Host-Microbe Interactions: Gut Microbiota and its Effects on Developmental Programming of the Brain, Placenta and testis

Reproduction of a mammalian organism involves inherited genetic programming and environmental factors that collectively shape organ development and function in the new offspring. One such factor are the indigenous microbiota and their interactions with the host. In mammals, the placenta ensures the supply of nutrition and oxygen to the fetus in utero. Microbes are thought to contribute to establishment of barrier functions, activation of the immune system and supply of nutrients to the host. The objectives of my thesis were to assess whether microbes can modulate barrier functions connected to the placenta, brain, and testis, as well as influence the physiological functions of these organs. All three have distinctive tissue barriers that control the passage of molecules between the blood and tissue in order to optimize function. Paper I – Maternal microbes influence placental development and reduce maternal metabolic stress during pregnancy. Germ-free (GF) pregnant mice exhibited elevated glucocorticoids levels and increased gluconeogenesis and ketone body production. As a result, these dams showed marked impairment of placental development and establishment of the blood-placental barrier (BPB), with impaired capillary microstructure and reduced expression of tight junction proteins (TJPs). Metabolically, GF dams showed altered lipid and carbohydrate metabolism and drastically reduced hepatic levels of glycogen, as well as elevated levels of angiopoietin-4 (ANGPTL4), which is known to inhibit lipoprotein lipase and thus lipogenesis. Paper II – Maternal microbes contribute to the establishment and integrity of the bloodbrain barrier (BBB). During intra-uterine life, the BBB in GF mice was more permeable than that of specific-pathogen-free (SPF) animals, a difference that persisted into adulthood and was associated with reduced expression of TJPs. Exposure of adult GF mice to the gut microbiota of SPF animals reduced this permeability and up-regulated the expression of some TJPs. Furthermore, perfusion with Evans blue revealed that monocolonization of the intestine of adult GF mice with either Clostridium tyrobutyricum, a bacterial strain that produces butyrate, or Bacteroides thetaiotaomicron, which produces mainly acetate and propionate, was sufficient to reduce BBB permeability. Moreover, oral administration of the bacterial metabolite butyrate mimicked this effect. This effect of gut microbiota and butyrate may be mediated by an epigenetic mechanism, since administration of butyrate or monocolonization with Clostridium tyrobutyricum elevated levels of histone acetylation in brain lysates. Paper III – Gut microbes modulate the permeability of the blood-testis barrier (BTB) and regulate endocrine functions of the testis. Establishment of the BTB, which normally occurs 16 days postpartum, was delayed in GF mice. Perfusion with Evans blue demonstrated increased BTB permeability associated with reduced expression of TJPs in these same mice during adulthood. The testis- pituitary axis was also affected by the lack of gut microbiota, since GF mice exhibited lower serum levels of gonadotropins (LH and FSH) and lower intratesticular levels of testosterone than the SPF animals. Interestingly, exposure of GF mice to Clostridium tyrobutyricum restored the integrity of the BTB and normalized testosterone levels. In conclusion, the present work documents the influence of indigenous microbiota on the functions of the murine BPP, BBB and BTB, as well as their ability to support the mother during pregnancy. These findings suggest that microbes contribute to programming during critical windows of development

Profiling the Oral Microbiome and Plasma Biochemistry of Obese Hyperglycemic Subjects in Qatar

