Mule Regulates the Intestinal Stem Cell Niche via the Wnt Pathway and Targets EphB3 for Proteasomal and Lysosomal Degradation

The E3 ubiquitin ligase Mule is often overexpressed in human colorectal cancers, but its role in gut tumorigenesis is unknown. Here, we show in vivo that Mule controls murine intestinal stem and progenitor cell proliferation by modulating Wnt signaling via c-Myc. Mule also regulates protein levels of the receptor tyrosine kinase EphB3 by targeting it for proteasomal and lysosomal degradation. In the intestine, EphB/ephrinB interactions position cells along the crypt-villus axis and compartmentalize incipient colorectal tumors. Our study thus unveils an important new avenue by which Mule acts as an intestinal tumor suppressor by regulation of the intestinal stem cell niche

Reduced Exercise Tolerance and Pulmonary Capillary Recruitment with Remote Secondhand Smoke Exposure

RATIONALE: Flight attendants who worked on commercial aircraft before the smoking ban in flights (pre-ban FAs) were exposed to high levels of secondhand smoke (SHS). We previously showed never-smoking pre-ban FAs to have reduced diffusing capacity (Dco) at rest. METHODS: To determine whether pre-ban FAs increase their Dco and pulmonary blood flow (Qc) during exercise, we administered a symptom-limited supine-posture progressively increasing cycle exercise test to determine the maximum work (watts) and oxygen uptake (VO2) achieved by FAs. After 30 min rest, we then measured Dco and Qc at 20, 40, 60, and 80 percent of maximum observed work. RESULTS: The FAs with abnormal resting Dco achieved a lower level of maximum predicted work and VO2 compared to those with normal resting Dco (mean±SEM; 88.7±2.9 vs. 102.5±3.1%predicted VO2; p = 0.001). Exercise limitation was associated with the FAs' FEV(1) (r = 0.33; p = 0.003). The Dco increased less with exercise in those with abnormal resting Dco (mean±SEM: 1.36±0.16 vs. 1.90±0.16 ml/min/mmHg per 20% increase in predicted watts; p = 0.020), and amongst all FAs, the increase with exercise seemed to be incrementally lower in those with lower resting Dco. Exercise-induced increase in Qc was not different in the two groups. However, the FAs with abnormal resting Dco had less augmentation of their Dco with increase in Qc during exercise (mean±SEM: 0.93±0.06 vs. 1.47±0.09 ml/min/mmHg per L/min; p<0.0001). The Dco during exercise was inversely associated with years of exposure to SHS in those FAs with ≥10 years of pre-ban experience (r = -0.32; p = 0.032). CONCLUSIONS: This cohort of never-smoking FAs with SHS exposure showed exercise limitation based on their resting Dco. Those with lower resting Dco had reduced pulmonary capillary recruitment. Exposure to SHS in the aircraft cabin seemed to be a predictor for lower Dco during exercise

Association between the metabolic syndrome and its components and gait speed among U.S. adults aged 50 years and older: a cross-sectional analysis

BACKGROUND: To examine the relationship between the metabolic syndrome and its components and gait speed among older U.S. men and women. Whether these associations are independent of physical activity was also explored. METHODS: Eight hundred and thirty-five men and 850 women aged ≥50 years from the continuous National Health and Nutrition Examination Survey 1999–2002 were examined. We used the definition of the metabolic syndrome developed by the U.S. National Cholesterol Education Program Adult Treatment Panel III. Gait speed was measured with a 6.10-meter timed walk examination. RESULTS: The prevalence of the metabolic syndrome was 40.2% in men and 45.6% in women (P = .127). The prevalence of gait speed impairment was 29.3% in men and 12.5% in women (P < .001). No association was found between the metabolic syndrome and gait speed impairment. After including the individual components of the metabolic syndrome in a logistic model adjusted for age and leisure-time physical activity, abdominal obesity, low HDL cholesterol, and high fasting glucose were significantly associated with gait speed impairment among women (adjusted odds ratio [AOR] = 0.48, 95% confidence interval [CI] = 0.26 to 0.89; AOR = 2.26, 95% CI = 1.08 to 4.75; and AOR = 2.05, 95% CI = 1.12 to 3.74, respectively). Further adjustment for race/ethnicity, education, smoking status, alcohol consumption, arthritis status, and use of an assistive device attenuated these associations; among women, abdominal obesity and low HDL cholesterol remained significantly associated with gait speed impairment (AOR = 0.37, 95% CI = 0.18 to 0.76 and AOR = 2.45, 95% CI = 1.07 to 5.63, respectively) while the association between hyperglycemia and impaired gait speed attenuated to nonsignificance. CONCLUSION: Among women, gait speed impairment is associated with low HDL cholesterol and inversely with abdominal obesity. These associations may be sex-dependent and warrant further research

Mule Regulates the Intestinal Stem Cell Niche via the Wnt Pathway and Targets EphB3 for Proteasomal and Lysosomal Degradation

The E3 ubiquitin ligase Mule is often overexpressed in human colorectal cancers, but its role in gut tumorigenesis is unknown. Here, we show in vivo that Mule controls murine intestinal stem and progenitor cell proliferation by modulating Wnt signaling via c-Myc. Mule also regulates protein levels of the receptor tyrosine kinase EphB3 by targeting it for proteasomal and lysosomal degradation. In the intestine, EphB/ephrinB interactions position cells along the crypt-villus axis and compartmentalize incipient colorectal tumors. Our study thus unveils an important new avenue by which Mule acts as an intestinal tumor suppressor by regulation of the intestinal stem cell niche