Engineered Probiotics for the Management of Congenital Metabolic Diseases: A Systematic Review.

Engineered probiotics (EPs) can be used to treat/manage chronic and congenital diseases. However, to the best of our knowledge, no systematic review has evaluated the effects of EPs on congenital metabolic disorders in murine models and human subjects. Thus, the present study systematically reviewed interventional studies that assessed the effects of EPs on congenital metabolic disorders. PubMed, Web of Science, and Scopus databases were searched up to February 2023 to retrieve related publications. Seventy-six articles were obtained in the primary step. After screening the titles/abstracts based on the inclusion and exclusion criteria, 11 papers were included. Finally, only seven articles were included after performing full-text evaluation. The included articles evaluated the effects of EPs on managing phenylketonuria (PKU, n=4) and hyperammonemia (n=3). Moreover, these studies examined mice and/or rats (n=6), monkeys (n=1), and humans (n=2). Studies on EPs and hyperammonemia revealed that some wild strains such as Lactobacillus plantarum have an innate ammonia-hyper-consuming potential; thus, there was no need to manipulate them. However, manipulation is needed to obtain a phenylalanine-metabolizing strain. In conclusion, EPs can be used to manage or treat congenital metabolic diseases including PKU.

Determination of the level of evidence for the association between different food groups/items and dietary fiber intake and the risk of cardiovascular diseases and hypertension: An umbrella review.

Evidence has suggested that nutrition is a preventive factor against cardiovascular disease (CVD) risk. Because of a sharp growth in published meta-analyses and pooled analyses in recent years, a reassessment of old evidence is needed. We aimed to determine the level of evidence for the association between the consumption of different food groups/items and dietary fiber and the incidence risk of CVDs, hypertension, and atrial fibrillation from meta-analyses and pooled analyses of observational studies. Databases Scopus, PubMed/Medline, and Web of Science were searched for related studies. Fifty-eight articles met the inclusion criteria for evidence grading. In summary, grading the level of evidence showed a suggestive inverse association between the higher consumption of fruits, whole grains, fish, legumes, nuts, and dietary fibers with the incidence risk of hypertension and different types of CVD. Also, there was a probable inverse association between the higher consumption of total and low-fat dairy products and the risk of hypertension. Higher red meat consumption had a probable association with the increased risk of ischemic stroke. Higher consumption of processed meat and poultry also had a suggestive direct association with the incidence risk of stroke and hypertension. We have tried to present a comprehensive and useful overview of the level of evidence based on the most updated findings. The summary of results in the current umbrella review can be a helpful tool for nutritionists, dietitians, and researchers to establish new studies and identify research gaps in related issues.

Estimation of bioactive peptide content of milk from different species using an in silico method.

This study assessed the bioactive peptides content of milk from different species, including humans, camel, bovine, buffalo, donkey, sheep, goat, and horse. The highest and lowest concentrations of total digestion-resistant peptides were estimated in sheep and human milk. Donkey milk casein contains a higher angiotensin-converting enzyme (ACE) inhibitory, dipeptidyl peptidase III (DPP-III) inhibitory, DPP-IV inhibitory, and antioxidant peptides. On the other hand, camel whey protein contains the highest ACE-inhibitory peptides. To discover BPs with immunomodulatory and cholesterol-lowering functions, goat milk casein and sheep milk whey protein can be considered, respectively.

Diagnosis of Toxoplasma Infection in Allogenic Pre HCTSP Patients Using Molecular Methods.

Background: We aimed to estimate the incidence of Toxoplasma infection in T. gondiiseropositive patients under allogeneic hematopoietic stem cell transplantation (HSCT). Methods: The present research was a prospective study on 54 whole blood samples of allogeneic HSCT recipients, who were referring to bone narrow transplantation centers affiliated to Shahid Beheshti University of Medical Sciences, Tehran, Iran in 2018. All patients were IgG positive against T. gondii. Results: Overall, 54 Toxoplasma positive pre-HCTSP patients were enrolled. 53.7% (n= 29) were male, also 1.9% (n=1) had germ-line type of the disease. The Multiple myeloma patients had higher age in comparison with other disease, but pairwise comparison showed the difference of age between Multiple myeloma patients were statistically significant with Acute lymphoblastic leukemia, Acute myeloblastic leukemia and Huntington's disease (P< 0.05). The results of PCR assay showed 5.6% (n= 3) of the patients were infected with Toxoplasma. Conclusion: PCR method has detected considerable incidence of Toxoplasma infection for monitoring HSCT recipients at risk for toxoplasmosis, and many patients who showed the incidence of toxoplasmosis had previous infections with the Toxoplasma parasite.

