AJP - GI Fuel your research with LabChart
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Am J Physiol Gastrointest Liver Physiol 292: G165-G172, 2007. First published July 13, 2006; doi:10.1152/ajpgi.00152.2006
0193-1857/07 $8.00
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
292/1/G165    most recent
00152.2006v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via ISI Web of Science (2)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Melgar, S.
Right arrow Articles by Bohlooly-Y, M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Melgar, S.
Right arrow Articles by Bohlooly-Y, M.

INFLAMMATION/IMMUNITY/MEDIATORS

Mice with experimental colitis show an altered metabolism with decreased metabolic rate

Silvia Melgar,1 Mikael Bjursell,3,4 Anna-Karin Gerdin,3 Lennart Svensson,2 Erik Michaëlsson,1 and Mohammad Bohlooly-Y3

1Department of Integrative Pharmacology, Gastrointestinal Biology, 2Department of Molecular Pharmacology, and 3AstraZeneca Transgenics and Comparative Genomics Centre, AstraZeneca Research and Development, Mölndal; and 4Department of Physiology/Endocrinology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, Göteborg University, Göteborg, Sweden

Submitted 6 April 2006 ; accepted in final form 5 July 2006


   ABSTRACT
TOP
 ABSTRACT
MATERIAL AND METHODS
 RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
Patients with inflammatory bowel disease (IBD) suffer from body weight loss, malnutrition, and several other metabolic alterations affecting their quality of life. The aim of this study was to investigate the metabolic changes that may occur during acute and chronic colonic inflammation induced by dextran sulfate sodium (DSS) in mice. Clinical symptoms and inflammatory markers revealed the presence of an ongoing inflammatory response in the DSS-treated mice. Mice with acute inflammation had decreased body weight, respiratory exchange ratios (RER), food intake, and body fat content. Mice with chronic inflammation had decreased nutrient uptake, body fat content, locomotor activity, metabolic rates, and bone mineral density. Despite this, the body weight, food and water intake, lean mass, and RER of these mice returned to values similar to those in healthy controls. Thus, murine experimental colitis is associated with significant metabolic alterations similar to IBD patients. Our data show that the metabolic responses during acute and chronic inflammation are different, although the metabolic rate is reduced in both phases. These observations suggest compensatory metabolic alterations in chronic colitis resulting in a healthy appearance despite gross colon pathology.

dual-energy X-ray absorptiometry; dextran sulfate sodium; colon inflammation; respiratory exchange ratio

INFLAMMATORY BOWEL DISEASE (IBD) in humans consists of two main chronic diseases: ulcerative colitis (UC) and Crohn's disease (CD). Patients with CD can be affected anywhere along the gastrointestinal tract, with the majority being affected in the ileum or in the ileocolonic area. The inflammatory response can extend through all layers of the intestinal wall (28). In contrast, patients with UC are affected in the large intestine, where the inflammation starts in the rectum and spreads upward. The inflammatory response is usually confined to the mucosal layer (28). UC and CD are chronic diseases, and IBD patients have an affected quality of life, suffering from wasting and malnutrition, hypoalbuminemia, anemia, and various vitamin and mineral deficiencies (12). As a consequence, the body composition of an adult IBD patient is altered, e.g., with a reduction in bone mineral density (BMD), which implies that there is a high prevalence of osteopenia and osteoporosis in these patients (20). Nutritional impairment occurs in up to 60% of UC patients and in up to 75% of CD patients (6). It has been suggested that factors contributing to weight loss in CD patients are suppression of food intake secondary to anorexia and pain associated with eating (26, 29). Furthermore, an increased metabolic rate and a reduction in body fat mass may contribute to the decreased body weight in CD patients (6, 8, 30).

Several experimental IBD models have been developed, including several gene knockout and transgenic strains (e.g., IL-10-deficient mice) and chemically induced models (for a review, see Ref. 2). The dextran sulfate sodium (DSS) model is a chemically induced IBD model, in which mice receiving DSS in drinking water develop acute and chronic colonic inflammation (27). Previously, it has been described that C57BL/6 mice exposed to DSS for 5 days develop acute inflammation, which, upon DSS removal, progresses into chronicity (23). Mice in the acute phase display clinical symptoms such as body weight loss, rectal bleeding, and loose feces/diarrhea, whereas mice in the chronic phase show only mild clinical symptoms with loose feces. The local inflammation is accompanied by a high production of inflammatory markers such as IL-1beta, IL-12, and IFN-{gamma} as well as high levels of the acute-phase protein haptoglobin (23).

The presence of metabolic changes similar to those observed in IBD patients has not been assessed in experimental colitis models. Thus, the aim of this study was to investigate the types of metabolic changes that are associated with the acute and chronic phases of inflammation in an experimental colitis mouse model. For this purpose, indirect calorimetry, dual-energy X-ray absorptiometry (DEXA), and plasma levels of different metabolic markers were analyzed in mice with acute or chronic inflammation.


