The combination of sodium-glucose transporter-2 (SGLT-2) inhibitors and metformin is not associated with an increase in fracture risk among patients with type 2 diabetes (T2D), according to a new meta-analysis of 25 randomized, controlled trials.
Researchers at The Second Clinical College of Dalian Medical University in Jiangsu, China, compared fracture risk associated with the metformin/SLGT2 combination to metformin alone as well as other T2D therapeutics, and found no differences in risk. The study was published online Aug. 11 in Osteoporosis International.
T2D is associated with an increased risk of fracture, though causative mechanisms remain uncertain. Some lines of evidence suggest multiple factors may contribute to fractures, including hyperglycemia, oxidative stress, toxic effects of advanced glycosylation end-products, altered insulin levels, and treatment-induced hypoglycemia, as well as an association between T2D and increased risk of falls.
Antidiabetes drugs can have positive or negative effects on bone. thiazolidinediones, insulin, and sulfonylureas may increase risk of fractures, while dipeptidyl peptidase-4 (DPP-4) inhibitors and glucagon-like peptide-2 (GLP-2) receptor agonists may be protective. Metformin may also reduce fracture risk.
SGLT-2 inhibitors interrupt glucose reabsorption in the kidney, leading to improved glycemic control. Other benefits include improved renal and cardiovascular outcomes, weight loss, and reduced blood pressure, liver fat, and serum uric acid levels.
These properties have made SGLT-2 inhibitors combined with metformin an important therapy for patients at high risk of atherosclerotic disease, or who have heart failure or chronic kidney disease.
But SGLT-2 inhibition increases osmotic diuresis, and this could alter the mineral balance within bone. Some studies also showed that SGLT-2 inhibitors led to changes in bone turnover markers, bone mineral density, and bone microarchitecture. Observational studies of the SGLT-2 inhibitor canagliflozin found associations with a higher rate of fracture risk in patients taking the drug.
Such studies carry the risk of confounding factors, so the researchers took advantage of the fact that many recent clinical trials have examined the impact of SGLT-2 inhibitors on T2D. They pooled data from 25 clinical trials with a total of 19,500 participants, 9,662 of whom received SGLT-2 inhibitors plus metformin; 9,838 received other active comparators.
The fracture rate was 0.91% in the SGLT-2 inhibitors/metformin group, and 0.80% among controls (odds ratio, 0.97; 95% CI, 0.71-1.32), with no heterogeneity. Metformin alone was not associated with a change in fracture rate (OR, 0.95; 95% CI, 0.44-2.08), nor were other forms of diabetes control (OR, 0.95; 95% CI, 0.69-1.31).
There were some differences in fracture risk among SGLT-2 inhibitors when studied individually, though none differed significantly from controls. The highest risk was associated with the canagliflozin/metformin (OR, 2.19; 95% CI, 0.66-7.27), followed by dapagliflozin/metformin (OR, 0.91; 95% CI, 0.50-1.64), empagliflozin/metformin (OR, 0.94; 95% CI, 0.59-1.50), and ertugliflozin/metformin (OR, 0.76; 95% CI, 0.38-1.54).
There were no differences with respect to hip or lumbar spine fractures, or other fractures. The researchers found no differences in bone mineral density or bone turnover markers.
The meta-analysis is limited by the relatively short average follow-up in the included studies, which was 61 weeks. Bone damage may occur over longer time periods. Bone fractures were also not a prespecified adverse event in most included studies.
The studies also did not provide detailed information on the types of fractures experienced, such as whether they were result of a fall, or the location of the fracture, or bone health parameters. Although the results support a belief that SGLT-2 inhibitors do not adversely affect bone health, “given limited information on bone health outcomes, further work is needed to validate this conclusion,” the authors wrote.
The authors did not disclose any funding and had no relevant conflicts of interest.
SOURCE: B-B Qian et al. Osteoporosis Int. 2020 Aug 11. doi: 10.1007/s00198-020-05590-y.