Compositional Alterations of Gut Microbiota in Patients with Diabetic Kidney Disease and Type 2 Diabetes Mellitus

Role of bile acid-dependent Takeda G-coupled protein receptor 5 (TGR5) in regulating AMPK expression in human podocytes

Bile acids affect podocyte function by stimulating membrane-bound Takeda G protein-coupled receptor 5 (TGR5), the activity of which is linked to the regulation of glucose and lipid metabolism. In podocytes, adenosine monophosphate-dependent protein kinase (AMPK) is critical for maintaining energy balance, suggesting that the bile acid-dependent stimulation of TGR5 may impact AMPK activity to regulate metabolic processes in podocytes. Despite the beneficial effect of TGR5 activation on AMPK activity in podocytes that are exposed to hyperglycemic conditions, the effect of TGR5 signaling on AMPKα expression and phosphorylation state under control conditions have not been studied in podocytes. Our studies confirmed TGR5 expression in podocytes at both the mRNA and protein levels. Moreover, TGR5 inhibition decreased the protein expression of both AMPKα1 and AMPKα2 isoforms, which correlated with significantly lower levels of AMPKα phosphorylation at Thr172 in podocytes. Additionally, the immunofluorescent staining of podocytes with pharmacologically inhibited TGR5 activity were characterized by a lower mean intensity of the AMPKα fluorescence signal. TGR5 stimulation decreased the mRNA expression of AMPKα1 and AMPKα2 but did not change the degree of AMPKα phosphorylation at Thr172. These data suggest that TGR5 inactivation significantly downregulates AMPK activity. This may shed new light on the bile acid-dependent regulation of glucose and lipid metabolism in podocytes, especially under pathological conditions.

Gut Microbiota and Their Metabolites: The Hidden Driver of Diabetic Nephropathy? Unveiling Gut Microbe's Role in DN

BACKGROUND

Diabetic nephropathy (DN) is a severe microvascular complication of diabetes with a complex pathogenesis.

METHODS

Recent studies were reviewed to explore the role of gut microbiota and its metabolites in DN development.

RESULTS

Dysbiosis of gut bacteria contributes to pathological changes such as glomerular sclerosis and renal tubule injury. Microbial metabolites are involved in DN through immune and inflammatory pathways.

CONCLUSIONS

Understanding the relationship between gut microbiota, its metabolites, and DN may offer potential implications for DN diagnosis, prevention, and treatment. Translating this knowledge into clinical practice presents challenges and opportunities.

The gut microbiota and diabetic nephropathy: an observational study review and bidirectional Mendelian randomization study

BACKGROUND

Earlier studies have implicated a crucial link between diabetic nephropathy (DN) and the gut microbiota (GM) by considering the gut-kidney axis; however, the specific cause-and-effect connections between these processes remain unclear.

METHODS

To compare changes in the GM between DN patients and control subjects, a review of observational studies was performed. The examination focused on the phylum, family, genus, and species/genus categories. To delve deeper into the cause-effect relationship, instrumental variables for 211 GM taxa (9 phyla, 16 classes, 20 orders, 35 families, and 131 genera), which were eligible for the mbQTL (microbial quantitative trait locus) mapping analysis, were collected from the Genome Wide Association Study (GWAS). A Mendelian randomization investigation was then conducted to gauge their impact on DN susceptibility using data from the European Bioinformatics Institute (EBI) and the FinnGen consortium. The European Bioinformatics Institute data included 1032 DN patients and 451,248 controls, while the FinnGen consortium data consisted of 3283 DN patients and 210,463 controls. Two-sample Mendelian randomization (TSMR) was utilized to determine the link between the GM and DN. The primary method for analysis was the inverse variance weighted (IVW) approach. Moreover, a reverse Mendelian randomization analysis was carried out, and the findings were validated through sensitivity assessments.

RESULTS

This review examined 11 observational studies that satisfied the inclusion and exclusion criteria. There was a significant difference in the abundance of 144 GM taxa between DN patients and controls. By employing the MR technique, 13 bacteria were pinpointed as having a causal link to DN (including 3 unknown GM taxa). Even after Bonferroni correction, the protective impact of the phylum Proteobacteria and genus Dialister (Sequeira et al. Nat Microbiol. 5:304-313, 2020; Liu et al. EBioMedicine. 90:104527, 2023) and the harmful impact of the genus Akkermansia, family Verrucomicrobiaceae, order Verrucomicrobia and class Verrucomicrobiae on DN remained significant. No noticeable heterogeneity or horizontal pleiotropy was detected in the instrumental variables (IVs). However, reverse MR investigations have failed to reveal any substantial causal relationship between DN and the GM.

CONCLUSION

Differences in the GM among DN patients and healthy controls are explored in observational studies. We verified the possible connection between certain genetically modified genera and DN, thereby emphasizing the connection between the "gut-kidney" axis and new insights into the GM's role in DN pathogenesis underlying DN. Investigations into this association are necessary, and novel biomarkers for the development of targeted preventive strategies against DN are needed.

Phenylethanol Glycosides from Cistanche tubulosa Modulate the Gut Microbiota and Cecal Metabolites to Ameliorate Diabetic Nephropathy Induced by Streptozotocin Combined with High-Fat Diet in Rats

Diabetic nephropathy (DN) is a prevalent complication and serious microvascular of diabetes mellitus. After previous studies, we found that phenylethanol glycosides (CPhGs) derived from Cistanche tubulosa (Schenk) Wight exerts antidiabetic and renoprotective effects. However, the effects of CPhGs on DN remain incompletely understood. The study aimed to examine the effects of CPhGs on DN in rats and explore the underlying mechanism involved. A DN rat model was established by streptozotocin (STZ) combined with a high-fat diet. Reagent kits were used to assess the extent to which CPhGs ameliorate hyperglycemia, insulin resistance (IR), renal dysfunction, kidney oxidative stress, and peripheral inflammation. Histology and immunohistochemical staining were used to detect the changes in renal tissue structure and the expression levels of α-smooth muscle actin (α-SMA) and collagen I. Furthermore, we analyzed the cecal contents of DN rats to investigate the effect of CPhGs on gut microbiota by using 16S rRNA sequencing and broad-spectrum metabolite profiling. The results showed that CPhGs demonstrated a range of advantageous outcomes in DN, encompassing the enhancement of kidney function and alleviation of hyperglycemia, IR, renal injury, oxidative stress, and peripheral inflammatory reactions. In addition, CPhGs regulated the abundance of the [Eubacterium]_coprostanoligenes_group, Oscillospiraceae_UCG-005, etc. to modulate the gut microbiota. CPhGs significantly upregulated the content of vitamin B6 and tyrosyl-tryptophan and downregulated histamine, L-methionine, etc. In summary, the therapeutic efficacy of CPhGs on DN rats may be achieved by modulating the gut microbiota and cecal metabolites to restore the metabolic disorders of vitamin B6, histidine, etc.

Characteristics of tongue coating microbiota in diabetic and non-diabetic kidney patients receiving hemodialysis

BACKGROUND

Tongue-coating microbiota, especially known as the tongue microbiome, holds significant value as both a prospective clinical diagnostic biomarker and therapeutic target, which plays a crucial role in the oral microecological health. However, there is limited understanding of the composition and function of tongue coating microbiota in chronic kidney disease patients undergoing hemodialysis.

METHODS

Thirty-one non-diabetic hemodialysis patients (nonDM_HD), 29 diabetic hemodialysis patients (DM_HD) and 33 healthy controls (HC) were enrolled. Swabs from tongue coating were collected. The 16S rDNA (V3-V4 region) was sequenced to scrutinize the tongue-coating bacterial microbiome difference.

RESULTS

Both nonDM_HD and DM_HD showed distinct bacterial communities of oral microbiota compared to HC. The abundance of Streptococcus, Lactobacillus, Ruminococcaceae G1, Ligilactobacillus and Abiotrophia showed a significant increase (p < 0.05) in DM_HD and nonDM_HD compared to HC, while Haemophilus, Lachnoanaerobaculum, Peptostreptococcaceae G1, Peptostreptococcus showed a significant decrease (p < 0.05) respectively. Veillonella, Lactobacillus, Limosilactobacillus etc. may serve as potential biomarkers for DM_HD. While Streptococcus, Ruminococcaceae G1, Actinobacillus, Abiotrophia can be considered alternative biomarkers for nonDM_HD. Moreover, the enriched Haemophilus, Actinomyces, Lachnoanaerobaculum were prominent features of the tongue coating microbiota in HC, which could be used as the potential therapeutic targets of chronic kidney disease. Network analysis revealed a less complex interaction relationship among the tongue coating bacterial microbiota of nonDM_HD and DM_HD. Furthermore, correlations were identified between the microbiome composition and clinical parameters of the individuals.

CONCLUSION

In conclusion, deciphering the tongue coating microbiota of kidney patients undergoing hemodialysis will helpful in assessing the role of oral microbiota in pathobiology and development of kidney disease, which is expected to become a potential biomarkers and adjuvant therapeutic target.

