Effects of Roux-en-Y gastric bypass and sleeve gastrectomy on bone mineral density and marrow adipose tissue

Abstract

Bariatric surgery is associated with bone loss but skeletal consequences may differ between Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), the two most commonly performed bariatric procedures. Furthermore, severe weight loss is associated with high marrow adipose tissue (MAT); however, MAT is also increased in visceral adiposity. The purpose of our study was to determine the effects of RYGB and SG on BMD and MAT. We hypothesized that both bariatric procedures would lead to a decrease in BMD and MAT. We studied 21 adults with morbid obesity (mean BMI 44.1 ± 5.1 kg/m2) prior to and 12 months after RYGB (n=11) and SG (n=10). All subjects underwent DXA and QCT of the lumbar spine and hip to assess aBMD and vBMD. Visceral (VAT) and subcutaneous (SAT) adipose tissue was quantified at L1-2. MAT of the lumbar spine and femur was assessed by 1H-MR spectroscopy. Calcitropic hormones and bone turnover markers were determined. At 12 months after surgery, mean weight and abdominal fat loss was similar between the RYGB and SG groups. Mean serum calcium, 25(OH)-vitamin D, and PTH levels were unchanged after surgery and within the normal range in both groups. Bone turnover markers P1NP and CTX increased within both groups and P1NP increased to a greater extent in the RYGB group (p=0.03). There were significant declines from baseline in spine aBMD and vBMD within the RYGB and SG groups, although the changes were not significantly different between groups (p=0.3). Total hip and femoral neck aBMD by DXA decreased to a greater extent in the RYGB than the SG group (p<0.04) although the change in femoral vBMD by QCT was not significantly different between groups (p>0.2). MAT content of the lumbar spine and femoral diaphysis did not change from baseline in the RYGB group but increased after SG (p=0.03). Within the SG group, 12-month change in weight and VAT were positively associated with 12-month change in MAT (p<0.04), suggesting that subjects with less weight and VAT loss had higher MAT. In conclusion, RYGB and SG are associated with declines in lumbar spine BMD, however, the changes are not significantly different between the groups. RYGB may be associated with greater decline of aBMD at the total hip and femoral neck compared to SG. MAT content increased after SG and this was associated with lower weight and VAT loss.

Greater Bone Marrow Adiposity Predicts Bone Loss in Older Women

“…Others have found no association between change in marrow fat and bone loss in patients undergoing bariatric surgery. (18,19) The degree of bone loss that we report per each SD greater BMAT content is an increased loss of spine trabecular BMD of 0.9 mg/cm 3 /year. Other studies have reported that a difference in spine trabecular vBMD of about −0.04 mg/cm 3 /year is associated with increased risk of nonspine fracture (HR = 1.47), (20) hip fracture (HR = 1.8), and clinical spine fracture (HR = 3.7).…”

“…Kim and colleagues evaluated changes in vertebral BMAT and bone density in 30 obese women undergoing bariatric surgery, and found that greater increases in marrow fat correlated with greater bone loss at the spine (vBMD) and femoral neck (aBMD). Others have found no association between change in marrow fat and bone loss in patients undergoing bariatric surgery …”

Bone Marrow Fat Changes After Gastric Bypass Surgery Are Associated With Loss of Bone Mass

“…There may be common metabolic factors that regulate both marrow and visceral fat, just as marrow fat has been associated with intrahepatic and intramyocellular lipids . The positive relationship between the visceral and marrow fat depots has been observed in cross‐sectional studies and a longitudinal study of bariatric surgery, although it was not found in a longitudinal study of dietary weight loss . Thus, the relationship between changes in marrow fat and other fat depots does not appear uniform and may depend on the relative contribution of visceral fat loss.…”

“…Two other studies have examined vertebral marrow fat in subgroups of participants who have had RYGB. In 11 people undergoing RYGB, Bredella and colleagues found no significant change in vertebral marrow fat content after 12 months and no relationship between marrow fat and BMD changes . These RYGB participants, 2 of whom had diabetes, were compared with 10 individuals who underwent sleeve gastrectomy, in whom marrow fat content increased.…”

“…In 11 people undergoing RYGB, Bredella and colleagues found no significant change in vertebral marrow fat content after 12 months and no relationship between marrow fat and BMD changes. (56) These RYGB participants, 2 of whom had diabetes, were compared with 10 individuals who underwent sleeve gastrectomy, in whom marrow fat content increased. Similarly, Ivaska and colleagues found no significant 6-month change in vertebral marrow fat content in 7 RYGB patients or 14 sleeve gastrectomy patients.…”