Where genes meet environment-integrating the role of gut luminal contents, immunity and pancreas in type 1 diabetes

Microbiota in human breast milk: Noninfectious mastitis versus without mastitis

BACKGROUND

Long-term breastfeeding is beneficial for both mothers and infants and mastitis is associated with the premature interruption of breastfeeding. Mastitis can be infectious or noninfectious. However, the effect of noninfectious mastitis on milk microbiota is not well-understood. In this study, we aimed to clarify the relationship between noninfectious mastitis and the microbiota by conducting breast milk culture tests.

METHODS

We compared the milk microbiota between women with noninfectious mastitis and without mastitis. Bacterial cultures were compared in 143 milk samples from January to November 2022, and bacterial diversity was evaluated based on the total number of bacterial species and bacterial species found per specimen.

RESULTS

Women with noninfectious mastitis provided samples at a significantly later stage postpartum (p < 0.01). The total bacterial count was significantly lower in samples from participants with noninfectious mastitis (p < 0.01). The bacterial diversity of milk from participants with noninfectious mastitis was lower than that without mastitis: nine bacterial species identified in the former and 21 in the latter. The number of Rothia spp. was significantly higher, whereas the number of Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas fluorescens was significantly lower in samples from women with mastitis. There was no correlation between postpartum week and the number of bacterial species or presence of Rothia spp.

CONCLUSIONS

Noninfectious mastitis is associated with a decrease in the diversity of human milk microbiota, indicating impaired immune, metabolic, and neuroendocrine development functions in infants. Rothia spp. may also be associated with noninfectious mastitis, suggesting a possible target for future research.

Fecal and soil microbiota composition of gardening and non-gardening families

Historically, humans have interacted with soils, which contain a rich source of microorganisms. Fruit and vegetable gardening is the primary interaction humans have with soil today. Animal research reveals that soil microorganisms can be transferred to the rodent intestine. However, studies on fecal and soil microbial changes associated with gardening in humans are lacking. The current case-controlled cohort study aimed to characterize the fecal and soil microbiota of gardening families (n = 10) and non-gardening (control) families (n = 9). Families included two adults and one child (5–18 years) for a total of 56 participants. All participants provided a fecal sample, soil sample, and diet history questionnaires before the gardening season (April) and during the peak of the gardening season (August). Healthy Eating Index (HEI-2015) scores and nutrient analysis were performed. Fecal and soil DNA were extracted and amplified. Sequence data were then processed and analyzed. Peak season gardening families tended to have greater fecal operational features, a greater Faith's Phylogenetic Diversity score, greater fiber intake, and higher abundances of fiber fermenting bacteria than peak control families. Soil endemic microbes were also shared with gardening participant’s fecal samples. This study revealed that the fecal microbiota of gardening families differs from non-gardening families, and that there are detectable changes in the fecal microbial community of gardeners and their family members over the course of the gardening season. Additional research is necessary to determine if changes induced by gardening on the gut microbiota contribute to human health.

Age-Dependent Intestinal Repair: Implications for Foals with Severe Colic

Colic is a leading cause of death in horses, with the most fatal form being strangulating obstruction which directly damages the intestinal barrier. Following surgical intervention, it is imperative that the intestinal barrier rapidly repairs to prevent translocation of gut bacteria and their products and ensure survival of the patient. Age-related disparities in survival have been noted in many species, including horses, humans, and pigs, with younger patients suffering poorer clinical outcomes. Maintenance and repair of the intestinal barrier is regulated by a complex mucosal microenvironment, of which the ENS, and particularly a developing network of subepithelial enteric glial cells, may be of particular importance in neonates with colic. Postnatal development of an immature enteric glial cell network is thought to be driven by the microbial colonization of the gut and therefore modulated by diet-influenced changes in bacterial populations early in life. Here, we review the current understanding of the roles of the gut microbiome, nutrition, stress, and the ENS in maturation of intestinal repair mechanisms after foaling and how this may influence age-dependent outcomes in equine colic cases.

Angiotensin-(1-7) Expressed From Lactobacillus Bacteria Protect Diabetic Retina in Mice

Purpose

A multitude of animal studies substantiates the beneficial effects of Ang-(1–7), a peptide hormone in the protective axis of the renin angiotensin system, in diabetes and its associated complications including diabetic retinopathy (DR). However, the clinical application of Ang-(1–7) is limited due to unfavorable pharmacological properties. As emerging evidence implicates gut dysbiosis in pathogenesis of diabetes and supports beneficial effects of probiotics, we sought to develop probiotics-based expression and delivery system to enhance Ang-(1–7) and evaluate the efficacy of engineered probiotics expressing Ang-(1–7) in attenuation of DR in animal models.

