Vildagliptin has the same safety profile as a sulfonylurea on bone metabolism and bone mineral density in post-menopausal women with type 2 diabetes: a randomized controlled trial

This study is part of the BoneGLIC study (registered at Clinical Trials.gov with Number NCT01679899). It is a 12-month, one-center (Curitiba Diabetes Center, Brazil), randomized controlled trial. All study subjects were postmenopausal women diagnosed with T2D treated with metformin, who fulfilled the following inclusion criteria: age ≥40 years old and glycated hemoglobin (HbA1c) ≥6.5% (48 mmol/mol) at randomization. The exclusion criteria included an acute cardiovascular event (cardiac, cerebral or peripheral), chronic dialysis and/or renal transplantation, serum creatinine >1.5 mg/dL, human immunodeficiency virus infection, severe autoimmune disease, chronic treatment with oral steroids (>30 consecutive days), current or previous treatment with incretin mimetics (iDPP-4 or GLP-1 receptor agonists), current or previous treatment with pioglitazone or rosiglitazone, body mass index (BMI) >50 kg/m², HbA1c ≥9%, chronic or alcoholic liver disease, plasma triglycerides >1000 mg/dL (11.3 mmol/L), serum 25-hidroxi-vitamin D (25-OH-vit.D) <20 ng/mL, abnormal levels of parathyroid hormone (PTH), serum cortisol, insulin-like growth factor 1 (IGF-1) or growth hormone (GH) and history of previous fragility fracture. Patients were recruited via media outlets, including online and newspaper advertisements, flyers, radio announcements or after a search for T2D treatment at the research center.

The study protocol was approved by the site ethical review committee in agreement with the Declaration of Helsinki. All participating patients provided their written informed consent prior to screening.

Fifty-six postmenopausal women with T2D were enrolled from October 2012 to October 2014. Randomization occurred through the free online software Research Randomizer version 4.0 (https://​www.​randomizer.​org/​), which randomly generates numbers that indicate the specific group to which the research subject will be allocated [15]. Randomization and enrollment were performed by the study coordinator, and the medical investigators assigned participants to the intervention. Blinding was implemented when assessing outcomes, in which the staff personal who analyzed the outcomes did not have access to the identification of the patient examined or the group that the individual was allocated.

Vildagliptin (Novartis Pharma AG, Basel, Switzerland) was administered at 50 mg orally twice daily, and the comparator (control) gliclazide MR (Laboratoires Servier, Neuilly sur-Seine, France) was initially administered at 120 mg orally once daily (maximum dose). If the maximum dose of gliclazide MR was not tolerated or was otherwise associated with unacceptable adverse events, a dose reduction to 60 mg once daily was allowed at the discretion of the investigator. After randomization, the treatment with vildagliptin or gliclazide MR was open-label throughout the study. All patients in both groups received a similar orientation for diet and physical activity performed by the same study site nutritionist, with reinforcement throughout the study.

Coincidentally, all subjects randomized were treated with the oral antidiabetic metformin, and drug naïve or insulin-treated subjects were not randomized.

Anthropometric data were recorded at baseline and each study visit by the same investigator.

The primary study outcomes, the biochemical markers of bone turnover, serum carboxy-terminal telopeptide of type 1 collagen (CTX), serum osteocalcin (OC), serum amino-terminal propeptide of procollagen type I (PINP) and urinary amino-terminal telopeptide of type 1 collagen (U-NTX), were measured at baseline and month 6. Samples of U-NTX, CTX, and OC markers were also collected in month 12.

The secondary outcomes included the BMD of the lumbar spine, femoral neck and total hip that were measured at baseline and month 12. The safety secondary variables alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were collected at baseline, months 6 and 12, and calcitonin was assessed at baseline and month 12.

Exploratory variables, including fasting plasma glucose (FPG), postprandial glucose (PPG) and glycated hemoglobin (HbA1c), were assessed at baseline and every three months until the end of the study at month 12.

