24-25-dihydroxyvitamin-d-3 and Obesity

A forearm counter and double-isotope technique were used to measure intestinal calcium absorption in 21 patients after jejuno-ileal bypass for obesity or small intestinal resection. In all but 2 patients calcium absorption was below the normal range for 10 male controls. 3 weeks treatment with 1-alpha-hydroxyvitamin D, 1 microgram b.d., or 1,25-dihydroxyvitamin D, 1 microgram b.d., was associated with significant increases in absorption whereas 3 weeks treatment with 24,25-dihydroxyvitamin D had no effect. This study demonstrates that oral 1,25-dihydroxyvitamin D or 1-alpha-hydroxyvitamin D are effective in increasing calcium absorption.

Topics: 24,25-Dihydroxyvitamin D 3; Adult; Calcifediol; Calcitriol; Calcium; Crohn Disease; Dihydroxycholecalciferols; Female; Humans; Intestinal Absorption; Intestine, Small; Jejunoileal Bypass; Male; Middle Aged; Obesity; Reference Values

In order to investigate mineral and vitamin D metabolism in obese rats with hyperinsulinemia, plasma calcium and vitamin D metabolites were measured in Zucker fa/fa rats. Body weight, plasma insulin, and calcium in fa/fa rats were significantly increased compared to their lean littermates (p less than 0.01). However, no significant difference in plasma 25-hydroxyvitamin D (25(OH)D), 24,25-dihydroxyvitamin D, 1,25-dihydroxyvitamin D (1,25(OH)2D) or the ratio of 1,25(OH)2D to 25(OH)D was observed between fa/fa rats and their lean littermates. The hypercalcemia in the rats with hyperinsulinemia, therefore, might be caused by other calcium-regulating hormones or some factors other than 1,25(OH)2D. In addition, the hyperinsulinemia associated with obesity may not produce the accelerated conversion from 25(OH)D into 1,25(OH)2D.

Topics: 24,25-Dihydroxyvitamin D 3; Animals; Blood Glucose; Body Weight; Calcifediol; Calcitriol; Dihydroxycholecalciferols; Hypercalcemia; Hyperinsulinism; Male; Obesity; Rats; Rats, Zucker; Vitamin D

Ten obese subjects who had undergone intestinal bypass operation (end-to-side jejunoileostomy) were studied longitudinally with respect to vitamin D and other indices of calcium metabolism. Investigations were carried out before operation (t0) and after 6 months (t1), 12 months (t2), and a mean of 54 months (range, 49-58 months) (t3) postoperatively. Serum 25-hydroxyvitamin D (25OHD) was subnormal at t0 but after operation values declined gradually to an extremely low level at t3, possibly because of a loss through malabsorption. Serum 24,25-dihydroxyvitamin D remained normal at t1 and t2 but fell to about half the normal level at t3, probably owing to lack of its precursor, 25OHD. In contrast, serum 1,25-dihydroxyvitamin D (1,25(OH)2D) remained normal throughout the study, indicating a marked stimulation of kidney 1 alpha-hydroxylase activity. Serum calcium fell rapidly to a constant subnormal level, and it is concluded that the serum calcium malabsorption is due to factors other than impaired 1,25(OH)2D activity. Bone mineral content (BMC) was unchanged between t0 and t2, but thereafter (between t2 and t3) the mean BMC fell rapidly to about 90% of preoperative value, possibly due to a defective bone mineralization in the late postoperative period. The findings indicate a high risk of bone disease developing after intestinal bypass operation. Substitution with calcium and vitamin D should be given to these patients, but the optimal vitamin D metabolite (or combination of metabolites) for such treatment is still unknown.

Topics: 24,25-Dihydroxyvitamin D 3; Adult; Alkaline Phosphatase; Bone and Bones; Calcifediol; Calcitriol; Dihydroxycholecalciferols; Female; Humans; Hydroxycholecalciferols; Ileum; Jejunum; Longitudinal Studies; Male; Minerals; Obesity; Postoperative Complications

The serum levels of the three major vitamin D metabolites [25-hydroxyvitamin D (25-OHD), 1,25-dihydroxyitamin D (1,25-(OH)2D), 24,25-dihydroxyvitamin D (24,25-(OH)2 D)] and immunoreactive parathyroid hormone (iPTH) were measured in 14 morbid obese patients, who later on were subjected to jejunoileal bypass surgery. The preoperative median values of 25-OHD and 24,25-(OH)2D were reduced compared with controls (P less than 0.001), whereas elevated concentrations were found of 1,25-(OH)2D (P less than 0.005). Median levels of iPTH in the obese group were significantly higher than those found in normal subjects (P less than 0.001). A decrease was observed in serum concentrations of all three vitamin D metabolites following jejunoileal bypass (P less than 0.005). An increase in the serum levels of iPTH and alkaline phosphatase was seen postoperatively (P less than 0.002), probably indicating a secondary hyperparathyroidism. The results show that the vitamin D metabolism is slightly abnormal in severely obese patients. Jejunoileal bypass is followed by severe disturbances of vitamin D metabolism.

Topics: 24,25-Dihydroxyvitamin D 3; Adult; Alkaline Phosphatase; Calcifediol; Calcitriol; Dihydroxycholecalciferols; Female; Humans; Ileum; Jejunum; Male; Middle Aged; Obesity; Parathyroid Hormone; Vitamin D; Vitamin D Deficiency