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Background/Objectives: Increased adipose tissue mass closely associates with the development of insulin resistance and type 2 diabetes mellitus. Previously, we reported that CREB3L4 expressed in adipose tissue negatively regulates adipogenesis, and Creb3l4 knockout mice fed a high-fat diet for 16 weeks showed fat cell hyperplasia, with improved glucose tolerance and insulin sensitivity. These mice did not show significant weight gain and fat mass. Because fat diet or aging is known to be associated with the development of obesity, we examined the effects of Creb3l4 gene subjected to low-fat diet (LFD) or aging process on body composition and obesity risk. Subjects/Methods: We fed Creb3l4 knockout mice a low-fat diet for 16 weeks (LFD group) or chow diet for over 1 year (aged group) and observed various metabolic parameters in the LFD-fed and aged Creb3l4 knockout mice. Results: LFD-fed and aged Creb3l4 knockout mice showed significant weight gain and adiposity, impaired glucose tolerance and decreased insulin sensitivity, compared with wild-type mice. Conclusions: Creb3l4 has a critical role in metabolic phenotypes and a better understanding of its function may provide improved insight into the etiology of diabetes and other metabolic disorders.

Upon genotoxic stress, checkpoint machinery in eukaryotic cells induces cell-cycle arrest, thus allowing the cells to repair damaged DNA or stalled replication forks. The checkpoint machinery is mediated by phosphorylation cascades involving protein kinases and their target proteins. Since the genome is under constant threat from DNA damage due to radiation, chemicals and replication errors, checkpoint dysregulation can cause catastrophic DNA damage, resulting in chromosome instability, aneuploidy, and even tumorigenesis. Two parallel pathways that respond to DNA-damage stress have been extensively studied. The first is the ATM pathway, which responds to double-stranded DNA breaks, while the second is the ATR pathway, which primarily responds to agents that interfere with normal DNA replication. The ATM and ATR kinases activate their downstream target proteins by phosphorylating specific serine or threonine residues. Dephosphorylation by protein phosphatase (PP2A) also participates in the regulation of these phosphorylation signals. Of the target proteins, the two effector kinases CHK1 and CHK2 are particularly important because they phosphorylate additional substrates to maintain chromosome stability after various DNA damaging insults. Recent observations indicate that other protein kinases that control centrosome duplication and chromosome segregation during the cell cycle also play essential roles in maintaining genomic stability.

Understanding the molecular networks that regulate adipogenesis is crucial for combating obesity. However, the identity and molecular actions of negative regulators that regulate the early development of adipocytes remain poorly understood. In this study, we investigated the role of CREB3L4, a member of the CREB3-like family, in the regulation of adiposity. Constitutive overexpression of CREB3L4 resulted in the inhibition of adipocyte differentiation, whereas knockdown of Creb3l4 expression caused differentiation of preadipocytes into mature adipocytes, bypassing the mitotic clonal expansion step. In 3T3-L1 preadipocytes, Creb3l4 knockdown resulted in increased expression of peroxisome proliferator-activated receptor γ (PPARγ2) and CCAAT/enhancer binding protein (C/EBPα), either by increasing the protein stability of C/EBPβ or by decreasing the expression of GATA3, a negative regulator of PPARγ2 expression. Consequently, increased PPARγ2 and C/EBPα levels induced adipocyte differentiation, even in the presence of minimal hormonal inducer. Thus, it can be speculated that CREB3L4 has a role as gatekeeper, inhibiting adipogenesis in 3T3-L1 preadipocytes. Moreover, adipocytes of Creb3l4-knockout mice showed hyperplasia caused by increased adipogenesis, and exhibited improved glucose tolerance and insulin sensitivity, as compared with littermate wild-type mice. These results raise the possibility that Creb3l4 could be a useful therapeutic target in the fight against obesity and metabolic syndrome.

Expression of the cdc2 gene is induced steeply at the G1-S-phase boundary. The previous analysis of promoter elements that confer inducibility revealed the enhancer at positions -276 to -265. Enhancer activity is suppressed by the upstream sequence that seems to contain the silencer. The silencer element was analyzed by fusing several oligonucleotides covering the silencer region upstream of the enhancer in the cdc2 promoter-luciferase construct. Oligonucleotide IV, which suppressed enhancer activity, was further dissected by the introduction of base substitutions and by forming the DNA-protein complexes with quiescent rat cell extract. The silencer element, AAGTAGTAAAAATA, was finally identified at positions -374 to -360, which resembles the enhancer sequencer but contains extra internal AG residues. Silencer complexes were formed with the quiescent cell extract, whereas the amounts of the complexes decreased with the progression of the cell cycle, and nearly no complexes were formed with the late G1 cell extracts. Conversely, the enhancer complex begins to be formed after late G1. Among the three silencer complexes, the formation of the slowest-migrating complex (complex III) was inhibited by the enhancer sequence, suggesting that a common factor interacts with both the silencer and enhancer. These results suggest that the conversion of complex formation from the silencer to the enhancer site regulates the induction of cdc2 promoter activity at the G1-S-phase boundary.

We report a case of idiopathic hypertrophic cranial pachymeningitis in which a high accumulation of thallium-201 was observed on an early single-photon emission CT (SPECT) scan. The patient's symptoms initially improved with steroid therapy but recurred repeatedly. MR images failed to show any change with treatment; however, thallium-201 uptake correlated closely with the fluctuation of symptoms. 201Tl-SPECT was therefore useful in identifying inflammatory activity that was not detected by MR imaging.