Development of diabetic vascular lesions in normal kidneys transplanted into patients with diabetes mellitus

Effect of unilateral nephrectomy on three patients with histopathological evidence of diabetic glomerulosclerosis in the resected kidney

Diabetes mellitus and surgical ablation of renal tissue are two independent influences associated with hyperfiltration and elevated levels of the glomerular transcapillary hydraulic pressure differential (delta P). There is increasing evidence that hyperfiltration with elevated delta P is pathogenic and leads to glomerular damage. The authors questioned whether these two influences (surgical ablation of renal tissue and diabetes mellitus) would act in an additive fashion in human patients to produce an accelerated decline in renal function. Three patients with non-insulin-dependent diabetes mellitus who had undergone a unilateral nephrectomy (for a variety of reasons) were (retrospectively) identified. In each patient, morphologic evidence of diabetic glomerulonephropathy was present in the resected kidney. The charts from these patients were reviewed and post-nephrectomy renal function was estimated over time by plotting reciprocal serum creatine values versus time. Follow-up intervals after nephrectomy varied from 4 to 15 years. The results of our follow-up showed no obvious detrimental effect on renal function (as measured by 1/serum creatinine) attributable to the unilateral nephrectomy. The authors conclude that residual renal function (and ultimate outcome) in patients with non-insulin-dependent diabetes mellitus is highly variable, but does not seem to be adversely affected (at least over the time span of observation in these patients) by unilateral nephrectomy.

Insulin-dependent diabetes mellitus: pathophysiology

Diabetes mellitus is a heterogeneous disorder. About 80% of the patients with this disease are categorized as having non-insulin-dependent diabetes mellitus, a disorder resulting from varied degrees of insulin resistance and impaired insulin secretion; the causes for these abnormalities are unknown. The remaining 15 to 20% of patients have insulin-dependent diabetes mellitus, a disorder caused by the destruction of insulin-producing endocrine cells within the pancreas and currently considered to be the result of an autoimmune process. During the course of both types of diabetes mellitus, the so-called long-term complications of diabetes invariably occur to some extent in all patients. These complications include retinopathy, nephropathy, neuropathy, and premature atherosclerosis. The molecular basis for these complications is not completely understood, but recent evidence obtained from both experiments in animals and prospective clinical studies indicates that metabolic derangements associated with poor glycemic control are a major determinant of the frequency and severity of these complications. Such evidence is the rationale for current attempts to maintain near-normal glycemia in patients with diabetes mellitus.

Muscle capillary basement membrane width in patients with vacor-induced diabetes mellitus

Muscle capillary basement membrane width is a sensitive marker for the presence of diabetic microangiopathy. Studies have indicated that genetic factors and alterations in glucose metabolism influence muscle capillary basement membrane width. To define the role of these factors we have measured muscle capillary basement membrane thickness in controls, insulin dependent diabetics, and individuals with diabetes secondary to the ingestion of Vacor, a rat poison, which results in hyperglycemia. Hemoglobin A1 concentrations were increased in both diabetic groups, but hemoglobin A1 levels and the duration of diabetes were similar in the two diabetic groups. The muscle capillary basement membrane width was increased to a similar extent in the insulin-dependent diabetics (control, 1,781 +/- 46 vs. IDD, 2,287 +/- 144 A, P less than 0.001) and in the Vacor diabetic group (2,320 +/- 149 A, P less than 0.001). In the insulin-dependent diabetic group, 63% of the patients had a muscle capillary basement membrane width greater than two standard deviations above the mean of the controls, while in the Vacor diabetic group this figure was 56%. Despite the relatively short duration of diabetes (6.2 +/- 0.3 yr), 44% of the Vacor diabetic patients had retinopathy and 28% had proteinuria. The present study provides strong evidence that even in the absence of genetic diabetes mellitus, hyperglycemia or some other abnormality related to insulin lack can cause microvascular changes.

