β‐hydroxy‐β‐methylbutyrate (HMB) Improves Myogenesis and Maintains Strength in Male Mice during a 6‐Week Catabolic Condition

Abstract

Soldiers in combat undergo catabolic conditions due to prolonged physical activity and hypocaloric states which cause decrements in lean mass and physical performance. We investigated the impact of HMB on muscle mass and performance along with transcript factors during catabolic conditions. C57BL/6 male mice (N=61, 6wks) underwent a 4-wk run-in-phase to simulate basic training (1h/d for 3d/wk forced wheel walking). Twenty one mice were sacrificed for baseline and the remaining animals were divided into 4 groups (10/group): AL=ad lib fed+exercise (1h/d for 3d/wk), ALH=AL+HMB (0.5 g/kg BW/day), C=caloric restricted (−30% of ad lib groups)+exercise (2 km/d, 6d/wk) and CH=C+HMB to simulate 6 wks of normal and catabolic condition in soldiers. Grip strength and incline plane were assessed pre- and post-experiment. Gastrocnemius (GAS) and soleus (SOL) were isolated. C demonstrated a decline in grip strength (−10% vs pre) whereas CH showed no decrement. Sensorimotor function declined in CH (−12%) and showed a trend for decline in C (p=0.056). A decrease in GAS MyoD mRNA was shown only in C (−44% vs pre) and an increase in SOL MyoD mRNA expression was shown only in CH (+295% vs pre). GAS myogenin mRNA increased in both C (+73% vs pre) and CH (+69% vs pre) while only C increased SOL myogenin mRNA (+98% vs pre). It is suggested that HMB possibly improves myogenesis and maintains strength during a 6-wk catabolic condition.