   MATERIAL AND METHODS
TOP
 ABSTRACT
 MATERIAL AND METHODS
RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
Mice. Specific pathogen-free female C57BL/6JOlaHsD mice (Harlan) were used. Mice were housed individually and acclimatized for 2 wk before being entered into the study at the age of 9 wk (weight: 18–21 g). Animals were kept in the animal house facilities at AstraZeneca R&D (Mölndal, Sweden) with 50% humidity and 12:12-h light-dark cycles and fed with standard pellet chow (R3 pellets, Lactamin) and tap water ad libitum. This study was approved by the Local Animal Research Board Committee in Göteborg, Sweden.

Induction of colitis. Mice received 3% (wt/vol) DSS (45,000 Da; TDB Consultancy, Uppsala, Sweden) as previously described (23). Briefly, DSS was given for 7 days to induce acute inflammation in one group of mice. A second group of mice received DSS for 5 days followed by 3 wk of water to induce chronic inflammation. A third group of mice consisted of healthy controls receiving regular tap water. DSS solutions were prepared daily, and mice were monitored for their clinical symptoms as previously described (23). The numbers of animals per group were 14, 16, and 13 in the healthy control, acute inflamed, and chronic inflamed groups, respectively.

Treatment with methyl-prednisolone was performed in mice with chronic inflammation (n = 4) compared with a healthy group of mice (n = 6) and a vehicle-treated group of inflamed mice (n = 6). Methyl-prednisolone (1 mg/kg, Sigma Aldrich, St. Louis, MO) was administrated orally on three occasions (days 15, 18, and 21 post-DSS). Plasma was collected 14 days after the last methyl-prednisolone treatment.

Indirect calorimetry. Oxygen consumption (VO2), carbon dioxide production (VCO2), food intake, water intake, and locomotor activity were measured using an open-circuit calorimetry system (Oxymax, Columbus Instruments, Columbus, OH) (3). Metabolic parameters were assessed during a 24-h period following days 7 and 26 for the acute and chronic inflammation groups, respectively. Animals were placed in calorimeter chambers with ad libitum access to normal lab chow and water. An air sample was withdrawn for 75 s every 20 min, and O2 and CO2 content were measured by a paramagnetic O2 sensor and a spectrophotometric CO2 sensor. These values were used to calculate VO2 and VCO2. Data from the first 2 h were not used in the analysis of the results to allow mice to acclimatize to the novel environment. Data from corresponding hours were used in 2-h bins. The metabolic rate (in kcal/h) was calculated from the following equation: (3.815 + 1.232RER) x VO2, where RER is the respiratory exchange ratio [volume of CO2 produced per volume of O2 consumed (both in ml·kg–1·min–1)] and VO2 is the volume of O2 consumed per hour and kilogram mass of the animal. RER reflects the balance of substrate oxidation with a theoretical limit between 1.0 and 0.7. A RER of 1.0 reflects carbohydrate oxidation, whereas a RER of 0.7 reflects fat oxidation. The value of the metabolic rate was correlated to individual body weights. The RER and metabolic rate were analyzed for resting metabolism, taken at the lowest value of VO2 during the light period. The cumulative water intake was assessed by an automatic counter that recorded every droplet that the mouse licked from the drinking sipper. The size of the droplets was calibrated separately for each cage (~20 µl/droplet). The measurements of food and water intake were performed on days 1 and 21 after DSS removal.

Body composition. The body composition was determined by DEXA using a PIXImus imager (GE Lunar, Madison, WI) (31). Mice were anesthetized with an initial dose of 4% isoflurane (Abbot Scandinavia, Solna, Sweden) followed by a maintenance dose of 2%. Body fat, lean body mass, total BMD, and bone mineral content (BMC) were measured by dual-energy X-ray technology. The entire animal was exposed to a small cone-shaped beam of both high- and low-energy X-rays. The ratio of energy attenuation in the luminescent panel separates bone, lean, and fat tissue. Field calibration and calibration vs. the quality control phantom were performed before imaging. BMC is expressed in grams by DEXA normalized for body length (in g/cm) and BMD (in g/cm2).

Assessment of inflammation and sampling of tissue and plasma. After DEXA, mice were anesthetized with isoflurane, and blood was collected in EDTA-containing tubes by a retroorbital puncture followed by cervical dislocation. Plasma was frozen and kept at –80°C until analysis. The whole colon was excised and carefully rinsed with NaCl (GIBCO-BRL, Invitrogen). The inflammatory score, reflecting the degree of inflammation in the colon, was based on edema (0–3), the thickness of the tissue (0–4), stiffness of the tissue (0–2), and presence of ulcerations (0–1), resulting in a maximal total score of 10 (21). Three centimeters of the distal colon were removed and divided longitudinally in two pieces. One piece was frozen directly in liquid nitrogen and used to measure IL-1beta levels, whereas the other piece was fixed in zinc-formalin solution (pH 7.4, Histolab Products, Göteborg, Sweden), embedded in paraffin, and used for histological analysis using hematoxylin-eosin staining or Masson trichrome staining as previously described (23).

