Fig. 2

Dietary magnesium (Mg²⁺) deficiency decreased plasma Mg²⁺ concentration and liver catechol-O-methyltransferase (COMT) activity in non-diabetic mice, and empagliflozin increased plasma Mg²⁺ concentration in diabetic mice. (a) Male DBA/2J mice were fed a control diet (1,000 mg Mg²⁺·kg⁻¹) or a 0.03% Mg²⁺ diet (300 mg Mg²⁺·kg⁻¹) for 4 weeks, and plasma Mg²⁺ concentrations were measured. (b) Fasting blood glucose was measured after 16 h of fasting at 11 weeks of age. (c) A methyltransferase assay kit, which detects the S-adenosylhomocysteine (SAH) reaction product, was used to measure the SAH concentration in the liver. Norepinephrine (NE) was used as a substrate, and tolcapone was used as a COMT inhibitor. (d) The difference in liver SAH between samples with and without NE (ΔSAH), which represents liver COMT activity, was calculated. (e) Plasma Mg²⁺ concentrations were measured in db/ +, db/db control, and db/db EMPA mice at 24 weeks of age. (f) Urinary Mg²⁺ excretion was measured in db/ +, db/db control, and db/db EMPA mice at 24 weeks of age. DBA/2J control, n = 9. DBA/2J 0.03% Mg²⁺, n = 9. db/ +, n = 5. db/db control, n = 6. db/db EMPA, n = 6. The data are presented as the mean ± SEM. The data were analysed using the Student’s t test (a, b, d) and one-way ANOVA followed by Tukey’s test (c, e, f). *p < 0.05, **p < 0.01, ****p < 0.0001.