Effects of alpha-ketoglutarate on bone homeostasis and plasma amino acids in turkeys

In ovo feeding of α-ketoglutaric acid improves hepatic antioxidant-gene expression, plasma antioxidant activities and decreases body temperature without affecting broiler body weight under cyclic heat stress

The broiler industry is adversely affected by the rise in global temperature. This study investigated the effects of in ovo feeding of α-ketoglutaric acid (AKG) on growth performance, organ weight, plasma metabolite, plasma oxidative stress, rectal temperature (RT), and hepatic mRNA expression of antioxidant-related genes in Arbor Acres broilers subjected to cyclic heat stress (HS). Three hundred fifty fertile eggs during incubation were divided into 5 groups according to AKG concentrations and temperature conditions. After dissolving AKG in distilled water at 0, 0.5, 1.0, and 1.5, 0% AKG was in ovo administered to 2 of the 5 groups whereas the remaining 3 groups received 0.5, 1.0, and 1.5%, respectively. From d 29 to 34 of age, 4 groups of birds received heat stress (HS) at 31°C ± 1°C for 6 h per day while the other group was kept at room temperature (21°C ± 1°C; NT). So, the 5 treatment groups were: 1) 0AKG-NT, where chicks hatched from eggs receiving 0% AKG were reared under thermoneutral conditions. 2) 0AKG-HS, where chicks hatched from eggs receiving 0% AKG were reared under cyclic HS conditions. 3) 0.5AKG-HS, where chicks hatched from eggs receiving 0.5% AKG were reared under cyclic HS conditions. 4) 1.0AKG-HS, where chicks hatched from eggs receiving 1.0% AKG were reared under cyclic HS conditions. 5) 1.5AKG-HS, where chicks hatched from eggs receiving 1.5% AKG were reared under cyclic HS conditions. HS significantly reduced body weight change (ΔBW %) and average daily gain (ADG) without affecting average daily feed intake (ADFI). Feed conversion ratio (FCR) was significantly increased (P = 0.003) in all HS-treated groups. A significant linear decrease in the final RT (P = 0.005) and a change in RT (P = 0.003) were detected with increasing AKG concentration. Total antioxidant capacity (P = 0.029) and antioxidant balance (P = 0.001) in plasma increased linearly with increasing AKG concentration whereas malondialdehyde concentrations were linearly decreased (P = 0.001). Hepatic gene expression of CAT (P = 0.026) and GPX1 (P = 0.001) were dose-dependently upregulated while nicotinamide adenine dinucleotide phosphate oxidase (NOX)1, NOX4, and heat shock protein (HSP)70 were linearly downregulated (P < 0.05). Hence, in ovo injection of AKG was effective in mitigating HS-induced oxidative stress without attenuating the adverse effects on broiler growth.

α-ketoglutarate downregulates thiosulfate metabolism to enhance antibiotic killing

Potentiation of the effects of currently available antibiotics is urgently required to tackle the rising antibiotics resistance. The pyruvate (P) cycle has been shown to play a critical role in mediating aminoglycoside antibiotic killing, but the mechanism remains unexplored. In this study, we investigated the effects of intermediate metabolites of the P cycle regarding the potentiation of gentamicin. We found that α-ketoglutarate (α-KG) has the best synergy with gentamicin compared to the other metabolites. This synergistic killing effect was more effective with aminoglycosides than other types of antibiotics, and it was effective against various types of bacterial pathogens. Using fish and mouse infection models, we confirmed that the synergistic killing effect occurred in vivo. Furthermore, functional proteomics showed that α-KG downregulated thiosulfate metabolism. Upregulation of thiosulfate metabolism by exogenous thiosulfate counteracted the killing effect of gentamicin. The role of thiosulfate metabolism in antibiotic resistance was further confirmed using thiosulfate reductase knockout mutants. These mutants were more sensitive to gentamicin killing, and less tolerant to antibiotics compared to their parental strain. Thus, our study highlights a strategy for potentiating antibiotic killing by using a metabolite that reduces antibiotic resistance.

Dietary Alpha-Ketoglutarate Supplementation Improves Bone Growth, Phosphorus Digestion, and Growth Performance in Piglets

Phosphorus (P) pollution from modern swine production is a major environmental problem. Dietary interventions to promote bone growth can improve the utilization of dietary P, and thereby reduce its emission. Recent in vitro studies have shown that alpha-ketoglutarate (AKG) exerts a pro-osteogenic effect on osteoblast cells. This study aimed to evaluate the effects of AKG supplementation on bone growth, P and Ca digestion, and the gut microbial profile in piglets. Thirty-two piglets were randomly assigned into two dietary groups. The piglets were fed a basic diet containing 10 g/kg AKG or 10 g/kg maize starch (control) for 28 days. On days 21-28, titanium dioxide was used as an indicator to determine the apparent digestibility of P. AKG supplementation improved the bone mineral density, length, weight, and geometrical and strength properties of the femur and tibia. Furthermore, AKG supplementation increased apparent ileal and total tract digestibility of P. Colonic microbiota analysis results showed that AKG supplementation increased α-diversity and beneficial bacteria, including Lactobacillus and Clostridium butyricum, and decreased nitrogen fixation and chemoheterotrophy. Together, AKG supplementation improves bone growth, the utilization of dietary P, and the colonic microbial profile, which may provide a nutritional strategy for diminishing P pollution originating from the pig industry.

