Outcomes of integrated management versus specialized care for patients with type 2 diabetes: An observational study

AIMS

To compare type 2 diabetes (T2D) patients included in a Diabetes Integrated Management (DIM) program with those followed in Diabetes Specialized Care (DSC), investigating differences in general characteristics, changes in clinical outcomes, and factors related with the inclusion in the DIM program.

METHODS

T2D patients living in the ASLTO3 district and included into the DIM program, a shared disease management between general practitioners and diabetes specialists, from 2008 to 2014 were compared with T2D patients living in the same district and in charge of the local DSC. Demographic, anthropometric and clinical data for both groups of patients were obtained from the electronic records of DSC.

RESULTS

1326 DIM patients were compared with 3494 DSC patients. A higher proportion of females was observed among DIM patients than among DSC patients. DIM patients were older, more frequently in therapy with diet only or with oral hypoglycemic, and had HbA1c and creatinine lower than DSC patients. The analyses of changes in clinical parameters during the study period showed a good and statistically significant improvement of most parameters, independently of the inclusion in DIM or DSC, with the exception of creatinine level.

CONCLUSIONS

Integrated Management is an efficient and effective way to achieve good long-term clinical outcomes for patients with diabetes.

How can we monitor glycaemic variability in the clinical setting?

No universal consensus exists on how to express glycaemic variability. Among other parameters, standard deviation of blood glucose values, mean amplitude of glycaemic excursions (MAGE), the Low Blood Glucose Index (LBGI) and the High Blood Glucose Index (HBGI), which were subsequently combined into the Average Daily Risk Range (ADRR), mean of daily differences (MODD) and glycaemic variability index (GVI) are highlighted. The continuous glucose monitoring in research and clinical settings has been a great help for a comprehensive approach to circadian blood glucose evaluation and identification of individual patterns, mainly in type 1 diabetes, but recently also in type 2 diabetes. In everyday clinical practice the judicious use of self-monitoring of blood glucose in an educational setting involving the patient and the care team is an unreplaceable tool to effectively and safely guide behavioural and drug therapy.

Do data in the literature indicate that glycaemic variability is a clinical problem? Glycaemic variability and vascular complications of diabetes

In recent years glycaemic variability (GV) has emerged as a determinant of vascular complications of both type 1 and type 2 diabetes mellitus. In type 1 diabetes analysis of data of GV show conflicting results on both micro- and macro-vascular complications. In non-diabetic subjects blood glucose after loading is a stronger predictor of cardiovascular complications than fasting glucose. In type 2 diabetes both coefficient of variation of fasting blood glucose and postprandial blood glucose predict cardiovascular events. Also, long term variability of HbA1c has been associated predominantly with diabetic nephropathy, less frequently with retinopathy. Intervention trials to evaluate the effect of postprandial glucose have been conducted only in prediabetes or in type 2 diabetes and the data are not conclusive. In vitro and in vivo data have shown the mechanisms that are at the basis of the adverse cardiovascular effects of GV, mainly associated with oxidative stress; the atherogenic action of postprandial glucose also involves insulin sensitivity, postprandial increase in serum lipids and glycaemic index of food. Thus, correction of GV emerges as a target to be pursued in clinical practice in order to safely reduce mean blood glucose (and thus glycated haemoglobin) and for its direct effects on vascular complications of diabetes.

Women show worse control of type 2 diabetes and cardiovascular disease risk factors than men: results from the MIND.IT Study Group of the Italian Society of Diabetology

BACKGROUND AND AIMS

The study explores the degree of control of hyperglycaemia and cardiovascular (CV) disease risk factors in men and women with type 2 diabetes and the impact thereon of obesity, central adiposity, age and use of medications.

METHODS AND RESULTS

A cross-sectional survey was conducted at 10 hospital-based outpatients diabetes clinics. 1297 men and 1168 women with no previous CV events were studied. Women were slightly (only one year) older and more obese than men: average BMI was respectively 30.7 ± 5.7 vs 28.6 ± 4.1 kg/m(2) (p < 0.001), and prevalence of abdominal obesity was 86% vs 44% (p < 0.001). Women smoked less, but had higher HbA1c, LDL cholesterol, non-HDL cholesterol, systolic blood pressure and serum fibrinogen than men. Accordingly optimal targets for HbA1c (<7%), LDL cholesterol (<100 mg/dL), HDL cholesterol (>40 for men, >50 for women, mg/dL), and systolic blood pressure (<130 mmHg) were less frequently achieved by women than men (respectively 33.8% vs 40.2%; 14.6% vs 19.2%; 34.1% vs 44.5%; 68.8% vs 72%; p < 0.05 for all). Findings were confirmed after stratification for waist circumference (< or ≥ 88 cm for women; < or ≥ 102 cm for men), BMI (< or ≥ 25 kg/m(2)) or age (< or ≥ 65 years). As for treatment, women were more likely than men to take insulin, alone or in combination with oral hypoglycaemic drugs, to be under anti-hypertensive treatment, whereas the use of lipid lowering drugs was similar in men and women.

CONCLUSIONS

Control of hyperglycaemia and major CVD risk factors is less satisfactory in women than men. The gender disparities are not fully explained by the higher prevalence of total and central obesity in women; or by a less intensive medical management in women.

Metabolic syndrome in subjects at high risk for type 2 diabetes: the genetic, physiopathology and evolution of type 2 diabetes (GENFIEV) study

BACKGROUND AND AIM

We evaluated the relationship between insulin resistance (IR) and insulin secretion with the metabolic syndrome (MS) in 885 subjects (377 men/508 women, age 49±11 years, BMI 29±5.2kgm(-2)) at risk of diabetes enrolled in the genetics, pathophysiology and evolution of type 2 diabetes (GENFIEV) study.

METHODS AND RESULTS

All subjects underwent a 75-g oral glucose tolerance test (OGTT) for the estimation of plasma levels of glucose and C-peptide, as well as fasting insulin and lipid profile. IR was arbitrarily defined as HOMA-IR value above the 75th centile of normal glucose tolerance (NGT) subjects. Overall MS prevalence (National Cholesterol Treatment Panel-Adult Treatment Panel (NCEP-ATPIII) criteria) was 33%, 19% in subjects with NGT, 42% in impaired fasting glucose (IFG), 34% in impaired glucose tolerance (IGT), 74% in IFG+IGT subjects, and 56% in newly diagnosed diabetic patients. Prevalence was slightly higher with IDF criteria. MS prevalence was >50% in subjects with 2h glucose >7.8mmoll(-1), independently of fasting plasma glucose. IR prevalence was higher in subjects with MS than in those without (63% vs. 23%; p<0.0001) and increased from 54% to 73% and 88% in the presence of three, four or five traits, respectively. IR occurred in 42% of subjects with non-diabetic alterations of glucose homeostasis, being the highest in those with IFG+IGT (IFG+IGT 53%, IFG 45%, IGT 38%; p<0.0001). Individuals with MS were more IR irrespective of glucose tolerance (p<0.0001) with no difference in insulinogenic index. Hypertriglyceridaemia (OR: 3.38; Confidence Interval, CI: 2.294.99), abdominal obesity (3.26; CI: 2.18-4.89), hyperglycaemia (3.02; CI: 1.80-5.07) and hypertension (1.69; CI: 1.12-2.55) were all associated with IR.

CONCLUSIONS

These results show that in subjects with altered glucose tolerance (in particular IFG+IGT) MS prevalence is high and is generally associated to IR. Some combinations of traits of MS may significantly contribute to identify subjects with IR.

The clinical reality of guidelines for primary prevention of cardiovascular disease in type 2 diabetes in Italy

INTRODUCTION AND AIM

Guidelines for cardiovascular prevention in diabetes have been issued by the national and international scientific societies. No audit as ever been performed to evaluate the implementation of these documents in clinical practice in Italy. The study evaluates the prevalence, treatment, and control of major cardiovascular risk factors in type 2 diabetic patients, to assess the clinical practice of primary cardiovascular prevention in type 2 diabetes.

PATIENTS AND METHODS

Two thousand four hundred and sixty-five men and women with type 2 diabetes, aged 50-75 and free of cardiovascular events were recruited on a consecutive basis at 10 hospital based outpatients diabetes clinics. Clinical variables were measured by standard protocol. Biochemical parameters were evaluated at each centre. The laboratories were monitored by an external quality control assessment in order to reach and maintain a standard of quality and traceability among the participating centres.

