Combined PCSK9 and APOE Polymorphisms are Genetic Risk Factors Associated with Elevated Plasma Lipid Levels in a Thai Population

Proprotein convertase subtilisin/kexin type 9 (PCSK9) and apolipoprotein E (ApoE) play a key role in the regulation of lipid metabolism. We aimed to investigate the effects of PCSK9 (R46L, I474V, and E670G) and APOE polymorphisms on lipid levels in a Southern Thai population. A total of 495 participants (307 urban, 188 rural) were recruited for the study. Anthropometric and biochemical variables were evaluated. PCSK9 and APOE polymorphisms were analyzed using PCR–RFLP. The 46L urban male carriers had significantly higher diastolic blood pressure (DBP) and fasting blood sugar compared with non‐carriers. In contrast, the 46L urban female carriers had significantly lower total cholesterol (TC) and LDL‐C levels compared with non‐carriers. The 474V rural female carriers had significantly lower HDL‐C levels than non‐carriers. The 670G urban female carriers showed significantly higher TC and LDL‐C levels compared with non‐carriers. APOE4 carriers had increased TC and LDL‐C levels relative to APOE3 carriers in the urban males. APOE2 carriers had decreased TC and/or LDL‐C levels compared with APOE3 carriers in urban males and females. A significant trend of increased TC and LDL‐C levels was observed in non‐APOE4‐PCSK9 670EE carriers to APOE4‐PCSK9 670EG carriers in urban subjects. In summary, R46L, I474V, and E670G may be genetic risk factors for cardiovascular disease (CVD) in urban males, rural females, and urban females, respectively. In contrast, R46L had a favorable lipid profiles that may protect against CVD in urban females. The combination of PCSK9 E670G and APOE polymorphisms may represent an independent factor for the determination of lipid levels.     

Green strength of natural rubber: The origin of the stress–strain behavior of natural rubber

The variation of the green strength of natural rubber (NR) with the preparation method of the film was studied to elucidate the origin of the stress–strain behavior characteristics of NR in connection with the structure of branch points in NR. A rubber film prepared via casting from NR latex showed the highest modulus and green strength in comparison with films prepared via casting from a toluene solution and via the hot pressing of dry rubber. The modulus and green strength of the NR latex‐casting film decreased after the hot‐press treatment of the film. On the other hand, no difference was observed for synthetic cis‐1,4‐polyisoprene rubber with the preparation method of the film or the heat treatment. This stress–strain behavior characteristics of NR can be ascribed to the changes in the branch points of the NR film with the casting method, which may result in differences in entanglement and crystallizability on stretching. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Character of long‐chain branching in highly purified natural rubber

The nature of long‐chain branching in natural rubber (NR) from Hevea brasiliensis was analyzed for NR purified by enzymatic deproteinization in the latex state followed by acetone extraction in the solid state to remove the proteins and neutral lipids, respectively. The treatment of purified NR in a toluene solution with a polar solvent, such as methanol or acetic acid, resulted in a clear decrease in the molecular weight, gel content, and Huggins' constant; this was caused by the decomposition of branch points in the purified rubber. This finding clearly showed that long‐chain branching in the purified NR was mainly derived from the association of phospholipids linked with both terminal groups in the rubber chain via hydrogen bonds. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

New insights into the relationship between network structure and strain-induced crystallization in un-vulcanized and vulcanized natural rubber by synchrotron X-ray diffraction

The relationship between the network structure and strain-induced crystallization in un-vulcanized as well as vulcanized natural rubbers (NR) and synthetic poly-isoprene rubbers (IR) was investigated via synchrotron wide-angle X-ray diffraction (WAXD) technique. It was found that the presence of a naturally occurring network structure formed by natural components in un-vulcanized NR significantly facilitates strain-induced crystallization and enhances modulus and tensile strength. The stress-strain relation in vulcanized NR is due to the combined effect of chemical and naturally occurring networks. The weakness of naturally occurring network against stress and temperature suggests that vulcanized NR has additional relaxation mechanism due to naturally occurring network. The superior mechanical properties in NR compared with IR are mainly due to the existence of naturally occurring network structure.