Background: Type 2 diabetes (T2D) is one of the leading causes of mortality and is a public health challenge worldwide. Metformin is the first-choice treatment for T2D; its pharmacokinetics (PK) is facilitated by members of the solute carrier (SLC) superfamily of transporters, it is not metabolized, and it is excreted by the kidney. Although interindividual variability in metformin pharmacokinetics is documented in the Mexican population, its pharmacogenomics is still underexplored. We aimed to identify variants in metformin SLC transporter genes associated with metformin PK and response in Mexican patients. Methods: Using exome data from 2217 Mexican adults, we identified 86 biallelic SNVs in the eight known genes encoding SLC transporters, with a minor allele frequency ≥ 1%, which were analyzed in an inadequate glycemic control (IGC) association study in T2D metformin treated patients. Metformin PK was evaluated in a pediatric cohort and the effect of associated SNVs was correlated. Results: Functional annotation classified two SNVs as pathogenic. The association study revealed two blocks associated with IGC. These haplotypes comprise rs622591, rs4646272, rs4646273, and rs4646276 in SLC22A1; and rs1810126 and rs668871 in SLC22A3. PK profiles revealed that homozygotes of the SLC22A1 haplotype reached lower plasma metformin concentrations 2 h post administration than the other groups. Conclusions: Our findings highlight the potential of pharmacogenomics studies to enhance precision medicine, which may involve dosage adjustments or the exploration of alternative therapeutic options. These hold significant implications for public health, particularly in populations with a high susceptibility to develop metabolic diseases, such as Latin Americans.

Introduction: Quercetin, a dietary flavonoid typically consumed as a glycoside, is available in supplements in its aglycone form. This aglycone form is the most studied in preclinical and clinical research because of its antioxidant, anti-inflammatory, and metabolic properties. Several clinical trials have demonstrated the benefits of quercetin for enzymatic, metabolic and cardiovascular health, approximately 60% of these studies fail to verify the actual concentration administered, generating uncertainty on their findings. Objective: This study aimed to evaluate the concentration, stability, and cost–concentration of commercial quercetin nutraceutical formulations. Methodology: The concentrations of five commercial brands were quantified by high-performance liquid chromatography. Stability was assessed over 6 months at both room temperature and 40°C. Results: Only one brand contained the amount labeled; three contained approximately 80%, and one contained merely 14.8%. This study is the first to evaluate the long and thermal stability of quercetin in nutraceutical products, demonstrating that the active ingredient remains stable for at least 6 months. Brand C was identified as the most suitable option. Conclusion: There was significant variability in the quercetin concentration of commercial supplements. These findings underscore the need for stricter regulatory oversight to ensure the quality, therapeutic efficacy, and safety of nutraceutical products.