TAK-875, a GPR40/FFAR1 agonist, in combination with metformin prevents progression of diabetes and ß-cell dysfunction in Zucker diabetic fatty rats.

BACKGROUND AND PURPOSE: TAK-875, a selective GPCR40/free fatty acid receptor 1 agonist, improves glycaemic control by increasing glucose-dependent insulin secretion. Metformin is a first-line drug for treatment of type 2 diabetes that improves peripheral insulin resistance. Based on complementary mechanism of action, combining these agents is expected to enhance glycaemic control. Here, we evaluated the chronic effects of TAK-875 monotherapy and combination therapy with metformin in diabetic rats. EXPERIMENTAL APPROACH: Long-term effects on glycaemic control and ß-cell function were evaluated using Zucker diabetic fatty (ZDF) rats, which develop diabetes with hyperlipidaemia and progressive ß-cell dysfunction. KEY RESULTS: Single doses of TAK-875 (3-10 mg·kg(-1) ) and metformin (50-150 mg·kg(-1) ) significantly improved both postprandial and fasting hyperglycaemia, and additive improvements were observed in their combination. Six-week treatment with TAK-875 (10 mg·kg(-1) , b.i.d.) significantly decreased glycosylated Hb (GHb) by 1.7%, and the effect was additively enhanced by combination with metformin (50 mg·kg(-1) , q.d.; GHb: -2.4%). This improvement in glycaemic control in the combination group was accompanied by significant 3.2-fold increase in fasting plasma insulin levels. Pancreatic insulin content was maintained at a level comparable to that in normal rats by combination treatment (vehicle: 26, combination: 67.1; normal lean: 69.1 ng·mg(-1) pancreas) without affecting pancreatic glucagon content. Immunohistochemical analyses revealed normal morphology, enhanced pancreas duodenum homeobox-1 expression and increased PCNA-positive cells in islets of the combination group. CONCLUSION AND IMPLICATIONS: Our results indicate that combination therapy with TAK-875 and metformin could be a valuable strategy for glycaemic control and ß-cell preservation in type 2 diabetes.

A single amino acid substitution in a self protein is sufficient to trigger autoantibody response.

We determined if a single amino acid substitution in a self protein causes autoantibody responses. Mouse lysozyme (ML) was used as a model self protein, and a mutant ML (F57L ML) was prepared by replacing 57Phe of ML to Leu, an approach which resulted in introducing into ML the immunogenic sequence of peptide 50-61 of hen egg lysozyme (HEL) restricted to I-A(k) MHC class II molecule. We found that F57L ML but not native ML primed HEL specific T cells and triggered ML specific autoantibody responses in B10.A and C3H mice (I-A(k), I-E(k)). Peptide regions, ML 14-69 and ML 98-130, were major epitopes of autoantibodies in both strains of mice. These findings indicate that a single amino acid substitution in self proteins can cause an autoantibody response when the mutated region is presented by MHC class II molecules and recognized by T cells.

Mutant mouse lysozyme carrying a minimal T cell epitope of hen egg lysozyme evokes high autoantibody response.

Self proteins including foreign T cell epitope induce autoantibodies. We evaluated the relationship between the size of foreign Ag introduced into self protein and the magnitude of autoantibody production. Mouse lysozyme (ML) was used as a model self protein, and we prepared three different ML derivatives carrying T cell epitope of hen egg white lysozyme (HEL) 107-116, i.e, heterodimer of ML and HEL (ML-HEL), chimeric lysozyme that has residue 1-82 of ML and residue 83-130 of HEL in its sequence (chiMH), and mutant ML that has triple mutations rendering the most potent T cell epitope of HEL (sequence 107-116). Immunization of BALB/c mice with these three ML derivatives induced anti-ML autoantibody responses, whereas native ML induced no detectable response. In particular, mutML generated a 10(4) times higher autoantibody titer than did ML-HEL. Anti-HEL107-116 T cell-priming activities were almost similar among the ML derivatives. The heterodimerization of mutant ML and HEL led to significant reduction of the autoantibody response, whereas the mixture did not. These results show that size of the nonself region in modified self Ag has an important role in determining the magnitude of the autoantibody response, and that decrease in the foreign region in a modified self protein may cause high-titered autoantibody response.

The molecular weight ratio of monomethoxypolyethylene glycol (mPEG) to protein determines the immunotolerogenicity of mPEG proteins.

Immunotolerogenic activity of monomethoxypolyethylene glycol- (mPEG) conjugated proteins is a beneficial property in protein pharmaceutics. However, procedures for the preparation of tolerogenic mPEG proteins have not yet been defined. We prepared mPEG proteins with different mPEG contents using three proteins, hen egg lysozyme, ovalbumin and bovine gamma globulin, and their tolerogenicities to antigen-specific T and B cell responses were examined. We found the most appropriate ratio of tolerance induction to be 1.5-2.0, which is the molecular weight ratio of conjugated total mPEGs to protein. This value may assist in the preparation of tolerogenic mPEG proteins.