The Effect of Diabetes and Prediabetes on Mycobacterium tuberculosis Transmission to Close Contacts

BACKGROUND

It is unknown whether dysglycemia is associated with Mycobacterium tuberculosis transmission.

METHODS

We assessed epidemiological and clinical characteristics of patients with culture-confirmed pulmonary tuberculosis and their close contacts, enrolled in a multicenter prospective cohort in Brazil. Contacts were investigated at baseline and 6 months after enrollment. QuantiFERON positivity at baseline and conversion (from negative to positive at month 6) were compared between subgroups of contacts according to glycemic status of persons with tuberculosis (PWTB) as diabetes mellitus (DM) or prediabetes. Multivariable mixed-effects logistic regression models were performed to test independent associations with baseline QuantiFERON positive and QuantiFERON conversion.

RESULTS

There were 592 PWTB (153 DM, 141 prediabetes, 211 normoglycemic) and 1784 contacts, of whom 658 were QuantiFERON-positive at baseline and 106 converters. Multivariable analyses demonstrated that tuberculosis-prediabetes cases, acid-fast bacilli-positive, pulmonary cavities, and living with someone who smoked were independently associated with QuantiFERON positive in contacts at baseline. DM, persistent cough, acid-fast bacilli-positive, and pulmonary cavities in tuberculosis source cases were associated with QuantiFERON conversion.

CONCLUSIONS

Contacts of persons with pulmonary tuberculosis and dysglycemia were at increased risk of being QuantiFERON positive at baseline or month 6. Increased focus on such close contacts could improve tuberculosis control.

Comparison of two commercially available ELISAs for circulating sclerostin

This study investigates the performance and correlation of sclerostin measurements by two commercially available sclerostin ELISAs from TECOmedical and Biomedica. We found that the correlation between the results of two sclerostin assays is strong.

INTRODUCTION

Circulating sclerostin levels may provide insight into the pathophysiology of metabolic bone diseases such as osteoporosis. However, recent studies suggest that commercially available assays give different results. We compare the analytical performance of the two most used commercially available sclerostin ELISAs from TECOmedical and Biomedica.

METHODS

Sclerostin levels were assessed in 20 paired serum, EDTA, and heparin plasma convenience samples from hospitalized patients. In addition, sclerostin was measured in serum samples from 34 patients with metabolic bone diseases and from 10 patients with chronic kidney disease (CKD). Samples from three healthy donors were used to determine stability and intra- and inter- assay precision.

RESULTS

The average serum sclerostin concentration of all patients (n = 64) was 0.713 ± 0.58 ng/mL with the Biomedica assay and 0.734 ± 0.43 ng/mL with the TECO assay (p < 0.05). The results correlated strongly (r = 0.9; p < 0.0001), with Passing-Bablok regression showing a linear relationship but with a slight systematic and proportional difference between both assays. Sclerostin levels were about 30% higher in plasma than in serum for both assays, while no significant difference was seen between EDTA and heparin plasma. Intra- and inter- precision were <10% for TECO and <20% for Biomedica. Samples were stable for up to three freeze-thaw cycles with both assays.

CONCLUSIONS

The two commercially available ELISAs for measuring circulating levels of sclerostin are comparable. However, given the small but statistically significant systematic and proportional differences between both assays, results and reference ranges will be assay-specific. Results will also be specific to serum or plasma.

Catabolic and anabolic actions of parathyroid hormone on the skeleton

PTH, an 84-amino acid peptide hormone synthesized by the parathyroid glands, is essential for the maintenance of calcium homeostasis.While in its traditional metabolic role, PTH helps to maintain the serum calcium concentration within narrow, normal limits and participates as a determinant of bone remodeling, more specific actions, described as catabolic and anabolic are also well known. Clinically, the catabolic effect of PTH is best represented by primary hyperparathyroidism (PHPT), while the osteoanabolic effect of PTH is best seen when PTH or its biological amino-terminal fragment [PTH(1-34)] is used as a therapy for osteoporosis. These dual functions of PTH are unmasked under very specific pathological (PHPT) or therapeutic conditions. At the cellular level, PTH favors bone resorption, mostly by affecting the receptor activator of nuclear factor κ-B (RANK) ligand (RANKL)-osteoprotegerin- RANK system, leading to an increase in osteoclast formation and activity. Increased bone formation due to PTH therapy is explained best by its ability to enhance osteoblastogenesis and/or osteoblast survival. The PTH-induced bone formation is mediated, in part, by a decrease in SOST/sclerostin expression in osteocytes. This review focuses on the dual anabolic and catabolic actions of PTH on bone, situations where one is enhanced over the other, and the cellular and molecular mechanisms by which these actions are mediated.