RESUMO
Background: A risk haplotype in SLC16A11 characterized by alterations in fatty acid metabolism emerged as a genetic risk factor associated with increased susceptibility to type 2 diabetes (T2D) in Mexican population. Its role on treatment responses is not well understood. Objectives: We aimed to determine the impact of the risk haplotype on the metabolomic profile during a lifestyle intervention (LSI). Methods: We recruited Mexican-mestizo individuals with ≥1 prediabetes criteria according to the American Diabetes Association with a body mass index between 25 and 45 kg/m2. We conducted a 24-wk quasiexperimental LSI study for diabetes prevention. Here, we compared longitudinal plasma liquid chromatography/mass spectrometry metabolomic changes between carriers and noncarriers. We analyzed the association of risk haplotype with metabolites leveraging repeated assessments using multivariable-adjusted linear mixed models. Results: Before the intervention, carriers (N = 21) showed higher concentrations of hippurate, C16 carnitine, glycine, and cinnamoylglycine. After 24 wk of LSI, carriers exhibited a deleterious metabolomic profile. This profile was characterized by increased concentrations of hippurate, cinnamoglycine, xanthosine, N-acetylputrescine, L-acetylcarnitine, ceramide (d18:1/24:1), and decreased concentrations of citrulline and phosphatidylethanolamine. These metabolites were associated with higher concentrations of total cholesterol, triglycerides, and low density lipoprotein cholesterol. The effect of LSI on the risk haplotype was notably more pronounced in its impact on 2 metabolites: methylmalonylcarnitine (ß: -0.56; P-interaction = 0.014) and betaine (ß: -0.64; P-interaction = 0.017). Interestingly, lower consumption across visits of polyunsaturated (ß: -0.038; P = 0.017) fatty acids were associated with higher concentrations of methylmalonylcarnitine. Covariates for adjustment across models included age, sex, genetic ancestry principal components, and body mass index. Conclusions: Our study highlights the persistence of deleterious metabolomic patterns associated with the risk haplotype before and during a 24-wk LSI. We also emphasize the potential regulatory role of polyunsaturated fatty acids on methylmalonylcarnitine concentrations suggesting a route for improving interventions for individuals with high-genetic risk.
RESUMO
Glucosamine-6-phosphate (GlcN6P) deaminases from Escherichia coli (EcNagBI) and Shewanella denitrificans (SdNagBII) are special examples of what constitute nonhomologous isofunctional enzymes due to their convergence, not only in catalysis, but also in cooperativity and allosteric properties. Additionally, we found that the sigmoidal kinetics of SdNagBII cannot be explained by the existing models of homotropic activation. This study describes the regulatory mechanism of SdNagBII using enzyme kinetics, isothermal titration calorimetry (ITC), and X-ray crystallography. ITC experiments revealed two different binding sites with distinctive thermodynamic signatures: a single binding site per monomer for the allosteric activator N-acetylglucosamine 6-phosphate (GlcNAc6P) and two binding sites per monomer for the transition-state analog 2-amino-2-deoxy-D-glucitol 6-phosphate (GlcNol6P). Crystallographic data demonstrated the existence of an unusual allosteric site that can bind both GlcNAc6P and GlcNol6P, implying that the homotropic activation of this enzyme arises from the occupation of the allosteric site by the substrate. In this work we describe the presence of this novel allosteric site in the SIS-fold deaminases, which is responsible for the homotropic and heterotropic activation of SdNagBII by GlcN6P and GlcNAc6P, respectively. This study unveils an original mechanism to generate a high degree of homotropic activation in SdNagBII, mimicking the allosteric and cooperative properties of hexameric EcNagBI but with a reduced number of subunits.