The osmotic effectiveness of a large molecular weight glucose polymer fraction (Icodextrin) as a novel "colloid" osmotic agent in peritoneal dialysis was established, but the long-term safety remained undetermined. A randomized, controlled multicenter investigation of Icodextrin in ambulatory peritoneal dialysis (MIDAS) was undertaken to evaluate the long-term safety and efficacy by comparing daily overnight (8 to 12 hr dwell) use of isosmolar Icodextrin (282 mOsm/kg) with conventional 1.36% (346 mOsm/kg) and 3.86% (484 mOsm/kg) glucose exchanges over six months. Two hundred and nine patients were randomized from 11 centers, with 106 allocated to receive Icodextrin (D) and 103 to remain on glucose (control group; C); 138 patients completed the six month study (71 C, 67 D). All patients were divided into weak (1.36%) or strong (3.86%) subgroups based on their use of glucose solutions overnight during the pretreatment baseline period. The mean (+/- SEM) overnight ultrafiltration (UF) with D was 3.5 times greater than 1.36% glucose at eight hours [527 +/- 36 vs. 150 +/- 47 ml; 95% confidence interval (CI) for the difference +257 to +497 ml; P < 0.0001] and 5.5 times greater at 12 hours (561 +/- 44 vs. 101 +/- 48 ml, 95% CI for the difference +329 to +590; P < 0.0001) and no different from that of 3.86% glucose at eight hours (510 +/- 48 vs. 448 +/- 60 ml, 95% CI for the difference -102 to +226 ml; P = 0.44) and at 12 hours (552 +/- 44 vs. 414 +/- 78 ml, 95% CI for the difference -47 to +325 ml; P = 0.06).(ABSTRACT TRUNCATED AT 250 WORDS)
Fibroblast growth factor 21 (FGF21) is a promising drug candidate for the treatment of type 2 diabetes. However, the use of wild type native FGF21 is challenging due to several limitations. Among these are its short half-life, its susceptibility to in vivo proteolytic degradation and its propensity to in vitro aggregation. We here describe a rationale-based protein engineering approach to generate a potent long-acting FGF21 analog with improved resistance to proteolysis and aggregation. A recombinant Fc-FGF21 fusion protein was constructed by fusing the Fc domain of human IgG1 to the N-terminus of human mature FGF21 via a linker peptide. The Fc positioned at the N-terminus was determined to be superior to the C-terminus as the N-terminal Fc fusion retained the βKlotho binding affinity and the in vitro and in vivo potency similar to native FGF21. Two specific point mutations were introduced into FGF21. The leucine to arginine substitution at position 98 (L98R) suppressed FGF21 aggregation at high concentrations and elevated temperatures. The proline to glycine replacement at position 171 (P171G) eliminated a site-specific proteolytic cleavage of FGF21 identified in mice and cynomolgus monkeys. The derived Fc-FGF21(RG) molecule demonstrated a significantly improved circulating half-life while maintaining the in vitro activity similar to that of wild type protein. The half-life of Fc-FGF21(RG) was 11 h in mice and 30 h in monkeys as compared to 1-2 h for native FGF21 or Fc-FGF21 wild type. A single administration of Fc-FGF21(RG) in diabetic mice resulted in a sustained reduction in blood glucose levels and body weight gains up to 5-7 days, whereas the efficacy of FGF21 or Fc-FGF21 lasted only for 1 day. In summary, we engineered a potent and efficacious long-acting FGF21 analog with a favorable pharmaceutical property for potential clinical development.
Here we show that reversible protein acetylation carried out by HATs and HDACs also plays a role in regulating the myofilament contractile activity. We found that a Class II HDAC, HDAC4, and an HAT, PCAF, associate with cardiac myofilaments. Primary cultures of cardiomyocytes as well as mouse heart sections examined by immunohistochemical and electron microscopic analyses revealed that both HDAC4 and PCAF associate with the Z-disc and I-and A-bands of cardiac sacromeres. Increased acetylation of sarcomeric proteins by HDAC inhibition (using class I and II HDAC inhibitors or anti-HDAC4 antibody) enhanced the myofilament calcium sensitivity. We identified the Z-disc-associated protein, MLP, a sensor of cardiac mechanical stretch, as an acetylated target of PCAF and HDAC4. We also show that trichostatin-A, a class I and II HDAC inhibitor, increases myofilament calcium sensitivity of wild-type, but not of MLP knock-out mice, thus demonstrating a role of MLP in acetylation-dependent increased contractile activity of myofilaments. These studies provide the first evidence that HATs and HDACs play a role in regulation of muscle contraction.
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