Maternal dietary ratio of linoleic acid to alpha-linolenic acid during pregnancy has sex-specific effects on placental and fetal weights in the rat

Abstract

BackgroundIncreased consumption of linoleic acid (LA, omega-6) in Western diets coupled with the pro-inflammatory and adipogenic properties of its derivatives has led to suggestions that fetal exposure to this dietary pattern could be contributing to the intergenerational cycle of obesity.MethodThis study aimed to evaluate the effects of maternal consumption of a LA to alpha-linolenic acid (ALA) ratio similar to modern Western diets (9:1) compared to a lower ratio (1:1.5) on placental and fetal growth, and to determine any cumulative effects by feeding both diets at two total fat levels (18% vs 36% fat w/w). Female Wistar rats (n = 5–7/group) were assigned to one of the four experimental diets prior to mating until 20d of gestation.ResultsFatty acid profiles of maternal and fetal blood and placental tissue at 20d gestation were different between dietary groups, and largely reflected dietary fatty acid composition. Female fetuses were heavier (2.98 ± 0.06 g vs 3.36 ± 0.07 g, P < 0.01) and male placental weight was increased (0.51 ± 0.02 g vs 0.58 ± 0.02 g, P < 0.05) in the low LA:ALA groups. Female fetuses of dams exposed to a 36% fat diet had a reduced relative liver weight irrespective of LA:ALA ratio (7.61 ± 0.22% vs 6.93 ± 0.19%, P < 0.05). These effects occurred in the absence of any effect of the dietary treatments on maternal bodyweight, fat deposition or expression of key lipogenic genes in maternal and fetal liver or maternal adipose tissue.ConclusionThese findings suggest that both the total fat content as well as the LA:ALA ratio of the maternal diet have sex-specific implications for the growth of the developing fetus.

The effect of maternal dietary fat content andn-6:n-3 ratio on offspring growth and hepatic gene expression in the rat

“…Despite significant shifts in maternal fatty acid profiles and increased fat content of the 36 % fat diets, we saw no differences in maternal BW or fat deposition. This is consistent with our previous study (5) and is likely a result of the reduced feed intakes of the dams to compensate for the increased energy density of the higher fat diets, a phenomenon consistently seen with dietary intervention trials using rodents (35) . Despite the lack of an effect on maternal weight gain and fat deposition, BW was reduced in offspring of dams receiving a 36 % fat diet, irrespective of maternal dietary LA:ALA ratio.…”

“…These changes persisted after a further 6 weeks of exposure to the diets and, as expected, the dietary LA:ALA ratio had a greater impact on the maternal blood n-6 and n-3 status than total dietary fat content. Consistent with previous studies (5,9,26,27) , decreasing the dietary LA:ALA ratio resulted in substantial increases in relative maternal ALA and EPA levels but only a very modest increase in DHA proportions after a 4-week exposure, and no difference compared with the higher LA:ALA ratio after 10 weeks. Interestingly, and independent of dietary LA:ALA ratio, dams appeared to be more efficient at converting DPA to DHA when total dietary fat load was higher.…”

“…This resulted in four experimental diets (n 6-9 per dietary group): high LA (18 % fat), high LA (36 % fat), low LA (18 % fat) and low LA (36 % fat). The list of ingredients and final fatty acid composition of the four experimental diets have been reported previously (5) .…”

“…Lipogenic pathway and adipokine target genes were chosen based on previous data from our laboratory that indicated that these genes were sensitive to changes in the maternal diet (23) and included Pparg, sterol regulatory element-binding protein (variant 1c; Srebf1), fatty acid synthase (Fasn), lipoprotein lipase (Lpl) and leptin, with β-actin as the housekeeper. Primer efficiency ranged from 85 to 108 % and sequences have previously been published elsewhere (5) . Adipocyte and hepatic gene expression was quantified using SYBR Green (Roche Diagnostics) in a Light-Cycler 480 (Roche Diagnostics).…”

“…There is increasing evidence, however, that the impact of a high-fat diet on the metabolic health of the offspring depends not only on the amount of fat in the diet but also on the fatty acid composition (4,5) . There has been particular interest in the role of two classes of PUFA, due to the substantive increase in the amounts of n-6 PUFA, predominately linoleic acid (LA), being consumed in the diets of many Western countries over the past few decades (6,7) .…”