Effects of In Ovo Injection of α-Ketoglutaric Acid on Hatchability, Growth, Plasma Metabolites, and Antioxidant Status of Broilers

Recently, α-ketoglutaric acid (AKG) has gained importance as an antioxidant. Its dietary supplementation in animals and humans has proved beneficial. Moreover, an extensive group of studies on in ovo feeding has proved that it produces better day-old chicks and overall performance. Combining the two, we hypothesized that in ovo feeding of AKG could improve the antioxidant status in addition to chick quality and broiler performance. At 17.5 days of incubation, eggs were divided into one of five groups: eggs that received (i) no injection (U-CON), (ii) distilled water (DDW) only (0 AKG), (iii) 0.5% AKG dissolved in DDW (0.5 AKG), (iv) 1.0% AKG dissolved in DDW (1.0 AKG), or (v) 1.5% AKG dissolved in DDW (1.5 AKG). Chicks were raised until 21 days of age. Biological samples were collected on day 0 and day 21. Body weight (p = 0.020), average daily gain (p = 0.025), and average daily feed intake (p = 0.036) were found to quadratically increase with the amount of AKG during the grower phase. At day 0, the absolute (p = 0.040) and relative weight (p = 0.035) of the liver increased linearly with an increasing amount of AKG. The 0.5 AKG group had significantly higher plasma protein (p = 0.025), absolute and relative heart indices at day 0 (p = 0.006). An in ovo feeding of AKG improved the plasma antioxidant capacity of chicks at day 0 as compared to 0 AKG. AKG effect was seen on the plasma antioxidant balance, which increased linearly with the increasing dose of in ovo AKG. Furthermore, 1.0 AKG and 1.5 AKG showed a significant (p = 0.002) upregulation of the hepatic mRNA expression of nuclear factor erythroid 2-related factor (NRF2) in comparison to 0 AKG. The results imply that without negatively affecting hatchability performance, in ovo feeding of AKG has beneficial effects on the antioxidant status of broilers.

Heritability and genetic correlations of plasma metabolites of pigs with production, resilience and carcass traits under natural polymicrobial disease challenge

Metabolites in plasma of healthy nursery pigs were quantified using nuclear magnetic resonance. Heritabilities of metabolite concentration were estimated along with their phenotypic and genetic correlations with performance, resilience, and carcass traits in growing pigs exposed to a natural polymicrobial disease challenge. Variance components were estimated by GBLUP. Heritability estimates were low to moderate (0.11 ± 0.08 to 0.19 ± 0.08) for 14 metabolites, moderate to high (0.22 ± 0.09 to 0.39 ± 0.08) for 17 metabolites, and highest for l-glutamic acid (0.41 ± 0.09) and hypoxanthine (0.42 ± 0.08). Phenotypic correlation estimates of plasma metabolites with performance and carcass traits were generally very low. Significant genetic correlation estimates with performance and carcass traits were found for several measures of growth and feed intake. Interestingly the plasma concentration of oxoglutarate was genetically negatively correlated with treatments received across the challenge nursery and finisher (− 0.49 ± 0.28; P < 0.05) and creatinine was positively correlated with mortality in the challenge nursery (0.85 ± 0.76; P < 0.05). These results suggest that some plasma metabolite phenotypes collected from healthy nursery pigs are moderately heritable and genetic correlations with measures of performance and resilience after disease challenge suggest they may be potential genetic indicators of disease resilience.

The Protective Role of Alpha-Ketoglutaric Acid on the Growth and Bone Development of Experimentally Induced Perinatal Growth-Retarded Piglets

The effect of alpha-ketoglutaric acid (AKG) supplementation to experimentally-induced, perinatal growth-retarded piglets was examined. Sows were treated with a synthetic glucocorticoid (Gc) during the last 25 days of pregnancy, and after the birth, piglets were randomly divided into three groups depending on the treatment. The Gc/Gc + AKG and Gc/AKG groups born by Gc-treated sows after the birth were treated with Gc or Gc + AKG for 35 days. Significantly lower serum growth hormone, IGF-I, osteocalcin, leptin, and cortisol concentrations were observed in the Gc/Gc + AKG group, while the bone alkaline phosphatase activity was significantly higher. Serum insulin concentration was higher in the control group. Serum alanine, lysine, histidine, and tryptophan concentrations were higher in the Gc/Gc + AKG and Gc/AKG groups. The perinatal action of Gc significantly affects histomorphometry of articular cartilage and trabecular bone and bone mechanics. The results clearly showed that dietary AKG had positive effects with regards to the profile of free amino acids. Taking into account the function of AKG as an energy donor and stimulator of collagen synthesis, it can be concluded that the anabolic role of AKG may be the main mechanism responsible for its protective effect against the GC-induced perinatal intensified catabolic state.

