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Endocrinology Vol. 144, No. 6 2580-2587
Copyright © 2003 by The Endocrine Society

Corticotropin-Releasing Factor Receptor-2-Deficient Mice Display Abnormal Homeostatic Responses to Challenges of Increased Dietary Fat and Cold

Tracy L. Bale, Keith R. Anderson, Amanda J. Roberts, Kuo-Fen Lee, Tim R. Nagy and Wylie W. Vale

The Clayton Foundation Laboratories for Peptide Biology (T.L.B., K.R.A., K.-F.L., W.W.V.), The Salk Institute, and Department of Neuropharmacology (A.J.R.), Scripps Research Institute, La Jolla, California 92037; Department of Nutrition Sciences (T.R.N.), University of Alabama at Birmingham, Birmingham, Alabama 35294

Address all correspondence and requests for reprints to: Tracy L. Bale, Ph.D., Clayton Foundation for Peptide Biology, The Salk Institute, 10010 North Torrey Pines Road, La Jolla, California 92037. E-mail: bale{at}salk.edu.


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Corticotropin-releasing factor (CRF) and its family of ligands are key regulators of energy balance. These ligands function via activation of their two receptors, CRFR1 and CRFR2. CRFR1 has been shown to be the dominant receptor in activation of the hypothalamic-pituitary-adrenal axis in response to stress as well as a key mediator of anxiety in the limbic system. To specifically examine the role of CRFR2 in energy balance, mice deficient for CRFR2 were exposed to physiological perturbations of homeostasis, including high-fat diet, repeated cold stress, and glucose and insulin challenges, and their responses measured. While on a high-fat diet, CRFR2-mutant mice consumed substantially more food and maintaining the same weight but had significantly lower body fat and lower plasma lipids than their wild-type littermates. These mice were also less inclined to develop diet-induced insulin resistance and more sensitive to changes in plasma glucose, indicating increased insulin sensitivity. Following repeated cold stress, mutant mice had significantly lower body fat and a transient reduction in feed efficiency, despite similar body weights, suggesting a possible preference for fat as an energy substrate. Elevated levels of uncoupling protein-1 in brown adipose tissue as well as smaller white and brown adipocytes from CRFR2-mutant mice were indications of possible increased sympathetic tone. These results demonstrate that CRFR2 plays a critical role in regulation of energy expenditure and is important for responses to homeostatic challenges.


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
CORTICOTROPIN-RELEASING FACTOR (CRF) and its family of ligands including urocortin (Ucn) I, UcnII, and UcnIII are key regulators of energy balance. This family of neuropeptides has been shown to be important in the regulation of food intake (1, 2, 3, 4, 5, 6), anxiety (7, 8, 9, 10), and stress (11, 12, 13, 14, 15, 16). These ligands function via activation of their two receptors (CRFRs), CRFR1 and CRFR2 (17, 18, 19, 20). Although UcnI has a high affinity for both CRFR1 and CRFR2, UcnII and UcnIII are specific for CRFR2. The roles these CRFRs play in central nervous system (CNS) functions have been deciphered through various pharmacological and genetic manipulations. CRFR1 has been shown to be the dominant receptor in activation of the hypothalamic-pituitary-adrenal (HPA) axis in response to stress (21) as well as a key mediator of anxiety in the limbic system (7, 22, 23, 24, 25, 26, 27, 28, 29, 30). Intracerebroventricular (icv) infusions of specific antagonists to CRFR1 diminish anxiety-like behaviors and inhibit the HPA axis response to stress. Similarly, mice deficient for CRFR1 have a decreased stress response and display anxiolytic-like behaviors. Results from icv infusion of agonists, antagonists, or antisense oligonucleotides for CRFR2 have been inconsistent (6, 30, 31, 32, 33). Although several studies have shown an anxiogenic response of antagonists to CRFR2, others have found little effect or even an anxiolytic response. Mice deficient for CRFR2 display a phenotype in opposition to the phenotype of the CRFR1-deficient mice, with the CRFR2-mutant mice being hypersensitive to stress (34, 35) and displaying anxiogenic-like behaviors (34, 36). Despite the opposing phenotypes produced by single CRFR mutations, mice deficient for both CRFRs display an unexpected phenotype. These mice not only have a more exaggerated impairment of their HPA-stress response than the CRFR1-mutant mice, but they also display sexually dichotomous anxiety-like behaviors (37). Although overall data seem to support a modulatory or inhibitory role for CRFR2 on CRFR1 actions, results from examination of these double-mutant mice bring to light possible independent actions of CRFR2.

Regulation of homeostasis is an important function of the CNS that requires adaptive responses to maintain and support life. CRF has been shown to be a key player in this process because it rapidly mobilizes the organism for behavioral responses to stress. The icv infusion of CRF elevates sympathetic outflow as measured by increased glucose (38, 39), increased brown adipose tissue (BAT) thermogenesis (40), increased uncoupling protein (UCP)-1 in BAT (41), elevated sympathetic nervous activity to BAT (42, 43), increased plasma catecholamines (11, 44), and increased plasma corticosterone (11, 45). Because CRF has a 10-fold higher affinity for CRFR1 than for CRFR2, and the CRF fiber distribution in the CNS more closely matches that of CRFR1, it is likely that these actions of CRF are due to activation of CRFR1 (46). The role CRFR2 plays in energy balance has been less well defined. We have previously shown that mice deficient for CRFR2 have an altered response to the stress of food deprivation such that mutant mice consume less food on refeeding (34). Others have reported significant alterations of CRFR2 expression in the hypothalamus by stress, food deprivation, and leptin (47, 48, 49, 50), suggesting a tight regulation and important role of this receptor in homeostasis. Because CRF and UcnI levels are elevated in the CNS of CRFR2-deficient mice (34, 35), increased activity at CRFR1 is possible and may explain the increased anxiety-like behaviors and hypersensitivity to stress in these mice. To examine the role CRFR2 plays in energy balance, we have examined the responses of mice deficient for CRFR2 to perturbations of homeostasis, including repeated cold stress, high-fat diet, and glucose and insulin challenges.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Animals
CRFR2-mutant mice were generated as previously described (34). All animals were housed under a 12-h light, 12-h dark cycle. All studies were done according to experimental protocols approved by The Salk Institute Institutional Animal Care and Use Committee, and all procedures were conducted in accordance with institutional guidelines.

