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Acute dietary fat intake initiates alterations in energy metabolism and insulin resistance

ABSTRACT: BACKGROUND. Dietary intake of saturated fat is a likely contributor to nonalcoholic fatty liver disease (NAFLD) and insulin resistance, but the mechanisms that initiate these abnormalities in humans remain unclear. We examined the effects of a single oral saturated fat load on insulin sensitivity, hepatic glucose metabolism, and lipid metabolism in humans. Similarly, initiating mechanisms were examined after an equivalent challenge in mice. METHODS. Fourteen lean, healthy individuals randomly received either palm oil (PO) or vehicle (VCL). Hepatic metabolism was analyzed using in vivo 13C/31P/1H and ex vivo 2H magnetic resonance spectroscopy before and during hyperinsulinemic-euglycemic clamps with isotope dilution. Mice underwent identical clamp procedures and hepatic transcriptome analyses. RESULTS. PO administration decreased whole-body, hepatic, and adipose tissue insulin sensitivity by 25%, 15%, and 34%, respectively. Hepatic triglyceride and ATP content rose by 35% and 16%, respectively. Hepatic gluconeogenesis increased by 70%, and net glycogenolysis declined by 20%. Mouse transcriptomics revealed that PO differentially regulates predicted upstream regulators and pathways, including LPS, members of the TLR and PPAR families, NF-κB, and TNF-related weak inducer of apoptosis (TWEAK). CONCLUSION. Saturated fat ingestion rapidly increases hepatic lipid storage, energy metabolism, and insulin resistance. This is accompanied by regulation of hepatic gene expression and signaling that may contribute to development of NAFLD.

ORGANISM(S): Mus musculus

PROVIDER: GSE80259 | GEO | 2017/02/02

SECONDARY ACCESSION(S): PRJNA318412

REPOSITORIES: GEO

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Project description:We studied the effect of dietary fat type, varying in polyunsaturated/saturated fatty acid ratio's (P/S) on development of metabolic syndrome. C57Bl/6J mice were fed purified high-fat diets (45E% fat) containing palm oil (HF-PO; P/S 0.4), olive oil (HF-OO; P/S 1.1) or safflower oil (HF-SO; P/S 7.8) for 8 weeks. A low-fat palm oil diet (LF-PO; 10E% fat) was used as a reference. Additionally, we analyzed diet-induced changes in gut microbiota composition and mucosal gene expression. The HF-PO diet induced a higher body weight gain and liver triglyceride content compared to the HF-OO, HF-SO or LF-PO diet. In the intestine, the HF-PO diet reduced microbial diversity and increased the Firmicutes/Bacteroidetes ratio. Although this fits a typical obesity profile, our data clearly indicate that an overflow of the HF-PO diet to the distal intestine, rather than obesity itself, is the main trigger for these gut microbiota changes. A HF-PO diet-induced elevation of lipid metabolism-related genes in the distal small intestine confirmed the overflow of palm oil to the distal intestine. Some of these lipid metabolism-related genes were previously already associated with the metabolic syndrome. In conclusion, our data indicate that saturated fat (HF-PO) has a more stimulatory effect on weight gain and hepatic lipid accumulation than unsaturated fat (HF-OO and HF-SO). The overflow of fat to the distal intestine on the HF-PO diet induced changes in gut microbiota composition and mucosal gene expression. We speculate that both are directly or indirectly contributive to the saturated fat-induced development of obesity and hepatic steatosis. Keywords: Diet intervention study Nine-week-old C57Bl/6J mice were fed a low-fat diet (LF-PO) and three different types of high-fat diet, based on palm oil (HF-PO; P/S1.0), olive oil (HF-OO; P/S4.6) and safflower oil (HF-SO; P/S10.1) for 8 weeks. Body weight was recorded weekly and after 7 weeks of diet intervention an oral glucose tolerance test was performed. After 2 weeks of diet intervention, 6 mice per high-fat diet group were anaesthetized with a mixture of isofluorane (1.5%), nitrous oxide (70%) and oxygen (30%) and the small intestines were excised. Adhering fat and pancreatic tissue were carefully removed. The small intestines were divided in three equal parts along the proximal to distal axis (SI 1, SI 2 and SI 3) and microarray analysis was performed on mucosal scrapings.

Project description:A time course of the effect of overexpressing GPI-PLD on global gene expression in HepG2 cells was compared to control virus. Experiment Overall Design: This experiment compares the global gene expression in HepG2 cells that were either transduced with an adenovirus expressing GPI-phospholipase D or an adenovirus expressing beta galactosidase as a control. Treatment was for 6 or 12 hrs. Four replicates for each condition were used. 10 micrograms of total RNA was assayed per genechip using standard Affymetrix protocols. CONTEXT: Recent studies demonstrated that de novo lipogenesis is increased in patients with nonalcoholic fatty liver disease (NAFLD). Patients with NAFLD also have plasma lipid abnormalities. These lipid abnormalities may in part be related to insulin resistance, which is common in patients with NAFLD. Insulin resistance is associated with alterations in proteins involved in lipid metabolism including glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD), which is involved in triglyceride metabolism. OBJECTIVE: The objective of the study was to determine whether alterations in serum and hepatic levels of GPI-PLD occur in patients with NAFLD. DESIGN AND PATIENTS: We examined the following: 1) levels of serum GPI-PLD in nondiabetics with nonalcoholic steatohepatitis, compared with matched controls; 2) hepatic expression of GPI-PLD mRNA in patients with normal liver or NAFLD; and 3) effect of overexpressing GPI-PLD vs. beta-galactosidase (control) on global gene expression in a human hepatoma cell line. RESULTS: The serum levels of GPI-PLD were significantly higher in patients with nonalcoholic steatohepatitis than in matched controls (119 +/- 24 vs.105 +/- 15 microg/ml, P = 0.047). The hepatic expression of GPI-PLD mRNA was increased nearly 3-fold in NAFLD patients, compared with patients with normal liver (3.1 +/- 2.6 vs. 1.1 +/- 1.0 arbitrary units per microgram total RNA, P = 0.026). Finally, overexpressing GPI-PLD was associated with an increase in de novo lipogenesis genes. CONCLUSIONS: Patients with NAFLD have elevated serum levels and hepatic expression of GPI-PLD, and its overexpression in vitro is associated with increased expression of de novo lipogenesis genes. These results suggest that GPI-PLD may play a role in the pathogenesis of NAFLD and/or its metabolic features and warrants further investigation.

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Acute dietary fat intake initiates alterations in energy metabolism and insulin resistance

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