Time course of the development of non-alcoholic hepatic steatosis in response to high-fat diet-induced obesity in rats.

The aim of the study was to characterize the time course of the development of high-fat diet-induced hepatic steatosis and its relation to body fat accretion and changes in plasma lipid profile. Female Sprague-Dawley rats were high-fat fed (HF; 42 %, kJ) for 1, 2, 4, 6, 12 and 16 weeks and compared to standard fed rats (SD). Data obtained from HF rats were further analysed by classifying the animals into obesity-prone and obesity-resistant. In HF rats, liver lipid content increased rapidly by approximately 200 % during the first 2 weeks, decreased almost to baseline levels between weeks 2 and 6, and re-increased by 17 % between weeks 6 and 16 (P<0.05). Body weight, body fat accretion, plasma leptin, NEFA and glycerol concentrations were higher in HF than in SD rats (P<0.05). These higher values were established in 2 weeks and the differences between the groups did not further enlarge from weeks 2 to 16. Obesity-prone rats depicted higher body weight and body fat accretion than obesity-resistant and SD rats. Surprisingly, however, liver lipid content was the same in obesity-prone as in obesity-resistant rats as they were both higher than in SD rats (weeks 2 and 16; P<0.05). Our data support the hypothesis that the liver acts as a systemic buffer, largely increasing its lipid content in the early stage of high-fat feeding. Our results also suggest that the development of non-alcoholic hepatic steatosis is more linked to dietary fat ingestion than to body weight gain.