Monday, September 23, 2013

The Satiating Secret of Arginine, Lysine and Glutamic Acid. Plus: Things You May Not Know About These Aminos

No, no and no. No amino acids = no satiety = no weight loss.
Personally, I have never been interested in products that would increase satiety. Being a born masochist, at least, when it comes to cutting body fat, I always liked being hungry... well, at least until I had to learn that there is an intricate hormonal connection between "being hungry" and the diet-induced reduction in metabolic rate, hormonal production etc. That changed my whole perspective on agents that increase satiety completely, and I started to read read papers like the one Jordi et al. are about to publish in one of the upcoming issues of the Journal of Physiology (Jordi. 2013).

The satiety shoot-out

According to the researchers from the University of Zurich, the top-dogs, or rather the most satiating among the so-called proteogenic amino acids, which are ...
  • L-Leucine (Leu / L)
  • L-Lysine (Lys / K)
  • L-Methionine (Met / M)
  • L-Phenylalanine (Phe / F)
  • L-Proline (Pro / P)
  • L-Serine (Ser / S)
  • L-Threonine (Thr / T)
  • L-Tryptophan (Trp / W)
  • L-Tyrosine (Tyr / Y)
  • L-Valine (Val / V)
  • L-Alanine (Ala / A)
  • L-Arginine (Arg / R)
  • L-Asparagine (Asn / N)
  • L-Aspartic acid (Asp / D)
  • L-Cysteine (Cys / C)
  • L-Glutamic acid (Glu / E)
  • L-Glutamine (Gln / Q)
  • Glycine (Gly / G)
  • L-Histidine (His / H)
  • L-Isoleucine (Ile / I)
... are L-arginine (Arg), L-lysine (Lys) and L-glutamic acid (Glu). The Swiss scientists were able to demonstrate that these three amino acids induced neuronal activity in the area postrema and the nucleus of the solitary tract. That sounds funky, but non-significant, right? Well, it wouldn't be, as long as you did not take into consideration that we know from previous studies that these brain regions are responsible for the regulation of energy intake - specifically our appetite for more.
L-arginine has research to support its use as anti-diabetic weight-loss adjuvants (learn more); and the results of the study at hand suggest that its benefits may be mediated by its effects on the brain & gut.
From a "what are the downstream effects on my metabolism"-perspective, however, it may in fact be even more important that the amino acids also provoked an increase in gastric distension by differentially altering gastric secretion and/or emptying. After all, ...
"[...] these peripheral mechanical vagal stimuli were dissociated from the amino acids' effect on food intake. [So that it is prudent to assume that] Arg, Lys and Glu had a selective impact on food processing and intake suggesting them as direct sensory input to assess dietary protein content and quality in vivo. " (Jordi. 2013; my emphasis)
In other words: L-arginine, L-lysine and L-glutamic acid are not simply going to reduce your cravings they will also tell your body: Hey there's some good quality protein coming in.

Hold on! Where are the proven benefits? I have to admit all that sounds as if it would be of questionable relevance but any SuppVersity reader for whom this is not the first visit to this webpage will probably have read about the surprisingly profound weight loss benefits of L-arginine, which have only recently been tracked down to its interactions with the GLP-1 one of the so-called satiety proteins with far-reaching downstream effects on glucose and fatty acid metabolism (learn more about the fat burning prowess of L-arginine).

As far as glutamic acid is concerned, it may be worth mentioning that Freiberg et al. reported more than 20 years ago that certain glutamic acid derivates can act directly on the cholecystokinin receptor, which is - along the the PYY receptor one of the major "You are full! Now stop eating"-switches of the mammalian body (Freiberg. 1990).

Figure 1: AUC in response to ingestion of 25g of glucose or water w/ or w/out 150mg/kg lysine (Kalogeropoulou. 2009)
Similarly unknown as the involvement of glutamic acid in the concert of satiety hormones is the effect lysine (150mg/kg) had on the glucose, insulin and glucagon resonse of healthy volunteers, when Kalogeropoulou et al. administered it either alone or in conjunction with 25g of glucose to thirteen healthy volunteers, where it triggered an increase in glucagon and insulin, when it was administered alone and significant reduction in the blood sugar response, when it was administered in conjunction with the 25g of glucose (Kalogeropoulou. 2009). Interestingly the increased glucsose disposal did not depend on an increase in insulin, so that it must be related to downstream improvements in insulin sensitivity and the efficacy of glucose uptake.

  • Freidinger RM, Whitter WL, Gould NP, Holloway MK, Chang RS, Lotti VJ. Novel glutamic acid derived cholecystokinin receptor ligands. J Med Chem. 1990 Feb;33(2):591-5.
  • Kalogeropoulou D, LaFave L, Schweim K, Gannon MC, Nuttall FQ. Lysine ingestion
    markedly attenuates the glucose response to ingested glucose without a change in
    insulin response. Am J Clin Nutr. 2009 Aug;90(2):314-20.
  • Jordi J, Herzog B, Camargo SM, Boyle CN, Lutz TA, Verrey F. Specific Amino Acids Inhibit Food Intake via the Area Postrema or Vagal Afferents. J Physiol. 2013 Jul 29. [Epub ahead of print] 
  • Solon CS, Franci D, Ignacio-Souza LM, Romanatto T, Roman EA, Arruda AP, Morari J, Torsoni AS, Carneiro EM, Velloso LA. Taurine enhances the anorexigenic effects of insulin in the hypothalamus of rats. Amino Acids. 2012 Jun;42(6):2403-10.