Plasma analysis. The analysis of plasma was performed by using the following commercial kits: triglycerides (TG) and total cholesterol from Roche Diagnostics [nos.12146029216 (TG) and 2016630 (cholesterol), Mannheim, Germany]; alanine aminotransferase (ALT), total protein, and albumin from Randox Laboratories [AL 7904 (ALT), TP245 (total protein), and AB 362 (albumin)]; nonesterified fatty acids (NEFA) from Wako Chemicals (NEFA C-999-75406); and glucose from ABX Diagnostics-Parch Euromedecine (HK 125, Montpellier, France). Insulin, leptin, triiodothyronine (T3), thyroxine (T4), and corticosterone were determined with radioimmunoassays purchased from Linco Research [RI-13 K (insulin) and ML-82 K (leptin)], Diagnostic [Coat-A-Count, TKT 31 (T3) and TKT 41 (T4), Los Angeles, CA], and Amersham Biosciences [RPA 548 (corticosterone), Biotrak Assay System, Uppsala, Sweden]. The ACTH assay was from Nichols Institute Diagnostics (36T-2194). Osteocalcin was determined using an immunoradiometric assay from Immunotopics.

Feces analysis. Feces from individual mice were collected, dried overnight at 55°C, and stored air tight at –18°C until being assayed. The gross energy content was determined in a bomb calorimeter (C 5000, IKA, Werke, Germany). A tablet of benzoic acid (IKA, Werke, Germany) was used as a combustion aid when the material was not sufficient (1).

Statistics. One- or two-way ANOVA was used to analyze the indirect calorimetry data. Values are presented as means ± SE. P < 0.05 was considered as significant.


   RESULTS
TOP
 ABSTRACT
 MATERIAL AND METHODS
 RESULTS
DISCUSSION
 GRANTS
 REFERENCES
 
Assessment of inflammation and clinical symptoms. Mice exposed to 7 days of DSS developed acute inflammation characterized by decreased body weight (Fig. 1A), loose feces/diarrhea (Fig. 1B), and visible fecal blood. Mice with chronic inflammation started to decrease their body weights during DSS treatment and continued 1 wk after DSS removal. Thereafter, they slowly recovered the weight, reaching their initial weights after 3 wk of water (Fig. 1A). The only clinical sign of disease in these mice was loose feces (Fig. 1B). In addition, the inflammatory score was higher in mice with chronic inflammation compared with mice with acute inflammation or healthy controls (Fig. 1C). The thickness of the colonic tissue was increased, as reflected by the significantly increased colonic weight in both groups of inflamed mice compared with healthy controls (114.4 ± 6.3, 259.6 ± 16.8, and 63.0 ± 3.5 mg in acute inflamed, chronic inflamed, and healthy control mice, respectively). The increased thickness was due to the infiltration of inflammatory cells, edema, and fibrosis (Fig. 1, e, f, h, and I). Furthermore, plasma haptoglobin was elevated in mice with acute (4.05 ± 0.36 g/l) and chronic inflammation (3.06 ± 0.43 g/l) compared with healthy controls (0.13 ± 0.03 g/l). Similarly, the colonic levels of IL-1beta were increased in acute inflamed mice and were even higher in chronic inflamed mice (6,045 ± 1,360, 13,815 ± 2,350, and 70 ± 14 pg/100 mg colonic tissue in acute inflamed, chronic inflamed, and healthy control mice, respectively). Thus, mice in the acute phase have an acute inflammatory response characterized by clinical symptoms and elevated systemic and local inflammatory markers. Mice in the chronic phase show mild clinical symptoms with severe colonic inflammation characterized by high levels of proinflammatory cytokines and enlarged colonic tissue.


Figure 1
View larger version (33K):
[in this window]
[in a new window]

  		Fig. 1. Assessment of inflammation in C57BL/6 mice during acute and chronic inflammation. A: body weight was recorded daily, and changes over time are expressed as percentages from the weight at day 0 (start of dextran sulfate sodium treatment). B: the diarrhea score was assessed at the time of necropsy and graded as 0–3, where 0 was normal feces, 1 was slight loose feces, 2 was loose feces, and 3 was watery diarrhea. C: the total colon inflammatory score was characterized by the degree of edema (0–3), thickness (0–4), stiffness (0–2), and ulceration (0–1), resulting in a total score of 10. *P < 0.05, mice with acute inflammation compared with healthy controls; §P < 0.05, mice with chronic inflammation compared with healthy controls; #P < 0.05, mice with chronic inflammation compared with mice with acute inflammation. d–i: histology sections of the inflamed colon. Representative tissue sections are of a healthy control mouse (d and g); a mouse with acute inflammation showing edema, infiltration of inflammatory cells, and crypt and epithelial disruption (e and h); and a mouse with chronic inflammation showing severe infiltration in the mucosa and submucosa and irregular epithelial regeneration (f and i). Paraffin-embedded sections were stained with hematoxylin-eosin (d–f) or Masson trichrome (g–i). Original magnification: x5.

