Understanding the mechanism underlying the anti-diabetic effect of dietary component: a focus on gut microbiota

The role of fecal microbiota transplantation in diabetes

Fecal microbiota transplantation (FMT) has emerged as a potential therapeutic strategy for modulating gut dysbiosis in diabetes mellitus. This review critically evaluates preclinical and clinical evidence on FMT in type 1 (T1D) and type 2 diabetes (T2D). Studies suggest that FMT can restore microbial diversity, improve glycemic control, and modulate immune responses, with varying effects across diabetes subtypes. In T1D, preclinical models demonstrate that FMT influences regulatory T-cell expansion and β-cell preservation, though clinical translation remains limited. In T2D, FMT has shown transient improvements in insulin sensitivity, with sustained effects observed only in patients with specific microbiome signatures. However, heterogeneity in patient responses, donor variability, and methodological limitations complicate its clinical application. This review highlights the interplay between FMT, immune modulation, and microbial metabolism, advocating for phenotype-stratified trials and multi-omics integration to enhance therapeutic precision.

Assessment of Immobilized Lacticaseibacillus rhamnosus OLXAL-1 Cells on Oat Flakes for Functional Regulation of the Intestinal Microbiome in a Type-1 Diabetic Animal Model

The aim of this study was to examine the effect of free or immobilized Lacticaseibacillus rhamnosus OLXAL-1 cells on oat flakes on the gut microbiota and metabolic and inflammatory markers in a streptozotocin (STZ)-induced Type-1 Diabetes Mellitus (T1DM) animal model. Forty-eight male Wistar rats were assigned into eight groups (n = 6): healthy or diabetic animals that received either a control diet (CD and DCD), an oat-supplemented diet (OD and DOD), a diet supplemented with free L. rhamnosus OLXAL-1 cells (CFC and DFC), or a diet supplemented with immobilized L. rhamnosus OLXAL-1 cells on oat flakes (CIC and DIC). Neither L. rhamnosus OLXAL-1 nor oat supplementation led to any significant positive effects on body weight, insulin levels, plasma glucose concentrations, or lipid profile parameters. L. rhamnosus OLXAL-1 administration resulted in a rise in the relative abundances of Lactobacillus and Bifidobacterium, as well as increased levels of lactic, acetic, and butyric acids in the feces of the diabetic animals. Additionally, supplementation with oat flakes significantly reduced the microbial populations of E. coli, Enterobacteriaceae, coliforms, staphylococci, and enterococci and lowered IL-1β levels in the blood plasma of diabetic animals. These findings suggested that probiotic food-based strategies could have a potential therapeutic role in managing dysbiosis and inflammation associated with T1DM.

Dietary patterns and diabetic microvascular complications risk: a Mendelian randomization study of European ancestry

Purpose

Previous observational studies about the link between dietary factors and diabetic microvascular complications (DMCs) is controversial. Thus, we systemically assessed the potential causal relationship between diet and DMCs risk using Mendelian randomization (MR) methods.

Methods

We used genome-wide association studies (GWAS) statistics to estimate the causal effects of 17 dietary patterns on three common DMCs in European. Summary statistics on dietary intakes were obtained from the UK biobank, and data on DMCs [diabetic retinopathy (DR), diabetic nephropathy (DN), and diabetic neuropathy (DNP)] were obtained from the FinnGen Consortium. A two-sample MR (TSMR) was conducted to explore the causal relationships of dietary habits with DMCs. In addition, multivariable MR analysis (MVMR) was performed to adjust for traditional risk factors for eating habits, and evaluated the direct or indirect effects of diet on DMCs.

