Paneth cells in intestinal physiology and pathophysiology

Small intestinal mucosa is characterised by villus forming connective tissues with highly specialised surface lining epithelial cells essentially contributing to the establishment of the intestinal border.In order to perform these diverse functions,spatially distinct compartments of epithelial differentiation are found along the crypt-villus axis,including Paneth cells as a highly specialised cell type.Paneth cells locate in crypts and assist undifferentiated columnar cells,called crypt base columnar cells,and rapidly amplifying cells in the regeneration of absorptive and secretory cell types.There is some evidence that Paneth cells are involved in the configuration and function of the stem cell zone as well as intestinal morphogenesis and crypt fission.However,the flow of Paneth cells to crypt bottoms requires strong Wnt signalling guided by EphB3 and partially antagonised by Notch.In addition,mature Paneth cells are essential for the production and secretion of antimicrobial peptides including α-defensins/cryptdins.These antimicrobials are physiologically involved in shaping the composition of the microbiome.The autophagy related 16-like 1(ATG16L1) is a genetic risk factor and is involved in the exocytosis pathway of Paneth cells as well as a linker molecule to PPAR signalling and lipid metabolism.There is evidence that injuries of Paneth cells are involved in the etiopathogenesis of different intestinal diseases.The review provides an overview of the key points of Paneth cell activities in intestinal physiology and pathophysiology.     

Fatty acid binding receptors in intestinal physiology and pathophysiology

Free fatty acids are essential dietary components and recognized as important molecules in the maintenance of cellular homeostasis. In the last decade, the molecular pathways for free fatty acid sensing in the gastrointestinal tract have been further elucidated by molecular identification and functional characterization of fatty acid binding receptors. These sensing molecules belong to the family of G protein-coupled receptors. In the intestine, four important receptors have been described so far. They differ in molecular structure, ligand specificity, expression pattern, and functional properties. In this review, an overview of intestinal fatty acid binding receptors and their role in intestinal physiology and pathophysiology is given.     

Vasoactive intestinal polypeptide in the respiratory tract: physiology and pathophysiology

Peptidergic neuromediators have gained importance in the field of respiratory physiology and pathophysiology due to the characterisation of numerous pulmonary effects in the past years. With regard to the multitude of mediators, the neuropeptide vasoactive intestinale polypeptide (VIP) plays a special role as it exerts potent anti-inflammatory and immunomodulatory effects. Neurophysiologically the peptide has been attributed to the family of the inhibitory non-adrenergic non-cholinergic (i-NANC) neuromediators of the pulmonary innervation. VIP-containing nerve fibres are localized in the airway and vascular smooth muscle layers of trachea and bronchi in the human respiratory tract. Apart from strong vasodilatory effects, the peptide also shows a high bronchodilatory potency. In a large number of respiratory diseases VIP may play a pathophysiological role. In this respect, increased levels of VIP have been demonstrated for inflammatory diseases of the upper and lower airways and the peptide may also play a role in pulmonary hypertension. Due to its fast enzymatic cleavage, VIP-based therapies have not been used in routine therapy so far. Also, the use of synthetic VIP-agonists did not lead to an improved outcome in patients with bronchial asthma if compared to classical drugs. However, recent data from animal experiments indicate potent immunomodulatory effects which suggest a future use of this mediator and its agonists in the therapy of immune diseases.     

Purkinje physiology and pathophysiology

There has always been an appreciation of the role of Purkinje fibers in the fast conduction of the normal cardiac impulse. Here, we briefly update our knowledge of this important set of cardiac cells. We discuss the anatomy of a Purkinje fiber strand, the importance of longitudinal conduction within a strand, circus movement within a strand, conduction, and excitability properties of Purkinjes. At the cell level, we discuss the important components of the ion channel makeup in the nonremodeled Purkinjes of healthy hearts. Finally, we discuss the role of the Purkinjes in forming the heritable arrhythmogenic substrates such as long QT, heritable conduction slowing, CPVT, sQT, and Brugada syndromes.     

Blood vessel physiology and pathophysiology

The vascular system is complex, with functions in the active modulation of metabolic and hemodynamic processes as well as in transport. Vascular smooth muscle is the primary effector component of the vessel wall and is regulated in its activity by local endothelial cell and neural activity in addition to circulating substances. The vascular endothelial cell has only recently been fully recognized to possess a vast array of metabolic capabilities that are yet to be completely understood. Endothelial cell-derived vasoactive substances, their release, and interactions with blood constituents and vascular smooth muscle are new areas of clinical research which hold significant implications for the physiology and pathophysiology of blood vessels.     

