Type I insulin-dependent diabetic patients show an impaired renal hemodynamic response to protein intake

Human kidney responds to a meat meal with an increase in glomerular filtration rate (GFR), but the mechanisms regulating kidney hemodynamics following protein intake are poorly understood in Type I insulin-dependent diabetes. In the present study we investigated GFR response to protein intake (600 gr/1.73 m² meat meal) in nine normal subjects and 21 Type I insulin-dependent diabetic patients with normal albumin excretion rates as well as proximal tubular sodium reabsorption rates and distal sodium delivery (PRNa and DDNa). The same study was reperformed in normal subjects and diabetic patients, with less than a 5 year diabetes duration, following one week of indomethacin treatment. Normal subjects showed a 38% increase in GFR following protein intake, whereas diabetic patients showed a significantly lower response (18%, p < 0.01). the response of GFR to protein challenge was negatively related to diabetes duration but not to baseline glomerular filtration rate. Indomethacin treatment completely prevented the protein induced GFR increase in normal subjects but not in diabetic patients. Sodium reabsorption rate was increased following protein challenge both at the proximal and distal tubular level, as was net natriuresis. These findings demonstrate that 1) Type I diabetic subjects show an impaired GFR response to protein intake that seems to be related to diabetes duration rather than baseline glomerular hyperfiltration; 2) the inhibition of kidney hemodynamic response to proteinby indomethacin in normal, but not diabetic, patients suggests that a prostaglandin mediated GFR increase following protein challenge occurs in normal, but not in diabetic patients; 3) the macula densa feedback system does not seem to play a major role in protein effect of kidney function, as an increased sodium reabsorption at the proximal tubular level was assoclated with concomitant distal sodium delivery.     

Reduced capillary hydraulic conductivity in skeletal muscle and skin in Type I diabetes: a possible cause for reduced transcapillary fluid absorption during hypovolaemia

Aims/hypothesis. Patients with Type I (insulin-dependent) diabetes mellitus have a reduced transcapillary fluid absorption from skeletal muscle and skin and thus defective plasma volume regulation during hypovolaemia. Our aim was to find whether a defective capillary filtration coefficient or impaired transcapillary driving force are aetiologic factors for this reduction. Methods. We investigated 11 diabetic patients (diabetes duration 6.9 ± 1.1 years, age 26 ± 1 years), without complications and 12 control subjects (26 ± 1 years). Their capillary filtration coefficient was measured in the upper arm using a volumetric technique at rest and during lower body negative pressure (LBNP). We calculated the driving force for transcapillary fluid transfer. Results. The increase in heart rate and the decrease in systolic blood pressure during lower body negative pressure were similar in diabetic and control subjects. The resting capillary filtration coefficient was decreased in the diabetic subjects, 0.033 ± 0.003 vs 0.051 ± 0.007 ml · 100 ml^–1· min^–1· mmHg^–1 (p < 0.05). During lower body negative pressure, the capillary filtration coefficient increased 35 % in both groups compared with resting capillary filtration coefficient and was still decreased in diabetes; 0.046 ± 0.004 compared with 0.069 ± 0.006 ml · 100ml^–1· min^–1· mmHg^–1 (p < 0.01). The established driving force during lower body negative pressure was 1.37 ± 0.11 vs 1.30 ± 0.15 mmHg (NS) in diabetic and control subjects, respectively. Conclusions/interpretation. Our study indicates that a reduced capillary filtration coefficient rather than defective regulation of transcapillary driving force, is the reason for the reduced transcapillary fluid absorption during hypovolaemic circulatory stress found in Type I diabetic patients. [Diabetologia (2000) 43: 1178–1184] Received: 28 January 2000 and in revised form: 8 May 2000     

Urinary excretion of the carboxy terminal domain of type IV collagen is associated with kidney size and function in IDDM

We evaluated whether urinary excretion of the carboxy terminal domain (NC1) of Type IV collagen is associated with glomerular filtration rate and kidney size in Type I (insulin-dependent) diabetes mellitus (IDDM). Urinary excretion rate of NC1, glomerular filtration rate (GFR), and kidney size were measured in 16 men with Type I diabetes. Their mean age was 33.3 ± 6.1 years with a duration of diabetes of 14.9 ± 3.7 years (mean ± SD). The urinary excretion rate of NC1 was higher in the diabetic patients than in 18 healthy control subjects. Urinary excretion of NC1 was associated with both kidney size, parenchymal width, and GFR (r = 0.73, p = 0.001; r = 0.63, p = 0.009; r = 0.53, p = 0.04, respectively). The exact relationship between these factors and basement membrane turnover/synthesis remains to be elucidated.     

