The Effect of Metformin Consumption on Mortality in Hospitalized COVID-19 patients: a systematic review and meta-analysis

Metformin for covid-19: systematic review and meta-analysis of randomised controlled trials

Objective

To summarise the effects of metformin on covid-19 to inform a World Health Organization (WHO) clinical practice guideline.

Design

Systematic review and meta-analysis.

Data sources

As part of a living systematic review and network meta-analysis of drug treatments for covid-19 (covid-19 LNMA), a search was performed of the WHO covid-19 database, six Chinese databases, and the Epistemonikos Foundation's Living Overview of the Evidence covid-19 Repository (covid-19 L-OVE).

Eligibility criteria for selecting studies

Randomised controlled trials that compared metformin with placebo in patients with acute covid-19 infection.

Data synthesis

Frequentist pairwise meta-analyses were performed using the restricted maximum likelihood random effects model. The effects of interventions on selected outcomes were summarised using risk ratios, risk difference, and mean difference when appropriate, along with their corresponding 95% confidence intervals (CIs). To estimate absolute effects, the control arm event rate was used as the baseline risk. The risk of bias of the included studies was assessed using a modification of the Cochrane risk of bias 2.0 tool and the certainty of evidence using the GRADE (grading of recommendations assessment, development and evaluation) approach, with the minimally important difference in effect as the threshold.

Results

Three randomised controlled trials of 1869 patients were included; one study provided long term follow-up on long covid. Metformin might have little or no impact on mortality (risk ratio 0.76, 95% CI 0.30 to 1.90; risk difference 3 fewer per 1000, 95% CI 8 fewer to 11 more; low certainty). The effects of metformin on admission to hospital because of covid-19 remain uncertain (risk ratio 0.74, 95% CI 0.28 to 1.95; risk difference 15 fewer per 1000, 95% CI 42 fewer to 55 more; very low certainty). Metformin results in little or no difference in adverse effects leading to discontinuation (risk difference 0.2 more per 1000, 95% CI 2.7 fewer to 3.1 more; high certainty). Metformin might decrease the development of long covid (risk ratio 0.6, 95% CI 0.4 to 0.9; risk difference 41 fewer per 1000, 95% CI 62 fewer to 10 fewer; low certainty). However, the effect is based on a single trial of 1126 patients, which has a high risk of bias owing to missing data, and nearly half of the participants were unvaccinated.

Conclusions

Current evidence based on randomised trials suggests no significant effect of metformin on acute clinical outcomes in patients with non-severe covid-19. Metformin might reduce the incidence of long covid when used to treat patients with non-severe acute covid-19 infection, but this was suggested by low certainty evidence from a single trial.

Antidiabetic agent use and clinical outcomes in patients with diabetes hospitalized for COVID-19: a systematic review and meta-analysis

Background

The effect of antidiabetic agents on mortality outcomes is unclear for individuals with diabetes mellitus (DM) who are hospitalized for COVID-19.

Purpose

To examine the relationship between antidiabetic agent use and clinical outcomes in individuals with DM hospitalized for COVID-19.

Methods

A systematic review of the literature (2020-2024) was performed across five databases. Included articles reported primary research (English) reporting clinical outcomes of adult patients (≥18 yrs.) with DM receiving antidiabetic agents who were hospitalized for COVID-19. Following PRISMA guidelines articles underwent independent dual review. Quality appraisal was completed for included studies. Independent reviewers used a structured data extraction form to retrieve relevant data. Aggregated data were synthesized by treatment regimen and reported descriptively. Random effects meta-analyses were performed to assess relative risk and prevalence of mortality.

Results

After removing duplicates, title and abstract screening of 4,898 articles identified 118 articles for full-text review and 35 articles were retained for analysis. Included articles were primarily from China (15/35, 43%) and retrospective in nature (31/35, 89%). Fourteen studies (40%) assessed multiple antidiabetic agents, fifteen studies (42%) focused on metformin, three studies (9%) assessed the use of DPP-4 inhibitors, and three single studies (9%) investigated the use of insulin, TZD, and SGLT2 inhibitors. Despite differences among studies, the overall relative risk of mortality among metformin and DPP-4 inhibitor users was 0.432 (95% CI = 0.268-0.695, z = 3.45, p < 0.001) and the overall prevalence of mortality among all antidiabetic users was 16% (95% CI = 13%-19%, z = 10.70, p < 0.001).

Conclusions and implications

Synthesis of findings suggest that patients who remained on oral agents (with/without supplemental insulin therapy) exhibited decreased mortality and lower inflammatory markers. Results indicate that individuals with DM should continue oral antidiabetic agents with additional basal insulin as needed to improve glycemic control and reduce mortality. Further work is needed to uncover mechanism(s) and clarify medical management approaches.

Does the Consumption of Metformin Correlate With a Reduction in Mortality Among Patients With Type 2 Diabetes and COVID-19 in Morocco?

OBJECTIVES

To assess whether metformin therapy for type 2 diabetes (T2DM) was associated with a reduced mortality rate in patients hospitalized for COVID-19 compared to other antihyperglycemic drugs.

METHODS

This retrospective study included patients with T2DM who tested positive for SARS-CoV-2 between 1 August 2020 and 1 August 2021. The patients were required to be aged over 18 years old and to be undergoing treatment for hyperglycemia, whether with metformin, other oral antidiabetic drugs, or insulin. A data exploitation sheet was completed for each patient. The Jamovi (https://www.jamovi.org/) software was applied to conduct the statistical analyses. Multivariate logistic regression was used to determine whether metformin use was associated with reduced mortality among patients with T2DM and COVID-19.

RESULTS

We identified 115 COVID-19 patients with T2DM, of whom 41 were on metformin, 35 patients were on insulin, and 39 patients were on other oral antihyperglycemic agents; the average age of patients was 65.5±13.2 years, and 52.2% were male. The mortality rate was lower in the metformin user group (21.1%) compared to the non-user group (78.9%). The multivariate logistic regression model indicated that age (OR=1.06; 95% CI (1.02-1.10); p=0.002) and glycemia (OR=1.49; 95% CI (1.05-2.11); p=0.024) were significantly associated with mortality in patients with T2DM and COVID-19. Whereas, the use of metformin was identified as a protective factor (OR=0.34 95% CI (0.12-0.95); p=0.041).

CONCLUSION

This study highlighted that metformin seems to be associated with significantly decreased mortality in adults with T2DM and COVID-19.

AMP kinase: A promising therapeutic drug target for post-COVID-19 complications

The COVID-19 pandemic, caused by SARS-CoV-2, has resulted in severe respiratory issues and persistent complications, particularly affecting glucose metabolism. Patients with or without pre-existing diabetes often experience worsened symptoms, highlighting the need for innovative therapeutic approaches. AMPK, a crucial regulator of cellular energy balance, plays a pivotal role in glucose metabolism, insulin sensitivity, and inflammatory responses. AMPK activation, through allosteric or kinase-dependent mechanisms, impacts cellular processes like glucose uptake, fatty acid oxidation, and autophagy. The tissue-specific distribution of AMPK emphasizes its role in maintaining metabolic homeostasis throughout the body. Intriguingly, SARS-CoV-2 infection inhibits AMPK, contributing to metabolic dysregulation and post-COVID-19 complications. AMPK activators like capsaicinoids, curcumin, phytoestrogens, cilostazol, and momordicosides have demonstrated the potential to regulate AMPK activity. Compounds from various sources improve fatty acid oxidation and insulin sensitivity, with metformin showing opposing effects on AMPK activation compared to the virus, suggesting potential therapeutic options. The diverse effects of AMPK activation extend to its role in countering viral infections, further highlighting its significance in COVID-19. This review explores AMPK activation mechanisms, its role in metabolic disorders, and the potential use of natural compounds to target AMPK for post-COVID-19 complications. Also, it aims to review the possible methods of activating AMPK to prevent post-COVID-19 diabetes and cardiovascular complications. It also explores the use of natural compounds for their therapeutic effects in targeting the AMPK pathways. Targeting AMPK activation emerges as a promising avenue to mitigate the long-term effects of COVID-19, offering hope for improved patient outcomes and a better quality of life.

Preadmission Metformin Use Is Associated with Reduced Mortality in Patients with Diabetes Mellitus Hospitalized with COVID-19

BACKGROUND

Observational studies have reported an association between metformin and improved outcomes in COVID-19, but most have been small and with significant limitations.

OBJECTIVE

To evaluate the association between preadmission metformin exposure and mortality in patients with diabetes mellitus hospitalized with coronavirus disease 2019 (COVID-19) infection.

DESIGN

Retrospective cohort analysis using electronic health records extracted from the American Heart Association COVID-19 Registry.

PARTICIPANTS

Adults (n = 11,993) with diabetes mellitus but without chronic kidney disease (CKD) or need for hemodialysis who were hospitalized with COVID-19 between January 25, 2020, and February 9, 2022.

MAIN MEASURES

We used propensity score modeling to address differences between metformin and non-metformin users prior to multivariable log-binomial models to examine the association between metformin use at time of hospital admission for COVID-19 infection and in-hospital death; composite of in-hospital death or discharge to hospice; composite of in-hospital death, discharge to hospice, or ICU admission; and composite of in-hospital death, discharge to hospice, ICU admission, or mechanical ventilation.

