Elena Duner

Effect of Metformin on Insulin-Stimulated Glucose Turnover and Insulin Binding to Receptors in Type II Diabetes

Euglycemic insulin glucose-clamp and insulin-binding studies on erythrocytes and monocytes were performed in seven type II (non-insulin-dependent) diabetic subjects before and after 4 wk of metformin treatment (850 mg 3 times/day) and in five obese subjects with normal glucose tolerance. Glucose turnover was also measured at basal insulin concentrations and during hyperinsulinemic euglycemic clamps. During euglycemic insulin-glucose clamps, diabetic subjects showed glucose disposal rates of 3.44 ± 0.42 and 7.34 ± 0.34 mg · kg−1 · min−1 (means ± SD) before metformin at insulin infusion rates of 0.80 and 15.37 mU · kg−1 · min−1, respectively. With the same insulin infusion rates, glucose disposal was 4.94 ± 0.55 (P < .01) and 8.99 ± 0.66 (P < .01), respectively, after metformin treatment. Glucose disposal rates in normal obese subjects were 5.76 ± 0.63 (P < .01) and 10.92 ± 1.11 (P < .01) at 0.80 and 15.37 mU · kg−1 · min−1, respectively. Insulin maximum binding to erythrocytes in diabetics was 9.6 ± 4.2 and 5.8 ± 2.6 × 109 cells (means ± SD) before and after metformin treatment, respectively (NS). Insulin maximum binding to monocytes in diabetics was 6.2 ± 2.3 × 107 cells before and 5.0 ± 1.6% after metformin. Hepatic glucose production was higher in the diabetic patients at basal insulin levels, but not at higher insulin concentrations, and was not significantly changed by drug treatment. Basal glucose and insulin concentrations decreased with metformin. Thus, metformin treatment improved glucose disposal rate without significant effect on insulin-binding capacity on circulating cells. Basal hepatic glucose output was slightly lower after metformin treatment in view of lower (9 vs. 15 μU/ml) insulin levels, potentially indicating increased sensitivity of the liver to insulin.

Defective suppression by insulin of leucine-carbon appearance and oxidation in type 1, insulin-dependent diabetes mellitus. Evidence for insulin resistance involving glucose and amino acid metabolism.

To determine whether a resistance to insulin in type 1, insulin-dependent diabetes mellitus (IDDM) is extended to both glucose and amino acid metabolism, six normal subjects and five patients with IDDM, maintained in euglycemia with intravenous insulin administration, were infused with L-[4,5-3H]leucine (Leu) and [1-14C]alpha ketoisocaproate (KIC). Steady-state rates of leucine-carbon appearance derived from protein breakdown (Leu + KIC Ra) and KIC (approximately leucine) oxidation were determined at basal and during sequential euglycemic, hyperinsulinemic (approximately 40, approximately 90 and approximately 1,300 microU/ml) clamps. In the euglycemic postabsorptive diabetic patients, despite basal hyperinsulinemia (24 +/- 6 microU/ml vs. 9 +/- 1 microU/ml in normals, P less than 0.05), Leu + KIC Ra (2.90 +/- 0.18 mumol/kg X min), and KIC oxidation (0.22 +/- 0.03 mumol/kg X min) were similar to normal values (Leu + KIC Ra = 2.74 +/- 0.25 mumol/kg X min) (oxidation = 0.20 +/- 0.02 mumol/kg X min). During stepwise hyperinsulinemia, Leu + KIC Ra in normals decreased to 2.08 +/- 0.19, to 2.00 +/- 0.17, and to 1.81 +/- 0.16 mumol/kg X min, but only to 2.77 +/- 0.16, to 2.63 +/- 0.16, and to 2.39 +/- 0.08 mumol/kg X min in the diabetic patients (P less than 0.05 or less vs. normals at each clamp step). KIC oxidation decreased in normal subjects to a larger extent than in the diabetic subjects. Glucose disposal was reduced at all insulin levels in the patients. In summary, in IDDM: (a) Peripheral hyperinsulinemia is required to normalize both fasting leucine metabolism and blood glucose concentrations. (b) At euglycemic hyperinsulinemic clamps, lower glucose disposal rates and a defective suppression of leucine-carbon appearance and oxidation were observed. We conclude that in type 1 diabetes a resistance to the metabolic effects of insulin on both glucose and amino acid metabolism is present.

Hyperaminoacidaemia reduces insulin-mediated glucose disposal in healthy man

SummaryTo determine whether hyperaminoacidaemia may modify insulin-mediated glucose disposal, normal subjects were studied with the euglycaemic glucose-clamp technique, with or without an amino acid infusion, at a rate sufficient to duplicate the plasma concentration of most amino acids. Steady-state glucose infusion rates to maintain euglycaemia were 36% lower during hyperaminoacidaemia (7.3±1.0 versus 11.4±0.8mg· kg−1· min−1, p<0.01) at comparable insulin concentrations (92±6 versus 93±7 mU/l respectively). Thus, under conditions of hyperinsulinaemia, amino acids could compete with glucose as metabolic fuels.

