UBIAD1 and hyperinsulinemic hypoglycemia, familial, 4: Considered together with current studies, these findings unequivocally position UBIAD1 as a major regulator of HMGCR and mevalonate metabolism in vivo, provide new links between synthesis of sterols and MK-4, and establish Ubiad1-/-: :HmgcrKi/Ki mice as a model of MK-4 deficiency.