Consequences of Weight Cycling: An Increase in Disease Risk?

Research indicates that weight cycling, or “yo-yo dieting” is a common occurrence in obese populations. The long term negative health consequences of weight cycling are debated and it is unclear whether or not this weight change pattern poses a greater disease risk compared to obesity maintenance. This review discusses the prevalence of weight cycling and physiological alterations occurring during weight loss that promotes weight regain. We also discuss the effect weight regain has upon adipose tissue in terms of rate and type of accumulation. Also within this review are discussions surrounding the previously published literature based upon human and rodent research. We focus on previous limitations and difference in experimental design that have perhaps resulted in mixed findings concerning independent effects of weight cycling on health parameters. The final purpose of this review is to discuss future directions in evaluating the pro-inflammatory response to weight cycling in order to compare the disease risk compared to obesity maintenance

Cell-Surface Receptor Expression on Monocytes of Young and Old Mice

Background. Monocyte assessment is used in aging research. In humans, reduced expression of toll-like receptors, T-lymphocyte priming receptors and increases in intracellular adhesion molecules on monocytes have been associated with functional decrements, resulting in increased disease risk. While use of mouse models is extensive in aging research, mouse monocyte assessment is rare. We aimed to evaluate differences in cell-surface protein expression in classic (CD115+/Gr-1high) and non-classic (CD115+/Gr-1low) monocyte subsets of old and young mice. Methods. Venous blood was drawn from 18 old (80-wks) and 18 young CD-1 mice (15-20-wks). Flow cytometry was used to assess subpopulations of CD115+ monocytes for TLR2, TLR4, CD80, CD86, MHC II, CD54 and CD25. Data were analyzed with 2 (age groups) x 2 (monocyte populations) repeated measures ANOVA; significance was set at P\u3c0.05. Results. Old mice had greater proportions of classic monocytes (P\u3c0.05). TLR4 and CD80 was 27% and 37% lower in classic monocytes of old mice (P\u3c0.05). Body weight was not a significant covariate in the analysis. Conclusions. We found that old mice had elevated classic monocyte proportions and with lower expression of TLR4 and CD80. Because similar findings in older adults have been associated with increased risk of cardiovascular disease and infection, we surmise that old mice were also had increased disease risk compared to young mice. These findings support the use of monocyte subset phenotyping in murine models of aging

Long-term Weight Gain in Response to High-fat Feeding in CD-1 mice

Background. Excessive weight gain is known to cause numerous health related consequences in humans and rodents. Due to ethical issues, it is not appropriate to cause weight gain in humans. From an experimental design prospective, murine models are often used to measure the effect of weight gain. Despite the validity of murine models, there is little published information concerning long-term weight gain when mice consume a high-fat (60% of calories from fat) diet. The purpose of this study was to examine weight gain during high-fat feeding in wild type CD-1 male mice. Methods. This study utilized data collected during the completion of four separate experiments. These experiments were selected so that we could compare: 1) the effects of husbandry type (i.e. individual vs. small groups), 2) weight gain following discontinuation of aerobic exercise training, and 3) the effect of changing to a high-fat diet following long-term acclimation to a stock diet. Two separate data sets were used for experiment 1 (N=120 and N=36). The data set used for experiment 2 demonstrates the long-term effects of the discontinuation of an exercise program (N=24). The data set for experiment 3 allows us to examine the effects of switching diets after an extended period of time (N=36). Change data was analyzed using separate linear mixed models (LMM) for weight gain and food intake. Results. Weight gain was similar over time between mice housed in groups or individually (experiment one). Following discontinuation of an aerobic exercise-training program, mice gained weight similar to that of sedentary controls that did not exercise (experiment two). When mice are switched to a high-fat diet at 25 weeks of age, they gain less weight than when they eat a high-fat diet at 6 weeks of age (experiment three). Conclusions. The results our investigation document long-term changes in mouse weight gain during ad libitum consumption of a high-fat diet. These findings will be useful to future researchers interested in using murine weight gain models

Aerobic Exercise Training May Not Offset the Pro-inflammatory Effects of a High Fat Feeding

Aerobic Exercise Training May Not Offset the Pro-inflammatory Effects of a High Fat Feeding. Katie C. Carpenter, Lisa Esposito, Kelley A. Strohacker, Richard J. Simpson, Brian K. McFarlin. University of Houston, Houston, TX Increased adiposity is associated with an increase in systemic inflammation, which is involved in the pathophysiology of various disease states. A current hypothesis in our laboratory suggests that the toll-like receptor 4 (TLR4) pathway may link physical activity and systemic inflammation. PURPOSE: The primary purpose was to determine if 6-weeks of aerobic exercise training (5 days per week, 1 hour per day. 21-22m/min) would limit the increase in systemic inflammation resulting from high-fat (60% of calories from fat) feeding. A secondary purpose was to determine if changes in cell-surface TLR4 expression would account for observed differences in inflammatory status between mice which exercise and those that remain sedentary. METHODS: 36 CD-1 male mice were randomly assigned to one of three groups (N=12/group): HF (remained sedentary and consumed a high-fat chow (60% fat)), HF-EX (consumed the high-fat chow and underwent an aerobic exercise intervention (running 4.56±0.08 h/week for 6 weeks, or LF (sedentary and consumed a low-fat chow (10% fat)). Key outcome measurements were made on weekly saphenous vein blood samples (~40 uL) using 3-color flow cytometry. Blood glucose and cholesterol concentration were analyzed by an enzymatic assay. RESULTS: Absolute and percent body weight gain over 6-weeks was similar between HF and HF-EX, but significantly greater than LF (P\u3c0.001). HF and HF-EX had 66% more leukocytes than LF at weeks 3-5 (P\u3c0.0001). HF and HF-EX had 145% greater CD11b+/14+/TLR4+ cells than LF (P=0.001). There was no difference in the concentration of CD11b+ cells expressing IL-6 or TNF-alpha following LPS-stimulation between HF and HF-EX. No significant difference was found for blood glucose and cholesterol concentrations between groups. CONCLUSIONS: Exercise training did not prevent weight gain during 6-weeks of high fat feeding. Since HF and HF+EX gained a similar amount of weight, they did not differ with regarding to blood monocytes expressing TLR4. Both HF and HF+EX were elevated above LF. More research is needed to determine how changes in the blood relate to changes in peripheral tissue compartments

