CKD: Progression and Diabetes (2001)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To discuss diabetic nephropathy (DN), a complication of diabetes characterized by early hyperfiltration progressing to albuminuria and a decline in renal function. Clinical trials indicate good glycemic control and blood pressure control can reduce the risk of developing or delay the progression of DN. Dietary protein restriction may also be beneficial, but needs further study.
Inclusion Criteria:
Article inclusion criteria not specified.
Exclusion Criteria:
Not specified.
Description of Study Protocol:

Recruitment: Article selection methods not specified.

Design: Narrative Review.

Blinding Used (if applicable): Not specified.

Intervention Used (if applicable):  Not specified.

Statistical Analysis:  Not specified.

Data Collection Summary:

Timing of Measurements: Not specified.

Dependent Variables: Not specified.

Independent Variables: Not specified.

Control Variables: Not specified.

Description of Actual Data Sample:

Initial N: not specified, 57 articles included in review

Attrition (Final N): not specified.

Age: not specified.

Ethnicity: not specified.

Other relevant demographics: not specified.

Anthropometrics: not specified.

Location: not specified.

 

Summary of Results:

Progression of Diabetic Nephropathy

1. Early Renal Changes

Nearly all individuals have renal hypertrophy (increased kidney size) and hyperfiltration (increased GFR) when diagnosed with Type I diabetes. Increased GFR is also found in type 2 diabetes.

Hyperfiltration is a consequence of an increase in glomerular capillary pressure and appears to play an important function in the progression of diabetic nephropathy.

Other changes are:

    a. Microalbuminuria: 30 to 300 mg urinary albumin excreted/d

    b. elevated serum creatinine: >2 mg/dL

    c. elevated BUN: >40 mg/dL

Initiation of insulin therapy (type 1 diabetes) and restoration of glycemic control can reduce hypertrophy and restore normal kidney function.

2. Progression to microalbuminuria. Microalbuminuria is a result of a loss of functioning glomeruli and generally occurs 7 to 15 yr after the diagnosis of type 1 diabetes and is a strong predictor of overt nephropathy leading to ESRD during the next 10 – 15 yr.

Microalbuminuria may be present upon diagnosis of type 2 diabetes and is less a predictor of clinical disease in this group.

Once overt diabetic nephropathy has been diagnosed, GRF begins to decline by 1 mL/min/month unless aggressive treatment for hypertension is begun.

2. Progression to overt nephropathy

The diagnosis of nephropathy is made when urinary albumin is >300 mg/d. If proteinuria has not developed within 25 to 30 yr after the diagnosis of diabetes, the risk of developing nephropathy is sharply reduced.

Nearly all persons will develop ESRD within 10 yr after diagnosis of overt nephropathy. During this stage, GFR continues to fall an average of 10 mL/min/yr.

Controlling Risk Factors

1. Noncontrollable risk factors should be identified so these patients can be targeted for early intervention: duration of diabetes, type of diabetes, presence of macrovascular disease, presence of retinopathy, family history of hypertension or renal disease and ethnicity.

2. Controllable risk factors should be treated (hyperglycemia, hypertension, high dietary protein intake).

Glycemic control

In the DCCT a decrease of HbA1c from 9% to 7% (normal, 4.5% to 6.05%) was associated with a 39% decrease in the development of microalbuminuria in subjects without early signs of diabetes complications.

Blood pressure control

Hypertension is a strong risk factor for the development of proteinuria and overt nephropathy in persons with diabetes. Mild albuminuria can be reversed and the progression of nephropathy delayed if hypertension can be identified and controlled early.

Treatment options are weight control, moderate sodium intake, and ACE inhibitors. The Collaborative Study Group reported a 50% reduction in the risk of progression to ESRD in subjects with type 1 diabetes and nephropathy when treated with ACE inhibitors during a 3-yr period. Similar improvements have been shown in individuals with type 2 diabetes.

Clinical Applications

 Dietary protein restriction:

1. Before microalbuminuria. The goal is to prevent or delay progression to persistent microalbuminuria with near normal blood glucose, blood pressure and moderate protein intake. With persistent microabluminuria, additional treatments include controlling blood pressure with weight loss, sodium restriction to 2,400 mg/d and ACE inhibitors, and decrease protein intake to 0.8 g/kg/d.

2.  Excessive protein intake may contribute to hyperfiltration. Studies with a small number of subjects have shown that reduced protein intake to 0.6 to 0.79 g/kg/d is associated with a decrease in the rate of decline in GFR. A concern for low protein diets in individuals with renal failure is protein malnutrition shown by a study with a small number of subjects. The subjects were in negative nitrogen balance, decline in quadriceps muscle strength and increase in body fat mass. Poor glycemic control is a major risk factor in the development of nephropathy in both type 1 and 2 diabetes.

Author Conclusion:

Although diabetic nephropathy remains a serious complication of diabetes, clinical studies have suggested treatment strategies to prevent and delay the progression of the disease. Poor glycemic control and hypertension have been identified as risk factors in the development of diabetic nephropathy and early control can prevent or slow decline in renal function.

Dietary protein restriction may also retard the progression of renal failure but no firm recommendations have yet been established. A moderate protein diet should be encouraged (0.8 g/kg/d).

 

Funding Source:
University/Hospital: University of Tennessee Medical Center
Reviewer Comments:

Good review of the progression of diabetic nephropathy, mostly focused on type 1 diabetes. Good recommendations for prevention of nephropathy.

Quality Criteria Checklist: Review Articles
Relevance Questions
  1. Will the answer if true, have a direct bearing on the health of patients? Yes
  2. Is the outcome or topic something that patients/clients/population groups would care about? Yes
  3. Is the problem addressed in the review one that is relevant to dietetics practice? Yes
  4. Will the information, if true, require a change in practice? Yes
 
Validity Questions
  1. Was the question for the review clearly focused and appropriate? Yes
  2. Was the search strategy used to locate relevant studies comprehensive? Were the databases searched and the search termsused described? No
  3. Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified andappropriate? Wereselectionmethods unbiased? No
  4. Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methodsspecified,appropriate, andreproducible? No
  5. Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined? Yes
  6. Was the outcome of interest clearly indicated? Were other potential harms and benefits considered? Yes
  7. Were processes for data abstraction, synthesis, and analysis described? Were they applied consistently acrossstudies and groups? Was thereappropriate use of qualitative and/or quantitative synthesis? Was variation in findings among studies analyzed? Were heterogeneity issued considered? If data from studies were aggregated for meta-analysis, was the procedure described? No
  8. Are the results clearly presented in narrative and/or quantitative terms? If summary statistics are used, are levels ofsignificance and/or confidence intervals included? Yes
  9. Are conclusions supported by results with biases and limitations taken into consideration? Are limitations ofthe review identified anddiscussed? ???
  10. Was bias due to the review's funding or sponsorship unlikely? Yes