosis, we have studied phenylalanine and leucine kinetics in cirrhotic (diabetic and nondiabetic) patients, and in normal subjects, both in the postabsorptive state and during a mixed meal, using combined intravenous and oral isotope infusions. Postabsorptive phenylalanine concentration and whole body rate of appearance (Ra) were approximately 40% greater (P < 0.05) in patients than in controls. Leucine concentrations were comparable, but intracellular leucine Ra was also increased (P < 0.05), suggesting increased whole body protein breakdown. Postprandial phenylalanine Ra was also greater (P < 0.05) in the patients. This difference was due to a diminished fractional splanchnic uptake of the dietary phenylalanine (approximately 40% lower in the cirrhotics vs. controls, P < or = 0.05). Postprandial leucine Ra was also increased in the patients, but splanchnic uptake of dietary leucine was normal. Thus both increased body protein breakdown and decreased splanchnic extraction of dietary phenylalanine can account for the increased phenylalanine concentrations in liver cirrhosis.

Sequelae of acute hypoglycaemia on 24 hour blood pressure and metabolic parameters in normal and type 1 (insulin-dependent) diabetic individuals

This study was performed to assess possible delayed after-effects of acute hypoglycaemia on blood pressure (BP) and heart rate (HR) over a 24-h period. Eleven insulin-dependent diabetic patients and 11 sex, age, and body mass index matched non-diabetic subjects were studied. Blood pressure was measured using a non-invasive ambulatory blood pressure monitor following acutely induced hypoglycaemia in the morning. No significant differences were observed in 24-h systolic and diastolic BP and HR in either groups, between the day when hypoglycaemia was induced and the day when plasma glucose was kept normal. In diabetic patients, hypoglycaemia induced a temporary but significant fall in mean BP (-7 +/- 1 mmHg vs -2 +/- 2; p < 0.05). Plasma glucose levels were significantly higher in insulin-dependent diabetic patients following hypoglycaemia than in those observed during the reference test. This study demonstrates that acute hypoglycaemia in insulin-dependent diabetic subjects does not cause significant alterations in 24-h BP in either diabetic or normal subjects.

Improvement of basal hepatic glucose production and fasting hyperglycemia of type I diabetic patients treated with human recombinant ultralente insulin

OBJECTIVE

To test whether a suppertime injection of human ultralente insulin in patients with type I diabetes would result in a larger inhibition of basal hepatic glucose production (HGP) and improvement in fasting and mean daily plasma glucose levels.

RESEARCH DESIGN AND METHODS

We studied 16 type I diabetic patients (41 +/- 4 years of age; body mass index [BMI] = 23.3 +/- 0.3 kg/m2; diabetes duration > 3 years) with a crossover protocol of therapy with an intermediate and ultralente insulin. All patients were already treated with three injections per day of regular insulin in addition to intermediate-acting (NPH) insulin at suppertime. After a 14-day run-in period, patients were randomly assigned to treatment with equivalent doses (10.8 +/- 0.8 U, at 1900) of intermediate (Humulin I) or ultralente (Humulin U) insulin. After 1 month of treatment, patients were crossed over. No change of the insulin dosage was performed during the study period. Basal HGP was measured by D-(6,6-2H2)-glucose infusion. Plasma glucose concentration was measured in the fasting state and monitored during the day.

RESULTS

Before starting the study period, fasting plasma glucose was 13.4 +/- 1.1 mM and plasma free-insulin was 48.0 +/- 4.8 pM. Daily plasma glucose concentration averaged 10.3 +/- 0.3 mM and the area under the curve (AUC) was 1.41 +/- 0.05 mol/14 h. NPH insulin, given at suppertime for a month, did not induce significant changes in fasting plasma insulin (40.2 +/- 4.8 pM), glucose concentration (14.0 +/- 0.9 mM) or HGP (20.2 +/- 2.2 mumol.kg-1.min-1). Accordingly, no change occurred in the average daily plasma glucose (10.3 +/- 0.3 mM) or AUC (1.41 +/- 0.9 mol/14 h). Glycated hemoglobin also was not affected (8.2 +/- 0.4 vs. 8.2 +/- 0.3%). On the contrary, a 4-week treatment with ultralente insulin, also given at suppertime, was associated with a decline in the basal HGP (16.0 +/- 1.3 mumol.kg-1.min-1), fasting (11.3 +/- 0.9 mM) and average daily (9.4 +/- 0.3 mM) plasma glucose concentrations, and AUC (1.29 +/- 0.07 mol/14 h) of plasma glucose level (all P < 0.05). Glycated hemoglobin was reduced (7.9 +/- 0.4%). In each condition, fasting plasma glucose concentration was correlated with the average daily plasma glucose level (basal = 0.78; intermediate = 0.89; ultralente = 0.62; all P < 0.05), which suggests that ultralente insulin likely induces the improvements of metabolic control through reducing fasting plasma glucose.