High-fat diet
Individually housed CRFR2-mutant and wild-type male mice were fed a high-fat (58%) or low-fat (11%) diet (Research Diets, Inc., New Brunswick, NJ) ad libitum (n = 7) for 16 wk. By calories, the low-fat diet contained 60% corn starch and 7% hydrogenated coconut oil, whereas the high-fat diet contained 13% corn starch and 54% coconut oil. Both diets contained 12% maltodextrin, 4% soybean oil, 16% casein, and identical vitamins and minerals. Food intake and body weight was measured three times per week during the 16-wk study. Preweighed food pellets were placed in the hopper, and, to allow for accurate food measurements, minimal bedding was used in the cage to allow for retrieval of all food pieces for weighing. Plasma samples were taken at the end of the study for lipid measurement. Carcasses were immediately frozen on dry ice. Carcasses and plasma samples were shipped to the University of Alabama at Birmingham for analysis. Feed efficiency is calculated as: gram weight gained per gram food consumed.

Body composition and plasma lipid analysis
Carcasses were thawed at room temperature and the gastrointestinal tract removed (stomach, small and large intestine, and cecum) leaving the eviscerated carcass. Body water content was determined by drying the eviscerated carcass to a constant weight in a 60 C oven. The dried eviscerated carcass was then cut into small pieces, ground to a homogeneous mixture, and extracted with petroleum ether in a Soxhlet apparatus to determine fat mass and fat-free dry mass. Fat-free dry mass was then combusted overnight at 600 C (8 h minimum) to determine eviscerated carcass ash. Plasma triglycerides and cholesterol were measured with an Ektachem DTII System (Johnson \|[amp ]\| Johnson Clinical Diagnostics, Rochester, NY) in 10 µl plasma. Free fatty acids were assayed with nonesterified fatty acid-C reagents obtained from Wako Diagnostics (Richmond, VA) in which the assay was modified for use with 10 µl plasma.

Repeated cold stress
Wild-type and CRFR2-mutant mice (n = 10) were individually housed for 2 wk before testing. Mice were given a 4-d basal period to adjust to food pellets (standard chow) on cage floor and being handled. The experiment was conducted for a total of 15 d. During both basal and cold stress periods, weight gain and food consumption were measured daily at 1500 h. Mice were exposed to cold (4 C) for 1 h daily at 1545 h. The apparatus used for the cold stress was as follows: Two 50-gallon coolers were modified to each hold a rack of 10 containers. Each container was 13 cm deep with a diameter of 9 cm (each lid had five small air holes). Each container with lid housed one mouse, which was submerged and completely surrounded by an ice-water slurry, 6 cm from the bottom of the chest. The containers were numbered and housed the same mouse each time throughout the duration of the experiment. Extreme care was taken to prevent the mice from getting wet. The temperature per chest was recorded as the temperature of the air inside the container. In each of the two chests, five wild-type and five CRFR2-mutant mice were distributed alternately throughout the 10-container rack within the chest. Immediately following the 1-h cold stress, mice were returned to their respective cages containing preweighed fresh food. The containers and racks were washed and air dried overnight. For measurement of body temperature following cold stress, a rectal probe thermometer was used (n = 6) (Harvard Apparatus, Holliston, MA).

Glucose and insulin challenge tests
Individually housed male CRFR2-mutant and wild-type mice (on standard chow) were fasted overnight (dark cycle) before glucose or insulin challenge. Glucose (2 g/kg in saline) was administered ip and tail blood collected at 0 min (before ip injection), 5, 30, and 60 min after the injection. Glucose was measured immediately using the Lifescan One Touch glucometer, Johnson \|[amp ]\| Johnson, Milpitas, CA. For insulin tolerance, mice were ip injected with insulin (0.75 U/kg, Sigma, St. Louis, MO) and blood glucose measured at 0 min (before ip injection) and 5 and 60 min following the injection. For the high-fat diet, mouse basal glucose and insulin levels were measured before the start of the diet and following 4 wk on the high-fat diet (as described above), following an overnight fast.

Data analysis and statistics
All data are presented as means ± SEM and were evaluated by two-way ANOVA for repeated measures, followed by Fisher’s protected least significant difference post hoc test, using StatView SE+ (Abacus Concepts, Berkeley, CA). P < 0.05 was defined as statistically significant.

Tissue histology
White adipose tissue (WAT) and BAT from male mice 16–20 wk of age (on standard chow) were fixed in neutral-buffered formalin (Sigma) for 48 h, dehydrated in 70% ethanol, and paraffin embedded. Tissues were sectioned at 8-µm thickness, deparaffinized, and stained with hematoxylin and eosin.

