Loss of Sucrase-Isomaltase Function Increases Acetate Levels and Improves Metabolic Health in Greenlandic Cohorts

Bifidobacterium bifidum Ameliorates DSS-Induced Colitis in Mice by Regulating Microbial Metabolome and Targeting Gut Microbiota

Inflammatory bowel disease (IBD) is a recurrent inflammatory condition affecting the gastrointestinal tract, and its clinical treatment remains suboptimal. Probiotics have shown effectiveness in alleviating dextran sulfate sodium salt (DSS)-induced colitis, exhibiting strain-specific anti-inflammatory properties. In this study, we compared the therapeutic effects of five strains of Bifidobacterium bifidum isolated from healthy adult feces on DSS-induced colitis in mice. Additionally, we investigated the underlying mechanisms by examining gut microbiota composition and microbial metabolome. Our findings highlighted the superior efficacy of B. bifidum M1-3 compared to other strains. It significantly improved colitis symptoms, mitigated gut barrier disruption, and reduced colonic inflammation in DSS-treated mice. Moreover, gut microbiota composition analysis revealed that B. bifidum M1-3 treatment increased the abundance and diversity of gut microbiota. Specifically, it significantly increased the abundance of Muribaculaceae, Lactobacillus, Bacteroides, and Enterorhabdus, while decreasing the abundance of Escherichia-Shigella. Furthermore, our nontargeted metabolomics analysis illustrated that B. bifidum M1-3 treatment had a regulatory effect on various metabolic pathways, including tyrosine metabolism, lysine degradation, and tryptophan metabolism. Importantly, we confirmed that the therapeutic efficiency of B. bifidum M1-3 was dependent on the gut microbiota. These results are conducive to the development of probiotic products for alleviating colitis.

Healthcare Burden in Greenland of Gastrointestinal Symptoms in Adults with Inherited Loss of Sucrase-Isomaltase Function

Background

Congenital sucrase isomaltase deficiency (CSID) is in general a very rare disease. However, 2-3% of the Greenlandic population are homozygous (HO) carriers of an Arctic-specific loss-of-function (LoF) variant in the sucrase-isomaltase (SI) encoding gene, causing CSID. The condition is characterized by gastrointestinal symptoms such as stomachache, diarrhea, and weight loss when consuming sucrose, the most common dietary sugar. However, the awareness of the condition in the population and the healthcare system seems to be limited, potentially leading to a higher healthcare burden. Hence, we aimed to investigate whether HO-carriers visit the healthcare system more with gastrointestinal symptoms compared to the control groups by using registry data.

Methods

We performed a case-control study identifying cases and controls using genotype information from the 1999-2001 and 2005-2010 Greenlandic health population cohorts. The cases were defined as HO LoF SI-carriers and controls were defined as non-carriers and were matched (1:1) on sex, age, place of residence, and European genetic admixture. We used electronic medical records to assess the number of electronic medical record contacts (EMRc) related to gastrointestinal symptoms and the number of gastrointestinal-related diagnostic procedures.

Results

A total of 80 HO-carriers and 80 non-carriers were included. The HO-carriers had 19% more EMRc related to gastrointestinal symptoms (IRR, 1.19, 95% CI [1.02;1.40], p=0.02) and had a 41% higher incidence of gastrointestinal related diagnostic procedures compared to controls (IRR, 1.41, 95% CI [1.05-1.92], p=0.02). Only one HO-carrier was aware of the condition according to the electronic medical records.

Conclusion

HO-carriers of the LoF SI-variant had both significantly more gastrointestinal-related EMRc and significantly more diagnostic procedures conducted due to gastrointestinal symptoms. Only one HO-carrier was aware of the condition. Given the high prevalence of HO-carriers in the Greenlandic population, we anticipate that diagnosing more patients with CSID and providing dietary advice could potentially reduce symptom burden and healthcare visits among HO-carriers.