KEY RESULTS

Compared to metformin non-use, pre-admission metformin use was associated with lower risk of in-hospital death (risk ratio (RR) 0.81 [95% CI 0.75-0.90]); composite of in-hospital death or discharge to hospice (RR 0.79 [95% CI 0.74-0.87]); composite of in-hospital death, discharge to hospice, or ICU admission (RR 0.90 [95% CI 0.86-0.95]); and composite of in-hospital death, discharge to hospice, ICU admission, or mechanical ventilation (RR 0.9 [95% CI 0.84-0.98]). Metformin use was also associated with lower risk of death due to respiratory cause (RR 0.86 [95% CI 0.74-0.97]) but not cardiovascular (RR 0.84 [95% CI 0.58-1.2]) or other (RR 0.78 [95% CI 0.60-1.0]) causes.

CONCLUSIONS

Pre-admission metformin use was associated with lower risk of in-hospital mortality and markers of disease severity among adults with diabetes mellitus without CKD and not requiring hemodialysis who were hospitalized with COVID-19 infection.

Rethinking about Metformin: Promising Potentials

Metformin is widely used drugs in the treatment of type 2 diabetes mellitus. However, the mechanisms of action are complex and are still not fully understood yet. Metformin has a dose-dependent blood sugar-lowering effect. The most common adverse reactions of metformin are gastrointestinal symptoms, and women tend to be more experienced than men. A positive correlation between the administration of duration and the daily dose of metformin and the risk of vitamin B12 deficiency is confirmed. Novel glucose-lowering mechanism through the activation of AMP-activated protein kinase and alteration of gut microbiota composition is identified. In addition, metformin has immunomodulatory properties in various mechanisms, including anti-inflammatory actions, and so forth. Metformin improves insulin sensitivity, which may reduce the risk of tumor growth in certain cancers. The antiviral effects of metformin may occur through several mechanisms, including blocking angiotensin converting enzyme 2 receptor, and so forth. These potential mechanisms of metformin are promising in various clinical settings, such as inflammatory diseases, autoimmune diseases, cancer, and coronavirus disease 2019.

Metformin as a Therapeutic Agent for Obesity-Associated Immune Dysfunction

Obesity is associated with impaired immune function, characterized by inflammation, and leading to poor response to infection, impaired vaccine response, increased susceptibility to autoimmune disease, and increased risk of cancer and cancer mortality. Worse, there is evidence that weight loss alone may be insufficient to reverse the immune dysfunction caused by obesity. It is therefore critically important to identify alternative therapeutic approaches to decrease the negative effects of obesity-associated inflammation. In this article, we will review evidence that the antidiabetic drug metformin may be considered as a therapeutic agent for obesity-associated immune dysfunction. Metformin has immunomodulatory effects, stimulating or suppressing the immune response in both a cell-specific and disease-specific manner. Although the mechanism of action of metformin on the immune system remains to be fully elucidated, there is strong evidence that metformin enters select immune cells and disrupts electron transport, leading to both AMP-activated protein kinase (AMPK)-dependent and AMPK-independent effects on immune cell differentiation and cytokine production. These effects of metformin on immune cells have been shown to improve immune responses to infection, autoimmunity, and cancer.

Metformin use associated with lower rate of hospitalization for influenza in individuals with diabetes

AIM

To investigate if patients with diabetes taking metformin have better outcomes versus those not taking metformin following an emergency room visit for influenza.

METHODS

Using electronic medical records, we performed a retrospective chart review of all adult patients with a diagnosis of diabetes seen in any Duke University Medical Center-affiliated emergency department for influenza over a 6-year period. We documented patient characteristics and comorbidities, and compared outcomes for patients taking metformin versus patients not taking metformin using both univariable and multivariable analyses. Our primary outcome was hospital admission rate. Secondary outcomes were in-hospital length of stay and in-hospital death.

RESULTS

Our cohort included 1023 adult patients with diabetes, of whom 59.9% were female. The mean age was 62.9 years, 58.4% were African American, 36.1% were White, and 81.9% were obese or overweight. Of these patients, 347 (34%) were taking metformin. Patients with diabetes taking metformin were less likely to be hospitalized following an emergency department visit for influenza than patients with diabetes not taking metformin (56.8% vs. 70.1%; p < 0.001). Of those patients admitted, there was no statistically significant difference in length of stay or death.

CONCLUSIONS

In patients with diabetes, metformin use is associated with lower rate of hospitalization following an emergency department visit for influenza.

Effect of metformin (vs. placebo or sulfonylurea) on all-cause and cardiovascular mortality and incident cardiovascular events in patients with diabetes: an umbrella review of systematic reviews with meta-analysis

Purpose

The current umbrella review aimed to evaluate the effect of metformin on all-cause mortality (ACM), cardiovascular mortality, and cardiovascular disease (CVD) incidence in DM patients.

Methods

PubMed, Scopus, Cochrane, Google Scholar, and Web of Science databases were searched with special keywords. Related studies were included after screening by two independent investigators based on title and full texts. The AMSTAR2 checklist was used to assess the quality of studies, and Cochran tests were used to assess the heterogeneity between studies. Overall, seventeen systematic reviews and meta-analysis studies were included. The results revealed that the risk of ACM in patients who received metformin was lower than in patients who did not receive metformin. (OR: 0.80, 95% CI:0.744,0.855); also, the risk of CVD mortality in metformin patients was lower than in the other two groups (placebo and other anti-diabetic drugs) (OR: 0.771, 95% CI:0.688,0.853, P:0.001). The risk of CVD in metformin users was also lower than in the other two groups (OR: 0.828, 95% CI:0.781,0.785).

Summary

This comprehensive review showed that the risk of ACM, death due to CVD, and incidents of CVD in DM who use metformin was lower than the patients who received a placebo only or other diabetic drugs, which can guide clinicians in medical decision-making.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-023-01309-y.

SARS-CoV-2, periodontal pathogens, and host factors: The trinity of oral post-acute sequelae of COVID-19

COVID-19 as a pan-epidemic is waning but there it is imperative to understand virus interaction with oral tissues and oral inflammatory diseases. We review periodontal disease (PD), a common inflammatory oral disease, as a driver of COVID-19 and oral post-acute-sequelae conditions (PASC). Oral PASC identifies with PD, loss of teeth, dysgeusia, xerostomia, sialolitis-sialolith, and mucositis. We contend that PD-associated oral microbial dysbiosis involving higher burden of periodontopathic bacteria provide an optimal microenvironment for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. These pathogens interact with oral epithelial cells activate molecular or biochemical pathways that promote viral adherence, entry, and persistence in the oral cavity. A repertoire of diverse molecules identifies this relationship including lipids, carbohydrates and enzymes. The S protein of SARS-CoV-2 binds to the ACE2 receptor and is activated by protease activity of host furin or TRMPSS2 that cleave S protein subunits to promote viral entry. However, PD pathogens provide additional enzymatic assistance mimicking furin and augment SARS-CoV-2 adherence by inducing viral entry receptors ACE2/TRMPSS, which are poorly expressed on oral epithelial cells. We discuss the mechanisms involving periodontopathogens and host factors that facilitate SARS-CoV-2 infection and immune resistance resulting in incomplete clearance and risk for 'long-haul' oral health issues characterising PASC. Finally, we suggest potential diagnostic markers and treatment avenues to mitigate oral PASC.

View on Metformin: Antidiabetic and Pleiotropic Effects, Pharmacokinetics, Side Effects, and Sex-Related Differences

Metformin is a synthetic biguanide used as an antidiabetic drug in type 2 diabetes mellitus, achieved by studying the bioactive metabolites of Galega officinalis L. It is also used off-label for various other diseases, such as subclinical diabetes, obesity, polycystic ovary syndrome, etc. In addition, metformin is proposed as an add-on therapy for several conditions, including autoimmune diseases, neurodegenerative diseases, and cancer. Although metformin has been used for many decades, it is still the subject of many pharmacodynamic and pharmacokinetic studies in light of its extensive use. Metformin acts at the mitochondrial level by inhibiting the respiratory chain, thus increasing the AMP/ATP ratio and, subsequently, activating the AMP-activated protein kinase. However, several other mechanisms have been proposed, including binding to presenilin enhancer 2, increasing GLP1 release, and modification of microRNA expression. Regarding its pharmacokinetics, after oral administration, metformin is absorbed, distributed, and eliminated, mainly through the renal route, using transporters for cationic solutes, since it exists as an ionic molecule at physiological pH. In this review, particular consideration has been paid to literature data from the last 10 years, deepening the study of clinical trials inherent to new uses of metformin, the differences in effectiveness and safety observed between the sexes, and the unwanted side effects. For this last objective, metformin safety was also evaluated using both VigiBase and EudraVigilance, respectively, the WHO and European databases of the reported adverse drug reactions, to assess the extent of metformin side effects in real-life use.