Methods

Ang-(1–7) was expressed in the Lactobacillus species as a secreted fusion protein with a trans-epithelial carrier to allow uptake into circulation. To evaluate the effects of Ang-(1–7) expressed from Lactobacillus paracasei (LP), adult diabetic eNOS^−/− and Akita mice were orally gavaged with either 1 × 10⁹ CFU of LP secreting Ang-(1–7) (LP-A), LP alone or vehicle, 3 times/week, for 8 and 12 weeks, respectively.

Results

Ang-(1–7) is efficiently expressed from different Lactobacillus species and secreted into circulation in mice fed with LP-A. Oral administration of LP-A significantly reduced diabetes-induced loss of retinal vascular capillaries. LP-A treatment also prevented loss of retinal ganglion cells, and significantly decreased retinal inflammatory cytokine expression in both diabetic eNOS^−/− and Akita mice.

Conclusions

These results provide proof-of-concept for feasibility and efficacy of using engineered probiotic species as live vector for delivery of Ang-(1–7) with enhanced bioavailability.

Translational Relevance

Probiotics-based delivery of Ang-(1–7) may hold important therapeutic potential for the treatment of DR and other diabetic complications.

Human Pluripotent Stem Cells: A Unique Tool for Toxicity Testing in Pancreatic Progenitor and Endocrine Cells

Diabetes prevalence is increasing worldwide, and epidemiological studies report an association between diabetes incidence and environmental pollutant exposure. There are >84,000 chemicals in commerce, many of which are released into the environment without a clear understanding of potential adverse health consequences. While in vivo rodent studies remain an important tool for testing chemical toxicity systemically, we urgently need high-throughput screening platforms in biologically relevant models to efficiently prioritize chemicals for in depth toxicity analysis. Given the increasing global burden of obesity and diabetes, identifying chemicals that disrupt metabolism should be a high priority. Pancreatic endocrine cells are key regulators of systemic metabolism, yet often overlooked as a target tissue in toxicology studies. Immortalized β-cell lines and primary human, porcine, and rodent islets are widely used for studying the endocrine pancreas in vitro, but each have important limitations in terms of scalability, lifespan, and/or biological relevance. Human pluripotent stem cell (hPSC) culture is a powerful tool for in vitro toxicity testing that addresses many of the limitations with other β-cell models. Current in vitro differentiation protocols can efficiently generate glucose-responsive insulin-secreting β-like cells that are not fully mature, but still valuable for high-throughput toxicity screening in vitro. Furthermore, hPSCs can be applied as a model of developing pancreatic endocrine cells to screen for chemicals that influence endocrine cell formation during critical windows of differentiation. Given their versatility, we recommend using hPSCs to identify potential β-cell toxins, which can then be prioritized as chemicals of concern for metabolic disruption.

Rat Models of Human Type 1 Diabetes

Rat models of human type 1 diabetes have been shown to be of great importance for the elucidation of the mechanisms underlying the development of autoimmune diabetes. The three major well-established spontaneous rat models are the BioBreeding (BB) diabetes-prone rat, the Komeda diabetes-prone (KDP) rat, and the IDDM (LEW.1AR1-iddm) rat. Their distinctive features are described with special reference to their pathology, immunology, and genetics and compared with the situation in patients with type 1 diabetes mellitus. For all three established rat models, a distinctive genetic mutation has been identified that is responsible for the manifestation of the diabetic syndrome in these rat strains.

Gut microbiota-brain axis in depression: The role of neuroinflammation

Major depressive disorder (MDD) is a psychiatric condition that affects a large number of people in the world, and the treatment existents do not work for all individuals affected. Thus, it is believed that other systems or pathways which regulate brain networks involved in mood regulation and cognition are associated with MDD pathogenesis. Studies in humans and animal models have been shown that in MDD there are increased levels of inflammatory mediators, including cytokines and chemokines in both periphery and central nervous system (CNS). In addition, microglial activation appears to be a key event that triggers changes in signaling cascades and gene expression that would be determinant for the onset of depressive symptoms. Recent researches also point out that changes in the gut microbiota would lead to a systemic inflammation that in different ways would reach the CNS modulating inflammatory pathways and especially the microglia, which could influence responses to treatments. Moreover, pre- and probiotics have shown antidepressant responses and anti-inflammatory effects. This review will focus on studies that show the relationship of inflammation with the gut microbiota-brain axis and its relation with MDD.

