Nicotinamide phosphoribosyltransferase production in human spermatozoa is influenced by maturation stage.

High amounts of nicotinamide phosphoribosyltransferase (NAMPT) were found in human seminal plasma. This enzyme influences energy metabolism and apoptosis and is essential for the regulation of cellular nicotinamide adenine dinucleotide (NAD)+ levels in somatic cells. NAD+ is required as a co-substrate for dehydrogenases, which are potentially important for spermatogenesis. The functional significance of intra- and extracellular NAMPT in human reproduction, however, has not been defined yet. The objectives of the study were therefore to determine NAMPT protein expression in human spermatozoa and testes, the secretion of NAMPT by spermatozoa depending on their maturation stage and the impact of NAMPT enzymatic function on sperm viability, motility, fertilisation capacity and induction of apoptosis. Firstly, we detected NAMPT protein in different cell types of human testes. NAMPT protein was also detected in spermatozoa, with significantly higher amounts in immature than in mature ejaculated spermatozoa. Additionally, NAD+ levels were significantly higher in immature than in mature spermatozoa. Secondly, NAMPT was released into the supernatant of human spermatozoa, with significantly higher NAMPT levels in supernatant of immature spermatozoa compared with mature cells. Finally, the specific inhibition of the enzyme by FK866 did not influence motility, capacitation or apoptosis signalling. In summary, NAMPT is produced in human spermatozoa in a maturation-dependent manner.

The insulin-like growth factors in adipogenesis and obesity.

Adipose tissue has been recognized as a major target of growth hormone (GH) action. GH was shown to inhibit adipocyte differentiation but stimulated preadipocyte proliferation in vitro. GH acts directly via its receptor or via upregulating insulin-like growth factor (IGF)-I, which is a critical mediator of preadipocyte proliferation, differentiation, and survival. Results from clinical studies on GH treatment in patients with GH deficiency or GH insensitivity syndrome can be used to dissect GH and IGF as well as IGF-binding protein (IGFBP) actions in vivo. In this article, changes of the GH/IGF system during adipocyte differentiation in vitro as well as related signaling pathways and their impact on adipose tissue growth and function are discussed. Clinical considerations include the effects of GH and IGF-I on adipose tissue during treatment of GH deficiency, differences in the IGF system between visceral and subcutaneous adipose tissue depots as well as the recently emerging role for adipose tissue in the regulation of glucose homeostasis.

Leucocytes are a major source of circulating nicotinamide phosphoribosyltransferase (NAMPT)/pre-B cell colony (PBEF)/visfatin linking obesity and inflammation in humans.

AIMS/HYPOTHESIS: Nicotinamide phosphoribosyltransferase (NAMPT) is a multifunctional protein potentially involved in obesity and glucose metabolism. We systematically studied the association between circulating NAMPT, obesity, interventions and glucose metabolism and investigated potential underlying inflammatory mechanisms. METHODS: Fasting morning NAMPT serum levels were measured in cohorts of lean vs obese children, cohorts of intervention by lifestyle, exercise and bariatric surgery, and during an OGTT. In addition, mRNA expression, protein production and enzymatic activity of NAMPT were assessed from isolated leucocytes and subpopulations. RESULTS: Circulating NAMPT was significantly elevated in obese compared with lean children and declined after obesity interventions concomitantly with the decline in BMI, high-sensitivity C-reactive protein (hsCrP) and leucocyte counts. Circulating NAMPT significantly correlated with glucose metabolism and cardiovascular variables in univariate analyses, but only the association with glucose response during an OGTT was independent from BMI. We therefore assessed the NAMPT dynamic following an oral glucose load and found a significant decline of NAMPT levels to 77.0 ± 0.1% as a function of time, and insulin-to-glucose ratio during an OGTT in obese insulin-resistant adolescents. Circulating NAMPT was, however, most strongly associated with leucocyte counts (r = 0.46, p < 0.001). The leucocyte count itself determined significantly and independently from BMI insulin resistance in multiple regression analyses. We systematically evaluated NAMPT expression among several tissues and found that NAMPT was predominantly expressed in leucocytes. In subsequent analyses of leucocyte subpopulations, we identified higher NAMPT protein concentrations in lysates of granulocytes and monocytes compared with lymphocytes, whereas granulocytes secreted highest amounts of NAMPT protein into cell culture supernatant fractions. We confirmed nicotinamide mononucleotide enzymatic activity of NAMPT in all lysates and supernatant fractions. In monocytes, NAMPT release was significantly stimulated by lipopolysaccharide (LPS) exposure. CONCLUSIONS: Leucocytes are a major source of enzymatically active NAMPT, which may serve as a biomarker or even mediator linking obesity, inflammation and insulin resistance.

