Does metformin reduce the risk of cancer in obesity and diabetes? A systematic review and meta-analysis.

AIM: To evaluate the effect of metformin on cancer incidence in subjects with overweight/obesity and/or prediabetes/diabetes. MATERIALS AND METHODS: We searched MEDLINE, Embase and CENTRAL for randomized controlled trials (RCTs) in adults with overweight/obesity and/or prediabetes/diabetes that compared metformin to other interventions for ≥24 weeks. Independent reviewers selected and extracted data including population and intervention characteristics and new diagnoses of cancer. We used the RoB 2.0 risk-of-bias tool and the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) framework to assess risk of bias and certainty of evidence. RESULTS: From 14 895 records after removal of duplicates, 27 trials were included, providing a total of 10 717 subjects in the metformin group and 10 003 in the control group, with 170 and 208 new cases of cancer, respectively. Using a random-effects model, the relative risk was 1.07 (95% confidence interval 0.87-1.31), with similar results in subgroup analyses by study duration or effect of control intervention on weight. Risk of bias in most studies was low, and no evidence of publication bias was found. Trial sequential analysis provided evidence that the cumulative sample size was large enough to exclude a significant effect of metformin on cancer incidence. CONCLUSIONS: Metformin did not reduce cancer incidence in RCTs involving subjects with overweight/obesity and/or prediabetes/diabetes.

Sodium-glucose cotransporter-2 inhibitors and cancer outcomes: A systematic review and meta-analysis of randomized controlled trials.

AIMS: Concerns regarding breast and bladder cancer risk with Sodium-glucose cotransporter-2 (SGLT2) inhibitors remain controversial and its effect on cancer mortality is unknown. We aim to evaluate the association between SGLT2 inhibitors and the risk of cancer outcomes. METHODS: We searched PubMed, Embase and CENTRAL up to June 20th, 2022, for randomized controlled trials of SGLT2 inhibitors in adults, with a minimum follow-up of 48 weeks. Researchers extracted study-level data and assessed within-study risk of bias with the RoB 2.0 tool and quality of evidence with GRADE. We performed meta-analyses summarizing the relative risks (RRs) of cancer outcomes. RESULTS: Seventy-six trials encompassing 116,375 participants were selected. Overall risk of bias was low. SGLT2 inhibitors did not reduce/increase the overall risk of cancer (RR, 1.03; 95% confidence interval [CI], 0.96-1.10) and cancer mortality (RR, 0.99; 95% CI, 0.85-1.16). SGLT2 inhibitors likely result in little to no difference in the risk of breast (RR, 1.01; 95% CI 0.77-1.32) and bladder cancers (RR, 0.93; 95% CI 0.71-1.21). Trial sequential analysis provided evidence that the sample size was sufficient to avoid missing alternative results. CONCLUSIONS: SGLT2 inhibitors are not associated with an increased risk of cancer outcomes, providing reassuring data regarding previous safety concerns.

Effects of transcranial direct current stimulation associated with hypocaloric diet on glucose homeostasis in obesity.

OBJECTIVE: The aim of this study was to test the effects of repetitive active transcranial direct current stimulation (tDCS) over the right dorsolateral prefrontal cortex (rDLPFC) associated with a hypocaloric diet on glucose homeostasis in people with excessive weight. METHODS: Adults with overweight or obesity were selected in a randomized, double-blind pilot study to complete 4 weeks (20 sessions) of fixed-dose tDCS (2 mA, 20 minutes) delivered over the rDLPFC and associated with a standard hypocaloric diet. Participants were randomly assigned (1:1) and stratified by sex to the active tDCS group (active) or the sham tDCS group (sham). Changes in glucose homeostasis were assessed in a 4-hour liquid meal tolerance test, performed before and after the intervention. RESULTS: Twenty-eight participants were randomized (79% with obesity; mean [SD] age 37.6 [5.8] years). After the intervention, fasting plasma glucose (mean [95% CI], -7.8 mg/dL [-14.0 to -1.6]) and insulin levels (-7.7 µIU/mL [-13.9 to -1.6]) decreased in the active compared with the sham. Similarly, the Matsuda insulin sensitivity index increase in the active (4.7 pmol-1  × mmol-1 [1.6 to 7.8]) compared with the sham (0.6 pmol-1  × mmol-1 [-1.4 to 3.2]). CONCLUSIONS: Repetitive, active tDCS over the rDLPFC could be a promising noninvasive technique to improve glucose homeostasis in individuals with overweight or obesity on a low-calorie diet, highlighting the importance of investigating this intervention modality in individuals with type 2 diabetes mellitus.