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This prospective cohort study evaluates associations between structural and ultrastructural parameters in baseline biopsies from human kidney transplants and long-term graft survival after more than 14 years’ follow-up. Baseline kidney graft biopsies were obtained prospectively from 54 consecutive patients receiving a kidney transplant at a single institution. Quantitative measurements were performed on the baseline biopsies by computer-assisted light microscopy and electron microscopy. Stereology-based techniques estimated the fraction of interstitial tissue, the volume of glomeruli, mesangial fraction, and basement membrane thickness of glomerular capillaries. The fraction of occluded glomeruli and scores according to the Banff classification were achieved. Kidney graft survival was analyzed by Kaplan–Meier estimates and Cox regression. Association to long-term kidney function was also analyzed. The long-term surviving kidney transplants were characterized at implantation by less arteriolar hyaline thickening (P < 0.001) and less interstitial fibrosis (P = 0.001), as well as a lower fraction of occluded glomeruli (P = 0.004) and lower glomerular volume (P = 0.03). At the latest follow-up, eGFR was decreased by 12 ml/min/1.73 m2 per unit increase in the score for arteriolar hyalinosis at implantation (P = 0.02), and eGFR was decreased by 19 ml/min/1.73 m2 per 106 μm3 increase in glomerular volume at baseline (P = 0.03). The unbiased Cavalieri estimate of glomerular volume and the ultrastructural parameters are the first to be evaluated in a cohort study with prospective follow-up for more than 14 years. The study shows that baseline biopsies from human kidney grafts contain extraordinary long-term prognostic information, and it highlights the importance of these intrinsic graft factors.

Background. The aim of the study was to evaluate how well a biopsy from one region of a human renal allograft represented biopsies from other regions regarding the renal interstitial tissue assessed by stereology. Furthermore, we wanted to evaluate the reproducibility of the measurements. Methods. Punch biopsies (3 mm) from six regions in each kidney were obtained from seven explanted renal grafts with varying degrees of clinically diagnosed chronic and acute rejection. One kidney, removed for a minor pelvic tumour, served as reference material. Using point counting on PAS-stained sections, the volume fraction of the interstitial tissue per glomerular cortex VV(interstitiumucortex) was estimated. From each kidney, two of the six biopsies were re-evaluated by the same observer. Results. VV(interstitiumucortex) varied from 0.25 to 0.78 between the explanted kidneys vs 0.26 in the reference kidney. Variations within the kidneys were low, expressed by standard deviations (SD) of between 0.04 and 0.06, and coefficients of variation (CV) between 0.06 and 0.22. The SD estimated from repeated measurements was 0.04 and CV was 0.07. Conclusions. Biopsies from one region of the kidney were found to be representative for estimates of interstitial tissue in explanted human kidney grafts, and the degree of reproducibility was high when using point counting, as in the present study.

Aim: To determine the long-term changes of the juxtaglomerular apparatus in incipient diabetic nephropathy. Methods: Three renal needle biopsies were performed on 15 young type 1 diabetic patients with microalbuminuria; at baseline and after an average of 2.4 and 8.2 years. Using light microscopy, 1 μm serial sections of the plastic-embedded biopsies were investigated and volumes of the juxtaglomerular apparatus and glomerulus and areas of the macula densa and lumina of the afferent and efferent arterioles were measured. Results: From baseline to second follow-up there was a significant decrease in JGA relative to glomerular volume. There was an increase in luminal area of the efferent arteriole which was paralleled by (non-significant) changes in the afferent arteriole. Conclusion: Over a period of 8.2 years JGA size remained stable, but decreased relative to glomerular size. Also, an increase in luminal area was noted in efferent arterioles. This may be due to increased single nephron blood flow secondary to nephron loss.

