The developmental potential of skeletal muscle stem cells (satellite cells) remains controversial. The authors investigated satellite cell developmental potential in single fiber and clonal cultures derived from MyoD ^iCre/+; R26R ^EYFP/+ muscle, in which essentially all satellite cells are permanently labeled. Approximately 60% of the clones derived from cells that co-purified with muscle fibers spontaneously underwent adipogenic differentiation. These adipocytes stained with Oil-Red-O and expressed the terminal differentiation markers, adipsin and fatty acid binding protein 4, but did not express EYFP and were therefore not of satellite cell origin. Satellite cells mutant for either MyoD or Myf-5 also maintained myogenic programming in culture and did not adopt an adipogenic fate. Incorporation of additional wash steps prior to muscle fiber plating virtually eliminated the non-myogenic cells but did not reduce the number of adherent Pax7+ satellite cells. More than half of the adipocytes observed in cultures from Tie2-Cre mice were recombined, further demonstrating a non-satellite cell origin. Under adipogenesis-inducing conditions, satellite cells accumulated cytoplasmic lipid but maintained myogenic protein expression and did not fully execute the adipogenic differentiation program, distinguishing them from adipocytes observed in muscle fiber cultures. The authors conclude that skeletal muscle satellite cells are committed to myogenesis and do not spontaneously adopt an adipogenic fate.

Collagen tripeptide (CTP) is a collagen hydrolysate containing a high concentration of tripeptides with a Gly-X-Y sequence, such as Gly-Pro-Hyp. To test the effects of this preparation, we compared the absorption of peptides in humans after ingestion of a tripeptide fraction of CTP (CTP-100), a CTP preparation containing ca. 50% Gly-X-Y tripeptides (CTP-50), and a collagen peptide that did not contain tripeptides (CP). The postprandial levels of Gly-Pro-Hyp and Pro-Hyp in the plasma increased in those subjects who ingested CTP-100 and CTP-50, and were higher with greater Gly-Pro-Hyp ingestion. This demonstrated that collagen hydrolysates were efficiently absorbed when the collagen was ingested in the tripeptide form. Gly-Pro-Hyp and Pro-Hyp were also found in the urine after ingestion of CTP-100 or CTP-50. Similar to the results for the plasma concentration, the urinary excretion of Gly-Pro-Hyp and Pro-Hyp was also dependent on the amount of Gly-Pro-Hyp ingested. This indicates that ingested Gly-Pro-Hyp and generated Pro-Hyp were relatively stable in the body and were transported to the urine in the peptide form. The concentration of Hyp-Gly in the plasma was low after the ingestion of CP and CTP-100 but higher after the ingestion of CTP-50. Overall, our results suggest that tripeptides derived from collagen are absorbed efficiently by the body.

Collagen tripeptide (CTP) is a collagen-derived compound containing a high concentration of tripeptides with a Gly-X-Y sequence. In this study, the concentrations and metabolites of CTP were monitored in rat plasma after its administration. We performed a quantitative analysis using high-performance liquid chromatography tandem mass spectrometry according to the isotopic dilution method with stable isotopes. We confirmed that the tripeptides Gly-Pro-Hyp, Gly-Pro-Ala, and Gly-Ala-Hyp were transported into the plasma. Dipeptides, which are generated by degradation of the N- or C-terminus of the tripeptides Gly-Pro-Hyp, Gly-Pro-Ala, and Gly-Ala-Hyp, were also present in plasma. The plasma kinetics for peroral and intraperitoneal administration was similar. In addition, tripeptides and dipeptides were detected in no-administration rat blood. The pharmacokinetics were monitored in rats perorally administered with Gly-[3H]Pro-Hyp. Furthermore, CTP was incorporated into tissues including skin, bone, and joint tissue. Thus, administering collagen as tripeptides enables efficient absorption of tripeptides and dipeptides.

Collagen tripeptide (CTP) is a functional food with a high content of Gly-X-Y tripeptides derived from collagen. The objective of this study was to evaluate the effect of CTP administration on the development of atherosclerosis in healthy individuals. The present study was conducted in the form of an open-label, single-dose trial for 6 months. All subjects ingested CTP twice daily: at breakfast and supper (total intake per day: 16 g). The effect of CTP on atherosclerosis was verified by measuring several indices, including serum lipid levels, toxic advanced glycation end-products (TAGE), and the cardio-ankle vascular index (CAVI), at baseline and 6 months. The low-density lipoprotein cholesterol (LDL-C) to high-density lipoprotein cholesterol (HDL-C) ratio (LDL-C/HDL-C ratio) was significantly reduced in patients with an initial ratio of ≥2.5 (p=0.025). A significant reduction in TAGE was observed in all the subjects (p=0.031) and in the high-risk group (p=0.024). A significant reduction in CAVI was observed in all the subjects (right side: p=0.048, left side: p=0.047). As a result of multiple regression analysis, a significant relationship between the change in CAVI and that in each factor was not observed. No adverse events were observed during the study period. The results of the present study indicate that CTP contributes to the prevention and treatment of atherosclerosis in healthy humans (UMIN000018525).