There is increasing evidence suggesting the important role of gut microbiota in human health, and dysbiosis may contribute to pathological conditions. Recent studies have found a connection between gut microbiota and type 2 diabetes (T2DM). Specifically, imbalances in gut microbiota may lead to abnormal glucose metabolism and increase the risk of developing T2DM. Current research [12, 27] has identified various microbial characteristics. Under normal physiological conditions, Firmicutes account for the largest proportion (64%) in the gut microbiota, followed by Bacteroidetes (23%), Proteobacteria (8%), and Actinobacteria (3%). Differences in gut microbiota have been observed between T2DM patients and individuals with normal glucose tolerance [17]. Increased abundance of Bacteroides caccae, Clostridium hathewayi, Clostridium ramosum, Clostridium symbiosum, Coprococcus eutactus, Clostridia, Collinsella, Desulfovibrio sp., Eggerthella lenta, Escherichia coli, Lactobacillus gasseri, Streptococcus mutans, Lachnospiraceae bacterium, Prevotella, Ruminococcus, Verrucomicrobia, Dorea, and Fusobacterium has been observed in T2DM patients. On the other hand, decreased abundance of Clostridiales sp. SS3/4, Eubacterium rectale, Faecalibacterium prausnitzii, Roseburia intestinalis, Roseburia inulinivorans, Eubacterium eligens, Bacteroides intestinalis, Oscillibacter, Bifidobacterium, Coprococcus, Butyrivibrio, Clostridium hathewayi, Clostridium bolteae, Clostridium symbiosum, Bacteroides, Streptococcus, Bifidobacterium, and Parabacteroides has been observed in T2DM patients. The abundance of Akkermansia muciniphila, Streptococcus, and Dorea is controversial, with some studies showing increased expression while others show decreased expression. Additionally, there are differences in gut microbiota between T2DM obese patients, T2DM non-obese patients, obese individuals, and individuals with normal glucose tolerance. For example, the abundance of Akkermansia muciniphila [28] was decreased in T2DM and obese patients. Disruption in circadian rhythms is associated with gut microbiota dysbiosis in comparison to individuals with normal sleep-wake cycles [21, 23, 26]. The relative abundance of Bacteroidetes, Bacteroidia, and Spirillum is decreased, while Actinobacteria, Firmicutes, Delta-proteobacteria, Desulfuromonadales, Desulfuromonadaceae, Campylobacteriaceae, Corynebacteriaceae, Dorea longicatena, and Dorea formicigenerans is increased. During clinical work, we have observed a portion of T2DM patients who exhibit disrupted circadian rhythms. These individuals typically have poor blood glucose control, possibly due to the nature of their professions (e.g., doctors, train drivers, and truck drivers) that result in irregular eating, resting, and medication schedules, leading to a series of adverse effects. However, there is still a small portion of individuals who are able to achieve good blood glucose control.
Since there have been no reports on gut microbiota in individuals with T2DM combined with circadian rhythm disruption under different blood glucose control conditions, we recruited T2DM patients with circadian rhythm disruption for gut metagenomic sequencing. We discovered that the microbial composition in W-T2D-RD group was more diverse compared to those P-T2D-RD group. This suggests that the abundance of microbiota may be associated with blood glucose control in individuals with circadian rhythm disruption and may influence glucose metabolism. Our study revealed significant differences in the composition of microbial communities at the phylum, genus, and species levels between the two groups. The relative abundance of Firmicutes was decreased in the P-T2D-RD group, while the abundance of Actinobacteria was increased. These findings are consistent with previous studies on gut microbiota changes in individuals with normal rhythm disruption and in individuals with different blood glucose control states of T2DM (increased relative abundance of Firmicutes), but there are also differences (decreased relative abundance of Actinobacteria).
In order to study the biological mechanism of P-T2D-RD, we have also identified some potential markers that can be considered indicative of P-T2D-RD. we found an increased abundance of Faecalibacterium prausnitzii, Streptococcus equi, Bifidobacterium adolescentis, Clostridium arbusti, Clostridium cadaveris, and Candidatus Dorea massiliensis in P-T2D-RD patients, indicating Faecalibacterium prausnitzii, Streptococcus equi, Bifidobacterium adolescentis, Clostridium arbusti, Clostridium cadaveris, and Candidatus Dorea massiliensis can be taken as novel biomarker for the diagnosis of P-T2D-RD, and that increased Faecalibacterium prausnitzii, Streptococcus equi, Bifidobacterium adolescentis, Clostridium arbusti, Clostridium cadaveris, and Candidatus Dorea massiliensis may be attributed to the biological mechanism of P-T2D-RD.
