Associations between estimated fatty acid desaturase activities in serum lipids and adipose tissue in humans: links to obesity and insulin resistance

Abstract

Fatty acid composition of serum lipids and adipose tissue triacylglycerols (AT-TAG) partly reflect dietary fatty acid intake. The fatty acid composition is, besides the diet, also influenced by desaturating enzymes that can be estimated using product-to-precursor fatty acid ratios. The interrelationships between desaturase indices derived from different serum lipid fractions and adipose tissue are unclear, as well as their associations with obesity and insulin resistance. We aimed to investigate cross-sectional correlations between desaturase indices as measured in serum lipid fractions (phospholipids; PL and free fatty acids; FFA) and in adipose tissue (AT-TAG). In a population-based sample of 301 healthy 60-year-old men various desaturase indices were assessed: stearoyl-CoA-desaturase (16:1n-7/16:0; SCD-16 and 18:1n-9/18:0; SCD-18, respectively), delta-6-desaturase (20:3n-6/18:2n-6; D6D) and delta-5-desaturase (20:4n-6/20:3n-6; D5D). Correlations with BMI and insulin resistance (HOMA-IR) were also examined. SCD-16 and D5D were significantly correlated between fractions and tissues (all r > 0.30), whereas SCD-18 and D6D were not. Desaturase indices in serum FFA and AT-TAG were significantly correlated; SCD-16 (r = 0.63), SCD-18 (r = 0.37), and D5D (r = 0.43). In phospholipids, SCD-16 was positively correlated to BMI (r = 0.15), while D5D negatively to both BMI (r = -0.30) and HOMA-IR (r = -0.31), all p < 0.01. D6D in both phospholipids and AT-TAG was positively correlated to HOMA-IR and BMI (all p < 0.01). In conclusion, SCD-1 and D5D activity indices showed overall strong correlations between lipid pools. SCD-1 activity index in adipose tissue is best reflected by 16:1/16:0-ratio in serum FFA, but associations with obesity and insulin resistance differ between these pools. D5D in PL was inversely related to obesity and insulin resistance, whereas D6D index showed positive associations.

Docosahexaenoic Acid Content in Plasma Phospholipids and Desaturase Indices in Obese Children

“…The plasma phospholipid fraction was used to obtain the desaturase indices in our study because the turnover of plasma phospholipids is slower than that of plasma triglyceride fatty acids and there is minimal day-to-day variation; however, it is controversial which fraction of desaturase indices is most appropriate to [37][38][39][40] . In conclusion, DHA content in plasma phospholipids had a negative association with SCD indices, which may explain the anti-obesity effect of DHA.…”

Omega-3 fatty acid supplementation and cardiovascular disease

“…In 301 Swedish men (60 years of age), for example, FADS1 products (20:4, 6/20:3, 6) in adipose tissue and plasma phospholipids were inversely correlated with obesity and insulin resistance, whereas FADS2 products (18:3, 6/18:2, 6) showed a positive association ( 74 ). A study involving 97 Japanese men ( ‫ف‬ 50 years of age) showed reduced 20:4, 6/20:3, 6 (FADS1 product), but higher levels of 18:3, 6/18:2, 6 (FADS2 product) in obese and MetS patients versus control ( 75 ).…”

Plasma fatty acids as predictors of glycaemia and type 2 diabetes

“…Finally, fatty acid methyl esters were analysed using a 7890A gas chromatograph (Agilent Technologies, Wilmington, DE, USA) equipped with a 25 m NEFA phase column (Agilent Technologies). Cholesteryl nonadecanoate [21,22]. The ratio of docosahexaenoic acid (DHA; 22:6n-3) to osbond acid (22:5n-6) was used as a marker of DHA sufficiency [23].…”