RESUMEN
Duchenne muscular dystrophy (DMD) is caused by mutations in the dystrophin gene that result in loss of the dystrophin-glycoprotein complex, a laminin receptor that connects the myofiber to its surrounding extracellular matrix. Utrophin, a dystrophin ortholog that is normally localized to the neuromuscular junction, is naturally upregulated in DMD muscle, which partially compensates for the loss of dystrophin. Transgenic overexpression of utrophin causes broad sarcolemma localization of utrophin, restoration of laminin binding and amelioration of disease in the mdx mouse model of DMD. We previously demonstrated that overexpression of sarcospan, a dystrophin- and utrophin-binding protein, ameliorates mdx muscular dystrophy. Sarcospan boosts levels of utrophin to therapeutic levels at the sarcolemma, where attachment to laminin is restored. However, understanding the compensatory mechanism is complicated by concomitant upregulation of α7ß1 integrin, which also binds laminin. Similar to the effects of utrophin, transgenic overexpression of α7 integrin prevents DMD disease in mice and is accompanied by increased abundance of utrophin around the extra-synaptic sarcolemma. In order to investigate the mechanisms underlying sarcospan 'rescue' of muscular dystrophy, we created double-knockout mice to test the contributions of utrophin or α7 integrin. We show that sarcospan-mediated amelioration of muscular dystrophy in DMD mice is dependent on the presence of both utrophin and α7ß1 integrin, even when they are individually expressed at therapeutic levels. Furthermore, we found that association of sarcospan into laminin-binding complexes is dependent on utrophin and α7ß1 integrin.
Asunto(s)
Antígenos CD/metabolismo , Proteínas Portadoras/metabolismo , Cadenas alfa de Integrinas/metabolismo , Laminina/metabolismo , Proteínas de la Membrana/metabolismo , Distrofia Muscular de Duchenne/metabolismo , Proteínas de Neoplasias/metabolismo , Utrofina/metabolismo , Animales , Antígenos CD/genética , Proteínas Portadoras/genética , Femenino , Humanos , Cadenas alfa de Integrinas/genética , Integrinas/genética , Integrinas/metabolismo , Laminina/genética , Masculino , Proteínas de la Membrana/genética , Ratones , Ratones Endogámicos mdx , Ratones Noqueados , Músculo Esquelético/metabolismo , Distrofia Muscular de Duchenne/genética , Proteínas de Neoplasias/genética , Unión Proteica , Utrofina/genéticaRESUMEN
Abdominal pain with elevated transaminases from inferior vena cava (IVC) obstruction is a relatively common reason for referral and further workup by a hepatologist. The differential for the cause of IVC obstruction is extensive, and the most common etiologies include clotting disorders or recent trauma. In some situations the common etiologies have been ruled out, and the underlying process for the patient's symptoms is still not explained. We present one unique case of abdominal pain and hepatomegaly secondary to IVC constriction from extrinsic compression of the diaphragm. Based on this patient's presentation, we urge that physicians be cognizant of the IVC diameter and consider extrinsic compression as a contributor to the patient's symptoms. If IVC compression from the diaphragm is confirmed, early referral to vascular surgery is strongly advised for further surgical intervention.
RESUMEN
Over the past 40 years, meal skipping and snacking in US adults have increased, and currently most eating occasions occur later in the day than previously. Whether these changes have played a causal role in the obesity epidemic is poorly understood. Observational studies are largely inconclusive due to methodological limitations. Experimental evidence does not support a causal role for eating frequency or breakfast skipping in weight control. Emerging evidence suggests that eating irregularity and eating later in the day may be detrimental for weight control, but more studies are needed. This article summarizes studies and highlights areas needing attention.