The Low-Carbohydrate Diet: Short-Term Metabolic Efficacy Versus Longer-Term Limitations.

BACKGROUND: Diets have been a central component of lifestyle modification for decades. The Low-Carbohydrate Diet (LCD), originally conceived as a treatment strategy for intractable epilepsy (due to its association with ketogenesis), became popular in the 1970s and since then has risen to prominence as a weight loss strategy. OBJECTIVE: To explore the efficacy, limitations and potential safety concerns of the LCD. DATA SOURCES: We performed a narrative review, based on relevant articles written in English from a Pubmed search, using the terms 'low carbohydrate diet and metabolic health'. RESULTS: Evidence supports the efficacy of the LCD in the short-term (up to 6-months) for reduction in fat mass and remission of Type 2 Diabetes Mellitus (T2D). However, the longer-term efficacy of the LCD is disappointing, with diminishment of weight loss potential and metabolic benefits of the LCD beyond 6-months of its adoption. Furthermore, practical limitations of the LCD include the associated restriction of food choices that restrict the acceptability of the LCD for the individual, particularly over the longer term. There are also safety concerns of the LCD that stem from nutritional imbalances (with a relative excess of dietary fat and protein intake with associated dyslipidaemia and increased risk of insulin resistance and T2D development) and ketotic effects. Finally, the LCD often results in a reduction in dietary fibre intake, with potentially serious adverse consequences for overall health and the gut microbiota. CONCLUSIONS: Although widely adopted, the LCD usually has short-lived metabolic benefits, with limited efficacy and practicality over the longer term. Dietary modification needs tailoring to the individual, with careful a priori assessments of food preferences to ensure acceptability and adherence over the longer term, with avoidance of dietary imbalances and optimization of dietary fibre intake (primarily from plant-based fruit and vegetables), and with a posteriori assessments of the highly individual responses to the LCD. Finally, we need to change our view of diets from simply an excipient for weight loss to an essential component of a healthy lifestyle.

Cetoacidosis como complicación de una dieta baja en hidratos de carbono / Ketoacidosis as a complication of a low carbohydrate diet

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Reproductive failure in Arabidopsis thaliana under transient carbohydrate limitation: flowers and very young siliques are jettisoned and the meristem is maintained to allow successful resumption of reproductive growth.

The impact of transient carbon depletion on reproductive growth in Arabidopsis was investigated by transferring long-photoperiod-grown plants to continuous darkness and returning them to a light-dark cycle. After 2 days of darkness, carbon reserves were depleted in reproductive sinks, and RNA in situ hybridization of marker transcripts showed that carbon starvation responses had been initiated in the meristem, anthers and ovules. Dark treatments of 2 or more days resulted in a bare-segment phenotype on the floral stem, with 23-27 aborted siliques. These resulted from impaired growth of immature siliques and abortion of mature and immature flowers. Depolarization of PIN1 protein and increased DII-VENUS expression pointed to rapid collapse of auxin gradients in the meristem and inhibition of primordia initiation. After transfer back to a light-dark cycle, flowers appeared and formed viable siliques and seeds. A similar phenotype was seen after transfer to sub-compensation point irradiance or CO2 . It also appeared in a milder form after a moderate decrease in irradiance and developed spontaneously in short photoperiods. We conclude that Arabidopsis inhibits primordia initiation and aborts flowers and very young siliques in C-limited conditions. This curtails demand, safeguarding meristem function and allowing renewal of reproductive growth when carbon becomes available again.

