A 55-year-old obese woman complains of declining visual acuity. Funduscopic examination shows peripheral retinal microaneurysms. Urinalysis reveals 3+ proteinuria and 3+ glucosuria. Serum albumin is 3 g/dL, and serum cholesterol is 350 mg/dL. These clinicopathologic findings are best explained by which of the following mechanisms of disease?

**Core Concept**
Diabetic retinopathy, characterized by peripheral retinal microaneurysms, is a complication of diabetes mellitus that arises due to chronic hyperglycemia-induced damage to the retinal microvasculature. The pathogenesis involves multiple factors, including increased glucose levels, oxidative stress, and inflammation, ultimately leading to microvascular damage and leakage.

**Why the Correct Answer is Right**
Peripheral insulin resistance is a hallmark of type 2 diabetes mellitus, leading to hyperglycemia and subsequent damage to various organs, including the eyes. Insulin resistance impairs glucose uptake in peripheral tissues, causing an increase in glucose levels in the blood. Elevated glucose levels in the blood lead to the activation of various pathways, including the polyol pathway, protein kinase C activation, and advanced glycosylation end-product formation, which ultimately contribute to the development of diabetic retinopathy. The presence of proteinuria and glucosuria further supports the diagnosis of diabetic nephropathy, a complication of diabetes mellitus. The low serum albumin level is consistent with hypoalbuminemia, which is often seen in patients with nephrotic syndrome.

**Option A:** This option is incorrect because peripheral insulin resistance is a characteristic feature of type 2 diabetes mellitus, not a mechanism of disease.

**Option B:** Increased peripheral insulin uptake is not a mechanism of disease that would lead to the development of diabetic retinopathy and nephropathy.

**Option C:** Irregular insulin secretion is a feature of type 1 diabetes mellitus, which typically presents with hyperglycemia due to absolute insulin deficiency.

**Clinical Pearl / High-Yield Fact**
The patient's symptoms and findings are consistent with diabetic retinopathy and nephropathy, which are complications of type 2 diabetes mellitus. The presence of peripheral retinal microaneurysms and proteinuria are key indicators of these complications.

**Correct Answer:**
✓ Correct Answer: A. Peripheral insulin resistance

✓ Correct Answer: A. Peripheral insulin resistance