(-)-Hydroxycitric acid (HCA) suppresses fatty acid synthesis in animals, but its biochemical mechanism in poultry is unclear. This study identified the key proteins associated with fat metabolism and elucidated the biochemical mechanism of (-)-HCA in broiler chickens. Four groups (n = 30 each) received a diet supplemented with 0, 1000, 2000 or 3000 mg/kg (-)-HCA for 4 weeks. Of the differentially expressed liver proteins, 40 and 26 were identified in the mitochondrial and cytoplasm respectively. Pyruvate dehydrogenase E1 components (PDHA1 and PDHB), dihydrolipoyl dehydrogenase (DLD), aconitase (ACO2), a-ketoglutarate dehydrogenase complex (DLST), enoyl-CoA hydratase (ECHS1) and phosphoglycerate kinase (PGK) were upregulated, while NADP-dependent malic enzyme (ME1) was downregulated. Biological network analysis showed that the identified proteins were involved in glycometabolism and lipid metabolism, whereas PDHA1, PDHB, ECHS1, and ME1 were identified in the canonical pathway by Ingenuity Pathway Analysis. The data indicated that (-)-HCA inhibited fatty acid synthesis by reducing the acetyl-CoA supply, via promotion of the tricarboxylic acid cycle (upregulation of PDHA1, PDHB, ACO2, and DLST expression) and inhibition of ME1 expression. Moreover, (-)-HCA promoted fatty acid beta-oxidation by upregulating ECHS1 expression. These results reflect a biochemically relevant mechanism of fat reduction by (-)-HCA in broiler chickens.
Background/Aims: (-)-Hydroxycitric acid (HCA) had been shown to suppress fat accumulation in animals and humans, while the underlying biochemical mechanism is not fully understood, especially little information is available on whether (-)-HCA regulates energy metabolism and consequently affects fat deposition. Methods: Hepatocytes were cultured for 24 h and then exposed to (-)-HCA (0, 1, 10, 50 µM), enzyme protein content was determined by ELISA; lipid metabolism gene mRNA levels were detected by RT-PCR. Results: (-)-HCA significantly decreased the number and total area of lipid droplets. ATP-citrate lyase, fatty acid synthase and sterol regulatory element binding protein-1c mRNA level were significantly decreased after (-)-HCA treatment, whereas peroxisome proliferator-activated receptor α mRNA level was significantly increased. (-)-HCA significantly decreased ATP-citrate lyase activity and acetyl-CoA content in cytosol, but significantly increased glucose consumption and mitochondrial oxygen consumption rate. (-)-HCA promoted the activity/content of glucokinase, phosphofructokinase-1, pyruvate kinase, pyruvate dehydrogenase, citrate synthase, aconitase, succinate dehydrogenase, malate dehydrogenase, NADH dehydrogenase and ATP synthase remarkably. Conclusions: (-)-HCA decreased lipid droplets accumulation by reducing acetyl-CoA supply, which mainly achieved via inhibition of ATP-citrate lyase, and accelerating energy metabolism in chicken hepatocytes. These results proposed a biochemical mechanism of fat reduction by (-)-HCA in broiler chickens in term of energy metabolism.
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