In a current examine printed in Nature Metabolism, researchers performed scientific research on murine animals and people to judge the affect of excessive protein consumption on the amino acid-mammalian goal of the rapamycin advanced 1 (mTORC1) autophagy signaling pathway. In addition they assessed the dose-response relationship, downstream results, and amino acid specificity of mTORC1 activation.
Examine: Identification of a leucine-mediated threshold impact governing macrophage mTOR signalling and cardiovascular danger. Picture Credit score: Crevis/Shutterstock.com
Background
Animal research have reported excessive protein consumption related to heart problems in Western nations. Excessive-protein diets improve atherogenesis by means of amino-acid-mediated mTORC1 signaling and impair autophagy and mitophagy in macrophages. The particular articular processes underlying this activation stay unknown, though the authors speculate that the stimulatory affect could also be associated to sure ‘pathogenic’ amino acids.
Concerning the examine
Within the current examine, researchers performed two scientific experiments to analyze the dose-response connection between dietary protein consumption and the amino acid specificity of the amino acid-mTOR-autophagy pathway in human monocytes or macrophages.
The primary experiment examined protein consumption extremes by assessing the affect of fluid meals containing 50% or 10% protein content material on mTORC1 pathway activation in monocytes. The second experiment used a extra practical setting, assessing these leads to topics who acquired commonplace protein meals or blended meals with extra protein (15% kilocalories vs. 22% kilocalories). The examine analyzed monocytes expressing cluster of differentiation 14 (CD14+) however not CD16 since they symbolize most monocytes in circulation and are probably to grow to be atherosclerotic macrophages.
The group carried out circulation cytometry and monocyte isolation from platelets. They used western blotting, fluorescence-activated cell sorting (FACS), and immunofluorescence to analyze the affect of various protein content material meals on serological amino acid ranges, monocyte mTORC1 signaling, and downstream penalties.
The group investigated 14 obese people [based on body mass index (BMI)] twice following a 12-hour in a single day quick. The contributors consumed low- and really high-level protein meals. The researchers used cultured human monocyte-derived macrophages to analyze the macrophage-specific mTORC1 response to amino acids and to evaluate dosage results.
They measured amino acid concentrations in plasma and macrophages utilizing fuel chromatography-mass spectrometry and quantified the arginine quantities in plasma utilizing liquid chromatography-mass spectrometry. They decided the dimensions of atherosclerotic lesions utilizing Oil Purple O staining of aortic root slices.
The researchers investigated whether or not leucine-dependent mTORC1 activation happens in vivo in mice and cultured murine macrophages. ApoE knockout mice have been fed six meals over eight weeks, together with a moderate-protein western weight-reduction plan, a high-protein western weight-reduction plan, a moderate-protein western weight-reduction plan with leucine and amino acids, extra amino acids, and a nitrogen-adjusted model of moderate-protein plus amino acids.
They investigated whether or not serum amino acids have been current in C57BL/6J mice weaned at three weeks outdated. In vivo, atherosclerosis-related investigations started at eight weeks utilizing male mice of the given genotype fed assorted diets.
Outcomes
The examine recognized leucine as the first activator of mTOR signaling in macrophages, displaying a threshold affect of consuming protein in giant portions and circulating leucine on monocytes or macrophages. Solely protein above 25g per meal prompts mTOR and has practical penalties. Ingestion of proteins above 22% of dietary power wants triggers the dangerous amino acid-mTORC1-autophagy signaling pathway in human monocytes and macrophages, which causes atherosclerosis in male mice. The examine discovered a robust hyperlink between excessive protein consumption and atherosclerotic heart problems danger, indicating the likelihood for weight-reduction plan recommendation and remedy measures.
The full amino acid content material in plasma elevated after having the high-protein liquid meal however not after ingesting the low-protein one. Through the three-hour postprandial interval, consuming the very excessive protein stage boosted mTORC1 signaling and progressively lowered LC3 sign depth, indicating mTORC1-mediated autophagy suppression. Western blot evaluation confirmed a sturdy dose-dependent affect of leucine-mediated mTORC1 activation in HMDMs, as evaluated by phosphorylation of ribosomal protein S6 and ribosomal protein S6 kinase (p-S6K).
The group additionally discovered a dose-dependent threshold impact for mTOR-LAMP2 colocalization, suppression of autophagy (diminished LC3 puncta formation), and mitophagy (lowered colocalization of the mitochondrial marker COXIV with the autophagosome marker LC3). They noticed considerably elevated ranges of 4 amino acids (Leu, Ile, Val, and Thr) in mice following protein gavage in comparison with management gavage.
Leucine was the best mTORC1 activator, with 1.6 g of protein per kg of gavage leading to larger mTORC1 activation than 0.8 g of protein per kg of gavage. The examine revealed that elevated dietary leucine is each required and adequate to provide the pro-atherogenic affect of a high-protein weight-reduction plan in vivo.
The examine findings confirmed that prime protein consumption, notably by means of elevated plasma leucine, may suppress mTORC1-mediated autophagy and atherogenesis in monocytes and macrophages, with crucial scientific and public well being implications.
Though larger protein consumption than the advisable allowance of 0.8 grams/kg/day is regarded secure, the examine suggests warning and extra scientific research. Leucine was the first amino acid liable for activating mTOR in macrophages, and growing protein consumption had a threshold impact on the detrimental signaling pathway.
A complete examination is required to find out the correct threshold between dietary protein advantages and unfavourable well being impacts.
Journal reference:
- Zhang, X., Kapoor, D., Jeong, SJ. et al. Identification of a leucine-mediated threshold impact governing macrophage mTOR signalling and cardiovascular danger. Nat Metab 6, 359–377 (2024). doi: https://doi.org/10.1038/s42255-024-00984-2
