Microbially Produced Imidazole Propionate Impairs Insulin Signaling through mTORC1.

Interactions between the gut microbiota, diet, and the host potentially contribute to the development of metabolic diseases. Here, we identify imidazole propionate as a microbially produced histidine-derived metabolite that is present at higher concentrations in subjects with versus without type 2 diabetes. We show that imidazole propionate is produced from histidine in a gut simulator at higher concentrations when using fecal microbiota from subjects with versus without type 2 diabetes and that it impairs glucose tolerance when administered to mice. We further show that imidazole propionate impairs insulin signaling at the level of insulin receptor substrate through the activation of p38γ MAPK, which promotes p62 phosphorylation and, subsequently, activation of mechanistic target of rapamycin complex 1 (mTORC1). We also demonstrate increased activation of p62 and mTORC1 in liver from subjects with type 2 diabetes. Our findings indicate that the microbial metabolite imidazole propionate may contribute to the pathogenesis of type 2 diabetes.

Synergy and oxygen adaptation for development of next-generation probiotics.

The human gut microbiota has gained interest as an environmental factor that may contribute to health or disease1. The development of next-generation probiotics is a promising strategy to modulate the gut microbiota and improve human health; however, several key candidate next-generation probiotics are strictly anaerobic2 and may require synergy with other bacteria for optimal growth. Faecalibacterium prausnitzii is a highly prevalent and abundant human gut bacterium associated with human health, but it has not yet been developed into probiotic formulations2. Here we describe the co-isolation of F. prausnitzii and Desulfovibrio piger, a sulfate-reducing bacterium, and their cross-feeding for growth and butyrate production. To produce a next-generation probiotic formulation, we adapted F. prausnitzii to tolerate oxygen exposure, and, in proof-of-concept studies, we demonstrate that the symbiotic product is tolerated by mice and humans (ClinicalTrials.gov identifier: NCT03728868 ) and is detected in the human gut in a subset of study participants. Our study describes a technology for the production of next-generation probiotics based on the adaptation of strictly anaerobic bacteria to tolerate oxygen exposures without a reduction in potential beneficial properties. Our technology may be used for the development of other strictly anaerobic strains as next-generation probiotics.

6α-hydroxylated bile acids mediate TGR5 signalling to improve glucose metabolism upon dietary fiber supplementation in mice.

OBJECTIVE: Dietary fibres are essential for maintaining microbial diversity and the gut microbiota can modulate host physiology by metabolising the fibres. Here, we investigated whether the soluble dietary fibre oligofructose improves host metabolism by modulating bacterial transformation of secondary bile acids in mice fed western-style diet. DESIGN: To assess the impact of dietary fibre supplementation on bile acid transformation by gut bacteria, we fed conventional wild-type and TGR5 knockout mice western-style diet enriched or not with cellulose or oligofructose. In addition, we used germ-free mice and in vitro cultures to evaluate the activity of bacteria to transform bile acids in the caecal content of mice fed with western-style diet enriched with oligofructose. Finally, we treated wild-type and TGR5 knockout mice orally with hyodeoxycholic acid to assess its antidiabetic effects. RESULTS: We show that oligofructose sustains the production of 6α-hydroxylated bile acids from primary bile acids by gut bacteria when fed western-style diet. Mechanistically, we demonstrated that the effects of oligofructose on 6α-hydroxylated bile acids were microbiota dependent and specifically required functional TGR5 signalling to reduce body weight gain and improve glucose metabolism. Furthermore, we show that the 6α-hydroxylated bile acid hyodeoxycholic acid stimulates TGR5 signalling, in vitro and in vivo, and increases GLP-1R activity to improve host glucose metabolism. CONCLUSION: Modulation of the gut microbiota with oligofructose enriches bacteria involved in 6α-hydroxylated bile acid production and leads to TGR5-GLP1R axis activation to improve body weight and metabolism under western-style diet feeding in mice.

To assess the role of cataract extraction in glaucoma management by its intraocular pressure lowering effect.

