Adipose Tissue Blood Flow in Aging Humans

Overview

The goal of this basic science clinical trial is to understand whether adipose tissue blood flow changes between younger and older healthy adults. The main question\[s\] it aims to answer are: * Is basal and nutrient responsive adipose tissue blood flow (ATBF) different between younger and older adults * What molecular and systemic signatures related to adipose tissue blood flow are altered between these two groups. Participants will undergo measurements of adipose tissue blood flow using the xenon washout technique, undergo 2 abdominal subcutaneous adipose tissue biopsies, and drink a sugary drink.

On Visit 1, volunteers will provide written informed consent (and urine pregnancy test for women of childbearing age), complete a Dual x-ray absorptiometry scan, baseline labs (comprehensive metabolic panel) and a cardiopulmonary exercise test. Participants will arrive fasted at 08:00, and urine pregnancy test for women of childbearing age administered and an intravenous catheter will be placed. Following 30min of supine rest, baseline venous blood samples will be collected. ATBF will be assessed on participants' left abdomen first by measurement of blood flow using 133Xenon washout method. Immediately thereafter, an abdominal adipose tissue biopsy of the left side will be performed but ≥6 cm distant from location of 133Xenon injections. Subjects will them consume 75 gm glucose; because ATBF peaks 30-60 minutes following ingestion of glucose, ATBF measures will start 30 minutes after ingestion on the contralateral side followed immediately by plasma measures and another adipose tissue biopsy. During ATBF measurements, brachial blood pressure will be assessed in two-minute intervals.