F. Gregorio

Osteopenia associated with non-insulin-dependent diabetes mellitus: what are the causes?

This study investigated whether alterations in bone mineral content (BMC) and/or in the phosphate-calcium metabolism exist in non-insulin-dependent diabetes mellitus (NIDDM); whether they are linked to glycaemic control and whether antidiabetic therapy--oral agents or insulin--influences BMC and mineral metabolism. A cross-section assessment compared BMC and mineral metabolism in 60 well-controlled and 50 poorly controlled diabetic patients under oral hypoglycaemic therapy with 50 healthy controls. A longitudinal assessment improved the high glucose levels of the poorly controlled diabetic group either by increasing oral treatment or by adding a bedtime NPH insulin. Glycaemic control, BMC and mineral metabolism were followed-up for 1 year. In NIDDM patients BMC is reduced. This reduction is more marked in poorly controlled diabetic patients. In well-controlled diabetes osteocalcin levels are low. In poorly controlled patients glycosuria, hypercalcuria and parathyroid hyperactivity are present. In both groups vitamins 25(OH)-D, 1,25(OH)2-D and calcitonin levels are normal. Improving metabolic control increased BMC, normalized urinary calcium excretion and parathyroid activity and reduced osteocalcin levels. The type of anti-diabetic therapy does not have any significant effect upon BMC or upon phosphate-calcium metabolism. In conclusion, in NIDDM a hard-to-define osteoblast deficit appears to exist. In poorly controlled diabetes the loss of BMC is aggravated by the negative calcium balance caused by the renal calcium leak. This is due to glucosuric-induced osmotic diuresis and is maintained by parathyroid activation.

Partial gastrectomy and mineral metabolism: effects on gastrin-calcitonin release

Bone mineral metabolism was studied in 20 male patients, between 8 and 18 years, after surgical treatment for peptic ulcer (ten Billroth 1 and ten Billroth 2 gastrectomies) and in 16 sex- and aged-matched healthy controls. The bone mineral content was statistically reduced only in the Billroth 2 group. Serum 25(OH)D was lower in all patients, but fractional calcium absorption was similar to the control value. This may be due to increases in 1,25(OH)2D and parathyroid activity (particularly in Billroth 2). Serum osteocalcin levels and hydroxyproline excretion were higher than in the controls. A positive linear correlation emerged not only between serum 1,25(OH)2D and PTH levels but also between each of these and serum osteocalcin and urine hydroxyproline. Both PTH and calcitriol were inversely correlated with the bone mineral mass in Billroth 2, confirming a trend observed in Billroth 1. Although calcitonin values were normal, basal gastrin levels were severely impaired in all patients. In response to a mixed meal, increases in gastrin and calcitonin were significantly lower than in the controls. The calcitonin response to intravenous calcium and pentagastrin infusion was not significantly different to the controls. The percentage increase in gastrin and calcitonin responses to oral calcium correlated positively with the reduction in bone mineral content only in the Billroth 2 group, suggesting a reduction in calcitonin release may contribute to gastric surgery osteopenia in these patients.

Determination of plasma metformin by a new cation-exchange HPLC technique.

Metformin is an oral antihyperglycemic agent used in the therapy of noninsulin-dependent diabetic patients. This biguanide can induce dangerous complications such as lactic acidosis when its plasma concentration is too high. For this reason, the determination of plasma metformin should always be done during treatment. We developed a new HPLC method, for the routine determination of plasma metformin, with good reliability, rapid execution, and low costs. Sample preparation involved precipitation of the plasma proteins containing the internal standard buformin with a mixture of methanol, zinc sulfate, and ethylene glycol; the diluted supernatant was injected into a cation-exchange column. The mobile phase was potassium dihydrogenphosphate buffer-containing acetonitrile. The eluent was monitored at 236 nm. The calibration curve is linear within the range of 20-4000 ng/mL; the within-day coefficients of variation were less than 2.2% for metformin and 1.5% for buformin; the day-to-day coefficients of variation were less than 2.5% for metformin and 1.9% for buformin. The mean recoveries obtained from supplemented samples were included between 99.4 and 104.2% for metformin. Many characteristics make this method useful and easily accessible to all clinical laboratories equipped with HPLC instrumentation.

Low dose metformin in the treatment of type II non-insulin-dependent diabetes: Clinical and metabolic evaluations

