The decrease in the OPG/RANKL ratio in girls with AN could partly explain the increase in bone loss that occurs in these patients.

At the level of prevention of bone mineral loss produced by ovariectomy, the aim of the present study was to determine the effect produced by supplementation of Ca in the diet and a moderate exercise programme (treadmill), simultaneously or separately, in ovariectomized rats, an experimental model of postmenopausal bone loss. Female Wistar rats (n 110, 15 weeks old) were divided into five groups: (1) OVX, rats ovariectomized at 15 weeks of age, fed a standard diet; (2) SHAM, rats sham operated at 15 weeks of age, fed a standard diet; (3) OVX -EX, ovariectomized rats, fed a standard diet and performing the established exercise programme; (4) OVX -Ca, ovariectomized rats fed a diet supplemented with Ca; (5) OVX -EXCa, ovariectomized rats with the exercise programme and diet supplemented with Ca. The different treatments were initiated 1 week after ovariectomy and were continued for 13 weeks for subgroup 1 and 28 weeks for subgroup 2, to look at the interaction of age and time passed from ovariectomy on the treatments. Bone mineral density (BMD) was determined, at the end of the study, in the lumbar spine (L2, L3 and L4) and in the left femur using a densitometer. Bone turnover was also estimated at the end of the study, measuring the serum formation marker total alkaline phosphatase (AP) and the resorption marker serum tartrate-resistant acid phosphatase (TRAP). As expected, OVX rats showed a significant decrease (P,0 : 05) in BMD, more pronounced in subgroup 2, and a significant increase in AP and TRAP with regard to their respective SHAM group. The simultaneous treatment with Ca and exercise produced the best effects on lumbar and femoral BMD of ovariectomized rats, partially avoiding bone loss produced by ovariectomy, although it was not able to fully maintain BMD levels of intact animals. This combined treatment produced a significant increase in AP, both in subgroups 1 and 2, and a decrease in TRAP in subgroup 1, with regard to OVX group. The exercise treatment alone was able to produce an increase in BMD with regard to OVX group only in subgroup 1 of rats (younger animals and less time from ovariectomy), but not in subgroup 2. In agreement with this, there was an increase of AP in both subgroups, lower than that observed in animals submitted to exercise plus Ca supplement, and a decrease of TRAP in subgroup 1, without significant changes in this marker in the older rats. Ca treatment did not produce any significant effect on BMD in OVX rats in both subgroups of animals, showing a decrease of AP and TRAP levels in the younger animals with no significant variations in markers of bone remodelling in the older female rats compared with their respective OVX group. Bone is a dynamic tissue in a continuous process of formation and resorption, activities performed by the osteoblasts and the osteoclasts respectively. The increase in bone mass or, on the contrary, bone loss, depends on the balance between these two processes (Canalis, 1996). Bone turnover is regulated by systemic hormones and by local factors. Oestrog...

Previous studies have made references to prolonged treatment with phenytoin as a possible risk factor in the development of osteoporosis and/or osteomalacia. We studied a group of 30 epileptic patients who were under long-term treatment with phenytoin (DPH) in an ambulatory regimen. We found the prevalence of osteoporosis to be 3.3% and of osteopenia to be 56.6%, affecting predominantly the femur, without any significant decrease in bone mineral density of the lumbar spine. These patients were showing signs of bone turnover uncoupling with increases in bone resorption markers. At this time, they also exhibited slight alterations in their phosphocalcium metabolism with trends to hypocalcemia and secondary hyperparathyroidism that was found not to be caused by a vitamin D deficiency as the serum levels of 25(OH)D and 1,25(OH)₂D were normal. With the aims of corroborating these results and to investigate the physiopathological effects on the bone induced by anticonvulsant drugs we developed a further experimental study in which we administered DPH over a 6-week period with a dose of 5 g/kg/day to male Wistar rats that were in the growth phase. This treatment produced a decrease in overall BMD and bone mineral content in the femur. We did not find osteomalacia in the vertebral biopsy, but the administration of DPH to these animals decreased trabecular volume as well as lessened the thickness of osteoid edges together with an uncoupling in bone turnover. There was also a marked decrease in bone formation and a tendency towards increased bone resorption. We have also found a decrease in resistance to fracture by torsion in the biomechanical assay, which translates into an increase in bone fragility. In these male Wistar rats, the administration of DPH produced a tendency towards increasing the markers of resorption and, though changes in serum levels of calcium and phosphorus were not observed, to provoke an increase in the parathyroid hormone levels; with normal levels of 1,25(OH)₂D which has produced the same inclination in rats as in humans.

