Osteocalcin improves glucose tolerance, insulin sensitivity and secretion in older male mice

Osteocalcin deficient mice (OC-/-), on a mixed 129/BL6J background, were reported to show glucose intolerance, insulin insensitivity and reduced insulin secretion at 1-6 mos of age. This is controversial as two studies in OC-/- mice on different backgrounds (C3H/BL6 (5-6 mos.) and C57BL/6N (5 and 9 mos.)) found no effect on glucose metabolism. To determine the role of OC in glucose metabolism we conducted glucose tolerance tests (GTT), insulin tolerances tests (ITT) and glucose stimulated insulin secretion (GSIS) on 6 and 9.5 month-old male OC-/- and OC+/+ mice on a pure C57BL/6J background and fed a normal chow diet. All results were analyzed with a two-way repeated measures ANOVA. The GTT results showed no effect on males at 6 months of age but glucose intolerance was significantly increased (p < 0.05) in male OC-/- mice at 9.5 months of age. The ITT results indicated significantly increased insulin resistance in male OC-/- mice. Glucose stimulated insulin secretion (GSIS) showed insulin significantly (p < 0.05) reduced in OC-/- at several time points. Mouse Osteocalcin injected into OC-/- mice decreased the glucose level. Our results confirm the role of OC in glucose metabolism and insulin sensitivity and demonstrate a role in insulin secretion in older male mice on a C57BL/6J background. Differences in background, age, or experimental procedures could explain controversial results. A delayed onset of the effect of OC on glucose metabolism at 9.5 months in male C57BL/6J mice highlights the importance of background on phenotype. Consideration of genetic background and age may be beneficial for human studies on osteocalcin and glucose homeostasis and may be relevant to the elderly where osteocalcin is reduced.

Shots fired: evaluation of vascular injury, compartment syndrome, and transfusion rates among civilian ballistic orthopaedic fracture patients presenting to two Level I trauma centres

PURPOSE

This study investigates baseline patient demographics and predictors of vascular injury, blood transfusion, and compartment syndrome in patients with orthopaedic fractures secondary to GSWs at two high-volume Level I trauma centres.

METHODS

A retrospective chart review of all GSW-related trauma patients at two Level I trauma centres between July 2019 and September 2021 was conducted. Chi-squared and two-tailed independent t tests were used for data analysis, and logistic regression with odds ratios (OR) determined predictors of primary outcomes.

RESULTS

Among 478 GSW patients, 94 (19.7%) sustained 130 orthopaedic fractures, most commonly at the lower extremity (77.7%). Orthopaedic fracture patients showed significantly higher rates of vascular injury (29.8 vs. 4.7%, p < 0.001), transfusion (27.7 vs. 12.8%, p = 0.006), and compartment syndrome (3.2 vs. 0.3%, p = 0.011) compared to non-orthopaedic injury patients. Univariable analysis identified ankle (OR = 47.50, p < 0.001) and hip/femur fractures (OR = 5.31, p < 0.001) as predictors of vascular injury. Multivariable logistic regression revealed lower extremity vascular injury (OR = 54.69, p = 0.006) and anatomic fracture sites of the humerus (OR = 15.17, p = 0.008), clavicle/scapula (OR = 11.30, p = 0.009), and acetabulum/pelvis (OR = 7.17, p = 0.025) as predictors of blood transfusion. Univariable analysis showed lower extremity vascular injury (OR = 30.14, p = 0.007) as a predictor of compartment syndrome.

CONCLUSION

These findings underscore the importance of diagnosing and managing vascular injuries and compartment syndrome in GSW-related orthopaedic fractures, emphasizing the necessity for targeted transfusion strategies in such cases.

Lead induced differences in bone properties in osteocalcin +/+ and −/− female mice

Lead (Pb) toxicity is a major health problem and bone is the major reservoir. Lead is detrimental to bone, affects bone remodeling and is associated with elderly fractures. Osteocalcin (OC) affects bone remodeling, improves fracture resistance and decreases with age and in some diseases. The effect of lead in osteocalcin depleted bone is unknown and of interest. We compared bone mineral properties of control and Pb exposed (from 2 to 6 months) femora from female adult C57BL6 OC+/+ and OC-/- mice using Fourier Transform Infrared Imaging (FTIRI), Micro-computed tomography (uCT), bone biomechanical measurements and serum turnover markers (P1NP, CTX). Lead significantly increased turnover in OC+/+ and in OC-/- bones producing increased total volume, area and marrow area/total area with decreased BV/TV compared to controls. The increased turnover decreased mineral/matrix vs. Oc+/+ and increased mineral/matrix and crystallinity vs. OC-/-. PbOC-/- had increased bone formation, cross-sectional area (Imin) and decreased collagen maturity compared OC-/- and PbOC+/+. Imbalanced turnover in PbOC-/- confirmed the role of osteocalcin as a coupler of formation and resorption. Bone strength and stiffness were reduced in OC-/- and PbOC-/- due to reduced material properties vs. OC+/+ and PbOC+/+ respectively. The PbOC-/- bones had increased area to compensate for weaker material properties but were not proportionally stronger for increased size. However, at low lead levels osteocalcin plays the major role in bone strength suggesting increased fracture risk in low Pb²⁺ exposed elderly could be due to reduced osteocalcin as well. Years of low lead exposure or higher blood lead levels may have an additional effect on bone strength.