Abnormal bone turnover in monoclonal gammopathy of undetermined significance: analyses of type I collagen telopeptide,osteocalcin, bone-specific alkaline phosphatase and propeptides of type I and type III procollagens

Abstract: The main difference between monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM) is the presence of lytic bone destructions in the latter. About 20% of MGUS patients develop MM, and histomorphometric studies have shown disturbed bone turnover rates in some of these patients. This study was performed in order to evaluate whether serum analyses of the C-terminal telopeptide of type I collagen (ICTP), as a reflector of bone degradation, and of osteocalcin, bone-specific alkaline phosphatase (bAP) and the C-terminal propeptide of type I procollagen (PICP), as markers of bone formation, might give information on disturbancies of bone metabolism in MGUS. Furthermore, serum N-terminal propeptide of procollagen III (PIIINP) might give information on disturbances in collagen III metabolism in the bone marrow. In the 35 patients examined, serum ICTP was elevated in 12 patients (34%), serum PIIINP elevated in 6 patients (17%), serum osteocalcin elevated in 11 patients (31%), serum bAP elevated in 6 patients (17%), and serum PICP elevated in 4 patients (11%). Serum ICTP correlated significantly with PIIINP (r=0.72, p<0.001), and with serum osteocalcin (r=0.57, p<0.001) and serum bAP (r=0.51, p=0.002). These findings indicate disturbancies of bone turnover and affected collagen metabolism in some MGUS patients. Follow-up observation may reveal any prognostic value of these findings.     

GM-CSF RAISES SERUM LEVELS OF β2-MICROGLOBULIN AND THYMIDINE KINASE IN PATIENTS WITH CHRONIC LYMPHOCYTIC LEUKAEMIA

The effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) on biochemical tumour markers β₂-microglobulin (β₂m), thymidine kinase (TK) and lactate dehydrogenase (LDH) were studied in eight patients with chronic lymphocytic leukaemia (CLL). The serum concentration of β₂m rose by a median of 30% (range 8–50%) and serum TK by 101% (range 30–1414%). Serum LDH concentration, on the other hand, significantly decreased in all patients. The significant increases of β₂m and TK could not be explained by progression of the disease or impaired renal function. Treatment with GM-CSF reduces the value of serum β₂m and TK in assessment of tumour mass and disease activity.     

Evaluation of bone disease in multiple myeloma: a comparison between the resorption markers urinary deoxypyridinoline/creatinine (DPD) and serum ICTP, and an evaluation of the DPD/osteocalcin and ICTP/osteocalcin ratios.

Markers of bone metabolism were measured in 73 newly diagnosed myeloma patients and in age-matched controls. Correlations to bone disease on X-rays and survival were performed. In urine deoxypyridinoline/creatinine (DPD) and in serum carboxyterminal pyridinoline cross-linked telopeptide of type I collagen (ICTP), procollagen type I carboxy-terminal extension peptide (PICP) and osteocalcin were analyzed. The ratios DPD/osteocalcin and ICTP/osteocalcin were calculated. Skeletal X-ray findings were divided into no, limited and extensive bone involvement. DPD and ICTP levels were significantly elevated in patients compared to controls. Levels increased with advancing skeletal involvement. Serum osteocalcin was elevated in patients without visible bone disease. The level decreased with more advanced bone involvement. The finding of significantly elevated osteocalcin and ICTP levels in patients without bone involvement on X-rays indicates that bone markers might reflect bone disease better than X-rays in untreated myeloma patients. Ratios between bone resorption and bone formation markers added no further information on bone disease or survival. Only ICTP had prognostic value with an inverse correlation between serum levels and survival.     

Increased degradation of type I collagen in patients with inflammatory bowel disease.

