Biosynthesis and Export of Bacterial Glycolipids.

Complex carbohydrates are essential for many biological processes, from protein quality control to cell recognition, energy storage, and cell wall formation. Many of these processes are performed in topologically extracellular compartments or on the cell surface; hence, diverse secretion systems evolved to transport the hydrophilic molecules to their sites of action. Polyprenyl lipids serve as ubiquitous anchors and facilitators of these transport processes. Here, we summarize and compare bacterial biosynthesis pathways relying on the recognition and transport of lipid-linked complex carbohydrates. In particular, we compare transporters implicated in O antigen and capsular polysaccharide biosyntheses with those facilitating teichoic acid and N-linked glycan transport. Further, we discuss recent insights into the generation, recognition, and recycling of polyprenyl lipids.

Distinct protein architectures mediate species-specific beta-glucan binding and metabolism in the human gut microbiota.

Complex glycans that evade our digestive system are major nutrients that feed the human gut microbiota (HGM). The prevalence of Bacteroidetes in the HGM of populations worldwide is engendered by the evolution of polysaccharide utilization loci (PULs), which encode concerted protein systems to utilize the myriad complex glycans in our diets. Despite their crucial roles in glycan recognition and transport, cell-surface glycan-binding proteins (SGBPs) remained understudied cogs in the PUL machinery. Here, we report the structural and biochemical characterization of a suite of SGBP-A and SGBP-B structures from three syntenic ß(1,3)-glucan utilization loci (1,3GULs) from Bacteroides thetaiotaomicron (Bt), Bacteroides uniformis (Bu), and B. fluxus (Bf), which have varying specificities for distinct ß-glucans. Ligand complexes provide definitive insight into ß(1,3)-glucan selectivity in the HGM, including structural features enabling dual ß(1,3)-glucan/mixed-linkage ß(1,3)/ß(1,4)-glucan-binding capability in some orthologs. The tertiary structural conservation of SusD-like SGBPs-A is juxtaposed with the diverse architectures and binding modes of the SGBPs-B. Specifically, the structures of the trimodular BtSGBP-B and BuSGBP-B revealed a tandem repeat of carbohydrate-binding module-like domains connected by long linkers. In contrast, BfSGBP-B comprises a bimodular architecture with a distinct ß-barrel domain at the C terminus that bears a shallow binding canyon. The molecular insights obtained here contribute to our fundamental understanding of HGM function, which in turn may inform tailored microbial intervention therapies.

"Enhanced recovery after surgery - ERAS in elective craniotomies-a non-randomized controlled trial".

BACKGROUND: Enhanced Recovery After Surgery (ERAS) is a multimodal perioperative care bundle aimed at the early recovery of patients. Well accepted in gastric and pelvic surgeries, there is minimal evidence in neurosurgery and neurocritical care barring spinal surgeries. We wished to compare the length of intensive care unit (ICU) or high dependency unit (HDU) stay of patients undergoing elective craniotomy for supratentorial neurosurgery: ERAS protocol versus routine care. The secondary objective was to compare the postoperative pain scores, opioid use, glycemic control, and the duration of postoperative hospital stay between the two groups. METHODS: In this pragmatic non-randomized controlled trial (CTRI/2017/07/015451), consenting adult patients scheduled for elective supratentorial intracranial tumor excision were enrolled prospectively after institutional ethical clearance and consent. Elements-of-care in the ERAS group were- Preoperative -family education, complex-carbohydrate drink, flupiritine; Intraoperative - scalp blocks, limited opioids, rigorous fluid and temperature regulation; Postoperative- flupiritine, early mobilization, removal of catheters, and initiation of feeds. Apart from these, all perioperative protocols and management strategies were similar between groups. The two groups were compared with regards to the length of ICU stay, pain scores in ICU, opioid requirement, glycemic control, and hospital stay duration. The decision for discharge from ICU and hospital, data collection, and analysis was by independent assessors blind to the patient group. RESULTS: Seventy patients were enrolled. Baseline demographics - age, sex, tumor volume, and comorbidities were comparable between the groups. The proportion of patients staying in the ICU for less than 48 h after surgery, the cumulative insulin requirement, and the episodes of VAS scores > 4 in the first 48 h after surgery was significantly less in the ERAS group - 40.6% vs. 65.7%, 0.6 (±2.5) units vs. 3.6 (±8.1) units, and one vs. ten episodes (p = 0.04, 0.001, 0.004 respectively). The total hospital stay was similar in both groups. CONCLUSION: The study demonstrated a significant reduction in the proportion of patients requiring ICU/ HDU stay > 48 h. Better pain and glycemic control in the postoperative period may have contributed to a decreased stay. More extensive randomized studies may be designed to confirm these results. TRIAL REGISTRATION: Clinical Trial Registry of India ( CTRI/2018/04/013247 ), registered retrospectively on April 2018.

