Benfluorex in obese noninsulin dependent diabetes mellitus patients poorly controlled by insulin: a double blind study versus placebo

Most obese patients with noninsulin-dependent diabetes mellitus (NIDDM) are initially treated with diet, then with oral hypoglycemic agents, eventually with insulin. However several reports indicate that in these patients insulin therapy has little chance to control glucose metabolism, promotes weight gain and arterial hypertension, and is likely to aggravate insulin resistance. In this randomized, double-blind trial vs. placebo (P) we evaluated in 29 obese NIDDM patients poorly controlled by insulin (daily insulin doses 48.7 +/- 4.0 U/day, HbA1c 10 +/- 0.27%, mean daily blood glucose levels 12.3 +/- 0.3 mmol/L, fasting C-peptide 1.8 +/- 0.2, C-peptide after 1 mg iv glucagon 3.2 +/- 0.3 ng/mL, means +/- SE), the clinical and metabolic effects of benfluorex (B), a lipid-lowering drug able to improve insulin sensitivity. After a 2-3 week run-in period (1 tablet P at dinner and diet 800 cal/day to lose 5% of the initial body weight (BWi), patients received a 1000 kcal/day diet and were randomized to B, 150 mg/ tablet, or P (3 tablets/day); the time limit was set at a 10% decrease of BWi or at 90 days. At the end of run-in there was a significant reduction of BWi (P < 0.001), fasting (P = 0.002) and mean daily blood glucose levels (P < 0.001), triglycerides (P = 0.02), cholesterol (P < 0.001) and daily insulin doses (P < 0.001). At the end of the double-blind trial, weight-loss was greater (P < 0.05), faster (P = 0.018), and more frequent (P < 0.05) with B than with P, and systolic blood pressure (P < 0.05) decreased only with B. Considering only patients with a 10% decrease of BWi (B = 15, P = 10), HbA1c (P < 0.001) decreased only with B, while fasting insulin levels decreased with both B (P < 0.01) and with P (P < 0.05). Insulin sensitivity was evaluated by means of a double infusion test (LDIGIT, insulin 25 mU/Kg/h plus glucose 4 mg/kg/min, lasting 150 min) at the end of run-in and at the end of the double-blind trial; at the end of the double-blind trial steady state blood glucose (SSBG, P < 0.05), free fatty acids (FFA, P < 0.05) and blood beta-hydroxybutyrate (P < 0.05) decreased only with B, while blood glycerol decreased both with both P (P < 0.05) and B (P < 0.06). At the end of the double-blind trial, C-peptide release was unchanged with either P or B. In conclusion, benfluorex potentiates the effects of hypocaloric diet on weight loss and on glycemic control in obese NIDDM patients treated with insulin, and this effect seems to be the result of an improved insulin sensitivity.

Dihydropyridine-sensitive and -insensitive voltage-operated calcium channels participate in the control of glucose-induced insulin release from human pancreatic beta cells

Calcium ion entry through voltage-operated calcium channels is a crucial step in the coupling of beta cell depolarization with insulin secretion. Various calcium channel subtypes have been shown to be coexpressed in single neurons and endocrine cells. Using the patch-clamp technique, we investigated the biophysical and pharmacological properties of calcium channels in freshly dispersed human pancreatic beta cells. Both low and high voltage activated currents were expressed, the two current types being easily distinguishable on the basis of biophysical criteria. The high voltage activated currents were not homogeneous: one component was affected by the dihydropyridine antagonist nitrendipine and the agonist Bay-K-8644; the other was insensitive to both dihydropyridines and omega-conotoxin GVIA. In line with this pharmacology, nitrendipine reduced and Bay-K-8644 increased glucose-induced insulin secretion from perifused human islets, whereas omega-conotoxin GVIA had no effect. However, about 20% of the glucose-induced insulin release was found to be resistant to high nitrendipine concentrations. These data show that human pancreatic beta cells express heterogeneous voltage-operated calcium channels, only one of which is dihydropyridine-sensitive (L type). The L type channels are clearly involved in the control of insulin secretion, but our data suggest that dihydropyridine- and omega-conotoxin GVIA-insensitive channels may also play a role in the stimulus-secretion coupling of human beta cells.

