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.

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.

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.

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.

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.