RESULTS

A minority of patients (5%) met the recommended targets for LDL cholesterol, blood pressure, glycated haemoglobin and smoking habits, whereas the vast majority (66%) had unsatisfactory control of three or more of the above. Achievement of desirable control of risk factors differed according to gender and known diabetes duration. Lipid lowering and, to a lesser extent, antihypertensive medications were under-used and their titration insufficiently target-driven. Prophylactic use of antiplatelet agents was scarce, only one out of five patients was treated independent of absolute cardiovascular risk.

CONCLUSION

In clinical practice there is poor adherence to national and international guidelines for primary cardiovascular prevention in type 2 diabetes in Italy. The study underlines the great potential for prevention, particularly in women and in high-risk patients.

Dietary habits in type II diabetes mellitus: how is adherence to dietary recommendations?

OBJECTIVE

To clarify adherence of type II diabetic patients to dietary recommendations.

SUBJECTS AND METHODS

The dietary habits of a group of 540 patients, with type II diabetes (male 322/female 218, mean age 61+/-5 years, body mass index (BMI) 29.7+/-5.2 kg/m(2); mean+/-s.d.) referring to six Italian diabetes centres were evaluated by means of a 3-day diet record (2 workdays, 1 holiday). Diet records were analysed according to Italian food composition tables and compared with the dietary recommendations of the Diabetes and Nutrition Study Group of the European Association for the study of Diabetes.

RESULTS

Calorie intake was 1725+/-497 kcal (1800 for men, 1610 for women). Mean intake for each nutrient was close to the recommended amount, except for fibre (12/1000 vs 20 g/1000 kcal). Calculating the percentage of patients who complied with each recommendation, the intakes of saturated fat and fibre least reflected the dietary target: in 43% of patients saturated fat was >10% of total calories, in only 6% was fibre intake > or =20 g/1000 kcal (considered ideal), and in 25% it was > or =15 g/1000 kcal (acceptable).

CONCLUSIONS

These results indicate that compliance to dietary recommendations is not completely satisfactory, even in Italy. Calorie intake is a bit elevated, given the high BMI of our diabetic population. As to dietary composition, there are two crucial issues: the high intake of saturated fat and--most importantly--the low intake of fibre. All strategies aiming to a proper implementation of guidelines should take these results into due account.

Postprandial blood glucose is a stronger predictor of cardiovascular events than fasting blood glucose in type 2 diabetes mellitus, particularly in women: lessons from the San Luigi Gonzaga Diabetes Study

OBJECTIVE

The influence of postprandial blood glucose on diabetes complications is intensively debated. We aimed to evaluate the predictive role of both fasting and postprandial blood glucose on cardiovascular events in type 2 diabetes and the influence of gender.

METHODS

In a population of 529 (284 men and 245 women) consecutive type 2 diabetic patients attending our diabetes clinic, we evaluated the relationships, corrected for cardiovascular risk factors and type of treatment, between cardiovascular events in a 5-yr follow-up and baseline values of hemoglobin A1c (HbA1c) and blood glucose measured: 1) after an overnight fast, 2) after breakfast, 3) after lunch, and 4) before dinner. Continuous variables were categorized into tertiles.

RESULTS

We recorded cardiovascular events in 77 subjects: 54 of 284 men (19%) and 23 of 245 women (9.4%). Univariate analysis indicated that cardiovascular events were associated with increasing age, longer diabetes duration, and higher HbA1c and fibrinogen in men, and higher systolic blood pressure, albumin excretion rate, HbA1c, and all blood glucose values in women. Smoking was more frequent in subjects with events. When all blood glucose values and HbA1c were introduced simultaneously in the models, only blood glucose after lunch predicted cardiovascular events, with hazard ratio of the third tertile vs. the first and the second tertiles greater in women (5.54; confidence interval, 1.45-21.20) than in men (2.12; confidence interval, 1.04-4.32; P < 0.01).

CONCLUSIONS

Postprandial, but not fasting, blood glucose is an independent risk factor for cardiovascular events in type 2 diabetes, with a stronger predictive power in women than in men, suggesting that more attention should be paid to postprandial hyperglycemia, particularly in women.

Blood glucose pre-prandial baseline decreases from morning to evening in type 2 diabetes: role of fasting blood glucose and influence on post-prandial excursions

BACKGROUND

To know the relationships between pre- and postprandial blood glucose (BG), i.e. BG profile shape, is a requisite for an appropriate therapy for type 2 diabetic patients. In non diabetic subjects, pre-breakfast, pre-lunch and pre-dinner BG are similar, so that BG postprandial excursions are superimposed on a stable BG preprandial baseline. We aimed to clarify: (a) whether BG preprandial baseline is stable also in type 2 diabetes and (b) whether fasting BG (FBG) influences the slope of BG preprandial baseline and the relationships between pre- and postprandial BG.

DESIGN

We evaluated self-measured BG profiles of 237 type 2 diabetic patients on diet alone (M/F, 152/85; age 58.6 +/- 0.7 years; years from diagnosis 4.8 +/- 0.6; BMI 28.0 +/- 0.3 kg m-2): 536 profiles containing preprandial BG (corresponding HbA1c 6.8 +/- 0.06%) and 208 profiles containing both pre- and postprandial BG (corresponding HbA1c 6.8 +/- 0.09%). The profiles, measured by nurses, of 866 type 2 diabetic patients on diet alone were also considered (corresponding HbA1c 6.7 +/- 0.04%).

RESULTS

In self-measured profiles containing only preprandial BG: (i) FBG (6.77 +/- 0.07 mmol L(-1)) is higher than pre-lunch BG (6.09 +/- 0.07 mmol L(-1)), P = 0.0001) and pre-dinner BG (5.84 +/- 0.06 mmol L(-1)), P =0.0001); (ii) the delta value between FBG and pre-dinner BG is correlated with FBG (r = 0.57, P = 0.0001), the highest FBG, the steepest the fall of BG preprandial baseline throughout the day. This trend is confirmed in profiles measured by nurses. In profiles containing both pre- and postprandial BG: (i) there is a trend to preprandial BG fall (P = 0.0001) and to postprandial BG increase (P = 0.0001) from morning to evening; (ii) postprandial excursions are influenced and sometimes masked by the slope of BG preprandial baseline, thus, in profiles with FBG < or = 6.7 mmol L(-1), all postprandial values are higher than FBG (P = 0.0001), whereas in profiles with FBG > 7.8 mmol L(-1), postprandial values are not significantly higher than FBG.

CONCLUSION

In type 2 diabetes, the shape of BG profiles changes in relation to FBG, because it deeply influences the slope of BG preprandial baseline on which postprandial excursions are superimposed. Thus, before planning treatment policies, not only the extent of fasting and postprandial hyperglycaemia, but also the shape of profiles should be considered, to safely correct hyperglycaemia without inducing hypoglycaemia.

Studies on inhibition of human platelet function by sodium nitroprusside. Kinetic evaluation of the effect on aggregation and cyclic nucleotide content

In this study, we explored the ability of sodium nitroprusside to inhibit the aggregation of human platelets in platelet-rich plasma (PRP) and whole blood and its effects on intracellular levels of guanosine 3',5'-cyclic monophosphate (cGMP) and adenosine 3',5'-cyclic monophosphate (cAMP). The experiments investigated dose-dependent effects of nitroprusside starting from concentrations in the range of circulating levels achievable in vivo during drug administration in humans. Furthermore, we investigated the time-course of both antiaggregating action and the influence on cyclic nucleotide synthesis. Results showed that sodium nitroprusside inhibited the aggregation induced by adenosine 5-diphosphate (ADP) and collagen starting from concentration as low as 2 micromol/l. The IC(50) value for ADP-induced aggregation in PRP was 18.7+/-2.4 micromol/l. The inhibition of platelet aggregation showed a time-dependent behaviour and was not reversible within 90 min. The accumulation of intraplatelet cGMP in the presence of sodium nitroprusside exhibited a comparable time-course characterized by an early increase, a steady state and a late further increase. The time-course of cAMP synthesis was very similar to that of cGMP. Our data evidenced a long-lasting inhibition of platelet responses by sodium nitroprusside and excluded a desensitization of platelet guanylyl cyclase after 3-h exposure to nitric oxide (NO). Furthermore, they indicated a role of cAMP accumulation in the antiaggregating effects of nitroso donor: the simultaneous increase of intracellular content of cAMP and cGMP can synergize in the reduction of the platelet responses.

