The dietary protein, IGF-I, skeletal health axis

Abstract

Abstract:Dietary protein represents an important nutrient for bone health and thereby for the prevention of osteoporosis. Besides its role as a brick provider for building the organic matrix of skeletal tissues, dietary protein stimulates the production of the anabolic bone trophic factor IGF-I (insulin-like growth factor I). The liver is the main source of circulating IGF-I. During growth, protein undernutrition results in reduced bone mass and strength. Genetic defect impairing the production of IGF-I markedly reduces bone development in both length and width. The serum level of IGF-I markedly increases and then decreases during pubertal maturation in parallel with the change in bone growth and standing height velocity. The impact of physical activity on bone structure and strength is enhanced by increased dietary protein consumption. This synergism between these two important environmental factors can be observed in prepubertal boys, thus modifying the genetically determined bone growth trajectory. In anorexia nervosa, IGF-I is low as well as bone mineral mass. In selective protein undernutrition, there is a resistance to the exogenous bone anabolic effect of IGF-I. A series of animal experiments and human clinical trials underscore the positive effect of increased dietary intake of protein on calcium-phosphate economy and bone balance. On the contrary, the dietary protein-induced acidosis hypothesis of osteoporosis is not supported by several experimental and clinical studies. There is a direct effect of amino acids on the local production of IGF-I by osteoblastic cells. IGF-I is likely the main mediator of the positive effect of parathyroid hormone (PTH) on bone formation, thus explaining the reduction in fragility fractures as observed in PTH-treated postmenopausal women. In elderly women and men, relatively high protein intake protects against spinal and femoral bone loss. In hip fracture patients, isocaloric correction of the relatively low protein intake results in: increased IGF-I serum level, significant attenuation of postsurgical bone loss, improved muscle strength, better recovery, and shortened hospital stay. Thus, dietary protein contributes to bone health from early childhood to old age. An adequate intake of protein should be recommended in the prevention and treatment of osteoporosis.

Protein intake and risk of hip fractures in postmenopausal women and men age 50 and older

“…Low protein intake on the other hand, can induce secondary hyperparathyroidism [6] and high levels of parathyroid hormone is associated with low bone mineral density [33]. Dietary protein stimulates the production of insulin-like growth factor-1 (IGF-1) [34]which in turn stimulates formation of osteoblasts and reduces apoptosis [35]. Cross-sectional studies have shown a direct association between IGF-1 and bone mineral density [35] and fractures [36].…”

The Impact of Fat and Obesity on Bone Microarchitecture and Strength in Children

“…IGF-1 also acts indirectly to promote renal tubular reabsorption of phosphate and on the synthesis of calcitriol [111]. Impaired GH secretion may be compounded by highly caloric low protein diets in obese children that impacts on the synthesis of IGF-1 [112, 113]. …”

Resistence Exercise Improves Anxiety and Depression in Middle- Age Women

“…Existe uma tendência de início precoce da doença, sendo que os homens apresentam risco estimado entre 5-12%, e as mulheres entre 10-25% 2 . Com o avanço da idade, principalmente depois dos 50 anos, ocorrem mudanças significativas no metabolismo de homens e mulheres, como diminuições nas concentrações de hormônio do crescimento (growth hormone -GH), crescimento insuline-símile 1 (insulin-like growth fator 1 IGF-1), da quantidade de massa óssea (osteopenia) 3,4 , massa muscular (sarcopenia) 5,6 , entre outras alterações. A perda de massa muscular pode chegar a 40% 7 .…”