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Biomedical subjects

G C Viberti

Publications and source records attributed to G C Viberti.

At least 55 records · Page 3Linked to original sources
PubMed1995

Glomerular epithelial foot processes and filtration slits in IDDM patients.

Diabetic nephropathy is associated with functional changes in the glomerular filtration barrier but the structural counterpart remains unknown. Width of glomerular epithelial cell foot processes and of filtration slits were determined by morphometric methods in 11 non-diabetic kidney donors and in 28 diabetic patients with albumin excretion rates ranging from normal to proteinuria. Foot process width was estimated from the ratio of tuft surface density to length density of slits. At high magnification independently sampled, perpendicularly cut slits were classified. Foot process width on peripheral basement membrane was increased in microalbuminuric compared to normoalbuminuric diabetic patients (p<0.05) but showed no significant correlation with the level of albumin excretion when patients with increased barrier permeability were considered. Width of filtration slits in normo- and microalbuminuric diabetic patients exceeded that in non-diabetic control subjects (p<0.05). Filtration slits were narrower in patients with overt proteinuria than in patients with microalbuminuria (p<0.05) and correlated with glomerular filtration rate in all of the diabetic patients (r=0.65, p<0.005). The results show that insulin-dependent diabetic patients with nephropathy present changes of epithelial cells and filtration slits, demonstrable already in the stage of microalbuminuria. The mechanism of albumin leakage is not achieved by these measures. The dimension of filtration slits may play a contributing role in the level of glomerular filtration rate in diabetic patients.

Adolescent↗
PubMed1994

Hypertension and the renal vascular complications of diabetes: a structural basis to guide management.

The biochemical and structural alterations responsible for the renal and vascular complications of diabetes mellitus are likely to be the result of common processes. It is now well recognized that microalbuminuria is a powerful predictor of cardiovascular morbidity and mortality in diabetic patients. Increased cell growth and vascular tone and insulin resistance are among the contributors that lead to the renal and vascular complications of diabetes. Angiotensin-converting enzyme inhibitors, which may decrease the negative impact of these contributors, are effective therapeutic agents that reduce the risk of progression of renal disease and early mortality.

Albuminuria↗
PubMed1994

LDL subclasses in IDDM patients: relation to diabetic nephropathy.

To answer the question whether the elevation of LDL-cholesterol in IDDM patients with incipient and established diabetic nephropathy is accompanied by changes in LDL size or composition, we studied distribution of LDL particles in 57 normoalbuminuric [AER 7 (1-9) micrograms/min, median and range], in 46 microalbuminuric [AER 50 (20-192) micrograms/min] and in 33 proteinuric [AER 422 (233-1756) micrograms/min] IDDM patients as well as in 49 non-diabetic control subjects with normoalbuminuria. The three diabetic groups were matched for duration of diabetes and glycaemic control. The mean particle diameter of the major LDL peak was determined by nondenaturing gradient gel electrophoresis. Composition and density distribution of LDL were determined in the subgroups of each patient group by density gradient ultracentrifugation. Normoalbuminuric IDDM patients had larger LDL particles than non-diabetic control subjects (260 A vs 254 A, p < 0.05). LDL particle diameter was inversely correlated with serum triglycerides in all groups (p < 0.05 for normoalbuminuric and p < 0.001 for other groups). Triglyceride content of LDL was higher in three IDDM groups compared to control group (p < 0.05). The elevation of LDL mass in microalbuminuric and proteinuric IDDM groups compared to normoalbuminuric IDDM group (p < 0.05 for both) was mainly due to the increment of light LDL (density 1.0212-1.0343 g/ml). There were no significant changes in the density distribution or composition of LDL between the three diabetic groups. In conclusion the increase of LDL mass without major compositional changes suggests that the elevation of LDL in incipient and established diabetic nephropathy is primarily due to the increased number of LDL particles.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Familial, hemodynamic and metabolic factors in the predisposition to diabetic kidney disease.

