Long-term effects of metformin on endothelial function in type 2 diabetes: a randomized controlled trial.

OBJECTIVES: We investigated whether metformin can improve endothelial function and decrease inflammatory activity, and thereby decrease the risk of atherothrombotic disease. SUBJECTS AND DESIGN: A randomized, placebo-controlled trial with a follow-up period of 4.3 years set in the outpatient clinics of three nonacademic hospitals (Hoogeveen, Meppel and Coevorden Hospitals, the Netherlands). A total of 390 patients with type 2 diabetes treated with insulin were included. Either metformin 850 mg or placebo (one to three times daily) was added to insulin therapy. Urinary albumin excretion and plasma levels of von Willebrand factor (vWf), soluble vascular adhesion molecule-1 (sVCAM-1), soluble E-selectin (sE-selectin), tissue-type plasminogen activator (t-PA), plasminogen activator inhibitor-1 (PAI-1), C-reactive protein (CRP) and soluble intercellular adhesion molecule-1 (sICAM-1) were measured at baseline and after 4, 17, 30, 43 and 52 months. RESULTS: Metformin significantly reduced levels of vWF, sVCAM-1, t-PA, PAI-1, CRP and sICAM-1, which, except for CRP, remained significant after adjustment for baseline differences in age, sex, smoking and severity of previous cardiovascular (CV) disease. No effects on urinary albumin excretion or sE-selectin were observed. The improvements in vWf and sVCAM-1 statistically explained about 34% of the reduction in the risk of CV morbidity and mortality associated with metformin treatment in this study. CONCLUSIONS: Metformin is associated with improvement in some (vWF and sVCAM-1) but not all markers of endothelial function, which may explain why it is associated with a decreased risk of CV disease in type 2 diabetes.

Does metformin decrease blood pressure in patients with Type 2 diabetes intensively treated with insulin?

AIMS: We investigated in a double-blind study whether metformin reduces blood pressure (BP) in patients with Type 2 diabetes intensively treated with insulin. METHODS: A total of 220 patients with Type 2 diabetes were asked to undergo 24-h ambulatory BP monitoring (24-h ABPM). One hundred and eighty-two gave informed consent. Eighty-nine were randomized to metformin and 93 to placebo. Thirty-five subjects dropped out (13 placebo, 22 metformin users); 147 patients underwent a second 24-h ABPM, 16 weeks after randomization. RESULTS: Systolic BP (SBP), diastolic BP (DBP), pulse BP (PP), mean BP (MP) and heart rate (HR) were measured as office BP measurements and as 24-h ABPM for 24-h, day and night. Office BP measurements did not differ significantly between the placebo- and metformin-treated groups for any BP measure, but showed a non-significant trend for SBP reduction with metformin use (mean baseline-adjusted difference, metformin minus placebo: -4.2 mmHg, 95% CI, -9.9 to +1.5; P = 0.15). The baseline-adjusted differences of the ambulatory measurements were -0.2 mmHg (95% CI, -2.9 to +2.6) for the 24-h SBP, and +1.1 mmHg (95% CI, -0.7 to +2.8) for the 24-h DBP. On the whole, BP differences between metformin- and placebo-treated groups were not statistically significant. The only significant difference was for night-time PP (baseline-adjusted difference: -2.2 mmHg; 95% CI, -4.2 to -0.2). These results were not different after adjustment for age and diabetes duration, or for (changes in) body mass index, glycated haemoglobin, insulin dose or plasma homocysteine. CONCLUSION: Metformin does not significantly affect BP in patients with Type 2 diabetes intensively treated with insulin.

Effects of short-term treatment with metformin on markers of endothelial function and inflammatory activity in type 2 diabetes mellitus: a randomized, placebo-controlled trial.

