title: Cysteic Acid in Dietary Keratin is Metabolized to Glutathione and Liver Taurine in a Rat Model of Human Digestion.
abstract: Poultry feathers, consisting largely of keratin, are a low-value product of the poultry industry. The safety and digestibility of a dietary protein produced from keratin (KER) was compared to a cysteine-supplemented casein-based diet in a growing rat model for four weeks. KER proved to be an effective substitute for casein at 50% of the total dietary protein, with no changes in the rats' food intake, weight gain, organ weight, bone mineral density, white blood cell counts, liver glutathione, or blood glutathione. Inclusion of KER in the diet reduced total protein digestibility from 94% to 86% but significantly increased total dietary cysteine uptake and subsequent liver taurine levels. The KER diet also significantly increased caecum weight and significantly decreased fat digestibility, resulting in a lower proportion of body fat, and induced a significant increase in blood haemoglobin. KER is therefore a safe and suitable protein substitute for casein, and the cysteic acid in keratin is metabolised to maintain normal liver and blood glutathione levels.
authors.affiliation: School of Food and Nutrition, Massey University, Palmerston North 4442, New Zealand. f.m.wolber@massey.ac.nz.
authors.forename: Frances M
authors.initials: FM
authors.lastname: Wolber
authors.affiliation: School of Food and Nutrition, Massey University, Palmerston North 4442, New Zealand. m.mcgrath@massey.ac.nz.
authors.forename: Michelle
authors.initials: M
authors.lastname: McGrath
authors.affiliation: Riddet Innovation, Massey University, Palmerston North 4442, New Zealand. f.s.jackson@massey.ac.nz.
authors.forename: Felicity
authors.initials: F
authors.lastname: Jackson
authors.affiliation: School of Food and Nutrition, Massey University, Palmerston North 4442, New Zealand. yacanto@slingshot.co.nz.
authors.forename: Kim
authors.initials: K
authors.lastname: Wylie
authors.affiliation: School of Food and Nutrition, Massey University, Palmerston North 4442, New Zealand. a.m.broomfield@massey.ac.nz.
authors.forename: Anne
authors.initials: A
authors.lastname: Broomfield
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D001823:Body Composition; D002364:Caseins; D002432:Cecum / Q000187:drug effects; D003544:Cysteic Acid / Q000378:metabolism* / Q000494:pharmacology; D003545:Cysteine / Q000008:administration & dosage / Q000378:metabolism; D004032:Diet; D004041:Dietary Fats / Q000378:metabolism; D004044:Dietary Proteins / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D004063:Digestion; D005978:Glutathione / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007633:Keratins / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D008099:Liver / Q000378:metabolism*; D008297:Male; D023421:Models, Animal; D017207:Rats, Sprague-Dawley; D013654:Taurine / Q000378:metabolism*
chemical_list: D002364:Caseins; D004041:Dietary Fats; D004044:Dietary Proteins; D006454:Hemoglobins; D013654:Taurine; D007633:Keratins; D003544:Cysteic Acid; D005978:Glutathione; D003545:Cysteine
keywords: cysteine; glutathione; keratin; rat model