Impact of Genetic Determinants of HbA1c on Type 2 Diabetes Risk and Diagnosis

Establishing causal relationships between insomnia and gestational diabetes mellitus using Mendelian randomization

Background

Gestational diabetes mellitus (GDM) is a common condition observed globally, and previous studies have suggested a link between GDM and insomnia. The objective of this study was to elucidate the causative relationship between insomnia and GDM, and to investigate the influence of factors related to insomnia on GDM.

Methods

We performed bidirectional Mendelian randomization (MR) analyses using single nucleotide polymorphisms (SNPs) as genetic instruments for exposure and mediators, thereby minimizing bias due to confounding and reverse causation. The Cochran Q test was utilized for heterogeneity analysis, MR-Egger regression for pleiotropy assessment, and the leave-one-out method for evaluating the robustness of the results. Additionally, we determined the causal relationships between GDM and other factors such as coffee consumption, alcohol intake, and household income.

Results

Insomnia was positively associated with GDM, as indicated by 39 SNPs (OR = 1.27, 95 % CI 1.12-1.439, P-value = 0.008). Conversely, the MR analysis did not reveal any causal relationship between GDM and insomnia (OR = 1.032, 95 % CI 0.994-1.071, P-value = 0.99). Additionally, no causal relationship was observed between coffee consumption, alcohol intake, household income, and GDM (all P-values >0.05).

Conclusion

Our study indicates that insomnia elevates the risk of GDM, thereby establishing a causal link with GDM, independent of coffee consumption, alcohol intake, and household income.

Genetics and Epigenetics: Implications for the Life Course of Gestational Diabetes

Gestational diabetes (GDM) is one of the most common complications of pregnancy, affecting as many as one in six pregnancies. It is associated with both short- and long-term adverse outcomes for the mother and fetus and has important implications for the life course of affected women. Advances in genetics and epigenetics have not only provided new insight into the pathophysiology of GDM but have also provided new approaches to identify women at high risk for progression to postpartum cardiometabolic disease. GDM and type 2 diabetes share similarities in their pathophysiology, suggesting that they also share similarities in their genetic architecture. Candidate gene and genome-wide association studies have identified susceptibility genes that are shared between GDM and type 2 diabetes. Despite these similarities, a much greater effect size for MTNR1B in GDM compared to type 2 diabetes and association of HKDC1, which encodes a hexokinase, with GDM but not type 2 diabetes suggest some differences in the genetic architecture of GDM. Genetic risk scores have shown some efficacy in identifying women with a history of GDM who will progress to type 2 diabetes. The association of epigenetic changes, including DNA methylation and circulating microRNAs, with GDM has also been examined. Targeted and epigenome-wide approaches have been used to identify DNA methylation in circulating blood cells collected during early, mid-, and late pregnancy that is associated with GDM. DNA methylation in early pregnancy had some ability to identify women who progressed to GDM, while DNA methylation in blood collected at 26-30 weeks gestation improved upon the ability of clinical factors alone to identify women at risk for progression to abnormal glucose tolerance post-partum. Finally, circulating microRNAs and long non-coding RNAs that are present in early or mid-pregnancy and associated with GDM have been identified. MicroRNAs have also proven efficacious in predicting both the development of GDM as well as its long-term cardiometabolic complications. Studies performed to date have demonstrated the potential for genetic and epigenetic technologies to impact clinical care, although much remains to be done.

Cytoskeletal protein SPTA1 mediating the decrease in erectile function induced by high-fat diet via Hippo signaling pathway

BACKGROUND

The mechanism of high-fat diet (HFD)-induced decrease in erectile function has not been elucidated, and in previous studies, spectrin alpha, erythrocytic 1 (SPTA1) is a cytoskeletal protein that regulates cellular function, which belongs to a family of proteins that can affect cell and tissue growth and development by regulating YAP, an effector on the Hippo signaling pathway, but its particular role has not been elucidated.