Glomerular hypertension as one cause of albuminuria in Type II diabetic patients

Aims/hypothesis. Results from animal models of glomerular hypertension have suggested that this disorder is one cause of albuminuria in diabetic nephropathy. We evaluated this hypothesis clinically. Methods. The subjects were 20 patients with Type II (non-insulin-dependent) diabetes mellitus but without uraemia or hypertension: 8 had normoalbuminuria and 12 had albuminuria ( ≥ 20 μg/min). In the 2-week study, patients were on a diet with ordinary amounts of sodium for 1 week and on a sodium-restricted diet for 1 week. Urinary excretion of sodium and albumin and the systemic blood pressure were measured daily. Intrarenal haemodynamics, in terms of the glomerular pressure and resistance of afferent and efferent arterioles, were calculated from renal clearance, the plasma total protein concentration, and the pressure-natriuresis relation. In 8 of the 12 patients with albuminuria, an angiotensin-converting enzyme inhibitor, cilazapril, was given orally (2 mg/day) and the 2-week study was repeated. Results. In patients with albuminuria, resistance of efferent arterioles and the glomerular pressure were higher than in patients with normoalbuminuria (glomerular pressure, 53 ± 5 vs 43 ± 5 mmHg, means ± SD, p < 0.001). Urinary excretion of albumin correlated (n = 20, r = 0.675, p < 0.001) with the glomerular pressure but not with systemic pressure. The increased glomerular pressure and the albuminuria were decreased by cilazapril but systemic pressure was not. Conclusion/interpretation. These findings are consistent with the hypothesis that glomerular hypertension is present in Type II diabetic patients with early nephropathy and can cause albuminuria. [Diabetologia (1999) 42: 999–1005] Received: 25 January 1999 and in revised form: 15 March 1999     

Detection of monocyte-derived microparticles in patients with Type II diabetes mellitus

Aims/hypothesis. The role of plasma monocyte-derived microparticles (MDMPs) and platelet-activation markers (platelet-derived microparticle [PDMP], platelet-bound CD62P [plt-CD62P], and platelet-bound CD63 [plt-CD63]) in diabetic vascular complications is not clear. We measured and compared plasma concentrations of MDMPs and the platelet-activation markers to investigate their possible contribution to diabetic vascular complications. Methods. Activated platelets and microparticles (PDMP and MDMP) were analysed by flow cytometry. Concentrations of serum sE-selectin were measured with enzyme-linked immunosorbent assay. Results. The concentration of MDMPs in diabetic patients was higher than in normal subjects. We found no differences in the binding of anti-GPIIb/IIIa and anti-GPIb monoclonal antibodies between groups. There were differences, however, in the concentrations of PDMPs, plt-CD62P, and plt-CD63 between Type II (non-insulin-dependent) diabetes mellitus patients and control subjects (PDMPs: 585 ± 25 vs 263 ± 9, p < 0.01; plt-CD62P: 28.1 % ± 1.4 % vs 9.4 % ± 0.6 %, p < 0.001; plt-CD63: 28.1 % ± 1.4 % vs 8.6 % ± 0.5 %, p < 0.001). Amounts of MDMPs correlated positively with these platelet activation markers, and the relation between PDMP and MDMP was the most significant. The concentration of MDMP in patients who had diabetes complicated with nephropathy, retinopathy, or neuropathy was higher than in those without diabetes-related complications. The increase in MDMP was particularly significant in patients with nephropathy. Concentrations of sE-selectin were higher in Type II diabetes patients than in control subjects, and correlated with MDMP, PDMP, plt-CD62P, and plt-CD63 levels in nephropathy patients. Conclusion/interpretation. In Type II diabetes patients, we detected increased activation of monocytes, which could have been stimulated by activated platelets and PDMPs. Because the activation of monocytes is associated with vascular endothelial damage, high concentrations of MDMPs could indicate vascular complications in diabetes patients, especially those who have diabetes-related nephropathy. [Diabetologia (2002) 45: ▪–▪] Received: 21 May 2001 and in revised form: 13 November 2001     

Physical training decreases plasma thrombomodulin in Type I and Type II diabetic patients

