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After RYGB, BMD decreases tied to bone marrow fat increases in women
Declines in bone mineral density are associated with increases in bone marrow fat in women with obesity who underwent Roux-en-Y gastric bypass, regardless of diabetes status, according to findings published in the Journal of Bone and Mineral Research.
Tiffany Y. Kim, MD, of the University of California, San Francisco at the San Francisco VA Health Care System, and colleagues evaluated women (mean age, 48 years) with obesity and with (n= 14) or without (n = 16) type 2 diabetes who underwent Roux-en-Y gastric bypass (RYGB) to determine the relationship between marrow fat content and BMD changes after RYGB.
BMD was measured by DXA and quantitative CT and vertebral marrow fat content was measured by magnetic resonance spectroscopy before and 6 months after RYGB.
Participants with type 2 diabetes had lower preoperative weight and BMI compared with participants without diabetes.
During the 6 months after RYGB, all participants lost a mean 27.3 kg in weight and 19.3 kg of total body fat.
The observed decrease in HbA1c was greater in participants with diabetes (–1.9%) compared with those without diabetes (–0.4%; P < .01). Insulin-like growth factor I increased by 33 ng/mL from baseline in participants with diabetes and remained stable in participants without diabetes (P = .01 for difference between groups).
Overall, marrow fat content did not significantly decrease overall; however, there was a significant different between participants with diabetes and without diabetes for marrow fat change (8.3% for difference; P = .03). Marrow fat content was stable in participants without diabetes but significantly decreased in participants with diabetes.
Among all participants, declines in marrow fat were associated with greater declines in HbA1c (P = .01) and increases in IGF-I levels (P = .05).
After RYGB, overall areal BMD decreased by 4.3% at the femoral neck and 4.1% at the total hip and spinal volumetric BMD decreased by 6.4% (P < .01 for all). Participants with diabetes experienced greater declines in femoral neck areal BMD compared with participants without diabetes.
Participants with increases in marrow fat content experienced greater reductions in spine volumetric BMD (P < .01) and femoral neck areal BMD (P = .01) compared with participants with decreases in marrow fat content. Vertebral volumetric BMD decreased by an additional 2.9% (P = .02) and femoral neck areal BMD by an additional 2.5% (P < .001) with each standard deviation increase in vertebral marrow fat content change after adjustment for age and menopausal status.
“Regulators of the marrow fat-bone relationships are uncertain, but our data suggest that IGF-I may play a role,” the researchers wrote. “Further research is needed to understand the mechanisms for the marrow fat-bone interaction and possible regulation by glucose metabolism. Ultimately, understanding the role of marrow fat in bone metabolism could lead to the development of strategies targeted to the prevention and treatment of osteoporosis, skeletal complications of bariatric surgery, and diabetic bone fragility.” – by Amber Cox
Disclosures: The authors report no relevant financial disclosures.