CONCLUSIONS

Our results suggest that treating type I diabetic patients with ultralente insulin at suppertime provides a better modulation of basal HGP so that lower fasting plasma glucose levels are ensured. The reduction of fasting hyperglycemia is likely to affect positively daily plasma glucose control.

Mechanism(s) of the blood glucose lowering action of benfluorex

Benfluorex is a hypolipidaemic agent with biguanide-like properties. To evaluate its blood glucose lowering action, a single-blind study protocol was designed. Two groups of seven type II (non-insulin-dependent) diabetic patients matched for age (50 +/- 4 vs. 53 +/- 1 years), sex, body mass index (27.8 +/- 0.6 vs. 26.5 +/- 0.7 kg/m2), and duration of diabetes were studied before and after 1 month of treatment with benfluorex 150 mg tid (= tres in die = three times a day), PO (= per os = by mouth) or a placebo, respectively. All patients had previously been treated by diet alone. In all patients, parameters of glucose and lipid metabolism were obtained. Insulin sensitivity was assessed by means of a euglycaemic (5.1 +/- 0.1 mM) hyperinsulinaemic (516 +/- 28 pM) clamp performed in combination with [3(-3)H]glucose infusion and indirect calorimetry. In no case was there a significant change in body mass index (27.6 +/- 0.5 vs. 26.4 +/- 0.7 kg/m2). After 1 month of treatment, fasting plasma glucose (6.8 +/- 0.2 vs. 8.1 +/- 0.6 mM) and HbA1C (glycated haemoglobin; 6.5 +/- 0.2 vs. 8.0 +/- 0.7%) were lower in the benfluorex group than in the placebo-treated patients (both p < 0.05). No change was observed in hepatic glucose production (HGP) (13.5 +/- 1.4 vs. 13.9 +/- 1.1 mumol/min per kg), the basal rate of glucose, and lipid oxidation and non-oxidative glucose metabolism, or in plasma triglyceride and total cholesterol concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of different plasma glucose concentrations on lipolytic and ketogenic responsiveness to epinephrine in type I (insulin-dependent) diabetic subjects

The effects of two different plasma glucose concentrations (5 and 10 mmol/L) on lipolysis and ketogenesis during baseline and in response to epinephrine infusion were evaluated in insulin-dependent diabetic patients. Each insulin-dependent diabetic subject was studied during euglycemia, hyperglycemia with hypoinsulinemia, and hyperglycemia with hyperinsulinemia. Total ketone body (TKB) concentrations were significantly higher in hyperglycemic-hypoinsulinemic diabetics than in hyperglycemic-hyperinsulinemic and normoglycemic diabetics. Hyperglycemic-hyperinsulinemics had higher TKB concentrations than euglycemic diabetics. During epinephrine infusion, the ketone body rate of appearance and concentration significantly increased in all groups. Plasma FFA concentrations were significantly higher in hyperglycemic-hypoinsulinemic diabetics than in the other groups. During epinephrine infusion, the plasma FFA rate of appearance and concentration significantly increased in all groups. The apparent fraction of FFA converted to ketones was increased by epinephrine in all groups, except in hyperglycemic-hyperinsulinemic diabetics. In conclusion, this study demonstrates that although insulin alone decreases FFA and TKB concentrations, it does not affect the fraction of FFA converted to ketones. If hyperinsulinemia is superimposed on hyperglycemia, there is both a reduction of ketogenesis capacity, compared to hyperglycemia alone, and a decrease in the apparent fraction of FFA converted to ketone bodies.