Renal physiology and pathophysiology of aging

Aging is associated with significant changes in renal structure and function. Ability of many normal subjects to maintain stable renal function over long periods of time, however, suggests that decline in renal function with age observed in cross-sectional studies is related to the superimposition of disease, often undetected, rather than to any unrelenting involutional process common to aging individuals.     

Intestinal bile acid physiology and pathophysiology

Bile acids （BAs） have a long established role in fat di- gestion in the intestine by acting as tensioactives, due to their amphipatic characteristics. BAs are reabsorbed very efficiently by the intestinal epithelium and recycled back to the liver via transport mechanisms that have been largely elucidated. The transport and synthesis of BAs are tightly regulated in part by specific plasma membrane receptors and nuclear receptors. In addition to their primary effect, BAs have been claimed to play a role in gastrointestinal cancer, intestinal in- flammation and intestinal ionic transport. BAs are not equivalent in any of these biological activities, and structural requirements have been generally identified. In particular, some BAs may be useful for cancer chemoprevention and perhaps in inflammatory bowel disease, although further research is necessary in this field. This review covers the most recent developments in these aspects of BA intestinal biology.     

Aging and sleep: physiology and pathophysiology

Aging effects on sleep are important to consider for the practicing pulmonologist due to the increase in prevalence of major respiratory disorders as well as the normal changes that occur in sleep patterns with aging. Typically, aging is associated with decreases in the amount of slow wave sleep and increases in stage 1 and 2 non-rapid eye movement sleep, often attributed to an increased number of spontaneous arousals that occur in the elderly. Elderly individuals tend to go to sleep earlier in the evening and wake earlier due to a phase advance in their normal circadian sleep cycle. Furthermore the development of sleep-related respiratory disorders such as obstructive sleep apnea (OSA) and central sleep apnea or Cheyne-Stokes respiration (CSA-CSR) associated with congestive heart failure (CHF) occur with increasing prevalence in the elderly. The development of such disorders is often of major concern because they are associated with systemic hypertension and cardiovascular disease, metabolic disorders such as diabetes, and impaired neurocognition. The present review reflects the current understanding of the normal changes in sleep patterns and sleep needs with advancing age, in addition to the effect that aging has on the predisposition to and consequences of OSA and CSA-CSR associated with CHF.     

Rho kinases in cardiovascular physiology and pathophysiology

Rho kinases (ROCKs) are the first and the best-characterized effectors of the small G-protein RhoA. In addition to their effect on actin organization, or through this effect, ROCKs have been found to regulate a wide range of fundamental cell functions such as contraction, motility, proliferation, and apoptosis. Abnormal activation of the RhoA/ROCK pathway has been observed in major cardiovascular disorders such as atherosclerosis, restenosis, hypertension, pulmonary hypertension, and cardiac hypertrophy. This review, based on recent molecular, cellular, and animal studies, focuses on the current understanding of ROCK signaling and its roles in cardiovascular physiology and pathophysiology.     

New insights in growth hormone physiology and pathophysiology

This review focuses on new aspects in growth hormone (GH) biology and pathophysiology presented at the Endocrine Society's meeting, in San Diego, in June 2010. First, we will describe recent advances in the understanding of cytokine hormone signaling via STAT5 in mammary gland development, highlighting the primary role of miR193b for differentiation of mammary stem cells into alveolar progenitor cells. We will examine the potential implication of endocrine and autocrine GH for mammary gland carcinogenesis. Three novel murine models bearing tissue-specific inactivation of GH receptor or JAK2 bring new insights into the large spectrum of GH effects on energy homeostasis. We will also report new data supporting a paracrine regulation of GH secretion in women by estrogen's action in the brain. Thereafter we will question the reasons for GH abuse for doping by assessing the hormonal impact on body composition and physical performance in recreational athletes. Finally, we will discuss the controversial issue of GH replacement in acromegalic patients presenting GH deficiency after treatment of acromegaly.     

Complement factor H: physiology and pathophysiology.

