Glycaemic Index of Maternal Dietary Carbohydrate Differentially Alters Fto and Lep Expression in Offspring in C57BL/6 Mice.

Maternal diet and gestational hyperglycaemia have implications for offspring health. Leptin (LEP) and fat mass and obesity-associated (FTO) alleles are known to influence body fat mass in humans, potentially via effects on appetite. We hypothesized that expression of Fto, Lep, and other appetite-related genes (Argp, Npy, Pomc, Cart, Lepr) in the offspring of female mice are influenced by the glycaemic index (GI) of carbohydrates in the maternal diet. C57BL/6 mice were randomly assigned to low or high GI diets and mated with chow-fed males at eight weeks of age. Male pups were weaned at four weeks and randomly divided into two groups, one group following their mother's diet (LL and HH), and one following the standard chow diet (LC and HC) to 20 weeks. Fto expression was 3.8-fold higher in the placenta of mothers fed the high GI diet (p = 0.0001) and 2.5-fold higher in the hypothalamus of 20-week old offspring fed the high GI (HH vs. LL, p < 0.0001). By contrast, leptin gene (Lep) expression in visceral adipose tissue was 4.4-fold higher in four-week old offspring of low GI mothers (LC vs. HC, p < 0.0001) and 3.3-fold higher in visceral adipose tissue of 20-week old animals (LL vs. HH, p < 0.0001). Plasma ghrelin and leptin levels, and hypothalamic appetite genes were also differentially regulated by maternal and offspring diet. These findings provide the first evidence in an animal model that maternal high GI dietary carbohydrates that are digested and absorbed faster may contribute to programming of appetite in offspring.

Hepatic free fatty acids accumulate in experimental steatohepatitis: role of adaptive pathways.

BACKGROUND/AIMS: We determined the effects of dietary lipid composition on steatohepatitis development with particular attention to the nature of lipid molecules that accumulate in the liver and pathways of hepatic triglyceride synthesis. METHODS: Mice were fed methionine and choline deficient (MCD) diets supplemented with 20% fat as lard (saturated) or olive oil (monounsaturated), for 3 weeks. RESULTS: Irrespective of dietary lipid composition, MCD-fed mice developed steatosis, ballooning degeneration and lobular inflammation. MCD-feeding increased hepatic free fatty acid (FFA) levels 2-3-fold, as well as total triglyceride levels. Hepatic FFA composition was characterized by increased ratio of monounsaturated: saturated FFA. There were reduced nuclear levels of the lipogenic transcription factor sterol regulatory element binding protein-1 in MCD-fed mice, but no consistent reduction in fatty acid synthesis genes (acetyl-CoA carboxylase and fatty acid synthase). Consistent with pathways of hepatic triglyceride synthesis, expression of diacylglycerol acyltransferase-1 and -2 was increased, as were delta-5- and delta-6- fatty acid desaturase mRNA levels. CONCLUSIONS: In this nutritional model of steatohepatitis, accumulation of FFA occurs despite substantial suppression of lipogenesis and induction of triglyceride synthesis genes. Accumulation of FFA supports a lipotoxicity mechanism for liver injury in this form of fatty liver disease.

Activation of peroxisome proliferator-activated receptor alpha by dietary fish oil attenuates steatosis, but does not prevent experimental steatohepatitis because of hepatic lipoperoxide accumulation.

BACKGROUND AND AIM: Non-alcoholic fatty liver disease is the result of an imbalance in hepatic lipid partitioning that favors fatty acid synthesis and storage over fatty acid oxidation and triglyceride secretion. The progressive, inflammatory disorder of steatohepatitis can be prevented or reversed by correcting this lipid imbalance by activating peroxisome proliferator-activated receptor (PPAR) alpha, a transcription factor which regulates fatty acid oxidation. n-3 polyunsaturated fatty acids (PUFA), such as those found in fish oil (FO), are naturally occurring PPARalpha ligands which also suppress lipid synthesis. METHODS: We tested the role of dietary activation of PPARalpha by feeding mice a n-3 PUFA-enriched FO diet in the methionine and choline deficient (MCD) model of steatohepatitis. Results were compared with mice fed the corresponding diet supplemented with monounsaturated fatty acids as olive oil (OO). RESULTS: As expected, FO feeding led to robust hepatic PPARalpha activation in control mice, and decreased expression of genes involved with fatty acid synthesis. Such lipolytic gene expression profile was also clearly evident in FO MCD-fed mice, and was associated with reduced hepatic lipid accumulation in comparison with mice fed OO MCD diet. FO feeding in control mice also caused marked hepatic accumulation of lipoperoxides compared with OO and chow-fed mice. This was further exacerbated in FO MCD-fed animals, which developed steatohepatitis characterized by mild steatosis and moderate inflammation in comparison with OO MCD-fed mice; such inflammatory recruitment was not related to NF-kappaB activation or enhanced cyclooxygenase-2 activity. CONCLUSIONS: Feeding an n-3 PUFA-enriched diet activated PPARalpha and suppressed hepatic de novo lipogenesis, but failed to prevent development of steatohepatitis in the presence of methionine and choline deficiency. Instead, the very high levels of hepatic lipoperoxides may have abrogated the protection that would otherwise be conferred by PPARalpha activation, and could also be responsible for lipotoxic hepatocellular injury and inflammatory recruitment.