Venous blood samples were collected between 7:30 and 9:00 a.m. in the fasting state to measure FPG, HbA1c, lipids, ALT, AST, bone formation markers OC, PINP and the bone resorption marker CTX. Samples were left to clot for 30 min and subsequently centrifuged. The serum was frozen and maintained at –70 °C and then unfrozen for the evaluation of bone turnover markers. PPG was collected 2 h after lunch. The second-morning void urine sample was collected to evaluate the bone resorption marker U-NTX (2 mL urine in a sterile screw cap container), and the results were reported in nmol of bone collagen equivalents per mmol creatinine (nmol BCE/mmol creatinine).

FPG and PPG were measured using the hexokinase method. HbA1c was measured via high-pressure liquid chromatography (HPLC). OC, CTX, and PINP were assessed using an electrochemiluminescence assay (Roche Diagnostics, Basel, Switzerland). The OC inter-assay and intra-assay variabilities are 3.2 and 1.2%, respectively (normal range 15.0–46.0 ng/mL for postmenopausal women). The CTX inter-assay and intra-assay variabilities are 7.8 and 3.9%, respectively (normal range 0.106–1.008 ng/mL for postmenopausal women). The PINP inter-assay and intra-assay variabilities are 2.0 and 1.6%, respectively (normal range 16.3–73.9 µg/L for postmenopausal women). U-NTX were measured via enzyme immunoassay (EIA, Grifols Asia Pacific Pte. Ltd, Singapore). The inter-assay and intra-assay variabilities are 17.2 and 8.6%, respectively (normal range 26.0–83.0 nmol BCE/mmol creatinine for postmenopausal women). The BMD was assessed in agreement with the standards of the International Society for Clinical Densitometry (ISCD) via dual-energy X-ray absorptiometry (DXA, Discovery W, Hologic Inc., Marlborough, MA, USA). The short-term in vivo precision error (root-mean-square standard deviation) was 0.027 g/cm² for L1–L4 (1.1%); 0.034 g/cm² for the femoral neck (2.0%) and 0.032 g/cm² (1.6%) for the total hip.

Physical activity (PA) was defined using the WHO concept (available at http://​www.​who.​int/​topics/​physical_​activity/​en/​) as any bodily movement produced by skeletal muscles that requires energy expenditure, and it was qualitatively evaluated as yes or no. The calcium daily intake was estimated by the sum of the dietary and supplemental ingestion.

The safety and tolerability were recorded at each visit by the investigators. Major hypoglycemia was defined as an event that required the assistance of another individual to actively administer glucagon, carbohydrate, or other resuscitative measures. Minor hypoglycemia was defined as an event during which typical symptoms of hypoglycemia were accompanied by a measured plasma glucose ≤70 mg/dL (3.9 mmol/L) or not accompanied by classic symptoms of hypoglycemia but with a measured plasma glucose ≤70 mg/dL. An event during which symptoms of hypoglycemia were not accompanied by a plasma glucose determination, but that was presumably caused by a plasma glucose ≤70 mg/dL was considered minor hypoglycemia.

The sample size was calculated to obtain a significant result in at least one of the primary outcomes (difference >30% in bone remodeling markers). The change in the OC marker was applied for the calculation. Nineteen patients per group were required to provide 80% power and a 0.05% significance level to detect a difference between means of at least 30% among the two treatments. The expected screening failure rate was 30%, and the estimated dropout rate was 8%; thus, 56 patients were planned for enrollment.

The baseline characteristics were summarized based on the dataset of the intention to treat (ITT) population. The key features at baseline were represented, and comparisons among groups were made using Student t tests (parametric variables with normal distribution) or Mann–Whitney tests (non-normal distribution). For primary and secondary variables, which were all quantitative and of a normal distribution, Student t tests were used for the statistical analysis. The final statistical analysis of the results was performed taking into consideration only the difference between the means of the analyzed parameters in the 6th and 12th months and the baseline value. Statistical analysis was performed using SPSS for Windows (version 20.0; SPSS, Chicago, IL, USA). All inferential statistical tests were conducted at a p < 0.05 (two-sided). Unless otherwise stated, data are presented as the mean ± standard deviation (SD).