OBJECTIVES: The UK Prospective Diabetes Study (UKPDS) showed that treatment with metformin decreases macrovascular morbidity and mortality independent of glycaemic control. We hypothesized that metformin may achieve this by improving endothelial function and chronic, low-grade inflammation. Data on this issue are scarce and we therefore tested, in the setting of a randomized, placebo-controlled trial, whether metformin can affect endothelial function and low-grade inflammation. DESIGN: The Hyperinsulinaemia the Outcome of its Metabolic Effects (HOME) trial is a double-blind trial, in which all patients were randomized to receive either metformin or placebo in addition to insulin therapy. At the beginning and the end of a 16-week treatment period fasting blood samples were drawn and a physical examination was carried out. SETTING: The trial was conducted in the outpatient clinics of three nonacademic hospitals (Hoogeveen, Meppel and Coevorden; the Netherlands). SUBJECTS: Patients were included if they were between 30 and 80 years of age; had received a diagnosis of diabetes after the age of 25; had never had an episode of ketoacidosis; and their blood glucose-lowering treatment previously consisted of oral agents but now only consisted of either insulin (n = 345) or insulin and metformin (n = 45). We excluded pregnant women and women trying to become pregnant, patients with a Cockroft-Gault-estimated creatinine clearance <50 mL min(-1), or low plasma cholinesterase (reference value <3.5 units L(-1)), patients with congestive heart failure (New York Heart Association class III/IV), or patients with other serious medical or psychiatric disease. A total of 745 eligible patients were approached; 390 gave informed consent and were randomized (196 metformin, 194 placebo). About 353 patients completed 16 weeks of treatment (171 metformin, 182 placebo). MAIN OUTCOME MEASURES: The HOME trial was designed to study the metabolic and cardiovascular effects of metformin during a follow-up of 4 years. Presented here are the results of an interim analysis after 16 weeks of treatment. RESULTS: When compared with placebo, metformin treatment was associated with an increase in urinary albumin excretion of 21% (-1 to +48; P = 0.06); a decrease in plasma von Willebrand factor of 6% (-10 to -2; P = 0.0007); a decrease in soluble vascular cell adhesion molecule-1 of 4% (-7 to -2; P = 0.0002); a decrease in soluble E-selectin of 6% (-10 to -2; P = 0.008); a decrease in tissue-type plasminogen activator of 16% (-20 to -12; P < 0.0001); and a decrease in plasminogen activator inhibitor-1 of 20% (-27 to -10; P = 0.0001). These changes could not be explained by metformin-associated changes in glycaemic control, body weight or insulin dose. Markers of inflammation, i.e. C-reactive protein and soluble intercellular adhesion molecule-1, did not change with metformin treatment. CONCLUSIONS: In patients with type 2 diabetes treated with insulin, metformin treatment was associated with improvement of endothelial function, which was largely unrelated to changes in glycaemic control, but not with improvement of chronic, low-grade inflammation.

Autonomic nervous function, arterial stiffness and blood pressure in patients with Type I diabetes mellitus and normal urinary albumin excretion.

Type I diabetic patients (DM-1) with an elevated urinary albumin excretion (UAE>30 mg/24 h) have a high cardiovascular risk. However, DM-1 patients with normal UAE have incipient abnormalities of the cardiovascular and nervous systems, such as elevations of blood pressures, increases in arterial stiffness and deterioration of autonomic nervous function. We studied the interrelationships of these abnormalities in normoalbuminuric DM-1 patients. In 76 patients, we performed two cardiovascular reflex tests (deep in- and expiration test (IE test) and lying-to-standing test (LS test)), and determined aortic pulse wave velocity (PWV), local arterial compliances of the common carotid, femoral and brachial arteries, and 24-h blood pressures. The DeltaRRmax value of the LS test was associated with aortic PWV (negatively) and the compliance coefficients of the carotid, femoral and brachial arteries. Per 100-ms increase in DeltaRRmax, pulse wave velocity decreased by 0.39 m/s, compliance coefficients of the carotid, femoral and brachial arteries increased by 0.06, 0.08 and 0.05 mm2/kPa, respectively. These associations were independent of age, 24-h mean arterial pressure and 24-h heart rate. Increases in arterial stiffness were associated with increases in 24-h systolic and pulse pressure (per 1 m/s increase in PWV, systolic and pulse pressure increased by 2.1 and 1.7 mmHg, respectively). In normoalbuminuric DM-1 patients, deterioration of autonomic nervous function is associated with an increase in arterial stiffness, which, in turn, was associated with, and may cause, increased systolic and pulse pressure. These findings suggest that preventive strategies targeting autonomic dysfunction may reduce cardiovascular morbidity in diabetes.

Effectiveness of clinical rotations as a learning environment for achieving competences.

