Abstract Ti/Al/Mg/Al/Ti laminated composites were fabricated via hot-pressing at 350 °C, 400 °C and 450 °C successfully. The influences of interface morphology, diffusion zone, constraint effect on the mechanical properties were investigated. At Ti/Al interface, intermetallic compounds aren’t found. Whereas, they form at Al/Mg interface. With the increasing temperature, the bonding strength of Al/Mg interface doesn’t change linearly, and the maximum strength is obtained at 400 °C because of intermetallic compounds with appropriate thickness. With the increase of temperature, the hardness at both Ti/Al and Al/Mg interfaces increases owing to the solid solution and the intermetallic phases. Also, the ultimate tensile strength of LMCs increases with sacrificing the fracture elongation. The rule of mixture is used to predict the theoretical strength. It is found that the theoretical values are less than the measured, and the reasons may relate to interfaces in Ti/Al/Mg/Al/Ti laminated composites.

Objective: The role of epigenetic modifications on leptin expression during the development of obesity has not been clearly determined. This study aimed to investigate changes in the expression of DNA methyltransferases (DNMTs) at the leptin promoter and their effect on gene transcription during the development of obesity. Methods: Using a high-fat diet (HFD)-induced obese (DIO) mouse model, we examined adipose expression of leptin, its promoter associated DNMTs and the methyl CpG-binding domain protein 2 (MBD2) at different time points after HFD feeding. Results: The leptin expression levels in epididymal fat were significantly increased after feeding the mice a HFD for 4, 8, 12 and 18 weeks (w), as opposed to feeding them a standard diet (SD). However, the CpG promoter methylation fractions were significantly reduced at 8 w with a decreased association of MBD2 and DNMT1, and increased at 12 w and 18 w with an increased association of MBD2, DNMT3A and DNMT3B, after HFD feeding. Additionally, the binding of RNA polymerase II was increased at 8 w and decreased at 18 w after HFD feeding compared with SD feeding. Conclusions: These data indicate that time-specific changes in promoter associated DNMTs may be associated with the regulation of leptin expression, indicating that a complex and dynamic epigenetic mechanism underlies aberrant leptin expression during the development of obesity.

Objetivo: El objetivo de las modificaciones epigenéticas sobre la expresión de la leptina durante el desarrollo de obesidad no ha podido ser claramente establecido. Este estudio tiene por objetivo investigar los cambios en la expresión de ADN-metiltransferasas (ADNMTs) en el promotor de leptina y su efecto sobre la trascripción génica durante el desarrollo de obesidad. Métodos: Empleando un modelo de ratones con obesidad inducida por dieta rica en grasa (DRG), examinamos la expresión adiposa de leptina, su promotor asociado ADNMTs y la proteína 2 con dominio de unión a metil-CpG (MBD2) en diferentes momentos tras la alimentación DRG. Resultados: Los niveles de expresión de leptina en grasa epididimal aumentaron significativamente tras la alimentación de los ratones con una dieta DRG durante 4, 8, 12 y 18 semanas (s), contrariamente a la alimentación con dieta estándar (DE). Sin embargo, las fracciones de metilación del promotor CpG se redujeron significativamente en la s8 con una menor asociación de MBD2 y DNMT1, y aumentaron en la s12 y s18 con una mayor asociación de MBD2, DNMT3A y DNMT3B, tras la DRG. Además, la unión de ARN polimerasa II aumentó en la s8 y disminuyó en la s18 tras la DRG en comparación con la alimentación de DE. Conclusiones: Estos datos indican que los cambios en puntos temporales específicos en ADNMTs en relación con un promotor podrían estar relacionados con la regulación de la expresión de leptina, indicando que existe un mecanismo epigenético dinámico y complejo subyacente en la expresión de leptina aberrante durante el desarrollo de obesidad.