Adaptation to a high-protein diet progressively increases the postprandial accumulation of carbon skeletons from dietary amino acids in rats

The Effects of Mesenchymal Stem Cells-Derived Exosomes on Metabolic Reprogramming in Scar Formation and Wound Healing

Pathological scarring results from aberrant cutaneous wound healing due to the overactivation of biological behaviors of human skin fibroblasts, characterized by local inordinate inflammation, excessive extracellular matrix and collagen deposition. Yet, its underlying pathogenesis opinions vary, which could be caused by increased local mechanical tension, enhanced and continuous inflammation, gene mutation, as well as cellular metabolic disorder, etc. Metabolic reprogramming is the process by which the metabolic pattern of cells undergoes a systematic adjustment and transformation to adapt to the changes of the external environment and meet the needs of their growth and differentiation. Therefore, the abnormality of metabolic reprogramming in cells within wounds and scars attaches great importance to scar formation. Mesenchymal stem cells-derived exosomes (MSC-Exo) are the extracellular vesicles that play an important role in tissue repair, cancer treatment as well as immune and metabolic regulation. However, there is not a systematic work to detail the relevant studies. Herein, we gave a comprehensive summary of the existing research on three main metabolisms, including glycometabolism, lipid metabolism and amino acid metabolism, and MSC-Exo regulating metabolic reprogramming in wound healing and scar formation for further research reference.

Role of liver AMPK and GCN2 kinases in the control of postprandial protein metabolism in response to mid-term high or low protein intake in mice

PURPOSE

Protein synthesis and proteolysis are known to be controlled through mammalian target of rapamycin, AMP-activated kinase (AMPK) and general control non-derepressible 2 (GCN2) pathways, depending on the nutritional condition. This study aimed at investigating the contribution of liver AMPK and GCN2 on the adaptation to high variations in protein intake.

METHODS

To evaluate the answer of protein pathways to high- or low-protein diet, male wild-type mice and genetically modified mice from C57BL/6 background with liver-specific AMPK- or GCN2-knockout were fed from day 25 diets differing in their protein level as energy: LP (5%), NP (14%) and HP (54%). Two hours after a 1 g test meal, protein synthesis rate was measured after a ¹³C valine flooding dose. The gene expression of key enzymes involved in proteolysis and GNC2 signaling pathway were quantified.

RESULTS

The HP diet but not the LP diet was associated with a decrease in fractional synthesis rate by 29% in the liver compared to NP diet. The expression of mRNA encoding ubiquitin and Cathepsin D was not sensitive to the protein content. The deletion of AMPK or GCN2 in the liver did not affect nor protein synthesis rates and neither proteolysis markers in the liver or in the muscle, whatever the protein intake. In the postprandial state, protein level alters protein synthesis in the liver but not in the muscle.

CONCLUSIONS

Taken together, these results suggest that liver AMPK and GCN2 are not involved in this adaptation to high- and low-protein diet observed in the postprandial period.

Effect of omnivorous and vegan diets with different protein and carbohydrate content on growth and metabolism of growing rats

The purpose of this study was to observe, in a rat animal model, the short and medium term effects of vegan (VEG) or omnivorous (OMNI) diets with different energy partition between nutrients (zone or classic). Six different diets were administered, for 72 days to 120 growing male Sprague-Dawley rats: (i) VEG zone diet; (ii) VEG classic diet; (iii) OMNI zone diet; (iv) OMNI classic diet; (v) OMNI zone diet with added fibre and (vi) OMNI classic diet with added fibre. Zone diets (high protein and low carbohydrates), resulted in better growth , feed efficiency, lower blood glucose and insulin responses. VEG diets have lowered cholesterol blood level. Histopathological analysis evidenced no damage to liver and kidney tissue by the intake of any of the diet types. Further longer animal and human duration studies should be performed to exclude detrimental effect of higher protein diet.