Effects and mechanisms of clothing temperature on body fat and muscle distributions

Abstract

Growth in research into fat and muscle metabolisms suggests that the human body is dependent on them for optimal health. Adipose tissue and skeletal muscles play a central role in lipid metabolism, which not only used for energy storage and expenditure, but also be regarded as secretary and endocrine organs. Modulation of fat and muscle in physiological condition closely associates with prevention of overweight and obesity. Temperature plays a crucial role to directly or indirectly affect essentially every aspect of an organism's physiology. As the fat and muscle act as an insulating layer beneath the skin, it more likely has close relationships with changes in environmental temperature near the body, which is directly regulated by clothing as an effective intervention to influence body temperature. However, how the effects and underlying mechanisms of temperature on fat and muscle metabolisms and how the clothing act as an intervention to regulate body surface temperature for the purpose of providing the optimal operating thermal environment for fat and muscle cells is indeed still in its infancy. The ultimate purpose of this research is to investigate the effects of body temperature on fat and muscle by clothing, and establish a multi-disciplinary theoretical understanding to provide guidance for novel interventions and therapies development for fat and muscle health management. This study was divided into three phases to investigate the effects and mechanisms from cell models (phase 1), human model of laboratory wear trials (phase 2) and human model of field wear trials (phase 3). In the phase 1, classical 3T3-L1 adipocytes and C2C12 myotubes were selected as cell models, the underlying mechanisms about effects of temperature on fat and muscle were explored at a cellular level. Palmitate was used as an incentive to provoke differentiated 3T3-L1 adipocytes and C2C12 myotubes in terms of establishing an obese model as references. Biological methods were employed to clarify the interactions between temperature and cell viability, intracellular reactive oxygen species (ROS), lipid peroxidation, lipid droplet size, as well as protein content. Results shown in the 3T3-L1 adiposity model indicated, although the lipid droplet size was declined by hyperthermia, both hypothermia and hyperthermia could regulate physiological ROS and lipid peroxidation to ultimately maintain viability of 3T3-L1 adipocytes; whereas, in palmitate mediated 3T3-L1 adiposity model, excessive ROS and lipid peroxidation has been attenuated by hypothermia, but it still not positively remedies the damage caused by palmitate to cell death. Observations in the C2C12 myotubes revealed that hyperthermia could suppress the intracellular ROS and lipid peroxidation in physiological condition to improve protein synthesis, but not significantly promote cell viability. Moreover, intracellular ROS and lipid peroxidation were significant inhibited through hyperthermia in palmitate treated C2C12 myotubes to prevent palmitate induced proteolysis and final improve the cell proliferation. In the phase 2, influence of clothing on the body temperature distribution by clothing design and the usage of functional fabrics were examined. A parallel, random wear trial was conducted first to investigate the body temperature variation under different activity conditions when wearing designed pants by the usage of functional fabrics with infrared radiation properties. There is no significant difference in core temperature, but the body means skin temperature has drawn a significant higher in pants of functional fabrics with infrared radiation properties. Additionally, functional bra was developed by the usage of fabrics with dynamic moisture transferring properties to further explore its influence on the regional body temperature of the particular adipose tissue model, female breast, which is mostly made up of a collection of fat. Another parallel, random wear trial study revealed that local breast skin temperatures of bra made of fabrics with dynamic moisture transfer properties are significantly lower than bras without these dynamic moisture transfer properties in the running condition, whereas the body mean skin temperature were revealed to undergo greater decreasing effects in bras made of fabrics with dynamic moisture transfer properties than those without the dynamic moisture transfer properties. These findings proved the hypotheses that clothing could be used as an effective means to regulate mean skin temperature and also regional skin surface temperature could be controlled by clothing design and usage of functional fabrics. In the phase 3, the influences of clothing on fat and muscle by clothing design and usage of functional fabrics was examined by conducting field wear trials. Functional pants used in the phase two were optimized to increase the ability for regulating skin surface by designing and welding with heat press sticker. A parallel, randomly crossover designed wear trial study was carried out to explore whether clothing has an influence on body fat, muscle and also lipid profiles under free living conditions. Significant decrease of the body mass index and waist-hip ratio were found when wearing functional clothing to relatively elevate the body surface temperature for four weeks, but indexes, including body fat mass, visceral fat area, truck fat mass, as well as skeletal muscle mass were not being significantly affected. It also found out that there are no significant differences in blood lipid profiles, such as triacylglycerol, total cholesterol, HDL cholesterol, LDL cholesterol and total lipid during the experiment period. In summary, the effects and underlying mechanisms of clothing temperature on fat and muscle have been explored. The results obtained cell model experiments demonstrated that temperature has significant influence on the metabolisms of fat and muscle cells, particularly the size of lipid droplets in fat cells. The results from human model laboratory wear trials demonstrated that clothing with different designs and use of different fabrics can be used as an effective means to regulate local skin surface temperature. The results from human model field wear trial studies showed that clothing could have significant influence on body mass index (BMI) and waist-hip ratio (WHR) on human subjects. These findings suggest that clothing design and using functional fabrics had potential to be utilized as novel interventions for fat and muscle health management.