D. Giugliano

Metformin for obese, insulin-treated diabetic patients: improvement in glycaemic control and reduction of metabolic risk factors

SummaryThe efficacy and safety of metformin in the treatment of obese, non-insulin-dependent, diabetic subjects poorly controlled by insulin after secondary failure to respond to sulphonylureas has been investigated. Fifty insulin-treated, obese diabetics participated in this prospective, randomised double-blind six-month trial. After a four-week run-in period, during which all patients were given placebo (single-blind), patients were randomly assigned to continue to receive placebo or to active treatment with metformin.At six months, there was a relevant and significant improvement in glycaemic control in diabetics receiving the combined insulin-metformin treatment (decrease in glucose −4.1 mmol·l−1; glycosylated haemoglobin A1 decrease −1.84%). No significant changes were seen in diabetics receiving insulin and placebo. There was a significant decrease in blood lipids (trygliceride and cholesterol), an increase in HDL-cholesterol and a reduction in blood pressure in diabetics taking metformin. These postive findings were most marked in the 14 diabetics who experienced a good response to metformin (glucose profile <10 mmol·l−1), and were less marked but still significant in the remaining 13 diabetics, whose response to therapy was not so good (glucose profile >10 mmol·l−1). The fasting insulin level was significantly lower after six months of combined insulin-metformin treatment as shown by a 25% reduction in the daily dose of insulin (−21.6 U/day).Metformin was well tolerated by all diabetics. Combining metforming with insulin in obese, insulin-treated and poorly controlled diabetics may represent a safe strategy to achieve better glycaemic control with a reduction in certain metabolic risk factors associated with the increased incidence of cardiovascular disease in diabetes mellitus.

Metformin Improves Hemodynamic and Rheological Responses to L-Arginine in NIDDM Patients

OBJECTIVE The endothelium plays a pivotal role in the regulation of vascular tone by releasing nitric oxide (NO). Increased availability of L-arginine, the natural precursor of NO, induces vasodilatation and inhibits platelet activity. We studied the effect of metformin on hemodynamic and rheological responses to L-arginine in patients with NIDDM. RESEARCH DESIGN AND METHODS Ten newly diagnosed NIDDM patients with mild fasting hyperglycemia (7.5 ± 0.3 mmol/l) and without evidence of both micro- and macrovascular complications were investigated. They received an intravenous infusion of L-arginine (1 g/min for 30 min) with evaluation of plasma glucose and insulin, systolic (sBP) and diastolic (dBP) blood pressure, heart rate and plasma catecholamines, platelet aggregation, and blood viscosity and filterability. The L-arginine test was repeated after an 8-week treatment with metformin (850 mg b.i.d.). RESULTS Metformin treatment significantly reduced basal fasting plasma glucose, HbA1c, and platelet aggregation to ADP (P < 0.05); the other parameters did not change. During pretreatment test, L-arginine infusion decreased sBP (from 137 ± 4.1 to 129 ± 4.5 mmHg, P < 0.01) and dBP (from 79 ± 1.9 to 75 ± 1.2 mmHg, P < 0.01) without affecting heart rate or plasma catecholamines. Both platelet aggregation and blood viscosity showed significant decrements after L-arginine, while blood filterability did not change. After metformin treatment, the decrease in blood pressure after L-arginine infusion was significantly enhanced, with a maximal decrease of sBP of 12 ± 3.4 mmHg (8 ± 2.5 mmHg pretreatment, P < 0.05) and dBP of 9.5 ± 2.4 mmHg (4.5 ± 1.9 mmHg pretreatment, P < 0.01). Heart rate, plasma norepinephrine levels, and blood filterability also rose significantly (P < 0.05–0.01). The decrease in both platelet aggregation and blood viscosity after L-arginine was significantly amplified after metformin. CONCLUSIONS We conclude that L-arginine infusion in newly diagnosed NIDDM patients without vascular complications produces relevant hemodynamic and theological changes, which are amplified by an 8-week treatment with metformin. Whether these vascular effects of metformin will improve the poor cardiovascular outlook of the diabetic patient is still unknown.

