A Clinical Study on Using Multimodal Ultrasound to Assess Muscle Mass in Metabolic Diseases

Inclusion Criteria: * Diagnosis of metabolic syndrome according to the Chinese Consensus on Diagnosis and Management of Metabolic Syndrome (2020 edition), meeting at least 3 of the following 5 criteria: abdominal obesity, hypertension, hyperglycemia, hypertriglyceridemia, and low HDL-C. * Diagnosis of type 2 diabetes according to the ADA 2023 diagnostic criteria, with disease duration of at least 1 year. * Body mass index (BMI) \>= 28 kg/m², without hypertension, hyperglycemia, dyslipidemia, or other metabolic abnormalities. * Healthy volunteers without metabolic diseases, muscle diseases, chronic liver or kidney dysfunction, malignancies, cardiovascular diseases, or neurological disorders, and without long-term use of corticosteroids or other medications affecting muscle metabolism. * Age and sex matched across all four groups. * Willing and able to provide written informed consent and comply with all study procedures including ultrasound examination, DXA scan, and follow-up visits. Exclusion Criteria: * Severe hepatic or renal failure, malignancy, stroke, severe cardiovascular disease, or autoimmune diseases. * Long-term use of corticosteroids, muscle relaxants, or other medications affecting muscle metabolism. * Presence of movement disorders, joint diseases, muscle injury, muscular dystrophy, or other conditions affecting muscle function. * Pregnancy or lactation. * Inability to cooperate with ultrasound examination, DXA scanning, or follow-up assessments. * Any other condition that, in the opinion of the investigator, would interfere with the study objectives or participant safety.