Obesity and fat quantification in lean tissues using three-point Dixon MR imaging.
BACKGROUND: It has been suggested that increased hepatic and intramuscular fat is associated with insulin resistance, and that increased pancreatic fat is related to impaired insulin secretion. OBJECTIVE: We postulated that in obese nondiabetic teenagers insulin levels would be directly related to increases in intramuscular and hepatic fat and inversely related to increases in pancreatic fat. MATERIALS AND METHODS: MRI was used to assess the percentage of fat in the liver, muscle and pancreas in 15 healthy Mexican-American girls, 14-17 years old, with body mass indexes (BMIs) ranging from 17.7 kg/m(2) to 46 kg/m(2). RESULTS: Strong correlations were observed between BMI and fat content in the liver, muscle, and pancreas (r(2)s between 0.50 and 0.89; P<0.003). Serum insulin levels were closely associated with fat measures in the muscle and liver (r(2s)=0.63 and 0.29, and P=0.001 and P=0.023, respectively). In contrast to our hypothesis, fat content in the pancreas was also directly related to insulin secretion (r(2)=0.74; P=0.001). SUMMARY: We conclude that in nondiabetic teenagers, obesity is associated with an increased accumulation of fat in the pancreas without impairment of insulin secretion.