Effect of glycaemic control on cardiovascular disease in individuals with type 2 diabetes with pre-existing cardiovascular disease: A systematic review and meta-analysis

Glycaemic control and macrovascular and microvascular outcomes: A systematic review and meta-analysis of trials investigating intensive glucose-lowering strategies in people with type 2 diabetes

AIM

We aimed to determine the macrovascular and microvascular outcomes of intensive versus standard glucose-lowering strategies in type 2 diabetes (T2D) and investigate the relationships between these outcomes and trial arm glycated haemoglobin (HbA1c) reduction.

MATERIALS AND METHODS

In this systematic review and meta-analysis, we identified relevant trials from MEDLINE, Embase, the Cochrane Library, and bibliographies up to August 2023. Macrovascular and microvascular outcomes, along with safety outcomes, were evaluated. Pooled study-specific hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated, and meta-regression was employed to analyse the relationships between outcomes and HbA1c reduction.

RESULTS

We included 11 unique RCTs involving 51 469 patients with T2D (intensive therapy, N = 26 691; standard therapy, N = 24 778). Intensive versus standard therapy reduced the risk of non-fatal myocardial infarction (MI) (HR 0.84; 95% CI 0.75-0.94) with no difference in the risk of major adverse cardiovascular events (HR 0.97; 95% CI 0.92-1.03) and other adverse cardiovascular outcomes. Intensive versus standard therapy reduced the risk of retinopathy (HR 0.85; 0.78-0.93), nephropathy (HR 0.71; 0.58-0.87) and composite microvascular outcomes (HR 0.88; 0.77-1.00). Meta-regression analyses showed modest evidence of inverse linear relationships between HbA1c reduction and the outcomes of major adverse cardiovascular events, non-fatal MI, stroke and retinopathy, but these were not statistically significant.

CONCLUSIONS

In people with T2D, intensive glucose control was associated with a reduced risk of non-fatal MI and several microvascular outcomes, particularly retinopathy and nephropathy. The lack of an effect of intensive glucose-lowering on most macrovascular outcomes calls for a more comprehensive approach to managing cardiovascular risk factors alongside glycaemic control.

A synthesis of pathways linking diet, metabolic risk and cardiovascular disease: a framework to guide further research and approaches to evidence-based practice

Cardiovascular disease (CVD) is the most common non-communicable disease occurring globally. Although previous literature has provided useful insights into the important role that diet plays in CVD prevention and treatment, understanding the causal role of diets is a difficult task considering inherent and introduced weaknesses of observational (e.g. not properly addressing confounders and mediators) and experimental research designs (e.g. not appropriate or well designed). In this narrative review, we organised current evidence linking diet, as well as conventional and emerging physiological risk factors, with CVD risk, incidence and mortality in a series of diagrams. The diagrams presented can aid causal inference studies as they provide a visual representation of the types of studies underlying the associations between potential risk markers/factors for CVD. This may facilitate the selection of variables to be considered and the creation of analytical models. Evidence depicted in the diagrams was systematically collected from studies included in the British Nutrition Task Force report on diet and CVD and database searches, including Medline and Embase. Although several markers and disorders linked to conventional and emerging risk factors for CVD were identified, the causal link between many remains unknown. There is a need to address the multifactorial nature of CVD and the complex interplay between conventional and emerging risk factors with natural and built environments, while bringing the life course into the spotlight.

Cardiorenal diseases in type 2 diabetes mellitus: clinical trials and real-world practice

Patients with type 2 diabetes mellitus (T2DM) can have multiple comorbidities and premature mortality due to atherosclerotic cardiovascular disease, hospitalization with heart failure and/or chronic kidney disease. Traditional drugs that lower glucose, such as metformin, or that treat high blood pressure and blood levels of lipids, such as renin-angiotensin-system inhibitors and statins, have organ-protective effects in patients with T2DM. Amongst patients with T2DM treated with these traditional drugs, randomized clinical trials have confirmed the additional cardiorenal benefits of sodium-glucose co-transporter 2 inhibitors (SGLT2i), glucagon-like peptide 1 receptor agonists (GLP1RA) and nonsteroidal mineralocorticoid receptor antagonists. The cardiorenal benefits of SGLT2i extended to patients with heart failure and/or chronic kidney disease without T2DM, whereas incretin-based therapy (such as GLP1RA) reduced cardiovascular events in patients with obesity and T2DM. However, considerable care gaps exist owing to insufficient detection, therapeutic inertia and poor adherence to these life-saving medications. In this Review, we discuss the complex interconnections of cardiorenal-metabolic diseases and strategies to implement evidence-based practice. Furthermore, we consider the need to conduct clinical trials combined with registers in specific patient segments to evaluate existing and emerging therapies to address unmet needs in T2DM.

