New Research:

By Steve Blechman

Research studies have found that branched-chain amino acids (BCAAs) are associated with diabetes and obesity, and the branched-chain amino acid valine is the culprit! A study published in the journal Metabolife (January 14, 2019) found a strong association between branched-chain amino acids and the risk of incident for type 2 diabetes in China. The branched-chain amino acid valine had the highest risk prediction of incidents of type 2 diabetes! These findings could aid in diabetes risk assessment in the Chinese and global population!

There’s an overwhelming amount of evidence over the years that elevated branched-chain amino acids are associated with obesity and insulin resistance. A meta-analysis study (Acta Diabetologica, November 9, 2018) found that oral BCAA elevates circulating dietary BCAA and were positively and inversely related to type 2 diabetes mellitus and overweight/obesity risk respectively! The researchers said, “Eight articles on randomized clinical trials of oral BCAA supplementation and seven articles on dietary BCAA intake and type 2 diabetes/obesity risks were eligible for inclusion in our meta-analysis.”

Branched-chain amino acids supplements (BCAAs) have been associated with insulin resistance in obese individuals. Recently, the valine catabolite 3-hydroxyisobuterate (3HIB) was shown to promote insulin resistance in skeletal muscle by increasing lipid content in vivo. The purpose of this study was to investigate the mechanistic effects of 3HIB on skeletal muscle insulin signaling, metabolism, and related gene expression in vitro. These findings were recently published in the Journal of Nutrition Research (June 2019). This most recent study found that 3HIB can reduce muscle insulin sensitivity and support a role of 3HIB in the development of insulin resistance. This study is significant because it confirms the mechanism of 3HIB and insulin resistance in muscle!

As I mentioned above, high levels of BCAAs are associated with hyperglycemia, diabetes and insulin resistance. In a most recent study in the journal Mediators of Inflammation, on November 11, 2019, researchers undertook a study, “aimed at assessing circulating valine concentrations in subjects with type 2 diabetes,” noting that “Circulating valine level might be a novel biomarker for type 2 diabetes.”  

The researchers analyzed blood valine levels in type 2 diabetes after sitagliptin treatment, an anti-diabetic drug. “Valine levels were higher in type 2 diabetes patients, while decreased in sitagliptin monotherapy.” Research has also shown that the anti-diabetic drug metformin can also lower valine in the blood of diabetics. “These results suggest that valine might be involved in the pathogenesis in type 2 diabetes,” the researchers said.

It was reported in the journal Nature Medicine in 2015 that valine catabolite 3-hydroxyisobuterate (3HIB) promoted the accumulation of fat within muscle tissue by directly stimulating fatty uptake in the muscle. The intramuscular fat activates certain signaling cascades within the muscle cell that diminish insulin signaling, leading to insulin resistance. This study also found that inhibiting the production of 3HIB prevented the uptake of fat. Other studies support the negative effect of 3HIB on insulin signaling with elevated 3HIB in the muscle of human subjects with diabetes (J Lipid Res, 1989; Diabetologia, 2015). An article titled “Insulin Resistance, And What May Contribute to It” by Lila Abassi and published on the American Council on Science & Health website March 14, 2016 reported on “… a study published in Nature Medicine, [that] scientists have discovered that 3-hydroxyisobuterate (3HIB), one of the intermediate products in the breakdown of the BCAA valine, plays a role in the transport of fatty acids into skeletal muscle cells, which creates fatty muscles — a contributor to insulin resistance.” Abassi also also states, “Thus far, it has been a relative mystery as to how BCAAs play a role in insulin resistance. Skeletal muscles display resistance to insulin when there is excess fat inside their cells.” In closing of the article, Abassi said, “What the researchers found was that 3HIB acted as a shuttle in muscle cells, allowing blood vessels in skeletal muscle tissue to move fat into skeletal muscle. The more 3HIB, the more fat was transported — and conversely, when scientists blocked 3HIB from being made, there was less uptake of fat into skeletal muscle.”

