Armin Raible

Critical role of NF-κB and stress-activated protein kinases in steroid unresponsiveness

Glucocorticoid resistance is a serious clinical problem in chronic inflammatory diseases, because many patients with rheumatoid arthritis, asthma, or Crohns disease fail to respond to steroid treatment. The molecular mechanisms underlying this unresponsiveness, however, are completely unknown. The effects of steroids are largely mediated by the interference of the glucocorticoid receptor (GR) with proinflammatory transcription factors. In the present study, we therefore investigated the activation of the transcription factors nuclear factor‐κB (NF‐κB), activator protein‐1 (AP‐1), and the upstream kinases p38 and c‐Jun N‐terminal kinase (JNK) in steroid‐sensitive and steroid‐resistant patients with Crohns disease. We demonstrated that steroid‐sensitive and steroid‐resistant patients reveal a remarkably different cellular activation pattern of these proinflammatory mediators. In steroid‐sensitive patients, activation of NF‐κB, AP‐1, p38, and JNK was mainly found in lamina propria macrophages. In contrast, steroid‐ resistant patients revealed activation of all these mediators mostly in epithelial cells. The functional interference of the proinflammatory mediators with the glucocorticoid response was supported by reporter gene assays. Expression of NF‐κB and, interestingly, also JNK1 and p38 inhibited the activity of the GR. Thus, our results suggest that steroid resistance is associated with increased epithelial activation of stress‐activated protein kinases and NF‐κB, which might inhibit the anti‐inflammatory action of a limited number of GRs.

Is glutamine essential for the maintenance of intestinal function? A study in the isolated perfused rat small intestine

Abstract Glutamine has received considerable interest as a gut-targeted nutrient due to its proposed key role in the maintenance of intestinal structure and function. We used a preparation of isolated vascularly perfused rat small intestine to investigate whether glutamine is essential for the maintenance of intestinal function. When glutamine was available, arterial glutamine was extracted at 15±2%, and net uptake was –89±5 nmol min–1 g–1. Nitrogenous metabolites ammonia, alanine, and citrulline (41±7, 41±4, and 11±2 nmol min–1 g–1, respectively) were released into the venous perfusate, but only ammonia was also excreted into the lumen (36±3 nmol min–1 g–1). In the absence of exogenous glutamine alanine release was halved and that of citrulline and ammonia nullified. Additional inhibition of glutamine synthetase yielded the same results. In all cases variables of tissue function were fully maintained also in the absence of exogenous and/or endogenous glutamine. The inhibition of glutaminase/amidotransferase reactions, however, was accompanied by a reduction in glutamine consumption and a graded deterioration in tissue function. In conclusion, glutamine seems to be dispensable as a metabolic fuel to be fully oxidized by the mucosa. However, the inhibition of major glutamine consuming pathways was associated with impaired tissue function and viability. Therefore the role of intestinal glutamine metabolism seems to be threefold: (a) providing affluent amounts of nitrogen precursors for mucosal anabolic pathways to maintain intestinal structure and function, (b) feeding the liver with an optimal substrate mix, and (c) providing citrulline and thereby arginine for the whole organism.

Osteodensitometry of human heel bones by MR spin-echo imaging: Comparison with MR gradient-echo imaging and quantitative computed tomography

The aim of the study was to investigate whether quantitative magnetic resonance (MR) fast spin‐echo (FSE) imaging with moderate spatial resolution enables osteodensitometry in peripheral yellow bone marrow. Signal intensities in T1‐weighted FSE images from yellow bone marrow indicate the amount of adipose tissue per volume. The signal intensity in marrow regions with spongy bone was assessed and compared to signal intensity of pure fatty marrow (100%). Heel bones of 30 patients with suspected osteoporosis were analyzed and the FSE images were compared with results from parallel MR gradient‐echo (GE) imaging and quantitative computed tomography (QCT) examinations. High correlation was found between FSE imaging and QCT [r = 0.91 in the dorsal region of interest (ROI); r = 0.86 in ventral ROI]. Linear correlation coefficients between GE imaging and QCT were slightly lower in the dorsal part (r = –0.86) and considerably lower in the ventral part (r = –0.68). Correlation between the two MR techniques amounted to r = –0.72/–0.61 (dorsal/ventral). The high correlation between FSE imaging and bone mineral density (BMD) allows possible clinical applications of FSE imaging for diagnosis of osteoporosis. Further improvements of the accuracy using reference phantoms might be possible. J. Magn. Reson. Imaging 2001;14:147–155.

