Enrico Brocco

Patterns of renal injury in NIDDM patients with microalbuminuria.

Summary Microalbuminuria predicts overt nephropathy in non-insulin-dependent diabetic (NIDDM) patients; however, the structural basis for this functional abnormality is unknown. In this study we evaluated renal structure and function in a cohort of 34 unselected microalbuminuric NIDDM patients (26 male/8 female, age: 58 ± 7 years, known diabetes duration: 11 ± 6 years, HbA1 c: 8.5 ± 1.6 %). Systemic hypertension was present in all but 3. Glomerular filtration rate (GFR) was 101 ± 27 ml · min–1· 1.73 m–2 and albumin excretion rate (AER) 44 (20–199) μg/min. Light microscopic slides were categorized as: C I) normal or near normal renal structure; C II) changes “typical” of diabetic nephropathology in insulin-dependent diabetes (IDDM) (glomerular, tubulo-interstitial and arteriolar changes occurring in parallel); C III) “atypical” patterns of injury, with absent or only mild diabetic glomerular changes associated with disproportionately severe renal structural changes including: important tubulo-interstitial with or without arteriolar hyalinosis with or without global glomerular sclerosis. Ten patients (29.4 %) were classified as C I, 10 as C II (29.4 %) and 14 as C III (41.2 %); none of these patients had any definable non-diabetic renal disease. GFR, AER and blood pressure were similar in the three groups, while HbA1 c was higher in C II and C III than in C I patients. Diabetic retinopathy was present in all C II patients (background in 50 % and proliferative in 50 %). None of the patients in C I and C III had proliferative retinopathy, while background retinopathy was observed in 50 % of C I and 57 % of C III patients. In summary, microalbuminuric NIDDM patients are structurally heterogeneous with less than one third having “typical” diabetic nephropathology. The presence of both “typical” and “atypical” patterns of renal pathology was associated with worse metabolic control, suggesting that hyperglycaemia may cause different patterns of renal injury in older NIDDM compared to younger IDDM patients. [Diabetologia (1996) 39: 1569–1576]

Effects of Cilazapril and Amlodipine on Kidney Function in Hypertensive NIDDM Patients

Contrasting information has been reported concerning the course of renal function in NIDDM with hypertension alone or in association with renal damage. The aim of the present study was to elucidate the course of the glomerular filtration rate (GFR) in hypertensive NIDDM patients during antihypertensive therapy. Furthermore, we compared the effects of ACE inhibitors (cilazapril, Inibace, Roche, Milan, Italy) and Ca2+-channel blockers (amlodipine, Norvasc, Pfizer, Rome, Italy). Of the hypertensive NIDDM patients attending the outpatients clinic of the internal medicine departments of the University of Padova and Sassari, 44 participated in the present study. Of these patients, 26 were normoalbuminuric and 18 microalbuminuric. They were randomly treated with either cilazapril or amlodipine. The target of antihypertensive treatment was a value <140 mmHg for systolic and 85 mmHg for diastolic blood pressure (BP). Microalbuminuria was defined as an albumin excretion rate (AER) between 20 and 200 μg/min. GFR was measured by plasma clearance of 51Cr-labeled EDTA at baseline and every 6–12 months during a 3-year follow-up interval. A significant decrease was observed in the values of GFR, AER, and systolic and diastolic BP in normoalbuminuric and microalbuminuric patients during antihypertensive therapy. The GFR fall in the overall population of NIDDM patients was significantly and inversely related to the decrease of mean BP (diastolic + 1/3 pulse pressure) (r = −0.80, P < 0.0001) but not to that of HbA1c, triglycerides, and BMI. The GFR decline (mean ± SE) per year in the normoalbuminuric patient was 2.03 ± 0.66 ml · min−1 · 1.73 m−2 (95% CI 0.92–3.17) during cilazapril and 2.01 ± 0.71 ml · min−1 · 1.73 m−2 (95% CI 0.82–3.11) during amlodipine therapy. The GFR decline per year in the microalbuminuric patient was 2.15 ± 0.69 ml · min−1 · 1.73 m−2 (95% CI 0.86–3.89) during cilazapril and 2.33 ± 0.83 ml · min−1 · 1.73 m−2 per year (95% CI 1.03–3.67) during amlodipine therapy. Cilazapril and amlodipine lowered AER to a similar extent in normoalbuminuric and microalbuminuric patients. No significant changes were observed concerning other clinical and biochemical features between the two antihypertensive therapies and particularly HbA1c, BMI, triglycerides, and cholesterol plasma values. These results support the tenet that arterial hypertension plays a pivotal role in contributing to renal damage in NIDDM, even when AER is normal. However, the degree of BP control, with both cilazapril and amlodipine, can successfully delay the slope of GFR decline in hypertensive NIDDM patients with or without incipient nephropathy.