In another most recent study published in the American Journal of Physiology-Endocrinology and Metabolism on November 26, 2019, it was found that leucine can prevent intracellular muscle lipid accumulation and storage in skeletal muscle, which is commonly observed in obese patients, resulting in mitochondrial damage. We normally store fat in adipose sites (often referred to as white fat) mainly around our waistline and hips, but we also store fat in muscles. Fatty muscles interfere with the function of insulin a hormone produced in the pancreas and can cause insulin resistance, elevated blood sugar and type 2 diabetes. 

An article published in the The New York Times on December 3, 2019 reported that, “cyclists who peddled on an empty stomach burned twice as much fat.” This new study that was reported in the Times’ article was recently published in the Journal of Clinical Endocrinology and Metabolism. The study found that exercising on an empty stomach can lower muscle fat! 

The latest research supports my position over the last two years that BCAAs are linked to insulin resistance, diabetes, obesity, with valine being the culprit! That’s why I have always recommended leucine as a dietary supplement rather than BCAA mixtures containing valine.

Researchers found that leucine supplementation can increase insulin sensitivity by activating SIRT1 activity and promote mitochondrial biogenesis and prevent the mitochondrial dysfunction in skeletal muscle. By increasing insulin sensitivity, leucine may enhance fat loss and improve lean body mass. Research has shown that leucine amplifies the effect of the diabetic drug metformin on insulin sensitivity and glycemic control in diet-induced obesity. Adding leucine to metformin has been shown to be synergistic, enabling a 65% to 80% metformin reduction with no loss of diabetic efficacy and a 40% metformin dose reduction in a recent clinical trial (Diabetes, June 12, 2016; Metabolism 2016 and Alimentary Pharmacology & Therapeutics, 2018). Metformin has been approved by the FDA for over 25 years as an anti-diabetic drug and has recently been reviewed as a possible FDA-approved anti-aging drug. Recent research has also shown that metformin can lower elevated valine levels in diabetics.

A meta-analysis that combined the results of seven studies showed that BCAAs or leucine supplements are best taken after exercise, not before or during exercise (intra-workout) for reducing muscle soreness and creatine kinase, a marker of muscle damage, better than rest alone. Leucine consumption before your workout promotes sluggishness and fatigue. Recent research has shown that leucine competitively inhibits the dopamine precursor tyrosine into the brain and reduces dopamine levels. Increased dopamine allows the body to perform at higher levels than normal. Increasing dopamine reduces fatigue and increases mental arousal, focus, confidence, and greater levels of motivation. Pre-workout leucine and BCAA consumption is not best for optimal muscle performance

Leucine is the key anabolic trigger to protein synthesis! For best results as an anabolic trigger, take 5 grams of leucine, as found in Advanced Molecular Labs™ (AML™) Post Workout, on an empty stomach after resistance training workout and 15-30 minutes before a post-workout meal. By taking pure leucine on an empty stomach, you will get a better spike in blood levels than if you take leucine with food, because food can slow leucine’s absorption. When leucine is taken on an empty stomach, it’s a powerful metabolic switch that turns on protein synthesis. Leucine increases mTOR activity for several hours after training. When leucine is taken after resistance exercise and before a post-workout, protein-containing meal rich in essential amino acids, it triggers greater protein synthesis for improved recovery and greater gains.

References:

1. Xiaoyu Liao, Bingyao Liu, Hua Qu, et al. A High Level of Circulating Valine Is a Biomarker for Type 2 Diabetes and Associated with the Hypoglycemic Effect of Sitagliptin, Mediators of Inflammation, vol. 2019, Article ID 8247019, 7 pages, 2019. https://doi.org/10.1155/2019/8247019

2. Leucine Decreases Intramyocellular Lipid Deposition in an mTORC1-independent Manner in Palmitate-treated C2C12 Myotubes. Hexirui Wu, Sami Dridi, Yan Huang, and Jamie I. Baum. American Journal of Physiology-Endocrinology and Metabolism November 26, 2019. https://www.ncbi.nlm.nih.gov/pubmed/31770014

