DNA Methylation Profiling of Hepatic Insulin Response in Young and Aged Mice

To investigate age-related differences in hepatic insulin response at the epigenetic level, we profiled genome-wide DNA methylation in liver tissue from young (6-month-old) and old (20-month-old) male C57BL/6J mice following a hyperinsulinemic-euglycemic clamp. Mice underwent detailed metabolic phenotyping, including body composition analysis and indirect calorimetry, followed by surgical catheterization and a standardized insulin clamp procedure with stable isotope tracer infusions. Liver tissue was collected immediately after the clamp, and DNA was extracted for methylation profiling using Illumina Infinium arrays. The tracer studies enabled quantification of hepatic fluxes through pyruvate dehydrogenase, fatty acid oxidation, citrate synthase, and pyruvate carboxylase. This study investigates age-related differences in hepatic DNA methylation in response to insulin stimulation using methylation array profiling. Male C57BL/6J mice aged 6 months (young) and 20 months (old) were obtained from The Jackson Laboratory (stock number: 000664). Mice were maintained under standard housing conditions and underwent comprehensive metabolic phenotyping. Body composition was assessed using Bruker’s Minispec Whole Body Composition Analyzer. Mice were acclimated to single housing before being placed in metabolic cages (Columbus Instruments CLAMS) for measuring. Following phenotyping, mice underwent jugular vein catheterization and recovery. After a 14-hour overnight fast, a 150-minute hyperinsulinemic-euglycemic clamp was performed, during which [2H7]glucose was infused to maintain euglycemia (~115 mg/dL), along with continuous infusion of metabolic tracers [3-13C]lactate and [U-13C]palmitate to assess substrate flux (results contained in metadata). After the clamp, mice were euthanized, and liver tissues were collected and snap-frozen. Genomic DNA was extracted from liver tissue, and genome-wide DNA methylation profiling was performed using Illumina Infinium arrays. The design comprises two biological groups: young (6-month-old, n=8) and old (20-month-old, n=10) insulin-stimulated mice.