Heterogeneous nature of microalbuminuria in NIDDM: studies of endothelial function and renal structure

Summary Microalbuminuria (MA) is associated with microangiopathy (renal and retinal lesions) in insulin-dependent diabetic (IDDM) patients. In contrast MA does not reflect microvascular damage in a substantial number of non-insulin-dependent diabetic (NIDDM) patients. MA predicts cardiovascular disease in NIDDM patients with increased von Willebrand factor (vWF) plasma levels which are hypothesized to reflect endothelial dysfunction. However, it is not known whether MA is consequent to generalised endothelial dysfunction or to renal injury. Thus, this study evaluated vWF plasma levels in relation to renal and retinal structural abnormalities in NIDDM patients with MA. Kidney biopsies, fundoscopy and measures of vWF plasma levels were performed in 32 NIDDM patients with MA. These patients were allocated to two renal structural categories: A) Without renal structural abnormalities (C I, n = 10): normal or near-normal renal structure, and B) With renal structural abnormalities (n = 22), further divided into: C II (n = 12) with typical diabetic nephropathology, predominantly glomerulopathy, and C III (n = 10) with atypical patterns of renal injury (more advanced tubulo-interstitial and arteriolar than glomerular changes). vWF plasma levels were significantly higher in category B (C II: 195 ± 49 % and C III: 161 ± 46 %) than in category A (C I: 119 ± 42 %), (chi-square, p < 0.05). Diabetic retinopathy was also related to vWF plasma levels (ANOVA, p < 0.05). These data suggest that there are two types of MA in NIDDM: one associated with increased vWF levels, established renal injury and frequently retinopathy, and the other characterized by normal vWF levels, normal renal structure and absent or mild diabetic retinopathy. We propose that vWF plasma levels in NIDDM patients with MA may help to identify patients with important renal structural changes, increased retinopathy risk and, perhaps, generalised endothelial dysfunction. Whether vWF plasma levels predict end-stage renal disease and cardiovascular events deserves longitudinal studies. [Diabetologia (1998) 41: 233–236]

Insulin sensitivity and glucose effectiveness: minimal model analysis of regular and insulin-modified FSIGT

The minimal model is widely used to evaluate insulin action on glucose disappearance from frequently sampled intravenous glucose tolerance tests (FSIGT). The common protocols are a regular (rFSIGT, single injection of 0.3 g/kg of glucose) and an insulin-modified test (mFSIGT, with an additional insulin administration at 20 min). This study compared the insulin sensitivity index (SI) and glucose effectiveness (SG) obtained in the same individual (16 normal subjects) with the two tests. SI was 7.11 ± 0.80 10-4 ⋅ min-1 ⋅ μU-1 ⋅ ml in rFSIGT and 6.96 ± 0.83 in mFSIGT ( P = 0.656), regression r = 0.92, P < 0.0001; SG was 0.0260 ± 0.0028 min-1 and 0.0357 ± 0.0052, respectively, statistically different ( P = 0.013) but still with a good regression ( r = 0.66, P = 0.0051). SG and insulin amount during the early period correlated ( r = 0.6, P = 0.015 in rFSIGT and r = 0.76, P = 0.0006 in mFSIGT). In summary, both FSIGTs with minimal model analysis provide the same SI, which is a very robust index. SG was different by 28% due probably to the relationship between SG and the amount of circulating insulin. In studies comparing groups, the simpler rFSIGT can still be used with the advantage of accounting for endogenous insulin, thus offering the possibility of direct inferences on the β-cell activity.The minimal model is widely used to evaluate insulin action on glucose disappearance from frequently sampled intravenous glucose tolerance tests (FSIGT). The common protocols are a regular (rFSIGT, single injection of 0.3 g/kg of glucose) and an insulin-modified test (mFSIGT, with an additional insulin administration at 20 min). This study compared the insulin sensitivity index (SI) and glucose effectiveness (SG) obtained in the same individual (16 normal subjects) with the two tests. SI was 7.11 +/- 0.80 10(-4).min-1.microU-1.ml in rFSIGT and 6.96 +/- 0.83 in mFSIGT (P = 0.656), regression r = 0.92, P < 0.0001; SG was 0.0260 +/- 0.0028 min-1 and 0.0357 +/- 0.0052, respectively, statistically different (P = 0.013) but still with a good regression (r = 0.66, P = 0.0051). SG and insulin amount during the early period correlated (r = 0.6, P = 0.015 in rFSIGT and r = 0.76, P = 0.0006 in mFSIGT). In summary, both FSIGTs with minimal model analysis provide the same SI, which is a very robust index. SG was different by 28% due probably to the relationship between SG and the amount of circulating insulin. In studies comparing groups, the simpler rFSIGT can still be used with the advantage of accounting for endogenous insulin, thus offering the possibility of direct inferences on the beta-cell activity.

