Irisin has been recently identified as an adipomyokine produced during physical activity and involved in the browning of adipose tissue. Despite the emerging evidence suggesting an inverse relationship between irisin plasma concentrations and adverse metabolic outcomes, the exact impact of diet on irisin levels remains obscure. Thus, we aimed to assess the effects of two dietary patterns, Christian Orthodox fasting (OF) and 16:8 time-restricted eating (TRE), on circulating irisin levels among overweight, metabolically healthy, adults. Plasma irisin, glucose and lipid parameters, calcium homeostasis, and anthropometry were evaluated in 29 Orthodox fasters and 14 age and body mass index (BMI)-matched TRE controls (mean age and BMI, 48.8 years and 28.7 kg/m², respectively) at three, distinct time points—before the implementation of the energy-restricted diets (baseline), at the end of the dietary intervention (7 weeks) and 5 weeks after participants returned to their typical dietary habits (12 weeks from baseline). Repeated measures analysis was applied to assess differences between the two groups and the effect of several indices on irisin levels at all three time points. At 12 weeks, the OF group manifested higher irisin concentrations compared with both its baseline values (64.3 ± 54.4 vs. 43.6 ± 42.2 ng/mL, p = 0.01) and those of the TRE group at the same time point (64.3 ± 54.4 vs. 44.2 ± 26.6 ng/mL, p = 0.04). Glycemic, lipid, and anthropometric parameters were not found to correlate with irisin levels. In contrast, parathyroid hormone (PTH) concentrations at 12 weeks correlated with irisin concentrations (p = 0.04), indicating that lower values of irisin are expected for higher PTH measurements. The findings of this pilot study suggest favorable long-term effects of OF on irisin levels. The interplay between irisin, PTH, and diet warrants further investigation.

Athonian Orthodox fasting (AOF) is characterized by energy- and time-restricted eating (TRE) and is based on the Mediterranean diet. We aimed to investigate the impact of AOF compared to another TRE model on vaspin, omentin, nesfatin, and visfatin levels. We included 25 individuals (mean age 50.3 ± 8.6 years, 24% men) who practiced AOF and abstained from animal products, with the exception of seafood and fish. This group adopted a 12 h eating interval (08.00 to 20.00). In total, 12 participants (mean age 47.7 ± 8.7 years, 33.3% men) who practiced 16:8 TRE (eating from 09:00 to 17:00) and were allowed to consume meat served as the controls. Anthropometric and dietary data and adipokine levels were prospectively collected at three time points: at baseline, after the end of the diets (7 weeks), and 5 weeks after the participants returned to their typical eating habits (12 weeks from baseline). Vaspin levels decreased [795.8 (422.1–1299.4) (baseline) vs. 402.7 (203.8–818.9) (7 weeks) pg/mL, p = 0.002] and omentin levels increased [568.5 (437.7–1196.5) (baseline) vs. 659.0 (555.7–1810.8) (12 weeks) pg/mL, p = 0.001] in the AOF group, while none of the analyzed adipokines changed significantly in the TRE group. The variations observed in vaspin and omentin concentrations in the AOF group were independent of age, sex, changes in anthropometry and fat intake. In conclusion, AOF can significantly reduce vaspin and increase omentin, whose levels are known to increase and decrease, respectively, in obesity and type 2 diabetes. The implications of these findings for cardiometabolic health warrant further investigation.

Background/Objectives: Inflammation is a hallmark of diabetes, with interleukin-6 (IL-6) emerging as a key mediator linking immune activation with metabolic regulation. Although IL-6 has been studied in both type 1 (T1D) and type 2 diabetes (T2D), its relationship with glycemic control across diabetes subtypes remains unexplored. Methods: We conducted a cross-sectional pilot study including 82 participants divided into the following subgroups: healthy controls (n = 14), individuals with T1D [n = 11 with glycated hemoglobin (HbA1c) < 7%; n = 11 with HbA1c ≥ 7%] and T2D (n = 21 with HbA1c < 7%; n = 25 with HbA1c ≥ 7%). Demographic, anthropometric, and laboratory parameters were collected. Group comparisons were performed, adjusted for age and body mass index (BMI) to account for significant demographic differences between groups. Correlations between IL-6, high-sensitivity C-reactive protein (hs-CRP), ferritin, and presepsin were evaluated using Spearman’s rank correlation. Results: IL-6 levels were approximately four-fold higher in T1D individuals with HbA1c ≥ 7% compared with controls [fold-change 4.06 (95% CI: 1.36–12.1), p = 0.013], with optimally managed T1D showing a non-significant trend (p = 0.079). No significant differences were observed in T2D groups. Advancing age demonstrated a borderline association with IL-6 (p = 0.068), whereas BMI was not significantly related. IL-6 correlated positively with hs-CRP (ρ = 0.463, p < 0.001), but not with ferritin or presepsin. Conclusions: IL-6 concentrations were significantly elevated in individuals with suboptimally managed T1D compared with controls, independent of age and BMI, suggesting that poor metabolic control amplifies systemic inflammation in autoimmune diabetes. These findings support IL-6 as a biomarker of inflammatory burden in T1D and provide a rationale for larger, longitudinal studies to determine its clinical utility.

