Diagnosing type 2 diabetes using Hemoglobin A1c: a systematic review and meta-analysis of the diagnostic cutpoint based on microvascular complications

Molecular dissection of the role of ACE2 in glucose homeostasis

Angiotensin-converting enzyme 2 (ACE2) was discovered 25 years ago as a negative regulator of the renin-angiotensin system, opposing the effects of angiotensin II. Beyond its well-demonstrated roles in cardiovascular regulation and COVID-19 pathology, ACE2 is involved in a plethora of physiopathological processes. In this review, we summarize the latest discoveries on the role of ACE2 in glucose homeostasis and regulation of metabolism. In the endocrine pancreas, ACE2 is expressed at low levels in β-cells, but loss of its expression inhibits glucose-stimulated insulin secretion and impairs glucose tolerance. Conversely, overexpression of ACE2 improved glycemia, suggesting that recombinant ACE2 might be a future therapy for diabetes. In the skeletal muscle of ACE2-deficient mice a progressive triglyceride accumulation was observed, whereas in diabetic kidney the initial increase in ACE2 is followed by a chronic reduction of expression in kidney tubules and impairment of glucose metabolism. At the intestinal level dysregulation of the enzyme alters the amino acid absorption and intestinal microbiome, whereas at the hepatic level ACE2 protects against diabetic fatty liver disease. Not least, ACE2 is upregulated in adipocytes in response to nutritional stimuli, and administration of recombinant ACE2 decreased body weight and increased thermogenesis. In addition to tissue-specific regulation of ACE2 function, the enzyme undergoes complex cellular posttranslational modifications that are changed during diabetes evolution, with at least proteolytic cleavage and ubiquitination leading to modifications in ACE2 activity. Detailed characterization of ACE2 in a cellular and tissue-specific manner holds promise for improving therapeutic outcomes in diabetes and metabolic disorders.

The Prevalence and Progression of Microvascular Complications and the Interaction With Ethnicity and Socioeconomic Status in People With Type 2 Diabetes: A Systematic Review and Meta-Analysis

Introduction: Diabetic nephropathy (DN) and diabetic retinopathy (DR) are serious complications of type 2 diabetes mellitus (T2DM). The reported estimates of prevalence and progression of DN and DR vary widely across studies. We undertook a systematic review and meta-analysis to determine the extent to which these variations in prevalence and progression of DN and DR may relate to different ethnic groups and socioeconomic status (SES). Methods: We searched the databases Ovid MEDLINE, Global Health, APA Psych Info, Embase, and PubMed for publications from 2005 to September 2023, based on T2DM and DN or DR, which included patient's ethnicities and SES. Prevalence estimates were summarized by meta-analysis using random effects models for each microvascular complication, stratified by ethnicity and SES. Data on progression was summarized narratively. Results: Twenty-seven studies were included. The overall prevalence of DN was 18% (95% CI: 14%, 22%) with no differences noted by ethnic group. Low economic status and low education levels were associated with a 4% increased risk of DN compared to higher levels. Higher prevalence of DR was noted among the Afro-Caribbeans, 28% (95% CI: 11%, 46%), compared to the White/Caucasian 19% (95% CI: 11%, 27%), and Asian/Indo Asians 25% (95% CI: 9%, 41%). Low-SES populations have a higher prevalence of DR than high-SES populations. The average prevalence was 16% (95% CI: 11%, 22%) among the high economic status group, compared to 25% (95% CI:20%, 30%) for the low economic status. Our study showed that Black ethnicity was associated with a higher risk of progression to end-stage renal disease (ESRD) and diabetic maculopathy compared to other ethnicities. People with high SES had a lower rate of DR progression than those with low SES, odds ratio (OR) (0.63, 95% CI: 53%, 74%). Conclusion: Ethnicity and SES may be associated with differential risk of development and progression of DN and DR. The available evidence was limited by the number of studies and small samples for certain ethnic/socioeconomic groups.