Aims/hypothesis. Endothelial damage is an early step in the pathogenesis of atherosclerosis and its improvement through physical training can contribute to the known reduction of cardiovascular risk associated with exercise. An increase in some endothelium-dependent haemostatic parameters, considered as markers of endothelial damage, has been observed in diabetic patients. Methods. The effect of a three-month physical exercise programme on thrombomodulin, tissue factor pathway inhibitor, plasminogen activator inhibitor, tissue-type plasminogen activator and von-Willebrand factor was evaluated in 14 well-controlled patients with Type I (insulin-dependent) diabetes mellitus and 13 patients with Type II (non-insulin-dependent) diabetes mellitus (HbA_{1 c} 6.5 ± 0.8 and 7.4 ± 0.8 %, respectively). A matched control group was also studied. Results. Thrombomodulin at baseline was higher in both Type I and Type II diabetic patients than in their respective matched control subjects (50.0 ± 16 vs 31.1 ± 8.7 μg/l, p < 0.05; 51.0 ± 10 vs 28.5 ± 11 μg/l, p < 0.05, respectively). After the exercise programme, thrombomodulin plasma concentrations had decreased (p < 0.05) in both groups of patients, with final thrombomodulin values being similar to those observed in their control groups (38.2 ± 11 μg/l for Type I and 34.6 ± 12 μg/l for Type II patients). The thrombomodulin decrement correlated with baseline thrombomodulin and VO_2max increase in Type I diabetic patients. A decrease in tissue factor pathway inhibitor was also observed in Type II diabetic patients. Conclusion/interpretation. We conclude that the normalisation of plasma thrombomodulin concentrations in Type I and Type II diabetic patients after physical training might reflect the improvement in endothelial function associated with physical exercise. [Diabetologia (2001) 44: 693–699]     

The influence of the ACE (<Emphasis Type="Italic">I/D</Emphasis>) polymorphism on systemic and renal vascular responses to angiotensins in normotensive,normoalbuminuric Type 1 diabetes mellitus

Aim/hypothesis The renin-angiotensin-aldosterone system is important in diabetic nephropathy, with the angiotensin-converting-enzyme DD-genotype being a renal risk factor. The D-allele is associated with higher ACE concentrations, but functional consequences in diabetes mellitus are not known. To analyse these consequences, we assessed renal and systemic responsiveness to angiotensin I infusion, with the response to angiotensin II as reference.Methods Uncomplicated Type 1 (insulin-dependent) diabetic patients with contrasting genotypes (11 II and 11 DD) were studied, during low (50 mmol/24 h) and liberal (200 mmol/24 h) sodium diet, during a euglycaemic clamp. Angiotensin I was infused at 4 and 8 ng·kg^–1·min^–1, 1 h each, followed by infusions of angiotensin II after a 2-h wash-out period.Results During low sodium, DD-homozygotes showed higher blood pressure sensitivity to angiotensin I (DD 21±5% vs II 15±5%, p<0.01). With liberal sodium, no differences in blood pressure were detected, whereas angiotensin I induced a higher response of ERPF (DD 40±5% vs II 35±4%, p<0.05) and RVR (DD 105±20% and II 89±16% p<0.05) in DD-homozygotes. Differences were not explained by altered angiotensin II sensitivity. Multiple-linear regression analysis showed that angiotensin I induced responses of blood pressure and renal haemodynamics are higher in subjects carrying the DD-genotype. The magnitude of the responses was modulated by sodium intake and long-term glycaemic control.Conclusion/interpretation This study showed that responses of blood pressure and renal haemodynamics to angiotensin I are increased in diabetic subjects carrying the DD-genotype. Genotype-associated differences in ACE concentrations could, under certain circumstances, have functional consequenses in uncomplicated Type 1 diabetes mellitus.Abbreviations RAAS Renin-angiotensin-aldosterone system - ERPF effective renal plasma flow - GFR glomerular filtration rate - RVR renal vascular resistance - FF filtration fraction - MAP mean arterial pressure - PRA plasma renin activity - Ang Angiotensin     

The influence of human C-peptide on renal function and glucose utilization in Type 1 (insulin-dependent) diabetic patients