Glucose tolerance and hormonal responses in heroin addicts. A possible role for endogenous opiates in the pathogenesis of non-insulin-dependent diabetes

Plasma glucose, insulin, glucagon, and growth hormone responses to intravenous glucose stimulation were investigated in 15 heroin-dependent men and in 15 control subjects matched for age, sex, and weight. Although the fasting concentrations of insulin, glucagon, and GH were significantly higher in the heroin addicts, they had markedly reduced plasma insulin responses to intravenous glucose (acute insulin response, calculated as the mean change in insulin levels over 3 to 10 minutes: 10 +/- 5 microU/mL in the addicts v 44 +/- 9 microU/mL in the controls, P less than 0.001) and glucose utilization rates in the diabetic range (KG: 0.96 +/- 0.09%/min in the addicts v 1.65 +/- 0.10%/min in the controls, P less than 0.01). These results show that chronic heroin administration produces a state of fasting hyperinsulinemia even in the absence of obesity, glucose intolerance, and a marked reduction of the first phase of insulin secretion. A possible role for endogenous opiates in the pathogenesis of non-insulin-dependent diabetes is hypothesized.

Nicardipine does not cause deterioration of glucose homoeostasis in man: a placebo controlled study in elderly hypertensives with and without diabetes mellitus.

SummaryThe effect of the calcium antagonist nicardipine on insulin secretion and glucose homoeostasis was investigated in elderly hypertensives with and without diabetes mellitus; 15 patients with essential hypertension for at least 10 years and normal glucose tolerance according to standard criteria (Group I) and 15 elderly hypertensive patients affected by Type 2 diabetes mellitus and on treatment with diet or oral drugs (Group 2).In the basal state, all patients were submitted to an oral glucose tolerance test (OGTT, 75 g) and an iv arginine test (30 g), on two different days and in random order. The same tests were repeated after one month of treatment with nicardipine 60 mg/day, in three spaced doses, the last being given 1 h before the post-treatment test. Nicardipine did not change overall glucose homoestasis, as assessed by haemoglobin Alc and fructosamine, nor did it significantly affect the plasma insulin response either to glucose or arginine in Groups 1 and 2. Only the glucagon response to arginine was significantly reduced in diabetic hypertensives. Small, non-significant variations in the metabolic and hormonal parameters were seen in additional two groups of patients (Groups 3 and 4), matched with Groups 1 and 2 for age, sex and diseases, who took capsules containing placebo.Thus, nicardipine did not produce any significant over-all alteration in glucose homoestasis when given to elderly diabetic or nondiabetic hypertensive subjects.

Hyperinsulinemia in glucose intolerance: Is it true?

To evaluate whether beta-cell hyperfunction characterizes glucose intolerant states per se independent of fasting glycemia, we conducted a case-control study among 430 subjects who were classified, by NDGG criteria, as having normal glucose tolerance (n=230, 130M/130F), nondiagnostic tolerance (NDT, n=100, 50M/50F) and impaired glucose tolerance (IGT, n=100, 50M/50F). Thirty-four subjects (17M/17F) with normal glucose tolerance were matched by age, sex, body mass index (BMI), waist-to-hip ratio (WHR), fasting glucose and HbA1c with 30 NDT (15M/15F) and 30 IGT (15M/15F) subjects. The continuous and significant increase in insulin and C-peptide levels across categories of glucose tolerance (from normal to NDT to IGT) was no longer evident in the case-control study: at a fasting plasma glucose ranging from 5.2–5.5 mmol/L (HbA1c was 5%) the concentration of fasting C-peptide was 0.793±225 nmol/L (mean±SD) in subjects with normal glucose tolerance, 0.805+200 nmol/L in NDT and 0.807±231 nmol/L in IGT subjects (p=NS). Similarly, plasma concentrations of triglycerides and blood pressure values were similar when subjects of different categories were compared at the same level of glycemia. Sixteen normal subjects were rendered mildly hyperglycemic by a 24-h glucose infusion to match the fasting glucose level of NDT (1 mg/kg/min) and IGT (2 mg/kg/min) subjects. At the same fasting glucose level, normal subjects presented elevations of fasting C-peptide significantly (p<0.01) higher than subjects belonging to the NDT and IGT categories. In conclusion, overweight people with impaired glucose tolerance present beta-cell hyperfunction in the fasting state which, however, is largely inappropriate for the prevailing glucose level; in these persons, glucose intolerance per se is not associated with hyperinsulinemia.