Influence of Sex and a High-Fiber Diet on the Gut Microbiome of Alentejano Pigs Raised to Heavy Weights.

This study investigates the influence of sex and a dietary transition on the gut microbiota of a local Portuguese pig breed. Three groups of male Alentejano pigs (n = 10 each) were raised between ~40 and 160 kg LW. Group C included pigs that were surgically castrated, while the I group included intact ones; both were fed with commercial diets. The third group, IExp, included intact pigs that were fed commercial diets until ~130 kg, then replaced by an experimental diet based on legumes and agro-industrial by-products between ~130 and 160 kg. Fecal samples were collected two weeks before slaughter. The total DNA was extracted and used for 16S metabarcoding on a MiSeq® System. The dietary transition from a commercial diet to the experimental diet substantially increased and shifted the diversity observed. Complex carbohydrate fermenting bacteria, such as Ruminococcus spp. and Sphaerochaeta spp., were significantly more abundant in IExp (q < 0.05). On the other hand, castrated pigs presented a significantly lower abundance of the potential probiotic, Roseburia spp. and Lachnospiraceae NK4A136 group (q < 0.01), bacteria commonly associated with better gut health and lower body fat composition. Understanding the role of gut microbiota is paramount to ensure a low skatole deposition and consumers' acceptance of pork products from non-castrated male pigs.

Dietary Utilization Drives the Differentiation of Gut Bacterial Communities between Specialist and Generalist Drosophilid Flies.

Gut bacteria play vital roles in the dietary detoxification, digestion, and nutrient supplementation of hosts during dietary specialization. The roles of gut bacteria in the host can be unveiled by comparing communities of specialist and generalist bacterial species. However, these species usually have a long evolutionary history, making it difficult to determine whether bacterial community differentiation is due to host dietary adaptation or phylogenetic divergence. In this regard, we investigated the bacterial communities from two Araceae-feeding Colocasiomyia species and further performed a meta-analysis by incorporating the published data from Drosophila bacterial community studies. The compositional and functional differentiation of bacterial communities was uncovered by comparing three (Araceae-feeding, mycophagous, and cactophilic) specialists with generalist flies. The compositional differentiation showed that Bacteroidetes and Firmicutes inhabited specialists, while more Proteobacteria lived in generalists. The functional prediction based on the bacterial community compositions suggested that amino acid metabolism and energy metabolism are overrepresented pathways in specialists and generalists, respectively. The differences were mainly associated with the higher utilization of structural complex carbohydrates, protein utilization, vitamin B12 acquisition, and demand for detoxification in specialists than in generalists. The complementary roles of bacteria reveal a connection between gut bacterial communities and fly dietary specialization. IMPORTANCE Gut bacteria may play roles in the dietary utilization of hosts, especially in specialist animals, during long-term host-microbe interaction. By comparing the gut bacterial communities between specialist and generalist drosophilid flies, we found that specialists harbor more bacteria linked to complex carbohydrate degradation, amino acid metabolism, vitamin B12 formation, and detoxification than do generalists. This study reveals the roles of gut bacteria in drosophilid species in dietary utilization.

Structural features underlying recognition and translocation of extracellular polysaccharides.