Levels of evidence for the association between different food groups/items consumption and the risk of various cancer sites: an umbrella review.

This study aimed to determine the level of evidence on the association between food groups/items consumption and the risk of different cancer sites from the meta-analyses/pooled analyses of observational studies. A systematic search was executed in Scopus, PubMed/MEDLINE, and Web of Science. The criteria from the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) Expert Report were adopted for evidence grading. In summary, there was convincing evidence for the association between fibre intake and decreased risk of colon and breast cancer. Also, consumption of dairy products, milk, fruits, and fibre was associated with a probable decreased risk of breast cancer. Consumption of whole grains, dairy products, milk, fruits, vegetables, and fibre had a probable inverse association with the incidence risk of gastrointestinal tract cancers. More qualified studies are needed to find reliable findings on the association between various food groups/items consumption and the risk of different cancer sites.

The engineered probiotics for the treatment of chronic diseases: A systematic review.

Engineered probiotics (EPs) are a group of probiotics whose proteome is manipulated by biotechnological techniques. EPs have attracted a lot of attention in recent researches for preventing and treating chronic diseases. The current study has been conducted to provide an overview regarding the EPs application in the treatment of chronic disease by a comprehensive systematic review of the published articles up to January 2022. To retrieve the related publications, three databases (PubMed/MEDLINE, Web of Sciences, and Scopus) were searched systematically. Finally, all human (n = 2) and animal (n = 37) studies were included. The included articles evaluated the effects of EPs on treatment of arthritis (n = 3), cancer (n = 2), autoimmune encephalomyelitis (EAE; n = 6), Parkinson disease (PD; n = 1), Alzheimer diseases (AD; n = 1), colitis (n = 11), celiac disease (n = 1), diabetes (n = 8) and cardiovascular disease (CVD; n = 6). Induction of oral tolerance (OT) is the most important mechanism of EPs action in the treatment of chronic disease. Providing oral vaccine and bioactive compounds are the other mechanisms of EPs action. PRACTICAL APPLICATIONS: The current systematic review gathered evidence about the application of EPs in the treatment of chronic diseases. Evidence suggests that EPs have very broad and potent effects in the treatment of chronic and even genetic diseases.

Is collagen supplementation friend or foe in rheumatoid arthritis and osteoarthritis? A comprehensive systematic review.

Rheumatoid arthritis (RA) and osteoarthritis (OA) both are chronic diseases affecting joints. Immune response against collagen in both diseases may have a role in the initiation and progression of the disease. There is a hypothesis that suppression of immune response vs collagen could be a therapeutic approach in RA and OA. Exposure of gut immune system to collagen is a way to suppress immune response against collagen in the joints. So, the current systematic review is aimed to evaluate the effects of collagen supplementation in OA and RA patients. In the current systematic review, online electronic databases including PubMed/MEDLINE, Web of Sciences and Scopus were searched and finally 19 articles were included. The enrolled articles evaluated the effects of collagen supplementation on treatment of OA (n = 9) and RA (n = 10). Intact (n = 4) and hydrolyzed (n = 5) collagen were used to treat OA. All of the studies on RA used intact and type II collagen in their intervention. The last trials on collagen supplementation in RA and OA patients were performed in 2011 and 2016, respectively. High adverse effects of collagen supplementation and its low efficiency compared to routine treatments were reported by several included studies. Also, risk of bias assessment showed that most of the studies had poor quality. Therefore, it is not possible to definitely decide on the beneficial or detrimental effects of collagen supplementation on OA and RA patients. Further studies are needed to reach a final decision.

Antioxidant nutrients can increase high-dose Methotrexate efficacy in 4T1 breast tumor Model: An experimental study on Vitamin E Succinate and Methyl-selenic acid.

