Hypothesis

Berberine’s metabolic benefits stem from targeted epigenetic remodeling rather than hormetic stress signaling. We hypothesize that berberine induces proteasomal degradation of the epigenetic regulator UHRF1 in hepatocytes, leading to reduced DNMT1 recruitment and passive demethylation of the PCSK9 promoter. This epigenetic shift lowers PCSK9 transcription independently of AMPK activation, thereby increasing hepatic LDLR expression and enhancing LDL clearance. Consequently, berberine improves glucose tolerance and lipid profile even when canonical AMPK signaling is absent, and its synergy with low-dose metformin arises from simultaneous suppression of SREBP-1c-driven lipogenesis via AMPK-dependent and -independent routes.

Experimental Design

We will use liver-specific AMPKalpha1/alpha2 double-knockout (L-AMPK DKO) mice and matched wild-type controls. Animals will receive oral berberine (200 mg/kg/day) or vehicle for 4 weeks. Primary outcomes: hepatic UHRF1 protein levels, PCSK9 promoter methylation (bisulfite sequencing), PCSK9 mRNA and plasma concentrations, hepatic LDLR abundance, glucose tolerance test (GTT), and serum triglycerides. Secondary outcomes: AMPK phosphorylation (to confirm pathway ablation) and TRIM21 ubiquitination activity (immunoprecipitation-Western).

Predicted Outcomes

Berberine will reduce hepatic UHRF1 and PCSK9 promoter methylation, increase LDLR, and improve GTT and lipid levels in both wild-type and L-AMPK DKO mice. Hepatic over-expression of a degradation-resistant UHRF1 mutant will abolish berberine-induced PCSK9 suppression and LDLR up-regulation, confirming the mechanistic link.

Falsification Criteria

If berberine fails to lower PCSK9 expression or LDLR in L-AMPK DKO mice, or if UHRF1 degradation does not correlate with metabolic improvements, the hypothesis that berberine acts via an UHRF1-dependent epigenetic route independent of AMPK will be falsified.