Regulation of intestinal flora by Suaeda salsa extract ameliorates hyperglycemia in a mouse model of type 2 diabetes mellitus

Introduction

Type 2 diabetes mellitus (T2DM) often leads to elevated blood glucose levels and lipid metabolism disorder, which is generally accompanied by dysbiosis of gut microbiota and metabolic dysfunction.

Methods

In this study, a mouse model of T2DM was established by feeding a high-fat/sucrose diet combined with injecting a low dose of streptozotocin. The aim of this study was to analyze the regulatory effect of Suaeda salsa extract (SSE) on T2DM and its effect on the intestinal flora of mice.

Results

The results showed that SSE could significantly improve the body weight, fasting blood glucose (FBG), area under the curve (AUC) of the oral glucose tolerance test (OGTT), glycosylated serum protein (GSP) and islet function index. Moreover, 4-week body weight, FBG, AUC of OGTT, GSP, as well as intestinal acetic and butyric acid were significantly better in the SSE-L than in the MET group (p < 0.05). In addition, it was also found that the potential hypoglycemic mechanism of SSE was related to the expression of Akt serine/threonine kinase (AKT-1) and glucose transporter-2 (GLUT-2) genes. Compared with the model group, SSE intervention significantly increased the abundance of probiotics, such as Soleaferrea, Alloprevotella, Lactobacillus and Faecalibaculum, while decreasing the relative abundance of harmful bacteria, such as Phocaeicola and Bilophila. Analysis of the correlation among intestinal microbiota, short chain fatty acids (SCFAs) and the hypoglycemic index showed that Dwaynesavagella was significantly correlated with acetic, propionic and butyric acid, as well as all the diabetes-related indexes analyzed in this study.

Discussion

Thus, this taxon can potentially be used as a microbiological marker of type 2 diabetes. Taken together, these findings demonstrate that SSE can alleviate T2DM and its complications by improving glycemia-related indicators and modulating the structure of intestinal flora.

Causal Relationships Between Gut Microbiota, Metabolites, and Diabetic Nephropathy: Insights from a Two-Sample Mendelian Randomization Analysis

Background

 Previous studies have established a correlation between gut microbiota, metabolites, and diabetic nephropathy (DN). However, the inherent limitations of observational studies, including reverse causality and confounding factors, made this relationship uncertain.

Methods

In this study, we compiled summary statistics from a genome-wide association study (GWAS) conducted on gut microbiota, metabolites, and DN. We employed a two-sample Mendelian randomization (MR) approach, utilizing inverse variance weighted (IVW), MR-Egger, weighted median, and weighted mode methods.

Results

 We detected the protective nature of genetically predicted representatives from the family Bacteroidaceae (OR: 0.716, 95% CI: 0.516-0.995, p = 0.046), family Victivallaceae (OR: 0.871, 95% CI: 0.772-0.982, p = 0.026), genus Bacteroides (OR: 0.716, 95% CI: 0.516-0.995, p = 0.046), genus Coprococcus 2 (OR: 0.745, 95% CI: 0.576-0.963, p = 0.025), and genus Lactococcus (OR: 0.851, 95% CI: 0.730-0.992, p = 0.039) against the development of DN. Conversely, we identified a positive correlation between the incidence of DN and entities, such as Phylum Bacteroidetes (OR: 1.427, 95% CI: 1.085-1.875, p = 0.011), class Bacteroidia (OR: 1.304, 95% CI: 1.036-1.641,p = 0.024), order Bacteroidales (OR: 1.304, 95% CI: 1.035-1.641, p = 0.028), genus Catenibacterium (OR: 1.312, 95% CI: 1.079-1.594, p = 0.006), genus Lachnoclostridium (OR: 1.434, 95% CI: 1.129-1.821, p = 0.003), and genus Parasutterella (OR: 1.270, 95% CI: 1.070-1.510, p = 0.006). In our analysis, none of the gut metabolites demonstrated a causal relationship with DN.

Conclusion

 Our results substantiated the potential causal association between specific gut microbiota and DN. Therefore, our study offers novel insight into the mechanisms underlying DN. This finding provides a theoretical foundation for the future development of targeted strategies for the prevention and treatment of DN.

The potential mediating role of the gut microbiome and metabolites in the association between PFAS and kidney function in young adults: A proof-of-concept study

BACKGROUND

Chronic kidney disease (CKD) affects over 10 % of the global population and can lead to kidney failure and death. Exposure to per- and polyfluoroalkyl substances (PFAS) is associated with increased risk of CKD, yet studies examining the mechanisms linking PFAS and kidney function are lacking. In this exploratory study, we examined longitudinal associations of PFAS exposure with kidney function, and tested if associations were mediated by altered gut bacterial taxa or plasma metabolites using a multi-omics mediation analysis.

METHODS

Seventy-eight young adults from the Children's Health Study were included in this longitudinal cohort study. At baseline, seven plasma PFAS and untargeted plasma metabolomics were measured using liquid chromatography/mass-spectrometry. Baseline gut bacterial abundance was characterized using 16S rRNA sequencing and examined at the genus level. At follow-up, serum creatinine and cystatin-C concentrations were quantified to estimate glomerular filtration rate (eGFR). High-dimensional multi-omics analyses were conducted to assess the association between baseline PFAS exposure with follow-up eGFR, mediated by gut microbiome and circulating metabolite levels.

RESULTS

PFAS burden score, a variable developed to estimate exposure to chemical mixtures, was associated with kidney function. Each standard deviation increase in baseline PFAS burden score was associated with a 2.4 % lower eGFR at follow-up (95 % CI:[0.1 %,4.8 %]). Following high-dimensional mediation analyses with the microbiome and circulating metabolites, a joint component (characterized by reduced Lachnospiraceae and 17b-estradiol and increased succinate, retinoate and dodecanoic acid) and a metabolite component (characterized by increased hypotaurine and decreased D-pinitol and ureidopropionate) mediated 38 % and 50 % of the effect between PFAS burden score and eGFR, respectively.

CONCLUSION

Our proof-of-concept analysis provides the first evidence that reduced short-chain fatty acid-producing bacteria and anti-inflammatory metabolites may link PFAS exposure with impaired kidney function. This study raises the possibility of future targeted interventions that can alter gut microbiome or circulating metabolite profiles to prevent PFAS induced kidney damage.

Genetic Evidence for the Causal Relationship Between Gut Microbiota and Diabetic Kidney Disease: A Bidirectional, Two-Sample Mendelian Randomisation Study

Aims: According to the gut-kidney axis theory, gut microbiota (GM) has bidirectional crosstalk with the development of diabetic kidney disease (DKD). However, empirical results have been inconsistent, and the causal associations remain unclear. This study was aimed at exploring the causal relationship between GM and DKD as well as the glomerular filtration rate (GFR) and urinary albumin-to-creatinine ratio (UACR). Materials and Methods: Two-sample Mendelian randomisation (MR) analysis was performed with inverse-variance weighting as the primary method, together with four additional modes (MR-Egger regression, simple mode, weighted mode, and weighted median). We utilised summary-level genome-wide association study statistics from public databases for this MR analysis. Genetic associations with DKD were downloaded from the IEU Open GWAS project or CKDGen consortium, and associations with GM (196 taxa from five levels) were downloaded from the MiBioGen repository. Results: In forward MR analysis, we identified 13 taxa associated with DKD, most of which were duplicated in Type 2 diabetes with renal complications but not in Type 1 diabetes. We observed a causal association between genetic signature contributing to the relative abundance of Erysipelotrichaceae UCG003 and that for both DKD and GFR. Similarly, host genetic signature defining the abundance of Ruminococcaceae UCG014 was found to be simultaneously associated with DKD and UACR. In reverse MR analysis, the abundance of 14 other GM taxa was affected by DKD, including the phylum Proteobacteria, which remained significant after false discovery rate correction. Sensitivity analyses revealed no evidence of outliers, heterogeneity, or horizontal pleiotropy. Conclusion: Our findings provide compelling causal genetic evidence for the bidirectional crosstalk between specific GM taxa and DKD development, contributing valuable insights for a comprehensive understanding of the pathological mechanisms of DKD and highlighting the possibility of prevention and management of DKD by targeting GM.