3. R M Edinburgh, H E Bradley, N-F Abdullah, S L Robinson, O J Chrzanowski-Smith, J -P Walhin, S Joanisse, K N Manolopoulos, A Philp, A Hengist, A Chabowski, F M Brodsky, F Koumanov, J A Betts, D Thompson, G A Wallis, J T Gonzalez, Lipid metabolism links nutrient-exercise timing to insulin sensitivity in men classified as overweight or obese, The Journal of Clinical Endocrinology & Metabolism, dgz104, https://doi.org/10.1210/clinem/dgz104

4. Skip Breakfast Before the Gym by Gretchen Reynolds. NY Times. December 3, 2019 

5. Actions of chronic physiological 3-hydroxyisobuterate treatment on mitochondrial metabolism and insulin signaling in myotubes. Nutrition Research June 2019. Vol: 66, Page: 22-Lyon, Emily S; Rivera, Madison E; Johnson, Michele A; Sunderland, Kyle L; Vaughan, Roger A. DOI 1016/j.nutres.2019.03.012

6. Cummings, N.E., Williams, E.M., Kasza, I., Konon, et al. (2018), Restoration of metabolic health by decreased consumption of branched‐chain amino acids. J Physiol, 596: 623-645. doi:10.1113/JP275075 

7. Duke University. Diabetes researchers find switch for fatty liver disease: Carbs, fats and protein: One molecule to rule them all? ScienceDaily. ScienceDaily, 17 May 2018. sciencedaily.com/releases/2018/05/180517113847.htm

8. J. White, R.W. McGarrah, P.A. Grimsrud, S. Tso, W. Yang, J. M. Haldeman, C. Newgard et al. The BCKDH Kinase and Phosphatase Integrate BCAA and Lipid Metabolism via Regulation of ATP-Citrate Lyase. Cell Metabolism, 2018; DOI: 10.1016/j.cmet.2018.04.015

9. NutraIngredients-USA.com, December 17, 2017. Nathan Gray. Could dropping specific amino acids from diet be key to weight loss? 

10. B Newgard, J. An, J.R Bain et al. A Branched-Chain Amino Acid-Related Metabolic Signature that Differentiates Obese and Lean Humans and Contributes to Insulin Resistance Cell Metab. 2009 April; 9(4): 311-326. doi:10.1016/j.cmet.2009.02.002 

11. Zheng Y, Li Y, Qi Q et al. Cumulative consumption of branched-chain amino acids and incidence of type 2 diabetes. Int J Epidemiol. 2016; 45: 1482-92. 

12. Isanejad M, LaCroix AZ, Thomson CA et al. Branched-chain amino acid, meat intake and risk of type 2 diabetes in the Women’s Health Initiative. Br J Nutr. 2017; 117:1523-30.

13. Newgard CB, An J, Bain JR et al. A branched-chain amino acid-related metabolic signature that differentiates obese and lean humans and contributes to insulin resistance. Cell Metab. 2009; 9: 311-26 

14. Tremblay F, Krebs M, Dombrowski L et al. Overactivation of S6 kinase 1 as a cause of human insulin resistance during increased amino acid availability. Diabetes. 2005; 54: 2674-84.

15. Lee CC, Watkins SM, Lorenzo C et al. Branched-chain amino acids and insulin metabolism: The Insulin Resistance Atherosclerosis Study (IRAS). Diabetes Care.2016; 39: 582-8.

16. Yoon M-S. The emerging role of branched-chain amino acids in insulin resistance and metabolism. Forum Nutr.2016; 8: 405-17.

17. Abdul-Ghani MA, Tripathy D, DeFronzo RA. Contributions of beta-cell dysfunction and insulin resistance to the pathogenesis of impaired glucose tolerance and impaired fasting glucose. Diabetes Care. 2006; 29:1130-9.

18. Binder E, Bermudez-Silva FJ, Andre C et al. Leucine supplementation protects from insulin resistance by regulating adiposity levels. PLoS One. 2013; 8:e74705. 

