| 1. |
- García, Maria C, et al.
(author)
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Mature-onset obesity in interleukin-1 receptor I knockout mice.
- 2006
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In: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 55:5, s. 1205-13
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Journal article (peer-reviewed)abstract
- Interleukin-1 (IL-1) is a major mediator of inflammation that exerts its biological activities through the IL-1 type I receptor (IL-1RI). The body weights of IL-1RI(-/-) mice of both sexes started to deviate from those of wild-type mice at 5-6 months of age and were 20% higher at 9 months of age. Visceral and subcutaneous fat mass, measured by dual-energy X-ray absorptiometry and magnetic resonance imaging, was markedly (1.5- to 2.5-fold) increased. Lean body mass and crown-rump length were also slightly (11 and 5%, respectively) increased, as was serum IGF-I. Obese IL-1RI(-/-) mice were insulin resistant, as evidenced by hyperinsulinemia, decreased glucose tolerance, and insulin sensitivity. To elucidate the mechanisms for the development of obesity, young pre-obese IL-1RI(-/-) mice were investigated. They showed decreased suppression of body weight and food intake in response to systemic leptin treatment. The decreased leptin responsiveness was even more pronounced in older obese animals. Moreover, spontaneous locomotor activity and fat utilization, as measured by respiratory quotient, were decreased in pre-obese IL-1RI(-/-) mice. In conclusion, lack of IL-1RI-mediated biological activity causes mature-onset obesity. This obese phenotype is preceded by decreased leptin sensitivity, fat utilization, and locomotor activity.
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| 2. |
- Sjögren, Klara, 1970, et al.
(author)
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Liver-derived insulin-like growth factor I (IGF-I) is the principal source of IGF-I in blood but is not required for postnatal body growth in mice.
- 1999
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In: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424. ; 96:12, s. 7088-92
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Journal article (peer-reviewed)abstract
- The body growth of animals is regulated by growth hormone and IGF-I. The classical theory of this regulation is that most IGF-I in the blood originates in the liver and that body growth is controlled by the concentration of IGF-I in the blood. We have abolished IGF-I production in the livers of mice by using the Cre/loxP recombination system. These mice demonstrated complete inactivation of the IGF-I gene in the hepatocytes. Although the liver accounts for less than 5% of body mass, the concentration of IGF-I in the serum was reduced by 75%. This finding confirms that the liver is the principal source of IGF-I in the blood. However, the reduction in serum IGF-I concentration had no discernible effect on postnatal body growth. We conclude that postnatal body growth is preserved despite complete absence of IGF-I production by the hepatocytes.
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| 3. |
- Wallenius, Kristina, 1973, et al.
(author)
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Liver-derived IGF-I regulates GH secretion at the pituitary level in mice.
- 2001
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In: Endocrinology. - 0013-7227. ; 142:11, s. 4762-70
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Journal article (peer-reviewed)abstract
- We have reported that liver-specific deletion of IGF-I in mice (LI-IGF-I-/-) results in decreased circulating IGF-I and increased GH levels. In the present study, we determined how elimination of hepatic IGF-I modifies the hypothalamic-pituitary GH axis to enhance GH secretion. The pituitary mRNA levels of GH releasing factor (GHRF) receptor and GH secretagogue (GHS) receptor were increased in LI-IGF-I-/- mice, and in line with this, their GH response to ip injections of GHRF and GHS was increased. Expression of mRNA for pituitary somatostatin receptors, hypothalamic GHRF, somatostatin, and neuropeptide Y was not altered in LI-IGF-I-/- mice, whereas hypothalamic IGF-I expression was increased. Changes in hepatic expression of major urinary protein and the PRL receptor in male LI-IGF-I-/- mice indicated an altered GH release pattern most consistent with enhanced GH trough levels. Liver weight was enhanced in LI-IGF-I-/- mice of both genders. In conclusion, loss of liver-derived IGF-I enhances GH release by increasing expression of pituitary GHRF and GHS receptors. The enhanced GH release in turn affects several liver parameters, in line with the existence of a pituitary-liver axis.
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| 4. |
- Bratlie, Svein-Olav, et al.
