IngredientsArginine alpha-ketoisocaproate (AAKG) is a compound formed by combining the amino acid L-arginine with alpha-ketoisocaproate (KIC), a metabolite of the branched-chain amino acid leucine. It is distinct from the more commonly discussed supplement arginine alpha-ketoglutarate, which pairs L-arginine with a different co-acid (alpha-ketoglutarate, a Krebs cycle intermediate); the two compounds are frequently abbreviated "AAKG" in the literature, and care must be taken to distinguish them by their full names.
The CAS Registry Number is 72087-40-2, and recognized synonyms include L-arginine mono(4-methyl-2-oxovalerate), L-arginine KIC, 2-amino-5-(diaminomethylideneamino)pentanoic acid 4-methyl-2-oxopentanoic acid, and KIC-arginine. Its molecular formula is C₁₂H₂₄N₄O₅ and its molecular weight is approximately 304.34 g/mol.
The SMILES notation for the compound is CC(C)CC(=O)C(O)=O combined with L-arginine, with the InChIKey MOZIGXHKOXEDLJ-WCCKRBBISA-N. The ornithine and arginine salts of alpha-keto acid analogs of the branched-chain essential amino acids do not persist in water because they dissociate completely, presumably into the amino acid cation and the keto acid anion. This means that in aqueous solution or in the body's fluids, the compound separates into free L-arginine and free alpha-ketoisocaproate.
Alpha-ketoisocaproic acid (α-KIC), also known as 4-methyl-2-oxovaleric acid, and its conjugate base alpha-ketoisocaproate, are metabolic intermediates in the metabolic pathway for L-leucine. Leucine is an essential amino acid, and its degradation is critical for many biological duties. α-KIC is produced in one of the first steps of the pathway by branched-chain amino acid aminotransferase, by transferring the amine on L-leucine onto alpha-ketoglutarate and replacing that amine with a ketone.
Arginine alpha-ketoisocaproate is sold as a dietary supplement ingredient, typically as a white to off-white crystalline or powder material. One common commercial form is L-Arginine Alpha Ketoisocaproate (KIC) Calcium 1:1, a specialized compound that chemically bonds L-arginine with alpha-ketoisocaproate (the keto analogue of the branched-chain amino acid L-leucine), with the 1:1 ratio formulation stabilized with calcium, making it a functional ingredient for the food and food supplement industries. The compound is also encountered as a free-acid salt and as a hydrochloride derivative in various commercial formulations.
It is frequently incorporated into pre-workout powders and capsules, often alongside glycine and free L-arginine to create the triple-component formulation known as GAKIC (glycine-arginine-alpha-ketoisocaproate). In GAKIC, 3.2 g of KIC is combined with 6.0 g of glycine and 2.0 g of L-arginine. Arginine alpha-ketoisocaproate is also available as a standalone ingredient for use in custom supplement blends.
Arginine alpha-ketoisocaproate is a synthetic salt without a history of use in traditional herbal or botanical medicine. It was developed as a deliberate pharmaceutical and nutritional research compound in the 1970s and 1980s.
The novel compounds formed by early synthesis work include arginine alpha-ketoisocaproate, arginine alpha-ketoisovalerate, arginine alpha-keto-beta-methylvalerate, ornithine alpha-ketoisocaproate, ornithine alpha-ketoisovalerate, and ornithine alpha-keto-beta-methylvalerate. Early US patent filings from the late 1970s and early 1980s document its synthesis and initial proposed applications in the management of hepatic and renal disorders. Salts of basic L-amino acids, such as L-arginine and L-ornithine, and alpha-keto analogs of branched-chain essential amino acids, including alpha-ketoisocaproate, alpha-ketoisovalerate, and alpha-keto-beta-methylvalerate, were disclosed in US Patent Nos. 4,228,099, 4,296,127, and 4,320,146 for use in the treatment of hepatic disorders characterized by hyperammonemia and portal-systemic encephalopathy, and for treatment of renal failure.