 
Mice with chronic inflammation have decreased metabolic rates. VO2 and VCO2 were measured by indirect calorimetry to determine the effect of colonic inflammation on energy metabolism. Mice with acute inflammation had a tendency toward reduced resting metabolic rates compared with healthy controls (P = 0.07), whereas mice with chronic inflammation had significantly decreased resting metabolic rates (Fig. 2A). Resting RER was significantly decreased in mice with acute inflammation compared with healthy controls and mice with chronic inflammation (Fig. 2B; RER of 0.7 in mice with acute inflammation vs. 0.9 in healthy mice and mice with chronic inflammation). Although mice with chronic inflammation had significantly decreased VO2 and VCO2 compared with healthy controls, no differences were measured in RER (Fig. 2B). Thus, the data suggest that mice with acute inflammation use fat as an energy substrate, whereas mice with chronic inflammation use carbohydrates as an energy substrate, similarly to healthy controls.


Figure 2
View larger version (13K):
[in this window]
[in a new window]

  		Fig. 2. Decreased resting metabolic rates in mice with chronic inflammation. A: resting metabolic rates (in kcal/h) were calculated according to the following equation: (3.815 + 1.232RER) x VO2, where RER is the respiratory exchange ratio and VO2 is the volume of O2 consumed per hour per kilogram mass of the animal. These values were correlated with individual body weights. B: the RER (y-axis) was measured by indirect calorimetry and calculated as the volume of CO2 produced per volume of O2 consumed (both in ml·kg–1·min–1). *P < 0.05, mice with acute inflammation compared with healthy controls; §P < 0.05, mice with chronic inflammation compared with healthy controls; #P < 0.05, mice with chronic inflammation compared with mice with acute inflammation.

 
Food and water intake are reduced in mice with acute but not chronic inflammation. Food and water intake and activity were measured in a calorimetry system to investigate their impact on metabolic changes. Mice with acute inflammation showed a significantly decreased food and water intake and a tendency toward decreased locomotor activity compared with healthy controls (P = 0.12; Fig. 3, A–C). In contrast, a tendency toward increased food and water intake was observed in mice with chronic inflammation compared with healthy mice (Fig. 3, A and B). Significantly decreased locomotor activity was observed in mice with chronic and acute inflammation during the dark period compared with healthy controls (Fig. 3C). Furthermore, the amount of energy lost in feces was determined to investigate whether the changes in metabolism were related to an altered intestinal uptake of nutrients. A significantly increased energy loss was found during the acute as well as chronic inflammatory phase, suggesting an impaired nutrient uptake in these animals compared with controls (Fig. 3D). No significant differences in feces energy content were observed between mice with acute and chronic inflammation (Fig. 3D). Thus, a reduction in food/water intake is associated with mice with acute inflammation.


Figure 3
View larger version (20K):
[in this window]
[in a new window]

  		Fig. 3. Decreased food and water intake in mice with acute inflammation. Food intake (A), water intake (B), and locomotor activity (C) were determined as described in MATERIALS AND METHODS during a 24-h time period. D: the gross energy content (in J/g) in feces collected from individual mice was determined in a bomb calorimeter as described in MATERIAL AND METHODS. *P < 0.05, mice with acute inflammation compared with healthy controls; §P < 0.05, mice with chronic inflammation compared with healthy controls; #P < 0.05, mice with chronic inflammation compared with mice with acute inflammation.

 
Body fat content is reduced in mice with acute or chronic inflammation. The body composition in mice with colitis and healthy controls was determined by DEXA. Mice with acute inflammation contained less body fat and had a reduced body lean mass compared with healthy controls (Fig. 4, A and B). Furthermore, mice with acute inflammation had significantly less lean mass than mice with chronic inflammation (Fig. 4B). The loss of fat content persisted in mice with chronic inflammation, whereas the lean mass recovered to values similar to those in healthy controls (Fig. 4, A and B). No significant changes in BMC levels were found in mice with either acute or chronic inflammation (data not shown). However, a significant reduction in BMD was measured during chronic inflammation (39.6 ± 0.7 mg/cm2) compared with either healthy controls (44.4 ± 0.5 mg/cm2) or mice with acute inflammation (44.7 ± 0.8 mg/cm2). Furthermore, the plasma levels of osteocalcin were increased by 50% in mice with chronic inflammation compared with healthy controls (202 ± 26 and 134 ± 12 ng/ml in chronic inflamed and healthy mice, respectively, P < 0.05). Osteocalcin levels were reduced by 18% upon treatment with methyl-prednisolone in mice with chronic inflammation; however, this reduction was not statistically significant (158 ± 6 ng/ml for the methyl-prednisolone-treated mice). No differences in BMD were found between controls and mice with acute inflammation. Thus, the body fat content is reduced in mice during acute inflammation and remains reduced during chronic inflammation, despite the normalized food intake and body weight.


