Etabolic rate, the function from the trend line was used to extrapolate physical activity to zero, with the point at which the line crosses the X-axis signifying basal metabolic rate. While there was no genotypic difference in basal metabolic rate between males (Fig. 6A), female MIC-12/2 displayed a significantly lower basal metabolic rate compared to wild type controls (p,0.01) (Fig. 6B). These data indicate that there is a fundamental metabolic difference between the male and female MIC-12/2 mice relatively to their matched controls, suggesting MIC-1/GDF15 exerts its effects differentially on male and female mice. The difference in total energy expenditure between the female genotypic groups may have been more affected by changes in basal metabolic rate and less by the physical activity. Both of these are likely to contribute to the body weight difference displayed in female MIC-12/2 versus control mice.MIC-1/GDF15 Reduces Food Intake and Induces Weight Loss in 
MIC-12/2 and MIC-1+/+ MiceTo investigate whether the increased body weight of MIC-12/2 mice was specifically due to germline gene MK 8931 deletion of MIC-1/ GDF15 and not resulting from any unrecognized compensatory or developmental changes in MIC-12/2 mice, we continuously infused male MIC-12/2 and MIC+/+ mice with MIC-1/GDF15 (1? mg/d) via osmotic minipumps. Infusion of MIC-1/GDF15 over 5 days resulted in increased circulating human MIC-1/ GDF15 levels from zero to 643667 pg/ml and 576645 pg/ml in MIC-12/2 and MIC-1+/+ mice, respectively. As discussed below, this would have the effect of increasing total MIC-1/GDF15 levels in MIC-12/2 mice to about the middle of the human normal range and in MIC-1+/+ mice to the top of the human normal range. This infusion of MIC-1/GDF15 resulted in reduced body weight gain relative to LY2409021 web syngeneic vehicle-infused controls (Fig. 7A and 7B, MIC-12/2 p,0.01; MIC-1+/+ p = 0.01), coupled with a significant reduction in food intake (Fig. 7C and 7D, MIC-12/2 p = 0.04; MIC-1+/+ p,0.01).DiscussionIn addition to high circulating levels of MIC-1/GDF15 mediating anorexia/cachexia in disease states [9], this study demonstrates that changes in MIC-1/GDF15 in the physiological range modifies feeding behavior and body weight in mice. The physiological range of MIC-1/GDF15 in mouse blood is currently unknown due to the lack of any 10457188 immunoassay for, or monoclonal antibody to murine MIC-1/GDF15. Taken that the normal range for MIC-1/GDF15 in human serum 
is 150?150 pg/ml [8] and assuming MIC-1/GDF15 serum levels are similar in humans andin mice, this means that the level of human MIC-1/GDF15 introduced in MIC-12/2 and MIC-1+/+ mice was at middle or the upper limit of the normal human physiological range, respectively. Since this resulted in decreased body weight and food intake in both groups relatively to its control, it indicates that receptor upregulation or developmental changes in MIC-12/2 mice are not responsible for human MIC-1/GDF15-induced changes in food intake and body weight, suggesting that there is a specific physiological role of MIC-1/GDF in regulation of energy intake, storage and expenditure. Although there were distinct differences between male and female mice that are discussed below, in general MIC-1/GDF15 deficient mice exhibited increased body weight, adiposity and ?in female mice ?food intake. This phenotype was associated with a decrease in physical activity and basal metabolic energy expenditure in female animals. These changes in food intake and.Etabolic rate, the function from the trend line was used to extrapolate physical activity to zero, with the point at which the line crosses the X-axis signifying basal metabolic rate. While there was no genotypic difference in basal metabolic rate between males (Fig. 6A), female MIC-12/2 displayed a significantly lower basal metabolic rate compared to wild type controls (p,0.01) (Fig. 6B). These data indicate that there is a fundamental metabolic difference between the male and female MIC-12/2 mice relatively to their matched controls, suggesting MIC-1/GDF15 exerts its effects differentially on male and female mice. The difference in total energy expenditure between the female genotypic groups may have been more affected by changes in basal metabolic rate and less by the physical activity. Both of these are likely to contribute to the body weight difference displayed in female MIC-12/2 versus control mice.MIC-1/GDF15 Reduces Food Intake and Induces Weight Loss in MIC-12/2 and MIC-1+/+ MiceTo investigate whether the increased body weight of MIC-12/2 mice was specifically due to germline gene deletion of MIC-1/ GDF15 and not resulting from any unrecognized compensatory or developmental changes in MIC-12/2 mice, we continuously infused male MIC-12/2 and MIC+/+ mice with MIC-1/GDF15 (1? mg/d) via osmotic minipumps. Infusion of MIC-1/GDF15 over 5 days resulted in increased circulating human MIC-1/ GDF15 levels from zero to 643667 pg/ml and 576645 pg/ml in MIC-12/2 and MIC-1+/+ mice, respectively. As discussed below, this would have the effect of increasing total MIC-1/GDF15 levels in MIC-12/2 mice to about the middle of the human normal range and in MIC-1+/+ mice to the top of the human normal range. This infusion of MIC-1/GDF15 resulted in reduced body weight gain relative to syngeneic vehicle-infused controls (Fig. 7A and 7B, MIC-12/2 p,0.01; MIC-1+/+ p = 0.01), coupled with a significant reduction in food intake (Fig. 7C and 7D, MIC-12/2 p = 0.04; MIC-1+/+ p,0.01).DiscussionIn addition to high circulating levels of MIC-1/GDF15 mediating anorexia/cachexia in disease states [9], this study demonstrates that changes in MIC-1/GDF15 in the physiological range modifies feeding behavior and body weight in mice. The physiological range of MIC-1/GDF15 in mouse blood is currently unknown due to the lack of any 10457188 immunoassay for, or monoclonal antibody to murine MIC-1/GDF15. Taken that the normal range for MIC-1/GDF15 in human serum is 150?150 pg/ml [8] and assuming MIC-1/GDF15 serum levels are similar in humans andin mice, this means that the level of human MIC-1/GDF15 introduced in MIC-12/2 and MIC-1+/+ mice was at middle or the upper limit of the normal human physiological range, respectively. Since this resulted in decreased body weight and food intake in both groups relatively to its control, it indicates that receptor upregulation or developmental changes in MIC-12/2 mice are not responsible for human MIC-1/GDF15-induced changes in food intake and body weight, suggesting that there is a specific physiological role of MIC-1/GDF in regulation of energy intake, storage and expenditure. Although there were distinct differences between male and female mice that are discussed below, in general MIC-1/GDF15 deficient mice exhibited increased body weight, adiposity and ?in female mice ?food intake. This phenotype was associated with a decrease in physical activity and basal metabolic energy expenditure in female animals. These changes in food intake and.