Treatment with Gac Fruit Extract and Probiotics Reduces Serum Trimethylamine N-Oxide in Chronic Kidney Disease Rats

Chronic kidney disease (CKD) affects more than 850 million people worldwide, contributing to morbidity and mortality, particularly through cardiovascular disease (CVD). The altered composition in CKD patients leads to increased production and absorption of uremic toxins such as trimethylamine (TMA) and its oxidized form, trimethylamine N-oxide (TMAO), which are associated with cardiovascular risks. This study investigated the potential of supplementary interventions with high-carotenoid-content gac fruit extract and probiotics to mitigate serum TMAO by modulating the gut microbiota. We conducted an animal study involving 48 male Wistar rats, divided into six groups: the control, CKD control, and four treatment groups receiving gac fruit extract, carotenoid extract, or combinations with Ligilactobacillus salivarius and Lactobacillus crispatus and Lactobacillus casei as a standard probiotic. CKD was induced in rats using cisplatin and they were supplemented with choline to enhance TMA production. The measures included serum creatinine, TMAO levels, gut microbiota composition, and the expression of fecal TMA lyase and intestinal zonula occluden-1 (ZO-1). CKD rats showed increased TMA production and elevated serum levels of TMAO. Treatment with gac fruit extract and selective probiotics significantly altered the composition of the gut microbiota by decreasing Actinobacteriota abundance and increasing the abundance of Bacteroides. This combination effectively promoted ZO-1 expression, reduced fecal TMA lyase, and subsequently lowered serum TMAO levels, demonstrating the therapeutic potential of these interventions. Our results highlight the benefits of gac fruit extract combined with probiotics for the effective reduction in serum TMAO levels in rats with CKD, supporting the further exploration of dietary and microbial interventions to improve outcomes in patients with CKD.

Association between the Maternal Gut Microbiome and Macrosomia

Fetal macrosomia is defined as a birthweight ≥4000 g and causes harm to pregnant women and fetuses. Studies reported that the maternal intestinal microbiome plays a key role in the establishment, growth, and development of the fetal intestinal microbiome. However, whether there is a relationship between maternal gut microbiota and macrosomia remains unclear. Our study aimed to identify gut microbiota that may be related to the occurrence of macrosomia, explore the possible mechanisms by which it causes macrosomia, and establish a prediction model to determine the feasibility of predicting macrosomia by early maternal gut microbiota. We conducted a nested case-control study based on an early pregnancy cohort (ChiCTR1900020652) in the Maternity and Child Health Hospital of Hunan Province on fecal samples of 93 women (31 delivered macrosomia as the case group and 62 delivered normal birth weight newborns as the control group) collected and included in this study. We performed metagenomic analysis to compare the composition and function of the gut microbiome between cases and controls. Correlation analysis was used to explore the association of differential species and differential functional pathways. A random forest model was used to construct an early pregnancy prediction model for macrosomia. At the species level, there were more Bacteroides salyersiae, Bacteroides plebeius, Ruminococcus lactaris, and Bacteroides ovatus in the intestinal microbiome of macrosomias' mothers compared with mothers bearing fetuses that had normal birth weight. Functional pathways of the gut microbiome including gondoate biosynthesis, L-histidine degradation III, cis-vaccenate biosynthesis, L-arginine biosynthesis III, tRNA processing, and mannitol cycle, which were more abundant in the macrosomia group. Significant correlations were found between species and functional pathways. Bacteroides plebeius was significantly associated with the pathway of cis-vaccenate biosynthesis (r = 0.28, p = 0.005) and gondoate biosynthesis (r = 0.28, p < 0.001) and Bacteroides ovatus was positively associated with the pathway of cis-vaccenate biosynthesis (r = 0.29, p = 0.005) and gondoate biosynthesis (r = 0.32, p = 0.002). Bacteroides salyersiae was significantly associated with the pathway of cis-vaccenate biosynthesis (r = 0.24, p = 0.018), gondoate biosynthesis (r = 0.31, p = 0.003), and L-histidine degradation III (r = 0.22, p = 0.291). Finally, four differential species and four clinical indicators were included in the random forest model for predicting macrosomia. The areas under the working characteristic curves of the training and validation sets were 0.935 (95% CI: 0.851~0.979) and 0.909 (95% CI: 0.679~0.992), respectively. Maternal gut microbiota in early pregnancy may play an important role in the development of macrosomia and can be used as potential predictors to prevent macrosomia.

Unravelling the role of gut microbiota in acute pancreatitis: integrating Mendelian randomization with a nested case-control study

Background

Gut microbiota may influence the development of acute pancreatitis (AP), a serious gastrointestinal disease with high morbidity and mortality. This study aimed to identify a causal link by investigating the relationship between gut microbiota and AP.

Methods

Mendelian randomization (MR) and a nested case-control study were used to explore associations between gut microbiota composition and AP. 16S rRNA sequencing, random forest modelling (RF), support vector machine (SVM), and Kaplan-Meier survival analysis was applied to identify significant gut microbiota and their correlation with hospitalization duration in AP patients.

Results

Bidirectional MR results confirmed a causal link between specific gut microbiota and AP (15 and 8 microbial taxa identified via forward and reverse MR, respectively). The 16S rRNA sequencing analysis demonstrated a pronounced difference in gut microbiota composition between cases and controls. Notably, after a comprehensive evaluation of the results of RF and SVM, Bacteroides plebeius (B. plebeius) was found to play a significant role in influencing the hospital status. Using a receiver operating characteristic (ROC) curve, the predictive power (0.757) of B. plebeius. Kaplan-Meier survival analysis offered further insight that patients with an elevated abundance of B. plebeius experienced prolonged hospital stays.

Conclusion

Combining MR with nested case-control studies provided a detailed characterization of interactions between gut microbiota and AP. B. plebeius was identified as a significant contributor, suggesting its role as both a precursor and consequence of AP dynamics. The findings highlight the multifactorial nature of AP and its complex relationship with the gut microbiota. This study lays the groundwork for future therapeutic interventions targeting microbial dynamics in AP treatment.

The impact of gut microbial dysbiosis on the atrophy of the hippocampus and abnormal metabolism of N-acetyl aspartate in type 2 diabetic rats

Rationale and objectives

This study aimed to investigate the effect of intestinal dysbiosis on the hippocampal volume using proton magnetic resonance spectroscopy (1H-MRS) in a type 2 diabetes mellitus (T2DM) rat model.

Materials and methods

We established a T2DM animal model with high-fat diet and streptozotocin (HFD/STZ) administration to Sprague-Dawley rats. Short-term ceftriaxone sodium administration was used to establish a T2DM intestinal dysbiosis (T2DM-ID) model. After establishing the model, fecal microbiota were detected using 16S rRNA sequencing. The models were then subjected to magnetic resonance imaging (MRI). Associations between MRI findings and fecal microbiota were evaluated.

Results

Magnetic resonance imaging (MRI) showed that the bilateral hippocampal voxel value and N-acetylaspartate (NAA) level were lower in the experimental group than in the normal control (NC) group (p < 0.05) and that NAA/creatine in the left hippocampus was lower in the T2DM-ID group than in the NC group (p < 0.05). α and β diversities differed significantly among the three groups (p < 0.05). In the T2DM and T2DM-ID groups, the abundance of bacteria in the phylum Proteobacteria increased significantly, whereas that of bacteria in the phylum Firmicutes decreased. The relative abundance of Actinobacteria was significantly increased in the T2DM-ID group. The Chao1 index (r = 0.33, p < 0.05) and relative abundance of Firmicutes (r = 0.48, p < 0.05) were positively correlated with the left hippocampal voxel, while the relative abundance of Proteobacteria was negatively correlated with the left hippocampal voxel (r = -0.44, p < 0.05). NAA levels, bilateral hippocampal voxels, and the relative abundance of Lactobacillus, Clostridia_UCG_014, and other genera were correlated positively (r = 0.34-0.70, p < 0.05). NAA levels and the relative abundances of Blautia and Enterococcus were correlated negatively (r = -0.32-0.44, p < 0.05).

Conclusion

The T2DM-ID rat model showed hippocampal volume atrophy and decreased levels of neuronal markers (such as NAA). The abnormal content of specific gut microorganisms may be a key biomarker of T2DM-associated brain damage.

Unveiling contrasts in microbiota response: A1c control improves dysbiosis in low-A1c T2DM, but fails in high-A1c cases-a key to metabolic memory?

INTRODUCTION

Type 2 diabetes mellitus (T2DM) is associated with dysbiosis in the gut microbiota (MB). Individually, each medication appears to partially correct this. However, there are no studies on the response of the MB to changes in A1c. Therefore, we investigated the MB's response to intensive glycemic control.

RESEARCH DESIGN AND METHODS

We studied two groups of patients with uncontrolled T2DM, one group with an A1c <9% (18 patients-G1) and another group with an A1c >9% (13 patients-G2), aiming for at least a 1% reduction in A1c. We collected A1c and fecal samples at baseline, 6, and 12 months. G1 achieved an average A1c reduction of 1.1%, while G2 a reduction of 3.13%.

RESULTS

G1's microbiota saw a decrease in Erysipelotrichaceae_UCG_003 and in Mollicutes order (both linked to metabolic syndrome and associated comorbidities). G2, despite having a more significant reduction in A1c, experienced an increase in the proinflammatory bacteria Megasphaera and Acidaminococcus, and only one beneficial genus, Phascolarctobacterium, increased, producer of butyrate.

CONCLUSION

Despite a notable A1c outcome, G2 could not restore its MB. This seeming resistance to change, leading to a persistent inflammation component found in G2, might be part of the "metabolic memory" in T2DM.

