Abstract
ABSTRACTAdequate protein intake during development is critical to ensure optimal bone gain and to attain a higher peak bone mass later. Using a mild protein restriction model in Balb/C mice consuming 6% of their total energy intake as soy protein (LP‐SOY)—for which we observed a significantly lower femoral cortical thickness, bone volume, trabecular number, and thickness reduction—we evaluated the effects of monosodium glutamate (MSG) supplementation at different concentrations (0.5, 1, 5, 10, and 20 g/kg of diet) on bone characteristics in LP‐SOY‐fed mice. After 6 and 12 weeks, LP‐SOY‐fed mice had lower BMD and reduced body weight related to lower lean mass, which was associated with a reduced IGF‐1 level. The negative effect of the LP‐SOY diet on BMD correlated with impaired bone formation. MSG supplementation, at 5, 10, and 20 g/kg of diet, and PTH injection, used as a positive control, were able to improve BMD and to increase osteoblast activity markers (P1NP and osteocalcin), as well as glutamine plasma concentration. An analysis of bone microarchitecture found that cortical bone was less sensitive to protein restriction than trabecular bone, and that MSG ingestion was able to preserve bone quality through an increase of collagen synthesis, although it did not allow normal bone growth. Our study reinforces the view that glutamate can act as a functional amino acid for bone physiology and support clinical investigation of glutamate supplementation in adults characterized by poor bone status, notably as a result of insufficient protein intake. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.
Highlights
Monosodium glutamate (MSG) is a worldwide-used flavor enhancer
In mice fed with low protein diet (6% of the total energy being supplied by soy protein), reduced body weight related to a lower lean mass and reduced bone mineral density when compared with mice receiving a sufficient protein supply [26]
According to dual energy X-ray absorptiometry (DEXA) measurements, the low protein (LP) diet appeared to affect only the lean mass, as the fat mass gain was similar to the values recorded in the NP group
Summary
Monosodium glutamate (MSG) is a worldwide-used flavor enhancer. Added glutamate represents approximately 0.4 g/day in Europe and 1.5 g/day in Asia [1]. Apart from its role as a quantitatively major amino acid precursor for protein biosynthesis, is involved as a precursor of compounds that play many roles in cell metabolism, regulation of cell metabolism, and cell physiology in mammals including humans [3, 4]. Glutamate is involved in several aspects of taste and gastro-intestinal physiology [5, 6]. Glutamate is well known to be an excitatory signaling molecule in the central nervous system [7], and to act as an energy substrate in many cell types [8, 9]
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