To assess the mechanisms of osteopenia in inflammatory bowel disease (IBD), the serum markers of bone formation (osteocalcin and carboxyterminal propeptide of type I procollagen (PICP)) and bone degradation (carboxyterminal telopeptide of type I collagen (ICTP)), the bone mineral density (BMD) of the lumbar spine and the proximal femur and calcium intake of 150 unselected IBD patients and 73 healthy controls were investigated. The patients had higher ICTP values (3.69 (SD 1.40) microgram/l) than the healthy controls (3.25 (1.00) microgram/l, p = 0.035), but no differences in serum PICP and osteocalcin between these groups were detected. In the patients, the ICTP, PICP, and osteocalcin values did not have any significant correlation with BMD, but the patients with ICTP values above 3.6 microgram/l had significantly lower Z scores than those with lower ICTP. In the controls, however, a positive correlation between serum ICTP and BMD was found. The ulcerative colitis patients with total colitis had higher values of ICTP (3.96 (1.58) microgram/l) than those with a left sided disease (3.04 (0.86) micrograms/l, p = 0.009). The patients with a history of clinically active disease (n = 20) had higher ICTP (4.58 (1.55) microgram/l) and osteocalcin (12.56 (5.64) microgram/l) values than the patients (n = 130) with quiescent disease (ICTP 3.56 (1.33), p = 0.002, and osteocalcin 9.76 (3.62), p = 0.017). Increased serum osteocalcin, PICP, and ICTP concentrations and reduced BMD Z scores were found in a subgroup of Crohn's disease patients with a history of an active disease (n = 11). Raised serum ICTP and normal values of osteocalcin and PICP in IBD patients show increased breakdown of type I collagen without a compensatory increase in its synthesis suggesting an increased rate of bone degradation as a probable mechanism for osteopenia in IBD. Raised ICTP values are related to reduced bone mineral densities.     

Connective tissue components in serum in multiple myeloma: Analyses of propeptides of type I and type III procollagens,type I collagen telopeptide,and hyaluronan

The present study was performed to evaluate whether information concerning synthesis and degradation of type I collagen in multiple myeloma (MM) as obtained by serum analyses of C-terminal propeptide of type I procollagen (PICP) and the C-terminal telopeptide of type I collagen (ICTP) may be useful in evaluating the development of osteolytic bone destruction. Serum N-terminal propeptide of type III procollagen (PIIINP) may give information about marrow fibrosis in MM. No data are available about MM and serum hyaluronan, another important component of bone marrow stroma. We examined 15 consecutive patients before treatment and 15 sex- and age-matched controls. We found highly significant elevations in serum ICTP (median 6.2 vs. 2.4 μg/L; P < 0.01), PIIINP (median 5.2 vs. 2.9 μ/L; P < 0.01) and hyaluronan (median 122 vs. 45 μ/L; P < 0.01). ICTP in serum correlated closely to bone morbidity (r = 0.69; P < 0.01). Furthermore, serum ICTP correlated highly significantly to serum PIIINP (P < 0.01) and serum β₂-microglobulin (P < 0.01), whereas there was no correlation between hyaluronan and any of the collagen-derived peptides or β₂-microglobulin. The MM group was followed for 9–25 months and analysis of survival data suggested that serum ICTP may be of predictive value (P < 0.05). We conclude that important changes in connective tissue metabolism occur in MM. ICTP in serum seems to be a noninvasive marker of bone morbidity and may be of prognostic value. Furthermore, elevation of hyaluronan in serum is common in MM, the significance of which is unknown. © 1994 Wiley-Liss, Inc.     

Insulin-like growth factor-I raises serum procollagen levels in children and adults with Laron syndrome

OBJECTIVE Recombinant IGF-I is now available for the treatment of GH insensitivity (Laron syndrome). We have determined the effects of IGF-I on soft connective tissue and bone metabolism in a group of patients with this disorder. PATIENTS AND DESIGN Thirteen patients with Laron syndrome (LS) (8 children and 5 adults) were included in the study. The children with LS were treated with IGF-I for 3 years with daily doses of 150–200 μg/kg. The adult LS patients were treated for 9 months with daily doses of 50–120 μg/kg. Blood samples for procollagens were collected before, during and at the end of IGF-I treatment. MEASUREMENTS Serum levels of the carboxyterminal propeptide of type I procollagen (PICP), the aminoterminal propeptide of type III procollagen (PIIINP) and of the pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP) were determined before and during IGF-I administration. RESULTS Untreated patients with LS had lower than normal serum levels of PICP and PIIINP for age. IGF-I treatment increased significantly the PIIINP levels in children from 7.2 ± 2.8 (SD) to 12.5 ± 2.2 μg/l (P < 0.001), and in adults from 2.7 ± 1.0 to 8.4 ± 3.6 μg/l (P < 0.001); serum PICP increased from 243 ± 123 to 384 ± 190 μg/l (P < 0.087) in children, and in adults from 43.4 ± 8.1 to 135.8 ± 41.9 μg/l (P < 0.001). ICTP levels in children increased from 9.7 ± 3.7 to 14.3 ± 5.9 μg/l (P < 0.001) and in adult patients levels increased from 3.6 ± 0.9 to 5.5 ± 2.2 μg/l (P < 0.001) during treatment and returned to basal values after stopping IGF-I administration. CONCLUSIONS Low procollagen levels in untreated Laron syndrome patients and their rise during replacement therapy with IGF-I provide evidence that IGF-I plays an important role in bone and soft connective tissue metabolism and that serum procollagen may serve as a marker to reflect some of the biochemical changes induced by IGF-I in connective tissue in the initial periods of treatment.     

