Metformin improves endothelial function in type 1 diabetic subjects: a pilot, placebo-controlled randomized study

Upregulation of Anti-Angiogenic miR-106b-3p Correlates Negatively with IGF-1 and Vascular Health Parameters in a Model of Subclinical Cardiovascular Disease: Study with Metformin Therapy

Well-controlled type 1 diabetes mellitus (T1DM) is regarded as a model of subclinical cardiovascular disease (CVD), characterized by inflammation and adverse vascular health. However, the underlying mechanisms are not fully understood. We investigated insulin-like growth factor-1 (IGF-1) and IGF-binding protein-3 (IGFBP-3) levels, their correlation to miR-106b-3p expression in a subclinical CVD model, and the cardioprotective effect of metformin. A total of 20 controls and 29 well-controlled T1DM subjects were studied. Plasma IGF-1, IGFBP-3 levels, and miR-106b-3p expression in colony-forming unit-Hills were analyzed and compared with vascular markers. miR-106b-3p was upregulated in T1DM (p < 0.05) and negatively correlated with pro-angiogenic markers CD34+/100-lymphocytes (p < 0.05) and IGF-1 (p < 0.05). IGF-1 was downregulated in T1DM (p < 0.01), which was associated with increased inflammatory markers TNF-α, CRP, and IL-10 and reduced CD34+/100-lymphocytes. IGFBP-3 had no significant results. Metformin had no effect on IGF-1 but significantly reduced miR-106b-3p (p < 0.0001). An Ingenuity Pathway analysis predicted miR-106b-3p to inhibit PDGFA, PIK3CG, GDNF, and ADAMTS13, which activated CVD. Metformin was predicted to be cardioprotective by inhibiting miR-106b-3p. In conclusion: Subclinical CVD is characterized by a cardio-adverse profile of low IGF-1 and upregulated miR-106b-3p. We demonstrated that the cardioprotective effect of metformin may be via downregulation of upregulated miR-106b-3p and its effect on downstream targets.

The Effect of Additional Treatment with Empagliflozin or Semaglutide on Endothelial Function and Arterial Stiffness in Subjects with Type 1 Diabetes Mellitus-ENDIS Study

We investigated the effect of additional treatment with newer antidiabetic drugs on endothelium function and arterial stiffness in subjects with type 1 diabetes mellitus (T1DM) without cardiovascular diseases. A total of 89 participants, all users of CGMS (continuous monitoring glucose system), were randomized into three comparable groups, receiving empagliflozin (E; n = 30), receiving semaglutide (S; n = 30), and a control group (C; n = 29). At baseline and 12 weeks post treatment, we measured FMD (brachial artery flow-mediated dilation) and FBF (forearm blood flow as reactive hyperemia assessed with strain gauge plethysmography) as parameters of endothelial function, as well as pulse wave velocity (PWV) and peripheral resistance as parameters of arterial stiffness. Improvement in FMD was significant in both intervention groups compared to controls (E group 2.0-fold, p = 0.000 and S group 1.9-fold, p = 0.000), with no changes between those two groups (p = 0.745). During the evaluation of FBF, there were statistically insignificant improvements in both therapeutic groups compared to controls (E group 1.39-fold, p = 0.074 and S group 1.22-fold, p = 0.701). In arterial stiffness parameters, improvements were seen only in the semaglutide group, with a decline in peripheral resistance by 5.1% (p = 0.046). We can conclude that, for arterial stiffness, semaglutide seems better, but both drugs positively impact endothelial function and, thus, could also have a protective role in T1DM.

Effects of metformin on glycaemic variability in combination with insulin in overweight/obese patients with type 1 diabetes

BACKGROUND

The prevalence of overweight and obesity in type 1 diabetes mellitus (T1DM) individuals is increasing. Overweight people with T1DM may be insulin resistant. Glycaemic variability (GV) is an emerging measure of glycaemic control. The aim of this study is to investigate whether metformin, in adjunct to insulin, would have any favourable effect on GV.

METHODS

This was a multi-centre, open-label randomised crossover study. Twenty-four overweight/obese T1DM patients aged ⩾18 years old with HbA1c ⩾ 7.0% (53 mmol/mol) were recruited and randomised into two study arms. For first 6-week, one arm remained on standard of care (SOC), the other arm received metformin, adjunctive to SOC. After 2-week washout, patients crossed over and continued for another 6 weeks. Glycaemic variability, other glycaemic parameters and metabolic profile were monitored.

RESULTS

There were significant reduction in metformin group for GV: mean (0.18 ± 1.73 vs -0.95 ± 1.24, p = 0.014), %CV (-15.84 (18.92) vs -19.08 (24.53), p = 0.044), glycemic risk assessment of diabetes equation (-0.69 (3.83) vs -1.61 (3.61), p = 0.047), continuous overlapping net glycaemic action (0.25 ± 1.62 vs -0.85 ± 1.22, p = 0.013), J-index (-0.75 (21.91) vs -7.11 (13.86), p = 0.034), time in range (1.13 ± 14.12% vs 10.83 ± 15.47%, p = 0.032); changes of systolic blood pressure (2.78 ± 11.19 mmHg vs -4.30 ± 9.81 mmHg, p = 0.027) and total daily dose (TDD) insulin (0.0 (3.33) units vs -2.17 (11.45) units, p = 0.012). Hypoglycaemic episodes were not significant in between groups.

CONCLUSION

Metformin showed favourable effect on GV in overweight/obese T1DM patients and reduction in systolic blood pressure, TDD insulin, fasting venous glucose and fructosamine.

A combination of metformin and insulin improve cardiovascular and cerebrovascular risk factors in individuals with type 1 diabetes mellitus

BACKGROUND

This study aims to further clarify whether the addition of metformin to insulin treatment improve cardiovascular and cerebrovascular risk factors in individuals with T1DM.

METHODS

Electronic databases were searched for randomized controlled trials in which the efficacy and safety of metformin were compared with those of a placebo for risk factors of cardiovascular and cerebrovascular disease among individuals with T1DM, and a meta-analysis was conducted.

RESULTS

Thirteen cardiovascular studies were identified. In the metformin group, mean carotid intimal media thickness was significantly reduced by 0.03 mm, ascending aortic pulse wave velocity by 6.3 m/s, descending aortic wall shear stress by 1.77 dyn/cm² (P = 0.02), insulin daily dose by 0.05 U/kg/d, body weight by 2.27 kg, fat-free mass by 1.32 kg, body mass index by 0.58 kg/m², hip circumference by 0.29 m, and low-density lipoprotein by 0.16 mmol/L, all above are P < 0.05. In the metformin group, flow-mediated dilation was increased by 1.29 %, glucose infusion rate/insulin by 18.22 mg/(kg⋅min)/μIU/μL, and waist-to-hip ratio by 0.02, all above are P < 0.00001. The metformin group showed no differences in blood pressure, reactive hyperemia index, waist circumference, triglyceride, total cholesterol, high-density lipoprotein cholesterol, or body mass index Z score. For cerebrovascular studies were identified. But none of them had a risk factor assessment.

CONCLUSIONS

Metformin can ameliorate cardiovascular and cerebrovascular risk factors through non-hypoglycemic multiple pathways in individuals with T1DM.

Metformin: Is it a drug for all reasons and diseases?

Metformin was first used to treat type 2 diabetes in the late 1950s and in 2022 remains the first-choice drug used daily by approximately 150 million people. An accumulation of positive pre-clinical and clinical data has stimulated interest in re-purposing metformin to treat a variety of diseases including COVID-19. In polycystic ovary syndrome metformin improves insulin sensitivity. In type 1 diabetes metformin may help reduce the insulin dose. Meta-analysis and data from pre-clinical and clinical studies link metformin to a reduction in the incidence of cancer. Clinical trials, including MILES (Metformin In Longevity Study), and TAME (Targeting Aging with Metformin), have been designed to determine if metformin can offset aging and extend lifespan. Pre-clinical and clinical data suggest that metformin, via suppression of pro-inflammatory pathways, protection of mitochondria and vascular function, and direct actions on neuronal stem cells, may protect against neurodegenerative diseases. Metformin has also been studied for its anti-bacterial, -viral, -malaria efficacy. Collectively, these data raise the question: Is metformin a drug for all diseases? It remains unclear as to whether all of these putative beneficial effects are secondary to its actions as an anti-hyperglycemic and insulin-sensitizing drug, or result from other cellular actions, including inhibition of mTOR (mammalian target for rapamycin), or direct anti-viral actions. Clarification is also sought as to whether data from ex vivo studies based on the use of high concentrations of metformin can be translated into clinical benefits, or whether they reflect a 'Paracelsus' effect. The environmental impact of metformin, a drug with no known metabolites, is another emerging issue that has been linked to endocrine disruption in fish, and extensive use in T2D has also raised concerns over effects on human reproduction. The objectives for this review are to: 1) evaluate the putative mechanism(s) of action of metformin; 2) analyze the controversial evidence for metformin's effectiveness in the treatment of diseases other than type 2 diabetes; 3) assess the reproducibility of the data, and finally 4) reach an informed conclusion as to whether metformin is a drug for all diseases and reasons. We conclude that the primary clinical benefits of metformin result from its insulin-sensitizing and antihyperglycaemic effects that secondarily contribute to a reduced risk of a number of diseases and thereby enhancing healthspan. However, benefits like improving vascular endothelial function that are independent of effects on glucose homeostasis add to metformin's therapeutic actions.

