Proline and hydroxyproline metabolism: implications for animal and human nutrition

Abstract

Proline plays important roles in protein synthesis and structure, metabolism (particularly the synthesis of arginine, polyamines, and glutamate via pyrroline-5-carboxylate), and nutrition, as well as wound healing, antioxidative reactions, and immune responses. On a pergram basis, proline plus hydroxyproline are most abundant in collagen and milk proteins, and requirements of proline for whole-body protein synthesis are the greatest among all amino acids. Therefore, physiological needs for proline are particularly high during the life cycle. While most mammals (including humans and pigs) can synthesize proline from arginine and glutamine/glutamate, rates of endogenous synthesis are inadequate for neonates, birds, and fish. Thus, work with young pigs (a widely used animal model for studying infant nutrition) has shown that supplementing 0.0, 0.35, 0.7, 1.05, 1.4, and 2.1% proline to a proline-free chemically defined diet containing 0.48% arginine and 2% glutamate dose dependently improved daily growth rate and feed efficiency while reducing concentrations of urea in plasma. Additionally, maximal growth performance of chickens depended on at least 0.8% proline in the diet. Likewise, dietary supplementation with 0.07, 0.14, and 0.28% hydroxyproline (a metabolite of proline) to a plant protein-based diet enhanced weight gains of salmon. Based on its regulatory roles in cellular biochemistry, proline can be considered as a functional amino acid for mammalian, avian, and aquatic species. Further research is warranted to develop effective strategies of dietary supplementation with proline or hydroxyproline to benefit health, growth, and development of animals and humans.

Separate feeding of calcium improves performance and ileal nutrient digestibility in broiler chicks

“…These effects suggest a link between the mechanism of action of phytase and axiomatically, phytate, and the impeding effects of consumption of limestone and/or Ca simultaneous with the mixed ration. Hydroxyproline together with proline forms~30% of collagen proteins, which in turn represent 30% of total body protein (Wu et al 2011). Of possible significance is that hydroxyproline has been recently recognised as a substrate for the synthesis of glycine (Wu et al 2011), suggesting possible links to the mechanisms presented above.…”

“…Hydroxyproline together with proline forms~30% of collagen proteins, which in turn represent 30% of total body protein (Wu et al 2011). Of possible significance is that hydroxyproline has been recently recognised as a substrate for the synthesis of glycine (Wu et al 2011), suggesting possible links to the mechanisms presented above. Further, as hydroxyproline is involved in collagen synthesis, its increased presence in the lumen may be indicative of increased turnover of the epithelium and/or reduced gastrointestinal tract integrity.…”

Chronic Exposure to Proline Causes Aminoacidotoxicity and Impaired Beta-Cell Function: StudiesIn Vitro

“…Proline is an abundant AA occurring in milk proteins, meat, poultry by-products, and salmon proteins [13]. We hypothesize that chronic exposure to elevated proline levels results in changes in β-cell function characteristic for the diabetic condition, i.e.…”

The in ovo administration of l-trans pyrrolidine-2,4-dicarboxylic acid regulates small intestinal growth in chicks

“…An adequate level of L-threonine in piglet diet improved the intestinal morphology and gut barrier function by favorably altering the secretion of mucin, which is the major constituent of the mucosal layer that protects against bacterial, chemical and mechanical injures (Wang et al, 2010). Proline is a nutritionally essential amino acid for animals and played a key role in the regulation of multiple biochemical and physiological processes in cells (Wu et al, 2011). The majority of proline in the small intestine is synthesized via the glutamate/pyrroline 5-carboxylate (P5C) synthase pathway.…”