Clustering of albumin excretion rate abnormalities in Caucasian patients with NIDDM

Summary Proteinuria and nephropathy have been found to cluster in families of non-insulin-dependent diabetic (NIDDM) Pima Indian, and in Caucasian insulin-dependent diabetic (IDDM) patients. No information is at present available for Caucasian NIDDM patients. The aim of the present study was to determine whether micro-macroalbuminuria (AER + ) is associated with albumin excretion rate abnormalities in diabetic and non-diabetic siblings of probands with NIDDM and AER + . We identified 169 Caucasian families with one NIDDM proband (the patient with longest known NIDDM duration) (101 families with only NIDDM siblings, 33 families with both NIDDM and non-NIDDM siblings and 35 families with only non-NIDDM siblings). Of the probands 56 had AER + [Prob-NIDDM-(AER + )], 78 had AER– [Prob-NIDDM-(AER–)], 74 siblings of Prob-NIDDM-(AER + ), and 113 siblings of Prob-NIDDM-(AER–) also had NIDDM. Data on albuminuria and retinopathy from multiple sibling pairs when the size of the sibship was more than two was adjusted according to a weighting factor. The odds ratio for AER + , in siblings of Prob-NIDDM-(AER + ) adjusted for age, hypertension, glycated haemoglobin A1 c and other confounding variables was 3.94 (95 % confidence intervals: 1.93–9.01) as compared to siblings of Prob-NIDDM-(AER–). The 74 siblings of Prob-NIDDM-(AER + ) had higher prevalence of proliferative retinopathy than siblings of Prob-NIDDM-(AER–) (14 vs 2 %; p < 0.01). We also identified 66 non-diabetic siblings of 41 NIDDM probands with AER + and 36 non-diabetic siblings of 27 NIDDM probands with AER–. Albumin excretion was two times higher, although still within the normal range, in the non-diabetic siblings of Prob-NIDDM-(AER + ) than in siblings of Prob-NIDDM-(AER–) [median = 13.5 (range 0.5–148) vs 6.6 (range 1–17) μg/min (p < 0.05)]. In conclusion higher rates of albumin excretion aggregate in Caucasian families with NIDDM. Proliferative retinopathy is more frequently observed in families showing a clustering of AER + and NIDDM. These findings suggest that familial factors play a role in the pathogenesis of renal and retinal complications in NIDDM. [Diabetologia (1997) 40: 816–823]

Role of Atrial Natriuretic Peptide in the Pathogenesis of Sodium Retention in IDDM With and Without Glomerular Hyperfiltration