The effect of sucrase-isomaltase deficiency on metabolism, food intake and preferences: protocol for a dietary intervention study

In Greenland, traditional marine foods are increasingly being replaced by sucrose- and starch-rich foods. A knock-out c.273_274delAG variant in the sucrase-isomaltase (SI) gene is relatively common in Greenland, with homozygous carriers being unable to digest sucrose and some starch. The variant is associated with a healthier metabolic phenotype in Greenlanders, which is confirmed by SI-knockout mice. We aim to assess if the healthy phenotype is explained by metabolic and microbial differences and if food and taste preferences differ between SI-genotypes. This paper describes the protocol for a randomised cross-over trial conducted in Greenland in 2022 with two dietary interventions of three days; a traditional meat- and fish-rich diet and a starch-rich Western diet with 11 energy% sucrose. The power calculation showed that 22 homozygous SI-carriers and 22 non-carriers were sufficient to detect a 0.5 mmol/L difference in glycaemic variability (80% power, α=0.05). We enrolled 18 carriers and 20 non-carriers. We examined food preferences at baseline and collected samples before and after each intervention for metabolic, metabolome, and microbiome profiling. Analyses of samples have not been completed yet. The Ethics Committee of Greenland approved the study. Results will be disseminated in international peer-reviewed journals and to the general Greenlandic population. NCT05375656.

Genetic Loss of Sucrase-Isomaltase Function: Mechanisms, Implications, and Future Perspectives

Genetic variants causing loss of sucrase-isomaltase (SI) function result in malabsorption of sucrose and starch components and the condition congenital sucrase-isomaltase deficiency (CSID). The identified genetic variants causing CSID are very rare in all surveyed populations around the globe, except the Arctic-specific c.273_274delAG loss-of-function (LoF) variant, which is common in the Greenlandic Inuit and other Arctic populations. In these populations, it is, therefore, possible to study people with loss of SI function in an unbiased way to elucidate the physiological function of SI, and investigate both short-term and long-term health effects of reduced small intestinal digestion of sucrose and starch. Importantly, a recent study of the LoF variant in Greenlanders reported that adult homozygous carriers have a markedly healthier metabolic profile. These findings indicate that SI inhibition could potentially improve metabolic health also in individuals not carrying the LoF variant, which is of great interest considering the massive number of individuals with obesity and type 2 diabetes worldwide. Therefore, the objectives of this review, are 1) to describe the biological role of SI, 2) to describe the metabolic impact of the Arctic SI LoF variant, 3) to reflect on potential mechanisms linking reduced SI function to metabolic health, and 4) to discuss what knowledge is necessary to properly evaluate whether SI inhibition is a potential therapeutic target for improving cardiometabolic health.

Mechanisms of gut microbiota-immune-host interaction on glucose regulation in type 2 diabetes

Intestinal absorption of food is one of the sources of glucose. Insulin resistance and impaired glucose tolerance caused by lifestyle and diet are the precursors of type 2 diabetes. Patients with type 2 diabetes have trouble controlling their blood sugar levels. For long-term health, strict glycemic management is necessary. Although it is thought to be well correlated with metabolic diseases like obesity, insulin resistance, and diabetes, its molecular mechanism is still not completely understood. Disturbed microbiota triggers the gut immune response to reshape the gut homeostasis. This interaction not only maintains the dynamic changes of intestinal flora, but also preserves the integrity of the intestinal barrier. Meanwhile, the microbiota establishes a systemic multiorgan dialog on the gut-brain and gut-liver axes, intestinal absorption of a high-fat diet affects the host's feeding preference and systemic metabolism. Intervention in the gut microbiota can combat the decreased glucose tolerance and insulin sensitivity linked to metabolic diseases both centrally and peripherally. Moreover, the pharmacokinetics of oral hypoglycemic medications are also influenced by gut microbiota. The accumulation of drugs in the gut microbiota not only affects the drug efficacy, but also changes the composition and function of them, thus may help to explain individual therapeutic variances in pharmacological efficacy. Regulating gut microbiota through healthy dietary patterns or supplementing pro/prebiotics can provide guidance for lifestyle interventions in people with poor glycemic control. Traditional Chinese medicine can also be used as complementary medicine to effectively regulate intestinal homeostasis. Intestinal microbiota is becoming a new target against metabolic diseases, so more evidence is needed to elucidate the intricate microbiota-immune-host relationship, and explore the therapeutic potential of targeting intestinal microbiota.