BACKGROUND: We aimed to evaluate the anti-cancer and immune system enhancing properties of Vitamin E succinate (VES) and methylselenic acid (MSA) administration on 4T1 breast tumor model under high-dose methotrexate (HDMTX) therapy and folinic acid (FA) rescue. METHODS: Thirty six 4T1 mammary carcinoma bearing mice were randomly divided into six groups: control (untreated; n = 6), treatment-1 (T1 group; HDMTX; n = 6), T2 (T1 + FA; n = 6), T3 (T2 + MSA; n = 6), T4 (T2 + VES; n = 6) and T5 (T3 + VES; n = 6). On day 21 of the study, all surviving mice were sacrificed and primary tumors and peripheral tissues were examined for histological and gene expression assays. The expression of GATA Binding Protein-3 (GATA3), forkhead box-P3 (FOXP3), T-bet and Retinoic acid receptor-related orphan receptor γt (RORγt) were evaluated in tumors and spleens. Also, vascular endothelial growth factor-A (VEGF-A) and UL16-Binding Protein 1 (ULBP-1) expression were evaluated in tumors. RESULTS: The control, T4 and T5 groups were able to complete the entire 21-day study period. Also, significant tumor shrinkage was occurred in T4 group (P < 0.05). Suppression of splenic FOXP3 and GATA3 were observed in the mice receiving T4 and T5 regimens. Also, induction of tumoral FOXP3 and GATA3 were achieved in the T4 and T5 groups, respectively (P < 0.05). No metastasis occurred in T4 receiving group; while, lung and liver metastasis were observed in T5 group. CONCLUSION: In this study, high and fixed dose of MTX was used. Further studies are needed to optimize MTX dose along with FA, VES and MSA.

The effect of nigella sativa supplementation on cardiometabolic outcomes in patients with non-alcoholic fatty liver: A randomized double-blind, placebo-controlled trial.

BACKGROUND AND PURPOSE: Non-alcoholic fatty liver disease (NAFLD) is one of the metabolic disturbances associated with liver cell inflammation. Nigella sativa (N.sativa) is a widely used medicinal plant known for its anti-inflammatory, antimicrobial, antioxidant, and hepato-protective properties. This study aimed to assess the effect of supplementation of N. sativa oil on plasma levels of adiponectin, leptin, and blood pressure (BP) in patients diagnosed with NAFLD. MATERIALS AND METHODS: This randomized, double-blind, placebo-controlled clinical trial was conducted on 44 NAFLD patients. Participants were randomly assigned to two groups (n = 22/group); the experimental group received 1000 mg of N. sativa oil per day, while the control group received a placebo for eight weeks. The primary outcome measures were serum levels of adiponectin, leptin, and systolic and diastolic blood pressure measured at the baseline and the end of the intervention. RESULTS: After eight weeks of supplementation with N. sativa oil, no statistically significant differences were found in serum levels of adiponectin (p = 0.40), leptin (p = 0.89), systolic BP (p = 0.13), and diastolic BP (p = 0.09) between the two groups. Furthermore, after supplementation with N. sativa, no significant changes were observed in leptin (p = 0.07), adiponectin (p = 0.13), systolic BP (p = 0.82), and diastolic BP (p = 0.38) within the two groups. CONCLUSION: These results indicate that administration of N. sativa oil 1000 mg/day for 8 weeks has no favorable effect on cardiometabolic measures in NAFLD patients. Further studies with higher dosage over a longer period are needed to investigate whether this effect is dose- and time-dependent.

Methylation and Polymorphism in CDH1 Gene Promoter Among Patients with Diffuse Gastric Cancer.

Background: The promoter methylation and single nucleotide polymorphisms (SNPs) affect the transcription activity of cancer-related genes in several cancers including diffuse gastric cancer (DGC). Here we aimed to evaluate the promoter methylation status and the rs16260 at the promoter region of the CDH1 gene in DGC. Methods: This case-control study was performed of 48 formalin-fixed paraffin-embedded (FFPE) blocks of DGC patients and 41 fresh frozen tissue samples of healthy individuals. Methylation status was evaluated using methylation-specific polymerase chain reaction (PCR) and the rs16260 at the promoter region of the CDH1 gene was assessed using PCR and sequencing method. Results: The occurrence of methylation at the promoter region of the CDH1 gene in DGC patients was significantly higher than control samples (P < 0.0001). The methylated status was significantly associated with the poor differentiated histological type of DGC (P = 0.0428). The frequency of AC genotype and the A allele in DGC patients was significantly higher than the control subjects (P = 0.006 and 0.003, respectively). Conclusions: Here we showed that methylation at the CDH1 promoter may contribute to the DGC development, and also the AC genotype was associated with the risk of DGC.