SummaryLow doses of metformin (500 mg twice daily) were administered to 20 diabetic patients, combined with the original sulfonylurea treatment which had become ineffective even at full dosage. After 1 and 5 weeks, the effects of the drug on glycemic control, blood intermediate metabolites and monocyte insulin receptors were monitored. Metformin clearly improved glycemic control by reducing both fasting blood glucose from 189.88±21.11 mg/dl to 131.12±16.02 mg/dl after 1 week and to 130.11±13.29 mg/dl after 5 weeks (p<0.025 both after 1 and 5 weeks); the diurnal blood glucose average fell from 235.33±24.11 mg/dl to 174.66±23.45 mg/dl (p<0.0025) after 1 week and to 177.65±21.71 mg/dl (p<0.0005) after 5 weeks. Consequently both blood glycosylated hemoglobin (p=n.s. after 1 week, p<0.025 after 5 weeks) and serum fructosamine (p<0.0025 after both 1 and 5 weeks) also decreased after metformin treatment. No change in plasma insulin and C-peptide levels was reported and no modification in diurnal rhythms of blood lactate, pyruvate, alanine glycerol and β-OH-butyrate was detected at any time during metformin treatment. All the changes documented in the binding values were already complete at the end of the first week: insulin binding to monocytes increased slightly but significantly (p<0.05) and the number of receptors per cell rose (p<0.05) but could not be correlated to any index of glycemic control. These data suggest that the antidiabetic action of metformin is neither related to its lactate-increasing activity nor does it depend upon its inducing an increase in insulin binding values. This metformin-related hypoglycemic effect might be the result, at least in part, of a reduced oxidative phosphorylation without inhibition of hepatic guconeogenesis and/or of decreased hepatic glucose output. Moreover, our data are also consistent with the hypothesis that metformin might affect insulin action at a post-receptor level.

Paget's Disease of Bone: Benefits of Neridronate as a First Treatment and in Cases of Relapse After Clodronate

This study assessed the efficacy of 200 mg of aminohexane bisphosphonate (neridronate) administered by intravenous infusion in a single dose or in two separate doses on consecutive days in 32 patients (16 males and 16 females, average age 66 years) affected by active Pagets disease of bone. Fifteen patients had never been treated with any antiresorptive agent and 17 had had unsatisfactory results from a prior clodronate treatment. All of the latter patients had failed to enter a remission stage (i.e., normalization of bone turnover was not reported at any time during treatment) and had had a full relapse within 6 months after clodronate infusion. In the present study bone-specific alkaline phosphatase (bAp), deoxypyridinoline (dPyr), and N- and C-terminal polypeptide of collagen type 1 (Ntx, Ctx) were determined before neridronate administration and at 1, 3, 6, and 12 months thereafter. Basal values of bAp were 51.7 +/- 2.3 microg/L, range 31.7-92.5 (normal range 6.2-23.6). No statistical differences in markers of bone turnover were evident in the basal state between new pagetic patients (bAp = 55.1 +/- 4.1) and those suffering a relapse after clodronate (bAp = 48.8 +/- 2.6). Neridronate induced an average percent change from baseline in excess bAp of 68.0 +/- 4.3 and in excess dPyr, Ntx, and Ctx of 68.1 +/- 11, 60.6 +/- 8.5, and 86.7 +/- 7.8, respectively. Markers of bone resorption declined more slowly in patients treated previously with clodronate, although the average change in percent decrement from baseline in excess bAp as well as in excess of bone resorption markers was not different from that registered in untreated pagetic patients. Response to treatment, defined as a percent decrement from baseline in excess bAp of 50% or more at any time during the 12-month follow-up, was observed in 27 patients (84.4%). Remission (a drop in bAp to within normal range) was achieved in 21 patients (65.6%) and was maintained in 12 at 12-month follow-up, with no significant differences between either 1- or 2-day infusions, or between new pagetic patients and those relapsing after clodronate. In 15 of 21 patients requiring analgesics to alleviate bone pain, pain was reduced or completely alleviated in 8. A slight, short-lived acute phase reaction (fever and/or arthromyalgia) occurred in 6 patients. To summarize, 200 mg of intravenous neridronate, in one or two doses, significantly reduced the biochemical indices of disease activity in the majority of patients, showing a normalization of bAp in more than 60%. We conclude that neridronate can be used safely in the treatment of patients with Pagets disease of bone either as a first bisphosphonate treatment or as retreatment for patients relapsing after clodronate.

Relationship between plasminogen activator inhibitor type-1 plasma levels and the lipoprotein(a) concentrations in non-insulin-dependent diabetes mellitus.

The first part of the paper deals with the relationship between two inhibiting factors of the complex enzyme cascade regulating fibrinolysis, namely plasminogen activator inhibitor type-1 (PAI-1) and lipoprotein(a) (Lp(a)). Blood concentrations of Lp(a), PAI-1 antigen (PAI-1 AG) and activity (PAI-1 AT), and the main parameters of lipo- and glyco-metabolic balance were studied in 80 type II diabetic patients. Roughly hyperbolic patterns have been found between PAI-1 and Lp(a). Negative statistically significant linear correlation can be elicited when Log PAI-1 AG and Log PAI-1 AT values are plotted versus Lp(a) values, the first one being particularly tight. These findings suggest a nearly on/off control of the two parameters, limiting the risk of hypofibrinolysis. The second part of the paper was aimed at verifying this hypothesis. A group of 30 diabetic patients were treated for 3 months with metformin, an antidiabetic biguanide compound which has been reported to reduce PAI-1 levels both in diabetic and in non-diabetic patients. Metformin significantly reduced PAI-1 AG and PAI-1 AT but did not influence plasma Lp(a) levels. A clear linear correlation between the basal Lp(a) values and the changes in PAI-1 AG levels was found. An even tighter correlation was elicited between the decrease in PAI-1, and PAI-1 pretreatment values.

