Magnesium accumulation upon cyclin M4 silencing activates microsomal triglyceride transfer protein improving NASH.

ABSTRACT:

Background & aims

Perturbations of intracellular magnesium (Mg²⁺) homeostasis have implications for cell physiology. The cyclin M family, CNNM, perform key functions in the transport of Mg²⁺ across cell membranes. Herein, we aimed to elucidate the role of CNNM4 in the development of non-alcoholic steatohepatitis (NASH).

Methods

Serum Mg²⁺ levels and hepatic CNNM4 expression were characterised in clinical samples. Primary hepatocytes were cultured under methionine and choline deprivation. A 0.1% methionine and choline-deficient diet, or a choline-deficient high-fat diet were used to induce NASH in our in vivo rodent models. Cnnm4 was silenced using siRNA, in vitro with DharmaFECT and in vivo with Invivofectamine® or conjugated to N-acetylgalactosamine.

Results

Patients with NASH showed hepatic CNNM4 overexpression and dysregulated Mg²⁺ levels in the serum. Cnnm4 silencing ameliorated hepatic lipid accumulation, inflammation and fibrosis in the rodent NASH models. Mechanistically, CNNM4 knockdown in hepatocytes induced cellular Mg²⁺ accumulation, reduced endoplasmic reticulum stress, and increased microsomal triglyceride transfer activity, which promoted hepatic lipid clearance by increasing the secretion of VLDLs.

Conclusions

CNNM4 is overexpressed in patients with NASH and is responsible for dysregulated Mg²⁺ transport. Hepatic CNNM4 is a promising therapeutic target for the treatment of NASH.

Lay summary

Cyclin M4 (CNNM4) is overexpressed in non-alcoholic steatohepatitis (NASH) and promotes the export of magnesium from the liver. The liver-specific silencing of Cnnm4 ameliorates NASH by reducing endoplasmic reticulum stress and promoting the activity of microsomal triglyceride transfer protein.

SUBMITTER: Simon J 

PROVIDER: S-EPMC8217299 | biostudies-literature | 2021 Jul

REPOSITORIES: biostudies-literature