N-acetyl-L-cysteine exerts direct anti-aggregating effect on human platelets

BACKGROUND

N-acetyl-L-cysteine, a thiol compound, has been shown to potentiate the inhibition of platelet aggregation exerted by organic nitrates and to increase the anti-aggregating effect of L-arginine, which promotes endogenous synthesis of nitric oxide (NO) acting as substrate of platelet constitutive nitric oxide synthase (NOS). It is not known whether this thiol can exert direct effects on platelet aggregability.

MATERIALS AND METHODS

14 healthy male volunteers provided platelet samples to investigate whether N-acetyl-L-cysteine directly influences platelet function and intraplatelet levels of 3',5' cyclic guanosine monophosphate (cGMP), which represents the second messenger involved in NO-induced antiaggregation. Some experiments were repeated in the presence of NOS inhibitor NG-monomethyl-L-arginine (L-NMMA), of nitric oxide-sensitive guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), of the selective cGMP phosphodiesterase inhibitor zaprinast and of calcium ionophores (A23187, ionomycin).

RESULTS

N-acetyl-L-cysteine at 3000-6000 micromol L-1 decreases the responses of human platelets both in platelet-rich plasma (aggregation induced by adenosine 5-diphosphate) and in whole blood (aggregation induced by collagen). The anti-aggregating effect was prevented by preincubation with L-NMMA and guanylyl cyclase inhibitor ODQ. In resting platelets, N-acetyl-L-cysteine increased the levels of cGMP starting from a concentration of 3000 micromol L-1. Permeabilized platelets exhibited an increased sensitivity to the anti-aggregating effect of N-acetyl-L-cysteine. Also, cGMP phosphodiesterase inhibition or the increase in calcium availability, enhanced N-acetyl-L-cysteine effects on platelets.

CONCLUSION

N-acetyl-L-cysteine exerts direct anti-aggregating effects through an increased bioavailability of platelet nitric oxide.

Human vascular smooth muscle cells express a constitutive nitric oxide synthase that insulin rapidly activates, thus increasing guanosine 3':5'-cyclic monophosphate and adenosine 3':5'-cyclic monophosphate concentrations

AIMS/HYPOTHESIS

Insulin incubation of human vascular smooth muscle cells (hVSMC) for 120 min increases both guanosine 3':5'-cyclic monophosphate (cGMP) and adenosine 3':5'-cyclic monophosphate (cAMP) and these effects are blocked by inhibiting nitric oxide synthase (NOS). These data suggest that insulin activates a constitutive Ca2+-dependent NOS (cNOS), not described at yet in hVSMC. To test this hypothesis, we evaluated in hVSMC: i) the kinetics of the insulin-induced enhancement of the two cyclic nucleotides; ii) the ability of nitric oxide (NO) to increase both cyclic nucleotides; iii) NO involvement in the short-term influence of insulin on both cyclic nucleotides; iv) the ability of insulin to increase NO production in a few minutes; v) the presence of a cNOS activity; vi) the expression of mRNA for cNOS.

METHODS

In hVSMC incubated with insulin, NO donors and the Ca2+ ionophore ionomycin, we measured cAMP and cGMP (RIA); in hVSMC incubated with insulin and ionomycin we measured NO, evaluated as L-(3H)-citrulline production from L-(3H)-arginine; by northern blot hybridization, we measured the expression of cNOS mRNA.

RESULTS

i) By incubating hVSMC with 2 nmol/l insulin for 0-240 min, we observed an increase of both cGMP and cAMP (ANOVA: p = 0.0001). Cyclic GMP rose from 0.74 +/- 0.01 to 2.62 +/- 0.10 pmol/10(6) cells at 30 min (p = 0.0001); cAMP rose from 0.9 +/- 0.09 to 11.65 +/- 0.74 pmol/10(6) cells at 15 min (p=0.0001). ii) Sodium nitroprusside (100 mol/l) and glyceryltrinitrate (100 micromol/l) increased both cGMP and cAMP (p = 0.0001). iii) The effects of insulin on cyclic nucleotides were blocked by NOS inhibition. iv) An increase of NO was observed by incubating hVSMC for 5 min with 2 nmol/l insulin (p = 0.0001). v) Ionomycin (1 micromol/l) enhanced NO production (p = 0.0001) and increased both cyclic nucleotides (p = 0.0001). vi) hVSMC expressed mRNA of cNOS.

CONCLUSION/INTERPRETATION

Human VSMC express cNOS, which is rapidly activated by insulin with a consequent increase of both cGMP and cAMP, suggesting that insulin-induced vasodilation in vivo is not entirely endothelium-mediated.

Modulation of human platelet function by L-canavanine: differential effects of low and high concentrations

L-Canavanine is a naturally occurring L-amino acid that interferes with L-arginine-utilizing enzymes owing to its structural analogy with this L-amino acid. In macrophages and polymorphonuclear leukocytes, which express inducible nitric oxide synthase (iNOS), L-canavanine is able to prevent the L-arginine-derived synthesis of nitric oxide (NO). Its effects on constitutive NOS (cNOS) are far less clear. Because human platelets synthesize NO from L-arginine through a cNOS and because intracellular NO levels modulate platelet function, we have investigated the effects of L-canavanine on parameters potentially influenced by NO, such as platelet levels of 3',5'-cyclic guanosine monophosphate (cGMP) and responses to different aggregating agents. In our experimental conditions, L-canavanine was able to influence the response of human platelets to different aggregating agents such as catecholamines, 5-hydroxytryptamine, and ADP. Low L-canavanine concentrations (10-100 micromol/l) decreased platelet responses, whereas a high concentration (1 mmol/l) was unable to exert antiaggregating effects. In resting platelets, L-canavanine reduced the levels of cGMP, starting from a concentration of 1 mmol/l; furthermore, at the same concentrations, it was able to reduce cGMP levels at the end of the aggregation induced by collagen. In conclusion, L-canavanine exerts differential effects on human platelets in relation to the concentrations: at low levels, it exerts antiaggregating effects by actions independent of NOS inhibition, whereas, at high levels, it inhibits NO synthesis and does not exert antiaggregating effects.

Platelet resistance to nitrates in obesity and obese NIDDM, and normal platelet sensitivity to both insulin and nitrates in lean NIDDM

OBJECTIVE

Previous studies in our laboratory showed that the platelet anti-aggregating effect exerted by insulin, mediated by a nitric oxide (NO)-induced increase of guanosine-3',5'-cyclic monophosphate (cGMP), is lost in the insulin-resistant of obesity and obese NIDDM. It is not clear 1) whether the alterations observed in obese NIDDM patients are attributable to the obesity-related insulin resistance or to diabetes per se and 2) whether insulin-resistant states present a normal or a blunted response to NO. This study has been conducted to investigate 1) the platelet sensitivity to insulin in lean NIDDM and 2) the platelet sensitivity to an NO donor, glyceryl trinitrate (GTN), in obesity and in both lean and obese NIDDM.

RESEARCH DESIGN AND METHODS

We determined 1) ADP-induced platelet aggregation and platelet cGMP content in platelet-rich plasma (PRP) obtained from 11 lean NIDDM patients, after a 3-min incubation with insulin (0, 240, 480, 960, 1,920 pmol/l) and 2) ADP-induced platelet aggregation and platelet cGMP content in PRP obtained from 9 obese subjects, 11 lean and 8 obese NIDDM patients, and 18 control subjects, after a 3-min incubation with 0, 20, 40, and 100 mumol/l GTN.

RESULTS

Insulin dose-dependently decreased platelet aggregation in lean NIDDM patients (P = 0.0001): with 1,920 pmol/l of insulin, ADP ED50 was 141.5 +/- 6.4% of basal values (P = 0.0001). Furthermore, insulin increased platelet cGMP (P = 0.0001) from 7.5 +/- 0.2 to 21.1 +/- 3.7 pmol/10(9) platelets. These results were similar to those previously described in healthy subjects. GTN reduced platelet aggregation in all the groups (P = 0.0001) at all the concentrations tested (P = 0.0001), but GTN IC50 values were much higher in insulin-resistant patients: 36.3 +/- 5.0 mumol/l in healthy control subjects, 26.0 +/- 6.0 mumol/l in lean NIDDM patients (NS vs. control subjects), 123.6 +/- 24.0 mumol/l in obese subjects (P = 0.0001 vs. control subjects), and 110.1 +/- 19.2 mumol/l in obese NIDDM patients (P = 0.0001 vs. control subjects). GTN dose-dependently increased platelet cGMP in all the groups (P = 0.0001 in control subjects, lean NIDDM patients, and obese subjects; P = 0.04 in obese NIDDM patients). Values reached by obese subjects and obese NIDDM patients, however, were lower than those reached by control subjects (with 100 mumol/l of GTN, P = 0.001 and P = 0.0001, respectively). In healthy control subjects and in obese subjects, the insulin:glucose ratio, used as an indirect measure of insulin sensitivity, was positively correlated to GTN IC50 (r = 0.530, P = 0.008), further suggesting that the sensitivity to NO is reduced in the presence of insulin resistance.