Competences are becoming more and more prominent in undergraduate medical education. Workplace learning is regarded as crucial in competence learning. Assuming that effective learning depends on adequate supervision, feedback and assessment, the authors studied the occurrence of these three variables in relation to a set of clinical competences. They surveyed students at the end of their rotation in surgery, internal medicine or paediatrics asking them to indicate for each competence how often they had received observed and unobserved supervision, the seniority of the person who provided most of their feedback, and whether the competence was addressed in formal assessments. Supervision was found to be scarce and mostly unobserved. Senior staff did not provide much feedback, and assessment mostly targeted patient-related competences. For all variables, the variation between students exceeded that between disciplines. We conclude that conditions for adequate workplace learning are poorly met and that clerkship experiences show huge inter-student variation.

Effects of short-term treatment with metformin on serum concentrations of homocysteine, folate and vitamin B12 in type 2 diabetes mellitus: a randomized, placebo-controlled trial.

OBJECTIVE: Metformin is a key treatment option in type 2 diabetes. However, metformin may decrease vitamin B12 levels and increase levels of homocysteine, a cardiovascular risk factor. We investigated whether 16 weeks of treatment with metformin affects serum concentrations of homocysteine, folate and vitamin B12 in subjects with type 2 diabetes treated with insulin. DESIGN: Placebo-controlled, randomized trial. MEASUREMENTS: at baseline and 16 weeks later. SETTING: This trial was conducted in the outpatient clinics of three general hospitals in The Netherlands. SUBJECTS: A total of 745 patients with type 2 diabetes, treated with insulin and not known with a contraindication for the use of metformin, were approached; 390 gave informed consent and entered the study. Thirty-seven subjects dropped out (12 placebo and 25 metformin users). INTERVENTION: Addition of metformin or placebo to insulin therapy. PRIMARY OUTCOME PARAMETERS: Serum homocysteine, folate, vitamin B12, indices of glycaemic control and body weight. RESULTS: Amongst those who completed 16 weeks of treatment, metformin use, as compared with placebo, was associated with an increase in homocysteine of 4% (0.2 to 8; P=0.039) and with decreases in folate [-7% (-1.4 to -13); P=0.024] and vitamin B12 [-14% (-4.2 to -24); P<0.0001]. In addition, the increase in homocysteine could be explained by the decreases in folate and vitamin B12. CONCLUSION: In patients with type 2 diabetes, 16 weeks of treatment with metformin reduces levels of folate and vitamin B12, which results in a modest increase in homocysteine. The clinical significance of these findings remains to be investigated.

Protein restriction, glomerular filtration rate and albuminuria in patients with type 2 diabetes mellitus: a randomized trial.

OBJECTIVE: Protein restriction delays the progression of non-diabetic and type 1 diabetic renal disorders. This study assessed whether protein restriction delays the onset or early progression of renal disorders in type 2 diabetes. DESIGN: Randomized controlled trial. Outcomes were albuminuria (mg/24 h) and, as an estimate of the glomerular filtration rate, cimetidine-influenced creatinine clearance. SETTING: Primary care. SUBJECTS: Patients with type 2 diabetes and microalbuminuria or at least detectable albuminuria, or a diabetes duration >5 y. INTERVENTIONS: The experimental group received dietary counselling on protein restriction (n=63); a control group (n=68) received the usual dietary advice. The duration of intervention and follow-up was 28+/-7 months. RESULTS: After 6 months, protein intake differed only by 0.08 g/kg/day between the study groups. Subsequently, this difference decreased and eventually disappeared. An initial effect of protein restriction on albuminuria in favor of the experimental group was not sustained, and the glomerular filtration rate decreased in the experimental group at a 1.6+/-2.2 ml/min/1.73 m(2) y lower rate than in the control group (P=0.5). Comparison of patients in the experimental group with a decrease in protein intake of at least 0.20 g/kg/day, with controls with no decrease, indicated a similarly small and insignificant effect on glomerular filtration rate. CONCLUSIONS: It is concluded that, in the longer term prevention or delay of renal damage in patients with type 2 diabetes, protein restriction is neither feasible nor efficacious.

Discontinuation of metformin in type 2 diabetes patients treated with insulin.

