A 58-year-old man from Delhi with a 12-year history of Type 2 diabetes mellitus presents with progressive fatigue and dyspnea on exertion. His HbA1c is 8.9% despite metformin and glibenclamide therapy. Fasting blood glucose is 165 mg/dL. On examination, he has central obesity (waist circumference 105 cm), hypertension (148/92 mmHg), and mild peripheral edema. Serum creatinine is 1.8 mg/dL (eGFR 38 mL/min/1.73m²), and urinary albumin-to-creatinine ratio (UACR) is 320 mg/g. Fundoscopy reveals dot-blot hemorrhages and hard exudates. What is the primary pathological lesion in the kidney that accounts for his albuminuria?