Figure 4
View larger version (13K):
[in this window]
[in a new window]

  		Fig. 4. Mice with acute and chronic inflammation have reduce body fat content. The body composition, as fat (A) and lean mass (B), was determined by dual-energy X-ray absorptiometry using a PIXImus imager. Amounts of fat and lean mass are given in grams. *P < 0.05, mice with acute inflammation compared with healthy controls; §P < 0.05, mice with chronic inflammation compared with healthy controls; #P < 0.05, mice with chronic inflammation compared with mice with acute inflammation.

 
Metabolic plasma markers are differentially regulated during acute and chronic inflammation. The levels of TG, cholesterol, NEFA, insulin, glucose, leptin, corticosterone, ACTH, ALT, thyroid hormones (T3 and T4), and albumin were determined in plasma from mice with acute and chronic inflammation and in healthy controls. The results are summarized in Table 1. The levels of glucose, leptin, T4, and albumin were significantly decreased in mice with acute and chronic inflammation compared with healthy controls. Markers related to lipid metabolism (TG and cholesterol) were differentially regulated during acute and chronic inflammation. In mice with acute inflammation, the levels of TG were reduced, whereas cholesterol levels were increased, compared with controls. In contrast, mice with chronic inflammation had increased levels of TG and decreased cholesterol levels compared with mice with acute inflammation (Table 1). NEFA, insulin, ALT, T3, and ACTH were not significantly affected by inflammation.


View this table:
[in this window]
[in a new window]

  		Table 1. Plasma markers delineating metabolic changes during acute and chronic inflammation

 

   DISCUSSION
TOP
 ABSTRACT
 MATERIAL AND METHODS
 RESULTS
 DISCUSSION
GRANTS
 REFERENCES
 
Patients with IBD (UC and CD) have an affected quality of life with altered metabolic status (12). To investigate the metabolic changes in mice that have developed acute or chronic inflammation, we used indirect calorimetry and DEXA and measured the energy content in feces and levels of different metabolic plasma markers. It was observed that mice with acute inflammation had decreased body weights, fat and lean mass, RER, and food and water intake and a tendency to lower locomotor activity and metabolic rates compared with healthy controls. In contrast, mice with chronic inflammation were recovered and had comparable RER, food intake, body weight, and lean mass to healthy control mice. However, their metabolic rates and body fat content were significantly reduced compared with healthy controls. Mice with acute and chronic inflammation had decreased intestinal nutrient uptake compared with healthy mice. The recovery or metabolic adaptation during the chronic inflammatory phase is shown by the significantly higher RER, food/water intake, and increased lean mass compared with mice with acute inflammation. Thus, mice having acute or chronic inflammation alter their metabolism as a response or adaptation to severe colonic inflammation, although there are some differences in the adaptive mechanisms between the two inflammatory phases.

Lipid metabolism is altered during an acute inflammatory response. LPS-induced inflammation causes acutely increased serum TG levels (2–24 h after administration) by mechanisms involving increased lipolysis and suppression of fatty acid oxidation (11, 19). LPS administration also causes increased total serum cholesterol levels in rodents (10, 19). Previously, it has been shown that an acutely induced systemic inflammation results in increased protein catabolism and altered protein synthesis (24, 33), showing the importance of inflammation in protein metabolism. Furthermore, chronic inflammation induced by DSS treatment in rats resulted in a stimulation of protein synthesis in various splanchnic organs, i.e., the spleen and intestine, whereas muscle protein turnover was reduced (24). It has also been shown that several proinflammatory cytokines have major roles in appetite regulation and energy homeostasis. Among these, IL-1beta, TNF, and IL-6 have been shown to have reducing effects on food intake, resulting in weight loss (for a review, see Ref. 34). In this study, the induction of acute inflammation was over a 7-day DSS exposure and, consistent with previous findings, mice with acute inflammation had lower food and water intake and lost weight. At this time point, the plasma levels of IL-6 and keratinocyte-derived cytokine (IL-8/ growth-related oncogene analog in mice), but not IL-1beta or TNF, were highly elevated (S. Melgar, unpublished results). Mice with acute inflammation had a tendency toward lower locomotor activity and resting metabolism. Furthermore, reduced plasma glucose levels in the acute phase of inflammation were observed, correlating with the decreased food intake. In humans, it has been reported that patients with CD show weight loss due to an increased metabolic rate (energy expenditure) and decreased dietary intake and malabsortion (8, 29, 32), which are in line with the findings in inflamed mice in the present study. Consistent with the reduced food intake, mice in the acute phase used fat as the main source of energy, as shown by the lower resting RER, fat mass, and leptin levels. Notably, this, as well as the reduced plasma levels of TG, is in contrast to the suppression of fatty acid oxidation after LPS (19), suggesting that the results obtained during the DSS-induced acute inflammation differs considerably from the data obtained from LPS-induced acute inflammation. However, the total cholesterol levels in DSS-induced acute inflammation were elevated, in agreement with previous findings (10).