19. Zhang Y, Guo K, LeBlanc RE, Loh D, Schwartz GJ, Yu YH. Increasing dietary leucine intake reduces diet-induced obesity and improves glucose and cholesterol metabolism in mice via multimechanisms. Diabetes.2007; 56: 1647-54.

20. Lynch, C.J. and Adams, S.H. (2014) Branched-chain amino acids in metabolic signaling and insulin resistance. Nat Rev Endrocrinol 10, 723-736.

21. Xiao, F., Yu, J, Guo, Y, Deng, J, Li, K, et al (2014) Effects of individual branched-chain amino acids deprivation on insulin sensitivity and glucose metabolism in mice. Metabolism 63, 841-850. 

22. Jang C, Oh, S.F., et al A branched-chain amino acid metabolite drives vascular fatty acid transport and causes insulin resistance. Nat. Med. 22, 421-426 

23. Sara B Seidelmann, Brian Claggett, Susan Cheng, Mir Henglin, Amil Shah, Lyn M Steffen, Aaron R Folsom, Eric B Rimm, Walter C Willett, Scott D Solomon, Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis, The Lancet Public Health, 2018, ISSN 2468-2667, https://doi.org/10.1016/S2468-2667(18)30135-X. 

24. Zhaoping Li, Professor of Medicine, UCLA, US National Library of Medicine www. ClinicalTrials.gov Identifier: NCT02684565 Last Update Posted: February 12, 2018 https://clinicaltrials.gov/ct2/show/NCT02684565

25. Lotta LA, Scott RA, Sharp SJ, Burgess S, Luan J, et al. (2016) Genetic Predisposition to an Impaired Metabolism of the Branched-Chain Amino Acids and Risk of Type 2 Diabetes: A Mendelian Randomisation Analysis. PLOS Medicine 13(11): e1002179. https://doi.org/10.1371/journal.pmed.1002179

26. Avogaro, A. and Bier, D.M. (1989.) Contribution of 3-hydroxyisobutyrate to the measurement of 3-hydroxybutyrate in human plasma: comparison of enzymatic and gas-liquid chromatography-mass spectrometry assays in normal and in diabetic subjects. J Lipid Res 30, 1811-1817 

27. Giesbertz, P, Padberg, I, et al. (2015) Metabolite profiling in plasma and tissues of ob/ob and db/db mice identifies novel markers of obesity and type 2 diabetes. Diabetologia 58, 2133-2143.

28. Insulin Resistance, And What May Contribute To It by Lila Abassi on March 14, 2016. American Council on Science & Health https://www.acsh.org/news/2016/03/14/branched-chain-amino-metabolite-a-culprit-in-insulin-resistance

29. Alterations in 3-Hydroxyisobutyrate and FGF21 Metabolism Are Associated With Protein Ingestion–Induced Insulin Resistance Lydia-Ann L.S. Harris, Gordon I. Smith, Bruce W. Patterson, Raja S. Ramaswamy et al. Diabetes 2017;66:1871-1878 https://doi.org/10.2337/db16-1475

30. Elevated Plasma Levels of 3-Hydroxyisobutyric Acid Are Associated With Incident Type 2 Diabetes Mardinoglu, Adil et al. EBioMedicine, Volume 27, 151-155, Jan. 2018.

31. Ulrika Andersson-Hall, Carolina Gustavsson, Anders Pedersen, Daniel Malmodin, Louise Joelsson, and Agneta Holmäng, Higher Concentrations of BCAAs and 3-HIB Are Associated with Insulin Resistance in the Transition from Gestational Diabetes to Type 2 Diabetes, Journal of Diabetes Research, vol. 2018, Article ID 4207067, 12 pages, 2018. https://doi.org/10.1155/2018/4207067.

32. Macotela, Y. Emanuelli, B, Bang, A.M. et al. (2011) Dietary leucine – an environmental modifier of insulin resistance acting on multiple levels of metabolism. PLoS One 6, e21187.

