Nobuo Kondo

Hypoglycaemic and insulinotropic effects of a novel oral antidiabetic agent, (−)-N-(trans-4-isopropylcyclohexane-carbonyl)-d-phenylalanine (A-4166)

(−)‐N‐(trans‐4‐isopropylcyclohexanecarbonyl)‐d‐phenylalanine (A‐4166), a novel oral hypoglycaemic agent is a non‐sulphonylurea insulin secretagogue. We investigated the insulin‐releasing action and hypoglycaemic effect of A‐4166 compared to sulphonylureas in vitro and in vivo. A‐4166 stimulated insulin secretion from rat freshly isolated pancreatic islets at concentrations from 3×10‐6m to 3×10‐4m in the presence of 2.8 mm glucose. There was no obvious difference in glucose dependency between the insulinotropic effect of A‐4166 and that of glibenclamide, and no additive or synergistic effect was observed between these two drugs. A‐4166 displaced [3H]‐glibenclamide bound to intact HIT‐T15 cells in a concentration‐dependent manner. The Ki value was 4.34±0.04×10−7m, and the displacement potency of A‐4166 was between that of glibenclamide and tolbutamide, being similar to that of gliclazide. In fasted beagle dogs, A‐4166 showed a dose‐dependent hypoglycaemic effect after oral administration over the range 1 to 10 mg kg−1. The hypoglycaemic action of A‐4166 showed an earlier onset and a shorter duration than that of sulphonylureas. Simultaneous measurement of plasma insulin levels revealed that the hypoglycaemic effect of A‐4166 was caused by a rapid‐onset and brief burst of insulin secretion. The pharmacokinetic profile of A‐4166 was consistent with the changes of the blood glucose and plasma insulin levels. Although the in vitro insulin‐releasing effect of A‐4166 was similar to that of sulphonylureas, its hypoglycaemic effect was more rapid and shorter‐lasting, associated with rapid absorption and clearance. Thus, A‐4166 may be useful in suppressing postprandial hyperglycaemia in patients with non‐insulin‐dependent diabetes mellitus.

Pyrazole-O-glucosides as novel Na+-glucose cotransporter (SGLT) inhibitors

O-glucuronides and O-glucosides of a series of pyrazoles analogues were synthesized and evaluated for their SGLT inhibitory activity in brush border membrane vehicles (BBMVs) of rat kidney. O-glucosides of certain pyrazole analogues inhibited the transport of [(14)C]-glucose in BBMVs, and induced glucosuria in Wistar rats by intravenous injection.

A soluble ’anchorminus‘ interleukin 2 receptor suppresses in vitro interleukin 2-mediated immune responses

The immunosuppressive effects of a recombinant soluble IL-2 receptor L chain (s-IL-2R) were analyzed. S-IL-2R protein was obtained from the conditioned medium of L cells transfected with a mutant cDNA clone encoding the extracytoplasmic portion of the IL-2 receptor (IL-2R) and was purified to homogeneity by an IL-2-coupled sepharose column, following by reverse phase chromatography (HPLC). Soluble IL-2R protein thus prepared retained the ability to bind IL-2 specifically and suppressed the in vitro IL-2-mediated immune responses, including proliferation of IL-2-dependent cell line (CTLL-2), induction of secondary cytotoxic T lymphocytes (CTL) and the mixed lymphocyte reaction (MLR), but did not suppress the growth of IL-3-dependent cell line. Kinetic studies revealed that s-IL-2R exhibited the suppressive effects on the proliferative responses of alloantigen stimulated human tonsillar cells, only when added at an early stage, namely 0-48 h after culture onset, whereas cyclosporin A (CsA) exhibited an inhibitory effect only when added at between 0 and 24 h. This implies that s-IL-2R exerts its effect on an early stage of lymphocyte activation. The observed immunosuppressive effects of s-IL-2R suggest the possibility that s-IL-2R might be useful for the protection of rejection crisis in organ transplantation.

Determining important regulatory relations of amino acids from dynamic network analysis of plasma amino acids

The changes in the concentrations of plasma amino acids do not always follow the flow-based metabolic pathway network. We have previously shown that there is a control-based network structure among plasma amino acids besides the metabolic pathway map. Based on this network structure, in this study, we performed dynamic analysis using time-course data of the plasma samples of rats fed single essential amino acid deficient diet. Using S-system model (conceptual mathematical model represented by power-law formalism), we inferred the dynamic network structure which reproduces the actual time-courses within the error allowance of 13.17%. By performing sensitivity analysis, three of the most dominant relations in this network were selected; the control paths from leucine to valine, from methionine to threonine, and from leucine to isoleucine. This result is in good agreement with the biological knowledge regarding branched-chain amino acids, and suggests the biological importance of the effect from methionine to threonine.

The Interaction of Recombinant IL-2 with Human Resting Lymphocytes : Blocking Effects of Monoclonal Antibodies to IL-2 Receptors

Several lines of evidence suggest that subsets of resting lymphocytes naturally express interleukin‐2 receptors (IL‐2·R). Recombinant IL‐2 (rIL‐2) induced the enhancement of natural killer (NK) activity, the generation of activated killer (AK) cells, the proliferation of resting lymphocytes, and the production of interferon‐γ (IFN‐γ) in lymphocyte cultures. The subsets of lymphocytes mediating these responses appeared to be heterogeneous, but reside predominantly in nylon wool‐passed non‐T, non‐B cells (“lnull cells” or T3‐ cells); in response to rIL‐2, only Leul 1+T3‐ cells showed enhanced NK activity, and both Leul 1+T3‐ and Leul 1‐T3‐ cells showed predominantly AK activity, proliferation and production of IFN‐γ. These findings suggest that the T3‐ fraction (null cell fraction) contains predominantly cells expressing IL‐2·R at the resting state. Unlike the case with activated T cells, however, none of these responses was blocked by any of three monoclonal antibodies to IL‐2·R, including anti‐Tac antibody at any dilution. These results indicate that IL‐2·R on the resting T3‐ cells possess unique biological features compared to those on activated T or B cells. A most likely explanation is that T3‐ cells possess higher affinity IL‐2·R than activated T or B cells. Other possibilities are also discussed.