OBJECTIVE

To explore the role of SPTA1 in the abnormality of erectile function induced by HFD.

METHODS

We analyzed the penile tissues of mice on normal diet and HFD by transcriptomics and screened for differentially expressed genes, further identified closely related target genes in rat penile tissues, and verified target gene expression in in vitro construction of high-glucose (HG)-treated corpus cavernosum endothelial cells (CCECs) and corpus cavernosum smooth muscle cells (CCSMCs) models. The distribution of target genes in various cell populations in penile tissues was retrieved by single-cell sequencing Male Health Atlas database. Moreover, interfering with target genes was further applied to explore the mechanisms involved in erectile function decline.

RESULTS

Transcriptomic analysis screened out down-regulated differential gene SPTA1; Western blot and immunohistochemistry results showed that SPTA1 expression significantly decreased in the penile tissues of Sprague-Dawley (SD) rats in the HFD group. Immunofluorescence staining showed a positive expression of CD31 and VWF in CCECs and a positive expression of α-SMA in CCSMCs. The expression level of SPTA1 protein significantly decreased in the HG group of CCECs and CCSMCs. The expression of SPTA1 mRNA significantly decreased in CCSMCs while significantly increased in CCECs. SPTA1 may have various expression patterns and biological functions in different cell populations. Real-time quantitative PCR results showed that the siSPTA1 transfected in CCSMCs had a significant interference effect compared with the control siNC. Transfection of siSPTA1 into CCSMCs resulted in the significant down-regulation of mRNA and protein expression of eNOS, and significant up-regulation of YAP, Caspase-1, GSDMD, GSDMD-N IL-18, and IL-1β protein expression levels. The expression level of CCSMCs contractile-type protein α-SMA was significantly down-regulated.

CONCLUSIONS

The down-regulation of SPTA1 in SD rats fed with HFD may induce cell pyroptosis and lead to the decrease of erectile function by activating the Hippo pathway; these findings may provide new therapeutic targets for improving erectile function.

Preoperatively elevated HbA1c levels can meaningfully improve following total joint arthroplasty

BACKGROUND

Prior literature has demonstrated that diabetic (DM) patients undergoing total joint arthroplasty (TJA) with elevated preoperative HbA1c scores have poorer clinical outcomes. However, no literature has reported the effect of undergoing TJA on laboratory markers of glycemic control. This study sought to evaluate effect of undergoing TJA on postoperative glycemic control and outcomes.

METHODS

This retrospective study reviewed all patients with DM who underwent primary, elective TJA at our high volume orthopedic institution. Included patients had at least one HbA1c value 3 months to 2 weeks pre-surgery and 3-6 months after surgery. Changes in HbA1c from before to after surgery were calculated. Change in HbA1c greater than 1.0% was considered clinically meaningful. Change in HbA1c was analyzed and stratified into subgroups.

RESULTS

In total, 770 primary TJA patients were included. Patients with preoperative HbA1c > 7% vs. ≤ 7% were significantly more likely to have clinically meaningful post-TJA decrease in HbA1c (24.5 vs. 2.9%, p < 0.001). Patients with preoperative HbA1c > 8 were significantly more likely to have decrease of > 2.0 compared to those with HbA1c < 8 (p < 0.001). Multivariate regression revealed that preop HbA1c > 7.0, former and current smokers, males, and African-Americans were significantly more likely to achieve clinically meaningful decrease in HbA1c. Additionally, postoperative increase in HbA1c > 1% was associated with significantly higher 90-day ED visits.

DISCUSSION

Patients with higher preoperative HbA1c were more likely to have clinically meaningful decreases in HbA1c postoperatively. A combination of preoperative medical optimization and improvements in mobility after TJA may play a role in these changes. Those with elevated HbA1c can have meaningful improvement in HbA1c after TJA.

