Dietary GABA Research Articles

Effects of rumen-protected γ-aminobutyric acid on feed intake, lactation performance, and antioxidative status in early lactating dairy cows

The objective of this study was to investigate effects of rumen-protected γ-aminobutyric acid (GABA) on dry matter intake, milk performance, and serum metabolites in Chinese Holstein lactating cows. Thirty-nine multiparous cows were blocked based on days in milk (60±6.3 d; mean ± SD) and milk production (30.9±4.17kg; mean ± SD), and were randomly assigned to 1 of 4 treatments, with rumen-protected GABA added at levels of 0, 0.8, 1.6, or 2.4g/d, the actual predicted available amounts being 0, 0.30, 0.61, or 0.91g of GABA/d, respectively. The experiment lasted for 8 wk, with the first week for adaptation. Milk yield and milk compositions were recorded weekly, and serum concentrations of GABA, neuropeptide Y, and biochemical and antioxidant variables were analyzed in the first, fourth, and seventh weeks of the study. Dry matter intake linearly increased in cows receiving added GABA compared with that for the control. Addition of 0.8g of GABA/d was associated with higher milk yield than the other treatments, but contents of milk protein and fat did not differ across the treatments. Dietary GABA tended to quadratically enhance the serum content of GABA (23.6, 30.2, 29.8, or 28.3mmol/L for 0, 0.8, 1.6, or 2.4g/d, respectively), and increased neuropeptide Y, with the highest value (3.07ng/L) for 0.8g of GABA/d. Nonesterified fatty acid quadratically decreased with GABA addition, with the lowest value (218.1μmol/L) for 0.8g of GABA/d. Serum glutathione peroxidase and superoxide dismutase quadratically increased in cows fed GABA, whereas serum malondialdehyde was quadratically reduced for all GABA groups. Rumen-protected GABA quadratically improved N efficiency across all treatments, contributing to the enhanced production of milk and milk protein and reduced N emission to the environment. In conclusion, addition of rumen-protected GABA is beneficial for early lactation dairy cows in terms of feed intake, lactation performance, and animal health.

Effects of dietary glutamine and gamma-aminobutyric acid on meat colour, pH, composition, and water-holding characteristic in broilers under cyclic heat stress

1. An experiment was conducted to evaluate the effects of dietary glutamine (Gln, 0 and 5 g/kg) and gamma-aminobutyric acid (GABA, 0 and 100 mg/kg) on raw breast meat colour, pH, composition and water-holding characteristic of broilers under cyclic heat stress (HS). 2. A total of 360 21-d-old Arbor Acres male chicks were randomly assigned to 5 treatment groups (6 replicates of 12 birds per cage). The positive control (PC) broilers were kept in a thermoneutral chamber (22–24°C) and fed on the basal diet. The other 4 groups were kept in a cyclic HS chamber (30–34°C) for 9 h (from 09:00 to 18:00). 3. A significant increase was observed in breast meat lightness at 28, 35 and 42 d; and pH values at 28, 35 and 42 d; while a significant decrease was observed in breast meat cooking loss (CL) and contents of moisture, crude protein (CP), crude fat (CF) and crude ash (CA) due to HS. 4. The supplementation with 0·5 g Gln/kg decreased lightness at 28, 35 and 42 d; while increasing redness at 28 d, yellowness at 35 d, contents of CP, CF and CA, thawing loss (TL) and drip loss (DL). The addition of 100 mg GABA/kg decreased lightness at 28 and 35 d, pH value at 28, 35 and 42 d, and TL; while increasing redness at 28 d, 35 and 42 d, contents of moisture, CP and CF. 5. The lightness, redness, and pH value; contents of moisture, CP, CF and CA; and TL, DL and CL of breast meat of broilers fed with the mixture of Gln and GABA under cyclic HS were similar to those of the broilers in the PC group. 6. Significant interactions were found between Gln and GABA for yellowness at 28 and 35 d; pH at 28, 35 and 42 d; moisture content, CP content, water-holding capacity and TL. 7. These results demonstrated that dietary Gln and GABA offer a potential nutritional strategy to prevent cyclic HS-related depression in broiler meat chemical composition and quality.

