A Multi-modal Cohort Study of Brown Adipose Tissue Based on Paired Comparisons at Room Temperature and After Cold Exposure

This study is a single-center, prospective clinical study that plans to prospectively recruit volunteers aged 18-40 years, including metabolically healthy individuals and those with diabetes mellitus and hyperlipidemia. Participants will undergo \[¹⁸F\]fluorodeoxyglucose positron emission tomography/computed tomography (\[¹⁸F\]FDG PET/CT) scans both at room temperature and after cold exposure. The planned sample size is 500 participants. The study will systematically collect baseline data, questionnaire responses, \[¹⁸F\]FDG PET/CT images acquired under both conditions, as well as saliva and blood samples. The study aims to establish a clinical-imaging-biological multimodal brown adipose tissue (BAT) cohort with paired pre- and post-cold exposure comparisons. Based on this cohort, we expect to achieve new breakthroughs in BAT detection methods, assessment criteria, and the understanding of its genetic mechanisms.

Inclusion Criteria: * Aged 18 to 40 years, regardless of sex; * Stable body weight within the past 3 months, with a weight change of \< 3 kg; * Able to tolerate the cold exposure test (without severe cold allergy, Raynaud's phenomenon, cold urticaria, or other related conditions). Exclusion Criteria: * Any diagnosed chronic metabolic disease (excluding diabetes mellitus and hyperlipidemia); no major organic diseases (including but not limited to cardiovascular, respiratory, endocrine, neuropsychiatric disorders) and no history of malignancy * Pregnant women, breastfeeding women, or those planning to become pregnant during the study period; * Use of β-blockers (e.g., propranolol), benzodiazepines (e.g., diazepam), or other medications that may affect brown adipose tissue metabolism (such as glucocorticoids, sympathomimetic agents, some antidepressants, etc.) within the past 4 weeks, as determined by the investigator; * Presence of contraindications to PET-CT examination (e.g., claustrophobia, inability to remain supine for 30 minutes, allergy to FDG, etc.);