Alimentary lipemia is enhanced in fiber-fed rats

The effect of dietary fiber on the pattern of postprandial lipemia was examined in two studies with male Wistar rats. In the first study, groups of rats were killed after food deprivation (0 h) or 1, 4.5 or 8.5 h after a high fat test meal containing either cellulose (CL) or oat bran (OB). Plasma triglycerides (TG) were higher in the OB group at 4.5 h compared with both the 0-h and the CL-groups at 4. 5 h. In both groups, LDL and TG-rich lipoprotein cholesterol (TRL-C) concentrations were higher at 8.5 h than at 0 h; HDL cholesterol was significantly lower at 8.5 h than at 0 h for the OB group only. The enhanced lipemia when OB was fed may stimulate cholesterol movement from HDL to LDL and TRL. To examine whether TRL secretion rates were responsible for the enhanced lipemia, a second study was conducted. Rats were fitted with jugular catheters and allowed to recover. Two groups were fed either CL or OB and infused with Triton-1339 (400 mg/kg). Two control groups were not fed and were infused with either Triton or saline. Rats were killed 2.5 h after infusion. Plasma TG was 10-fold higher in the Triton group than in the saline group, but did not differ between the OB and CL groups. The relative contribution of TRL-C to total cholesterol was significantly greater in the Triton control than in the OB and CL groups. Enhanced secretion of TRL was not responsible for the lipemia observed in the first study. Rather, alterations in clearance rate were responsible.