The Causal Relationships Between Gut Microbiota, Brain Volume, and Intelligence: A Two-Step Mendelian Randomization Analysis

BACKGROUND

Growing evidence indicates that dynamic changes in gut microbiome can affect intelligence; however, whether these relationships are causal remains elusive. We aimed to disentangle the poorly understood causal relationship between gut microbiota and intelligence.

METHODS

We performed a 2-sample Mendelian randomization (MR) analysis using genetic variants from the largest available genome-wide association studies of gut microbiota (N = 18,340) and intelligence (N = 269,867). The inverse-variance weighted method was used to conduct the MR analyses complemented by a range of sensitivity analyses to validate the robustness of the results. Considering the close relationship between brain volume and intelligence, we applied 2-step MR to evaluate whether the identified effect was mediated by regulating brain volume (N = 47,316).

RESULTS

We found a risk effect of the genus Oxalobacter on intelligence (odds ratio = 0.968 change in intelligence per standard deviation increase in taxa; 95% CI, 0.952-0.985; p = 1.88 × 10-4) and a protective effect of the genus Fusicatenibacter on intelligence (odds ratio = 1.053; 95% CI, 1.024-1.082; p = 3.03 × 10-4). The 2-step MR analysis further showed that the effect of genus Fusicatenibacter on intelligence was partially mediated by regulating brain volume, with a mediated proportion of 33.6% (95% CI, 6.8%-60.4%; p = .014).

CONCLUSIONS

Our results provide causal evidence indicating the role of the microbiome in intelligence. Our findings may help reshape our understanding of the microbiota-gut-brain axis and development of novel intervention approaches for preventing cognitive impairment.

Multi-tissue transcriptome-wide association study reveals susceptibility genes and drug targets for insulin resistance-relevant phenotypes

AIM

Genome-wide association studies (GWAS) have identified multiple susceptibility loci associated with insulin resistance (IR)-relevant phenotypes. However, the genes responsible for these associations remain largely unknown. We aim to identify susceptibility genes for IR-relevant phenotypes via a transcriptome-wide association study.

MATERIALS AND METHODS

We conducted a large-scale multi-tissue transcriptome-wide association study for IR (Insulin Sensitivity Index, homeostasis model assessment-IR, fasting insulin) and lipid-relevant traits (high-density lipoprotein cholesterol, triglycerides, low-density lipoprotein cholesterol and total cholesterol) using the largest GWAS summary statistics and precomputed gene expression weights of 49 human tissues. Conditional and joint analyses were implemented to identify significantly independent genes. Furthermore, we estimated the causal effects of independent genes by Mendelian randomization causal inference analysis.

RESULTS

We identified 1190 susceptibility genes causally associated with IR-relevant phenotypes, including 58 genes that were not implicated in the original GWAS. Among them, 11 genes were further supported in differential expression analyses or a gene knockout mice database, such as KRIT1 showed both significantly differential expression and IR-related phenotypic effects in knockout mice. Meanwhile, seven proteins encoded by susceptibility genes were targeted by clinically approved drugs, and three of these genes (H6PD, CACNB2 and DRD2) have been served as drug targets for IR-related diseases/traits. Moreover, drug repurposing analysis identified four compounds with profiles opposing the expression of genes associated with IR risk.

CONCLUSIONS

Our study provided new insights into IR aetiology and avenues for therapeutic development.

Laser-cooled 171Yb+ microwave frequency standard with a short-term frequency instability of 8.5 × 10-13/√τ

We report on the development of a microwave frequency standard based on a laser-cooled ¹⁷¹ Y b ⁺ ion trap system. The electronics , lasers, and magnetic shields are integrated into a single physical package. With over 10⁵ ions are stably trapped, the system offers a high signal-to-noise ratio Ramsey line-shape. In comparison with previous work, the frequency instability of a ¹⁷¹ Y b ⁺ microwave clock was further improved to 8.5×10^-13/τ for averaging times between 10 and 1000 s. Essential systematic shifts and uncertainties are also estimated.

Precision determination of the ground-state hyperfine splitting of trapped 113Cd+ ions

We measured the ground-state hyperfine splitting of trapped ¹¹³Cd⁺ ions to be 15199862855.02799(27) Hz with a fractional uncertainty of 1.8×10^-14. The ions were trapped and laser-cooled in a linear quadrupole Paul trap. The fractional frequency stability was measured to be 4.2×10^-13/τ, obtained from Ramsey fringes of high signal-to-noise ratios and taken over a measurement time of nearly 5 h, which is close to the short-term stability limit estimated from the Dick effect. Our result is consistent with previously reported values, but the measurement precision is four times better than the best result obtained to date.