Glucose-Lowering Therapy beyond Insulin in Type 1 Diabetes: A Narrative Review on Existing Evidence from Randomized Controlled Trials and Clinical Perspective

Background: In Type 1 diabetes (T1D), according to the most recent guidelines, the everyday glucose-lowering treatment is still restricted to the use of subcutaneous insulin, while multiple therapeutic options exist for Type 2 diabetes (T2D). Methods: For this narrative review we unsystematically screened PubMed and Embase to identify clinical trials which investigated glucose-lowering agents as an adjunct to insulin treatment in people with T1D. Published studies up to March 2022 were included. We discuss the safety and efficacy in modifying cardiovascular risk factors for each drug, the current status of research, and provide a clinical perspective. Results: For several adjunct agents, in T1D, the scientific evidence demonstrates improvements in HbA1c, reductions in the risk of hypoglycemia, and achievements of lower insulin requirements, as well as positive effects on cardiovascular risk factors, such as blood lipids, blood pressure, and weight. As the prevalence of obesity, the major driver for double diabetes, is rising, weight and cardiovascular risk factor management is becoming increasingly important in people with T1D. Conclusions: Adjunct glucose-lowering agents, intended to be used in T2D, bear the potential to beneficially impact on cardiovascular risk factors when investigated in the T1D population and are suggested to be more extensively considered as potentially disease-modifying drugs in the future and should be investigated for hard cardiovascular endpoints.

Empagliflozin-Metformin Combination Has Antioxidative and Anti-Inflammatory Properties that Correlate with Vascular Protection in Adults with Type 1 Diabetes

Methods

40 individuals with type 1 diabetes (average age of 44.7 ± 2.5 years) were randomized into four groups: (1) control (placebo), (2) empagliflozin 25 mg daily, (3) metformin 2000 mg daily, and (4) empagliflozin-metformin combination (25 mg and 2000 mg daily, respectively). At inclusion and after 12 weeks of treatment, the blood samples were collected, and the oxidative stress (total antioxidative status (TAS), superoxide dismutase (SOD), glutathione peroxidase (GPx), uric acid, advanced oxidation protein products (AOPP), advanced glycosylation end products ((AGE) and isoprostane), and inflammation (C-reactive protein (CRP) and interleukin-6 (IL-6)) parameters were determined.

Results

The empagliflozin-metformin combination increased levels of the antioxidants (TAS, SOD, and GPx up to 1.1-fold; P < 0.01), decreased the levels of prooxidants (AOPP and isoprostanes up to 1.2-fold, P < 0.01; AGE up to 1.5-fold, P < 0.01), and decreased inflammatory parameters (up to 1.5-fold, CRP P < 0.01; IL-6 P < 0.001). Antioxidative action was associated with the improvement in arterial function (obtained in the previous study) in the empagliflozin-metformin combination group.

Conclusion

Empagliflozin-metformin combination has strong antioxidative and anti-inflammatory capacity, in adults with type 1 diabetes that is greater than that for the individual drugs. Its antioxidative activity at least partially explains the improvement in arterial function. Therefore, it appears that the combination provides the most powerful vascular protection.

Metformin in cardiovascular diabetology: a focused review of its impact on endothelial function

As a first-line treatment for diabetes, the insulin-sensitizing biguanide, metformin, regulates glucose levels and positively affects cardiovascular function in patients with diabetes and cardiovascular complications. Endothelial dysfunction (ED) represents the primary pathological change of multiple vascular diseases, because it causes decreased arterial plasticity, increased vascular resistance, reduced tissue perfusion and atherosclerosis. Caused by “biochemical injury”, ED is also an independent predictor of cardiovascular events. Accumulating evidence shows that metformin improves ED through liver kinase B1 (LKB1)/5'-adenosine monophosphat-activated protein kinase (AMPK) and AMPK-independent targets, including nuclear factor-kappa B (NF-κB), phosphatidylinositol 3 kinase-protein kinase B (PI3K-Akt), endothelial nitric oxide synthase (eNOS), sirtuin 1 (SIRT1), forkhead box O1 (FOXO1), krüppel-like factor 4 (KLF4) and krüppel-like factor 2 (KLF2). Evaluating the effects of metformin on endothelial cell functions would facilitate our understanding of the therapeutic potential of metformin in cardiovascular diabetology (including diabetes and its cardiovascular complications). This article reviews the physiological and pathological functions of endothelial cells and the intact endothelium, reviews the latest research of metformin in the treatment of diabetes and related cardiovascular complications, and focuses on the mechanism of action of metformin in regulating endothelial cell functions.

Insulin resistance in type 1 diabetes managed with metformin (INTIMET): Study protocol of a double-blind placebo-controlled, randomised trial

BACKGROUND

Insulin resistance is an under-recognised metabolic defect and cardiovascular risk factor in Type 1 diabetes. Whether metformin improves hepatic, muscle or adipose tissue insulin sensitivity has not been studied in adults with Type 1 diabetes. We initiated the INTIMET study (INsulin resistance in Type 1 diabetes managed with METformin), a double-blind randomised, placebo-controlled trial to measure the effect of metformin on tissue-specific insulin resistance in adults with Type 1 diabetes.

METHODS

We will study 40 adults aged 20-55 years with Type 1 diabetes (HbA1c ≤ 80 mmol/mol [9.5%], fasting C-peptide <0.3 nmol/L) and 20 age-, gender- and body mass index (BMI)-matched controls. Insulin sensitivity will be determined by the two-step hyperinsulinaemic-euglycaemic clamp method with deuterated glucose to document liver, muscle and adipose insulin sensitivity. Subjects with Type 1 diabetes will be randomised to metformin extended-release 1500 mg daily or matched placebo for 26 weeks. The primary outcome is change in hepatic insulin sensitivity, assessed by change in basal rate of appearance (Ra) of glucose and suppression of endogenous glucose production (EGP) during the low-dose stage of the clamp.

CONCLUSION

The INTIMET study is the first clinical trial to quantify the impact of metformin on liver, muscle and adipose insulin resistance in adults with Type 1 diabetes. This study may identify factors that predict an individual's response to metformin in Type 1 diabetes.

TRIAL REGISTRATION

ACTRN12619001440112.

Pathophysiological Association between Diabetes Mellitus and Endothelial Dysfunction

Endothelial dysfunction plays a critical role in atherosclerosis progression, leading to cardiovascular complications. There are significant associations between diabetes mellitus, oxidative stress, and endothelial dysfunction. Oxidative stress is increased by chronic hyperglycemia and acute glucose fluctuations induced by postprandial hyperglycemia in patients with diabetes mellitus. In addition, selective insulin resistance in the phosphoinositide 3-kinase/Akt/endothelial nitric oxide (NO) synthase pathway in endothelial cells is involved in decreased NO production and increased endothelin-1 production from the endothelium, resulting in endothelial dysfunction. In a clinical setting, selecting an appropriate therapeutic intervention that improves or augments endothelial function is important for preventing diabetic vascular complications. Hypoglycemic drugs that reduce glucose fluctuations by decreasing the postprandial rise in blood glucose levels, such as glinides, α-glucosidase inhibitors and dipeptidyl peptidase 4 inhibitors, and hypoglycemic drugs that ameliorate insulin sensitivity, such as thiazolidinediones and metformin, are expected to improve or augment endothelial function in patients with diabetes. Glucagon-like peptide 1 receptor agonists, metformin, and sodium-glucose cotransporter 2 inhibitors may improve endothelial function through multiple mechanisms, some of which are independent of glucose control or insulin signaling. Oral administration of antioxidants is not recommended in patients with diabetes due to the lack of evidence for the efficacy against diabetic complications.