Dysregulated liver lipid metabolism and innate immunity associated with hepatic steatosis in neonatal BBdp rats and NOD mice

In a previous study we reported that prediabetic rats have a unique gene signature that was apparent even in neonates. Several of the changes we observed, including enhanced expression of pro-inflammatory genes and dysregulated UPR and metabolism genes were first observed in the liver followed by the pancreas. In the present study we investigated further early changes in hepatic innate immunity and metabolism in two models of type 1 diabetes (T1D), the BBdp rat and NOD mouse. There was a striking increase in lipid deposits in liver, particularly in neonatal BBdp rats, with a less striking but significant increase in neonatal NOD mice in association with dysregulated expression of lipid metabolism genes. This was associated with a decreased number of extramedullary hematopoietic clusters as well as CD68⁺ macrophages in the liver of both models. In addition, PPARɣ and phosphorylated AMPKα protein were decreased in neonatal BBdp rats. BBdp rats displayed decreased expression of antimicrobial genes in neonates and decreased M2 genes at 30 days. This suggests hepatic steatosis could be a common early feature in development of T1D that impacts metabolic homeostasis and tolerogenic phenotype in the prediabetic liver.

Current understanding of the role of gut dysbiosis in type 1 diabetes

Type 1 diabetes (T1D) is a chronic autoimmune disorder that results from destruction of the insulin-producing pancreatic β-cells. The disease mainly affects juveniles. Changes in the composition of the gut microbiota (dysbiosis) and changes in the properties of the gut barrier have been documented in T1D subjects. Because these factors affect immune system functions, they are likely to play a role in disease pathogenesis. However, their exact role is currently not fully understood and is under intensive investigation. In this article we discuss recent advancements depicting the role of intestinal dysbiosis on immunity and autoimmunity in T1D. We also discuss therapies aimed at maintaining a healthy gut barrier as prevention strategies for T1D.

Expression of Human ACE2 in Lactobacillus and Beneficial Effects in Diabetic Retinopathy in Mice

The angiotensin converting enzyme 2 (ACE2) catalyzes the degradation of Angiotensin II (Ang II) to generate Angiotensin-(1-7), which reduces inflammation and oxidative stress stimulated by Ang II. ACE2 has been shown to be protective in cardiovascular and metabolic diseases including diabetes and its complications. However, the challenge for its clinical application is large-scale production of high-quality ACE2 with sufficient target tissue bioavailability. We developed an expression and delivery system based on the use of probiotic species Lactobacillus paracasei (LP) to serve as a live vector for oral delivery of human ACE2. We show that codon-optimized ACE2 can be efficiently expressed in LP. Mice treated with the recombinant LP expressing the secreted ACE2 in fusion with the non-toxic subunit B of cholera toxin, which acts as a carrier to facilitate transmucosal transport, showed increased ACE2 activities in serum and tissues. ACE2-LP administration reduced the number of acellular capillaries, blocked retinal ganglion cell loss, and decreased retinal inflammatory cytokine expression in two mouse models of diabetic retinopathy. These results provide proof of concept for feasibility of using engineered probiotic species as live vector for delivery of human ACE2 with enhanced tissue bioavailability for treating diabetic retinopathy, as well as other diabetic complications.

Ameliorating gut microenvironment through staphylococcal nuclease-mediated intestinal NETs degradation for prevention of type 1 diabetes in NOD mice

AIMS

Recent studies have revealed that neutrophil extracellular traps (NETs) provide negative feedback in the progression to chronic inflammation and contribute to the pathogenesis of multiple autoimmune diseases including type 1 diabetes (T1D). In addition, accumulating evidences suggest that gut immunity play a key role in T1D pathogenesis. Our study aimed to evaluate whether staphylococcal nuclease (SNase) targeting intestinal NETs can ameliorate the intestinal inflammatory environment and protect against T1D development in non-obese diabetic(NOD) mice.

MAIN METHODS

Degradation of NETs with SNase in vitro was examined using SYTOX green assay. NOD/LtJ mice were oral administration of Lactococcus lactisl (L. lactis) pCYT: SNase and blood glucose levels were monitored weekly. Several biomarkers of NETs formation, gut leakage and inflammation were determined using a commercial ELISA kit. T Cell phenotypes in peripheral immune system were analyzed in flow cytometry and fecal samples were isolated to investigate intestinal microbiota.