Results

TSMR analysis revealed that salad/raw vegetable intake (odd ratio [OR]: 2.830; 95% confidence interval [CI]: 1.102-7.267; p = 0.0306) and fresh fruit intake (OR: 2.735; 95% CI: 1.622-4.611; p = 0.0002; false discovery rate [FDR] = 0.0082) increased the risk of DR, whereas cheese intake (OR: 0.742; 95% CI: 0.563-0.978; p = 0.0339) and cereal intake (OR: 0.658; 95% CI: 0.444-0.976; p = 0.0374) decreased the risk of DR. Salad/raw vegetable (OR: 6.540; 95% CI: 1.061-40.300; p = 0.0430) and fresh fruit consumption (OR: 3.573; 95% CI: 1.263-10.107; p = 0.0164) are risk factors for DN, while cereal consumption (OR: 0.380; 95% CI: 0.174-0.833; p = 0.0156) is the opposite. And genetically predicted higher pork intake increased the risk of DNP (OR: 160.971; 95% CI: 8.832-2933.974; p = 0.0006; FDR = 0.0153). The MVMR analysis revealed that cheese intake may act as an independent protective factor for DR development. Moreover, fresh fruit intake, salad/raw vegetable intake and pork intake may be independent risk factors for DR, DN and DNP, respectively. Other causal associations between dietary habits and DMCs risk may be mediated by intermediate factors.

Conclusion

This causal relationship study supports that specific dietary interventions may reduce the risk of DMCs.

Dietary eugenol ameliorates long-term high-fat diet-induced skeletal muscle atrophy: mechanistic insights from integrated multi-omics

Eugenol (EU), the major constituent of clove oil, possesses a range of bioactivities. Here, the therapeutic potential of oral EU for mitigating skeletal muscle wasting was investigated in a long-term high-fat diet (HFD)-induced obese mice model. Male C57BL/6J mice, aged six weeks, were assigned to either a chow or a HFD for 10 weeks. Subsequently, the weight-matched HFD-fed mice were allocated into two groups, receiving either 0.2% (w/w) EU supplementation or no supplementation for 14 weeks. Our findings revealed that EU supplementation enhanced grip strength, increased hanging duration, and augmented skeletal muscle mass. RNA sequencing analysis demonstrated that EU modified the gastrocnemius muscle transcriptomic profile, and the differentially expressed genes between HFD and EU groups were mainly involved in the HIF-1 signaling pathway, TCR signaling pathway, and cGMP-PKG signaling pathway, which is well-known to be related to skeletal muscle health. Untargeted metabolomics analysis further showed that EU supplementation significantly altered the nucleotide metabolism in the GAS muscle. Analysis of 16S rRNA sequencing demonstrated that EU supplementation ameliorated the gut dysbiosis caused by HFD. The alterations in gut microbiota induced by EU were significantly correlated with indexes related to skeletal muscle atrophy. The multi-omics analysis presented the robust interaction among the skeletal muscle transcriptome, metabolome, and gut microbiome altered by EU supplementation. Our results highlight the potential of EU in skeletal muscle atrophy intervention as a functional dietary supplement.

Mulberry polyphenols restored both small and large intestinal microflora in db/db mice, potentially alleviating type 2 diabetes

Polyphenols in mulberry fruit have potential anti-diabetic effects by targeting the gut microbiota. This study investigated how mulberry polyphenols (MPs) influence the microbiota of the small and large intestines and their effects on type 2 diabetes symptoms. The results showed lower microbiota densities in the small intestine. MP treatments improved microbiota richness and diversity in both intestines, similar to metformin. In particular, at a 400 mg kg-1 dose, mulberry polyphenols decreased Firmicutes, Lactobacillus, and Bacilli, while increasing Bacteroidetes, leading to elevated propionate and butyrate levels. Less abundant small intestinal microbiota, like Enterobacterales, Mycoplasmatales, Enterobacteriaceae, and Ureaplasma, were involved in regulating blood glucose and insulin levels. Functional analysis suggested that mulberry polyphenols reshaped the small intestinal microbiota to influence blood glucose balance via unknown pathways, while in the large intestine, they primarily affected blood glucose through carbohydrate transport and metabolism. Based on their ability to regulate the composition of intestinal flora, MPs likely improved glucose homeostasis by enhancing glucose utilization, supporting pancreatic tissue health, and increasing serum antioxidant capacity. However, the specific mechanisms underlying this potential are yet to be fully explored. This study provides new insights into the influence of MPs on remodeling the microbiota residing in both the small and large intestines, which thereby may contribute to the improvement of the pathophysiology of type 2 diabetes.

