The impact of standing desks on cardiometabolic and vascular health.

Sedentary behavior is associated with cardiovascular disease (CVD) and mortality, independent of physical activity. The biological mechanisms underlying these associations are largely unknown. We hypothesized that obese subjects with sedentary desk jobs, when assigned a sit-stand desk, will reduce daily sedentary time, and show improvement in arterial flow-mediated dilation (FMD), an early indicator of CVD. Overweight and obese subjects without known CVD were recruited at our institution and given an adjustable sit-stand desk at work. Activities were quantified with an accelerometer for 7 days at baseline and during the intervention. FMD of the brachial and superficial femoral arteries, fasting lipids, insulin and glucose labs, and anthropometrics were measured at baseline, and 12 and 24 weeks. Repeated one-way ANOVA tests were used to compare measurements over time. Fifteen participants were enrolled (93% female, mean age 40 ± 5 years, mean body mass index [BMI] 33 ± 5). Mean daily sedentary time at work decreased by 90 minutes from baseline (385 ± 49 minutes) to 12 weeks (297 ± 80 minutes, p = 0.002) and 24 weeks (295 ± 127 minutes, p = 0.015). Femoral FMD increased from baseline (4.9 ± 1.7%) to 12 weeks (6.4 ± 2.3%, p = 0.043) and further to 24 weeks (8.1 ± 3.2%, p = 0.009). Significant improvement in fasting triglycerides and insulin resistance occurred. There was no change in brachial FMD, exercise activity, step counts, weight, or BMI. A significant reduction in sedentary time during working hours was identified with utilization of a sit-stand desk and sustained over 24 weeks. Improvements in FMD, triglycerides, and insulin resistance provide insight into mechanisms of adverse health risks associated with sedentary behavior.

The Effect of Surgical Insertion and Proinflammatory Cytokines on Osteochondral Allograft Survival and Metabolism.

Objective To investigate the responses of refrigerated osteochondral allograft cartilage (OCA) and fresh cartilage (FC), including cell survival and metabolism, to surgical impaction and proinflammatory cytokines. Design Osteochondral plugs (8 mm diameter) were harvested from prolonged-refrigerated (14-28 days) and fresh (≤24 hours postmortem) human femoral hemicondyles and subjected to a 0.2 N s pneumatic impaction impulse. Cartilage explants were removed from subchondral bone and randomized to 1 of 6 treatment groups: (1) Unimpacted control (UIC), (2) Impacted control (IC), (3) Impacted + interleukin (IL)-1ß (0.1 ng/mL), (4) Impacted + IL-1ß (0.1 ng/mL) + IL-6, (5) Impacted + IL-1ß (10 ng/mL), and (6) Impacted + IL-1ß (10 ng/mL) + IL-6. Samples were measured for cell viability, histology, and proteoglycan (PG) content at days 0, 2, 7, and 14 of culture. Results In UIC, cell viability was indistinguishable between OCA and FC and remained constant. Impaction alone decreased cell viability by 30% ( P < 0.01) in the OCA superficial layer and by 26% ( P < 0.01) in the entire tissue, but did not affect viability in FC. Cytokine addition did not further influence cell viability. Impaction alone did not affect PG synthesis. Addition of cytokines to impacted tissue decreased PG synthesis by ~3-fold in both tissue types in comparison with corresponding impacted controls ( P < 0.01). Throughout 2-week culture, PG release remained stable in all FC groups, but peaked at day 14 in OCA cartilage subjected to cytokines. Conclusions Mechanical impaction, mimicking surgical insertion, has a more profound effect on cell viability in OCA than in FC. Addition of proinflammatory cytokines further decreases OCA tissue metabolism and integrity.

Bone marrow cavity: a supportive environment for islet engraftment.

An important goal in advancing islet transplantation for the treatment for type 1 diabetes, is to discover transplantation sites that promote long-term islet engraftment. Here, we investigate the bone marrow cavity in rats as a potential site for islet transplantation. Dark agouti streptozotocin diabetic recipients received DA islets to one of three sites: to the renal subcapsular, intrahepatic or bone marrow cavity site. Assessment of graft function was made by measuring blood glucose concentrations using a wireless continuous glucose monitoring system (CGM), performing a glucose tolerance test (GTT), and histological analysis. To determine if bone tissue secretes factors supportive to islet function and survival, human islets were cultured in the presence of osteoblast conditioned medium. Gene expression, insulin secretion and content were assessed in islets after culture. All transplant recipients with islets transplanted to the bone marrow cavity site had reversal of hyperglycemia and remained diabetes free until the end of the experiment at four months. Mean blood glucose concentrations, glucose variability and GTT, using CGM in recipients, yielded similar results between all transplantation sites. Histological assessments at four months after transplantation showed viable islets within the bone marrow space. Incubation of human islets in the presence of osteoblast conditioned medium resulted in positive changes in gene expression, insulin secretion and content. These positive changes were mediated by osteocalcin which was present in the conditioned medium. In summary, islets transplanted to the bone marrow cavity in diabetic rats showed good engraftment. In addition, the bone marrow cavity may provide an environment that is protective against post-transplant cellular stress thus increasing the chances of long-term islet function and survival.