Effects of dietary glutamine and gamma-aminobutyric acid on performance, carcass characteristics and serum parameters in broilers under circular heat stress

This experiment was conducted on broilers to evaluate the effects of dietary glutamine (Gln, 0 and 5 g/kg) and gamma-aminobutyric acid (GABA, 0 and 100 mg/kg) on growth performance, carcass characteristics and serum parameters in broilers under circular heat stress (HS). A total of 360 21-day-old Arbor Acre male chicks were randomly assigned to five treatment groups (6 replicates of 12 birds per cage). The positive control (PC) broilers were kept in a thermoneutral chamber (average 23 °C) and fed with a basal diet. The other four groups were kept in a circular HS chamber (30–34 °C) for 9 h (from 09:00 to 18:00). The experiment lasted from 22 to 42 day posthatch. Circular HS decreased (P<0.001 or 0.05) body weight (BW), weight gain (WG), feed consumption (FC), eviscerated weight (EW), breast muscle weight (BMW), breast muscle yield (BMY), thigh muscle weight (TMW), abdominal fat weight (AFW), abdominal fat yield (AFY), serum concentrations of T3, T4, insulin, Gln and glutamate (Glu), while increased feed-to-gain ratio (FGR), thigh muscle yield (TMY), serum concentrations of nitric oxide synthase (NOS) activity and corticosterone (CS) compared to the PC group. The diet supplemented with 5 g/kg Gln increased (P<0.001 or 0.05) BW, WG, FC, EW, BMW, BMY, TMW, AFW, AFY, serum concentrations of insulin and Gln, while decreased FGR, NOS activity and CS concentration. The addition of 100 mg/kg GABA increased (P<0.001 or 0.05) WG, FC, EW, BMW, BMY, AFW, AFY, serum concentrations of T3, insulin, Gln, GABA and Glu, while decreased CS concentration (P<0.05). Interactions were found between Gln and GABA for FGR (P=0.044), EW (P=0.042), eviscerated yield (P<0.001), BMW (P=0.002), BMY (P<0.001), TMY (P=0.001), AFW (P<0.001), AFY (P<0.001), serum concentrations of T3 (P<0.001), T4 (P<0.001), insulin (P=0.003), GABA (P=0.034) and Glu (P<0.001) in broilers under circular HS. These results demonstrated that dietary Gln and GABA offered a potential nutritional strategy to prevent HS-related depression in performance and carcass characteristics of broiler.

Dietary &amp;lt;i&amp;gt;γ&amp;lt;/i&amp;gt;-Aminobutyric Acid Shortens the Life Span of Stroke-Prone Spontaneously Hypertensive Rats

Dietary γ-amino butyric acid (GABA) has been suggested to decrease systolic blood pressure. This study aimed to ex-amine the effects of dietary GABA on the life span of stroke-prone spontaneously hypertensive rats (SHRSPs). In this study, life span was determined for SHRSPs provided 1% NaCl solution or 0.01% GABA in 1% NaCl solution as drinking water. The life span of the GABA-fed group (76.3 ± 1.65 days) was significantly shorter than that of the control group (81.6 ± 0.88 days). The results of this study may not be applicable to humans. Future studies will be necessary to elucidate the mechanism underlying this phenomenon.

Choices by rats between water and solutions of GABA or other amino acids

Responses differed widely when rats were offered choices between water and solutions of GABA, its isomers alpha-aminobutyric acid (AABA) and alpha-aminoisobutyric acid (AIB), or of another 4-carbon amino acid, threonine. They preferred solutions of threonine and AABA starting at concentrations of about 30 mM; preference for threonine declined when its concentration was 330 mM or above. Rats never preferred GABA or AIB, but instead avoided these amino acids when concentrations were approximately 100 mM or above. Control rats showed strong preferences for drinking from a given location. Limited studies with humans showed variations in the concentrations at which they could detect GABA; the mean was about 0.06 mM, a concentration far below that at which rats began to avoid this amino acid. The ability of dietary GABA to depress food intake of rats (as shown in earlier studies) does not seem related to a uniquely high sensitivity to its gustatory qualities.