Diabetes-induced muscle wasting: molecular mechanisms and promising therapeutic targets

Diabetes has become a serious public health crisis, presenting significant challenges to individuals worldwide. As the largest organ in the human body, skeletal muscle is a significant target of this chronic disease, yet muscle wasting as a complication of diabetes is still not fully understood and effective treatment methods have yet to be developed. Here, we discuss the targets involved in inducing muscle wasting under diabetic conditions, both validated targets and emerging targets. Diabetes-induced skeletal muscle wasting is known to involve changes in various signaling molecules and pathways, such as protein degradation pathways, protein synthesis pathways, mitochondrial function, and oxidative stress inflammation. Recent studies have shown that some of these present potential as promising therapeutic targets, including the neuregulin 1/epidermal growth factor receptor family, advanced glycation end-products, irisin, ferroptosis, growth differentiation factor 15 and more. This study's investigation and discussion of such pathways and their potential applications provides a theoretical basis for the development of clinical treatments for diabetes-induced muscle wasting and a foundation for continued focus on this disease.

Differential effects of four laboratory animal control diets on gut microbiota in mice

BACKGROUND

The gut microbiota is intricate and susceptible to multiple factors, with diet being a major contributor. The present study aimed to investigate the impact of four commonly used laboratory animal control diets, namely Keao Xieli's maintenance diet (KX), HFK's 1025 (HF), Research Diets' D12450B (RD), and Lab Diet's 5CC4 (LD), on the gut microbiota of mice.

RESULTS

A total of 40 mice were randomly assigned to four groups, and each group was fed one of the four diets for a duration of 8 weeks. The assessment of gut microbiota was conducted using 16S rRNA sequencing both at the beginning of the study (week 0) and the end (week 8), which served as the baseline and endpoint samples, respectively. Following the 8-week feeding period, no significant differences were observed in physiological parameters, including body weight, visceral weight, and blood biochemical indices, across the four groups. Nonetheless, relative to the baseline, discernible alterations in the gut microbiota were observed in all groups, encompassing shifts in beta-diversity, hierarchical clustering, and key genera. Among the four diets, HF diet exhibited a significant influence on alpha-diversity, RD diet brought about notable changes in microbial composition at the phylum level, and LD diet demonstrated an interconnected co-occurrence network. Mantel analysis indicated no significant correlation between physiological parameters and gut microbiota in the four groups.

CONCLUSION

Overall, our study demonstrated that the four control diets had a minimal impact on physiological parameters, while exerting a distinct influence on the gut microbiota after 8 weeks. © 2024 Society of Chemical Industry.

Adhere to the Chinese dietary guidelines associated with better subjective well-being: evidence from a cross-sectional survey and a daily diary investigation

BACKGROUND

Subjective well-being (SWB) plays an essential role in general health. Although beneficial effects of selected micronutrients and foods on SWB have been reported, they do not reflect the impact of the habitual diet on SWB. Therefore, the purpose of this study is to investigate the association between adherence to the Chinese Dietary Guidelines (CDG) with SWB.

METHODS

This study combined a cross-sectional survey and a daily diary investigation. The cross-sectional survey was conducted on 1,433 students from 8 universities in southern China between October and November 2020. The daily diary investigation was conducted in November 2022, collecting 10-day daily data from 115 students at two universities in southern China over ten consecutive days, resulting in 1,020 valid matched daily responses. Adherence to the CDG was assessed by the China Prime Diet Quality Score (CPDQS), SWB was measured by the Index of Well-being (IWB) and the Affect Valuation Index (AVI). Correlation analysis, multiple regression analyses, and hierarchical regression were conducted to examine the associations of adherence to the CDG with its components, and SWB.

RESULTS

The cross-sectional survey revealed significant predictors of SWB, including adherence to the CDG (β = 0.24, p<0.001) and its components: cereals and tubers (β = 0.07, p = 0.024), vegetables and fruits (β = 0.11, p<0.001), dairy/soy/nuts (β = 0.11, p = 0.002), and condiments and alcoholic beverages (β = 0.08, p = 0.002). The daily diary investigation showed positive associations between adherence to the CDG (β = 0.19, p<0.001), and its components: vegetables and fruits (β = 0.11, p = 0.001), dairy/soy/nuts (β = 0.06, p = 0.009), animal source food (β = 0.06, p = 0.026), and condiments and alcoholic beverages (β = 0.07, p = 0.026), with higher levels of daily SWB.