Metabolic effects of successful intraportal islet transplantation in insulin-dependent diabetes mellitus

The intraportal injection of human pancreatic islets has been indicated as a possible alternative to the pancreas transplant in insulin-dependent diabetic patients. Aim of the present work was to study the effect of intraportal injection of purified human islets on: (a) the basal hepatic glucose production; (b) the whole body glucose homeostasis and insulin action; and (c) the regulation of insulin secretion in insulin-dependent diabetes mellitus patients bearing a kidney transplant. 15 recipients of purified islets from cadaver donors (intraportal injection) were studied by means of the infusion of labeled glucose to quantify the hepatic glucose production. Islet transplanted patients were subdivided in two groups based on graft function and underwent: (a) a 120-min euglycemic insulin infusion (1 mU/kg/min) to assess insulin action; (b) a 120-min glucose infusion (+75 mg/di) to study the pattern of insulin secretion. Seven patients with chronic uveitis on the same immunosuppressive therapy as grafted patients, twelve healthy volunteers, and seven insulin-dependent diabetic patients with combined pancreas and kidney transplantation were also studied as control groups. Islet transplanted patients have: (a) a higher basal hepatic glucose production (HGP: 5.1 +/- 1.4 mg/kg/ min; P < 0.05 with respect to all other groups) if without graft function, and a normal HGP (2.4 +/- 0.2 mg/kg/min) with a functioning graft; (b) a defective tissue glucose disposal (3.9 +/- 0.5 mg/kg/min in patients without islet function and 5.3 +/- 0.4 mg/kg/min in patients with islet function) with respect to normals (P < 0.01 for both comparisons); (c) a blunted first phase insulin peak and a similar second phase secretion with respect to controls. In conclusion, in spite of the persistence of an abnormal pattern of insulin secretion, successful intraportal islet graft normalizes the basal HGP and improves total tissue glucose disposal in insulin-dependent diabetes mellitus.

Hypertriglyceridemia and hyperinsulinemia are potent inducers of endothelin-1 release in humans

The purpose of the study was to evaluate fasting endothelin-1 levels in subjects with syndrome X, in subjects with insulinoma, and in normal subjects. The single and synergistic contributions of insulin and triglyceride levels to endothelin-1 release were studied in normal subjects. This was achieved by the evaluation of endothelin-1 levels in response to an insulin bolus combined with a euglycemic clamp (protocol A) and during intralipid (test 1) or saline (test 2) infusions lasting 360 min (protocol B). In protocol B, a euglycemic two-step hyperinsulinemic (25 and 125 mU x kg-1 x h-1) clamp was started at 120 min. Subjects with syndrome X showed significantly higher endothelin-1 levels than normal subjects and subjects with insulinoma (7.22 +/- 0.89 vs. 2.61 +/- 0.38 and 2.49 +/- 0.24 pg/ml, P < 0.01). After an insulin bolus, endothelin-1 levels peaked at 10 min (3.71 +/- 0.96 pg/ml). The incremental area of endothelin-1 was significantly higher after insulin than after a saline bolus. In test 1, an acute increase in triglyceride levels significantly enhanced endothelin-1 levels, with were further increased by the synergistic contribution of high insulin and triglyceride levels. In test 2, endothelin-1 release was achieved at high insulin levels but remained significantly lower than in test 1. In conclusion, subjects with syndrome X showed higher endothelin-1 levels than normal subjects and subjects with insulinoma. These levels were reproduced in normal subjects by a simultaneous increase in insulin and triglyceride levels.