Metformin as an activator of AMP-activated protein kinase. Known and new mechanisms of action

Metformin, known in the medical community as the drug of first choice for type 2 diabetes mellitus, belongs to the group of biguanides and has proven to be an effective treatment in clinical practice. Our knowledge of the pharmacodynamic properties of metformin has long been limited to the following well-known mechanisms: a decrease in hyperglycemia due to an increase in peripheral insulin sensitivity, glucose utilization by cells, inhibition of hepatic gluconeogenesis, an increase in the capacity of all types of membrane glucose transporters, activation of fibrinolysis, and a decrease in the levels of atherogenic lipoproteins. Recent studies show that the range of positive pleiotropic effects of metformin is not limited to the above, and that the molecular mechanisms of its action are more complex than previously thought. This article presents a less known, but equally important action of metformin, in particular, its anti-oncogenic, antiviral, and anti-aging effects. In our study, we highlight that the activation of 5’-adenosine monophosphate-activated protein kinase (AMPK) should be considered as the primary mechanism of action through which almost all beneficial effects are achieved. In the light of recent scientific advances in metformin pharmacology, together with the pathogenetic uncertainty of the term «biguanide», it seems fair and reasonable to apply a more relevant definition to the drugn, namely «AMPK activator».

The Association of the Levels of High-Density Lipoprotein and Apolipoprotein A1 with SARS-CoV-2 Infection and COVID-19 Severity: An Analysis of the N3C Database

This study analyzed data from the National COVID Cohort Collaborative (N3C) database to investigate whether high-density lipoprotein (HDL) and its major protein component, apolipoprotein A1 (apoA1), are associated with severe COVID-19 sequelae, specifically acute kidney injury (AKI) and severe COVID-19 disease as defined by the infection resulting in hospitalization, extracorporeal membrane oxygenation (ECMO), invasive ventilation, or death. Our study included a total of 1,415,302 subjects with HDL values and 3589 subjects with apoA1 values. Higher levels of both HDL and apoA1 were associated with a lower incidence of infection as well as a lower incidence of severe disease. Higher HDL levels were also associated with a lower incidence of developing AKI. Most comorbidities were negatively correlated with SARS-CoV-2 infection, presumably due to the behavioral changes that occurred as a result of the precautions taken by individuals with underlying comorbidities. The presence of comorbidities, however, was associated with developing severe COVID-19 disease and AKI. African American and Hispanic populations experienced worse outcomes, including a higher incidence of infection and the development of severe disease, as well as AKI. Smoking and being male were associated with a lower incidence of infection, while they were risk factors for the development of severe disease and AKI. The results on cholesterol and diabetes drugs warrant further research, given that the database included multiple drugs in each category impeding for analysis of specific medications. Despite the current limitations in the N3C data, this study is the first to investigate the roles of HDL and apoA1 on the outcomes of COVID-19 using the US population data.

Drugs in primary care that may alter COVID-19 risk and severity

ABSTRACT

This article describes drugs used in primary care that could alter patients' risk for and severity of COVID-19. The risks and benefits of each drug class were differentiated according to the strength of evidence from 58 selected randomized controlled trials, systematic reviews, and meta-analyses. Most of the studies reported on drugs affecting the renin-angiotensin-aldosterone system. Other classes included opioids, acid suppressants, nonsteroidal anti-inflammatory drugs, corticosteroids, vitamins, biguanides, and statins. Current evidence has not fully differentiated drugs that may increase risk versus benefits in COVID-19 infection. Further studies are needed in this area.

Diabetes and the COVID-19 pandemic

Almost immediately after the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus emerged, it was evident that people with chronic diseases, including diabetes, were disproportionately affected, with an increased risk of hospitalisation and mortality. Over the ensuing 2 years, the indirect effects of the pandemic on healthcare delivery in the short term have become prominent, along with the lingering effects of the virus in those directly infected. In the wake of the pandemic and without any evidence from high quality studies, a number of national and international consensus recommendations were published, which were subsequently rapidly updated based on observational studies. There have been unprecedented disruptions from both direct and indirect impacts of coronavirus disease-2019 (COVID-19) in people with diabetes. In this review, we summarise the impact of acute COVID-19 in people with diabetes, discuss how the presentation and epidemiology during the pandemic, including presentation of diabetic ketoacidosis and new-onset diabetes, has changed, and we consider the wider impact of the pandemic on patients and healthcare service delivery, including some of the areas of uncertainty. Finally, we make recommendations on prioritising patients as we move into the recovery phase and also how we protect people with diabetes for the future, as COVID-19 is likely to become endemic.

Whole patient knowledge modeling of COVID-19 symptomatology reveals common molecular mechanisms

Infection with SARS-CoV-2 coronavirus causes systemic, multi-faceted COVID-19 disease. However, knowledge connecting its intricate clinical manifestations with molecular mechanisms remains fragmented. Deciphering the molecular basis of COVID-19 at the whole-patient level is paramount to the development of effective therapeutic approaches. With this goal in mind, we followed an iterative, expert-driven process to compile data published prior to and during the early stages of the pandemic into a comprehensive COVID-19 knowledge model. Recent updates to this model have also validated multiple earlier predictions, suggesting the importance of such knowledge frameworks in hypothesis generation and testing. Overall, our findings suggest that SARS-CoV-2 perturbs several specific mechanisms, unleashing a pathogenesis spectrum, ranging from "a perfect storm" triggered by acute hyper-inflammation, to accelerated aging in protracted "long COVID-19" syndromes. In this work, we shortly report on these findings that we share with the community via 1) a synopsis of key evidence associating COVID-19 symptoms and plausible mechanisms, with details presented within 2) the accompanying "COVID-19 Explorer" webserver, developed specifically for this purpose (found at https://covid19.molecularhealth.com). We anticipate that our model will continue to facilitate clinico-molecular insights across organ systems together with hypothesis generation for the testing of potential repurposing drug candidates, new pharmacological targets and clinically relevant biomarkers. Our work suggests that whole patient knowledge models of human disease can potentially expedite the development of new therapeutic strategies and support evidence-driven clinical hypothesis generation and decision making.

Potential Therapeutic Benefits of Metformin Alone and in Combination with Sitagliptin in the Management of Type 2 Diabetes Patients with COVID-19

Type 2 diabetes mellitus (T2DM) is a potential risk factor for the development of COVID-19 and is associated with higher severity and mortality rates. T2DM patients are commonly treated with metformin monotherapy or metformin plus sitagliptin. In the present case-control, single-center cohort study, a total number of 112 T2DM patients suffering from COVID-19 and aged 44−62 years old were compared with 78 T2DM patients without COVID-19 and aged 42−56 years old. Both the patient group and the control group were allocated into four groups. Group A: T2DM patients with COVID-19 on metformin treatments plus standard therapy (n = 60); group B: T2DM patients with COVID-19 on metformin plus sitagliptin plus standard therapy (n = 52); group C: T2DM patients without COVID-19 on metformin treatments (n = 40); and group D: T2DM patients without COVID-19 on metformin plus sitagliptin (n = 38). The investigation duration was 2−3 weeks. Anthropometric measurements, serological and biochemical investigations, pulmonary radiological findings, and clinical outcomes were evaluated. Only 101 T2DM patients with COVID-19 continued the study, 71 (70.29%) with mild-moderate COVID-19 and 30 (29.7%) with severe COVID-19 were compared with 78 T2DM patients as a control. Inflammatory biomarkers (C reactive protein, ferritin, and procalcitonin), a lung injury biomarker (lactate dehydrogenase), and a coagulopathy biomarker (D-dimer) were elevated in severe COVID-19 patients compared with mild-moderate COVID-19 (p < 0.05) and T2DM patients (p < 0.05). However, metformin plus sitagliptin was more effective than metformin monotherapy in T2DM patients with COVID-19, as evidenced by the mitigation of oxidative stress, CT scan score, and clinical outcomes. The present study confirmed the protective effects of this combination against the development of COVID-19 severity, as most T2DM COVID-19 patients develop mild-moderate forms. Herein, the combination of metformin and sitagliptin may lead to more beneficial effects than metformin monotherapy.

Metformin: Activation of 5' AMP-activated protein kinase and its emerging potential beyond anti-hyperglycemic action

Metformin is a plant-based drug belonging to the class of biguanides and is known to treat type-2 diabetes mellitus (T2DM). The drug, combined with controlling blood glucose levels, improves the body's response to insulin. In addition, trials have identified the cardioprotective potential of metformin in the diabetic population receiving the drug. Activation of 5' AMP-activated protein kinase (AMPK) is the major pathway for these potential beneficial effects of metformin. Historically, much emphasis has been placed on the potential indications of metformin beyond its anti-diabetic use. This review aims to appraise other potential uses of metformin primarily mediated by the activation of AMPK. We also discuss various mechanisms, other than AMPK activation, by which metformin could produce beneficial effects for different conditions. Databases including PubMed/MEDLINE and Embase were searched for literature relevant to the review's objective. Reports from both research and review articles were considered. We found that metformin has diverse effects on the human body systems. It has been shown to exert anti-inflammatory, antioxidant, cardioprotective, metabolic, neuroprotective, anti-cancer, and antimicrobial effects and has now even been identified as effective against SARS-CoV-2. Above all, the AMPK pathway has been recognized as responsible for metformin's efficiency and effectiveness. Owing to its extensive potential, it has the capability to become a part of treatment regimens for diseases apart from T2DM.