Background: Our goal was to investigate the effect of antihypertensive drugs on the juxtaglomerular apparatus (JGA) in young type-1 diabetic patients with microalbuminuria. Methods: Twelve patients were allocated to treatment with either an angiotensin-converting enzyme inhibitor (group 1, six subjects) or a beta-receptor blocker (group 2, six subjects). A comparable group of nine patients without antihypertensive treatment provided reference values (group 3, nine subjects). Renal biopsies were taken at baseline and after a median of 40 months (groups 1 and 2) and 30 months (group 3). Using light microscopy with 1-µm serial sections of the plastic-embedded biopsies, volumes of the JGA and glomerulus and areas of the macula densa and lumina of the afferent and efferent arterioles were obtained. Results: A significant decrease of the volume of the JGA (P=0.026) and of the volume of the JGA relative to that of its corresponding glomerulus (P=0.0005) was noted in the reference group only. Negative correlations existed between the increase in the luminal area of the afferent arteriole and mean diastolic blood pressure in the study period in group 1 (P=0.024) and group 2 (P=0.032). Conclusions: Our results showed that a decrease in the size of the JGA is offset by antihypertensives. The negative correlation between the change in the luminal area of the afferent arteriole and mean diastolic blood pressure in groups 1 and 2 suggest that renal protection in antihypertensive treatment may be through a better constriction of the afferent arteriole protecting the glomerulus from systemic blood pressure.

Glomerular structural modifications were measured in kidney biopsies from two follow-up studies in type-1 diabetic patients with microalbuminuria and in kidney donors. Stereologic methods were used to obtain data on glomerular composition and absolute quantities per glomerulus to supplement data on diabetic glomerulopathy previously published. Diabetic patients at baseline (n=37) showed significant changes compared with controls (n=11). The volume fraction of tuft/glomerulus was increased, the proportion of capillary surface facing peripheral basement membrane was decreased (0.72±0.04 vs 0.77±0.03, P=0.0008), the ratio of mesangial surfaces, urinary/capillary, was decreased (0.67±0.17 vs 1.11±0.28, P

ity may develop as a consequence of a long-standing diabetic glomerulopathy and might lead to less proBackground. Diabetic nephropathy is associated with renal structural changes involving all of the compart- nounced elevation of albumin excretion. ments. Most characteristic is the diabetic glomerulopa- Key words: diabetic glomerulopathy; glomerular vascuthy. Studies of the histological changes during the early lar pole; juxtaglomerular arterioles; microalbuminuria; phases of nephropathy have included the glomerulopa- neovascularization thy and also the juxtaglomerular structures. Neovascularization, well-known in diabetic retinopathy, has also been observed in the kidney. The present study concerns estimates of frequency of neovasculariz- Introduction ation at the vascular pole region in early stages of diabetic nephropathy. The diabetic angiopathy as first described by Lundbaek Methods. Extra eVerent arterioles at the glomerular [1] aVects the vascular beds all over the body. The vascular pole were detected during measurements of involvement of the smallest blood vessels, the microanthe vascular pole area applying 1-mm serial sections giopathy, is well known in its localization to the retinal through kidney biopsies. It was observed that more and renal capillaries. One special appearance of the than one eVerent arteriole existed occasionally. The diabetic retinopathy is the proliferative stage defined present study was carried out with the aim of estimating by the new vessel formation. the frequency of this phenomenon in diabetic patients Neovascularization at the glomerular vascular pole and in non-diabetic controls, the diabetic patients in diabetic patients has been described a few years ago categorized according to the level of albumin excre- [2]. A very comprehensive study of a few cases includtion rate. ing three-dimensional reconstruction showed elegantly Results. Neovascularization was first observed in IDDM the formation of new vessels connecting the glomerular patients with microalbuminuria. Some of the cases pre- tuft with the interstitial blood vessels. sented the phenomenon in all of the glomeruli studied. The present report deals with registration of the As the examinations of many kidney biopsies continued frequency of this particular neovascularization in insuthe phenomenon was observed also in the non-diabetic lin-dependent diabetic patients (IDDM patients) with control group and in one IDDM patient with normoal- the main focus on patients with microalbuminuria. buminuria. However, the frequency was statistically The observations are based on serial sectioning of highly significantly increased in patients with elevated kidney biopsies. This procedure was established in our albumin-excretion. Within this group a strong correla- laboratory primarily to obtain sampling of several tion between frequency of neovascularization and the levels of glomeruli for electron microscopy for a better severity of diabetic glomerulopathy is seen. estimate of mesangial volume fraction during early Conclusions. The vascular abnormality localized to the stages of nephropathy [3]. Next, the serial sections vascular pole region is observed occasionally in the were used for the estimation of glomerular volume and normal kidney, but the frequency is increased in the vascular pole area [4]. With these procedures patients with diabetic glomerulopathy. The abnormal- examination of many vascular pole regions was per