(author)
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Proteomic Approach to the Potential Role of Angiotensin II in Barrett Dysplasia
- 2019
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In: Proteomics - Clinical Applications. - : Wiley. - 1862-8346 .- 1862-8354. ; 13:4
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Journal article (peer-reviewed)abstract
- Background and Aim: Dysplasia in Barrett's esophagus (BE) is regarded as a preneoplastic lesion. The renin–angiotensin system (RAS), known for its role in electrolyte homeostasis and hemodynamics, has also been shown to have tissue-based features linked to proliferation, inflammation, and cancer. RAS is associated with BE dysplasia. The aim of this study is to investigate possible effects of the RAS in BE dysplasia by using RAS-interfering pharmaceutical agents and by assessment of global protein expression in esophageal mucosal biopsies. Methods: Endoscopic biopsies are taken from 18 BE in patients with low-grade dysplasia before and after 3 weeks of treatment with either angiotensin-converting enzyme inhibitors (enalapril 5 mg; n = 6) or angiotensin II receptor type 1 blockers (candesartan 8 mg; n = 6), or no treatment (n = 6). A global proteomics analysis by 2D gel electrophoresis and mass spectrometry (MS) is then performed to identify proteins that are regulated after interference with RAS. Results: Three proteins are identified to show significant modulation of expression 60 kDa heat shock protein (downregulated), protein disulfide isomerase A3 (downregulated), and inorganic pyrophosphatase (upregulated). Conclusion: Three proteins with no previously known links to esophageal RAS, but with possible relevance for the development of esophageal adenocarcinoma (EAC) are detected. Altered expression by interference with the RAS suggests an involvement of angiotensin II in the development of EAC in BE. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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| 5. |
- Casselbrant, Anna, 1970, et al.
(author)
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Angiotensin II exerts dual actions on sodium-glucose transporter 1-mediated transport in the human jejunal mucosa
- 2015
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In: Scandinavian Journal of Gastroenterology. - : Informa UK Limited. - 0036-5521 .- 1502-7708. ; 50:9, s. 1068-1075
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Journal article (peer-reviewed)abstract
- Objectives. Intestinal glucose absorption is mainly mediated via the sodium-glucose transporter 1 (SGLT1) at the apex of the enterocytes, whereas the glucose transporter 2 (GLUT2) provides a basolateral exit. It has been shown in rats that Angiotensin II (AngII), the principal mediator of renin-angiotensin system (RAS), inhibits jejunal SGLT1-mediated glucose absorption. The aim of the present study was to investigate if a similar mechanism exists also in the human jejunal mucosa. Material and methods. Enteroscopy with mucosal biopsy sampling was performed in 28 healthy volunteers. Functional assessments were performed in Ussing chambers using a pharmacological approach. Western blotting and immunohistochemistry were used to assess the presence of the AngII type 1 (AT1R) and type 2 receptor (AT2R), as well as the glucose transporters SGLT1 and GLUT2. Results. Exposure of the mucosa to 10 mM glucose elicited a »50% increase in the epithelium-generated current (Iep). This glucose-induced electrogenic response was sensitive to the competitive SGLT1 inhibitor phlorizin, but not to AngII when given alone. AngII combined with the AT2R blocker PD123319 markedly inhibited the response. AngII in combination with the AT1R antagonist losartan tended to increase the electrogenic response, whereas direct activation of AT2R using the agonist C21 significantly enhanced the mucosal response to glucose. The AT1R and AT2R as well as SGLT1 and GLUT2 were detected inside the human enterocytes. Conclusions. The pharmacological analysis indicated that activation of AT1R inhibits, whereas activation of AT2R enhances SGLT1-mediated glucose transport in the human jejunal mucosa.
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| 6. |
- Casselbrant, Anna, 1970, et al.
(author)
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Expression of tight-junction proteins in human proximal small intestinal mucosa before and after Roux-en-Y gastric bypass surgery
- 2015
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In: Surgery for Obesity and Related Diseases. - : Elsevier BV. - 1550-7289. ; 11:1, s. 45-53
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Journal article (peer-reviewed)abstract
- Background Increased permeability and uptake of proinflammatory bacterial endotoxins from gut microbiota has been suggested as a mechanism for obesity-associated chronic inflammation that causes obesity-associated insulin resistance. We hypothesized that intestinal barrier function may be restored after Roux-en-Y gastric bypass (RYGB) surgery and thereby contribute to decreased inflammation. The objective of this study was to investigate levels of the permeability-regulating tight-junction proteins in human small intestinal mucosa before and after RYGB surgery. Methods Paired intraindividual jejunal mucosa samples were retrieved at the time of surgery and 6 to 8 months after surgery. Mucosal cell surface area was calculated by histomorphometry. Mucosal samples were analyzed by proteomics to find patterns of protein regulations. Based on these findings further analyses were performed by Western blotting. Ussing chambers were used to analyze permeability in the retrieved mucosal samples. Results Mucosal surface area was significantly decreased after surgery. Global protein expression analysis showed a significant increase in the cytokeratin-8 (Ck8), which was confirmed by Western blotting. Further analyses showed a significant increase in claudin-3 and -4 expression after surgery, whereas occludin and zonula occludens-1 levels were decreased. Expressions of claudin-1, -2, -5 and vinculin were unchanged. Ussing chamber experiments revealed a linear correlation between the epithelial electrical resistance and claudin-3 protein expression. Conclusion Several alterations were found in the rerouted small intestine after surgery, indicating a decreased jejunal mucosal surface area and decreased paracellular permeability. These changes could contribute to decreased uptake of luminal microbiota-derived inflammatory mediators such as endotoxins after RYGB.