Alpha-Ketoglutarate: An Effective Feed Supplement in Improving Bone Metabolism and Muscle Quality of Laying Hens: A Preliminary Study

The aim of the experiment was to assess the effect of dietary alpha-ketoglutarate (AKG) supplementation on performance, serum hormonal indices, duodenum and jejunum histomorphometry, meat quality characteristics, bone quality traits and cartilage degradation in laying hens with a mature skeletal system. Forty-eight 30 week-old Bovans Brown laying hens were randomly assigned to a control group or the group fed the basal diet plus 1.0% AKG. The experimental trial lasted 30 weeks. The supplementation of AKG increases blood serum content of leptin, ghrelin, bone alkaline phosphatate and receptor activator of nuclear factor kappa-Β ligand, while osteoprotegerin and osteocalcin decrease. While dietary AKG was given to laying hens negatively influenced villus length, crypt depth, villus/crypt ratio and absorptive surface area in duodenum and jejunum, these changes have no effect on feed intake, weight gain, nor laying performance. In breast muscles, no significant changes in skeletal muscle fatty acid composition were observed, however, a higher shear force and decreased cholesterol content following AKG supplementation were noted, showing the improvement of muscle quality. While dietary AKG supplementation did not affect the general geometric and mechanical properties of the tibia, it increased collagen synthesis and enhanced immature collagen content. In medullary bone, an increase of bone volume fraction, trabecular thickness, fractal dimension and decrease of trabecular space were observed in AKG supplemented group. The trabeculae in bone metaphysis were also significantly thicker after AKG supplementation. AKG promoted fibrillogenesis in articular cartilage, as indicated by increased cartilage oligomeric matrix protein immunoexpression. By improving the structure and maintaining the proper bone turnover rate of highly reactive and metabolically active medullar and trabecular bones AKG showed its anti-osteoporotic action in laying hens.

Alpha-Ketoglutaric Acid Production from a Mixture of Glycerol and Rapeseed Oil by Yarrowia lipolytica Using Different Substrate Feeding Strategies

The microbiological biosynthesis of α-ketoglutaric acid (KGA) has recently captured the attention of many scientists as an alternative to its common chemical synthesis. The present study aimed to evaluate the effect of the feeding strategy of substrates, i.e., glycerol (G = 20 g·dm−3) and rapeseed oil (O = 20 g·dm−3), on yeast growth and the parameters of KGA biosynthesis by a wild strain Yarrowia lipolytica A-8 in fed-batch and repeated-batch cultures. The effectiveness of KGA biosynthesis was demonstrated to depend on thiamine concentration and the substrate feeding method. In the fed-batch culture incubated with 3 µg·dm−3 of thiamine and a substrate feeding variant 2G(_OGO), KGA was produced in the amount of 62.1 g·dm−3 at the volumetric production rate of 0.37 g·dm−3·h−1. These values of KGA production parameters were higher than these obtained in the control culture (with rapeseed oil only). During 10 cycles of the 1788-h repeated-batch culture carried out acc. to the feeding strategy 2G(_OGO), in the last 5 cycles the yeast produced from 55.6 to 58.2 g·dm−3 of KGA and maximally 2.9 g·dm−3 of the pyruvic acid as a by-product.

Is Dietary 2-Oxoglutaric Acid Effective in Accelerating Bone Growth and Development in Experimentally-Induced Intrauterine Growth Retarded Gilts?

Simple Summary

Intrauterine growth restriction (IUGR) is a significant health issue that not only affects infant mortality or term body weight, but may also predispose individuals to a reduced rate of weight gain and the development of numerous diseases later in life. In livestock production, growth restricted (IUGR) animals require more time to reach slaughter weight. In this study, we examined the effects of long-term administration of 2-oxoglutaric acid (2-Ox) to experimentally-induced intrauterine growth retarded gilts.

Abstract

In this study, the effect of long-term 2-oxoglutaric acid (2-Ox) supplementation to experimentally-induced intrauterine growth retarded gilts was examined. Sows were treated with synthetic glucocorticoid (dexamethasone) every second day, during the last 45 days of pregnancy, at a dose of 0.03 mg/kg b.w. At birth, the gilts were randomly divided into two groups: unsupplemented and supplemented with 2-Ox for nine months (0.4 g/kg body weight/day). Oral supplementation of 2-Ox to experimentally-induced intrauterine growth retarded gilts increased body weight at weaning as well as final body weight at the age of nine months, and showed a regenerative effect on bone mineralization and morphology of trabeculae and articular cartilage. The positive effects on bone structure were attributed to the 2-Ox-induced alterations in bone metabolism, as evidenced by the changes in the expression of proteins involved in bone formation and remodeling: osteocalcin (OC), osteoprotegerin (OPG), receptor activator of nuclear factor kappa-Β ligand (RANKL), tissue inhibitor of metalloproteinases 2 (TIMP-2), bone morphogenetic protein 2 (BMP-2), cartilage oligomeric matrix protein (COMP), and vascular endothelial growth factor (VEGF).

Alpha ketoglutarate exerts a pro-osteogenic effect in osteoblast cell lines through activation of JNK and mTOR/S6K1/S6 signaling pathways