Kidney biopsies from 15 insulin-dependent diabetes mellitus (IDDM) patients with microalbuminuria were investigated to obtain quantitative data on the juxtaglomerular apparatus. The IDDM patients were young and normotensive with a mean duration of microalbuminuria of 2 years. Eight healthy kidney donors served as controls. Measurements taken by light microscopy, using 1-microm serial sections of epon blocks, included volumes of the juxtaglomerular apparatus and of glomeruli, areas of the macula densa and luminal area of the juxtaglomerular (afferent and efferent) arterioles at the level of the glomerular vascular pole. The volume of the juxtaglomerular apparatus was significantly larger in the IDDM group than in controls [6.08 (2.96-18.8) 10(4) microm3 vs 3.48 (1.84-5.21) 10(4) microm3, P=0.003, median and (range)], as was the volume of the juxtaglomerular apparatus relative to glomerular volume [1.89(1.28-4.21)% vs 1.48 (1.13-1.71)%, P=0.004]. The area of the macula densa was also larger in the IDDM patients (1370 microm2 vs 937 microm2, P=0.03). Luminal areas of the afferent and efferent arterioles and the ratio between them did not differ significantly between the two groups. In conclusion, the juxtaglomerular apparatus is enlarged more than would be expected from the glomerular hypertrophy in IDDM patients with microalbuminuria.

The key change in diabetic glomerulopathy is accumulation of extracellular material. Basement membrane thickening and matrix expansion develop concomitantly. In insulin-dependent diabetic patients persistent microalbuminuria is associated with an early stage of glomerulopathy. Albuminuria in non-insulin-dependent patients does not always reflect glomerulopathy. Renal and glomerular hypertrophy in the early stages of insulin-dependent diabetes mellitus is unlikely to play a dominant role in the development of glomerulopathy. Loss of capillary surface, closely associated with loss of glomerular function, is only partly explained by mesangial expansion--glomerular occlusion plays an important role. Possible mechanisms of albuminuria are qualitative changes of the basement membrane, eg, loss of proteoglycans and excess glycosylation; epithelial cell changes; new vessel formation; remodeling of glomerular structures; and impeded function of juxtaglomerular arterioles. The interplay among abnormalities in individual compartments of the diabetic kidney should be explored.

Glomerular structure in type-1 (insulin-dependent) diabetic patients with normo- and microalbuminuria. Kidney biopsies from 15 type-1 (insulin-dependent) diabetic patients with a range of albumin excretion (AER) were analyzed. Nine patients had normal AER, and six had microalbuminuria. Basement membrane thickness, BMT, and mesan-gial matrix volume fraction, Vv(mat/glom), were obtained from at least three glomeruli per biopsy. Mesangial structures were estimated with electron microscopic analysis at three levels in each glomerulus. Glomerulopathy parameters were significantly increased in micro-versus normoalbuminuric patients with the following means and (CV): BMT 571 nm (0.12) and 442 nm (0.25), = 0.03; Vv(mes/glom) 0.31 (0.20) and 0.22 (0.14), = 0.002; Vv(matrix/glom) 0.17 (0.25) and 0.11 (0.28), = 0.006; matrix star volume 56 3 (0.47) and 22 ^m3 (0.43), = 0.02. A positive correlation obtained between AER and each of the glomerulopathy parameters, BM thickness, Vv(mes/glom) and Vv(ma-trix/glom), as well as between AER and a structural index expressing the sum of changes in the peripheral BM and in the mesangium (r = 0.62, = 0.01). The results indicated a parallel course of mesangial and peripheral BM changes: a positive correlation obtained between BM thickness and mesangial parameters [BMT versus Vv(matrix/glom): r -0.82, = 0.0001] and the ratio of the two subsets of glomerular BM material (PBM:matrix) did not show significant difference between normo- and microalbuminuric groups. The data give strong support to the contention that the transition from normo- into the microalbuminuric phase is linked to progressing glomerulopathy.

Kidney biopsies from 14 insulin-dependent diabetes mellitus patients with persistent albuminuria were studied by light and electron microscopy. In terms of kidney function, the patients spanned stages from early to advanced nephropathy. The clinical parameters were (ranges, with medians in parentheses) urinary albumin excretion (UAE) 158–5494 μg/min (1153 μg/min), glomerular filtration rate (GFR) 30–128 ml · min −1 · 1.73 m−2 (90 mh ml · min−1 · 1.73 m−2) and mean arterial blood pressure () 87–122 mmHg (109 mmHg). The severity of clinical nephropathy (UAE, GFR, and BP together) correlated with an index of the structural lesions (basement membrane [BM] thickness, mesangial expansion, and glomerular occlusion together; r = 0.62, 2P < 0.05). GFR compared with remnant surface of glomerular capillaries (filtration surface; FS) gave values of r = 0.72 and 2P = 0.004, and UAE compared with the percentage of the peripheral BM surface carrying fluffy loose intrinsic fine structure gave r = 0.62 and 2P = 0.02. BP per se did not correlate with structural parameters. The area of FS per open glomerulus did not decrease with increasing mesangial volume fraction, which indicates compensatory changes of the capillaries in early and advanced stages of glomerulopathy. In 7 patients with

