Resistance training modulates the matrix mtalloproteinase-2 activity in different trabecular bones in aged rats

Background: Aging decreases osteogenic ability, inducing harmful effects on the bone extracellular matrix (ECM), while exercise training has been indicated as a tool to counteract bone disorders related to advancing age. The modulation of bone ECM is regulated by several types of matrix metalloproteinase (MMP); however, MMP-2 activity in different trabecular bones in response to resistance training (RT) has been neglected. Remodeling differs in different bones under the application of the same mechanical loading. Thus, we investigated the effects of 12 weeks of RT on MMP-2 activity in the lumbar vertebra (L6), tibia, and femur of young (3 months) and older rats (21 months). Methods: Twenty Wistar rats were divided into four groups (five animals per group): young sedentary or trained and older sedentary or trained. The 12-week RT consisted of climbing a 1.1-m vertical ladder three times per week with progressive weights secured to the animals’ tails. The animals were killed 48 h after the end of the experimental period. The MMP-2 activity was assessed by the zymography method. Results: The aging process induced lower MMP-2 activity in the lumbar vertebrae and tibia (p=0.01). RT upregulated pro, intermediate, and active MMP-2 activity in the tibia of young rats (p=0.001). RT also upregulated pro and active MMP-2 activity in the lumbar vertebrae and tibia with advancing age (p=0.01). There was no significant difference (p> 0.05) between groups for MMP-2 of the femur, regardless of age and RT. Conclusion: The aging process impairs MMP-2 activity, but RT is a potential therapeutic approach to minimize the deleterious effects of ECM degeneration in different aged bones. Distinct MMP-2 responses to exercise training may result in specific remodeling processes

Efeito do envelhecimento e do treinamento resistido sobre ossos de ratos

The purpose of this study was to investigate the influence of high-intensity resistance training on the activity of bone matrix metalloproteinases (MMPs), biometric, biomechanical, biophysical and biochemical properties of young and aged rats. We used 62 intact male rats, Rattus norvegicus albinos ("Wistar") randomly distributed into 4 groups: young sedentary (YS), young trained (YT), older sedentary (OS) and old trained (OT). The rats (YT and OT) performed resistance training, during 12 weeks, consisted of climbing a vertical ladder with weights fixed on their tails. The sessions were executed three times a week, every other day. The biomechanical, physical, biochemical and MMP-2 activity of bones analysis were performed, respectively, using a universal testing machine, Archimedes principle, commercial kit and zymography. In this study, the training promoted a reduction of body mass in YT animals, and reduced bone stiffness and pro MMP activity in the OT group. With aging occured differences of the charge of loading (absolute and relative) between the trained groups (YT greater than OT), body mass (increased among youth, increased initial mass and decreased final mass in the elderly), an increase in the right femur length, mineral material (calcium and phosphorus) and stiffness, however, a decrease of organic material. In this study, the training protocol did not cause effects on bone tissue chosen for analysis. In this study, the training protocol did not cause effects on bone tissue chosen for analysis.Financiadora de Estudos e ProjetosA proposta deste estudo foi investigar a influência do treinamento resistido de alta intensidade sobre a atividade das metaloproteinases de matriz (MMPs), propriedades biométricas, biomecânicas, biofísicas e bioquímicas de ossos de ratos jovens e idosos. Foram utilizados 62 ratos intactos, Ratus novergicus albinos ( Wistar ), do gênero masculino, distribuídos aleatoriamente em 4 grupos: jovens sedentários (JS), jovens treinados (JT), idosos sedentários (IS) e idosos treinados (IT). Os ratos (JT e IT) realizaram treinamento resistido durante 12 semanas, que consistia em escalar em uma escada vertical de 1,1m com pesos fixados em suas caudas. As sessões foram realizadas três vezes por semana, em dias intercalados. As análises biomecânicas, biofísicas, bioquímicas e atividade da MMP-2 dos ossos foram realizadas, respectivamente, utilizou-se uma máquina de ensaio universal, princípio de Arquimedes, kit comercial específico e zimografia. No presente estudo, o protocolo de treinamento promoveu diminuição da massa corporal dos animais JT, e redução da rigidez óssea e da atividade da pro MMP-2 no grupo IT. Com o envelhecimento ocorreu diferenças da carga de carregamento (absoluta e relativa) entre os grupos treinados (JT maior que IT) e massa corporal (aumento nos jovens; aumento da massa inicial e diminuição da massa final nos idosos), aumento do comprimento do fêmur direito, material mineral (cálcio e fósforo) e rigidez, porém, uma diminuição do material orgânico. No presente estudo, o protocolo de treinamento não promoveu efeito sobre o tecido ósseo escolhido para análise

Remodeling process in bone of aged rats in response to resistance training

Aims We investigate the effects of RT on the mechanical function, gene, and protein expression of key factors involved in bone remodeling during aging. Main methods Male rats of 3 and 21 months of age were randomly allocated into four groups (8 per group): young sedentary (YS), young trained (YT), old sedentary (OS), and old trained (OT). RT was performed three times per week (12 weeks). Bone tenacity and stiffness were measured by biomechanical tests and mRNA levels of COL1A1, MEPE, SOST, OPG, BMP-2, PPAR-y, MMP-2-9-13, and TIMP-1 were evaluated by quantitative PCR. COL1A1 protein and MMP-2 activity were detected by western blotting and zymography assays. Key findings Aging increased stiffness, while BMP-2, OPG, COL1A1 and MMP-2 mRNA levels reduced (OS vs YS; p ≤ 0.05). RT increased the tenacity of the femur and reduced PPAR-γ regardless of age (YT vs. YS; OT vs. OS; p ≤ 0.05). RT downregulated SOST mRNA levels only in the OT group (vs. OS group, p ≤ 0.05). RT mitigated the age-associated increase in MMP-9 mRNA levels (p ≤ 0.05). In young animals, upregulation in MEPE, MMP-13, TIMP-1 were observed after RT, as well an increase in COL1A1 protein and MMP-2 activity (p ≤ 0.05). Significance RT improved bone tenacity independent of aging, which is relevant for mechanical function, while, at protein levels, RT upregulated MMP-2 activity and collagen 1 only in young rats. This study highlights the importance of exercise on bone health and identifies specific molecular changes in response to RT. Our findings provide insights into the mechanisms involved in age-related changes