Corticosterone Levels in Sedentary, Wheel, and Treadmill Acclimated Mice following a Bout of Forced Treadmill Running

Murine models have been used to study the immune response to exercise under various diet and training interventions .Our laboratory has previously studied the effect of forced exercise versus voluntary exercise on fasting blood glucose measurements. However, forced exercise may result in increased corticosterone levels. This may affect glucose levels and subsequent weight gain. Male, wild-type CD-1 mice were randomly divided into the following groups: forced exercise, wheel running, and sedentary. After a 8- weeks of the intervention, all mice were placed on a treadmill and forced to run for 30 minutes. Blood was collected from the mice prior to exercise, immediately following exercise, and one hour post exercise. Plasma corticosterone levels were assessed using an ELISA. 3-color flow cytometry was used to assess blood leukocytes. We found that despite treadmill acclimation in the forced exercise group, there was no significant difference between groups in corticosterone or leukocyte levels when forced to run on a treadmill. All groups showed a spike in corticosterone levels immediately following exercise which returned to baseline at one-hour post

Longitudinal, Diet-induced Weight Gain is Associated with Increased Blood Monocytes and Reduced TLR4 Expression

Excessive weight gain increases systemic inflammation resulting in increased disease risk. Toll-like receptor 4 (TLR4) reportedly mediates increases in inflammation; however, its role has not been fully evaluated. Objective. The purpose of this study was to determine the longitudinal effect of diet-induced weight gain on blood monocyte concentration and cell-surface TLR4 expression. Research Methods & Procedures. Male CD-1 mice were randomly assigned to high-fat (HF, n = 12) or low-fat (LF, n = 13) groups. Non-lethal, saphenous vein blood samples were collected at 0, 4, 8 and 12 weeks of treatment. Three-color flow cytometry was used to measure monocyte (CD11b+/CD14+) concentration and TLR4 cells-surface expression. Data were analyzed with a repeated measures ANOVA; significance was set at P\u3c0.05. Results. Body weight at week 12 was 21% greater in HF than LF (P\u3c0.05). At week 12 HF had 155% more monocytes (P\u3c0.05) with 24% less TLR4; Monocyte concentration and body weight at week 12 was negatively correlated with TLR4 gMFI (P\u3c0.05). Conclusions. The observed effects of high-fat feeding on blood monocytes are consistent with a phenotype, which may be associated with premature morbidity. The observed monocyte responses may be associated with immune dysfunction and diminished response to infection

Exercise as a Prevention and Countermeasure to Diet-Induced Weight Gain

The purpose of this study was to evaluate the effectiveness of treadmill running at attenuating weight gain and immune dysfunction prior to or during a period of high-fat feeding in outbred CD-1 male mice. Mice were divided into four groups (N=10 mice/group): 4-weeks of treadmill running followed by 4-weeks sedentary (EX-SED), 4-weeks sedentary followed by 4 weeks of treadmill running (SEDEX), 8 weeks of treadmill running (EX), and 8 weeks sedentary (SED). After the first four weeks of the study, all groups began consumption of a high-fat diet to elicit a weight gain response. In order to track immune dysfunction, we measured peripheral blood monocytes and monocyte TLR4 expression at the conclusion of the study. We also completed a detailed analysis of body weight change over time. SED-EX was the only group that did not gain a significant amount of weight during the high-fat feeding. SED-EX had the lowest percentage of monocytes, as well as the highest total monocyte and classic subset cell surface TLR4 expression. EX and SED were not significantly different in any measurement. The present study demonstrates the importance of exercise training in counteracting the pro-inflammatory effects of diet-induced weight gain, as seen in SED-EX. Contrary to our hypothesis, exercise training prior to and throughout high-fat feeding did not prevent weight gain or attenuate the pro-inflammatory effects of weight gain. This could be due to an acclimation to the exercise intervention that blunted the anti-inflammatory effects of the exercise training during the high-fat feeding phase of the study. Similarly, exercise prior to high-fat feeding did not provide a lasting protective effect against the pro-inflammatory effects of diet-induced weight gain. Future research will endeavor to expand the current knowledge about monocyte subpopulations and to further elucidate the relationship between exercise and TLR4

Leveraging Online Learning Resources to Teach Core Research Skills to Undergraduates at a Diverse Research University

Int J Exerc Sci 3(2) : 49-54, 2010. Today’s students have unique learning needs and lack knowledge of core research skills. In this program report, we describe an online approach that we developed to teach core research skills to freshman and sophomore undergraduates. Specifically, we used two undergraduate kinesiology (KIN) courses designed to target students throughout campus (KIN1304: Public Health Issues in Physical Activity and Obesity) and specifically kinesiology majors (KIN1252: Foundations of Kinesiology). Our program was developed and validated at the 2nd largest ethnically diverse research university in the United States, thus we believe that it would be effective in a variety of student populations