Effect of pancreas transplantation on free fatty acid metabolism in uremic IDDM patients

To assess the effect of pancreas transplantation on free fatty acid (FFA) and glucose metabolism, we studied seven uremic IDDM patients (HbA1c 9.1%), nine IDDM patients after combined kidney-pancreas transplantation (HbA1c 5.8%), seven patients with chronic uveitis (HbA1c 5.6%), and nine normal control subjects (HbA1c 5.5%) by means of the [3(- 3)H]glucose and [1(-14)C]palmitate infusion techniques combined with indirect calorimetry and euglycemic insulin clamp. In the postabsorptive state, pancreas-transplant patients had similar plasma glucose and FFA concentrations and non-statistically different rates of hepatic glucose production (HGP) and FFA turnover, while demonstrating a reduced rate of FFA oxidation (42 +/- 5 vs. 73 +/- 10 micromol x m-2 x min-1; P < 0.05) compared with control subjects. After 180 min of tracer equilibration, all subjects underwent a low-dose (100 min, 8 mU x m-2 x min-1) followed by a high-dose (100 min, 40 mU x m-2 x min-1) euglycemic insulin infusion. During insulin infusion, pancreas-transplant patients showed a greater inhibition of FFA concentration (609 +/- 76 to 58 +/- 15 micromol/l) compared with healthy subjects (681 +/- 90 to 187 +/- 25 micromol/l; P < 0.01 vs. pancreas-transplant patients). FFA turnover and oxidation rates during both low-dose and high-dose insulin infusions were lower in pancreas-transplant patients compared with healthy subjects (P < 0.03 and P < 0.01, for turnover and oxidation, respectively). Uremic IDDM patients demonstration altered basal and insulin-mediated glucose metabolism. Pancreas transplantation normalized only insulin-mediated glucose oxidation, leaving the stimulation of non-oxidative glucose disposal still markedly defective. In conclusion, patients after pancreas transplantation have normal basal FFA turnover and reduced basal FFA oxidation rates. During hyperinsulinemia, pancreas-transplant patients show a normal inhibition of FFA turnover and FFA oxidation. Insulin-mediated glucose metabolism remained abnormal after pancreas transplantation. Our findings may be related to the effect of chronic immunosuppressive therapy on glucose and FFA metabolism.

Intercellular Ca2+ waves sustain coordinate insulin secretion in pig islets of Langerhans

Insulin release was investigated in parallel with changes in cytosolic calcium concentration, [Ca2+]i, in pig islets stimulated by glucose. After two days in culture, glucose stimulation failed to induce insulin release, and caused limited [Ca2+]i changes in few cells. After ten days, insulin response was partially restored and [Ca2+]i recordings revealed a slow oscillatory activity of the whole islet. Slow oscillations appeared to be due to the average [Ca2+]i variations resulting from the spreading of waves throughout the islet. These waves demonstrate the reestablishment of functional cell coupling, which appears to play a critical role in insulin release.

Effects of an acute decrease in non-esterified fatty acid levels on muscle glucose utilization and forearm indirect calorimetry in lean NIDDM patients

The aim of the study was to evaluate an acute decrease in NEFA levels during an oral glucose tolerance test and its effects on glucose tolerance, muscle glucose uptake and muscle indirect calorimetry in ten lean non-insulin-dependent diabetic subjects. Two 75-g oral glucose tolerance tests were performed in random order. Placebo or 250 mg acipimox (to inhibit lipolysis) were administered orally 2 h before the start of the oral glucose tolerance test. Two hours after acipimox administration (time 0), non-esterified fatty acid, glycerol and 3-hydroxybutyrate levels decreased by 84, 68 and 77% respectively, compared to basal levels. Concomitantly, muscle lipid oxidation and non-oxidative glycolysis also decreased significantly. After placebo administration, non-esterified fatty acids, glycerol and 3-hydroxybutyrate and lipid oxidation increased by 29, 28, 106 and 33%, respectively (NS vs basal levels; p < 0.001 vs acipimox). There was a negative rate of net glucose storage (interpreted as glycogenolysis) during post-absorptive conditions and at time 0 after administration of both drugs. After oral glucose tolerance test, the incremental areas of blood glucose and insulin were significantly decreased by 18 and 19% after acipimox compared to placebo. In addition, the ratio between the incremental area of forearm muscle glucose uptake and the insulin levels was significantly increased by 45% during acipimox compared to placebo administration. Glucose oxidation and non-oxidative glycolysis were significantly higher while lipid oxidation was significantly lower after acipimox than after placebo. In conclusion, our study found that in lean non-insulin-dependent diabetic subjects, an acute decrease in non-esterified fatty acid levels improves glucose tolerance, muscle glucose uptake, glucose oxidation and non-oxidative glycolysis, but is unable to normalize glucose storage.

