Maintained malnutrition produces a progressive decrease in (OPG)/RANKL ratio and leptin levels in patients with anorexia nervosa

OBJECTIVE

Osteoprotegerin (OPG) and receptor activator of nuclear factor-kappaB ligand (RANKL) are key factors in bone remodeling in patients with anorexia nervosa (AN) and osteopenia. The purpose of this study was to investigate basal serum levels of OPG, RANKL and leptin, as well as bone mineral density (BMD) measured by DEXA at lumbar vertebrae L1-L4, and their evolution during one year in two groups of patients with AN.

MATERIAL AND METHODS

Group I included 10 adolescent girls suffering from malnutrition and secondary amenorrhea with an evolution of more than one year at the beginning of the study who received oral estrogen treatment throughout the follow-up period. Group II comprised 10 girls with malnutrition and secondary amenorrhea with an evolution of less than one year who received nutritional treatment only. All parameters were compared with those of a control group of 19 healthy, age-matched girls with normal BMI and regular menstrual cycles.

RESULTS

The OPG/RANKL ratio was significantly decreased (p<0.05) after 1 year in group I, a fact that was due to an increase (p<0.05) in serum RANKL values. A correlation between OPG/RANKL and BMD was found in group I at the beginning of the study (r = 0.95; p<0.001). Patients in this group showed lower BMD values (p<0.01), both at diagnosis and at the end of the study, than those of group II patients, who showed normal BMD values.

CONCLUSION

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

Effects of 17beta-estradiol, tamoxifen and raloxifene on the protein and mRNA expression of interleukin-6, transforming growth factor-beta1 and insulin-like growth factor-1 in primary human osteoblast cultures

We investigated the effects of 17betaestradiol and two selective estrogen receptor modulators, tamoxifen and raloxifene, on the expression and release of constitutive and interleukin-1-stimulated interleukin (IL)-6, transforming growth factor-beta1 (TGF-beta1) and insulin-like growth factor-1 by osteoblasts in primary culture from trabecular bone of healthy post-menopausal women. After 24 h incubation with 10(-8) M concentration of these compounds, there was no decrease in: a) the constitutive or IL-1beta-induced levels of IL-6 protein released to culture medium; b) the constitutive IL-6 mRNA expression after incubation of osteoblasts with 10(-8) M 17betaestradiol or 10(-8) M tamoxifen for 1, 3, 6, 24 or 30 h. Although a decrease after 30 h of treatment with 10(-8) M, raloxifene was found in mRNA IL-6 expression, and this fact was not reflected by a decrease in the release of IL-6 protein to the culture medium after 48 h of incubation with 10(-8) M or 10(-7) M raloxifene. Tumoral growth factorTGF-betal expression was not influenced by incubation with these compounds. Gene expression of IGF-I increased following 24 or 30 h incubation with 10(-8) M 17beta-estradiol and 30 h incubation with raloxifene. Tamoxifen did not affect IGF-I expression. In conclusion, the effects of estradiol or tamoxifen on bone metabolism do not appear to be mediated through the regulation of osteoblast IL-6 release or synthesis, but raloxifene produces a decrease in mRNA IL-6 expression. The actions of estradiol, tamoxifen and raloxifene do not appear to be mediated by tumoral growth factor TGF-beta1. On the other hand, an increase in IGF-I synthesis induced by raloxifene and estradiol could mediate, in part, the effects of these compounds on bone.

A variation in Bone Alkaline Phosphatase levels that correlates positively with bone loss and normal levels of aminoterminal propeptide of collagen I in girls with anorexia nervosa