CONCLUSIONS

The insulin anti-aggregating effect is preserved in lean NIDDM; platelet sensitivity to GTN in preserved in lean NIDDM but is reduced in the insulin-resistant states of obesity and obese NIDDM. Resistance to nitrates, therefore, could be considered another feature of the insulin-resistance syndrome.

Insulin stimulates nitric oxide synthesis in human platelets and, through nitric oxide, increases platelet concentrations of both guanosine-3', 5'-cyclic monophosphate and adenosine-3', 5'-cyclic monophosphate

The insulin-induced platelet anti-aggregating effect is attributed to a nitric oxide (NO)-mediated increase of cyclic guanosine monophosphate (cGMP). The aim of this work, carried out in human platelets, is to show whether insulin increases NO synthesis in platelets and whether it enhances not only cGMP but also cyclic adenosine monophosphate (cAMP) in these cells. We observed that 1) insulin dose-dependently increases NO production, evaluated as citrulline synthesis from L-arginine (n = 4, P = 0.015); 2) insulin dose-dependently increases not only cGMP but also cAMP: for instance, after 8 min of insulin incubation at 1,920 pmol/l, cAMP increased from 39.8 +/- 1.4 to 121.3 +/- 12.6 pmol/10(9) platelets (n = 16, P = 0.0001); 3) when insulin is incubated for 120 min, the increase of cGMP and cAMP shows a plateau between 2 and 20 min, and while the effect on cGMP is significant until 120 min, the effect on cAMP is no more significant at 60 and 120 min; 4) insulin increases the effects on cAMP of the adenylate cyclase agonists Iloprost and forskolin (n = 5, P = 0.0001) and enhances their platelet anti-aggregating effects (n = 6 and 8, respectively; P = 0.0001); and 5) the inhibition of NO synthase by N(G)-monomethyl-L-arginine blunts both the insulin effects on basal cGMP and cAMP (n = 4) and those on the Iloprost- and forskolin-induced cAMP increase (n = 5). Thus, insulin increases NO synthesis in human platelets, and, through NO, enhances both cGMP and cAMP. The platelet anti-aggregating effect exerted by insulin is, therefore, a NO-mediated phenomenon involving both cGMP and cAMP.

Influence of protamine on adhesion, chemotaxis and proliferation of human vascular smooth muscle cells

It has been shown that, in streptozotocin diabetic rats, protamine-retarded insulin administered in vivo stimulates intimal hyperplasia in balloon-injured carotid artery. The aim of this study was to evaluate the influence of protamine on cultured human vascular smooth muscle cells (h VSMC), by observing its effects on adhesion, chemotaxis and proliferation. hVSMC were isolated during abdominal surgery, cultured and utilized at passages 6-10. We observed that protamine stimulates: 1) cell adhesion in the concentration range 0.04-20 micrograms/ml (analysis of variance, ANOVA, p < 0.0001); 2) cell chemotaxis in the absence of fetal calf serum (FCS) in the concentration range 1-200 micrograms/ml (ANOVA, p < 0.0001) and in the presence of 1% FCS in the concentration range 5-200 micrograms/ml (ANOVA, p < 0.0001), further enhancing the chemotaxis induced by 10% FCS in the concentration range 20-200 micrograms/ml (ANOVA, p < 0.0001); 3) cell proliferation and 3H-thymidine incorporation from 1 to 5 micrograms/ml (ANOVA, p < 0.0001); 4) cell c-fos oncoprotein nuclear expression. We also observed that protamine effects on chemotaxis, proliferation and c-fos expression are inhibited by heparin that human insulin stimulates cell proliferation and 3H-thymidine incorporation (ANOVA, p < 0.0001) at concentrations equal to or greater than 480 pmol/l and that these effects of insulin persist in the presence of protamine. In conclusion, protamine influences hVSMC behaviour by interfering with biological functions involved in atherogenesis. The concentrations used in this short-term in vitro study were higher than those probably occurring in vivo in patients chronically treated by protamine-retarded insulin preparations: further studies, therefore, are needed to evaluate the safety of protamine as a retardant of insulin action in vivo.

Interplay between milrinone and adenosine in the inhibition of human platelet response

1. In this study, we investigated the influence of the inotropic agent and coronary vasodilator milrinone on platelet aggregation and intracellular levels of 3',5' cyclic adenosine monophosphate (cAMP) in human platelet-rich plasma (PRP) and whole blood (WB). Furthermore, we evaluated the influence of milrinone on the effects of adenosine, which reduces the platelet aggregation through an elevation of intraplatelet cAMP levels. 2. Milrinone decreased the platelet aggregation in response to agonists in both PRP and WB. A dose-dependent increase of intraplatelet cAMP levels was demonstrated: this result is in accordance with an effect on platelet phosphodiesterases. 3. Milrinone at low concentration and adenosine exerted additive effects on platelet aggregation and intraplatelet cAMP levels. 4. An interplay between milrinone and adenosine was shown in WB. Furthermore, dipyridamole, which prevents the uptake of endogenous adenosine, markedly enhanced the milrinone antiaggregating effect, whereas the adenosine receptor blocker, theophylline, decreased it. 5. The present data provide evidence that milrinone modulates the platelet function through an influence on intraplatelet levels of cAMP and it is able to interplay with substances stimulating adenylyl cyclase. 6. The interplay between milrinone and adenosine in the inhibition of the human platelet function could be effective during milrinone administration in the treatment of heart failure, when blood adenosine levels are significantly increased. These milrinone effects could be advantageous from a therapeutic point of view, since patients with heart failure are at risk of thrombosis and ischemic heart disease.

Studies on the influence of insulin on cyclic adenosine monophosphate in human vascular smooth muscle cells: dependence on cyclic guanosine monophosphate and modulation of catecholamine effects

Insulin increases both cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) in human vascular smooth muscle cells (hVSMC) and attenuates noradrenaline-induced vasoconstriction. In the present study, we aimed at investigation in hVSMC: 1) the interrelationships between insulin-induced increases of cGMP and cAMP; 2) the insulin effect on the catecholamine modulation of cAMP. Catecholamines cause both vasoconstriction and vasodilation. Vasoconstriction is attributable to the reduced synthesis of cAMP in hVSMC through alpha 2-adrenoceptors and to direct effects on calcium fluxes through alpha 1-adrenoceptors; vasodilation is attributable to the increased synthesis of cAMP through beta-adrenoceptors. In the present study, we determined the influence of insulin on cAMP in hVSMC incubated with or without: a) the inhibitor of guanylate cyclase methylene blue or the inhibitor of nitric oxide synthase NG-monomethyl-L-arginine (L-NMMA); b) the beta-adrenergic agonists isoproterenol and salbutamol; c) the physiological catecholamines noradrenaline and adrenaline; d) noradrenaline+the beta-adrenergic antagonist propranolol or the alpha 2-adrenergic antagonist yohimbine; e) noradrenaline+methylene blue of L-NMMA. We demonstrated that: 1) the inhibition of the insulin-induced cGMP synthesis blunts the insulin-induced increase of cAMP; 2) insulin induces a significant increase of cAMP also in the presence of isoproterenol, salbutamol, noradrenaline and adrenaline: the combined effects of insulin and catecholamines were additive in some, but not in all the experiments; 3) insulin enhances the cAMP concentrations induced by noradrenaline also in the presence of alpha 2- or beta-adrenergic antagonists; 4) in the presence of methylene blue or L-NMMA insulin does not modify the noradrenaline effects on cAMP.