Genetics of Type 2 Diabetes: Past, Present, and Future

Diabetes has reached epidemic proportions worldwide. Currently, approximately 537 million adults (20–79 years) have diabetes, and the total number of people with diabetes is continuously increasing. Diabetes includes several subtypes. About 80% of all cases of diabetes are type 2 diabetes (T2D). T2D is a polygenic disease with an inheritance ranging from 30 to 70%. Genetic and environment/lifestyle factors, especially obesity and sedentary lifestyle, increase the risk of T2D. In this review, we discuss how studies on the genetics of diabetes started, how they expanded when genome-wide association studies and exome and whole-genome sequencing became available, and the current challenges in genetic studies of diabetes. T2D is heterogeneous with respect to clinical presentation, disease course, and response to treatment, and has several subgroups which differ in pathophysiology and risk of micro- and macrovascular complications. Currently, genetic studies of T2D focus on these subgroups to find the best diagnoses and treatments for these patients according to the principles of precision medicine.

Associations between the TNMD rs4828038 and ACE2 rs879922 polymorphisms and preeclampsia susceptibility: a case-control study

A case-control study was designed to investigate the association between the angiotensin converting enzyme 2 (ACE2) rs879922, glucose-6-phosphate dehydrogenase (G6PD) rs1050828, and tenomodulin (TNMD) rs4828038 single nucleotide polymorphisms (SNPs), and preeclampsia. A total of 356 Han Chinese pregnant women (170 controls and 186 cases) were recruited into the study. ACE2 rs879922, G6PD rs1050828, and TNMD rs4828038 were tested by the targeted next-generation sequencing technology and the data were analyzed using SPSS version 18. Genotyping of results revealed that patients with the CC/CT genotype in SNP rs4828038 or CC/CG genotype in SNP rs879922 had a significantly decreased susceptibility to late-onset preeclampsia (CC/CT versus TT: OR = 0.543, 95% CI = 0.378 to 0.779, p = .001; CC/CG versus GG: OR = 0.510, 95% CI = 0.038 to 0.860, p = .012). Our study found that the polymorphisms TNMD rs4828038 and ACE2 rs879922 might be associated with late-onset preeclampsia.IMPACT STATEMENTWhat is already known on this subject? Preeclampsia is associated with multiple SNPs, and ACE2 rs879922, G6PD rs1050828, and TNMD rs4828038 are related to essential hypertension and glucose and lipid metabolism disorders. Essential hypertension, diabetes, and dyslipidemia are risks for preeclampsia. The associations between those three SNPs and preeclampsia have not been reported.What do the results of this study add? The polymorphisms of TNMD rs4828038 and ACE2 rs879922 might be associated with the risk of late-onset preeclampsia. There was no relationship between SNP rs1050828 and preeclampsia.What are the implications of these findings for clinical practice and/or further research? TNMD rs4828038 and ACE2 rs879922 might be target sites for genetic diagnosis and therapy, and the levels of mRNA and protein in pregnant women with preeclampsia should be further tested.

HbA1c Performance in African Descent Populations in the United States With Normal Glucose Tolerance, Prediabetes, or Diabetes: A Scoping Review

Introduction

African descent populations in the United States have high rates of type 2 diabetes and are incorrectly represented as a single group. Current glycated hemoglobin A_1c (HbA_1c) cutoffs (5.7% to <6.5% for prediabetes; ≥6.5% for type 2 diabetes) may perform suboptimally in evaluating glycemic status among African descent groups. We conducted a scoping review of US-based evidence documenting HbA_1c performance to assess glycemic status among African American, Afro-Caribbean, and African people.

Methods

A PubMed, Scopus, and Cumulative Index to Nursing and Allied Health Literature (CINAHL) search (January 2020) yielded 3,238 articles published from January 2000 through January 2020. After review of titles, abstracts, and full texts, 12 met our criteria. HbA_1c results were compared with other ethnic groups or validated against the oral glucose tolerance test (OGTT), fasting plasma glucose (FPG), or previous diagnosis. We classified study results by the risk of false positives and risk of false negatives in assessing glycemic status.

