Final answer:
A 38-year-old Native American man with diabetes mellitus and elevated hemoglobin A1C is at the highest risk for developing metabolic syndrome due to existing impaired glucose homeostasis and high prevalence of type 2 diabetes in that population.
Step-by-step explanation:
The patient at the highest risk for developing metabolic syndrome is a 38-year-old Native American man who has diabetes mellitus and elevated hemoglobin A1C. The key factors contributing to metabolic syndrome include abdominal obesity, high blood pressure, high blood glucose and triglyceride levels, and low blood HDL levels. These factors are a major risk factor for cardiovascular diseases and type 2 diabetes.
This particular patient already has diabetes mellitus, which indicates impaired glucose homeostasis, one of the components of metabolic syndrome. The elevated hemoglobin A1C further suggests poor control of blood glucose levels. Native Americans have a higher prevalence of obesity and type 2 diabetes, making this patient population more susceptible to developing metabolic syndrome. These factors combined put him at the highest risk among the presented options.