Alpha-adrenergic system in the modulation of pancreatic A and B cell function in normal rats

The role of the alpha-adrenergic system in the control of pancreatic A and B cell function was investigated in an isolated perfused rat pancreas model. Two experimental procedures were performed. In the first one we evaluated the effects of two distinct concentrations (10(-8) M and 10(-7) M) of five adrenergic substances, with varying degrees of potency on the alpha-adrenergic presynaptic receptor, on insulin (IRI) and glucagon (IRG) release induced by arginine (20 mM) plus glucose (6.6 mM). In the second procedure we studied the effects of the two alpha-blocking agents yohimbine (alpha 2-blocker) and prazosin (alpha 1-blocker) at 10(-7) M on epinephrine-modulated IRI and IRG response to the same combined metabolic stimulus. The inhibitory activity on basal and metabolically induced IRI secretion of the agonists was superimposable on their potency on the presynaptic alpha 2-adrenergic receptors. Similarly, the alpha 1-blocking agent prazosin was less effective than the alpha 2-blocker yohimbine in counteracting the inhibitory effects of epinephrine on basal and arginine plus glucose-induced insulin release. The alpha-cell activity was clearly stimulated by epinephrine, whereas selective alpha-adrenergic drugs showed no significant action on IRG secretion. Both alpha-blockers were ineffective on basal IRG release, while they had some potentiating effect on the epinephrine-induced glucagon release in basal state and during the metabolic stimulus, without a significant difference between the two drugs. We conclude that, at least in the isolated perfused rat pancreas, alpha 2-adrenergic receptors are involved in the inhibition of IRI release induced by catecholamines. On the contrary, the alpha-adrenergic system does not seem to play an essential role in the regulation of IRG secretion; the potentiation of the epinephrine-induced stimulation of A cell function by the alpha-adrenergic blockade could be accounted for by a greater availability of the catecholamine at the beta-receptor binding sites.

Effects of glimepiride on insulin and glucagon release from isolated rat pancreas at different glucose concentrations

The effects of glimepiride, the newest sulphonylureic compound, on pancreatic insulin and glucagon secretion were studied using the classical, isolated, perfused rat pancreas model. The influence of four different environmental glucose conditions (during a glycaemic stimulus with glucose increasing from 5 to 8.33 mM and at stable 0, 5 and 2.22 mM glucose levels) on the effects of glimepiride was also assessed. At a pharmacological concentration glimepiride strongly stimulated beta-cell activity, producing a characteristic biphasic insulin release with a sharp first-phase secretory peak, followed by a prolonged and sustained second phase. Environmental glucose concentrations markedly influenced the extent, but not the pattern of glimepiride-induced insulin secretion, as hormone release dropped significantly when the glucose level was reduced. Glimepiride failed to influence alpha-cell activity at any of the environmental glycaemic levels.

Meformin, plasma glucose and free fatty acids in type II diabetic out-patients: results of a clinical study

Abnormalities in free fatty acid (FFA) metabolism are an intrinsic feature of type II diabetes mellitus and may even play a role in the development of glycaemic imbalance. This study investigated whether the anti-diabetic drug metformin can reduce FFA levels in clinical practice and whether this correlates with its anti-diabetic effect. For 6 months metformin was added to sulfonylurea therapy in 68 type II diabetic outpatients with poor glycaemic control, being administered before meals and at bed-time. Basal and daily area-under-the-curve (AUC) glucose levels dropped (both P < 0.0005) like basal and daily AUC FFA levels (P < 0.004 and P < 0.001 respectively) reductions were all correlated (P < 0.001 and P < 0.003 respectively). Reductions in fasting and daily AUC glucose correlated more closely with body fat distribution, expressed by waist-hip ratio (WHR) (P < 0.006 and P < 0.004 respectively), than with the body mass index (BMI) (P < 0.02 and P < 0.04 respectively). Similarly fasting and daily AUC FFA correlated with WHR (P < 0.007 and P < 0.01 respectively) but not with BMI (both P = ns). Subdividing male and female diabetic patients into groups with low and high WHRs, fasting and daily AUC glucose were reduced in men (P < 0.01 and P < 0.02) and in women (P < 0.02 and P < 0.04 respectively) with low WHRs less than in men and in women with higher WHRs (for each gender P < 0.0001 and P < 0.0002, respectively). Decreases in fasting and daily AUC FFA, which did not reach significance in either men or women with low WHRs, were statistically significant in men (P < 0.03 and P < 0.01 respectively) and in women (P < 0.02 and P < 0.005 respectively) with high WHRs. These findings suggest that an improvement in FFA plasma levels might contribute to metformins anti-diabetic activity which appears to be more marked in patients with high WHRs. Moreover adding a bed-time dosage to the standard administration at meal times seems to be an effective therapeutical strategy.

Apolipoprotein E polymorphisms and mortality in Italian Type 2 diabetic patients

Aims To determine if apolipoprotein E polymorphism is associated with cardiovascular or all‐cause mortality in Italian Type 2 diabetic patients.