The effects of long-term lithium administration on glomerular structure and intervention with angiotensin converting enzyme inhibitor (ACEI) were studied in rats. Male Wistar rats were fed a lithium-containing diet (Li) or control diet (C) for 16 weeks postnatally. Li-treated rats developed renal failure, hypertension and proteinuria. During the subsequent 24 weeks, subgroups were treated with ACEI. The kidneys were fixed by perfusion, and tissue blocks were serially cut for estimation of glomerular volume and glomerular characteristics by light microscopy. Mesangial and mesangial matrix volume fractions, surface density of capillary walls, basement membrane thickness and foot process width (FPW) were measured by electron microscopy. Glomerular volume was decreased in Li-rats, with increased intra-individual variation. In all Li-rats, some glomeruli (mean 27%) were abnormal, with severe changes in only three rats. Ultrastructural parameters obtained by systematic sampling of three glomeruli in each rat showed no differences among groups. Among Li-treated animals there was a significant correlation between FPW and albumin excretion per unit filtration surface, and between filtration surface per glomerulus and inulin clearance. In conclusion, long-term lithium administration to newborn rats caused marked changes in glomerular volume which were not associated with measurable changes in structural parameters. No effect of ACEI-treatment was detectable.

Associations between early stages of diabetic nephropathy and structural changes is far from clarified since some reports present rather marked changes in patients in the preclinical stage whereas others found very moderate changes in the early stage of nephropathy. Hence the issue is still a challenge to further studies. This chapter concentrates on the renal morphological changes in patients with Type 1 diabetes and early nephropathy and the possibilities of influencing the progression by blood glucose control and antihypertensive treatment.

Objective To investigate the effect of nitrendipine on the development of renal changes in experimental diabetes. Design Streptozotocin (STZ)-induced diabetic normotensive Wistar rats (WIS) and spontaneously hypertensive rats (SHR) were randomly allocated to nitrendipine treatment (250 mg/kg fodder) or placebo treatment for 6 months. Methods Blood pressure was assessed by the tail-cuff method, urinary albumin excretion (UAE) was determined, and glomerular basement membrane (GBM) thickness, mesangial volume, and mean glomerular volume (MGV) were estimated by morphometric measurements. Results In diabetic WIS, nitrendipine significantly reduced UAE after 2 months of treatment (P< 0.05), while no effect was was seen after 4-6 months. In diabetic SHR, no effect on UAE was seen at any time. Nitrendipine was unable to inhibit the renal and glomerular enlargement in diabetic WIS and SHR. Diabetes plus hypertension was associated with significant increase in GBM thickness, while diabetes or hypertension alone showed no significant increase in GBM. Nitrendipine treatment was unable to prevent increased GBM in diabetic SHR. Conclusion Nitrendipine inhibits an early increase in UAE in normotensive, diabetic rats, but fails to sustain this effect in long-term diabetes. No effect of nitrendipine was observed in SHR.

Antihypertensive drugs can slow or even reverse the progression of diabetic nephropathy at the microalbuminuric stage. This study was performed to obtain quantitative data on changes in the renal arterioles in a follow-up study. Twelve patients with type I diabetes and with microalbuminuria were allocated to treatment for 3 years with either an ACE inhibitor (group I, 6 patients) or a beta blocker (group II, 6 patients). Baseline and follow-up renal needle biopsy specimens were taken and serially sectioned at 1 microm for light microscopy, enabling identification of arterioles as afferent or efferent. Thin sections for electron microscopy were made at 50-microm intervals, and micrographs were taken of arteriolar profiles. Matrix volume fraction of the media and a calculated matrix thickness were obtained. At baseline, structural parameters were higher than normal values. At follow-up all patients were normoalbuminuric. Both groups showed only minor changes in arteriolar structures over 3 years. In the afferent arterioles in group II there was a significant increase in the matrix volume fraction of the media, and there was a tendency to an increase in matrix thickness in both groups. In the efferent arterioles there were no significant changes in parameters. There were no differences between the two groups in arteriolar structural changes from baseline to follow-up. Thus, this study shows a slight but significant matrix accumulation in the afferent arterioles during treatment with antihypertensive drugs. This may have implications for the progression to overt nephropathy, which indicates a need for more long-term studies of treatment with antihypertensive drugs in incipient nephropathy in type I diabetes.

