Tissue phospholipid fatty acid composition in genetically lean (Fa/−) or obese (fa/fa) zucker female rats on the same diet

Abstract

The fatty acid composition of serum total lipids, of phospholipids of various organs (liver, heart, kidney), and of nervous structures (brain, retina, sciatic nerve, myelin, synaptosomes) have been compared in lean (Fa/-) and genetically obese (fa/fa) Zucker female rats. Both received a standard commercial diet including 37% of 18:2n-6 and 5% of n-3 polyunsaturated fatty acids (PUFA), 1.7% of which were in the form of 20:5n-3 and 22:6n-3. In comparison with lean rats, the results for the obese rats pointed out (i) no difference in the fatty acid composition of nervous structures; (ii) a decrease of 18:2n-6 (from -8% to -35%) and of 20:4n-6 (from -9% to -49%) in serum, liver and in kidney; this was compensated for by an increase in 20:3n-6 (from +30% to +320%) and in total n-3 PUFA (from +68% to +76%); (iii) a decrease of 20:4n-6 (-18%) and of 22:6n-3 (-24%) in heart compensated for by an increase in 18:2n-6 (+39%) and in 20:3n-6 (+233%); and (iv) constant levels of total PUFA (n-6 and n-3) in the various fractions studied, except in serum where this level decreased (-23%). Finally, except for the nervous structures, tissue phospholipids of obese rats included a lower proportion of 20:4n-6 and a higher proportion of 20:3n-6. This resulted in a significant reduction in the 20:4n-6/20:3n-6 ratio; by contrast, the 20:3n-6/18:2n-6 ratio increased. The results suggest that in Zucker rats, the obese character (fa/fa) affects the desaturation-elongation process of 18:2n-6 to 20:4n-6 by specifically decreasing delta 5-desaturase activity.

Glucose oversupply increases Δ9-desaturase expression and its metabolites in rat skeletal muscle

“…These data are in accordance with recent reports showing decreased elongase activity (increased C16:0 on the costs of C18:0) in muscle of healthy subjects made insulin resistant [7]. In obesity and insulin resistance states, ∆5-desaturase activity was reported to be reduced [4,16,52,54], whereas that of ∆6-desaturase increased [16]. We found little change in ∆5-desaturase and no change in ∆6-desaturase activity indices.…”

“…Previous reports have indicated that elongase activity (18:0/16:0) is reduced in insulin resistance [16,50,52,53]. In this study, we found that elongase activity was decreased in day 5 as assessed by the activity indices found in triglycerides and diglycerides fractions.…”

“…In this context composition of the fat could also be important since the increase in saturated FA [4,5] was associated with insulin resistance. An increase in monounsaturated FAs (MUFA) in serum FA, in kidney and heart phospholipids fractions of obese Zucker rats in comparison to lean littermates has been reported [16]. In humans, MUFA concentrations in muscle phospholipids were positively correlated with fasting plasma insulin concentrations but negatively with muscle content of polyunsaturated Increased intramyocellular fat accumulation coincides with insulin resistance in humans [1,2,3,4,5,6,7] and in rodents, [8,9,10].…”

The effect of under- and overnutrition on essential fatty acid metabolism in childhood

“…Data obtained in genetically obese animals are also equivocal. Contributions of AA to plasma and tissue phospholipid fatty acids were lower in obese Zucker rats (fa/fa) than in lean (fa/-) animals (Guesnet et al, 1990). In contrast, increased conversion of LA to AA was reported in obese mice (Cunnane et al, 1985a).…”

Serum phospholipid and cholesteryl ester fatty acids and estimated desaturase activities are related to overweight and cardiovascular risk factors in adolescents

“…High D9 and D6 DAs are associated with adiposity and the metabolic syndrome. [14][15][16][17][18] High D5 DA has been associated with normal weight and insulin sensitivity in adults. 15,19 Few studies have assessed the relations of serum lipid fatty acid composition to overweight and CVD risk factors in adolescents and none have included measures of insulin resistance.…”