Lac-Leu (N-Lactoyl-Leucine)
N-Lactoyl-leucine (Lac-Leu) is a lactate-amino acid conjugate produced during exercise by the CNDP2 enzyme. A sister metabolite to Lac-Phe, Lac-Leu crosses the blood-brain barrier and is being investigated for exercise-induced neuroprotection, cognitive enhancement, and metabolic regulation.
N-Lactoyl-leucine (Lac-Leu) is a recently characterized exercise metabolite formed by the conjugation of lactate with the branched-chain amino acid leucine. Produced primarily by the cytosolic nonspecific dipeptidase CNDP2 during high-intensity exercise, Lac-Leu belongs to a growing family of lactate-amino acid conjugates (lac-amino acids) that are believed to mediate systemic benefits of physical activity.
Overview
Lac-Leu was identified through untargeted metabolomics screens of post-exercise plasma as part of a broader effort to catalog the exercise metabolome. The landmark work by Li et al. (2022) at Stanford and Baylor characterized Lac-Phe as a major exercise-induced metabolite that suppresses appetite and reduces obesity, but the same studies revealed that multiple lac-amino acid conjugates are produced simultaneously during exercise, including Lac-Leu, Lac-Ile, and Lac-Val. While Lac-Phe drew initial attention for its potent appetite-suppressing effects, Lac-Leu has attracted growing interest due to its distinct pharmacological profile -- particularly its ability to cross the blood-brain barrier and its potential role in mediating the cognitive benefits of exercise.
The CNDP2 enzyme (cytosolic nonspecific dipeptidase 2, also known as carnosine dipeptidase 2) catalyzes the reverse condensation of lactate with amino acids. During intense exercise, as intracellular lactate concentrations rise sharply, CNDP2 activity shifts toward synthesis of lac-amino acid conjugates. The branched-chain amino acids (leucine, isoleucine, valine) are among the preferred substrates, making Lac-Leu one of the most abundant lac-amino acids produced during sprint and resistance exercise.
Mechanism of Action
Lac-Leu is synthesized intracellularly when CNDP2 catalyzes the condensation of lactate with leucine under conditions of elevated intracellular lactate -- primarily during anaerobic glycolysis associated with high-intensity exercise. Once synthesized, Lac-Leu is exported into the circulation where it acts as a signaling metabolite.
The mechanism of action of Lac-Leu is not yet fully elucidated, but several pathways have been proposed based on early research:
- Blood-brain barrier permeability: Unlike Lac-Phe, Lac-Leu demonstrates significant BBB penetration. The branched-chain structure of leucine may facilitate transport via LAT1 (L-type amino acid transporter 1), a major BBB transporter with high affinity for branched-chain amino acids. This positions Lac-Leu as a potential mediator of exercise-induced neuroplasticity and neuroprotection.
- BDNF pathway modulation: Preliminary evidence suggests that lac-amino acid conjugates including Lac-Leu may enhance BDNF (brain-derived neurotrophic factor) expression in hippocampal neurons, potentially through CREB phosphorylation. This mechanism could explain a portion of the well-documented cognitive benefits of exercise.
- Metabolic signaling: As a lactate-leucine conjugate, Lac-Leu carries signals from both its constituent molecules. Lactate itself acts as a signaling molecule through the HCAR1 (hydroxycarboxylic acid receptor 1) receptor, while leucine is a potent activator of mTORC1 signaling. The conjugate may integrate these signals in a tissue-specific manner.
- Anti-inflammatory effects: Emerging data suggest that lac-amino acids may modulate inflammatory pathways, potentially through NF-kB suppression, though direct evidence for Lac-Leu specifically is limited.
Reconstitution Calculator
Reconstitution Calculator
Calculate your peptide dosing
Set up a clean workspace with all supplies ready.
7x / week for weeks
Research
Neuroprotection and Cognitive Effects
The ability of Lac-Leu to cross the blood-brain barrier distinguishes it from Lac-Phe and positions it as a candidate mediator of exercise-induced cognitive benefits. While direct mechanistic studies on Lac-Leu in neuronal models are still limited, the broader class of lac-amino acids has been linked to:
- Hippocampal neurogenesis enhancement
- Reduced neuroinflammation in rodent models of neurodegeneration
- Improved spatial memory and learning in exercised animals
The lactate component of Lac-Leu is itself neuroprotective -- lactate acts as an alternative energy substrate for neurons and signals through HCAR1 in the brain to promote neuronal survival. The leucine moiety activates mTORC1-dependent protein synthesis required for long-term memory consolidation.
Metabolic Regulation
While Lac-Phe has demonstrated clear appetite-suppressing effects through its action on peripheral receptors, Lac-Leu's metabolic role appears to be more nuanced. Preliminary observations suggest that Lac-Leu may contribute to post-exercise improvements in insulin sensitivity and glucose uptake, potentially through AMPK-related pathways, though these effects have not been isolated from those of other lac-amino acids in published studies.