[Epidemiological survey of suspected natural foci of schistosomiasis in Luxi City]

Three schistosomiasis patients pathologically diagnosed were detected in Luxi City, Yunnan Province, a non-endemic area of schistosomiasis. All the cases were hospitalized for serious intestinal diseases, and Schistosoma japonicum eggs were detected under their colonic mucosa. The 3 patients all denied they had contacted with infested water outside their resident place, and it was suggested that they might be infected in the local area.

[Levels of plasma TF and TFPI activities in patients with acute leukemia]

OBJECTIVE

To investigate the changes of plasma tissue factor(TF) and tissue factor pathway inhibitor(TFPI) activities in the patients with acute leukemia.

METHODS

TF and TFPI activities were measured by using chromogenic assays.

RESULTS

Plasma TF activity in the patients with acute leukemia was higher and TFPI activity was lower than those in normal(P < 0.01). In 7 patients who underwent the first chemotherapy, the plasma TF activity was decreased after chemotherapy(P < 0.01), while TFPI activity increased(P < 0.05).

CONCLUSION

The unbalance between plasma TF and TFPI activities contributes to the coagulant disorders in acute leukemia.

[Roles of intercellar Ca2+ and protein kinase C played in tissue factor pathway inhibitor and tissue factor expression in human umbilic vein endothelial cells]

The purpose of the present study was to elucidate the roles that protein kinase C (PKC) and calcium played in the tissue factor (TF) synthesis and tissue factor pathway inhibitory (TFPI) release in human umbilic vein endothelial cells (HUVEC). A23187 was used to represent calcium ionophore and phorbol 12-myristate 13-acetate (PMA) as that of PKC activator. TF activity in the lysed HUVEC was measured using one stage clotting assay. TFPI activity in the conditioned medium of HUVEC was assessed by the two-step chromogenic method. The results showed that the TF activities in A23187, PMA and A23187 + PMA groups were remarkably higher (P < 0.01) than that in control. Among the three treated groups, the TF activities in both A23187 group and A23187 + PMA group were lower than that in the PMA group (P < 0.05), but the difference between the former two groups was statically insignificant (P > 0.05). In contrast to the control group, the TFPI activity in the A23187 group was not statistically different (P > 0.05). However, the TFPI activities in the PMA group and the A23187 + PMA group were markedly higher than those in the control group and the A23187 group (P < 0.01). These findings indicate that PKC and calcium ion promote TF synthesis in HUVEC but the effect of the former is stronger than that of the latter, and that the release of TFPI from HUVEC is facilitated by PKC and not significantly affected by calcium ion.

The relationship of Oxalobacter formigenes and calcium oxalate calculi

The intestinal Oxalobacter Formigenes were isolated in 30 cases of urolithaiasis and in 45 controls. The biologic characters and morphology of the bacteria were also observed. The results showed that the colony counts in urolith group 9 (mean 10(3)/g. faeces) were significantly less than that of controls (mean 10(8)/g. faeces) (P < 0.001). It is believed that the lesser amount of oxalobacter formigenes in urolith was the important factor of the calcium oxalate calculi formation.

[Cytogenetic studies on 334 myelodysplastic syndrome (MDS), aplastic anemia (AA) and other hematological diseases]

In order to distinguish various types of MDS, such as RA/AA, RA/ITP or RA/HA, from AA, ITP or HA, bone marrow (BM) cells were studied by using cytogenetic techniques including R-banding karyotypic analysis and sister chromatid differentiation (SCD) assay in 334 cases of hematological diseases (160 MDS, 54 RA/AA, RA/ITP or RA/HA; 60 AA, 3 other known anemias, 38 PNH and 19 ITP). The results showed: (1) karyotypes and SCD values were both normal in more than 90% of AA, PNH, ITP and other known anemias, but they were both abnormal in about 35.6% of MDS and only 13.0% of RA/AA, RA/ITP or RA/HA. These results indicated that cytogenetic techniques were useful in hematological clinic and that RA/AA, or RA/ITP or RA/HA might be pre-RA or atypic RA. This was supported by the results of following up on some RA/AA, RA/ITP or RA/HA cases, (2) clonal abnormal karyotypes were found in 64.4% of MDS. The recurrent chromosomal alterations were +8, 20q-, -5/5q-, -7/7q-, similar to those reported in literatures. (3) 16 MDS cases were followed up and 15 MDS with SCD negative, but one with SCD positive developed leukemia in our hospital. It is suggested that change from SCD positive to negative was indicative of malignant transformation of BM cells. This was supported by the results of cytogenetic analysis in RA/AA, RA/ITP, RA, RAEB, RAEBT and leukemias. (4) Because more structural chromosome alterations occur in SCD negative than SCD positive MDS, the numerous chromosome alterations (monosomy) might occur in earliest development of MDS into leukemias.