Effects of Chronic Alcohol Intake on Carbohydrate and Lipid Metabolism in Subjects with Type II (Non-Insulin-Dependent) Diabetes

PURPOSE To study the effects of chronic alcohol intake on carbohydrate and lipid metabolism in subjects with non-insulin-dependent (type II) diabetes (NIDDM). To also evaluate the effect of alcohol withdrawal on metabolic control. PATIENTS AND METHODS The study group consisted of 46 alcohol-consuming patients with NIDDM (NIDDM-B group), 35 non-alcohol-consuming patients with NIDDM (NIDDM group), and 40 normal control subjects. All patients were admitted to the hospital. Carbohydrate and lipid metabolism was assessed in these individuals immediately on admission to the hospital and during the following days. RESULTS In the NIDDM-B group, blood alcohol (ethyl alcohol) concentration was very low. However, chronic alcohol intake was associated with higher fasting and postprandial glucose concentrations and higher hemoglobin A1c. No significant differences were found in C-peptide levels. Moreover, higher concentrations of 3-hydroxybutyrate and free fatty acids were observed in the NIDDM-B group than in the NIDDM group. No differences were found in triglyceride concentrations, acid-base patterns, or electrolyte levels. The metabolic effects of alcohol completely waned after 3 days of complete withdrawal. CONCLUSION Chronic alcohol intake causes deterioration in metabolic control of persons with NIDDM. The effects induced by alcohol are completely reversed after a few days of withdrawal. Strict metabolic assessment is necessary when alcohol is an important constituent of the diet.

Effect of insulin replacement on intermediary metabolism in diabetes secondary to pancreatectomy

SummaryPatients with diabetes due to pancreatectomy have metabolic features different from Type 1 (insulin-dependent) diabetes after insulin withdrawal. Whether or not glucagon by itself or combined glucagon-insulin absence are responsible for this metabolic behaviour is unknown. This study was carried out to evaluate the ability of insulin replacement to abolish differences between patients with Type 1 diabetes and patients with diabetes due to pancreatectomy. We studied the diurnal patterns of intermediary metabolites, free insulin, and glucagon using the Biostator (glucose-controlled insulin infusion system) and intensive subcutaneous insulin therapy in five patients after total pancreatectomy, five after partial pancreatectomy and seven patients with Type 1 diabetes. All were studied for 24 h after an overnight period of normoglycaemia. Insulin requirement was lower in the patients with total pancreatectomy than in patients with partial pancreatectomy or Type 1 diabetes during both types of insulin treatment (p< 0.05). Blood glucose and free insulin were similar in all the groups in both conditions. Immunoreactive glucagon was higher in the patients with diabetes secondary to pancreatectomy than in Type 1 diabetic patients. However, glucagon levels did not increase after arginine infusion in the patients with total pancreatectomy, and column chromatography of blood samples from two totally pancreatectomized patients showed no significant levels of immunoreactive pancreatic glucagon. Non-esterified fatty acids and ketone bodies were similar during Biostator and intensive subcutaneous insulin therapy. By contrast, gluconeogenic precursors (lactate, pyruvate, alanine and glycerol) were higher in patients with total pancreatectomy than in patients with partial pancreatectomy and Type 1 diabetes. In particular, alanine was significantly higher in the patients with total pancreatectomy (400±50 μmol/l during Biostator; 437±62 μmol/l during intensive subcutaneous insulin therapy) than in patients with partial pancreatectomy (207±13 μmol/l, p<0.005 and 226±14 μmol/l, p<0.005) and in Type 1 diabetic patients (191±11 μmol/l, p<0.005 and 216±10 μmol/l, p<0.005). Our data show that the high levels of gluconeogenic precursors, already reported in patients with diabetes due to total pancreatectomy after insulin withdrawal, do not become normal even in the presence of insulin. This finding shows that gluconeogenesis is primarily dependent on pancreatic glucagon and confirms the role of glucagon in the development of diabetic hyperglycaemia.

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.

Metabolic Control of Kidney Hemodynamics in Normal and Insulin-Dependent Diabetic Subjects: Effects of Acetoacetic, Lactic, and Acetic Acids

