DIFFERENTIAL EFFECTS OF ANIMAL VERSUS PLANT PROTEIN DIET ON CIRCULATING CONCENTRATIONS OF TRANSFORMING GROWTH FACTOR Β IN DIABETIC PATIENTS

Introduction:  Transforming growth factor β (TGFβ) is a pleiotropic cytokine known to exert both pro- and anti-inflammatory effects. Elevated concentrations of TGFβ are reported in patients with type 2 diabetes (T2D). However, little is known about the effect of diet on circulating TGFβ concentrations. We recently demonstrated beneficial metabolic effects of a high-protein diet in diabetic subjects. Aim:  We aimed to determine changes of TGFβ concentrations after a 6-week high-protein diet intervention in T2D patients and to evaluate potential differences according to dietary source of protein (animal versus plant). Materials and Methods :  37 individuals with T2D (age 64±6 years, HbA1c 7.0±0.6%) were randomly assigned to either high-animal protein or high-plant protein diet (30% protein, 40% carbohydrates, 30% fat) for 6 weeks. Clinical examinations were performed at the beginning and the end of the study. Levels of TGFβ and other cytokines were determined in blood serum using ELISA and Luminex technology. Results:  Levels of TGFβ were elevated in all participants [mean(±SD)=7594.1±2021.4 pg/mL]. Baseline TGFβ correlated inversely with body mass index (Rho=-0.10) and insulin levels (Rho=-0.32). After intervention, a non-significant decrease in TGFβ concentrations by 5% (7986.4±2226.6 pg/mL to 7594.4±2934.7 pg/mL, P=0.604) was observed in the high-plant protein group. In contrast, an increase of TGFβ by 13% (7155.7±1724.4 pg/mL to 8105.0±1903.2 pg/mL, P=0.004) was detected in the high animal protein group. Parallel evaluation of additional biomarkers revealed that the negative change in high-plant protein diet correlated negatively with changes of adiponectin, while the positive change in high-animal protein diet correlated negatively with changes of C-reactive protein and interleukin-8. Conclusion:  These data provide first line of evidence on the differential effects of animal versus plant protein diet on circulating concentrations of TGFβ in subjects with T2D. Further research is warranted to investigate the mechanism explaining potential role of protein diet in modulating TGFβ inflammatory cascade. Acknowledgements :  Federal Ministry of Food and Agriculture, German Center for Diabetes Research