The glucose-lowering effects of the PDE4 inhibitors roflumilast and roflumilast-N-oxide in db/db mice.

AIMS/HYPOTHESIS: The cAMP-degrading phosphodiesterase 4 (PDE4) enzyme has recently been implicated in the regulation of glucagon-like peptide-1 (GLP-1), an incretin hormone with glucose-lowering properties. We investigated whether the PDE4 inhibitor roflumilast elevates GLP-1 levels in diabetic db/db mice and whether this elevation is accompanied by glucose-lowering effects. METHODS: Plasma GLP-1 was determined in db/db mice after single oral administration of roflumilast or its active metabolite roflumilast-N-oxide. Diabetes-relevant variables including HbA(1c), blood glucose, serum insulin, body weight, food and water intake, and pancreas morphology were determined in db/db mice treated daily for 28 days with roflumilast or roflumilast-N-oxide. Pharmacokinetic/pharmacodynamic analysis clarified the contribution of roflumilast vs its metabolite. In addition, the effect of roflumilast-N-oxide on insulin release was investigated in primary mouse islets. RESULTS: Single treatment of db/db mice with 10 mg/kg roflumilast or roflumilast-N-oxide enhanced plasma GLP-1 2.5- and fourfold, respectively. Chronic treatment of db/db mice with roflumilast or roflumilast-N-oxide at 3 mg/kg showed prevention of disease progression. Roflumilast-N-oxide abolished the increase in blood glucose, reduced the increment in HbA(1c) by 50% and doubled fasted serum insulin compared with vehicle, concomitant with preservation of pancreatic islet morphology. Furthermore, roflumilast-N-oxide amplified forskolin-induced insulin release in primary islets. Roflumilast-N-oxide showed stronger glucose-lowering effects than its parent compound, consistent with its greater effect on GLP-1 secretion and explainable by pharmacokinetic/pharmacodynamic modelling. CONCLUSIONS/INTERPRETATION: Our results suggest that roflumilast and roflumilast-N-oxide delay the progression of diabetes in db/db mice through protection of pancreatic islet physiology potentially involving GLP-1 and insulin activities.

[The primary structure of the Bence-Jones protein Kue. The amino acid sequence of the variable part of a human L-chain of the kappa-type (author's transl)]. / Die Primärstruktur des Bence-Jones-Proteins Kue Aminosäuresequenz des variablen Abschnitts einer humanen L-Kette vom kappa-Typ.

The complete primary structure of the variable region of Bence-Jones protein Kue was elucitated with the aid of a few tryptic peptides, as well as one chymotryptic and one BNPS-scatol fragment. As a consequence of the evident homologies to other proteins this protein belongs to subgroup k/I. Protein Kue has some amino acid exchanges in certain positions in common with other proteins, probably giving rise to a new sub-subgroup. The constant region shows no amino acid exchanges in comparison with other human kappa L-chains. With valine covering position 191, protein Kue should be grouped per definition as an allotype Km (3).

[HbM Erlangen: alpha2beta263(e7) tyr. New mutation with haemolysis and NADH-methaemoglobin reductase deficiency (author's transl)]. / HbM Erlangen: alpha2beta263 (E7) Tyr. Eine neue Mutation mit Hämolyse und Diaphorasemangel

Report on a further hemoglobin M variant, discovered in a boy with congenital cyanosis. Chemical analysis of hemoglobin structure revealed indentity with HbM Saskatoon (= beta63 His leads to Tyr). The abnormal hemoglobin is characterized by normal oxygen transport function. The observed slight constant hemolysis is thought to be due to increased instability of the abnormal hemoglobin molecule. In addition to the hemoglobin anomaly, the activity of NADH-methemoglobin reductase was reduced by approximately 40% of normal. None of the parents presented with an abnormal hemoglobin, indicating that the occurrence of hemoglobin M Erlangen is most likely the result of a new mutation.