Association of BCAT2 and BCKDH polymorphisms with clinical, anthropometric and biochemical parameters in young adults.

BACKGROUND AND AIM: Circulating amino acids are modified by sex, body mass index (BMI) and insulin resistance (IR). However, whether the presence of genetic variants in branched-chain amino acid (BCAA) catabolic enzymes modifies circulating amino acids is still unknown. Thus, we determined the frequency of two genetic variants, one in the branched-chain aminotransferase 2 (BCAT2) gene (rs11548193), and one in the branched-chain ketoacid dehydrogenase (BCKDH) gene (rs45500792), and elucidated their impact on circulating amino acid levels together with clinical, anthropometric and biochemical parameters. METHODS AND RESULTS: We performed a cross-sectional comparative study in which we recruited 1612 young adults (749 women and 863 men) aged 19.7 ± 2.1 years and with a BMI of 24.9 ± 4.7 kg/m2. Participants underwent clinical evaluation and provided blood samples for DNA extraction and biochemical analysis. The single nucleotide polymorphisms (SNPs) were determined by allelic discrimination using real-time polymerase chain reaction (PCR). The frequencies of the less common alleles were 15.2 % for BCAT2 and 9.83 % for BCKDH. The subjects with either the BCAT2 or BCKDH SNPs displayed no differences in the evaluated parameters compared with subjects homozygotes for the most common allele at each SNP. However, subjects with both SNPs had higher body weight, BMI, blood pressure, glucose, and circulating levels of aspartate, isoleucine, methionine, and proline than the subjects homozygotes for the most common allele (P < 0.05, One-way ANOVA). CONCLUSION: Our findings suggest that the joint presence of both the BCAT2 rs11548193 and BCKDH rs45500792 SNPs induces metabolic alterations that are not observed in subjects without either SNP.

Prolactin and the dietary protein/carbohydrate ratio regulate the expression of SNAT2 amino acid transporter in the mammary gland during lactation.

The sodium coupled neutral amino acid transporter 2 (SNAT2/SAT2/ATA2) is expressed in the mammary gland (MG) and plays an important role in the uptake of alanine and glutamine which are the most abundant amino acids transported into this tissue during lactation. Thus, the aim of this study was to assess the amount and localization of SNAT2 before delivery and during lactation in rat MG, and to evaluate whether prolactin and the dietary protein/carbohydrate ratio might influence SNAT2 expression in the MG, liver and adipose tissue during lactation. Our results showed that SNAT2 protein abundance in the MG increased during lactation and this increase was maintained along this period, while 24 h after weaning it tended to decrease. To study the effect of prolactin on SNAT2 expression, we incubated MG explants or T47D cells transfected with the SNAT2 promoter with prolactin, and we observed in both studies an increase in the SNAT2 expression or promoter activity. Consumption of a high-protein/low carbohydrate diet increased prolactin concentration, with a concomitant increase in SNAT2 expression not only in the MG during lactation, but also in the liver and adipose tissue. There was a correlation between SNAT2 expression and serum prolactin levels depending on the amount of dietary protein/carbohydrate ratio consumed. These findings suggest that prolactin actively supports lactation providing amino acids to the gland through SNAT2 for the synthesis of milk proteins.

Soya protein stimulates bile acid excretion by the liver and intestine through direct and indirect pathways influenced by the presence of dietary cholesterol.