Several IBD models, e.g., the CD4+CD45RBHi transfer model and IL-2-deficient mice, show signs of wasting disease, e.g., reduced body weight, body fat, or lean mass (14, 18), which are in line with the data presented here. Reduced body weight, food intake, and protein loss in the liver, spleen, and muscles have also been reported in other models of wasting disease, e.g., upon intravenous Esherichia coli administration to rats (4) or in mice exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (22a).

Mice with chronic inflammation had recovered food intake, water intake, and body weight comparable with healthy controls, resulting in a relatively increased lean mass, whereas fat mass and leptin levels were still reduced. It could be speculated that a contribution to the normalized lean mass in mice with chronic inflammation might be due to the enlargement of the splanchnic organs, as previously reported in rats and mice (23, 24).

A similarly increased fecal energy content in the acute and chronic phases of inflammation and a reduced metabolic rate in mice with chronic inflammation, despite normalized RER and food intake, were observed. Furthermore, the reduced metabolic rate was reflected by decreased motor activity (mainly during the dark phase) and also by a downregulation of the thyroid axis with a reduction in plasma levels of T4. However, the T3 levels were unchanged. Thyroid hormones promote cellular metabolisms and have a calorigenic effect. The reduced levels of T4 might, therefore, directly correlate to a state of reduced metabolic rate during a wasting (acute inflammation) or a postwasting recovery phase (chronic inflammation). Interestingly, decreased levels of T4 have been reported in CD patients (25). Previous studies in rats have reported a dissociation between fever and colitis, suggesting that the observed changes in T4 levels during acute and chronic inflammation are linked to the metabolic rather than to thermogenic actions of this hormone. The reduction in fat in mice with chronic inflammation is similar to the reduction in fat in CD patients with active disease (29), but underweight CD patients have a higher RER/body mass due to greater loss of fat mass and sparing of lean mass (8). The normalization/recovery of the body weight in mice with chronic inflammation might be related to an adaptation of the metabolism in response to the presence of an ongoing inflammatory pathology rather than to a normalized nutrient uptake.

Patients with IBD are at risk of developing metabolic-related bone diseases, e.g., osteoporosis (20). In the present study, we observed that only mice with chronic inflammation had decreased BMD and increased levels of osteocalcin, a marker of bone formation, which may indicate a higher bone turnover osteoporosis. A reduction in BMD has been reported in newly diagnosed and long-standing CD patients but not in UC patients (15, 16). These abnormalities in IBD patients may be due to the worsened nutritional status (malnutrition), the inflammatory process by itself, or a combination of both (20). Osteopenia has been reported in other IBD models, e.g., the CD4+CD45RBhigh T cell transfer model (5), IL-10-deficient mice (9), and rats treated with trinitrobenzene sulfonic acid (22). We favor the idea that decreased BMD may not immediately be related to malabsorption but instead to inflammatory factors. Steroid treatment has also been shown to reduce BMD in the majority of IBD studies, although conflicting data exist (13). In the present study, methyl-prednisolone treatment of mice with chronic inflammation tended to reduce osteocalcin levels.

Overall, mice with colitis, irrespective of the state of the inflammatory condition (acute or chronic), had decreased metabolic rates, which appeared to be associated with different metabolic changes. The lower RER in mice with acute inflammation suggests that they used fat, whereas mice with chronic inflammation, to a higher extent, used carbohydrates as an energy source. Interestingly, it has been reported that CD patients use lipids as an energy source, whereas UC patients use carbohydrates (7). Taken together, these data indicate that mice in the acute phase share some metabolic similarities to CD patients, whereas mice in the chronic phase display changes toward a UC patient-type metabolism.

In conclusion, we have shown that acute and chronic colonic inflammation in mice is associated with distinct metabolic changes comparable with those observed in IBD patients. Therefore, the present colitis model not only reproduces the inflammatory response correspondent to IBD but also other metabolic alterations associated with the course of the disease. To cope with the chronic inflammatory condition, mice develop profound metabolic compensatory changes resulting in an "apparently healthy" state despite gross colon pathology.


   GRANTS
TOP
 ABSTRACT
 MATERIAL AND METHODS
 RESULTS
 DISCUSSION
 GRANTS
REFERENCES
 
This study was supported by AstraZeneca R&D (Mölndal, Sweden).


   ACKNOWLEDGMENTS
 
We are greatly thankful to Lisa Karlsson for technical assistance, to Liselotte Hallengren and colleagues for taking care of the mice, and to Lena Amrot Fors, Anna Tuneld, Charlotte Lindgren, Anne-Cristine Carlsson, Martina Johansson, Gisela Häggblad, and Marie-Louise Berglund Zackrisson, who kindly helped with the plasma analysis. The authors also thank Dr. Vicente Martinez for comments on the manuscript.


   FOOTNOTES
 

Address for reprint requests and other correspondence: S. Melgar, Dept. of Integrative Pharmacology, GI Biology, AstraZeneca R&D, Pepparedsleden 1, Mölndal SE-431 81, Sweden (e-mail: silvia.melgar{at}astrazeneca.com)

The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.


