Use of proton spectroscopy for detection of homozygous fatty ZDF-drt rats before weaning.

Genotypes of pre-obese and lean pups were distinguishable from 13 days of age onwards and the procedure allowed prediction of genotype with 98% accuracy at 12-15 days and was 100% reliable at 16 days and beyond.

Abstract

OBJECTIVE: To investigate the use of proton spectroscopy to measure abdominal fat content in pre-obese offspring of obese and lean Zucker diabetic fatty (ZDF-drt) rats. DESIGN: Large and small litters (size 4-15, 127 pups total) were serially measured during the suckling period to assess their abdominal fat index (AFI) and subsequently identified as to their genotype (fa/fa obese or Fa/? lean). MEASUREMENTS: Body weight, abdominal fat index (derived from percent fat by proton spectroscopy x body weight). When the abdominal fat index was plotted vs body weight, the data fell along two regression lines that distinguished pre-obese from lean pups. Percent fat by proton spectroscopy was validated against chemical measurement. RESULTS: Genotypes of pre-obese and lean pups were distinguishable from 13 days of age onwards. The procedure allowed prediction of genotype with 98% accuracy at 12-15 days and was 100% reliable at 16 days and beyond. The rate of fat accretion in the pups correlated directly with genotype, litter size and caloric density of the mother's food. CONCLUSION: Unlike currently available methods, the technique is rapid, simple, non-invasive and has the additional advantage of providing a measure of fat content sequentially over time in the same animal. It should be useful for the study of early metabolic derangements in the development of obesity and non-insulin dependent diabetes syndromes.