BACKGROUND: Metformin added to insulin therapy in type 2 diabetic patients improves glycaemic control and decreases the required daily dose of insulin (DDI). Metformin should be discontinued if cardiac, hepatic or renal failure develops. We examined whether glycaemic control can be maintained after metformin cessation. METHODS: We included 45 type 2 diabetic patients treated with insulin plus metformin, and 45 matched controls treated with insulin only. After discontinuation of metformin in the first group, we aimed for tight fasting and postprandial blood glucose levels, 4-7 and 4-10 mmol/l, respectively, in both groups. During 12 weeks we assessed glycaemic control every two weeks and, if necessary, adjusted the insulin dosage. RESULTS: In the group in which metformin was discontinued, DDI increased from 67.9 +/- 22.9 to 92.2 +/- 29.4 IU (p < 0.001) leaving glycaemic control unchanged. In the controls, glycated haemoglobin (GHb) decreased by 0.93% (p < 0.001), while DDI increased slightly from 62.4 +/- 22.9 to 72.3 +/- 27.3 IU (p < 0.001). The increase in DDI was larger in patients in whom metformin was discontinued than in the controls (p < 0.001). CONCLUSIONS: In type 2 diabetic patients treated with insulin plus metformin, glycaemic control can be maintained after discontinuation of metformin by increasing the DDI substantially (20 to 36%) during application of an intensified treatment protocol.

The effect of profiled hemodialysis on intradialytic hemodynamics when a proper sodium balance is applied.

BACKGROUND: Profiled hemodialysis (HD) has been claimed to ameliorate intradialytic complications such as hypotension. Frequently, these profiles are based on providing the patient with an accumulating sodium load. This increases the risk of interdialytic complications, such as hypertension and increased weight gain. The present study investigated the effect of profiled HD, without an accompanying sodium loading, on intradialytic hemodynamics in stable HD patients. METHODS: In eight stable HD patients a standard hemodialysis (S-HD) was compared to a decreasing Na(+)-profiled hemodialysis (Na-HD), and an ultrafiltration profiled hemodialysis (UF-HD). Care was taken to have the sodium balances similar during these sessions. The patients were monitored non-invasively during dialysis with respect to their cardiac performance by means of electrical impedance cardiography, their variation in blood volume by means of an on-line optical measurement, and their hydration state by means of body impedance analysis. RESULTS: Sodium balance and mean arterial sodium concentrations were similar in the three treatments. Intradialytic hemodynamics during UF-HD were similar to those of S-HD. However, Na-HD improved blood pressure preservation, remarkably without significant blood volume preservation, due to a better stroke volume preservation in the first hour of dialysis. CONCLUSION: Sodium-balanced, Na-profiled HD improves blood pressure preservation in stable HD patients without providing the patients with a sodium load. This effect is due to a better stroke volume preservation early in dialysis, without a significant reduction in blood volume decrease. UF-HD, as mono-therapy, has no beneficial effect on intradialytic hemodynamics in stable patients.

Renal sodium handling and haemodynamics are equally affected by hyperinsulinaemia in salt-sensitive and salt-resistant hypertensives.

OBJECTIVE: It is well-known that insulin induces renal sodium retention. It is not yet known whether insulin's renal effects are involved in the development of salt-sensitive hypertension. We assessed the effects of insulin on renal sodium handling and haemodynamics in 10 salt-sensitive (SS) and 10 salt-resistant (SR) essential hypertensives. DESIGN: After a baseline period of 90 min, all subjects underwent a euglycaemic clamp with sequential infusion of a physiological and supraphysiological dose of insulin (50 and 150 mU/kg per h) during 90 min periods each. Time-control studies were performed in the same subjects. Clearances of 131I-hippuran, 125I-iothalamate, sodium and lithium were used to evaluate renal plasma flow (RPF), CNa/glomerular filtration rate (GFR) and fractional proximal and distal sodium reabsorption. RESULTS: Plasma insulin levels and insulin-mediated glucose uptake did not differ between both groups. RPF and GFR showed similar increases during both insulin infusions in both groups. During physiological hyperinsulinaemia, fractional sodium excretion decreased 38% (P = 0.009) in the SS group and 36% (P = 0.002) in the SR group. During supraphysiological hyperinsulinaemia, fractional sodium excretion decreased 49% (P = 0.01) in the SS group and 19% (P = 0.2) in the SR group, not statistically different between both groups. Fractional proximal sodium reabsorption was unaffected and fractional distal sodium reabsorption increased to a similar magnitude in both groups. CONCLUSION: The comparable renal effects of acute exogenous hyperinsulinaemia in SS and SR hypertensives do not support a role for insulin in the development of salt-sensitive hypertension. However, the results do not yet exclude a role for chronic hyperinsulinaemia.

Impaired skin capillary recruitment in essential hypertension is caused by both functional and structural capillary rarefaction.