   REFERENCES
TOP
 ABSTRACT
 MATERIAL AND METHODS
 RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 

  1. Bjursell M, Gerdin AK, Ploj K, Svensson D, Svensson L, Oscarsson J, Snaith M, Tornell J, Bohlooly-Y M. Melanin-concentrating hormone receptor 1 deficiency increases insulin sensitivity in obese leptin-deficient mice without affecting body weight. Diabetes 55: 725–733, 2006.[Abstract/Free Full Text]
  2. Blumberg RS, Saubermann LJ, Strober W. Animal models of mucosal inflammation and their relation to human inflammatory bowel disease. Curr Opin Immunol 11: 648–656, 1999. [Erratum. Curr Opin Immunol 12 (2): 226, 2006.][CrossRef][ISI][Medline]
  3. Bohlooly-Y M, Olsson B, Bruder CEG, Linden D, Sjogren K, Bjursell M, Egecioglu E, Svensson L, Brodin P, Waterton JC, Isaksson OGP, Sundler F, Ahren B, Ohlsson C, Oscarsson J, Tornell J. Growth hormone overexpression in the central nervous system results in hyperphagia-induced obesity associated with insulin resistance and dyslipidemia. Diabetes 54: 51–62, 2005.[Abstract/Free Full Text]
  4. Breuille D, Voisin L, Contrepois M, Arnal M, Rose F, Obled C. A sustained rat model for studying the long-lasting catabolic state of sepsis. Infect Immun 67: 1079–1085, 1999.[Abstract/Free Full Text]
  5. Byrne FR, Morony S, Warmington K, Geng Z, Brown HL, Flores SA, Fiorino M, Yin SL, Hill D, Porkess V, Duryea D, Pretorius JK, Adamu S, Manuokian R, Danilenko DM, Sarosi I, Lacey DL, Kostenuik PJ, Senaldi G. CD4+CD45RBHi T cell transfer induced colitis in mice is accompanied by osteopenia which is treatable with recombinant human osteoprotegerin. Gut 54: 78–86, 2005.[Abstract/Free Full Text]
  6. Capristo E, Mingrone G, Addolorato G, Greco AV, Gasbarrini G. Metabolic features of inflammatory bowel disease in a remission phase of the disease activity. J Intern Med 243: 339–347, 1998.[CrossRef][ISI][Medline]
  7. Capristo E, De Gaetano A, Mingrone G, Addolorato G, Greco AV, Castagneto M, Gasbarrini G. Multivariate identification of metabolic features in inflammatory bowel disease. Metabolism 48: 952–956, 1999.[CrossRef][ISI][Medline]
  8. Chan AT, Fleming CR, O'Fallon WM, Huizenga KA. Estimated versus measured basal energy requirements in patients with Crohn's disease. Gastroenterology 91: 75–78, 1986.[ISI][Medline]
  9. Dresner-Pollak R, Rachmilewitz D, Karmeli F, Weinreb M. Interleukin 10-deficient mice develop osteopenia, decreased bone formation, and mechanical fragility of long bones. Gastroenterology 127: 792–801, 2004.[CrossRef][ISI][Medline]
  10. Feingold K, Hardardottir I, Memon R, Krul E, Moser A, Taylor J, Grunfeld C. Effect of endotoxin on cholesterol biosynthesis and distribution in serum lipoproteins in Syrian hamsters. J Lipid Res 34: 2147–2158, 1993.[Abstract]
  11. Feingold K, Staprans I, Memon R, Moser A, Shigenaga J, Doerrler W, Dinarello C, Grunfeld C. Endotoxin rapidly induces changes in lipid metabolism that produce hypertriglyceridemia: low doses stimulate hepatic triglyceride production while high doses inhibit clearance. J Lipid Res 33: 1765–1776, 1992.[Abstract]
  12. Fisher RL. Wasting in chronic gastrointestinal diseases. J Nutr 129, Suppl 1S: 252S–255S, 1999.[Free Full Text]
  13. Frei P, Fried M, Hungerbühler V, Rammert C, Rousson V, and Kullak-Ublick GA. Analysis of risk factors for low bone mineral density in inflammatory bowel disease. Digestion 73: 40–46, 2006.[ISI][Medline]
  14. Gaetke LM, Oz HS, de Villiers WJS, Varilek GW, Frederich RC. The leptin defense against wasting is abolished in the IL-2-deficient mouse model of inflammatory bowel disease. J Nutr 132: 893–896, 2002.[Abstract/Free Full Text]
  15. Ghosh S, Cowen S, Hannan WJ, Ferguson A. Low bone mineral density in Crohn's disease, but not in ulcerative colitis, at diagnosis. Gastroenterology 107: 1031–1039, 1994.[ISI][Medline]
  16. Jahnsen J, Falch J, Aadland E, Mowinckel P. Bone mineral density is reduced in patients with Crohn's disease but not in patients with ulcerative colitis: a population based study. Gut 40: 313–319, 1997.[Abstract/Free Full Text]
  17. Kanai T, Kawamura T, Dohi T, Makita S, Nemoto Y, Totsuka T, Watanabe M. TH1/TH2-mediated colitis induced by adoptive transfer of CD4+CD45RBhigh T lymphocytes into nude mice. Inflamm Bowel Dis 12: 89–99, 2006.[CrossRef][ISI][Medline]
