Table 1.
Animal models and clinical studies assessing the potential association between adipose tissue-derived bacteria and adipose tissue function/glucose homeostasis.
| Study | Animals/Participants | Adipose tissue bacteria | Adipose tissue-related findings | Glucose homeostasis-related findings |
|---|---|---|---|---|
| Amar et al. (113) | NC/HFD-fed mice | Gram-negative bacteria (experimental translocation model). | Increased TNF-α and IFN-γ in MAT, correlating with bacterial DNA concentration. | Increasing MAT bacterial DNA concentration in the progression of prediabetes to diabetes. Probiotic treatment reduced mucosal dysbiosis, bacterial translocation, and improved glucose metabolism. |
| Denou et al. (114) | NOD2-/- mice | Commensal bacteria (experimental translocation model). | Increased inflammation (IL-6, TNF-α) in visceral adipose tissue. | Increased insulin resistance. |
| Ahnê et al. (115) | Subjects with morbid obesity with T2D (n-20) and without T2D (n-20) | Different compartmentalization according to specific tissue (MAT, OAT, SAT). | Not assessed. | More evident T2D signatures in MAT: reduced bacterial diversity and Gram-positive bacteria (i.e., Faecalibacterium) and increased Gram-negative Enterobacteriaceae. |
| Massier et al. (116) | Subjects with obesity with T2D (n-33) and without T2D (n-42) | Proteobacteria and Firmicutes were the predominant phyla in adipose tissue (MAT, OAT, SAT). Higher bacterial quantity and diversity in MAT. | Bacterial DNA correlated with macrophage infiltration in OAT (especially in T2D), TNF-α in SAT, and IL-1B in MAT; bacterial DNA induced adipokine secretion. | Eighteen genera were shown to present different abundance between subjects with T2D and subjects without T2D. |
| Bakker et al. (117) | Subjects with obesity and metabolic syndrome receiving lean donor FMT (n-8); BMI- matched controls not receiving FMT (n-16) | Very low quantity of bacterial DNA in visceral adipose tissue. | FMT did not alter bacterial translocation to adipose tissue. No differences in visceral bacterial DNA content/macrophage infiltration between groups. | Not assessed. |
NC, normal chow; HFD, high-fat diet; MAT, mesenteric adipose tissue; OAT, omental adipose tissue; SAT, subcutaneous adipose tissue; TNF- α, tumor necrosis factor α; IFN- γ, interferon γ; NOD2, oligomerization domain-2; IL-6, interleukin 6; IL-1B, interleukin-1B; TD2, type 2 diabetes mellitus; FMT, fecal microbiota transplantation; BMI, body mass index.