Cardiovascular Safety and Benefits of Noninsulin Antihyperglycemic Drugs for the Treatment of Type 2 Diabetes Mellitus-Part 1

Cardiovascular disease (CVD) is a major contributor to the morbidity and mortality associated with type 2 diabetes mellitus (T2DM). With T2DM growing in pandemic proportions, there will be profound healthcare implications of CVD in person with diabetes. The ideal drugs to improve outcomes in T2DM are those having antiglycemic efficacy in addition to cardiovascular (CV) safety, which has to be determined in appropriately designed CV outcome trials as mandated by regulatory agencies. Available evidence is largely supportive of metformin's CV safety and potential CVD risk reduction effects, whereas sulfonylureas are either CV risk neutral or are associated with variable CVD risk. Pioglitazone was also associated with improved CVD risk in patients with diabetes. The more recent antihyperglycemic medications have shown promise with regards to CVD risk reduction in T2DM patients at a high CV risk. Glucagon-like peptide-1 receptor agonists, a type of incretin-based therapy, were associated with better CV outcomes and mortality in T2DM patients, leading to the Food and Drug Administration approval of liraglutide to reduce CVD risk in high-risk T2DM patients. Ongoing and planned randomized controlled trials of the newer drugs should clarify the possibility of class effects, and of CVD risk reduction benefits in low-moderate CV risk patients. While metformin remains the first-line antiglycemic therapy in T2DM, glucagon-like peptide-1 receptor agonists should be appropriately prescribed in T2DM patients with baseline CVD or in those at a high CVD risk to improve CV outcomes. Dipeptidyl peptidase-4 inhibitors and sodium-glucose cotransporter-2 inhibitors are discussed in the second part of this review.

The impact of pharmacological and lifestyle interventions on body weight in people with type 1 diabetes: A systematic review and meta-analysis

AIM

To systematically review the effects of pharmacological and lifestyle interventions on body weight as a secondary outcome in people with type 1 diabetes.

METHODS

The Ovid Medline, Embase and Cochrane Library databases were searched for relevant pharmacological (glucagon-like peptide-1 [GLP-1] receptor agonist, sodium-glucose co-transporter-2 [SGLT-2] inhibitor, dipeptidyl peptidase-4 [DPP-4] inhibitor and metformin) and lifestyle intervention studies (diet and exercise) for adults with type 1 diabetes reporting body weight change and HbA1c published from January 2000 to May 2020. Meta-analyses were performed for 16 randomized controlled trials (RCTs).

RESULTS

Thirty-three RCTs (n = 9344 participants), 26 pharmacological (on average 43.9 years, 83.1 kg, HbA1c 8.1%; 55.8% male) and seven lifestyle-based interventions (on average 37.0 years, 85.0 kg, HbA1c 8.1%; 84.6% male), were analysed. The GLP-1 receptor agonist liraglutide 0.6 mg (mean difference [MD]: -2.22 kg [95% CI: -2.55 to -1.90]), 1.2 mg (MD: -3.74 kg [95% CI: -4.16 to -3.33]) and 1.8 mg (MD: -4.85 kg [95% CI: -5.29 to -4.41]), and the SGLT-2 inhibitors empagliflozin 2.5 mg (MD: -1.47 kg [95% CI: -2.23 to -0.71]), 10 mg (MD: -2.77 kg [95% CI: -3.24 to -2.31]) and 25 mg (MD: -3.06 kg [95% CI: -3.57 to -2.55]) and sotagliflozin 200 mg (MD: -2.40 kg [95% CI: -2.87 to -1.94]) and 400 mg (MD: -3.23 [95% CI: -3.73 to -2.72]) were associated with significant reductions in body weight. No significant effect on body weight was found for DPP-4 inhibitors, other GLP-1-receptor agonists, metformin, or for lifestyle interventions (i.e. exercise and diet).

CONCLUSIONS

In people with type 1 diabetes, several adjuvant pharmacological interventions showed weight reduction as a secondary outcome. Future studies in overweight people with type 1 diabetes are needed to establish whether the lifestyle and pharmacological interventions reviewed here have potential as components of complex interventions aimed at body weight reduction as a primary outcome.

Can Metformin Exert as an Active Drug on Endothelial Dysfunction in Diabetic Subjects?

Cardiovascular mortality is a major cause of death among in type 2 diabetes (T2DM). Endothelial dysfunction (ED) is a well-known important risk factor for the development of diabetes cardiovascular complications. Therefore, the prevention of diabetic macroangiopathies by preserving endothelial function represents a major therapeutic concern for all National Health Systems. Several complex mechanisms support ED in diabetic patients, frequently cross-talking each other: uncoupling of eNOS with impaired endothelium-dependent vascular response, increased ROS production, mitochondrial dysfunction, activation of polyol pathway, generation of advanced glycation end-products (AGEs), activation of protein kinase C (PKC), endothelial inflammation, endothelial apoptosis and senescence, and dysregulation of microRNAs (miRNAs). Metformin is a milestone in T2DM treatment. To date, according to most recent EASD/ADA guidelines, it still represents the first-choice drug in these patients. Intriguingly, several extraglycemic effects of metformin have been recently observed, among which large preclinical and clinical evidence support metformin’s efficacy against ED in T2DM. Metformin seems effective thanks to its favorable action on all the aforementioned pathophysiological ED mechanisms. AMPK pharmacological activation plays a key role, with metformin inhibiting inflammation and improving ED. Therefore, aim of this review is to assess metformin’s beneficial effects on endothelial dysfunction in T2DM, which could preempt development of atherosclerosis.

Age, sex, disease severity, and disease duration difference in placebo response: implications from a meta-analysis of diabetes mellitus

BACKGROUND

The placebo response in patients with diabetes mellitus is very common. A systematic evaluation needs to be updated with the current evidence about the placebo response in diabetes mellitus and the associated factors in clinical trials of anti-diabetic medicine.

METHODS

Literature research was conducted in Medline, Embase, the Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov for studies published between the date of inception and June 2019. Randomized placebo-controlled trials conducted in type 1and type 2 diabetes mellitus (T1DM/T2DM) were included. Random-effects model and meta-regression analysis were accordingly used. This meta-analysis was registered in PROSPERO as CRD42014009373.

RESULTS

Significantly weight elevation (effect size (ES) = 0.33 kg, 95% CI, 0.03 to 0.61 kg) was observed in patients with placebo treatments in T1DM subgroup while significantly HbA1c reduction (ES = - 0.12%, 95% CI, - 0.16 to - 0.07%) and weight reduction (ES = - 0.40 kg, 95% CI, - 0.50 to - 0.29 kg) were observed in patients with placebo treatments in T2DM subgroup. Greater HbA1c reduction was observed in patients with injectable placebo treatments (ES = - 0.22%, 95% CI, - 0.32 to - 0.11%) versus oral types (ES = - 0.09%, 95% CI, - 0.14 to - 0.04%) in T2DM (P = 0.03). Older age (β = - 0.01, 95% CI, - 0.02 to - 0.01, P < 0.01) and longer diabetes duration (β = - 0.02, 95% CI, - 0.03 to - 0.21 × 10^-2, P = 0.03) was significantly associated with more HbA1c reduction by placebo in T1DM. However, younger age (β = 0.02, 95% CI, 0.01 to 0.03, P = 0.01), lower male percentage (β = 0.01, 95% CI, 0.22 × 10^-2, 0.01, P < 0.01), higher baseline BMI (β = - 0.02, 95% CI, - 0.04 to - 0.26 × 10^-2, P = 0.02), and higher baseline HbA1c (β = - 0.09, 95% CI, - 0.16 to - 0.01, P = 0.02) were significantly associated with more HbA1c reduction by placebo in T2DM. Shorter diabetes duration (β = 0.06, 95% CI, 0.06 to 0.10, P < 0.01) was significantly associated with more weight reduction by placebo in T2DM. However, the associations between baseline BMI, baseline HbA1c, and placebo response were insignificant after the adjusted analyses.

CONCLUSION

The placebo response in diabetes mellitus was systematically outlined. Age, sex, disease severity (indirectly reflected by baseline BMI and baseline HbA1c), and disease duration were associated with placebo response in diabetes mellitus. The association between baseline BMI, baseline HbA1c, and placebo response may be the result of regression to the mean.

Vascular and metabolic effects of metformin added to insulin therapy in patients with type 1 diabetes: A systematic review and meta-analysis

BACKGROUND

The incidence of type 1 diabetes mellitus (T1DM) is increasing among youth worldwide, translating to an increased risk ofearly-onset cardiovascular disease (CVD). Mounting studies have shown that metformin may reduce maximal carotidintima-media thickness (cIMT), improve insulin resistance and metabolic control in subjects with T1DM, and thus, may extend cardioprotective benefits. This systematic review and meta-analysis was performed to assess the efficacy and safety of metformin added to insulin therapy on reducing CVD risks and improving metabolism in T1DM.

METHODS

PubMed, EMBASE, and the Cochrane Library were systematically searched for randomized controlled trials (RCTs) that compared metformin and insulin combination (duration ≥3 months) to insulin treatment alone in T1DM. Data were expressed as weighted/standardized mean differences (MDs/SMDs) for continuous outcomes and risk ratios (RRs) for dichotomous outcomes, along with 95% confidence intervals (CIs). The Grading of Recommendations Assessment, Development and Evaluation (GRADE) was used to evaluate the overall certainty of the evidence.

