A high fat (HF) diet induces lipid accumulation in the liver and hepatic steatosis. The liver is the main venue for β-oxidation of fatty acids, and it maintains the balance of fat metabolism in the body through the synthesis and secretion of lipoproteins. Many studies showed that betaine, a modified amino acid consisting of glycine and three methyl groups, regulates fat metabolism. However, the key pathways and enzymatic activities involved in the metabolism and resynthesis of lipids affected by betaine are still not clear. In this work, the researchers investigated the protein metabolic profile in the liver of mice on an HF diet supplemented with 1% betaine by label free quantification analysis via liquid chromatography-tandem mass spectrometry (LC–MS/MS).

The addition of 1% betaine enhanced fatty acid oxidation metabolism in the liver of mice fed a HF diet by elevating protein expression levels of key enzymes involved in fatty acid β-oxidation, such as acyl-coenzyme A oxidase 1 (ACOX1), enoyl Coenzyme A hydratase 1 (ECHS1), and hydroxyacyl-Coenzyme A dehydrogenase (HADHA). Moreover, betaine supplementation regulated several proteins involved in peroxisome proliferator-activated receptor alpha (PPARα) signalling pathway. For example, HF + 1% betaine (HFB) diet group showed upregulated protein expression of acetyl-Coenzyme A acetyltransferase 1 (ACAT1) and 3-ketoacyl-CoA thiolase A peroxisomal (ACAA1) and downregulated apolipoprotein A2 (APOA2) protein expression when compared to the HF diet group. In addition, catalytic enzymes involved in the tricarboxylic acid cycle (TCA) cycle and glycolytic progress, succinate-CoA ligase (SUCLG1) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), were decreased in the HF diet group. With 1% betaine supplementation in the HF diet, the expression of SUCLG1 and GAPDH were increased. Taken together, it appears betaine reduces fat accumulation in the liver by increasing fatty acid oxidation and speeding up the TCA cycle and glycolytic process in the liver of mice fed a HF diet.

How was PEAKS used?

LC–MS/MS data were collected from mouse liver tissues. The raw MS data were searched against a UniProt database using PEAKS software, version 7.0. Identified proteins were quantified using a label-free strategy with spectral intensities.

Fan, Caiyun, et al. “Betaine Supplementation Causes an Increase in Fatty Acid Oxidation and Carbohydrate Metabolism in Livers of Mice Fed a High-Fat Diet: A Proteomic Analysis.” Foods 11.6 (2022): 881. doi:10.3390/foods11060881

Abstract

Betaine, a common methyl donor whose methylation is involved in the biosynthesis of carnitine and phospholipids in animals, serves as food and animal feed additive. The present study used liquid chromatography-mass spectrometry (LC-MS) to analyze the liver protein profile of mice on a high fat (HF) diet to investigate the mechanism by which betaine affects hepatic metabolism. Although betaine supplementation had no significant effect on body weight, a total of 103 differentially expressed proteins were identified between HF diet + 1% betaine group (HFB) and HF diet group by LC-MS (fold change > 2, p < 0.05). The addition of 1% betaine had a significant enhancement of the expression of enzymes related to fatty acid oxidation metabolism, such as hydroxyacyl-Coenzyme A dehydrogenase (HADHA), enoyl Coenzyme A hydratase 1 (ECHS1) (p < 0.05) etc., and the expression of apolipoprotein A-II (APOA2) protein was significantly reduced (p < 0.01). Meanwhile, the protein expression of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and succinate-CoA ligase (SUCLG1) were highly significant (p < 0.01). Pathway enrichment using the Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed that the functions of differential proteins involved fatty acid catabolism, carbohydrate metabolism, tricarboxylic acid cycle (TCA) and peroxisome proliferator-activated receptor alpha (PPARα) signaling pathway. Protein–protein interaction (PPI) analysis discovered that acetyl-Coenzyme A acetyltransferase 1 (ACAT1), HADHA and ECHS1 were central hubs of hepatic proteomic changes in the HFB group of mice. Betaine alleviates hepatic lipid accumulation by enhancing fatty acid oxidation and accelerating the TCA cycle and glycolytic process in the liver of mice on an HF diet.