The significance and potential of functional food ingredients for control appetite and food intake.

Dramatically rising global levels of obesity have raised consumers' commercial and public health interest in foods that may help control appetite and weight. The satiety cascade consists of sensory, cognitive, physical, and hormonal events following food intake, preventing overeating, and the desire to eat for a long time. Functional foods can be one of the most influential factors in reducing appetite as long as effective ingredients, such as fiber and protein, are used to design these products. Also, functional foods should be designed to reduce appetite at different levels of oral processing, stomach, small intestine, and large intestine by various mechanisms. Therefore, the satiety power of functional foods depends on the type of ingredients and their amount. Because each compound has a different mechanism of action, it is recommended to use different compounds to influence satiety in functional foods.

Association between IGF-1 levels ranges and all-cause mortality: A meta-analysis.

The association between IGF-1 levels and mortality in humans is complex with low levels being associated with both low and high mortality. The present meta-analysis investigates this complex relationship between IGF-1 and all-cause mortality in prospective cohort studies. A systematic literature search was conducted in PubMed/MEDLINE, Scopus, and Cochrane Library up to September 2019. Published studies were eligible for the meta-analysis if they had a prospective cohort design, a hazard ratio (HR) and 95% confidence interval (CI) for two or more categories of IGF-1 and were conducted among adults. A random-effects model with a restricted maximum likelihood heterogeneity variance estimator was used to find combined HRs for all-cause mortality. Nineteen studies involving 30,876 participants were included. Meta-analysis of the 19 eligible studies showed that with respect to the low IGF-1 category, higher IGF-1 was not associated with increased risk of all-cause mortality (HR = 0.84, 95% CI = 0.68-1.05). Dose-response analysis revealed a U-shaped relation between IGF-1 and mortality HR. Pooled results comparing low vs. middle IGF-1 showed a significant increase of all-cause mortality (HR = 1.33, 95% CI = 1.14-1.57), as well as comparing high vs. middle IGF-1 categories (HR = 1.23, 95% CI = 1.06-1.44). Finally, we provide data on the association between IGF-1 levels and the intake of proteins, carbohydrates, certain vitamins/minerals, and specific foods. Both high and low levels of IGF-1 increase mortality risk, with a specific 120-160 ng/ml range being associated with the lowest mortality. These findings can explain the apparent controversy related to the association between IGF-1 levels and mortality.

The Association between Consumption of Dairy-Originated Digestion Resistant and Bioactive Peptides and Breast Cancer Risk: A Case-Control Study.

Bioactive peptides (BPs) content of dairy products is suggested to be a significant ingredient for reducing breast cancer (BC) risk. There is no observational study regarding the correlation between BPs and the risk of chronic disease because BPs' content of food items has not been evaluated in any study. The goal of the current study was to assess the association of dairy-originated BPs with BC risk. One hundred thirty-four women with BC and 267 cancer-free controls were selected from referral hospitals in Tehran, Iran. The development of an in-silico model for estimation of the bioactive and digestion-resistant peptides content of dairy products was done in our previous research. The risk assessment for BPs and BC association was performed across the tertiles of the peptide's intake. Odds ratios (OR) were calculated by logistic regression. The negative association of all bioactive and digestion-resistant peptides except for peptides with high hydrophilicity and low bioactivity was seen in all models. In PR-negative subjects only the association of total dairy intake (OR: 0.61; 95% CI: 0.26-1.45; P for trend: 0.276), peptides with low bioactivity (OR: 0.40; 95% CI: 0.16-1.02; P for trend: 0.0.052), antidiabetic peptides (OR: 0.42; 95% CI: 0.17-1.05; P for trend: 0.0.062) and di-peptides (OR: 0.42; 95% CI: 0.17-1.05; P for trend: 0.0.062) were not significant in the final model. Also, no significant association between ER-negative subjects and total dairy intake (OR: 0.41; 95% CI: 0.16-1.07; P for trend: 0.0.068) was noted. Our findings deduced that milk-derived BPs negatively associate with the risk of ER/PR/HER2 negative BC among Iranian women.Supplemental data for this article is available online at https://doi.org/10.1080/01635581.2021.2009884.

Genotypes of ANKK1 and DRD2 genes and risk of metabolic syndrome and its components: A cross-sectional study on Iranian women.

