Age-related changes in fatty acids from different adipose depots in rat and their association with adiposity and insulin

Objective We studied age-related changes in fatty acids (FAs) from serum and adipose tissue in rats by comparing different adipose regions and analyzed their relations to adiposity and insulin function. Methods Female weaned rats were fed on a high-fat diet until 6, 14, and 20 mo of age (n = 12, n = 6, n = 10, respectively). Body weight, adiposity, serum insulin, serum glucose, and homeostatic model assessment index were measured. FA compositions from serum and interscapular brown, periovarian, mesenteric, and subcutaneous tissues were determined by gas chromatography. Results Body weight and adiposity increased with age; visceral depots grew by hypertrophy, whereas subcutaneous depots grew by hyperplasia and in a higher ratio. Initially, the mesenteric tissue showed greater saturated and trans-FA contents, whereas brown tissue had higher polyunsaturated FA (PUFA) proportions. Aging resulted in a lower saturation degree in adipose tissue, attenuating earlier differences among depots. There was an elevation in ω-6 PUFAs with age, mainly because of C18:2ω-6, whereas ω-3 long-chain PUFAs, C20:5ω-3 and C22:6ω-3, tended to decrease in serum and adipose tissue. Adiposity was associated positively with monounsaturated FAs and inversely with PUFAs; insulin-related variables correlated negatively with serum ω-6 PUFA but positively with serum monounsaturated FAs and subcutaneous depot trans-FAs. Conclusion The mesenteric tissue showed the least favorable FA profile compared with the other depots, but differences among adipose regions diminished with age. In rats fed a high-fat diet, aging resulted in a lower saturation degree, with increased values in the cardiometabolic risk factor ω-6/ω-3 ratio in serum and adipose tissue.