RESULTS

Nineteen RCTs (n = 1540) met the eligibility criteria. Metformin treatment significantly reduced carotid artery intima-media thickness (MD -0.06 mm [95% CI -0.88, -0.28], P < .001). Though no significant difference was found in insulin sensitivity (SMD 2.21 [95% CI -1.88, 6.29], P = .29), the total daily insulin dosage (SMD -0.81 [95% CI -1.25, -0.36], P < .001) along with traditional CVD risk factors showed improvement by better glycaemic control, partial lipid profiles, diastolic blood pressure, and limited weight gain, with neutral effect on diabetic ketoacidosis, lactic acidosis, and hypoglycaemia. However, metformin therapy increased the incidence of gastrointestinal adverse events.

CONCLUSIONS

Metformin with insulin has the potential to retard the progression of atherosclerosis and provides better metabolic control in patients with T1DM, and thus, providing a potential therapeutic strategy for patients with T1DM on reducing CVD risks.

Metformin May Contribute to Inter-individual Variability for Glycemic Responses to Exercise

Metformin and exercise independently improve glycemic control. Metformin traditionally is considered to reduce hepatic glucose production, while exercise training is thought to stimulate skeletal muscle glucose disposal. Collectively, combining treatments would lead to the anticipation for additive glucose regulatory effects. Herein, we discuss recent literature suggesting that metformin may inhibit, enhance or have no effect on exercise mediated benefits toward glucose regulation, with particular emphasis on insulin sensitivity. Importantly, we address issues surrounding the impact of metformin on exercise induced glycemic benefit across multiple insulin sensitive tissues (e.g., skeletal muscle, liver, adipose, vasculature, and the brain) in effort to illuminate potential sources of inter-individual glycemic variation. Therefore, the review identifies gaps in knowledge that require attention in order to optimize medical approaches that improve care of people with elevated blood glucose levels and are at risk of cardiovascular disease.

Diabetes and Vascular Disease: Is It All About Glycemia?

BACKGROUND

Diabetes is increasing over time, mainly driven by obesity, aging, and urbanization. Classical macro- and microvascular complications represent the final result of a complex interplay involving atherosclerosis at all stages.

METHODS

In this review, we aim at focusing on current updates in the pathophysiology of vascular disease in diabetes and discussing how new therapies might influence the management of these patients at high cardiovascular risk. Diabetes shows accelerated atherosclerosis with a larger inflammatory cell infiltrate, thus favoring the development of heart failure. 'Diabetic cardiomyopathy' perfectly describes a specific ischemia- and hypertension- independent entity due to diabetes-related metabolic alterations on myocardial function. Moreover, platelets from subjects with diabetes display a typical hyperreactivity explaining the stronger adhesion, activation, and aggregation. Additionally, diabetes provokes an exaggerated stimulation of the endothelium, with an increased release of reactive oxygen species and a reduced release of nitric oxide, both key elements of the endothelial dysfunction. Also, the coagulation cascade and leukocytes activate contributing to this pro-thrombotic environment. Neutrophils have been recently recognized to play a pivotal role by releasing neutrophil extracellular traps. Finally, microparticles from platelets, neutrophils or monocytes are detrimental effectors on the vessel wall and are involved both in vascular dysfunction and in thrombotic complications.

CONCLUSION

In light of these findings, the therapeutic management of diabetes needs to be mostly focused on limiting the progression of complications by targeting precise pathophysiological mechanisms rather than the mere glycemic control, which failed to markedly reduce the risk for macrovascular complications and mortality.

Endothelium as a Therapeutic Target in Diabetes Mellitus: From Basic Mechanisms to Clinical Practice

Endothelium plays an essential role in human homeostasis by regulating arterial blood pressure, distributing nutrients and hormones as well as providing a smooth surface that modulates coagulation, fibrinolysis and inflammation. Endothelial dysfunction is present in Diabetes Mellitus (DM) and contributes to the development and progression of macrovascular disease, while it is also associated with most of the microvascular complications such as diabetic retinopathy, nephropathy and neuropathy. Hyperglycemia, insulin resistance, hyperinsulinemia and dyslipidemia are the main factors involved in the pathogenesis of endothelial dysfunction. Regarding antidiabetic medication, metformin, gliclazide, pioglitazone, exenatide and dapagliflozin exert a beneficial effect on Endothelial Function (EF); glimepiride and glibenclamide, dipeptidyl peptidase-4 inhibitors and liraglutide have a neutral effect, while studies examining the effect of insulin analogues, empagliflozin and canagliflozin on EF are limited. In terms of lipid-lowering medication, statins improve EF in subjects with DM, while data from short-term trials suggest that fenofibrate improves EF; ezetimibe also improves EF but further studies are required in people with DM. The effect of acetylsalicylic acid on EF is dose-dependent and lower doses improve EF while higher ones do not. Clopidogrel improves EF, but more studies in subjects with DM are required. Furthermore, angiotensin- converting-enzyme inhibitors /angiotensin II receptor blockers improve EF. Phosphodiesterase type 5 inhibitors improve EF locally in the corpus cavernosum. Finally, cilostazol exerts favorable effect on EF, nevertheless, more data in people with DM are required.

Reducing Type 1 Diabetes Mortality: Role for Adjunctive Therapies?

Individuals with type 1 diabetes (T1D) frequently fail to achieve glycemic goals and have excess cardiovascular risk and premature death. Adjunctive agents may play a role in reducing morbidity, mortality, and the adverse sequelae of insulin treatment. A surge in type 2 diabetes drug development has revealed agents with benefits beyond glucose lowering, including cardiovascular risk reduction. Could these benefits translate to T1D? Specific trials for T1D demonstrate substantial hemoglobin (Hb)A1c reductions with sodium glucose cotransporter inhibitors (SGLTis) and glucagon-like peptide (GLP)1 agonists, and modest improvements with metformin, dipeptidyl peptidase-4 inhibitor (DPP4i), and pramlintide. Studies exploring cardiovascular risk reduction are warranted. This review synthesizes the emerging literature for researchers and clinicians treating people with T1D. Challenges in T1D research are discussed.

Effects of Metformin Added to Insulin in Adolescents with Type 1 Diabetes: An Exploratory Crossover Randomized Trial

BACKGROUND

To comprehensively assess the effects of metformin added to insulin on metabolic control, insulin sensitivity, and cardiovascular autonomic function in adolescents with type 1 diabetes.

MATERIALS AND METHODS

This was an exploratory, crossover, randomized trial conducted in adolescents with type 1 diabetes aged 12-18 years old. Participants were randomly received metformin (≤1000 mg/d) added to insulin for 24 weeks followed by insulin monotherapy for a subsequent 24 weeks or vice versa. Blood pressure, body mass index, insulin dose, estimated insulin sensitivity, glycated hemoglobin A1c (HbA1c), and lipid profiles were measured, with a 72-hour continuous glucose monitoring and 24-hour Holter monitoring performed at baseline, 24, and 50 weeks for the assessments of glucose variability and heart rate variability.

RESULTS

Seventeen patients with mean ± SD age 14.4 ± 2.3 years, body mass index 18.17 ± 1.81 kg/m², median (IQR) diabetes duration 4.50 (3.58, 6.92) years, and HbA1c 9.0% (8.5%, 9.4%) were enrolled. The between-group difference in HbA1c of 0.28% (95% CI -0.39 to 0.95%) was not significant (P = 0.40). Changes in body mass index, insulin dose, blood pressure, lipid profiles, and estimated insulin sensitivity were similar for metformin add-on vs. insulin monotherapy. Glucose variability also did not differ. Compared with insulin monotherapy, metformin add-on significantly increased multiple heart rate variability parameters.

CONCLUSIONS

Metformin added to insulin did not improve metabolic control or glucose variability in lean/normal-weight adolescents with type 1 diabetes. However, metformin added to insulin significantly increased heart rate variability, suggesting that metformin might improve cardiovascular autonomic function in this population.