Uso de azúcares y edulcorantes en la alimentación del niño. Recomendaciones del Comité de Nutrición de la Asociación Española de Pediatría / Use of sugars and sweeteners in children's diets. Recommendations of the Nutrition Committee of the Spanish Paediatric Association

El término edulcorante hace referencia a aquel aditivo alimentario que confiere un sabor dulce y que, habitualmente, no aporta o proporciona muy poca energía. Se utiliza para endulzar alimentos, medicamentos y complementos alimenticios cuando se persiguen fines no nutritivos. Desde hace años, se han empleado edulcorantes acalóricos como sustitutos de todo o parte del contenido en azúcares en comidas y bebidas. En las últimas décadas, se ha incrementado su consumo para prevenir la caries y para el correcto cumplimiento de la dieta en casos de control del peso corporal, obesidad y diabetes y, en general, como coadyuvantes para conseguir un balance energético adecuado. No obstante, el consumo de alimentos y de bebidas azucaradas y/o edulcoradas es elevado, reflejando o un aporte calórico importante, o un patrón de hábitos alimentarios inadecuados en los niños. Por otro lado, sigue habiendo dudas entre los consumidores sobre los riesgos para la salud asociados al uso de edulcorantes, ya sean artificiales o naturales. El principal interés en investigación sobre seguridad y los posibles usos terapéuticos se centra en los «edulcorantes artificiales». El objetivo de este documento es proporcionar información a los pediatras sobre las características de los distintos edulcorantes para aconsejar en la elección de un determinado edulcorante sobre la base de sus propiedades (AU)

The term «sweetener» refers to a food additive that imparts a sweet flavour and usually provides no or very low energy. It is used to sweeten foods, medicines and food supplements with no nutritional purposes. For years, no-calorie sweeteners have been used as substitutes for all or part of the sugar content in foods and beverages. In recent decades its consumption has risen to prevent tooth decay, or as an aid in weight control, obesity and diabetes and, in general, to achieve an optimal energy balance. However, consumption of sugary or sweetened food and soft drinks is high, making this situation of special interest in calorie intake and in the poor behavioural pattern of eating habits in children. In addition, questions remain among consumers about the risks to health associated with their use, whether they are artificial or natural. The «artificial sweeteners» are the group of greatest interest in research in order to demonstrate their safety and to provide firm data on their possible therapeutic effects. The aim of the present document is to increase information for paediatricians on the characteristics of different sweeteners, and to advise on the choice of sweeteners, based on their properties (AU)

Jasmonate-dependent depletion of soluble sugars compromises plant resistance to Manduca sexta.

Jasmonates regulate plant secondary metabolism and herbivore resistance. How they influence primary metabolites and how this may affect herbivore growth and performance are not well understood. We profiled sugars and starch of jasmonate biosynthesis-deficient and jasmonate-insensitive Nicotiana attenuata plants and manipulated leaf carbohydrates through genetic engineering and in vitro complementation to assess how jasmonate-dependent sugar accumulation affects the growth of Manduca sexta caterpillars. We found that jasmonates reduce the constitutive and herbivore-induced concentration of glucose and fructose in the leaves across different developmental stages. Diurnal, jasmonate-dependent inhibition of invertase activity was identified as a likely mechanism for this phenomenon. Contrary to our expectation, both in planta and in vitro approaches showed that the lower sugar concentrations led to increased M. sexta growth. As a consequence, jasmonate-dependent depletion of sugars rendered N. attenuata plants more susceptible to M. sexta attack. In conclusion, jasmonates are important regulators of leaf carbohydrate accumulation and this determines herbivore growth. Jasmonate-dependent resistance is reduced rather than enhanced through the suppression of glucose and fructose concentrations, which may contribute to the evolution of divergent resistance strategies of plants in nature.

Metabolic adaptation to sugar/O2 deficiency for anaerobic germination and seedling growth in rice.

Rice is characterized by a broad range of metabolic and morphological adaptations to flooding, such as germination and mobilization of stored nutrients under submergence until seedlings reach the water surface to carry out photosynthesis, and sustainable growth of mature plants for long durations under partial submergence. The underlying mechanisms of the molecular basis of adaptation to anaerobic germination and seedling growth in rice are being uncovered. Induction of an ensemble of hydrolases to mobilize endosperm nutrient reserves is one of the key factors for successful germination and coleoptile elongation in rice under submergence. To compensate for reduced efficiency of Tricarboxylic Acid cycle and oxidative respiration in mitochondria under O2 deficient conditions, α-amylases play a central role in the hydrolysis of starch to provide sugar substrates for glycolysis and alcohol fermentation for generating ATP. We review the progress on the molecular mechanism regulating α-amylase expression that involves the integration of signals generated by the hormone gibberellin (GA), sugar starvation and O2 deprivation that results in germination and sustainable seedling growth in rice under anaerobic conditions. Comparisons are also made between dicots and monocots for the molecular mechanism of induction of genes involved in alcohol fermentation and sugar/O2 deficiency sensing system.