33. Branched Chain Amino Acids: Beyond Nutrition Metabolism. Cunxi Nie, Ting He, Wenju Zhang, Guolong Zhang, Xi Ma Int J Mol Sci. 2018 Apr; 19(4): 954. Published online 2018 Mar 23. doi: 10.3390/ijms19040954

34. Increasing Dietary Leucine Intake Reduces Diet-Induced Obesity and Improves Glucose and Cholesterol Metabolism in Mice via Multimechanisms. Y. Zhang, K. Guo, R.E. LeBlanc, D. Loh, G.J. Schwartz, Y. Yu Diabetes Jun 2007, 56 (6) 1647-1654; DOI: 10.2337/db07-0123 

35. Dietary Intakes and Circulating Concentrations of Branched-Chain Amino Acids in Relation to Incident Type 2 Diabetes Risk Among High-Risk Women with a History of Gestational Diabetes Mellitus Deirdre K. Tobias, Clary Clish, Samia Mora, Jun Li, Liming Liang, Frank B. Hu, JoAnn E. Manson, Cuilin Zhang Clinical Chemistry Aug 2018, 64 (8) 1203-1210; DOI: 10.1373/clinchem.2017.285841 

36. McCormack, S. E., Shaham, O., McCarthy, M.A., Deik, A.A., Wang, T.J., Gerszten, R.E., Clish, C.B., Mootha, V.K., Grinspoon, S. K. and Fleischman, A. (2013), Branched‐chain amino acids and IR in children. Pediatric Obesity, 8: 52-61. doi:10.1111/j.2047-6310.2012.00087.x.

37. Sina S Ullrich, Penelope CE Fitzgerald, Gudrun Schober, Robert E Steinert, Michael Horowitz, Christine Feinle-Bisset; Intragastric administration of leucine or isoleucine lowers the blood glucose response to a mixed-nutrient drink by different mechanisms in healthy, lean volunteers, The American Journal of Clinical Nutrition, Volume 104, Issue 5, 1 November 2016, Pages 1274-1284, https://doi.org/10.3945/ajcn.116.140640.

38. Branched-chain and aromatic amino acids, insulin resistance and liver specific ectopic fat storage in overweight to obese subjects. Haufe, S. et al. Nutrition, Metabolism and Cardiovascular Diseases, Volume 26 , Issue 7, 637-642 

39. Li, H., Xu, M., Lee, J., He, C., & Xie, Z. (2012). Leucine supplementation increases SIRT1 expression and prevents mitochondrial dysfunction and metabolic disorders in high-fat diet-induced obese mice. American Journal of Physiology - Endocrinology and Metabolism, 303(10), E1234-E1244. http://doi.org/10.1152/ajpendo.00198.2012 

40. Chunzi Liang, Benjamin J. Curry, Patricia L. Brown, and Michael B. Zemel, Leucine Modulates Mitochondrial Biogenesis and SIRT1-AMPK Signaling in C2C12 Myotubes, Journal of Nutrition and Metabolism, vol. 2014, Article ID 239750, 11 pages, 2014. https://doi.org/10.1155/2014/239750. 

41. Activation of the AMPK/Sirt1 pathway by a leucine-metformin combination increases insulin sensitivity in skeletal muscle, and stimulates glucose and lipid metabolism and increases life span in Caenorhabditis elegans. Banerjee, Jheelam et al. Metabolism - Clinical and Experimental, Volume 65, Issue 11, 1679-1691 

42. Jiao, J., Han, S.-F., Zhang, W., Xu, J.-Y., Tong, X., Yin, X.-B., Qin, L.-Q. (2016). Chronic leucine supplementation improves lipid metabolism in C57BL/6J mice fed with a high-fat/cholesterol diet. Food & Nutrition Research, 60, 10.3402/fnr.v60.31304. http://doi.org/10.3402/fnr.v60.31304 