Capillary rarefaction occurs in many tissues in patients with essential hypertension and may contribute to an increased vascular resistance and impaired muscle metabolism. Rarefaction may be caused by a structural (anatomic) absence of capillaries, functional nonperfusion, or both. The aim of this study was to assess the extent of structural versus functional capillary rarefaction in the skin of subjects with essential hypertension. We examined skin capillary density with video microscopy before and during maximization of the number of perfused capillaries by venous congestion (structural capillary number) and before and during postocclusive reactive hyperemia (capillary recruitment, which may have a structural and/or functional basis). The study group was composed of 26 patients with never-treated essential hypertension and 26 normotensive control subjects. In both groups, intermittently perfused capillaries in the resting state were an important functional reserve for recruitment during postocclusive hyperemia. Recruitment of perfused capillaries during postocclusive reactive hyperemia was decreased in the hypertensive subjects compared with normotensive control subjects (47.9+/-6.8 versus 55.3+/-8.2 capillaries/mm(2), respectively; P<0.01). During venous occlusion, maximal capillary density was significantly lower in the hypertensive subjects than in the control subjects (52.5+/-6.6 versus 57.2+/-8.6 capillaries/mm(2), respectively; P<0.05), suggesting structural rarefaction. However, in the hypertensive subjects compared with the normotensive subjects, a smaller proportion of the maximal number of capillaries was perfused during postocclusive hyperemia (91.6+/-7.5% versus 97.2+/-2.7%, respectively; P<0.05), suggesting an additional functional impairment of capillary recruitment. If the difference in capillary numbers during venous congestion ( approximately 4.6 capillaries/mm(2)) truly reflects the structural difference between the normotensive and hypertensive subjects, then, at most, 62% (4.6/7.4x100%) of the difference in capillary numbers during postocclusive hyperemia ( approximately 7.4 capillaries/mm(2)) can be explained by structural defects, and at least 38% can be explained by functional defects. In conclusion, in patients with essential hypertension, recruitment of perfused capillaries is impaired, which can be explained by both functional and structural rarefaction.

Is pseudocholinesterase activity related to markers of triacylglycerol synthesis in Type II diabetes mellitus?

Hypertriglyceridaemia is a risk factor for cardiovascular disease in patients suffering from Type II diabetes mellitus, and is due to enhanced synthesis and/or impaired clearance of triacylglycerol-rich lipoproteins. In the present study we investigated whether pseudocholinesterase (PChE) activity could serve as a marker for the rate of triacylglycerol synthesis in these patients. Patients were stratified according to their apolipoprotein E (apoE) phenotype, i.e. E3E2, E3E3 or E3E4. In study I, the relationship between PChE activity and serum triacylglycerols was investigated in 224 insulin-treated patients with Type II diabetes. In study II, which had a cross-over design, PChE activity was measured in 45 dyslipidaemic, insulin-treated patients with Type II diabetes that were treated with bezafibrate or pravastatin. In study I, PChE activity was correlated positively with serum triacylglycerol concentrations, but did not differ significantly between apoE phenotypes. The strongest relationship was found in the E3E4 group (r=0.50; P=0.001), the phenotype for which hypertriglyceridaemia is expected to be the result of increased triacylglycerol synthesis. In a stepwise multiple regression analysis, serum triacylglycerol concentrations were found to be the strongest predictor of PChE activity in the E3E4 group. In study II, PChE activity decreased as a result of bezafibrate treatment in all three apoE groups. The decrease in PChE activity with bezafibrate treatment paralleled the decrease in serum triacylglycerol concentrations in the apoE subgroups. Pravastatin treatment did not significantly affect PChE activity. Thus the present study suggests an association between PChE activity and the rate of triacylglycerol synthesis. Measurement of PChE activity may therefore be a useful tool in the choice of drug for treatment of hypertriglyceridaemia in patients with Type II diabetes.

Determinants of albuminuria in people with Type 2 diabetes mellitus.