Elevación del antígeno carbohidratado 19-9 (CA 19-9) en un paciente con síntomas inespecíficos / Carbohydrate antigen 19-9 (CA 19-9) elevation in a patient with non-specific symptoms

El CA 19-9 es uno de los marcadores tumorales (MT) más inespecíficos. El incremento de este marcador puede estar influido por diversas circunstancias, por lo que un resultado elevado debe ser interpretado siempre considerando el contexto clínico. Se presenta el caso clínico de un varón de 79 años con síntomas digestivos inespecíficos y con una elevación de CA 19-9 sin ninguna otra prueba complementaria con valores alterados, por lo que desde el laboratorio se realizó un estudio de interferencias para determinar la verosimilitud de este resultado. El objetivo de este trabajo es resaltar el papel que desempeña el laboratorio clínico en la interpretación de los MT en el diagnóstico del cáncer (AU)

CA 19-9 is one of the most non-specific tumour markers (TM). It may be increased in different conditions, and thus a high result must be interpreted in a clinical context. In this article the case is presented of a 79 year-old man who had non-specific gastrointestinal symptoms and an elevation of CA 19-9, with no other alterations in the complementary tests. Because of this, the laboratory carried out a complete interference study. The objective of the present work is to emphasise the role of the clinical laboratory in the interpretation of the TM in cancer diagnosis (AU)

Impact of lactose starvation on the physiology of Lactobacillus casei GCRL163 in the presence or absence of tween 80.

The global proteomic response of the nonstarter lactic acid bacteria Lactobacillus casei strain GCRL163 under carbohydrate depletion was investigated to understand aspects of its survival following cessation of fermentation. The proteome of L. casei GCRL163 was analyzed quantitatively after growth in modified MRS (with and without Tween 80) with different levels of lactose (0% lactose, starvation; 0.2% lactose, growth limiting; 1% lactose, non-growth-limited control) using gel-free proteomics. Results revealed that carbohydrate starvation lead to suppression of lactose and galactose catabolic pathways as well as pathways for nucleotide and protein synthesis. Enzymes of the glycolysis/gluconeogenesis pathway, amino acid synthesis, and pyruvate and citrate metabolism become more abundant as well as other carbohydrate catabolic pathways, suggesting increased optimization of intermediary metabolism and scavenging. Tween 80 did not affect growth yield; however, proteins related to fatty acid biosynthesis were repressed in the presence of Tween 80. The data suggest that L. casei adeptly switches to a scavenging mode, using both citrate and Tween 80, and efficiently adjusts energetic requirements when carbohydrate starved and thus can sustain survival for weeks to months. Explaining the adaptation of L. casei during lactose starvation will assist efforts to maintain viability of L. casei and extend its utility as a beneficial dietary adjunct and fermentation processing aid.

[Content of mineral elements in the diet of students of physical education faculty].

