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Glomerular changes in normo- and microalbuminuric patients with long-standing insulin-dependent diabetes mellitus
1Department of Internal Medicine, University of Padova, Italy.
Abstract:
Normalbuminuric patients who have long-standing IDDM have a wide range of renal structure, from within normal limits to advanced lesions that overlap those of patients who have high levels of MA and border on those seen in patients who have overt DN. Patients who have low-level MA have reduced glomerular structure similar to that of patients who have NA. Low GFR, hypertension, or both can occur in patients who have NA or low-level MA and are associated with more advanced lesions. Patients who have MA and AER greater than 45 mg/24 hr have more advanced lesions than do patients with NA or low-level MA, but similar lesions are present in these patients whether AER is greater than or less than 100 mg/24 hr. Increasing AER in NA and MA patients who have long-standing IDDM is associated with GBM and mesangial expansion. A structural basis for MA cannot currently be deduced from studies of glomerular epithelial cell fine structure, capillary wall charge site analysis, or immunohistochemical studies of renal ECM composition. Hemodynamic adaptations to mesangial expansion and reduced filtration surface and, perhaps, hydraulic conductivity may accelerate glomerular damage, as expressed by increasing AER. Microalbuminuria derives its clinical utility in IDDM, as it identifies a population of patients at statistically increased risk of progression to overt DN by acting as a marker of already well-established DN lesions. Although MA is currently the best of the widely used indicators of DN risk, it is not precise. Therapies that reduce MA may ultimately slow or prevent progression toward ESRD, but this finding requires confirmation by demonstrating that a given treatment strategy can preserve GFR.
Insights
Microalbuminuria (MA) in long-standing insulin-dependent diabetes mellitus (IDDM) indicates advanced kidney lesions. Early detection and intervention are crucial for preventing diabetic nephropathy (DN) progression and end-stage renal disease (ESRD).
Area of Science:
- Nephrology
- Diabetology
- Pathology
Background:
- Patients with long-standing insulin-dependent diabetes mellitus (IDDM) exhibit diverse renal structures, even without significant albuminuria.
- Renal lesions in normalbuminuric IDDM patients can range from normal to advanced, overlapping with those in patients with microalbuminuria (MA) and overt diabetic nephropathy (DN).
Purpose of the Study:
- To investigate the spectrum of renal structural changes in normalbuminuric and microalbuminuric patients with long-standing IDDM.
- To understand the relationship between albumin excretion rate (AER), glomerular filtration rate (GFR), hypertension, and renal pathology in IDDM.
- To clarify the clinical utility and limitations of MA as a marker for DN progression.
Main Methods:
- Histopathological examination of renal biopsies from IDDM patients with varying albuminuria levels.
- Correlation of structural findings with clinical parameters such as GFR, blood pressure, and AER.
- Analysis of glomerular basement membrane (GBM) and mesangial expansion in relation to AER.
Main Results:
- Normalbuminuric patients can have renal lesions similar to those with MA or overt DN.
- Low GFR and hypertension are associated with more advanced lesions in both normalbuminuric and microalbuminuric patients.
- Increasing AER correlates with GBM and mesangial expansion, suggesting accelerated glomerular damage.
- MA identifies patients at increased risk for DN progression, but its predictive precision is limited.
Conclusions:
- MA is a valuable but not perfectly precise indicator of DN risk in IDDM.
- The presence of MA signifies established DN lesions, necessitating close monitoring.
- Therapies reducing MA may potentially slow progression to end-stage renal disease (ESRD), but GFR preservation must be demonstrated.