This study sought to identify determinants of albuminuria in people with Type 2 diabetes. In 335 primary care patients, we assessed albumin-creatinine ratio (ACR) in two 24-h urine samples, and its cross-sectional associations with protein and alcohol intake, cigarette smoking, body weight and height, glycosuria, blood pressure, hypoglycaemic and antihypertensive treatment, gender, age, age at diagnosis, diabetes duration, family history of diabetes and cardiovascular diseases, ethnic origin, and education. The prevalence of micro- or macro-albuminuria (ACR> or =2.0 mg/mmol) was 33%. Among these patients, compared to those with normo-albuminuria, there were more men, protein intake (g/kg) estimated from urinary urea as well as systolic blood pressure and glycosuria were higher, there were more smokers, men were shorter, and a family history of diabetes was less prevalent (all P<0.05). In linear and logistic regression (n=270) albuminuria was independently associated (P<0.05 unless indicated otherwise) with systolic blood pressure (OR(10 mmHg)=1.32), smoking (OR(ex/never)=2.36, OR(current/never)=4.89), glycosuria (OR(> or =7/<1 g/l)=2.41), gender (OR(men/women)=2.50), age in men (OR(10 year)=1.60) (P<0.10) and, inversely, in women (OR(10 year)=0.63) (P>0.10). On aggregation, the modifiable determinants systolic blood pressure, smoking and glycosuria explained 12% of the variation in albuminuria. These factors thus are, although to a moderate extent only, potential determinants of albuminuria. We also observed an independent, inverse association with body height (OR(0.10 m)=0.47). This is in line with the hypothesis that development in utero or during early life influences kidney function in later life.

Effects of insulin on glucose uptake and leg blood flow in patients with sickle cell disease and normal subjects.

The hemodynamic concept of insulin resistance assumes that vasodilatory effects of insulin determine glucose uptake. Sickle cell disease (SCD) is characterized by microangiopathy and microvascular occlusion. Therefore, we hypothesized that patients with SCD have a reduced insulin-mediated glucose uptake. In 8 patients with SCD and 8 matched normal controls, we studied the effects of a 4-hour insulin infusion (50 mU/kg/h) on glucose uptake and leg blood flow (LBF) using the euglycemic clamp technique and venous occlusion plethysmography. Time-control experiments were performed in the same subjects. Insulin-mediated glucose uptake (M value, mg/kg/min) did not differ between patients with SCD and control subjects during the second (6.3 +/- 4.6 and 7.6 +/- 2.6, P =.5), third (7.5 +/- 4.6 and 9.3 +/- 3.4, P =.4) and fourth hour (8.6 +/- 4.7 and 11.0 +/- 2.9, P =.2) of the clamp. At baseline, LBF was higher in the patients with SCD than in the controls (3.28 +/- 1.68 and 1.37 +/- 0.47 mL/min/dL, respectively; P =.005). Insulin-induced increases in LBF in patients with SCD and in normal subjects were not different (P =.9). Respectively, 56% and 24% of the changes in glucose uptake could be explained from changes in LBF in the course of the insulin infusion in the patients with SCD and controls. We suppose that the comparable insulin sensitivity between both groups is due to a compensatory hemodynamic state in SCD characterized by vasodilation and increased flow.

Amadori albumin and advanced glycation end-product formation in peritoneal dialysis using icodextrin.

OBJECTIVE: To study the influence of peritoneal dialysis (PD) solutions on the formation of early glycated products and advanced glycation end-products (AGEs). DESIGN AND PATIENTS: The formation of both Amadori albumin and AGEs in glucose- and icodextrin-based PD fluids was analyzed in vitro and in peritoneal effluents of continuous cyclic peritoneal dialysis (CCPD) patients. RESULTS: Albumin incubated with glucose-based PD fluids showed a time- and glucose concentration-dependent formation of Amadori albumin and AGEs. Aminoguanidine completely inhibited AGE but not Amadori albumin formation. Albumin incubated in icodextrin resulted in the lowest levels of Amadori albumin and AGE. Amadori albumin levels in effluents of 24 CCPD patients (12 glucose and 12 icodextrin for their daytime dwells) were similar. Dialysate samples collected during a mass transfer area coefficient test in 16 CCPD patients (8 glucose, 8 icodextrin) showed an increase in Amadori albumin formation from baseline (p < 0.0001), without a difference between the groups. In the total group, there was a positive relationship between duration on PD and dialysate Amadori albumin concentration at 240 minutes (p = 0.03). The Amadori albumin dialysate-to-plasma (D/P) ratio at 240 minutes was 0.82+/-0.11, and its clearance amounted to 7.71+/-1.14 mL/min, while the albumin D/P ratio was 0.010+/-0.003 and its clearance was 0.089+/-0.017 mL/min. In a peritoneal biopsy of a CCPD patient, Amadori albumin was observed in the mesothelial layer and the endothelium of the peritoneum. CONCLUSIONS: Using icodextrin-based instead of glucose-based PD fluids can largely reduce the formation of Amadori albumin and AGEs. However, CCPD patients using icodextrin during daytime dwells do not have lower effluent levels of Amadori albumin and AGEs, probably due to the exposure to glucose during their nighttime exchanges. Kinetic studies suggest washout of locally produced Amadori albumin.