Several studies using different animal models have demonstrated that the consumption of soya protein (SP) reduces serum cholesterol concentrations by increasing the excretion of bile acids (BA). However, the mechanism by which SP enhances BA excretion is not fully understood. Therefore, the aim of the present study was to determine whether the consumption of SP regulates the expression of key enzymes involved in hepatic BA synthesis and the transporters involved in reverse cholesterol transport (RCT) via fibroblast growth factor 15 (FGF15) and/or small heterodimer protein (SHP) in rats. To achieve this aim, four groups of rats were fed experimental diets containing 20 % casein (C) or SP with or without the addition of 0·2 % cholesterol and the expression of hepatic genes involved in BA synthesis and the ileal and hepatic RCT was measured. Rats fed the SP diet had higher concentrations of ileal FGF15 and hepatic FGF15 receptor (FGFR4) and increased expression of SHP and liver receptor homolog 1 (LRH1) than those fed the C diet; as a result, the excretion of faecal BA was greater. The addition of cholesterol to the diet repressed the protein abundance of FGF15 and FGFR4; however, SP increased the expression of SHP and LRH1 to a lesser extent. Nonetheless, the expression of ABCG5/8 was increased in the intestine of rats fed the SP diet, and the effect was enhanced by the addition of cholesterol to the diet. In conclusion, SP in the presence of cholesterol increases BA synthesis via the repressions of FGF15 and SHP and accelerates BA excretion to prevent cholesterol overload in the enterocytes by increasing RCT.

Flavonoids and saponins extracted from black bean (Phaseolus vulgaris L.) seed coats modulate lipid metabolism and biliary cholesterol secretion in C57BL/6 mice.

Black bean (Phaseolus vulgaris L.) seed coats are a rich source of natural compounds with potential beneficial effects on human health. Beans exert hypolipidaemic activity; however, this effect has not been attributed to any particular component, and the underlying mechanisms of action and protein targets remain unknown. The aim of the present study was to identify and quantify primary saponins and flavonoids extracted from black bean seed coats, and to study their effects on lipid metabolism in primary rat hepatocytes and C57BL/6 mice. The methanol extract of black bean seed coats, characterised by a HPLC system with a UV-visible detector and an evaporative light-scattering detector and HPLC-time-of-flight/MS, contained quercetin 3-O-glucoside and soyasaponin Af as the primary flavonoid and saponin, respectively. The extract significantly reduced the expression of SREBP1c, FAS and HMGCR, and stimulated the expression of the reverse cholesterol transporters ABCG5/ABCG8 and CYP7A1 in the liver. In addition, there was an increase in the expression of hepatic PPAR-α. Consequently, there was a decrease in hepatic lipid depots and a significant increase in bile acid secretion. Furthermore, the ingestion of this extract modulated the proportion of lipids that was used as a substrate for energy generation. Thus, the results suggest that the extract of black bean seed coats may decrease hepatic lipogenesis and stimulate cholesterol excretion, in part, via bile acid synthesis.

Production of 17 strains of edible mushroom grown on corn stover and its effect on the chemical composition and ruminal in vitro digestibility of the residual substrate.

The objective of this study was to evaluate the production (P) (g of fresh mushrooms /bag) and biological efficiency (BE) (g of fresh mushrooms per 100 g of dry substrate) of 17 fungal strains, namely Pleurotus ostreatus Po-IAP, Po-P38, Po-P14, Po-IE202, Po-Sfco, Po-JP, Po-Psma, and Po-POS, Pleurotus djamour Pd-PRO and Pd-UTMR, Pleurotus eryngii Pe-MB and Pe-PQ, Lentinula edodes L15, L9, L5, and LC, and Hericium erinaceus Heri, produced in corn stover (CS) and to assess the content of crude protein (CP), lignin (L), cellulose, hemicellulose, acid detergent fiber (ADF), and neutral detergent fiber (NDF) and in vitro digestibility of dry matter (IVDMD) of the residual substrate of CS, the so called spent mushroom substrate (SMS), in comparison to the non-inoculated substrate (C). The variables were analyzed as a completely randomized block design using R 4.0.3 software. Means were compared using Tukey's procedure. The Pleurotus spp. strains, compared to Lentinula spp. and Hericium spp., presented better BE and P. In comparison to C, the SMS increased the CP content (p < 0.05) from 10.8% (Po-JP) to 70.3% (LC), while NDF decreased (p < 0.05) from 11.5% (Pd-Pro) to 33.5% (L15) and IVDMD increased (p < 0.05) from 16.2% (Heri) to 47.7% (Pd-UTMR). In conclusion, of the 17 strains evaluated, the 3 strains of Lentinula edodes (L5, L15, and L9), one strain of Pleurotus djamour (Pd-UTMR), and one strain of Pleurotus ostreatus (Po-IAP) generated a SMS that, due to its nutritional improvement and increase in IVDMD, could be used as feed for ruminants. Our results also showed that corn stover is a suitable substrate to produce Pleurotus spp. fruiting bodies, with strain Po-IAP as the best yielding.