Role of sulfidogenic members of the gut microbiota in human disease

The human gut flora comprises a dynamic network of bacterial species that coexist in a finely tuned equilibrium. The interaction with intestinal bacteria profoundly influences the host's development, metabolism, immunity, and overall health. Furthermore, dysbiosis, a disruption of the gut microbiota, can induce a variety of diseases, not exclusively associated with the intestinal tract. The increased consumption of animal protein, high-fat and high-sugar diets in Western countries has been implicated in the rise of chronic and inflammatory illnesses associated with dysbiosis. In particular, this diet leads to the overgrowth of sulfide-producing bacteria, known as sulfidogenic bacteria, which has been linked to inflammatory bowel diseases and colorectal cancer, among other disorders. Sulfidogenic bacteria include sulfate-reducing bacteria (Desulfovibrio spp.) and Bilophila wadsworthia among others, which convert organic and inorganic sulfur compounds to sulfide through the dissimilatory sulfite reduction pathway. At high concentrations, sulfide is cytotoxic and disrupts the integrity of the intestinal epithelium and mucus barrier, triggering inflammation. Besides producing sulfide, B. wadsworthia has revealed significant pathogenic potential, demonstrated in the ability to cause infection, adhere to intestinal cells, promote inflammation, and compromise the integrity of the colonic mucus layer. This review delves into the mechanisms by which taurine and sulfide-driven gut dysbiosis contribute to the pathogenesis of sulfidogenic bacteria, and discusses the role of these gut microbes, particularly B. wadsworthia, in human diseases.

Causal relationship between gut microbiota and diabetic nephropathy: a two-sample Mendelian randomization study

Objective

Emerging evidence has provided compelling evidence linking gut microbiota (GM) and diabetic nephropathy (DN) via the "gut-kidney" axis. But the causal relationship between them hasn't been clarified yet. We perform a Two-Sample Mendelian randomization (MR) analysis to reveal the causal connection with GM and the development of DN, type 1 diabetes nephropathy (T1DN), type 2 diabetes nephropathy (T2DN), type 1 diabetes mellitus (T1DM), and type 2 diabetes mellitus (T2DM).

Methods

We used summary data from MiBioGen on 211 GM taxa in 18340 participants. Generalized MR analysis methods were conducted to estimate their causality on risk of DN, T1DN, T2DN, T1DM and T2DM from FinnGen. To ensure the reliability of the findings, a comprehensive set of sensitivity analyses were conducted to confirm the resilience and consistency of the results.

Results

It was showed that Class Verrucomicrobiae [odds ratio (OR) =1.5651, 95%CI:1.1810-2.0742,PFDR=0.0018], Order Verrucomicrobiales (OR=1.5651, 95%CI: 1.1810-2.0742, PFDR=0.0018) and Family Verrucomicrobiaceae (OR=1.3956, 95%CI:1.0336-1.8844, PFDR=0.0296) had significant risk of DN. Our analysis found significant associations between GM and T2DN, including Class Verrucomimicrobiae (OR=1.8227, 95% CI: 1.2414-2.6763, PFDR=0.0139), Order Verrucomimicrobiae (OR=1.5651, 95% CI: 1.8227-2.6764, PFDR=0.0024), Rhodospirillales (OR=1.8226, 95% CI: 1.2412-2.6763, PFDR=0.0026), and Family Verrucomicroniaceae (OR=1.8226, 95% CI: 1.2412-2.6763, PFDR=0.0083). The Eubacteriumprotogenes (OR=0.4076, 95% CI: 0.2415-0.6882, PFDR=0.0021) exhibited a protection against T1DN. Sensitivity analyses confirmed that there was no significant heterogeneity and pleiotropy.

Conclusions

At the gene prediction level, we identified the specific GM that is causally linked to DN in both T1DM and T2DM patients. Moreover, we identified distinct microbial changes in T1DN that differed from those seen in T2DN, offering valuable insights into GM signatures associated with subtype of nephropathy.

Bacteroides thetaiotaomicron enhances H2S production in Bilophila wadsworthia

Sulfate- and sulfite-reducing bacteria (SRB) are a group of strict anaerobes found within the human gut. Bilophila wadsworthia, a sulfite-reducing bacterium which produces hydrogen sulfide (H2S) from taurine and isethionate respiration, is a common member of the healthy commensal human gut microbiota but has been implicated in several disease states including inflammatory bowel disease and colorectal cancer. Bacteroides thetaiotaomicron, one of the most prominent gut bacteria, has sulfatases which release sulfate, serving as a potential substrate for sulfate-reducing bacteria. Here, we showed that when B. thetaiotaomicron and B. wadsworthia were in co-culture, there was a significant increase in B. thetaiotaomicron's growth and in H2S production by B. wadsworthia. Differential gene expression analysis revealed increased expression of B. wadsworthia's dsrMKJOP complex in co-culture, which delivers electrons for sulfite reduction to H2S. This was accompanied by a decreased expression of genes associated with taurine, sulfolactate, and thiosulfate respiration, indicating that B. thetaiotaomicron may provide an alternative source of sulfite to B. wadsworthia. We hypothesized adenosine 5'-phosphosulfate (APS) to be this intermediate. Indeed, B. wadsworthia was able to grow using APS or sulfite as electron acceptors. Endometabolomic and transcriptomic analyses revealed decreased production of indole by B. thetaiotaomicron in co-culture with B. wadsworthia due to enhanced tryptophan utilization by B. wadsworthia. The results of this microbe-microbe interaction could have significant pro-inflammatory effects in the human gut environment.

Role of Gut Microbiota, Immune Imbalance, and Allostatic Load in the Occurrence and Development of Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a prevailing complication arising from diabetes mellitus. Unfortunately, there are no trustworthy and efficacious treatment modalities currently available. In recent times, compelling evidence has emerged regarding the intricate correlation between the kidney and the gut microbiota, which is considered the largest immune organ within the human physique. Various investigations have demonstrated that the perturbation of the gut microbiota and its associated metabolites potentially underlie the etiology and progression of DKD. This phenomenon may transpire through perturbation of both the innate and the adaptive immunity, leading to a burdensome allostatic load on the body and ultimately culminating in the development of DKD. Within this literature review, we aim to delve into the intricate interplay between the gut microbiota, its metabolites, and the immune system in the context of DKD. Furthermore, we strive to explore and elucidate potential chemical interventions that could hold promise for the treatment of DKD, thereby offering invaluable insights and directions for future research endeavors.

Astragalus membranaceus and Salvia miltiorrhiza ameliorate diabetic kidney disease via the "gut-kidney axis"

BACKGROUND

The combination of Astragalus membranaceus and Salvia miltiorrhiza (AS) is an effective prescription for treating diabetic kidney disease (DKD) in traditional Chinese medicine. Its efficacy in treating DKD has been confirmed, but the potential regulatory mechanism has not yet been fully clarified.

PURPOSE

To explore the mechanism by which AS regulates the "gut-metabolism-transcription" coexpression network under the action of the "gut-kidney axis" to ameliorate DKD.

METHODS

SD rats were used to establish the DKD model by injecting STZ. After AS intervention, the structure and function of the kidney and colon were observed. We sequenced the gut microbiota utilizing 16S rDNA, identified serum differential metabolites using LC‒MS/MS, and observed renal mRNA expression by RNA seq. The "gut-metabolism-transcription" coexpression network was further constructed, and the target bacteria, target metabolites, and target genes of AS were ultimately screened and validated.

RESULTS

AS improved renal pathology and functional damage and increased the abundance of Akkermansia, Akkermansia_muciniphila, Lactobacillus and Lactobacillus_murinus. Fourteen target metabolites of AS were identified, which were mainly concentrated in 19 KEGG pathways, including sphingolipid metabolism and glycerophospholipid metabolism. Sixty-three target mRNAs of AS were identified. The top 20 pathways were closely related to glycolipid metabolism, and 14 differential mRNAs were expressed in these pathways. Correlation analysis showed that Akkermansia, Akkermansia muciniphila, Lactobacillus and Lactobacillus murinus were closely associated with sphingolipid metabolism, glycerophospholipid metabolism, arachidonic acid metabolism, ascorbate and aldarate metabolism and galactose metabolism. Moreover, the target metabolites and target mRNAs of AS were also enriched in five identical pathways of sphingolipid metabolism, glycerophospholipid metabolism, arachidonic acid metabolism, ascorbate and aldarate metabolism and galactose metabolism, including 8 different metabolites, such as sphingosine, and 5 different genes, such as Kng1. The 8 metabolites had high AUC prediction values, and the validation of the 5 genes was consistent with the sequencing results.

CONCLUSION

Our research showed that AS can improve DKD via the "gut-kidney axis". Akkermansia muciniphila and Lactobacillus murinus were the main driving bacteria, and five pathways related to glycolipid metabolism, especially sphingolipid metabolism and glycerophospholipid metabolism, may be important follow-up reactions and regulatory mechanisms.

Alterations of the gut microbiota in the lupus nephritis: a systematic review

BACKGROUND

Emerging evidence suggests that gut microbiota dysbiosis may play a critical role in the development of lupus nephritis (LN). However, the specific characteristics of the gut microbiota in individuals with LN have not been fully clarified.