Western blot analysis
For comparison of UCP1 levels, BAT tissues were taken from control and CRFR2-mutant male mice under basal conditions during the morning hours. Tissues were homogenized in buffer (50 mM Tris, pH 7.4; 1 mM dithiothreitol; 2 mM MgCl2; 1 mM EDTA; 0.5 mM phenylmethylsulfonyl fluoride; 5 µg/ml leupeptin; 2 µg/ml aprotinin). Protein extracts (40 µg/lane as determined by Bradford assay for protein content) were separated by 10% SDS-PAGE (Novex, San Diego, CA) and transferred to a nitrocellulose membrane. Blots were blocked in 5% nonfat dry milk for 1 h, washed in 1x Tris-buffered saline (TBS) plus 0.2% Tween 20 (TBST), incubated with anti-UCP1 antibody (1:1000) (Calbiochem, La Jolla, CA) 1 h, washed in TBST twice for 20 min each, incubated with antirabbit horseradish peroxidase (1:10,000) 1 h, and washed in TBST twice for 20 min each Blots were visualized with enhanced chemiluminescence reagent (Amersham, Piscataway, NJ).

Locomotor activity
Locomotor activity of male wild-type and CRFR2-mutant mice 6 months of age was examined across 24 h (n = 4). Testing took place in Plexiglas cages (42 x 22 x 20 cm) placed into frames (25.5 x 47 cm) mounted with two levels of photocell beams at 2 and 7 cm above the bottom of the cage (San Diego Instruments, San Diego, CA). These two sets of beams allowed for the recording of both horizontal (locomotion) and vertical (rearing) behavior. A thin layer of bedding material was applied to the bottom of the cage. Food pellets were scattered evenly across the bottom of the cage, and a waterspout was extended down into the cage just above the level of the vertical beams. Mice were placed in the activity boxes for the final 3 h of their light (inactive) cycle to habituate them to the testing environment. Immediately following this habituation test, mice were tested for 24 h, including a standard 12-h dark and a 12-h light phase.


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Lower body fat but higher food intake on high-fat diet
To determine the homeostatic responses of a high-fat challenge, mice on either high-fat or low-fat diet were monitored for food intake, weight gain, and body composition. Although both genotypes gained similar weight on the high-fat diet, the mutant mice consumed significantly more food than did the wild-type mice (Fig. 1Go, A and B). No difference was found between genotypes for food consumption while on the low-fat diet (wt = 257.2 ± 27, mut = 287.0 ± 2). Body composition analysis indicates that the mutant mice, despite consuming significantly more high-fat food during the study, had significantly less body fat than wild-type mice (Fig. 1CGo). Because the overall end body weight following the high-fat diet study was similar for mutant and wild-type mice, the difference in composition for the mutant mice was compensated by slightly more water, bone (ash), and muscle [fat-free dry mass (FFDM)-ash] than wild-type mice (Fig. 1DGo). The same differences in terms of absolute values were found for mice on the high-fat diet (fat: wt = 19.03 g, mut = 15.38 g; FFDM: wt = 7.0 g, mut = 8.76 g). Percentage of body fat was not different between genotypes while on the low-fat diet (Fig. 1CGo). Serum triglyceride, cholesterol, and free fatty acid levels were also significantly lower in the mutant mice despite the increased high-fat food intake (Fig. 1Go, E and F). No significant differences were detected for plasma lipids between genotypes while on the low-fat diet (triglycerides: wt = 111.2 ± 22, mut = 101.8 ± 10; cholesterol: wt = 105.3 ± 10, mut = 76.4 ± 9; free fatty acids: wt = 0.63 ± 0.08, mut = 0.57 ± 0.07). CRFR2-mutant mice had a lower feed efficiency, compared with wild-type mice following 16 wk of high-fat diet (Fig. 1GGo). No differences in feed efficiency were found between genotypes on the low-fat diet.



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  		Figure 1. Metabolic effects of high-fat diet. A, Start and end weights for CRFR2-mutant (mut) and wild-type (wt) male mice on low- (LF) and high-fat (HF) diets. Mice show similar body weights before and after low- and high-fat diet for 16 wk (n = 7). B, Total food intake for CRFR2-mutant and wild-type mice during 16 wk on high-fat diet. Mutant mice consumed significantly more high-fat food than wild-type mice did, despite similar body weights (**, P < 0.01). C, Percentage body fat for mutant and wild-type mice on low- and high-fat diets. CRFR2-mutant mice have significantly lower body fat than wild-type mice on high-fat diet (**, P < 0.01). No differences were detected for mice on low-fat diet. D, Body composition of mutant and wild-type mice was analyzed following 16 wk on high- or low-fat diet. Percentage body water (H2O), ash, and FFDM for mutant and wild-type mice on high-fat diet showing increased components for mutant mice, compared with littermates (**, P < 0.01). Plasma lipid levels for CRFR2-mutant and wild-type mice on high-fat diet were also determined at the end of the 16-wk study. E, Plasma triglyceride (trigly) and cholesterol (chol) levels showing decreased levels for mutant mice (***, P < 0.001). F, Decreased free fatty acid levels for mutant mice (***, P < 0.001). G, Feed efficiency for mutant and wild-type mice on low- or high-fat diet. Feed efficiency is calculated as gram weight gained per gram food consumed. CRFR2-mutant mice have a lower feed efficiency than wild-type mice following 16 wk on the high-fat diet (*, P < 0.05). All data are displayed as the mean ± SEM.