Glucagon improves insulin secretion from pig islets in vitro

It has been shown that peripheral glucagon secreting cells (A-cells) are lost during most of the isolation procedures employed for pig islets. Loss of A-cells decreases intra-islet glucagon levels and cAMP levels in B-cells and might reduce glucose-induced insulin release. This study was designed to test this hypothesis, by evaluating the effects of culture of porcine islets with exogenous glucagon on insulin secretion and on insulin and cAMP content in islets. Islets were isolated from adult 2-year old Large White pigs using an automated method. The number of A-cells was calculated by immunostaining for glucagon in islets before and after isolation and a significant decrease in A-cells was observed. After an overnight culture, islets were cultured for 48 h in a standard medium (CMRL 1066, 10% foetal calf serum, 1% antibiotics, 1% glutamine) alone or in the presence of glucagon at two different concentrations (1.0 and 10.0 microM); exposure to glucagon was either continuous or alternated with periods of incubation in CMRL 1066 alone. After the 48-h culture in standard medium, the islet glucagon response to arginine was almost negligible and significantly lower than that observed in human islets.(ABSTRACT TRUNCATED AT 250 WORDS)

Cephalic-phase insulin and glucagon release in normal subjects and in patients receiving pancreas transplantation

The aim of the study was to evaluate whether the cephalic phase of insulin release is still present in patients submitted to simultaneous kidney and pancreas transplantation. Subjects were five kidney-pancreas-transplanted patients (group P) and five control (group C). The experimental protocol lasted 30 minutes, and blood samples were collected at 1-minute intervals. After a 20-minute period of steady-state fasting (premeal period), subjects received a palatable standard meal (pizza). Samples were collected over the subsequent 10 minutes (meal period). No evidence of an increase in serum free insulin, serum C-peptide, and plasma glucagon during food ingestion was observed in group P whereas the test was effective in eliciting cephalic-phase insulin and glucagon release in group C. Gastric inhibitory polypeptide and somatostatin did not show any variation during the test in both groups. In conclusion, the absence of cephalic-phase insulin and glucagon release in group P could be explained by denervation of the grafted pancreas. This early alteration could contribute to the impairment in glucose tolerance frequently observed in successfully pancreas-transplanted patients.

Pharmacological management of erectile dysfunction

Pharmacological treatment of erectile dysfunction includes all therapeutic modalities based on the use of erectogenic drugs, regardless of the route of administration. Intracavernous vasoactive injection therapy is the most commonly used treatment for erectile dysfunction. Most patients respond to intracavernous injection of either single or multiple vasoactive drugs. Major adverse effects related to this treatment include priapism, corporeal pain and the formation of nodules or plaques in the corpora cavernosa. Oral administration of drugs aimed at improving erectile function has not produced results comparable with those obtained with intracavernous injection therapy. However, in patients with psychogenic or mild organic impotence, oral treatment with drugs that influence either central or peripheral pathways controlling erection may improve erectile function. Topical administration of vasoactive drugs in the form of gels, liquid solutions or plasters is another attractive alternative for the treatment of psychogenic and mild organic erectile dysfunction. Although the ideal drug for the treatment of erectile dysfunction has not yet been identified, extensive laboratory and clinical research is ongoing and successful results are expected in the near future.

Defective insulin action on protein and glucose metabolism during chronic hyperinsulinemia in subjects with benign insulinoma