Protein restriction during pregnancy affects maternal liver lipid metabolism and fetal brain lipid composition in the rat.

Suboptimal developmental environments program offspring to lifelong metabolic problems. The aim of this study was to determine the impact of protein restriction in pregnancy on maternal liver lipid metabolism at 19 days of gestation (dG) and its effect on fetal brain development. Control (C) and restricted (R) mothers were fed with isocaloric diets containing 20 and 10% of casein. At 19 dG, maternal blood and livers and fetal livers and brains were collected. Serum insulin and leptin levels were determinate in mothers. Maternal and fetal liver lipid and fetal brain lipid quantification were performed. Maternal liver and fetal brain fatty acids were quantified by gas chromatography. In mothers, liver desaturase and elongase mRNAs were measured by RT-PCR. Maternal body and liver weights were similar in both groups. However, fat body composition, including liver lipids, was lower in R mothers. A higher fasting insulin at 19 dG in the R group was observed (C = 0.2 +/- 0.04 vs. R = 0.9 +/- 0.16 ng/ml, P < 0.01) and was inversely related to early growth retardation. Serum leptin in R mothers was significantly higher than that observed in C rats (C = 5 +/- 0.1 vs. R = 7 +/- 0.7 ng/ml, P < 0.05). In addition, protein restriction significantly reduced gene expression in maternal liver of desaturases and elongases and the concentration of arachidonic (AA) and docosahexanoic (DHA) acids. In fetus from R mothers, a low body weight (C = 3 +/- 0.3 vs. R = 2 +/- 0.1 g, P < 0.05), as well as liver and brain lipids, including the content of DHA in the brain, was reduced. This study showed that protein restriction during pregnancy may negatively impact normal fetal brain development by changes in maternal lipid metabolism.

Genistein stimulates insulin sensitivity through gut microbiota reshaping and skeletal muscle AMPK activation in obese subjects.

OBJECTIVE: Obesity is associated with metabolic abnormalities, including insulin resistance and dyslipidemias. Previous studies demonstrated that genistein intake modifies the gut microbiota in mice by selectively increasing Akkermansia muciniphila, leading to reduction of metabolic endotoxemia and insulin sensitivity. However, it is not known whether the consumption of genistein in humans with obesity could modify the gut microbiota reducing the metabolic endotoxemia and insulin sensitivity. RESEARCH DESIGN AND METHODS: 45 participants with a Homeostatic Model Assessment (HOMA) index greater than 2.5 and body mass indices of ≥30 and≤40 kg/m2 were studied. Patients were randomly distributed to consume (1) placebo treatment or (2) genistein capsules (50 mg/day) for 2 months. Blood samples were taken to evaluate glucose concentration, lipid profile and serum insulin. Insulin resistance was determined by means of the HOMA for insulin resistance (HOMA-IR) index and by an oral glucose tolerance test. After 2 months, the same variables were assessed including a serum metabolomic analysis, gut microbiota, and a skeletal muscle biopsy was obtained to study the gene expression of fatty acid oxidation. RESULTS: In the present study, we show that the consumption of genistein for 2 months reduced insulin resistance in subjects with obesity, accompanied by a modification of the gut microbiota taxonomy, particularly by an increase in the Verrucomicrobia phylum. In addition, subjects showed a reduction in metabolic endotoxemia and an increase in 5'-adenosine monophosphate-activated protein kinase phosphorylation and expression of genes involved in fatty acid oxidation in skeletal muscle. As a result, there was an increase in circulating metabolites of ß-oxidation and ω-oxidation, acyl-carnitines and ketone bodies. CONCLUSIONS: Change in the gut microbiota was accompanied by an improvement in insulin resistance and an increase in skeletal muscle fatty acid oxidation. Therefore, genistein could be used as a part of dietary strategies to control the abnormalities associated with obesity, particularly insulin resistance; however, long-term studies are needed.