The human plasma protein factor H, which is a multifunctional, multidomain protein, acts as a central regulator of the complement system. In addition to its complement regulatory activities, factor H has multiple physiological activities and 1) acts as an extracellular matrix component, 2) binds to cellular receptors of the integrin type, and 3) interacts with a wide selection of ligands, such as the C-reactive protein, thrombospondin, bone sialoprotein, osteopontin, and heparin. Recent genetic reports, which show involvement of factor H in the human disease hemolytic-uremic syndrome (HUS), have attracted the attention of both clinicians and basic complement researchers to the role of factor H in the pathophysiology of HUS.     

Molecular physiology and pathophysiology of lysosomal membrane transporters

Summary In contrast to lysosomal hydrolytic enzymes, the lysosomal membrane remains poorly characterized. In particular, although the genetic study of cystinosis and sialic acid storage disorders led to the identification of two lysosomal transporters for cystine and sialic acids, respectively, ten years ago, most transporters responsible for exporting lysosomal hydrolysis products to the cytosol are still unknown at the molecular level. However, two lines of investigation recently started to fill this gap in the knowledge of lysosomal biology. First, novel proteomic approaches are now able to provide a reliable inventory of lysosomal membrane proteins. On the other hand, a novel functional approach based on intracellular trafficking mechanisms allows direct transport measurement in whole cells by redirecting recombinant lysosomal transporters to the cell surface. After surveying the current state of knowledge in this field, the review focuses on the sialic acid transporter sialin and shows how recent functional data using the above whole-cell approach shed new light on the pathogenesis of sialic acid storage disorders by revealing the existence of a residual transport activity associated with Salla disease. Competing interests: None declared References to electronic databases: Cystinosis, OMIM 219800; Salla disease, OMIM 604369; infantile sialic acid storage disorder, OMIM 269920; cobalamin F disease, OMIM 277380; infantile malignant osteopetrosis, OMIM 259700; mucolipidosis type IV, OMIM 252650); Niemann–Pick disease type C1, OMIM 257220; juvenile neuronal ceroid-lipofuscinosis, OMIM 204200); late-infantile neuronal ceroid-lipofuscinosis, OMIM 610951). Presented at the Annual Symposium of the SSIEM, Hamburg, 4–7 September 2007.     

Secretion radioimmunoassay, physiology and pathophysiology in man

Production of antibodies to secretin for radioimmunoassay is straightforward. Secretion is iodinated by weak oxydation with lactoperoxydase and subsequent purification by ionexchange chromatography (Sephadex C25). The specific activity of fresh label is between 650 and 900 mCi . mol-6. The label is highly purified and may be used in radioimmunoassay for several months. In order to eliminate plasma interference sepharose-beads with covalently coupled secretin antibodies are used to produce secretin-free standard plasma samples. Delay in the separation of plasma from fresh blood samples can lead to erronous results, even to falsely elevated secretin levels.--Duodental acidification only leads to physiological increases of secretin plasma levels. This may happen by intraduodenal instillation of acid, or by an acidic oral drink, or to a lesser extent after a meal. Secretin is distributed throughout the plasmavolume and has a short halflife of around 3 minutes. Impaired release of secretion is found in children with coeliac disease. The role of secretin in peptic ulcer however is not clear. Chronic pancreatitis and renal insufficiency are without effect on plasma secretin levels.     

Incretin physiology and pathophysiology from an Asian perspective

Incretin hormones, such as glucose‐dependent insulinotropic polypeptide and glucagon‐like peptide‐1, are secreted on oral nutrient ingestion and regulate postprandial glucose homeostasis by conveying the signal of intestinal glucose flux. In East Asians, the secretion of glucose‐dependent insulinotropic polypeptide and glucagon‐like peptide‐1 is not reduced in type 2 diabetes relative to normal glucose tolerance. Although the incretin effect is blunted in European patients with type 2 diabetes, a few East Asian studies showed no difference in the incretin effect between type 2 diabetes and normal glucose tolerance. Interestingly, the glucose‐lowering efficacy of dipeptidyl peptidase‐4 inhibitors or glucagon‐like peptide‐1 receptor agonists was reported to be greater in Asians than in non‐Asians. The difference in the treatment responses could be ascribed to a different pathophysiology of type 2 diabetes (lower insulin secretory function and less insulin resistance), lower body mass index, different genetic makeups, preserved incretin effect and different food compositions in East Asians compared with other ethnic groups. Based on the currently available data, incretin‐based therapies appear to be safe and well tolerated in East Asians. Nevertheless, continuous pharmacovigilance is required. The characteristics of incretin biology and treatment responses to incretin‐based therapies should be considered in developing ethnicity‐specific treatment guidelines and making patient‐centered decisions for patients with type 2 diabetes.     

