A non-linear pharmacokinetic-pharmacodynamic relationship of metformin in healthy volunteers: An open-label, parallel group, randomized clinical study

<div><p>Background</p><p>The aim of this study was to explore the pharmacokinetic-pharmacodynamic (PK-PD) relationship of metformin on glucose levels after the administration of 250 mg and 1000 mg of metformin in healthy volunteers.</p><p>Methods</p><p>A total of 20 healthy male volunteers were randomized to receive two doses of either a low dose (375 mg followed by 250 mg) or a high dose (1000 mg followed by 1000 mg) of metformin at 12-h intervals. The pharmacodynamics of metformin was assessed using oral glucose tolerance tests before and after metformin administration. The PK parameters after the second dose were evaluated through noncompartmental analyses. Four single nucleotide polymorphisms in MATE1, MATE2-K, and OCT2 were genotyped, and their effects on PK characteristics were additionally evaluated.</p><p>Results</p><p>The plasma exposure of metformin increased as the metformin dose increased. The mean values for the area under the concentration-time curve from dosing to 12 hours post-dose (AUC_0-12h) were 3160.4 and 8808.2 h·μg/L for the low- and high-dose groups, respectively. Non-linear relationships were found between the glucose-lowering effect and PK parameters with a significant inverse trend at high metformin exposure. The PK parameters were comparable among subjects with the genetic polymorphisms.</p><p>Conclusions</p><p>This study showed a non-linear PK-PD relationship on plasma glucose levels after the administration of metformin. The inverse relationship between systemic exposure and the glucose-lowering effect at a high exposure indicates a possible role for the intestines as an action site for metformin.</p><p>Trial registration</p><p>ClinicalTrials.gov <a href="https://clinicaltrials.gov/ct2/show/NCT01128790" target="_blank">NCT02712619</a></p></div

Mean concentration profile of metformin administered at 250 mg (Δ) and 1000 mg (●).

<p>(Inlet: log-linear scale; error bars present standard deviation).</p

Relationships between pharmacokinetic-pharmacodynamic parameters after metformin administration at 250 mg (triangle) and 1000 mg (circle). Reduction in (a) AUG_0-3h, (b) G_max, and (c) PP2 versus AUC_0-12h; reduction in (d) AUG_0-3h, (e) G_max, and (f) PP2 versus C_max.

<p>(The solid lines and dashed lines represent the linear and quadratic models, respectively. The black circle represents data included in the linear regression at high exposure. P-values are from the F-tests, and r² represents the coefficient of determination.).</p

Pharmacokinetic parameters after metformin administration.

<p>Pharmacokinetic parameters after metformin administration.</p

CONSORT flowchart.

<p>CONSORT flowchart.</p

Results of oral glucose tolerance test (OGTT) before and after administration of metformin.

<p>Results of oral glucose tolerance test (OGTT) before and after administration of metformin.</p

Autophagy and KRT8/keratin 8 protect degeneration of retinal pigment epithelium under oxidative stress

<p>Contribution of autophagy and regulation of related proteins to the degeneration of retinal pigment epithelium (RPE) in age-related macular degeneration (AMD) remain unknown. We report that upregulation of KRT8 (keratin 8) as well as its phosphorylation are accompanied with autophagy and attenuated with the inhibition of autophagy in RPE cells under oxidative stress. KRT8 appears to have a dual role in RPE pathophysiology. While increased expression of KRT8 following autophagy provides a cytoprotective role in RPE, phosphorylation of KRT8 induces pathologic epithelial-mesenchymal transition (EMT) of RPE cells under oxidative stress, which is mediated by MAPK1/ERK2 (mitogen-activated protein kinase 1) and MAPK3/ERK1. Inhibition of autophagy further promotes EMT, which can be reversed by inhibition of MAPK. Thus, regulated enhancement of autophagy with concurrent increased expression of KRT8 and the inhibition of KRT8 phosphorylation serve to inhibit oxidative stress-induced EMT of RPE cells as well as to prevent cell death, suggesting that pharmacological manipulation of KRT8 upregulation through autophagy with combined inhibition of the MAPK1/3 pathway may be attractive therapeutic strategies for the treatment of AMD.</p

Exosomal Proteins in the Aqueous Humor as Novel Biomarkers in Patients with Neovascular Age-related Macular Degeneration

Age-related macular degeneration (AMD) describes the progressive degeneration of the retinal pigment epithelium (RPE), retina, and choriocapillaris and is the leading cause of blindness in people over 50. The molecular mechanisms underlying this multifactorial disease remain largely unknown. To uncover novel secretory biomarkers related to the pathogenesis of AMD, we adopted an integrated approach to compare the proteins identified in the conditioned medium (CM) of cultured RPE cells and the exosomes derived from CM and from the aqueous humor (AH) of AMD patients by LC–ESI–MS/MS. Finally, LC–MRM was performed on the AH from patients and controls, which revealed that cathepsin D, cytokeratin 8, and four other proteins increased in the AH of AMD patients. The present study has identified potential biomarkers and therapeutic targets for AMD treatment, such as proteins related to the autophagy–lysosomal pathway and epithelial–mesenchymal transition, and demonstrated a novel and effective approach to identifying AMD-associated proteins that might be secreted by RPE in vivo in the form of exosomes. The proteomics-based characterization of this multifactorial disease could help to match a particular marker to particular target-based therapy in AMD patients with various phenotypes

Additional file 1 of Development of finely tuned liposome nanoplatform for macrophage depletion

Additional file 1: Figure S1. NTA analysis of Liposomes. The size distribution of (a) Clodrosome and m-Clodrosome and (b) liposome nanoplatforms in PBS was measured using the NTA system. Figure S2. Stability of liposomes at different physiological conditions (PBS, human serum, and cell media (DMEM). No visible aggregates or precipitates of liposomes were observed in any of the experimental groups after 14 days. Figure S3. Clodronate releasing test. The clodronate encapsulation efficiency of the liposomes was measured using a nanodrop. None of the groups showed significant differences. Statistical analysis was conducted using one-way analysis of variance. Figure S4. Cell viability test of RAW264.7 treated liposomes. Comparison of liposomes with Clodrosome® and m-Clodrosome®. None of the groups showed significant differences. Statistical analysis was conducted using one-way analysis of variance. Figure S5. RAW264.7 cell uptake of liposomes. Comparison of the cellular uptake of liposomes at different time points (0.5, 1, 2, 4, and 24 h). All scale bars are 75 µm. Figure S6. Confocal images of the liver tissue treated with liposomes. Ex vivo tissue fluorescence images were acquired 24 h post-injection of liposomes in normal mice. All scale bars represent 250 µm. Figure S7. Histological analysis of H&E stained liposome-treated liver tissue. Figure S8. Labeling efficiency of all the liposomes. The labeling efficiency of all the liposomes used in the experiments was assessed using click chemistry with [64Cu]Cu-NOTA-N3. The radiochemical purity of all the liposomes was determined using the radio TLC chromatogram and percentage of value at Rf = 0.0–0.1