Summary The possible influence of C-peptide administration on renal function and whole body glucose utilization was examined in 11 patients (Group 1) with Type 1 (insulin-dependent) diabetes mellitus. They were given an i. v. insulin infusion during the night before the study and were euglycaemic at the time of examination. The glomerular filtration rate and effective renal plasma flow were measured by clearance techniques using constant-rate infusions of inulin and sodium para-aminohippurate. After baseline measurements C-peptide was infused during two periods of 60 min at rates of 5 and 30 pmol·kg^–1·min^–1. In a control study 0.9% NaCl was infused during two 60 min periods in ten Type 1 diabetic patients (Group 2), Glomerular filtration rate decreased by 7%(p<0.001), effective renal plasma flow increased by 3%, (p<0.05) and whole-body glucose utilization rose by approximately 25%(p<0.05) above basal during low-dose C-peptide infusion. Group 2 showed an unaltered glomerular filtration rate, effective renal plasma flow and glucose utilization during 60 min of NaCl infusion. The differences between Group 1 and Group 2 in glomerular filtration rate and glucose utilization were statistically significant. It is concluded that short-term administration of C-peptide in physiological amounts to patients with Type 1 diabetes may reduce the glomerular filtration rate and increase whole-body glucose utilization. The results suggest the possibility that short-term C-peptide administration may exert a regulatory influence on renal function and stimulate glucose utilization in Type 1 diabetic patients.     

Endothelium-dependent and independent vasodilation studied at normoglycaemia in Type I diabetes mellitus with and without microalbuminuria

Aims/hypothesis. We examined whether endothelial function is impaired in patients with Type I (insulin-dependent) diabetes mellitus under conditions of near-normoglycaemia compared with age-matched healthy control subjects. Our aim was to determine whether microalbuminuria is associated with endothelial dysfunction in Type I diabetes. Methods. Endothelial function, measured as post-ischaemic flow-mediated dilatation of the brachial artery using ultrasound, was compared among 17 microalbuminuric and 17 normoalbuminuric diabetic patients, and 17 control subjects. Glyceryl trinitrate-mediated dilatation of the brachial artery was used to measure endothelium-independent function. All diabetic patients were studied at near-normoglycaemia, using insulin and 5 % dextrose infusions to maintain blood glucose between 3.5 and 8.0 mmol/l. Results. Flow-mediated dilatation was significantly lower in microalbuminuric diabetic patients (3.2 ± 0.3 %) compared with normoalbuminuric diabetic patients (5.4 ± 0.6 %) and control subjects (7.9 ± 0.6 %, p < 0.001). Normoalbuminuric diabetic patients also had significantly lower flow-mediated dilatation than control subjects (p = 0.01). Glyceryl trinitrate mediated dilatation was significantly lower in the microalbuminuric patients compared with the control subjects (11.9 ± 1.1 % vs 20.0 ± 1.2 %, p = 0.001). Albumin excretion rate and glycated haemoglobin showed a significant negative independent correlation with flow-mediated dilatation (both p < 0.05). Conclusion/interpretation. Type I diabetic patients show endothelial dysfunction at near-normoglycaemia compared with the control subjects, and this abnormality is more marked in diabetic patients with microalbuminuria. Endothelial dysfunction in Type I diabetes is related to the albumin excretion rate and glycaemic control. The presence of endothelial dysfunction in normoalbuminuric diabetic patients suggests it could precede microalbuminuria as an early risk marker for cardiovascular disease. [Diabetologia (2001) 44: 593–601] Received: 6 November 2000 and in revised form: 11 January 2001     

Glomerular hyperfiltration in microalbuminuric NIDDM patients

Summary Glomerular hyperfiltration and microalbuminuria are both regarded as risk factors for the development of diabetic nephropathy in insulin-dependent diabetic patients. Information on glomerular hyperfiltration is scarse in microalbuminuric non-insulin-dependent diabetic (NIDDM) patients. Therefore, we performed a cross-sectional study of glomerular filtration rate (single i. v. bolus injection of ⁵¹Cr-EDTA, plasma clearance for 4 h) in 158 microalbuminuric NIDDM patients compared to 39 normoalbuminuric NIDDM patients and 20 non-diabetic control subjects. The groups were well-matched with regard to sex, age and body mass index. The uncorrected (ml/min) and the adjusted (ml · min^–1· 1.73 m^–2) glomerular filtration rate were both clearly elevated in the microalbuminuric patients: 139 ± 29 and 117 ± 24 as compared to 115 ± 19 and 99 ± 15; 111 ± 23 and 98 ± 21 in normoalbuminuric NIDDM patients and control subjects, respectively (p < 0.001). The glomerular filtration rate (ml · min^–1· 1.73 m^–2) in NIDDM patients who had never received antihypertensive treatment was also clearly elevated in the microalbuminuric patients (n = 96): 119 ± 22 as compared to 100 ± 14 and 98 ± 21 in normoalbuminuric NIDDM patients (n = 27) and control subjects (n = 20), respectively (p < 0.001). Glomerular hyperfiltration (elevation above mean glomerular filtration rate plus 2 SD in normoalbuminuric NIDDM patients) was demonstrated in 37 (95 % confidence interval 30–45)% of the microalbuminuric patients. Multiple regression analysis revealed that HbA_{1 c}, 24-h urinary sodium excretion, age and known duration of diabetes were correlated with glomerular filtration rate in microalbuminuric NIDDM patients (r ² = 0.21, p < 0.01). Our cross-sectional study indicates that NIDDM patients at high risk of developing diabetic nephropathy are also characterized by an additional putative risk factor for progression, glomerular hyperfiltration. [Diabetologia (1996) 39: 1584–1589]     