Research of the diet of students of the Faculty of Physical Education found discrepancy of caloric content and correlation of macro- and micronutrients to physiological norms accompanied by a deficiency of some mineral elements. Thus, this research found discrepancy of a diet in caloric content and correlation of macro- and micronutrients to physiological norms. Calorie deficiency in both groups is caused for lack of all macro- and micronutrients, but mostly for lack of carbohydrates with an average glycemic index, fruit, and vegetables that have prebiotic properties and mineral-rich elements. Deficiency in the diet of young men 9.6% of the total protein and 23.5% of carbohydrates was accompanied for lack 15.5% of calcium. In the group of girls the results showed a decrease of the required amounts of calcium, magnesium and iron of 36.4; 7.5 and 1.5% respectively, which was displayed against a background of reducing the consumption of the total protein 25.1 and 36.0% of carbohydrates. As a result, basic nutrition of students practicing sports requires rationalization and adjustment. To improve the biological value of the diet it is advisable for students to use daily dairy products and other sources of animal protein in their diets. It is also necessary to introduce fruit and vegetables as a source of dietary fibers and mineral elements. Created in both groups deficiency of calcium and biologically high-grade proteins of animal origin can be eliminated by various dairy products in which calcium and phosphorus are in easily digestible form and in a balanced quantity. Despite the considerable amount of calcium in many foods (meat, bread, cereals, vegetables) calcium is assimilated with difficulty from these products. The exception is the calcium of milk, curd, cheese and other dairy products. The ration between calcium and phosphorus in milk is 1:1-1.4:1. For example, taking 0.5 liters of milk provides 600 mg of assimilable calcium intake.

Sugar starvation- and GA-inducible calcium-dependent protein kinase 1 feedback regulates GA biosynthesis and activates a 14-3-3 protein to confer drought tolerance in rice seedlings.

Germination followed by seedling growth constitutes two essential steps in the initiation of a new life cycle in plants, and in cereals, completion of these steps is regulated by sugar starvation and the hormone gibberellin. A calcium-dependent protein kinase 1 gene (OsCDPK1) was identified by differential screening of a cDNA library derived from sucrose-starved rice suspension cells. The expression of OsCDPK1 was found to be specifically activated by sucrose starvation among several stress conditions tested as well as activated transiently during post-germination seedling growth. In gain- and loss-of-function studies performed with transgenic rice overexpressing a constitutively active or RNA interference gene knockdown construct, respectively, OsCDPK1 was found to negatively regulate the expression of enzymes essential for GA biosynthesis. In contrast, OsCDPK1 activated the expression of a 14-3-3 protein, GF14c. Overexpression of either constitutively active OsCDPK1 or GF14c enhanced drought tolerance in transgenic rice seedlings. Hence, our studies demonstrated that OsCDPK1 transduces the post-germination Ca(2+) signal derived from sugar starvation and GA, refines the endogenous GA concentration and prevents drought stress injury, all essential functions to seedling development at the beginning of the life cycle in rice.

[Carbohydrate restriction in the larval diet causes oxidative stress in adult insects of Drosophila melanogaster].

The influence of 20 and 1% glucose and fructose, which were components of larval diet, on the level of oxidized proteins and lipids, low molecular mass antioxidant content as well as activities of antioxidant and associated enzymes in adult fruit fly Drosophila melanogaster were investigated. The restriction of carbohydrates in larval diet leads to oxidative stress in adult insects. It is supported by 40-50% increased content of protein carbonyl groups and by 60-70% decreased level of protein thiol groups as well as by a 4-fold increase of lipid peroxide content in 2-day-old flies of both sexes, developed on the diet with 1% carbohydrates. Oxidative stress, induced by carbohydrate restriction of the larval diet, caused the activation of antioxidant defence, differently exhibited in male and female fruit flies. Caloric restriction increased activity of superoxide dismutase and thioredoxin reductase associating only in males with 2-fold higher activity of NADPH-producing enzymes--glucose-6-phosphate dehydrogenase and isocitrate dehydrogenase. Carbohydrate restriction in the larval diet caused the increase of uric acid content, but the decrease in catalase activity in males. In females the values of these parameters were changed in opposite direction compared with males. The obtained results let us conclude the different involvement of low molecular mass antioxidants, glutathione and uric acid, and antioxidant enzyme catalase in the protection of male and female fruit fly macromolecules against oxidative damages, caused by calorie restriction of larval diet.

Sucrose transport is inhibited by okadaic acid during regeneration of sugar-starved Vicia faba root meristem cells.