The efficacy of the calcium channel blocker nitrendipine in preventing early renal and glomerular hypertrophy and increased urinary albumin excretion (UAE) was studied in experimental diabetes in rats, starting treatment at the onset of diabetes. Female Wistar rats were randomised into four groups: diabetic and non-diabetic rats were given either placebo or nitrendipine (250 mg/kg) in the diet for 8 weeks. After 8 weeks the kidneys in the diabetic animals had increased significantly compared to the non-diabetic controls. In the diabetic nitrendipine-treated animals renal and glomerular hypertrophy was significantly smaller than in the diabetic placebo-treated group (p < 0.05). After an initial increment within the first week, the UAE remained constant throughout the study period in the diabetic nitrendipine-treated animals, while a steady increase was seen in the diabetic placebo-treated group (p < 0.05). No differences were seen in systemic blood pressure between calcium- channel-blocker-treated groups and placebo-treated groups. In conclusion, administration of nitrendipine to diabetic rats for 8 weeks had a significant inhibitory effect on renal and glomerular hypertrophy, and showed a tendency towards a reduction in UAE (p = 0.06) without affecting metabolic control or systemic blood pressure.

Associations between early stages of diabetic nephropathy and structural changes is far from clarified. Some reports present rather marked changes in patients in the preclinical stage whereas others found very moderate changes in the early stage of nephropathy. Hence the issue is still a challenge to further studies. This chapter concentrates on the renal morphological changes in patients with insulin dependent diabetes mellitus (IDDM) and early nephropathy and the influence of blood glucose control on these structural changes. Associations between early stages of diabetic nephropathy and structural changes is far from clarified. Some reports present rather marked changes in patients in the preclinical stage whereas others found very moderate changes in the early stage of nephropathy. Hence the issue is still a challenge to further studies. This chapter concentrates on the renal morphological changes in patients with insulin dependent diabetes mellitus (IDDM) and early nephropathy and the influence of blood glucose control on these structural changes.

OBJECTIVE To evaluate the impact of glycemic control, blood pressure, lipid levels, glomerular filtration rate (GFR), age, and duration of IDDM on the degree of structural glomerular changes in the transitional stage of microalbuminuria. RESEARCH DESIGN AND METHODS Fifteen adolescents (seven boys and eight girls) with > 5 years of duration of IDDM and with low-grade microalbuminuria (15–30 micrograms/min) participated. Seventeen living kidney donors served as healthy control subjects. Five-year mean HbA1c; 5-year mean systolic and diastolic blood pressure; GFR, cholesterol, and triglycerides 2–5 years before renal biopsy; age; and duration of IDDM were investigated and related to basement membrane thickness (BMT), mesangial and matrix volume fractions, and the overall glomerulopathy index [(BMT/10 + mat/glom, %) + matrix star volume]. RESULTS BMT and the overall diabetic glomerulopathy were increased in diabetic patients as compared with control subjects (P < 0.001), whereas matrix volume fraction, but not mesangial volume fraction, tended to be increased (P = 0.11). In multivariate analysis, BMT was predicted by 5-year mean HbA1c, diabetes duration, and previous GFR (R2 = 0.71, P = 0.003). With matrix volume fraction as the dependent variable, BMT and diabetes duration were the only significant determinants (R2 = 0.63, P = 0.003). Diabetes duration, 5-year mean HbA1c, and GFR were the variables with an independent influence on the overall diabetic glomerulopathy index (R2 = 0.72, P = 0.003). Preceding blood pressure and lipid levels or age had no significant independent influence on these morphometric measures. CONCLUSIONS In the very early stage of microalbuminuria in IDDM adolescents, a high percentage of the variation in BMT and overall severity of glomerulopathy is explained by prolonged hyperglycemia and diabetes duration. Previous glomerular hyperfiltration may also add to the prediction of these morphological changes.

