The deleterious effects of dietary restriction on bone quality and the tibial growth plate in rats are partially reversed by refeeding

Author(s)

Patrícia Madalena San Gregório Guedes

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina de Ribeirão Preto (PCARP/BC)
• Defense date: 2023-11-06

Examining board members

José Batista Volpon; Marcello Henrique Nogueira Barbosa; Rodrigo Gonçalves Pagnano; Francisco Jose Albuquerque de Paula

• Advisor: José Batista Volpon

Abstract

Background: Malnutrition is the result of a general or specific deficiency of essential nutrients and is highly prevalent worldwide. This condition adversely affects various organ systems, with a more pronounced impact on children, whose effects may persist throughout life, even after the normalization of the diet. Adequate nutritional intake plays a crucial role in growth and maximize the bone mass acquisition during skeletal development, which may reduce the incidence of osteoporosis and the risk of fractures in adulthood. The impact of malnutrition on an individual\'s development is well-known; however, there are still various gaps that need to be addressed, and controversies that require clarification, regarding the mechanisms involved after reintroducing a regular diet. Aim: The aim of this investigation was to assess the impact of food restriction and subsequent refeeding on bone tissue and cartilage growth in rats at different stages of development Material and methods: Seventy-eight male Wistar Hannover variety rats, initially weighing 60 g, were divided into three experimental groups: (1) CON: control rats, monitored for 12 weeks without any specific intervention; (2) RA: rats subjected to 12 weeks of food restriction, and (3) REA: rats subjected to six weeks of food restriction and then re-fed for various periods (two, four, and six weeks). The groups were further subdivided based on the observation period after food restriction and refeeding. Euthanasia was conducted at different time points. Throughout the experiment, the animals were kept in individual cages. Malnutrition was induced starting from weaning by imposing a general food restriction of 50% in relation to the controls\' intake from the previous day. At the end of the experimental period, the bones underwent macroscopic analyses, computed microtomography (qualitative and quantitative evaluation of bone microstructure), bone densitometry (DXA), optical microscopy (tissue characterization), histomorphometry (quantification of collagen, trabecular volume, and growth cartilage morphometry), TRAP (osteoclast labeling), immunohistochemistry (OPG, RANK, and RANKL), real-time PCR to assess gene expression, and mechanical assay (evaluation of mechanical resistance). Results: The results indicated that a 50% dietary restriction caused damage to the structure and function of the growth plate, leading to cellular changes in the hypertrophic and proliferative zones. The other analyses revealed that postnatal malnutrition caused an imbalance in bone remodeling, impairing bone quality by deteriorating the microarchitecture and reducing bone density. Additionally, it compromised the mechanical strength of the bones. Refeeding stimulated growth cartilage cell activity, improving bone and inhibiting resorption. However, the detrimental effects were not completely reversed during the study period. Conclusions: In conclusion, refeeding improved some harmful changes caused by malnutrition in rat tibias, but complete recovery was not achieved. (AU)

• FAPESP's process: 20/00529-5 - Food restriction and refeeding: short and medium term effects on growth cartilage and tibial bone quality of growing rats
• Grantee: Patrícia Madalena San Gregório Guedes
• Support Opportunities: Scholarships in Brazil - Doctorate