Although numerous in vivo studies have suggested that alpha-ketoglutarate (AKG), i.e. the key intermediate in the Krebs cycle, may have an anabolic effect on bone tissue, the direct influence of AKG on osteoblasts and the underlying mechanism of its action have not been investigated so far. The aim of this study was to assess the impact of AKG (disodium salt dihydrate) on osteogenesis in vitro and identification of some signaling mechanisms involved in this activity. The human and mouse normal osteoblast cell lines hFOB 1.19 and MC3T3-E1 were used in this study. The results showed that AKG did not increase the proliferation of osteoblasts; however, it upregulated the expression of transcription factors RUNX2 and Osterix, the mRNA and protein levels of osteoblast differentiation markers (alkaline phosphatase, type I collagen, bone sialoprotein II, osteopontin, osteocalcin), and the mineralization levels in the hFOB 1.19 and MC3T3-E1 cell cultures. Moreover, AKG increased JNK, mTOR, S6K1, and S6 phosphorylation and decreased ERK1/2 phosphorylation in both osteoblast cell lines. The JNK inhibitor and rapamycin, but not the ERK inhibitor, abolished the AKG-promoted osteoblast differentiation. Using immunofluorescence staining, qRT-PCR, and Western blot analysis, we detected the presence of an AKG receptor GPR99 activated by alpha ketoglutaric acid in the tested osteoblast cell lines. However, AKG salt did not activate GPR99. Our findings suggest that AKG salt activates the JNK and mTOR/S6K1/S6 signaling pathways to promote differentiation of osteoblasts, independently of GPR99 activation. We can conclude that AKG salts might be promising candidates for bone anabolic drugs used for prevention or/and treatment of osteoporosis.

Supplementation with α-ketoglutarate to a low-protein diet enhances amino acid synthesis in tissues and improves protein metabolism in the skeletal muscle of growing pigs

α-Ketoglutarate (AKG) is a crucial intermediate in the tricarboxylic acid (TCA) cycle and can be used for the production of ATP and amino acids in animal tissues. However, the effect of AKG on the expression patterns of genes involved in muscle protein metabolism is largely unknown, and the underlying mechanism remains to be elucidated. Therefore, we used young pigs to investigate the effects of a low crude protein (CP) diet and a low CP diet supplemented with AKG on protein accretion in their skeletal muscle. A total of 27 growing pigs with an initial body weight of 11.96 ± 0.18 kg were assigned randomly to one of the three diets: control (normal recommended 20% CP, NP), low CP (17% CP, LP), or low CP supplemented with 1% AKG (ALP). The pigs were fed their respective diets for 35 days. Free amino acid (AA) profile and hormone levels in the serum, and the expression of genes implicated in protein metabolism in skeletal muscle were examined. Results showed that compared with the control group or LP group, low-protein diets supplemented with AKG enhanced serum and intramuscular free AA concentrations, the mRNA abundances of AA transporters, and serum concentrations of insulin-like growth factor-1 (IGF-1), activated the mammalian target of rapamycin (mTOR) pathway, and decreased serum urea concentration and the mRNA levels for genes related to muscle protein degradation (P < 0.05). In conclusion, these results indicated that addition of AKG to a low-protein diet promotes amino acid synthesis in tissues and improves protein metabolism in skeletal muscle.

The influence of dietary replacement of soybean meal with high-tannin faba beans on gut-bone axis and metabolic response in broiler chickens

Faba bean (FB) seeds can be a good protein-energy component in animal feed. However, the presence of anti-nutritional substances is a negative feature of FB seeds. The aim of this study was to examine the influence of different levels of unprocessed FB seeds in feed on the gut-bone axis and metabolic profile in broilers. Ninety six, 1-day-old Ross 308 broiler chickens were randomly selected to one of the 3 dietary treatments (32 chickens in each, divided into 8 pens with 4 birds per each pen): the control group fed standard diet with soybean meal and without FB seeds, group I fed 8/15% (starter/grower) of high-tannin FB seeds, and group II fed 16/22% of high-tannin FB seeds. Bone mechanical examination, hematological and serum biochemical analysis as well histomorphometry of small intestine and liver tissue were performed. The intake of high-tannin FB seeds, irrespective of their amount, did not alter the bone geometric, mechanical and densitometric parameters nor influenced basal hematological parameters, however it resulted in: decreased serum concentration of total cholesterol and calcium; a reduced longitudinal myenteron of small intestine; increased mucosa and villus epithelium thickness, villus length, thickness and absorptive surface in duodenum; increased number of active crypts in jejunum; unchanged collagen area, intercellular space, and total cell number in the liver; decreased number of multinuclear hepatocyte cells. Moreover, the livers of birds fed the higher dose of high-tannin FB seeds had lymphocytic infiltrates in portal tracts and sinusoids. Feeding of unprocessed high-tannin FB seeds exerted an influence on the gastrointestinal tract by increased absorptive surface. In conclusion, the dietary inclusion of unprocessed high-tannin FB seeds had no negative effects on broiler growth, tibial bone mechanical properties and intestinal characteristics. Unprocessed high-tannin FB seeds may be used in broiler diets, but their dietary levels should not be higher than those discussed.

Gut-bone axis response to dietary replacement of soybean meal with raw low-tannin faba bean seeds in broiler chickens