Results

In 5 studies of African American people, the HbA_1c test increased risk of false positives compared with White populations, regardless of glycemic status. Three studies of African Americans found that HbA_1c of 5.7% to less than 6.5% or HbA_1c of 6.5% or higher generally increased risk of overdiagnosis compared with OGTT or previous diagnosis. In one study of Afro-Caribbean people, HbA_1c of 6.5% or higher detected fewer type 2 diabetes cases because of a greater risk of false negatives. Compared with OGTT, HbA_1c tests in 4 studies of Africans found that HbA_1c of 5.7% to less than 6.5% or HbA_1c of 6.5% or higher leads to underdiagnosis.

Conclusion

HbA_1c criteria inadequately characterizes glycemic status among heterogeneous African descent populations. Research is needed to determine optimal HbA_1c cutoffs or other test strategies that account for risk profiles unique to African American, Afro-Caribbean, and African people living in the United States.

The Interaction between Hb A1C and Selected Genetic Factors in the African American Population in the USA

BACKGROUND

The global prevalence of diabetes mellitus has been growing in recent decades and the complications of longstanding type 2 diabetes continue to place a burden on healthcare systems. The hemoglobin A1c (Hb A1c) content of the blood is used to assess an individual's degree of glycemic control averaged over 2 to 3 months. In the USA, diabetes is the seventh leading cause of death. Black, indigenous, people of color (BIPOC) are disproportionately affected by diabetes compared to non-Hispanic whites. There are many reports of interaction of Hb A1c and hematologic conditions that have a high prevalence in the Black population; some of these effects are contradictory and not easily explained. This review attempts to document and categorize these apparently disparate effects and to assess any clinical impact.

METHODS

Hb A1C can be determined by a variety of techniques including cation-exchange chromatography, electrophoresis, immunoassays, and affinity chromatography. The amount of Hb A1c present in a patient specimen depends not only on blood glucose but is strongly influenced by erythrocyte survival and by structural variations in the globin chains. Sickling hemoglobinopathies are well-represented in the USA in African Americans and the effects of these hemoglobin disorders as well as G6PD deficiency is examined.

CONCLUSION

Hb A1c measurement should always be performed with a cautious approach. The laboratory scientist should be aware of possible pitfalls in unquestioningly determining Hb A1c without a consideration of hematologic factors, both inherited and acquired. This presents a challenge as often times, the laboratory is not aware of the patient's race.

Review of methods for detecting glycemic disorders

Prediabetes (intermediate hyperglycemia) consists of two abnormalities, impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) detected by a standardized 75-gram oral glucose tolerance test (OGTT). Individuals with isolated IGT or combined IFG and IGT have increased risk for developing type 2 diabetes (T2D) and cardiovascular disease (CVD). Diagnosing prediabetes early and accurately is critical in order to refer high-risk individuals for intensive lifestyle modification. However, there is currently no international consensus for diagnosing prediabetes with HbA1c or glucose measurements based upon American Diabetes Association (ADA) and the World Health Organization (WHO) criteria that identify different populations at risk for progressing to diabetes. Various caveats affecting the accuracy of interpreting the HbA1c including genetics complicate this further. This review describes established methods for detecting glucose disorders based upon glucose and HbA1c parameters as well as novel approaches including the 1-hour plasma glucose (1-h PG), glucose challenge test (GCT), shape of the glucose curve, genetics, continuous glucose monitoring (CGM), measures of insulin secretion and sensitivity, metabolomics, and ancillary tools such as fructosamine, glycated albumin (GA), 1,5- anhydroglucitol (1,5-AG). Of the approaches considered, the 1-h PG has considerable potential as a biomarker for detecting glucose disorders if confirmed by additional data including health economic analysis. Whether the 1-h OGTT is superior to genetics and omics in providing greater precision for individualized treatment requires further investigation. These methods will need to demonstrate substantially superiority to simpler tools for detecting glucose disorders to justify their cost and complexity.