The effect of low-dose dopamine on renal haemodynamics in patients with type 1 (insulin-dependent) diabetes does not differ from normal individuals

Summary It is well known that patients with Type 1 (insulin-dependent) diabetes exhibit both increased glomerular filtration rate and effective renal plasma flow, which can be found even when these patients are well controlled. Usually this is attributed to a decrease in renal vascular resistance and/or to enlarged kidney size and glomerular volume. Among the factors which govern glomerular filtration rate, renal plasma flow is most important. Renal plasma flow increases if renal vascular resistance decreases. The latter might exist in insulin-dependent diabetes mellitus because of either a predominantly afferent or a predominantly efferent vasodilatation. Dopamine is an agent which causes predominantly efferent vasodilatation. Therefore, the effects of infusing a low dose of dopamine on glomerular filtration rate and effective renal plasma flow in 12 well-controlled patients with Type I (insulin-dependent) diabetes and 28 healthy volunteers were compared to investigate whether the increased glomerular filtration rate in Type 1 diabetes is caused by an efferent vasodilatation. The median increase in glomerular filtration rate during dopamine infusion amounted to 13.0% in diabetic patients and 12.5% in healthy control subjects (n. s.). It is concluded that the elevated glomerular filtration rate in well-controlled Type 1 diabetes is not caused by a predominantly efferent vasodilatation.     

Erythrocyte Na/K ATPase activity and diabetes: relationship with C-peptide level

Summary Erythrocyte Na/K ATPase activity is decreased in Type I diabetic patients; for Type II diabetic patients, literature data are controversial. Therefore, we have compared this enzymatic activity in 81 patients with Type I diabetes mellitus, 87 with Type II diabetes mellitus and 75 control subjects. Mean erythrocyte Na/K ATPase activity was lower in the Type I diabetic patients (285 ± 8 nmol Pi · mg protein^–1· h^–1) than in the control subjects (395 ± 9 nmol Pi · mg protein^–1· h^–1) whereas that of the Type II diabetic patients did not differ from that of control subjects. Sex, age, body mass index, and HbA_{1 c} levels did not influence erythrocyte Na/K ATPase activity. The 25 Type II diabetic patients treated with insulin, however, had lower Na/K ATPase activity than the 62 on oral treatment (264 ± 18 vs 364 ± 16 nmol Pi · mg protein^–1· h^–1, p < 0.001) but similar to that of Type I diabetic patients. Among the Type II diabetic patients, stepwise regression analysis showed that fasting C-peptide level was the only factor independently correlated with Na/K ATPase activity; it explained 23 % of its variance. In fact, in the insulin-treated patients, those with almost total endogenous insulin deficiency (C-peptide < 0.2 nmol · l^–1) had the lower Na/K ATPase activity (181 ± 21 vs 334 ± 17 nmol Pi · mg protein^–1· h^–1, p < 0.0001). The biological effects of treatment with C-peptide have recently led to the suggestion that this peptide could have a physiological role through the same signalling pathway as insulin, involving G-protein and calcium phosphatase and thus restoring Na/K ATPase activity. The relationship we describe between endogenous C-peptide and this activity is a strong argument for this physiological role. [Diabetologia (1998) 41: 1080–1084] Received: 6 November 1997 and in final revised form: 10 April 1998     

Proximal glomerulo-tubular balance in patients with Type 1 (insulin-dependent) diabetes mellitus