Serum homocysteine levels are associated with the development of (micro)albuminuria: the Hoorn study.

Microalbuminuria is a strong indicator of the risk of future cardiovascular disease and renal dysfunction. Slightly increased levels of homocysteine, an independent risk factor for atherothrombotic disease, have recently been found to be associated with the presence of (micro)albuminuria. However, it is unknown whether increased homocysteine levels precede the occurrence of (micro)albuminuria. Normoalbuminuric subjects (n=316, 66 with non-insulin-dependent diabetes mellitus [NIDDM]) of an age-stratified, sex-stratified, and glucose tolerance-stratified sample of a population-based cohort study were investigated at baseline and after a mean follow-up duration of 6.1 years. Development of (micro)albuminuria was defined as a mean albumin-to-creatinine ratio >2.0 mg/mmol at the follow-up examination. The cumulative incidence of (micro)albuminuria was 14. 0% (9.7 % to 18.3%) among nondiabetic subjects and 22.7% (12.9% to 32.5%) among NIDDM patients. Age-adjusted, sex-adjusted, and glucose tolerance status-adjusted logistic regression analyses showed development of (micro)albuminuria to be significantly associated with baseline homocysteine levels >19.0 micromol/L compared with homocysteine levels <9.1 micromol/L (odds ratio [OR] 5.1, 95% CI 1.1 to 23.0). For homocysteine levels of 9.1 to 14.0 micromol/L and 14.1 to 19.0 micromol/L, the values were OR 1.2 (95% CI 0.5 to 3.0) and OR 1.8 (95% CI 0.6 to 5.3), respectively. Additional adjustment for baseline insulin resistance, blood pressure, body mass index, presence of cardiovascular disease and retinopathy, current smoking, or estimates of glomerular filtration rate did not materially affect the results. Substituting homocysteine levels as a continuous variable for categories of homocysteine levels showed that a 5-micromol/L increase of the homocysteine level was associated with an increased risk of developing (micro)albuminuria (OR 1.38, 95% CI 0.97 to 1.95). Analyses performed in nondiabetic and diabetic subjects separately gave similar results among nondiabetic subjects. Among diabetic subjects, the association between homocysteine level and (micro)albuminuria could not be estimated, because there was an insufficient number of diabetic subjects with high homocysteine levels. Hyperhomocysteinemia is an independent determinant of the development of (micro)albuminuria among nondiabetic subjects, even after adjustment for estimates of glomerular filtration rate. We could neither confirm nor reject an association between homocysteine levels and the development of (micro)albuminuria among NIDDM subjects. These data suggest that homocysteine may play a pathophysiological role in the development of (micro)albuminuria.

Capillary recruitment is impaired in essential hypertension and relates to insulin's metabolic and vascular actions.

OBJECTIVE: In patients with essential hypertension, defects in both the metabolic and vascular actions of insulin have been described. Impaired microvascular function, a well-established abnormality in essential hypertension, may explain part of these defects. In the present study we investigated whether microvascular function is impaired in essential hypertension and relates to insulin's metabolic and vasodilatatory actions. METHODS: We measured 24-h ambulatory blood pressure, capillary recruitment after arterial occlusion, and skin blood flow responses to iontophoresis of acetylcholine and sodium nitroprusside in 18 subjects with untreated essential hypertension and in 18 control subjects. Whole body insulin sensitivity and leg insulin-mediated vasodilatation were assessed with the hyperinsulinaemic clamp technique and plethysmography. RESULTS: Hypertensive, as compared to normotensive, subjects had a decreased insulin sensitivity (0.8+/-0.3 vs. 1.7+/-0. 6 mgkg(-1)min(-1) per pmoll(-1); P<0.001), capillary recruitment after arterial occlusion (21.5+/-5.8 vs. 45.9+/-10.4%; P<0.001), acetylcholine-mediated vasodilatation (331+/-84 vs. 688+/-192%; P<0. 001), and insulin-mediated vasodilatation (median 29.3 vs. 47.2%; P<0.05). Correlation analyses with adjustment for sex, age, body mass index and waist-to-hip ratio showed significant relationships of capillary recruitment after arterial occlusion with blood pressure (r=-0.68; P<0.01), insulin sensitivity (r=+0.55; P<0.01) and insulin-mediated vasodilatation (r=+0.51; P<0.05), which extended from the normotensive to the hypertensive range. CONCLUSION: Skin microvascular function is associated with blood pressure and insulin's metabolic and vasodilatatory actions, both in normotensive and hypertensive subjects. These findings offer a potential mechanistic explanation of the links among insulin resistance, impaired insulin-mediated vasodilatation and hypertension.