Targeting T cell (oxidative) metabolism to improve immunity to viral infection in the context of obesity

Disorders of systemic metabolism can influence immunity. Individuals with obesity are known to have increased inflammation, increased risk to select autoimmune diseases, impaired response to several infections, and impaired vaccine response. For example, over the last decade, it has become clear that individuals with obesity have increased risk of morbidity and mortality from influenza infection. Unsurprisingly, this finding is also observed in the current COVID-19 pandemic: individuals with obesity, particularly severe obesity, have increased risk of poor outcomes from SARS-CoV-2 infection, including increased rates of hospitalization, ICU admission, mechanical ventilation, and death. Several studies have now demonstrated a critical role for T cells in the context of obesity-associated immune dysfunction in response to viral infection, and one mechanism for this may be altered T cell metabolism. Indeed, recent studies have shown that activated T cells from obese mice have an altered metabolic profile characterized by increased glucose oxidation, both in vitro and in vivo following viral infection. For that reason, treatments that target abnormal immune cell metabolism in obesity may improve outcomes to viral infection. To that end, several recent studies have shown that use of the metabolic drug, metformin, can reverse abnormal T cell metabolism and restore T cell immunity, as well as survival, in response to viral infection. These findings will be discussed in detail here.

COVID-19 and Gestational Diabetes: The Role of Nutrition and Pharmacological Intervention in Preventing Adverse Outcomes

Pregnant women with GDM affected by COVID-19 seem to be at higher risk of adverse maternal and neonatal outcomes, especially those with overweight or obesity. Good glycemic control seems to be the most effective measure in reducing the risk of GDM and severe COVID-19. For such purposes, the Mediterranean diet, micronutrient supplementation, and physical activity are considered the first line of treatment. Failure to achieve glycemic control leads to the use of insulin, and this clinical scenario has been shown to be associated with an increased risk of adverse maternal and neonatal outcomes. In this review, we explore the current evidence pertaining to the pathogenesis of SARS-CoV-2 leading to the main complications caused by COVID-19 in patients with GDM. We also discuss the incidence of complications caused by COVID-19 in pregnant women with GDM according to their treatment.

Emerging role of neutrophil extracellular traps in the complications of diabetes mellitus

Immune dysfunction is widely regarded as one of the central tenants underpinning the pathophysiology of diabetes mellitus (DM) and its complications. When discussing immunity, the role of neutrophils must be accounted for: neutrophils are the most abundant of the circulating immune cells and are the first to be recruited to sites of inflammation, where they contribute to host defense via phagocytosis, degranulation, and extrusion of neutrophil extracellular traps (NETs). NETs are composed of DNA associated with nuclear and cytosolic neutrophil proteins. Although originally reported as an antimicrobial strategy to prevent microbial dissemination, a growing body of evidence has implicated NETs in the pathophysiology of various autoimmune and metabolic disorders. In these disorders, NETs propagate a pathologic inflammatory response with consequent tissue injury and thrombosis. Many diabetic complications—such as stroke, retinopathy, impaired wound healing, and coronary artery disease—involve these mechanisms. Therefore, in this review, we discuss laboratory and clinical data informing our understanding of the role of NETs in the development of these complications. NET markers, including myeloperoxidase, citrullinated histone H3, neutrophil elastase, and cell-free double-stranded DNA, can easily be measured in serum or be detected via immunohistochemical/immunocytochemical staining of tissue specimens. Therefore, NET constituents potentially constitute reliable biomarkers for use in the management of diabetic patients. However, no NET-targeting drug is currently approved for the treatment of diabetic complications; a candidate drug will require the outcomes of well-designed, robust clinical trials assessing whether NET inhibition can benefit patients in terms of morbidity, quality of life, health expenditures, and mortality. Therefore, much work remains to be done in translating these encouraging pieces of data into clinical trials for NET-targeting medications to be used in the clinic.

The spike of SARS-CoV-2 promotes metabolic rewiring in hepatocytes

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes a multi-organ damage that includes hepatic dysfunction, which has been observed in over 50% of COVID-19 patients. Liver injury in COVID-19 could be attributed to the cytopathic effects, exacerbated immune responses or treatment-associated drug toxicity. Herein we demonstrate that hepatocytes are susceptible to infection in different models: primary hepatocytes derived from humanized angiotensin-converting enzyme-2 mice (hACE2) and primary human hepatocytes. Pseudotyped viral particles expressing the full-length spike of SARS-CoV-2 and recombinant receptor binding domain (RBD) bind to ACE2 expressed by hepatocytes, promoting metabolic reprogramming towards glycolysis but also impaired mitochondrial activity. Human and hACE2 primary hepatocytes, where steatosis and inflammation were induced by methionine and choline deprivation, are more vulnerable to infection. Inhibition of the renin-angiotensin system increases the susceptibility of primary hepatocytes to infection with pseudotyped viral particles. Metformin, a common therapeutic option for hyperglycemia in type 2 diabetes patients known to partially attenuate fatty liver, reduces the infection of human and hACE2 hepatocytes. In summary, we provide evidence that hepatocytes are amenable to infection with SARS-CoV-2 pseudovirus, and we propose that metformin could be a therapeutic option to attenuate infection by SARS-CoV-2 in patients with fatty liver.

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.

Statin and mortality in COVID-19: a systematic review and meta-analysis of pooled adjusted effect estimates from propensity-matched cohorts

PURPOSE

Statin potentially improved outcome in patients with COVID-19. Patients who receive statin generally have a higher proportion of comorbidities than those who did not, which may introduce bias. In this meta-analysis, we aimed to investigate the association between statin use and mortality in patients with COVID-19 by pooling the adjusted effect estimates from propensity-score matching (PSM) matched studies or randomised controlled trials to reduce bias.

METHODS

A systematic literature search using the PubMed, Scopus and Embase databases were performed up until 1 March 2021. Studies that were designed the study to assess statin and mortality using PSM with the addition of Inverse Probability Treatment Weighting or multivariable regression analysis on top of PSM-matched cohorts were included. The effect estimate was reported in term of relative risk (RR).

RESULTS

14 446 patients were included in the eight PSM-matched studies. Statin was associated with decreased mortality in patients with COVID-19 (RR 0.72 (0.55, 0.95), p=0.018; I2: 84.3%, p<0.001). Subgroup analysis in patients receiving statin in-hospital showed that it was associated with lower mortality (RR 0.71 (0.54, 0.94), p=0.030; I2: 64.1%, p<0.025). The association of statin and mortality was not significantly affected by age (coefficient: -0.04, p=0.382), male gender (RR 0.96 (0.95, 1.02), p=0.456), diabetes (RR 1.02 (0.99, 1.04), p=0.271) and hypertension (RR 1.01 (0.97, 1.04), p=0.732) in this pooled analysis.

CONCLUSION

In this meta-analysis of PSM-matched cohorts with adjusted analysis, statin was shown to decrease the risk of mortality in patients with COVID-19.

PROSPERO REGISTRATION NUMBER

CRD42021240137.

Prognostic value of elevated lactate dehydrogenase in patients with COVID-19: a systematic review and meta-analysis

PURPOSE

This meta-analysis aimed to evaluate the prognostic performance of elevated lactate dehydrogenase (LDH) in patients with COVID-19.

METHODS

A systematic literature search was performed using PubMed, Embase and EuropePMC on 19 November 2020. The outcome of interest was composite poor outcome, defined as a combined endpoint of mortality, severity, need for invasive mechanical ventilation and need for intensive care unit care. Severity followed the included studies' criteria.

RESULTS

There are 10 399 patients from 21 studies. Elevated LDH was present in 44% (34%-53%) of the patients. Meta-regression analysis showed that diabetes was correlated with elevated LDH (OR 1.01 (95% CI 1.00 to 1.02), p=0.038), but not age (p=0.710), male (p=0.068) and hypertension (p=0.969). Meta-analysis showed that elevated LDH was associated with composite poor outcome (OR 5.33 (95% CI 3.90 to 7.31), p<0.001; I2: 77.5%). Subgroup analysis showed that elevated LDH increased mortality (OR 4.22 (95% CI 2.49 to 7.14), p<0.001; I2: 89%). Elevated LDH has a sensitivity of 0.74 (95% CI 0.60 to 0.85), specificity of 0.69 (95% CI 0.58 to 0.78), positive likelihood ratio of 2.4 (95% CI 1.9 to 2.9), negative likelihood ratio of 0.38 (95% CI 0.26 to 0.55), diagnostic OR of 6 (95% CI 4 to 9) and area under curve of 0.77 (95% CI 0.73 to 0.80). Elevated LDH would indicate a 44% posterior probability and non-elevated LDH would in indicate 11% posterior probability for poor prognosis. Meta-regression analysis showed that age, male, hypertension and diabetes did not contribute to the heterogeneity of the analyses.

CONCLUSION

LDH was associated with poor prognosis in patients with COVID-19.

PROSPERO REGISTRATION NUMBER

CRD42020221594.

Does metformin affect outcomes in COVID-19 patients with new or pre-existing diabetes mellitus? A systematic review and meta-analysis

AIMS

The COVID-19 pandemic is a global public health emergency and patients with diabetes mellitus (DM) are disproportionately affected, exhibiting more severe outcomes. Recent studies have shown that metformin is associated with improved outcomes in patients with COVID-19 and DM and may be a potential candidate for drug repurposing. We aimed to investigate the effects of metformin on outcomes in patients with COVID-19 and DM.

