Relationship between metformin use and vitamin B12 status in patients with type 2 diabetes in Japan

Bacteroides ovatus accelerates metformin-induced vitamin B12 deficiency in type 2 diabetes patients by accumulating cobalamin

Vitamin B12 (VB12) deficiency, which may lead to hematologic and neurologic symptoms, has been associated with metformin use, but the underlying mechanism is unclear. Here we report the B. ovatus as an effective VB12 catcher which was enriched in the type 2 diabetes patients suffered from VB12 deficiency after 3 to 6 months of metformin treatment. Colonization of B. ovatus increased the plasma levels of methylmalonic acid and homocysteine in high-fat diet (HFD)-fed mice treated with metformin, and compromised the efficacy of metformin against the HFD-induced metabolic disorders. Mechanistically, metformin increased the intracellular accumulation of VB12 in B. ovatus via btuB upregulation and promoted ATP production for energy-dependent translocation of VB12 transporters at the inner membrane, leading to an enhanced colonization of B. ovatus to compete for VB12 with hosts and subsequently an aggravated VB12 deficiency in the host. Our findings illustrate a previously unappreciated mechanism of metformin leads to host VB12 deficiency by acting directly on gut bacteria to increase their VB12 uptake and consumption, and suggest that inter-host-microbe competition for nutrients may broadly impact human health and drug safety.

Angiotensin receptor blockers significantly reduce hemoglobin level in patients with type 2 diabetes mellitus not suffered chronic cardiac failure and chronic kidney disease

Anemia due to angiotensin receptor blocker (ARB) therapy has been previously reported in patients with diabetes mellitus with glomerular filtration rates of <60 mL min^-1/1.73 m². However, whether Japanese patients with type 2 diabetes mellitus (T2DM) receiving ARB therapy for chronic cardiac failure and chronic kidney disease develop reduced hemoglobin (Hb) levels has not been elucidated. Thus, this cross-sectional study was conducted, and Hb levels were compared between patients with T2DM with and without ARB administration. No significant difference in the prescribed proportion of antidiabetic medicines such as biguanide, sodium glucose co-transporter 2 inhibitors, and α-glucosidase inhibitors was found between the group treated with ARBs and the group without ARBs. Thus, we considered that the effects of antidiabetic medicines on the results were minimum. In this study, the Hb levels of patients who received ARBs (13.8 ± 1.7 g/dL) were significantly lower than those of patients without ARBs (14.9 ± 1.35 g/dL) (p = 0.034). The difference between this study and a previous study relies on eGFR levels. Thus, the eGFR levels of the patients in this study and the previous study were above 60 and below 60 mL min^-1/1.73 m², respectively. Despite those differences, both studies showed that the use of ARBs was associated with a decrease in Hb levels in patients with T2DM. Thus, the evaluation of glycated Hb levels should be focused on whether ARBs are prescribed for patients with T2DM.

The effect of metformin on homocysteine levels in patients with polycystic ovary syndrome: A systematic review and meta-analysis

PURPOSE

Metformin is widely used as an insulin sensitizer in polycystic ovary syndrome (PCOS) patients. However, previous studies have found that the effect of metformin on the level of homocysteine were not consistent in PCOS patients. The aim of this review was to analyze the effect of metformin on homocysteine levels in patients with PCOS patients.

METHODS

The Cochrane Library, Pubmed, and Web of Science were searched according to predefined search terms. There is no restriction for publication time and language.

RESULTS

Eleven studies were included and the data were extracted. The homocysteine level in PCOS patients was significantly increased after taking metformin (mean difference [MD] -1.33; 95% confidence interval [CI] -2.16 to -0.49, p = 0.002). Subgroup analysis showed that the level of homocysteine was generally increased in PCOS patients with body mass index (BMI) ≥25 after taking metformin alone (MD -1.82; 95% CI -2.56 to -1.07, p < 0.00001). There was no significant change in homocysteine level in PCOS patients with BMI <25 (MD 0.69; 95% CI -0.41 to 1.79, p = 0.22). Subgroup analysis showed that there was no significant difference when taking metformin >3 months or taking metformin ≤3 months (p = 0.84). Taking metformin ≥1700 mg/days significantly increased homocysteine levels in PCOS patients (MD -2.05; 95% CI -2.40 to -1.70, p < 0.00001). When taking metformin <1700 mg/days, there was no significant difference in homocysteine level in PCOS patients (MD 0.15; 95% CI -1.06 to 1.37, p = 0.80). The difference between the two subgroups was significant (p = 0.0006). There was no significant difference in vitamin B12 level before and after metformin treatment (MD 24.70; 95% CI -22.54 to 71.93, p = 0.31). There was a decrease in serum folic acid level after metformin administration (MD 1.03; 95% CI 0.80 to 1.26, p < 0.00001).

CONCLUSION

Taking metformin alone increased homocysteine levels and decreased folic acid levels in nonpregnant PCOS patients. And, it was suggested that the dosage of metformin should be less than 1700 mg/days. The supplement of folic acid and B vitamins during metformin administration may be essential in nonpregnant PCOS patients. We should pay much attention to the potential effect of metformin in PCOS patients.

A 52-week randomized controlled trial of ipragliflozin or sitagliptin in type 2 diabetes combined with metformin: The N-ISM study

AIM

To compare the long-term efficacy of sodium-glucose co-transporter-2 inhibitors and dipeptidyl peptidase-4 inhibitors as second-line drugs after metformin for patients not at high risk of atherosclerotic cardiovascular disease (ASCVD).

MATERIALS AND METHODS

In a 52-week randomized open-label trial, we compared ipragliflozin and sitagliptin in Japanese patients diagnosed with type 2 diabetes, without prior ASCVD and treated with metformin. The primary endpoint was a glycated haemoglobin (HbA1c) reduction of ≥0.5% (5.5 mmol/mol) without weight gain at 52 weeks.

RESULTS

Of a total of 111 patients (mean age 59.2 years, mean body mass index [BMI] 26.6 kg/m² , 61.3% men), 54 patients received ipragliflozin and 57 received sitagliptin. After 52 weeks, achievement of the primary endpoint was not significantly different (37.0% and 40.3%; P = 0.72). HbA1c reduction rate at 24 weeks was greater for sitagliptin (56.1%) than for ipragliflozin (31.5%; P = 0.01). From 24 to 52 weeks, the HbA1c reduction with sitagliptin was attenuated, with no significant difference in HbA1c reduction after 52 weeks between sitagliptin (54.4%) and ipragliflozin (38.9%; P = 0.10). Improvements in BMI, C-peptide and high-density lipoprotein cholesterol were greater with ipragliflozin than with sitagliptin. Adverse events occurred in 17 patients with ipragliflozin and in 10 patients with sitagliptin (P = 0.11).

CONCLUSION

The HbA1c-lowering effect at 24 weeks was greater with sitagliptin than with ipragliflozin, but with no difference in efficacy related to HbA1c and body weight at 52 weeks. However, some ASCVD risk factors improved with ipragliflozin.