METHODS

The PubMed, Web of Science, and Embase databases were systematically searched for clinical and animal studies related to the relationship between LN and gut microbiota from inception until October 1, 2023. A semiquantitative analysis was used to assess the changes in gut microbial profiles.

RESULTS

A total of 15 clinical studies were selected for analysis, which included 138 LN patients, 441 systemic lupus erythematosus patients, and 1526 healthy controls (HCs). Five different types of LN mouse models were included in 5 animal studies. The alpha diversity was decreased in LN patients compared to HCs. A significant decrease in the Firmicutes/Bacteroidetes (F/B) ratio is considered a hallmark of pathological conditions. Specifically, alterations in the abundance of the phylum Proteobacteria, genera Streptococcus and Lactobacillus, and species Ruminococcus gnavus and Lactobacillus reuteri may play a critical role in the pathogenesis of LN. Remarkably, the gut taxonomic chain Bacteroidetes-Bacteroides-Bacteroides thetaiotaomicron was enriched in LN patients, which could be a crucial characteristic of LN patients. The increased level of interleukin-6, imbalance of regulatory T cells and T helper 17 cells, and decreased level of the intestinal tight junction proteins zonula occludens-1 and claudin-1 also might be related to the pathogenesis of LN.

CONCLUSIONS

Specific changes in the abundance of gut microbiota such as decreased F/B ratio, and the level of inflammatory indicators, and markers of intestinal barrier dysfunction may play a crucial role in the pathogenesis of LN. These factors could be effective diagnostic and potential therapeutic targets for LN.

The Dose-Response Effect of Fluoride Exposure on the Gut Microbiome and Its Functional Pathways in Rats

Metabolic activities within the gut microbiome are intimately linked to human health and disease, especially within the context of environmental exposure and its potential ramifications. Perturbations within this microbiome, termed "gut microbiome perturbations", have emerged as plausible intermediaries in the onset or exacerbation of diseases following environmental chemical exposures, with fluoride being a compound of particular concern. Despite the well-documented adverse impacts of excessive fluoride on various human physiological systems-ranging from skeletal to neurological-the nuanced dynamics between fluoride exposure, the gut microbiome, and the resulting dose-response relationship remains a scientific enigma. Leveraging the precision of 16S rRNA high-throughput sequencing, this study meticulously examines the ramifications of diverse fluoride concentrations on the gut microbiome's composition and functional capabilities within Wistar rats. Our findings indicate a profound shift in the intestinal microbial composition following fluoride exposure, marked by a dose-dependent modulation in the abundance of key genera, including Pelagibacterium, Bilophila, Turicibacter, and Roseburia. Moreover, discernible alterations were observed in critical functional and metabolic pathways of the microbiome, such as D-lyxose ketol-isomerase and DNA polymerase III subunit gamma/tau, underscoring the broad-reaching implications of fluoride exposure. Intriguingly, correlation analyses elucidated strong associations between specific bacterial co-abundance groups (CAGs) and these shifted metabolic pathways. In essence, fluoride exposure not only perturbs the compositional equilibrium of the gut microbiota but also instigates profound shifts in its metabolic landscape. These intricate alterations may provide a mechanistic foundation for understanding fluoride's potential toxicological effects mediated via gut microbiome modulation.

Glucose-lowering effects of a synbiotic combination containing Pediococcus acidilactici in C. elegans and mice

AIMS/HYPOTHESIS

Modulation of gut microbiota has emerged as a promising strategy to treat or prevent the development of different metabolic diseases, including type 2 diabetes and obesity. Previous data from our group suggest that the strain Pediococcus acidilactici CECT9879 (pA1c) could be an effective probiotic for regulating glucose metabolism. Hence, the objectives of this study were to verify the effectiveness of pA1c on glycaemic regulation in diet-induced obese mice and to evaluate whether the combination of pA1c with other normoglycaemic ingredients, such as chromium picolinate (PC) and oat β-glucans (BGC), could increase the efficacy of this probiotic on the regulation of glucose and lipid metabolism.

METHODS

Caenorhabditis elegans was used as a screening model to describe the potential synbiotic activities, together with the underlying mechanisms of action. In addition, 4-week-old male C57BL/6J mice were fed with a high-fat/high-sucrose diet (HFS) for 6 weeks to induce hyperglycaemia and obesity. Mice were then divided into eight groups (n=12 mice/group) according to dietary supplementation: control-diet group; HFS group; pA1c group (1010 colony-forming units/day); PC; BGC; pA1c+PC+BGC; pA1c+PC; and pA1c+BGC. Supplementations were maintained for 10 weeks. Fasting blood glucose was determined and an IPGTT was performed prior to euthanasia. Fat depots, liver and other organs were weighed, and serum biochemical variables were analysed. Gene expression analyses were conducted by real-time quantitative PCR. Sequencing of the V3-V4 region of the 16S rRNA gene from faecal samples of each group was performed, and differential abundance for family, genera and species was analysed by ALDEx2R package.

RESULTS

Supplementation with the synbiotic (pA1c+PC+BGC) counteracted the effect of the high glucose by modulating the insulin-IGF-1 signalling pathway in C. elegans, through the reversal of the glucose nuclear localisation of daf-16. In diet-induced obese mice, all groups supplemented with the probiotic significantly ameliorated glucose tolerance after an IPGTT, demonstrating the glycaemia-regulating effect of pA1c. Further, mice supplemented with pA1c+PC+BGC exhibited lower fasting blood glucose, a reduced proportion of visceral adiposity and a higher proportion of muscle tissue, together with an improvement in the brown adipose tissue in comparison with the HFS group. Besides, the effect of the HFS diet on steatosis and liver damage was normalised by the synbiotic. Gene expression analyses demonstrated that the synbiotic activity was mediated not only by modulation of the insulin-IGF-1 signalling pathway, through the overexpression of GLUT-1 and GLUT-4 mediators, but also by a decreased expression of proinflammatory cytokines such as monocyte chemotactic protein-1. 16S metagenomics demonstrated that the synbiotic combinations allowed an increase in the concentration of P. acidilactici, together with improvements in the intestinal microbiota such as a reduction in Prevotella and an increase in Akkermansia muciniphila.

CONCLUSIONS/INTERPRETATION

Our data suggest that the combination of pA1c with PC and BGC could be a potential synbiotic for blood glucose regulation and may help to fight insulin resistance, diabetes and obesity.

The potential mechanism of gut microbiota-microbial metabolites-mitochondrial axis in progression of diabetic kidney disease

Diabetic kidney disease (DKD), has become the main cause of end-stage renal disease (ESRD) worldwide. Lately, it has been shown that the onset and advancement of DKD are linked to imbalances of gut microbiota and the abnormal generation of microbial metabolites. Similarly, a body of recent evidence revealed that biological alterations of mitochondria ranging from mitochondrial dysfunction and morphology can also exert significant effects on the occurrence of DKD. Based on the prevailing theory of endosymbiosis, it is believed that human mitochondria originated from microorganisms and share comparable biological characteristics with the microbiota found in the gut. Recent research has shown a strong correlation between the gut microbiome and mitochondrial function in the occurrence and development of metabolic disorders. The gut microbiome's metabolites may play a vital role in this communication. However, the relationship between the gut microbiome and mitochondrial function in the development of DKD is not yet fully understood, and the role of microbial metabolites is still unclear. Recent studies are highlighted in this review to examine the possible mechanism of the gut microbiota-microbial metabolites-mitochondrial axis in the progression of DKD and the new therapeutic approaches for preventing or reducing DKD based on this biological axis in the future.

Sanjin Paishi Decoction improves the imbalance of gut microbiota and regulates MAPK signaling pathway to inhibit calcium oxalate stones in rats

INTRODUCTION

Sanjin Paishi Decoction (SJPSD) has positive effects on stone prevention; however, there is a lack of convincing evidence in the prevention of calcium oxalate stones. This study aimed investigates the effect of SJPSD on calcium oxalate stones and to explore its mechanism.

METHODS

The rat model of calcium oxalate stones was established and rats were treated with different doses of SJPSD. The pathological damage of kidney tissues was observed by HE staining, the deposition of calcium oxalate crystals in kidney tissues was examined by Von Kossa staining, and the levels of creatinine (CREA), urea (UREA), calcium (Ca), phosphorus (P), and magnesium (Mg) in serum were analyzed biochemically, the levels of IL-1β, IL-6, and TNF-α in serum were measured by ELISA, and the protein expression of Raf1, MEK1, p-MEK1, ERK1/2, p-ERK1/2, and Cleaved caspase-3 in kidney tissues was analyzed by Western blot. Moreover, the changes in gut microbiota were analyzed by 16S rRNA sequencing.

RESULTS

SJPSD attenuated the pathological damage of renal tissues, reduced the levels of CREA, UREA, Ca, P, and Mg, and inhibited the expression of Raf1, p-MEK1, p-ERK1/2, and Cleaved caspase-3 in renal tissues (P < 0.05). SJPSD treatment affected the composition of intestinal microbiota in rats with calcium oxalate stones.

