**Core Concept**
Diabetic nephropathy is a common complication of diabetes mellitus, characterized by glomerular damage leading to proteinuria. Early detection via microalbuminuria is critical, and interventions targeting glycemic control, blood pressure, and renal hemodynamics play a key role in slowing progression.

**Why the Correct Answer is Right**
In early-stage diabetic nephropathy, pancreatic islet cell or whole pancreas transplantation can restore insulin independence and improve glycemic control. This leads to reduced hyperglycemia, which directly decreases glomerular injury and proteinuria. Studies show that improved metabolic control post-transplantation correlates with reduced urinary protein excretion, especially when initiated early. This reflects the role of insulin in modulating renal hemodynamics and glomerular filtration.

**Why Each Wrong Option is Incorrect**
Option A: Microalbuminuria is a well-established predictor of long-term cardiovascular morbidity and mortality in diabetes, not a neutral marker.
Option B: Strict glycemic control, especially in early stages, is proven to prevent or delay microalbuminuria, as shown in trials like UKPDS.
Option D: Angiotensin receptor blockers (ARBs) have proven additive benefits beyond blood pressure control, including direct renoprotective effects via reduction of intraglomerular pressure and inhibition of fibrosis.

**Clinical Pearl / High-Yield Fact**
Early intervention with insulin normalization and blood pressure control is crucial—pancreatic transplantation, though not routine, offers a potent option in select patients with early nephropathy and insulin deficiency.

✓ Correct Answer: C. β-islet cell/pancreatic transplantation can improve the proteinuria in early stage.