43. Published: 07 March 2016. A branched-chain amino acid metabolite drives vascular fatty acid transport and causes insulin resistance. Cholsoon Jang, Sungwhan F Oh, Shogo Wada, Glenn C Rowe, Laura Liu, Mun Chun Chan, James Rhee, Atsushi Hoshino, Boa Kim, Ayon Ibrahim, Luisa G Baca, Esl Kim, Chandra C Ghosh, Samir M Parikh, Aihua Jiang, Qingwei Chu, Daniel E Forman, Stewart H Lecker, Saikumari Krishnaiah, Joshua D Rabinowitz, Aalim M Weljie, Joseph A Baur, Dennis L Kasper & Zoltan Arany Nature Medicine volume 22, pages 421-426 (2016) 

44. D’Antona, G., Ragni, M., Cardile, A., Tedesco, L., Dossena, M., Bruttini, F. et al. (2010). Branched-chain amino acid supplementation promotes survival and supports cardiac and skeletal muscle mitochondrial biogenesis in middle-aged mice. Cell Metab. 12, 362-372. doi: 10.1016/j.cmet.2010.08.016 

45. Szmelcman S, Guggenheim K. Interference between leucine, isoleucine and valine during intestinal absorption. Biochemical Journal. 1966;100(1):7-11. 

46. Branched-chain amino acids and muscle protein synthesis in humans: myth or reality? Robert R. Wolfe Journal of the International Society of Sports Nutrition201714:30 https://doi.org/10.1186/s12970-017-0184-9 

47. Antagonistic effects of leucine and glutamine on the mTOR pathway in myogenic C2C12 cells. Amino Acids, 2008, Volume 35, Number 1, Page 147 L. Deldicque, C. Sanchez Canedo, S. Horman 

48. Protein Recommendations for Weight Loss in Elite Athletes: A Focus on Body Composition and Performance. Amy Hector, Stuart M. Phillips Int J Sport Nutr Exerc Metab. 2017

49. Leucine, Not Total Protein, Content of a Supplement Is the Primary Determinant of Muscle Protein Anabolic Responses in Healthy Older Women, The Journal of Nutrition, nxy091, June 13, 2018

50. Dietary branched-chain amino acids intake exhibited a different relationship with type 2 diabetes and obesity risk: a meta-analysis. Okekunle, A.P., Zhang, M., Wang, Z. et al. Acta Diabetol (2018). https://doi.org/10.1007/s00592-018-1243-7

51. Elovaris, R.A.; Fitzgerald, P.C.E.; Bitarafan, V.; Ullrich, S.S.; Horowitz, M.; Feinle-Bisset, C. Intraduodenal Administration of L-Valine Has No Effect on Antropyloroduodenal Pressures, Plasma Cholecystokinin Concentrations or Energy Intake in Healthy, Lean Men. Nutrients 2019, 11, 99.

52. Rigamonti, A.E.; Leoncini, R.; Casnici, C.; Marelli, O.; De Col, A.; Tamini, S.; Lucchetti, E.; Cicolini, S.; Abbruzzese, L.; Cella, S.G.; Sartorio, A. Whey Proteins Reduce Appetite, Stimulate Anorexigenic Gastrointestinal Peptides and Improve Glucometabolic Homeostasis in Young Obese Women. Nutrients 2019, 11, 247. 

53. Lu, Y.; Wang, Y.; Liang, X.; Zou, L.; Ong, C.N.; Yuan, J.-M.; Koh, W.-P.; Pan, A. Serum Amino Acids in Association with Prevalent and Incident Type 2 Diabetes in A Chinese Population. Metabolites 2019, 9, 14.