Bioactive Food Abates Metabolic and Synaptic Alterations by Modulation of Gut Microbiota in a Mouse Model of Alzheimer's Disease.

Recent investigations have demonstrated an important role of gut microbiota (GM) in the pathogenesis of Alzheimer's disease (AD). GM modulates a host's health and disease by production of several substances, including lipopolysaccharides (LPS) and short-chain fatty acids (SCFAs), among others. Diet can modify the composition and diversity of GM, and ingestion of a healthy diet has been suggested to lower the risk to develop AD. We have previously shown that bioactive food (BF) ingestion can abate neuroinflammation and oxidative stress and improve cognition in obese rats, effects associated with GM composition. Therefore, BF can impact the gut-brain axis and improved behavior. In this study, we aim to explore if inclusion of BF in the diet may impact central pathological markers of AD by modulation of the GM. Triple transgenic 3xTg-AD (TG) female mice were fed a combination of dried nopal, soy, chia oil, and turmeric for 7 months. We found that BF ingestion improved cognition and reduced Aß aggregates and tau hyperphosphorylation. In addition, BF decreased MDA levels, astrocyte and microglial activation, PSD-95, synaptophysin, GluR1 and ARC protein levels in TG mice. Furthermore, TG mice fed BF showed increased levels of pGSK-3ß. GM analysis revealed that pro-inflammatory bacteria were more abundant in TG mice compared to wild-type, while BF ingestion was able to restore the GM's composition, LPS, and propionate levels to control values. Therefore, the neuroprotective effects of BF may be mediated, in part, by modulation of GM and the release of neurotoxic substances that alter brain function.

A direct HPLC method to estimate streptomycin and its putative ototoxic derivative, streptidine, in blood serum: application to streptomycin-treated humans.

Streptomycin is an aminoglycoside antibiotic with a well-known antituberculosis activity; it is commonly used in clinical practice because it is effective and cheap. However, streptomycin has severe ototoxic effects. The delayed and gradual onset may suggest that a metabolic derivative of the antibiotic could be a potential contributor to ototoxicity. As in a rat experimental model this compound was found to be streptidine, we investigated whether this ototoxic metabolite was also present in the blood of streptomycin-treated patients. To this end, we implemented and optimized a direct reverse-phase HPLC technique to identify and estimate streptomycin and streptidine in serum of streptomycin-treated patients. All criteria for validation of the method were implemented in standard curves in serum of healthy non-treated volunteers by addition of increasing concentration of both compounds and their determination in a trichloroacetic acid deproteinized extract. We found that recovery of streptomycin or streptidine was > or =91.5%. Linearity was r(2)> or =0.99. The intraday and interday precisions were < or =9.7 and < or =10.6%, respectively. The relative intraday and interday error ranged from -9.0 to 8.3% for both compounds in human serum. Studies in patients included five male individuals treated from 35 to 90 days with 1g/day of streptomycin, presenting inner ear malfunction from mild to severe, in whose serum streptidine was always present, and could be successfully separated from streptomycin. Therefore, the validated method used can be a valuable tool to measure and follow these compounds in serum of streptomycin-treated patients.

Food combination based on a pre-hispanic Mexican diet decreases metabolic and cognitive abnormalities and gut microbiota dysbiosis caused by a sucrose-enriched high-fat diet in rats.