KEY FINDINGS

The oral delivery of SNase by L. lactis can decrease the NETs levels and ameliorate inflammation both in the intestine and pancreatic islets and finally effectively regulate the blood glucose levels of NOD mice. Meanwhile, zonulin and lipopolysaccharide levels also reduced in SNase-fed NOD mice, suggesting SNase could improve gut barrier function via intestinal NETs degradation. Furthermore, the abundances of the intestinal microbiota and butyrate-producing gut bacteria were also increased with SNase treatment.

SIGNIFICANCE

SNase shows potential for intestinal NETs to prevent T1D based on the gut-pancreas axis.

Changes in insulin, glucagon and ER stress precede immune activation in type 1 diabetes

It is unknown whether there is a gene signature in pancreas which is associated with type 1 diabetes (T1D). We performed partial pancreatectomies on 30-day preinsulitic, diabetes-prone BioBreeding (BBdp) rats to prospectively identify factors involved in early prediabetes. Microarrays of the biopsies revealed downregulation of endoplasmic reticulum (ER) stress, metabolism and apoptosis. Based on these results, additional investigations compared gene expression in control (BBc) and BBdp rats age ~8, 30 and 60 days using RT-qPCR. Neonates had increased ER stress gene expression in pancreas. This was associated with decreased insulin, cleaved caspase-3 and Ins1 whereas Gcg and Pcsk2 were increased. The increase in ER stress was not sustained at 30 days and decreased by 60 days. In parallel, the liver gene profile showed a similar signature in neonates but with an early decrease of the unfolded protein response (UPR) at 30 days. This suggested that changes in the liver precede those in the pancreas. Tnf and Il1b expression was increased in BBdp pancreas in association with increased caspase-1, cleaved caspase-3 and decreased proinsulin area. Glucagon area was increased in both 30-day and 60-day BBdp rats. Increased colocalization of BIP and proinsulin was observed at 60 days in the pancreas, suggesting insulin-related ER dysfunction. We propose that dysregulated metabolism leads to ER stress in neonatal rats long before insulitis, creating a microenvironment in both pancreas and liver that promotes autoimmunity.

Lifestyle Factors Affecting the Gut Microbiota's Relationship with Type 1 Diabetes

PURPOSE OF REVIEW

The incidence of type 1 diabetes (T1D) is rising drastically for the past decades at a rate that cannot be explained by genetic changes alone. Environmental changes are considered to be the main drivers of this change. Recently, the gut microbiota has been suggested as a missing link between known environmental disease modulators and T1D promotion. Lifestyle factors have changed over time and have altered the gut microbiota-host interaction affecting T1D development. The purpose of this review is to discuss recent data emphasizing the modulatory potential of early lifestyle factors on gut microbiota and to elucidate their implication for T1D.

RECENT FINDINGS

Recent findings show that lifestyle factors, especially those that affect the early establishment of gut homeostasis and the education of the immune system, are crucial disease modulators. Changing lifestyle factors affecting the early establishment of gut homeostasis are suggested to be key drivers of the rising T1D incidence.

Evidence for the Role of the Cecal Microbiome in Maintenance of Immune Regulation and Homeostasis

OBJECTIVE (S)

Our objective was to investigate alterations in the cecal microbial composition during the development of type 1 diabetes (T1D) with or without IgM therapy, and correlate these alterations with the corresponding immune profile.

METHODS

(1) Female nonobese diabetic (NOD) mice treated with IgM or saline (n = 20/group) were divided into 5-week-old nondiabetic; 9 to 12-week-old prehyperglycemic stage-1; ≥13-week-old prehyperglycemic stage-2; and diabetic groups. 16S rRNA libraries were prepared from bacterial DNA and deep-sequenced. (2) New-onset diabetic mice were treated with IgM (200 μg on Days 1, 3, and 5) and their blood glucose monitored for 2 months.

RESULTS

Significant dysbiosis was observed in the cecal microbiome with the progression of T1D development. The alteration in microbiome composition was characterized by an increase in the bacteroidetes:firmicutes ratio. In contrast, IgM conserved normal bacteroidetes:firmicutes ratio and this effect was long-lasting. Furthermore, oral gavage using cecal content from IgM-treated mice significantly diminished the incidence of diabetes compared with controls, indicating that IgM specifically affected mucosa-associated microbes, and that the affect was causal and not an epiphenomenon. Also, regulatory immune cell populations (myeloid-derived suppressor cells and regulatory T cells) were expanded and insulin autoantibody production diminished in the IgM-treated mice. In addition, IgM therapy reversed hyperglycemia in 70% of new-onset diabetic mice (n = 10) and the mice remained normoglycemic for the entire post-treatment observation period.

