Skeletal effect of casein and whey protein intake during catch-up growth in young male Sprague–Dawley rats

Abstract

The aim of the present study was to determine whether the type of protein ingested influences the efficiency of catch-up (CU) growth and bone quality in fast-growing male rats. Young male Sprague-Dawley rats were either fed ad libitum (controls) or subjected to 36 d of 40 % food restriction followed by 24 or 40 d of re-feeding with either standard rat chow or iso-energetic, iso-protein diets containing milk proteins -casein or whey. In terms of body weight, CU growth was incomplete in all study groups. Despite their similar food consumption, casein-re-fed rats had a significantly higher body weight and longer humerus than whey-re-fed rats in the long term. The height of the epiphyseal growth plate (EGP) in both casein and whey groups was greater than that of rats re-fed normal chow. Microcomputed tomography yielded significant differences in bone microstructure between the casein and whey groups, with the casein-re-fed animals having greater cortical thickness in both the short and long term in addition to a higher trabecular bone fraction in the short term, although this difference disappeared in the long term. Mechanical testing confirmed the greater bone strength in rats re-fed casein. Bone quality during CU growth significantly depends on the type of protein ingested. The higher EGP in the casein-and whey-re-fed rats suggests a better growth potential with milk-based diets. These results suggest that whey may lead to slower bone growth with reduced weight gain and, as such, may serve to circumvent long-term complications of CU growth.

How Milk and Its Proteins Affect Growth, Bone Health, and Weight

“…In our previously described study in RES rats refed with casein- or whey-based diets [43], we found that re-feeding with whey led in the long term to linear growth and bone health similar to that achieved by re-feeding with casein, but with a lesser weight gain. These results suggest that a whey-based diet may circumvent long-term obesogenic complications of catch-up (CU) growth.…”

“…To study the effect of casein and whey on bone structure and quality we used a rat model of nutrition-induced CU growth in which animals were allowed to eat 1 of 3 isocaloric, isoprotein diets differing in the origin of the protein, whether vegetable, casein, or whey [43]. Animals were analyzed after 24 or 40 days of re-feeding.…”

“…This clearly indicates that bone quality during CU growth significantly depends on the type of protein ingested. At 40 days, the differences between the whey and casein groups were no longer significant [43]. …”

Effect of Nutrition on Statural Growth

“…Using microcomputed tomography analysis for the evaluation of bone morphology and micro-architecture ex vivo [7], we (G.G.-Y.) and others have shown that nutrition affects GP height as well as bone modeling of young bones and that the quality of the bone is affected by nutritional manipulation [7-9]. Fasting and food restriction impair the rate of longitudinal bone growth and reduce the height of the GP, the number of proliferative and hypertrophic chondrocytes per column, and the height of terminal hypertrophic chondrocytes [10, 11].…”

Milk Basic Protein Facilitates Increased Bone Mass in Growing Mice

“…It is generally accepted that milk intake contributes to the bone remodeling process because of its physiological role in promoting skeletal growth in newborn animals. In addition to their high nutritional value, milk proteins such as casein and whey protein significantly affect bone health (2)(3)(4)(5). We previously demonstrated in both in vitro and in vivo studies that milk whey protein promotes bone formation and inhibits bone resorption (6)(7)(8)(9).…”