Mechanisms of fasting hypoglycemia and concomitant insulin resistance in insulinoma patients

To gain further insight into the pathogenesis of fasting hypoglycemia in patients with insulin-secreting adenoma of the pancreas, we studied seven patients affected by insulinoma (age, 42 +/- 7 years; body mass index [BMI], 27 +/- 2 kg/m2) and seven normal subjects. In insulinoma patients, hepatic glucose production (HGP) and glucose utilization (Rd) were evaluated by infusion of 3-3H-glucose at spontaneous fasting plasma glucose concentration, after restoration of euglycemia and during euglycemic insulin clamp (40 mU/m2/min). In insulinoma patients, fasting plasma glucose concentration (2.8 +/- 0.2 v 4.5 +/- 0.1 mmol/L; P < .001), HGP, and glucose Rd (7.8 +/- 1.1 v 12.0 +/- 0.3 mumol/kg/min; P < .01) were lower than in normal subjects, while plasma insulin level was higher (138 +/- 19 v 38 +/- 3 pmol/L; P < .001). In insulinoma patients after attainment of euglycemia (4.7 +/- 0.2 mmol/L) by exogenous glucose infusion, insulin level increased slightly (174 +/- 18 pmol/L; P < .01) and glucose Rd was similar to that of normal individuals (12.8 +/- 0.6 v 12.0 +/- 0.3 mumol/kg/min). During the clamp studies, glucose Rd was lower in insulinoma patients (18.7 +/- 1.2 v 33.8 +/- 3.1 mumol/kg/min; P < .01) despite higher plasma insulin concentration (612 +/- 48 v 420 +/- 12 pmol/L). Therefore, glucose Rd/I x 100 ratio (where I is plasma insulin concentration) was much lower in insulinoma patients (3.1 +/- 0.9 v 8.0 +/- 0.7; P < .01), suggesting a marked degree of insulin resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal hemodynamics and albumin excretion rate in patients with diabetes secondary to acquired pancreatic disease

OBJECTIVE--To assess kidney function and AER in patients with PD. RESEARCH DESIGN AND METHODS--Thirty-three patients with PD (age 52 +/- 7 yr, duration of disease 11 +/- 6 yr, BMI 24 +/- 3 kg/m2) and 33 patients with IDDM were matched for sex, BMI, and duration of disease. GFR and RPF were determined by single injection of [51Cr]EDTA and [125I]hippurate. AER was measured by radioimmunoassay in a single timed overnight urine collection. RESULTS--GFR and RPF were, respectively, 113 +/- 35 and 441 +/- 145 ml.min-1.73 m2 in patients with PD and 123 +/- 30 and 549 +/- 94 (P < 0.001) in IDDM. FF was significantly higher in patients with PD (0.26 +/- 0.05 vs. 0.22 +/- 0.03; P < 0.001). Prevalence of hyperfiltration (GFR > 135 ml.min-1.1.73 m2) was similar in both groups (30% in patients with PD vs. 28% in those with IDDM). Geometric mean of urinary AER was 10.4 micrograms/min (range 1-186) in patients with PD and 11.2 (1-198) in IDDM patients. Some 30.3% of patients with PD and 18% of those with IDDM were microalbuminuric (AER > 20 micrograms/min). By multiple regression analysis, AER was significantly related to systolic (P < 0.04) and diastolic blood pressure (P < 0.01) and to BMI (P < 0.03) in patients with PD. Retinopathy was more frequent in microalbuminuric patients with PD than in those without elevated AER. CONCLUSIONS--We suggest that early renal abnormalities occur similarly in patients with PD and IDDM.

Fasting and postmeal phenylalanine metabolism in mild type 2 diabetes

We have investigated postabsorptive and postprandial phenylalanine kinetics in non-obese type 2 diabetic patients [non-insulin-dependent diabetes mellitus (NIDDM)], using a double-isotope technique and the constant oral administration of a synthetic mixed meal. Fasting and postmeal glucose levels were increased (P < 0.01) in NIDDM (165 +/- 16 to 226 +/- 24 mg/dl), with respect to normal controls (85 +/- 3 to 102 +/- 6 mg/dl). Fasting insulin concentrations were comparable in NIDDM (13 +/- 2 microU/ml) and in normals (12 +/- 2 microU/ml), but after the meal it increased less (P < 0.07) in NIDDM vs. normals (to 36 +/- 5 vs. 56 +/- 12 microU/ml, respectively; P < 0.01 vs. basal for both). Postabsorptive phenylalanine rate of appearance (R(a)) in NIDDM (0.63 +/- 0.08 mumol.kg-1 x min-1) was comparable to that of controls (0.73 +/- 0.05 mumol.kg-1 x min-1, not significant). During the meal, total and endogenous phenylalanine R(a), splanchnic uptake, oxidation, and nonoxidative disposal of the ingested phenylalanine were also comparable in the two groups. These data indicate that fasting and postprandial kinetics of the essential amino acid phenylalanine are normal in NIDDM.