Serum neural cell adhesion molecule in multiple myeloma and other plasma cell disorders

Serum embryonic neural cell adhesion molecule (eNCAM) levels were measured at diagnosis in 92 patients with plasma cell disorders. Significantly elevated levels of serum eNCAM were detected in patients with multiple myeloma when compared to both normal controls and patients with monoclonal gammopathy of uncertain significance (MGUS). Very high levels of serum eNCAM were seen in patients with high tumour burdens. There was a significant correlation between serum eNCAM and β2-microglobulin (β2m) ( r  = 0.33; P  = 0.002), but not between serum eNCAM and C-reactive protein or serum albumen. There was a trend towards longer survival for patients with low serum NCAM. The median survival of the low serum eNCAM group (eNCAM < 20 U/ml) was 36 months compared to 16 months for the high serum eNCAM group (log rank test χ² = 2.42, P  = 0.1). Serum eNCAM is a new marker of tumour mass in multiple myeloma and correlates with clinical stage and β2m. Patients with low serum eNCAM levels may have a survival advantage. Serum eNCAM warrants further evaluation as a tumour marker and prognostic factor in multiple myeloma.     

Serum immunoreactive interleukin-6 and C-reactive protein levels in patients with multiple myeloma at diagnosis

Summary Serum bioactive but not immunoreactive interleukin-6 (IL-6), and serum C-reactive protein (CRP), have been reported to be of prognostic significance in multiple myeloma (MM). We measured serum immunoreactive IL-6 by a sensitive enzyme-linked immunosorbent assay in 30 MM patients at diagnosis. In 30% of the patients serum immuno-reactive IL-6 exceeded the upper reference limit. The concentrations of CRP and IL-6 showed a linear association. Logarithmically transformed IL-6, CRP and β₂-microglobulin were significant variables by univariate survival analysis: by multivariate analysis CRP was a slightly stronger prognostic factor than IL-6 and the only one of independent prognostic significance.     

Biochemical markers of bone metabolism reflect osteoclastic and osteoblastic activity in multiple myeloma

In order to evaluate the use of recently developed assays of bone metabolism in multiple myeloma we performed a histomorphometric study of bone biopsies in 16 myeloma patients. Furthermore, we measured the levels of interleukin-6 (IL-6), soluble IL-6 receptor (IL-6sR), IL-1beta, tumour necrosis factor (TNF) alpha, TNFbeta, and transforming growth factor (TGF) beta in marrow plasma aspirated from the biopsy area. MARKERS OF BONE RESORPTION: The N-terminal telopeptide of collagen I (Ntx) in urine showed a strong positive correlation with the dynamic histomorphometric indices of bone resorption (r=0.68-0.72). Slightly weaker correlations were observed between the dynamic indices of bone resorption and the C-terminal telopeptide of collagen I (ICTP) in serum (r= 0.57-0.62) and deoxypyridinoline (Dpyr) in urine (r= 0.54), whereas urinary pyridinoline (Pyr) did not correlate with the histomorphometric findings. MARKERS OF BONE FORMATION: Serum C-terminal propeptide of procollagen I (PICP) and serum bone-specific alkaline phosphatase (bAP) showed significant correlations with the dynamic parameters of bone formation (r=0.57-0.58), whereas serum osteocalcin and serum total AP did not. CYTOKINES: Highly significant correlations were observed between marrow IL-6 and rates of bone resorption and activation frequency (r=0.76-0.82) and with serum ICTP (r=0.63). Minor, but also significant correlations were observed between the resorptive indices and IL-6sR and IL-1beta. The data indicate that measurements of the biochemical markers of bone metabolism may be useful in monitoring myeloma bone disease, and might thus be of use for dose titration of bisphosphonate therapy.     