Proteinuric diabetic patients have an increased risk of cardiovascular disease and almost always have hypertension. In the early stages of diabetic renal disease (microalbuminuria) when renal function is well preserved, systemic arterial blood pressure is already elevated compared to insulin-dependent diabetic patients without microalbuminuria. Prospective studies have shown that normoalbuminuric patients who progress to microalbuminuria have higher blood pressures (albeit within the normal range) than those who persistently remain normoalbuminuric. Parents of insulin-dependent diabetic patients with nephropathy have a higher prevalence of hypertension and cardiovascular disease compared to those of patients without nephropathy. Moreover, diabetic nephropathy clusters within families. Erythrocyte sodium-lithium countertransport activity, the most consistent marker for essential hypertension and its cardiorenal complications, is elevated in diabetic patients with nephropathy and in their non-diabetic parents. These data suggest that a familial predisposition to arterial hypertension and cardiovascular disease increases the risk for the development of nephropathy and its associated cardiovascular complications in insulin-dependent diabetes. Arterial hypertension is a state of insulin resistance and diabetic patients susceptible to nephropathy have been found to be less insulin sensitive. Preventive strategies of diabetic kidney disease in the future will have to take into account its metabolic hemodynamic and familial basis.

Albuminuria↗
PubMed1994

Lipoprotein(a) in type 1 diabetic patients with renal disease.

Lp(a) was measured in 64 normoalbuminuric, 52 microalbuminuric, and 37 proteinuric Type 1 diabetic patients and 54 healthy subjects. Microalbuminuric and proteinuric Type 1 diabetic patients had higher median Lp(a) values (133 (16-1932) and 169 (17-1149) mg l-1) than patients with normal AER (73 (15-1078) mg l-1; p = 0.048 and p = 0.027). Lp(a) in healthy subjects (110 (15-1630)mg l-1) did not differ from the diabetic subgroups. The frequency of Lp(a) values in the upper quarter of the normal distribution was similar in the diabetic groups and did not differ between diabetic and control subjects. The cumulative distribution of Lp(a) was similar in all groups. Lp(a) concentrations were not related to AER, age, gender, duration of diabetes, body mass index, glycaemic control, serum creatinine, free insulin or systolic blood pressure. Cholesterol, LDL-cholesterol, triglycerides, and apo B were higher in microalbuminuric and proteinuric than in normoalbuminuric Type 1 diabetic patients. Lp(a) was independently related to diastolic blood pressure, fibrinogen, and macroangiopathy. In conclusion, median Lp(a) concentrations tend to be higher in Type 1 diabetic patients with early and established renal disease, although the differences are small and the overlap between groups large. Lp(a) is related to diastolic blood pressure and fibrinogen, and this association of powerful risk factors suggests that Lp(a) may play a role in the pathogenesis of cardiovascular disease in Type 1 diabetic patients with proteinuria. Whether Lp(a) is an independent determinant of increased cardiovascular risk in these patients needs to be elucidated by prospective studies.

Adult↗
PubMed1993

Is screening and intervention for microalbuminuria worthwhile in patients with insulin dependent diabetes?

OBJECTIVE: To analyse the cost-benefit of screening for and antihypertensive treatment of early renal disease indicated by microalbuminuria in patients with insulin dependent diabetes mellitus. DESIGN: Previously published data were used to estimate transition probabilities for each step from normoalbuminuria until death. The effect of intervention on urinary albumin excretion rate by antihypertensive treatment was arbitrarily set at three different levels. All direct costs (screening, antihypertensive treatment, treatment of end stage renal failure) were included in the cost-benefit analysis by using real discount rates of 2.5% and 6%. SETTING: Computer simulation. SUBJECTS: Simulated cohort of 8000 patients. MAIN OUTCOME MEASURES: Mortality, incidence of diabetic nephropathy, incidence of end stage renal failure, and costs versus savings. RESULTS: Assuming treatment effects of 33% and 67% median life expectancy increased by four to 14 years, respectively, and the need for dialysis or transplantation decreased by 21% to 63%. Costs and savings would balance if the annual rate of increase of albuminuria was decreased from 20% to 18% a year. CONCLUSIONS: Screening and intervention programmes are likely to have life saving effects and lead to considerable economic savings.

Albuminuria↗
PubMed1993

Glucose-induced changes in renal haemodynamics in proteinuric type 1 (insulin-dependent) diabetic patients: inhibition by acetylsalicilic acid infusion.

