Improvement of enzymatic stability and intestinal permeability of deuterohemin-peptide conjugates by specific multi-site N-methylation.

The deuterohemin-peptide conjugate, DhHP-6 (Dh-ß-AHTVEK-NH(2)), is a microperoxidase mimetic, which has demonstrated substantial benefits in vivo as a scavenger of reactive oxygen species (ROS). In this study, specific multi-site N-methylated derivatives of DhHP-6 were designed and synthesized to improve metabolic stability and intestinal absorption, which are important factors for oral delivery of therapeutic peptides and proteins. The DhHP-6 derivatives were tested for (1) scavenging potential of hydrogen peroxide (H(2)O(2)); (2) permeability across Caco-2 cell monolayers and everted gut sacs; and (3) enzymatic stability in serum and intestinal homogenate. The results indicated that the activities of the DhHP-6 derivatives were not influenced by N-methylation, and that tri-N-methylation of DhHP-6 could significantly increase intestinal flux, resulting in a two- to threefold higher apparent permeability coefficient. In addition, molecules with N-methylation at selected sites (e.g., Glu residue) showed high resistance against proteolytic degradation in both diluted serum and intestinal preparation, with 50- to 140-fold higher half-life values. These findings suggest that the DhHP-6 derivatives with appropriate N-methylation could retain activity levels equivalent to that of the parent peptide, while showing enhanced intestinal permeability and stability against enzymatic degradation. The tri-N-methylated peptide Dh-ß-AH(Me)T(Me)V(Me)EK-NH(2) derived from this study may be developed as a promising candidate for oral administration.

[Non-invasive assessment of renal oxygenation with BOLD MRI in patients with type 2 diabetes].

OBJECTIVE: To evaluate renal oxygenation in patients with type 2 diabetes using blood oxygenation level-dependent magnetic resonance imaging (BOLD MRI). METHODS: The R2* values of cortex and medulla as well as cortical thickness were measured in 25 patients with type 2 diabetes and 30 normal controls. The associations between R2* values and clinical parameters were analyzed. RESULTS: The medulla R2* value of the patients with diabetes was significantly higher than that of the normal controls. No significant difference in cortical thickness was found between the patients with diabetes and the normal controls. The medulla R2* value increased with eGFR in the patients with diabetes. CONCLUSION: BOLD MRI is a non-invasive and efficient method to assess the oxygenation in different regions of kidney. Abnormality of kidney in diabetic patients can be detected earlier by BOLD MRI than traditional imaging.