Ketoanalogues of three branched-chain amino acids — leucine, isoleucine, and valine — were the principal constituents of ketoacid–amino acid mixtures placed under clinical trial in the United States, Canada, and France as dietary supplements for patients with chronic renal failure. They have also been studied as agents of possible therapeutic value in portal-systemic encephalopathy, congenital hyperammonemia, post-operative nitrogen wasting, muscular dystrophy, and McArdle's disease, and as feed additives for farm animals.
AAKG gained popularity in the sports nutrition industry in the late 1990s and early 2000s as a performance-enhancing supplement, often featured in pre-workout formulas. Its transition from clinical research into consumer sports supplements reflected growing interest in the individual components' roles in energy metabolism and muscle physiology.
Because arginine alpha-ketoisocaproate dissociates in aqueous media, its biological effects are attributable to the actions of its two released components: L-arginine and alpha-ketoisocaproate (KIC). Each has independently established biochemical roles.
Arginine is a precursor for nitric oxide, which can support vasodilation and blood flow. More specifically, physiological concentrations of L-arginine in healthy individuals are theoretically enough to saturate endothelial nitric oxide synthase (NOS), which operates at approximately 3 μmol/L. Therefore, supplementary L-arginine should not promote increased enzyme activity and no further NO production should occur. However, there is evidence describing NO-mediated biological effects associated with L-arginine supplementation despite NOS being theoretically saturated — a phenomenon known as the "L-arginine paradox."
Arginine is converted in the body into nitric oxide, which causes blood vessels to open wider for improved blood flow. Arginine also stimulates the release of growth hormone, insulin, and other substances in the body.
Leucine increases protein synthesis through activation of the mammalian target of rapamycin (mTOR) signaling pathway in skeletal muscle, adipose tissue, and placental cells. It promotes energy metabolism — including glucose uptake, mitochondrial biogenesis, and fatty acid oxidation — to provide energy for protein synthesis, while inhibiting protein degradation. Approximately 80% of leucine is normally used for protein synthesis, while the remainder is converted to α-ketoisocaproate (α-KIC) and β-hydroxy-β-methylbutyrate (HMB) in skeletal muscle.
Orally delivered KIC in humans is covalently aminated to form leucine in the splanchnic bed. Furthermore, KIC can be shunted into HMB via cytosolic KIC dioxygenase in situ in muscle tissues. This means KIC may serve as a precursor for two other bioactive compounds — leucine itself and HMB — adding complexity to its metabolic profile.
The keto analog of leucine, alpha-ketoisocaproate (KIC), is formed intracellularly from leucine and is released, in part, into the systemic circulation. KIC therefore acts as both an endogenous catabolite of leucine and an exogenous supplementable precursor to leucine and HMB.
Enhancing muscle recovery following trauma occurs not simply by administering oral or intravenous leucine alone, but instead responds to increasing the steady-state concentration of alpha-ketoisocaproic acid. This anabolic ketoacid has been described as a major factor in reducing protein catabolism, stimulating muscle synthesis, and sparing glucose oxidation, while stimulating insulin release.
With respect to insulin secretion, research has clarified that it remains unclear how alpha-ketoisocaproate and leucine are metabolized to stimulate insulin secretion. Mitochondrial BCATm (branched-chain aminotransferase) catalyzes reversible transamination of leucine and alpha-ketoglutarate to KIC and glutamate, the first step of leucine catabolism. Investigation using BCATm-knockout mice revealed that BCATm disruption abolished insulin secretion by KIC, D,L-α-keto-β-methylvalerate, and α-ketocaproate without altering stimulation by glucose, leucine, or alpha-ketoglutarate.
On the anti-catabolic side, recent preclinical work has identified that KIC suppressed mRNA expression of myostatin, a key regulator of muscle atrophy, more effectively than did L-leucine (−26.37 ± 4.11%, p < 0.01). KIC enhanced protein turnover in C2C12 myotubes and maintained 50% cell viability at high concentrations (KIC: 4.68 mM vs. HMB: 3.11 mM). Following conditioned media treatment, KIC suppressed MuRF1 and MAFbx expression in a myostatin-dependent manner, thereby reducing their polyubiquitination.
The molecular mechanism underlying these findings involves the Akt–FoxO3a axis: KIC attenuates cancer cachexia-induced muscle atrophy by inducing FoxO3a nuclear export, and this phenomenon is regulated in an Akt-dependent manner. The results reveal an Akt–FoxO3a–myostatin axis that underlies muscle atrophy, suggesting that KIC, through the Akt–FoxO3a pathway, is a potential therapeutic agent for mitigating muscle atrophy.