It seems that faba bean (FB) seeds could be a good protein-energy component in animal feed, but the presence of anti-nutritional substances limits their use as a substitute of soybean meal. The aim of the study was to examine the influence of different concentrations of raw, low-tannin, FB seeds on the gut-bone axis in Ross 308 broilers. One-day old chickens were randomly subjected to one of the 3 dietary treatments: the control group was fed standard diet based on soybean meal and without FB seeds, and two groups were fed 8%/15% and 16%/22% of raw low-tannin FB seeds in the starter and grower, respectively. On the 35th day, hematological and serum biochemical analyses as well histomorphometry of the small intestine and liver tissue and bone mechanical tests were performed. The diet type had no effect on the body weight gain and feed conversion ratio. However, the basal intestinal structures were significantly reduced in birds fed the lower concentration of FB. The enlargement of nerve plexuses was dependent on the concentration used in the diet and, additionally, on the kind of plexus and location in the intestinal tract. The liver was characterized by an increase in non-hepatocytes. There was no influence of the low-tannin FB seeds on most of the analyzed serum parameters in the 35-day-old broiler chickens, except the decreased concentration of total cholesterol and Ca in both experimental groups, triglycerides in group I, and P and uric acid in group II. Furthermore, the increasing concentration of the dietary low-tannin FB did not influence the activities of AspAT (except the group fed the higher amount of FB), ALAT, and LDH. The broiler chickens had no visible leg lesions and no problem in the locomotor function, but the tibiae were lighter mainly in birds fed the higher concentration of FB seeds. Geometric analysis revealed reduction of the cross section area and wall thickness, indicating a decline in the bone midshaft, which influenced the densitometric parameters and the results of mechanical tests. In conclusion, the dietary inclusion of raw low-tannin FB seeds had no negative effects on broiler growth, but disturbed the intestine structure and tibia characteristics. Therefore, all these negative effects necessitate additional examinations before inclusion of raw low-tannin FB seed into poultry diet.

Dose-dependent effects of probiotic supplementation on bone characteristics and mineralisation in meat-type female turkeys

To evaluate the influence of the probiotic on bone tissue in female turkeys, bone mineral density and geometrical and mechanical properties of the tibia and femur were determined in a dose-dependent manner (107 colony-forming units (cfu)/g, 108 cfu/g, 109 cfu/g). No effect of the treatments on bone mass and wall thickness of femur was observed, but the administration of the probiotic resulted in the elongation and the reduction of both strengths. The increase in the cross-sectional area of the femur was dose-dependent. Probiotic supplementation at a concentration of 108 cfu/g resulted in a reduction in ultimate strength, but at a concentration of 107 cfu/g, it resulted in the enhancement of the maximum elastic strength of the tibia compared with other groups. The influence of the probiotic administration on tibia geometry was dose-dependent. No effect of the treatments on the relative bone weight and the ratio of mass to length was observed. In general, the influence of the probiotic administration on bone mineral density, bone mineral concentration, bone tissue density, and bone ash, calcium and phosphorus concentrations was dose-dependent. The investigated properties of long bones in female turkeys are affected through probiotic-supplemented diets in a dose-dependent manner. However, on the basis of densitometry, it seems that the administration of the probiotic at a higher concentration of cells is more beneficial for bone development in turkeys.

Metabolomics and Gene Expression Analysis Reveal Down-regulation of the Citric Acid (TCA) Cycle in Non-diabetic CKD Patients

Chronic kidney disease (CKD) is a public health problem with very high prevalence and mortality. Yet, there is a paucity of effective treatment options, partly due to insufficient knowledge of underlying pathophysiology. We combined metabolomics (GCMS) with kidney gene expression studies to identify metabolic pathways that are altered in adults with non-diabetic stage 3-4 CKD versus healthy adults. Urinary excretion rate of 27 metabolites and plasma concentration of 33 metabolites differed significantly in CKD patients versus controls (estimate range-68% to +113%). Pathway analysis revealed that the citric acid cycle was the most significantly affected, with urinary excretion of citrate, cis-aconitate, isocitrate, 2-oxoglutarate and succinate reduced by 40-68%. Reduction of the citric acid cycle metabolites in urine was replicated in an independent cohort. Expression of genes regulating aconitate, isocitrate, 2-oxoglutarate and succinate were significantly reduced in kidney biopsies. We observed increased urine citrate excretion (+74%, p=0.00009) and plasma 2-oxoglutarate concentrations (+12%, p=0.002) in CKD patients during treatment with a vitamin-D receptor agonist in a randomized trial. In conclusion, urinary excretion of citric acid cycle metabolites and renal expression of genes regulating these metabolites were reduced in non-diabetic CKD. This supports the emerging view of CKD as a state of mitochondrial dysfunction.

Dietary α-ketoglutarate supplementation improves hepatic and intestinal energy status and anti-oxidative capacity of Cherry Valley ducks

α-Ketoglutarate (AKG) is an extensively used dietary supplement in human and animal nutrition. The aim of the present study was to investigate effects of dietary AKG supplementation on the energy status and anti-oxidative capacity in liver and intestinal mucosa of Cherry Valley ducks. A total of 80 1-day-old ducks were randomly assigned into four groups, in which ducks were fed basal diets supplemented with 0% (control), 0.5%, 1.0% and 1.5% AKG, respectively. Graded doses of AKG supplementation linearly decreased the ratio of adenosine monophosphate (AMP) to adenosine triphosphate (ATP) in the liver, but increased ATP content and adenylate energy charge (AEC) in a quadratic and linear manner, respectively (P < 0.05). Increasing dietary AKG supplemental levels produced linear positive responses in ATP content and AEC, and negative responses in AMP concentration, the ratio of AMP to ATP and total adenine nucleotide in the ileal mucosa (P < 0.05). All levels of dietary AKG reduced the production of jejunal hydrogen peroxide and hepatic malondialdehyde (P < 0.05). Hepatic and ileal messenger RNA expression of AMP kinase α-1 and hypoxia-inducible factor-1α were linearly up-regulated as dietary AKG supplemental levels increased (P < 0.05). In conclusion, dietary AKG supplementation linearly or quadratically enhanced hepatic and intestinal energy storage and anti-oxidative capacity of Cherry Valley ducks.