 
Increased sensitivity to repeated cold stress
Mutant mice exposed to repeated cold stress lost significantly more weight during the 15-d study and consumed significantly less food during the first half of the study than wild-type mice did (Fig. 2Go, A and B). Feed efficiency was calculated on a daily food consumption basis and found to be lower for the mutant mice during the first portion of the study (Fig. 2CGo). Body composition analysis, similar to the high-fat diet study, showed that the mutant mice had significantly lower body fat than wild-type mice following the cold stress despite overall body weights being similar at the end of the study (Fig. 2DGo). As before, the difference in body composition for the mutant mice was compensated by slightly more water, bone, and muscle than wild-type mice (Fig. 2DGo). No significant differences were detected for cholesterol, triglycerides, or free fatty acid levels (Fig. 2Go, E and F).



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  		Figure 2. Metabolic effects of cold stress. A, Body weight of CRFR2-mutant (mut) and wild-type (wt) mice during the daily cold stress (*, P < 0.05, n = 10). Mutant mice lose weight during the cold stress, whereas wild-type mice maintain their body weight. B, Food intake for mutant and wild-type mice during the cold stress (*, P < 0.05). Initially, mutant mice eat less than wild-type mice. However, although their food intake is similar after the first week, the mutant mice still weigh less. C, Feed efficiency for CRFR2-mutant and wild-type mice during the cold stress (**, P < 0.01). Feed efficiency is measured as the gram of weight gained per gram of food consumed. Body composition of mice following repeated acute cold stress. D, Percentage body fat of mutant and wild-type mice showing decreased body fat of mutant mice despite similar body weights (***, P < 0.001). Mutant mice have slightly increased water, ash, and FFDM, compared with wild-type mice (***, P < 0.001; **, P < 0.005). Plasma lipids following the cold stress show no significant differences between genotypes for cholesterol or triglycerides (E) or free fatty acids (F). All data are displayed as the mean ± SEM.

 
No difference between genotypes was detected for body temperatures before or after cold stress (wild-type basal 36.3 ± 0.38 C, CRFR2-mutant basal 36.0 ± 0.21 C; wild-type following 1 h cold = 37.8 ± 0.18 C, CRFR2-mutant following 1 h cold = 37.6 ± 0.07 C).

Glucose and insulin responses
Plasma glucose levels in response to glucose and insulin challenges were compared in mutant and wild-type mice. CRFR2-mutant mice demonstrated lower peak plasma glucose levels following a glucose challenge (Fig. 3AGo). Glucose levels in mutant mice declined more rapidly following an insulin challenge (Fig. 3BGo). Following 4 wk on a high-fat diet, mutant mice showed no elevation in their plasma glucose levels, compared with their baseline and only a slight rise in their plasma insulin levels, compared with wild-type animals (Fig. 3Go, C and D).



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  		Figure 3. Glucose and insulin responses. Glucose challenge glucose levels for male (A) (n = 10) CRFR2-mutant (mut) and wild-type (wt) mice. Mutant mouse glucose levels do not rise as high as wild-type levels following glucose challenge and decline at a faster rate (*, P < 0.05; **, P < 0.01). B, Insulin tolerance test in male (n = 20) CRFR2-mutant and wild-type mice. Mutant mouse glucose levels decrease faster than wild-type levels following insulin administration (*, P < 0.05). Glucose (C) and insulin (D) levels of male CRFR2-mutant and wild-type mice before and following 4 wk of high-fat diet (n = 12). Wild-type glucose levels significantly rise during the 4 wk of high-fat diet, whereas mutant levels remain unchanged (high-fat baseline significantly different between wild-type and mutant (*, P < 0.05). Insulin levels also rise to a greater extent in the wild-type mice (high-fat baseline significantly different from regular diet baseline (**, P < 0.01). All data are displayed as the mean ± SEM.

 
Abnormal adipose cell size and elevated UCP1
To examine indices of sympathetic tone, we analyzed BAT and WAT from CRFR2-mutant and wild-type littermate male mice. Additionally, protein levels of BAT UCP1 were compared in these mice. CRFR2-mutant mice have smaller WAT (Fig. 4AGo) and BAT cell size (Fig. 4BGo). The WAT from the wild-type mice is composed of large, polygonal cells with prominent triglyceride depots, whereas adipocytes from mutant mice appear smaller and more rounded with diminished triglyceride stores. Western blot analysis showed that basal BAT UCP1 levels were substantially elevated in the CRFR2-deficient mice, compared with wild-type mice levels (Fig. 4CGo).



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  		Figure 4. Adipose cell size and UCP1 expression. Representative histology of WAT (A) and BAT (B), showing that mutant mice have smaller adipocytes, compared with wild-type mice. Cell counts using number of nuclei per area indicates more cells in BAT from mutant mice (175 ± 14) than wild-type mice (105 ± 9), suggesting a smaller cell size. C, Changes in protein levels for UCP1 in CRFR2-mutant and wild-type BAT (40 µg protein per lane).

 
No significant differences in 24-h basal locomotor activity
To determine whether the metabolic differences detected in the CRFR2-mutant mice were due to possible differences in basal activity levels, mice were examined for 24-h locomotor activity. No differences were detected between genotypes for activity levels during either the light or dark cycles as measured by horizontal activity counts in a computerized activity chamber following a 3-h habituation period (Fig. 5AGo). Although it did not reach significance, we noted a possible trend in decreased rearing counts in the mutant mice (Fig. 5BGo). Because decreased rearing behavior is associated with increased anxiety-like behaviors, these results are supportive of the previously reported anxiety-like phenotype of these mice.