The effect of hyperglycaemia on renal function in diabetic nephropathy remains poorly understood. We investigated the renal haemodynamic response to an acute plasma glucose rise from sustained euglycaemia to sustained hyperglycaemia in eight persistently proteinuric Type 1 (insulin-dependent) diabetic patients. Studies were performed in a double-blind cross-over manner after i.v. injection of 450 mg lysine acetylsalicilate (equivalent to 250 mg acetylsalicilic acid) or equal volume of 0.9% NaCl (isotonic saline). In the isotonic saline experiments hyperglycaemia produced a significant rise, by approximately 35%, in glomerular filtration rate in all patients from 41.5 +/- 5.2 to 55 +/- 6 ml.min-1.1.73 m-2 (p < 0.005) and an increase in sodium paraminohippurate clearance from 178 +/- 22.7 to 220 +/- 20.0 ml.min-1.1.73 m-2 (p < 0.05). These changes took place within the first 30 min of glucose infusion and were maintained for a 90 min hyperglycaemic period. Filtration fraction did not change significantly. Infusion of lysine acetylsalicilate lowered baseline glomerular filtration rate (isotonic saline vs lysine acetylsalicilate 41.5 +/- 5.2 vs 30.0 +/- 5.7 ml.min-1.1.73 m-2; p < 0.05) and significantly blunted the rise in glomerular filtration rate during hyperglycaemia (glomerular filtration rate increment: saline vs lysine acetylsalicilate: 13.6 +/- 2.8 vs 5.3 +/- 1.8 ml.min-1.1.73 m-2; p < 0.005). The effects on renal plasma flow were similarly blunted. In five additional patients, time- and volume-controlled isotonic saline experiments during sustained euglycaemia showed no significant changes in glomerular filtration rate and sodium paraminohippurate clearance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Storage temperature and differing methods of sample preparation in the measurement of urinary albumin.

Microalbuminuria is a predictor of persistent proteinuria, renal failure and cardiovascular disease and therefore accurate determination of urinary albumin concentration is important. We examined the stability of albumin in urine under different conditions of storage, temperature and sample preparation. There was no significant difference in urinary albumin concentration between fresh urine and urine stored at either 4 degrees C or 20 degrees C for up to 7 days. Similarly in urine samples from diabetic patients there was no significant difference in albumin concentration at levels ranging from 1.3 to 1999.3 mg/l between fresh urine at 4 degrees C and urine stored frozen for 1 week, 1 month or 6 months. Neither storage temperature (-20 degrees C or -40 degrees C) nor centrifugation of sample prior to assay made a significant difference to the albumin concentration. Multiple freezing and thawing of urine samples during 6 weeks of storage at -20 degrees C made no difference to albumin concentrations. Storage of urine samples in either polypropylene, polystyrene or borosilicate glass tubes did not result in a significant change in urinary albumin concentration after either 1 week or 1 month at -20 degrees C although, after 1 month of storage, urinary albumin concentrations tended to be lower by an average of approximately 7%. In tubes to which gelatine had been added this was reduced to 4%. We conclude that fresh urine can be kept at 4 degrees C or 20 degrees C for up to 7 days. Frozen urine samples can be stored for up to 6 months before assay without any loss of albumin concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Albuminuria↗
PubMed1993

Inhibition of nitric oxide synthesis in forearm vasculature of insulin-dependent diabetic patients: blunted vasoconstriction in patients with microalbuminuria.

1. Microalbuminuria is a risk factor for cardiovascular disease in patients with insulin-dependent diabetes mellitus, and may be a marker of microvascular dysfunction including endothelial damage. The purpose of this study was to determine whether vasoconstrictor responses to NG-monomethyl-L-arginine, an inhibitor of endothelium-derived relaxing factor/nitric oxide biosynthesis, differ between healthy subjects and insulin-dependent patients with or without microalbuminuria. 2. Twenty-eight insulin-dependent diabetic patients (14 with normal albumin excretion, 14 with microalbuminuria) were studied under euglycaemic conditions, together with 14 healthy control subjects. Forearm vascular responses to brachial artery infusions of NG-monomethyl-L-arginine, sodium nitroprusside (an endothelium-independent nitrovasodilator) and carbachol (an endothelium-dependent vasodilator) were determined by strain gauge plethysmography. 3. Basal blood flow and vasodilator responses were similar in each group. NG-Monomethyl-L-arginine reduced blood flow by 41.3 +/- 2.3% (mean +/- SEM) in healthy control subjects, 34.0 +/- 3.4% in diabetic patients without microalbuminuria and 29.2 +/- 2.0% in diabetic patients with microalbuminuria. Diabetic patients differed from healthy subjects (P = 0.005), due to a difference between control subjects and microalbuminuric diabetic patients (P < 0.001). NG-Monomethyl-L-arginine did not influence nitroprusside responses but reduced carbachol responses in control subjects and normoalbuminuric diabetic patients but not in microalbuminuric diabetic patients. 4. These results provide evidence of abnormal endothelium-derived relaxing factor/nitric oxide biosynthesis in insulin-dependent diabetic patients with microalbuminuria.