54. The Profile of Plasma Free Amino Acids in Type 2 Diabetes Mellitus with Insulin Resistance: Association with Microalbuminuria and Macroalbuminuria. Saleem, T., Dahpy, M., Ezzat, G. et al. Appl Biochem Biotechnol (2019). https://doi.org/10.1007/s12010-019-02956-9

55. Development and validation of a simple LC-MS/MS method for the simultaneous quantitative determination of trimethylamine-N-oxide and branched chain amino acids in human serumLe, T.T., Shafaei, A., Genoni, A. et al. Anal Bioanal Chem (2019) 411: 1019. https://doi.org/10.1007/s00216-018-1522-8

56. Chalasani, N., Vuppalanchi, R., Rinella, M., Middleton, M. S., Siddiqui, M. S., Barritt, A. S., Kolterman, O., Flores, O., Alonso, C., Iruarrizaga-Lejarreta, M., Gil-Redondo, R., Sirlin, C. B., Zemel, M. B. (2018). Randomised clinical trial: a leucine-metformin-sildenafil combination (NS-0200) vs placebo in patients with non-alcoholic fatty liver disease. Alimentary pharmacology & therapeutics, 47(12), 1639-1651. 

57. Banerjee J, Bruckbauer A, Zemel MB. Activation of the AMPK/Sirt1 pathway by a leucine–metformin combination increases insulin sensitivity in skeletal muscle, and stimulates glucose and lipid metabolism and increases life span in Caenorhabditis elegans. Metabolism. 2016;65:1-13 

58. Niswender K, Kolterman O, Kosinski M, Zemel MB. The effects of leucine-metformin combinations on glycemic control in type 2 diabetes. Diabetes. 2016;65:1144. 

59. Fu L, Bruckbauer A, Li F, et al. Interaction between metformin and leucine in reducing hyperlipidemia and hepatic lipid accumulation in diet-induced obese mice. Metabolism. 2015:1-9. 

60. Yoshii at al. Nutrients 2018, 10(10), 1543; https://doi.org/10.3390/nu10101543Effect of Mixed Meal and Leucine Intake on Plasma Amino Acid Concentrations in Young Men/ 

61. Rahimi MH, Shab-Bidar S et al. Branched-chain amino acid supplementation and exercise-induced muscle damage in exercise recovery: A meta-analysis of randomized clinical trials. Nutrition 2017. 

62. Chad M Kerksick, Colin D Wilborn, Michael D. ISSN exercise & sports nutrition review update: research & recommendations.

63. Roberts, et al. Journal of the International Society of Sports Nutrition 2018 15:38 https://doi.org/10.1186/s12970-018-0242-y 1 June 2018 

64. Robert R. Wolfe. Branched-chain amino acids and muscle protein synthesis in humans: myth or reality? Journal of the International Society of Sports Nutrition201714:30 https://doi.org/10.1186/s12970-017-0184-9

65. Wilkinson, DJ et al. Effects of leucine and its metabolite beta-hydroxy-beta-methylbutyrateonhumanskeletalmuscleproteinmetabolism.J.Physiol.2013,591,2911-2923. 

66. Cummings NE, Williams EM, Kasza I, Konon EN et al. (2018), Restoration of metabolic health by decreased consumption of branched‐chain amino acids. J Physiol, 596: 623-645. doi:10.1113/JP275075 

67. Duke University. Diabetes researchers find switch for fatty liver disease: Carbs, fats and protein: One molecule to rule them all? ScienceDaily, 17 May 2018. www.sciencedaily.com/releases/2018/05/180517113847.htm 

68. PJ White, RW McGarrah, PA Grimsrud, S Tso, W Yang, JM Haldeman, C Newgard et al. The BCKDH Kinase and Phosphatase Integrate BCAA and Lipid Metabolism via Regulation of ATP-Citrate Lyase. Cell Metabolism, 2018; DOI: 10.1016/j.cmet.2018.04.015

69. NutraIngredients-USA.com, December 17, 2017. Nathan Gray. Could dropping specific amino acids from diet be key to weight loss? 

70. CB Newgard, J An, JR Bain et al. A Branched-Chain Amino Acid-Related Metabolic Signature that Differentiates Obese and Lean Humans and Contributes to Insulin Resistance Cell Metab. 2009 April; 9(4): 311-326. doi:10.1016/j.cmet.2009.02.002 

71. Zheng Y, Li Y, Qi Q et al. Cumulative consumption of branched-chain amino acids and incidence of type 2 diabetes. Int J Epidemiol. 2016; 45: 1482-92. 