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  		Figure 5. Locomotor activity for CRFR2-mutant and wild-type mice. A, 24-h horizontal activity counts for CRFR2-mutant and wild-type male mice (n = 4). B, Twenty-four-hour rearing behavior for CRFR2-mutant and wild-type male mice. Data are displayed as the mean ± SEM. The black bar represents the dark cycle.

 

   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
The present results demonstrate that CRFR2 is an important component of energy balance regulation. Following homeostatic stressors, such as high-fat diet (51) or repeated cold exposure, CRFR2-mutant mice respond by preferentially depleting their fat stores. Their decreased feed efficiency, compared with wild-type littermates during these challenges, also illustrates the involvement this receptor has in preserving physiological balance. On a high-fat diet, the mutant mice consumed substantially more food while maintaining the same body weight as their wild-type littermates but had lower cholesterol and remained leaner. The percentage of body fat was lower in mutant mice than wild-type mice following the high-fat diet and cold stress, suggesting a possible increase in sensitivity of the sympathetic nervous system in the mutant mice. The increased UCP1 detected in BAT from mutant mice supports a possible increase in sympathetic tone in these mice. Furthermore, increased BAT activity may then compete for serum triglycerides, depleting WAT and BAT stores and decreasing adipose cell size (52). Although it is possible that BAT thermogenesis may be affected in the mutant mice, no differences between genotypes were detected for basal or cold-stressed rectal body temperatures. Our previous report shows that CRFR2-mutant mice have elevated CRF levels in the central nucleus of the amygdala and UcnI levels in the edinger westphal nucleus (34). CRF neurons in the central nucleus of the amygdala project to and increase the firing rate of neurons in the locus coeruleus (53) and dorsal raphe (54, 55). Additionally, icv infusion of UcnI or CRF increases whole-body oxygen consumption and colonic temperature (56, 57) and direct infusion of UcnI into the paraventricular nucleus of the hypothalamus decreases the respiratory quotient (58) and increases BAT UCP1 levels (41). These data support the hypothesis that in the absence of CRFR2, unimpeded CRFR1 activity in the mice could be causing increased sympathetic stimulation. Further studies examining the metabolic rate and catecholamine levels in these mice under a variety of conditions will provide insight into the specific mechanisms involved.

Along with maintenance of body composition, homeostasis also involves a tight regulation of circulating and stored glucose. Under basal conditions, CRFR2-mutant and wild-type mice have similar glucose and insulin levels. However, following a glucose or insulin challenge, the mutant mice showed a lower maximal rise in glucose levels than the wild-type mice, suggesting that the mutant mice may be more sensitive to changes in plasma glucose and more insulin sensitive. While on a high-fat diet, glucose levels in the mutant mice were unaltered, whereas wild-type mice showed a rise in plasma glucose and insulin, indicative of rising insulin resistance that may correspond to increasing body fat in the control mice. Although insulin levels do rise in the mutant mice on the high-fat diet, this increase is significantly lower than that seen in the wild-type mice. Type 2 diabetes and insulin resistance are highly associated with obesity. Although the mechanism for this association is unclear, increasing evidence suggests that increased fat accumulation in the muscle may play a role. These results illustrate a possible role for CRFR2 in insulin sensitivity.

To compare basal activity levels, CRFR2-mutant and wild-type mice were monitored over 24 h for horizontal and vertical locomotor activity. Results revealed no significant differences between CRFR2-mutant and wild-type mice activity during either the light or dark cycle. The effect of genotype on rearing behavior neared significance because of slightly lower rearing counts in CRFR2-mutant mice relative to controls. This is consistent with greater anxiety-like behavior characteristic and previously reported of these mutant mice (34). These results support the hypothesis that the differences in body composition, food intake, and plasma lipids detected in the CRFR2-mutant mice likely are not due to differences in basal activity levels.

Our results support a hypothetical model in which CRFR1 and CRFR2 play important roles in regulation of organismal responses to stress and perturbations of homeostasis. This model suggests that following such a challenge, CRFR1 stimulates the sympathetic nervous system thereby increasing sympathetic outflow to maintain physiologic equilibrium in the organism under acute perturbations for energy mobilization and redistribution and may also function in allostasis under more chronic insults. CRFR2, however, appears to function as an inhibitory or modulatory receptor to dampen these actions of CRFR1. In the absence of CRFR2, CRFR1-mediated activity goes unimpeded, as seen in the CRFR2-mutant mice. CRFR2-deficient mice under basal conditions do not display significant differences in food intake or body composition from wild-type littermates, but rather these changes are seen following an insult to their homeostasis, thus supporting the hypothesis that CRFR2 normally functions in such a way as to harness the stimulatory actions of CRFR1. This hypothesis is further supported by the feed efficiency data presented here. While on a normal diet, the CRFR2-mutant and wild-type mice have a similar feed efficiency, but following exposure to stressors such as a high-fat diet or cold, the mutant mice become metabolically inefficient, causing calories to be wasted as heat and a depletion of fat stores. These results support a role for CRFR2 in the preservation of homeostasis.


   Acknowledgments
 
The authors would like to thank K. Creehan for animal assistance, G. Cano for editorial comments, and S. Guerra for help with the manuscript.


   Footnotes
 
This work was supported by NIH Grants DK-26741 (to W.W.V.), DK-54918 (to T.R.N.), DK-56336 (to T.R.N.), and grants from the Adler Foundation, Robert J. and Helen C. Kleberg Foundation, Ludwick Family Foundation, and Foundation for Research. W.W.V. is a senior FFR investigator.