The present study is designed to compare demographic characteristics, plasma biochemistry, and the oral microbiome in obese ( = 37) and lean control ( = 36) subjects enrolled at Qatar Biobank, Qatar. Plasma hormones, enzymes, and lipid profiles were analyzed at Hamad Medical Cooperation Diagnostic Laboratory. Saliva microbiome characterization was carried out by 16S rRNA amplicon sequencing using Illumina MiSeq platform. Obese subjects had higher testosterone and sex hormone-binding globulin (SHBG) concentrations compared to the control group. A negative association between BMI and testosterone ( < 0.001, r = -0.64) and SHBG ( < 0.001, r = -0.34) was observed. Irrespective of the study groups, the oral microbiome was predominantly occupied by , , and species. A generalized linear model revealed that the Firmicutes/Bacteroidetes ratio (2.25 ± 1.83 vs. 1.76 ± 0.58; corrected -value = 0.04) was higher, and phylum Fusobacteria concentration (4.5 ± 3.0 vs. 6.2 ± 4.3; corrected -value = 0.05) was low in the obese group compared with the control group. However, no differences in microbiome diversity were observed between the two groups as evaluated by alpha (Kruskal-Wallis ≥ 0.78) and beta (PERMANOVA = 0.37) diversity indexes. Certain bacterial phyla (Acidobacteria, Bacteroidetes, Fusobacteria, Proteobacteria, Spirochaetes, and Firmicutes/Bacteroidetes) were positively associated ( = 0.05, r ≤ +0.5) with estradiol, fast food consumption, creatinine, breastfed during infancy, triglycerides, and thyroid-stimulating hormone concentrations. In conclusion, no differences in oral microbiome diversity were observed between the studied groups. However, the Firmicutes/Bacteroidetes ratio, a recognized obesogenic microbiome trait, was higher in the obese subjects. Further studies are warranted to confirm these findings in a larger cohort.Qatar National Research Fun

Testing the Anticancer Effect of Matcha Using Zebrafish as an Animal Model

Cancer is the second leading cause of death worldwide, and triple-negative breast cancer (TNBC) patients show the poorest prognosis and survival and the highest metastasis prevalence among all breast cancer subtypes. Matcha has recently been associated with multiple health benefits, and in vitro studies showed the potential effect of matcha in inhibiting cancer development and metastasis. We aimed to determine the safe, non-toxic dose of matcha suitable for zebrafish and to investigate the anticancer effect of matcha on the metastasis and growth of human TBNC cells using a zebrafish xenograft model. Wild-type AB zebrafish were used to conduct multiple general toxicity assessments, including developmental, neuromuscular, and cardiovascular toxicities. The safe, non-toxic concentration of matcha was determined to be 50 µg/mL and 100 µg/mL. Afterward, the zebrafish xenograft model was successfully established for MDA-MB-468 and MDA-MB-231 TNBC cells. The tumor size and metastasis of the injected cancer cells were traced through CM-Dil red fluorescent dye. Upon exposure to matcha at the safe doses, MDA-MB-231 and MDA-MB-468 showed a trend toward reduction in tumor size in a dose-dependent manner, indicated by quantified fluorescence. Matcha also visibly suppressed metastasis of cancer cells in the zebrafish body. Our results point to a potential dose-dependent anticancer effect of matcha on TNBC cells; however, more extended observation periods after xenotransplantation are required to confirm the long-term anticancer effect of matcha on tumor growth and metastasis.This research was funded by Qatar University-internal grants (QUCP-CHS-2022-483) and QUST-1-CHS-2023-790 for M.A.-A.Scopu

The gut microbiota and developmental programming of the testis in mice

Nutrients and environmental chemicals, including endocrine disruptors, have been incriminated in the current increase in male reproductive dysfunction, but the underlying mechanisms remain unknown. The gastrointestinal tract represents the largest surface area exposed to our environment and thereby plays a key role in connection with exposure of internal organs to exogenous factors. In this context the gut microbiome (all bacteria and their metabolites) have been shown to be important contributors to body physiology including metabolism, cognitive functions and immunity. Pivotal to male reproduction is a proper development of the testis, including the formation of the blood-testis barrier (BTB) that encapsulates and protects germ cells from stress induced environmental cues, e.g. pathogenic organisms and xenobiotics. Here we used specific pathogen free (SPF) mice and germ-free (GF) mice to explore whether gut microbiota and/or their metabolites can influence testis development and regulation of BTB. Lumen formation in the seminiferous tubules, which coincides with the development of the BTB was delayed in the testes of GF mice at 16 days postpartum. In addition, perfusion experiments (Evans blue) demonstrated increased BTB permeability in these same mice. Reduced expressions of occludin, ZO-2 and E-cadherin in GF testis suggested that the microbiota modulated BTB permeability by regulation of cell-cell adhesion. Interestingly, exposure of GF mice to Clostridium Tyrobutyricum (CBUT), which secrete high levels of butyrate, restored the integrity of the BTB and normalized the levels of cell adhesion proteins. Moreover, the GF mice exhibited lower serum levels of gonadotropins (LH and FSH) than the SPF group. In addition, the intratesticular content of testosterone was lower in GF compared to SPF or CBUT animals. Thus, the gut microbiome can modulate the permeability of the BTB and might play a role in the regulation of endocrine functions of the testis.Scopu