The insulin-induced increase of guanosine-3',5'-cyclic monophosphate in human platelets is mediated by nitric oxide

To investigate whether the insulin-induced increase of guanosine-3',5'-cyclic monophosphate (cGMP) in human platelets is mediated by nitric oxide or is influenced by the nitric oxide precursor L-arginine, we measured cGMP in platelet-rich plasma obtained from healthy volunteers incubated for 3 min with human recombinant insulin (0, 240, 480, 960, and 1,920 pmol/l) both with and without 1) a 20-min incubation with the nitric oxide-synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA) (50, 70, 100, and 1,000 micromol/l; n = 5 for each dose) and 2) a 20-min incubation with the nitric oxide precursor L-arginine (300 micromol/l; n = 6). In a first set of experiments, insulin induced a dose-dependent cGMP increase, from 9.8 +/- 0.8 to 45.6 +/- 5.5 pmol/10(9) platelets (P = 0.0001); in the presence of 1 mmol/l L-NMMA, this increase was blunted, cGMP being 8.9 +/- 1.4 and 11.1 +/- 2.2 pmol/10(9) platelets at 0 and 1,920 pmol/l insulin, respectively (NS). In the experiments with 70 and 100 micromol/l L-NMMA, the insulin effect on cGMP was inhibited, whereas 50 micromol/l L-NMMA did not blunt this insulin effect. In another set of experiments carried out to investigate the effects of L-arginine, insulin induced a dose-dependent cGMP increase, from 23.6 +/- 6.9 to 59.0 +/- 12.0 pmol/10(9) platelets (P = 0.0001); with L-arginine, basal cGMP values increased to 35.5 +/- 6.6 pmol/10(9) platelets (P = 0.05), and insulin maintained its ability to enhance dose-dependently cGMP values, which rose to 76.8 +/- 19.4 pmol/10(9) platelets (P = 0.003). This study carried out in human platelets demonstrates that the cGMP increase induced by insulin, which accounts for the antiaggregating effect of the hormone, is mediated by nitric oxide.

Insulin exerts opposite effects on platelet function at physiological and supraphysiological concentrations

In this study, we investigated the effects of a 3-min insulin incubation both at physiological and at supraphysiological concentrations on platelet aggregation and intraplatelet cyclic guanosine monophosphate (cGMP) levels both in the absence and in the presence of phosphodiesterase inhibition. We observed that insulin at concentration in the range 0.25-2 nmol/L decreases platelet response to adenosine 5-diphosphate (ADP), being Effective Dose 50 (ED50) for ADP with 2 nmol/L insulin 164 +/- 15% of the basal value, p = 0.005; furthermore, insulin increases intraplatelet content of cGMP (from basal 7.3 +/-0.6 pmol/10(9) plts to 14.6 +/- 1.2 pmol/10(9) plts with 2 nmol/L insulin, p=0.0001) and does not affect the platelet cGMP increase induced by nitrates. On the contrary, at very elevated concentrations (25-200 nmol/L) insulin increases platelet aggregation to ADP (ADP ED50 with 200 nmol/L insulin being 81 +/- 4% of the basal value, p = 0.01), decreases intraplatelet content of cGMP (from basal 7.2 +/- 0.1 pmol/10(9) plts to 5.7 +/- 0.2 pmol/10(9) plts with 200 nmol/L insulin, p = 0.01) and attenuates the platelet cGMP increase induced by nitrates. When cGMP catabolism is inhibited by theophylline or the selective cGMP phosphodiesterase inhibitor zaprinast, insulin shows anti-aggregating effects also at highly supraphysiological concentration (25-200 nmol/L). These results indicate that insulin, depending on the concentrations employed, shows opposite effects on platelet function, and they provide information about the mechanisms involved: actually, insulin is able to increase both cGMP synthesis, through guanylate cyclase activation, and cGMP catabolism, through phosphodiesterase activation. At physiological or slightly supraphysiological concentrations the first phenomenon is prevailing, so that cGMP intraplatelet values increase and insulin shows antiaggregating properties, whereas, at supraphysiological concentrations, insulin reduces cGMP levels through a prevailing phosphodiesterase activation, as supported by the fact that, when cGMP catabolism is prevented, insulin shows anti-aggregating properties also at the highest concentrations used.

Nonenzymatic glycation of fibronectin impairs adhesive and proliferative properties of human vascular smooth muscle cells

Nonenzymatic glycation of proteins is involved in the pathogenesis of diabetes vascular complications. Extracellular matrix proteins are a prominent target for nonenzymatic glycation because of their slow turnover rates. The aim of this study was to investigate the influence of human fibronectin (F) nonenzymatic glycation on adhesion and proliferation of cultured human vascular smooth muscle cells (hVSMC). Incubation of human F with 500 mmol/L D-glucose at 37 degrees C induced a time-dependent increase in fluorescence detectable at 440 nm after excitation at 363 nm. Nonenzymatic glycation did not affect binding of F itself to the plates. Adhesion of hVSMC to F increased with the increase of incubation time of the cells on the protein from 30 minutes up to 120 minutes and remained stable thereafter. Adhesion to glycated fibronectin (GF) was reduced in comparison to control F at all the different adhesion times. Adhesion of hVSMC to GF was reduced when F was exposed to glucose for 4, 9, or 28 days (P=.0417 to .0025), but not when F was exposed for 1 day. Adhesion of hVSMC to GF was reduced compared with adhesion to nonglycated F at all coating concentrations from 0.2 to 10 micrograms/mL (P=.05 to .014). Thus, nonenzymatic glycation of F impairs adhesion of hVSMC in vitro. Proliferation of hVSMC on F increased with increasing concentrations of the protein as coating agent (ANOVA:P<.0001 for both nonglycated F and GF). Proliferation with F glycated for 4, 9, and 28 days was reduced at concentrations of 1, 3, and 10 micrograms/mL as compared with proliferation with nonglycated F (P=.0253 to .0001). Proliferation on F glycated for only 1 day was not significantly reduced. When the number of hVSMC plated on control F was reduced by 25% to take into account the reduced adhesion, the number of cells that proliferated on F was still reduced. In conclusion, nonenzymatic glycation of F impairs adhesive and proliferative properties of hVSMC.

Impaired insulin-induced platelet antiaggregating effect in obesity and in obese NIDDM patients

To investigate the effects of insulin on platelets in obesity and in non-insulin-dependent diabetes mellitus (NIDDM)--classic insulin-resistant states--we determined ADP-induced platelet aggregation and platelet cGMP (guanosine 3',5'-cyclic monophosphate) content in platelet-rich plasma obtained from nine obese subjects and nine age-matched healthy volunteers and from eight NIDDM obese patients and nine age-matched healthy volunteers after a 3-min incubation with human recombinant insulin (0, 240, 480, 960, and 1,920 pmol/l). Platelet aggregation was evaluated using different ADP doses to measure the ADP concentration determined on the basis of a dose-response curve necessary to elicit a maximal aggregation of 50% (ED50). Insulin induced a dose-dependent decrease of platelet aggregation to ADP (P = 0.0001) in healthy subjects. A significant effect was evident starting from an insulin concentration of 240 pmol/l. On the contrary, in insulin-resistant subjects, insulin reduced platelet sensitivity to ADP only at a concentration of 1,920 pmol/l. When ADP ED50 values obtained in platelet-rich plasma incubated with insulin were expressed in percentage of the ADP ED50 values obtained in platelet-rich plasma without insulin, considered as 100%, we observed that ADP ED50 with 1,920 pmol/l insulin was 153.6 +/- 13.2% in the younger healthy subject group (P = 0.004), 150.0 +/- 3.8% in the older healthy subject group (P = 0.0001), 116.1 +/- 6.1% in obese subjects (P = 0.031), and 120.0 +/- 8.6% in NIDDM patients (P = 0.05). In healthy subjects, insulin induced a dose-dependent increase of platelet cGMP (P = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Glyceryl trinitrate enhances the adenosine-induced inhibition of platelet responses: a mechanism potentially involved in the in vivo anti-aggregating effects of organic nitrates

1. The present study investigated the influence of the organic nitrate glyceryl trinitrate (GTN) on the anti-aggregating effects of adenosine. We determined the effects of adenosine, GTN and their combination on platelet responses in platelet-rich plasma and whole blood, and on intracellular levels of 3',5'-cyclic adenosine monophosphate (cAMP) and 3',5'-cyclic guanosine monophosphate (cGMP). 2. Adenosine inhibited the in vitro platelet aggregation in response to different agonists in a dose-dependent way through an elevation of intraplatelet cAMP levels. Effective adenosine concentrations were higher than those detectable under physiological conditions, but very close to levels achieved during myocardial ischaemia or haemorrhagic shock. 3. GTN was able to decrease platelet responses influencing intraplatelet cGMP levels. Furthermore, the drug increased the inhibitory effects of adenosine and enhanced its effects on intraplatelet cAMP levels. 4. The present data provides further evidence that compounds that increase intraplatelet levels of cGMP and cAMP act synergistically on the inhibition of platelet aggregability through the influence of increased cGMP levels on cAMP accumulation. The interplay between GTN and adenosine in the inhibition of platelet function could be effective during nitrate administration in the treatment of acute myocardial ischaemia when blood adenosine levels are significantly increased.