The ability of chronic endogenous hyperinsulinemia to induce a resistance to insulin action on protein and glucose metabolism was studied in 10 subjects affected by a benign (functioning) insulinoma and 18 healthy subjects by means of infusions of [1-(14)C]leucine and [3-(3)H] glucose. The insulinoma subjects were divided into two groups with moderate (139 +/- 12 pmol/l) (n = 5) and marked (438 +/- 42 pmol/l) (n = 5) hyperinsulinemia and were studied during a euglycemic dextrose infusion. Control subjects were studied postabsorptively and during a low-dose (0.3 mU.kg-1.min-1) (n = 3) and a high-dose (1 mU.kg-1.min-1) (n = 15) euglycemic insulin clamp to match peripheral insulin concentrations with those of insulinoma subjects. In insulinoma subjects there was no correlation among plasma insulin concentration and leucine concentration (r = 0.05), endogenous leucine flux (r = 0.44), hepatic glucose production (r = 0.47), and glucose uptake (r = 0.05). Insulinoma subjects with marked hyperinsulinemia demonstrated a defective suppression of leucine concentrations (100 +/- 11 vs. 65 +/- 5 mumol/l, P < 0.01), endogenous leucine flux (50.1 +/- 6.3 vs. 27.1 +/- 0.9 mumol.m-2.min-1, P < 0.01), and hepatic glucose production (5.4 +/- 2.0 vs. 0.6 +/- 0.6 mumol.kg-1.min-1, P < 0.05), and a defective stimulation of glucose uptake (13.5 +/- 1.6 vs. 41.1 +/- 2.8 mumol.kg-1.min-1, P < 0.001) with respect to normal subjects at a comparable degree of hyperinsulinemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Myocardial glucose uptake evaluated by positron emission tomography and fluorodeoxyglucose during hyperglycemic clamp in IDDM patients. Role of free fatty acid and insulin levels

Myocardial and whole-body glucose metabolism was assessed in 19 insulin-dependent diabetes mellitus (IDDM) patients. A hyperglycemic clamp was performed 1) in the absence of insulin at free fatty acid (FFA) levels of 1.0 mmol/l (test 1); 2) in the absence of insulin at low FFA levels (0.1 mmol/l) by means of a lipid-lowering drug, acipimox (test 2); 3) during insulin infusion to achieve systemic levels of 400 pmol/l and FFA levels of 0.1 mmol/l (test 3); and 4) at the insulin levels of test 3 but increasing FFA to 1.0 mmol/l by means of heparin and intralipid infusion (test 4). Myocardial glucose uptake was measured by positron emission tomography (PET) and 2-[18F]fluoro-2-deoxy-D-glucose. Whole-body glucose uptake was measured in the four conditions by the glucose infusion rate during the PET scanning period. Myocardial glucose uptakes were 40.3 +/- 18.0, 395.5 +/- 139.6, 852.2 +/- 99.1, and 1,388.4 +/- 199.1 mumol.kg tissue-1.min-1 (mean +/- SD) and whole-body glucose uptakes were 10.1 +/- 2.3, 10.1 +/- 3.4, 42.8 +/- 5.8, and 30.5 +/- 5.6 mumol.kg body wt-1.min-1 during tests 1, 2, 3, and 4, respectively. Thus, in IDDM patients without coronary artery disease under the condition of hyperglycemia, an increase of myocardial glucose uptake was obtained either by lowering of FFA levels during hypoinsulinemia or by an increase in FFA levels during hyperinsulinemia. In both conditions no significant changes of whole-body glucose uptake were demonstrated.

Lipoprotein profile after combined kidney-pancreas transplantation in insulin dependent diabetes mellitus

In order to evaluate the effect of a combined kidney-pancreas (KP) transplantation in insulin-dependent diabetes mellitus (IDDM) patients on the lipid and lipoprotein profile, 15 KP patients were compared with 11 kidney (K)--transplanted IDDM patients, 19 IDDM patients on hemodialysis (HD), and 15 nondiabetic control subjects. Cholesterol, triglycerides, apo AI, and apo B were measured in total plasma and in VLDL, LDL, and HDL of all participants. VLDL cholesterol, VLDL-triglycerides, and VLDL-apo B were significantly lower in KP patients, but not in K patients, than in HD patients. In addition, patients in the K, but not in the KP, group showed high levels of apo B in LDL and an increased triglyceride/apo B ratio in VLDL, compared with patients in the HD group. The percentage of apo AI associated with HDL was significantly higher in both transplanted groups than in the HD group. However, compared with a nondiabetic control population, an increase in VLDL particles and in triglyceride content in LDL and HDL still persisted following combined KP transplantation. Insulin resistance (probably due to steroid therapy) associated with high peripheral and potentially low hepatic insulin levels (due to the systemic drainage of the transplanted pancreas) could be the main causes of the remaining lipoprotein abnormalities.