72. Isanejad M, LaCroix AZ, Thomson CA et al. Branched-chain amino acid, meat intake and risk of type 2 diabetes in the Women’s Health Initiative. Br J Nutr. 2017; 117:1523-30.

73. Kate Samardzic, Kenneth J. Rodgers. Cytotoxicity and mitochondrial dysfunction caused by the dietary supplement l-norvaline. Toxicology in Vitro, 2019; 56: 163 DOI: 10.1016/j.tiv.2019.01.020 

74. University of Technology Sydney. Body building supplement could be bad for the brain: People taking the protein supplement L-norvaline should be aware of its potential for harm, scientists say. ScienceDaily, 7 February 2019. www.sciencedaily.com/releases/2019/02/190207102627.htm

75. Newgard CB, An J, Bain JR et al. A branched-chain amino acid-related metabolic signature that differentiates obese and lean humans and contributes to insulin resistance. Cell Metab. 2009; 9: 311-26 

76. Tremblay F, Krebs M, Dombrowski L et al. Overactivation of S6 kinase 1 as a cause of human insulin resistance during increased amino acid availability. Diabetes. 2005; 54: 2674-84.

77. Tremblay F, Krebs M, Dombrowski L et al. Overactivation of S6 kinase 1 as a cause of human insulin resistance during increased amino acid availability. Diabetes. 2005; 54: 2674-84. 

78. Lee CC, Watkins SM, Lorenzo C et al. Branched-chain amino acids and insulin metabolism: The Insulin Resistance Atherosclerosis Study (IRAS). Diabetes Care.2016; 39: 582-8.

79. Yoon M-S. The emerging role of branched-chain amino acids in insulin resistance and metabolism. Forum Nutr 2016; 8: 405-17. 

80. Abdul-Ghani MA, Tripathy D and DeFronzo RA. Contributions of beta-cell dysfunction and insulin resistance to the pathogenesis of impaired glucose tolerance and impaired fasting glucose. Diabetes Care. 2006; 29:1130-9. 

81. Jang C, Oh, SF, et al A branched-chain amino acid metabolite drives vascular fatty acid transport and causes insulin resistance. Nat. Med. 22, 421-426 

82. Sara B Seidelmann, Brian Claggett, Susan Cheng, Mir Henglin, Amil Shah, Lyn M Steffen, Aaron R Folsom, Eric B Rimm, Walter C Willett, Scott D Solomon, Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis, The Lancet Public Health, 2018, ISSN 2468-2667, https://doi.org/10.1016/S2468-2667(18)30135-X. 

83. Zhaoping Li, Professor of Medicine, UCLA, US National Library of Medicine www. ClinicalTrials.gov Identifier: NCT02684565 Last Update Posted: February 12, 2018 https://clinicaltrials.gov/ct2/show/NCT02684565 

84. Lotta LA, Scott RA, Sharp SJ, Burgess S, Luan J, et al. (2016) Genetic Predisposition to an Impaired Metabolism of the Branched-Chain Amino Acids and Risk of Type 2 Diabetes: A Mendelian Randomisation Analysis. PLOS Medicine 13(11): e1002179. https://doi.org/10.1371/journal.pmed.1002179 

85. Avogaro A and Bier DM (1989) Contribution of 3-hydroxyisobutyrate to the measurement of 3-hydroxybutyrate in human plasma: comparison of enzymatic and gas-liquid chromatography-mass spectrometry assays in normal and in diabetic subjects. J Lipid Res 30, 1811-1817 

86. Giesbertz P, Padberg I et al. (2015) Metabolite profiling in plasma and tissues of ob/ob and db/db mice identifies novel markers of obesity and type 2 diabetes. Diabetologia 58, 2133-2143.

87. Insulin Resistance, And What May Contribute to It, by Lila Abassi on March 14, 2016. American Council on Science & Health https://www.acsh.org/news/2016/03/14/branched-chain-amino-metabolite-a-culprit-in-insulin-resistance 

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