However, KIC also exhibits a metabolically complex and potentially double-edged relationship with insulin signaling. In skeletal muscle cell studies, alpha-ketoisocaproic acid (KIC) stimulated mTORC1 signaling but suppressed insulin-stimulated glucose transport (−34%, P < 0.05) in an mTORC1-dependent manner. Furthermore, metabolomics studies have linked elevated blood levels of BCAA metabolites to insulin resistance and T2DM, and high concentrations of the leucine metabolite KIC are associated with insulin resistance and T2DM in humans and animals. These findings pertain to elevated, possibly pathological concentrations and are relevant to understanding the compound's safety profile.
The glycine and L-arginine salt of alpha-ketoisocaproic acid (GAKIC) has been described as an ergogenic aid for muscle physiology and performance that fills the gap between the short anaerobic energetic benefits of creatine and the long-term aerobic benefits imparted by sodium-dependent carbohydrate/rehydration technology. Dynamic high-intensity use of skeletal muscle rapidly leads to fatigue and reductions in muscle force and work, especially when initiated during the anaerobic phase. The proposed mechanism involves the glycine component supplying substrate for creatine and porphyrin synthesis, the L-arginine supplying substrate for nitric oxide synthesis, and KIC contributing via the leucine/HMB pathway to reduce catabolism.
Branched-chain keto acids, and alpha-ketoisocaproate in particular, are known to exhibit a nitrogen- or protein-sparing effect in patients with chronic renal failure. That is, branched-chain keto acids reduce urinary nitrogen loss. These keto acids have been used to improve the nitrogen balance in patients suffering from a number of different nitrogen-wasting conditions. Keto acid analogs are also known to be adequate nutritional substitutes for several of the essential amino acids. Substitution of keto analogs for essential amino acids makes possible a reduction in nitrogen intake in uremic patients.
The mechanism underlying this nitrogen-sparing effect was described mechanistically in early patent literature: the salts dissociate in body fluids to form the branched-chain keto acids plus arginine and/or ornithine. The branched-chain keto acids then replenish the body stores of the branched-chain amino acids (leucine, valine, and isoleucine) at the expense of labile nitrogenous compounds, promote protein synthesis, and inhibit excessive brain uptake of aromatic amino acids, which is seen in patients with liver disease.
Arginine-based supplementation has produced mixed results, with some studies reporting ergogenic benefits in anaerobic power, muscular strength, and muscular endurance, while others have found no effect on these same performance variables. The following individual trials describe the principal human evidence specifically for arginine alpha-ketoisocaproate and the closely related GAKIC formulation.
Note: This key trial used arginine alpha-ketoglutarate (AAKG), not alpha-ketoisocaproate. It is included here because it is the most frequently cited long-term human AAKG safety and performance study, and it establishes a benchmark for the broader arginine salt class.
Subjects participated in two studies employing a randomized, double-blind, controlled design. In study 1, 10 healthy men (30–50 years old) fasted for 8 hours and then ingested 4 g of time-released or non-time-released AAKG; blood samples were taken for 8 hours after ingestion to assess the pharmacokinetic profile of L-arginine. In study 2, which was placebo-controlled, 35 resistance-trained adult men (30–50 years old) were randomly assigned to ingest 4 g of AAKG three times a day (12 g daily) or placebo. Participants performed 4 days of periodized resistance training per week for 8 weeks. Significant differences were observed in the AAKG group (p < 0.05) for one-repetition maximum (1RM) bench press, Wingate peak power, blood glucose, and plasma arginine. No significant differences were observed between groups in body composition, total body water, isokinetic quadriceps muscle endurance, or aerobic capacity. AAKG supplementation appeared to be safe and well tolerated, and positively influenced 1RM bench press and Wingate peak power performance. AAKG did not influence body composition or aerobic capacity.
Limitation: This study used arginine alpha-ketoglutarate, not arginine alpha-ketoisocaproate. The co-acid differs between the two compounds. The study also lacked a resistance-exercise-only control arm, making it difficult to isolate the supplement's contribution from training adaptations.