CONCLUSION

The mechanism of SJPSD inhibition of calcium oxalate stone injury in rats may be related to the inhibition of the MAPK signaling pathway and regulation of gut microbiota imbalance.

The roles of gut microbiota and its metabolites in diabetic nephropathy

Diabetic nephropathy (DN) is a severe microvascular complication of diabetes, which increases the risk of renal failure and causes a high global disease burden. Due to the lack of sustainable treatment, DN has become the primary cause of end-stage renal disease worldwide. Gut microbiota and its metabolites exert critical regulatory functions in maintaining host health and are associated with many pathogenesis of aging-related chronic diseases. Currently, the theory gut-kidney axis has opened a novel angle to understand the relationship between gut microbiota and multiple kidney diseases. In recent years, accumulating evidence has revealed that the gut microbiota and their metabolites play an essential role in the pathophysiologic processes of DN through the gut-kidney axis. In this review, we summarize the current investigations of gut microbiota and microbial metabolites involvement in the progression of DN, and further discuss the potential gut microbiota-targeted therapeutic approaches for DN.

Effectiveness and Safety of Colonic and Capsule Fecal Microbiota Transplantation for Recurrent Clostridioides difficile Infection

BACKGROUND & AIMS

Fecal microbiota transplantation (FMT) emerged as rescue treatment for multiply recurrent Clostridioides difficile infections (rCDIs) nonresponsive to standard therapy. However, estimation of FMT efficacy varies among different protocols and formulations, while placebo-controlled clinical trials have excluded most rCDI patients because of medical comorbidities. This study aimed to determine the safety and effectiveness of capsule FMT (cap-FMT) and colonoscopy FMT (colo-FMT) for rCDI using standardized products in a large, multicenter, prospective, real-world cohort.

METHODS

Clinical outcomes and adverse events after FMT performed for rCDI at 6 sites were captured in a prospective registry. FMT was performed using 1 of 2 standardized formulations of microbiota manufactured by the University of Minnesota Microbiota Therapeutics Program, freeze-dried/encapsulated or frozen-thawed/liquid. The FMT administration route was determined by the treating physician. The rCDI cure rate was assessed at 1 and 2 months. Safety data were collected within the first 72 hours and at 1 and 2 months. Logistic regression was used to investigate factors associated with FMT failure.

RESULTS

A total of 301 FMTs were performed in 269 unique patients. Two-thirds were cap-FMT. CDI cure rates were 86% (95% CI, 82%-90%) at 1 month and 81% (95% CI, 75%-86%) at 2 months. There was no difference in the 1-month or 2-month cure rate between cap-FMT and colo-FMT. Cap-FMT recipients were older and less likely to be immunosuppressed or have inflammatory bowel disease. Patient factors of older age and hemodialysis were associated with FMT failure by 2 months on multivariate logistic regression. In addition, post-FMT antibiotic use was associated with FMT failure at 2 months. One serious adverse event was related to colonoscopy (aspiration pneumonia), otherwise no new safety signals were identified.

CONCLUSIONS

Cap-FMT using freeze-dried capsules has a similar safety and effectiveness profile compared with colo-FMT, without the procedural risks of colonoscopy. Although highly effective overall, patient selection is a key factor to optimizing FMT success.

The Effects of Cardioprotective Antidiabetic Therapy on Microbiota in Patients with Type 2 Diabetes Mellitus-A Systematic Review

As the pathophysiologic mechanisms of type 2 diabetes mellitus (T2DM) are discovered, there is a switch from glucocentric to a more comprehensive, patient-centered management. The holistic approach considers the interlink between T2DM and its complications, finding the best therapies for minimizing the cardiovascular (CV) or renal risk and benefitting from the treatment's pleiotropic effects. Sodium-glucose cotransporter 2 inhibitors (SGLT-2i) and glucagon-like peptide-1 receptor agonists (GLP-1 RA) fit best in the holistic approach because of their effects in reducing the risk of CV events and obtaining better metabolic control. Additionally, research on the SGLT-2i and GLP-1 RA modification of gut microbiota is accumulating. The microbiota plays a significant role in the relation between diet and CV disease because some intestinal bacteria lead to an increase in short-chain fatty acids (SCFA) and consequent positive effects. Thus, our review aims to describe the relation between antidiabetic non-insulin therapy (SGLT-2i and GLP-1 RA) with CV-proven benefits and the gut microbiota in patients with T2DM. We identified five randomized clinical trials including dapagliflozin, empagliflozin, liraglutide, and loxenatide, with different results. There were differences between empagliflozin and metformin regarding the effects on microbiota despite similar glucose control in both study groups. One study demonstrated that liraglutide induced gut microbiota alterations in patients with T2DM treated initially with metformin, but another failed to detect any differences when the same molecule was compared with sitagliptin. The established CV and renal protection that the SGLT-2i and GLP-1 RA exert could be partly due to their action on gut microbiota. The individual and cumulative effects of antidiabetic drugs on gut microbiota need further research.

Gut Microbiota Dysbiosis in Diabetic Retinopathy-Current Knowledge and Future Therapeutic Targets

Diabetic retinopathy is one of the major causes of blindness today, despite important achievements in diagnosis and therapy. The involvement of a gut-retina axis is thought to be a possible risk factor for several chronic eye disease, such as glaucoma, age-related macular degeneration, uveitis, and, recently, diabetic retinopathy. Dysbiosis may cause endothelial disfunction and alter retinal metabolism. This review analyzes the evidence regarding changes in gut microbiota in patients with DR compared with diabetics and healthy controls (HCs). A systematic review was performed on PubMed, Web of Science, and Google Scholar for the following terms: "gut microbiota" OR "gut microbiome" AND "diabetic retinopathy". Ultimately, 9 articles published between 2020 and 2022 presenting comparative data on a total of 228 T2DM patients with DR, 220 patients with T2DM, and 118 HCs were analyzed. All of the studies found a distinctive microbial beta diversity in DR vs. T2DM and HC, characterized by an altered Firmicutes/Bacteroidetes ratio, a decrease in butyrate producers, and an increase in LPS-expressing and pro-inflammatory species in the Bacteroidetes and Proteobacteria phyla. The probiotic species Bifidobacterium and Lactobacillus were decreased when compared with T2DM. Gut microbiota influence retinal health in multiple ways and may represent a future therapeutic target in DR.

Intestinal microbiome diversity of diabetic and non-diabetic kidney disease: Current status and future perspective

A significant portion of the health burden of diabetic kidney disease (DKD) is caused by both type 1 and type 2 diabetes which leads to morbidity and mortality globally. It is one of the most common diabetic complications characterized by loss of renal function with high prevalence, often leading to acute kidney disease (AKD). Inflammation triggered by gut microbiota is commonly associated with the development of DKD. Interactions between the gut microbiota and the host are correlated in maintaining metabolic and inflammatory homeostasis. However, the fundamental processes through which the gut microbiota affects the onset and progression of DKD are mainly unknown. In this narrative review, we summarised the potential role of the gut microbiome, their pathogenicity between diabetic and non-diabetic kidney disease (NDKD), and their impact on host immunity. A well-established association has already been seen between gut microbiota, diabetes and kidney disease. The gut-kidney interrelationship is confirmed by mounting evidence linking gut dysbiosis to DKD, however, it is still unclear what is the real cause of gut dysbiosis, the development of DKD, and its progression. In addition, we also try to distinguish novel biomarkers for early detection of DKD and the possible therapies that can be used to regulate the gut microbiota and improve the host immune response. This early detection and new therapies will help clinicians for better management of the disease and help improve patient outcomes.

Gut microbiota and its metabolites - molecular mechanisms and management strategies in diabetic kidney disease

Diabetic kidney disease (DKD) is one of the major microvascular complications of diabetes mellitus and is also one of the serious risk factors in cardiovascular events, end-stage renal disease, and mortality. DKD is associated with the diversified, compositional, and functional alterations of gut microbiota. The interaction between gut microbiota and host is mainly achieved through metabolites, which are small molecules produced by microbial metabolism from exogenous dietary substrates and endogenous host compounds. The gut microbiota plays a critical role in the pathogenesis of DKD by producing multitudinous metabolites. Nevertheless, detailed mechanisms of gut microbiota and its metabolites involved in the occurrence and development of DKD have not been completely elucidated. This review summarizes the specific classes of gut microbiota-derived metabolites, aims to explore the molecular mechanisms of gut microbiota in DKD pathophysiology and progression, recognizes biomarkers for the screening, diagnosis, and prognosis of DKD, as well as provides novel therapeutic strategies for DKD.

The harmful intestinal microbial community accumulates during DKD exacerbation and microbiome-metabolome combined validation in a mouse model

OBJECTIVE

Diabetic kidney disease (DKD) is one of the most prevalent complications of diabetes mellitus (DM) and is associated with gut microbial dysbiosis. We aim to build a diagnostic model to aid clinical practice and uncover a crucial harmful microbial community that contributes to DKD pathogenesis and exacerbation.