Abbreviations: BAT, Brown adipose tissue; CNS, central nervous system; CRF, corticotropin-releasing factor; CRFR, CRF receptor; FFDM, fat-free dry mass; HPA, hypothalamic-pituitary-adrenal; icv, intracerebroventricular; TBS, Tris-buffered saline; TBST, TBS plus 0.2% Tween 20; UCP, uncoupling protein; Ucn, urocortin; WAT, white adipose tissue.

Received December 2, 2002.

Accepted for publication March 3, 2003.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Negri L, Noviello L, Noviello V 1985 Effects of sauvagine, urotensin I and CRF on food intake in rats. Peptides 6:53–57
  2. Heinrichs SC, Cole BJ, Pich EM, Menzaghi F, Koob GF, Hauger RL 1992 Endogenous corticotropin-releasing factor modulates feeding induced by neuropeptide Y or a tail-pinch stressor. Peptides 13:879–884[CrossRef][Medline]
  3. Spina M, Merlo-Pich E, Chan RK, Basso AM, Rivier J, Vale W, Koob GF 1996 Appetite-suppressing effects of urocortin, a CRF-related neuropeptide. Science 273:1561–1564[Abstract]
  4. Contarino A, Dellu F, Koob GF, Smith GW, Lee KF, Vale WW, Gold LH 2000 Dissociation of locomotor activation and suppression of food intake induced by CRF in CRFR1-deficient mice. Endocrinology 141:2698–2702[Abstract/Free Full Text]
  5. Bradbury MJ, McBurnie MI, Denton DA, Lee KF, Vale WW 2000 Modulation of urocortin-induced hypophagia and weight loss by corticotropin-releasing factor receptor 1 deficiency in mice. Endocrinology 141:2715–2724[Abstract/Free Full Text]
  6. Cullen MJ, Ling N, Foster AC, Pelleymounter MA 2001 Urocortin, corticotropin releasing factor-2 receptors and energy balance. Endocrinology 142:992–999[Abstract/Free Full Text]
  7. Britton KT, Lee G, Vale W, Rivier J, Koob GF 1986 Corticotropin releasing factor (CRF) receptor antagonist blocks activating and ‘anxiogenic’ actions of CRF in the rat. Brain Res 369:303–306[CrossRef][Medline]
  8. Liang KC, Melia KR, Miserendino MJ, Falls WA, Campeau S, Davis M 1992 Corticotropin-releasing factor: long-lasting facilitation of the acoustic startle reflex. J Neurosci 12:2303–2312[Abstract]
  9. Stenzel-Poore MP, Heinrichs SC, Rivest S, Koob GF, Vale WW 1994 Overproduction of corticotropin-releasing factor in transgenic mice: a genetic model of anxiogenic behavior. J Neurosci 14:2579–2584[Abstract]
  10. Buwalda B, de Boer SF, Van Kalkeren AA, Koolhaas JM 1997 Physiological and behavioral effects of chronic intracerebroventricular infusion of corticotropin-releasing factor in the rat. Psychoneuroendocrinology 22:297–309[CrossRef][Medline]
  11. Brown MR, Fisher LA, Spiess J, Rivier J, Rivier C, Vale W 1982 Comparison of the biologic actions of corticotropin-releasing factor and sauvagine. Regul Pept 4:107–114[CrossRef][Medline]
  12. Aguilera G, Harwood JP, Wilson JX, Morell J, Brown JH, Catt KJ 1983 Mechanisms of action of corticotropin-releasing factor and other regulators of corticotropin release in rat pituitary cells. J Biol Chem 258:8039–8045[Abstract/Free Full Text]
  13. Rivier C, Rivier J, Mormede P, Vale W 1984 Studies of the nature of the interaction between vasopressin and corticotropin-releasing factor on adrenocorticotropin release in the rat. Endocrinology 115:882–886[Abstract/Free Full Text]
  14. Pich EM, Heinrichs SC, Rivier C, Miczek KA, Fisher DA, Koob GF 1993 Blockade of pituitary-adrenal axis activation induced by peripheral immunoneutralization of corticotropin-releasing factor does not affect the behavioral response to social defeat stress in rats. Psychoneuroendocrinology 18:495–507[CrossRef][Medline]
  15. Menzaghi F, Howard RL, Heinrichs SC, Vale W, Rivier J, Koob GF 1994 Characterization of a novel and potent corticotropin-releasing factor antagonist in rats. J Pharmacol Exp Ther 269:564–572[Abstract/Free Full Text]
  16. Vaughan J, Donaldson C, Bittencourt J, Perrin MH, Lewis K, Sutton S, Chan R, Turnbull AV, Lovejoy D, Rivier C, Rivier J, Sawchenko PE, Vale W 1995 Urocortin, a mammalian neuropeptide related to fish urotensin I and to corticotropin-releasing factor. Nature 378:287–292[CrossRef][Medline]
  17. Chen R, Lewis KA, Perrin MH, Vale WW 1993 Expression cloning of a human corticotropin-releasing-factor receptor. Proc Natl Acad Sci USA 90:8967–8971[Abstract/Free Full Text]
  18. Perrin M, Donaldson C, Chen R, Blount A, Berggren T, Bilezikjian L, Sawchenko P, Vale W1995 Identification of a second corticotropin-releasing factor receptor gene and characterization of a cDNA expressed in heart. Proc Natl Acad Sci USA 92:2969–2973