Since the term »microalbuminuria« (MA) was coined in 1982 [1] elevated albumin excretion rate has been regarded as the best indicator to signal early diabetic nephropathy [2–5]. Two main aspects of renal function at this stage of diabetic nephropathy, are the relation to glomerular structure and the impact of blood glucose control. Improved blood glucose control has been shown to reduce the risk of developing overt nephropathy in patients with MA [6,7] and retard the progression of AER [8], but the concomitant ultrastructural changes were not investigated.

Biopsies taken at the time of renal transplantation in 12 non-diabetic and 23 diabetic patients were studied by quantitative light- and electron-microscopy. Repeat biopsies were taken at 6 months and/or after 2-3 years in patients who had acceptable graft function. All patients except two received cyclosporin as part of the immunosuppression. Glomerular volume was significantly increased, + 36(95% CI +6 to +65) % (p = 0.03), in the diabetic patients at 6 months which differed from the change of -20 (-50 to +10) % in the non-diabetic patients (p = 0.03). After 2-3 years glomerular volume was equal to the baseline value in the diabetic patients, while the change from baseline in the non-diabetic patients was -21 (-42 to -1) %. Substantial glomerular occlusion was seen in only three diabetic patients after 2-3 years. Total structural volumes per glomerulus in the 2-3-year biopsies showed an increase in basement membrane material of 0.09 x 10(6) microns 3 in the diabetic patients, significantly different from the change in non-diabetic patients (-0.10 x 10(6) microns 3, p = 0.003). No correlation was obtained between the 6-month increase in glomerular volume and the development of diabetic glomerulopathy at 2-3 years. The fact that glomerular hypertrophy was not present in the entire series may be due to the cyclosporin and to rejection. Nevertheless the diabetic group did show an early hypertrophy which did not seem to play a major role in the ensuing development of diabetic glomerulopathy.

There is general agreement that a fall rate in glomerular filtration rate (GFR) is the principal endpoint in diabetics with renal disease, and that abnormal albuminuria (including microalbuminuria) is an important intermediate end-point. The relative roles of blood pressure (BP) elevation and abnormal albuminuria in the prediction and genesis of renal disease are a matter of debate, and are further analysed in this paper. New studies show that neither genetic predisposition to hypertension (parental BP) nor parental abnormal albuminuria can be used to predict renal disease in patients with type 1 (insulin-dependent) diabetes. However, parental predisposition to proteinuria seems to be important to certain types of patients with type 2 (non-insulin-dependent) diabetes. Cross-sectional as well as follow-up studies document that GFR is generally well preserved in microalbuminuria (in both type 1 and type 2 patients), while the transition to clinical proteinuria is associated with a decline in GFR. Thus, prevention of overt proteinuria is important in clinical trials in microalbuminuric patients. In type 1 diabetes clear ultrastructural changes have been documented with microalbuminuria and a good correlation between abnormal albuminuria and structural damage is seen. Structural damage in normo- and microalbuminuric patients correlates poorly with BP. New studies in type 1 diabetes document that microalbuminuria (but not elevated BP) predicts not only clinical diabetic nephropathy but also end-stage renal failure and mortality. In type 2 diabetes microalbuminuria is the strongest predictor of mortality, whereas BP elevation is not a predictor. Several studies now document that antihypertensive treatment, especially with inhibitors of angiotensin converting enzyme, is able to reverse or reduce abnormal albuminuria, even in non-hypertensive type 1 patients, and possibly preserve GFR. Therefore, microalbuminuria may be the main indicator for starting antihypertensive treatment in these patients. With respect to organ damage in the retina, abnormal albuminuria is an important indicator of the risk of severe diabetic retinopathy. BP elevation seems not to be an initiating factor, but rather aggravates established retinopathy. Left ventricular hypertrophy has a stronger correlation with BP elevation than normoalbuminuria, suggesting that left ventricular hypertrophy is at least partially a phenomenon secondary to elevated BP in diabetic patients with abnormal albuminuria. Generally, abnormal albuminuria is a strong indicator of cardiovascular renal damage in diabetic patients and in most organs is a stronger factor than elevated BP.

