Increased physical activity does not improve obesity-induced decreases in muscle quality in zebrafish (Danio rerio)

Impacts of diethylhexyl phthalate and overfeeding on physical fitness and lipid mobilization in Danio rerio (zebrafish)

As the prevalence of obesity has steadily increased on a global scale, research has shifted to explore potential contributors to this pandemic beyond overeating and lack of exercise. Environmental chemical contaminants, known as obesogens, alter metabolic processes and exacerbate the obese phenotype. Diethylhexyl phthalate (DEHP) is a common chemical plasticizer found in medical supplies, food packaging, and polyvinyl materials, and has been identified as a probable obesogen. This study investigated the hypothesis that co-exposure to DEHP and overfeeding would result in decreased lipid mobilization and physical fitness in Danio rerio (zebrafish). Four treatment groups were randomly assigned: Regular Fed (control, 10 mg/fish/day with 0 mg/kg DEHP), Overfed (20 mg/fish/day with 0 mg/kg DEHP), Regular Fed + DEHP (10 mg/fish/day with 3 mg/kg DEHP), Overfed + DEHP (20 mg/fish/day with 3 mg/kg DEHP). After 24 weeks, swim tunnel assays were conducted on half of the zebrafish from each treatment to measure critical swimming speeds (U_crit); the other fish were euthanized without swimming. Body mass index (BMI) was measured, and tissues were collected for blood lipid characterization and gene expression analyses. Co-exposure to DEHP and overfeeding decreased swim performance as measured by U_crit. While no differences in blood lipids were observed with DEHP exposure, differential expression of genes related to lipid metabolism and utilization in the gastrointestinal and liver tissue suggests alterations in metabolism and lipid packaging, which may impact utilization and ability to mobilize lipid reserves during physical activity following chronic exposures.

Current perspectives on obesity and skeletal muscle contractile function in older adults

Obesity has become one of the most pressing public health issues of the 21st century and currently affects a substantial proportion of the older adult population. Although the cardiometabolic complications are well documented, research from the past 20 years has drawn attention to the detrimental effects of obesity on physical performance in older adults. Obesity-related declines in physical performance are due, in part, to compromised muscle strength and power. Recent evidence suggests there are a number of mechanisms potentially underlying reduced whole muscle function, including alterations in myofilament protein function and cellular contractile properties, and these may be related to morphological adaptations, such as shifts in fiber type composition and increased intramyocellular lipid content within skeletal muscle. To date, even less research has focused on how exercise and weight loss interventions for obese older adults affect these mechanisms. In light of this work, we provide an update on the current knowledge related to obesity and skeletal muscle contractile function and highlight a number of questions to address potential etiologic mechanisms as well as intervention strategies, which may help advance our understanding of how physical performance can be improved among obese older adults.

Is sodium carboxymethyl cellulose (CMC) really completely innocent? It may be triggering obesity

The toxicity of sodium carboxymethyl cellulose (CMC), which has GRAS status and has been determined as "ADI non specified", was re-evaluated with a new modelling and molecular-based data. For this purpose, CMC, a food additive, was injected to the yolk sac (food) of the zebrafish embryo by the microinjection method at the 4th hour of fertilization at different concentrations. As a result, it was found that CMC showed no toxic effects within the framework of the parameters studied. But, we determined increasing lipid accumulation in zebrafish embryos exposed to CMC in a dose-dependent manner. To elucidate the mechanism underlying this lipid accumulation, the expression levels of genes related to obesity-linked lipid metabolism were examined. Our findings show that while CMC does not cause a toxic effect in zebrafish embryos, it can lead important effects on lipid metabolism by causing changes in the expression of some genes associated with obesity.