Pancreatic nociception – Revisiting the physiology and pathophysiology

BackgroundPain management of many pancreatic diseases remains a major clinical concern. This problem reflects our poor understanding of pain signaling from the pancreas.ObjectivesThis review provides an overview of our current knowledge, with emphasis on current pain management strategies and recent experimental findings.MethodsA systematic search of the scientific literature was carried out using EMBASE, PubMed/MEDLINE, and the Cochrane Central Register of Controlled Trials for the years 1965–2011 to obtain access to all publications, especially randomized controlled trials, systematic reviews, and meta-analyses exploring pain and its management in disease states such as acute pancreatitis (AP), chronic pancreatitis (CP) and pancreatic cancer (PC).ResultsOver the last decade, numerous molecular mediators such as nerve growth factor and the transient receptor potential (TRP) cation channel family have been implicated in afferent nerve signaling. More recent animal studies have indicated the location of the receptive fields for the afferent nerves in the pancreas and shown that these are activated by agents including cholecystokinin octapeptide, 5-hydroxytryptamine and bradykinin. Studies with PC specimens have shown that neuro-immune interactions occur and numerous agents including TRP cation channel V1, artemin and fractalkine have been implicated. Experimental studies in the clinical setting have demonstrated impairment of inhibitory pain modulation from supraspinal structures and implicated neuropathic pain mechanisms.ConclusionsOur knowledge in this area remains incomplete. Characterization of the mediators and receptors/ion channels on the sensory nerve terminals are required in order to facilitate the development of new pharmaceutical treatments for AP and CP.     

New advances in pancreatic cell physiology and pathophysiology

The mammalian pancreas originates from two developing buds on the dorsal and ventral side of the duodenum which fuse and convert into a single mixed gland, composed of exocrine and endocrine cells. In the adult organism, the exocrine pancreas consists of acinar and ductal cells which are organised in a lobular branched tissue architecture and secrete and transport digestive enzymes into the duodenum. Mature endocrine cells, which represent only 1-2% of the pancreatic organ volume, form aggregates of so called islets of Langerhans within the exocrine pancreatic tissue and control glucose homeostasis by secretion of glucagon, insulin and other hormones into the bloodstream. Pancreatitis is the most common and a potentially lethal disorder of the exocrine pancreas with limited therapeutic options. A major obstacle in the development of successful treatment strategies has, until today, been our limited knowledge of the disease pathophysiology. This review will summarise recent advances in our understanding of the physiological mechanisms involved in the early disease processes of the exocrine pancreas.     

Bile acids： Chemistry, physiology, and pathophysiology

The family of bile acids includes a group of molecular species of acidic steroids with very peculiar physicalchemical and biological characteristics. They are synthesized by the liver from cholesterol through several complementary pathways that are controlled by mechanisms involving fine-tuning by the levels of certain bile acid species. Although their best- known role is their participation in the digestion and absorption of fat, they also play an important role in several other physiological processes. Thus, genetic abnormalities accounting for alterations in their synthesis, biotransformation and/or transport may result in severe alterations, even leading to lethal situations for which the sole therapeutic option may be liver transplantation. Moreover, the increased levels of bile acids reached during cholestatic liver diseases are known to induce oxidative stress and apoptosis, resulting in damage to the liver parenchyma and, eventually, extrahepatic tissues. When this occurs during pregnancy, the outcome of gestation may be challenged. In contrast, the physical-chemical and biological properties of these compounds have been used as the bases for the development of drugs and as pharmaceutical tools for the delivery of active agents.     

HDL cholesterol: physiology, pathophysiology, and management

Numerous epidemiological studies have identified high-density lipoprotein cholesterol (HDL) to be an independent risk factor for coronary heart disease (CHD). HDL is an emerging therapeutic target that could rival the impact of 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase inhibitors (statins) on LDL and CHD risk reduction. HDL metabolism, HDL kinetics, the concentration of various HDL subclasses, and other genetic factors affecting HDL functionality may all contribute to the anti-atherogenic properties of HDL; thus, standard plasma measurement may not capture the full range of HDL effects. Algorithms have been suggested to treat low HDL levels in subgroups of patients; however, no formal HDL target goals or treatment guidelines have been implemented as there is a lack of strong clinical evidence to support effective pharmacologic therapy for primary risk reduction. Available therapies have a modest impact on serum HDL levels; however, emerging therapies could have a more significant influence.