The sucrose-induced resumption of cell cycle in the Vicia faba root meristem cells, blocked in two principal control points PCP1/2 by carbohydrate starvation, occurs after 12 h of metabolic regeneration comprising increased activity of sucrose synthase (SuSy) and hexokinase (HK) as well as starch grain and cell wall matrix polysaccharide biosynthesis. Okadaic acid (OA), the specific protein phosphatase 1/2A inhibitor, supplied at the beginning of the recovery period (0-3 h) completely blocks these processes, making cell cycle resumption impossible. On the other hand, when added at the end (9-12 h), OA has a weak inhibitory effect. The aim of these studies was: (1) to establish how sucrose is transported into the cells and whether the above-mentioned effects are correlated with the intensity of its uptake at the beginning and at the end of the metabolic regeneration; and (2) to determine whether OA, blocking sucrose metabolism, also interferes with the process of sucrose uptake and distribution. The level of [(3)H]sucrose uptake was measured by liquid scintillation counting while sugar distribution was analyzed using microautoradiography and electron microscopy. The results showed that sucrose entered the meristematic cells along symplastic or apoplastic pathways and, to a lesser extent, through endocytosis. The cytoplasmic compartments (endoplasmic reticulum, vacuoles, plastids) and the nucleus were labeled. The intensity of [(3)H]sucrose uptake was nearly 2-fold lower during the initial than during the final period of metabolic regeneration. OA inhibited the apoplastic pathway of radioactive molecule uptake and its distribution between cell compartments, implicating PP1/2A involvement in the regulation of this transport.

Sucrose synthase activity and carbohydrates content in relation to phosphorylation status of Vicia faba root meristems during reactivation from sugar depletion.

Carbohydrate starvation of Vicia faba root meristems leads to readjustment of carbohydrate metabolism and blocks the cell cycle in two principal control points (PCP1/2). The cell cycle reactivation is possible after sucrose provision, although with a delay of about 12h. During this period, the cells are sensitive to 6-dimethylaminopurine (6-DMAP) and okadaic acid (OA), inhibitors of protein kinases and phosphatases, respectively. The aim of the present study was to investigate whether those inhibitors are involved in inhibition of cell cycle revival through interference with the activities of two sucrose-cleaving enzymes: sucrose synthase (SuSy; EC 2.4.1.13) and invertase (INV; EC 3.2.1.26). In sugar-starved cells, the in situ activity of both enzymes decreased significantly. Following supplementation of root meristems with sugar, INV remained inactive, but SuSy activity increased. Despite the lack of INV activity, glucose was present in meristem cells, but its content was low in cells treated with OA. In the latter case, the size of plastids was reduced, they had less starch, and Golgi structures were affected. In sugar-starved cells, SuSy activity was induced more by exogenous sucrose than by glucose. The sucrose-induced activity was strongly inhibited by OA (less by 6-DMAP) at early stages of regeneration, but not at the stages preceding DNA replication or mitotic activities. The results indicate that prolongation of regeneration and a marked decrease in the number of cells resuming proliferation (observed in previous studies) and resulting from the action of inhibitors, are correlated with the process of SuSy activation at the beginning of regeneration from sugar starvation.

Modulation of sugar metabolism by an INDETERMINATE DOMAIN transcription factor contributes to photoperiodic flowering in Arabidopsis.

There has been a long-standing interest in the role played by sugars in flowering. Of particular interest is how sugar-related signals are integrated into flowering genetic pathways. Here, we demonstrate that the INDETERMINATE DOMAIN transcription factor AtIDD8 regulates photoperiodic flowering by modulating sugar transport and metabolism. We found that whereas AtIDD8-deficient idd8 mutants exhibit delayed flowering under long days, AtIDD8-overexpressing plants (35S:IDD8) show early flowering. In addition, the sucrose synthase genes SUS1 and SUS4 were upregulated in 35S:IDD8 plants but downregulated in idd8 mutants, in which endogenous sugar levels were altered. AtIDD8 activates the SUS4 gene by binding directly to its promoter, resulting in promoted flowering in SUS4-overexpressing plants. SUS4 expression also responds to photoperiodic signals. Notably, the AtIDD8 gene is suppressed by sugar deprivation. Therefore, we conclude that AtIDD8 regulation of sugar transport and metabolism is linked to photoperiodic flowering.

