Thirty-day β-hydroxy-βmethylbutyrate supplementation with a controlled diet does not alter the morphological and morphometric characteristics of the rat diaphragm muscle

ABSTRACT Objective To evaluate the β-hydroxy-βmethylbutyrate supplementation influence on the morphological and morphometric characteristics of the diaphragm muscle of rats and verify whether there are sex differences. Methods Experimental study with 48 Wistar rats (24 of each sex) divided into 3 groups: Control Group: in which a daily diet with saline solution was offered; Experimental Group: the same amount of food from the Control group consumed in the previous day and 0.3g/kg of β-hydroxy-βmethylbutyrate; Ad libitum Experimental Group: ad libitum feeding with the same dose of the supplement. The analysis consisted of histomorphometry and classification in diaphragm muscle fiber area bands. The procedures occurred 30 days after the start of the experiment. Data were analyzed using the one-way ANOVA and Tukey tests (p<0.05). Results There was no increase in the cross-sectional area of the diaphragm muscle fibers with the supplementation protocol employed and a similar histological pattern in both sexes. No significant changes were observed in muscle fiber size ranges in the supplemented groups, suggesting that there was no hypertrophy of muscle fibers. Conclusion This study suggests that β-hydroxy-βmethylbutyrate supplementation does not cause changes in the morphological and morphometric characteristics of the diaphragm muscle, regardless of sex.

摘要 目的 评估补充β-羟基-β-甲基丁酸（β-hydroxy-βmethylbutyrate）对大鼠膈肌形态与形态计量学特征的影响，并验证是否存在性别差异。方法 本实验纳入48只Wistar大鼠，雌雄各24只，分为3组：对照组：每日饲喂含生理盐水的日粮；实验组：每日饲喂量与前一日对照组大鼠的摄食量相同，同时添加0.3g/kg体重的β-羟基-β-甲基丁酸；自由进食实验组：可自由采食，并给予与实验组相同剂量的补充剂。分析内容包括组织形态计量学分析及膈肌肌纤维面积带分类。全部实验操作于实验启动后30天进行。数据采用单因素方差分析（one-way ANOVA）与Tukey检验进行统计学分析，检验显著性水平设为p<0.05。结果 本研究采用的补充方案未使膈肌肌纤维横截面积出现增加，且雌雄大鼠均呈现相似的组织学特征。补充组的肌纤维尺寸区间未观察到显著变化，提示肌纤维未发生肥大。结论 本研究结果提示，补充β-羟基-β-甲基丁酸不会对大鼠膈肌的形态与形态计量学特征产生影响，且该效应不受性别因素影响。