Eight resistance-trained and eight untrained healthy males ingested either 3,000 mg of AAKG or a placebo 45 minutes prior to a resistance exercise protocol in a randomized, double-blind crossover design. The results indicated that acute AAKG supplementation provides no ergogenic benefit on 1RM or total load volume as measured by the standard barbell bench press and leg press, regardless of training status.
This study sought to determine the effects of AAKG supplementation on hemodynamics and brachial-artery blood flow and the circulating levels of L-arginine, nitric oxide metabolites (NOx), asymmetric dimethylarginine (ADMA), and the L-arginine:ADMA ratio after resistance exercise. Twenty-four physically active men underwent 7 days of AAKG supplementation with 12 g/day of either a commercial AAKG product or placebo. Before and after supplementation, a resistance-exercise session was performed involving 3 sets of 15 repetitions with 70–75% of one-repetition maximum. The AAKG product increased plasma L-arginine levels; however, the effects observed in hemodynamics, brachial-artery blood flow, and NOx could only be attributed to the resistance exercise, not to the AAKG supplementation.
The purpose of one study was to determine whether acute arginine α-ketoglutarate supplementation (AAKG) would affect local muscle endurance of the arm and shoulder girdle or the blood pressure response to anaerobic exercise. Twelve trained college-aged men (22.6 ± 3.8 years) performed 2 trials of exercise separated by at least 1 week. At 4 hours before and 30 minutes before exercise, a serving of AAKG (3,700 mg arginine alpha-ketoglutarate per serving) or placebo was administered. The AAKG supplementation did not improve muscle endurance or significantly affect the blood pressure response to anaerobic work.
Several human trials have specifically examined the tri-component formulation GAKIC, which directly incorporates the alpha-ketoisocaproate form of the salt.
Isokinetic dynamometry and cycle ergometry have demonstrated performance benefits of GAKIC in high-intensity training. In the Buford & Koch 2004 cycling study, the purpose was to determine the effect of GAKIC supplementation on repeated bouts of anaerobic cycling performance. Ten men completed a randomized, double-blinded, placebo-controlled exercise protocol of two sessions separated by 7 days. Subjects consumed either 11.2 g GAKIC or placebo during a 45-minute period between a rest blood draw and exercise. Mean power, peak power, and fatigue values were assessed from five supramaximal, 10-second cycle ergometer sprints separated by 1-minute rest intervals. Post-hoc analyses revealed a greater retention of mean power between sprints 1 and 2 after GAKIC (−1 ± 9 W) versus placebo treatment (−47 ± 18 W). No other performance variables differed between placebo and GAKIC.
Oral supplementation with GAKIC had previously been shown to improve exhaustive high-intensity exercise performance. However, there were no controlled studies involving GAKIC supplementation in well-trained subjects. To address this, 10 well-trained male cyclists completed 2 supramaximal sprint tests each involving 10 sprints of 10 seconds separated by 50-second rest intervals on an electrically braked cycle ergometer. Subjects ingested 11.2 g of GAKIC or placebo during a period of 45 minutes before the 2 experimental trials, in a randomized and double-blind fashion. Peak power declined from the 1st sprint to the 10th sprint and did not differ between conditions (p = .88). This failure to replicate suggests that the previously observed ergogenic effects may be specific to less-trained individuals or to particular exercise modalities.
Yarrow et al. explored the efficacy of short-term monotherapy supplementation of alpha-ketoisocaproate (KIC) given orally immediately before moderate- and high-intensity single-bout exercise performance measurements. In this study, resistance-trained men completed a trial with either 1.5 or 9.0 g of either KIC or isocaloric placebo control. The other components of GAKIC — glycine and L-arginine — were not included. Results demonstrated that ingestion of either a low (1.5 g) or high (9.0 g) dose of monotherapy KIC prior to exercise does not alter moderate- or high-intensity exercise performance. These results may suggest that the previously reported ergogenic effects of GAKIC are due to the inclusion of glycine and/or L-arginine in the GAKIC formulation.