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| 7. |
- Casselbrant, Anna, 1970, et al.
(author)
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Glycocholic acid and butyrate synergistically increase vitamin D-induced calcium uptake in Caco-2 intestinal epithelial cell monolayers
- 2020
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In: Bone Reports. - : Elsevier BV. - 2352-1872. ; 13
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Journal article (peer-reviewed)abstract
- Background: Roux-en-Y gastric bypass (RYGB) substantially decreases intestinal calcium absorption and may eventually lead to bone resorption. This is likely a consequence of bile diversion from the alimentary limb, as the presence of bile seems necessary for vitamin D-mediated calcium uptake. We recently suggested that the mediating mechanism may be a down-regulation of the vitamin D co-activator heat-shock protein (Hsp)90β. Recent evidence suggests that vitamin D may have effects on both active and passive calcium absorption. Aim: To identify mechanisms in vitro that may be responsible for the decreased calcium absorption after RYGB. We hypothesized that bile, alone or in concert with nutritional compounds, could be of importance. Material & methods: Caco-2 cells were grown confluent on semi-permeable membranes in a double-chamber setup to mimic small intestinal mucosa. The effect of bile acids chenodeoxycholic, lithocholic, glycocholic and taurocholic acid, with and without the addition of the fatty-acid butyrate, were tested for their effects on Hsp90β expression and active and passive calcium-flux monitored using radioactive 45Ca. Results: We initially found that whole human bile, but only together with the fatty acid butyrate, potently induced Hsp90β expression. In line with this, a single bile acid, e.g. glycocholic acid (GCA), in combination with butyrate, increased Hsp90β expression (40 ± 13% vs. GCA, butyrate or vehicle alone; p < 0,001; n = 14–25). Further, this combination together with vitamin D increased the passive gradient-driven flux of calcium, compared to stimulation with vitamin D alone or in combination with either GCA or butyrate (880 ± 217% vs. vitamin D and GCA or butyrate, or vitamin D only; p = 0,01–0.006; n = 5–11). Surprisingly, this combination had no effect on active calcium transport in the absence of calcium gradient. Conclusion: The combination of GCA and butyrate increased gradient-driven calcium uptake up to 9-fold in Caco-2 intestinal epithelial cells, but had no effect on active calcium absorption. This effect was mediated via the vitamin D receptor co-activator Hsp90β. © 2020 The Authors
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| 8. |
- Casselbrant, Anna, 1970, et al.
(author)
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Intestinal Ketogenesis and Permeability
- 2024
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In: INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES. - 1661-6596 .- 1422-0067. ; 25:12
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Journal article (peer-reviewed)abstract
- Consumption of a high-fat diet (HFD) has been suggested as a contributing factor behind increased intestinal permeability in obesity, leading to increased plasma levels of microbial endotoxins and, thereby, increased systemic inflammation. We and others have shown that HFD can induce jejunal expression of the ketogenic rate-limiting enzyme mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (HMGCS). HMGCS is activated via the free fatty acid binding nuclear receptor PPAR-alpha, and it is a key enzyme in ketone body synthesis that was earlier believed to be expressed exclusively in the liver. The function of intestinal ketogenesis is unknown but has been described in suckling rats and mice pups, possibly in order to allow large molecules, such as immunoglobulins, to pass over the intestinal barrier. Therefore, we hypothesized that ketone bodies could regulate intestinal barrier function, e.g., via regulation of tight junction proteins. The primary aim was to compare the effects of HFD that can induce intestinal ketogenesis to an equicaloric carbohydrate diet on inflammatory responses, nutrition sensing, and intestinal permeability in human jejunal mucosa. Fifteen healthy volunteers receiving a 2-week HFD diet compared to a high-carbohydrate diet were compared. Blood samples and mixed meal tests were performed at the end of each dietary period to examine inflammation markers and postprandial endotoxemia. Jejunal biopsies were assessed for protein expression using Western blotting, immunohistochemistry, and morphometric characteristics of tight junctions by electron microscopy. Functional analyses of permeability and ketogenesis were performed in Caco-2 cells, mice, and human enteroids. Ussing chambers were used to analyze permeability. CRP and ALP values were within normal ranges and postprandial endotoxemia levels were low and did not differ between the two diets. The PPAR alpha receptor was ketone body-dependently reduced after HFD. None of the tight junction proteins studied, nor the basal electrical parameters, were different between the two diets. However, the ketone body inhibitor hymeglusin increased resistance in mucosal biopsies. In addition, the tight junction protein claudin-3 was increased by ketone inhibition in human enteroids. The ketone body beta-Hydroxybutyrate (beta HB) did not, however, change the mucosal transition of the large-size molecular FD4-probe or LPS in Caco-2 and mouse experiments. We found that PPAR alpha expression was inhibited by the ketone body beta HB. As PPAR alpha regulates HMGCS expression, the ketone bodies thus exert negative feedback signaling on their own production. Furthermore, ketone bodies were involved in the regulation of permeability on intestinal mucosal cells in vitro and ex vivo. We were not, however, able to reproduce these effects on intestinal permeability in vivo in humans when comparing two weeks of high-fat with high-carbohydrate diet in healthy volunteers. Further, neither the expression of inflammation markers nor the aggregate tight junction proteins were changed. Thus, it seems that not only HFD but also other factors are needed to permit increased intestinal permeability in vivo. This indicates that the healthy gut can adapt to extremes of macro-nutrients and increased levels of intestinally produced ketone bodies, at least during a shorter dietary challenge.