A form of necrobiosis and atrophy of smooth muscle in diabetic gastric autonomic neuropathy

Pathological changes identified in the muscular wall of the stomach from two young insulin-dependent diabetic patients suffering from severe gastric autonomic neuropathy are presented. Scattered smooth muscle cells appearing as homogeneous round eosinophilic bodies ("M" bodies) among areas of sub-total smooth muscle cell atrophy together with intercellular collagen proliferation were identified in the muscularis propria of the stomach. Ultrastructurally, the "M" bodies are transformed smooth muscle cells undergoing a form of necrobiosis with peculiar intracellular features. These changes appear characteristic of end-stage diabetic gastric autonomic neuropathy when compared with other pathological conditions involving the gastric wall. The degree and extent of involvement of the various components of the gastric wall are discussed.

Renal vessel changes in diabetic KK-mice

Glomerular hyperfiltration is thought to be of pathogenic importance in the structural abnormalities seen in diabetic nephropathy but its cause is not known. It has been suggested that the changes in the preglomerular vascular system may lead to a disturbance of glomerular blood flow in diabetes. We therefore examined the potential role of changes in the vascular system supplying the glomerulus in diabetic mice. The kidneys of 15 diabetic KK-mice (aged 2, 5 and 12 months) were studied and compared with those of 15 non-diabetic NMRI-mice. We determined vessel cross-sectional, wall and lumen areas of 408 small intrarenal arteries, 5,140 arterioles and 518 preglomerular afferent arterioles using a morphometric method. At 2 months, diabetic arteries and arterioles were considerably smaller than the controls, while preglomerular afferent arterioles were the same size. At 12 months, however, all diabetic vessels measured were much larger than the controls. This was chiefly due to an excessive increase in lumen area: in the diabetic arteries the mean (+/- SEM) lumen area at 12 months was 1,057 +/- 142 vs 616 +/- 72 sq mu in controls (P less than 0.001), in arterioles 176 +/- 7 vs 115 +/- 4 sq mu (P less than 0.001) and in preglomerular afferent arterioles (at 5 months) 131 +/- 8 vs 95 +/- 7 sq mu (P less than 0.001). The dilatation of small intrarenal arteries and arterioles in diabetic mice may result from progressive impairment of vasoconstriction and may be a cause of the glomerular hyperfiltration in diabetes.

Value of glucose control in preventing complications of diabetes

Many functional, biochemical, and morphologic changes occur in diabetes in animal models and in humans. The responses of humans and animals to treatment with insulin indicate that these changes are induced by the diabetic milieu and are indirect or direct consequences of insulin deficiency and/or hyperglycemia. Guidelines for acceptable laboratory values in controlling diabetes are presented, as is evidence supporting a metabolic basis for vascular complications of the disease. On the basis of the results of a recently published prospective study of 59 patients with diabetes, fluorophotometry is cited as a technique that may predict development of retinopathy.

Studies of kidney and muscle biopsy specimens from identical twins discordant for type I diabetes mellitus

To distinguish metabolic from genetic factors in the development of microangiopathy in diabetes, we evaluated biopsy specimens of kidney and quadriceps muscle from seven pairs of identical twins who were discordant for Type I (insulin-dependent) diabetes mellitus. Two of the diabetic patients had clinical diabetic nephropathy, including hypertension, marked albuminuria, and a substantially reduced creatinine clearance; the other five had normal renal function and only minor clinical indications of complications. All the twins of the diabetic patients had normal glomerular basement membrane widths and normal fractional volumes of the glomerular mesangium. Values for glomerular basement membrane width, tubular basement membrane width, and mesangial volume in each diabetic twin exceeded the values in the respective sibling (P less than or equal to 0.0035), even if the value in the diabetic twin lay within established normal ranges. Values for muscle capillary basement membrane width in the diabetic twins did not differ from those in their siblings (P = 0.5). Our observations suggest that the metabolic abnormalities of diabetes are necessary, if not sufficient, for the development of glomerular abnormalities. We also conclude that in diabetic patients, alterations in muscle capillary basement membrane width do not necessarily accompany pathologic lesions in the kidney.