DESIGN

A total of 528 fecal samples from 180 DKD patients and 348 non-DKD populations (138 DM and 210 healthy volunteers) from the First Affiliated Hospital of Zhengzhou University were recruited and randomly divided into a discovery phase and a validation phase. The gut microbial composition was compared using 16S rRNA sequencing. Then, the 180 DKD patients were stratified into four groups based on clinical stages and underwent gut microbiota analysis. We established DKD mouse models and a healthy fecal microbiota transplantation (FMT) model to validate the effects of gut microbiota on DKD and select the potential harmful microbial community. Untargeted metabolome-microbiome combined analysis of mouse models helps decipher the pathogenetic mechanism from a metabolic perspective.

RESULTS

The diversity of the gut microbiome was significantly decreased in DKD patients when compared with that of the non-DKD population and was increased in the patients with more advanced DKD stages. The DKD severity in mice was relieved after healthy gut microbiota reconstruction. The common harmful microbial community was accumulated in the subjects with more severe DKD phenotypes (i.e., DKD and DKD5 patients and DKD mice). The harmful microbial community was positively associated with the serum injurious metabolites (e.g., cholic acid and hippuric acid).

CONCLUSION

The fecal microbial community was altered markedly in DKD. Combining the fecal analysis of both human and animal models selected the accumulated harmful pathogens. Partially recovering healthy gut microbiota can relieve DKD phenotypes via influencing pathogens' effect on DKD mice's metabolism.

Specific alterations of gut microbiota in diabetic microvascular complications: A systematic review and meta-analysis

BACKGROUND

The role of gut microbiota in diabetes mellitus (DM) and its complications has been widely accepted. However, the alternation of gut microbiota in diabetic microvascular complications (DC) remains to be determined.

METHODS

Publications (till August 20th, 2022) on gut microbiota in patients with DC were retrieved from PubMed, Web of Science, Embase and Cochrane. Review Manager 5.3 was performed to estimate the standardized mean difference (SMD) and 95% confidence interval (CI) and calculate alpha diversity indices and the relative abundance of gut microbiota between patients in DC v.s. DM and DC v.s. healthy controls (HC).

RESULTS

We included 13 studies assessing 329 patients with DC, 232 DM patients without DC, and 241 HC. Compared to DM, patients with DC shared a significantly lower Simpson index (SMD = -0.59, 95% CI [-0.82, -0.36], p < 0.00001), but a higher ACE index (SMD = 0.42, 95% CI[0.11, 0.74], p = 0.009). Compared to HC, DC patients held a lower ACE index (SMD = -0.61, 95% CI[-1.20, -0.02], p = 0.04). The relative abundances of phylum Proteobacteria (SMD = 0.03, 95% CI[0.01, 0.04], p = 0.003, v.s. HC) and genus Klebsiella (SMD = 0.00, 95% CI[0.00, 0.00], p < 0.00001, v.s. HC) were enriched, accompanying with depleted abundances of phylum Firmicutes (SMD = -0.06, 95% CI[-0.11, -0.01], p = 0.02, v.s. HC), genera Bifidobacterium (SMD = -0.01, 95% CI[-0.02,-0.01], p < 0.0001, v.s. DM), Faecalibacterium (SMD = -0.01, 95% CI[-0.02, -0.00], p = 0.009, v.s. DM; SMD = -0.02, 95% CI[-0.02, -0.01], p < 0.00001, v.s. HC) and Lactobacillus (SMD = 0.00, 95% CI[-0.00, -0.00], p < 0.00001, v.s. HC) in DC.

CONCLUSIONS

Gut microbiota perturbations with the depletion of alpha diversity and certain short-chain fatty acids (SCFAs)-producing bacteria were associated with the pathology of DC. Therefore, gut microbiota might serve as a promising approach for the diagnosis and treatment of DC. Further investigations are required to study the mechanisms by which gut dysbiosis acts on the onset and progression of DC.

Renal Health Improvement in Diabetes through Microbiome Modulation of the Gut-Kidney Axis with Biotics: A Systematic and Narrative Review of Randomized Controlled Trials

Diabetes mellitus is the most common endocrine disorder worldwide, with over 20% of patients ultimately developing diabetic kidney disease (DKD), a complex nephropathic complication that is a leading cause of end-stage renal disease. Various clinical trials have utilized probiotics, prebiotics, and synbiotics to attempt to positively modulate the gut microbiome via the gut-kidney axis, but consensus is limited. We conducted a multi-database systematic review to investigate the effect of probiotics, prebiotics, and synbiotics on various biomarkers of renal health in diabetes, based on studies published through 10 April 2022. Adhering to the Cochrane Collaboration and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, relevant articles were systematically screened and extracted by independent reviewers; subsequently, results were systematically compiled, analyzed, and expanded through a narrative discussion. A total of 16 publications encompassing 903 diabetic individuals met the inclusion criteria. Our findings show that some studies report statistically significant changes in common renal markers, such as serum creatinine, estimated glomerular filtration rate, blood urea nitrogen/urea, microalbuminuria, and uric acid, but not on serum albumin, sodium, potassium, phosphorous, or total urine protein. Interestingly, these nutraceuticals seem to increase serum uric acid concentrations, an inflammatory marker usually associated with decreased renal health. We found that probiotics from the Lactobacillus and Bifidobacterium families were the most investigated, followed by Streptococcus thermophilus. Prebiotics including inulin, galacto-oligosaccharide, and resistant dextrin were also examined. The single-species probiotic soymilk formulation of Lactobacillus plantarum A7 possessed effects on multiple renal biomarkers in DKD patients without adverse events. We further investigated the optimum nutraceutical formulation, discussed findings from prior studies, described the gut-kidney axis in diabetes and DKD, and finally commented on some possible mechanisms of action of these nutraceuticals on renal health in diabetics. Although probiotics, prebiotics, and synbiotics have shown some potential in ameliorating renal health degradation in diabetes via gut-kidney axis crosstalk, larger and more convincing trials with focused objectives and next-generation nutraceutical formulations are required to investigate their possible role as adjunct therapy in such patients.

A Review of Immunomodulatory Reprogramming by Probiotics in Combating Chronic and Acute Diabetic Foot Ulcers (DFUs)

Diabetic foot ulcers (DFUs) are characterized by a lack of angiogenesis and distal limb diabetic neuropathy. This makes it possible for opportunistic pathogens to protect the biofilm-encased micro-communities, causing a delay in wound healing. The acute and chronic phases of DFU-associated infections are distinguished by the differential expression of innate proinflammatory cytokines and tumor necrosis factors (TNF-α and -β). Efforts are being made to reduce the microbial bioburden of wounds by using therapies such as debridement, hyperbaric oxygen therapy, shock wave therapy, and empirical antibiotic treatment. However, the constant evolution of pathogens limits the effectiveness of these therapies. In the wound-healing process, continuous homeostasis and remodeling processes by commensal microbes undoubtedly provide a protective barrier against diverse pathogens. Among commensal microbes, probiotics are beneficial microbes that should be administered orally or topically to regulate gut-skin interaction and to activate inflammation and proinflammatory cytokine production. The goal of this review is to bridge the gap between the role of probiotics in managing the innate immune response and the function of proinflammatory mediators in diabetic wound healing. We also highlight probiotic encapsulation or nanoformulations with prebiotics and extracellular vesicles (EVs) as innovative ways to tackle target DFUs.

Specific alterations of gut microbiota in patients with membranous nephropathy: A systematic review and meta-analysis

Background: The pathogenesis of idiopathic membranous nephropathy (IMN) has not yet been thoroughly clarified, and gut dysbiosis may be a contributor to IMN. However, the characterization of gut microbiota in patients with IMN remains uncertain. Methods: Cochrane Library, PubMed, China National Knowledge Internet, Web of Science, and Embase were used to search for studies through 18 May 2022. A meta-analysis based on the standardized mean difference (SMD) with 95% confidence interval (CI) was conducted on the alpha diversity index. The between-group comparison of the relative abundance of gut microbiota taxa and the beta diversity were extracted and qualitatively analyzed. Results: Five studies were included involving 290 patients with IMN, 100 healthy controls (HCs), and 129 patients with diabetic kidney disease (DKD). The quantitative combination of alpha diversity indices indicated that although bacterial richness was impaired [ACE, SMD = 0.12, (-0.28, 0.52), p = 0.55, I 2 = 0%; Chao1, SMD = -0.34, (-0.62, -0.06), p < 0.05, I 2 = 36%], overall diversity was preserved [Shannon, SMD = -0.16, (-0.64, 0.31), p = 0.50, I 2 = 53%; Simpson, SMD = 0.27, (-0.08, 0.61), p = 0.13, I 2 = 0%]. The beta diversity was significantly varied compared to HCs or DKD patients. Compared to HCs, the abundance of Proteobacteria increased, while that of Firmicutes decreased at the phylum level. Furthermore, the abundance of Lachnospira were depleted, while those of Streptococcus were enriched at the genus level. Proteobacteria and Streptococcus were also increased compared to DKD patients. Conclusions: The expansion of Proteobacteria and depletion of Lachnospira may be critical features of the altered gut microbiota in patients with IMN. This condition may play an important role in the pathogenesis of IMN and could provide bacterial targets for diagnosis and therapy.

