Effect of high caffeine exposure on longitudinal bone growth during puberty in immature female rats

Abstract

Puberty is a critical period for skeletal growth. Although previous studies have demonstrated detrimental effects of caffeine on the skeletal system, most have used male rats to avoid the individual variability associated with rising estrogen in females. Hence, the effects of pubertal caffeine exposure on bone growth in females remain largely unknown. To investigate this, immature female Sprague–Dawley rats were assigned two experimental groups, which received caffeine doses of 120 and 180 mg/kg/day, respectively for 4 or 8 weeks, and a control group. At the end of the experiment, leg bone lengths and weights were measured, serum estradiol levels were determined, and histomorphometric analyses of the growth plates (GPs) were performed. Body weight was significantly lower in the two caffeine-fed groups than in the control group at both 4 and 8 weeks, and caffeine exposure significantly reduced leg bone length and weight, especially after 4 weeks of exposure. Bone mineral content was also reduced at both time points, whereas bone mineral density was affected only after 4 weeks. Notably, serum estradiol levels were significantly elevated in the caffeine-treated groups after 4 weeks of exposure. Histomorphometric analysis of the proximal tibial GP revealed that the caffeine-fed groups consistently had greater GP heights, lower bone formation parameters, and reduced spongiosa heights compared to controls. These findings suggest that caffeine directly or indirectly impairs the mineralization and osteoblastic activity required for proper bone maturation. Further research is needed to determine whether these adverse effects on long bone development in females persist following the cessation of caffeine exposure.