  18. Khovidhunkit W, Kim MS, Memon RA, Shigenaga JK, Moser AH, Feingold KR, Grunfeld C. Thematic review series: the pathogenesis of atherosclerosis. Effects of infection and inflammation on lipid and lipoprotein metabolism mechanisms and consequences to the host. J Lipid Res 45: 1169–1196, 2004.[Abstract/Free Full Text]
  19. Krok KL, Lichtenstein GR. Nutrition in Crohn's disease. Curr Opin Gastroenterol 19: 148–153, 2003.[CrossRef][ISI][Medline]
  20. Larsson AE, Melgar S, Rehnstrom E, Michaelsson E, Svensson L, Hockings P, Olsson LE. Magnetic resonance imaging of experimental mouse colitis and association with inflammatory activity. Inflamm Bowel Dis 12: 478–485, 2006.[CrossRef][ISI][Medline]
  21. Lin CL, Moniz C, Chambers TJ, Chow JW. Colitis causes bone loss in rats through suppression of bone formation. Gastroenterology 111: 1263–1271, 1996.[CrossRef][ISI][Medline]
  22. Linden J, Korkalainen M, Lensu S, Tuomisto J, Pohjanvirta R. Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and leptin on hypothalamic mRNA expression of factors participating in food intake regulation in a TCDD-sensitive and a TCDD-resistant rat strain. J Biochem Mol Toxicol 19: 139–148, 2005.[CrossRef][ISI][Medline]
  23. Melgar S, Karlsson A, Michaelsson E. Acute colitis induced by dextran sulfate sodium progresses to chronicity in C57BL/6 but not in BALB/c mice: correlation between symptoms and inflammation. Am J Physiol Gastrointest Liver Physiol 288: G1328–G1338, 2005.[Abstract/Free Full Text]
  24. Mercier S, Breuille D, Mosoni L, Obled C, and Patureau Mirand P. Chronic inflammation alters protein metabolism in several organs of adult rats. J Nutr 132: 1921–1928, 2002.[Abstract/Free Full Text]
  25. Messina G, Viceconti N, Trinti B. [The clinical and echographic assessment of thyroid function and structure in patients with a chronic inflammatory intestinal disease]. Recenti Prog Med 90: 13–16, 1999.[Medline]
  26. Mingrone G, Greco AV, Benedetti G, Capristo E, Semeraro R, Zoli G, Gasbarrini G. Increased resting lipid oxidation in Crohn's disease. Dig Dis Sci 41: 72–76, 1996.[CrossRef][ISI][Medline]
  27. Okayasu I, Hatakeyama S, Yamada M, Ohkusa T, Inagaki Y, Nakaya R. A novel method in the induction of reliable experimental acute and chronic ulcerative colitis in mice. Gastroenterology 98: 694–702, 1990.[ISI][Medline]
  28. Podolsky DK. Inflammatory bowel disease. N Engl J Med 347: 417–429, 2002.[Free Full Text]
  29. Royall D, Greenberg GR, Allard JP, Baker JP, Jeejeebhoy KN. Total enteral nutrition support improves body composition of patients with active Crohn's disease. J Parenter Enteral Nutr 19: 95–99, 1995.[Abstract]
  30. Simpson EJ, Chapman MAS, Dawson J, Berry D, Macdonald IA, Cole A. In vivo measurement of colonic butyrate metabolism in patients with quiescent ulcerative colitis. Gut 46: 73–77, 2000.[Abstract/Free Full Text]
  31. Sjogren K, Hellberg N, Bohlooly-Y M, Savendahl L, Johansson MS, Berglindh T, Bosaeus I, Ohlsson C. Body fat content can be predicted in vivo in mice using a modified dual-energy X-ray absorptiometry technique. J Nutr 131: 2963–2966, 2001.[Abstract/Free Full Text]
  32. Tjellesen L, Nielsen PK, Staun M. Body composition by dual-energy X-ray absorptiometry in patients with Crohn's disease. Scand J Gastroenterol 33: 956–960, 1998.[CrossRef][ISI][Medline]
  33. von Allmen D, Hasselgren PO, Higashiguchi T, Frederick J, Zamir O, Fischer JE. Increased intestinal protein synthesis during sepsis and following the administration of tumour necrosis factor alpha or interleukin-1 alpha. Biochem J 286: 585–589, 1992.
  34. Wong S, Pinkney J. Role of cytokines in regulating feeding behaviour. Curr Drug Targets 5: 251–263, 2004.[CrossRef][ISI][Medline]




This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
292/1/G165    most recent
00152.2006v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via ISI Web of Science (2)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Melgar, S.
Right arrow Articles by Bohlooly-Y, M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Melgar, S.
Right arrow Articles by Bohlooly-Y, M.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Visit Other APS Journals Online
Copyright © 2007 by the American Physiological Society.