Effects of Sodium-Glucose Cotransporter Inhibitor/Glucagon-Like Peptide-1 Receptor Agonist Add-On to Insulin Therapy on Glucose Homeostasis and Body Weight in Patients With Type 1 Diabetes: A Network Meta-Analysis

Many patients with type 1 diabetes (T1D) do not achieve the glycemic target goal with insulin treatment. In this study, we aimed to evaluate the efficacy and safety of add-on to insulin therapy in patients with T1D. We conducted direct and indirect network meta-analyses using Bayesian models and ranked hypoglycemic agents via mixed treatment comparison, using data from the CENTRAL, MEDLINE, EMBASE, and Science Citation Index Expanded databases. Randomized controlled trials (RCTs) involving patients with T1D treated with insulin and add-on metformin or sodium-glucose cotransporter inhibitors or glucagon-like peptide-1 receptor agonists from January 1970 to September 2019 were included in this study. Twenty-three RCTs with 5,151 subjects were divided into the following groups: insulin alone, insulin+metformin, insulin+canagliflozin, insulin+dapagliflozin, insulin+empagliflozin, insulin+sotagliflozin, insulin+liraglutide, and insulin+exenatide. HbA1c level in the insulin+sotagliflozin group was significantly lower than that in the insulin alone group (mean difference: -0.43, 95% credible interval: -0.62 to -0.23). Total daily insulin dose in the insulin+sotagliflozin group was significantly lower than that in the insulin alone group. Compared with that in the insulin alone group, body weight in the groups treated with insulin+add-on canagliflozin, sotagliflozin, and exenatide was significantly decreased by 4.5, 2.8, and 5.1 kg, respectively. Hypoglycemic episodes did not differ among the groups. In patients with T1D, insulin+sotagliflozin decreased the HbA1c level, daily insulin dose, and body weight without hypoglycemia compared with insulin monotherapy. Insulin+canagliflozin or insulin+exenatide was effective in reducing body weight compared with insulin alone. In conclusion, sotagliflozin treatment decreased not only the HbA1c levels and insulin dose but also the body weight without causing hypoglycemia in patients with T1D. Treatment with canagliflozin and exenatide effectively reduced body weight in patients with T1D. However, ketoacidosis associated with the use of SGLT inhibitors should be considered in these patients. Thus, our results suggest that sotagliflozin has a high probability of being ranked first as an adjunctive therapy to insulin in patients with T1D.

Non-insulin treatments for Type 1 diabetes: critical appraisal of the available evidence and insight into future directions

Intensive insulin therapy is the mainstay of treatment for people with Type 1 diabetes, but hypoglycaemia and weight gain are often limiting factors in achieving glycaemic targets and decreasing the risk of diabetes-related complications. The inclusion of pharmacological agents used traditionally in Type 2 diabetes as adjuncts to insulin therapy in Type 1 diabetes has been explored, with the goal of mitigating such drawbacks. Pramlintide and metformin result in modest HbA_1c and weight reductions, but their use is limited by poor tolerability and, in the case of pramlintide, by frequency of injections and cost. The addition of glucagon-like peptide-1 receptor agonists to insulin results in improved glycaemic control, reduced insulin doses and weight loss, but this is at the expense of higher rates of hypoglycaemia and hyperglycaemia with ketosis. Sodium-glucose co-transporter-2 and dual sodium-glucose co-transporter-2 and -1 inhibitors also improve glucose control, but with reductions in weight and insulin requirements potentiating the risk of acidosis-related events and hypoglycaemia. The high proportion of people with Type 1 diabetes not achieving glycaemic targets, the negative clinical impact of intensive insulin therapy and the rise in obesity and cardiovascular disease and mortality, underline the need for individualized clinical care. The evaluation of new therapies, effective in Type 2 diabetes, as adjuncts to insulin therapy represents a promising strategy, particularly given the beneficial effects on cardiovascular and renal outcomes in people with Type 2 diabetes with or at high risk of complications that are also observed in patients with Type 1 diabetes. As the population with Type 1 diabetes ages, our mission is to evolve and provide better tools and improved therapies to excel, not only in glycaemic control but also in risk reduction and reduction of complications.

The early detection of atherosclerosis in type 1 diabetes: why, how and what to do about it

The major cause of morbidity and often premature mortality in people with type I diabetes (T1D) is cardiovascular disease owing to accelerated atherosclerosis. We review publications relating to the rationale behind, and clinical tests for, detecting and treating early atherosclerosis in people with T1D. Currently available tools for atherosclerosis assessment include risk equations using vascular risk factors, arterial intima-media thickness, the ankle-brachial index, coronary artery calcification and angiography, and for more advanced lesions, intravascular ultrasound and optical coherence tomography. Evolving research tools include risk equations incorporating novel clinical, biochemical and molecular tests; vascular MRI and molecular imaging. As yet there is little information available to quantify early atherosclerosis. With better means to control the vascular risk factors, such as hypertension, dyslipidaemia and glycaemic control, and emerging therapies to control novel risk factors, further epidemiologic and clinical trials are merited to facilitate the translation into clinical practice of robust means to detect, monitor and treat early atherosclerosis in those with T1D.

Metformin prevents vascular damage in hypertension through the AMPK/ER stress pathway

Metformin is an antidiabetic drug. However, the pleiotropic beneficial effects of metformin in nondiabetic models still need to be defined. The objective of this study is to investigate the effect of metformin on angiotensin II (Ang II)-induced hypertension and cardiovascular diseases. Mice were infused with Ang II (400 ng/kg per min) with or without metformin for 2 weeks. Mice infused with angiotensin II displayed an increase in blood pressure associated with enhanced vascular endoplasmic reticulum (ER) stress markers, which were blunted after metformin treatment. Moreover, hypertension-induced reduction in phosphorylated AMPK, endothelial nitric oxide synthase (eNOs) phosphorylation, and endothelium-dependent relaxation (EDR) in mesenteric resistance arteries (MRA) were rescued after metformin treatment. Infusion of ER stress inducer (tunicamycin, Tun) in control mice induced ER stress in MRA and reduced phosphorylation of AMPK, eNOS synthase phosphorylation, and EDR in MRA without affecting systolic blood pressure (SBP). All these factors were reversed subsequently with metformin treatment. ER stress inhibition by metformin improves vascular function in hypertension. Therefore, metformin could be a potential therapy for cardiovascular diseases in hypertension independent of its effects on diabetes.

Empagliflozin on top of metformin treatment improves arterial function in patients with type 1 diabetes mellitus

Background

Deteriorated arterial function and high incidence of cardiovascular events characterise diabetes mellitus. Metformin and recent antidiabetic drugs, SGLT2 inhibitors, reduce cardiovascular events. We explored the possible effects of empagliflozin’s effect on top of metformin treatment on endothelial function and arterial stiffness parameters in type 1 diabetes mellitus (T1DM) patients.

Methods

Forty T1DM patients were randomised into three treatment groups: (1) empagliflozin (25 mg daily), (2) metformin (2000 mg daily) and (3) empagliflozin/metformin (25 mg daily and 2000 mg daily, respectively). The fourth group received placebo. Arterial function was assessed at inclusion and after 12 weeks treatment by: endothelial function [brachial artery flow-mediated dilation (FMD), reactive hyperaemia index (RHI)], arterial stiffness [pulse wave velocity (PWV) and common carotid artery stiffness (β-stiffness)]. For statistical analysis one-way analysis of variance with Bonferroni post-test was used.

Results

Empagliflozin on top of metformin treatment significantly improved endothelial function as did metformin after 12 weeks of treatment: FMD [2.6-fold (P < 0.001) vs. 1.8-fold (P < 0.05)] and RHI [1.4-fold (P < 0.01) vs. 1.3-fold (P < 0.05)]. Empagliflozin on top of metformin treatment was superior to metformin in improving arterial stiffness parameters; it significantly improved PWV and β-stiffness compared to metformin [by 15.8% (P < 0.01) and by 36.6% (P < 0.05), respectively]. Metformin alone did not influence arterial stiffness.

Conclusion

Empagliflozin on top of metformin treatment significantly improved arterial stiffness compared to metformin in T1DM patients. Endothelial function was similarly improved in all treatment groups. Empagliflozin seems to possess a specific capacity to decrease arterial stiffness, which could support its cardioprotective effects observed in large clinical studies.

Trial registration Clinical trial registration: NCT03639545

Adjunct Antihyperglycemic Agents in Overweight and Obese Adults With Type 1 Diabetes

OBJECTIVE

People with type 1 diabetes often have suboptimal glycemic control. The gold standard of treatment is basal-bolus insulin or subcutaneous insulin infusion via insulin pump. Although insulin therapy improves glycemic control, weight gain and hypoglycemia often limit achievement of hemoglobin A_1C (A1C) goals. The number of people with type 1 diabetes who are overweight or obese is increasing, and there are many similarities between what was historically called type 1 and type 2 diabetes. Therefore, there is rationale for using antihyperglycemic agents that target other pathophysiological abnormalities to facilitate weight loss and improve glycemic control.

DATA SOURCES

We performed a MEDLINE search from 1975 through October 2018 to identify articles that studied noninsulin agents in adults with type 1 diabetes and body mass index (BMI) ≥25 kg/m².

STUDY SELECTION AND DATA EXTRACTION

Identified articles were included if the study duration was ≥4 weeks, included ≥20 patients, and set mean baseline BMI ⩾25kg/m².

DATA SYNTHESIS

This review summarizes 32 clinical trials. Amylin mimetics, sodium-glucose-like transporter-2 inhibitors, and glucagon-like-peptide-1 receptor agonists demonstrate the greatest improvements in body weight and A1C. The most common adverse effects are hypoglycemia and ketosis. Relevance to Patient Care and Clinical Practice: Patients with type 1 diabetes may have interest in starting noninsulin agents. Clinicians need to be knowledgeable in the efficacy and adverse effect profile of these agents, specifically in people with type 1 diabetes.

CONCLUSIONS

Adding noninsulin antihyperglycemic agents may benefit select overweight or obese adults with type 1 diabetes. These agents are off-label, and if used, close monitoring is essential.