CONCLUSIONS

Adherence to healthy dietary patterns such as the CDG, rather than focusing on individual components in isolation, is associated with better SWB. Furthermore, the consumption of CDG components had an impact on SWB, although the specific effects varied between the two studies. This study offers modest evidence supporting the role of the CDG in promoting positive mental health.

Dietary supplementation of ark clams protects gut health and modifies gut microbiota in d-galactose-induced aging rats

BACKGROUND

Ark clams, a seafood abundant in various nutrients, are widely consumed worldwide. This study aimed to investigate the protective benefits of two common ark clams in Korea, Scapharca subcrenata (SS) and Tegillarca granosa (TG), on gut health in d-galactose (d-gal)-induced aging rats.

RESULTS

Thirty-two Wistar rats (11 weeks old) were randomly allocated into four groups: a CON group (normal diet + saline intraperitoneal (i.p.) injection), a CD group (normal diet + d-gal i.p. injection), an SS group (normal diet with 5% SS supplementation + d-gal i.p. injection), and a TG group (normal diet with 5% TG supplementation + d-gal i.p. injection). After 12 weeks of treatment, histopathological results showed that gut barrier damage was alleviated in rats of the SS and TG groups, as evidenced by increases in mucus layer thickness and goblet cell numbers. Meanwhile, the two groups supplemented with ark clams showed an evident reduction in oxidative stress biomarkers (malondialdehyde and protein carbonyl content levels in the colon) and an increase in the immune-related factor (immunoglobulin A level in the plasma) in rats. The 16S ribosomal RNA analysis revealed that SS and TG ark clams significantly increased the proliferations of Bacteroidetes at the phylum level and Parabacteroides at the genus level. Additionally, the levels of the three main short-chain fatty acids in the cecal contents were also significantly increased in the SS and TG groups.

CONCLUSION

Our results indicated a potent preventive effect of SS and TG ark clams on d-gal-induced gut injury, suggesting that ark clams may be a promising dietary component for intervening in aging. © 2023 Society of Chemical Industry.

Therapeutic applications of gut microbes in cardiometabolic diseases: current state and perspectives

Cardiometabolic disease (CMD) encompasses a range of diseases such as hypertension, atherosclerosis, heart failure, obesity, and type 2 diabetes. Recent findings about CMD's interaction with gut microbiota have broadened our understanding of how diet and nutrition drive microbes to influence CMD. However, the translation of basic research into the clinic has not been smooth, and dietary nutrition and probiotic supplementation have yet to show significant evidence of the therapeutic benefits of CMD. In addition, the published reviews do not suggest the core microbiota or metabolite classes that influence CMD, and systematically elucidate the causal relationship between host disease phenotypes-microbiome. The aim of this review is to highlight the complex interaction of the gut microbiota and their metabolites with CMD progression and to further centralize and conceptualize the mechanisms of action between microbial and host disease phenotypes. We also discuss the potential of targeting modulations of gut microbes and metabolites as new targets for prevention and treatment of CMD, including the use of emerging technologies such as fecal microbiota transplantation and nanomedicine. KEY POINTS: • To highlight the complex interaction of the gut microbiota and their metabolites with CMD progression and to further centralize and conceptualize the mechanisms of action between microbial and host disease phenotypes. • We also discuss the potential of targeting modulations of gut microbes and metabolites as new targets for prevention and treatment of CMD, including the use of emerging technologies such as FMT and nanomedicine. • Our study provides insight into identification-specific microbiomes and metabolites involved in CMD, and microbial-host changes and physiological factors as disease phenotypes develop, which will help to map the microbiome individually and capture pathogenic mechanisms as a whole.

Cedrol, a Major Component of Cedarwood Oil, Ameliorates High-Fat Diet-Induced Obesity in Mice

SCOPE

Excellent health-promoting effects of cedrol (CED), including anti-inflammatory, anti-arthritic, and antinociceptive effects, have been reported. The present study aims to investigate the preventive effects of CED on high-fat diet (HFD)-induced obesity and the related metabolic syndrome, and to delineate the underlying mechanism.