Neutrophil-to-Lymphocyte Ratio as a Potential Biomarker to Managing Type 2 Diabetes Mellitus and Predicting Disease Progression

Introduction Diabetes is a chronic disease that causes dysregulation of blood glucose. Type 2 diabetes mellitus (T2DM) could result in long-term inflammatory conditions that affect different organs of the body. Despite the availability of diagnostic markers like glycated hemoglobin (HbA1c) for T2DM, it is essential to find an appropriate marker that could predict long-term complications. This study evaluates the potential role of neutrophil-to-lymphocyte ratio (NLR) in predicting disease progression and treatment responses.  Methods This case-control study was carried out among 160 T2DM patients and 132 non-diabetic persons. Blood samples were collected from each participant and were processed for hemoglobin, HbA1c, iron, ferritin, and complete blood picture (NLR).  Results The study showed that there was a significant variation in the serum levels of ferritin (264.8±611.6 ng/ml versus 168.3±364.7 ng/ml, p=0.392), iron (4.095±8.851 mcg/dl versus 55.20±37.62 mcg/dl, p=0.0111), and HbA1c (8.169±1.635% versus 5.668±0.5260% p<0.0001) among T2DM patients compared to non-diabetic persons. The NLR values (4.189±4.154 versus 4.095±8.851, p=0.009) among patients with T2DM significantly varied with that of non-diabetic persons. A significant negative correlation was noticed between the serum levels of iron and NLR (r=-0.17, p=0.014) and a positive correlation was noticed between HbA1c and NLR (r=0.19, p=0.014). The serum levels of iron revealed a significant positive correlation with the serum levels of ferritin (r=0.24, p=0.002) and hemoglobin percentage (r=0.41, p=0.008). HbA1c revealed a significant positive correlation with NLR (r=0.19, p=0.014). Additionally, a significant negative correlation was observed between iron with NLR (r=-0.17, p=0.029) and hemoglobin percentage with NLR (r=-0.30, p=0.005). However, no such correlation was demonstrated among non-diabetic persons. With an accuracy of 89.85% and high sensitivity and specificity, NLR showed diagnostic accuracy like HbA1c.  Conclusions NLR demonstrated equivalent efficacy to HbA1c in predicting glycemic control. Since diabetes affects different organs of the body, evaluating NLR probably predicts inflammation. Therefore, NLR could be useful in the management of T2DM and in predicting long-term complications.

Marker-dependent observation and carry-forward of internal covariates in Cox regression

Studies of chronic disease often involve modeling the relationship between marker processes and disease onset or progression. The Cox regression model is perhaps the most common and convenient approach to analysis in this setting. In most cohort studies, however, biospecimens and biomarker values are only measured intermittently (e.g. at clinic visits) so Cox models often treat biomarker values as fixed at their most recently observed values, until they are updated at the next visit. We consider the implications of this convention on the limiting values of regression coefficient estimators when the marker values themselves impact the intensity for clinic visits. A joint multistate model is described for the marker-failure-visit process which can be fitted to mitigate this bias and an expectation-maximization algorithm is developed. An application to data from a registry of patients with psoriatic arthritis is given for illustration.

Glycated Hemoglobin as an Integrator of Cardiovascular Risk in Individuals Without Diabetes: Lessons from Recent Epidemiologic Studies

PURPOSE OF REVIEW

Prediabetes, or dysglycemia in the absence of diabetes, is a prevalent condition typically defined by a glycated hemoglobin (HgbA1c) of 5.7- < 6.5%. This article reviews current contemporary data examining the association between prediabetes and cardiovascular disease (CVD) as well as HgbA1c as a continuous measure of cardiovascular risk across the glycemic spectrum.

RECENT FINDINGS

Dysglycemia in the prediabetic range is associated with an increased risk of both subclinical and clinical CVD, including atherosclerotic CVD, chronic kidney disease, and heart failure. Several recent large, prospective studies demonstrate roughly linear risk with increasing HgbA1c, even below the threshold for prediabetes. "High-risk" patients with prediabetes have similar CVD risk as those with diabetes. HgbA1c below the threshold for diabetes stratifies CVD risk. Use of HgbA1c as a continuous measure, rather than simply dichotomized, may inform current and future prevention strategies. Given the high population attributable risk associated with prediabetes, targeted prevention strategies in this population warrant dedicated study.