METHODS

Databases (PubMed, Scopus, Web of Science, EMBASE, Clinicaltrials.gov and Cochrane library) were searched up to 10 April 2021 for studies reporting data on metformin use in COVID-19 patients with DM. The risk of bias was assessed using the Newcastle-Ottawa scale. Certainty of evidence was rated using the GRADE approach. The primary outcome was mortality reported as odds ratio (OR). A random-effects meta-analysis was carried out on both unadjusted and adjusted ORs. This study is registered with PROSPERO, CRD42020221842.

RESULTS

In total, 2 916 231 patients from 32 cohort studies were included in the quantitative and qualitative synthesis. The meta-analysis showed that metformin was significantly associated with lower mortality in COVID-19 patients with DM in both unadjusted (OR 0.61 [95% confidence interval: 0.53-0.71], P < .00001, I2  = 70%) and adjusted (OR 0.78 [95% confidence interval: 0.69-0.88], P < .00001, I2  = 67%) models.

CONCLUSION

Poor outcomes in COVID-19 patients with DM can be attributed to inadequate glycaemic control and weakened immune responses. Metformin has multiple effects that can improve outcomes in patients with DM and our findings highlight a possible role of its use. However, robust randomised trials are needed to thoroughly assess its use.

Preadmission use of antidiabetic medications and mortality among patients with COVID-19 having type 2 diabetes: A meta-analysis

BACKGROUND

Diabetes is an independent predictor of poor outcomes in patients with COVID-19. We compared the effects of the preadmission use of antidiabetic medications on the in-hospital mortality of patients with COVID-19 having type 2 diabetes.

METHODS

A systematic search of PubMed, EMBASE, Scopus and Web of Science databases was performed to include studies (except case reports and review articles) published until November 30, 2021. We excluded papers regarding in-hospital use of antidiabetic medications. We used a random-effects meta-analysis to calculate the pooled OR (95% CI) and performed a sensitivity analysis to confirm the robustness of the meta-analyses.

MAIN FINDINGS

We included 61 studies (3,061,584 individuals), which were rated as having low risk of bias. The OR (95% CI) indicated some medications protective against COVID-related death, including metformin [0.54 (0.47-0.62), I² 86%], glucagon-like peptide-1 receptor agonist (GLP-1RA) [0.51 (0.37-0.69), I² 85%], and sodium-glucose transporter-2 inhibitor (SGLT-2i) [0.60 (0.40-0.88), I² 91%]. Dipeptidyl peptidase-4 inhibitor (DPP-4i) [1.23 (1.07-1.42), I² 82%] and insulin [1.70 (1.33-2.19), I² 97%] users were more likely to die during hospitalization. Sulfonylurea, thiazolidinedione, and alpha-glucosidase inhibitor were mortality neutral [0.92 (95% CI 0.83-1.01, I² 44%), 0.90 (95% CI 0.71-1.14, I² 46%), and 0.61 (95% CI 0.26-1.45, I² 77%), respectively]. The sensitivity analysis indicated that our findings were robust.

CONCLUSIONS

Metformin, GLP-1RA, and SGLT-2i were associated with lower mortality rate in patients with COVID-19 having type 2 diabetes. DPP-4i and insulin were linked to increased mortality. Sulfonylurea, thiazolidinedione, and alpha-glucosidase inhibitors were mortality neutral. These findings can have a large impact on the clinicians' decisions amid the COVID-19 pandemic.

Metformin use is associated with a decrease in the risk of hospitalization and mortality in COVID-19 patients with diabetes: A population-based study in Lombardy

AIM

To compare the association of metformin use and coronavirus disease 2019 (COVID-19) outcomes in a cohort of 31 966 patients with diabetes in Lombardy.

METHODS

We used a COVID-19 linkable administrative regional database to select patients with diabetes who were aged 40 years or older. They had at least two prescriptions of antidiabetic drugs in 2019 and a positive test for severe acute respiratory syndrome coronavirus-2 from 15 February 2020 to 15 March 2021. The association of metformin use and clinical outcomes was assessed by multivariable logistic regression analyses and after propensity score matching (PSM). Clinical outcomes were all-cause mortality, in-hospital mortality, hospitalization for COVID-19, and admission to an intensive care unit (ICU).

RESULTS

In multivariable models, metformin use was associated with a significantly lower risk of total mortality (OR 0.70; 95% CI 0.66-0.75), in-hospital mortality (OR 0.68; 95% CI 0.63-0.73), hospitalization for COVID-19 (OR 0.86; 95% CI 0.81-0.91), and ICU admission (OR 0.81; 95% CI 0.69-0.94) compared with metformin non-users. Results were similar after PSM; metformin was associated with a significantly lower risk of total mortality (OR 0.79; 95% CI 0.73-0.86), in-hospital mortality (OR 0.74; 95% CI 0.67-0.81), and ICU admission (OR 0.77; 95% CI 0.63-0.95).

CONCLUSIONS

In this large cohort, metformin use was associated with a protective effect in COVID-19 clinical outcomes, suggesting that it might be a potentially useful drug to prevent severe COVID-19 disease, although randomized controlled trials (RCTs) are needed to confirm this. While awaiting the results of RCTs, we suggest continuing prescribing metformin to COVID-19 patients with diabetes.

Associations and Disease-Disease Interactions of COVID-19 with Congenital and Genetic Disorders: A Comprehensive Review

Since December 2019, the COVID-19 pandemic, which originated in Wuhan, China, has resulted in over six million deaths worldwide. Millions of people who survived this SARS-CoV-2 infection show a number of post-COVID complications. Although, the comorbid conditions and post-COVID complexities are to some extent well reviewed and known, the impact of COVID-19 on pre-existing congenital anomalies and genetic diseases are only documented in isolated case reports and case series, so far. In the present review, we analyzed the PubMed indexed literature published between December 2019 and January 2022 to understand this relationship from various points of view, such as susceptibility, severity and heritability. Based on our knowledge, this is the first comprehensive review on COVID-19 and its associations with various congenital anomalies and genetic diseases. According to reported studies, some congenital disorders present high-risk for developing severe COVID-19 since these disorders already include some comorbidities related to the structure and function of the respiratory and cardiovascular systems, leading to severe pneumonia. Other congenital disorders rather cause psychological burdens to patients and are not considered high-risk for the development of severe COVID-19 infection.

Diabetes and COVID-19: The potential role of mTOR

Diabetes is the most frequent comorbidity among patients with COVID-19. COVID-19 patients with diabetes have a more severe prognosis than patients without diabetes. However, the etiopathogenetic mechanisms underlying this more unfavorable outcome in these patients are not clear. Probably the etiopathogenetic mechanisms underlying diabetes could represent a favorable substrate for a greater development of the inflammatory process already dysregulated in COVID-19 with a more severe evolution of the disease. In the attempt to shed light on the possible etiopathogenetic mechanisms, we wanted to evaluate the possible role of mTOR (mammalian Target Of Rapamycin) pathway in this context. We searched the PubMed and Scopus databases to identify articles involving diabetes and the mTOR pathway in COVID-19. The mTOR pathway could be involved in this etiopathogenetic mechanism, in particular, the activation and stimulation of this pathway could favor an inflammatory process that is already dysregulated in itself, while its inhibition could be a way to regulate this dysregulated inflammatory process. However, much remains to be clarified about the mechanisms of the mTOR pathway and its role in COVID-19. The aim of this review is to to understand the etiopathogenesis underlying COVID-19 in diabetic patients and the role of mTOR pathway in order to be able to search for new weapons to deal with this disease.

Preadmission usage of metformin and mortality in COVID-19 patients including the post-discharge period

BACKGROUND

The effect of preadmission metformin usage (PMU) on the mortality of coronavirus disease-2019 (COVID-19) patients with diabetes is conflicting. Most studies have focused on in-hospital mortality; however, mortality after discharge also increases in COVID-19 patients.

AIMS

Examining the effect of PMU on all-cause mortality, including the post-discharge period.

METHODS

Patients with diabetes who were hospitalised in 2020 due to COVID-19 were included in the study. They were divided into two groups: those with a history of metformin use (MF( +)) and those without such history (MF( -)). Propensity score matching (PSM) was performed at a ratio of 1:1 for age and sex. COX regression analyses were used to demonstrate risk factors for mortality.

RESULTS

We investigated 4103 patients hospitalised for COVID-19. After excluding those without diabetes or with chronic liver/kidney disease, we included the remaining 586 patients, constituting 293 women (50%) with an overall mean age of 66 ± 11.9 years. After PSM analysis, the in-hospital and post-discharge mortality rates were higher in the MF( -) group though not significantly different. However, overall mortality was higher in the MF( -) group (51 (42.5%) vs. 35 (29.2%), p = 0.031). For overall mortality, the adjusted HR was 0.585 (95% CI: 0.371 - 0.920, p = 0.020) in the MF( +) group.

CONCLUSION

PMU is associated with reducing all-cause mortality. This effect starts from the in-hospital period and becomes more significant with the post-discharge period. The main limitations were the inability to evaluate the compliance with metformin and the effects of other medications due to retrospective nature.