OBJECTIVE: To measure the mean change of intraocular pressure in glaucoma patients with cataract after uncomplicated phacoemulsification surgery with intraocular lens implanted in capsular bag. METHODS: The quasi-experimental study was conducted at the Ophthalmology Department of Pakistan Institute of Medical Sciences Shaheed Zulfiqar Ali Bhutto Medical University, Islamabad, Pakistan, from June 11 to December 10, 2018, and comprised patients who had uncomplicated cataract extraction by phacoemulsification with intraocular lens implant in the capsular bag in glaucomatous eyes of age 30-80 years. Visual acuity, intraocular pressure, slit lamp examination, fundoscopy, visual fields, details about topical medication and relevant history were recorded not more than 5 days before cataract extraction. Intraocular pressure was recorded using Goldman's applanation tonometer one day before surgery, and post-surgery 1 month and 3 months. Data was analysed using SPSS 20. RESULTS: Of the 40 patients, 19(47.50%) were males and 21(52.50%) were females. The overall mean age was 52.23±9.44 years. Mean pre-operation intraocular pressure was 20.42±1.69mmHg, while at 1 month post-surgery it was 18.55±0.90mmHg and at 3 months it was 17.03±1.19mmHg (p=0.0001). CONCLUSIONS: There was a significant change in intraocular pressure readings in glaucoma patients with cataract after uncomplicated phacoemulsification surgery with intraocular lens implanted in capsular bag.

Donor metabolic characteristics drive effects of faecal microbiota transplantation on recipient insulin sensitivity, energy expenditure and intestinal transit time.

OBJECTIVE: Bariatric surgery improves glucose metabolism. Recent data suggest that faecal microbiota transplantation (FMT) using faeces from postbariatric surgery diet-induced obese mice in germ-free mice improves glucose metabolism and intestinal homeostasis. We here investigated whether allogenic FMT using faeces from post-Roux-en-Y gastric bypass donors (RYGB-D) compared with using faeces from metabolic syndrome donors (METS-D) has short-term effects on glucose metabolism, intestinal transit time and adipose tissue inflammation in treatment-naïve, obese, insulin-resistant male subjects. DESIGN: Subjects with metabolic syndrome (n=22) received allogenic FMT either from RYGB-D or METS-D. Hepatic and peripheral insulin sensitivity as well as lipolysis were measured at baseline and 2 weeks after FMT by hyperinsulinaemic euglycaemic stable isotope (2H2-glucose and 2H5-glycerol) clamp. Secondary outcome parameters were changes in resting energy expenditure, intestinal transit time, faecal short-chain fatty acids (SCFA) and bile acids, and inflammatory markers in subcutaneous adipose tissue related to intestinal microbiota composition. Faecal SCFA, bile acids, glycaemic control and inflammatory parameters were also evaluated at 8 weeks. RESULTS: We observed a significant decrease in insulin sensitivity 2 weeks after allogenic METS-D FMT (median rate of glucose disappearance: from 40.6 to 34.0 µmol/kg/min; p<0.01). Moreover, a trend (p=0.052) towards faster intestinal transit time following RYGB-D FMT was seen. Finally, we observed changes in faecal bile acids (increased lithocholic, deoxycholic and (iso)lithocholic acid after METS-D FMT), inflammatory markers (decreased adipose tissue chemokine ligand 2 (CCL2) gene expression and plasma CCL2 after RYGB-D FMT) and changes in several intestinal microbiota taxa. CONCLUSION: Allogenic FMT using METS-D decreases insulin sensitivity in metabolic syndrome recipients when compared with using post-RYGB-D. Further research is needed to delineate the role of donor characteristics in FMT efficacy in human insulin-resistant subjects. TRIAL REGISTRATION NUMBER: NTR4327.

Induction of farnesoid X receptor signaling in germ-free mice colonized with a human microbiota.

The gut microbiota influences the development and progression of metabolic diseases partly by metabolism of bile acids (BAs) and modified signaling through the farnesoid X receptor (FXR). In this study, we aimed to determine how the human gut microbiota metabolizes murine BAs and affects FXR signaling in colonized mice. We colonized germ-free mice with cecal content from a mouse donor or feces from a human donor and euthanized the mice after short-term (2 weeks) or long-term (15 weeks) colonization. We analyzed the gut microbiota and BA composition and expression of FXR target genes in ileum and liver. We found that cecal microbiota composition differed between mice colonized with mouse and human microbiota and was stable over time. Human and mouse microbiota reduced total BA levels similarly, but the humanized mice produced less secondary BAs. The human microbiota was able to reduce the levels of tauro-ß-muricholic acid and induce expression of FXR target genes Fgf15 and Shp in ileum after long-term colonization. We show that a human microbiota can change BA composition and induce FXR signaling in colonized mice, but the levels of secondary BAs produced are lower than in mice colonized with a mouse microbiota.

Modified Treatment Of Shallow Fornix For Better Retention Of Ocular Prosthesis.