Adult↗
PubMed1993

Effect of beta-blocker therapy on serum lipoprotein profiles in patients on renal dialysis and in diabetic nephropathy.

We determined whether the serum lipoprotein levels in insulin-dependent diabetic patients (IDDM) with nephropathy and in patients on haemodialysis or continuous ambulatory peritoneal dialysis were affected by beta-blocker therapy. A case control study was performed in 18 IDDM patients with diabetic nephropathy, in 18 patients receiving chronic haemodialysis (HD) and 16 patients undergoing continuous ambulatory peritoneal dialysis (CAPD). In IDDM patients with diabetic nephropathy very low density lipoprotein-cholesterol (VLDL-CHOL) (0.680 +/- 0.17 vs 0.197 +/- 0.04 mmol/l, p = 0.004), total triglycerides (1.71 +/- 0.23 vs 0.808 +/- 0.14 mmol/l, p = 0.004) and very low density lipoprotein triglyceride (VLD-TG) were higher in the beta-blocker therapy group. In haemodialysis patients, beta-blocker therapy caused no significant changes in the serum lipoprotein profiles compared to the control group. In patients receiving continuous ambulatory peritoneal dialysis VLDL-CHOL was significantly higher (1.47 +/- 0.24 vs 1.08 +/- 0.21 mmol/l, p = 0.042) and cholesterol-high density lipoprotein (HDL-CHOL) was lower in the beta-blocker therapy group. The elevated VLDL-CHOL level (0.96 +/- 0.12 vs 1.24 +/- 0.14 mmol/l, p = 0.021) was correlated with the duration of CAPD in patients receiving beta-blocker therapy. Antihypertensive therapy with beta-blockers in IDDM patients with persistent proteinuria and in patients on continuous ambulatory peritoneal dialysis appears to adversely effect serum lipoproteins which may add to their cardiovascular risk.

Adrenergic beta-Antagonists↗
PubMed1993

Effect of selective inhibition of thromboxane synthesis on renal function in diabetic nephropathy.

Studies of nondiabetic renal disease suggest that thromboxane may be an important mediator of abnormal renal function. The role of thromboxane in diabetic nephropathy is not fully understood. We measured in a double-blind, randomized, placebo-controlled crossover study the effect of a thromboxane synthase inhibitor (FCE 22178, 400 mg two or three times per day) on urinary excretion of thromboxane B2 and 6-keto-prostaglandin F1 alpha, glomerular filtration rate (measured as clearance of polyfructosan), effective renal plasma flow (clearance of para-aminohippuric acid), fractional clearances of albumin and immunoglobin G and the reabsorption rate of beta 2-microglobulin in 15 patients with type 1 (insulin-dependent) diabetic nephropathy. In seven additional patients, the effect of the thromboxane synthase inhibitor given as 400 mg twice per day was compared with that of the thromboxane synthase inhibitor given as 400 mg three times per day. FCE 22178 administration caused a significant inhibition in the excretion of urinary thromboxane B2 and 2,3-dinor-thromboxane B2 compared with placebo (12.3 +/- 2.1 vs 24.6 +/- 5.1 ng/gm creatinine, p = 0.006, and 78.5 +/- 20.3 vs 335.5 +/- 84.1 ng/gm creatinine, p = 0.004, respectively) without any compensatory increase of 6-keto- prostaglandin F1 alpha or 2,3-dinor-6-keto-prostaglandin F1 alpha that reflect prostacyclin I2 biosynthesis. Glomerular filtration rate, effective renal plasma flow, renal vascular resistance, and filtration fraction were not significantly different after placebo or thromboxane synthase inhibitor treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Prognostic significance of microalbuminuria in insulin-dependent diabetes mellitus: a twenty-three year follow-up study.

A cohort of 63 Type 1 insulin-dependent diabetic patients were first characterized for overnight urinary albumin excretion rate (AER) in 1967. In 1981, seven out of eight (87%) patients with initial AER greater than or equal to 30 less than or equal to 140 micrograms/min (microalbuminuria) developed clinical proteinuria compared to only 2 out of 55 (4%) patients with initial AER less than 30 micrograms/min. The same cohort of patients was reassessed in 1990 after a total follow-up period of 23 years. The aim was to investigate the role of microalbuminuria in the prediction of total/cardiovascular mortality and the development of renal failure, in addition to clinical proteinuria. The initially microalbuminuric patients had a significantly higher risk of developing not only clinical proteinuria (relative risk 9.3, 95% C.I. 1.36 to 3.10, P less than 0.05), but also of dying from a cardiovascular cause (relative risk 2.94, 95% C.I. 1.18 to 7.34, P less than 0.05). The rate of progression to renal failure was higher but not significantly so in the microalbuminuric (2 of 8) compared to the normoalbuminuric (4 of 53) group (relative risk 3.31, 95% C.I. 0.72 to 15.24, NS). In insulin-dependent diabetic patients microalbuminuria is a powerful predictor of clinically overt diabetic renal disease as well as cardiovascular mortality.