Summary To evaluate the glomerulo-tubular balance of sodium and water in the proximal tubules of diabetic patients with elevated glomerular filtration rate, the renal plasma clearance of lithium and the glomerular filtration rate (⁵¹Cr-EDTA plasma clearance) were determined simultaneously in 11 ambulatory Type 1 (insulin-dependent) diabetic patients (aged 25–35 years) with no evidence of diabetic nephropathy and in 10 age-matched healthy subjects. The renal plasma clearance of lithium, which is a measure of flow from the proximal tubule into the thin descending limb of the loop of Henle, did not differ between diabetic and control subjects (28.9±4.0 versus 28.3±5.1 ml/min per 1.73m² surface area, mean±SD), whereas the glomerular filtration rate in the diabetic patients was significantly higher than in the control sub jects (136±10.2 versus 108±13.6 ml/min per 1.73m², p< 0.001). The same held true for the fractional reabsorption rate in the proximal tubules (78.7±3.2 versus 73.6±4.9%, p< 0.02). The results indicate that the elevation of the glomerular filtration rate in diabetic patients is associated with a parallel increase in the proximal reabsorption rate. This type of glomeralo-tubular balance implies that the flow of water and flux of sodium to the segments distal to the proximal tubule are kept constant during variations in the glomerular filtration rate.     

Evidence of changes in renal charge selectivity in patients with Type 1 (insulin-dependent) diabetes mellitus

Summary Altered filtration of macromolecules due to decreased electrical charge of the glomerular basement membrane might be the initial step in the development of albuminuria in patients with Type 1 (insulin-dependent) diabetes mellitus. We therefore investigated the selectivity index, i. e. renal clearance of non-glycated plasma albumin/clearance of glycated plasma albumin in 38 patients with Type 1 diabetes mellitus. The two albumin molecules differed slightly in charge, non-enzymatic glycated albumin being more anionic at physiological pH compared with unmodified plasma albumin. Glycated albumin in plasma and urine was determined by a specific, sensitive and highly reproducible chromatographic procedure. In diabetic patients with normal urinary albumin excretion, the selectivity index was increased threefold compared with that of non-diabetic subjects (2p< 0.01). A significant correlation (r=0.53, 2p < 0.01) between haemoglobin A_1c and selectivity index was demonstrated in these patients, indicating a change in charge-dependent renal filtration could possibly be attributed to non-enzymatic glycation of components in the glomerular basement membrane and tubuli. Diabetic patients with increased albumin excretion rate had a significantly lower selectivity index compared with patients with normal albumin excretion (2p < 0.01). A significant negative correlation (r=0.85, 2p <0.001, exponential curve fit) was seen between urinary albumin excretion and selectivity index in the diabetic patients, indicating that the capability of differentiating between macromolecules of different charges is again lost with increasing urinary albumin excretion.In conclusion, the selectivity index is significantly increased in Type 1 diabetic patients with normal urinary albumin excretion, possibly due to non-enzymatic glycation of structural glomerular proteins. The selectivity index is again reduced with increasing urinary albumin excretion, possibly due to structural changes different from non-enzymatic glycation. This observation is in accordance with the hypothesis that loss of anionic charges due to reduced heparan sulphate content in glomerular basement membranes plays an important role in the early stages of diabetic renal disease.     

Renal autoregulation is normal in newly diagnosed, normotensive, NIDDM patients

Summary Abnormalities of renal autoregulation with glomerular hyperfiltration and raised intraglomerular pressure have been suggested as important factors in the initiation and development of diabetic nephropathy. Angiotensin converting enzyme (ACE) inhibition appears to have a specific reno-protective role in diabetic nephropathy, possibly by reducing intraglomerular pressure. The acute effects of ACE inhibition on renal haemodynamics in normotensive, non-insulin-dependent diabetes mellitus (NIDDM) have not been previously reported. We measured simultaneous glomerular filtration rate (GFR) and renal plasma flow (RPF) in 29 (4 female) subjects, mean age 52 years (range 27–70), using ⁵¹Cr EDTA and ¹²⁵I Hippuran. Clearances were corrected to 1.73 m^–2. All patients were normotensive (blood pressure < 75^th centile for age and sex), newly diagnosed ( < 30 days), taking no antihypertensive or hypoglycaemic medication. Subjects were randomly allocated (double blind) to receive the ACE inhibitor trandolapril 4 mg day^–1 (H) (hypotensive dose), trandolapril 0.5 mg day^–1 (L) (non-hypotensive dose) or placebo (P) for 10 days after which renal haemodynamics were remeasured. For all subjects baseline GFR, RPF and filtration fraction (FF) were 97 ± 21 ml min^–1 mean ± SD, 439 ± 120 ml min^–1 and 22.3 ± 2.9 % respectively. Glomerular hyperfiltration (GFR > 120 ml min^–1) was only demonstrated in 3 subjects (10.3 %). In group H mean arterial pressure (103 ± 8 vs 93 ± 9 mmHg, p < 0.001) and FF (23.8 ± 2.3 vs 20.0 ± 4.0 %, p = 0.03) fell while RPF increased (376 ± 111 vs 426 ± 60 ml min^–1, p = 0.02), there was no significant change in GFR. No significant change in mean arterial pressure, GFR, RPF or FF occurred in groups P and L. These studies suggest that in newly diagnosed normotensive NIDDM subjects normal renal autoregulation occurs and glomerular hyperfiltration is uncommon. [Diabetologia (1998) 41: 206–211] Received: 2 July 1997 and in revised form: 16 September 1997     

