Fermented milk retains beneficial effects on skeletal muscle protein anabolism after processing by centrifugation and supernatant removal

Abstract

Lactobacillus-fermented milk can stimulate anabolic effects in skeletal muscle. Fermented milk containing Lactobacillus produces aqueous molecules, such as free AA and lactate. This study aimed to investigate how processing fermented milk by centrifugation and removal of supernatant affects AA absorption and postprandial skeletal muscle protein synthesis (MPS) when mice are fed fermented milk. We gavaged male Sprague-Dawley rats with skim milk (S), fermented milk (F), or processed fermented milk (P), and examined the total AA content in portal vein blood (reflecting AA absorption) and plantaris muscle MPS at 30, 60, and 90 min following administration. Relative to fasted rats, at 30 min the total AA concentration in portal vein blood from rats in the P groups was significantly higher, followed by F and S, respectively. The MPS rates were higher for the F or P groups compared with the S group. Phosphorylation levels of p70S6 kinase in the P and F groups were significantly higher than those for the S group 30 min after administration, although the level of Akt phosphorylation was similar among the groups. These results suggested that fermentation improves AA absorption that in turn enhances postprandial MPS via Akt-independent mechanisms, and that processed fermented milk retains these favorable effects on MPS.

Nutritional Value of Yogurt as a Protein Source: Digestibility/Absorbability and Effects on Skeletal Muscle

“…As a result, we confirmed that MPS is lower not only after unfermented milk but also after acidified unfermented milk ingestion than after yogurt consumption over the entire measured time [69]. In addition, in a study using yogurt fermented by another lactic acid bacterium, postprandial MPS was increased by yogurt than the original unfermented milk, too [70]. Looking at these reports in more detail, the concentration of blood amino acids, such as leucine, was higher in fermented milk and acidified unfermented milk than in unfermented milk at 30 and 60 min after ingestion [69,70].…”

“…On the other hand, proton pump inhibitors do not affect amino acid absorption after ingestion of acidified milk but reduce it after ingestion of fermented milk [69]. Casein protein may be more highly digestible by pepsin in fermented milk than in raw milk in the stomach [70]. These results indicate that casein protein in fermented milk is partially digested by lactic acid bacterial fermentation, potentially contributing to its reduced resistance to pepsin.…”

“…Almost the same results were obtained in an experiment in which a portal vein catheter was introduced in rats to measure changes in portal TAA concentrations over time in the same individuals (unpublished data). In another study comparing original milk and yogurt produced by a different fermentation starter, the portal TAA concentration was significantly higher 30 min after yogurt than the original skim milk administration and was comparable after 60 and 90 min [70]. It has been shown that dairy beverages stabilized in an acidified state have better protein absorption compared with non-acidified dairy beverages [71].…”

From the past to the future: Fermented milks and their health effects against human diseases

“…The high-quality amino acid pattern that yoghurt has therefore reduces energy intake by stimulating satiety and regulates blood sugar levels (Baspinar & Güldaş, 2021). Sumi et al (2021) found that fermented milk improved amino acid absorption and postprandial skeletal muscle protein synthesis, thus stimulating the anabolic action in skeletal muscle.…”

“…Sumi et al. (2021) found that fermented milk improved amino acid absorption and postprandial skeletal muscle protein synthesis, thus stimulating the anabolic action in skeletal muscle.…”