A. Riccio

Insulin regulation of glucose and lipid metabolism in massive obesity.

SummaryEight obese patients and 12 normal individuals underwent a euglycaemic insulin clamp (20 and 40 mU · m2−1 · min−1) along with continuous infusion of 3-3H-glucose and 1-14C-palmitate and indirect calorimetry. Basal plasma glucose concentration (4.7±0.3 vs 4.4±0.2 mmol/l) was similar in the two groups, whereas hepatic glucose production was slightly higher in obese individuals (1.11±0.06 vs 0.84±0.05 mmol/min) in spite of higher plasma insulin levels (17±2 vs 6±1 mU/l; p<0.01). Insulin inhibition of hepatic glucose production was impaired in obese subjects. Glucose disposal by lean body mass was markedly reduced both at baseline (11.7±1.1 vs 15.6±0.6 μmol · kg−1 · min−1; p<0.05) and during clamp (15.0±1.1 vs 34.4±2.8 and 26.7±3.9 vs 62.2±2.8 μmol · kg−1 · min−1; p<0.01) Oxidative (12.2±1.1 vs 17.8±1 and 16.1±1.1 vs 51.1±1.7 μmol · kg−1 · min−1; p<0.05−0.002) and non-oxidative glucose metabolism (3.9±1.1 vs 15.0±2.8 and 12.8±3.3 vs 38.3±2.2 μmol · kg−1 · min−1; p<0.01−0.001) were impaired. Basal plasma concentrations of non-esterified fatty acids (635±75 vs 510±71 μmol/l) and blood glycerol (129±17 vs 56±5 μmol/l; p<0.01) were increased in obese patients. Following hyperinsulinaemia, plasma non-esterified fatty acids (244±79 vs 69±16 and 140±2 vs 36±10 μmol/l; p<0.01) and blood glycerol levels (79±20 vs 34±6 and 73±22 vs 29±5 μmol/l; p<0.01) remained higher in obese subjects. Baseline non-esterified fatty acid production rate per kg of fat body mass was significantly larger in normal weight subjects (37.7±6.7 vs 14.0±1.8 μmol/l; p<0.01) and insulin inhibition was reduced in obese patients (−41±9 vs −74±3 and −53±11 vs −82±3%; p<0.05). Basal plasma non-esterified fatty acid utilization by lean body mass was similar in the two groups (9.8±0.9 vs 8.8±2.0 μmol · kg−1 · min−1), whereas during clamp it remained higher in obese patients (6.0±1.2 vs 2.8±2.5 and 4.9±1.3 vs 1.5±0.6 μmol · kg−1 · min−1; p<0.1−0.05). Lipid oxidation was higher in obese individuals in spite of hyperinsulinaemia (3.7±0.3 vs 2.4±0.4 and 2.3±0.4 vs 0.9±0.3 μmol · kg−1 · min−1; p<0.05− 0.02). An inverse correlation was found between lipid oxidation and glucose oxidation (r=0.82 and 0.93; p<0.001) and glucose utilization (r=0.54 and 0.83; p<0.05−0.001) both in obese and control subjects. A correlation between lipid oxidation and non-oxidative glucose metabolism was present only in normal weight individuals (r=0.75; p<0.01). We conclude that in obesity all tissues (muscles, liver, and adipose tissue) are resistant to insulin action. Insulin resistance involves glucose as well as lipid metabolism.

Partial recovery of insulin secretion and action after combined insulin-sulfonylurea treatment in type 2 (non-insulin-dependent) diabetic patients with secondary failure to oral agents