Fecal Microbiota Transplantation (FMT) involves transferring healthy gut microbiota from individuals with normal glucose tolerance to the intestines of type 2 diabetes patients using methods such as capsules, gastroscopy, and colonoscopy. This process helps to restore the imbalanced gut microbiota in T2DM patients and improve glucose metabolism disorders[29, 30]. Previous studies have also demonstrated the efficacy of FMT in alleviating T2DM through numerous animal experiments [31–34]. These studies involved collecting fecal samples from normal mice, processing them, and then transplanting them into T2DM mouse models. FMT was found to potentially improve damaged islets by reducing the secretion of pro-inflammatory cytokines and increasing the secretion of anti-inflammatory cytokines [31]. FMT also showed unique effects in terms of islet regeneration, increased functional β-cell mass, and improved insulin sensitivity [32]. Furthermore, FMT was found to be a safe treatment option, effectively inhibiting weight gain, reducing albuminuria, decreasing local TNF-α expression in the ileum and ascending colon, and improving insulin resistance in mice [33]. Some studies using metagenomic or 16S sequencing have also identified decreased relative abundance of certain bacterial genera in T2DM patients, such as Blautia wexlerae [35] and Akkermansia muciniphila [28]. Transplanting these strains to T2DM mice has been found to improve blood glucose levels and insulin resistance in these animals.we found an decreased abundance of L.johnsonii in P-T2D-RD patients, indicating that lactobacillus johnsonii can be taken as a novel biomarker for the treatment of P-T2D-RD, and that decreased L.johnsonii may be attributed to the biological mechanism of P-T2D-RD. L.johnsonii has not been used in the treatment of T2DM yet, so we chose L.johnsonii for fecal microbiota transplantation. This will help us further understand the pathogenesis of T2DM and discover new therapeutic targets.
we used metagenomics to study the compositional (profiles of microbiota) and functional capabilities (KEGG functional categories,and CAZymes) of the gut microbiomes of P-T2D-RD patients compared to W-T2D-RD. We found that there are significant overlaps and differences in microbial transformation and functional characteristics between the gut microbiota of the two groups.The identified CAZymes enable both P-T2D-RD patients and W-T2D-RD patients to utilize plant material as a significant source of nutrients due to the enzymatic activities of gut microbes.The increased abundance of greenhouse gases in each group indicates the enrichment of different gut microbiota that specialize in utilizing different plant polysaccharides. The overexpression of GHs may lead to an excessive rate of nutrient absorption, thus contributing to the pathogenesis of T2DM with circadian rhythm disruption at the microsystem level.Our results suggest that high carbohydrate intake in the gut may be one of the mechanisms underlying the development of T2DM with circadian rhythm disruption. The pathways and CAZymes identified in our study can serve as a possible biological explanation for hyperglycemia in T2DM with circadian rhythm patients. The significant contraction of carbohydrate metabolism-related enzymes and pathways leading to excessive nutrient absorption resulting in energy surplus increases the risk of obesity and overweight, ultimately leading to poor blood sugar control in T2D with circadian rhythm disruption patients.
Our experimental results show that circadian rhythm disruption leads to poor PBG control in both T2DM-RD and T2DM-RD-L groups of mice, which is consistent with the previous mention of circadian rhythm disruption causing poor blood glucose control. Furthermore, our experimental results indicate that after administration of Lactobacillus johnsonii, postprandial blood glucose in the T2DM-RD-L group of mice improves compared to the T2DM-RD group. Therefore, we consider L.johnsonii to be an effective method for improving the poor postprandial blood glucose control caused by circadian rhythm disruption. Proper regulation of insulin levels is crucial for maintaining normal blood glucose metabolism and overall metabolic balance. Previous studies have mentioned that gut microbiota can improve insulin secretion and insulin resistance.Our experimental results indicate that after L.johnsonii administration, the insulin levels in the T2DM-RD-L group of mice are lower compared to the T2DM-C group. This may be because the T2DM-C group of mice does not have circadian rhythm disruption and has relatively normal insulin levels, while the administration of L.johnsonii leads to a normalization of insulin levels in the T2DM-RD-L group of mice, resulting in a trend of decrease. Dysbiosis of the gut microbiota leads to pathological changes in mice with diabetes and circadian rhythm disruption, including insulin secretion and blood glucose regulation. Our experimental results suggest that gut microbiota transplantation treatment leads to a decrease in fasting insulin levels in patients with type 2 diabetes and circadian rhythm disruption, indicating the potential of microbiota transplantation in improving insulin levels in diabetes. Therefore, L.johnsonii may regulate the gut microbiota of diabetic mice, restoring partial functionality to these physiological processes and improving blood glucose control and insulin secretion in the T2DM-RD-L group of mice.