The use of an anti-β2-glycoprotein-I assay for discrimination between anticardiolipin antibodies associated with infection and increased risk of thrombosis

Summary. Antiphospholipid antibodies (aPAs), occurring in association with infection, are not generally associated with an increased risk of thrombosis. Anticardiolipin antibodies (aCL) from patients with infection, unlike those from patients with SLE, do not have the β₂GPI cofactor requirements. Antibodies to β₂GPI (αβ₂GPI) are more closely associated with a previous history of thrombosis than aCL in patients with SLE. In the present study we have investigated the reactivity of the αβ₂GPI assay for aPAs associated with infection. Serum from 114 patients with infections including syphilis ( n = 11), tuberculosis ( n = 63) and Klebsiella ( n =42) were assayed for αβ₂GPI and aCL antibodies. The incidence of aCL in serum of patients with tuberculosis, Klebsiella infection and syphilis was 6.0%. 5.0% and 64.0%. respectively, but all patients were negative for αβ₂GPI. These results indicate that the αβ₂GPI assay is negative in patients with transiently positive aCL assays associated with infection.     

Prognostic value of serum markers of bone metabolism in untreated multiple myeloma patients

Bone involvement is a central feature of multiple myeloma (MM). We investigated whether serum markers of osteoblastic and osteoclastic activity correlate with the presence of bone disease and survival in 313 MM patients enrolled in a phase III trial (E9486). Five markers were measured, including osteocalcin (OC), carboxy-terminal propeptide of type I collagen (PICP), bone alkaline phosphatase (BAP), carboxy-terminal telopeptide of type I collagen (ICTP) and tartrate-resistant acid phosphatase (TRAP). We analysed the relationship between serum levels of these markers and the presence of bone manifestations, and survival. Serum levels of ICTP and BAP correlated significantly with bone pain, lesions and fractures. Serum level of ICTP was also higher in stage II-III compared with stage I disease. The serum level of ICTP was significantly associated with shortened survival in the univariate analysis. The median survival times were 4.1 and 3.5 years for low and high ICTP respectively (P = 0.02). There was a strong relationship between ICTP and beta-2-micrgolobulin (B2M). ICTP stands out as a significant marker of bone disease. Incorporation of these markers into clinical trials assessing the use of bisphosphonates in MM is needed to determine whether they might serve as indicators of effectiveness of these agents.     

Presenting Features and Prognosis in 72 Patients With Multiple Myeloma Who Were Younger Than 40 Years

The purpose of this study was to analyse the presenting clinical and laboratory features and the outcome of 72 patients with multiple myeloma (MM) who were younger than 40 years. The records of all Mayo Clinic patients with MM younger than 40 years who were seen between 1 January 1956 and 31 December 1992 were reviewed. Survival was measured from the date when treatment was required to the date of last follow-up or death. The frequency of MM in patients younger than 40 and 30 years in 3278 Mayo Clinic patients was 2.2% and 0.3%, respectively. The main presenting clinical features were bone pain (66%), fatigue (26%), extramedullary plasmacytomas (19%) and bacterial infection (11%). Renal function impairment (creatinine level ≥ 177 μmol/l) and hypercalcaemia (serum calcium value ≥2.75 mmol/l) occurred in 29% and 30% of patients, respectively. Among the 57 patients evaluable for response the objective response rate was 54%. 14/35 patients treated with a single alkylating agent achieved an objective response, whereas 17/22 patients given combination chemotherapy had an objective response ( P  = 0.013). However, this higher response rate did not result in a significantly longer survival. The median survival for the 72 patients was 54 months. Patients with good prognostic features (normal renal function or low β₂-microglobulin level) had a median survival of 8 years. The actuarial survival at 5 and 10 years after initiation of therapy was 43% and 13%, respectively. In summary, survival in very young patients with myeloma is longer than that observed in series of patients of all ages, especially in those with good prognostic factors.     

Elevated serum levels of soluble ICAM-1 in non-Hodgkin's lymphomas correlate with tumour burden, disease activity and other prognostic markers

The serum levels of soluble ICAM-1 (CD54) were significantly elevated in patients with non-Hodgkin's lymphomas (NHL, n  = 127) and hairy cell leukaemia (HCL, n  = 15) compared with healthy controls ( n  = 31). In high-grade malignant NHL ( n  = 79) the sICAM-1 levels correlated with the tumour mass as reflected in the Ann Arbor staging system but not with bulky disease. Further, the sICAM-1 levels correlated with disease activity as reflected by the presence of B symptoms and with other known prognostic markers, in particular serum thymidine kinase (sTK). In patients with low-grade malignant NHL ( n  = 48) a trend towards higher serum levels of sICAM-1 was found in patients with advanced stage and B symptoms. In both low- and high-grade malignant NHL, elevated levels of sICAM-1 were associated with poorer overall and disease-free survival. The present results indicate that sICAM-1 levels have a prognostic power equal to that of other serum markers claimed to be of prognostic value in NHL, namely serum lactate dehydrogenase (LDH), erythrocyte sedimentation rate (ESR), beta-2-microglobulin (β₂m), serum thymidine kinase (sTK), albumin and orosomucoid. The cellular origin and the possible interactions between soluble and surface ICAM-1 and its ligands needs further exploration.     

