Brown fat is a type of fat, found in both children and adults, which can produce heat and regulate the body's metabolism and energy use. White fat is the more common type of fat which is used to store extra calories. Understanding more about differences between brown and white fat may allow us to develop new approaches to improve the body's metabolism.

The overarching goal of this study, is to map fat (adipose) tissue differences in humans. The investigators will probe multiple aspects of fat cell (adipocyte) identity by integrating quantitative chemical imaging, single-cell and single-nucleus RNA sequencing (sc and snRNAseq), and site-specific collection of adipocytes and adipocyte precursors.

Deidentified data from these studies will be submitted to the Human Cell Atlas. The investigators anticipate that these studies will ultimately increase understanding of mechanisms by which fat (adipose) tissue regulates systemic metabolism (energy transformation in the body), and promotes risk for metabolic disease. Knowledge gained from this research may be used to set the stage for disease-specific analyses, and aid in the development of personalized medicine for metabolic diseases such as type 2 diabetes.

Inclusion criteria:

1. Healthy participants between age 18 and 75 years undergoing planned clinically indicated procedure at BIDMC.

Exclusion Criteria:

1. Body mass index (BMI) greater than or equal to 40 kg/m2
2. History of any local or systemic infectious disease with fever or requiring antibiotic within four weeks of drug administration;
3. Diabetes, either previously diagnosed or hemoglobin A1c greater than or equal to 6.5%
4. Use of oral or parenteral corticosteroids (epidural permitted) or other medication known to cause insulin resistance in the previous 6 weeks.
5. Willingness to provide informed consent and follow study procedures, including attending scheduled visits.
6. Chronic kidney disease stage 4 or 5 (including end-stage renal disease);
7. Hepatic disease, including serum alanine aminotransferase (ALT) or aspartate transaminase (AST) greater than or equal to 3 times the upper limit of normal; hepatic synthetic insufficiency as defined as serum albumin < 3.0 g/dL; or serum bilirubin > 2.0;
8. Active malignancy (except squamous or basal cell carcinoma of skin)
9. Bleeding disorder, treatment with anticoagulants (if not discontinued prior to surgery), or platelet count <50,000;
10. Current addiction to alcohol or substances of abuse;
11. Mental incapacity, unwillingness or language barriers precluding adequate understanding or cooperation;
12. Use of an investigational drug within 30 days prior to screening.
13. There will be no involvement of special vulnerable populations such as fetuses, neonates, pregnant women, children, prisoners, institutionalized or incarcerated individuals, or others who may be considered vulnerable populations.
14. Because the goal is to study adult human brown adipose tissue, children are not eligible to participate.

Participants planning a procedure will be recruited from clinical practices of Dr. Andrew White, Dr. Peter Mowschenson, and Dr. Per-Olof Hasselgren at BIDMC.

Deidentified participant data will be shared with other researchers with permission of local institutional review boards via the Human Cell Atlas database.

6 months after publication of study results

Data will be shared with academic investigators with approval of local institutional review boards.