Effects of vascular or luminal administration and of simultaneous glucose availability on glutamine utilization by isolated rat small intestine

Abstract This study examined whether the route of glutamine administration and the simultaneous availability of glucose affect intestinal glutamine metabolism. We measured net substrate exchange rates of glutamine and its nitrogenous products in the isolated vascularly and luminally perfused rat small intestine (a) as a function of glutamine provision from either the vascular or the luminal or simultaneously from both sides and (b) as a function of simultaneous availability of glucose from various routes. When glutamine was provided from the lumen, only 19–32% of absorbed glutamine appeared intact in the venous effluent, but the release of metabolic products was 170±5 nmol N min–1 g–1. This measure of intestinal glutamine metabolism was unchanged when glutamine was available only in the vascular perfusate (164±6 nmol N min–1 g–1). It increased, however, to 271±14 nmol N min–1 g–1 (P<0.001) when glutamine was available simultaneously from both the luminal and the vascular perfusate. Glutamine consumption (–110±6 vs. –70±5 or –91±5 vs. –73±7 nmol min–1 g–1; P<0.05 each) and the production of citrulline (11.4±0.7 vs. 10.0±0.8 or 9.8±0.5 vs. 7.8±0.4 nmol min–1 g–1; P<0.05 each) or ammonia (124±7 vs. 88±4; P<0.01 or 78±4 vs. 68±5 nmol min–1 g–1) decreased when glucose (vascular or luminal perfusate) became available in addition to glutamine. We conclude that glutamine is utilized by the small intestine very efficiently regardless of the route of administration being enteral or parenteral. The two routes can be used interchangeably to provide the intestinal mucosa with glutamine. Glucose and glutamine may partially substitute each other, most likely for the purpose as a metabolic fuel.

Magnetic resonance osteodensitometry in human heel bones: correlation with quantitative computed tomography using different measuring parameters.

RATIONALE AND OBJECTIVES Density of trabecular bone structures in human heel bones was assessed by 3D magnetic resonance (MR) gradient echo imaging (GEI) with multiple echoes. Different spatial resolutions were applied to investigate the influence of the pixel size on signal characteristics in GEI and to find suitable measuring parameters for a maximum correlation between GEI and bone mineral density obtained by quantitative computed tomography (QCT). METHODS Thirty-five patients aged 31 to 65 years with suspected osteoporosis underwent MR and QCT examinations of the heel bones. The MR protocol included 3D GEI with three echo times (TE1 = 9.3, TE2 = 27.9, and TE3 = 46.5 ms) and isotropic pixel sizes of (0.6 mm)3, (1.2 mm)3, and (2.4 mm)3. Several subregions in the heel bones were analyzed. For determination of signal reduction with increasing TE, signal intensity ratios were calculated pixelwise from images with TE2/TE1 and TE3/TE1. RESULTS All examinations showed that the T2*-related signal decrease was more pronounced for lower spatial resolution. In the dorsal part of the heel bones, the correlation between signal ratios in GEI and QCT-based bone mineral density values was between r = -0.86 for a spatial resolution of (0.6 mm)3 and r = -0.73 for (2.4 mm)3. Areas with low trabecular density in the ventral part of the heel bones showed clearly lower correlation coefficients (-0.65 < r < -0.67). CONCLUSIONS Spatial resolution in 3D GEI clearly influences the T2*-related signal characteristics. Despite measuring different physical properties of spongy bone by GEI and QCT, a relatively high correlation between GEI with small pixel sizes and QCT was obtained in the dorsal part of the heel bones, but not in the ventral part with partly thickened trabeculae and irregular distribution. However, standardized measuring protocols with preferably small pixel sizes (as low as [0.6 mm]3) should be applied, and correlation curves must be determined, dependent on the actual bone marrow site, before clinical routine MR osteodensitometry becomes possible.