Trastornos congénitos de la glicosilación de las proteínas. Patogenia y aspectos clínicos / Congenital disorders of glycosylation of proteins. Pathogeny and clinical features

Objetivo. Este trabajo se propone actualizar los conocimientos a cerca de los trastornos congénitos de la glicosilación de las proteínas (CDG), en los aspectos referentes a lapatogenia y manifestaciones clínicas. Desarrollo. Realizamos una revisión de la literatura considerando la evolución histórica de estas enfermedades, las bases bioquímicas y genéticas que permiten una clasificación, así como las manifestaciones clínicas; se hace especial hincapié en la descripción de la variante CDG Ia, la forma más frecuente, de la que se describen las tres etapas evolutivas: infantil multisistémica, infantil tardía y del adulto; deforma más breve se comentan las características de las variantes CDG Ib y CDG Ic. Conclusiones. Los CDG constituyen una patología emergente que dada su heterogeneidad clínica debe sospecharse en todo paciente con un cuadro neurológico inexplicable, en particular si junto a retraso psicomotor, hipotonía y epilepsia, asocia alteraciones hepáticas o de la coagulación, así como en casos de hipoplasia cerebelosa u olivo pontocerebelosa de aparición en el período neonatal (AU)

Objective. This work aims to provide an up-date on the knowledge regarding congenital disorders of glycosylation(CDG) of proteins in aspects on pathogeny and clinical manifestations. Development. We performed a review of the literature, considering the historical course of these diseases, biochemical and genetic bases that permit their classification and the clinical manifestations. Special emphasis is placed on the description of the CDG Ia variant, the most frequent form, describing the three evolutive states: infantile multisystemlate-infantile and adult. Briefly, we comment on the characteristics of the CDG Ib and CDG Ic variants. Conclusions. CDG is an emerging disease that, given its clinical heterogeneity, should be suspected in all patients with an unexplainable neurological picture, especially if it is accompanied by psychomotor retardation, hypotony andepilepsy, if it associates hepatic alterations of coagulation disorders and in cases of cerebellar hypoplasia or pontocerebellar and olive hypoplasia appearing in the neonatal period (AU)

Diagnóstico y tratamiento de los trastornos congénitos de laglicosilación de las proteínas / Diagnosis and treatment of congenital disorders of glycosylation of proteins

Objetivo. Se realiza una revisión actualizada de los procedimientos diagnósticos y del tratamiento de los trastornos congénitos de la glicosilación de las proteínas. Desarrollo. Con la revisión de la literatura referente a estas enfermedades, se detallan los datos clínicos que permiten realizar una sospecha fundada, destacando los hallazgos de laboratorio, tanto los referentes a las isoformas de la transferrina (se encuentra un aumento de la disialotransferrina y de la asialotransferrina y un descenso de la tetrasialotransferrina), los enzimáticos específicos -deficiencia de fosfomanonomutasa-, así como las pruebas hepáticas (elevación de transaminasas) y de coagulación (descenso de los factores) y los aspectos radiológicos (atrofia del cerebelo y del tronco cerebral, con normalidad de estructuras supratentoriales). Además, se refieren las situaciones clínicas con las que hay que realizar un diagnóstico diferencial y se comentan los aspectos terapéuticos, destacando que sólo dos trastornos: CDG-Ib (manosa oral) y CDG IIc (mucosa) tienen un tratamiento etiopatogénico eficaz. Conclusiones. En los pacientes con sospecha clínica de esta patología, la determinación de la transferrina es el primer paso para su diagnóstico, completándose con la demostración de la deficiencia enzimática, para confirmar mediante el análisis de las mutaciones del gen PMM2. En la actualidad no se dispone de un tratamiento para la forma CDGIa, la variante más frecuente (AU)

