Marrow adipose tissue gradient is preserved through high protein diet and bed rest. A randomized crossover study

CONTEXT: Marrow adipose tissue (MAT) has a peripheral to central distribution in adults, higher in peripheral bones. Similarly, the spine has a caudal to cephalad MAT distribution, higher in lumbar vertebras. Diet and the level of physical activities are known modulators of MAT with significant impact on bone; however, whether these can modulate the MAT gradient is unknown. OBJECTIVE: To measure the effect of high protein diet and bed rest interventions on the lumbar MAT gradient. DESIGN, PARTICIPANTS, INTERVENTION: In a prospective randomized crossover trial, 10 healthy men participated in 2 consecutive campaigns of 21days head-down-tilt-bed-rest (HDTBR). They received either whey protein and potassium bicarbonate-supplemented or control diet separated by a 4-month washout period. MAIN OUTCOME MEASURE(S): Ten serial MRI measures of lumbar vertebral fat fraction (VFF) were performed at baseline, 10days and 20days of HDTBR and 3 and 28days after HDTBR of each bed rest campaign. RESULTS: The mean L5-L1 VFF difference of 4.2 ± 1.2 percentage point higher at L5 (p = 0.008) constituted a caudal to cephalad lumbar MAT gradient. High protein diet did not alter the lumbar VFF differences during both HDTBR campaigns (all time points p > 0.05). Similarly, 2 campaigns of 21days of HDTBR did not change the lumbar VFF differences (all time points p > 0.05). CONCLUSIONS: This pilot study established that the lumbar vertebral MAT gradient was not altered by a high protein nor by 2 × 21days bed rest interventions. These findings demonstrated that this lack of mechanical stimulus was not an important modulator of the lumbar MAT gradient. The highly preserved MAT gradient needs to be measured in more situations of health and disease and may potentially serve to detect pathological situations.