Conjugated linoleic acid (CLA) has drawn significant attention since the 1980s for its various biological activities. CLA consists mainly of two isomers, cis-9,trans-11 and trans-10,cis-12, and the mixture of these two (CLA mix or 50:50) has been approved for food as GRAS (generally recognized as safe) in the United States since 2008. Along with its original discovery as an anticancer component, CLA has been shown to prevent the development of atherosclerosis, reduce body fat while improving lean body mass, and modulate immune and/or inflammatory responses. This review summarizes the clinical trials involving CLA since 2012; additional uses of CLA for age-associated health issues are discussed; and CLA's potential health concerns, including glucose homeostasis, oxidative stress, hepatic steatosis, and milk-fat depression, are examined. With ongoing applications to food products, CLA consumption is expected to rise and close monitoring of not only its efficacy but also its known and unknown consequences are required to ensure proper applications of CLA.

Caenorhabditis elegans (C. elegans) is a free-living nematode that has been extensively utilized as an animal model for research involving aging and neurodegenerative diseases, like Alzheimer's and Parkinson's, etc. Compared with traditional animal models, this small nematode possesses many benefits, such as small body size, short lifespan, completely sequenced genome, and more than 65% of the genes associated with human disease. All these characteristics make this organism an ideal living system for obesity and aging studies. This review gives a brief introduction of C. elegans as an animal model, highlights some advantages of research using this model and describes methods to evaluate the effect of treatments on obesity and aging of this organism.

Caenorhabditis elegans is a small free-living nematode that lives in temperate soil environments. It has been widely employed as an animal model in research involving obesity, aging, and neurodegenerative diseases, including Alzheimer's disease, because of its various advantages, such as small size, large number of progeny, completely sequenced genome, and short life span, over traditional animal models of vertebrates. These benefits contribute to an ideal research model organism. In this review, we provide an introduction to C. elegans and its applications in obesity, aging, and Alzheimer's disease studies, with the aim of stimulating scientists to use C. elegans as an experimental model in various fields of research.

Imidacloprid, a neonicotinoid insecticide widely used in agriculture worldwide, has been reported to promote adipogenesis and cause insulin resistance in vitro. The purpose of the current study was to determine the effects of imidacloprid and its interaction with dietary fat in the development of adiposity and insulin resistance using male C57BL/6J mice. Imidacloprid (0.06, 0.6, or 6 mg/kg bw/day) was mixed in a low-fat (4% w/w) or high-fat (20% w/w) diet and given to mice ad libitum for 12 weeks. Imidacloprid significantly promoted high fat diet-induced body weight gain and adiposity. In addition, imidacloprid treatment with the high fat diet resulted in impaired glucose metabolism. Consistently, there were significant effects of imidacloprid on genes regulating lipid and glucose metabolisms, including the AMP-activated protein kinase-α (AMPKα) pathway in white adipose tissue and liver. These results suggest that imidacloprid may potentiate high fat diet-induced adiposity and insulin resistance in male C57BL/6J mice.

Per- and polyfluoroalkyl substances, a group of fluoro-surfactants widely detected in the environment, wildlife, and humans, have been linked to adverse health effects. A growing body of literature has addressed their effects on obesity, diabetes and non-alcoholic fatty liver disease/non-alcoholic steatohepatitis. This review summarizes the brief historical use and chemistry of per- and polyfluoroalkyl substances, routes of human exposure, as well as the epidemiologic evidence for associations between exposure to per- and polyfluoroalkyl substances and the development of obesity, diabetes and non-alcoholic fatty liver disease/non-alcoholic steatohepatitis. We identified 22 studies on obesity and 32 studies on diabetes, while only 1 study was found for non-alcoholic fatty liver disease/non-alcoholic steatohepatitis by searching PubMed for human studies. Approximately two-third of studies reported positive associations between per- and polyfluoroalkyl substances exposure and the prevalence of obesity and/or type 2 diabetes. Causal links between per- and polyfluoroalkyl substances and obesity, diabetes and non-alcoholic fatty liver disease/non-alcoholic steatohepatitis, however, require further large-scale prospective cohort studies combined with mechanistic laboratory studies to better assess these associations.