Miro Smriga

l-Lysine acts like a partial serotonin receptor 4 antagonist and inhibits serotonin-mediated intestinal pathologies and anxiety in rats

The purpose of this investigation was to determine whether a nutritionally essential amino acid, l-lysine, acts like a serotonin receptor 4 (5-HT4) antagonist, and if l-lysine is beneficial in animal models of serotonin (5-HT)-induced anxiety, diarrhea, ileum contractions, and tachycardia and in stress-induced fecal excretion. The radioligand-binding assay was used to test the binding of l-lysine to various 5-HT receptors. The effects of l-lysine on 5-HT-induced contractions of isolated guinea pig ileum were studied in vitro. The effects of oral administration of l-lysine on diarrhea, stress-induced fecal excretion, and 5-HT-induced corticosterone release, tachycardia, and anxiety (an elevated plus maze paradigm) were studied in rats in vivo. l-Lysine (0.8 mmol/dl) inhibited (9.17%) binding of 5-HT to the 5-HT4 receptor, without any effect on 5-HT1A,2A,2B,2C,3 binding. l-Lysine (0.07 and 0.7 mmol/dl) blocked 5-HT-induced contractions of an isolated guinea pig ileum in vitro (P < 0.05 and P < 0.01). Orally applied l-lysine (1 g/kg of body weight) inhibited (P < 0.12) diarrhea triggered by coadministration of restraint stress and 5-hydroxytryptophane (10 mg/kg of body weight), and significantly blocked anxiety induced by the 5-HT4 receptor agonist (3.0 mmol/liter) in rats in vivo. No effects of l-lysine or the 5-HT4 receptor agonist on plasma corticosterone and heart rate were recorded. l-Lysine may be a partial 5-HT4 receptor antagonist and suppresses 5-HT4 receptor-mediated intestinal pathologies and anxiety in rats. An increase in nutritional load of l-lysine might be a useful tool in treating stress-induced anxiety and 5-HT-related diarrhea-type intestinal dysfunctions.

Thirteen-week oral toxicity study of branched-chain amino acids in rats.

Branched-chain amino acids (l-isoleucine, l-valine, and l-leucine) are being increasingly used in sport supplements. This study evaluated toxicological and behavioral effects of l-isoleucine (Ile), l-valine (Val), and l-leucine (Leu) during a dosing study with male and female Sprague-Dawley rats. The amino acids were incorporated into a standard diet at doses equal to 1.25%, 2.5%, and 5.0% (w/w). A control group of rats received a standard diet. All diets were administered ad libitum for 13 consecutive weeks. To examine stability of any potential effects, the administration period was followed by a 5-week recovery period, during which only the standard diet was provided to all animals. No significant, dose-related effects on body weight were found in rats fed a Leu-and Ile-supplemented diet. Val mixed into a diet at 5.0% (w/w) decreased slightly, but significantly body weight gain in females, but not males. Ile (5.0% w/w) affected the urine electrolytes, protein, ketone bodies, urine glucose, and urobilinogen in both genders, yet the observed changes remained mostly within the range observed in controls. The random findings in hepatology and ophthalmology at the 13-week sacrifice were not considered toxicologically relevant to effects of the tested amino acids. No significant changes in organ weights were recorded. We estimate the no-observed-adverse-effect level (NOAEL) for Ile at 2.5% for both genders (male, 1.565 ± 0.060 g/kg/day; females, 1.646 ± 0.095 g/kg/day), Val at 5.0% for males (3.225 ± 0.135 g/kg/day) and 2.5% for females (1.853 ± 0.060 g/kg/day), and Leu at 5.0% for both genders (males, 3.333 ± 0.101 g/kg/day: females, 3.835 ± 0.257 g/kg/day).

Use of thermal photography to explore the age-dependent effect of monosodium glutamate, NaCl and glucose on brown adipose tissue thermogenesis

Using a sensitive thermocamera and a hairless substrain of Sprague-Dawley rats, we developed a novel in vivo method for the evaluation of diet-induced thermogenesis. The technique enabled time-dependent monitoring of spatial heat dissipation emanating from brown adipose tissue (BAT) during diet intake. Drinking of monosodium glutamate (MSG) solution (0.12 M) enhanced standard protein (15%) diet-induced heat dissipation in young (9-12 weeks old) hairless male rats. No significant enhancement was found in 9- to 12-week-old rats that received sodium chloride (0.12 M) or glucose solution (0.6 M). The enhancing effect of MSG was age-dependent and it was not observed in 18- to 22-week-old rats due to an age-dependent decrease of thermogenic responses. No age-related changes in MSG preference or diet intake were recorded. Although it is unclear whether the effect of MSG was purely enhancing or whether the effect was independently superimposed on the diet-induced thermic activity, the results suggest that in 9- to 12-week-old rats, preference for umami taste might be associated with its enhancing effect on diet-induced thermogenesis.

