Hypoxia-regulated therapeutic gene as a preemptive treatment strategy against ischemia/reperfusion tissue injury

Ischemia and reperfusion represent major mechanisms of tissue injury and organ failure. The timing of administration and the duration of action limit current treatment approaches using pharmacological agents. In this study, we have successfully developed a preemptive strategy for tissue protection using an adenoassociated vector system containing erythropoietin hypoxia response elements for ischemia-regulated expression of the therapeutic gene human heme-oxygenase-1 (hHO-1). We demonstrate that a single administration of this vector several weeks in advance of ischemia/reperfusion injury to multiple tissues such as heart, liver, and skeletal muscle yields rapid and timely induction of hHO-1 during ischemia that resulted in dramatic reduction in tissue damage. In addition, overexpression of therapeutic transgene prevented long-term pathological tissue remodeling and normalized tissue function. Application of this regulatable system using an endogenous physiological stimulus for expression of a therapeutic gene may be a feasible strategy for protecting tissues at risk of ischemia/reperfusion injury.     

Detection of lung perfusion abnormalities using computed tomography in a porcine model of pulmonary embolism

The purpose of this study was to identify perfusion defects of the lung using computed tomography (CT). A balloon catheter was placed in a lobar pulmonary artery of six anesthetized, ventilated, juvenile pigs to simulate occlusive segmental embolus. Contrast medium was injected via a central venous catheter at rates of 1.5, 3, 4.5, and 9 ml/s in each pig. A 40-second single-level cine CT was acquired distal to the inflated balloon during suspended inspiration. Three computer-manipulated images (time to maximal enhancement, change in maximal attenuation, maximal contrast minus precontrast subtraction) were generated using custom software and compared with the unmodified maximal enhancement and precontrast images. Two independent observers identified perfusion defects and scored the level of confidence (5-point scale) on all five images. Regions of interest were drawn in perfused and nonperfused lung and time-attenuation curves were generated. Perfusion defects were accurately (99.8 +/- 0.3%) and confidently (4.5 +/- 0.6) detected and there was excellent interobserver agreement (Kappa 0.99 +/- 0.02) on all computer-manipulated images. There was a significant increase in confidence (p < 0.05) between contrast medium injection rates of 1.5 and 9 ml/s. A linear relationship exists (r = 0.88) between injection rate and change in maximal attenuation. In conclusion, perfusion defects of the lung are seen using computer-manipulated CT images.     

S6K1 controls pancreatic β cell size independently of intrauterine growth restriction

Type 2 diabetes mellitus (T2DM) is a worldwide heath problem that is characterized by insulin resistance and the eventual loss of β cell function. As recent studies have shown that loss of ribosomal protein (RP) S6 kinase 1 (S6K1) increases systemic insulin sensitivity, S6K1 inhibitors are being pursued as potential agents for improving insulin resistance. Here we found that S6K1 deficiency in mice also leads to decreased β cell growth, intrauterine growth restriction (IUGR), and impaired placental development. IUGR is a common complication of human pregnancy that limits the supply of oxygen and nutrients to the developing fetus, leading to diminished embryonic β cell growth and the onset of T2DM later in life. However, restoration of placental development and the rescue of IUGR by tetraploid embryo complementation did not restore β cell size or insulin levels in S6K1^–/– embryos, suggesting that loss of S6K1 leads to an intrinsic β cell lesion. Consistent with this hypothesis, reexpression of S6K1 in β cells of S6K1^–/– mice restored embryonic β cell size, insulin levels, glucose tolerance, and RPS6 phosphorylation, without rescuing IUGR. Together, these data suggest that a nutrient-mediated reduction in intrinsic β cell S6K1 signaling, rather than IUGR, during fetal development may underlie reduced β cell growth and eventual development of T2DM later in life.     