Adult↗
PubMed1992

Introduction to a structural basis for renal and vascular complications in diabetes and hypertension.

BACKGROUND: An understanding of the structural basis for cardiovascular and renal complications in diabetes and hypertension is critical to design-focused intervention strategies. HYPOTHESIS: The processes leading to vascular damage in the kidney and in the arteries in diabetes and hypertension appear to be characterized by hypertrophic/hyperplastic changes in a number of cell types (such as smooth muscle cells, fibroblasts, mesangial cells) and by excessive deposition of extracellular matrix material. Markers of cell growth/proliferation, such as Na(+)-H+ exchange, show increased activity in diabetic patients with renal disease and in patients with essential hypertension. Insulin resistance is a feature of arterial hypertension and diabetes and may contribute to renal and cardiovascular damage in these patients. A number of risk factors for cardiovascular disease cluster in the subset of diabetic patients prone to renal disease. These include dyslipidaemia, left ventricular hypertrophy and hypertension. It is postulated that a familial predisposition to renal and cardiovascular disease is the underlying reason for the susceptibility to the diabetic cardiorenal syndrome. CONCLUSION: In the management of diabetes and hypertension, it may prove possible to instigate preventive strategies by using therapeutic agents such as angiotensin converting enzyme inhibitors, which have the potential to interfere with the haemodynamic, growth and insulin sensitivity processes that contribute to vascular damage.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1992

Predisposition to essential hypertension and the development of diabetic nephropathy.

Only a subset of insulin-dependent diabetic patients are at risk of developing nephropathy. Prospective studies of uncomplicated insulin-dependent diabetic cohorts have shown that a rise in systemic arterial pressure is a concomitant feature of the progression to early nephropathy. The development of hypertension is an integral feature of established nephropathy in diabetes, and its amelioration retards the progression of disease and may improve overall mortality. Family studies have suggested that nondiabetic parents of insulin-dependent diabetic patients with nephropathy have a greater prevalence of hypertension, and in certain groups of non-insulin dependent patients, it has been found that the blood pressure before the onset of diabetes correlates with the development of nephropathy after the onset of diabetes. These results indicate that a propensity to hypertension may be part of the genetic predisposition to nephropathy. This contention is further supported by the finding that a raised erythrocyte sodium-lithium countertransport, a biochemical marker of hypertension and cardiovascular disease whose activity is largely genetically determined, occurs with greater frequency in proteinuric diabetic patients and their nondiabetic parents than in those diabetic patients without nephropathy and their parents. Recent family studies have also shown that a family history of cardiovascular disease significantly increases the risk of nephropathy by up to three-fold in insulin-dependent diabetes. It is suggested that the cardiorenal complications of diabetes mellitus may be linked to reduced insulin sensitivity, which itself is associated with hypertension, raised sodium-lithium countertransport rates, and cardiovascular disease.

Antiporters↗
PubMed1992

Diabetic nephropathy. Future avenue.

Diabetes mellitus has become the leading cause of ESRF in the United States. Patients with diabetic nephropathy suffer high cardiovascular morbidity and mortality. Because only 40% of diabetic patients eventually develop diabetic kidney disease, it may be possible to devise primary prevention measures targeted at the subset of patients at risk. Recently, a predisposition to hypertension, a family history of diabetic nephropathy, and a family history of CVD disease each have been associated independently with the development of diabetic renal complication in IDDM. Risk factors for macrovascular damage, including raised arterial BP, dyslipidemia, and insulin resistance, can be detected early in the course of progression to diabetic nephropathy. These risk indicators recently have been shown to be already present at the stage of normoalbuminuria in those patients who eventually will progress to microalbuminuria. Treatment of established renal disease can only delay the onset of ESRF, and lowering of microalbuminuria has been shown to retard the onset of persistent proteinuria. However, no study to date has demonstrated prevention of renal disease in these patients. The ultimate aim should, therefore, be the prevention of the transition from normoalbuminuria to microalbuminuria in individuals who are at higher risk of diabetic renal disease and CVD.

Diabetic Nephropathies↗