Fasting glucose-to-HbA1c ratio is a good indicator of G6PD deficiency, but not thalassemia, in patients with type 2 diabetes mellitus

AIMS

Patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency or thalassemia have a shorter red blood cell lifespan; therefore, HbA1c is underestimated in these patients. To address these issues, we sought an early indicator for G6PD deficiency or thalassemia in DM patients.

METHODS

A total of 4908 patients with DM and 1848 subjects without DM were included in this study. Fasting glucose (FG) levels, HbA1c levels, hemogram profiles and G6PD activities were measured. Genotypic analyses of G6PD deficiency and thalassemia were performed.

RESULTS

DM patients with G6PD deficiency had significantly higher FG/HbA1c ratios than did those without G6PD deficiency (26.54 vs. 18.36; p < 0.0001). We divided the FG level into four categories: ≤150, 151-250, 251-350, and ≥351 mg/dL. Among all groups, only patients with DM and G6PD deficiency had higher FG/HbA1c ratios than those of patients with DM alone or DM with thalassemia. To evaluate the reliability of the FG/HbA1c ratio, receiver operating characteristic analyses were performed. The areas under the curve for detecting FG ≤ 150, 151-250, 251-350, and ≥351 mg/dL with G6PD deficiency based on the FG/HbA1c ratio were 0.839 (p < 0.001), 0.888 (p < 0.001), 0.891 (p < 0.001), and 0.640 (p = 0.3954), respectively. G6PD deficiency was confirmed by genetic analysis. We found common mutations that influenced G6PD activity and HbA1c levels.

CONCLUSIONS

The FG/HbA1c ratio is a good indicator of DM with G6PD deficiency. If this ratio is determined to be high in a clinical setting, then the clinician must consider whether the patient has a G6PD deficiency, and HbA1c reference values must be adjusted to avoid misdiagnosis and incorrect treatment decisions.

Impact of Rare and Common Genetic Variants on Diabetes Diagnosis by Hemoglobin A1c in Multi-Ancestry Cohorts: The Trans-Omics for Precision Medicine Program

Hemoglobin A1c (HbA1c) is widely used to diagnose diabetes and assess glycemic control in individuals with diabetes. However, nonglycemic determinants, including genetic variation, may influence how accurately HbA1c reflects underlying glycemia. Analyzing the NHLBI Trans-Omics for Precision Medicine (TOPMed) sequence data in 10,338 individuals from five studies and four ancestries (6,158 Europeans, 3,123 African-Americans, 650 Hispanics, and 407 East Asians), we confirmed five regions associated with HbA1c (GCK in Europeans and African-Americans, HK1 in Europeans and Hispanics, FN3K and/or FN3KRP in Europeans, and G6PD in African-Americans and Hispanics) and we identified an African-ancestry-specific low-frequency variant (rs1039215 in HBG2 and HBE1, minor allele frequency (MAF) = 0.03). The most associated G6PD variant (rs1050828-T, p.Val98Met, MAF = 12% in African-Americans, MAF = 2% in Hispanics) lowered HbA1c (-0.88% in hemizygous males, -0.34% in heterozygous females) and explained 23% of HbA1c variance in African-Americans and 4% in Hispanics. Additionally, we identified a rare distinct G6PD coding variant (rs76723693, p.Leu353Pro, MAF = 0.5%; -0.98% in hemizygous males, -0.46% in heterozygous females) and detected significant association with HbA1c when aggregating rare missense variants in G6PD. We observed similar magnitude and direction of effects for rs1039215 (HBG2) and rs76723693 (G6PD) in the two largest TOPMed African American cohorts, and we replicated the rs76723693 association in the UK Biobank African-ancestry participants. These variants in G6PD and HBG2 were monomorphic in the European and Asian samples. African or Hispanic ancestry individuals carrying G6PD variants may be underdiagnosed for diabetes when screened with HbA1c. Thus, assessment of these variants should be considered for incorporation into precision medicine approaches for diabetes diagnosis.

