Rare genetic diseases with human lean and/or starvation phenotype open new avenues for obesity and type II diabetes treatment.

Treatments of obesity and type II diabetes target often gene functions involved in appetite-satiety, fat and carbohydrate metabolism or thermogenesis. None of these, have provided efficient drug therapy due to a large number of genes involved in weight and energy management, the redundancy of biochemical pathways and the environmental factors. Here I discuss a new approach based on studies of genes/proteins that are associated with human "lean or starvation" phenotype that became very rare in the course of evolution. This approach has led to the identification of the congenital enteropeptidase deficiency gene and the Anderson's Disease gene as a potential targets for obesity and type II diabetes treatment. The advantages of these targets are: 1) they are expressed exclusively in the intestine; 2) they are peripheral targets as opposed to systemic targets; 3) they are not redundant targets. These targets open new hopes for the development of novel drugs for the treatment of common metabolic syndrome.

Enteropeptidase, a type II transmembrane serine protease.

Enteropeptidase, a type II transmembrane serine protease, is localized to the brush border of the duodenal and jejunal mucosa. It is synthesized as a zymogen (proenteropeptidase) that requires activation by another protease, either trypsin or possibly duodenase. Active enteropeptidase then converts the pancreatic precursor, trypsinogen, to trypsin by cleavage of the specific trypsinogen activation peptide, Asp-Asp-Asp-Asp-Lys- Ile that is highly conserved in vertebrates. Trypsin, in turn, activates other digestive zymogens such as chymotrypsinogen, proelastase, procarboxypeptidase and prolipase in the lumen of the gut. The important biological function of enteropeptidase is highlighted by the manifestation of severe diarrhea, failure to thrive, hypoproteinemia and edema as a result of congenital deficiency of enteropeptidase activity in the gut. Conversely, duodenopancreatic reflux of proteolytically active enteropeptidase may cause acute and chronic pancreatitis.

Enterokinase.

Enterokinase is a glycoprotein and is now designated enteropeptidase (E.C.3.4.4.8.). It is present in the duodenal and jejunal mucosa. Pancreatic proteolytic enzymes are secreted as proenzymes. Enterokinase converts trypsinogen to trypsin in the duodenal lumen. Duodenopancreatic reflux of duodenal enterokinase may be important in the pathogenesis of experimental and clinical acute pancreatitis. Congenital enterokinase deficiency is a distinct clinical entity characterized by diarrhea, failure to thrive, hypoproteinemia, and edema. Acquired enterokinase deficiency may occur in some diffuse small bowel diseases. Steatorrhea of celiac spruce may be due partly to the fact that deficiency of secretin and cholecystokinin may interfere with the action of enterokinase. The interrelationship between secretin, cholecystokinin, enterokinase, and bile salts is not completely understood.

Isolated congenital enterokinase deficiency. Recent findings and review of the literature.

We report a 13-mo-old patient with isolated congenital enterokinase deficiency and review the clinical features, diagnostic approach, and management of all 8 reported patients. Our patient presented with failure to thrive, diarrhea, and hypoproteinemia since birth. A normal sweat chloride with small intestinal histology, and nondetectable trypsin activity in the duodenal fluid should alert the physician to the possibility of isolated enterokinase deficiency. All reported patients, including our own, responded favorably to pancreatic enzyme replacement. In vitro studies of the small intestinal mucosal biopsy specimen suggest that enterokinase deficiency at least in part is due to altered enzymes with low enterokinase activity.

Primary intestinal enteropeptidase deficiency.

A rare case of primary enteropeptidase deficiency is reported. Details are given of the initial clinical presentation, treatment, and response of the patient from birth to the age of 18 months. Biochemical analysis of a small intestinal biopsy and duodenal juice samples confirmed the total absence of enteropeptidase activity. Proteolytic activity was very low in native duodenal juice, but normal levels could be induced by activation in vitro with a small amount of porcine enteropeptidase.

[Malnutrition in congenital deficiency of enterokynase (author's transl)]. / Malnutrición proteico-calórica por déficit de enterokinasa.

A case of Congenital deficiency of Enterokynase is presented. The main clinical findings are: Chronic diarrhea, malnutrition and edema. Diagnosis was made by determination of tripsine activity in duodenal juice before and later to confront it to Enterokynase. The patient was treated with pancreatic supplements and protein hidrolysate with favourable results.

Arrhythmogenic right ventricular dysplasia in a child with congenital enteropeptidase deficiency and hypogammaglobulinaemia.

A case of arrhythmogenic right ventricular dysplasia in a 10 year old girl is described which provides some evidence for an inherited aetiology of this unusual form of heart disease. The parents of this child were first cousins, thus increasing the possibility of inherited disorders in their offspring. She had been known from infancy to have the rare disorder of congenital deficiency of intestinal enteropeptidase, and low serum immunoglobulins G and A. An untyped adenovirus was grown from a myocardial biopsy taken early in the course of her cardiac disease. However, it is unlikely that this virus was a major factor in the aetiology of her cardiac disease. Both the cardiac and intestinal diseases are now commonly believed to result from hereditary factors, and this report provides further support for this view.

