Advanced Nephropathy Research Articles

Glomerular structural changes in type 1 (insulin-dependent) diabetes mellitus: causes, consequences, and prevention.

Diabetic nephropathy is caused primarily by advanced glomerulopathy, the renal expression of diabetic microangiopathy. With stereological methods a quantitative description of the structural changes is achieved. The glomerulopathy is characterized by an increase in basement membrane material: thickening of the capillary wall and an increase in mesangial volume relative to glomerular volume, comprising increase in matrix. Among groups of patients conformity between renal function stage and structure exists. The parameters measuring glomerulopathy are normal at the onset of diabetes; patients with normoalbuminuria may show slight basement membrane thickening, or normal parameters; the microalbuminuric group shows a measurable, but moderate glomerulopathy; patients with overt nephropathy have advanced lesions; at this stage heterogeneity among glomeruli makes the estimates weaker. Recent data indicate that the changes in peripheral basement membrane and in mesangial matrix develop in concert and both contribute to the early stage of glomerulopathy in patients with microalbuminuria. As to the consequences of the structural changes the mechanism of albuminuria is not clear. It is suggested that the early glomerulopathy entails other structural modifications, including formation of new vessels which may be the site of leakage. The marked deviations in glomerular filtration rate correspond well with estimates of filtration surface area: in the early hyperfunction state it is increased; in advanced nephropathy it is decreased, due to advanced glomerulopathy in conjunction with glomerular occlusion. The diabetic state is the necessary condition for the glomerulopathy. In relating structural changes to presumed contributing causes no supporting evidence of a relationship with glomerular hyperfunction or hypertrophy was observed. The structural parameters may be useful tools in clinical trials aiming at arresting the development of glomerulopathy, and thereby providing a prevention of diabetic nephropathy.

Predisposition to hypertension: Risk factor for nephropathy and hypertension in IDDM

Less than a quarter of the patients with juvenile-onset IDDM develop diabetic nephropathy during the first 20 years of diabetes. To study the determinants of this complication, we selected patients who had come with newly diagnosed IDDM to the Joslin Clinic between 1967 to 1972, and we examined them in 1986 to 1988, that is, 15 to 21 years after onset of diabetes. Using a case control design we compared three groups of cases, that is, advanced nephropathy (N = 43), only microalbuminuria (N = 41), and hypertension alone (N = 17), with a group of controls who remained normoalbuminuric and normotensive despite the long duration of IDDM (N = 61). In comparison with controls, patients with advanced nephropathy had more parents with hypertension (odds ratio 3.8), higher Vmax values of Na/Li countertransport in red blood cells (odds ratio 10.0 for the highest tertile), and higher mean arterial pressure during adolescence and early adulthood (odds ratio 3.1 for those above the median). They also had significantly poorer glycemic control during their first 12 years of diabetes. Patients with hypertension alone were similar to those with advanced nephropathy with regard to markers of predisposition to hypertension but differed from them with regard to glycemic control, having the best glycemic control of all the study groups. Patients who developed only microalbuminuria during 15 to 21 years of IDDM (some of whom will progress to overt proteinuria later) did not differ significantly from controls with regard to predisposition to hypertension. In conclusion, predisposition to hypertension is a major risk factor for the development of advanced diabetic nephropathy and essential hypertension during the first 20 years of IDDM.

Increased levels of plasma homocysteine are associated with nephropathy, but not severe retinopathy in type 1 diabetes mellitus

The reactive vascular-injuring amino acid homocysteine was measured in plasma samples from 79 well-characterized type 1 diabetic patients and 46 control subjects. Patients with proliferative retinopathy had higher homocysteine levels (15.0 +/- 6.3 mumols l-1; mean +/- SD, p less than 0.001; n = 42) than those with progressive retinopathy during a two-year period (10.4 +/- 1.6 mumols l-1; n = 12), no or minimal retinopathy (10.7 +/- 4.3 mumols l-1; n = 25), and the control subjects (11.0 +/- 3.4 mumols l-1). Within the group of patients with proliferative retinopathy increased homocysteine levels were confined to those patients that had serum creatinine levels greater than 115 mumols l-1 and/or an albumin:creatinine clearance ratio greater than or equal to 0.02 x 10(-3) (17.0 +/- 5.9 mumols l-1; n = 23), whereas those with no or only minimal nephropathy had levels (12.1 +/- 5.5 mumols l-1; n = 18) that were not different from the control group. We conclude that neither type 1 diabetes mellitus nor diabetic retinopathy per se is associated with increased plasma homocysteine levels. In contrast, homocysteine accumulates, probably owing to reduced glomerular filtration, in diabetic patients with advanced nephropathy. This suggests that homocysteine might contribute to the accelerated development of macroangiopathy seen especially in this subgroup of diabetic patients.

