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Bone. 2019 Oct 5:115069. doi: 10.1016/j.bone.2019.115069. [Epub ahead of print]

Changes in bone quality after Roux-en-Y gastric bypass: A prospective cohort study in subjects with and without type 2 diabetes.

Author information

1
Department of Endocrinology, Morbid Obesity and Preventive Medicine, Oslo University Hospital, Oslo, Norway; Institute of Clinical Medicine, University of Oslo, Oslo, Norway. Electronic address: ingvild.hogestol@gmail.com.
2
Department of Endocrinology, Morbid Obesity and Preventive Medicine, Oslo University Hospital, Oslo, Norway; Department of Gastrointestinal Surgery and Paediatric Surgery, Oslo University, Norway.
3
Oslo Centre for Biostatistics and Epidemiology, Research Support Services, Oslo University Hospital, Oslo, Norway.
4
Department of Endocrinology, Morbid Obesity and Preventive Medicine, Oslo University Hospital, Oslo, Norway; Department of Chronic Diseases and Ageing, Norwegian Institute of Public Health, Norway.
5
Department of Endocrinology, Morbid Obesity and Preventive Medicine, Oslo University Hospital, Oslo, Norway; Institute of Clinical Medicine, University of Oslo, Oslo, Norway.

Abstract

BACKGROUND:

Obesity and type 2 diabetes (T2D) are associated with an increased risk of skeletal fractures despite a normal areal bone mineral density (aBMD) and low bone turnover, possibly due to reduced bone material strength. Roux-en-Y gastric bypass (RYGB) enables a substantial and persistent weight loss and resolution of obesity related comorbidities such as T2D. However, the procedure induces a decrease in aBMD and increased bone turnover and fracture rate. To our knowledge, changes in bone material strength after RYGB have not been explored. This study aimed to evaluate changes in factors influencing bone quality; bone material strength, aBMD and bone turnover markers, in a population with morbid obesity undergoing RYGB and whether these changes differed in participants with and without T2D. We also sought to assess factors associated with bone material strength and bone mineral density in obese subjects before and after RYGB.

METHODS:

We examined 34 participants before and one year after RYGB, of whom 13 had T2D. Bone material strength index (BMSi) was evaluated by impact microindentation, aBMD and body composition by Dual energy X-ray absorptiometry, levels of bone turnover markers and calciotropic hormones were estimated from fasting serum samples. Participants with and without T2D were comparable before surgery, with the exception of glycosylated hemoglobin (HbA1c).

RESULTS:

Preoperatively, BMSi was inversely associated with BMI, βunadjusted -1.1 (-1.9 to -0.28), R2 = 0.19, p = 0.010, and this association remained significant after adjusting for age and gender. After RYGB the participants had lost a mean ± SD of 33.9 ± 10.9 kg, 48.7 ± 14.2% of total body fat, increased physical activity, unchanged vitamin D levels, and all but one of the 13 participants with T2D were in diabetes remission. BMSi increased from 78.1 ± 8.5 preoperatively to 82.0 ± 6.4 one year after RYGB, corresponding to an increase of 4.0 ± 9.8 in absolute units or 6.3 ± 14.0%, p = 0.037. The increase was comparable in participants with and without T2D. In subjects with T2D, a larger decrease in HbA1c was associated with a larger increase in BMSi βunadjusted -9.2 (-16.5 to -1.9), R2 = 0.47, p = 0.019. Bone turnover markers (CTX-1 and PINP) increased by 195.1 ± 133.5% and 109.5 ± 70.6%, respectively. aBMD decreased by 3.9 ± 5.5% in the lumbar spine, 8.2 ± 4.6% in the femoral neck, 11.6 ± 4.9% in total hip and 9.4 ± 3.8% in total body.

CONCLUSION:

Our findings indicate that bone material strength improves despite an increase in bone turnover and a decrease in aBMD one year after RYGB. Trends were statistically comparable in participants with and without T2D. However, improved glucose control was associated with improved bone material strength in participants with T2D.

KEYWORDS:

Bone mineral density; Bone turnover; Impact microindentation; Roux-en-Y gastric bypass; Type 2 diabetes

PMID:
31593823
DOI:
10.1016/j.bone.2019.115069

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