The effect of binge alcohol consumption on the development of adolescent Sprague Dawley rat mandibles

Abstract

Underage binge drinking has become a major public concern as it can have a negative impact on the growth and development of the adolescent skeleton, affecting many people worldwide, including in South Africa. Peak bone mass is attained during adolescence and any disturbances during this stage can lead to long term consequences on the skeleton. Little is known about the effects of binge drinking on the craniofacial structures such as the mandible, which is essential for mastication and is also involved in processes such as speech, facial expression, and dentition. Improving our understanding of the effects of binge drinking on the adolescent mandible can help us identify potential intervention measures and raise public awareness about the dangers of alcohol use. The present study was conducted to investigate the impact of acute and chronic binge drinking on mandibular parameters in adolescent Sprague Dawley (SD) rats and to evaluate if recovery of the mandible is possible once alcohol is removed from the diet. The study involved seventy-two (36 male and 36 female) Sprague Dawley rats, aged 7 weeks, divided into either an alcohol-exposed group or a pair-fed control group for acute binge, chronic binge, or alcohol abstinence models for both males and females. The alcohol-exposed group received 3 g/kg of 20 % alcohol 3 days a week for 7 or 28 days, followed by a 30-day abstinence period in the abstinence model. The pair-fed control groups received a caloric equivalent dose of maltose dextrin. The animals were euthanized on day 7, 28, or 54 using pentobarbital injections. Food and water intake, body mass gain, mandibular osteometry, trabecular morphometry (using 3D-MicroCT analysis), biomechanical tensile testing, cytoarchitecture and immunohistochemistry using the Ki-67 and ALP proteins were analysed. vi Results indicated that alcohol-exposed female rats ate less during acute binge drinking but increased their food and water intake after abstinence. In males, alcohol reduced water consumption during the abstinence phase. Body mass changes mirrored food intake: female rats lost weight during acute binge drinking but gained after abstinence, while males exhibited decreased body mass after abstinence. Mandibular measurements indicated increased lower mandibular length (M3-Id) in alcohol-exposed males during acute binge drinking and greater ramus height (Cd-Go) in females. In the chronic model, females had increased coronoid height (Cr-Ag), while abstinent animals, especially females, exhibited increases in anterior mandibular dimensions (MF-AlI and MF-M1). Trabecular parameters were disrupted across all binge models, with females most affected, especially after chronic exposure. These changes, involving bone volume to total volume ratio (BV/TV), trabecular thickness (TbTh), trabecular number (TbN), and trabecular spacing (TbSp), persisted even after abstinence, indicating lasting effects. Tensile strength was unchanged in the acute model but decreased in alcohol-exposed males after chronic binge drinking, with no female changes. After abstinence, males displayed no differences, while females had increased maximum and break forces. Across all three groups, alcohol exposure increased trabecular spacing and resulted in less mature bone with disorganized, wavy collagen in both male and female animals compared to the pair-fed controls. Acute binge drinking did not alter cell proliferation, while chronic exposure reduced it in both sexes. After abstinence, proliferation remained decreased in females but was unchanged in males. Binge alcohol exposure reduced osteoblast numbers, affecting only females in the acute model and both sexes in the chronic and abstinent models, with a marked decline in males after abstinence. vii Differences between male and female animals was evident throughout the parameters analysed in this study, where alcohol had a more pronounced effect on females when compared to males, highlighting sexual dimorphism. We concluded that binge alcohol exposure negatively impacts the adolescent skeleton across all models, with more severe and lasting effects after prolonged exposure. The female mandible was particularly vulnerable, showing persistent damage even after alcohol withdrawal.