[Diagnostic strategy in diarrhea]. / Diagnostische Strategie bei Diarrhoen

Planning the strategy in diagnosis of diarrhea some questions need to be answered: 1. Do the complaints in question fulfill the defined criteria of diarrhea? 2. Is it an acute diarrhea of infectious origin requiring fast microbiologic diagnosis? 3. Is it a chronic diarrhea? A) Do anamnestic findings and present status induce a certain suspected diagnosis, as in hyperthyreoidism, drugs, intestinal resections? B) Is a complete stepwise diagnostic planning needed as in Crohn's disease, insufficiency of the pancreas, non tropical sprue? Diagnostic measures have to be taken into consideration according to the answers given.

Intestinal enterokinase deficiency.

Deficiency of intestinal enterokinase results in failure to thrive, diarrhoea, anaemia, hypoproteinaemia and oedema. A case arising in the neonatal period is described, in which several of the characteristic features were lacking. Difficulties encountered in the diagnosis and methods of assay are discussed.

The role of enteropeptidase in the digestion of protein and its development in human fetal small intestine.

Enteropeptidase converts trypsinogen into active trypsin, which not only hydrolyses some peptide bonds of food proteins but also activates a number of pancreatic zymogens. For this reason enteropeptidase is a key enzyme in the digestion of dietary proteins and its absence may result in gross protein malabsorption.

Celiac disease in a patient with a congenital deficiency of intestinal enteropeptidase.

We report on a 40-yr-old man with both primary enteropeptidase deficiency and celiac disease. He suffered from severe intestinal malabsorption and growth failure as a child. Enteropeptidase deficiency was found and pancreatic enzyme replacement therapy resulted in a growth spurt. Enteropeptidase levels in his intestinal mucosa and intraluminal fluid remained very low throughout childhood and early adult life. Celiac disease was confirmed by characteristic abnormalities in tests of intestinal function and in mucosal biopsies, which recovered when he instituted a gluten-free diet. He remains clinically intolerant to gluten as an adult. Enteropeptidase levels have remained abnormally low whether or not his intestinal mucosa has been normal in response to gluten restriction. Enteropeptidase levels have previously been shown to be normal in untreated celiac patients. The relationship between the two disorders remains unclear.

[Exocrine pancreatic insufficiency (author's transl)]. / Klinik der exokrinen Pankreasinsuffizienz.

Exocrine pancreatic insufficiency usually does not develop before reduction of enzyme output by more than 90%. Patients with pancreatic insufficiency have a ravenous appetite but fail to thrive from malnutrition. The caloric deprivation is primarily due to fat malabsorption, recognized by the passage of bulky foul smelling greasy stools. Several isolated enzyme deficiencies can be separated from diseases with generalised pancreatic insufficiency. Under replacement therapy with pancreatic enzyme supplements most patients improve and gain weight, although fat and bile acid malabsorption are not abolished.

Clinical significance of enzymatic deficiencies in the gastrointestinal tract with particular reference to lactase deficiency.

The study of deficiencies of small intestinal brush-border hydrolases increased our knowledge about the specific functions of hydrolases in the digestion of smaller molecules on the microvillus surface of the absorptive cells. The sucrase-isomaltase (SI) complex has been shown to be synthesized as a precursor (pro-sucrase-isomaltase) which is then incorporated into the membrane. The hydrophobic N-terminal end of the molecule is anchored in the lipid bilayer. In SI deficiency the molecular base of the disease is still not clear. Absence of SI activity could be due to complete lack of precursor synthesis or to structural changes within the N-terminal end of the SI-complex. Deficiencies of peptide hydrolases have not been reported with the exception of enteropeptidase (EP). Here a congenital deficiency of the enzyme was observed as the primary defect in enzyme synthesis within the enterocytes and as a secondary defect due to exocrine pancreatic insufficiency. In contrast to the primary EP deficiency, the activity of EP can be restored in the cases of exocrine pancreatic insufficiency by treatment with pancreatic extracts. Primary lactase deficiency exists in various forms. Besides congenital lactase deficiency, the late onset or adult type of lactase deficiency has been observed. The latter occurs in many different ethnic groups around the world. Here, using gel electrophoresis and immunoelectrophoresis, the lack of enzyme activity could be shown to be a primary defect in enzyme protein synthesis. In man and in the rat, two different lactases have been identified. In contrast to adult lactase, fetal lactase contains sialic acid at the end of carbohydrate side chains.(ABSTRACT TRUNCATED AT 250 WORDS)

Intestinal enterokinase deficiency. Occurrence in two sibs and age dependency of clinical expression.

Intestinal enterokinase deficiency in 2 sibs in described. A boy failed to gain weight and had vomiting, diarrhoea, oedema, hypoproteinaemia, and anaemia in early infancy. His duodenal juice contained very low or absent proteolytic enzyme activity, which increased markedly after addition of enterokinase. He was treated with pancreatic extract and gained weight rapidly. At 44 months of age he is normal, apart from some development delay, and no longer needs pancreatic extract. His older sister, who had had similar symptoms in early infancy but then grew normally, had the same abnormality in her duodenal juice when seen at 4 years of age. Enterokinase activity was virtually absent in the duodenal mucosa of both patients. Mucosal morphology was normal. The findings suggest that enterokinase deficiency is an inherited congenital defect and not the result of mucosal damage. Affected patients may show spontaneous improvement and normal growth after the age of 6 to 12 months. This phenomenon may be related to the decreasing growth volocity during the first 2 years of life and the concimitant decrease in protein requirements per unit bodyweight.