Ketone body metabolism in NIDDM. Effect of sulfonylurea treatment

We assessed the metabolism of the two KBs, AcAc and 3-BOH; the relationships between ketogenesis and FFA inflow rate; and the effect of chronic sulfonylurea treatment in mild NIDDM patients (plasma glucose less than 10 mM). We studied 10 nonobese NIDDM patients in a crossover, randomized, double-blind, placebo-controlled fashion. Each patient was studied 4 times: after a run-in period with placebo, after 3 mo of placebo treatment, after 3 mo of glibenclamide treatments, respectively, and after 3 mo of sulfonylurea treatment during an acute exogenous Intralipid infusion. Ten normal, nondiabetic subjects served as the control group. Glibenclamide treatment decreased plasma FFAs. When these substrates were exogenously increased, plasma FFAs were comparable with placebo and baseline concentrations. In NIDDM patients, baseline and placebo blood total KB concentration was significantly higher than in control subjects (216 +/- 22 and 244 +/- 25, respectively vs. 127 +/- 18 microM; P less than 0.01). Glibenclamide treatment significantly decreased total KBs to 177 +/- 19 microM (P less than 0.05). When FFAs were exogenously increased, total KBs were similar to the placebo and baseline period. In the baseline study, the AcAc/3-BOH ratio was 0.72 +/- 0.06 in control subjects, whereas in NIDDM patients, the ratio was 1.61 +/- 0.13 at baseline (P less than 0.001 vs. control subjects), 1.66 +/- 0.15 during placebo, 1.57 +/- 0.09 during glibenclamide (NS vs. baseline), and 1.51 +/- 0.23 during glibenclamide plus placebo FFAs. Both the AcAc interconversion rate to 3-BOH and the 3-BOH interconversion rate to AcAc were significantly lower in NIDDM patients than in control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Forearm ketone body metabolism in normal and in insulin-dependent diabetic patients

In insulin deficiency, there is excessive arterial delivery of free fatty acid (FFA) to muscles where they are converted to acetoacetyl-CoA and acetyl-CoA. These intermediates may be metabolized further to acetoacetate and beta-hydroxybutyrate, which can be released into the venous circulation. When ketone body (KB) tracers are infused in vivo, they are diluted across muscle tissue. This dilution may be due to 1) KB newly formed within muscle (ketogenesis); 2) exchange of tracer between labeled and unlabeled acetyl-CoA and acetoacetyl-CoA, intermediates common to the metabolism of both FFA and KB (pseudoketogenesis). Thus this study assessed whether such label exchange could be detected across the human forearm and whether an increased delivery of FFA in insulin-sufficient controls provoked dilution of labeled KB tracer comparable to that observed in insulin-deficient diabetics. Five normal and five insulin-dependent diabetic (IDDM) subjects were infused with labeled [3,4-13C2]-acetoacetate. [13C]KB enrichments were lower in forearm vein than in the artery, and dilution of labeled KB was always higher than that which could be explained by arterial-venous differences of unlabeled KB. When arterial FFA concentrations in normals were raised (Intralipid+heparin) to values comparable to those of the diabetics, no additional increase in forearm arteriovenous dilution of labeled KB was observed. Neither in the basal state nor under conditions of increased plasma FFA were we able to detect venous appearance of KB labeled in the first and in the second carbon atoms, a necessary consequence of pseudoketogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Retrospective analysis of daily glucose profile in type 1 diabetic patients with continuous subcutaneous insulin infusion (CSII)

A retrospective analysis of blood glucose control was performed in 17 type 1 diabetic patients who regularly monitored their blood glucose concentration by visual strips over a period of 3-83 months. Analysis was performed by a patient management software loaded on a personal computer. In this cohort of patients the average daily blood glucose reading was 1.6 +/- 0.3. Blood glucose readings were collected more frequently following meal ingestion (40.3%) than in the post-absorptive state (24.6%; P less than 0.05). Blood glucose concentration fluctuated from a basal level of 146 +/- 5 mg/dl to 167 +/- 4 mg/dl in the post-prandial phases with an average daily value of 156 +/- 2 mg/dl. Blood glucose values below 80 mg/dl were evenly distributed throughout the day, while hyperglycemia (greater than 300 mg/dl) occurred more commonly after meals (42%). Daily blood glucose was higher during weekends (164 +/- 5 mg/dl) than during weekdays (155 +/- 2 mg/dl; P less than 0.05). A weak correlation was found between the number of blood glucose readings/day and daily blood glucose level. These results suggest that long-term maintenance of satisfactory metabolic control is attainable in type 1 diabetic patients and that this is mainly dependent upon subject self awareness.