Atrial natriuretic peptide in Type 2 diabetes mellitus: response to a physiological mixed meal and relationship to renal function

Relatively few data exist on atrial natriuretic peptide (ANP) characteristics in Type 2 diabetes mellitus (DM). Therefore, plasma immunoreactive ANP concentrations were measured before and for 4 h following the ingestion of a physiological mixed meal in 8 newly diagnosed, normotensive, normoalbuminuric, patients with Type 2 DM and 6 normotensive, non-diabetic controls. In patients with Type 2 DM, basal plasma ANP concentrations were 4.0 ± 2.0 and not significantly changed following ingestion of the meal, with peak levels of 4.9 ± 2.8 pmol l⁻¹. Non-diabetic controls had higher basal plasma ANP concentrations, 8.7 ± 3.4 pmol l⁻¹ (p < 0.05), significantly increasing to a peak of 11.9 ± 6.3 pmol l⁻¹ at 30 min post meal. Extracellular fluid volume (ECV) was not different between diabetic patients and controls (15877 ± 2679 vs 13668 ± 1792 ml³). Glomerular filtration rate (GFR) (isotopic clearance corrected for body surface area) was elevated in diabetic patients (mean ± SD) 130 ± 39 vs 98 ± 10 ml min⁻¹, p < 0.05). For the DM subjects, basal ANP levels were negatively correlated with GFR (r_s − 0.74, p < 0.05) and effective renal plasma flow (ERPF) (r_s − 0.8, p < 0.05). We conclude that patients with Type 2 DM demonstrate reduced basal plasma ANP concentrations which are inversely correlated to renal function. In contrast to non-diabetic controls, ANP in Type 2 DM does not rise in response to feeding. © 1998 John Wiley & Sons, Ltd.     

Increased Proximal Tubular Sodium Reabsorption in Hypertensive Patients with Type 2 Diabetes

Hyperinsulinaemia and sodium retention have been studied in 22 Type 2 diabetic patients (10 normotensive, 12 hypertensive) and 10 normal control subjects matched for age, sex, and body mass index. Exchangeable sodium was similar in the three groups. Plasma renin activity and plasma angiotensin II were lower in both groups of diabetic patients than in the normal control subjects (p<0.01). Plasma atrial natriuretic peptide was increased in the hypertensive patients (7.3 ± 1.1 vs normotensive 4.7 ± 1.1 pmol I^?1 and control 4.0 ± 0.2 pmol I^?1, p<0.01). Fractional lithium clearance, a measure of sodium clearance from the proximal tubule, was decreased (18.5 ± 1.4, p<0.01) and fractional excretion of sodium in the distal tubule was increased (6.66 ± 0.66, p<0.01) in untreated hypertensive diabetic patients compared with both normotensive diabetic patients (25.3 ± 1.6 and 3.96 ± 0.52 respectively) and normal control subjects (25.2 ± 2.9 and 3.31 ± 0.38, respectively). Fasting serum insulin was higher in hypertensive than in normotensive diabetic patients (18.5 ± 3.0 vs 10.7 ± 1.1 mU I^?1, p<0.01) and higher in both groups than in normal control subjects (5.6 ± 0.1 mU I^?1, both p<0.01). Creatinine clearance was higher in both groups of diabetic patients than in normal control subjects (p<0.05). Thus there appears to be increased proximal renal tubular sodium reabsorption in these hypertensive Type 2 diabetic patients, matched by a reduction in distal sodium reabsorption so that net sodium excretion was maintained. This was associated with fasting hyperinsulinaemia.     