Endotheliopathy marked by high von Willebrand factor (vWF) antigen in COVID-19 is associated with poor outcome: a systematic review and meta-analysis

BACKGROUND

This systematic review and meta-analysis aimed to compare the levels of von Willebrand Factor (vWF) antigen in patients with coronavirus disease 2019 (COVID-19) with a poor outcome compared with those with a good outcome, and explored factors that may affect the difference in terms of vWF antigen between the two groups.

METHODS

A comprehensive literature search of PubMed, Embase and Scopus databases was undertaken from inception until 7 April 2021. The primary outcome was poor outcome, which is a composite of mortality and severity of COVID-19.

RESULTS

Ten studies including a total of 996 patients were included in this systematic review and meta-analysis. vWF antigen was higher in patients with poor outcomes [standardized mean difference (SMD) 0.84 [0.45-1.23], P<0.001; I2=87.3, P<0.001). For subgroup analysis on studies that reported the vWF antigen level as a percentage, the mean difference was 121.6 [(53.7-189.4), P<0.001; I2=92.0, P<0.001]. Meta-regression showed that the SMD between poor outcome and good outcome was affected by the platelet count (coefficient 0.0061, P=0.001), d-dimer level (coefficient 0.0007, P=0.026) and factor VIII level (coefficient 0.0057, P=0.031), but not by age (coefficient -0.0610, P=0.440), gender (coefficient 0.0135, P=0.698), obesity (coefficient 0.0282, P=0.666), hypertension (coefficient 0.0273, P=0.423), diabetes (coefficient 0.0317, P=0.398) or malignancy (coefficient 0.0487, P=0.608).

CONCLUSION

This meta-analysis showed that the level of vWF antigen was significantly higher in patients with COVID-19 with a poor outcome, signalling marked endotheliopathy. Meta-regression showed that the differences became larger as the platelet count, d-dimer level and factor VIII level increased.

Glycemia control and choice of antihyperglycemic therapy in patients with type 2 diabetes mellitus and COVID-19: a consensus decision of the board of experts of the Russian association of endocrinologists

A dangerous viral disease COVID-19, caused by a new RNA coronavirus SARS-COV-2, has been actively spreading in the world since December 2019. The main manifestations of this disease are bilateral pneumonia, often accompanied by the development of acute respiratory syndrome and respiratory failure. Patients with diabetes mellitus (DM) are at high risk of infection with the SARS-COV-2 virus, severe illness and death.

Maintaining of target glycemic levels is the most important factor in a favorable outcome of COVID-19 in both type 1 and type 2 DM. The choice of antihyperglycemic therapy in a patient with DM in the acute period of COVID-19 depends on the initial therapy, the severity of hyperglycemia, the severity of the viral infection and the patient’s clinical condition.

The article presents the recommendations of the board of experts of the Russian Association of Endocrinologists on glycemic control and the choice of antihyperglycemic therapy in patients with type 2 DM and COVID-19, and also on the use of glucocorticosteroids used in the treatment of COVID-19 in patients with type 2 DM.

Metformin: Sex/Gender Differences in Its Uses and Effects—Narrative Review

Metformin (MTF) occupies a major and fundamental position in the therapeutic management of type 2 diabetes mellitus (T2DM). Gender differences in some effects and actions of MTF have been reported. Women are usually prescribed lower MTF doses compared to men and report more gastrointestinal side effects. The incidence of cardiovascular events in women on MTF has been found to be lower to that of men on MTF. Despite some promising results with MTF regarding pregnancy rates in women with PCOS, the management of gestational diabetes, cancer prevention or adjunctive cancer treatment and COVID-19, most robust meta-analyses have yet to confirm such beneficial effects.

Diabetes, Metformin and the Clinical Course of Covid-19: Outcomes, Mechanisms and Suggestions on the Therapeutic Use of Metformin

Objectives: Pre-existing or new diabetes confers an adverse prognosis in people with Covid-19. We reviewed the clinical literature on clinical outcomes in metformin-treated subjects presenting with Covid-19. Methods: Structured PubMed search: metformin AND [covid (ti) OR covid-19 (ti) OR covid19 (ti) OR coronavirus (ti) OR SARS-Cov2 (ti)], supplemented with another PubMed search: "diabetes AND [covid OR covid-19 OR covid19 OR coronavirus (i) OR SARS-Cov2 (ti)]" (limited to "Clinical Study", "Clinical Trial", "Controlled Clinical Trial", "Meta-Analysis", "Observational Study", "Randomized Controlled Trial", "Systematic Review"). Results: The effects of metformin on the clinical course of Covid-19 were evaluated in retrospective analyses: most noted improved clinical outcomes amongst type 2 diabetes patients treated with metformin at the time of hospitalisation with Covid-19 infection. These outcomes include reduced admission into intensive care and reduced mortality in subgroups with versus without metformin treatment. Conclusion: The pleiotropic actions of metformin associated with lower background cardiovascular risk may mediate some of these effects, for example reductions of insulin resistance, systemic inflammation and hypercoagulability. Modulation by metformin of the cell-surface ACE2 protein (a key binding target for SARS-CoV 2 spike protein) via the AMP kinase pathway may be involved. While pre-existing metformin treatment offers potentially beneficial effects and can be continued when Covid-19 infection is not severe, reports of increased acidosis and lactic acidosis in patients with more severe Covid-19 disease remind that metformin should be withdrawn in patients with hypoxaemia or acute renal disease. Prospective study of the clinical and metabolic effects of metformin in Covid-19 is warranted.

Dipeptidyl peptidase-4 (DPP-IV) inhibitor was associated with mortality reduction in COVID-19 - A systematic review and meta-analysis

INTRODUCTION

This systematic review and meta-analysis aimed to synthesize the latest evidence on the effect of dipeptidyl peptidase-4 (DPP-IV) inhibitor in patients with COVID-19.

METHODS

We performed a systematic literature search from the PubMed, Scopus, Embase, and Clinicaltrials.gov up until 15 July 2021. Studies that met the following criteria were included: prospective or retrospective observational studies or case series or randomized controlled trials (RCTs) reporting DPP-IV inhibitor use in patients with COVID-19 and mortality. The intervention group was patients receiving DPP-IV inhibitor. The control group was patients that did not receive DPP-IV inhibitor. The outcome was mortality reported as odds ratio (OR).

RESULTS

There were 11 studies consisting of 5950 patients in this meta-analysis. DPP-IV inhibitor use was associated with reduced mortality (OR 0.75 [0.56, 0.99], p = 0.043, I2: 42.9, p = 0.064) compared to those that did not receive DPP-IV inhibitor. Sensitivity analysis using the fixed-effect model (OR 0.75 [0.63, 0.88], p < 0.001, I2: 42.9, p = 0.064) also showed mortality benefit. The association between DPP-IV inhibitor and mortality was not significantly affected by age (p = 0.540), sex (p = 0.054), hypertension (p = 0.320), location (continent; p = 0.532), and retrospective/prospective nature of the study (p = 0.840). However, the association was affected by metformin (OR 1.03 [95% CI 1.01, 1.06], p = 0.010) and ACEI/ARB use (OR 1.06 [95% CI 1.02, 1.10], p = 0.004).

CONCLUSION

This meta-analysis showed that DPP-IV inhibitor was associated with reduced mortality in patients with COVID-19.

Effect of colchicine on mortality in patients with COVID-19 - A systematic review and meta-analysis

BACKGROUND AND AIM

This systematic review and meta-analysis aimed to evaluate the latest evidence on the association between colchicine and mortality in patients with COVID-19.

METHODS

We performed a comprehensive literature search from the PubMed, Scopus, Embase, EuropePMC, and Clinicaltrials.gov up until 02 January 2022. We include randomized controlled trials (RCTs) and observational studies reporting colchicine use in patients with COVID-19 and mortality within 30 days. The intervention group was patients given colchicine during the course of treatment. The control group was patients given placebo or standard of care at the respective institutions. The outcome was mortality. The effect estimate was reported as risk ratio (RR).

RESULTS

There were 12 studies comprising of 6953 patients included in this meta-analysis. Mortality rate was 0.18 [95%CI 0.10, 0.26] in the colchicine group and 0.26 [95%CI 0.15, 0.38] in the control group. Colchicine was associated with reduction in mortality (RR 0.66 [95%CI 0.53, 0.83], p < 0.001; I2: 42%). Sensitivity analysis using fixed-effect model (RR 0.73 [95%CI 0.63, 0.83], p < 0.001; I2: 42%. Subgroup analysis on the four RCTs showed non-significant result (RR 0.81 [95%CI 0.54, 1.20], p = 0.29; I2: 10%). Meta-regression showed that the association between colchicine and reduced mortality was not affected by age (p = 0.613) [Fig. 3], sex (p = 0.915), diabetes (p = 0.795), and hypertension (p = 0.403).

CONCLUSION

Though the meta-analysis showed decreased mortality with colchicine in patients with COVID-19, the meta-analysis of randomized trials did not show any significant effect of colchicine on mortality.