Insulin increases cyclic nucleotide content in human vascular smooth muscle cells: a mechanism potentially involved in insulin-induced modulation of vascular tone

It has been suggested that insulin exerts a vasodilating effect, but the mechanisms involved are not completely understood. Since cyclic nucleotides mediate the vasodilation induced by endogenous substances, such as prostacyclin and nitric oxide, we aimed to investigate the influence of insulin (concentration range 240-960 pmol/l) on both cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) content in human vascular smooth muscle cells. Insulin dose-dependently increased both nucleotides (cAMP: from 0.7 +/- 0.1 to 2.6 +/- 0.4 pmol/10(6) cells, p = 0.0001; cGMP: from 1.3 +/- 0.2 to 3.4 +/- 0.7 pmol/10(6) cells, p = 0.033). This increase is receptor-mediated, since it was blunted when cells were preincubated with the tyrosine kinase inhibitor genistein. The effect of insulin remained significant (p = 0.0001) when preincubation with the phosphodiesterase inhibitor theophylline prevented cyclic nucleotide catabolism. The increase of cGMP was blunted when the cells were preincubated with the guanylate cyclase inhibitor methylene blue, and with the nitric oxide-synthase inhibitor NG-monomethyl-L-arginine. At all the concentrations tested, insulin potentiated the increase of cAMP induced by the stable prostacyclin analogue Iloprost (p = 0.0001), whereas only at 1920 pmol/l did it potentiate the cGMP increase induced by glyceryltrinitrate (p = 0.05). This study demonstrates that the vasodilating effects exerted by insulin may at least in part be attributable to an increase of both cGMP and cAMP via a receptor-mediated activation of adenylate and guanylate cyclases in human vascular smooth muscle cells and that the insulin effect on cGMP is mediated by nitric oxide.

Studies on in vitro effect of picotamide on human platelet aggregation in platelet-rich plasma and whole blood

Picotamide is a new antiaggregating agent influencing the platelet prostaglandin pathway through an inhibition of thromboxane A2 (TXA2) synthesis and a competitive antagonism of platelet TXA2 receptors. In the present study, we investigated the in vitro effect of this drug on human platelet aggregation induced by different agents (adenosine 5'-diphosphate [ADP], collagen, Na arachidonate) both in platelet-rich plasma (PRP; Born's method) and whole blood (WB; impedance method). For each aggregating agent, ED50 value (agonist concentration necessary to induce a maximal aggregation of 50%) was determined in control samples and following addition of different picotamide concentrations on the basis of dose-response curves. Picotamide decreased the response to each aggregating agent in both WB and PRP samples. In WB, 25 microM picotamide was able to induce a highly significant enhancement of ED50 values for ADP (from 6.6 +/- 1 microM to 12.7 +/- 1.7 microM, p < 0.01), Na arachidonate (from 740 +/- 240 microM to 1,080 +/- 280 microM, p < 0.01) and collagen (from 2.4 +/- 0.3 micrograms/ml to 3.8 +/- 0.15 micrograms/ml, p < 0.01). In PRP, the same picotamide concentration significantly enhanced ED50 for each aggregating agent (from 2.0 +/- 0.1 microM to 3.1 +/- 0.3 microM for ADP, p < 0.01; from 960 +/- 80 microM to 1,850 +/- 260 microM for Na arachidonate, p < 0.001; from 3.0 +/- 0.3 microgram/ml to 5.0 +/- 0.8 micrograms/ml for collagen, p < 0.01). Present results show that picotamide effect on platelet response is present also in WB. Data might support the use of picotamide as antiaggregating agent in vascular diseases.

Effects of forskolin and organic nitrate on aggregation and intracellular cyclic nucleotide content in human platelets

1. The present study investigated the effect of a combination between forskolin, a naturally occurring diterpene which directly activates adenylyl cyclase, and glyceryl trinitrate (GTN), which enhances intraplatelet cyclic guanosine monophosphate levels, on human platelet aggregation and intracellular content of cyclic nucleotides 3',5'-cyclic adenosine monophosphate (cAMP) and 3',5'-cyclic guanosine monophosphate (cGMP). 2. Forskolin inhibited, in a dose-dependent way, platelet aggregation in response to collagen and adrenaline in platelet-rich plasma. In whole blood samples, forskolin inhibited collagen-stimulated aggregation. In presence of forskolin the intraplatelet cAMP levels were significantly increased. 3. GTN directly decreased the platelet response to collagen in whole blood samples (IC50 = 122 mumol/l) and it increased the intraplatelet levels of both cGMP and cAMP. 4. GTN at 20 and 40 mumol potentiated the inhibitory effects of forskolin on platelet aggregation in both platelet-rich plasma and whole blood. 5. Our results suggest a synergistic effect of the simultaneous increase of both cAMP and cGMP on the biochemical steps involved in the inhibition of the platelet response.

Insulin increases guanosine-3',5'-cyclic monophosphate in human platelets. A mechanism involved in the insulin anti-aggregating effect

To investigate whether insulin reduces platelet aggregability through a modulation of the guanosine-3',5'-cyclic monophosphate (cGMP) concentrations, we determined by a radioimmunoassay the cGMP values in the platelet-rich plasma (PRP) obtained from 17 healthy volunteers and incubated for 3 min with different concentrations of human recombinant insulin (0, 240, 480, 720, 960, and 1,920 pM). Insulin induced a dose-dependent cGMP increase, from 18.5 +/- 3.3 to 42.0 +/- 6.4 pmol/10(9) platelets (P = 0.0001). This increase was completely blunted when PRP was preincubated for 20 min with the tyrosine kinase inhibitor genistein (10 microM) or with the guanylate cyclase inhibitor methylene blue (10 microM), but the increase remained highly significant (P = 0.003 and 0.009) when PRP was preincubated for 20 min with the phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine (IBMX, 500 microM) or with the nitric oxide synthase inhibitor NG-mono-methyl-L-arginine (L-NMMA, 30 microM). Finally, the insulin-induced decrease of platelet aggregability to collagen and ADP was completely blunted when PRP was preincubated with 10 microM of the guanylate cyclase inhibitor methylene blue. This study demonstrates that the platelet anti-aggregatory effect exerted by insulin is attributable to the insulin-induced increase of cGMP that is due to a direct receptor-mediated platelet guanylate cyclase activation.

Na+/H+ antiporter activity in peripheral blood lymphocytes of obese and type 2 diabetic patients is increased only in the presence of arterial hypertension

The aim of this work is to evaluate whether type 2 diabetes mellitus, obesity and arterial hypertension, three conditions characterized by the presence of insulin resistance, share some common genetic markers. A potential candidate is the Na+/H+ antiporter, the increased activity of which is considered a marker of essential hypertension. This ion exchanger seems to be related to the Na+/Li+ countertransport, that is considered a marker of insulin resistance in essential hypertension and in type 1 diabetes mellitus. In this study we wished to clarify whether the activity of the Na+/H+ antiporter is increased not only in hypertensive subjects, but also in obese and type 2 diabetic patients, both in the presence and in the absence of arterial hypertension. The activity of the ion exchanger was measured in peripheral blood lymphocytes (PBL) by clamping intracellular pH (pHi) at 5.8-6.2 and then detecting the rate of the proton efflux after sodium addition. In the absence of arterial hypertension, no significant difference in this parameter was observed in obese and type 2 diabetic patients in comparison with normal subjects. In the presence of arterial hypertension, there was a significant increase in the Na(+)-induced H+ efflux at the internal pH (pHi) values of 5.8 and 6.2 both in hypertensive controls and in hypertensive obese and type 2 diabetic patients (P = 0.05-0.0001 vs. normotensive subjects and patients).(ABSTRACT TRUNCATED AT 250 WORDS)

Organic nitrates and compounds that increase intraplatelet cyclic guanosine monophosphate (cGMP) levels enhance the antiaggregating effects of the stable prostacyclin analogue iloprost

The present study investigated the effect of a combination between the stable prostacyclin (PGI2) analogue iloprost and compounds, glyceryl trinitrate (GTN) and L-arginine-, which enhance the intraplatelet cyclic guanosine monophosphate (cGMP) levels on platelet aggregation, release reaction and cyclic nucleotide content: in particular cyclic adenosine monophosphate (cAMP) and cGMP. Iloprost inhibited in a dose-dependent way the platelet aggregation in response to collagen, adenosine diphosphate (ADP) and adrenaline and it increased the intraplatelet cAMP concentrations. GTN directly decreased the platelet responses and increased the intraplatelet levels of both cGMP and cAMP. GTN (20 x 10(-6) mol/l) and L-arginine (0.2 x 10(-3) mol/l) potentiated the inhibitory effects of iloprost on platelet aggregation and release reaction. Our results suggest: 1. A synergistic effect of the simultaneous increase of both cAMP and cGMP on the biochemical steps involved in the inhibition of the platelet response; 2. An influence of cGMP on cAMP accumulation.

