Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024523 (malabsorption)
 7,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hereditary defects in the renal handling of filtered NaCl and water have important implications for understanding the physiological mechanisms that enable the kidney to optimize the match between glomerular filtration rate and tubular reabsorption. Null mutations in the water channel aquaporin 1 (AQP1) or the Na/H exchanger NHE3, two major fluid transporters in the proximal tubule, are states in which a reduction in proximal fluid absorption is accompanied by proportionate decrements in glomerular filtration rate. Compensation of the transport defect by a reduction in filtered load is so efficient that clinically symptomatic Na losses are not observed in either AQPI or NHE3 deficiency. On the other hand, severe syndromes of salt wasting are caused by transport deficiencies in the thick ascending limb or the collecting duct, indicating that the severity of Na dysregulation is unrelated to the basal absorption of NaCl in a given nephron segment. Loss of function of the Na,K,2Cl-cotransporter (NKCC2) or of the epithelial Na channel (ENaC) reduces Na absorption in thick ascending limbs or collecting ducts. In these states, the increased delivery of Na to downstream segments is not monitored by a sensor linked to the site of filtrate formation. In the absence of adaptations in the filtered load, intrarenal compensation of a circumscribed NaCl malabsorption by adjustment of NaCl transport in other nephron segments is remarkably insufficient, particularly in the immature kidney of the newborn.
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PMID:NaCl transport deficiencies--hemodynamics to the rescue. 1078 41

Animals with induced or natural null mutations in renal NaCl and water transporter genes provide a powerful tool to study the physiological mechanisms that enable the kidney to optimize the match between glomerular filtration rate and tubular reabsorption. Deficiencies in the Na/H exchanger NHE3 and in the water channel aquaporin 1 (AQP1) cause reductions in proximal fluid absorption which are accompanied by proportionate decrements in glomerular filtration rate (GFR). Compensation of the transport defect by a reduction in filtered load is so efficient that clinically symptomatic Na losses are not observed in either NHE3 or AQP1 deficient animals. On the other hand, severe syndromes of salt wasting are caused by loss of function of the Na,K,2Cl-cotransporter (NKCC2) in the thick ascending limb, or of the epithelial Na channel (ENaC) the collecting duct indicating that the severity of Na dysregulation is unrelated to the basal absorption of NaCl in a given nephron segment. In these states, the increased delivery of Na to downstream segments is not monitored by a sensor linked to the site of filtrate formation. In the absence of adaptations in the filtered load intrarenal compensation of a circumscribed NaCl malabsorption by adjustment of NaCl transport in other nephron segments is sometimes insufficient, particularly in the immature kidney of the newborn.
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PMID:Sodium transport deficiency and sodium balance in gene-targeted mice. 1167 27

Liver X receptors (LXRs) alpha and beta are nuclear oxysterol receptors with a key role in cholesterol, triglyceride, and glucose metabolism. In LXRbeta(-/-) mice on a normal diet, there is a reduction in size of perigonadal fat pad and, on high-fat diet there is resistance to obesity. In the present study, we investigated the reason for the resistance of LXRbeta(-/-) mice to weight gain. In LXRbeta(-/-) mice we found pancreatic exocrine insufficiency with reduced serum levels of amylase and lipase, reduced proteolytic activity in feces, chronic inflammatory infiltration, and, in the ductal epithelium, an increased apoptosis without compensatory proliferation. Electron microscopy revealed ductal dilatation with intraductal laminar structures characteristic of cystic fibrosis. To investigate the relationship between LXRbeta and pancreatic secretion, we studied the expression of LXRbeta and the water channel, aquaporin-1 (AQP1), in the ductal epithelium of the pancreas. In WT mice, ductal epithelial cells expressed LXRbeta in the nuclei and AQP1 on the plasma membrane. In LXRbeta(-/-) mice neither LXRbeta nor AQP1 was detectable. Moreover, in WT mice the LXR agonist (T2320) increased AQP1 gene expression. These data demonstrate that in LXRbeta(-/-) mice dietary resistance to weight gain is caused by pancreatic insufficiency and that LXRbeta regulates pancreatic exocrine secretion through the control of AQP1 expression. Pancreatic exocrine insufficiency is the main cause of malabsorption syndrome responsible for weight loss in adults and growth failure in children. Several genes are known to be involved in the pathogenesis and susceptibility to pancreatic insufficiency. LXRbeta should be included in that list.
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PMID:Pancreatic exocrine insufficiency in LXRbeta-/- mice is associated with a reduction in aquaporin-1 expression. 1880 27