Mechanisms of posttransplant hypertension

Posttransplant hypertension is an important risk factor for cardiovascular mortality and graft function. We performed metabolic studies in 35 hypertensive patients with well-maintained graft function on maintenance immunosuppressive drugs and in 17 normotensive control transplant recipients. The group of hypertensive recipients were characterized by increased peripheral plasma renin activity, lack of change in blood pressure in response to salt loading and restriction, and by increased peripheral and renal resistance. In contrast, on the same protocol in a group of patients with essential hypertension, blood pressure fell significantly on a low-salt intake. Peripheral resistance in hypertensive transplant recipients fell in response to saline loading, in contrast to the effects in normotensive transplant recipients. Hypertensive patients with retained native kidneys as compared to those who had these removed prior to transplant, but were still hypertensive, differed only with regard to reduced renal plasma flow in the former group. These data are consistent with a predominantly renin-dependent hypertension in these renal transplant recipients. When bilateral nephrectomy or repair of graft renal artery stenosis is being considered, response to captopril may offer a means of selection; acute renal failure on captopril suggests functionally significant renal artery stenosis.

Simultaneous anti-glomerular basement membrane and membranous glomerulonephritis: case report and literature review

A 20-year-old male experienced a sore throat, fever, and lumbar pain. Examination revealed haematuria, proteinuria, and transiently impaired renal function. Renal biopsy revealed minor mesangial widening and small cellular crescents in 20% of the glomeruli under the light microscope, whereas immunofluorescence showed bright, linear staining of IgG along the glomerular basement membrane (GBM). Ultrastructural analysis showed minute subepithelial deposits analogous to early membranous glomerulonephritis (MGN). Anti-GBM antibodies were detected in the patient's serum. These findings were suggestive of simultaneous anti-GBM and immune complex glomerulonephritis in a patient with a mild, reversible renal illness.

[Recurrence of the original disease in the transplanted kidney]

Recurrence of the original disease in the transplanted kidney is observed in 5.6%-9.3% of the patients. However, the clinical significance of recurrence is often minor. Diagnosis is easy in diseases with specific renal lesions, e.g., in dense deposit disease and IgA-nephropathy, but may be difficult if such a marker is missing. Recurrence is of special clinical importance in the following conditions: Membranoproliferative GN type I (in 33%, often severe) and type II (= dense deposit disease, recurrence in 90%, often minor), focal segmental glomerulosclerosis (in 48% of patients with a rapid course (less than 3 years) and in 12% of patients with a longer duration of the original disease; often severe), membranous nephropathy (recurrence rather rare, but often serious), and primary hyperoxaluria (in 100%). Mesangial IgA deposits recur in half of the patients with IgA-nephropathy and anaphylactoid purpura, but clinical findings are often minimal. Recurrence in anti-GBM-nephritis and SLE is rare. The study of recurrence may contribute to a better understanding of many renal diseases.

Status of renal transplantation. A clinical perspective

Although the survival of patients on chronic dialysis has improved in recent years, the quality and status of rehabilitation remains poor. Renal transplantation must be used to complement chronic dialysis in the management of these patients. Physicians should not be biased and commit their patients to one or the other form of long-term treatment.

Are the 'second generation' oral hypoglycemic agents really different?

The common denominator of the numerous data collected from experimental studies on isolated organs, on healthy subjects and on diabetic patients, is a specific effect of sulfonylureas on insulin release in the presence (or absence) of glucose. However, there are significant differences in the capacity of the various chemical preparations active in that respect. There are biochemical data suggesting that the glyburide- and chlorpropamide-type of preparations are affecting sites of the B-cells that are different from both the glucose and the tolbutamide receptors. Thus, glibenclamide seems to be qualitatively different from the older sulfonylureas, being more a potentiator than a stimulator. Therefore, we called this type the representative of 'the second generation' drugs. The extra-B-cell actions of these drugs, predominantly the stimulation of somatostatin and the inhibition of glucagon, are favorably adding to these antidiabetic actions. In clinical therapy, these specific properties make it possible to diagnose and to treat patients successfully who were regarded before as being non-responsive to sulfonylureas and being insulin-dependent. On the basis of blood glucose decreases and C-peptide increases, a specific glibenclamide-glucose-response-test has been described which is a valuable medium for predicting the outcome of oral antidiabetic therapy.

