Postprandial effect to decrease soluble epoxide hydrolase activity: roles of insulin and gut microbiota

J Nutr Biochem. 2017 Nov;49:8-14. doi: 10.1016/j.jnutbio.2017.07.006. Epub 2017 Jul 21.

Abstract

Epoxides of free fatty acids (FFAs), especially epoxyeicosatrienoic acids (EETs), are lipid mediators with beneficial effects in metabolic and cardiovascular (CV) health. FFA epoxides are quickly metabolized to biologically less active diols by soluble epoxide hydrolase (sEH). Inhibition of sEH, which increases EET levels, improves glucose homeostasis and CV health and is proposed as an effective strategy for the treatment of diabetes and CV diseases. Here, we show evidence that sEH activity is profoundly reduced in postprandial states in rats; plasma levels of 17 sEH products (i.e., FFA diols), detected by targeted oxylipin analysis, all decreased after a meal. In addition, the ratios of sEH product to substrate (sEH P/S ratios), which may reflect sEH activity, decreased ~70% on average 2.5 h after a meal in rats (P<.01). To examine whether this effect was mediated by insulin action, a hyperinsulinemic-euglycemic clamp was performed for 2.5 h, and sEH P/S ratios were assessed before and after the clamp. The clamp resulted in small increases rather than decreases in sEH P/S ratios (P<.05), indicating that insulin cannot account for the postprandial decrease in sEH P/S ratios. Interestingly, in rats treated with antibiotics to deplete gut bacteria, the postprandial effect to decrease sEH P/S ratios was completely abolished, suggesting that a gut bacteria-derived factor(s) may be responsible for the effect. Further studies are warranted to identify such a factor(s) and elucidate the mechanism by which sEH activity (or sEH P/S ratio) is reduced in postprandial states.

Keywords: Cardiovascular disease; Diabetes; Dietary potassium; FFA epoxides; Oxylipin analysis.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, N.I.H., Extramural

MeSH terms

  • Algorithms
  • Animals
  • Anti-Bacterial Agents / pharmacology
  • Biomarkers / blood
  • Cardiovascular Diseases / blood
  • Cardiovascular Diseases / metabolism
  • Cardiovascular Diseases / prevention & control
  • Eicosanoids / blood
  • Eicosanoids / metabolism
  • Epoxide Hydrolases / blood*
  • Epoxide Hydrolases / chemistry
  • Epoxide Hydrolases / metabolism
  • Gastrointestinal Microbiome / drug effects
  • Gastrointestinal Microbiome / physiology*
  • Glucose Clamp Technique
  • Insulin / analysis
  • Insulin / metabolism*
  • Insulin Secretion
  • Male
  • Meals*
  • Models, Biological*
  • Oxidative Stress* / drug effects
  • Oxylipins / blood
  • Postprandial Period
  • Potassium, Dietary / administration & dosage*
  • Potassium, Dietary / therapeutic use
  • Rats, Wistar
  • Reproducibility of Results
  • Solubility

Substances

  • Anti-Bacterial Agents
  • Biomarkers
  • Eicosanoids
  • Insulin
  • Oxylipins
  • Potassium, Dietary
  • Epoxide Hydrolases
  • EPHX2 protein, rat