In vivo metabolic effects of insulin-like growth factor-I not mediated through the insulin receptor

Patients with mutations affecting insulin receptor function may maintain some degree of metabolic control. The hypothesis has been put forth that in these patients, fuels may be metabolized through pathways (i.e. receptor activation) that become relevant in such abnormal conditions. The aim of our study was to evaluate the metabolic effects of insulin-like growth factor-I (IGF-I) in a 19-yr-old patient with homozygous mutation of the insulin receptor alpha-subunit. Her metabolic and hormonal features were marked hyperglycemia (11-33 mmol/L) and hyperinsulinemia (1000-2000 pmol/L); normal free fatty acids and lactate; low IGF-I; glycerol, alanine, and pyruvate below the normal range; and elevated beta-hydroxybutyrate. Unlike diabetic ketoacidosis, no triglyceride or protein breakdown was present, suggesting a compensatory mechanism, possibly sustained by the insulin concentration acting on IGF-I receptors. Subcutaneous administration of IGF-I (40, 80, and 120 micrograms/kg), although not affecting plasma glucose, resulted in a rapid decrease in free fatty acids and prevented the rise of beta-hydroxybutyrate levels compared to placebo. Therefore, IGF-I can exert direct metabolic effects in vivo, probably through activation of its own receptor, even at a concentration not affecting blood glucose levels. Furthermore, these findings are consistent with the hypothesis that IGF-I receptors may be activated by high insulin levels, providing lipid and protein regulation in patients with nonfunctional insulin receptors.

A sensitive and reliable method for assaying true human insulin without interaction with human proinsulin-like molecules

In the present study our interests focused on the evaluation of a high capacity assay (MEIA) which allows true insulin determinations in the absence of cross-reactivity with proinsulin-like molecules. This method was compared to a commercially available radioimmunoassay (RIA) for insulin determination. As the latter gives insulin levels which represent a mixture of insulin and proinsulin-like molecules, the proinsulin-like molecules were quantitated by subtracting the true insulin levels measured using MEIA from the total insulin levels obtained using RIA. These methods were applied for the analysis of blood samples drawn in 63 normal subjects, 16 obese subjects, 3 patients submitted to islet transplantation and 4 patients with insulinoma. The MEIA was precise, fully automated and time-saving, making its application on a routine basis particularly attractive. MEIA and RIA were equally able to correctly quantify human insulin molecules. On the contrary, the antibody present in the true insulin assay did not interact with proinsulin-like molecules, which were recognized even in the presence of increasing insulin levels. In normal subjects, the true and total insulin levels in the fasting state and at the time peak after glucose- or arginine-induced endogenous insulin release were well correlated at r = 0.88 and 0.89, respectively. Interestingly, total insulin values were overestimated by 10%-16% as compared with true insulin levels, which represent proinsulin values superimposable on previously reported data. Proinsulin-like molecules made up 50% of the total insulin in obese and transplanted patients, and about 70% in patients with insulinoma.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of personality on metabolic control in IDDM patients

OBJECTIVE

The aim of this study was to evaluate the relationship between poor metabolic control and maladaptive personality traits (according to the Diagnostic and Statistical Manual of Mental Disorders, Third Edition-Revised) in an adult-onset insulin-dependent diabetes mellitus sample group (n = 77).

RESEARCH DESIGN AND METHODS

Metabolic control was evaluated through glycosylated hemoglobin (HbA1c). Personality traits were assessed with the Personality Diagnostic Questionnaire-Revised, a self-administered questionnaire. Residual pancreatic secretion (fasting serum C-peptide) was also evaluated.

RESULTS

Principal components analysis revealed three personality profiles: "withdrawn-suspicious" (P1), "dramatic-dependent" (P2), and "aggressive-irresponsible" (P3). Multiple linear regression analysis showed that C-peptide levels and P2 personality profiles were significant and independent predictors of HbA1c plasma levels: P2 predicted high HbA1c values and C-peptide predicted low HbA1c levels.

CONCLUSIONS

These data suggest that a P2 personality profile is a significant predictor of poor metabolic control.