Increased capillary permeability in diabetes mellitus and its relationship to microvascular angiopathy

Increased capillary permeability to large molecular weight plasma proteins is an early phenomenon in diabetes that affects the microvasculature of the kidney, eye, brain, and many other peripheral tissues such as skin and muscle. This widespread vascular leakiness is related to the metabolic disturbance of diabetes and associated changes in blood flow and intravascular pressure. Correction of hyperglycemia and increased blood flow reduces and often normalizes the excessive leakage. The relevance of increased small vessel permeability to eventual organ and tissue damage remains largely speculative. However, recent experimental evidence has suggested that certain levels of subclinical elevated urinary albumin excretion rate strongly predict the onset of Albustix-positive proteinuria, a certain precursor of renal failure. Hemodynamic factors in the genesis of diabetic microangiopathy are discussed, and a hypothetic sequence of events leading from increased capillary permeability to end stage organ or tissue failure is suggested.

Diabetic nephropathy. Is end-stage renal disease inevitable?

The appearance of proteinuria in an insulin-dependent diabetic patient is an ominous sign. Proteinuria heralds the presence of diabetic nephropathy and early death, or chronic renal failure requiring dialysis or transplantation, in 50% of patients. The pathogenesis of diabetic nephropathy is unknown. Adequate insulin administration is the most important preventive measure. Hypertension, if present, should be aggressively treated to delay progression of renal disease. Good nutrition, prompt treatment of urinary tract infections, and caution in the use of radiocontrast agents are other important preventive measures. Hemodialysis, peritoneal dialysis, and transplantation are options for patients with end-stage renal disease. No matter which is selected, the patient may still have multiple amputations, blindness, congestive heart failure, infections, and uncontrolled glycemia. Advancements are being made, however, that promise a better future for insulin-dependent diabetics.

Hemodynamic factors in the genesis of diabetic microangiopathy

There are many candidate mechanisms to explain the phenomenon of delayed microvascular disease in the diabetic. All may play some part in determining the genesis, the evolution or the ultimate degree and form of the angiopathy. General metabolic and humoral factors may provide the pathogenetic background against which special local conditions, e.g., in the retina or renal cortex, will determine the morphology of the angiopathy and its functional and structural consequences. Some of the processes occurring in the diabetic person may, however, be of major importance in initiating and maintaining conditions for the evolution of microvascular disease. The hemodynamic changes and the vascular responses to them that we have described are, we suggest, very likely to be an important component of this sort. Unlike the later structural changes, these hemodynamic phenomena are to be found very early in the diabetic state. Of most clinical importance, perhaps, is that they appear, with the achievement of adequate metabolic correction, to be reversible.

[Treatment of chronic kidney failure in diabetes mellitus]

27 patients suffering from end stage diabetic renal failure were treated by hemodialysis (HD) [8], continuous ambulatory peritoneal dialysis (CAPD) [13] or kidney allotransplantation after previous dialysis (KT) [13]. The mean age of the patients was 39.8 +/- 9.8, 44.8 +/- 11.3 and 33.8 +/- 5.7 for HD, CAPD and KT groups respectively. The cumulative patient survival after 1 and 2 years of treatment was 24%/0%, 56%/0% and 70%/50% for HD, CAPD and KT treatment. The cumulative allotransplant survival amounted to 40% after 1 year and to 20% after 2 and 3 years. Causes of death included cardiovascular complications in 7 patients, especially during HD treatment; infections occurred in 6 patients during CAPD treatment and after kidney allografting. Hypertension persisted during HD treatment and disappeared in 1/3 of the patients after KT. Nonlethal cardiovascular problems were observed during all treatment regimens and were more prominent in HD patients. In 2 patients, 3 amputations of the legs had to be performed after KT. Visual power deteriorated in more than half of the patients on HD and in one third during CAPD; it remained stable in half of the patients after KT. Neuropathy deteriorated during HD, was stable during CAPD and improved after KT. Rehabilitation was better during CAPD or after KT than during HD. The results of kidney replacement therapy in diabetics are worse than in non diabetic patients due to extrarenal organ damage. Early renal transplantation might prove to ameliorate this situation.