Fundectomy-Evoked Osteopenia in Pigs Is Mediated by the Gastric-Hypothalamic-Pituitary Axis

The aim of the study was to determine the effects of gastric impairment in pigs on the axial and peripheral skeletal system properties and to test the hypothesis that fundectomy-evoked osteopenia is related to disturbed gastric-hypothalamic-pituitary axis function. Forty-day-old male piglets were subjected to experimental fundectomy (FX group, n = 6) to induce osteopenia, while sham operation was performed in the controls (SHO group, n = 6). At the age of 8 months, serum samples were collected, and the animals were sacrificed to obtain lumbar vertebrae (L1–L6) and right humerus for analysis. Using quantitative computed tomography (QCT) and dual-energy x-ray absorptiometry (DEXA) methods, bone mineral density and bone mineral content of the vertebrae and humerus were measured. The compression and three-point bending tests were applied to determine mechanical properties of lumbar vertebrae and humerus, respectively. Furthermore, geometric properties of humerus were assessed. Serum concentrations of ghrelin, growth hormone (GH), insulin-like growth factor-1 (IGF-1), and selected macro- and microelements were also determined. Performed fundectomy decreased body weight in pigs by 66% compared with pair-fed sham operated pigs ( P < 0.0001). Bone weight, bone mineral density, and bone mineral content of the lumbar vertebrae and humerus were significantly decreased in the fundectomized pigs ( P < 0.01). Mechanical parameters of the lumbar spine and humerus were decreased after the fundectomy, as well. Serum concentrations of ghrelin, GH, and IGF-1 were lowered by 74.4%, 90.6%, and 54.6% in the fundectomized pigs, respectively (all P < 0.001). Moreover, the serum concentrations of calcium, magnesium, iron and copper in the fundectomized animals were significantly decreased by 15.5%, 45.3%, 26.7%, and 26.2%, respectively ( P ≤ 0.05). In conclusion, the results obtained showed that both the disturbed gastric-hypothalamic-pituitary axis function and impaired mineral metabolism are associated with development of postfundectomy osteopenia of axial and peripheral skeleton in pigs.

Alpha-Ketoglutarate as a Molecule with Pleiotropic Activity: Well-Known and Novel Possibilities of Therapeutic Use

Alpha-ketoglutarate (AKG), an endogenous intermediary metabolite in the Krebs cycle, is a molecule involved in multiple metabolic and cellular pathways. It functions as an energy donor, a precursor in the amino acid biosynthesis, a signalling molecule, as well as a regulator of epigenetic processes and cellular signalling via protein binding. AKG is an obligatory co-substrate for 2-oxoglutarate-dependent dioxygenases, which catalyse hydroxylation reactions on various types of substrates. It regulates the activity of prolyl-4 hydroxylase, which controls the biosynthesis of collagen, a component of bone tissue. AKG also affects the functioning of prolyl hydroxylases, which, in turn, influences the function of the hypoxia-inducible factor, an important transcription factor in cancer development and progression. Additionally, it affects the functioning of enzymes that influence epigenetic modifications of chromatin: ten-eleven translocation hydroxylases involved in DNA demethylation and the Jumonji C domain containing lysine demethylases, which are the major histone demethylases. Thus, it regulates gene expression. The metabolic and extrametabolic function of AKG in cells and the organism open many different fields for therapeutic interventions for treatment of diseases. This review presents the results of studies conducted with the use of AKG in states of protein deficiency and oxidative stress conditions. It also discusses current knowledge about AKG as an immunomodulatory agent and a bone anabolic factor. Additionally, the regulatory role of AKG and its structural analogues in carcinogenesis as well as the results of studies of AKG as an anticancer agent are discussed.

Alpha-Ketoglutarate: Physiological Functions and Applications

Alpha-ketoglutarate (AKG) is a key molecule in the Krebs cycle determining the overall rate of the citric acid cycle of the organism. It is a nitrogen scavenger and a source of glutamate and glutamine that stimulates protein synthesis and inhibits protein degradation in muscles. AKG as a precursor of glutamate and glutamine is a central metabolic fuel for cells of the gastrointestinal tract as well. AKG can decrease protein catabolism and increase protein synthesis to enhance bone tissue formation in the skeletal muscles and can be used in clinical applications. In addition to these health benefits, a recent study has shown that AKG can extend the lifespan of adult Caenorhabditis elegans by inhibiting ATP synthase and TOR. AKG not only extends lifespan, but also delays age-related disease. In this review, we will summarize the advances in AKG research field, in the content of its physiological functions and applications.

The effect of supplementation of a glutamine precursor on the growth plate, articular cartilage and cancellous bone in fundectomy-induced osteopenic bone

The aim of the study was to investigate the effect of 2-oxoglutaric acid (2-Ox) supplementation (a precursor of glutamine and hydroxyproline, the most abundant amino acid of collagen) on cartilage and bone in pigs after fundectomy. Pigs at the age of forty days were subjected to fundectomy and divided into two groups depending on 2-Ox supplementation (at the daily dosage of 0.4 g/kg of body weight). Other pigs were sham operated. Pigs were euthanized at the age of eight months. An analysis of the morphometry of trabeculae, growth plate and articular cartilage in fundectomy-induced osteopenic bone was performed. Moreover, the levels of expression of osteocalcin, osteopontin and osteoprotegerin in trabecular bone and osteocalcin in articular cartilage were evaluated. Articular cartilage was thinnest in fundectomized pigs and thickest in 2-Ox-supplemented animals after fundectomy. Moreover, 2-Ox supplementation after fundectomy enhanced the total thickness of the growth plate and trabeculae in fundectomized pigs. The most evident signal for osteocalcin and osteoprotegerin in trabecular bone was in sham-operated and 2-Ox-supplemented pigs; a low reaction was observed in the fundectomized group. Additionally, as a long-term postoperative consequence, a change was observed in the expression of osteocalcin in articular cartilage. It seems that 2-Ox is suitable for use in preventing the negative effects of fundectomy on cancellous bone and cartilage.