METHODS AND RESULTS

Ten-week-old C57BL/6J mice are fed chow, HFD, or HFD supplemented with CED (0.2% w/w) for 19 weeks. Results demonstrate that CED effectively reduces HFD-induced body weight gain, decreases visceral fat pad weight, and significantly prevents adipocyte hypertrophy in mice. HFD-induced hepatic steatosis, glucose intolerance, insulin resistance, and gluconeogenesis are ameliorated by CED supplementation. 16S rRNA analysis reveals that CED does not change gut microbiota composition at the phylum and genus levels, indicating that CED may have limited effects on gut microbiota in HFD-fed mice. Further transcriptome analysis of epididymal white adipose tissue reveals reprogrammed RNA profiles by CED.

CONCLUSION

These results demonstrate that incorporating CED in the diet can prevent HFD-induced obesity and related metabolic syndrome, and highlight that CED can be a promising dietary component for obesity therapeutic intervention.

Dietary Supplementation of Methyl Cedryl Ether Ameliorates Adiposity in High-Fat Diet-Fed Mice

Methyl cedryl ether (MCE) is a derivative of cedrol and is widely used as a fragrance compound. The aim of this study was to evaluate the preventative effects of MCE on obesity and related metabolic syndromes and to delineate the mechanisms from the perspective of gut microbiota and white adipose tissues (WAT) transcriptomic profiles. Five-week-old male C57BL/6J mice were randomly assigned into 3 groups and fed with chow diet, high-fat diet (HFD), or HFD supplemented with 0.2% (w/w) MCE for 13 weeks. We found that MCE significantly reduced body weight, inhibited adipocyte hypertrophy, and ameliorated hepatic steatosis under HFD conditions. MCE dietary supplementation downregulated the expression of adipogenesis genes (FAS and C/EBPα) and upregulated the mRNA levels of thermogenesis genes (PGC-1α, PRDM16, UCP1, Cidea, Cytc, and COX4) in epididymal WAT. 16S rRNA sequencing revealed that MCE improved gut microbiota dysbiosis in HFD-fed mice, as manifested by the alteration of strains associated with obesity. Further transcriptome analysis of WAT indicated that MCE dramatically changed the gene expression profiles. Our results demonstrate the anti-obesity effect of MCE under HFD conditions, highlighting the nutraceutical potential of MCE for preventing obesity.

Eugenol, A Major Component of Clove Oil, Attenuates Adiposity and Modulates Gut Microbiota in High-Fat Diet-fed Mice

SCOPE

Eugenol (EU), the major aromatic compound derived from clove oil, is being focused recently due to its potential in preventing several chronic conditions. Herein, we aimed to evaluate the potential of EU in obesity prevention and to delineate the mechanisms involved.

METHODS AND RESULTS

Five-week-old male C57BL/6J mice were fed with high-fat diet (HFD) or HFD supplemented with EU (0.2%, w/w) for 13 weeks. EU significantly reduced obesity-related indexes including final body weight, body weight gain, adipocyte size, visceral fat-pad weight, and fasting blood glucose. EU prevented HFD-induced gut dysbiosis, as indicated by the increase of Firmicutes and decrease of Desulfobacterota at phylum level, and the increase of Dubosiella, Blautia, unclassified_f_Oscillospiraceae, and unclassified_f_Ruminococcaceae, and the decrease of Alistipes, Alloprevotella, and Bilophila at genus level. Notably, the obesity-related indexes were positively correlated with the relative abundances of Bacteroides, unclassified_f_Lachnospiraceae, Colidextribacter, and Bilophila, and negatively correlated with the relative abundances of norank_f_Muribaculaceae and Lachnospiraceae_NK4A136_group. Moreover, the preventive effects of EU on obesity were accompanied by the transcriptomic reprogramming of white adipose tissue.

CONCLUSION

These findings demonstrated that EU prevents the HFD-induced adiposity and modulates gut dysbiosis, and highlighted the potential of EU in obesity intervention as a functional dietary supplement. This article is protected by copyright. All rights reserved.