The Microbiota and Gut-Related Disorders: Insights from Animal Models

Over the past decade, the scientific committee has called for broadening our horizons in understanding host–microbe interactions and infectious disease progression. Owing to the fact that the human gut harbors trillions of microbes that exhibit various roles including the production of vitamins, absorption of nutrients, pathogen displacement, and development of the host immune system, particular attention has been given to the use of germ-free (GF) animal models in unraveling the effect of the gut microbiota on the physiology and pathophysiology of the host. In this review, we discuss common methods used to generate GF fruit fly, zebrafish, and mice model systems and highlight the use of these GF model organisms in addressing the role of gut-microbiota in gut-related disorders (metabolic diseases, inflammatory bowel disease, and cancer), and in activating host defense mechanisms and amending pathogenic virulence.The authors are supported by internal grants from Qatar University (QUCP-CHS-2019-1)

Human microbiome and its association with health and diseases

Human microbiota are distinct communities of microorganisms that resides at different body niches. Exploration of the human microbiome has become a reality due to the availability of powerful metagenomics and metatranscriptomic analysis technologies. Recent advances in sequencing and bioinformatics over the past decade help provide a deep insight into the nature of the host-microbial interactions and identification of potential deriver genes and pathways associated with human health, well-being, and predisposition to different diseases. In the present review, we outline recent studies devoted to elucidate the possible link between the microbiota and various type of diseases. The present review also highlights the potential utilization of microbiota as a potential therapeutic option to treat a wide array of human diseases

The impact of microbial composition on postprandial glycaemia and lipidaemia: A systematic review of current evidence

Postprandial hyperglycaemia is associated with increased risk of cardiovascular disease. Recent studies highlight the role of the gut microbiome in influencing postprandial glycaemic (PPG) and lipidaemic (PPL) responses. The authors of this review sought to address the question: “To what extent does individual gut microbiome diversity and composition contribute to PPG and PPL responses?” CINAHL Plus, PubMed, Web of Science, and the Cochrane Central Register of Controlled Trials (CENTRAL) databases were searched from January 2010 to June 2020. Following screening, 22 studies were eligible to be included in the current review. All trials reported analysis of gut microbiome diversity and composition and PPG and/or PPL. Results were reported according to the ‘Preferred Reporting Items for Systematic Reviews and Meta-Analysis’ (PRISMA) statement. Individual microbiota structure was found to play a key role in determining postprandial metabolic responses in adults and is attributed to a complex interplay of diet, microbiota composition, and metagenomic activity, which may be predicted by metagenomic analysis. Alterations of gut microbiota, namely relative abundance of bacterial phylum Actinobacteria and Proteobacteria, along with Enterobacteriaceae, were associated with individual variation in postprandial glycaemic response in adults. The findings of the current review present new evidence to support a personalised approach to nutritional recommendations and guidance for optimal health, management, and treatment of common metabolic disorders. In conclusion, personalised nutrition approaches based on individual microbial composition may improve postprandial regulation of glucose and lipids, providing a potential strategy to ameliorate cardiometabolic health outcomes

The Immunomodulatory Role of Microbiota in Rheumatic Heart Disease: What Do We Know and What Can We Learn from Other Rheumatic Diseases?