胰岛素、胰岛素原对胰岛素抵抗状态下HepG2细胞PAI-1分泌的影响

目的研究胰岛素、胰岛素原对胰岛素抵抗状态下ＨｅｐＧ２细胞ＰＡＩ１分泌的影响。方法选择在合成ＰＡＩ１方面与肝细胞相似的ＨｅｐＧ２细胞，以高浓度胰岛素诱导胰岛素抵抗后，分别用生理浓度的胰岛素、胰岛素原刺激２４小时，以观察胰岛素抵抗状态下ＰＡＩ１活性的变化。结果基础状态下胰岛素抵抗ＨｅｐＧ２细胞与非胰岛素抵抗ＨｅｐＧ２细胞相比，ＰＡＩ１活性差异不明显；胰岛素、胰岛素原刺激后，胰岛素抵抗ＨｅｐＧ２细胞ＰＡＩ１活性明显高于非胰岛素抵抗ＨｅｐＧ２细胞。当培液中同时加入１０－４Ｍ二甲双胍后，胰岛素、胰岛素原介导的ＰＡＩ１过量分泌得到明显抑制。结论在胰岛素抵抗状态下，胰岛素、胰岛素原刺激后ＨｅｐＧ２细胞ＰＡＩ１活性明显增加，而二甲双胍可明显抑制此现象。     

Biochemical Studies of a New Class of Alcohol Dehydrogenase Inhibitors from Radix puerariae

Two potent, reversible inhibitors of human alcohol dehydrogenase; (ADH) isozymes were isolated from Radix puerariae (RP, commonly, known as kudzu root) and identified as the isoflavones daidzein and genistein. The 4-methoxy derivatives of daidzein (trivial name, for-mononetin) and genistein (biochanin A), minor constituents of RP, were also shown to be ADH inhibitors. All of these isoflavones inhibit 1 the human -γ₁γ₂-ADH isozyme competitively with respect to ethanol] and uncompetitively with respect to NAD⁺. A survey of more than 40 structurally related compounds revealed one more isoflavone (prunetin) and four flavones (7-hydroxyflavone, apigenin, galangin, and kaempferol) that inhibit ADH. The isoflavone inhibitors, however, are far more potent than the flavone inhibitors. Among the isoflavones studied, genistein is the most potent with K_i , = 0.1 μM toward γ₂γ₂- ADH. Human ADH isozymes differ in their sensitivity to these inhibitors in the order γ₂γ₂- , γ₁γ₁ > α₁α₁⁻,>⁻ > xx-ADH. These inhibitors, do not affect the β₁β₁ ,⁻ and β₂β₂ -ADH isozymes at concentrations as high as 20 μM. Rat and rabbit class I ADHs are also inhibited by these. isoflavone inhibitors. The 7-O-glucosyl derivatives of daidzein, genistein, formononetin, and biochanin A do not inhibit ADH, but are potent aldehyde dehydrogenase inhibitors.     

BK channel subunit composition modulates molecular tolerance to ethanol

Background:  The large conductance calcium-activated potassium channel (also called BK channel or Slo channels) is a well-studied target of alcohol action, and plays an important role in behavioral tolerance.
Methods:  Using patch clamp electrophysiology, we examined human BK channels expressed in HEK293 cells to test whether tolerance to ethanol occurs in excised patches and whether it is influenced by subunit composition. Three combinations were examined: hSlo, hSlo + β₁, and hSlo + β₄.
Results:  The 2 components of BK alcohol adaptation (Component 1: rapid tolerance to acute potentiation, and Component 2: a more slowly developing decrease in current density) were observed, and varied according to subunit combination. Using a 2-exposure protocol, Component 1 tolerance was evident in 2 of the 3 combinations, because it was more pronounced for hSlo and hSlo + β₄.
Conclusions:  Thus, rapid tolerance in human BK occurs in cell-free membrane patches, independent of cytosolic second messengers, nucleotides or changes in free calcium. Alcohol pretreatment for 24 hours altered subsequent short-term plasticity of hSlo + β₄ channels, suggesting a relationship between classes of tolerance. Finally, Component 2 reduction in current density showed a striking dependency on channel composition. Twenty-four hour exposure to 25 mM ethanol resulted in a down-regulation of BK current in hSlo and hSlo + β₄ channels, but not in hSlo + β₁ channels. The fact that hSlo + β₁ channels show less sensitivity to acute challenge, in conjunction with less Component 1 and Component 2 tolerance, suggests subunit composition is an important factor for these elements of alcohol response.     