The Role of Feeding Characteristics in Shaping Gut Microbiota Composition and Function of Ensifera (Orthoptera)

Feeding habits were the primary factor affecting the gut bacterial communities in Ensifera. However, the interaction mechanism between the gut microbiota and feeding characteristics is not precisely understood. Here, the gut microbiota of Ensifera with diverse feeding habits was analyzed by shotgun metagenomic sequencing to further clarify the composition and function of the gut microbiota and its relationship with feeding characteristics. Our results indicate that under the influence of feeding habits, the gut microbial communities of Ensifera showed specific characteristics. Firstly, the gut microbial communities of the Ensifera with different feeding habits differed significantly, among which the gut microbial diversity of the herbivorous Mecopoda niponensis was the highest. Secondly, the functional genes related to feeding habits were in high abundance. Thirdly, the specific function of the gut microbial species in the omnivorous Gryllotalpa orientalis showed that the more diverse the feeding behavior of Ensifera, the worse the functional specificity related to the feeding characteristics of its gut microbiota. However, feeding habits were not the only factors affecting the gut microbiota of Ensifera. Some microorganisms' genes, whose functions were unrelated to feeding characteristics but were relevant to energy acquisition and nutrient absorption, were detected in high abundance. Our results were the first to report on the composition and function of the gut microbiota of Ensifera based on shotgun metagenomic sequencing and to explore the potential mechanism of the gut microbiota's association with diverse feeding habits.

Recent advances of gut microbiota in chronic kidney disease patients

Chronic kidney disease (CKD) is a worldwide public health issue and has ultimately progressed to an end-stage renal disease that requires life-long dialysis or renal transplantation. However, the underlying molecular mechanism of these pathological development and progression remains to be fully understood. The human gut microbiota is made up of approximately 100 trillion microbial cells including anaerobic and aerobic species. In recent years, more and more evidence has indicated a clear association between dysbiosis of gut microbiota and CKD including immunoglobulin A (IgA) nephropathy, diabetic kidney disease, membranous nephropathy, chronic renal failure and end-stage renal disease. The current review describes gut microbial dysbiosis and metabolites in patients with CKD thus helping to understand human disease. Treatment with prebiotics, probiotics and natural products can attenuate CKD through improving dysbiosis of gut microbiota, indicating a novel intervention strategy in patients with CKD. This review also discusses therapeutic options, such as prebiotics, probiotics and natural products, for targeting dysbiosis of gut microbiota in patients to provide more specific concept-driven therapy strategy for CKD treatment.

The Preventive Effects of Fermented and Germinated Foxtail Millet Whole Grain on Kidney Damage in a Diabetic Mouse Model

Diabetic kidney disease (DKD) is an important complication of diabetes. The prevention of DKD can effectively reduce the mortality rate of diabetic patients and improve their quality of life. The present study examined the effects of fermented and germinated foxtail millet whole grain (FG-FM) on kidney lesions in a diabetic mouse model (Db/Db mice). The results proved that the FG-FM consumption significantly alleviated the kidney tissue damage in the diabetic mouse model. The transcriptome analysis of kidney tissues demonstrated that the overactivation of signaling pathways related to inflammation and immunity in the diabetic mouse model was significantly inhibited with the FG-FM intake. Moreover, the consumption of the FG-FM diet effectively elevated the bacterial diversity, increased the relative abundance of probiotics and decreased the relative abundance of previously reported DKD-related bacteria in the gut microbiota of diabetic mice. Our study confirmed foxtail millet as a potential source of functional food for the non-pharmacological intervention of DKD.

Quercetin: an effective polyphenol in alleviating diabetes and diabetic complications

Various studies, especially in recent years, have shown that quercetin has beneficial therapeutic effects in various human diseases, including diabetes. Quercetin has significant anti-diabetic effects and may be helpful in lowering blood sugar and increasing insulin sensitivity. Quercetin appears to affect many factors and signaling pathways involved in insulin resistance and the pathogenesis of type 2 of diabetes. TNFα, NFKB, AMPK, AKT, and NRF2 are among the factors that are affected by quercetin. In addition, quercetin can be effective in preventing and ameliorating the diabetic complications, including diabetic nephropathy, cardiovascular complications, neuropathy, delayed wound healing, and retinopathy, and affects the key mechanisms involved in the pathogenesis of these complications. These positive effects of quercetin may be related to its anti-inflammatory and anti-oxidant properties. In this article, after a brief review of the pathogenesis of insulin resistance and type 2 diabetes, we will review the latest findings on the anti-diabetic effects of quercetin with a molecular perspective. Then we will review the effects of quercetin on the key mechanisms of pathogenesis of diabetes complications including nephropathy, cardiovascular complications, neuropathy, delayed wound healing, and retinopathy. Finally, clinical trials investigating the effect of quercetin on diabetes and diabetes complications will be reviewed.

A systematic review and meta-analysis of gut microbiota in diabetic kidney disease: Comparisons with diabetes mellitus, non-diabetic kidney disease, and healthy individuals

BACKGROUND

Gut microbiota has been reported to play an important role in diabetic kidney disease (DKD), however, the alterations of gut bacteria have not been determined.

METHODS

Studies comparing the differences of gut microbiome between patients with DKD and non-DKD individuals using high-throughput sequencing technology, were systematically searched and reviewed. Outcomes were set as gut bacterial diversity, microbial composition, and correlation with clinical parameters of DKD. Qualitative data were summarized and compared through a funnel R script, and quantitative data were estimated by meta-analysis.

RESULTS

A total of 15 studies and 1640 participants were included, the comparisons were conducted between DKD, diabetes mellitus (DM), non-diabetic kidney disease (NDKD), and healthy controls. There were no significant differences of α-diversity between DKD and DM, and between DKD and NDKD, however, significant lower microbial richness was found in DKD compared to healthy controls. Different bacterial compositions were found between DKD and non-DKD subjects. The phylum Actinobacteria were found to be enriched in DKD compared to healthy controls. At the genus level, we found the enrichment of Hungatella, Bilophila, and Escherichia in DKD compared to DM, patients with DKD showed lower abundances of Faecalibacterium compared to those with NDKD. The genera Butyricicoccus, Faecalibacterium, and Lachnospira were depleted in DKD compared to healthy controls, whereas Hungatella, Escherichia, and lactobacillus were significantly enriched. The genus Ruminococcus torques group was demonstrated to be inversely correlated with estimated glomerular filtration rate of DKD.

CONCLUSIONS

Gut bacterial alterations was demonstrated in DKD, characterized by the enrichment of the genera Hungatella and Escherichia, and the depletion of butyrate-producing bacteria, which might be associated with the occurrence and development of DKD. Further studies are still needed to validate these findings, due to substantial heterogeneity.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/, identifier CRD42022340870.

Association of Lipopolysaccharide-Toll-Like Receptor 4 Signaling and Microalbuminuria in Patients with Type 2 Diabetes Mellitus

PURPOSE

Intestinal flora imbalance has been implicated in the activation of innate immunity in the kidneys. However, little is known about the potential links between lipopolysaccharide (LPS)-toll-like. receptor 4 (TLR4) signaling activated by intestinal barrier dysfunction and microalbuminuria in type 2 diabetes mellitus (T2DM).

PATIENTS AND METHODS

61 patients with T2DM were stratified based on the absence (n=32) or presence (n=29) of microalbuminuria. There were also 28 control subjects. Urinary albumin excretion rate (UAER), serum levels of LPS, D-lactic acid (DLA), diamine oxidase (DAO), fasting blood glucose (FBG), interleukin-6 (IL-6), glycosylated hemoglobin A1 (HbA1c), and high-sensitivity C-reactive protein (hs-CRP), and TLR4 expression in peripheral blood mononuclear cells (PBMCs) were measured.

RESULTS

hs-CRP, IL-6, LPS, DLA, DAO, and TLR4 were markedly increased in subjects with T2DM compared to the controls (P < 0.05 for all). Moreover, LPS was positively correlated with FBG, HbA1c, hs-CRP, IL-6, UAER, DLA, DAO, and TLR4 (P < 0.05 for all). In addition, TLR4 was positively correlated with UAER, hs-CRP, FBG, DLA, HbA1c, and LPS (P < 0.05 for all). In regression analyses, TLR4, LPS, HbA1c, and hs-CRP were independently associated with UAER (P < 0.05 for all), while FBG, LPS, TLR4, and hs-CRP (P < 0.05 for all) were found to be risk factors for microalbuminuria in T2DM.

CONCLUSION

Intestinal integrity is compromised in subjects with T2DM, and the activation of LPS-TLR4 signaling might play an important role in the development of microalbuminuria in T2DM.