Rheumatic heart disease (RHD) represents a serious cardiac sequela of acute rheumatic fever, occurring in 30-45% of patients. RHD is multifactorial, with a strong familial predisposition and known environmental risk factors that drive loss of immunological tolerance. The gut and oral microbiome have recently been implicated in the pathogenesis of RHD. Disruption of the delicate balance of the microbiome, or dysbiosis, is thought to lead to autoimmune responses through several different mechanisms including molecular mimicry, epitope spreading, and bystander activation. However, data on the microbiomes of RHD patients are scarce. Therefore, in this comprehensive review, we explore the various dimensions of the intricate relationship between the microbiome and the immune system in RHD and other rheumatic diseases to explore the potential effect of microbiota on RHD and opportunities for diagnosis and treatment.This publication was supported by Qatar University, internal grant no. QUCP-CHS-2022-551 and QU Health cluster, Qatar University. The findings achieved herein are solely the responsibility of the authors.Scopu

Antibacterial and Antibiofilm Activity of Mercaptophenol Functionalized-Gold Nanorods Against a Clinical Isolate of Methicillin-Resistant Staphylococcus aureus

Gold nanorods (AuNRs) were synthesized by the seed-mediated wet chemical method using a binary surfactant system. AuNRs were stabilized with polyethylene glycol, then functionalized with 4-mercaptophenol (4-MPH) ligand by surface ligand exchange. The surface-functionalized AuNRs (4-MPH-AuNRs) exhibited a typical UV–vis spectrum of AuNRs with a slightly shifted longitudinal peak. Furthermore, 4-MPH-AuNRs demonstrated a similar Fourier-Transformed Infrared spectrum to 4-MPH and a fading of the thiol band, which suggests a successful functionalization through thiol-gold binding. The antibacterial and antibiofilm activities of 4-MPH-AuNRs were evaluated against a clinical isolate of Methicillin-Resistant Staphylococcus aureus (MRSA). The results indicate that 4-MPH-AuNRs exhibit a bactericidal activity with a minimum inhibitory concentration (MIC) of ~ 6.25 μ g/mL against a planktonic suspension of MRSA. Furthermore, 4-MPH-AuNRs resulted in a 1.8–2.9 log-cycle reduction of MRSA biofilm viable count over a concentration range of 100–6.0 μ g/mL. The bacterial uptake of the surface-modified nanorods was investigated by inductively coupled plasma-optical emission spectroscopy (ICP-OES) and scanning electron microscopy (SEM) imaging; the results reveal that the nanorods were internalized into the bacterial cells after 6 h (h) of exposure. SEM imaging revealed a significant accumulation of the nanorods at the bacterial cell wall and a possible cellular internalization. Thus, 4-MPH-AuNRs can be considered a potential antibacterial agent, particularly against MRSA strain biofilms.Open Access funding provided by the Qatar National Library. Funding was provided by Al-Zaytoonah University of Jordan (2020-2019/12/28) and Qatar University (BRC-2021-ID-02, QUST-2-CHS-2021-2019)

The effect of surface-modified gold nanorods on the early stage of embryonic development and angiogenesis: Insight into the molecular pathways

Gold nanorods have been implicated in several biomedical applications. Herein, the effect of two surface-modified gold nanorods on the early stages of embryogenesis and angiogenesis was investigated using avian embryos at three days and their chorioallantoic membrane (CAM) at five days of incubation. We found that gold nanorods (GNR) modified with PEGylated phospholipid moiety show a high mortality rate in embryos after four days of exposure compared to GNR modified with PEGylated cholesterol moiety. Meanwhile, our data revealed that surface modified-GNR significantly inhibit the formation of new blood vessels in the treated CAM model after 48 h of exposure. Moreover, we report that surface-modified GNR significantly deregulate the expression of several genes implicated in cell proliferation, invasion, apoptosis, cellular energy metabolism, and angiogenesis. On the other hand, our data point out that GNR treatments can modulate the expression patterns of JNK1/2/3, NF-KB/p38, and MAPK, which could be the main molecular pathways of the nanorods in our experimental models.This research was funded by the following Qatar University Grant: (QUCG-CMED-20/21-2) and the Deanship of Scientific Research at Al-Zaytoonah University of Jordan (2020–2019/12/28