Arrhythmogenic cardiomyopathy (ACM) is characterized by redistribution of junctional proteins, arrhythmias, and progressive myocardial injury. We previously reported that SB216763 (SB2), annotated as a GSK3β inhibitor, reverses disease phenotypes in a zebrafish model of ACM. Here, we show that SB2 prevents myocyte injury and cardiac dysfunction in vivo in two murine models of ACM at baseline and in response to exercise. SB2-treated mice with desmosome mutations showed improvements in ventricular ectopy and myocardial fibrosis/inflammation as compared with vehicle-treated (Veh-treated) mice. GSK3β inhibition improved left ventricle function and survival in sedentary and exercised Dsg2mut/mut mice compared with Veh-treated Dsg2mut/mut mice and normalized intercalated disc (ID) protein distribution in both mutant mice. GSK3β showed diffuse cytoplasmic localization in control myocytes but ID redistribution in ACM mice. Identical GSK3β redistribution is present in ACM patient myocardium but not in normal hearts or other cardiomyopathies. SB2 reduced total GSK3β protein levels but not phosphorylated Ser 9–GSK3β in ACM mice. Constitutively active GSK3β worsens ACM in mutant mice, while GSK3β shRNA silencing in ACM cardiomyocytes prevents abnormal ID protein distribution. These results highlight a central role for GSKβ in the complex phenotype of ACM and provide further evidence that pharmacologic GSKβ inhibition improves cardiomyopathies due to desmosome mutations.

An activated ras oncogene induces a program of differentiation in the human medullary thyroid cancer cell line TT. This differentiation process is accompanied by a marked increase in the transcription of the human calcitonin (CT) gene. We have localized a unique Ras-responsive transcriptional element (RRE) in the CT gene promoter. DNase I protection indicates two domains of protein-DNA interaction, and each domain separately can confer Ras-mediated transcriptional inducibility. This bipartite RRE was also found to be Raf responsive. By affinity screening, we have cloned a cDNA coding for a zinc finger transcription factor (RREB-1) that binds to the distal RRE. The consensus binding site for this factor is CCCCAAACCACCCC. RREB-1 is expressed ubiquitously in human tissues outside the adult brain. Overexpression of RREB-1 protein in TT cells confers the ability to mediate increased transactivation of the CT gene promoter-reporter construct during Ras-or Raf-induced differentiation. These data suggest that RREB-1 may play a role in Ras and Raf signal transduction in medullary thyroid cancer and other cells.

Among institutions with a tracheostomy team, the practice of tracheostomy with concomitant PEG placement may be considered as feasible as delayed PEG in carefully selected neurocritically ill patients with possible advantages of overall shorter NCCU and hospital LOS, higher predischarge prealbumin, and lower hospital costs. These findings may aid in decisions regarding the timing of PEG placement in the NCCU. Further prospective studies are warranted.

Learning Objectives: Stress hyperglycemia (SH) of critical illness is multifaceted; it involves elevated stress hormones, insulin resistance (IR), and insulin deficiency (ID). The effect of insulin drip adjustments on glucose can be mathematically modeled for various IR and ID combinations, providing insight into the glucoseinsulin dynamics found in SH. Methods: A glucose-insulin model was used to simulate two groups of 20 virtual patients: those receiving, or not receiving, a continuous nutritional source; SH was created by doubling the gluconeogenesis rate, varying IR from borderline to high, and changing insulin secretion from a normal to severely deficient state. This produced pre-insulin glucose oscillations with maximum (Gmax) values between 160-170 mg/dl with minimum (Gmin) values between 80-115 mg/dl. Next, an insulin infusion was titrated to produce two tight glycemic control (TGC) goals with Gmax values of 110 and 125 mg/dl; the insulin was then abruptly stopped. After the glucose oscillations returned to pre-insulin levels, the insulin infusions were restarted at the same TGC rates. The effects on glucose oscillations were studied. Results: Abruptly stopping an insulin infusion caused significant temporary rebound hyperglycemia (RH) when TGC 110 mg/dl infusions were the starting point, provided IR was high (largest increase 20 mg/dl) without dependence on ID. Abruptly restarting an insulin infusion resulted in Gmin values that were temporarily lower than those in the steady state insulin infusions (largest decrease 20 mg/dl); this was most pronounced when the TGC 110 mg/dl rates were used with severe ID. With no nutritional source, RH was not produced; however, mild hypoglycemia occurred when the insulin infusions were restarted when IR was high. Conclusions: Glucose-insulin dynamics are nonlinearly affected by IR, ID, and the nutritional source; each of which may change over time. It is unlikely that a traditional insulin drip protocol, based on a single simple algorithm, could optimally handle such complexity. Mathematical glucose-insulin models may prove the most adaptive in the critical care setting.