The most frequent alterations in plasma amino acid concentrations in type 1 and type 2 diabetes are decreased L-serine and increased branched-chain amino acid (BCAA; valine, leucine, and isoleucine) levels. The likely cause of L-serine deficiency is decreased synthesis of 3-phosphoglycerate, the main endogenous precursor of L-serine, due to impaired glycolysis. The BCAA levels increase due to decreased supply of pyruvate and oxaloacetate from glycolysis, enhanced supply of NADH + H+ from beta-oxidation, and subsequent decrease in the flux through the citric acid cycle in muscles. These alterations decrease the supply of α-ketoglutarate for BCAA transamination and the activity of branched-chain keto acid dehydrogenase, the rate-limiting enzyme in BCAA catabolism. L-serine deficiency contributes to decreased synthesis of phospholipids and increased synthesis of deoxysphinganines, which play a role in diabetic neuropathy, impaired homocysteine disposal, and glycine deficiency. Enhanced BCAA levels contribute to increased levels of aromatic amino acids (phenylalanine, tyrosine, and tryptophan), insulin resistance, and accumulation of various metabolites, whose influence on diabetes progression is not clear. It is concluded that amino acid concentrations should be monitored in patients with diabetes, and systematic investigation is needed to examine the effects of L-serine and glycine supplementation on diabetes progression when these amino acids are decreased.

• Klíčová slova
• branched-chain amino acids, glycine, insulin resistance, serine,
• MeSH
• aminokyseliny metabolismus   MeSH
• diabetes mellitus 2. typu * metabolismus   MeSH
• glycin metabolismus   MeSH
• glykolýza MeSH
• kyselina pyrohroznová MeSH
• lidé MeSH
• serin metabolismus   MeSH
• větvené aminokyseliny metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• aminokyseliny MeSH
• glycin MeSH
• kyselina pyrohroznová MeSH
• serin MeSH
• větvené aminokyseliny MeSH

(1) Background: empagliflozin, sodium-glucose co-transporter 2 (SGLT-2) inhibitor, is an effective antidiabetic agent with strong cardio- and nephroprotective properties. The mechanisms behind its cardio- and nephroprotection are still not fully clarified. (2) Methods: we used male hereditary hypertriglyceridemic (hHTG) rats, a non-obese model of dyslipidaemia, insulin resistance, and endothelial dysfunction fed standard diet with or without empagliflozin for six weeks to explore the molecular mechanisms of empagliflozin effects. Nuclear magnetic resonance (NMR)-based metabolomics; quantitative PCR of relevant genes involved in lipid and glucose metabolism, or senescence; glucose and palmitic acid oxidation in isolated tissues and cell lines of adipocytes and hepatocytes were used. (3) Results: empagliflozin inhibited weight gain and decreased adipose tissue weight, fasting blood glucose, and triglycerides and increased HDL-cholesterol. It also improved insulin sensitivity in white fat. NMR spectroscopy identified higher plasma concentrations of ketone bodies, ketogenic amino acid leucine and decreased levels of pyruvate and alanine. In the liver, adipose tissue and kidney, empagliflozin up-regulated expression of genes involved in gluconeogenesis and down-regulated expression of genes involved in lipogenesis along with reduction of markers of inflammation, oxidative stress and cell senescence. (4) Conclusion: multiple positive effects of empagliflozin, including reduced cell senescence and oxidative stress, could contribute to its long-term cardio- and nephroprotective actions.

• Klíčová slova
• cell senescence, empagliflozin, hereditary hypertriglyceridemic rat model, hypertriglyceridemia, insulin sensitivity, metabolic syndrome,
• MeSH
• aplikace orální MeSH
• benzhydrylové sloučeniny aplikace a dávkování   MeSH
• buňky 3T3-L1 MeSH
• buňky Hep G2 MeSH
• down regulace účinky léků   MeSH
• dyslipidemie farmakoterapie   MeSH
• glifloziny aplikace a dávkování   MeSH
• glukoneogeneze účinky léků   genetika   MeSH
• glukosidy aplikace a dávkování   MeSH
• hmotnostní přírůstek účinky léků   MeSH
• hypertriglyceridemie farmakoterapie   metabolismus   MeSH
• hypoglykemika aplikace a dávkování   MeSH
• inzulinová rezistence MeSH
• játra metabolismus   MeSH
• krysa rodu Rattus MeSH
• ledviny metabolismus   MeSH
• lidé MeSH
• lipogeneze účinky léků   genetika   MeSH
• modely nemocí na zvířatech MeSH
• myši MeSH
• oxidační stres účinky léků   MeSH
• stárnutí buněk účinky léků   MeSH
• tuková tkáň metabolismus   MeSH
• upregulace účinky léků   MeSH
• viabilita buněk účinky léků   MeSH
• výsledek terapie MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• lidé MeSH
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• benzhydrylové sloučeniny MeSH
• empagliflozin MeSH Prohlížeč
• glifloziny MeSH
• glukosidy MeSH
• hypoglykemika MeSH

