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

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.