Insulin influences immunoreactive endothelin release by human vascular smooth muscle cells

This study sought to investigate whether insulin influences immunoreactive endothelin release from cultured human vascular smooth muscle cells. For this purpose, we incubated cultured vascular smooth muscle cells (VSMC) obtained from human microvessels with 0, 80, and 320 microU/mL insulin with or without arginine vasopressin (10 nmol/L) and angiotensin II (10 nmol/L). After 6 hours, the culture supernatant was collected and immunoreactive endothelin was determined by radioimmunoassay. Insulin at a concentration of 320 microU/mL induced a significant increase of immunoreactive endothelin levels in medium (from 15.2 +/- 0.8 to 20.6 +/- 0.8 pg/200 microL, P < .01) and potentiated arginine vasopressin- and angiotensin II-induced immunoreactive endothelin release (P < .0001 and P < .04, respectively). Insulin at a concentration of 80 microU/mL did not induce a significant increase of spontaneous immunoreactive endothelin release, but significantly increased the effects of arginine vasopressin (P < .05). In conclusion, insulin influences immunoreactive endothelin release from human VSMC in culture.

Effect of dopamine on adenosine 3',5'-cyclic monophosphate levels in human platelets

1. The dopamine effect on intraplatelet adenosine 3',5'-cyclic monophosphate (cAMP) levels was evaluated in healthy subjects. 2. Dopamine levels over 30 nmol/l increased cAMP concentration in a concentration-dependent way. 3. The platelet preincubation with propranolol (beta-adrenoceptor antagonist) prevented the dopamine effect, whereas phentolamine (alpha-adrenoceptor antagonist) failed to modify the platelet response to this catecholamine. Dopamine receptor antagonist domperidone directly increased cAMP levels and it enhanced the dopamine effects. 4. Our results indicate that dopamine effect is mainly mediated by beta-adrenoceptor stimulation.

Moderate exercise increases platelet function in type I diabetic patients without severe angiopathy and in good control

OBJECTIVE

The aim of this study was to investigate whether a 45-min moderate exercise, performed postprandially with a timing that partially prevented the risk of hypoglycemia, was able to modify platelet function in patients affected by insulin-dependent (type I) diabetes mellitus without severe late complications and in a good metabolic control.

RESEARCH DESIGN AND METHODS

We submitted 6 male type I diabetic patients (27.2 +/- 3.4 yr; body mass index, 21.4 +/- 0.6 kg/m2; HbA1c, 7.6 +/- 0.9%) on a daily three-insulin injection regimen, without severe late complications of diabetes, to a 45-min moderate exercise (about 50% of maximal oxygen consumption) with a cycle ergometer, beginning 180 min after breakfast and 195 min after a subcutaneous shot of regular insulin. Serial venous blood samples were conducted to measure plasma glucose, free insulin, counterregulatory hormones (glucagon, growth hormone, cortisol, and catecholamines), platelet sensitivity to ADP, platelet activating factor and collagen, and plasma concentrations of the platelet-specific protein beta-thromboglobulin (a marker of the platelet release reaction in vivo).

RESULTS

Exercise was accompanied by a decrease of plasma glucose (from 5.9 +/- 1.2 to 4.6 +/- 1 mmol/L, P = 0.067) and free insulin (from 180 +/- 36 to 114 +/- 30 pmol/L, P = 0.003), and by a significant increase of growth hormone (from 5 +/- 1 to 15 +/- 4 micrograms/L, P = 0.045), cortisol (from 240 +/- 30 to 406 +/- 69 nmol/L, P = 0.018), epinephrine (from 1005 +/- 240 to 5143 +/- 1753 pmol/L, P = 0.077), and norepinephrine (from 5.04 +/- 1.08 to 13.48 +/- 2.98 nmol/L, P = 0.009). Platelet sensitivity to the agonists and plasma concentrations of beta-thromboglobulin increased during the exercise period. In particular, ADP ED50 reached during exercise 61 +/- 16% of basal values (P = 0.048), platelet activating factor ED50 reached 73 +/- 11% (P = 0.043), and collagen ED50 reached 68 +/- 9% (P = 0.008). beta-Thromboglobulin rose from 24 +/- 2 to 32 +/- 3 micrograms/L (P = 0.007).

CONCLUSIONS

Moderate exercise enhances platelet function in type I diabetic patients without severe angiopathy and in a good metabolic control.

Antibodies in rabbits immunized with cationized IgG react with histones H3 and H4

OBJECTIVE

Rabbits immunized with cationized rabbit IgG develop antinuclear antibodies. This study was aimed at identifying the reactive antigens.

METHODS

Rabbits were immunized with homotypic or allotypic IgG that were physicochemically altered to produce positively charged dimethylpropanamide (polycationic) side chains.

RESULTS

Seven of 11 rabbits injected with cationized IgG produced antinuclear antibodies detected by indirect immunofluorescence. By enzyme-linked immunosorbent assay, these were IgG antibodies reacting with histone (H3-H4)2 tetramer and with individual histone polypeptides H3 and H4. The antihistone antibodies were absorbed by cationized IgG but not by normal IgG.

CONCLUSION

Cationized IgG appears to possess antigenic determinants of sufficient similarity to produce antibody responses cross-reactive with histones H3 and H4.

Studies on the effect of dopamine on the human platelet response

1. The present study investigated the in vitro effect of dopamine on platelet responses in healthy subjects. 2. Dopamine concentrations over 5 mumol/L induced a primary aggregating response and a slight release of alpha-granule proteins, beta-thromboglobulin and platelet factor-4 in all subjects. In 25% of investigated subjects a delayed secondary aggregation was observed with dopamine concentrations over 100 mumol/L. 3. Low dopamine concentrations (5-7.5 nmol/L) increased the platelet sensitivity to other aggregating agents (adenosine diphosphate, collagen and sodium arachidonate). The effect of subaggregating concentrations of serotonin was potentiated by dopamine. 4. The effect of dopamine on platelet responses was prevented by low concentrations of alpha-adrenoceptor antagonists (phentolamine and yohimbine); antagonists of dopamine receptors (haloperidol and domperidone) were able to decrease the extent of the dopamine-induced secondary aggregating wave in the responders, but they failed to prevent the primary aggregation and the effects on platelet response to other aggregating agents. 5. The present data demonstrated that the effects of dopamine on human platelets are mainly mediated by interactions with alpha-adrenoceptors.

Insulin, at physiological concentrations, enhances the polymorphonuclear leukocyte chemotactic properties

We investigated the influence of insulin on human polymorphonuclear leukocyte (PMN) chemotaxis induced by mediators in a microchamber assay. Insulin increased, with a dose-response relationship, chemotaxis induced by formyl-methionyl-leucyl-phenylalanine, calcium ionophore and phorbol-miristyl acetate (p = 0.0057, p = 0.0001 and p = 0.0215, respectively). The hormone effect was present also at the physiological concentration of 40 microU/ml. Our data show that insulin affects PMN activity in normal subjects and therefore support the hypothesis that insulin deficiency may be responsible for the impaired PMN function observed in diabetic patients in poor metabolic control.

Glomerular lesions induced in the rabbit by physicochemically altered homologous IgG

Immunization of rabbits with physicochemically altered homologous or even autologous IgG induces formation of antibodies combining with IgG of rabbit and of foreign species. Cardiac but not renal lesions were reported in such animals. This study examined the nephritogenic potential of the immune response to cationized or heat-aggregated homologous IgG of b9 or b4 allotype in rabbits of the b4 allotype. Rabbits injected with either b9 or b4 cationized IgG produced antibodies reactive with rabbit and human IgG and with histones; they also developed abnormal glomerular deposits of IgG b4 and C3 corresponding to alterations of the glomerular basement membranes (GBM). Rabbits injected with either b9 or b4 aggregated IgG developed antibodies reactive with rabbit and human IgG and abnormal glomerular deposits of IgG b4 and C3 in the GBM and in the mesangium with subendothelial and mesangial electron-dense deposits. Some rabbits in both groups had proliferative and exudative glomerulonephritis and proteinuria. The results showed that immunization of rabbits with physicochemically altered homologous IgG induces an immune response to rabbit and human IgG and to histones as well as glomerular deposits of autologous IgG and C3 and other glomerular lesions.