  19. Lovenberg TW, Liaw CW, Grigoriadis DE, Clevenger W, Chalmers DT, De Souza EB, Oltersdorf T 1995 Cloning and characterization of a functionally distinct corticotropin-releasing factor receptor subtype from rat brain. Proc Natl Acad Sci USA 92:836–840[Abstract/Free Full Text]
  20. Kishimoto T, Pearse 2nd RV, Lin CR, Rosenfeld MG 1995 A sauvagine/corticotropin-releasing factor receptor expressed in heart and skeletal muscle. Proc Natl Acad Sci USA 92:1108–1112[Abstract/Free Full Text]
  21. Preil J, Muller MB, Gesing A, Reul JM, Sillaber I, van Gaalen MM, Landgrebe J, Holsboer F, Stenzel-Poore M, Wurst W 2001 Regulation of the hypothalamic-pituitary-adrenocortical system in mice deficient for CRH receptors 1 and 2. Endocrinology 142:4946–4955[Abstract/Free Full Text]
  22. Smagin GN, Harris RB, Ryan DH 1996 Corticotropin-releasing factor receptor antagonist infused into the locus coeruleus attenuates immobilization stress-induced defensive withdrawal in rats. Neurosci Lett 220:167–170[CrossRef][Medline]
  23. Rodriguez de Fonseca F, Rubio P, Menzaghi F, Merlo-Pich E, Rivier J, Koob GF, Navarro M 1996 Corticotropin-releasing factor (CRF) antagonist [D-Phe12, Nle21, 38, C {alpha} MeLeu37]CRF attenuates the acute actions of the highly potent cannabinoid receptor agonist HU-210 on defensive-withdrawal behavior in rats. J Pharmacol Exp Ther 276:56–64[Abstract/Free Full Text]
  24. Lundkvist J, Chai Z, Teheranian R, Hasanvan H, Bartfai T, Jenck F, Widmer U, Moreau JL 1996 A nonpeptidic corticotropin releasing factor receptor antagonist attenuates fever and exhibits anxiolytic-like activity. Eur J Pharmacol 309:195–200[CrossRef][Medline]
  25. Baram TZ, Chalmers DT, Chen C, Koutsoukos Y, De Souza EB 1997 The CRF1 receptor mediates the excitatory actions of corticotropin releasing factor (CRF) in the developing rat brain: in vivo evidence using a novel, selective, non-peptide CRF receptor antagonist. Brain Res 770:89–95[CrossRef][Medline]
  26. Griebel G, Perrault G, Sanger DJ 1998 Characterization of the behavioral profile of the non-peptide CRF receptor antagonist CP-154, 526 in anxiety models in rodents. Comparison with diazepam and buspirone. Psychopharmacology (Berl) 138:55–66[CrossRef][Medline]
  27. Timpl P, Spanagel R, Sillaber I, Kresse A, Reul JM, Stalla GK, Blanquet V, Steckler T, Holsboer F, Wurst W 1998 Impaired stress response and reduced anxiety in mice lacking a functional corticotropin-releasing hormone receptor. Nat Genet 19:162–166[CrossRef][Medline]
  28. Smith GW, Aubry JM, Dellu F, Kresse A, Reul JM, Stalla GK, Blanquet V, Steckler T, Holsboer F, Wurst W 1998 Corticotropin releasing factor receptor 1-deficient mice display decreased anxiety, impaired stress response, and aberrant neuroendocrine development. Neuron 20:1093–1102[CrossRef][Medline]
  29. Contarino A, Dellu F, Koob GF, Smith GW, Lee KF, Vale W, Gold LH 1999 Reduced anxiety-like and cognitive performance in mice lacking the corticotropin-releasing factor receptor 1. Brain Res 835:1–9[CrossRef][Medline]
  30. Liebsch G, Landgraf R, Engelmann M, Lorscher P, Holsboer F 1999 Differential behavioural effects of chronic infusion of CRH 1 and CRH 2 receptor antisense oligonucleotides into the rat brain. J Psychiatr Res 33:153–163[CrossRef][Medline]
  31. Heinrichs SC, Lapsansky J, Lovenberg TW, De Souza EB, Chalmers DT 1997 Corticotropin-releasing factor CRF1, but not CRF2, receptors mediate anxiogenic-like behavior. Regul Pept 71:15–21[CrossRef][Medline]
  32. Martinez V, Barquist E, Rivier J, Tache Y 1998 Central CRF inhibits gastric emptying of a nutrient solid meal in rats: the role of CRF2 receptors. Am J Physiol 274:G965–G970
  33. Smagin GN, Howell LA, Ryan DH, De Souza EB, Harris RB 1998 The role of CRF2 receptors in corticotropin-releasing factor- and urocortin-induced anorexia. Neuroreport 9:1601–1606[Medline]
  34. Bale TL, Contarino A, Smith GW, Chan R, Gold LH, Sawchenko PE, Koob GF, Vale WW, Lee KF 2000 Mice deficient for corticotropin-releasing hormone receptor-2 display anxiety-like behaviour and are hypersensitive to stress. Nat Genet 24:410–414[CrossRef][Medline]
  35. Coste SC, Kesterson RA, Heldwein KA, Stevens SL, Heard AD, Hollis JH, Murray SE, Hill JK, Pantely GA, Hohimer AR, Hatton DC, Phillips TJ, Finn DA, Low MJ, Rittenberg MB, Stenzel P, Stenzel-Poore MP 2000 Abnormal adaptations to stress and impaired cardiovascular function in mice lacking corticotropin-releasing hormone receptor-2. Nat Genet 24:403–409[CrossRef][Medline]
  36. Kishimoto T, Radulovic J, Radulovic M, Lin CR, Schrick C, Hooshmand F, Hermanson O, Rosenfeld MG, Spiess J 2000 Deletion of crhr2 reveals an anxiolytic role for corticotropin-releasing hormone receptor-2. Nat Genet 24:415–419[CrossRef][Medline]