SCOPE: There is few information about the possible health effects of a food combination based on a pre-hispanic Mexican diet (PMD). This diet rich in fiber, polyphenols, a healthy ratio of omega 6/omega 3 fatty acids, and vegetable protein could improve carbohydrate and lipid metabolism, gut microbiota and cognitive function. METHODS AND RESULTS: We examined the effect of a PMD in a sucrose enriched high-fat model. The PMD contains corn, beans, tomato, nopal, chia and pumpkin seeds in dehydrated form. Following induction of obesity, rats were fed PMD. PMD consumption decreased glucose intolerance, body weight gain, serum and liver triglycerides and leptin. In addition, PMD decreased the size of the adipocytes, and increased the protein abundance of UCP-1, PPAR-α, PGC1-α and Tbx-1 in white adipose tissue. Finally, the PMD significant decreased hepatic levels of ROS, oxidized proteins and GSSG/GSH ratio and an increase in the relative abundance of Bifidobacteria and the improvement of cognitive function. CONCLUSION: Consumption of a PMD decreased the glucose intolerance and the biochemical abnormalities caused by the obesity by increasing the abundance of proteins involved in fatty acid oxidation, decreasing the oxidative stress and modifying the gut microbiota.

The mTORC1-Signaling Pathway and Hepatic Polyribosome Profile Are Enhanced after the Recovery of a Protein Restricted Diet by a Combination of Soy or Black Bean with Corn Protein.

Between 6% and 11% of the world's population suffers from malnutrition or undernutrition associated with poverty, aging or long-term hospitalization. The present work examined the effect of different types of proteins on the mechanistic target of rapamycin (mTORC1)-signaling pathway in: (1) healthy; and (2) protein restricted rats. (1) In total, 200 rats were divided into eight groups and fed one of the following diets: 20% casein (C), soy (S), black bean (B), B + Corn (BCr), Pea (P), spirulina (Sp), sesame (Se) or Corn (Cr). Rats fed C or BCr had the highest body weight gain; rats fed BCr had the highest pS6K1/S6K1 ratio; rats fed B, BCr or P had the highest eIF4G expression; (2) In total, 84 rats were fed 0.5% C for 21 day and protein rehabilitated with different proteins. The S, soy + Corn (SCr) and BCr groups had the highest body weight gain. Rats fed SCr and BCr had the highest eIF4G expression and liver polysome formation. These findings suggest that the quality of the dietary proteins modulate the mTORC1-signaling pathway. In conclusion, the combination of BCr or SCr are the best proteins for dietary protein rehabilitation due to the significant increase in body weight, activation of the mTORC1-signaling pathway in liver and muscle, and liver polysome formation.

PPARα via HNF4α regulates the expression of genes encoding hepatic amino acid catabolizing enzymes to maintain metabolic homeostasis.

The liver is the main organ involved in the metabolism of amino acids (AA), which are oxidized by amino acid catabolizing enzymes (AACE). Peroxisome proliferator-activated receptor-α (PPARα) stimulates fatty acid ß-oxidation, and there is evidence that it can modulate hepatic AA oxidation during the transition of energy fuels. To understand the role and mechanism of PPARα's regulation of AA catabolism, the metabolic and molecular adaptations of Ppara-null mice were studied. The role of PPARα on AA metabolism was examined by in vitro and in vivo studies. In wild-type and Ppara-null mice, fed increasing concentrations of the dietary protein/carbohydrate ratio, we measured metabolic parameters, and livers were analyzed by microarray analysis, histology and Western blot. Functional enrichment analysis, EMSA and gene reporter assays were performed. Ppara-null mice presented increased expression of AACE in liver affecting AA, lipid and carbohydrate metabolism. Ppara-null mice had increased glucagon/insulin ratio (7.2-fold), higher serum urea (73.1 %), lower body protein content (19.7 %) and decreased several serum AA in response to a high-protein/low-carbohydrate diet. A functional network of differentially expressed genes, suggested that changes in the expression of AACE were regulated by an interrelationship between PPARα and HNF4α. Our data indicated that the expression of AACE is down-regulated through PPARα by attenuating HNF4α transcriptional activity as observed in the serine dehydratase gene promoter. PPARα via HNF4α maintains body protein metabolic homeostasis by down-regulating genes involved in amino acid catabolism for preserving body nitrogen.

Omental adipose tissue gene expression, gene variants, branched-chain amino acids, and their relationship with metabolic syndrome and insulin resistance in humans.