Leucine and phenylalanine kinetics during mixed meal ingestion: a multiple tracer approach

To estimate whole body and splanchnic metabolism of dietary amino acids, phenylalanine and leucine kinetics were determined simultaneously in six normal volunteers before and during the constant administration of a complete mixed meal, employing multiple tracers of these amino acids. L-[5,5,5-2H]leucine and L-[2,6-3H]-phenylalanine were infused intravenously; L-[1-13C]leucine and L-[1-14C]phenylalanine were administered orally with the meal. During the meal, steady-state leucine concentration rose from 136 +/- 6 to 190 +/- 14 mumol/l (P less than 0.01), phenylalanine from 44 +/- 4 to 61 +/- 6 mumol/l (P less than 0.01), total leucine rate of appearance (Ra) from 1.29 +/- 0.03 to 1.77 +/- 0.07 (P less than 0.01, +37 +/- 3%), and phenylalanine Ra from 0.73 +/- 0.05 to 0.80 +/- 0.07 mumol.kg-1.min-1 (P less than 0.05, +8 +/- 3%). Splanchnic uptake of dietary phenylalanine was greater (P less than 0.001) than that of leucine (58 +/- 4 vs. 25 +/- 4%, respectively), 44 +/- 3% of circulating leucine derived from the diet vs. 20 +/- 2% of circulating phenylalanine (P less than 0.01). Endogenous leucine and phenylalanine Ra were significantly suppressed (P less than 0.05). In summary: 1) splanchnic uptake of dietary phenylalanine is onefold greater than that of leucine; 2) dietary contribution to systemic phenylalanine Ra is about half of that to leucine Ra; and 3) endogenous appearance of both leucine and phenylalanine after the meal is suppressed. In conclusion, splanchnic metabolism of dietary leucine and phenylalanine differs markedly and can be quantitated in vivo without catheterization.

The contribution of hyperglycaemia and hypoinsulinaemia to the insulin resistance of streptozotocin-diabetic rats

The relative contribution of hyperglycaemia and hypoinsulinaemia was evaluated in rats made diabetic by streptozotocin administration. Four groups of rats were studied: untreated normal rats; streptozotocin-diabetic; streptozotocin-diabetic treated with phlorizin (0.4 mg/kg body weight per day); streptozotocin-diabetic mildly treated with insulin (0.7 IU/day). In all groups, insulin action (responsiveness) was assessed with the euglycaemic (5.3 mmol/l) hyperinsulinaemic (524 mU/l) clamp technique combined with 3H-2-deoxy-D-glucose method, enabling determination of the glucose utilization index in various tissues. Responsiveness of the overall glucose utilization process to insulin was reduced by 28% in streptozotocin-diabetic rats (12.0 +/- 1.2 vs 16.5 +/- 0.6 mg.kg-1.min-1, p less than 0.001). This was associated with a significant reduction (p less than 0.05) in the glucose utilization index in all muscles studied (average = 17.0 vs 32.1 ng.mg of tissue-1.min-1), in the heart (19.6 vs 39.5 ng.mg-1.min-1), brown adipose tissue (98.9 vs 178.0 ng.mg-1.min-1), skin (6.4 vs 13.1 ng.mg-1.min-1). Phlorizin treatment normalized plasma glucose levels without affecting those of insulin, and restored overall glucose utilization to normal (16.6 +/- 1.0 mg.kg-1.min-1). This normalization was accompanied by a normalization of the glucose utilization index in all muscle types studied (29.2 ng.mg-1.min-1), in the heart (50.0 ng.mg-1.min-1), brown adipose tissue (157.2 ng.mg-1.min-1), and skin (10.0 ng.mg-1.min-1). White adipose tissue, brain and gut were not affected.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationships among natriuresis, atrial natriuretic peptide and insulin in insulin-dependent diabetes