Fragments derived from degradation of type I collagen C-telopeptide (CTX) can be nonisomerized (alpha) or beta-isomerized (beta) depending on the age of bone; i.e., mainly the alpha form is derived from new bone and the beta form from old bone. We have studied 41 female patients with anorexia nervosa (AN), aged 18.5 +/- 2.2 years (range 16-24 years), and with an evolution time between 1.5 and 11 years, and 31 healthy control females (C), with a mean age of 19 +/- 2.3 years (range 16-24 years). The AN patients showed a significant decrease in bone mass, with a mean Z-score of bone mineral density (BMD) of -3.2 +/- 0.8 (range -0.9 to -5.4). The aim of our study was to determine the levels of urinary alpha- and beta-CTX markers of bone resorption, the alpha/beta ratio (alpha/beta), and the level of bone alkaline phosphatase (bAP), a biochemical marker of bone formation, in order to relate them to the degree of osteopenia and the status of bone remodeling. Statistical analysis was by the Mann-Whitney test. The degree of osteopenia correlated with bAP levels (p = 0.0027) but not with the other parameters. Patients with AN were divided into three groups according to their levels of bAP: high (H), normal (N) or low (L). We found that BMD was significantly lower, and alpha- and beta-CTX were significantly higher, in groups H and N than in group L. Bone AP correlated significantly with alpha-CTX (p = 0.0042) and alpha/beta (0.0095) in the controls, but not with beta-CTX, while in AN patients bAP correlated with beta-CTX (p = 0.0000) and with alpha-CTX (p = 0.022) but not with the alpha/beta ratio. The ratio CTX/bAP (resorption/formation) was similar in AN patients and controls. It is concluded that: (1) patients with AN have a high degree of osteopenia which correlated with bAP levels; (2) urinary CTX fragments found in AN patients seem to come mainly from old bone (beta-CTX), while CTX found in healthy adolescent control females come from new bone (alpha-CTX). For this reason, alpha-CTX is more suitable than beta-CTX for measuring bone resorption in controls and beta-CTX is more suitable in patients with AN; (3) the resorption/formation ratio (CTX/bAP) was similar in AN patients and controls. From points (2) and (3) it is possible to suggest that, although bAP reflects bone formation in control females, this marker does not reflect effective bone mineralization in AN patients, a similar feature to that of patients with osteomalacia.

Osteocalcin is a protein synthesized by the osteoblast. Before being released into the extracellular matrix, human osteocalcin undergoes gamma-carboxylation, as gamma-carboxy-glutamic acid binds at positions 17, 21 and 24. Part of the carboxylated and decarboxylated osteocalcin passes into the circulation. Since its discovery in the late 70s, it has been used as a marker of bone formation as it is an osteoblastic product and its role in the body is unknown. In recent years, osteocalcin has been identified as a hormone. Bone is considered an endocrine organ. Osteocalcin acting as a hormone is the decarboxylated form. Osteocalcin is involved in glucose homeostasis, skeletal muscle function, brain development, male fertility, hepatic steatosis, and arterial calcification. All of these facts have actually been tested in mice, but there is strong evidence that this could occur in humans. We are faced with facts that, if proven, would have enormous clinical significance.