Nicotinamide phosphoribosyltransferase (NAMPT/PBEF/visfatin) is constitutively released from human hepatocytes.

Circulating NAMPT (PBEF/visfatin) has pleiotropic functions and is secreted from adipocytes. Since it is doubtful whether serum levels can be explained by secretion from adipocytes alone, we asked whether hepatocytes are also able to liberate NAMPT. Using HepG2 cells and primary rat and human hepatocytes, release of NAMPT into the cell culture supernatant was found to occur constitutively in a time-dependent manner. In primary human hepatocytes, secretion within 24h was far higher than the cellular content, but was neither influenced by inhibitors of secretion nor by glucose, insulin or TNFalpha. As determined by size exclusion chromatography, HepG2 lysates and supernatants primarily contained the dimeric form of NAMPT which exhibited similar in vitro specific enzymatic activity. In primary human hepatocytes, secreted NAMPT was less active. Our results demonstrate that human hepatocytes are a potential source of circulating NAMPT.

Glucose regulates expression of the nerve growth factor (NGF) receptors TrkA and p75NTR in rat islets and INS-1E beta-cells.

BACKGROUND: The function and survival of pancreatic beta-cells strongly depend on glucose concentration and on autocrine secretion of peptide growth factors. NGF and its specific receptors TrkA and p75NTR play a pivotal role in islet survival and glucose-dependent insulin secretion. We therefore investigated whether or not glucose concentration influences expression of TrkA and p75NTR in rat islets and in INS-1E beta-cells at the mRNA and protein level (INS-1E). METHODS: Gene expression of the NGF receptors TrkA and p75NTR but also of the metabolic gene liver-type pyruvate kinase (L-PK) and the neurotrophin receptors TrkB and TrkC was studied by semi-quantitative PCR and by real-time PCR in islets and INS-1E beta-cells. RESULTS: In rat islets, high glucose exposure (25 mmol/l) increased gene expression of TrkA, p75NTR and L-PK. Expression of TrkA, p75NTR and L-PK reflected insulin secretion at the respective glucose concentration. In rat INS-1E insulinoma cells, expression of L-PK and p75NTR was suppressed by low glucose as in the islets, while expression of TrkA was strongly increased by low glucose levels and thus was regulated differently than in islets. Expression of TrkB and TrkC was not regulated by glucose concentration at all. TrkA protein was regulated in the same fashion as its mRNA expression, while p75NTR protein was not significantly regulated within 24 h. CONCLUSION: Glucose interacts with gene expression of TrkA and p75NTR that are strongly involved in beta-cell growth and glucose-dependent insulin secretion. The fact that TrkA expression is regulated the opposite way in islets and in INS-1E beta-cells might reflect their specific grade of differentiation and tendency to proliferate.

Glucose concentration and AMP-dependent kinase activation regulate expression of insulin receptor family members in rat islets and INS-1E beta cells.

AIMS/HYPOTHESIS: Glucose and the peptide growth factors insulin, IGF-I and IGF-II strongly regulate beta cell mass. Furthermore, beta cell expression of IGF-I receptor (Igf1r) and insulin receptor (Insr) is mandatory for several steps of insulin secretion. MATERIALS AND METHODS: We hypothesised that glucose concentration might regulate expression of Igf1r, Insr and insulin receptor-related receptor (Insrr) in islets and beta cells. Moreover, since the ratio of ATP:ADP is the most important intracellular mechanism involved in insulin secretion, and since depletion of ATP leads to AMP accumulation, we evaluated the role of AMP-activated protein kinase (AMPK) in glucose-dependent receptor regulation. RESULTS: In rat islets, high glucose exposure (25 mmol/l) increased gene expression of Igf1r, Insr and Insrr but also of the metabolic glycolysis gene liver-type pyruvate kinase (Pklr) compared with intermediate (6.2 mmol/l) or low glucose concentration (1.6 mmol/l) after 24 h. In rat INS-1E beta cells, only Pklr expression was suppressed by low glucose as in islets, while Insr and Insrr were suppressed by high and increased by low glucose levels. Igf1r expression was suppressed by both high- and low- glucose concentration. Activation of AMPK by 5-amino-imidazolecarboxamide riboside (AICAR, 0.5 mmol/l) suppressed Pklr expression, but strongly stimulated gene expression of Igf1r, Insr and Insrr. Protein expression of IR and IGF-IR reflected glucose and AICAR-regulated mRNA expression of both receptors in INS-1E cells. CONCLUSIONS/INTERPRETATION: We conclude that glucose directly interacts with islet and beta cell expression of growth factor receptors that are mandatory for both beta cell growth and insulin secretion. Stimulation of Igf1r and Insr gene expression by the AMPK-activator AICAR might indicate involvement of AMPK in the regulation of Igf1r, Insr and Insrr expression in beta cells.