Taken as a group, the overall net interpretation of the GAKIC supplementation studies is that muscle performance is enhanced during the time frame of anaerobic energy deficit generated by different modalities of high-intensity exercise and testing, and that this enhancement can be exploited by both recreational and competitive athletes of both genders. Additional studies are warranted to expand comparisons among these modalities. However, the evidence is mixed; several well-controlled trials — especially in trained athletes and with acute arginine alpha-ketoglutarate dosing — have found no benefit, and the specific contribution of the alpha-ketoisocaproate moiety versus the arginine or glycine components has not been isolated in most positive trials.
Branched-chain keto acids, and alpha-ketoisocaproate in particular, are known to exhibit a nitrogen- or protein-sparing effect in patients with chronic renal failure, reducing urinary nitrogen loss. These keto acids have been used to improve the nitrogen balance in patients suffering from a number of different nitrogen-wasting conditions.
It has been well established that a diet with 0.3 to 0.4 g of protein per kilogram per day that is supplemented with keto acids and essential amino acids reduces the generation of potentially toxic metabolic products, as well as the burden of potassium and phosphorus. Restriction of dietary protein intake to 0.6–0.8 g/kg of ideal body weight per day appears to have an acceptable safety profile, and supplementation with keto acids is associated with decreased urine protein excretion.
The evidence from this application is considered more clinically established than the sports performance evidence, having been evaluated in controlled clinical settings over decades. However, most clinical keto acid research in renal disease uses multi-component keto acid preparations (e.g., the commercial product Ketosteril) containing multiple keto analogs of essential amino acids, making it difficult to attribute effects specifically to arginine alpha-ketoisocaproate in isolation.
The branched-chain keto acids, after dissociation, replenish the body stores of the branched-chain amino acids (leucine, valine, and isoleucine) at the expense of labile nitrogenous compounds, promote protein synthesis, and inhibit excessive brain uptake of aromatic amino acids, which is observed in patients with liver disease. The beneficial effects from using arginine or ornithine alpha-ketoisocaproate alone are believed to be related to a regulatory role that the essential amino acid leucine plays in protein synthesis.
Administration of the compounds appears to give synergistic effects greater than the total effects of administering either arginine or ornithine alone or administering branched-chain keto acids alone. This synergistic effect may be explained by the mechanism whereby ornithine (given as such or derived from arginine) that is destroyed by ornithine transaminase gives rise to nitrogen in the form of glutamate, which then reacts with the keto acid to give rise to essential amino acids that are then used for protein synthesis.
Cancer-associated cachexia (CAC) is a multifactorial syndrome characterized by progressive loss of muscle mass. Although emerging evidence suggests that L-leucine and HMB have potential for treating CAC, the role of alpha-ketoisocaproate (KIC), a metabolite of L-leucine, in this context has only recently been explored. A 2025 study explored the use of KIC as a therapeutic agent for CAC-induced muscle atrophy by targeting myostatin. The study used mouse models and cultured myotube cells and found promising anti-atrophic effects. This evidence is at the preclinical stage only; no human clinical trials have confirmed these effects in cancer cachexia.
A study was designed to examine the glucose-sparing effect of leucine and its keto acid alpha-ketoisocaproate (KIC) in vivo using overnight-fasted normal volunteers. In the first group, eight subjects received an intravenous infusion of leucine and six subjects received KIC at 2.3 μmol × kg⁻¹ × min⁻¹ for 3 hours; on another occasion, all subjects received saline and acted as their own controls. The researchers (Buckspan et al., 1986) concluded that alpha-ketoisocaproate was superior to leucine in sparing glucose utilization in humans.
In contrast, more recent cell-based research has found that KIC, in an mTORC1-dependent manner, inhibited insulin-stimulated glucose transport, and this inhibition was relieved in cells depleted of BCAT2. Because liver and muscle activity of branched-chain keto acid dehydrogenase (BCKDH), the enzyme that irreversibly catabolizes KIC, is diminished in obesity and type 2 diabetes mellitus, mechanisms that prevent KIC accumulation may have therapeutic potential for the management of insulin resistance and its sequelae. The glucose-related evidence is thus genuinely mixed and the clinical relevance of supplemental KIC doses to these cell-based findings remains unclear.