The Minnesota diabetes complications clinical trial. The first three years

A prospective and randomized clinical trial of an inception cohort of diabetic kidney recipients to test the hypothesis that maximized metabolic control of diabetes prevents or delays diabetic nephropathy in the renal allografts was initiated approximately three years ago. Notwithstanding the fact that all our diabetic patients were on prednisone and therefore metabolically unstable, we achieved and maintained a clear difference between the standard control (group A) and the maximized control patients (group B). At 13 months of study, the mean fasting blood glucose mg% (A: 242 +/- 22, B: 130 +/- 9, p less than 0.001), nonfasting blood glucose (A: 276 +/- 40, B: 135 +/- 10, p less than 0.001), 24 hour urine glucose (A: 85 +/- 16, B: 5 +/- 1, p less than 0.001), and glycosylated hemoglobin % (A: 13 +/- 0.9, B: 10 +/- 0.8, p less than 0.01) were all clearly and statistically significantly higher for the group A patients. These results show the feasibility of such a trial using the tools available today to treat diabetes.

The natural history of diabetic nephropathy in type I diabetes and the role of metabolic control in its prevention, reversibility and clinical course

The authors present a contemporary picture of the pathogenesis and clinical course of diabetic nephropathy in type I diabetics describing the stages of the disease and the possible evidence for reversibility of the kidney damage with tight metabolic control. During the so-called latency period, which is clinically non-detectable, the predominant functional abnormalities (increase in GFR with sub-clinical glomerular proteinuria) can be corrected by strict control although there is no evidence for the regression of the associated anatomical changes such as the enlarged filtration area. As for the described increase in thickness of the glomerular basement membrane, from experimental data and pancreatic transplants in man, delay in its development and to some extent regression of the glomerular lesions can be expected. The problem of how the renal lesions in experimental diabetes mirror the changes in the human kidney is discussed. During the symptomatic period, with intermittent and subsequently constant proteinuria and progressive decline in renal function, which are observed in only about 30% of type I diabetics, the role of arterial hypertension and its effective control is emphasized. Finally, the renal failure period is indicative of irreversible damage to the kidneys. The progression from its early to its late stages is variable between different patients but each individual patient shows a constant rate of deterioration. The evidence for the efficacy of medical treatment in slowing down its progression is very limited at present but much can be done to improve the quality of life by dietary measures, treatment of fluid overload and hypertension. When the end-stage diabetic kidney disease is reached, with serum creatinine above 8 mg/dl, renal transplantation from a living donor offers a good chance for a relatively acceptable quality of life for years. In conclusion, it is stressed that the morbidity of diabetic nephropathy could eventually be reduced through effective control of the metabolic abnormalities of diabetes with the methods presently available.

Renal transplantation in diabetics nephropathy

Forty diabetics who had developed end-stage renal failure from diabetic nephropathy and underwent renal transplantation have been followed up from one to six years. After one and two years 63% and 42% survived (45% and 33% respectively with functioning kidneys). Older patients, those with coronary and peripheral vascular disease, and those with severe neuropathy are prone to higher postoperative morbidity and mortality. The presence of advanced retinopathy, on the other hand, does not appear to influence the outcome.

Pancreas transplantation

Between December, 1966 and October, 1981, 183 pancreas transplants were performed in attempts to correct the metabolic defect in 171 insulin-dependent diabetic patients. Nearly half of the transplants have been performed in the last two years. Currently, 20 patients have functioning grafts and are insulin independent. Twelve grafts (including six current ones) functioned for more than a year (the longest for four years). A variety of techniques have been used to drain or suppress the secretions of the exocrine pancreas; the most frequent method is injection of the pancreatic duct with a synthetic polymer. In most patients carbohydrate metabolism has been normal or nearly normal while the graft was functioning. Although the technical problems are not entirely solved, the major cause of graft failure has been rejection. The need for antirejection therapy has limited the application of pancreas transplantation to diabetic renal allograft recipients or to non-uraemic patients whose complications of diabetes are, or predictably will be, worse than the side- effects of chronic immunosuppression. If consistently effective methods to suppress the immune response of the recipient to donor histocompatibility antigens are developed, pancreas transplantation could be applied to a wider variety of diabetic patients.

