Bone Marrow Metabolism Is Impaired in Insulin Resistance and Improves After Exercise Training

Abstract

Bone marrow (BM) insulin sensitivity has been suggested to play an important role in bone health and whole-body insulin sensitivity. Exercise training improves bone mineral density, but little is known about the effects of training on BM metabolism. We studied the effects of sprint interval training (SIT) and moderate-intensity continuous training (MICT) on BM metabolism.

54 sedentary subjects (healthy n=28, insulin resistant (IR) n=26, aged=40-55) were randomized into two weeks of SIT or MICT. Femoral, lumbar and thoracic BM insulin-stimulated glucose uptake (GU) and fasting free fatty acid uptake (FFAU) were measured using positron-emission tomography. Bone turnover markers osteocalcin and procollagen type 1 N-terminal propeptide (PINP) were measured from plasma.

At baseline, GU was highest in lumbar, followed by thoracic and lowest in femoral BM. FFAU was higher in lumbar and thoracic than in femoral BM. Femoral BM GU was higher in healthy compared to IR men and in females compared to males. BM FFAU was higher in healthy compared to IR men and higher in females than males. Exercise increased femoral BM GU similarly in all groups and decreased lumbar BM FFAU in men. Osteocalcin and PINP were lower in IR than healthy men and correlated positively with femoral BM GU and glycemic status.

BM substrate uptake differs regarding anatomical location and is impaired in insulin resistance. Short-term exercise training improves BM metabolism in healthy and IR subjects. Bone turnover rate is decreased in insulin resistance and associates positively with BM metabolism and glycemic control.