Predictive Capacity of Beat-to-Beat Blood Pressure Variability for Cardioautonomic and Vascular Dysfunction in Early Metabolic Challenge

Diabetic patients present established cardiovascular disease at the onset of diagnostic metabolic symptoms. While premature autonomic and vascular deterioration considered risk factors for major cardiovascular complications of diabetes, present in initial stages of metabolic impairment, their early detection remains a significant challenge impeding timely intervention. In the present study, we examine the utility of beat-to-beat blood pressure variability (BPV) parameters in capturing subtle changes in cardiac autonomic and vascular control distinguishing between various risk categories, independent of the average BP. A rat model of mild hypercaloric (HC) intake was used to represent the insidious cardiovascular changes associated with early metabolic impairment. Invasive hemodynamics were used to collect beat-to-beat BP time series in rats of either sex with different durations of exposure to the HC diet. Linear (standard deviation and coefficient of variation) and nonlinear (approximate entropy, ApEn, and self-correlation of detrended fluctuation analysis, α) BPV parameters were calculated to assess the impact of early metabolic impairment across sexes and feeding durations. HC-fed male, but not female, rats developed increased fat:lean ratio as well as hyperinsulinemia. Unlike linear parameters, multivariate analysis showed that HC-fed rats possessed lower ApEn and higher α, consistent with early changes in heart rate variability and blunting of parasympathetic baroreceptor sensitivity, particularly in males. Moreover, logistic regression demonstrated the superiority of nonlinear parameters of diastolic BPV in predicting a prediabetic disease state. Our findings support the use of nonlinear beat-to-beat BPV for early detection of cardiovascular derangements in the initial stages of metabolic impairment.

Association of type 2 diabetes remission and risk of cardiovascular disease in pre-defined subgroups

AIM

To quantify the association between type 2 diabetes remission and 5-year incidence of cardiovascular disease outcomes, overall and in pre-defined subgroups.

METHODS

Retrospective cohort analysis of 60,287 adults with type 2 diabetes from the Care and Health Information Analytics (CHIA) database. Multivariable Cox models were used to assess the association between remission within the first two years of follow-up and incidence of cardiovascular disease (CVD) outcomes including events, microvascular and macrovascular complications at 7-year follow-up. Effect modification by age, sex, diabetes duration, pre-existing CVD, baseline body mass index (BMI) and HbA1c level was assessed.

RESULTS

7489 (12.4%) people achieved remission during the first two years of follow-up. Overall, remission was associated with lower risk of CVD outcomes. Remission was associated with lower risk of microvascular complications for younger compared with older age groups (eg aHR: 0.59 (0.41-0.84) and aHR: 0.78 (0.67-0.92) for those aged <45 years and 75-84 years, respectively). Amongst those achieving remission, those with no or 1-2 comorbidities had lower risk of microvascular complications (aHR: 0.65 (0.56-0.75)) compared to those with more than three comorbidities (aHR: 0.83 (0.69-0.99), respectively). There were no significant interactions in the remaining subgroups or for models assessing CVD events or macrovascular complications.

CONCLUSIONS

Achieving remission of type 2 diabetes is associated with a lower risk of microvascular complications, particularly for younger groups and those with fewer comorbidities. Targeted interventions that focus on promoting remission in these groups may reduce the impact of microvascular complications and associated health costs.

Peri-renal adipose inflammation contributes to renal dysfunction in a non-obese prediabetic rat model: Role of anti-diabetic drugs

Diabetic nephropathy is a major health challenge with considerable economic burden and significant impact on patients' quality of life. Despite recent advances in diabetic patient care, current clinical practice guidelines fall short of halting the progression of diabetic nephropathy to end-stage renal disease. Moreover, prior literature reported manifestations of renal dysfunction in early stages of metabolic impairment prior to the development of hyperglycemia indicating the involvement of alternative pathological mechanisms apart from those typically triggered by high blood glucose. Here, we extend our prior research work implicating localized inflammation in specific adipose depots in initiating cardiovascular dysfunction in early stages of metabolic impairment. Non-obese prediabetic rats showed elevated glomerular filtration rates and mild proteinuria in absence of hyperglycemia, hypertension, and signs of systemic inflammation. Isolated perfused kidneys from these rats showed impaired renovascular endothelial feedback in response to vasopressors and increased flow. While endothelium dependent dilation remained functional, renovascular relaxation in prediabetic rats was not mediated by nitric oxide and prostaglandins as in control tissues, but rather an upregulation of the function of epoxy eicosatrienoic acids was observed. This was coupled with signs of peri-renal adipose tissue (PRAT) inflammation and renal structural damage. A two-week treatment with non-hypoglycemic doses of metformin or pioglitazone, shown previously to ameliorate adipose inflammation, not only reversed PRAT inflammation in prediabetic rats, but also reversed the observed functional, renovascular, and structural renal abnormalities. The present results suggest that peri-renal adipose inflammation triggers renal dysfunction early in the course of metabolic disease.

