Increased in vivo glucose utilization in 30-day-old obese Zucker rat: role of white adipose tissue.

In vivo whole-body glucose utilization and uptake in multiple individual tissues were investigated in conscious 30-day-old Zucker rats, which when obese are hyperphagic, hyperinsulinemic, and normoglycemic. Whole-body glucose metabolism (assessed by [3-3H]glucose) was 40% higher in obese (fa/fa) than in lean (Fa/fa) rats, suggesting that obese rats were quite responsive to their hyperinsulinemia (140 vs. 55 microU/ml). In obese compared with lean rats, tissue glucose uptake (assessed by the 2-deoxyglucose technique) was increased by 15, 12, and 6 times in dorsal, inguinal, perigonadal white depots, respectively; multiplied by 2.5 in brown adipose tissue; increased by 50% in skin from inguinal region but not in that from cranial, thoracic, or dorsal area; and increased twofold in diaphragm but similar in heart, in proximal intestine, and in total muscular mass of limbs. Our data establish that in young obese rats the hypertrophied white adipose tissue was a major glucose-utilizing tissue whose capacity for glucose disposal compared with that of half the muscular mass. Adipose tissue could therefore play an important role in the homeostasis of glucose in obese rats in the face of their increased carbohydrate intake.