Dynamics of bone turnover in children with GH deficiency treated with GH until final height

OBJECTIVE: To examine the dynamics of bone turnover in children with growth hormone deficiency (GHD) during long-term treatment. DESIGN: We longitudinally measured growth velocity and serum concentrations of osteocalcin (OC), carboxyterminal propeptide of type I procollagen (PICP), and cross-linked carboxyterminal telopeptide of type I collagen (ICTP) in 24 patients with GHD during long-term GH treatment until final height (age: 7.7+/-0.7 and 16.9+/-0.5 years at baseline and at final height respectively). RESULTS: At baseline, OC, PICP, and ICTP levels were significantly (P<0.0001) reduced in comparison with prepubertal bone age-matched controls (10.2+/-2.3 microgram/l and 22.5+/-7.6 microgram/l; 187.8+/-26.2 microgram/l and 328. 4+/-74.3 microgram/l; 7.7+/-2.0 microgram/l and 14.2+/-1.3 microgram/l respectively). During the first year of treatment mean levels of the bone markers increased significantly (P<0.0001) with a peak at 12 months. After the first year of treatment, OC and PICP levels progressively declined, whereas ICTP levels remained stable until the final height; in any case, bone marker levels remained significantly higher (P<0.03-P<0.0001) than baseline. The change in bone marker levels at 6 and 12 months of treatment with respect to the baseline values was not related to growth rate during long-term treatment or final height. CONCLUSIONS: The results show that children with GHD have reduced bone turnover at baseline, and that long-term GH treatment is associated with a stimulation of bone turnover. OC, PICP, and ICTP do not predict growth rate during long-term treatment or final height in children with GHD.     

TRANSIENT DECREASE IN OSTEOCALCIN AND MARKERS OF TYPE 1 COLLAGEN TURNOVER DURING HIGH-DOSE CORTICOSTEROID PULSE THERAPY IN RHEUMATOID ARTHRITIS

The effect of corticosteroid pulse therapy on bone metabolismwas studied in 10 patients with active RA. We measured alkalinephosphatase, osteocalcin and two recently introduced markersof collagen type 1 metabolism, reflecting synthesis (PICP) anddegradation (ICTP). The day after the pulse therapy, there was a statistically significant(P<0.05) decrease in osteocalcin, PICP and ICTP from thevalue at start. Three weeks after pulse therapy, these valueshad returned to baseline. During pulse treatment there is a transient decrease in boneformation, as shown by the changes in osteocalcin and PICP.Because of the changes in ICTP, we conclude that bone resorptionis transiently reduced as well, but whether these changes resultfrom a direct or an indirect effect on bone is not clear. ICTPhas to be investigated further as a (serum) marker of bone resorption. KEY WORDS: Corticosteroids, Bone metabolism, Osteocalcin, Rheumatoid arthritis     

The Binding of Vitamin B12 by Serum Proteins in Normal and B12-Deficient Subjects

Endogenous B₁₂ in normal serum has been shown to be associated with α globulins (Pitney, Beard and Van Loon, 1954; Heinrich and Erdmann-Oehlecker, 1956; Mendelsohn, Watkin, Horbett and Fahey, 1958). When B₁₂ has been added to normal serum, however, most or all of the added B₁₂ has been associated with the β- and α₂-globulins (Miller, 1958). In the present investigation with radioactive ₅₇cobalt cyanocobalamin (B₁₂*) added to serum, it was possible to define at least two B₁₂-binding proteins (BP), a β-globulin, and an α₁ globulin. B₁₂* added to the serum of normal subjects migrated mainly with the β-globulins on electrophoresis, but when added to the serum of B₁₂-deficient subjects, a small fraction of the B₁₂* was also associated with the α₂-globulins.