High Plasma Prorenin in Diabetes Mellitus and Its Correlation with Some Complications

Plasma prorenin is abnormally high, whereas renin is normal or even low, in many patients with long-standing diabetes mellitus complicated by microvascular disease. Nephropathy or autonomic neuropathy has been put forward as a cause. We found that in 223 consecutive diabetics prorenin correlated positively with serum creatinine, the presence of macroalbuminuria (greater than 250 mg/L), and the presence of diabetic retinopathy, particularly the proliferative type. This correlation did not depend on the presence of neuropathy or whether the patient was receiving insulin. It was also independent of sex, age, duration of diabetes, blood pressure, and blood levels of glucose and hemoglobin-A1c. The association between elevated prorenin and retinopathy remained significant after adjustment for creatinine and the presence of macroalbuminuria. Of the whole group of diabetics 94 consecutive patients were assessed for the presence of microalbuminuria (30-300 mg/24 h). Independently of the presence of micro- or macroalbuminuria, the mean level of prorenin was not above normal in the patients without retinopathy and was 2-3 times normal in those with proliferative retinopathy. Thus, retinopathy appears to be a more important determinant of abnormally high prorenin than nephropathy. In addition, the renal vein to artery ratio of prorenin in 7 diabetics with both advanced nephropathy and proliferative retinopathy was not elevated, despite the high peripheral venous prorenin level and the impaired renal perfusion. Thus, the abnormally high prorenin level in these patients could not be explained by abnormal secretion by the kidneys. Finally, prorenin was not high in 16 nondiabetics with loss of sympathetic activity due to chronic autonomic neuropathy, which indicates that in the absence of diabetes, this type of autonomic failure is not sufficient to cause the high prorenin levels seen in diabetics. Our findings are evidence that abnormally high plasma prorenin levels in diabetics are not an immediate consequence of altered glucose metabolism. This abnormality is related to the development of microvascular disease in the eye and kidney and is at least in part due to decreased clearance of prorenin from the circulation, increased production from extrarenal sources, or both.

Glomerular Structure and Function in Diabetic Nephropathy: Early to Advanced Stages

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 micrograms/min (1153 micrograms/min), glomerular filtration rate (GFR) 30-128 ml.min-1 x 1.73 m-2 (90 ml.min-1 x 1.73 m-2) and mean arterial blood pressure (BP) 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 less than 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 less than 10% occluded glomeruli, correlations between glomerular volume and the parameters of diabetic glomerulopathy (i.e., BM thickness and volume fractions of mesangium and mesangial matrix) failed to reach statistical significance. The actual glomerular volume, however, is a product of the individual's original glomerular volume, probably the early diabetic hypertrophy and modifying changes consequent to the development of glomerulopathy.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum concentrations of laminin P1 in diabetics with advanced nephropathy.

In 97 patients with type I diabetes mellitus, 155 patients with type II diabetes mellitus, and two matched control groups, serum concentrations of laminin P1, a non-collagenous component of basement membranes, were determined by radioimmunoassay to see whether laminin P1 might be a valuable indicator of microangiopathic complications in diabetics. Independent of the type of diabetes, serum laminin concentrations in patients without nephropathy or with early renal damage as assessed by microalbuminuria were comparable with those of the control subjects. Patients with macroproteinuria or with renal insufficiency had significantly increased serum laminin P1 concentrations. Diabetic retinopathy was not found to influence serum laminin P1 concentrations. These data indicate that serum laminin P1 concentrations are increased in advanced diabetic nephropathy.