The pathogenetic determinants of sodium retention in IDDM are not fully understood. The aim of this study was to elucidate the action of ANP in 11 IDDM patients with high GFR (≥ 135 ml · min−1 · 1.73 m−2), referred to here as HF patients; in 10 IDDM patients with normal GFR (>90 and <135 ml·min−1 · 1.73 m−2), referred to here as NF patients; and 12 control subjects, here called C subjects, at baseline and during saline infusion administered on the basis of either body weight (2 mmol × kg−1 · 60 min−1; Saline 1) or of ECV (12 mM.ECVL−1 · 90 min−1; Saline 2) during euglycemic insulin-glucose clamp. C subjects and both HF and NF IDDM patients received a second Saline 1 infusion accompanied by ANP infusion (0.02 μg · kg−1 · min−1) at euglycemic levels. HF and NF patients were studied again after 3 mo of treatment with (10 mg/day). Quinapril (CI 906, Malesci, Florence, Italy), an ACE inhibitor without sulfhydryl group. At baseline, both HF and NF IDDM patients had higher plasma ANP concentrations than C subjects (HF, 36 ± 4, P < 0.01 and NF, 34 ± 3, P < 0.01 vs. C, 19 ± 3 pg/ml). Plasma ANP and natriuretic response to isotonic volume expansion was impaired both in HF (44 ± 8 pg/ml, NS vs. base) and NF (40 ± 7 pg/ml, NS vs. base) compared with C (41 ± 4 pg/ml, P < 0.01 vs. base) during Saline 1. On the contrary, plasma ANP response to Saline 2 was similar in HF and NF patients and C subjects, but IDDM patients had still lower urinary sodium excretion rates. The simultaneous administration of ANP and Saline 1 resulted in comparable plasma ANP plateaus in C subjects and HF and NF patients. However, urinary sodium excretion rate was significantly lower in HF and NF patients than in C subjects: HF, 267 ± 64, P < 0.01 and NF, 281 ± 42, P < 0.01 vs. C, 424 ± 39 μmol · min−1 · 1.73 m−2. During simultaneous administration of ANP and Saline 1, GFR and FF increased in C subjects, but not in HF and NF patients. HF and NF patients had higher urinary vasodilatory prostanoid excretion rates than C subjects at baseline. Saline infusion did not change urinary excretion rate of prostanoids either in C subjects or IDDM patients (both NF and HF). Quinapril significantly decreased baseline plasma ANP concentrations in both HF and NF, near normalized ANP response to Saline 1, and increased sodium excretion rate both during Saline 1 and 2, without any change in GFR and urinary prostanoid excretion rates. The results of this study suggest that in IDDM patients with high or normal GFR, 1) natriuresis is impaired during saline infusion, even when ANP levels are normal, suggesting the presence of resistance to ANP action, 2) ANP release is normal if volume expansion is proportionate to ECV magnitude, 3) urinary excretion rate of vasodilatory prostanoids is high, and 4) ACE inhibitors ameliorate natriuretic and ANP response to saline infusion. These findings suggest that a resistance to the natriuretic action of ANP, and possibly of vasodilatory prostanoids, contribute to sodium retention in IDDM, irrespective of glomerular hyperfiltration.

Impaired response to angiotensin II in Type 1 (insulin-dependent) diabetes mellitus. Role of prostaglandins and sodium-lithium countertransport activity

SummaryThe pathogenesis of diabetic nephropathy remains elusive. A role for renal prostaglandins in antagonizing the hormonal effects of renin-angiotensin II has been postulated as a putative factor leading to hyperfiltration in patients with Type 1 (insulin-dependent) diabetes mellitus. Our aim was to elucidate the effects of angiotensin II on kidney haemodynamics and on blood pressure in eight normal subjects, in nine normotensive, in nine hypertensive with normal sodium-lithium countertransport activity in erythrocytes, in seven hypertensive without and in eight hypertensive Type 1 diabetic patients with microalbuminuria and with high sodium-lithium countertransport activity in erythrocytes. Angiotensin II infusion 4ng·kg−1·min−1 for 60 min) decreased the glomerular filtration rate to a greater extent in normal subjects (−20%), than in normotensive patients (−5% p<0.01), in hypertensive patients with normal sodium-lithium countertransport activity in erythrocytes (−8% p<0.01) in hypertensive patients with high sodium-lithium countertransport (−6% p<0.01) and in hypertensive microalbuminuric patients (−5% p<0.01) with Type 1 diabetes. The urinary excretion rate of vasodilatory prostaglandins was two-three fold higher in all patients than in normal subjects. Acute indomethacin treatment restored a normal response to angiotensin II infusion in normotensive patients, but did not change the renal haemodynamic response in normal subjects. With regard to hypertensive patients with and without microalbuminuria indomethacin treatment restored a normal response to angiotensin II in some but not all patients. An inverse relation was found between angiotensin II-induced decrease in the glomerular filtration rate and the sodium-lithium countertransport activity in erythrocytes during indomethacin treatment. Hypertensive and microalbuminuric patients with a sodium-lithium countertransport activity higher than 0.41 mmol·l erythrocyte−1·h−1 (the upper limit in normal subjects) also had a greater intimal plus medial thickness of the carotid artery using an ultrasonic imaging technique. Chronic indomethacin administration (30 days) significantly decreased the baseline overnight fasting glomerular filtration rate in normotensive and in hypertensive patients with normal but not in hypertensive and microalbuminuric patients with high sodium-lithium countertransport activity.In conclusion these results demonstrate that: (1) excessive synthesis of vasodilatory prostaglandins antagonizes the regulation of renal haemodynamics by angiotensin II, at least partially accounting for hyperfiltration in Type 1 diabetes, (2) elevated sodium-lithium countertransport activity in erythrocytes identifies a subgroup of patients with Type 1 diabetes and hypertension, with and without microalbuminuria, in whom the normalization of urinary excretion rate of prostaglandins does not restore a normal response to angiotensin II.