Obesity is a complex disorder caused by several factors. Thus, the aim of the present study was to assess whether the expression of genes in the omental white adipose tissue (AT) of subjects with insulin resistance (IR) or metabolic syndrome (MetS) is associated with an elevation in serum branched-chain amino acids (BCAAs) and whether this response depends on specific genetic variants. Serum BCAA concentration, the adipocyte area, and gene variants of PPARγ, ABCA1, FTO, TCF7L2, GFOD2, BCAT2, and BCKDH were determined in 115 Mexican subjects. The gene expression in the AT and adipocytes of BCAT, BCKDH E1α, C/EBPα, PPARγ2, SREBP-1, PPARα, UCP1, leptin receptor, leptin, adiponectin, and TNFα was measured in 51 subjects. Subjects with IR showed higher values for the BMI, HOMA-IR, and adipocyte area and higher levels of serum glucose, insulin, leptin, and C-reactive protein, as well as an elevation of the AT gene expression of SREBP-1, leptin, and TNFα and a significant reduction in the expression of adiponectin, BCAT2, and BCKDH E1α, compared with non-IR subjects. The presence of MetS was associated with higher HOMA-IR as well as higher serum BCAA concentrations. Subjects with the genetic variants for BCAT2 and BCKDH E1 α showed a lower serum BCAA concentration, and those with the ABCA1 and FTO gene variant showed higher levels of insulin and HOMA-IR than non-IR subjects. AT dysfunction is the result of a combination of the presence of some genetic variants, altered AT gene expression, the presence of MetS risk factors, IR, and serum BCAA concentrations.

Differential modulation of the functionality of white adipose tissue of obese Zucker (fa/fa) rats by the type of protein and the amount and type of fat.

Recent evidence indicates that several metabolic abnormalities developed during obesity are associated with the presence of dysfunctional adipose tissue. Diet is a key factor that modulates several functions of adipose tissue; however, each nutrient in the diet produces specific changes. Thus, the aim of this work was to study the effect of the interaction of the type (coconut or soybean oil) and amount (5% or 10%) of fat with the type of dietary protein (casein or soy protein) on the functionality of white adipose tissue of Zucker (fa/fa) rats. The results showed that soybean oil reduced adipocyte size and decreased esterified saturated fatty acids in white adipose tissue. Excess dietary fat also modified the composition of esterified fatty acids in white adipose tissue, increased the secretion of saturated fatty acids to serum from white adipose tissue and reduced the process of fatty acids re-esterification. On the other hand, soy protein sensitized the activation of the hormone-sensitive lipase by increasing the phosphorylation of this enzyme (Ser 563) despite rats fed soy protein were normoglucagonemic, in contrast with rats fed casein that showed hyperglucagonemia but reduced hormone-sensitive lipase phosphorylation. Finally, in white adipose tissue, the interaction between the tested dietary components modulated the transcription/translation process of lipid and carbohydrate metabolism genes via the activity of the PERK-endoplasmic reticulum stress response. Therefore, our results showed that the type of protein and the type and amount of dietary fat selectively modify the activity of white adipose tissue, even in a genetic model of obesity.

Dietary type and amount of fat modulate lipid metabolism gene expression in liver and in adipose tissue in high-fat diet-fed rats.

BACKGROUND AND AIMS: Dietary fat plays a central role in the development of obesity. However, the metabolic consequences of dietary fat can vary depending on their fatty acid composition. Therefore, the aim of the present work was to study the effect of the type and amount of dietary fat on the expression of genes controlling lipogenesis and fatty acid oxidation in the liver or adipose tissue of rats. METHODS: The expression of hepatic or adipose tissue lipid metabolic genes from Sprague Dawley or Zucker(fa/fa) rats, respectively, was measured after chronic consumption of diets containing different types/amounts of dietary fats or after rats were adapted for 2 months to a high-fat Western diet and then fed different types and amounts of fats. RESULTS: Each fat or oil in the diet regulated differentially the expression of transcription factors involved in lipogenesis and fatty acid oxidation as well as some of its target genes in liver. The expression of these genes after a chronic consumption of a high-fat Western diet was reestablished in the presence of less dietary fat and was dependent on the type of fat. In obese Zucker(fa/fa) rats, consumption of a high-fat diet repressed the expression of lipogenic, fatty acid oxidation and thermogenic genes in adipose tissue. CONCLUSIONS: Type of fat influences the expression of genes that are involved in lipid metabolism in liver and adipose tissue, but this response is repressed when the amount of dietary fat is excessive, diminishing the differences between each type of fat.

