FAHFA footprint in the visceral fat of mice across their lifespan.

Fatty acid esters of hydroxy fatty acids (FAHFAs) are a new class of endogenous lipids with anti-inflammatory and anti-diabetic effects, having the potential to treat type 2 diabetes (T2D). In view of the important regulatory and therapeutic actions of FAHFAs on age-related diseases such as T2D, we hypothesized that they may also play crucial roles in the growth, development, and aging process. Here, we investigated the FAHFA footprint in the visceral adipose tissue (VAT) of mice across lifespan to attain potential clues for understanding the roles of FAHFAs in growth, development, and aging using chemical isotope labeling assisted liquid chromatography-mass spectrometry. VAT samples were harvested from 80 C57BL/6J male mice of nine different ages (1, 2, 3, 6, 9, 12, 15, 18, and 24 months). The results showed that a total of 51 FAHFA families, including 301 regioisomers, were detected in the VAT of mice of all ages, and the number of FAHFAs (both family and regioisomer) in VAT increased with age, from 35 families (186 ± 0 regioisomers) at 1-month-old mice to 46 families (278 ± 6 regioisomers) in 18-month-old mice. Furthermore, the content of 12 FAHFA families per 100 mg of VAT of mice was highly correlated with age, and was usually low in the middle-age (3-15 months). However, because the VAT mass was 4-5 fold higher in middle-aged mice compared to younger or older mice, the total amount of most of the FAHFA regioisomers in VAT was increased in middle-aged mice. To the best of our knowledge, this is the first study to show that the number of regioisomers from 51 FAHFA families and abundance of 15 FAHFA families are strongly dependent on age, which would be helpful for understanding the mechanisms underlying the effects of FAHFAs on growth, development, and aging.