Carvedilol improves glucose tolerance and insulin sensitivity in treatment of adrenergic overdrive in high fat diet-induced obesity in mice.

Catecholamine excess reflecting an adrenergic overdrive of the sympathetic nervous system (SNS) has been proposed to link to hyperleptinemia in obesity and may contribute to the development of metabolic disorders. However, relationship between the catecholamine level and plasma leptin in obesity has not yet been investigated. Moreover, whether pharmacological blockade of the adrenergic overdrive in obesity by the third-generation beta-blocker agents such as carvedilol could help to prevent metabolic disorders is controversial and remains to be determined. Using the high fat diet (HFD)-induced obese mouse model, we found that basal plasma norepinephrine, the principal catecholamine as an index of SNS activity, was persistently elevated and highly correlated with plasma leptin concentration during obesity development. Targeting the adrenergic overdrive from this chronic norepinephrine excess in HFD-induced obesity with carvedilol, a third-generation beta-blocker with vasodilating action, blunted the HFD-induced hepatic glucose over-production by suppressing the induction of gluconeogenic enzymes, and enhanced the muscular insulin signaling pathway. Furthermore, carvedilol treatment in HFD-induced obese mice decreased the enlargement of white adipose tissue and improved the glucose tolerance and insulin sensitivity without affecting body weight and blood glucose levels. Our results suggested that catecholamine excess in obesity might directly link to the hyperleptinemic condition and the therapeutic targeting of chronic adrenergic overdrive in obesity with carvedilol might be helpful to attenuate obesity-related metabolic disorders.

Rab15 alternative splicing is altered in spheres of neuroblastoma cells.

Neuroblastoma is an aggressive pediatric tumor that accounts for 15% of cancer-related deaths in children. More than half of high-risk neuroblastoma patients develop tumor relapse that is lethal in most cases. A small population of tumor-initiating cells (TICs), recently identified from high-risk neuroblastoma patients as spheres, is believed to be responsible for tumor relapse. Rab family small G proteins are essential in controlling membrane traffic and their misregulation results in several cancers. Rab15 was originally isolated as a brain-specific Rab protein regulating the endocytic recycling pathway and was recently identified as a downstream target of the neural transcription factor Atoh1. Previously, we identified two alternatively spliced Rab15 isoforms in neuroblastoma cells and showed a significant correlation between Rab15 expression and neuronal differentiation. As aberrant alternative splicing is intimately associated with an increasing number of cancers, its use as a new diagnostic and/or prognostic biomarker has attracted considerable attention. In the present study, we explored cancer-associated changes of Rab15 alternative splicing in neuroblastoma TICs. We found that Rab15 alternative splicing generated two novel isoforms designated as Rab15(AN2) and Rab15(AN3) in addition to two known isoforms designated as Rab15(CN) and Rab15(AN1). Although both Rab15(AN2) and Rab15(AN3) contained premature termination codons, they were detected in not only neuroblastoma cells but also in normal human tissues. One isoform was predominantly expressed in the brain and testis, while the other isoform was more specifically expressed in the brain. In neuroblastoma, Rab15 isoform balance measured by the Rab15(CN)/Rab15(AN1+AN2+AN3) ratio was significantly decreased in spheres compared to parental cells. These results suggest that Rab15 alternative splicing may serve as a biomarker to discriminate TICs from non-TICs in neuroblastoma.

Epigallocatechin gallate inhibits sphere formation of neuroblastoma BE(2)-C cells.

OBJECTIVES: A growing number of epidemiological studies have demonstrated that the consumption of green tea inhibits the growth of a variety of cancers. Epigallocatechin gallate (EGCG), the most abundant catechin in green tea, has been shown to have an anti-cancer effect against many cancers. Most cancers are believed to be initiated from and maintained by a small population of tumor-initiating cells (TICs) that are responsible for chemotherapeutic resistance and tumor relapse. In neuroblastoma, an aggressive pediatric tumor that often relapses and has a poor prognosis, TICs were recently identified as spheres grown in a serum-free non-adherent culture used for neural crest stem cell growth. Although EGCG has been reported to induce growth arrest and apoptosis in neuroblastoma cells, its effect on neuroblastoma TICs remains to be defined. METHODS: Gene expression was analyzed by real-time reverse transcription polymerase chain reaction (RT-PCR). The effects of EGCG on cell proliferation, apoptosis, and sphere formation were determined by cell counting, propidium iodide staining, and sphere (>100 µm in diameter) counting, respectively. RESULTS: Neuroblastoma BE(2)-C cells showed increased expression of stem cell markers (nanog homeobox [NANOG] and octamer-binding transcription factor 4 [OCT4]), as well as decreased expression of neuronal differentiation markers (Cu(2+)-transporting ATPase alpha polypeptide [ATP7A] and dickkopf homolog 2 [DKK2]) in spheres grown in serum-free non-adherent culture, compared to parental cells grown in conventional culture. Although EGCG induced growth arrest and apoptosis in the parental cells in a dose-dependent manner, it was not effective against spheres. However, EGCG potently inhibited sphere formation in the BE(2)-C cells. CONCLUSIONS: The present results suggest that EGCG may inhibit the development of TICs in BE(2)-C cells.