Insulin-dependent diabetic patients have a large exchangeable body sodium pool, secondary to sodium retention. The pathogenesis of impaired natriuresis in insulin dependent diabetes remains to be elucidated. The present study examines the role of hyperinsulinemia, impaired atrial natriuretic release, and resistance to atrial natriuretic peptide action in determining sodium retention in normotensive and hypertensive insulin-dependent diabetic patients. Eight insulin-dependent diabetic patients had significantly higher daily sodium excretion rate (147 +/- 16 mmol/day; mean +/- SE) during conventional insulin treatment (daily plasma glucose: 11.6 +/- 1.2 mmol/liter; daily plasma insulin: 27 +/- 3 microU/ml) than during intensified insulin treatment (daily sodium excretion rate: 91 +/- 12, P less than 0.01; daily plasma glucose: 6.8 +/- 0.7, P less than 0.01; daily plasma insulin: 44 +/- 4, P less than 0.01). Daily sodium excretion rate was also significantly lower (107 +/- 13, P less than 0.01) in the same diabetic patients during intensified insulin treatment along with hyperglycemic clamp (daily plasma glucose: 12.8 +/- 0.3, NS; plasma insulin 48 +/- 4, P less than 0.01). Seven control subjects had lower extracellular liquid volume than eight insulin-dependent diabetic patients (11.0 +/- 0.8 l/1.73 m2 vs. 14.8 +/- 0.9, P less than 0.05) and also had baseline plasma atrial natriuretic peptide concentrations (18 +/- 5 pg/ml vs. 37 +/- 4, P less than 0.05). Atrial natriuretic peptide response to saline challenge was blunted in insulin-dependent diabetic patients when saline was administered on the basis of body surface area (90 mmol/1.73 m2.90 min) but not when administered on the basis of extracellular liquid volume (ECV) (8.2 mmol/liter ECV.90 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of insulin and amino acid infusion on leucine and phenylalanine kinetics in type 1 diabetes

To evaluate the anabolic effects of hyperinsulinemia and hyperaminoacidemia on amino acid (and protein) metabolism in type 1 (insulin-dependent) diabetes mellitus (IDDM), we studied leucine and phenylalanine kinetics in nine IDDM and seven control subjects, both at basal euglycemic conditions and during a euglycemic hyperinsulinemic clamp (approximately 60-80 microU/ml of plasma free insulin), combined with an intravenous infusion of amino acids (AA), which doubled plasma concentrations of most AA. In the basal state, euglycemia was maintained in IDDM subjects at the expense of a peripheral free insulin level (16 +/- 2 microU/ml) greater (P less than 0.05) than controls (9 +/- 1 microU/ml). Despite that, leucine rate of appearance (Ra), alpha-ketoisocaproate oxidation (approximating leucine-carbon oxidation), and nonoxidative leucine disposal, were greater (P less than 0.05) in IDDM than in control subjects. Phenylalanine Ra was slightly but not significantly greater in IDDM vs. control subjects. During the clamp, at comparable plasma free insulin and amino acid concentrations, oxidation was similar in the two groups, endogenous leucine and phenylalanine Ra remained significantly greater (P less than 0.05) in IDDM than in normal subjects, and leucine disposal tended also to be greater in IDDM subjects. Thus, in IDDM subjects maintained at euglycemia, endogenous Ra of essential amino acid(s) (index of endogenous proteolysis) is increased, both in the postabsorptive state and after hyperinsulinemia combined with hyperaminoacidemia, while leucine utilization for protein synthesis is not impaired.

The effects of different plasma insulin concentrations on lipolytic and ketogenic responses to epinephrine in normal and type 1 (insulin-dependent) diabetic humans