Alfa-Glucosidasa con Posible Acción Hidrolítica Sobre Aminoglicósidos en la Sangre y el Vestíbulo de Ratas / Alpha-glucosidase with possible hydrolytic action over aminoglycosides in the blood and vestibule of rats

Antecedentes e hipótesis. La estreptomicina (STP)es un antibiótico aminoglicósido que se usa en el tratamiento de la tuberculosis, con efectos tóxicos importantes sobre la función vestibular. Los antecedentes farmacocinéticos muestran que la STP se acumula en un principio en la parte perilinfática y por mecanismos aún no descritos pasa a la endolinfa donde su principal blanco de acción son los cilios sensorios de las células pilosas vestibulares. Consideramos importante averiguar que parte de la molécula de STP es la responsable de su toxicidad vestibular, y tenemos evidencias que señalan la parte estreptidina (STD)como la porción activa, por lo que se propone que la STP actúa fragmentada por acción de una alfa-glucosidasa que hidroliza el enlace -1,4 con la liberación de la STD y que esté presente ya sea en el vestíbulo, en el torrente sanguíneo o en ambos. Método. Se determinó la actividad de alfa-glucosidasa en el suero y en homogeneizado vestibular de la rata usando p-nitrofenil--d-glucósido como sustrato; siguiendo el p-nitrofenilo (pNP)liberado espectrofotométricamente a 400 nm. Resultados. Se encontró alfa-glucosidasa tanto en el suero como en el vestíbulo de la rata con actividades específicas de 0.035 y 1.3 nmol de pNP/mg proteína/min respectivamente. Conclusión. La actividad encontrada en vestíbulo es semejante a la de la alfa-glucosidasa lisosomal del hígado de la rata (1.5 nmol de pNP/mg proteína/min)por lo que es posible que la alfa-glucosidasa presente en el suero y en el vestíbulo pueda romper a la STP, liberando la parte STD que actuaría sobre el oído

Estreptomicina: propiedades fisicoquímicas y toxicidad vestibular / Streptomycin, physical and chemical characteristics and vestibular toxicity

Propósito: Los antibióticos aminoglucósidos estreptomicina (STP) y kanamicina (KAN) son tóxicos para las células sensoriales del vestíbulo y de la cóclea, respectivamente. Químicamente están constituidos por estreptidina (STD) un derivado del inositol y dos azúcares, la esteptosa (Stosa) y la N-metilglucosamida (nm-GLUN); sin embargo, en la STP, la STD tiene dos sustituyentes guanidino, los que están ausentes en la KAN. Por lo tanto, se propone estudiar si la vestíbulo-toxicidad específica de la STP se debe a los grupos guanidino. Material y Métodos: Se incubaron en vitro, membranas celulares aisladas de los órganos vestibulares, con 3H-espermidina (3H-Spdina), un análogo estructural de la STP. Se midió la capacidad de los siguientes compuestos: STP, STD, KAN, guanidina (GUA) y n-acetilglucosamina (na-GLUN) para desplazarlos específicamente. Resultados: Se encontró que el orden de desplazamiento de la 3HSPdina para esas sustancia era STP=STD KanGUAn-a-GLUN. Conclusiones: Los resultados sugieren fuertemente que la STP debe su especificidad vestibulotóxica, a la presencia de los grupos guanidino en la porción de STD de su molécula, los que interactuarían por sus cargas positivas con estructuras membranales vestibulares relacionadas con la transducción, muy probablemente los cilios sensorios de las células ciliadas vestibulares