GDF15 and metabolic syndrome: In our study, we selected markers that reflect aging and/or metabolic syndrome, biochemical parameters (blood lipids), telomerase, GDF11 and 15 (Growth Differentiation Factor 15 and 11), sirtuin 1, follistatin, NLRP3 (NOD-like Receptor family Pyrin domain-containing 3), AGEs (Advanced Glycation End products), klotho, DNA/RNA damage, NAD+ (Nicotamide Adenine Dinucleotide), and vitamin D.