Branched-chain amino acids (BCAAs; valine, leucine, and isoleucine) are increased in starvation and diabetes mellitus. However, the pathogenesis has not been explained. It has been shown that BCAA catabolism occurs mostly in muscles due to high activity of BCAA aminotransferase, which converts BCAA and α-ketoglutarate (α-KG) to branched-chain keto acids (BCKAs) and glutamate. The loss of α-KG from the citric cycle (cataplerosis) is attenuated by glutamate conversion to α-KG in alanine aminotransferase and aspartate aminotransferase reactions, in which glycolysis is the main source of amino group acceptors, pyruvate and oxaloacetate. Irreversible oxidation of BCKA by BCKA dehydrogenase is sensitive to BCKA supply, and ratios of NADH to NAD+ and acyl-CoA to CoA-SH. It is hypothesized that decreased glycolysis and increased fatty acid oxidation, characteristic features of starvation and diabetes, cause in muscles alterations resulting in increased BCAA levels. The main alterations include (i) impaired BCAA transamination due to decreased supply of amino groups acceptors (α-KG, pyruvate, and oxaloacetate) and (ii) inhibitory influence of NADH and acyl-CoAs produced in fatty acid oxidation on citric cycle and BCKA dehydrogenase. The studies supporting the hypothesis and pros and cons of elevated BCAA concentrations are discussed in the article.

• Klíčová slova
• alanine, glucose, insulin, insulin resistance, obesity, pyruvate,
• MeSH
• alanin metabolismus   MeSH
• diabetes mellitus metabolismus   MeSH
• glykolýza MeSH
• hladovění metabolismus   MeSH
• inzulin metabolismus   MeSH
• inzulinová rezistence MeSH
• kyseliny ketoglutarové metabolismus   MeSH
• lidé MeSH
• mastné kyseliny metabolismus   MeSH
• obezita metabolismus   MeSH
• oxidace-redukce MeSH
• pyruváty farmakokinetika   MeSH
• svaly enzymologie   metabolismus   MeSH
• transaminasy metabolismus   MeSH
• větvené aminokyseliny metabolismus   MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• alanin MeSH
• branched-chain-amino-acid transaminase MeSH Prohlížeč
• inzulin MeSH
• kyseliny ketoglutarové MeSH
• mastné kyseliny MeSH
• pyruváty MeSH
• transaminasy MeSH
• větvené aminokyseliny MeSH

In hyperammonemic states, such as liver cirrhosis, urea cycle disorders, and strenuous exercise, the catabolism of branched-chain amino acids (BCAAs; leucine, isoleucine, and valine) is activated and BCAA concentrations decrease. In these conditions, BCAAs are recommended to improve mental functions, protein balance, and muscle performance. However, clinical trials have not demonstrated significant benefits of BCAA-containing supplements. It is hypothesized that, under hyperammonemic conditions, enhanced glutamine availability and decreased BCAA levels facilitate the amination of branched-chain keto acids (BCKAs; α-ketoisocaproate, α-keto-β-methylvalerate, and α-ketoisovalerate) to the corresponding BCAAs, and that BCKA supplementation may offer advantages over BCAAs. Studies examining the effects of ketoanalogues of amino acids have provided proof that subjects with hyperammonemia can effectively synthesize BCAAs from BCKAs. Unfortunately, the benefits of BCKA administration have not been clearly confirmed. The shortcoming of most reports is the use of mixtures intended for patients with renal insufficiency, which might be detrimental for patients with liver injury. It is concluded that (i) BCKA administration may decrease ammonia production, attenuate cataplerosis, correct amino acid imbalance, and improve protein balance and (ii) studies specifically investigating the effects of BCKA, without the interference of other ketoanalogues, are needed to complete the information essential for decisions regarding their suitability in hyperammonemic conditions.