[Innovative course concept for small group teaching in clinical methods. Results of a longitudinal, 2-cohort study in the setting of the medical didactic pilot project in Dusseldorf]. / Innovative Kurskonzepte für Kleingruppenpraktika in bildgebenden Verfahren. Ergebnisse einer Längsschnitt-2-Kohorten-Studie im Rahmen des medizindidaktischen Pilotprojektes Düsseldorf.

BACKGROUND AND OBJECTIVE: Medical students in Germany often criticize the anonymous and not practice-orientated way they are taught. It was the aim of this study to develop, try out and evaluate cost-effectiveness of practice-oriented interdisciplinary teaching in small groups. PATIENTS AND METHODS: The study was based on ca. 300 medical students/year, a practicable number in relation the average annual total intake by German medical schools. Between 1995 and 1998, 300 medical students annually, chosen by lot, were offered voluntary additional teaching of imaging methods (computed tomography, endoscopy and sonography), from a total of 2485 students (1276 females, 1209 males; mean age 25.8 years), the reminder serving as controls. After lecture-demonstration to all, the selected small groups were separately taught. They performed sonography on each other in small cohorts of 5 or they practised endoscopies on phantom models under supervision of a student tutor. In addition, lecturers circulated among the groups to answer additional questions and provide further help. All participants evaluated the course concept and the instructors on a questionnaire provided by the interdisciplinary centre for tertiary education. The effects of teaching on the participants were tested by a practical test in the form of an objective structured clinical examination (OSCE). RESULTS: Ca. 80% of course participants reached the intended aim and passed the OSCE examination. They gave the instructions in the pilot project highest marks, in all its criteria nearly one mark higher than those of other evaluated teaching sessions. Pre-clinical students judged the programme even more favourably than those in their clinical years. The additional cost incurred was moderately low at ca. DM 67 per year per student. CONCLUSION: Modern practice-oriented small group teaching will provide high quality results even with large numbers of students. The concept has already been taken over by other medical faculties.

Abscess formation in desmoid tumors of Gardner's syndrome and percutaneous drainage: a report of three cases.

PURPOSE: To describe abscess formation complications in desmoid tumors of patients with Gardner's syndrome and percutaneous drainage. METHODS: Three patients with Gardner's syndrome and intramesenteric desmoid tumors were diagnosed as having intratumor abscess formation. Percutaneous drainage was the initial method of treatment in each case. Two subsequently underwent surgical resection and one patient refused surgery and was lost to follow-up. RESULTS: In each case, percutaneous drainage and antibiotics resulted in clinical improvement. In two, fistulous communication with the small bowel could be demonstrated, presumed to be the cause of abscess formation. Surgical resection confirmed fistula communication to the small bowel. In the third patient, no fistula was seen and only percutaneous drainage was performed. CONCLUSION: Abdominal pain and fever in patients with Gardner's syndrome and desmoids is suggestive of abscess formation in these tumors. Percutaneous drainage is useful as initial management.

Intrahepatic gas formation without abscess after hepatic artery thrombosis in the setting of liver transplantation.

We present a case in which intraparenchymal hepatic gas was observed in the absence of an abscess. This occurred following hepatic artery thrombosis in the setting of liver transplantation. An analogy is drawn to the postinfarction syndrome seen following therapeutic embolization and intrauterine fetal death. The unique features of the liver transplant and how they relate to the mechanisms of gas formation are discussed.

CT manifestations of infectious mononucleosis.

A case of infectious mononucleosis (IM) which, on computed tomography (CT) scan, mimicked the morphologic features of lymphoma is reported. The CT findings in this case include generalized lymphadenopathy, splenomegaly, and focal low-attenuation splenic lesions in a fifty-three year old woman; these findings have not previously been described in patients with IM. This is most likely because IM is usually a clinical diagnosis confirmed by serologic testing. Imaging modalities such as CT scan have not routinely been utilized to support this diagnosis.