HbA1c Screening for Diabetes in Patients with Acute Coronary Syndrome: A Worthwhile Test or a Pitfall?

Background: Diagnostic concordance between HbA1c and other glucose-based tests is imperfect, and data on this problem in acute coronary syndrome (ACS) are still lacking. The aim of this study was to identify undiagnosed glucose abnormalities in ACS patients, and to compare the effectiveness and consistency of the diagnostic screening based on HbA1c to the oral glucose tolerance test (OGTT). Methods: The study group consisted of 121 ACS patients, mean age 62.3 ± 11.6 years, without known glucose abnormalities. HbA1c, admission and fasting plasma glucose in the first days of hospitalization were assessed and referred to the results of OGTT performed two weeks after discharge. Results: OGTT identified normoglycemia in 45%, pre-diabetes in 39.4%, and diabetes in 15.6%, while HbA1c revealed these categories in 39.7%, 51.2%, and 9.1%, respectively. With an HbA1c cut-off ≥6.5% (48 mmol/mol) diagnostic for diabetes, the sensitivity of the method was 41%, while specificity was 98%, compared to the OGTT. The optimal HbA1c cut-off value at the crossing of sensitivity and specificity curves was 5.9%. The HbA1c value recommended for the diagnosis of pre-diabetes and optimal cut-off point were the same (5.7%). Conclusions: Using HbA1c without OGTT in an early but stable phase of ACS may result in a significant underdiagnosis of diabetes.

Definition and Classification of Diabetes and Prediabetes and Emerging Data on Phenotypes

Diabetes diagnosis has important implications for individuals. Diagnostic criteria for fasting and 2-hour plasma glucose and HbA1c are universally agreed. Intermediate hyperglycemia/prediabetes is a risk factor for diabetes and cardiovascular disease. Because risk is a continuum, determining cut-point is problematic and reflected in significant differences in recommended fasting glucose and HbA1c criteria. Many types of diabetes are recognized. Diabetes classification systems are limited by a lack of understanding of etiopathogenetic pathways leading to diminished β-cell function. The World Health Organization classification system is designed to assist clinical care decisions. Newly recognized phenotypic clusters of diabetes might inform future classification systems.

The retinopathy-derived HbA1c threshold of 6.5% for type 2 diabetes also captures the risk of diabetic nephropathy in NHANES

AIM

To determine if an HbA1c diagnostic threshold of less than 6.5% (<48 mmol/mol) could be identified based on a urinary albumin-creatinine ratio (UACR) of 30 mg/g or higher in subjects not known to have diabetes.

METHODS

A UACR was measured for 20 158 participants in the 2011-2018 nationally representative cross-sectional National Health and Nutrition Examination Surveys (NHANES; cycles 7-10 inclusive).

RESULTS

There was a significant trend for an increasing risk with a UACR of 30 mg/g or higher across increasing HbA1c categories (P < .0001). This trend was mainly attributable to the high prevalence of raised UACR in the 7.0% or higher HbA1c subgroup of subjects not previously diagnosed with diabetes. None of the odds ratios in the lower HbA1c subgroups versus the HbA1c subgroup of less than 5.0% reached significance. There were racial/ethnic differences in UACR risk (P < .0001), with White and Black subjects exhibiting little increased risk (vs. HbA1c <5.0%) until they reached an HbA1c of 7.0%, while Asian and Hispanic subjects showed some increased, but non-significant, risks at lower HbA1c levels. Maximizing the area under receiver operating characteristic curves from logistic regressions predicted an ideal HbA1c threshold of 5.8%, but there was little variation in area from 5.5% to 7.0%.

CONCLUSION

A clinically useful diagnostic threshold below 6.5% for HbA1c for elevated UACR risk was not identified, with an increased risk only obvious at an HbA1c of 7.0% or higher. Thus, the retinopathy-derived HbA1c threshold of 6.5% also captures the risk of diabetic nephropathy in NHANES.