Prolonged Treatment with L-Lysine and L-Arginine Reduces Stress-induced Anxiety in an Elevated Plus Maze

Abstract The aim of this study was to investigate whether a chronic pretreatment with a combination of l-lysine (Lys) and l-arginine (Arg) reduces anxiogenic effects of acute stress in rats. Male rats were orally infused with a distilled water solution of l-glutamine (200 mg/kg), Lys (200 mg/kg), or a combination of Lys (200 mg/kg) plus Arg (200 mg/kg) for four consecutive days (twice daily) and subjected to restraint stress on the fifth day. Immediately thereafter, rats were placed on an elevated plus maze (EPM) and their behavior was evaluated for 10 min. Lys and Arg significantly increased exploration time rats spent on open arms of the EPM, as compared to l-glutamine controls. In addition, the combination of Lys and Arg partly, but significantly, decreased stress-enhanced plasma corticosterone measured at the end of behavioral testing. Data suggest that a treatment with a solution of Lys and Arg reduces anxiety in stressed rats.

Thirteen-week oral toxicity study of L-arginine in rats.

The amino acid l-arginine (Arg) has been used extensively in dietary and pharmacological products. This study evaluated toxicological and behavioral effects of Arg produced by Ajinomoto Co. (Tokyo, Japan) during a dosing study with male and female Sprague-Dawley rats. The amino acid was incorporated into a standard diet at doses equal to 1.25%, 2.5%, and 5.0% (w/w). A control group of rats received only a standard diet. All diets were administered ad libitum for 13 continuous weeks. To examine recoverability of any potential effects, the administration period was followed by a 5-week-long recovery, during which only a standard diet was provided. In male and female rats in each concentration group, treatment-related changes were not observed for clinical signs, body weights, diet consumption, ophthalmology, gross pathology, organ weight, or histopathology. An elevated level of plasma glucose was detected in some male rats (5.0%, w/w) during the analysis conducted in the fifth week of administration; however, the degree of the change was within the physiological range, and no changes were observed at the end of the administration period. In the same group, an increase in hemoglobin, together with a tendency toward an increase in the red blood cell counts, was found, but the change was considered toxicologically insignificant. The no-observed-adverse-effect level (NOAEL) for Arg was estimated at 5.0% (w/w) for both genders (males, 3.3 ±0.1 g/kg/day; females, 3.9 ±0.2 g/kg/day).

A Diet Fortified with l-lysine and l-arginine Reduces Plasma Cortisol and Blocks Anxiogenic Response to Transportation in Pigs

Abstract We studied the effects of diet fortified with l-lysine HCl (Lys) and l-arginine (Arg) on stress (transportation) responses in male finishing pigs (Landrace×LargeWhite×Duroc). Pigs (n=16) were randomly divided into two equally sized groups so that the average starting body weight in the groups was identical. For 1 week immediately preceding the transportation, the first group of pigs received a control diet while the second group received a Lys and Arg fortified diet. Plasma aminogram, cortisol and body weight were evaluated. Behavior of pigs was measured with the help of a video camera, recorded for 2 h at the same time, as on the day, before a day and immediately after transportation. The study revealed main stimulatory effects of transportation and main inhibitory effect of Lys and Arg on plasma cortisol (P<0.05) without transportation × treatment interactions. Pigs fed with Lys and Arg diet tend to have higher body weight at the end of the experiment, when compared to their normally fed counterparts, but the difference did not reach a significant level (P<0.21). Lys and Arg diet significantly inhibited stress-induced increase in locomotion (P<0.05), without affecting feeding pattern. Transportation stress decreased plasma Lys and Arg. This decrease was reversed in the fortified group, and what is more the plasma Lys and Arg levels were significantly higher than in controls (P<0.05). Lys and Arg enhanced plasma urea production (P<0.05), without regards to stress. The behavioral results indicate a reduction in stress-induced anxiety in pigs fed with Lys and Arg fortified diet, that parallels similar observations in research with rats and broilers. The mechanism probably involves a decreased plasma cortisol, and/or normalized plasma Lys, Arg levels.