Relapsing pancreatitis due to a novel compound heterozygosity in the CFTR gene involving the second most common mutation in central and eastern europe [CFTRdele2,3(21 kb)]

A 43-year-old otherwise healthy female patient presented with mild pancreatitis. Her family history revealed that her only son had cystic fibrosis. Genotyping of the patient demonstrated CFTR compound heterozygosity CFTRdele2,3(21 kb) and R117H and wild type alleles of the poly-T-tract in intron 8 (7T/7T). No mutations were detected in the cationic pancreatic trypsinogen (PRSS1) and the pancreatic secretory trypsinogen inhibitor (SPINK1) genes. CFTRdele2,3(21 kb) has only been described in 2000 and is the second most frequent severe CFTR mutation after ΔF508 in central and eastern Europe. This haplotype should be included in the genetic panel when evaluating patients of central or eastern European genetic background for possible CFTR related pancreatitis.

Mystery or Misery? Primary Group A Streptococcal Peritonitis in Women: Case Report

Acute primary peritonitis in the absence of other comorbid conditions such as liver cirrhosis, immunosuppression, or nephrotic syndrome is a rare disorder in young adults. In women, ascending genital infections are thought to be a major pathogenic cause of this type of peritonitis. Pus was detected in the peritoneal cavity by abdominal paracentesis in a 27-year-old woman who had no predisposing features for severe peritonitis. Abdominal computed tomography showed perirectal edema. Laparotomy was performed, but no intra-abdominal focus of infection could be detected. The abdomen was irrigated via a subhepatic and retroperitoneal presacral approach, and broad-spectrum antibiotic therapy was started. Blood cultures revealed group A streptococci, usually a common cause of upper respiratory tract infections or erysipelas. Within a few days, the patient recovered completely and returned to normal life.

Glutamine-dependence of rat enterocyte functions as assessed in cell cultures

Glutamine has been shown to be of critical importance for various cell functions (1-5). A number of mammalian cells in culture including fibroblasts (6), HeLa cells (7) and other tumour cell lines exhibit a positive correlation between cell growth and glutamine support. Zetterberg (6) demonstrated the dependence on glutamine of DNA/ RNA replication and cell multiplication in fibroblasts. In non-proliferating cells, i.e. primary cell cultures, the importance of glutamine as an essential substrate has not yet been established. However, studies on cell differentiation are contradictory: Beaulieu (8) reported a permissive effect of glutamine on differentiation of foetal small intestine, whereas in Viallard’s study differentiation of a human colon cancer cell line occurred only in the absence of glutamine (9). Under physiological conditions, the small intestine exhibits a high net glutamine utilisation in many species, including man, exceeding that of all other organs measured (for review, see (10,ll)). Apart from its relevance as a metabolic fuel for intestinal epithelial cells, only few data are available on the glutamine-dependence of characteristic enterocyte functions (12-15). The experimental use of glutaminase as an anti-neoplastic agent resulted in a decrease of serum glutamine to undetectable levels and acute necrotising colitis as a severe side-effect (16). Conversely, glutamine exerted a beneficial effect on intestinal mucosa after TPN induced atrophy (17, 18) or methotrexate induced enterocolitis (19). We therefore investigated the glutamine dependence of various intestinal cell functions in shortterm cell cultures of freshly isolated differentiated enterocytes of adult rats.

LAPSG Society News

The LAPSG is a multidisciplinary group dedicated to the study of the biology, pathophysiology and disease of the endocrine and exocrine pancreas. In particular the fi elds of gastroenterology, endocrinology, oncology, surgery, pharmacology, cell and molecular biology, nutrition, immunology and epidemiology will receive attention. It is also the study group’s aim to enhance the communication among scientists from different areas (especially the fi elds of gastroenterology and endocrinology) who otherwise rarely meet. The means to achieve these goals will be meetings of the members, postgraduate courses, clinical-research workshops and symposia. Pancreatologists and those working in related areas that live and work in Latin America, and who have published at least once during the last 5 years, are warmly invited to join the LAPSG. Members of the LAPSG will automatically become members of the International Association of Pancreatology (IAP) and the European Pancreatic Club (EPC) and will get a free online and print subscription to the journal Pancreatology.