We aimed to investigate the association between polymorphism of DRD2/ANKK1 gene with MetS and its components. Women (n = 531, aged 19-50 years) from the North-west of Iran were included by cluster sampling method. Polymorphisms of ANKK1 and DRD2 genes were defined in the study population. D/D (OR: 3.16; 95%CI: 1.31-7.60) and I/D (OR: 1.76; 95%CI: 1.12-2.78) genotypes of DRD2 (rs1799732) increased risk of MetS compared to I/I genotype. The D/D genotype of DRD2 (rs1799732) increased odds of hypertriglyceridemia in the study population. T/T (OR: 6.72; 95%CI: 1.99-22.71) and C/T (OR: 4.42; 95%CI: 2.79-7.01) genotypes of ANKK1 (rs1800497) increased risk of MetS compared to C/C genotype. Also, C/T genotype increased the odds of HTN, high FBS, high TG and low HDL-C levels compared to C/C genotype. These polymorphisms can affect the MetS components via their relation to the signaling of dopaminergic pathways and eating behaviors.

Dairy-originated digestion-resistant and bioactive peptides increase the risk of hypertension: Tehran Lipid and Glucose Study.

Milk-protein-derived bioactive peptides (BPs) have been proposed as modulators of different regulatory processes involved in blood pressure regulation. Studies on the long-term effects of BPs on blood pressure have not yet been conducted. We aimed to investigate the association of dairy-originated BPs with the risk of hypertension (HTN) in the Tehran Lipid and Glucose Cohort Study (TLGS). In this cohort study, 4378 subjects with a mean follow-up period of 3.1 years were included in the final analysis. Dietary intake, physical activity, demographic, and anthropometric data and blood pressure measurements were obtained for all participants. Various types of dairy-originated BPs were determined by an in silico method. High intake of total digestion-resistant and bioactive peptides (OR: 1.31, CI 95%: 1.01-1.70), dipeptides (OR: 1.33, CI 95%: 1.03-1.73), peptides with more than seven residues (OR: 1.32, CI 95%: 1.01-1.71), glycosylated residues (OR: 1.39, CI 95%: 1.07-1.80), highly hydrophilic peptides (OR: 1.32, CI 95%: 1.01-1.71), and low hydrophobic peptides (OR: 1.32, CI 95%: 1.01-1.71) was associated with an increased risk of HTN in the adjusted model. In addition, subjects in the higher tertile of anti-HTN peptide (OR: 1.33, CI 95%: 1.02-1.72) and antidiabetic peptide (OR: 1.35, CI 95%: 1.04-1.76) intake had a higher risk of HTN than those in the lower tertile. No significant association emerged between calcium intake from dairy and incident risk of HTN. Our results showed that the intake of some forms of digestion-resistant and BPs, such as anti-HTN peptides, dipeptides, and peptides with more than seven residues, can increase the risk of HTN in the TLGS population.

The interplay between fasting, gut microbiota, and lipid profile.

BACKGROUND: This study aimed to investigate the consequence of Ramadan fasting on gut bacterium (Bacteroides and Firmicutes), serum concentration for butyrate, and lipid profile. METHODS: Thirty healthy subjects were enlisted and investigated two times (before and at the end of Ramadan). Fasting blood samples were obtained for measuring fasting blood sugar (FBS) and lipid profile and serum butyrate concentration. Anthropometrics variables were measured before and after Ramadan for all 30 subjects. Quantitative reverse transcription polymerase chain reaction (RT-PCR) analysis, targeting the genome of Bacteroides and Firmicutes was performed to determine its presence in the stool samples. Food intake was assessed by a 3-day food record before and after Ramadan. Statistical analysis was performed by SPSS ver.13 and Minitab ver.17. P < 0.05 considered the level of significance. RESULTS: The study results showed that serum levels of butyrate significantly increase during the month from 0.23 ± 0.02 mM to 0.46 ± 0.03 mM (P < 0.05). The gut Bacteroides and Firmicutes increased by 21 and 13 percent after Ramadan compared to before (P < 0.05). The increment in Bacteroides occurred in both sexes, but Firmicutes significantly increased only in women. Food intake was decreased during Ramadan. Ramadan fasting caused significant reduction in BMI from 25.72 ± 0.58 kg/m2to 25.25 ± 0.55 kg/m2 (P < 0.05). Serum levels of LDL, HDL, LDL/HDL ratio, and total cholesterol significantly decreased during Ramadan (P < 0.05). However, the decrease in FBS and TG level were not statistically significant (P > 0.05). CONCLUSION: It can be stated that the promotion of Bacteroides and Firmicutes in the gut might play a crucial role in health promotion. However, more research is needed to achieve a definite conclusion.