Diabetes mellitus is associated with important changes in renal hemodynamics. The purpose of this study was to determine whether an increase in blood concentration patterns of ketone bodies and lactic acid, organic acids often elevated in poorly controlled insulin-dependent diabetes mellitus (IDDM), could contribute to increase glomerular filtration rate (GFR) and renal plasma flow (RPF) regardless of changes in circulating levels of glucose and insulin. Six IDDM patients and six normal subjects were given a saline infusion (15 μmol · min−1 · kg−1) for 2 h, an acetoacetic acid infusion (15 μmol · min−1 · kg−1) for another 2 h, and then a saline infusion after an overnight fast during euglycemic insulin-glucose clamp. Acetoacetic acid infusion resulted in an increase of blood ketone bodies in the range of 0.7–1.5 mM from a basal value of 0.1–0.3 mM. GFR was 125 ± 16 and 136 ± 17 ml · min−1 · 1.73 m−2 in normal and IDDM subjects, respectively, during baseline saline infusion and 138 ± 21 (P < .01 vs. basal level) and 158 ± 15 ml · min−1 · 1.73 m−2 (P < .001 vs. basal level) during acetoacetic acid infusion. During the last saline infusion, renal hemodynamic patterns decreased again to baseline levels. Another six IDDM patients and six normal subjects were given saline, lactic acid, and saline infusions at the same rates of infusion after an overnight fast during euglycemic insulin-glucose clamp. Lactic acid concentration increased from ∼0.5–0.8 to 1.0–1.5 mM in both groups. GFR was 125 ± 9 and 144 ± 18 ml · min−1 · 1.73 m−2 in normal and IDDM subjects, respectively, during baseline saline infusion and 135 ± 8 and 158 ± 16 ml · min1 · 1.73 m−2 during lactic acid infusion (P < .01 vs. basal level). Acetoacetic acid and lactic acid infusion resulted in a 14.7 and 7.6% increase, respectively, in RPF compared with baseline values in normal subjects and in a 12.6 and 6.9% increase, respectively in IDDM subjects. With the same protocol of the previous organic acid infusion, another five normal and six IDDM patients were given an acetic acid infusion (15 μmol · kg−1 · min−1), resulting in an increase of plasma circulating levels of acetic acid from 0.1–0.2 to 0.3–0.4 mM, which was associated with negligible changes in ketone body and lactic acid concentrations. Neither GFR nor RPF were influenced by acetic acid administration. During acetoacetic acid and lactic acid infusion, both lactic and ketone body acid tubular reabsorption rates were three to five times higher than during saline infusion. In conclusion, lactic acid and acetoacetic acid infusion resulting in circulating patterns of these intermediate metabolites comparable with those often found in poorly controlled IDDM subjects induced a significant increase in GFR and RPF in normal and IDDM subjects. The increased GFR was associated with stimulation of organic acid tubular reabsorption rate and was not related to sodium and liquid overload, because it returned to basal value when saline alone was administered again.

Ketone bodies increase glomerular filtration rate in normal man and in patients with Type 1 (insulin-dependent) diabetes mellitus

SummaryThe purpose of this study was to investigate whether the administration of acetoacetic and hydrochloric acids in a group of control and Type 1 (insulin-dependent) diabetic patients influenced renal haemodynamics. Renal plasma flow increased from 657±88 to 762±81 ml·min−1. 1.73 m−2 in diabetic patients (p<0.01) and from 590±71 to 691±135 in control subjects (p<0.01). Glomerular filtration rate increased from 135±9 to 180±8 ml·min−1·1.73 m−2 in diabetic patients (p< 0.001) and from 117±8 to 145±7 in control subjects (p<0.01). Similar effects on renal haemodynamics, even if less pronounced, were observed with low dose acetoacetic but not with hydrochloric acid infusion. Total protein, β2-microglobulin but not albumin excretion rates were increased by acetoacetic acid. We conclude that an acute increase in blood concentration of ketone bodies within the range found in diabetic patients with poor metabolic control (1) increases renal plasma flow and glomerular filtration rate both in control subjects and diabetic patients and (2) causes a tubular proteinuria.

Heparin-Induced Thrombocytopenia in Patients with Philadelphia-Negative Myeloproliferative Disorders and Unusual Splanchnic or Cerebral Vein Thrombosis

Background: Philadelphia-negative myeloproliferative disorders (Ph-MPD) are common causes of unusual splanchnic or cerebral vein thrombosis, which is treated with unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH). Heparin-induced thrombocytopenia (HIT) is a dangerous potential complication of this therapy, but it has rarely been reported in Ph-MPD. Patients and Methods: We retrospectively reviewed clinical records of 29 patients with Ph-MPD who have been treated with UFH or LMWH for unusual splanchnic or cerebral vein thrombosis (3 cerebral sinus, 6 portal and 20 hepatic vein). The goal of the study was to determine the occurrence of new thrombotic events during heparin therapy secondary to HIT (HITT). Results: During heparin therapy, 5 out of the 29 patients (17%) developed a new thrombotic episode (pulmonary embolism) with a high clinical probability of HIT based on the 4 T’s score even though not all the patients developed ‘true’ thrombocytopenia. A diagnosis of HIT was established in 2 patients (6.8%) through the presence of heparin-related antibodies. Conclusions: Ph-MPD patients on heparin warrant careful monitoring and HIT has to be suspected whenever platelet counts drop or a new thrombosis is detectable.

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

SummaryThis 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 μU/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<0.05) in Type 1 diabetic patients and from 4.94±0.20 to 7.11±0.38 mmol/l (p<0.05) in normal subjects, respectively). At intermediate insulin levels (35 μU/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<0.05) in Type 1 diabetic patients, and from 5.05±0.13 to 6.61±0.22 mmol/l (p<0.05) in normal subjects. At high insulin levels (70 μU/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.