Metabolic Control in Type 1 Diabetes: Is Adjunctive Therapy the Way Forward?

Despite advances in insulin therapies, patients with type 1 diabetes (T1DM) have a shorter life span due to hyperglycaemia-induced vascular disease and hypoglycaemic complications secondary to insulin therapy. Restricting therapy for T1DM to insulin replacement is perhaps an over-simplistic approach, and we focus in this work on reviewing the role of adjuvant therapy in this population. Current data suggest that adding metformin to insulin therapy in T1DM temporarily lowers HbA1c and reduces weight and insulin requirements, but this treatment fails to show a longer-term glycaemic benefit. Agents in the sodium glucose co-transporter-2 inhibitor (SGLT-2) class demonstrate the greatest promise in correcting hyperglycaemia, but there are safety concerns in relation to the risk of diabetic ketoacidosis. Glucagon-like peptide-1 agonists (GLP-1) show a modest effect on glycaemia, if any, but significantly reduce weight, which may make them suitable for use in overweight T1DM patients. Treatment with pramlintide is not widely available worldwide, although there is evidence to indicate that this agent reduces both HbA1c and weight in T1DM. A criticism of adjuvant studies is the heavy reliance on HbA1c as the primary endpoint while generally ignoring other glycaemic parameters. Moreover, vascular risk markers and measures of insulin resistance-important considerations in individuals with a longer T1DM duration-are yet to be fully investigated following adjuvant therapies. Finally, studies to date have made the assumption that T1DM patients are a homogeneous group of individuals who respond similarly to adjuvant therapies, which is unlikely to be the case. Future longer-term adjuvant studies investigating different glycaemic parameters, surrogate vascular markers and harder clinical outcomes will refine our understanding of the roles of such therapies in various subgroups of T1DM patients.

Endothelial function and dysfunction: Impact of metformin

Cardiovascular and metabolic diseases remain the leading cause of morbidity and mortality worldwide. Endothelial dysfunction is a key player in the initiation and progression of cardiovascular and metabolic diseases. Current evidence suggests that the anti-diabetic drug metformin improves insulin resistance and protects against endothelial dysfunction in the vasculature. Hereby, we provide a timely review on the protective effects and molecular mechanisms of metformin in preventing endothelial dysfunction and cardiovascular and metabolic diseases.

Effect of metformin on glycaemic control in patients with type 1 diabetes: A meta-analysis of randomized controlled trials

BACKGROUND

For type 1 diabetes (T1D) patients, adding metformin to insulin therapies is thought to improve blood glucose levels, but current evidence does not support this clinical benefit. Additional data from large clinical trials are now available; therefore, we conducted a meta-analysis of studies on assessing the efficacy and adverse effects of metformin.

METHODS

We searched the MEDLINE, EMBASE, and Cochrane Library databases for data from randomized controlled trials. We performed statistical analyses by using Review Manager 5.2.

RESULTS

Thirteen randomized controlled trials that compared metformin versus placebo met our inclusion criteria and were included in the study. The final meta-analysis included a total of 1183 participants with T1D. Metformin was associated with reductions in BMI (-1.14, 95% CI -2.05 to -0.24, P = .01), insulin requirements (-0.47, 95% CI -0.70 to -0.23, P = .0001), total cholesterol (-0.23, 95% CI -0.34 to -0.12, P < .0001), and low-density lipoprotein cholesterol (-0.20, 95% CI -0.29 to -0.11, P < .0001) in T1D patients. No clear evidence indicated that metformin improved HbA1c, triglyceride, or high-density lipoprotein cholesterol levels. A safety analysis showed that metformin slightly increased the risk of severe hypoglycaemia (1.23, 95% CI 1.00 to 1.52, P = .05) and mainly gastrointestinal adverse events (2.67, 95% CI 2.06 to 3.45, P < .00001). No evidence showed that metformin increased diabetic ketoacidosis events.

CONCLUSIONS

Compared with placebo, metformin was not associated with glycaemic control in T1D patients. Although it exhibited other benefits, such as lower BMI and reduced insulin requirements, total cholesterol, and low-density lipoprotein cholesterol, negative outcomes, such as gastrointestinal adverse effects and severe hypoglycaemia, should also be considered in the use of metformin for T1D patients.

Novel blood glucose lowering therapies for managing type 1 diabetes in paediatric patients

INTRODUCTION

Therapy for type 1 diabetes (T1D) is mainly restricted to insulin treatment. The management of paediatric patients with T1D should tackle not only glucose control, but also insulin resistance, beta-cell preservation, quality of life and cardiovascular disease risk factors, which are increasingly recognized to occur in adolescents with T1D.

AREAS COVERED

This review examines the recently published literature from PubMed on non-insulin agents for the management of T1D in paediatric patients.

EXPERT OPINION

Few paediatric patients with T1D are achieving their metabolic targets. Current data support the need for new strategies and the consideration of additional therapies that not only may help patients, their families and their physicians to meet HbA1c targets, but also may preserve residual islet mass and good quality of life and prevent microvascular and macrovascular complications, thereby, reducing hypoglycaemic episodes. Non-insulin adjunctive therapies may improve not only glucose control, but also insulin sensitivity, in addition to preserving beta-cell function in T1D patients. Thus, more studies are required to define the potential role of these therapies in the management of paediatric patients.

A Review of Insulin Resistance in Type 1 Diabetes: Is There a Place for Adjunctive Metformin?

There is a rising trend of overweight and obesity among individuals with type 1 diabetes. This is often associated with insulin resistance, increased insulin dose requirements and poor glycemic control. Insulin resistance is also seen during puberty and is strongly related to increased risk of cardiovascular disease. The role of metformin as an adjunct to ongoing intensive insulin therapy in type 1 diabetics has been evaluated in several randomized trials, including the recently concluded T1D Exchange Network trial in adolescents and the REMOVAL trial in adults. Metformin reduces the insulin dose requirement, insulin-induced weight gain, and total and LDL cholesterol, but results in an increased risk of gastrointestinal adverse effects and a minor increase in the risk of hypoglycemia. In addition, metformin has been shown to reduce maximal carotid intima media thickness and therefore may extend cardioprotective benefits in type 1 diabetes. The role of metformin as adjunctive therapy in type 1 diabetes needs to be explored further in outcome trials.

Effect of Metformin on Vascular Function in Children With Type 1 Diabetes: A 12-Month Randomized Controlled Trial

CONTEXT

Children with type 1 diabetes have vascular dysfunction preceding atherosclerosis. Early interventions are needed to reduce cardiovascular disease.

OBJECTIVE

To evaluate the effect of metformin on vascular function in children with type 1 diabetes.

DESIGN

Twelve-month double-blind, randomized, placebo-controlled trial.

SETTING

Tertiary pediatric diabetes clinic.

PARTICIPANTS

Ninety children (8 to 18 years of age), >50th percentile body mass index (BMI), with type 1 diabetes.

INTERVENTION

Metformin (up to 1 g twice a day) or placebo.

MAIN OUTCOME MEASURE

Vascular function measured by brachial artery ultrasound [flow-mediated dilatation/glyceryl trinitrate-mediated dilatation (GTN)].

RESULTS

Ninety participants were enrolled [41 boys, 13.6 (2.5) years of age, 45 per group], 10 discontinued intervention, and 1 was lost to follow-up. On metformin, GTN improved, independent of glycosylated hemoglobin (HbA1c), by 3.3 percentage units [95% confidence interval (CI) 0.3, 6.3, P = 0.03] and insulin dose reduced by 0.2 U/kg/d (95% CI 0.1, 0.3, P = 0.001) during 12 months, with effects from 3 months. Metformin had a beneficial effect on HbA1c at 3 months (P = 0.001) and difference in adjusted HbA1c between groups during 12 months was 1.0%; 95% CI 0.4, 1.5 (10.9 mmol/mol; 95% CI 4.4, 16.4), P = 0.001. There were no effects on carotid/aortic intima media thickness, BMI, lipids, blood pressure, or other cardiovascular risk factors. Median (95% CI) adherence, evaluated by electronic monitoring, was 75.5% (65.7, 81.5), without group differences. More gastrointestinal side effects were reported on metformin (incidence rate ratio 1.65, 95% CI 1.08, 2.52, P = 0.02), with no difference in hypoglycemia or diabetic ketoacidosis.

CONCLUSIONS

Metformin improved vascular smooth muscle function and HbA1c, and lowered insulin dose in type 1 diabetes children. These benefits and good safety profile warrant further consideration of its use.

