Animal models in type 2 diabetes research: an overview.

Type 2 diabetes is a complex and heterogeneous disorder presently affecting more than 100 million people worldwide and causing serious socio-economic problems. Appropriate experimental models are essential tools for understanding the pathogenesis, complications, and genetic or environmental influences that increase the risks of type 2 diabetes and testing of various therapeutic agents. The animal models of type 2 diabetes can be obtained either spontaneously or induced by chemicals or dietary or surgical manipulations and/or by combination thereof. In recent years, large number of new genetically modified animal models including transgenic, generalized knock-out and tissue-specific knockout mice have been engineered for the study of diabetes. This review gives an overview on the animal models of type 2 diabetes with reference to their origin/source, characteristic features, underlying causes/mechanism(s), advantages and disadvantages to the investigators in diabetes research. In addition, it especially describes the appropriate selection and usefulness of different animal models in preclinical testing of various new chemical entities (NCEs) for the treatment of type 2 diabetes.

Cell proliferation and natural killer cell activity by polyherbal formulation, Immu-21 in mice.

Immunomodulatory activity of an Ayurvedic polyherbal formulation, Immu-21 containing extracts of Ocimum sanctum, Withania somnifera, Emblica officinalis and Tinospora cordifolia was studied on proliferative response of splenic leukocytes to T cell mitogens, concanavalin (Con)-A and phytohemagglutinin (PHA) and B cell mitogen, lipopolysaccharide (LPS) in vitro by [3H]-thymidine uptake assay in mice. The cytotoxic activity of Immu-21 was tested by measuring the splenic leukocyte natural killer (NK) cell activity against K 562 cells. Intraperitoneal (i.p.) treatment with Immu-21 (30 mg/kg) once a day for 14 and 21 days did not cause change in body weight and spleen weight, where as splenocytes/spleen count was increased. Treatment of Immu-21 (30 mg/kg, i.p.) for 14 days and 1 mg/kg for 21 days significantly increased LPS induced leukocyte proliferation. NK cell activity was significantly increased when mice were pretreated with Immu-21 (10 and 30 mg/kg, i.p.) once a day for 7 days. The results indicate that pretreatment with Immu-21 selectively increased the proliferation of splenic leukocyte to B cell mitogen, LPS and cytotoxic activity against K 562 cells in mice.

Receptor-operated calcium-channels in isolated rabbit jejunum.

Calcium channels were studied in isolated spontaneously rhythmic rabbit jejunum using the muscarinic agonist carbachol as stimulant. Carbachol failed to produce the characteristic phasic and tonic components of smooth muscle contractions. A variety of chemically distinct calcium antagonists, viz. bepridil, diltiazem, isradipine (PN 200-110), nifedipine, and verapamil, non-competitively inhibited the contractions. Diltiazem was most potent (-logIC50 = 8.30) and bepridil least potent (-logIC50 = 6.19) in inhibiting the contractions. The findings conclude with the presence of pharmacologically distinct receptor-operated calcium-channels, besides the potential-dependent calcium-channels, in the rabbit jejunum.