Alterations in glomerular RNA in diabetic rats: roles of glucagon and insulin

Incorporation in vivo of labeled orotate into RNA and total nucleotides was measured in isolated glomeruli and whole renal cortex. In 2-day diabetic animals, glomerular RNA was increased, and there was greater incorporation of orotate into total nucleotides and RNA as compared with controls. Insulin reversed the exaggerated incorporation at infusion rates that corrected hyperglucagonemia without reducing plasma glucose and with only minimal changes in insulin concentrations. The addition of glucagon to insulin infusions reproduced the increased incorporation observed in untreated diabetics. Similar changes occurred in renal cortex, where differences in orotate incorporation into nucleotide precursors seemed to be the main cause for alterations in RNA labeling. Isotope incorporation in glomeruli correlated positively with plasma glucagon, but not with insulin or glucose concentrations. Although in 7-month diabetic animals orotate incorporation into RNA was less than in controls, probably as a consequence of renal disease, 24-hour insulin infusion decreased it further. Our results confirm that in the diabetic kidney, abnormal uracil nucleotide metabolism and increased cellular content of RNA are demonstrable in glomeruli as in the renal cortex. These changes appear to be related directly to hyperglucagonemia.

Systemic amyloidosis involving two renal transplants

Two patients with primary amyloidosis, each of whom had received a renal transplant for chronic renal failure, developed amyloid in their allografts. In one patient amyloid was present primarily in glomeruli and to a lesser extent in the interstitial tissue. This patient developed renal failure necessitating retransplantation. In the second patient amyloid was seen in the interstitium and interlobular blood vessels. Minimal amyloid was present in the glomeruli. This patient died of cardiac amyloidosis with good graft function at the time of death. Of the several patients recorded in the literature with amyloid in renal allografts, our first patient is the only one to exhibit glomerular amyloid and failure of the graft. Amyloid in areas other than the glomerulus does not appear to be incompatible with satisfactory graft function.

The kidney in diabetes

The kidneys as a target organ for secondary microvascular complications of diabetes mellitus represents a health problem of enormous social cost. Recent studies in man and animals strongly support the concept that the primary responsibility for diabetic nephropathy rests with the metabolic derangements of the diabetic state. However, these metabolic derangements have complex biological effects; it is unlikely that hyperglycemia, per se, produces all of the nephropathic influences of diabetes. Alterations in microvascular hemodynamics in diabetes probably contribute to glomerular pathology. These alterations may be based upon disturbed vasoactive control mechanisms regulating angiotensin and prostaglandin secretion and metabolism. Although much remains to be learned about the pathogenesis of glomerular basement membrane and mesangial thickening in diabetes, these central structural abnormalities appear separable. Mesangial thickening is reversible by cure of the diabetic state in rats whereas glomerular basement membrane thickening is not. Treatment for the diabetic patient with end-stage renal failure has recently improved markedly. Although presently, kidney transplants from living related donors appear best, cadaver transplants and long-term hemodialysis are reasonable options.

Control of Blood Glucose in Diabetics on CAPD

The relationship between diabetic control and the incidence of vascular complications remains a subject of controversy. Hyperglycemia induces glycosylation of different proteins, sorbitol accumulation, disturbance in the function of blood cells, hyperlipoproteinemia and osmotic changes. Pathological studies show that the kidneys of diabetics and kidneys transplanted to diabetics undergo capillary basement-membrane thickening. Clinical studies using a variety of criteria for assessing control clearly show a relationship between hyperglycemia and microvascular, but not macrovascular complications. Animal studies indicate that vascular changes are secondary to the metabolic derangements of diabetics and that they improve with better control. Thus, the data available indicate a strong relationship between diabetic control and microvascular complications, but there is no evidence that hyperglycemia per se is a significant risk factor for macrovascular disease. However, the relationship to microvascular complications makes it highly desirable to strive for strict control of hyperglycemia, especially in young diabetics.