COVID-19 and Diabetes

The prevalence of diabetes in people with coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has varied worldwide. Most of the available evidence suggests a significant increase in severity and mortality of COVID-19 in people with either type 1 (T1DM) or type 2 diabetes mellitus (T2DM), especially in association with poor glycemic control. While new-onset hyperglycemia and new-onset diabetes (both T1DM and T2DM) have been increasingly recognized in the context of COVID-19 and have been associated with worse outcome, no conclusive evidence yet suggests direct tropism of SARS-CoV-2 on the β cells of pancreatic islets. While all approved oral antidiabetic agents appear to be safe in people with T2DM having COVID-19, no conclusive data are yet available to indicate a mortality benefit with any class of these drugs, in the absence of large randomized controlled trials.

Metformin use in patients hospitalized with COVID-19: lower inflammation, oxidative stress, and thrombotic risk markers and better clinical outcomes

Diabetes mellitus (DM) is associated with a greater risk of COVID-19 and an increased mortality when the disease is contracted. Metformin use in patients with DM is associated with less COVID-19-related mortality, but the underlying mechanism behind this association remains unclear. Our aim was to explore the effects of metformin on markers of inflammation, oxidative stress, and hypercoagulability, and on clinical outcomes. Patients with DM on metformin (n = 34) and metformin naïve (n = 41), and patients without DM (n = 73) were enrolled within 48 h of hospital admission for COVID-19. Patients on metformin compared to naïve patients had a lower white blood cell count (p = 0.02), d-dimer (p = 0.04), urinary 11-dehydro thromboxane B₂ (p = 0.01) and urinary liver-type fatty acid binding protein (p = 0.03) levels and had lower sequential organ failure assessment score (p = 0.002), and intubation rate (p = 0.03), fewer hospitalized days (p = 0.13), lower in-hospital mortality (p = 0.12) and lower mortality plus nonfatal thrombotic event occurrences (p = 0.10). Patients on metformin had similar clinical outcomes compared to patients without DM. In a multiple regression analysis, metformin use was associated with less days in hospital and lower intubation rate. In conclusion, metformin treatment in COVID-19 patients with DM was associated with lower markers of inflammation, renal ischemia, and thrombosis, and fewer hospitalized days and intubation requirement. Further focused studies are required to support these findings.

Metformin Use in Relation to Clinical Outcomes and Hyperinflammatory Syndrome Among COVID-19 Patients With Type 2 Diabetes: A Propensity Score Analysis of a Territory-Wide Cohort

AIM

This study was conducted in order to evaluate the association between metformin use and clinical outcomes in type 2 diabetes mellitus (T2DM) patients hospitalized with coronavirus disease 2019 (COVID-19).

METHODS

Patients with T2DM with confirmed diagnosis of COVID-19 and admitted between January 21, 2020, and January 31, 2021 in Hong Kong were identified in our cohort. Exposure was defined as metformin use within 90 days prior to admission until hospital discharge for COVID-19. Primary outcome was defined as clinical improvement of ≥1 point on the WHO Clinical Progression Scale (CPS). Other outcomes were hospital discharge, recovery, in-hospital death, acidosis, hyperinflammatory syndrome, length of hospitalization, and changes in WHO CPS score.

RESULTS

Metformin use was associated with greater odds of clinical improvement (OR = 2.74, p = 0.009), hospital discharge (OR = 2.26, p = 0.009), and recovery (OR = 2.54, p = 0.005), in addition to lower odds of hyperinflammatory syndrome (OR = 0.71, p = 0.021) and death (OR = 0.41, p = 0.010) than control. Patients on metformin treatment had a shorter hospital stay (-2.76 days, p = 0.017) than their control counterparts. The average WHO CPS scores were significantly lower in metformin users than non-users since day 15 (p < 0.001). However, metformin use was associated with higher odds of acidosis.

CONCLUSIONS

Metformin use was associated with lower mortality and lower odds for hyperinflammatory syndrome. This provides additional insights into the potential mechanisms of the benefits of metformin use in T2DM patients with COVID-19.

Risk factors for COVID-19 case fatality rate in people with type 1 and type 2 diabetes mellitus: A nationwide retrospective cohort study of 235,248 patients in the Russian Federation

THE AIM

To study the association of demographic, clinical, and laboratory factors and the use of glucose-lowering drugs and anti-coronavirus disease (COVID-19) vaccination with the COVID-19-related case fatality rate (CFR) in diabetes mellitus (DM) patients.

METHODS

This study is a nationwide observational cohort study based on the data from the National Diabetes Register (NDR) that is the database containing online clinical information about the population with DM. The outcomes (death or recovery) for COVID-19 were registered in 235,248 patients with DM [type 1 diabetes mellitus (T1DM), n = 11,058; type 2 diabetes mellitus (T2DM), n = 224,190] from March 20, 2020, until November 25, 2021. The unadjusted odds ratio (OR) and 95% confidence interval (CI) were used to estimate the risk factors for CFR. Then the ranging of significant factors was performed and the most vulnerable groups of factors for the lethal outcome were chosen.

RESULTS

The CFR due to COVID-19 was 8.1% in T1DM and 15.3% in T2DM. Increased CFR was associated with the male population [OR = 1.25 (95% CI: 1.09-1.44) in T1DM and 1.18 (95% CI: 1.15-1.21) in T2DM], age ≥65 years [OR = 4.44 (95% CI: 3.75-5.24) in T1DM and 3.18 (95% CI: 3.09-3.26) in T2DM], DM duration ≥10 years [OR = 2.46 (95% CI: 2.06-2.95) in T1DM and 2.11 (95% CI: 2.06-2.16) in T2DM], body mass index (BMI) ≥30 kg/m² [OR = 1.95 (95% CI: 1.52-2.50)] in T1DM, HbA1c ≥7% [OR = 1.35 (95% CI: 1.29-1.43)] in T2DM. The atherosclerotic cardiovascular disease (ASCVD) and chronic kidney disease (CKD) were associated with higher CFR in T1DM but not in T2DM. The pre-COVID-19 glucose-lowering therapy in T2DM was differently associated with CFR (OR): 0.61 (95% CI: 0.59-0.62) for metformin, 0.59 (95% CI: 0.57-0.61) for dipeptidyl peptidase-4 inhibitors (DPP-4 inhibitors), 0.46 (95% CI: 0.44-0.49) for sodium-glucose co-transporter-2 (SGLT2) inhibitors, 0.38 (95% CI: 0.29-0.51) for glucagon-like peptide-1 receptor agonists (arGLP-1), 1.34 (95% CI: 1.31-1.37) for sulfonylurea (SU), and 1.47 (95% CI: 1.43-1.51) for insulin. Anti-COVID-19 vaccination was associated with a lower fatality risk in both DM types: OR = 0.07 (95% CI: 0.03-0.20) in T1DM and OR = 0.19 (95% CI: 0.17-0.22) in T2DM.

CONCLUSIONS

The results of our study suggest that increased COVID-19-related fatality risk in both T1DM and T2DM patients associated with the male population, older age, longer DM duration, and absence of anti-COVID-19 vaccination. In T2DM, pre-COVID-19 glucose-lowering therapy with metformin, DPP-4 inhibitors, SGLT2 inhibitors, and arGLP-1 had a positive effect on the risk of death. The most vulnerable combination of risk factors for lethal outcome in both DM types was vaccine absence + age ≥65 years + DM duration ≥10 years.

Infection Rates and Impact of Glucose Lowering Medications on the Clinical Course of COVID-19 in People with Type 2 Diabetes: A Retrospective Observational Study

PURPOSE

Diabetes is a risk factor for COVID-19 severity, but the role played by glucose lowering medications (GLM) is still unclear. The aim of this study was to assess infection rates and outcomes of COVID-19 (hospitalization and mortality) in adults with diabetes assisted by the Local Health Unit of Padua (North-East Italy) according to the ongoing GLM.

PATIENTS AND METHODS

People with diabetes were identified using administrative claims, while those with SARS-CoV-2 infection were detected by cross referencing with the local COVID-19 surveillance registry. A multivariate logistic regression model was used to verify the association between GLM classes and the outcome.

RESULTS

SARS-CoV-2 infection rates were marginally but significantly higher in individuals with diabetes as compared to those without diabetes (RR 1.04, p = 0.043), though such relative 4% increase may be irrelevant from a clinical and epidemiological perspective. 1923 individuals with GLM-treated diabetes were diagnosed with COVID-19; 456 patients were hospitalized and 167 died. Those treated with insulin had a significantly higher risk of hospitalizations for COVID-19 (OR 1.48 p < 0.01) as were those treated with sulphonylureas/glinides (OR 1.34, p = 0.02). Insulin use was also significantly associated with higher mortality (OR 1.90, p < 0.01). Use of metformin was significantly associated with lower death rates (OR 0.62, p = 0.02). The association of other GLM classes with the outcome was not significant.

CONCLUSION

Diabetes does not appear to modify the risk of SARS-CoV-2 infection in a clinically meaningful way, but strongly increases the rates of hospitalization and death. Insulin use was associated with worse outcomes, whereas metformin use was associated with lower mortality.

Metformin for Cardiovascular Protection, Inflammatory Bowel Disease, Osteoporosis, Periodontitis, Polycystic Ovarian Syndrome, Neurodegeneration, Cancer, Inflammation and Senescence: What Is Next?