We quantitated glomerular structure by light microscopy in 19 subjects with non-insulin-dependent diabetes mellitus (NIDDM) and studied the possible connection between morphology and urinary albumin concentration. Autopsy material was collected retrospectively from diabetic subjects in whom urinary albumin concentration had been measured within 1.5 yr. Nineteen consecutive sex- and age-matched nondiabetic subjects were controls. A quantitative study of a random sample of glomeruli was performed blindly on periodic acid–Schiff (PAS)-stained sections. The main parameters obtained were 1) mean volume of open glomeruli, 2) frequency of glomerular occlusion, and 3) volume fraction of red-stained material (PAS-positive substance) in open glomeruli [Vv(R/G)]. There was no increase in glomerular volume in these NIDDM subjects, contrary to the glomerular hypertrophy found early as well as late in insulin-dependent diabetes mellitus. An increase in Vv(R/G) was found in diabetic subjects, demonstrating the presence of glomerulopathy as it is diagnosed by light microscopy. The frequency of glomerular occlusion was not significantly different between the groups. A high urinary albumin concentration did not necessarily reflect more advanced glomerulopathy.

Quantitative ultrastructural data were obtained from kidney biopsy material of 12 long-term insulindependent diabetics. All patients had overt diabetic nephropathy with increased urinary albumin excretion and reduced glomerular filtration rate. Renal clearance of 51Cr-EDTA was in the range of 16-50 ml · min−1 · 1.73 m−2. All patients received antihypertensive treatment. A combined light- and electron-microscope study was performed. A significant proportion of the glomeruli was totally occluded (mean 36%, range 24-67%). Structural data presented relate only to the open, still-functioning glomeruli. Comparison with data previously obtained showed that 1) the thickness of the peripheral basement membrane [647 nm, coefficient of variation (C.V.) 0.22] was more than twice the normal value (310 nm, C.V. 0.08); 2) the width of epithelial foot processes (352 nm, C.V. 0.07) was significantly greater than in normal biopsies (224 nm, C.V. 0.06); and 3) the mean volume of the open glomeruli was markedly increased compared with normal and clearly exceeded that in the early diabetic hypertrophy. Total mesangial volume and total basement membrane material per open glomerulus were increased by 277 and 614%, respectively. However, capillary length and surface per open glomerulus were similar to those observed in early diabetic hypertrophy. These findings suggest that a late glomerular hypertrophy with preservation of capillary surface occurs as a compensatory phenomenon, prolonging renal survival for diabetic nephropathy patients.

Summary Diabetic glomerulopathy is characterized by a very slow development of basement membrane (BM) accumulation, manifested as thickening of the peripheral BM and increased volume of the mesangial BM-like material (BMLM) with mesangial expansion. The initiation of the process is probably at the onset of diabetes since the BM thickening is detectable after a few years. The BM accumulations at the two sites (PBM and BMLM) in the glomerular tuft are considered as two different expressions of a fundamental BM abnormality. The two locations present different conditions for quantitation, may have a different biochemical make-up, and immediate functional implications of the abnormalities may differ as well. In the long run, however, the two in concert lead to the ultimate solidification of the glomerular tuft with loss of capillary surface. The end-stage is glomerular closure, with elimination of glomerular function. A very close correlation has been found between the total remnant surface area of the glomerular capillaries and the level of GFR. Along with the classical changes of the diabetic glomerulopathy, changes in glomerular size are detectable. In early diabetes during the stages of glomerular hyperfunction, hypertrophy develops acutely at the onset of diabetes, leading to an increase in capillary surface corresponding to the increase in filtration rate. In the advanced stages when glomerular closure involves a proportion of the nephrons compensatory hypertrophy develops, thereby probably helping to preserve capillary surface for a period of time. The exact mechanisms that may influence these developments are not known, but underlying them all are the metabolic abnormalities of diabetes.

Exact parameters for relevant glomerular structures in the course of streptozotocin diabetes in rats with 1 to 18 months' duration were obtained with stereological methods. Renal cortical tissue from diabetic (D) and control animals (C) was processed for light- and electron microscopy and measurements were performed on systematically sampled glomeruli. The thickness of the basement membrane (BM) increased with age in both groups, but the rate of increase was 50% higher in D: 19 +/- 1.2 nm/month (mean +/- SD) vs. 13 +/- 0.9 nm/month, P = 0.0003. The time course of other structural quantities was characterized by the acute changes constituting the glomerular hypertrophy, earlier shown to develop within the first few days of diabetes. All these changes were confirmed in the present study: In the earliest phase the diabetic rats showed an increased total volume of glomeruli, mesangium, and mesangial BM material, as well as an increased surface of the capillary walls. However, none of these differences between the groups showed progression with increasing duration. Mesangial changes corresponding to those of the glomerulopathy in long-term diabetes were not demonstrable within the experimental period. The streptozotocin diabetic rat, therefore, is not useful as a model of advanced diabetic glomerulopathy. But the BM thickness follows the same predictable time course as in human diabetes insofar as moderately advanced cases are concerned. BM thickness is the parameter of choice when a potential effect of different variables on the development of diabetic glomerulopathy is under study.