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| 9. |
- Casselbrant, Anna, 1970, et al.
(author)
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Morphological Adaptation in the Jejunal Mucosa after Iso-Caloric High-Fat versus High-Carbohydrate Diets in Healthy Volunteers: Data from a Randomized Crossover Study
- 2022
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In: Nutrients. - : MDPI AG. - 2072-6643. ; 14:19
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Journal article (peer-reviewed)abstract
- Background and aims: The conditions for jejunal glucose absorption in healthy subjects have not been thoroughly studied. In this study we investigated differences in the jejunal villi enlargement factor, as well as ultrastructural aspects of the surface enterocytes and mitochondria, comparing 2 weeks of high-carbohydrate (HCD) versus high-fat diets (HFD). We also measured the ketogenesis rate-limiting enzyme 3-hydroxy-3-methylglutaryl-CoA synthase (HMGCS2) in relation to jejunal mitochondria. Methods: A single-centre, randomized, unblinded crossover study in 15 healthy volunteers ingesting strictly controlled equicaloric diets (either HCD or HFD), with 60% energy from the respective source. An enteroscopy was carried out after 2 weeks of each diet and jejunal mucosal biopsies were acquired. Conventional histology, immunofluorescent staining, transmission electron microscopy and confocal microscopy were used. Results: The villi did not demonstrate any change in the epithelial enlargement factor. Despite an increased mitosis, there were no changes in apoptotic indices. However, the ultrastructural analysis demonstrated a significant increase in the enlargement factor at the bases of the villi. The mitochondria demonstrated increased amounts of cristae after the HFD. The confocal microscopy revealed increased HMGCS2 per mitochondrial marker at the top of the villi after the HFD compared to the HCD. Conclusion: There is a morphometric adaption in the jejunal mucosa following the 2-week diets, not only on a histological level, but rather on the ultrastructural level. This study supports the notion that mitochondrial HMGCS2 is regulated by the fat content of the diet and is involved in the expression of monosaccharide transporters.
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| 10. |
- Cervin, Jakob, et al.
(author)
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GM1 ganglioside-independent intoxication by Cholera toxin
- 2018
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In: PLoS Pathogens. - : Public Library of Science (PLoS). - 1553-7366 .- 1553-7374. ; 14:2
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Journal article (peer-reviewed)abstract
- Cholera toxin (CT) enters and intoxicates host cells after binding cell surface receptors via its B subunit (CTB). We have recently shown that in addition to the previously described binding partner ganglioside GM1, CTB binds to fucosylated proteins. Using flow cytometric analysis of primary human jejunal epithelial cells and granulocytes, we now show that CTB binding correlates with expression of the fucosylated Lewis X (LeX) glycan. This binding is competitively blocked by fucosylated oligosaccharides and fucose-binding lectins. CTB binds the LeX glycan in vitro when this moiety is linked to proteins but not to ceramides, and this binding can be blocked by mAb to LeX. Inhibition of glycosphingolipid synthesis or sialylation in GM1-deficient C6 rat glioma cells results in sensitization to CT-mediated intoxication. Finally, CT gavage produces an intact diarrheal response in knockout mice lacking GM1 even after additional reduction of glycosphingolipids. Hence our results show that CT can induce toxicity in the absence of GM1 and support a role for host glycoproteins in CT intoxication. These findings open up new avenues for therapies to block CT action and for design of detoxified enterotoxin-based adjuvants.
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