SummaryMetabolic control, insulin secretion and insulin action were evaluated in seven Type 2 (non-insulin-dependent) diabetic patients with secondary failure to oral antidiabetic agents before and after two months of combined therapy with supper-time insulin (Ultratard: 0.4 U/kg body weight/day) plus premeal glibenclamide (15 mg/day). Metabolic control was assessed by 24 h plasma glucose, NEFA, and substrate (lactate, alanine, glycerol, ketone bodies) profile. Insulin secretion was evaluated by glucagon stimulation of C-peptide secretion, hyperglycaemic clamp (+7 mmol/l) and 24 h free-insulin and C-peptide profiles. The repeat studies, after two months of combined therapy, were performed at least 72 h after supper-time insulin withdrawal. Combining insulin and sulfonylurea agents resulted in a reduction in fasting plasma glucose (12.9±7 vs 10.4±1.2 mmol/l; p<0.05) and hepaic glucose production (13.9±1.1 vs 11.1±1.1 μmol·kgc-min−1; p<0.05). Mean 24 h plasma glucose was also lower (13.7±1.2 vs 11.1±1.4 mmol/l; p<0.05). Decrements in fasting plasma glucose and mean 24 h profile were correlated (r=0.90; p<0.01). HbA1c also improved (11.8±0.8 vs 8.9±0.5%; p<0.05). Twenty-four hour profile for NEFA, glycerol, and ketone bodies was lower after teatment, while no difference occurred in the blood lactate and alanine profile. Insulin secretion in response to glucagon (C-peptide =+0.53±0.07 vs +0.43±0.07 pmol/ml) and hyperglycaemia (freeinsulin = 13.1±2.0 vs 12.3±2.2 mU/l) did not change. On the contrary, mean 24 h plasma freeinsulin (13.2±2.6 vs 17.5±2.2 mU/l; p<0.01) and C-peptide (0.76±0.10 vs 0.98±0.13 pmol/l; p<0.02) as well as the area under the curve (19.1±4.1 vs 23.6±3.1 U/24 h;p<0.01 and 1.16±0.14 vs 1.38±0.18 μmol/24 h; p<0.02 respectively) were significantly increased. The ratio between glucose infusion (M) and plasma insulin concentration (I) during the hyperglycaemic clamp studies (M/I, an index of insulin sensitivity), was not statistically different (1.40±0.25 vs 1.81±0.40 μmol·kg−1· min−1/mU·l−1). These data suggest that, in Type 2 diabetic patients with secondary failure to oral antidiabetic agents, the combination of supper-time longacting insulin and premeal sulfonylurea agents can improve metabolic control. This positive effect is possibly mediated through an increased secretion of insulin in response to physiologic stimuli.

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)

Metabolic control during total parenteral nutrition: Use of an artificial endocrine pancreas

The metabolic impact of total parenteral nutrition (TPN) was evaluated in nine subjects who underwent esophagogastroplasty for esophageal carcinoma. On the second day after operation all subjects were connected to an artificial endocrine pancreas. In four patients only glucose was infused (5.5 mg/kg X min). The remaining five subjects received glucose (4.0 mg/kg X min), amino acid (0.5 mg/kg X min), and lipid emulsion (0.6 mg/kg X min). Plasma glucose concentration was kept constant over 24 hours. However, both insulin requirement (111 +/- 15 v 70 +/- 2 mU/kg X h) and plasma insulin level (99 +/- 15 v 30 +/- 7 microU/mL; P less than .01) were higher during combined TPN. Blood lactate concentration was higher during glucose infusion (P less than .05). No difference was found in blood concentrations of pyruvate, alanine, and ketone bodies. Both glycerol and FFA were higher during combined TPN. The ratio between glucose infusion rate and the average plasma insulin level was calculated as an index of insulin-mediated glucose metabolism; G/I X 100 was markedly reduced during combined TPN (4.5 +/- 0.8 v 20.7 +/- 3.7; P less than .05). Plasma FFA levels were positively correlated with plasma insulin concentration (r = .76) and inversely correlated to G/I X 100 (r = -.73; both P less than .05). In conclusion, during combined TPN a state of insulin resistance is induced and more insulin is required to achieve a normal glucose utilization.

Gliclazide potentiates suppression of hepatic glucose production in non-insulin-dependent diabetic patients.

The mechanism of the hypoglycemic action of gliclazide was evaluated in 17 diet-treated non-insulin-dependent diabetes mellitus (NIDDM) patients. In study A, five patients received a 240-minute glucose infusion along with [3-3H]glucose infusion. In study B, seven patients received a 240-minute isoglycemic insulin clamp along with [3-3H]glucose infusion. And in study C, five patients received a somatostatin infusion with basal replacing doses of insulin and glucagon. The three studies (A, B, and C) were repeated twice. Gliclazide (240 mg orally) was administered on one occasion, and placebo was given on the second occasion. Basal hepatic glucose production (HGP) and utilization and plasma glucose, insulin, C-peptide, glucagon, and free fatty acid (FFA) concentrations were similar before administration of gliclazide and placebo. In study A, plasma glucose, its incremental area, and HGP were reduced by gliclazide administration (all P < .05), but glucose utilization was not significantly affected. The increase in plasma insulin and C-peptide concentrations was similar with gliclazide and placebo, although the plasma insulin to glucose ratio was increased with gliclazide. HGP decremental area was correlated with the reduction in plasma glucose incremental area (r = -.63, P < .05). In study B, gliclazide administration produced a larger suppression of HGP, but the overall rate of glucose utilization was not different in the two studies. In study C, plasma glucose concentration and HGP progressively decreased in both studies, without a difference between gliclazide and placebo. These results suggest that under conditions of hyperglycemia and hyperinsulinemia gliclazide elicits a larger suppression of HGP.

