Caffeine has been shown to directly increase fatty acid oxidation, in part, by promoting mitochondrial biogenesis. Mitochondrial biogenesis is often coupled with mitophagy, the autophagy-lysosomal degradation of mitochondria. Increased mitochondrial biogenesis and mitophagy promote mitochondrial turnover, which can enhance aerobic metabolism. In addition, recent studies have revealed that cellular lipid droplets can be directly utilized in an autophagy-dependent manner, a process known as lipophagy. Although caffeine has been shown to promote autophagy and mitochondrial biogenesis in skeletal muscles, it remains unclear whether caffeine can increase lipophagy and mitochondrial turnover in skeletal muscle as well. The purpose of this study was to determine the possible contribution of lipophagy to caffeine-dependent lipid utilization. Furthermore, we sought to determine whether caffeine could increase mitochondrial turnover, which may also contribute to elevated fatty acid oxidation. Treating fully differentiated C2C12 skeletal myotubes with 0.5 mM oleic acid (OA) for 24 hr promoted an approximate 2.5fold increase in cellular lipid storage. Treating skeletal myotubes with 0.5 mM OA plus 0.5 mM caffeine for an additional 24 hr effectively returned cellular lipid stores to control levels, and this was associated with an increase in markers of autophagosomes and autophagic flux, as well as elevated autophagosome density in TEM images. The addition of autophagy inhibitors 3-methyladenine (10 mM) or bafilomycin A1 (10 μM) reduced caffeine-dependent lipid utilization by approximately 30%. However, fluorescence and transmission electron microscopy analysis revealed no direct evidence of lipophagy in skeletal myotubes, and there was also no lipophagy-dependent increase in fatty acid oxidation. Finally, caffeine treatment promoted an 80% increase in mitochondrial turnover, which coincided with a 35% increase in mitochondrial fragmentation. Our results suggest that caffeine administration causes an autophagy-dependent decrease in lipid content by increasing mitochondrial turnover in mammalian skeletal myotubes. K E Y W O R D Scaffeine, lipid utilization, mitochondrial turnover, mitophagy, skeletal muscle

Foodborne illnesses are a significant public health concern as they cause approximately 48 million illnesses per year in the U.S.A. It is important to identify and control potential sources of microbial contamination in restaurants to reduce the number of foodborne illnesses. In this study, we aimed to measure microbial contamination on nonfood‐contact surfaces in restaurants. These surfaces include tables, chairs, highchairs and booster seats. We found the highest levels of total microbial contamination and staphylococci on booth seats and table chairs with total microbial counts of 151 and 184 CFU/100 cm2, respectively. Other surfaces found to have over 100 CFU/100 cm2 were booster seats and cleaning dishcloths. The cleaning dishcloth also contained 59 CFU/100 cm2 of enteric bacteria. These results suggest the need for more studies aimed to determine the levels of microbial contamination on nonfood‐contact surfaces in restaurants with the goal of providing better recommendations for cleaning practices and procedures. Practical Applications The cleaning procedures for restaurant furniture and other nonfood‐contact surfaces in restaurants are not highly regulated. The information from this study suggests the need for improved cleaning practices and procedures of nonfood‐contact surfaces in restaurants. Development and implementation of better guidelines for cleaning has the potential to reduce microbial burden on these surfaces and therefore reduce the risk of foodborne illness.