Diabetic glomerulopathy may be preventable

Variation in blood glucose levels throughout the day was assessed in six diabetic maintenance hemodialysis patients and six diabetic renal transplant recipients. None of the twelve studied patients had good control. Glucose levels greater than 300 mg/dl were noted in four of six dialysis patients and five of six transplant recipients. A regimen of self blood glucose measurement and multiple insulin doses was instituted for four transplant and three dialysis patients. Each patient achieved the desired glucose range of 60 to 120 mg/dl most of the time, with a resultant fall in mean hemoglobin A1c concentration from 10.3% to 7.9%. It is suggested that a long term trial of self glucose monitoring might prove beneficial to treated uremic diabetics.

[Diabetic glomerulosclerosis: current status of its morphology and pathogenesis (author's transl)]

The diabetic glomerulosclerosis as a consequence of the abnormal metabolic state is characterized by an uniform thickening of the glomerular basement membrane (GBM) and an augmentation of the mesangial matrix. Both alterations begin already few years after the onset of the diabetes and are observed in all glomeruli to the same extent (=diffuse type). Later on, nodular deposits of glycoproteins are additionally found in the mesangium (=nodular type). Only these nodules are morphologically specific for the diabetic disorder. In association with both the diffuse and the nodular glomerulosclerosis, insudation of plasma can be seen in the afferent and efferent vessels and the glomerular capillary loops. The mechanism of the increase in the amount of GBM-material is not known, since contradictory data have been reported with regards to both the chemical composition and metabolism of the GBM in human and experimental diabetes. Some postulate that the abnormal deposition of GBM-mateiral is due to an excessive synthesis (anabolic disorder), others argue that a further decrease in the normally slow breakdown and disposal (catabolic disorder) might be responsible. This review presents the different pathogenetic concepts of the glomerulosclerosis and attemps to explain the possible causes for the current discrepancies.

Uremia in diabetics: the prognosis improves

Chronic uremia caused by diabetic glomerulopathy accounts for about 25 percent of new patients treated by maintenance hemodialysis. At the onset of glucose intolerance, insulin dependent diabetics have larger than normal kidneys, with a markedly increased glomerular filtration rate. During the subsequent 15 to 20 years of insulin use, glomerulosclerosis progresses silently, until a clinically overt nephrotic syndrome becomes evident. Thereafter, the clinical manifestations of nephropathy appear rapidly with an exponential decline in creatinine clearance to less than 5 ml/min within one to five years. Putting together a life plan for a nephrotic and azotemic diabetic involves awareness, and coordinated management of not only renal but extrarenal vasculopathic complications of diabetes, especially proliferative retinopathy. Carefully made preparations for hemodialysis and/or renal transplantation with increase changes for at least a short-term favorable outcome, which can now be anticipated in a growing proportion of patients.

Effect of islet transplantation on the glomerular changes in streptozotocin-diabetic rats

Glomerular changes develop in rats with streptozotocin diabetes. The structure of these lesions (nodular and diffuse glomerulosclerosis, mesangial cell proliferation, basement membrane thickening, glomerular aneurysms, fibrinoid caps, glomerular adhesions) is described in the present paper and the effect of normalization of metabolism by islet transplantation on the glomerular changes is studied with histological, immunohistological and morphometric methods. Isogenous islets were transplanted into the portal vein of streptozotocin-diabetic rats after diabetes of 7 months' duration. The kidneys of normal, diabetic and transplanted animals of the same age were studied 2.5 months later. Studies of the kinetics of immunocomplexes in the mesangium were also performed. The renal changes (glomerulosclerosis, mesangial cell proliferation) were largely reversible after islet transplantation and the blood glucose level and glucose tolerance were normalized. In the diabetic animals the delayed uptake and elimination of immunocomplexes in the mesangium was normalized after the transplantation. It is possible, that the cause of the lesions is a functional disturbance of the mesangium induced by insulin deficiency and/or hyperglycaemia.

Early micro- and macro-angiopathy in the streptozotocin diabetic minipig

Streptozotocin diabetes in the minipig constitutes an outstanding model for the study of diabetic angiopathies. Changes which are classified as macroangiopathy are evident after 6 months, while the first changes indicative of microangiopathy appear already after about 18 months. The degree of pronouncement of the microangiopathy depends on the duration and severity of the induced diabetes. These results constitute a cogent argument in favour of the "metabolic theory" of the development of diabetic microangiopathy.