The brains of rats with streptozocin-induced diabetes treated with a low-dose insulin regimen (1 IU/day) were studied with morphometric techniques. After 1 yr of diabetes, brain weight decreased slightly (1350 +/- 71 vs. 1521 +/- 55 mg, 2P less than .01) as did the volume of the neocortex (498 +/- 36 vs. 567 +/- 40 mm3, 2P less than .05). A significant loss of neocortical neurons occurred (38 +/- 2 X 10(6) vs. 46 +/- 3 X 10(6), 2P less than .01), and the length of the capillary network in the neocortical tissue shortened disproportionately (405 +/- 102 vs. 631 +/- 47 m, 2P less than .01), leading to increased diffusion distance. The mechanisms underlying cerebral loss in this model are unknown, but abnormalities of the vascular supply with prolongation of the route of diffusion might play a role.

Glomerular structure in diabetes presents a number of very intriguing questions that have been dealt with in the past. The most important aspect of the alterations in the diabetic kidney is the fact that, due to the glomerular abnormalities, a great proportion of young diabetic patients will eventually succumb to end-stage renal failure.

Publisher Summary This chapter discusses the kidney structural abnormalities in early diabetes. An estimate of the mass of peripheral basement membrane in a glomerulus can be obtained by estimating an average membrane thickness as it appears on section. In an experiment described in the chapter, it was found that the distribution of these measurements covered a very wide range, indicating a large variation in basement membrane within one glomerular cross section. It was also regularly seen that the distribution curves were skewed to the right. To compare mean values in different groups of patients, the curves were transformed to a symmetrical distribution, replacing basement membrane thickness and calculating a mean for these distributions. The results obtained in different groups of diabetics and in controls and the age range of the series are presented in the chapter. It was found that mesangial size, relative to any other glomerular space, varied within the same range in normals and in juvenile diabetics of all groups.

The objective of this study was to compare the effect of an angiotensin-converting enzyme (ACE) inhibitor and a calcium channel blocker on the development of renal changes in diabetic rats. Diabetes was induced by an intravenous injection of streptozotocin in normotensive Wistar rats. Treatment was commenced immediately in 1 set of rats with 4 treatment arms: nitrendipine (250 mg/kg fodder), enalapril (35 mg/L drinking water), both treatments in combination, or placebo. Treatment was continued for 9 weeks. Another set of rats was left with untreated diabetes for 3 months followed by 7 weeks treatment as above. When starting treatment right after induction of diabetes, nitrendipine significantly reduced urinary albumin excretion (UAE) to the nondiabetic level (P< .05) without reducing blood pressure (BP), whereas enalapril failed to significantly reduce UAE despite a reduction in BP. Combining the two treatments showed no further reduction in UAE compared to monotherapy with nitrendipine, despite a lower BP. When leaving diabetic rats untreated for 3 months, only the coadministration of nitrendipine and enalapril showed a significant reduction in UAE compared to monotherapy and placebo treatment, but showed no significant effect on BP.

This study investigates the efficacy of late intervention with the calcium channel blockers (CCBs) nitrendipine and nisoldipine in preventing development of albuminuria and glomerular hypertrophy in experimental diabetes. Streptozotocin (STZ)-induced diabetic rats were treated with nitrendipine or nisoldipine for 6 weeks after 3 or 6 months of untreated diabetes. The CCBs were administered in the fodder in a concentration of 250 mg/kg. After 3 months of untreated diabetes, nitrendipine treatment for 6 weeks significantly reduced urinary albumin excretion (UAE; P < 0.05) and glomerular hypertrophy. Nitrendipine also prevented an increase in systemic blood pressure compared with untreated diabetes. Nisoldipine showed no significant effect on UAE or glomerular hypertrophy despite systemic blood pressures similar to those of the diabetic nitrendipine-treated group. After 6 months of untreated diabetes, treatment with nitrendipine or nisoldipine for 6 weeks did not show effects on UAE, glomerular hypertrophy, or systemic blood pressure. No effect was found on renal growth in the treatment groups, and neither nitrendipine nor nisoldipine had any effect on body weight, blood glucose level, or food intake.