Metformin as add-on to intensive insulin therapy in type 1 diabetes mellitus

We aimed to evaluate the effect of adjuvant metformin to intensive insulin therapy in patients with type 1 diabetes mellitus (T1DM). A 10-year retrospective study in 2 cohorts was performed: the MET cohort (n = 181) consisted of patients with T1DM on adjuvant metformin for ≥6 months and the CTR cohort (n = 62) consisted of patients with T1DM who refused metformin (n = 25) or adhered to metformin for <6 months (n = 36). Data on glycated haemoglobin (HbA1c), body mass index (BMI) and daily insulin dose were recorded yearly. A third cross-sectional cohort, the REF cohort (n = 961), consisting of patients with T1DM not offered adjuvant metformin, was used as a reference for baseline comparison. At the study start, BMI was significantly higher and insulin doses were lower in patients in the MET cohort, while HbA1c levels were similar. In the first years of metformin therapy, small but non-significant decreases were seen in BMI and insulin dose in patients in the MET cohort, while after 10 years no persistent effect on HbA1c, insulin dose or BMI was seen. In conclusion, although metformin may have short-term effects on BMI and insulin dose when used as adjunct therapy in patients with T1DM, no long-term beneficial effects were observed when patients were followed for 10 years.

Metformin Improves Endothelial Function and Reduces Blood Pressure in Diabetic Spontaneously Hypertensive Rats Independent from Glycemia Control: Comparison to Vildagliptin

Metformin confers vascular benefits beyond glycemia control, possibly via pleiotropic effects on endothelial function. In type-1-diabetes-mellitus (T1DM-)patients metformin improved flow-mediated dilation but also increased prostaglandin(PG)-F_2α, a known endothelial-contracting factor. To explain this paradoxical finding we hypothesized that metformin increased endothelial-vasodilator mediators (e.g. NO and EDHF) to an even larger extent. Spontaneously-hypertensive-rats (SHR) display impaired endothelium-dependent relaxation (EDR) involving contractile PGs. EDR was studied in isolated SHR aortas and the involvement of PGs, NO and EDHF assessed. 12-week metformin 300 mg/kg/day improved EDR by up-regulation of NO and particularly EDHF; it also reduced blood pressure and increased plasma sulphide levels (a proxy for H₂S, a possible mediator of EDHF). These effects persisted in SHR with streptozotocin (STZ)-induced T1DM. Vildagliptin (10 mg/kg/day), targeting the incretin axis by increasing GLP-1, also reduced blood pressure and improved EDR in SHR aortas, mainly via the inhibition of contractile PGs, but not in STZ-SHR. Neither metformin nor vildagliptin altered blood glucose or HbA_1c. In conclusion, metformin reduced blood pressure and improved EDR in SHR aorta via up-regulation of NO and particularly EDHF, an effect that was independent from glycemia control and maintained during T1DM. A comparison to vildagliptin did not support effects of metformin mediated by GLP-1.

Cardiovascular and metabolic effects of metformin in patients with type 1 diabetes (REMOVAL): a double-blind, randomised, placebo-controlled trial

BACKGROUND

Metformin might reduce insulin requirement and improve glycaemia in patients with type 1 diabetes, but whether it has cardiovascular benefits is unknown. We aimed to investigate whether metformin treatment (added to titrated insulin therapy) reduced atherosclerosis, as measured by progression of common carotid artery intima-media thickness (cIMT), in adults with type 1 diabetes at increased risk for cardiovascular disease.

METHODS

REMOVAL was a double-blind, placebo-controlled trial undertaken at 23 hospital diabetes clinics in five countries (Australia, Canada, Denmark, the Netherlands, and the UK). Adults aged 40 years and older with type 1 diabetes of at least 5 years' duration and at least three of ten specific cardiovascular risk factors were randomly assigned (via an interactive voice response system) to oral metformin 1000 mg twice daily or placebo. Participants and site staff were masked to treatment allocation. The primary outcome was averaged mean far-wall cIMT, quantified annually for 3 years, analysed in a modified intention-to-treat population (all randomly assigned participants with post-randomisation data available for the outcome of interest at any given timepoint, irrespective of subsequent adherence or study participation), using repeated measures regression. Secondary outcomes were HbA1c, LDL cholesterol, estimated glomerular filtration rate (eGFR), incident microalbuminuria (not reported), incident retinopathy, bodyweight, insulin dose, and endothelial function, also analysed in all participants with post-randomisation data available for the outcome of interest at any given timepoint. This trial is registered with ClinicalTrials.gov, number NCT01483560.

FINDINGS

Between Dec 14, 2011, and June 24, 2014, 493 participants entered a 3 month run-in to optimise risk factor and glycaemic control (single-blind placebo in the final month). Of 428 randomly assigned patients, 219 were allocated to metformin and 209 to placebo. Progression of mean cIMT was not significantly reduced with metformin (-0·005 mm per year, 95% CI -0·012 to 0·002; p=0·1664), although maximal cIMT (a prespecified tertiary outcome) was significantly reduced (-0·013 mm per year, -0·024 to -0·003; p=0·0093). HbA1c (mean 8·1% [SD 0·9] for metformin and 8·0% [0·8] for placebo at baseline) was reduced on average over 3 years by metformin (-0·13%, 95% CI -0·22 to -0·037; p=0·0060), but this was accounted for by a reduction at the 3-month timepoint (-0·24%, -0·34 to -0·13; p<0·0001) that was not sustained thereafter (p=0·0163 for visit-by-treatment interaction). Bodyweight (-1·17 kg, 95% CI -1·66 to -0·69; p<0·0001) and LDL cholesterol (-0·13 mmol/L, -0·24 to -0·03; p=0·0117) were reduced with metformin over 3 years of treatment, and eGFR was increased (4·0 mL/min per 1·73m2, 2·19 to 5·82; p<0·0001). Insulin requirement was not reduced on average over 3 years (-0·005 units per kg, 95% CI -0·022 to 0·012; p=0·545), but there was a significant visit-by-treatment interaction (p=0·0018). There was no effect on endothelial function as measured by reactive hyperaemia index, or on retinopathy. Discontinuation of treatment in 59 (27%) participants on metformin versus 26 (12%) on placebo (p=0·0002) was mainly due to an excess of gastrointestinal adverse effects, and there was no increase in hypoglycaemia with metformin. Five deaths occurred among patients allocated to metformin and two occurred among those allocated to placebo; none were judged by site principal investigators to be related to study medication.

INTERPRETATION

These data do not support use of metformin to improve glycaemic control in adults with long-standing type 1 diabetes as suggested by current guidelines, but suggest that it might have a wider role in cardiovascular risk management.

FUNDING

JDRF.

Macro- and microvascular endothelial dysfunction in diabetes

Endothelial cells, as well as their major products nitric oxide (NO) and prostacyclin, play a key role in the regulation of vascular homeostasis. Diabetes mellitus is an important risk factor for cardiovascular disease. Diabetes-induced endothelial dysfunction is a critical and initiating factor in the genesis of diabetic vascular complications. The present review focuses on both large blood vessels and the microvasculature. The endothelial dysfunction in diabetic macrovascular complications is characterized by reduced NO bioavailability, poorly compensated for by increased production of prostacyclin and/or endothelium-dependent hyperpolarizations, and increased production or action of endothelium-derived vasoconstrictors. The endothelial dysfunction of microvascular complications is primarily characterized by decreased release of NO, enhanced oxidative stress, increased production of inflammatory factors, abnormal angiogenesis, and impaired endothelial repair. In addition, non-coding RNAs (microRNAs) have emerged as participating in numerous cellular processes. Thus, this reviews pays special attention to microRNAs and their modulatory role in diabetes-induced vascular dysfunction. Some therapeutic strategies for preventing and restoring diabetic endothelial dysfunction are also highlighted.

Metformin improves circulating endothelial cells and endothelial progenitor cells in type 1 diabetes: MERIT study

Background

Type 1 diabetes is associated with increased cardiovascular disease (CVD). Decreased endothelial progenitor cells (EPCs) number plays a pivotal role in reduced endothelial repair and development of CVD. We aimed to determine if cardioprotective effect of metformin is mediated by increasing circulating endothelial progenitor cells (cEPCs), pro-angiogenic cells (PACs) and decreasing circulating endothelial cells (cECs) count whilst maintaining unchanged glycemic control.

Methods

This study was an open label and parallel standard treatment study. Twenty-three type 1 diabetes patients without overt CVD were treated with metformin for 8 weeks (treatment group-TG). They were matched with nine type 1 diabetes patients on standard treatment (SG) and 23 age- and sex-matched healthy volunteers (HC). Insulin dose was adjusted to keep unchanged glycaemic control. cEPCs and cECs counts were determined by flow cytometry using surface markers CD45^dimCD34⁺VEGFR-2⁺ and CD45^dimCD133⁻CD34⁺CD144⁺ respectively. Peripheral blood mononuclear cells were cultured to assess changes in PACs number, function and colony forming units (CFU-Hill’s colonies).