Transplantation of insulinoma into the diabetic Syrian hamster

Syrian hamsters were rendered diabetic with intraperitoneal streptozotocin and were maintained in the diabetic state for a minimum of 14 days. A hamster islet cell tumor was transplanted subcutaneously with a prompt return of water intake (38 +/- 9.1 ml/day to 7.1 +/- 2.2 ml/day, mean +/- SD), urine glucose (4.8 +/- 0.84 g/day to less than 250 mg/day), urine output (37.4 +/- 10.9 ml/day to 7.6 +/- 2.1 ml/day), blood glucose (297 +/- 31.9 mg/dl to 87.6 +/- 28 mg/dl), and weight gain (1.0 to 0.8 g/day) to normal control levels. Histologic examination of the engrafted tumors revealed a well encapsulated tumor with no evidence of metastatic disease. The transplanted insulinomas maintained well differentiated histologic features without evidence of necrosis. Immunopathologic studies failed to reveal any evidence of either humoral or cell mediated immunity directed toward the allograft. Each animal was successfully transplanted with a 1 mm tumor explant. A single rodent tumor donor provided adequate material for engraftment for five recipients. The transplanted insulinomas maintained full functional and enzymatic capabilities. Similar studies utilizing the hamster insulinoma engrafted into the athymic nude mouse showed amelioration of the same diabetic symptomatology. Many of the technical difficulties encountered with whole organ and isolated islet transplantation encourages development of a more practical model. These experimental results suggest an alternative method for supplying the diabetic with an endogenous insulin source.

Effect of insulin treatment on prostacyclin in experimental diabetes

Diabetic patients have a high susceptibility to microvascular complications, atherosclerosis and thrombosis. Platelet hyperreactivity possibly related to an imbalance in arachidonic acid metabolism may be involved. Aortic rings or renal cortex produced a potent inhibitor of platelet aggregation, identified as prostacyclin (PGI2). Release of PGI2 by tissues from streptozotocin -- diabetic rats (aorta: 0.07 +/ 0.1 ng/mg wet weight; renal cortex 0.004 +/- 0.001 ng/mg wet weight) was significantly depressed when compared with controls (aorta: 0.26 +/- 0.07 ng/mg wet weight; renal cortex: 0.009 +/- 0.001 ng/mg wet weight). Treatment of diabetic animals with insulin for 8 days restored PGI2 production to normal. The finding that PGI2 is depressed in the aorta and in the kidney, tissues which develop angiopathy, and that this is normalised by insulin, suggests that impaired PGI2 production, perhaps associated with platelet hyperreactivity may play a role in the vascular complications of diabetes.

Streptozotocin-induced diabetes in the spontaneously hypertensive rat

Spontaneously hypertensive rats (SHR) were more sensitive to the diabetogenic effects of streptozotocin than normotensive Wistar-Kyoto (WKY) rats. Thus, 10 days after intravenous administration of 25 mg/kg streptozotocin in SHR, mean pancreatic insulin content was decreased by 42% (p less than 0.05), and mean plasma glucose concentration was increased from 85 to 215 mg/dl (p less than 0.001), whereas between 37.5 and 50 mg/kg of streptozotocin was required to produce similar effects in normotensive WKY rats. Also, there was a progressive decrease in blood pressure in SHR injected with 25, 35.7, or 50 mg/kg of streptozotocin, whereas blood pressure was progressively increased after streptozotocin in normotensive WKY rats. The opposite effects of streptozotocin-induced diabetes on blood pressure in SHR and WKY rats could be observed at similar degrees of hyperglycemia and are presently unexplained.

Induction of chronic diabetes by streptozotocin in the miniature pig

The rapid i.v. injection of 60 mg streptozotocin/kg body weight 8 days after an initial dose of 30 mg/kg was the best method to produce a distinct insulin-deficient diabetes in minipigs. Even in the absence of any therapy the further course of this diabetes remained stable without tending to exhibit ketoacidosis. Besides hyperglycaemia and the loss of insulin response to glucose there was significant increase of triglycerides and a decrease of plasma albumin. In the oldest animals this diabetes has so far been observed for more than 3 years. Because of some special advantages this experimental diabetes could provide a useful model for studying diabetic angiopathies.