The relative dietary efficacy of arginine α-ketoisocaproate (AKIC) and ornithine α-ketoisocaproate (OKIC) was evaluated in a rat trauma (bilateral femur fracture) model. Both control and traumatized rats were starved for 2 days and then pair-fed for 2 or 4 days one of three liquid diets: a basic casein diet; or the basic diet in which 10% of nitrogen was replaced by AKIC or OKIC nitrogen, respectively. Irrespective of the diet, the protein-efficiency ratio was 27% less in traumatized rats than in control rats. More improvement in apparent nitrogen balance, particularly in traumatized rats, was seen with the AKIC supplement. This animal evidence supports the rationale for arginine alpha-ketoisocaproate in post-operative or trauma settings, but human clinical data in this specific application are very limited.
The following dosages are reported directly from human clinical studies and trial descriptions:
In the 8-week AAKG trial, supplementation appeared to be safe and well tolerated at 12 g/day. The preponderance of clinical reporting identifies nausea, vomiting, and diarrhea as the typical side effects of oral arginine (and to a degree its salts), with symptoms more likely at larger single doses and higher daily regimens; single doses of 3–6 g rarely provoke problems whereas doses above approximately 9 g have been associated with gastrointestinal symptoms and laxative-type effects in athletes and healthy adults.
The athletic performance supplement industry is a multibillion-dollar business and one popular category claims to increase nitric oxide production. Three patients presenting to the emergency department with adverse effects have been reported: a 33-year-old man presented with palpitations, dizziness, vomiting, and syncope after the use of a commercial AAKG-containing product (NO₂ Platinum); his ECG was normal but dizziness required overnight admission. A 21-year-old man with palpitations and near syncope had used a "nitric oxide" supplement; he was tachycardic to 115 bpm with otherwise normal examination. These cases involve multi-ingredient pre-workout products, making causal attribution to arginine alpha-ketoisocaproate specifically uncertain. The efficacy of AAKG is unclear, and more data are needed to determine the risk versus benefit of these supplements.
Because arginine alpha-ketoisocaproate releases free L-arginine in vivo, the safety considerations of high-dose L-arginine are directly relevant. Both amino acids act on the nitric oxide pathway, which can lower blood pressure and modify vascular function; randomized trials and meta-analyses have examined those effects but results are mixed and context-dependent. Short-term reductions in arterial stiffness or modest blood-pressure improvements have been reported in some trials, yet long-term trials of L-arginine failed to show consistent cardiovascular benefit and have raised concerns about a lack of durable efficacy. Because NO-mediated vasodilation can lower systemic blood pressure, supplements may pose a risk for people with low baseline blood pressure or those on antihypertensive therapy.
In the context of Maple Syrup Urine Disease (MSUD), KIC accumulates pathologically and at high concentrations has been shown to exert adverse neurological effects. At concentrations relevant to MSUD, KIC acts as an uncoupler of oxidative phosphorylation and as a metabolic inhibitor, possibly through its inhibitory effect on alpha-ketoglutarate dehydrogenase activity. Impairment in hippocampal mitochondrial function appears to be involved in the neurotoxicity induced by KIC in these pathological settings. It is important to note that these findings relate to the abnormal, pathological KIC accumulation seen in MSUD, not to supplemental doses in healthy individuals; however, they caution against excessive dosing.
Metabolomics studies have linked elevated blood levels of BCAA metabolites to insulin resistance and type 2 diabetes mellitus. High concentrations of the leucine metabolite alpha-ketoisocaproic acid (KIC) are associated with insulin resistance and T2DM in humans and animals. The relevance of this association at supplemental doses in healthy individuals has not been established, but it suggests the need for caution in populations at risk for metabolic disease.
The overall safety and efficacy picture for arginine alpha-ketoisocaproate is summarized by reviewers of the related compound literature: the efficacy of AAKG is unclear, and more data are needed to determine the risk versus benefit of these supplements. Arginine-based supplementation has produced mixed results, with some studies reporting ergogenic benefits in anaerobic power, muscular strength, and muscular endurance, while others have found no effect on these same performance variables.
Health conditions that Arginine alpha-ketoisocaproate may help support.
Body systems that Arginine alpha-ketoisocaproate may help support.
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