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The Low-Carbohydrate Diet: Short-Term Metabolic Efficacy Versus Longer-Term Limitations.
Barber, TM, Hanson, P, Kabisch, S, Pfeiffer, AFH, Weickert, MO
Nutrients. 2021;(4)
Abstract
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.
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Understanding the roles of osmolytes for acclimatizing plants to changing environment: a review of potential mechanism.
Ghosh, UK, Islam, MN, Siddiqui, MN, Khan, MAR
Plant signaling & behavior. 2021;(8):1913306
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Abstract
Abiotic stresses are significant environmental issues that restrict plant growth, productivity, and survival while also posing a threat to global food production and security. Plants produce compatible solutes known as osmolytes to adapt themselves in such changing environment. Osmolytes contribute to homeostasis maintenance, provide the driving gradient for water uptake, maintain cell turgor by osmotic adjustment, and redox metabolism to remove excess level of reactive oxygen species (ROS) and reestablish the cellular redox balance as well as protect cellular machinery from osmotic stress and oxidative damage. Perceiving the mechanisms how plants interpret environmental signals and transmit them to cellular machinery to activate adaptive responses is important for crop improvement programs to get stress-tolerant varieties. A large number of studies conducted in the last few decades have shown that osmolytes accumulate in plants and have strong associations with abiotic stress tolerance. Production of abundant osmolytes is needed for tolerance in many plant species. In addition, transgenic plants overexpressing genes for different osmolytes showed enhanced tolerance to various abiotic stresses. Many important aspects of their mechanisms of action are yet to be largely identified, especially regarding the relevance and relative contribution of specific osmolytes to the stress tolerance of a given species. Therefore, more efforts and resources should be invested in the study of the abiotic stress responses of plants in their natural habitats. The present review focuses on the possible roles and mechanisms of osmolytes and their association toward abiotic stress tolerance in plants. This review would help the readers in learning more about osmolytes and how they behave in changing environments as well as getting an idea of how this knowledge could be applied to develop stress tolerance in plants.
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Electrosynthesis of Biobased Chemicals Using Carbohydrates as a Feedstock.
Vedovato, V, Vanbroekhoven, K, Pant, D, Helsen, J
Molecules (Basel, Switzerland). 2020;(16)
Abstract
The current climate awareness coupled with increased focus on renewable energy and biobased chemicals have led to an increased demand for such biomass derived products. Electrosynthesis is a relatively new approach that allows a shift from conventional fossil-based chemistry towards a new model of a real sustainable chemistry that allows to use the excess renewable electricity to convert biobased feedstock into base and commodity chemicals. The electrosynthesis approach is expected to increase the production efficiency and minimize negative health for the workers and environmental impact all along the value chain. In this review, we discuss the various electrosynthesis approaches that have been applied on carbohydrate biomass specifically to produce valuable chemicals. The studies on the electro-oxidation of saccharides have mostly targeted the oxidation of the primary alcohol groups to form the corresponding uronic acids, with Au or TEMPO as the active electrocatalysts. The investigations on electroreduction of saccharides focused on the reduction of the aldehyde groups to the corresponding alcohols, using a variety of metal electrodes. Both oxidation and reduction pathways are elaborated here with most recent examples. Further recommendations have been made about the research needs, choice of electrocatalyst and electrolyte as well as upscaling the technology.
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CH/π Interactions in Carbohydrate Recognition.
Spiwok, V
Molecules (Basel, Switzerland). 2017;(7)
Abstract
Many carbohydrate-binding proteins contain aromatic amino acid residues in their binding sites. These residues interact with carbohydrates in a stacking geometry via CH/π interactions. These interactions can be found in carbohydrate-binding proteins, including lectins, enzymes and carbohydrate transporters. Besides this, many non-protein aromatic molecules (natural as well as artificial) can bind saccharides using these interactions. Recent computational and experimental studies have shown that carbohydrate-aromatic CH/π interactions are dispersion interactions, tuned by electrostatics and partially stabilized by a hydrophobic effect in solvated systems.
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Understanding the roles of nonstructural carbohydrates in forest trees - from what we can measure to what we want to know.
Hartmann, H, Trumbore, S
The New phytologist. 2016;(2):386-403
Abstract
Contents 386 I. 386 II. 388 III. 392 IV. 392 V. 396 VI. 399 399 References 399 SUMMARY Carbohydrates provide the building blocks for plant structures as well as versatile resources for metabolic processes. The nonstructural carbohydrates (NSC), mainly sugars and starch, fulfil distinct functional roles, including transport, energy metabolism and osmoregulation, and provide substrates for the synthesis of defence compounds or exchange with symbionts involved in nutrient acquisition or defence. At the whole-plant level, NSC storage buffers the asynchrony of supply and demand on diel, seasonal or decadal temporal scales and across plant organs. Despite its central role in plant function and in stand-level carbon cycling, our understanding of storage dynamics, its controls and response to environmental stresses is very limited, even after a century of research. This reflects the fact that often storage is defined by what we can measure, that is, NSC concentrations, and the interpretation of these as a proxy for a single function, storage, rather than the outcome of a range of NSC source and sink functions. New isotopic tools allow direct quantification of timescales involved in NSC dynamics, and show that NSC-C fixed years to decades previously is used to support tree functions. Here we review recent advances, with emphasis on the context of the interactions between NSC, drought and tree mortality.
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Metabolic adaptation to sugar/O2 deficiency for anaerobic germination and seedling growth in rice.
Lee, KW, Chen, PW, Yu, SM
Plant, cell & environment. 2014;(10):2234-44
Abstract
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.