Alleviation in the rat of a GABA-induced reduction in food intake and growth

Cold exposure and diet dilution which stimulate food intake of normal rats lessened depressions of food intake and growth induced by dietary GABA. During a 3-day adaptation to the cold, rats fed a diet containing 4.5% GABA lost weight; thereafter, food intake and growth rate differed little from those of cold control rats and were usually greater than those of normal rats fed GABA. Hepatic GABA-aminotransferase activity of cold-exposed rats fed the GABA diet increased to about twice that of normal control rats. Rats fed a control diet diluted by half with cellulose ate 50% more of this diet than of the undiluted diet but gained only 20% less weight. Rats ate twice as much of a diluted, 9% GABA diet as of an undiluted, 4.5% GABA diet (thus doubling their GABA intake) and gained three times as much weight. A novel food (condensed milk) barely lessened the adverse responses to GABA. These results show that conditions requiring rats to increase their food intake in order to maintain body weight can also increase their acceptance of a diet high in GABA.

Effect of dietary protein and GABA on food intake, growth and tissue amino acids in cats

GABA at 5%, but not 3%, of a low protein diet depressed food intake and growth of kittens. Adaptation to high protein prevented these effects. When cats adapted to low or high protein were fed a meal containing GABA, plasma GABA concentration after 2 hr was 8-fold higher in the low than in the high protein group; clearance was almost complete within 6 hr. Concentrations of proline, branched-chain, other large neutral and basic (especially ornithine) amino acids increased more when cats were fed a high rather than a low protein meal; glycine decreased. At 6 hr, concentrations had consistently returned to initial levels only in the low protein group. Feeding the high protein diet ad lib increased tissue concentrations of threonine, proline and the branched-chain amino acids. Hepatic or renal GABA-aminotransferase activity was not altered in kittens fed the high protein diet. Kidney activity was 10-fold that of liver, which may contribute to the better tolerance of GABA by cats than by rats.

Dietary GABA decreases body weight of genetically obese mice

Body weight and food intake were decreased more in lean than in genetically obese (ob/ob) mice fed a low protein diet containing GABA. Young lean and obese mice, when fed a 4.5% GABA diet, lost 30% or 20% of their initial weight over periods of 10 or 32 days, respectively. When refed the control diet both groups of mice gained weight rapidly but the obese grew more over a longer period of time. With GABA at 2 or 2.5% of the diet, respectively, lean and obese mice could be maintained at constant low weights for weeks. The obese were less sensitive than the lean mice to dietary GABA. Weights increased rapidly when a high protein diet containing GABA was fed. Hepatic GABA aminotransferase activity increased in all mice fed the high protein diet.

Effect of dietary GABA and protein on growth, food intake and GABA metabolism in the rat

GABA, when present as 4.5% of a 6% casein diet, decreased food intake and almost completely suppressed growth in young rats. Growth and food intake increased as dietary protein content increased; growth of rats receiving a 60% casein diet+GABA was 86% of that in the absence of GABA. Plasma, liver and kidney concentrations of GABA became lower as dietary protein content increased; brain GABA levels were unaltered by dietary GABA. GABA transaminase (GABA-T; E.C. 2.6.1.19) activity per mg tissue protein increased 2–3 fold in liver as dietary protein content increased but activity in brain and kidney did not change. Total hepatic enzyme activity in rats fed 80% casein was about 7 fold greater than in rats fed a protein-free diet. Rats fed 20% or 60% casein converted in 6 hrs about twice as much 14C-GABA to 14CO 2 as did rats fed 6% casein. Urinary excretion of 14C-GABA was not altered by changes in dietary protein content. Relationships between the suppression of food intake and growth by dietary GABA and its neurotransmitter functions are not clear.

Depression of food intake and growth by dietary GABA: Alleviation by dietary protein

Depression of food intake and growth by dietary GABA: Alleviation by dietary protein

Associations among food and protein intake, serine dehydratase, and plasma amino acids.

Associations among food and protein intake, serine dehydratase, and plasma amino acids.