Release of hypothalamic norepinephrine during MSG intake in rats fed normal and nonprotein diet

Effects of monosodium L-glutamate (MSG) solution (0.06 M) on interstitial levels of norepinephrine (NE) were measured in the lateral hypothalamus (LH). Wistar male rats, housed in standard operant boxes, were fed either normal or nonprotein diet for 3 days. Beside a daily bar-mediated drinking session (75 min), animals were without access to fluids. Microdialysates, collected from the LH during the 75 min of drinking, were analyzed using high-pressure liquid chromatography. No significant responses of the LH NE to the drinking of distilled water, MSG, NaCl (0.06 M), and glucose solution (0.6 M) were found in normally fed rats. However, a specific decline in LH NE release was detected during MSG solution-drinking in rats fed nonprotein diet. As MSG preference indicates protein intake, it is possible that LH NE is, at least partially, one of the brain signals that relate MSG preference to dietary protein intake.

Thirteen-week oral toxicity study of L-lysine hydrochloride in rats.

l-Lysine hydrochloride (Lys) is an essential amino acid in humans and animals, and it is used in animal feeds, in prevention of herpes simplex recurrence, and cereal fortification in some developing countries. This study evaluated toxicological and behavioral effects of Lys during a dosing study with male and female Sprague-Dawley rats. The amino acid was incorporated into a standard diet at doses equal to 1.25%, 2.5%, and 5.0% (w/w). A control group of rats received a standard diet. All diets were administered ad libitum for 13 consecutive weeks. To examine stability of any potential effects, the administration period was followed by a 5-week recovery period, during which only the standard diet was provided to all animals. In male and female rats in each concentration group, treatment-related changes were not observed in the clinical signs, body weights, diet consumption, water intake, ophthalmology, gross pathology, organ weights, or histology. A Lys-related drop in serum concentration and an increase in urine excretion of chlorides was a compensatory reaction to the ingested hydrochloride. No functional, biochemical, or histological changes in renal function were found. The no-observed-adverse-effect level (NOAEL) for Lys was estimated at 5.0% for both genders (male, 3.36 ± 0.12 g/kg/day; female, 3.99 ± 0.28 g/kg/day).

Thirteen-Week Oral Toxicity Study of l-Glutamine in Rats

l-Glutamine (Gln) is a semiessential amino acid used in enteral feeding in critically ill patients, and is contained in numerous dietary supplements available to the general public. This study evaluated toxicological effects of Gln in male and female Sprague-Dawley rats. Gln produced by Ajinomoto Co. (Tokyo, Japan) was incorporated into a standard diet at doses equal to 1.25%, 2.5%, and 5.0% (w/w), respectivelly. A control group of rats received only a standard diet. All diets were administered ad libitum for 13 consecutive weeks. To examine recoverability of any potential effects, the administration period was followed by a 5-week recovery period, during which only the standard diet was provided to all animals. Throughout the administration and recovery periods, no deaths were observed, and no changes in diet consumption, ophthalmologic findings, gross pathology, and histopathology were detected. Several changes in urine parameters (total protein, urine pH, and a positive incidence (±) of ketone bodies) were observed in the 2.5% and 5.0% groups at the end of the administration period. Minor increases were found in hematology parameters for the 5.0% group (platelet count, γ-globulin, lactate dehydrogenase [LDH]), but all changes were within physiological range. No effects of administration were observed in the 1.25% group. The no-observed-adverse-effect level (NOAEL) for Gln was estimated at 1.25% for both genders (males 0.83 ± 0.01 g/kg/day; females, 0.96 ± 0.06 g/kg/day).

Effect of selected thallophytic glucans on learning behaviour and short-term potentiation.

This paper reviews the effects of thallophytic glucans on rodent cognitive performance modelled by a combination of behavioural and electrophysiological approaches. Glucans were isolated from thallophytic plants, based on prescriptions used in traditional Chinese and Japanese medicine. In parallel with the already described enhancement of hippocampal synaptic plasticity by disaccharides, polysaccharides isolated from lichens Flavoparmelia caperata and Cetrariella islandica, enhanced hippocampal plasticity and behavioural performance in rats. Copyright