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 < 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 μM; P < 0.01). Glibenclamide treatment significantly decreased total KBs to 177 ± 19 μM (P < 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 < 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. In conclusion, in NIDDM patients the major portion of overall ketogenesis must be ascribed to AcAc production. 3-BOH production is decreased because of an impaired interconversion between the two ketones. A direct effect of glibenclamide on ketogenesis in vivo is disputable because blood KB concentrations increase to a similar extent for a given plasma FFA concentration in the presence or absence of this drug.

Hepatic sensitivity to insulin: Effects of sulfonylurea drugs

Insulin regulation of hepatic glucose production (HGP) is altered in non-insulin-dependent diabetes mellitus (NIDDM), resulting in increased glucose output by the liver; this contributes to the elevation in plasma glucose concentration observed both in the basal state and postprandially. Therefore, restoration of normal insulin action in the liver must be a goal of hypoglycemic therapy. Sulfonylureas have been widely used for treatment of NIDDM over the past 30 years. In addition to their stimulatory effect on insulin secretion, these compounds seem to possess extrapancreatic effects. Early in vitro studies showed that addition of sulfonylureas to the perfusion medium of liver preparations could exert a significant suppressive effect on HGP. Subsequent experience suggested that these compounds could act at the level of the insulin receptor as well as at various postreceptor sites. These studies showed that sulfonylureas may inhibit glycogenolysis and gluconeogenesis while stimulating glycogen synthesis. Results obtained in vivo in NIDDM patients are in agreement with the in vitro studies. Long-term treatment with sulfonylureas is associated with a decline in fasting plasma glucose concentration and a parallel reduction in HGP. Nevertheless, the direct effect of sulfonylurea administration on the liver remains unclear, since the reduction in HGP that occurs during sulfonylurea treatment may be secondary to an overall improvement in insulin secretion. It is also of interest that in insulin-dependent diabetic patients, sulfonylurea administration in combination with insulin injections is not followed by a significant change in HGP. Possible effects of sulfonylureas on glucagon secretion and on the metabolism of free fatty acids (FFAs) may also contribute to improved sensitivity of the liver to the suppressive action of insulin, since these agents appear to reduce plasma glucagon and FFA concentrations. Thus, present data support an extrapancreatic action of sulfonylureas on the liver. However, it does appear that a certain degree of residual insulin secretion is required for sulfonylurea agents to elicit their hepatic effect.

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

Abstract. 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 mUkg‐1min‐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 l.9mmol 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 ±l.9vs. 23.0 ± 1.6 kgm‐2; P0.005), 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 ± 1.11μmol kg‐1min‐1). Before the operation, insulin‐mediated glucose disposal was significantly lower than in the controls (30.8 ±3.1 vs. 4.91± 3.1 μmol kg‐1min‐1). Six to nine months after surgical removal of the adenoma, glucose utilization was unchanged (30.5 ±3.3 μmol kg‐1min‐1) and still significantly lower than in controls (P<0.0). After the euglycaemic phase, the plasma glucose level dropped to the same hypoglycaemic nadir (2.0±0.1 vs. 2.2 ±0.2 mmol L‐1) in both studies. Upon withdrawal of insulin infusion, recovery from hypoglycaemia was much slower before than after removal of the insulinoma (0.66±0.16vs. 2.50 ± 0.38 μmol min‐1; P<0.01). The impaired recovery from hypoglycaemia was associated with a sluggish rise in plasma glucagon concentration (+ 49 ± 15vs. +95 ±27 ng L‐1), growth hormone (+16±6vs.+ 30±3*mu;g L‐1), and cortisol (+156 ±41 vs. +361 ±62nmol L‐1; all P<0.05–0.005). In contrast to that found after adenoma removal, hepatic glucose production in insulinoma patients remained suppressed even after induction of hypoglycaemia. Our data suggest that in hyperinsulinaemic insulinoma patients restoration of normal insulin levels (a) ameliorates the response of some parameters of the counter‐regulation to acute hypoglycaemia; but (b) is not able to restore normal insulin sensitivity.

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 1) 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 β-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 jamol · 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 /Ltmol · 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 aily plasma glucose control.

Intermediary metabolite profiles during euglycemic glucose-insulin clamp: Effects of ethanol

SummaryWe evaluated the effects of different doses of i.v. alcohol on tissue insulin sensitivity, by means of insulin-glucose clamp technique, in 10 young healthy men. The most important intermediary metabolites were assayed. Insulin-dependent glucose disposal was impaired at different levels of alcoholemia, probably through an impairment of the glycolytic pathway. Exogenous insulin administration does not restore the more reduced redox state caused by alcohol oxidation. Alcohol does not interfere with the antiketogenic and antilipolytic insulin effects.