title: Roux-en-Y gastric bypass surgery reduces bone mineral density and induces metabolic acidosis in rats.
abstract: Roux-en-Y gastric bypass (RYGB) surgery leads to bone loss in humans, which may be caused by vitamin D and calcium malabsorption and subsequent secondary hyperparathyroidism. However, because these conditions occur frequently in obese people, it is unclear whether they are the primary causes of bone loss after RYGB. To determine the contribution of calcium and vitamin D malabsorption to bone loss in a rat RYGB model, adult male Wistar rats were randomized for RYGB surgery, sham-operation-ad libitum fed, or sham-operation-body weight-matched. Bone mineral density, calcium and phosphorus balance, acid-base status, and markers of bone turnover were assessed at different time points for 14 wk after surgery. Bone mineral density decreased for several weeks after RYGB. Intestinal calcium absorption was reduced early after surgery, but plasma calcium and parathyroid hormone levels were normal. 25-hydroxyvitamin D levels decreased, while levels of active 1,25-dihydroxyvitamin D increased after surgery. RYGB rats displayed metabolic acidosis due to increased plasma lactate levels and increased urinary calcium loss throughout the study. These results suggest that initial calcium malabsorption may play a key role in bone loss early after RYGB in rats, but other factors, including chronic metabolic acidosis, contribute to insufficient bone restoration after normalization of intestinal calcium absorption. Secondary hyperparathyroidism is not involved in postoperative bone loss. Upregulated vitamin D activation may compensate for any vitamin D malabsorption.
authors.affiliation: Institute of Veterinary Physiology, Vetsuisse Faculty University of Zurich, Zurich, Switzerland;
authors.forename: Kathrin
authors.initials: K
authors.lastname: Abegg
authors.forename: Nicole
authors.initials: N
authors.lastname: Gehring
authors.forename: Carsten A
authors.initials: CA
authors.lastname: Wagner
authors.forename: Annette
authors.initials: A
authors.lastname: Liesegang
authors.forename: Marc
authors.initials: M
authors.lastname: Schiesser
authors.forename: Marco
authors.initials: M
authors.lastname: Bueter
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Lutz
mesh_terms: D000138:Acidosis / Q000209:etiology* / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D000818:Animals; D015415:Biomarkers / Q000097:blood / Q000652:urine; D015519:Bone Density; D016723:Bone Remodeling; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000503:physiopathology; D002118:Calcium / Q000097:blood / Q000652:urine; D002908:Chronic Disease; D015390:Gastric Bypass / Q000009:adverse effects*; D006962:Hyperparathyroidism, Secondary / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology; D007408:Intestinal Absorption; D007668:Kidney / Q000378:metabolism; D019344:Lactic Acid / Q000097:blood; D008286:Malabsorption Syndromes / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D010281:Parathyroid Hormone / Q000097:blood; D011859:Radiography; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood
chemical_list: D015415:Biomarkers; D010281:Parathyroid Hormone; D014807:Vitamin D; D019344:Lactic Acid; C097949:1,25-dihydroxyvitamin D; C104450:25-hydroxyvitamin D; D002118:Calcium
keywords: Roux-en-Y gastric bypass; metabolic acidosis; secondary hyperparathyroidism; vitamin D