British Journal of Nutrition

Full Papers

Metabolism and Metabolic Studies

Flax oil-mediated activation of PPAR-γ correlates with reduction of hepatic lipid accumulation in obese spontaneously hypertensive/NDmcr-cp rats, a model of the metabolic syndrome

Kanta Chechia1a2, Naomi Yasuia1, Katsumi Ikedaa1, Yukio Yamoria3 and Sukhinder K. Cheemaa2 c1

a1 Department of Pharmacy, School of Pharmacy and Pharmaceutical Sciences, Mukogawa Women's University, Nishinomiya 663-8179, Japan

a2 Department of Biochemistry, Memorial University, St John's, NL, Canada A1B-3X9

a3 Institute of World Health Development, Mukogawa Women's University, Nishinomiya 663-8558, Japan

Abstract

Flax oil feeding has been proposed to have beneficial effects on the outcome of the metabolic syndrome due to the high n-3 fatty acid content of flax oil; however, the mechanisms of its action remain largely unknown. We investigated the effects of flax oil feeding on hyperlipidaemia, hyperglycaemia, hepatic steatosis and oxidative stress in the spontaneously hypertensive (SHR)/NDmcr-cp rats, a genetic model of the metabolic syndrome. Hepatic gene expression of PPAR-α, PPAR-γ and sterol-regulatory element-binding protein-1c was also assessed in order to investigate the possible underlying mechanisms. Obese and lean SHR/NDmcr-cp rats were fed high-fat diets enriched with either lard or flax oil for a period of 4 weeks. Obese rats exhibited higher body weight, liver weight and mesenteric fat-, epididymal fat- and renal fat-pad weights, and also TAG and cholesterol concentrations in serum and VLDL, LDL and HDL fractions, when compared with the lean rats (P < 0·001), irrespective of the diets. Concentrations of fasting serum insulin and urinary thiobarbituric acid reactive substances were lower in flax oil-fed obese (FO) rats compared with the lard-fed obese (LO) rats (P < 0·01). Flax oil feeding also revealed a significant reduction in hepatic TAG and cholesterol concentrations in obese rats compared with the LO rats (P < 0·05). In addition, FO rats exhibited significantly higher hepatic mRNA expression of PPAR-γ, which negatively correlated (r − 0·98, P < 0·05) with their hepatic lipid levels. These findings suggest that flax oil feeding may activate PPAR-γ-dependent pathways to alter the hepatic lipid metabolism and to increase insulin sensitivity in the obese SHR/NDmcr-cp rats.

(Received January 11 2010)

(Revised April 09 2010)

(Accepted April 21 2010)

(Online publication June 15 2010)

Correspondence:

c1 Corresponding author: Dr S. K. Cheema, fax +1 709 737 2422, email skaur@mun.ca

Footnotes

Abbreviations: ALA, α-linolenic acid; FL, flax oil-fed lean rats; FO, flax oil-fed obese rats; LL, lard-fed lean rats; LO, lard-fed obese rats; NAFLD, non-alcoholic fatty liver disease; SHR, spontaneously hypertensive rats; SREBP, sterol regulatory element-binding protein; TBARS, thiobarbituric acid-reactive substances

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