# Possible Extracellular Signals to Ameliorate Sarcopenia in Response to Medium-Chain Triglycerides (8:0 and 10:0) in Frail Older Adults

## TL;DR

A low dose of medium-chain triglycerides (MCTs) improved muscle mass and function in frail older adults, possibly through signals like increased energy expenditure and growth hormone stimulation.

## Contribution

The paper proposes three potential extracellular signals by which MCTs may ameliorate sarcopenia in older adults.

## Key findings

- MCT supplementation increased muscle mass and function while decreasing fat mass in frail older adults.
- MCTs may stimulate the sympathetic nervous system, promoting mitochondrial biogenesis and muscle hypertrophy.
- Plasma acyl-ghrelin and ketone bodies are suggested as possible signals to enhance muscle protein synthesis.

## Abstract

In frail older adults (mean age 85 years old), a 3-month supplementation with a low dose (6 g/day) of medium-chain triglycerides (MCTs; C8:0 and C10:0) given at a meal increased muscle mass and function, relative to supplementation with long-chain triglycerides (LCTs), but it decreased fat mass. The reduction in fat mass was partly due to increased postprandial energy expenditure by stimulation of the sympathetic nervous system (SNS). However, the extracellular signals to ameliorate sarcopenia are unclear. The following three potential extracellular signals to increase muscle mass and function after MCT supplementation are discussed: (1) Activating SNS—the hypothesis for this is based on evidence that a beta2-adrenergic receptor agonist acutely (1–24 h) markedly upregulates isoforms of peroxisomal proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) mRNAs, promotes mitochondrial biogenesis, and chronically (~1 month) induces muscle hypertrophy. (2) An increased concentration of plasma acyl-ghrelin stimulates growth hormone secretion. (3) A nitrogen-sparing effect of ketone bodies, which fuel skeletal muscle, may promote muscle protein synthesis and prevent muscle protein breakdown. This review will help guide clinical trials of using MCTs to treat primary (age-related) sarcopenia.