Essentially all living systems produce complex carbohydrates as an energy source, structural component, protective coat or adhesive for cell attachment. Many polysaccharides are displayed on the cell surface or are threaded through proteinaceous tunnels for degradation. Dictated by their chemical composition and mode of polymerization, the physical properties of complex carbohydrates differ substantially, from amphipathic water-insoluble polymers to highly hydrated hydrogel-forming macromolecules. Accordingly, diverse recognition and translocation mechanisms evolved to transport polysaccharides to their final destinations. This review will summarize and compare diverse polysaccharide transport mechanisms implicated in the biosynthesis and degradation of cell surface polymers in pro- and eukaryotes.

Dietary Fiber and Telomere Length in 5674 U.S. Adults: An NHANES Study of Biological Aging.

The relationship between fiber intake and telomere length was evaluated using a cross-sectional design and an NHANES sample of 5674 U.S. adults. Another purpose was to test the impact of potential confounders on the association. Fiber consumption was measured using a 24 h recall and telomere length was indexed using the quantitative polymerase chain reaction method. Overall, the U.S. adults had low fiber intake (median: 6.6 g per 1000 kcal)-less than one-half the recommendation of the Dietary Guidelines for Americans. With age, gender, race, housing status, and misreported energy intake controlled, the relationship between fiber intake per 1000 kcal and telomere length was linear (F = 9.5, p = 0.0045). Specifically, for each 1 g increment in fiber intake per 1000 kcal, telomeres were 8.3 base pairs longer. Because each additional year of chronological age was associated with telomeres that were 15.5 base pairs shorter, results suggest that a 10 g increase in fiber intake per 1000 kcal would correspond with telomeres that are 83 base pairs longer. On average, this would equate to 5.4 fewer years of biologic aging (83 ÷ 15.5). With smoking, BMI, alcohol use, and physical activity controlled, as well as the other covariates, each 10 g increment in fiber accounted for telomeres that were 67 base pairs longer (F = 7.6, p = 0.0101), a biologic aging difference of about 4.3 years. In conclusion, significant fiber consumption accounts for longer telomeres and less biologic aging than lower levels of fiber intake.

Fiber Intake and Insulin Resistance in 6374 Adults: The Role of Abdominal Obesity.

A cross-sectional design was used to evaluate the relationship between fiber intake and insulin resistance, indexed using HOMA (homeostatic model assessment), in a National Health and Nutrition Examination Study (NHANES) sample of 6374 U.S. adults. Another purpose was to test the influence of covariates on the association. A third aim was to compare HOMA levels between two groups based on the recommended intake of 14 grams of fiber per 1000 kilocalories (kcal). Fiber intake was measured using a 24-hour recall. With demographic variables controlled, results showed that HOMA differed across High, Moderate, and Low fiber categories (F = 5.4, p = 0.0072). Adjusting for the demographic variables, the possible misreporting of energy intake, smoking, and physical activity strengthened the relationship (F = 8.0, p = 0.0009), which remained significant after adjusting for body fat (F = 7.0, p = 0.0019) and body mass index (BMI) (F = 4.9, p = 0.0108), with the other covariates. However, the fiber-HOMA relationship was eliminated after adjusting for waist circumference (F = 2.3, p = 0.1050). Dividing participants based on the recommended 14-gram standard resulted in meaningful HOMA differences (F = 16.4, p = 0.0002), and the association was not eliminated after controlling for waist circumference. Apparently, adults with high fiber consumption have less insulin resistance than their counterparts. However, much of the association is due to differences in waist circumference, unless the recommended intake of fiber is attained.

Specific carbohydrate diet for pediatric inflammatory bowel disease in clinical practice within an academic IBD center.

