Lysine-rich rice partially enhanced the growth and development of skeletal system with better skeletal microarchitecture in young rats

• Published in: Nutrition research (New York, N.Y.) Vol. 121; pp. 67 - 81
• Main Authors: Suen, Pui Kit, Zheng, Lizhen, Yang, Qing-qing, Mak, Wan Sheung, Pak, Wan Yu, Mo, Kit Ying, Chan, Man-ling, Liu, Qiao-quan, Qin, Ling, Sun, Samuel Sai-Ming
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.01.2024
• Subjects: Animals; Body Weight; Growth Hormone - metabolism; Lysine; Lysine biofortification; Lysine-rich rice; Male; Mammals - metabolism; Oryza - genetics; Oryza - metabolism; Plants, Genetically Modified - chemistry; Plants, Genetically Modified - metabolism; Rats; Rats, Sprague-Dawley; Skeletal development; Skeletal growth; X-Ray Microtomography; TV; Lysine biofortification; P1NP; Tb.N; mRNA; HFL; CSA; CSMI; BV; BV/TV; ANOVA; BMD; mTOR; BMC; WT; Skeletal growth; Lysine-rich rice; Skeletal development; IGF-1; CT; Ct.Th; Lysine; Osx; Tb.Th; CTX-1; ELISA
• ISSN: 0271-5317; 1879-0739
• DOI: 10.1016/j.nutres.2023.11.005

•Lysine-rich rice diet improved bone growth, strength, and quality.•Higher serum growth hormone and bone formation markers were also observed.•Lysine-rich rice diet was comparable to wild-type rice with lysine supplementation, provided an alternative strategy to conventional lysine fortification strategy.•Lysine-activated IGF-1/Akt/mTOR signaling and subsequent bone formation Rice is the primary staple food for half of the world's population but is low in lysine content. Previously, we developed transgenic rice with enhanced free lysine content in rice seeds (lysine-rich rice), which was shown safe for consumption and improved the growth in rats. However, the effects of lysine-rich rice on skeletal growth and development remained unknown. In this study, we hypothesized that lysine-rich rice improved skeletal growth and development in weaning rats. Male weaning Sprague–Dawley rats received lysine-rich rice (HFL) diet, wild-type rice (WT) diet, or wild-type rice with various contents of lysine supplementation diet for 70 days. Bone microarchitectures were examined by microcomputed tomography, bone strength was investigated by mechanical test, and dynamics of bone growth were examined by histomorphometric analysis. In addition, we explored the molecular mechanism of lysine and skeletal growth through biochemical testing of growth hormone, bone turnover marker, and amino acid content of rat serum analysis, as well as in a cell culture system. Results indicated that the HFL diet improved rats' bone growth, strength, and microarchitecture compared with the WT diet group. In addition, the HFL diet increased the serum essential amino acids, growth hormone (insulin-like growth factor-1), and bone formation marker concentrations. The cell culture model showed that lysine deficiency reduced insulin-like growth factor-1 and Osterix expression, Akt/mammalian target of rapamycin signaling, and matrix mineralization, and inhibited osteoblast differentiation associated with bone growth. Our findings showed that lysine-rich rice improved skeletal growth and development in weaning rats. A further increase of rice lysine content is highly desirable to fully optimize bone growth and development. A rat-feeding study was performed. Bone strength and quality were then assessed, and the molecular mechanism for bone growth was evaluated. Lysine-rich rice diets improved the growth of rats. Lysine induced serum IGF-1 expression and activated the downstream signaling pathway. The active signaling and higher intracellular amino acid pool led to subsequent bone formation. Abbreviations: CT, computed tomography; IGF-1, insulin-like growth factor-1; mTOR, mammalian target of rapamycin; SD, Sprague–Dawley. [Display omitted]