In conclusion, these results suggest that L.johnsonii improves blood glucose control and insulin levels by regulating the gut microbiota and restoring partial functionality to physiological processes such as insulin secretion and blood glucose regulation in diabetic mice. Although most studies on gut microbiota transplantation for type 2 diabetes treatment have been conducted on diabetic mouse models, as mentioned in the introduction, there have been studies transplanting fecal samples from healthy individuals, after purification, into the intestines of diabetic patients, which have shown positive effects such as weight loss, decreased blood glucose levels, and reduced insulin resistance. Although there have been limited studies on single strain microbiota transplantation, we believe that L.johnsonii can have positive implications for diabetes management in a clinical setting. Further research and clinical trials are needed to confirm the applicability and efficacy of these results in patients with type 2 diabetes.
The gut microbiota transplantation also has a positive effect on lipid metabolism. Our experimental results indicate that after L.johnsonii administration, the high-density lipoprotein (HDL) levels in the T2DM-RD-L group are improved compared to the T2DM-C group, suggesting that L.johnsonii administration may have some benefits in improving HDL metabolism in the T2DM-RD-L group of mice. However, the difference is not significant compared to the T2DM-RD group, which may be attributed to the positive effects of forced exercise and intermittent fasting due to sleep disturbance in the T2DM-RD group. The low-density lipoprotein (LDL) levels in the T2DM-RD-L group are decreased compared to both the T2DM-RD and T2DM-C groups, indicating that L.johnsonii administration may have some benefits in improving LDL metabolism in T2DM mice. Total cholesterol and triglyceride levels are important indicators of lipid metabolism, and studies have shown that the T2DM-RD-L group has improved total cholesterol and triglyceride levels compared to the T2DM-C group, indicating that L.johnsonii helps improve total cholesterol and triglyceride levels in T2DM mice.
In summary, L.johnsonii administration improves certain lipid metabolism indicators (such as HDL levels, total cholesterol levels, triglyceride levels) in the T2DM-RD-L group compared to the T2DM-C group. Therefore, we believe that L.johnsonii administration can help improve lipid metabolism in T2DM mice with disrupted circadian rhythms, manifested by increased HDL levels, decreased LDL levels, and improved total cholesterol and triglyceride levels. This may be attributed to the effects of L.johnsonii on the gut microbiota, which in turn regulates the balance of lipid metabolism in the body. L.johnsonii may improve the composition of the gut microbiota, promote the activity of lipid metabolism-related enzymes, or influence the absorption and utilization of lipids in the intestines, thus improving lipid metabolism.
Through animal experimentation, we have demonstrated the potential benefits of L.johnsonii in improving blood lipid levels in diabetic mice. Furthermore, several studies have shown that the transplantation of fecal matter from individuals with normal glucose tolerance to diabetic patients can significantly improve their blood lipid levels. Based on the potential of L.johnsonii in improving lipid metabolism in diabetic mice, we believe that it may also have the potential to improve blood lipid levels in diabetic patients. However, this hypothesis needs to be verified through subsequent clinical trials. Although we have not yet applied this to clinical diabetic patients, these findings provide new prospects for the clinical application of L.johnsonii.
Our study has several limitations. First, the sample size was small, and we did not include female patients or individuals with normal glucose tolerance. Second, in the animal experiment, we did not perform glucose tolerance tests and insulin tolerance tests on the mice due to considerations of the number of experimental animals and their condition. As a result, we were unable to evaluate their pancreatic function. Third, in the animal experiment, we found some improvements in certain glucose and lipid metabolism indicators in the T2DM-RD group compared to the T2DM-C group, which could be attributed to the beneficial effects of forced exercise. However, this was not further validated. Fourth, we did not conduct further metagenomic sequencing and untargeted metabolomics sequencing on the fecal samples of the mice in each group to validate or explore the relationship between the gut microbiota and metabolites.