OBJECTIVE: Despite dietary factors being implicated in the pathogenesis of inflammatory bowel disease (IBD), nutritional therapy, outside of exclusive enteral nutrition (EEN), has not had a defined role within the treatment paradigm of pediatric IBD within IBD centers. Based on emerging data, Seattle Children's Hospital IBD Center has developed an integrated dietary program incorporating the specific carbohydrate diet (SCD) into its treatment paradigm. This treatment paradigm uses the SCD as primary therapy as well as adjunctive therapy for the treatment of IBD. The aim of this study was to evaluate the potential effects of the SCD on clinical outcomes and laboratory studies of pediatric patients with Crohn's disease (CD) and ulcerative colitis (UC). METHODS: In this retrospective study, we reviewed the medical records of patients with IBD on SCD. RESULTS: We analyzed 26 children on the SCD: 20 with CD and 6 with UC. Duration of the dietary therapy ranged from 3 to 48 mo. In patients with active CD (Pediatric Crohn's Disease activity index [PCDAI] >10), PCDAI dropped from 32.8 ± 13.2 at baseline to 20.8 ± 16.6 by 4 ± 2 wk, and to 8.8 ± 8.5 by 6 mo. The mean Pediatric Ulcerative Colitis Activity Index for patients with active UC decreased from a baseline of 28.3 ± 10.3 to 20.0 ± 17.3 at 4 ± 2 wk, to 18.3 ± 31.7 at 6 mo. CONCLUSION: This retrospective review provides evidence that the SCD can be integrated into a tertiary care center and may improve clinical and laboratory parameters for pediatric patients with nonstructuring, nonpenetrating CD as well as UC. Further prospective studies are needed to fully assess the safety and efficacy of the SCD in pediatric patients with IBD.

A pilot trial on subjects with lactose and/or oligosaccharides intolerance treated with a fixed mixture of pure and enteric-coated α- and ß-galactosidase.

AIM: Lactose and complex carbohydrates maldigestion, common food intolerances due to low gut content of α- and ß-galactosidase, lead to abdominal symptoms including pain, diarrhea, bloating, flatulence, and cramping. Commonly, intolerant patients are advised by physicians to avoid the offending foods (dairy foods, cereals, beans, etc). This food-limiting option, however, has possible nutritional risks. We have therefore evaluated the impact of using pure, enteric-coated α- plus ß-galactosidase on gut symptoms in intolerant subjects instead of avoidance of the offending foods. METHODS: Sixteen subjects intolerant to lactose and/or complex carbohydrates were enrolled and evaluated in terms of gut symptoms with 1) uncontrolled diet, 2) diet devoid of offending foods, and 3) uncontrolled diet along with pure, enteric-coated α- and ß-galactosidase (DDM Galactosidase(®)). RESULTS: Even with the uncontrolled diet, intolerant subjects treated with DDM Galactosidase(®) exhibited reduced gut symptoms (bloating, flatulence, diarrhea, and constipation) significantly better than the control treatment as well as having a diet devoid of offending foods. CONCLUSION: DDM Galactosidase(®) is a valid and safe optional treatment to counteract lactose and complex carbohydrate intolerance in subjects who prefer not to avoid, at least partially, offending foods.

Bone quality and strength are greater in growing male rats fed fructose compared with glucose.

Optimization of peak bone mass during adolescence is important for osteoporosis prevention. Studies in rodents and humans have demonstrated the harmful effects of sugar intake on bone health. With the high levels of sucrose in the diets of adolescents, it is necessary to understand the influence of glucose and fructose on growing bones. This study compared the effects of dietary glucose and fructose on bone formation, microarchitecture, and strength. Because of the different metabolic effects of glucose and fructose, we hypothesized that their individual effects on bone would be different. Eighteen male Sprague-Dawley rats (age, 60 days) were randomly assigned to high-fructose (n = 9; 40% fructose, 10% glucose) or high-glucose diet (n = 9; 50% glucose) for 12 weeks. Bone measurements included histology and histomorphometry of trabecular bone in the distal femur and a 3-point bending test of the whole tibia. Whole liver mass and postprandial serum glucose, insulin, and triglycerides were used to assess differences in energy metabolism between the diets. There were no differences in food intake, body weight, or visceral adiposity between groups, but fructose consumption led to heavier livers (P = .001) and elevated serum triglycerides (P = .00). The distal femurs of fructose-fed rats had greater bone volume (bone volume/total volume; P = .03), lower bone surface (bone surface/bone volume; P = .02), and thicker trabeculae (trabecular thickness; P = .01). The tibias of the fructose-fed rats also withstood a greater maximum flexure load (P = .032). These results indicate that consumption of the high-fructose diet resulted in stronger bones with enhanced microarchitecture than consumption of the high-glucose diet.