Exercise Metabolomics and Discovery
The systematic identification of lac-amino acids as exercise metabolites emerged from large-scale metabolomics studies. Li et al. (2022) performed untargeted metabolomics on plasma from humans, racehorses, and mice after acute exercise, identifying Lac-Phe as the most significantly elevated metabolite post-exercise. In the same dataset, Lac-Leu and other branched-chain lac-amino acids were among the top exercise-responsive metabolites, with plasma levels increasing 2-5 fold following sprint exercise (Li et al., 2022).
CNDP2 Enzyme Biology
CNDP2 (also known as CN2 or carnosine dipeptidase 2) was identified as the biosynthetic enzyme responsible for lac-amino acid production. CNDP2 knockout mice show dramatically reduced post-exercise levels of all lac-amino acids including Lac-Leu, confirming the enzyme's essential role. CNDP2 is highly expressed in immune cells (macrophages, monocytes), skeletal muscle, and liver, suggesting multiple tissue sources contribute to circulating lac-amino acid pools (Li et al., 2022).
Safety Profile
Lac-Leu is an endogenous metabolite naturally produced in human tissues during exercise, which confers a highly favorable theoretical safety profile. Circulating Lac-Leu levels fluctuate physiologically with exercise intensity and duration, and no adverse effects have been associated with elevated post-exercise Lac-Leu concentrations. As a naturally occurring metabolite rather than a synthetic compound, Lac-Leu is not subject to pharmaceutical regulatory pathways in the same manner as peptide therapeutics. No exogenous administration studies in humans have been published, so formal safety data for supplemental Lac-Leu do not yet exist.
Potential considerations include:
- mTORC1 activation: The leucine moiety could theoretically contribute to excessive mTORC1 signaling in specific contexts (e.g., active malignancies), though physiological concentrations are likely too low for clinically meaningful effects.
- Drug interactions: Not characterized. Theoretical interactions with diabetes medications (via metabolic pathway overlap) have not been evaluated.
Pharmacokinetic Profile
- Half-life
- Not established
Molecular Structure
- Formula
- C9H17NO4
- CAS
- Not yet assigned (emerging metabolite)
Research Protocols
oral
Future protocols would likely require synthetic GMP-grade Lac-Leu, pharmacokinetic profiling for oral versus parenteral bioavailability, and dose-finding studies benchmarked against physiological post-exercise concentrations (estimated at 0.5-5 micromolar peak plasma).
Interactions
Peptide Interactions
Both are exercise-responsive molecules that activate AMPK-related pathways. MOTS-c is a mitochondrial-derived peptide that functions as an exercise mimetic, while Lac-Leu is a glycolytic byproduct-derived metabolite. Their distinct biosynthetic origins (mitochondrial DNA vs. cytosolic enzyme acti...
Lac-Leu may enhance endogenous BDNF expression, and co-administration with exogenous BDNF or BDNF-enhancing peptides could amplify neuroplasticity effects. The interaction between lac-amino acid signaling and neurotrophin pathways is an active area of investigation.
As sister metabolites produced simultaneously during exercise, Lac-Leu and Lac-Phe likely exert complementary effects -- Lac-Phe mediating peripheral appetite suppression and metabolic regulation, while Lac-Leu crosses the BBB to mediate central neuroprotective and cognitive effects. Combined adm...
For cognitive and neuroprotective applications, combining Lac-Leu (exercise-mimetic neuroprotection via BBB-penetrant lactate-leucine signaling) with nootropic peptides such as Semax (BDNF upregulation) or Selank (anxiolytic, immunomodulatory) could provide multi-target cognitive enhancement. The...
Quality Indicators
What to look for
- Naturally occurring compound
Frequently Asked Questions
References (5)
- [3]
- [6]Li VL, Kim JT, Long JZ Lac-Phe and lactate-amino acid conjugates as exercise factors Trends Endocrinol Metab (2023)
- [1]Li VL, He Y, Contrepois K, et al An exercise-inducible metabolite that suppresses feeding and obesity Nature (2022)
- [2]Reddy A, Bozi LHM, Yagber O, et al pH-gated succinate secretion regulates muscle remodeling in response to exercise Cell (2020)
- [5]Scheiman J, Luber JM, Chavkin TA, et al Meta-omics analysis of elite athletes identifies a performance-enhancing microbe that functions via lactate metabolism Nat Med (2019)
Kristagen
Kristagen is a complex peptide bioregulator preparation derived from thymus tissue, developed to support immune function and T-cell-mediated immunity. Research focuses on its potential for countering thymic involution, restoring age-related immune decline, and supporting T-cell differentiation through tissue-specific peptide signaling.
Lac-Phe (N-Lactoyl-Phenylalanine)
Lac-Phe (N-lactoyl-phenylalanine) is a lactate-amino acid conjugate produced by the enzyme CNDP2 during exercise. It is the most significantly elevated blood metabolite after intense physical activity and suppresses food intake through a brain-fat axis signaling mechanism, with implications for obesity treatment.