Effects of total gastrectomy on plasma silicon and amino acid concentrations in men

The aim of the study was to determine one-year effects of total gastrectomy on plasma silicon and free amino acid concentrations in patients and evaluate changes of volumetric bone mineral density (vBMD) in lumbar spine. Eight patients were enrolled to the control (CTR) group. Six patients subjected to total gastrectomy (GX group) were included to the experimental group. vBMD in trabecular and cortical bone was measured in lumbar vertebrae at baseline (before surgery) and one year later using quantitative computed tomography. Plasma concentrations of silicon and free amino acids were determined at baseline and one year later using photometric method and ion-exchange chromatography. Body weights within CTR and GX groups were not different after one-year follow-up when compared to the baseline values (P > 0.05). An average annual decrease of vBMD in the trabecular bone in the gastrectomized patients reached 15.0% in lumbar spine and was significantly different in comparison to the percentage changes observed in CTR group (P = 0.02). One-year percentage change of vBMD in the cortical bone in L1 and L2 has shown significantly decreased values by 10.5 and 9.1% in the GX group when compared to the percentage change observed in the controls (P < 0.05). Plasma concentration of adipic acid was significantly higher by 101.6% one year after total gastrectomy procedure in the patients when compared to the baseline value (P = 0.01). Plasma concentration of silicon was significantly lowered by 26.7% one year after the total gastrectomy when compared to the baseline value (P = 0.009). Total gastrectomy in patients has induced severe osteoporotic changes in lumbar spine within one-year period. The observed osteoporotic changes were associated with decreased plasma concentration of silicon indicating importance of exocrine and endocrine functions of stomach for silicon homeostasis maintenance. Gastrectomy-induced bone loss was not related to decreased amino acid concentration in plasma obtained from overnight fasted patients.

Effects of combined maternal administration with alpha-ketoglutarate (AKG) and β-hydroxy-β-methylbutyrate (HMB) on prenatal programming of skeletal properties in the offspring

BACKGROUND

Nutritional manipulations during fetal growth may induce long-term metabolic effects in postnatal life. The aim of the study was to test whether combined treatment of pregnant sows with alpha-ketoglutarate and β-hydroxy-β-methylbutyrate induces additive long-term effects on skeletal system properties in the offspring.

METHODS

The study was performed on 290 pigs obtained from 24 sows divided into 4 equal groups and subjected to experimental treatment during two weeks before delivery. The first group consisted of control sows, while the second group received alpha-ketoglutarate. The third group was treated with β-hydroxy-β-methylbutyrate and the fourth group underwent combined administration of alpha-ketoglutarate and β-hydroxy-β-methylbutyrate. Piglets obtained from sows were reared until slaughter age to perform morphometric, densitometric and mechanical analyses of femur. Serum evaluations of growth hormone, insulin-like growth factor-1, bone-specific alkaline phosphatase and osteocalcin were performed in newborns and 90-day old piglets; additionally, plasma amino acid concentration was measured in newborns.

RESULTS

Maternal treatment with alpha-ketoglutarate and β-hydroxy-β-methylbutyrate significantly reduced fattening time and increased birth body weight, daily body weight gain, bone weight, volumetric bone mineral density, geometrical parameters and mechanical endurance of femur. These effects were associated with increased serum concentrations of growth hormone, insulin-like growth factor-1, bone-specific alkaline phosphatase and osteocalcin. Furthermore, alpha-ketoglutarate and β-hydroxy-β-methylbutyrate administered solely or in combination significantly increased plasma level of 19 amino acids.

CONCLUSIONS

Hormonal and amino acid evaluations in pigs indicate additive effects of AKG and HMB on systemic growth and development; however, determination of bone properties has not shown such phenomenon.

Effect of β-hydroxy-β-methylbutyrate (HMB) administration on volumetric bone mineral density, and morphometric and mechanical properties of tibia in male turkeys

This study was performed to investigate the effects of β-hydroxy-β-methylbutyrate (HMB) administration on skeletal system properties in turkeys. Thirty-two males were randomly divided into two groups at the age of 35 days of life. The first group included control turkeys (n = 16) treated with placebo, while the second group of birds (HMB group; n = 16) was administered orally with calcium salt of HMB during the last 15 weeks of life. The turkeys were sacrificed at the age of 20 weeks and tibia was isolated for analysis of bone geometrical parameters, volumetric bone mineral density (vBMD) and mechanical properties. Furthermore, assessment of free amino acid concentrations in plasma was performed. The results showed a 6.3% increase of vBMD of tibia in response to HMB treatment (p < 0.01). Cross-sectional area, second moment of inertia, maximum elastic strength and ultimate strength of tibia were significantly increased in HMB-treated turkeys by 21.3%, 49.0%, 27.2% and 28.3%, respectively (p ≤ 0.01). β-hydroxy-β-methylbutyrate administration increased plasma concentrations of proline,glutamate, leucine, isoleucine, valine, alanine, aspartate, phenylalanine and cysteic acid (p < 0.05). These results indicate that long-term administration of HMB improves vBMD, and geometrical and mechanical properties of skeletal system in turkeys, and that these effects are associated with improved plasma amino acid concentrations.