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Phospholipid membrane protection by sugar molecules during dehydration-insights into molecular mechanisms using scattering techniques.
Garvey, CJ, Lenné, T, Koster, KL, Kent, B, Bryant, G
International journal of molecular sciences. 2013;(4):8148-63
Abstract
Scattering techniques have played a key role in our understanding of the structure and function of phospholipid membranes. These techniques have been applied widely to study how different molecules (e.g., cholesterol) can affect phospholipid membrane structure. However, there has been much less attention paid to the effects of molecules that remain in the aqueous phase. One important example is the role played by small solutes, particularly sugars, in protecting phospholipid membranes during drying or slow freezing. In this paper, we present new results and a general methodology, which illustrate how contrast variation small angle neutron scattering (SANS) and synchrotron-based X-ray scattering (small angle (SAXS) and wide angle (WAXS)) can be used to quantitatively understand the interactions between solutes and phospholipids. Specifically, we show the assignment of lipid phases with synchrotron SAXS and explain how SANS reveals the exclusion of sugars from the aqueous region in the particular example of hexagonal II phases formed by phospholipids.
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[Randomized clinical trials on the sugar sweetened beverages on adiposity in olders than 13 y; systematic review].
Gómez-Miranda, LM, Jiménez-Cruz, A, Bacardí-Gascón, M
Nutricion hospitalaria. 2013;(6):1792-6
Abstract
INTRODUCTION An association between consumption of sugar sweetened beverages (SSB) and metabolic diseases has been observed. OBJECTIVE The aim of this study was to analyze randomized clinical trials (RCT) of 18 or more weeks of intervention among ≥ 13 year old individuals, which examined the consumption of SSB on adiposity indicators. METHODS An electronic literature search was conducted in the PubMed database of RCT studies published up to April 10th, 2013. Term used for this search was "Sugar Sweetened Beverages". RESULTS Four studies were found. In one of the studies, after the reduction of SSB consumption, a small reduction of BMI was observed (p = 0.045). Another study showed that the reduction of 355 ml/day was associated with a weight loss of 0.7 kg (95% CI: 0.2-1.1, p = 0.01). In a different study, in the group consuming regular Coke, an increase in the visceral: abdominal subcutaneous fat ratio, was observed (p = 0.01). In another study, there were no differences on adiposity between the intervention and control groups. CONCLUSION The results of this review indicate a trend toward an effect of the consumption of SSB on adiposity.
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Dietary fructose, carbohydrates, glycemic indices and pancreatic cancer risk: a systematic review and meta-analysis of cohort studies.
Aune, D, Chan, DSM, Vieira, AR, Navarro Rosenblatt, DA, Vieira, R, Greenwood, DC, Cade, JE, Burley, VJ, Norat, T
Annals of oncology : official journal of the European Society for Medical Oncology. 2012;(10):2536-2546
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Abstract
BACKGROUND Dietary carbohydrates, glycemic load and glycemic index have been hypothesized to influence pancreatic cancer risk, but epidemiological studies have been inconsistent. We conducted a systematic review and meta-analysis of prospective studies to clarify these results. METHODS PubMed and several other databases were searched for prospective studies of intake of carbohydrates, glycemic index and glycemic load and pancreatic cancer up to September 2011. Summary relative risks were estimated using a random effects model. RESULTS Ten cohort studies (13 publications) were included in the meta-analysis. The summary relative risk (RR) per 10 glycemic index units was 1.02 [95% confidence interval (CI): 0.93-1.12, I(2) = 0%], per 50 glycemic load units was 1.03 (95% CI: 0.93-1.14, I(2) = 10%), per 100 g/day of total carbohydrates was 0.97 (95% CI: 0.81-1.16, I(2) = 35%), and per 25 g/day of sucrose intake was 1.05 (95% CI: 0.85-1.23, I(2) = 53%). A positive association was observed with fructose intake, summary RR = 1.22 (95% CI: 1.08-1.37, I(2) = 0%) per 25 g/day. CONCLUSIONS This meta-analysis does not support an association between diets high in glycemic index, glycemic load, total carbohydrates or sucrose and pancreatic cancer risk. The finding of an increased risk with fructose intake warrants further investigation in studies with better adjustment for confounding and in non-American populations.
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Carbohydrates - Guidelines on Parenteral Nutrition, Chapter 5.
Bolder, U, Ebener, C, Hauner, H, Jauch, KW, Kreymann, G, Ockenga, J, Traeger, K, ,
German medical science : GMS e-journal. 2009;:Doc23
Abstract
The main role of carbohydrates in the human body is to provide energy. Carbohydrates should always be infused with PN (parenteral nutrition) in combination with amino acids and lipid emulsions to improve nitrogen balance. Glucose should be provided as a standard carbohydrate for PN, whereas the use of xylite is not generally recommended. Fructose solutions should not be used for PN. Approximately 60% of non-protein energy should be supplied as glucose with an intake of 3.0-3.5 g/kg body weight/day (2.1-2.4 mg/kg body weight/min). In patients with a high risk of hyperglycaemia (critically ill, diabetes, sepsis, or steroid therapy) an lower initial carbohydrate infusion rate of 1-2 g/kg body weight/day is recommended to achieve normoglycaemia. One should aim at reaching a blood glucose level of 80-110 mg/dL, and at least a glucose level <145 mg/dL should be achieved to reduce morbidity and mortality. Hyperglycaemia may require addition of an insulin infusion or a reduction (2.0-3.0 g/kg body weight/day) or even a temporary interruption of glucose infusion. Close monitoring of blood glucose levels is highly important.