Background/Objectives: The role of intestinal dysbiosis as an important driver of inflammation in metabolic disorders is becoming increasingly evident. Beta-defensin 2 is an antimicrobial peptide that contributes to innate immunity, while recently it has been suggested as a novel biomarker of gut dysbiosis. However, its role in obesity remains unexplored. This study aimed to compare circulating beta-defensin 2 levels between individuals with overweight and obesity and lean controls. An additional objective was to explore potential correlations between beta-defensin 2 and other inflammatory markers in this population. Methods: The study population consisted of 81 participants (61.7% females) divided into obesity (n = 27), overweight (n = 34), and normal body mass index (n = 20) groups. All participants were free of infection and diabetes mellitus. Beta-defensin 2, interleukin-6, presepsin, high-sensitivity C-reactive protein (hs-CRP), and ferritin were evaluated in the study groups. Results: We did not find significant differences in beta-defensin 2 levels between the groups (p = 0.936). In contrast, hs-CRP levels were higher in people with obesity compared to the sum of participants in the overweight and control groups (p = 0.044), after adjusting for the effects of age, sex, smoking, and vitamin D status. Furthermore, a positive correlation was established between beta-defensin 2 and presepsin values (p = 0.012). Conclusions: The results of the present study demonstrate that obesity is characterized by an aggravation of inflammation, as expressed by elevated hs-CRP levels. Although the study design cannot prove causal relationships, our findings also suggest that beta-defensin 2 levels correlate with the magnitude of systemic inflammation in infection-free individuals living with obesity. The value of the combined evaluation of different biomarkers in obesity-related outcomes warrants further investigation by larger studies.

Objective: Obesity is characterized by chronic inflammation and gut dysbiosis, yet circulating markers reflecting intestinal immune activation remain limited. Regenerating islet-derived protein 3 alpha (REG3α), an antimicrobial peptide secreted by intestinal Paneth cells, plays a pivotal role in mucosal defense and mirrors microbial–epithelial interactions. In this cross-sectional study, we aimed to examine circulating REG3α levels in infection-free adults with obesity, overweight, and normal weight, and to explore their associations with vitamin D supplementation and biomarkers of inflammation and dysbiosis. Methods: Sixty-nine participants were stratified into control, overweight, and obesity groups. Serum REG3α, interleukin-6 (IL-6), β-defensin-2, high-sensitivity c-reactive protein, ferritin, and presepsin were assessed. Vitamin D status and supplementation history were recorded. Multivariable linear regression, principal component analysis (PCA), and bootstrap mediation models were applied to explore associations and potential indirect effects. Results: REG3α concentrations were higher in overweight and obesity compared to controls (646 ± 217 vs. 521 ± 311 ng/mL); however, the difference was not significant (p = 0.15). Vitamin D supplementation was inversely associated with REG3α (p = 0.06), and this effect appeared weaker in obesity. REG3α correlated positively with IL-6 (ρ = 0.28) and β-defensin-2 (ρ = 0.43). PCA revealed a shared inflammatory–mucosal activation component that predicted REG3α levels. Exploratory mediation suggested a partial indirect effect of vitamin D via reduced inflammatory activity. Conclusions: Circulating REG3α shows associations with indicators of inflammation and vitamin D supplementation in individuals with overweight and obesity. Although differences between groups did not reach statistical significance, the observed trends suggest possible links between mucosal immune activity and metabolic status. These exploratory results warrant validation in larger, longitudinal studies before any biomarker role can be established.