Relationship between the urinary excretion of albumin and retinol-binding protein in insulin-dependent diabetics

The glomerular and proximal tubular function of the diabetic kidney was investigated. The urinary excretion (relative clearance) of albumin, a marker of glomerular function, and retinol binding protein (RBP), a low molecular weight (LMW) protein and marker of proximal tubular function, was determined in insulin-dependent diabetics. No correlation between the relative clearances of albumin and RBP was observed. LMW proteinuria without microalbuminuria was observed in 27 patients which suggests that tubular dysfunction may be an early stage in the development of diabetic nephropathy. Microalbuminuria was found in 16 patients while a mixed type of proteinuria (microalbuminuria and LMW proteinuria) was present in 56 patients several of whom had advanced nephropathy with elevated serum levels of RBP and creatinine. It is suggested that a combination of tubular and glomerular malfunction may be responsible for some cases of mixed proteinuria.

New vessel formation in the renal corpuscles in advanced diabetic glomerulopathy

Glomerular ultrastructure was studied in 12 long-term insulin dependent diabetic patients with fairly advanced nephropathy. This article discusses the observation of capillary profiles in the glomerular tuft of a deviating ultrastructure: the basement membrane (BM) is focally extremely thin and in between it presents a very loose fluffy texture, resembling the BM in immature glomeruli. Such thin-walled capillaries (TWC) constituted 1 to 5% of total capillary length and surface. The second observation reported here is the presence of vessels within the BM of Bowman's capsule. These capillaries were lined with fenestrated endothelium, and the capsular epithelium sometimes presented foot process formation. It is suggested that both types of capillaries represent new vessel formation in the renal corpuscle in these cases of advanced diabetic glomerulopathy.

Increased blood pressure in diabetes: Essential hypertension or diabetic nephropathy?

This study was performed to evaluate whether it is possible to distinguish between diabetics with essential hypertension and diabetics with elevated blood pressure due to diabetic nephropathy. We investigated 46 young diabetics, 21 having incipient nephropathy defined as urinary albumin excretion (UAE) persistently above 15 micrograms/min and total urinary protein less than 0.5 g per 24 h, and 25 patients having overt nephropathy with total protein excretion equal to or above 0.5 g per 24 h. Twenty-three patients with essential hypertension were also studied as well as 24 healthy controls. Only males and females between the age of 25 years and 40 years were included. We found a positive correlation between UAE and blood pressure (BP) but a considerable overlap in BP and UAE values between diabetics and patients with essential hypertension. However, plotting urinary albumin excretion against BP, diabetics and non-diabetics with essential hypertension could be nearly totally separated. Comparison at a similar blood pressure level, for example, mean arterial blood pressure of 125 mmHg, shows that diabetics have UAE 100 times higher than non-diabetic essential hypertensives. Conversely, UAE of 100 micrograms/min would imply that mean arterial blood pressure is about 70 mmHg higher in the non-diabetic essential hypertensives than in the diabetics. Five diabetics with normal UAE and elevated blood pressure higher or equal to 160/95 mmHg were clearly within the area of the essential hypertensive patients. Our observations indicate that it seems possible to distinguish diabetic patients with essential hypertension from diabetics with elevated blood pressure due to early or advanced nephropathy.

Current thinking on the management of the uremic diabetic.

BOUT HALF of all type-1 diabetics, and an undefined but lesser proportion of type-II diabetics, will develop chronic renal failure (CRF). Diabetics constitute about one-fourth of end-stage renal disease patients in the United States, and a lesser but steadily increasing proportion (7.3% in 1981) in Europe.’ In general it has been found that diabetics suffer inordinately high morbidity and mortality compared to non-diabetic CRF patients. Data from the European Dialysis and Transplant Association Registry found only 70% one-year, and 28% five-year survival of diabetic CRF patients, roughly equivalent to the survival of nondiabetics 20 to 30 years older. The costs in human terms are enormous, and are reflected in dollar expense as well: we examined the first-year costs of transplanting 30 type-1 diabetics at our center and found that hospital charges were one-third higher for diabetics compared to a group of non-diabetic recipients.2 We will discuss aspects of treating the diabetic with advanced nephropathy that we feel are of importance in optimizing survival and rehabilitation. It is our strongly held opinion that effective application of currently available modalities offers much more to the diabetic patient than past statistics might indicate.