Anorexia nervosa (AN) is a very extended pathology among adolescent girls nowadays. These patients show a high degree of osteopenia; hence, study of their bone remodelling is of great interest. Serum bone alkaline phosphatase (bAP) and aminoterminal propeptide of procollagen I (PINP) provide good sensitivity in the analysis of bone alterations in postmenopausal osteoporosis. The aim of this study was to compare the usefulness of bAP and PINP in the study of bone remodelling in AN, and their possible correlation with the degree of osteopenia in this pathology. In order to help in the interpretation of the results, levels of the beta-isomer of urinary carboxyterminal propeptide of collagen I (beta-CTX) have also been included. Serum bAP (IRMA) Tandem R-Ostase, Hybritech), PINP (RIA, Orion Diagnostica) and CTX (CrossLaps ELISA, Osteometer) were determined in 41 girls with AN, aged 18.5+/-2.2 years (mean+/-SD) and in 31 healthy control women, aged 19+/-2.3 years. Bone mineral density (BMD) in lumbar spine was measured by DEXA in the AN group. We found that 41 of the 43 patients had BMD z-scores under -2. No significant differences were found in the levels of serum bAP nor in PINP and beta-CTX levels between controls and patients, although values in the AN group were highly variable. All the BMD z-score values were negative, and their absolute value correlates positively with bAP (P = 0.0279) and almost with beta-CTX (P = 0.0921) but not with PINP (P = 0.4627). Bone AP correlates with PINP in control girls (P = 0.017), but not in the AN group (P = 0.3573). Patients with AN were divided into three groups according to their levels of bAP: low (I), normal (II) or high (III). Patients with the highest bAP levels also presented the highest increase in bone resorption, according to their beta-CTX levels, and the highest degree of osteopenia. However, values of PINP were similar in the three groups of patients. The bAP/beta-CTX ratios in subgroups I, II and III of AN patients were 0.035, 0.065 and 0.073, a finding that suggests that bAP is not indicating the real degree of bone mineralization in these patients, because it is a contradiction that the formation/resorption ratio should be higher in the patients who have the highest bone loss. These results could suggest that bone loss in AN is produced by an increase in bone resorption (beta-CTX), without variations in bone matrix formation (PINP); bAP levels are a good marker in the follow-up of osteopenia degree, but not a real indicator of bone mineralization, a similar situation to that of osteomalacia.

Aminoterminal propeptide of type I collagen and bone alkaline phosphatase in the study of bone metastases associated with prostatic carcinoma

The aim of this work was to evaluate the usefulness of serum aminoterminal propeptide of type I collagen (PINP) in the early detection of bone metastases associated with prostatic carcinoma. The results were compared with those of bone isoenzyme of alkaline phosphatase (bAP). Levels of total alkaline phosphatase (TAP) and prostatic specific antigen (PSA), related to the existence of bone metastases, are also evaluated. Fifty-five male patients aged 70-80 years were studied. Nine presented a benign prostatic hyperplasia (BPH) and the rest clinically confirmed prostatic cancer. Cancer patients were classified in accordance with the staging grouping of the International Union Against Cancer/American Joint Committee on Cancer TNM 1992 Revision: stage 0 or BPH (n=9), I (n=6), II (n=12), III (n=18) and IV (n=10). According to this classification, patients of groups BPH, I, II and III have no evidence of metastases. Those of stage IV present any type of metastases. In the case of this work, all patients of group IV presented bone metastases. Some patients of group BPH, I and II were untreated. The rest of the patients were under treatment (radical prostatectomy, telecobaltotherapy or hormonal therapy) for a period of between 6 months and 15 years. Serum PSA (Quimioluminiscence, IMMULITE), PINP (RIA, Orion Diagnostica), bAP (IRMA, Tamdem R-Ostase, Hybritech), and TAP (autoanalyzer) were determined. We found the following sensitivities and specificities (relating the presence of bone metastases to values higher than the upper limit of normality and, in the case of PSA, to values higher than 100 microg/L): (1) PINP: 100% (10/10) and 87% (39/45), (2) bAP: 90% (9/10) and 82% (37/45), (3) TAP: 60% (6/10) and 93% (42/45), (4) PSA: 40% (4/10) and 100% (45/45). These results suggest that PINP and bAP are adequate biochemical markers of bone formation to be used in the detection of bone metastases in prostatic carcinoma, improving the sensitivity and specificity of TAP and PSA. With respect to PINP, bAP presents the disadvantage of its cross-reactivity with liver isoenzyme.