Diabetes is accompanied by several complications. Higher prevalence of cancers, cardiovascular diseases, chronic kidney disease (CKD), obesity, osteoporosis, and neurodegenerative diseases has been reported among patients with diabetes. Metformin is the oldest oral antidiabetic drug and can improve coexisting complications of diabetes. Clinical trials and observational studies uncovered that metformin can remarkably prevent or alleviate cardiovascular diseases, obesity, polycystic ovarian syndrome (PCOS), osteoporosis, cancer, periodontitis, neuronal damage and neurodegenerative diseases, inflammation, inflammatory bowel disease (IBD), tuberculosis, and COVID-19. In addition, metformin has been proposed as an antiaging agent. Numerous mechanisms were shown to be involved in the protective effects of metformin. Metformin activates the LKB1/AMPK pathway to interact with several intracellular signaling pathways and molecular mechanisms. The drug modifies the biologic function of NF-κB, PI3K/AKT/mTOR, SIRT1/PGC-1α, NLRP3, ERK, P38 MAPK, Wnt/β-catenin, Nrf2, JNK, and other major molecules in the intracellular signaling network. It also regulates the expression of noncoding RNAs. Thereby, metformin can regulate metabolism, growth, proliferation, inflammation, tumorigenesis, and senescence. Additionally, metformin modulates immune response, autophagy, mitophagy, endoplasmic reticulum (ER) stress, and apoptosis and exerts epigenetic effects. Furthermore, metformin protects against oxidative stress and genomic instability, preserves telomere length, and prevents stem cell exhaustion. In this review, the protective effects of metformin on each disease will be discussed using the results of recent meta-analyses, clinical trials, and observational studies. Thereafter, it will be meticulously explained how metformin reprograms intracellular signaling pathways and alters molecular and cellular interactions to modify the clinical presentations of several diseases.

Association of clinical characteristics, antidiabetic and cardiovascular agents with diabetes mellitus and COVID-19: a 7-month follow-up cohort study

BACKGROUND

The prognostic factors of long-term outcomes in hospitalized patients with diabetes mellitus and COVID-19 are lacking.

METHODS

In this retrospective cohort study, we evaluated patients aged ≥ 18-years-old with the COVID-19 diagnosis who were hospitalized between Feb 20 and Oct 29, 2020, in the Sina Hospital, Tehran, Iran. 1323 patients with COVID-19 entered in the final analysis, of whom 393 (29.7%) patients had diabetes. We followed up patients for incurring in-hospital death, severe COVID-19, in-hospital complications, and 7-month all-cause mortality. By doing univariate analysis, variables with unadjusted P-value < 0.1 in univariate analyses were regarded as the confounders to include in the logistic regression models. We made adjustments for possible clinical (model 1) and both clinical and laboratory (model 2) confounders.

RESULTS

After multivariable regression, it was revealed that preadmission use of sulfonylureas was associated with a borderline increased risk of severity in both models [model 1, OR (95% CI):1.83 (0.91-3.71), P-value: 0.092; model 2, 2.05 (0.87-4.79), P-value: 0.099] and major adverse events (MAE: each of the severe COVID-19, multi-organ damage, or in-hospital mortality) in model 1 [OR (95% CI): 1.86 (0.90-3.87), P-value: 0.094]. Preadmission use of ACEIs/ARBs was associated with borderline increased risk of MAE in the only model 1 [OR (95% CI):1.83 (0.96-3.48), P-value: 0.066].

CONCLUSIONS

Preadmission use of sulfonylureas and ACEIs/ARBs were associated with borderline increased risk of in-hospital adverse outcomes.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40200-021-00901-4.

Proton pump inhibitor on susceptibility to COVID-19 and its severity: a systematic review and meta-analysis

BACKGROUND

The negative impacts of proton pump inhibitor (PPI), including the risk of pneumonia and mortality, have been reported previously. This meta-analysis aimed to address the current interest of whether the administration of PPI could increase the susceptibility and risk of poor outcome in COVID-19.

METHODS

We performed a systematic literature search from PubMed, Embase, EBSCOhost, and EuropePMC databases up until 3 December 2020. The main outcome was composite poor outcome which comprised of mortality and severe COVID-19. Severe COVID-19 in this study was defined as patients with COVID-19 that fulfill the criteria for severe CAP, including the need for intensive unit care or mechanical ventilation. The secondary outcome was susceptibility, based on cohort comparing COVID-19 positive and COVID-19 negative participants.

RESULTS

There were a total of 290,455 patients from 12 studies in this meta-analysis. PPI use was associated with increased composite poor outcome (OR 1.85 [1.13, 3.03], p = 0.014; I2 90.26%). Meta-regression analysis indicate that the association does not vary by age (OR 0.97 [0.92, 1.02], p = 0.244), male (OR 1.05 [0.99, 1.11], p = 0.091), hypertension (OR 9.98 [0.95, 1.02], p = 0.317), diabetes (OR 0.99 [0.93, 1.05], p = 0.699), chronic kidney disease (OR 1.01 [0.93, 1.10], p = 0.756), non-steroidal anti-inflammatory drug use (OR 1.02 [0.96, 1.09], p = 0.499), and pre-admission/in-hospital PPI use (OR 0.77 [0.26, 2.31], p = 0.644). PPI use was not associated with the susceptibility to COVID-19 (OR 1.56 [0.48, 5.05], p = 0.46; I2 99.7%).

CONCLUSION

This meta-analysis showed a potential association between PPI use and composite poor outcome, but not susceptibility.

PROSPERO ID

CRD42020224286.

Risks of and From SARS-CoV-2 Infection and COVID-19 in People With Diabetes: A Systematic Review of Reviews

BACKGROUND

This review was commissioned by the World Health Organization and presents a summary of the latest research evidence on the impact of coronavirus disease 2019 (COVID-19) on people with diabetes (PWD).

PURPOSE

To review the evidence regarding the extent to which PWD are at increased risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and/or of suffering its complications, including associated mortality.

DATA SOURCES

We searched the Cochrane COVID-19 Study Register, Embase, MEDLINE, and LitCOVID on 3 December 2020.

STUDY SELECTION

Systematic reviews synthesizing data on PWD exposed to SARS-CoV-2 infection, reporting data on confirmed SARS-CoV-2 infection, admission to hospital and/or to intensive care unit (ICU) with COVID-19, and death with COVID-19 were used.

DATA EXTRACTION

One reviewer appraised and extracted data; data were checked by a second.

DATA SYNTHESIS

Data from 112 systematic reviews were narratively synthesized and displayed using effect direction plots. Reviews provided consistent evidence that diabetes is a risk factor for severe disease and death from COVID-19. Fewer data were available on ICU admission, but where available, these data also signaled increased risk. Within PWD, higher blood glucose levels both prior to and during COVID-19 illness were associated with worse COVID-19 outcomes. Type 1 diabetes was associated with worse outcomes than type 2 diabetes. There were no appropriate data for discerning whether diabetes was a risk factor for acquiring SARS-CoV-2 infection.

LIMITATIONS

Due to the nature of the review questions, the majority of data contributing to included reviews come from retrospective observational studies. Reviews varied in the extent to which they assessed risk of bias.

CONCLUSIONS

There are no data on whether diabetes predisposes to infection with SARS-CoV-2. Data consistently show that diabetes increases risk of severe COVID-19. As both diabetes and worse COVID-19 outcomes are associated with socioeconomic disadvantage, their intersection warrants particular attention.

COVID-19 and Cardiovascular Complications: An Updated Review

COVID-19 has become a global pandemic. Patients with pre-existing comorbidities such as hypertension, diabetes, and cardiovascular disease (CVD) are associated with greater severity and higher mortality. COVID-19 can cause cardiovascular complications, including myocardial injury, myocarditis, heart failure, acute coronary syndrome, and coagulation abnormalities. Possible pathophysiology and molecular pathways driving these disease processes are cytokine release syndrome, RAAS system dysregulation, plaque destabilization and coagulation disorders  Myocarditis is one concern among persons who received mRNA-Based COVID-19 vaccines. There are several cardiovascular complications that are possibly caused by COVID-19 treatments, such as QT interval prolongation, arrhythmia, and hypotension. Due to increasingly recognized CVD damage in COVID-19, we need to understand about COVID-19 related to cardiovascular complications and treatment strategies.

Managing diabetes in diabetic patients with COVID: where do we start from?

AIMS

COVID-19 has and still is sweeping away the national health systems worldwide. In this review, we sought to determine the evidence base proofs on the antidiabetic treatment capable to reduce the risk of COVID-19-related mortality.

METHODS

We have performed a systematic search of published articles using PubMed, and EMBASE from March 2020 to March 31st, 2021. We excluded editorials, commentary, letters to the editor, reviews, and studies that did not have mortality as an outcome. For metformin and insulin only, we performed a meta-analysis using Cochrane RevMan 5.2.

RESULTS

Among antidiabetic drugs, metformin was the only drug associated with a reduced risk of mortality. Conversely, insulin appears associated with an increased risk. The other classes of drugs were neutral.

CONCLUSIONS

The totality of articles reports retrospective data strongly affected by "channeling bias" so that most of the existing results on each class of drugs are driven by the phenotype of patients likely to receive that specific drug by prescription.