# Effect of Oral Skim Milk Administration on Skeletal Muscle Protein Synthesis after Total Gastrectomy in Rat

## TL;DR

This study shows that giving skim milk to rats after total gastrectomy helps increase muscle protein synthesis, despite impaired digestion.

## Contribution

The study demonstrates that oral skim milk can stimulate muscle protein synthesis after total gastrectomy in rats.

## Key findings

- TG rats had significantly lower gastrocnemius muscle weight compared to sham surgery rats.
- Skim milk consumption increased skeletal muscle protein synthesis similarly in both TG and sham groups.
- Plasma leucine concentration increased sufficiently after skim milk administration in TG rats.

## Abstract

Leucine is a branched-chain amino acid that is present in protein, and it is an essential factor in activating the mechanistic target of the rapamycin complex 1 signaling pathway and increasing muscle protein synthesis. However, the loss of digestive function after total gastrectomy leads to impaired protein absorption, potentially failing to stimulate muscle protein synthesis. Therefore, this study aimed to investigate whether muscle protein synthesis is enhanced by oral skim milk administration after total gastrectomy. Male Sprague Dawley rats were divided into total gastrectomy (TG) and sham surgery (S) groups. After five weeks postoperatively, we orally administered skim milk to achieve 3.1 g protein/kg body weight and collected blood and gastrocnemius muscle. The gastrocnemius muscle weight was significantly lower in the TG group than in the S group (p < 0.05). The increase in plasma leucine concentration was significantly lower in the TG group than in the S group (p < 0.05). The skeletal muscle protein synthesis and the phosphorylation of p70S6K and 4E-BP1 showed a similar increase in both groups. Even after TG, muscle protein synthesis was stimulated by consuming skim milk, accompanied by a sufficient rise in plasma leucine concentration.