Insulin infusion therapy

A mass of evidence favors the concept of euglycemic management of insulin-dependent diabetes, despite significant potential complications. Patients with advanced nephropathy and/or autonomic neuropathy are very poor risks, and infusion therapy does not reverse well-established complications. To well-motivated, educated patients, infusion therapy offers the conveniences of more flexible timing of meals and of having a premeal bolus infusion rather than a premeal injection. With improvement in the technology of continuous glucose monitoring and closed-loop systems, as well as basic improvements in immunologic techniques for islet transplantation, the future may offer a choice of excellent euglycemic therapies for insulin-dependent diabetes. Meanwhile, infusion therapy, which was once only a research tool, is now widely available and is appropriate for near-euglycemic management of diabetes in selected patients.

糖尿病と基底膜

Alteration of basement membrane component in diabetes mellitus was reviewed. Recently, it has become evident that the basement membrane was composed of type 4 collagen, laminine and glycosaminoglycans. Presence of entactin and type 5 collagen was also claimed. Existence of fibronectin is controversial. Previously, studies on the basement membrane in diabetes were mainly concerned in the collagenous components. However, studies on the components other than collagen will be more important because they bear roles for the morphogenesis, metabolism and functions of basement membrane.Recently it was demonstrated that the glycosaminoglycans were reduced in diabetic basement membrane. Reduction of negative charge of basement membrane due to the loss of acidic residue of glycosaminoglycans was claimed to be the cause of the loss of charge selectivity observed in diabetic nephropathy. Fibronectin was reported to be increased in the renal glomeruli of the initial stage of diabetic glomerulosclerosis and to be decreased in the advanced nephropathy. Studies on laminin produced by EMS tumor implanted to the diabetic mice revealed no consistent changes. In diabetic glomerulosclerosis, laminin was reported to be decreased. Speculation on the mechanisms of the basement membrane thickening in diabetic microangiopathy was made on the bases of the reported evidences on the alteration of basement membrane components.

In vitro culture of cells exfoliated in the urine by patients with diabetes mellitus.

As an approach to facilitate the understanding of the progression of diabetic renal disease, we assessed the urine of diabetic patients and normal volunteers for the presence of cells that could be cultured in vitro. The results suggest that both normal control subjects and diabetic patients, without clinically detectable microangiopathy, exfoliate few culturable cells into the urine. In contrast, diabetics with documented retinopathy but without nephropathy exfoliate substantially higher numbers of culturable cells (5.2 cells/100 ml urine), whereas diabetics with both retinopathy and advanced nephropathy exfoliate even greater numbers of culturable cells (50.8 cells/100 ml urine). The cells that are exfoliated and culturable can be divided into five distinct cell types based on morphology at the light microscope level. The exfoliated cells proliferate at clonal density after isolation from urine and are epithelial in appearance. These data suggest that the culture of cells from urine might have diagnostic value as an early indicator of diabetic renal disease and provide a convenient, noninvasive new source of human kidney epithelial cells.

Mechanisms of proteinuria in diabetic nephropathy: A study of glomerular barrier function

The fractional clearance of neutral dextrans (theta D) with Einstein-Stokes radii between 30 and 64 A was determined in normal subjects (controls, N = 15) and in diabetic patients with heavy proteinuria (advanced nephropathy, N = 16) or trace proteinuria (early nephropathy, N = 8). When plotted on log normal probability coordinates, the correlation between theta D and radius in controls and in early diabetic nephropathy was linear, suggesting that glomerular pores form one population with a normal distribution. In advanced diabetic nephropathy, however, theta D for large molecules (radius greater than 46 A) was elevated and departed from linearity suggesting a bimodal pore size distribution within the glomerular membrane. A mathematical model was devised, which revealed the mean fraction of glomerular filtrate permeating the upper pore mode to be 0.009 +/- 0.002, and the pores to be totally nondiscriminatory toward molecules with radii up to 64 A. We conclude that the development of large pores (or defects) within the glomerular membrane in advanced diabetic nephropathy permits the unrestricted passage of large plasma proteins into the urine.