Single-Port Robotic-Assisted Adrenalectomy: Feasibility,Safety, and Cost-Effectiveness

Methods:We performed a matched-cohort study comparing 16 single-port robotic-assisted adrenalectomies with 16 patients from a pool of 148 laparoscopic adrenalectomies, matched for age, gender, operative side, pathology, and body mass index. All were operated on by 1 surgeon.Results:The pathology included aldosteronoma in 44% of patients, adrenocorticotropic hormone–dependent Cushing syndrome (bilateral adrenalectomy) in 19%, pheochromocytoma in 13%, and other pathology in 24%. The operative time was 183 ± 33 minutes for single-port robotic-assisted adrenalectomy and 173 ± 40 minutes for laparoscopic adrenalectomy (P = .58). The total time in the operating room was 246 ± 33 minutes for single-port robotic-assisted adrenalectomy and 240 ± 39 minutes for laparoscopic adrenalectomy (P = .57). There was 1 conversion to open adrenalectomy (6%) in each group, both because of bleeding on the right side during bilateral adrenalectomy. Two right-sided single-port robotic-assisted adrenalectomy patients required conversion to laparoscopic adrenalectomy, one because of poor visualization. There were no deaths. Complications occurred in 2 patients in each group (intensive care unit admission, prolonged ileus). Both groups had similar pain scores (mean of 3.7 on a scale from 1 to 10) on postoperative day 1, and patients in the single-port robotic-assisted adrenalectomy group used less narcotic pain medication in the first 24 hours after surgery (43 mg vs 84 mg in laparoscopic adrenalectomy group, P < .001). The differences between the single-port robotic-assisted adrenalectomy group and laparoscopic adrenalectomy group in length of stay (2.3 ± 0.5 days vs 3.1 ± 0.9 days, P = .23), percentage of patients discharged on postoperative day 1 (56% vs 31%, P = .10), and hospital cost (16% lower in single-port robotic-assisted adrenalectomy group, P = .17) did not reach statistical significance.Conclusion:Single-port robotic adrenalectomy is feasible; patients require less narcotic pain medication whereas costs appear equivalent compared with laparoscopic adrenalectomy.     

Renal Function Is Associated With Peak Exercise Capacity in Adolescents With Type 1 Diabetes

OBJECTIVE

Diabetic nephropathy and cardiovascular disease are strongly related in adults with type 1 diabetes, yet little is known about this relationship in adolescents prior to the onset of detectable clinical disease. We hypothesized that cardiopulmonary fitness would be directly associated with albumin-to-creatinine ratio (ACR) and inversely related to estimated glomerular filtration rate (eGFR) in adolescents with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Sixty-nine adolescents with type 1 diabetes and 13 nondiabetic control subjects of similar pubertal stage and BMI had insulin sensitivity (glucose infusion rate [GIR]), measured by hyperinsulinemic-euglycemic clamp, and lean body mass, measured by DEXA. Cardiopulmonary fitness was measured by cycle ergometry to obtain peak volume of oxygen (VO₂peak), and renal function was measured by eGFR using the Bouvet equation (measuring creatinine and cystatin C levels) and ACR.

RESULTS

Adolescents (15.5 ± 2.2 years of age) with type 1 diabetes (6.3 ± 3.8 years diabetes duration) had reduced VO₂peak (31.5 ± 6.3 vs. 36.2 ± 7.9 mL/kg ⋅ min, P = 0.046) and VO₂peak/lean kg (43.7 ± 7.0 vs. 51.0 ± 8.6 mL/lean kg ⋅ min, P = 0.007) compared with nondiabetic control subjects. eGFR was inversely associated with VO₂peak and VO₂peak/lean kg after adjusting for sex, Tanner stage, GIR, HbA_1c level, systolic blood pressure, and LDL cholesterol level (β ± SE, VO₂peak: −0.19 ± 0.07, P = 0.02; VO₂peak/lean kg: −0.19 ± 0.09, P = 0.048). Moreover, participants in the highest tertile for eGFR had significantly lower sex- and Tanner-adjusted VO₂peak and VO₂peak/lean kg compared with participants in the lowest tertile.

CONCLUSIONS

Adolescents with type 1 diabetes had reduced exercise capacity, which was strongly associated with renal health, independent of insulin sensitivity. Future studies should examine the underlying interrelated pathophysiology in order to identify probable targets for treatment to reduce cardiovascular and renal complications.