Background: The gut microbiome, which is the collection of microorganisms living in the gastrointestinal tract, has been shown to play a significant role in the development of metabolic disorders such as obesity and type 2 diabetes mellitus (T2DM). Studies have found that the ratio of Firmicutes to Bacteroidetes (F/B) is higher in obese individuals compared to lean individuals and tends to decrease with weight loss. However, the relationship between the F/B ratio and T2DM in Korean individuals, with or without obesity, is not fully understood. Objective: The objective of this study is to compare the F/B ratios and metabolic profiles of lean and obese Korean individuals with T2DM. Methods: In this study, 36 individuals with type 2 diabetes mellitus (T2DM) were recruited and classified into four groups (I, II, III, and IV) based on their body mass index (BMI). Group I had a BMI of less than 23.0, group II had a BMI between 23.0 and 24.9, group III had a BMI between 25.0 and 29.9, and group IV had a BMI of 30 kg/m² or greater. Fecal samples were collected from all participants and sent to Chunlab Inc. (located in Seoul, Republic of Korea) for analysis. The changes in the major microbial phyla within the samples were investigated using quantitative real-time PCR. The collected data were then statistically analyzed using the SPSS program. Results: The levels of triglycerides and alanine transaminase in group I were significantly lower than in the other three groups. The amount of Actinobacteria in group IV was the highest among all four groups. The ratio of Firmicutes to Bacteroidetes increased as BMI increased, and this ratio was positively correlated with AST activity. Conclusions: Our study showed that there is a correlation between the degree of obesity in individuals with diabetes and their gut microbiome. Additionally, the ratio of Firmicutes to Bacteroidetes (F/B ratio) may play a role in the metabolic effects of fatty liver disease, as it may contribute to obesity.

Background: The interplay between glomerular hyperfiltration (GHF) and renal dysfunction and hepatic fibrosis in metabolic-associated steatotic (or fatty) liver disease (MASLD or MAFLD) remains insufficiently understood. Therefore, we examined the association in a relatively healthy population. Methods: Between 2002 and 2019, 47,741 adults (18–70 years old) participated in the study and underwent baseline liver ultrasonography and annual renal function assessments. Hepatic steatosis was diagnosed using ultrasonography, and GHF was defined as an estimated residual glomerular filtration rate exceeding the 95th percentile based on age- and sex-specific thresholds. The progression of liver fibrosis was assessed using noninvasive markers. Chronic kidney disease (CKD) and advanced liver fibrosis progression were the primary and secondary endpoints, respectively. Results: Patients with MASLD but without GHF did not exhibit an increased risk of CKD progression. However, GHF was independently associated with a higher risk of CKD progression, particularly in patients with MASLD (adjusted hazard ratio (HR): 3.88 [95% CI 3.66–4.11]). GHF alone led to a slight increase in advanced liver fibrosis risk, whereas its presence in patients with MASLD significantly exacerbated fibrosis progression (adjusted HR, 1.36 [95% CI 1.24–1.48]). In patients with coexisting GHF and MASLD, CKD development was associated with a 24% additional risk of advanced liver fibrosis (adjusted HR, 1.24; 95% CI, 1.19–1.29). Consistent findings were also noted based on the MAFLD definition. Conclusions: GHF is associated with future CKD and liver fibrosis progression, serving as a prognostic marker in patients with MASLD (or MAFLD), emphasizing the need for timely identification and monitoring.