The aim of the present study was to investigate the potential nutritional and metabolic impact oftrans(t) fatty acids (FA) on an appropriate experimental dietary model. Since previously reported experimental designs have been matter of concern, we developed a dietary model to compare the effect oftisomers and/or the saturation of FA independently of other variables. Wistar rats were fed diets containing identical amounts of nutrients and high levels of dietary fats (200 g/kg) for 30 d. Dietary fat rich int-FA was compared with fat rich in saturated (s) FA or rich incis(c) FA, maintaining the same length of C chain of the FA. The fats were obtained through isomerization or hydrogenation of thec-FA present in the control fat. Apparent fat absorption, energy efficiency and triacylglycerol levels in serum and liver were different in rats fedt-FA or s-FA thanc-FA. The apparent fat absorption was (%): s-FA 85·7 (SD 3·4)<T-FA 93·1 (sd 0·4)<c-FA 96·7 (sd 1·1) (P<0·05). The efficiency of energy utilization was lower int-FA (11·7 %) and s-FA (18·5 %) diets, reaching statistical significance only between s-FA andc-FA. A striking finding was the change in the lipid profile in serum and liver. Serum and hepatic triacylglycerol levels were greater fort-FA and s-FA diets than inc-FA; however, the increases on serum triacylglycerol concentrations were greater with the s-FA diet and the increases on hepatic triacylglycerol content were greater witht-FA. Knowledge of thet-FA effects on this kind of experimental dietary model could contribute to determine the potential risk oft-FA intake for man.

Potential effect of functional milk fat, naturally enriched in conjugated linoleic acid, on the prevention of liver lipid accumulation and some biochemical mechanisms involved in the liver triacylglycerol regulation in high-fat fed rats.

The aim of the present study was to examine whether the level of dietarycisfatty acid (c FA), or the isomers (trans or cis) and/or the saturation of the fatty acids at high dietary fat levels altered the intracellular glucose metabolites and certain regulatory enzyme activities in the skeletal muscle and liver of rats. The animals were fed for 30 d on either a recommended control diet (7% c FA, w/w) or a high-fat diet (20% fatty acids, w/w). The high-fat diet was enriched with either c FA,trans fattyacid (tFA), a moderate proportion of saturated fatty acid (MSFA), or a high proportion of saturated fatty acid (HSFA). The most striking findings were observed in the gastrocnemius muscle with a HSFA diet. There was a significant increase in glucose-6-phosphate (306 %), glucose-1-phosphate (245 %), fructose-6-phosphate (400 %), fructose-1,6-bisphosphate (86 %), glyceraldehyde- 3-phosphate (38 %), pyruvate (341 %), lactate (325 %), citrate (79 %) and the bisphosphorylated sugars as compared with the cFA diet. These changes were paralleled by an increase in muscle triacylglycerol content (49 %) and a decrease in glucose (39 %). In addition, the amount of cFA and the other types of fatty acid (i.e.tFA and MSFA) led to no great differences in glucose metabolism as compared with the respective control group. These data support the hypothesis that glucose changes induced by a HSFA diet are a multifaceted abnormality. Glucose and lactate transport and intracellular glucose metabolism could be the key biochemical defects involved in this detrimental effect on glucose metabolism.

Conjugated linoleic acid (CLA) might regulate the lipid depots in liver and adipose tissue. As there is an association between maternal nutrition, fat depots and risk of offspring chronic disease, the aim was to investigate the effect of maternal CLA consumption on TAG regulation and some inflammatory parameters in adult male rat offspring receiving or not receiving CLA. Female Wistar rats were fed control (C) or CLA-supplemented (1 %, w/w) diets during 4 weeks before and throughout pregnancy and lactation. After weaning, male offspring of CLA rats were fed C or CLA diets (CLA/C and CLA/CLA groups, respectively), whereas C male rat offspring were fed a C diet (C/C group) for 9 weeks. Serum TAG levels were increased in the CLA/CLA and CLA/C groups, associated with a reduction of lipoprotein lipase activity and weights of adipose tissue. The liver TAG levels were decreased in the CLA/CLA group, related to a significant reduction of fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC) and glucose-6-phosphate dehydrogenase enzyme activities, as well as to the mRNA levels of FAS, ACC, stearoyl-CoA desaturase-1 and sterol regulatory element-binding protein-1c. Even though normal TAG levels were found in the liver of CLA/C rats, a reduction of lipogenesis was also observed. Thus, these results demonstrated a programming effect of CLA on the lipid metabolic pathways leading to a preventive effect on the TAG accretion in adipose tissue and the liver of male rat offspring. This knowledge could be important to develop some dietary strategies leading to a reduced incidence of obesity and fatty acid liver disease in humans.