Background: The purpose of this study is to share the experience of a modified surgical technique for treating shallow inferior fornix to enhance the retention of cosmetic ocular prosthesis in a tertiary care hospital. It was a Quasi experimental study, carried out at Khalid Eye Hospital, Karachi, Pakistan from January to December 2018. Methods: This study included twenty-five patients between the ages of 20-40 years belonging to either gender having an anophthalmic socket with shallow inferior fornices unable to retain cosmetic ocular prosthesis. Three pieces of Silicone tube were placed deep within the inferior fornix with the help of 2-0 Vicryl suture, taking bite of the inferior orbital rim periosteum. Main outcome measure was deepening of the inferior fornix with better retention of the ocular prosthesis. All the patients were followed up for a period of one year after the surgery. Study dynamics were briefed to all the patients and study approval obtained from the hospital ethical review committee. Results: This study included a total of twenty-five patients of both genders. Mean age was 29.6±6.53 years. By the end of the follow up period, twenty-four (96%) out of the twenty-five patients were satisfied with a proper retention of ocular prosthesis within the fornix along with complete lid closure. One (4%) patient required revision surgery because of extrusion of the silicone tube piece after one month. Mean follow up period was 358.5±16.76 days. Conclusion: This modified technique does not require expensive consumables and proved to be effective in terms of cosmetic and functional outcome.

Dynamics of the normal gut microbiota: A longitudinal one-year population study in Sweden.

Temporal dynamics of the gut microbiota potentially limit the identification of microbial features associated with health status. Here, we used whole-genome metagenomic and 16S rRNA gene sequencing to characterize the intra- and inter-individual variations of gut microbiota composition and functional potential of a disease-free Swedish population (n = 75) over one year. We found that 23% of the total compositional variance was explained by intra-individual variation. The degree of intra-individual compositional variability was negatively associated with the abundance of Faecalibacterium prausnitzii (a butyrate producer) and two Bifidobacterium species. By contrast, the abundance of facultative anaerobes and aerotolerant bacteria such as Escherichia coli and Lactobacillus acidophilus varied extensively, independent of compositional stability. The contribution of intra-individual variance to the total variance was greater for functional pathways than for microbial species. Thus, reliable quantification of microbial features requires repeated samples to address the issue of intra-individual variations of the gut microbiota.

The Experience Of Intralesional Bleomycin For Orbital Vascular Anomalies.

BACKGROUND: Orbital vascular anomalies are congenital and pose a challenge. They require various treatment modalities which are often unsuccessful. The use of intralesional Bleomycin has gained popularity in recent times as a scar less procedure when other treatment modalities are not effective. PURPOSE: To share the experience of using intra lesional Bleomycin in orbital vascular anomalies in a Tertiary care hospital. METHODS: This quasi-experimental study was carried out at Layton Rahmatullah Benevolent Trust (LRBT) Teaching Tertiary care hospital, Karachi from 1st June to 31st December 2018. It included fifteen patients of various orbital vascular anomalies treated with injection of intra lesional sclerosing (Bleomycin) agent. Patients were given multiple injections and the effects of sclerosing agent on orbital vascular anomalies were observed. RESULTS: Results were excellent in terms of regression of vascular anomalies. CONCLUSIONS: Intralesional sclerosing agent (Bleomycin) has an outstanding role in vascular tumour.

Outcome Of Recurrent Macular Hole Closure With Amniotic Membrane Plug.

BACKGROUND: The surgery of macular hole is a complex and intricate micro-surgery and chances of recurrence of macular hole are always high. Therefore, in order to provide a medium to close this hole, we carried out this research on subjects using amniotic membrane, in light of the studies being conducted around the world. This in turn led to benefitting the patients by improving their vision over time. PURPOSE: To assess the rate of recurrent macular hole closure with amniotic membrane plug. It was a Quasi-experimental study, conducted at Layton Rahmatullah Benevolent Trust (LRBT) Free Eye Hospital Karachi, from January 2019 to January 2020. METHODS: This study was conducted using 13 eyes of 13 patients with recurrent macular hole who underwent amniotic membrane plugging via pars plana approach. Outcomes measured were changes in best corrected visual acuity (BCVA) and change in hole size with the help of optical coherence tomography (OCT). RESULTS: Anatomic closure was attained in 100% of the cases whereas BCVA improved from 1.7±0.33 (6/300) to 0.9±0.15 (6/48). CONCLUSIONS: The use of AM is a functional method for management of large RMH.

Structural characterization of the microbial enzyme urocanate reductase mediating imidazole propionate production.