The residual cardiorenal risk in type 2 diabetes

In this commentary, we introduce the concepts of removed and residual risks in conditioning thecardiorenal outlook of patients with type 2 diabetes (T2D). The removed cardiorenal risk represents the risk of progression of CV events (major adverse cardiovascular events, MACE; heart failure, HF) and diabetes kidney disease (DKD) taken away by optimal glycemic control or the use of newer antihyperglycemic drugs (glucagon-like peptide-1 receptor agonists, GLP-1RA, andsodium-glucose transporter-2 inhibitors, SGLT-2i) in patients with T2D, as demonstrated by the results of intensive glucose lowering trials (IGT) and cardiovascular outcome trials (CVOT). IGT have shown that successful glycemic control has modest benefits, as the removed cardiorenal risk ranges from 9% for MACE, to 20% for progression of DKD and to 0% for HF. The removed risk of MACE is 13% for GLP-1RA and 12% for SGLT-2i. However, SGLT-2i, as compared with GLP-1RA, removed twofold more risk (39% vs 17%) for kidney outcomes and fourfold more risk (33% vs 9%) for HF. Dipeptidyl peptidase-4 inhibitors have no clinically important cardiorenal benefits, as residual risk is 99% for MACE, 100% for kidney outcomes (excluding new albuminuria), and 100% for HF. Although the results of some real world, population-based cohort studies suggest the possibility that the cardiorenal protection afforded by newer antihyperglycemic drugs is additive to that of optimal glycemic control, only specific randomized controlled trials could answer this question.

Sodium-glucose transporter-2 inhibitors for prevention and treatment of cardiorenal complications of type 2 diabetes

Hospitalization for major diabetes complications, including myocardial infarction, stroke, lower-extremity amputation, and end-stage kidney disease, is on the rise and represents a great health burden for patients with type 2 diabetes (T2D), in particular for older people. Newer glucose-lowering medications have generated some optimism on the possibility to influence the natural history of cardiorenal complications of T2D. This review summarizes work in the area of sodium–glucose cotransporter 2 inhibitors (SGLT-2i) treatment and prevention of cardiorenal complications in patients with T2D (major adverse cardiovascular events, hospitalization for heart failure, kidney outcomes), with a particular emphasis on the effect of age, the role of primary versus secondary prevention and the possible extension of their cardiorenal benefits to the entire class of SGLT-2i.

Worsening baroreflex sensitivity on progression to type 2 diabetes: localized vs. systemic inflammation and role of antidiabetic therapy

Cardiac autonomic neuropathy (CAN) is an early cardiovascular manifestation of type 2 diabetes (T2D) that constitutes an independent risk factor for cardiovascular mortality and morbidity. Nevertheless, its underlying pathophysiology remains poorly understood. We recently showed that localized perivascular adipose tissue (PVAT) inflammation underlies the incidence of parasympathetic CAN in prediabetes. Here, we extend our investigation to provide a mechanistic framework for the evolution of autonomic impairment as the metabolic insult worsens. Early metabolic dysfunction was induced in rats fed a mild hypercaloric diet. Two low-dose streptozotocin injections were used to evoke a state of late decompensated T2D. Cardiac autonomic function was assessed by invasive measurement of baroreflex sensitivity using the vasoactive method. Progression into T2D was associated with aggravation of CAN to include both sympathetic and parasympathetic arms. Unlike prediabetic rats, T2D rats showed markers of brainstem neuronal injury and inflammation as well as increased serum levels of IL-1β. Experiments on PC12 cells differentiated into sympathetic-like neurons demonstrated that brainstem injury observed in T2D rats resulted from exposure to possible proinflammatory mediators in rat serum rather than a direct effect of the altered metabolic profile. CAN and the associated cardiovascular damage in T2D only responded to combined treatment with insulin to manage hyperglycemia in addition to a nonhypoglycemic dose of metformin or pioglitazone providing an anti-inflammatory effect, coincident with the effect of these combinations on serum IL-1β. Our present results indicate that CAN worsening upon progression to T2D involves brainstem inflammatory changes likely triggered by systemic inflammation.