• Klíčová slova
• exercise, glutamine, liver cirrhosis, urea-cycle disorders, α-ketoglutarate,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Branched-chain amino acids (BCAAs; valine, leucine, and isoleucine) are essential amino acids with protein anabolic properties, which have been studied in a number of muscle wasting disorders for more than 50 years. However, until today, there is no consensus regarding their therapeutic effectiveness. In the article is demonstrated that the crucial roles in BCAA metabolism play: (i) skeletal muscle as the initial site of BCAA catabolism accompanied with the release of alanine and glutamine to the blood; (ii) activity of branched-chain keto acid dehydrogenase (BCKD); and (iii) amination of branched-chain keto acids (BCKAs) to BCAAs. Enhanced consumption of BCAA for ammonia detoxification to glutamine in muscles is the cause of decreased BCAA levels in liver cirrhosis and urea cycle disorders. Increased BCKD activity is responsible for enhanced oxidation of BCAA in chronic renal failure, trauma, burn, sepsis, cancer, phenylbutyrate-treated subjects, and during exercise. Decreased BCKD activity is the main cause of increased BCAA levels and BCKAs in maple syrup urine disease, and plays a role in increased BCAA levels in diabetes type 2 and obesity. Increased BCAA concentrations during brief starvation and type 1 diabetes are explained by amination of BCKAs in visceral tissues and decreased uptake of BCAA by muscles. The studies indicate beneficial effects of BCAAs and BCKAs in therapy of chronic renal failure. New therapeutic strategies should be developed to enhance effectiveness and avoid adverse effects of BCAA on ammonia production in subjects with liver cirrhosis and urea cycle disorders. Further studies are needed to elucidate the effects of BCAA supplementation in burn, trauma, sepsis, cancer and exercise. Whether increased BCAA levels only markers are or also contribute to insulin resistance should be known before the decision is taken regarding their suitability in obese subjects and patients with type 2 diabetes. It is concluded that alterations in BCAA metabolism have been found common in a number of disease states and careful studies are needed to elucidate their therapeutic effectiveness in most indications.

• Klíčová slova
• Ammonia, Cachexia, Cirrhosis, Diabetes, Glutamine, Nutrition,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Phenylbutyrate (PB) acts as chemical chaperone and histone deacetylase inhibitor, which is used to decrease ammonia in urea cycle disorders and has been investigated for use in the treatment of a number of lethal illnesses. We performed in vivo and in vitro experiments to examine the effects of PB on glutamine (GLN), branched-chain amino acid (BCAA; valine, leucine and isoleucine) and protein metabolism in rats. In the first study, animals were sacrificed one hour after three injections of PB (300mg/kg b.w.) or saline. In the second study, soleus (SOL, slow twitch) and extensor digitorum longus (EDL, fast twitch) muscles were incubated in a medium with or without PB (5 mM). L-[1-14 C] leucine was used to estimate protein synthesis and leucine oxidation, and 3-methylhistidine release was used to evaluate myofibrillar protein breakdown. PB treatment decreased GLN, BCAA and branched-chain keto acids (BCKAs) in blood plasma, decreased BCAA and increased GLN concentrations in muscles, and increased GLN synthetase activities in muscles. Addition of PB to incubation medium increased leucine oxidation (55% in EDL, 29% in SOL), decreased BCKA and increased GLN in medium of both muscles, increased GLN in muscles, decreased protein synthesis in SOL and increased proteolysis in EDL. It is concluded that PB decreases BCAA, BCKA and GLN in blood plasma, activates BCAA catabolism and GLN synthesis in muscle and exerts adverse effects on protein metabolism. The results indicate that BCAA and GLN supplementation is needed when PB is used therapeutically and that PB may be a useful prospective agent which could be effective in management of maple syrup urine disease.

• Klíčová slova
• Phenylbutyrate, branched-chain amino acids, glutamine, leucine, maple syrup urine disease, muscle protein,
• MeSH
• fenylbutyráty farmakologie   MeSH
• glutamin metabolismus   MeSH
• kosterní svaly účinky léků   metabolismus   MeSH
• leucin metabolismus   MeSH
• oxidace-redukce účinky léků   MeSH
• potkani Wistar MeSH
• proteosyntéza účinky léků   MeSH
• svalové proteiny metabolismus   MeSH
• techniky tkáňových kultur MeSH
• větvené aminokyseliny metabolismus   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• fenylbutyráty MeSH
• glutamin MeSH
• leucin MeSH
• svalové proteiny MeSH
• větvené aminokyseliny MeSH