The human microbiome can produce metabolites that modulate insulin signaling. Type 2 diabetes patients have increased circulating concentrations of the microbially produced histidine metabolite, imidazole propionate (ImP) and administration of ImP in mice resulted in impaired glucose tolerance. Interestingly, the fecal microbiota of the patients had increased capacity to produce ImP, which is mediated by the bacterial enzyme urocanate reductase (UrdA). Here, we describe the X-ray structures of the ligand-binding domains of UrdA in four different states, representing the structural transitions along the catalytic reaction pathway of this unexplored enzyme linked to disease in humans. The structures in combination with functional data provide key insights into the mechanism of action of UrdA that open new possibilities for drug development strategies targeting type 2 diabetes.

Enterococci vs coliforms as a possible fecal contamination indicator: baseline data for Karachi.

Fecal contamination of drinking water is the major cause of water borne illnesses. For long time coliforms are exploited as fecal contamination indicator. However, recent studies indicate low survival rate of coliforms in stress conditions, hence it's use as indicator of fecal pollution is being abandoned in many parts of the developed world. Implementation of such strategy demands availability of local data in the cities like Karachi. The present study provides a comparison between coliforms and enterococcal load and its variation in sewage samples collected (June, August and November, 2006) from eighteen towns of Karachi. All the diluted samples were selective media to obtain colony-forming units (CFU) mainly for coliforms and enterococci. The bacteria isolated were identified on the basis of conventional microbiological methods. Observations thus obtained were subjected to rigorous statistical analysis. The total load of enterococci was found in range of 1.27-8.47 X 10(7) as compared to coliforms (3.03-13.9 X 10(7)). However, segregation of data reveals greater inter town variability in CFU/ml both in coliforms and enterococci as suggested by their cumulative standard deviation +/-1.5 X 107. Furthermore, CFU/ml of both coliforms and enterococci also varies to variable scale when collected at different time intervals and at intra town level. Conclusively, the studies suggest high survival rate and lower variability of Enterococci compared to escherichia hence indicating its potential advantage to be used as fecal contamination indicator.

Metformin alters the gut microbiome of individuals with treatment-naive type 2 diabetes, contributing to the therapeutic effects of the drug.

Metformin is widely used in the treatment of type 2 diabetes (T2D), but its mechanism of action is poorly defined. Recent evidence implicates the gut microbiota as a site of metformin action. In a double-blind study, we randomized individuals with treatment-naive T2D to placebo or metformin for 4 months and showed that metformin had strong effects on the gut microbiome. These results were verified in a subset of the placebo group that switched to metformin 6 months after the start of the trial. Transfer of fecal samples (obtained before and 4 months after treatment) from metformin-treated donors to germ-free mice showed that glucose tolerance was improved in mice that received metformin-altered microbiota. By directly investigating metformin-microbiota interactions in a gut simulator, we showed that metformin affected pathways with common biological functions in species from two different phyla, and many of the metformin-regulated genes in these species encoded metalloproteins or metal transporters. Our findings provide support for the notion that altered gut microbiota mediates some of metformin's antidiabetic effects.

Dynamics and Stabilization of the Human Gut Microbiome during the First Year of Life.

The gut microbiota is central to human health, but its establishment in early life has not been quantitatively and functionally examined. Applying metagenomic analysis on fecal samples from a large cohort of Swedish infants and their mothers, we characterized the gut microbiome during the first year of life and assessed the impact of mode of delivery and feeding on its establishment. In contrast to vaginally delivered infants, the gut microbiota of infants delivered by C-section showed significantly less resemblance to their mothers. Nutrition had a major impact on early microbiota composition and function, with cessation of breast-feeding, rather than introduction of solid food, being required for maturation into an adult-like microbiota. Microbiota composition and ecological network had distinctive features at each sampled stage, in accordance with functional maturation of the microbiome. Our findings establish a framework for understanding the interplay between the gut microbiome and the human body in early life.

Microbial modulation of insulin sensitivity.

The gut microbiota has emerged as an integral factor that impacts host metabolism and has been suggested to play a vital role in metabolic diseases such as obesity, insulin resistance, type 2 diabetes, and cardiovascular disease. In humans, cross-sectional studies have identified microbiota profiles associated with metabolic diseases, whereas causation mainly has been demonstrated in animal models. Recent studies involving microbiota-based interventions in humans, or transfer of disease-associated microbiota into germ-free mice, underscore that an altered microbiota may directly modulate host metabolism in humans. However, it will be essential to determine whether an altered gut microbiota precedes development of insulin resistance and diabetes and to identify the underlying molecular mechanisms. Increased mechanistic insights of how the microbiota modulates metabolic disease in humans may pave the way for identification of innovative microbiota-based diagnostics and/or therapeutics.