Long-Term High-Fat Diet Decreases Renal Insulin-Degrading Enzyme Expression and Function by Inhibiting the PPARγ Pathway.
Level 5 - mechanism / opinion, no new human data
Bench and animal research (mouse model and cell culture)
PubMed 36726048 · doi:10.1002/mnfr.202200589
What was done
C57BL/6 mice were fed a high-fat diet for 24 weeks to assess insulin resistance, insulin clearance, and renal insulin-degrading enzyme (IDE) expression and activity. In vitro, HK-2 human renal proximal tubule cells were exposed to palmitic acid with or without the PPARγ agonist rosiglitazone. Mechanistic pathways were examined using RNA-Seq, promoter-binding assays for PPARγ, and in vivo intervention with rosiglitazone in high-fat diet-fed mice.
What was found
The abstract reports directional changes without exact numerical values, effect sizes, or confidence intervals. A 24-week high-fat diet decreased renal IDE expression, enzyme activity, and renal PPARγ mRNA levels (without altering PPARα or PPARβ/δ expression), accompanied by impaired insulin clearance and insulin resistance in mice. In HK-2 cells, palmitic acid reduced IDE mRNA and protein expression and decreased PPARγ binding to the IDE promoter; these in vitro decreases were prevented by rosiglitazone. In vivo, rosiglitazone treatment increased renal IDE expression and improved insulin clearance and insulin resistance in high-fat diet-fed mice.
Why it matters
This study identifies a specific molecular mechanism—renal IDE downregulation mediated by PPARγ inhibition—linking high-fat diet-induced obesity to defective renal insulin clearance and systemic insulin resistance.
Limits
The study is restricted to mouse and cell culture models; findings may not directly translate to human renal physiology. The abstract does not provide sample sizes, quantitative effect sizes, variance measures, or statistical test values. Potential off-target effects of rosiglitazone and long-term systemic impacts beyond renal clearance were not detailed in the abstract.
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