Insulin-mediated increases in renal plasma flow are impaired in insulin-resistant normal subjects.

BACKGROUND: Impaired vasodilatation in skeletal muscle is a possible mechanism linking insulin resistance to blood pressure regulation. Increased renal vascular resistance has been demonstrated in the offspring of essential hypertensives. We assessed whether insulin-mediated renal vasodilatation is impaired in insulin-resistant normal subjects. DESIGN: In two groups of 10 insulin-resistant and 10 insulin-sensitive normal subjects, we compared the effects of sequential physiological and supraphysiological insulin dosages (50 and 150 mU kg(-1) h(-1)) on renal plasma flow (RPF) and leg blood flow using the euglycaemic clamp technique, 131I-labelled Hippuran clearances and venous occlusion plethysmography. Time-control experiments were performed in the same subjects. RESULTS: Whole-body glucose uptake amounted to 4.9 +/- 2.1 and 11.0 +/- 2.4 mg kg(-1) min(-1) in the insulin-resistant and to 12.7 +/- 2.3 and 17.4 +/- 2.6 mg kg(-1) min(-1) in the insulin-sensitive subjects during physiological and supraphysiological hyperinsulinaemia, respectively. RPF increased more in insulin-sensitive compared to insulin-resistant subjects during physiological hyperinsulinaemia (13.7 vs. 6.8%, P < 0.05). RPF increased to comparable levels during supraphysiological hyperinsulinaemia. Insulin-mediated changes in leg blood flow did not differ between groups. In the combined group, we found a positive correlation between insulin-mediated glucose uptake and changes in RPF during physiological hyperinsulinaemia (r = 0.57, P = 0.009), whereas insulin-mediated glucose uptake correlated with changes in leg blood flow during supraphysiological hyperinsulinaemia (r = 0.54. P = 0.017). CONCLUSIONS: Our results suggest that the sensitivities of the skeletal muscle and renal vascular bed differ for insulin's vasodilatory action. Insulin-mediated increases in RPF are impaired in insulin-resistant but otherwise normal subjects during physiological hyperinsulinaemia.

Birth weight relates to blood pressure and microvascular function in normal subjects.

OBJECTIVE: The relationship between low birth weight and elevated blood pressure in adult life is well established but presently unexplained. Both microvascular dysfunction and insulin resistance have been proposed as a possible explanation. We have examined the relation between birth weight and blood pressure in 30 healthy subjects exhibiting a wide range of insulin sensitivity, and assessed whether microvascular function and/or insulin resistance may underlie this relationship. METHODS: Birth weight data were obtained from birth announcements. Blood pressure was measured with an ambulatory blood pressure monitor and insulin sensitivity was assessed by the hyperinsulinaemic, euglycaemic clamp technique. Microvascular function, i.e. capillary recruitment and endothelium-dependent and -independent vasodilatation in the skin, was evaluated by videomicroscopy and iontophoresis of acetylcholine and sodium nitroprusside. RESULTS: Birth weight was significantly associated with blood pressure (r= -0.50; P< 0.05), capillary recruitment (r= +0.52; P< 0.05), acetylcholine-mediated vasodilatation (r= +0.40; P< 0.05), insulin sensitivity (r= +0.62; P< 0.01) and waist-to-hip ratio (r= -0.42; P< 0.05). Regression analysis showed a significant association of birth weight with 24 h systolic blood pressure (regression coefficient: -7.6 mmHg/kg; 95% confidence interval: -13.0 to -1.0). Adjustment for capillary recruitment and waist-to-hip ratio decreased the regression coefficient by 39 and 41%, respectively. The results were similar after adjustment for age, sex or body mass index. CONCLUSION: These results suggest that capillary recruitment and body fat distribution may partly explain the relationship between birth weight and blood pressure.