Dietary keto-acid feed-back on pituitary activity in gilthead sea bream: effects of oral doses of AKG. A proteomic approach

The influence of a daily oral dose of alpha-ketoglutarate (AKG, 0.1 g/kg body weight), an intermediate metabolite in the Krebs cycle and a dietary additive, on the pituitary proteome of gilthead sea bream was determined by two-dimensional electrophoresis (2-DE). A high-resolution map of the sea bream pituitary proteome was generated. Proteins with a modified expression between Controls and AKG treated fish were further analysed by MALDI-TOF/TOF-MS and liquid chromatography combined with a nanoelectrospray (LC-MS/MS). The main changes in the proteome induced by AKG treatment were grouped. Metabolic proteins up-regulated with AKG supplementation included fructose-bis-phosphate aldolase, glyceraldehyde-phosphate dehydrogenase and malate dehydrogenase, all related to glucose metabolism (p<0.000). Protein folding related up-regulation with AKG supplementation included two isoforms of heat shock proteins as well as cyclophylin and chaperonin (p<0.000). An unexpected form of apolipoprotein-A-1 with lower molecular weight (15-16 kDa) was evidenced as being highly abundant in the pituitary proteome of Controls, yet it was down-regulated by AKG treatment. Finally, proteins found to be associated with regeneration of neural function namely cofilin and Vat-protein were up-regulated after AKG supplementation. The only hormone to be modified by AKG treatment was somatolactin, which was significantly down-regulated cf. Controls. In summary, these results provide evidence of a potential endocrine/metabolic regulatory loop activated by AKG supplementation.

3-Hydroxy-3-methylbutyrate administration diminishes fundectomy-induced osteopenia of the lumbar spine in pigs

OBJECTIVE

The aim of the study was to test the hypothesis that oral administration with 3-hydroxy-3-methylbutyrate (HMB) positively influences bone metabolism and diminishes fundectomy-induced osteopenia of the axial skeleton in pigs. The pig model was chosen because of its recognized physiologic and anatomic similarities of the gastrointestinal tract and skeletal system to those of humans.

METHODS

Eighteen male pigs were divided into three weight-matched groups at 40 d of life. Animals from the first and second groups were subjected to experimental fundectomy and the third group was sham operated. Starting the day after the fundectomy, the first and second groups received placebo and HMB, respectively. Animals were sacrificed at the age of 8 mo to obtain L(5) and L(6) vertebrae for analysis. The effects of HMB administration on plasma amino acids concentrations, bone mineral density, morphology, and mechanical properties of the lumbar vertebrae were determined.

RESULTS

The HMB treatment increased the weight of the vertebrae, bone mineral density, bone mineral content, total bone volume, trabecular bone mineral density, mean volumetric bone mineral density, calcium hydroxyapatite density in the trabecular and cortical bones, and plasma amino acid concentrations in the fundectomized pigs (P < 0.05). Mechanical strength of the spine, expressed by the values of ultimate force, Young's modulus, ultimate stress, stiffness, and work to the ultimate force point was increased in HMB-treated pigs (P < 0.05).

CONCLUSION

HMB administration to fundectomized pigs improved plasma amino acids concentrations and diminished development of fundectomy-induced osteopenia of the axial skeleton.

Ornithine alpha-ketoglutarate increases mineralization and mechanical properties of tibia in turkeys

Skeletal disorders in rapidly growing poultry are commonplace. This study was performed to investigate the effect of ornithine alpha-ketoglutarate (OKG) administration during the last 7 weeks of life on structural properties, mineralization, and mechanical endurance of skeleton in turkeys at slaughter. Healthy HB Medium Bronze female turkeys were randomly assigned to two weight-matched groups at the age of 12 weeks. OKG was administered orally to the experimental group (N=17) at the dose of 0.4 g/kg body weight per day, while the control group (N=16) received an equal dose of the vehicle. The turkeys were slaughtered at the age of 19 weeks and the tibiae were isolated for analysis. The effect of OKG on skeletal system development in turkeys was evaluated in relation to both geometrical and mechanical properties as well as quantitative computed tomography (QCT). Free amino acids concentrations were assessed with the use of ion-exchange chromatography. Significantly increased bone mineral density of the trabecular and the cortical bone of tibia in the turkeys given OKG for the last 7 weeks of production cycle were observed (P<0.05). OKG administration improved mechanical endurance of the tibia estimated by the three-point bending test (P<0.01). Plasma amino acid analyses showed increased level of aspartate, proline, alanine, valine, isoleucine, leucine, and ornithine (all P<0.05) after OKG treatment, whereas cystathionine concentration was decreased (P=0.03). Obtained results indicate that oral OKG administration has beneficial effects on skeletal development in fast growing turkeys and this effect is connected with increased amino acid synthesis. These observations may serve to improve skeletal properties in birds, especially when considering that skeletal disorders often affect the tibia and the proper function of the skeletal system plays an essential role in animal welfare and poultry production.