CONCLUSIONS

The cecal microbiome appears to be important in maintaining immune homeostasis and normal immune responses.

Type-I Interferons Inhibit Interleukin-10 Signaling and Favor Type 1 Diabetes Development in Nonobese Diabetic Mice

Destruction of insulin-producing β-cells by autoreactive T lymphocytes leads to the development of type 1 diabetes. Type-I interferons (TI-IFN) and interleukin-10 (IL-10) have been connected with the pathophysiology of this disease; however, their interplay in the modulation of diabetogenic T cells remains unknown. We have discovered that TI-IFN cause a selective inhibition of IL-10 signaling in effector and regulatory T cells, altering their responses. This correlates with diabetes development in nonobese diabetic mice, where the inhibition is also spatially localized to T cells of pancreatic and mesenteric lymph nodes. IL-10 signaling inhibition is reversible and can be restored via blockade of TI-IFN/IFN-R interaction, paralleling with the resulting delay in diabetes onset and reduced severity. Overall, we propose a novel molecular link between TI-IFN and IL-10 signaling that helps better understand the complex dynamics of autoimmune diabetes development and reveals new strategies of intervention.

Dietary quality and markers of inflammation: No association in youth with type 1 diabetes

BACKGROUND

Systemic inflammation is a key process underlying cardiovascular disease (CVD) development, and CVD risk is significantly elevated in persons with type 1 diabetes (T1D). Youth with T1D exhibit increased levels of inflammation. Studies in persons without diabetes suggest that dietary quality influences inflammation, yet little is known about dietary influences on inflammation in youth with T1D.

METHODS

This study evaluated the association of four distinct dietary quality indices (Dietary Approaches to Stop Hypertension (DASH), Healthy Eating Index 2010 (HEI2010), modified KIDMED and Total Antioxidant Capacity (TAC)) with biomarkers of inflammation (C-reactive protein (CRP), fibrinogen and interleukin-6 (IL-6)) in a sample of 2520 youth with T1D participating in the SEARCH for Diabetes in Youth Study.

RESULTS

Average diet quality was moderate to poor, with mean scores of 43 (DASH, range 0-80), 55 (HEI2010, range 0-100), 3.7 (mKIDMED, range 3-12) and 7237 (TAC). None of the four diet quality scores was associated with the selected biomarkers of inflammation in any analyses. Evaluation of a non-linear relationship or interactions with BMI or levels of glycemic control did not alter the findings. Replication of analyses using longitudinal data yielded consistent findings with our cross-sectional results.

CONCLUSIONS

Biomarkers of inflammation in youth with T1D may not be directly influenced by dietary intake, at least at the levels of dietary quality observed here. More work is needed to understand what physiologic mechanisms specific to persons with T1D might inhibit the generally beneficial influence of high dietary quality on systemic inflammation observed in populations without diabetes.

Mechanisms and consequences of intestinal dysbiosis

The composition of the gut microbiota is in constant flow under the influence of factors such as the diet, ingested drugs, the intestinal mucosa, the immune system, and the microbiota itself. Natural variations in the gut microbiota can deteriorate to a state of dysbiosis when stress conditions rapidly decrease microbial diversity and promote the expansion of specific bacterial taxa. The mechanisms underlying intestinal dysbiosis often remain unclear given that combinations of natural variations and stress factors mediate cascades of destabilizing events. Oxidative stress, bacteriophages induction and the secretion of bacterial toxins can trigger rapid shifts among intestinal microbial groups thereby yielding dysbiosis. A multitude of diseases including inflammatory bowel diseases but also metabolic disorders such as obesity and diabetes type II are associated with intestinal dysbiosis. The characterization of the changes leading to intestinal dysbiosis and the identification of the microbial taxa contributing to pathological effects are essential prerequisites to better understand the impact of the microbiota on health and disease.

Antibiotics, gut microbiota, environment in early life and type 1 diabetes

The gut microbiota interact with innate immune cells and play an important role in shaping the immune system. Many factors may influence the composition of the microbiota such as mode of birth, diet, infections and medication including antibiotics. In diseases with a multifactorial etiology, like type 1 diabetes, manipulation and alterations of the microbiota in animal models have been shown to influence the incidence and onset of disease. The microbiota are an important part of the internal environment and understanding how these bacteria interact with the innate immune cells to generate immune tolerance may open up opportunities for development of new therapeutic strategies. In this review, we discuss recent findings in relation to the microbiota, particularly in the context of type 1 diabetes.

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