The gut viral community (virome) may play an important role in the development of obesity and type 2 diabetes (T2D), according to a study published in Gastroenterology.

Obesity and T2D are global public health challenges. Controlling obesity is vital, as it is associated with an increased risk for cardiac and neurological comorbidities and complications, as well as T2D. While obesity and T2D have been related to changes in gut bacterial composition, little is known about the role of the virome in disease development.

Therefore, researchers sought to characterize gut virome alterations in patients with obesity with or without T2D. They recruited 128 patients with obesity (body mass index [BMI] ≥ 28 kg/m2) and 101 lean controls (BMI ≥ 18.5 kg/m2 and < 23 kg/m2) from Hong Kong (HK cohort) and Kunming (KM cohort), China. Virus-like particles and whole DNA were extracted from fecal samples for gut virome and bacteriome analysis, respectively. The samples then underwent shotgun metagenomic sequencing.


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The median age for lean controls in the HK and KM cohorts were 47.0 and 48.5 years, respectively. The median age for patients with obesity was 53 and 37 years, respectively. Overall, 87.2% of patients in the HK cohort had obesity with concurrent T2D (ObT2), while only 12% in the KM cohort were diagnosed with both.

ObT2 patients had decreased gut viral richness and diversity compared with lean controls in the HK cohort (P <.05), while no significant differences were observed in the KM cohort (P =.23). Analysis revealed greater changes in gut virome composition among patients with obesity in the HK cohort vs the KM cohort when compared with lean controls. Investigators inferred that these results indicate geographic factors may contribute to alterations in the gut virome as well. 

Eleven viruses, including Escherichia phage, Geobacillus phage, and Lactobacillus phage, were enriched in patients with obesity, suggesting different taxonomic compositions between patients with obesity and lean controls. Additionally, 17 differentially abundant viruses were identified between ObT2 and lean controls.

Ecological analysis revealed that the trans-kingdom correlations between viruses and bacteria in lean controls were significantly decreased in ObT2 patients. Further, Enterobacteria phage and Psuedomonas phage, both known to host on certain bacteria associated with metabolic diseases, were more positively correlated with healthy bacteria in the lean controls cohort. These results suggest a positive relationship between bacterial predators and helpful bacteria may contribute to the health of the gut microbiome.

This study was limited by its use of only fecal samples, as virome composition likely differs throughout the body (eg, use of mucus or mucosa samples). Additionally, the study did not include patients with pre-diabetes, preventing researchers from analyzing the use of gut viral profiles for the prediction of full diabetes. 

The authors concluded that, “[O]besity is characterized by significantly altered viral taxonomic composition and weaken[ed] viral-bacterial correlations compared with lean controls.” “Further investigations are needed to verify the cause-effect relationship of gut virome in the pathogenesis of obesity and T2D,” they concluded.

Reference

Yang K, Niu J, Zuo T, et al. Alterations in the gut virome in obesity and type 2 diabetes mellitus. Gastroenterol. Published online June 23, 2021. doi: 10.1053/j.gastro.2021.06.056