(p-ClPhSe)2 modulates hippocampal BDNF/TrkB signaling and reverses memory impairment induced by diabetes in mice

Diabetes is a metabolic disease characterized by hyperglycemia because of insulin resistance and/or insufficient insulin release. The most common diabetic brain complications include cognitive decline and depression. The present study investigated whether the 4-4'-dichlorodiphenyl diselenide (p-ClPhSe)₂ is effective against memory impairment induced by diabetes in mice and the role of hippocampal BDNF/TrkB signaling in this effect. Male adult Swiss mice received an injection of streptozotocin (STZ) (200 mg/kg, i.p.) to induce diabetes. The results revealed that STZ injection in mice resulted in resilience (glycemia <200 mg/dl) or diabetes (glycemia ≥200 mg/dl). The vehicle-control group received citrate buffer (5 ml/kg). The animals were subchronically treated with (p-ClPhSe)₂ (1 or 5 mg/kg, i.g.) for 7 days. Mice performed a battery of well-validated behavior tests designated to evaluate memory, object recognition (ORT), object location (OLT), and Morris water maze (MWM). The hippocampal protein contents of the BDNF/TrkB pathway were determined in the samples of experimental groups. Fluoro Jade C (FJC) was used for staining degenerating neurons. The STZ administration resulted in memory impairment that was demonstrated in the mouse ORT, OLT, and MWM tests. The molecular findings indicate an increase in hippocampal protein levels of proBDNF and TrKB but a decrease in those of mBDNF and pCREB in diabetic mice. The number of FJC-positive cells was increased in the hippocampus of diabetic mice. (p-ClPhSe)₂ at the dose of 5 mg/kg modulated the hippocampal BDNF/TrkB pathway, reduced FJC-positive cells and reversed memory impairment induced by STZ in mice. These findings demonstrate the effectiveness of (p-ClPhSe)₂ against memory impairment caused by diabetes in mice. (p-ClPhSe)₂ modulated the hippocampal BDNF/TrkB signaling pathway in diabetic mice.

Higher oxidative balance score is associated with better glycemic control among Iranian adults with type-2 diabetes

The oxidative balance score (OBS) is a measure of combined pro- and anti-oxidant exposure status, with a higher OBS representing a predominance of anti- over pro-oxidant exposures. We aimed to examine the association of OBS and glycemic control among Iranian adults with type-2 diabetes. This cross-sectional study was conducted among 476 adults with type-2 diabetes (mean age 56.2 y; 66.6% female). Fasting glycosylated hemoglobin (HbA_1c) and serum glucose (FSG) levels were measured as markers of glycemic control. The OBS was calculated by combining information from a total of 18 a priori selected pro- and anti-oxidant components. These components were comprised of the following four categories: dietary anti-oxidants (i.e., dietary intakes of selenium, fiber, retinol, α-carotene, β-carotene, β-cryptoxanthin, lutein, lycopene, vitamin D, vitamin E, folate, and vitamin C); dietary pro-oxidants (i.e., dietary intakes of iron, saturated fatty acid, and poly-unsaturated fatty acid); non-dietary anti-oxidants (i.e., physical activity); and non-dietary pro-oxidants (i.e., smoking and obesity). After adjusting for several potential confounders in the analysis of covariance models, multivariable adjusted means of HbA_1c and FSG of subjects in the highest tertile of OBS were significantly lower than those in the lowest tertile (for HbA_1c: mean difference -0.73%; and for FSG: mean difference -10.2 mg/dL; both P < 0.050). The findings suggest that a higher OBS, indicating a predominance of anti- over pro-oxidant exposures, is associated with a better glycemic control among Iranian adults with type-2 diabetes. However, future prospective studies of adequate methodological quality are warranted to confirm these findings.