Can Oral Tolerance Explain the Inconsistencies Associated with Total Dietary Diversity and Colon Cancer? A Mechanistic Systematic Review.

Among the gastrointestinal tract cancers, the risk of colon cancer is strongly dependent on dietary factors. For the first time in the current review, all the original case-control studies, associated with the correlation between total dietary diversity score and colon cancer risk, were evaluated. In this regard, three databases, including PubMed/MEDLINE, Scopus, and Web of Sciences, were investigated to retrieve the related citations from 1990 until 2019. Among the included citations, three studies were finally included. In these included studies, the dietary diversity score was evaluated with 129-item and 800-item FFQs. Findings reveal that total dietary diversity can increase the risk of colon cancer in men, but not women; while, one study using 57-item FFQ reported the beneficial association of total dietary diversity with colon cancer among men. Significant demand for conducting more research to investigate the real mechanistic effects of dietary diversity on the risk of colon cancer development was demonstrated due to the inconsistent, questionable, and incomplete findings associated with the included studies.

Effects of sodium selenite and selenium-enriched yeast on cardiometabolic indices of patients with atherosclerosis: A double-blind randomized clinical trial study.

Introduction: Atherosclerosis and related cardiovascular diseases (CVDs) are the major causes of mortality worldwide. The available reports regarding the effects of selenium (Se) supplementation in the realm of atherosclerosis have been equivocal. The present investigation is aimed to assess the effects of sodium selenite and Se-enriched yeast supplementation on metabolic parameters among atherosclerotic patients. Methods: In this double-blind placebo-controlled randomized clinical trial, 60 patients diagnosed with atherosclerosis were randomly allocated into either 200 µg/day selenite, yeast, or placebo groups for eight consecutive weeks. Serum levels of lipid profile and glycemic indices were measured at the baseline and end of the intervention. Results: There were no significant within-or between-group changes in levels of total cholesterol, triglycerides, high-density lipoprotein cholesterol (HDL-c), fasting blood sugar, insulin, and homeostatic model assessment for IR throughout the study (P ≥0.05). Only the low density lipoprotein cholesterol (LDL-c) levels were significantly lower in the yeast group in comparison with the placebo group (P = 0.015). Conclusion: The administration of Se-enriched yeast is significantly effective in decreasing LDL-c levels in patients with atherosclerosis. Additional clinical trial studies investigating the effect of Se administration on glucose homeostasis parameters and lipid profiles in atherosclerotic patients are suggested for a more definitive conclusion.

Association between rs1049174 NKG2D gene polymorphism and idiopathic recurrent spontaneous abortion in Iranian women: a case-control study.

Natural killer group 2, member D (NKG2D) is one of the best known activating receptors of NK cells, which recognises its ligand on altered or stressed cells and activates NK cells to kill them. In this study, the single nucleotide polymorphism of the NKG2D gene for rs1049174 mutation was compared in 140 women with recurrent spontaneous abortion (RSA) and 175 control women with at least one successful pregnancy and without any known pregnancy loss. The findings just revealed that GG genotype and G allele were significantly higher in the case group compared with the control group (p < .001). Our results regarding decreased risk of RSA in C allele (OR = 0.438; 95%CI = 0.310-0.619; p < .001), and GC genotype (OR = 0.492; 95%CI = 0.214-0.574; p < .001) compared with G allele and GG genotype respectively. This study demonstrated a significant association between NKG2D gene polymorphism (rs1049174 G/C) and the risk of RSA in Iranian women.Impact statementWhat is already known on this subject? According to previous investigations, maternal immune responses may affect the foetus, causing recurrent spontaneous abortion (RSA). The main cause of RSA has not yet been detected in nearly 50% of the cases.What do the results of this study add? The results showed that the frequency of G allele and C allele were significantly different in the case group and control group.What are the implications of these findings for clinical practice and/or further research? The results suggest a protective function of C allele because it significantly decreased the risk of RSA compared to G allele. It improves inhibition of NK cells and probably participates in maintaining pregnancy in fertile controls; whereas, G allele is related to a slight inhibition of NK cells, probably leading to increase effectiveness of NK activation and undesirable inflammation, which consequently causes foetal rejection.