Apple Pectin and a Polyphenol-Rich Apple Concentrate Are More Effective Together Than Separately on Cecal Fermentations and Plasma Lipids in Rats1

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To evaluate the effect of apple components on cecal fermentations and lipid metabolism, rats were fed diets containing 5 g/100 g apple pectin (PEC), 10 g/100 g high polyphenol freeze-dried apple (PL) or both (PEC + PL). The cecal pH was slightly acidic (6.49) only in rats fed the PEC + PL diet (controls, 7.02). The cecal short-chain fatty acid pool was enlarged by all the apple fractions, with a peak of 560 μmol in rats fed the PEC + PL diet compared with 189 μmol in controls. Butyrate concentrations were 2-fold greater in rats fed the PL diet than in controls. Substantial concentrations of galacturonate and succinate (≈40 mmol/L) were found in the cecum of rats fed the PEC diet and, to a lesser extent, the PEC + PL diet. The PEC + PL diet significantly lowered plasma cholesterol, whereas both the PL and PEC + PL diets lowered plasma triglycerides. Liver cholesterol and triglyceride concentrations were lower in rats fed the PEC and PEC + PL diets. Fecal bile acid excretion was markedly reduced, whereas sterol excretion was significantly increased by dietary PEC. Rats fed the PEC and PEC + PL diets also had lower apparent cholesterol absorption than controls (30 compared with 43%). In conclusion, apple pectin and the polyphenol-rich fraction were more effective when fed combined together than when fed separately on large intestine fermentations and lipid metabolism, suggesting interactions between fibers and polyphenols of apple.

Key words:

apple
cecal fermentations
cholesterol
pectin
polyphenols

Abbreviations used:

ABC
ATP-binding cassette
FCE
food conversion efficiency
FFA
free fatty acids
HMGCoA
hydroxymethylglutaryl coenzyme A
iBAT
ileal bile acid transporter
PEC
apple pectin
PL
high polyphenol freeze-dried apple

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Supported by the French Ministry for Research and Technology, under grant AQS 2001.