A comparison of the predictive power for overall blood glucose control of a 'good' fasting level in type 2 diabetic patients on diet alone or with oral agents

The European NIDDM Policy Group classifies both fasting and post-prandial blood glucose concentrations into 'good', 'acceptable', and 'poor' categories. The aim of the present study was to evaluate whether a 'good' fasting blood glucose concentration in Type 2 diabetic patients on diet or diet + oral hypoglycaemic agents is able to predict 'good' blood glucose values throughout the day, and therefore to discover whether or not it is necessary to perform blood glucose profiles in Type 2 diabetic patients when their fasting value is 'good'. Capillary blood glucose profiles (n = 417) were measured in 287 Type 2 diabetic patients, on diet alone (279 profiles), or on diet + tablets (138 profiles). We observed that 66% of profiles on diet and 44% of profiles on diet + tablets had only 'good' blood glucose concentrations (p less than 0.001). Eleven percent of profiles on diet and 30% of profiles on diet + tablets included 'poor' blood glucose concentrations (p less than 0.001). Despite matched fasting blood glucose concentrations (diet 5.69 +/- 0.04 (+/- SE) vs tablets 5.75 +/- 0.05 mmol l-1), levels were higher in the diet + tablet treated patients at all later time-points (p less than 0.01-0.001). HbA1c was significantly higher in tablet-treated patients than in patients on diet alone (6.6 +/- 0.1 vs 5.9 +/- 0.1%, p less than 0.001), and correlated with the mean blood glucose concentration (r = 0.43, p less than 0.001) but not with the fasting glucose concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium-channel blocking agents verapamil and diltiazem are inhibitors of vasopressin-induced human platelet activation

1. This study investigated the influences of calcium-channel blocking agents verapamil and diltiazem on platelet responses induced by arginine vasopressin (AVP) and lysine vasopressin (LVP). 2. The substances inhibited platelet aggregation induced by both low and high AVP concentrations, LVP and adrenaline plus AVP. IC50 values of each drug are lower than those determined for ADP- and collagen-elicited aggregation. Verapamil and diltiazem also decreased AVP-induced thromboxane B2 synthesis. 3. Other series of experiments showed that the addition of ethyleneglycol-bis-(beta-amino-ethyl ether) N, N'-tetra-acetic acid to platelet-rich plasma samples also prevented the platelet response to vasopressin polypeptides. 4. Our data provide evidence that the effects of verapamil and diltiazem on vasopressin-induced platelet responses may be directly related to inhibition of extracellular calcium entry.

Effects of diltiazem on thromboxane B2 production from platelet-rich plasma and whole blood

The present study evaluated the effects of the calcium-channel blocking agent diltiazem on platelet aggregation and on synthesis of thromboxane B2 (the stable metabolite of thromboxane A2) from platelet-rich plasma (PRP) and whole blood samples. Our results showed that diltiazem inhibits collagen- and thrombin-induced platelet aggregation and TXB2 production from PRP. Since no significant interference with conversion of arachidonate to thromboxane A2 was demonstrated, inhibition of phospholipase A2 activity may be the prevailing mechanism of the diltiazem effect. The drug demonstrated a dose-related inhibitory activity on TXB2 synthesis from whole blood samples during spontaneous clotting or following stimulation with collagen or thrombin. The present results give further evidences for an antiplatelet activity of diltiazem and support the hypothesis that inhibition of platelet function contributes to the therapeutic efficacy of this drug in the treatment of cardiovascular diseases.

Occurrence of low blood glucose concentrations during the afternoon in type 2 (non-insulin-dependent) diabetic patients on oral hypoglycaemic agents: importance of blood glucose monitoring

The European NIDDM Policy Group states that the lowest target for good control of Type 2 (non-insulin-dependent) diabetic patients is a blood glucose level 4.4 mmol/l, both fasting and postprandially. The aim of this study is to evaluate the occurrence and temporal distribution of values under this target in the clinical records of 463 Type 2 diabetic patients, treated by diet or diet and oral hypoglycaemic agents, monitored for at least 2 years. The protocol includes blood glucose measurements after overnight fasting (08.00 hours), 120-150 min after breakfast (11.00 hours) and 120 and 240 min after lunch (14.00 and 16.00 hours). At least one blood glucose concentration of less than 4.4 mmol/l was presented by 42% of the patients. The only difference between patients showing and not showing glycaemic levels under this target was the higher percentage on oral hypoglycaemic agents in the first group (68.4% vs 56.9%, p = 0.016). We considered 299 blood glucose profiles containing at least one value of less than 4.4 mmol/l, observing that a) 46.9% of profiles from patients treated by diet alone and 68.7% of profiles from patients treated both by diet and oral hypoglycaemic agents presented the lowest blood glucose concentration at 16.00 hours (p = 0.002). b) No correlation existed between fasting blood glucose and values at 16.00 hours in profiles from diet-treated patients, whereas a negative correlation was present in patients on diet and oral hypoglycaemic agents, indicating that an excess of oral agents, administered to correct fasting hyperglycaemia, was the cause of the low glycaemic values in the afternoon.(ABSTRACT TRUNCATED AT 250 WORDS)

[Primary sclerosing cholangitis associated with colonic Crohn disease and marked eosinophilia. Description of a case]

We report a case of primary sclerosing cholangitis associated with Crohn disease of the large intestine and marked eosinophilia in a 64 year old woman. Clinical features, histologic findings at biopsy of the intestine and liver and the endoscopic retrograde cholangiopancreatography are described. The case report is discussed, particularly as regards treatment with biliary salts and aminosalicilic acid.

Phenothiazines inhibit collagen-induced thromboxane B2 synthesis and increase forskolin anti-aggregating effects in human platelets

1. The aim of the present study was to investigate the effects of phenothiazine compounds chlorpromazine and trifluoperazine on human platelet response to collagen and sodium arachidonate. 2. The results demonstrated that phenothiazines inhibit collagen-induced platelet aggregation and thromboxane B2 synthesis in a dose-dependent way and increase the antiaggregating properties of forskolin. 3. Phenothiazines at high concentrations decreased the platelet aggregation in response to arachidonate, without a significant reduction of thromboxane B2 production. 4. The data provides evidence that phenothiazine effects could involve calmodulin-dependent enzymatic activities.

A Platelet Defect Characterised by Absent Adrenaline-induced Aggregation and Lack of Secondary Aggregation in Response to ADP and Platelet-activating Factor

We describe a platelet defect characterised by absence of aggregation to adrenaline and lack of secondary aggregation to ADP and platelet-activating factor (PAF) in a male subject without a significant bleeding tendency. The platelets also exhibited a decreased response to the phorbol ester PMA and to vasopressin polypeptides. We obtained evidence that the defect did not involve the cyclooxygenase pathway and that it was not dependent on altered intraplatelet levels of cyclic AMP (cAMP). Furthermore, adrenaline-stimulated cAMP production was normal. Irreversible aggregation was obtained in response to a combination of two stimuli at subaggregating concentrations. This observation indicates that the lack of a bleeding tendency in this subject may be ascribed to subthreshold concentrations of agonists in vivo overcoming the defect to a single agonist.

Phenothiazine compounds enhance phentolamine effects on platelet aggregation and thromboxane B2 production

In the present study we investigated the influence of phentolamine and the phenothiazine compounds chlorpromazine and trifluoperazine on human platelet aggregation as well as the effect of the association of phentolamine and the phenothiazines on responses to adenosine diphosphate, collagen, thrombin, ionophore A23187 and phorbol-myristate acetate, release reaction, thromboxane B2 synthesis and intraplatelet cyclic adenosine monophosphate levels. Phentolamine and phenothiazines exerted a dose-dependent inhibitory effect on aggregation induced by different concentrations of adenosine diphosphate and decreased the response to other agonists; furthermore, the phenothiazines enhanced the inhibitory effects of phentolamine on aggregation and thromboxane B2 synthesis, without influencing intraplatelet cyclic adenosine monophosphate levels. Phorbol ester-induced platelet activation was also inhibited in a dose-dependent way by each compound and by an association of phentolamine and phenothiazines, suggesting that the antiplatelet properties of these compounds might also be ascribed to intracellular events.