  37. Bale TL, Picetti R, Contarino A, Koob GF, Vale WW, Lee KF 2002 Mice deficient for both corticotropin-releasing factor receptor 1 (CRFR1) and CRFR2 have an impaired stress response and display sexually dichotomous anxiety-like behavior. J Neurosci 22:193–199[Abstract/Free Full Text]
  38. Brown MR, Fisher LA, Spiess J, Rivier C, Rivier J, Vale W 1982 Corticotropin-releasing factor: actions on the sympathetic nervous system and metabolism. Endocrinology 111:928–931[Abstract/Free Full Text]
  39. Brown MR, Fisher LA, Rivier J, Spiess J, Rivier C, Vale W 1982 Corticotropin-releasing factor: effects on the sympathetic nervous system and oxygen consumption. Life Sci 30:207–210[CrossRef][Medline]
  40. Rivest S, Deshaies Y, Richard D 1989 Effects of corticotropin-releasing factor on energy balance in rats are sex dependent. Am J Physiol 257:R1417–R1422
  41. Kotz CM, Wang C, Levine AS, Billington CJ 2002 Urocortin in the hypothalamic PVN increases leptin and affects uncoupling proteins-1 and -3 in rats. Am J Physiol Regul Integr Comp Physiol 282:R546–R551
  42. Egawa M, Yoshimatsu H, Bray GA 1990 Preoptic area injection of corticotropin-releasing hormone stimulates sympathetic activity. Am J Physiol 259:R799–R806
  43. Egawa M, Yoshimatsu H, Bray GA 1990 Effect of corticotropin releasing hormone and neuropeptide Y on electrophysiological activity of sympathetic nerves to interscapular brown adipose tissue. Neuroscience 34:771–775[CrossRef][Medline]
  44. Dunn AJ, Berridge CW 1987 Corticotropin-releasing factor administration elicits a stress-like activation of cerebral catecholaminergic systems. Pharmacol Biochem Behav 27:685–691[CrossRef][Medline]
  45. Andreis PG, Neri G, Nussdorfer GG 1991 Corticotropin-releasing hormone (CRH) directly stimulates corticosterone secretion by the rat adrenal gland. Endocrinology 128:1198–1200[Abstract/Free Full Text]
  46. Nijsen MJ, Croiset G, Stam R, Bruijnzeel A, Diamant M, de Wied D, Wiegant VM 2000 The role of the CRH type 1 receptor in autonomic responses to corticotropin-releasing hormone in the rat. Neuropsychopharmacology 22:388–399[CrossRef][Medline]
  47. Hashimoto K, Makino S, Asaba K, Nishiyama M 2001 Physiological roles of corticotropin-releasing hormone receptor type 2. Endocr J 48:1–9[Medline]
  48. Makino S, Asaba K, Nishiyama M, Hashimoto K 1999 Decreased type 2 corticotropin-releasing hormone receptor mRNA expression in the ventromedial hypothalamus during repeated immobilization stress. Neuroendocrinology 70:160–167[CrossRef][Medline]
  49. Nishiyama M, Makino S, Asaba K, Hashimoto K 1999 Leptin effects on the expression of type-2 CRH receptor mRNA in the ventromedial hypothalamus in the rat. J Neuroendocrinol 11:307–314[CrossRef][Medline]
  50. Makino S, Nishiyama M, Asaba K, Gold PW, Hashimoto K 1998 Altered expression of type 2 CRH receptor mRNA in the VMH by glucocorticoids and starvation. Am J Physiol 275:R1138–R1145
  51. Tannenbaum BM, Brindley DN, Tannenbaum GS, Dallman MF, McArthur MD, Meaney MJ 1997 High-fat feeding alters both basal and stress-induced hypothalamic-pituitary-adrenal activity in the rat. Am J Physiol 273:E1168–E1177
  52. Cummings DE, Brandon EP, Planas JV, Motamed K, Idzerda RL, McKnight GS 1996 Genetically lean mice result from targeted disruption of the RII ß subunit of protein kinase A. Nature 382:622–626[CrossRef][Medline]
  53. Valentino RJ 1989 Corticotropin-releasing factor: putative neurotransmitter in the noradrenergic nucleus locus ceruleus. Psychopharmacol Bull 25:306–311[Medline]
  54. Price ML, Curtis AL, Kirby LG, Valentino RJ, Lucki I 1998 Effects of corticotropin-releasing factor on brain serotonergic activity. Neuropsychopharmacology 18:492–502[CrossRef][Medline]
  55. Kirby LG, Rice KC, Valentino RJ 2000 Effects of corticotropin-releasing factor on neuronal activity in the serotonergic dorsal raphe nucleus. Neuropsychopharmacology 22:148–162[CrossRef][Medline]
  56. Dagnault A, Richard D 1997 Involvement of the medial preoptic area in the anorectic action of estrogens. Am J Physiol 272:R311–R317
  57. De Fanti BA, Martinez JA 2002 Central urocortin activation of sympathetic-regulated energy metabolism in Wistar rats. Brain Res 930:37–41[CrossRef][Medline]
  58. Currie PJ, Coscina DV, Bishop C, Coiro CD, Koob GF, Rivier J, Vale W 2001 Hypothalamic paraventricular nucleus injections of urocortin alter food intake and respiratory quotient. Brain Res 916:222–228[CrossRef][Medline]



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