Over 40% of adults in the United States are considered obese. Obesity is known to cause abnormal metabolic effects and lead to other negative health consequences. Interestingly, differences in metabolism and contractile performance between obese and healthy weight individuals are associated with differences in skeletal muscle fiber type composition between these groups. Each fiber type is characterized by unique metabolic and contractile properties, which are largely determined by the myosin heavy chain isoform (MHC) or isoform combination that the fiber expresses. In previous studies, SDS-PAGE single fiber analysis has been utilized as a method to determine MHC isoform distribution and single fiber type distribution in skeletal muscle. Herein, a methodological approach to analyze MHC isoform and fiber type distribution in skeletal muscle was fine-tuned for use in human and rodent studies. In the future, this revised methodology will be implemented to evaluate the effects of obesity and exercise on the phenotypic fiber type composition of skeletal muscle.

Seven human subjects with body mass indices (BMIs) ranging from 19.4 kg/ m2 to 26.7 kg/ m2 and six human subjects with BMIs ranging from 32.1 kg/ m2 to 37.6 kg/ m2 were recruited and subjected to 45-minute bouts of acute exercise to look at the changes in the plasma concentration of the dopamine metabolite homovanillic acid (HVA) in response to acute physical activity. Plasma HVA concentration was measured before exercise and during the last 10 minutes of the exercise bout via competitive ELISA. On average the optical density (OD) of the samples taken from lean subjects decreased from 0.203 before exercise to 0.192 during exercise, indicating increased plasma HVA concentration. In subjects with obesity OD increased from 0.210 before exercise to 0.219 during exercise, indicating reduced plasma HVA concentration. These differences in OD were not statistically significant. Between the lean group and the group with obesity no significant difference was observed between the OD of the plasma samples taken before exercise, but a significant difference (p = 0.0209) was observed between the ODs of the samples taken after exercise. This indicated that there was a significant difference between the percent changes in OD between the lean group and the group with obesity, which suggested that there may be a body weight-dependent difference in the amount of dopamine released in response to exercise. Because of the lack of significance in the changes in OD within the lean group and the group with obesity the results of this study were insufficient to conclude that this difference is not due to chance, but further investigation is warranted.

The prevalence of obesity continues to increase in the United States, along with its risk for other associated cardiovascular and metabolic diseases. Several therapeutic methods are aimed at targeting and reducing obesity, now defined as a state of chronic, low-grade inflammation (in addition to BMI > 30 kg/m2). In an attempt to expand on these therapeutic methods, research on the concept of browning in white adipose tissue (WAT) and brown adipose tissue (BAT) is being conducted. Brown adipose tissue (BAT), and a newly discovered type of adipocyte, beige adipocytes, are heavily involved in thermogenesis with the use of uncoupling protein-1 (UCP-1). This paper focuses on the analysis of common browning genes, ATP-related genes, and metabolic genes in varying biological groups in mice (Chow/High-Fat Diet and Inguinal FAT and Perigonadal Fat) and in humans (Lean/Obese and Subcutaneous WAT (SC) and Omental WAT (OM)) using methods such as RT-PCR and immunohistochemistry. The data obtained shows an increase in browning in the leaner group, specifically in the subcutaneous fat. Further, browning is significantly reduced in the obese groups of subjects and mice tested, in addition to omental/perigonadal versus subcutaneous/inguinal fat depots. Interestingly, two key ATP genes, UCP-1 and COX4I1 are vastly elevated in the OM WAT, indicating that browning may not be as important in the OM, but rather may have a potential role in SC. This is contrary to prior research findings that attempt to exclude mice surrogates in future experimentation of the browning phenomenon. Further experimentation is needed to expand on the findings of this paper.