Phospholipid methylation in mammals: from biochemistry to physiological function.

Area of Science:

• Biochemistry
• Cell Biology
• Metabolic Diseases

Background:

• Phosphatidylcholine synthesis occurs via the CDP-choline pathway or phosphatidylethanolamine N-methyltransferase (PEMT) using AdoMet.
• PEMT, an endoplasmic reticulum and mitochondria-associated membrane protein, is primarily active in the liver.
• PEMT activity is influenced by substrate concentrations and the AdoMet/AdoHcy ratio, with estrogen enhancing and Sp1 repressing its transcription.

Purpose of the Study:

• To investigate the physiological roles of PEMT using knockout mouse models.
• To elucidate the impact of PEMT deficiency on hepatic membrane integrity, lipoprotein secretion, and metabolic health.

Main Methods:

• Utilized PEMT-deficient mice to study the enzyme's function in vivo.
• Assessed hepatic membrane integrity, very low-density lipoprotein (VLDL) secretion, atherosclerosis development, obesity, insulin resistance, and diet-induced fatty liver.

Main Results:

• PEMT deficiency maintains hepatic membrane integrity and supports choline formation during limited dietary choline.
• Lack of PEMT protects against diet-induced atherosclerosis, obesity, and insulin resistance.
• PEMT-deficient mice exhibit increased susceptibility to diet-induced fatty liver and steatohepatitis.

Conclusions:

• PEMT plays a critical role in maintaining liver health and metabolic homeostasis.
• PEMT deficiency offers protection against certain metabolic disorders but exacerbates others, highlighting its complex role in lipid metabolism.