Cardiovascular effects of glucagon-like peptide 1 receptor agonists: from mechanistic studies in humans to clinical outcomes

Type 2 diabetes mellitus (T2DM) is currently one of the most prevalent diseases, with as many as 415 million patients worldwide. T2DM is characterized by elevated blood glucose levels and is often accompanied by several comorbidities, such as cardiovascular disease. Treatment of T2DM is focused on reducing glucose levels by either lifestyle changes or medical treatment. One treatment option for T2DM is based on the gut-derived hormone glucagon-like peptide 1 (GLP-1). GLP-1 reduces blood glucose levels by stimulating insulin secretion, however, it is rapidly degraded, and thereby losing its glycaemic effect. GLP-1 receptor agonists (GLP-1RAs) are immune to degradation, prolonging the glycaemic effect. Lately, GLP-1RAs have spiked the interest of researchers and clinicians due to their beneficial effects on cardiovascular disease. Preclinical and clinical data have demonstrated that GLP-1 receptors are abundantly present in the heart and that stimulation of these receptors by GLP-1 has several effects. In this review, we will discuss the effects of GLP-1RA on heart rate, blood pressure, microvascular function, lipids, and inflammation, as measured in human mechanistic studies, and suggest how these effects may translate into the improved cardiovascular outcomes as demonstrated in several trials.

Amelioration of perivascular adipose inflammation reverses vascular dysfunction in a model of nonobese prediabetic metabolic challenge: potential role of antidiabetic drugs

The onset of vascular impairment precedes that of diagnostic hyperglycemia in diabetic patients suggesting a vascular insult early in the course of metabolic dysfunction without a well-defined mechanism. Mounting evidence implicates adipose inflammation in the pathogenesis of insulin resistance and diabetes. It is not certain whether amelioration of adipose inflammation is sufficient to preclude vascular dysfunction in early stages of metabolic disease. Recent findings suggest that antidiabetic drugs, metformin, and pioglitazone, improve vascular function in prediabetic patients, without an indication if this protective effect is mediated by reduction of adipose inflammation. Here, we used a prediabetic rat model with delayed development of hyperglycemia to study the effect of metformin or pioglitazone on adipose inflammation and vascular function. At the end of the metabolic challenge, these rats were neither obese, hypertensive, nor hyperglycemic. However, they showed increased pressor responses to phenylephrine and augmented aortic and mesenteric contraction. Vascular tissues from prediabetic rats showed increased Rho-associated kinase activity causing enhanced calcium sensitization. An elevated level of reactive oxygen species was seen in aortic tissues together with increased Transforming growth factor β1 and Interleukin-1β expression. Although, no signs of systemic inflammation were detected, perivascular adipose inflammation was observed. Adipocyte hypertrophy, increased macrophage infiltration, and elevated Transforming growth factor β1 and Interleukin-1β mRNA levels were seen. Two-week treatment with metformin or pioglitazone or switching to normal chow ameliorated adipose inflammation and vascular dysfunction. Localized perivascular adipose inflammation is sufficient to trigger vascular dysfunction early in the course of diabetes. Interfering with this inflammatory process reverses this early abnormality.

Glycemic Control, Preexisting Cardiovascular Disease, and Risk of Major Cardiovascular Events in Patients with Type 2 Diabetes Mellitus: Systematic Review With Meta-Analysis of Cardiovascular Outcome Trials and Intensive Glucose Control Trials

Background

The value of glycemic control and preexisting cardiovascular disease in determining the risk of major cardiovascular events (MACE) in type 2 diabetes mellitus is uncertain. Intensive glucose control trials suggest that the 9% lower risk of MACE associated with intensive glycemic control, as compared with conventional glycemic control, is only driven by patients with type 2 diabetes mellitus without cardiovascular disease at baseline.

Methods and Results

We did a meta‐analysis of cardiovascular outcome trials dividing patients with or without preexisting cardiovascular disease; we found that the lower risk of MACE is confined to patients with cardiovascular disease at baseline. Compared with placebo, the use of both glucagon‐like peptide‐1 receptor agonists and sodium‐glucose cotransporter‐2 inhibitors was associated with a significant 14% lower MACE risk in patients with preexisting cardiovascular disease and with a nonsignificant 2% higher MACE risk in those without preexisting cardiovascular disease (P for interaction=0.021). The meta‐regression analysis of all 12 trials demonstrated a significant (P=0.002) association between reductions of glycated hemoglobin in glycated hemoglobin A_1C. Accordingly, the reduction of MACE expected if all cardiovascular outcome trials had achieved a 0.9% glycated hemoglobin reduction would have been 33%. Routine clinical care data complement the results of cardiovascular outcome trials but with some differences: the lower risk of MACE with sodium‐glucose cotransporter‐2 inhibitor use is evident in patients with type 2 diabetes mellitus with or without preexisting cardiovascular disease.

Conclusions

Sodium‐glucose cotransporter‐2 inhibitors and glucagon‐like peptide‐1 receptor agonists should be included in the therapeutic plan of patients with type 2 diabetes mellitus and overt cardiovascular disease, with due attention paid to improvement of glycemic control, which may amplify their benefit on MACE.