This study was performed to verify: (1) the ability of different insulin concentrations to restrict the lipolytic and ketogenic responses to exogenous epinephrine administration; (2) whether the ability of insulin to suppress the lipolytic and ketogenic responses during epinephrine administration is impaired in Type 1 (insulin-dependent) diabetic patients. Each subject was infused on separate occasions with insulin at rates of 0.2, 0.4, and 0.8 mU.kg-1.min-1 while normoglycaemic. To avoid indirect adrenergic effects on endocrine pancreas secretions, the so-called "islet clamp" technique was used. Rates of appearance of palmitic acid, acetoacetate, and 3-hydroxybutyrate were simultaneously measured with an infusion of 13C-labelled homologous tracers. After a baseline observation period epinephrine was exogenously administered at a rate of 16 ng.kg-1.min-1. At low insulin levels (20 microU/ml) the lipolytic response of comparable magnitude was detected in normal and Type 1 diabetic patients. However, the ketogenic response was significantly higher in Type 1 diabetic patients. During epinephrine administration, similar plasma glucose increments were observed in the two groups (from 4.74 +/- 0.53 to 7.16 +/- 0.77 mmol/l (p less than 0.05) in Type 1 diabetic patients and from 4.94 +/- 0.20 to 7.11 +/- 0.38 mmol/l (p less than 0.05) in normal subjects, respectively). At intermediate insulin levels (35 microU/ml) no significant differences were found between Type 1 diabetic patients and normal subjects, whereas plasma glucose levels rose from 4.98 +/- 0.30 to 6.27 +/- 0.66 mmol/l (p less than 0.05) in Type 1 diabetic patients, and from 5.05 +/- 0.13 to 6.61 +/- 0.22 mmol/l (p less than 0.05) in normal subjects. At high insulin levels (70 microU/ml) the lipolytic response was detectable only in Type 1 diabetic patients; the ketogenic response was reduced in both groups. During the third clamp, a significant rise in plasma glucose concentration during epinephrine infusion was observed in both groups. In conclusion this study shows that at low insulin levels Type 1 diabetic patients show an increased ketogenic response to epinephrine, despite their normal nonesterified fatty acid response. Instead, high insulin levels are able to restrict the ketogenic response to epinephrine in both normal and Type 1 diabetic subjects, although there is a still detectable lipolytic response in the latter. In the presence of plasma free insulin levels that completely restrict the ketogenic response in the same group, there is still a distinct glycaemic response. Plasma insulin levels in Type 1 diabetic patients are a major determinant of the metabolic response to epinephrine.

Relationship between plasma leucine concentration and clearance in normal and type 1 diabetic subjects

In a series of studies in normal and type 1 diabetic subjects, we analysed the relationship between isotope-calculated leucine clearance and plasma leucine concentration. All studies were performed under euglycaemic conditions. Plasma leucine concentrations were either experimentally decreased by means of insulin infusion, or increased by means of exogenous amino acid infusion in the presence of hyperinsulinaemia. Leucine clearance rates were compared in normal and diabetic subjects at similar plasma insulin levels. The effect of hyperinsulinaemia was examined by measuring clearance rates in normal subjects at comparable leucine levels but different insulin concentrations. Our data show that leucine clearance is inversely related to leucine concentration, and that it is not independently stimulated by hyperinsulinaemia. Type 1 diabetes is not associated with decreased leucine clearance. A general equation relating leucine concentration and clearance is proposed. These data support the view that peripheral leucine utilization is not decreased in type 1 diabetes mellitus.

No effects of high-fiber diets on metabolic control and insulin-sensitivity in type 1 diabetic subjects

The metabolic effects of a three-month treatment with a high-fiber diet (15 grams of guar-gum added to a standard diet) were investigated in seven type 1 diabetic subjects, with a moderately poor metabolic control. HbA1c levels, daily insulin requirement, cholesterol, triglyceride, amino acid and intermediate metabolite concentrations were evaluated before and following the high fiber diet, both in the postabsorptive state at euglycemia and during a euglycemic, hyperinsulinemic, hyperaminoacidemic clamp. Insulin-mediated glucose utilization, an index of insulin-sensitivity, was also measured during the clamp. Following the diet, no differences in HbA1c levels (7.6 +/- 0.7%----7.3 +/- 0.6%), daily insulin requirement (50 +/- 5----51 +/- 3 U/d), triglyceride, amino acid and intermediary metabolite concentrations in the basal, euglycemic state, were observed. Only cholesterol concentrations decreased significantly (from 165 +/- 12 to 142 +/- 12 mg/dl, P less than 0.01) after the diet. During the clamp, the concentrations of all measured substrates were comparable before and after high fiber treatment. Insulin-mediated glucose disposal was also unchanged by guar-gum treatment. Patients' body weights were not modified by the diet. In conclusion, our study shows that a high fiber diet, obtained with the addition of 15 grams of guar-gum to a standard diet, is of no benefit to IDDM either as regards the metabolic control or insulin sensitivity. Only cholesterol levels were decreased. Therefore, the costs and benefits of these diets in the treatment of IDDM should be reconsidered.