Objective. An up-dated review is made of the diagnostic procedures and treatment of congenital disorders of glycosylation of proteins. Development. With the review of the literature regarding these diseases, details are given of the clinical data that make it possible to perform a well-founded suspicion, stressing the laboratory findings, both those regarding the transferrin isoforms (an increase is found in the disialotransferrin and asialotransferrin and decrease of the tetrasialotransferrin), specific enzymes - deficiency of the enzyme phosphomano mutase and hepatic (transaminase elevation) and coagulation (decrease of the factors) tests and radiological features (cerebellum and brain stem atrophy with normality of supratentorial structures). Furthermore, the clinical situations needed to make a differential diagnosisare mentioned and the therapeutic aspects are discussed, it standing out that only two disorders: CDG-Ib (oral mannose) and CDG IIc (mucose) have an effective etiopathogenic treatment. Conclusions. In patients with clinical suspicion of this condition, determination of transferrin is the first step for its diagnosis, completing it with the demonstration of the enzyme deficiency, to confirm the mutations of the PMM2 gene through the analysis. Currently, there is no treatment available for the CDG-Ia form, this being the most frequent variant (AU)

Modified Atkins diet for the treatment of nonconvulsive status epilepticus in children.

The authors describe the use of a modified Atkins diet for the treatment of 2 children with nonconvulsive status epilepticus. Patient 1 was a 4-year-and-11-month-old girl diagnosed with frontal lobe epilepsy. Since the age of 3 years and 10 months, she had daily nonconvulsive status epilepticus resistant to antiepileptic agents. Patient 2 was a 5-year-and-5-month-old girl with subcortical band heterotopia. She had nonconvulsive status epilepticus daily since the age of 5 years. They were treated with the modified Atkins diet, in which carbohydrate intake was restricted to 10 g/d without restriction on protein, caloric, or fluid intake. The nonconvulsive status epilepticus disappeared 5 and 10 days after the initiation of the diet treatment, respectively. They have been on the diet treatment and free from nonconvulsive status epilepticus for 19 and 4 months, respectively. The modified Atkins diet appears to be very effective for the treatment of nonconvulsive status epilepticus.

Replacement of lipopolysaccharide with free lipid A molecules in Escherichia coli mutants lacking all core sugars.

Escherichia coli mutants deficient in 2-keto-3-deoxy-D-manno-octulosonic acid (Kdo) biosynthesis are conditionally lethal, but their phenotypes are bypassed by certain suppressor mutations or by overexpression of MsbA, the inner membrane flippase for core-lipid A. These strains grow on broth with the tetraacylated precursor lipid IV(A) replacing lipopolysaccharide [Meredith, T. C., et al. (2006) ACS Chem. Biol. 1, 33-42]. Deletion of kdtA, which encodes the Kdo transferase, is possible under these conditions. We now show that lipid IV(A) reaches the outer surface of the outer membrane in these strains, as judged by its accessibility to the lipase PagL. On the assumption that MsbA is optimized to transport penta- or hexaacylated lipid A, we overexpressed the lauroyl- or the myristoyltransferase of lipid A biosynthesis, encoded by lpxL and lpxM, respectively, and demonstrated that kdtA deletion mutants were also viable in this setting. Although E. coli LpxL is stimulated by the presence of the Kdo disaccharide in its acceptor substrate, LpxL does slowly acylate lipid IV(A). Overexpression of LpxL from a plasmid suppressed the lethality of kdtA deletions on nutrient broth at 30 or 37 degrees C without the need for MsbA overproduction. These strains accumulated penta- and hexaacylated free lipid A containing a secondary laurate chain or a laurate and a myristate chain, respectively. Deletion of kdtA in strains overexpressing LpxM accumulated pentaacylated lipid A with a secondary myristate moiety. None of the strains lacking kdtA grew in the presence of bile salts at any temperature or on nutrient broth at 42 degrees C. Our findings show that the main function of Kdo is to provide the right substrates for the acyltransferases LpxL and LpxM, resulting in the synthesis of penta- and hexaacylated lipid A, which is optimal for the MsbA flippase.