Abelmoschus esculentus subfractions ameliorate hepatic lipogenesis and lipid uptake via regulating dipeptidyl peptidase-4-With improving insulin resistance

PLoS One. 2022 Mar 15;17(3):e0265444. doi: 10.1371/journal.pone.0265444. eCollection 2022.

Abstract

Nonalcoholic fatty liver disease (NAFLD) is recognized as the liver component of metabolic syndrome. The regulation of hepatic lipid should be emphasized to prevent accompanying illness. As AMP-activated protein kinase (AMPK) and sterol regulatory element binding protein (SREBP) regulate lipid metabolism, CD36 and fatty acid synthase (FAS) promote lipid uptake and lipogenesis respectively, while acetyl-CoA carboxylase (ACC) is an indicator of negative feedback. The increase of IRS-1 phosphorylation at the residue ser307 (p-ser307-IRS-1) and decrease of p-ser473-Akt (p-Akt) are viewed as the insulin resistance markers, and our previous reports suggested dipeptidyl peptidase-4 (DPP-4) mediates insulin resistance, the crucial factor of metabolic syndrome. Abelmoschus esculentus (AE) fruit is well-known for its antidiabetic utility. We had isolated several AE subfractions by successive steps, and found that F1 and F2 were especially valid in suppressing DPP-4 signaling. Since little is known if AE works on NAFLD, now we first attempt to investigate whether AE is useful to attenuate hepatic lipogenesis and lipid uptake in liver cells, along with improving the metabolic targets. We demonstrated that AE subfractions attenuated the hepatic lipid accumulation induced by free fatty acids. Treatment of AE alleviated FAS and returned the level of p-ser79-ACC (p-ACC). Although F1 was more effective on AMPK, F2 seemed more stable to attenuate SREBP-1. Moreover, as fatty acids stimulated the expression of CD36, F2 showed a superior effect to down-regulate the lipid uptake. Both AE subfractions reduced the generation of ROS, decreased the level of p-ser307-IRS-1, and restored the expression of p-Akt. Moreover, treatment of DPP-4 inhibitor linagliptin revealed that, AE could prevent the hepatic lipogenesis, oxidative burden, and the related insulin resistance via downregulating DPP-4. In conclusion, the present investigation revealed that AE, especially F2, is potential to be developed as adjuvant to prevent NAFLD.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • AMP-Activated Protein Kinases / metabolism
  • Abelmoschus* / chemistry
  • Acetyl-CoA Carboxylase / metabolism
  • Fatty Acids, Nonesterified / metabolism
  • Insulin Resistance*
  • Lipid Metabolism
  • Lipogenesis
  • Liver / metabolism
  • Metabolic Syndrome* / metabolism
  • Non-alcoholic Fatty Liver Disease* / drug therapy
  • Non-alcoholic Fatty Liver Disease* / metabolism
  • Proto-Oncogene Proteins c-akt / metabolism
  • Sterol Regulatory Element Binding Protein 1 / metabolism

Substances

  • Fatty Acids, Nonesterified
  • Sterol Regulatory Element Binding Protein 1
  • Proto-Oncogene Proteins c-akt
  • AMP-Activated Protein Kinases
  • Acetyl-CoA Carboxylase

Grants and funding

This work was financially supported by the following five grants, 1. Ministry of Science and Technology, Taiwan (110-2320-B-241-001); Recipient: Chiung-Huei Peng. 2. Ministry of Science and Technology, Taiwan (105-2314-B-040-013-MY3, 108-2314-B-040-021-MY3); Recipient: Chien-Ning Huang. 3. Ministry of Science and Technology, Taiwan (108-2314-B-040-023-MY3); Recipient: Chih-Li Lin. 4. Industry Academic Cooperation Project (HK109-164); Recipient: Chiung-Huei Peng. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.