Juxtaglomerular apparatus T-cell infiltration affects glomerular structure in Type 1 diabetic patients

Aims/hypothesis Type 1 diabetes is an autoimmune disorder associated with T-cell mediated injury to multiple endocrine tissues. T-cell infiltration of the juxtaglomerular apparatus could be associated with changes in local renin angiotensin system activity and, thus, with changes in the renal microenvironment. We examined the frequency of juxtaglomerular apparatus T-cell infiltration early in Type 1 diabetes and tested whether this is associated with renal structure and function.Methods We classified 89 Type 1 diabetic patients by immunohistochemical analysis as either juxtaglomerular apparatus T-cell positive (n=37) or T-cell negative (n=38). Borderline cases (n=14) were not considered further.Results T-cell positive patients had a shorter duration of diabetes (6.7±2.5 years) than T-cell negative patients (9.2±5.0 years, p=0.011) and lower albumin excretion rate, but they had a similar glomerular filtration rate and blood pressure. Renal biopsy morphometric analysis showed similar glomerular basement membrane width and mesangial fractional volume in these two groups. However, glomerular capillary surface density (p=0.0012) and filtration surface per glomerulus (p=0.0155) were greater in the T-cell positive patients.Conclusion/Interpretation Increased filtration surface per glomerulus could be associated with glomerular filtration rate preservation in diabetes. Thus, juxtaglomerular apparatus immunologic injury in Type 1 diabetes patients could delay the clinical consequences of diabetic nephropathy.Abbreviations ECM Extracellular matrix - RAS renin-angiotensin-system - JGA juxtaglomerular apparatus - NHDN natural history of diabetic nephropathy - IP immunoperoxidase - GV mean glomerular volume - TGF-B transforming growth factor-B - Vv(Mes/glom) mesangial fractional volume per glomerulus - GBM glomerular basement membrane - Sv(PGBM/glom) surface density of the peripheral glomerular capillary perglomerulus - TFS total filtration surface per glomerulus - Vv(Int/cortex) fractional volume of renal cortical interstitium See the Acknowledgements for the list of investigators of the International Diabetic Nephropathy Study Group (IDNSG)     

Relationship of renal size to nephropathy in Type 1 (insulin-dependent) diabetes

Summary Thirty-five patients with Type 1 (insulin-dependent) diabetes mellitus and 90 normal subjects had renal size (renal area index) determined by X-ray and also had examination of renal biopsies by light and electron microscopy. Renal area index of 206±32 cm²/1.73 m² (mean±SD) in the Type 1 diabetic patients exceeded that in the normal subjects (180±25 cm²/1.73 m², p<0.001). In the diabetic patients, the renal area index correlated with creatinine clearance (r=+0.43, p<0.05), but did not correlate with urinary albumin excretion, or the electron microscopic measurements of percentage total mesangium and glomerular basement membrane width. In diabetic patients with clinical nephropathy or severe glomerulopathy on biopsy, the kidneys may remain large. Thus, renal size does not indicate the severity of diabetic renal lesions on biopsy.     

Effects of Long-term Enalapril Treatment on Persistent Microalbuminuria in Normotensive Type 2 Diabetic Patients: Results of a 4-year,Prospective, Randomized Study

The beneficial effect of long-term treatment with an angiotensin-converting enzyme (ACE) inhibitor on urinary microalbumin excretion (UAE) and renal function was investigated in a 4 year, randomized prospective study in normotensive patients with non-insulin-dependent (Type 2) diabetes mellitus. Sixty-two normotensive patients with Type 2 diabetes mellitus and microalbuminuria but normal renal function were randomized to receive either enalapril 5 mg day⁻¹ or no treatment. In the enalapril-treated patients, UAE was reduced from 115.4 ± 80.1 to 95.6 ± 61.7 mg 24 h⁻¹ after 12 months (p<0.05) and to 75.3 ± 44.8 mg 24 h⁻¹ after 48 months (p<0.001). In the untreated group, UAE increased slowly from 93.9 ± 69.9 to 150.0 ± 144.5 mg 24 h⁻¹ after 48 months. No changes in creatinine clearance, blood pressure or HbA_1C were seen in either group during the 4-year period. In normotensive Type 2 diabetic patients with early stage of diabetic nephropathy, the ACE inhibitor enalapril may have a beneficial effect by decreasing microalbuminuria. This effect is long-lasting and probably independent of the antihypertensive action of the drug.