Results

At baseline TG had lower cEPCs, PACs, CFU-Hills’ colonies and PACs adhesion versus HC (p < 0.001-all variables) and higher cECs versus HC (p = 0.03). Metformin improved cEPCs, PACs, CFU-Hill’s colonies number, cECs and PACs adhesion (p < 0.05-all variables) to levels seen in HC whilst HbA1c (one-way ANOVA p = 0.78) and glucose variability (average glucose, blood glucose standard deviation, mean amplitude of glycaemic excursion, continuous overall net glycaemic action and area under curve) remained unchanged. No changes were seen in any variables in SG. There was an inverse correlation between CFU-Hill’s colonies with cECs.

Conclusions

Metformin has potential cardio-protective effect through improving cEPCs, CFU-Hill’s colonies, cECs, PACs count and function independently of hypoglycaemic effect. This finding needs to be confirmed by long term cardiovascular outcome studies in type 1 diabetes.

Trial registration ISRCTN26092132

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-016-0413-6) contains supplementary material, which is available to authorized users.

Metformin improves endothelial function in aortic tissue and microvascular endothelial cells subjected to diabetic hyperglycaemic conditions

The cellular mechanisms whereby metformin, the first line drug for type 2 diabetes (T2DM), mediates its antidiabetic effects remain elusive, particularly as to whether metformin has a direct protective action on the vasculature. This study was designed to determine if a brief 3-h exposure to metformin protects endothelial function against the effects of hyperglycaemia. We investigated the protective effects of metformin on endothelial-dependent vasodilatation (EDV) in thoracic aortae from T2DM db/db mice and on high glucose (HG, 40 mM) induced changes in endothelial nitric oxide synthase (eNOS) signaling in mouse microvascular endothelial cells (MMECs) in culture. Exposure of aortae from db+/? non-diabetic control mice to high glucose (HG, 40 mM) containing Krebs for 3-h significantly (P<0.05) reduced acetylcholine (ACh)-induced EDV compared to ACh-induced EDV in aortae maintained in normal glucose (NG, 11 mM) Krebs. The reduction of EDV was partially reversed following a 3-h exposure to 50 μM metformin; metformin also improved ACh-induced EDV in aortae from diabetic db/db mice. Immunoblot analysis of MMECs cultured in HG versus NG revealed a significant reduction of the ratio of phosphorylated (p-eNOS)/eNOS and p-Akt/Akt, but not the expression of total eNOS or Akt. The 3-h exposure of MMECs to metformin significantly (P<0.05) reversed the HG-induced reduction in phosphorylation of both eNOS and Akt; however, no changes were detected for phosphorylation of AMPK or the expression of SIRT1. Our data indicate that a 3-h exposure to metformin can reverse/reduce the impact of HG on endothelial function, via mechanisms linked to increased phosphorylation of eNOS and Akt.

Management of Severe Insulin Resistance in Patients with Type 1 Diabetes

Managing severe insulin resistance (IR) in patients with type 1 diabetes (T1DM) can be challenging for both clinicians and patients. As average weight for patients with T1DM has increased in recent decades, IR in this population has become more widespread. Currently, almost 50 % of patients with T1DM are overweight or obese. While intensive insulin therapy is associated with reduction in complications, aggressive treatment can lead to weight gain. With increasing weight, insulin can become less effective to control glycemia, resulting in higher insulin doses and hence more weight gain. Novel strategies to break this vicious cycle are needed. This review will investigate current research on insulin formulations, lifestyle modification, adjunct therapies, and surgery that may help better manage patients with T1DM and IR.

Efficacy and safety of metformin for patients with type 1 diabetes mellitus: a meta-analysis

BACKGROUND

Insulin is an essential therapy for patients with type 1 diabetes mellitus (T1DM). With the progression of the disease, many patients with T1DM may have an increased prevalence of insulin resistance; thus the common standard insulin therapy requires a high insulin dosage (>1 unit/kg/day) and is usually associated with many side effects. Studies have shown that metformin may benefit those insulin-resistant individuals with T1DM. This meta-analysis was performed to provide the evidence of clinical efficacy and safety of metformin in T1DM.

MATERIALS AND METHODS

We conducted a search on Medline, EMBASE, and the Cochrane Library for relevant studies published before May 2014 based on "metformin" and "diabetes mellitus, type 1." The following outcomes were evaluated: hemoglobin A1c (HbA1c), fasting plasma glucose (FPG), lipid metabolism, weight, insulin dosage, hypoglycemia, diabetic ketoacidosis, or gastrointestinal adverse events (AEs). The meta-analysis was performed using Review Manager version 5.2 software (The Nordic Cochrane Centre, Copenhagen, Denmark).

RESULTS

In total, eight randomized controlled trials were included. Metformin was associated with a reduction in daily insulin dosage, body weight, total cholesterol level, low-density lipoprotein level, and high-density lipoprotein level but an increase in risk of gastrointestinal AEs compared with placebo treatment in T1DM patients. No significant difference was found between the metformin group and the placebo group in HbA1c level, FPG level, or triglycerides level. No significant difference was found between the metformin group and the placebo group in the risk of severe hypoglycemia or diabetic ketoacidosis.

CONCLUSIONS

Metformin may decrease the daily insulin dosage, body weight, and lipid levels in T1DM. However, metformin does not increase the incidence of hypoglycemia and ketoacidosis. High-quality, large-sample, and long-term follow-up clinical trials are needed to confirm these conclusions.

Elevation in blood flow and shear rate prevents hyperglycemia-induced endothelial dysfunction in healthy subjects and those with type 2 diabetes

Hyperglycemia, commonly present after a meal, causes transient impairment in endothelial function. We examined whether increases in blood flow (BF) protect against the hyperglycemia-mediated decrease in endothelial function in healthy subjects and patients with type 2 diabetes mellitus (T2DM). Ten healthy subjects and 10 age- and sex-matched patients with T2DM underwent simultaneous bilateral assessment of brachial artery endothelial function by means of flow-mediated dilation (FMD) using high-resolution echo-Doppler. FMD was examined before and 60, 120, and 150 min after a 75-g oral glucose challenge. We unilaterally manipulated BF by heating one arm between minute 30 and minute 60. Oral glucose administration caused a statistically significant, transient increase in blood glucose in both groups (P < 0.001). Forearm skin temperature, brachial artery BF, and shear rate significantly increased in the heated arm (P < 0.001), and to a greater extent compared with the nonheated arm in both groups (interaction effect P < 0.001). The glucose load caused a transient decrease in FMD% (P < 0.05), whereas heating significantly prevented the decline (interaction effect P < 0.01). Also, when correcting for changes in diameter and shear rate, we found that the hyperglycemia-induced decrease in FMD can be prevented by local heating (P < 0.05). These effects on FMD were observed in both groups. Our data indicate that nonmetabolically driven elevation in BF and shear rate can similarly prevent the hyperglycemia-induced decline in conduit artery endothelial function in healthy volunteers and in patients with type 2 diabetes. Additional research is warranted to confirm that other interventions that increase BF and shear rate equally protect the endothelium when challenged by hyperglycemia.

Treating coronary disease and the impact of endothelial dysfunction

Ischemic heart disease is the leading cause of morbidity and mortality throughout the world. Many clinical trials have suggested that lifestyle and pharmacologic interventions are effective in attenuating atherosclerotic disease progression and events development. However, an individualized approach with careful consideration to comprehensive vascular health is necessary to perform successful intervention strategies. Endothelial dysfunction plays a pivotal role in the early stage of atherosclerosis and is also associated with plaque progression and occurrence of atherosclerotic complications. The assessment of endothelial function provides us with important information about individual patient risk, progress and vulnerability of disease, and guidance of therapy. Thus, the application of endothelial function assessment might enable clinicians to innovate ideal individualized medicine. In this review, we summarize the current knowledge on the impact of pharmacological therapies for atherosclerotic cardiovascular disease on endothelial dysfunction, and argue for the utility of non-invasive assessment of endothelial function aiming at individualized medicine.

Alternative Agents in Type 1 Diabetes in Addition to Insulin Therapy: Metformin, Alpha-Glucosidase Inhibitors, Pioglitazone, GLP-1 Agonists, DPP-IV Inhibitors, and SGLT-2 Inhibitors

Insulin is the mainstay of current treatment for patients with type 1 diabetes mellitus (T1DM). Due to increasing insulin resistance, insulin doses are often continually increased, which may result in weight gain for patients. Medications currently approved for the treatment of type 2 diabetes offer varying mechanisms of action that can help to reduce insulin resistance and prevent or deter weight gain. A MEDLINE search was conducted to review literature evaluating the use of metformin, alpha-glucosidase inhibitors, pioglitazone, glucagon-like peptide 1 agonists, dipeptidyl peptidase, and sodium-dependent glucose transporter 2 inhibitors, in patients with T1DM. Varying results were found with some benefits including reductions in hemoglobin A1c, decreased insulin doses, and favorable effects on weight. Of significance, a common fear of utilizing multiple therapies for diabetes treatment is the risk of hypoglycemia, and this review displayed limited evidence of hypoglycemia with multiple agents.