Meta-analysis links dietary branched-chain amino acids to metabolic health in rodents

Samantha M Solon-Biet,Sophie Fosh,Alistair M Senior,Stephen J Simpson,Lucy Griffiths,David G Le Couteur

doi:10.1186/s12915-021-01201-2

Abstract

BackgroundThe role of dietary branched chain amino acids (BCAAs) and their effect on metabolic health is complex. How dietary BCAA levels and their interaction with background nutrition affect health is unclear. Here, we used meta-analysis and meta-regression, together with the nutritional modelling, to analyse the results of rodent studies that increased the level of dietary BCAAs and measured circulating levels, outcomes related to metabolic health, body mass and food intake.ResultsAcross all studies, increasing dietary BCAAs resulted in increased levels of circulating BCAAs. These effects, however, were heavily moderated by background dietary levels whereby on high BCAA diets, further increases were not reflected in the blood. Impaired glucose tolerance was associated with elevated dietary BCAAs, with the greatest effect occurring with a simultaneous increase in total protein intake. Effects of dietary BCAAs on plasma glucose, insulin, or HOMA emerged only when dietary macronutrient background was considered. We found that elevated dietary BCAAs increases % body fat, with largest increases in adiposity occurring when BCAAs are increased on a high protein, low carbohydrate dietary background. Finally, we found that increased dietary BCAAs were associated with increased food intake when the background diet was low in BCAAs.ConclusionOur data highlights the interaction between BCAAs and background nutrition. We show that the effects of BCAAs on metabolic health cannot be studied in isolation but must be considered as part of complex mixture of dietary components.

Highlights

The role of dietary branched chain amino acids (BCAAs) and their effect on metabolic health is complex
Circulating BCAAs reflects dietary levels To determine the relationship between dietary BCAAs and circulating levels, we extracted data on circulating levels of total BCAAs (Fig. 1; 52 diet groups; 5 articles), isoleucine (165 diet groups; 34 articles), leucine (168 diet groups; 36 articles) and valine (155 diet groups; 34 articles) (Additional File 1: Table S1)
For total BCAA levels, 64% of the data came from groups of mice, for isoleucine and leucine 50% of the groups were mice, and valine 57% were mice

Summary

Introduction

The role of dietary branched chain amino acids (BCAAs) and their effect on metabolic health is complex. We used meta-analysis and meta-regression, together with the nutritional modelling, to analyse the results of rodent studies that increased the level of dietary BCAAs and measured circulating levels, outcomes related to metabolic health, body mass and food intake. The relationship between dietary branched chain amino acids (BCAAs), blood levels of BCAAs and their effects on body composition and metabolic health is gaining increasing attention. Studies in humans and animals have yielded conflicting outcomes and conclude that dietary BCAAs and/ This complexity, in part, reflects the physiology and regulation of BCAAs, which are both signalling. Beyond the postprandial period and during fasting, blood levels of BCAAs are tightly regulated through catabolism by branched chain α-ketoacid dehydrogenase complex (BCKDH) [17, 18]. Any relationship between dietary BCAAs and blood levels of BCAAs can be influenced by many factors, including the timing of the blood samples, the BCAA content of the food, endogenous factors such as insulin which regulate BCAA metabolism and degradation, and numerous comorbid conditions (such as obesity, diabetes, renal failure, liver cirrhosis, cancer, sepsis) that influence BCAAs independently of dietary BCAA content [19]

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Discussion

Conclusion