Glycosylated serum proteins and glycosylated hemoglobin in the assessment of glycemic control in insulin-dependent and non-insulin-dependent diabetes mellitus

Infection with SARS-CoV-2 can cause pancreatic impairment

Evidence suggests associations between COVID-19 patients or vaccines and glycometabolic dysfunction and an even higher risk of the occurrence of diabetes. Herein, we retrospectively analyzed pancreatic lesions in autopsy tissues from 67 SARS-CoV-2 infected non-human primates (NHPs) models and 121 vaccinated and infected NHPs from 2020 to 2023 and COVID-19 patients. Multi-label immunofluorescence revealed direct infection of both exocrine and endocrine pancreatic cells by the virus in NHPs and humans. Minor and limited phenotypic and histopathological changes were observed in adult models. Systemic proteomics and metabolomics results indicated metabolic disorders, mainly enriched in insulin resistance pathways, in infected adult NHPs, along with elevated fasting C-peptide and C-peptide/glucose ratio levels. Furthermore, in elder COVID-19 NHPs, SARS-CoV-2 infection causes loss of beta (β) cells and lower expressed-insulin in situ characterized by islet amyloidosis and necrosis, activation of α-SMA and aggravated fibrosis consisting of lower collagen in serum, an increase of pancreatic inflammation and stress markers, ICAM-1 and G3BP1, along with more severe glycometabolic dysfunction. In contrast, vaccination maintained glucose homeostasis by activating insulin receptor α and insulin receptor β. Overall, the cumulative risk of diabetes post-COVID-19 is closely tied to age, suggesting more attention should be paid to blood sugar management in elderly COVID-19 patients.

Rapid estimation approach for glycosylated serum protein of human serum based on the combination of deep learning and TD-NMR technology

Rapid and precise estimation of glycosylated serum protein (GSP) of human serum is of great importance for the treatment and diagnosis of diabetes mellitus. In this study, we propose a novel method for estimation of GSP level based on the combination of deep learning and time domain nuclear magnetic resonance (TD-NMR) transverse relaxation signal of human serum. Specifically, a principal component analysis (PCA)-enhanced one-dimensional convolutional neural network (1D-CNN) is proposed to analyze the TD-NMR transverse relaxation signal of human serum. The proposed algorithm is proved by accurate estimation of GSP level for the collected serum samples. Furthermore, the proposed algorithm is compared with 1D-CNN without PCA, long short-term memory network (LSTM) and some conventional machine learning algorithms. The results indicate that PCA-enhanced 1D-CNN (PC-1D-CNN) has the minimum error. This study proves that proposed method is feasible and superior to estimate GSP level of human serum using TD-NMR transverse relaxation signals.

Investigation of 1H nuclear magnetic resonance relaxometry to screen metabolic syndrome and diabetes

The purpose of this study was to investigate and compare the abilities of ¹H nuclear magnetic resonance (NMR) transverse relaxation constant time (T₂) and longitudinal relaxation constant time (T₁) to screen people at the risk of diabetes and metabolic syndrome. Human blood samples were collected for NMR detection and biochemical examinations. Bivariate correlations, categorical analyses were performed to explore the relationship between NMR relaxation time and metabolic biomarkers. Results show that NMR relaxation time of human serum correlated well with some biomarkers associated with diabetes and metabolic syndrome. Statistically significant differences in NMR relaxation time between subjects with normal and poor metabolic health were observed. NMR relaxation time, especially T₂, can be used to screen people at risk of diabetes and metabolic syndrome.

Evaluation of a dimeric-cRGD peptide for targeted PET-CT imaging of peripheral angiogenesis in diabetic mice

The α V  β3 integrin plays an important role in many physiological functions and pathological disorders. α V  β3 is minimally expressed in normal quiescent endothelial cells, but significantly upregulated during neovascularization. In this study, we evaluated a 64Cu-labeled dimeric cRGD tracer targeted at α V  β3 integrin and report its applicability to assess peripheral angiogenesis in diabetes mellitus (DM). We established a murine model of type-1 DM characterized by elevated glucose, glycated serum protein (GSP), and glycated hemoglobin A1c (HbA1c). We demonstrated that our imaging probe is specific to α V  β3 integrin under both normo- and hyperglycemic conditions. We found that the analysis of in vivo PET-CT images correlated well with gamma well counting (GWC). Both GWC and PET-CT imaging demonstrated increased uptake of 64Cu-NOTA-PEG4-cRGD2 in the ischemic hindlimb in contrast to non-ischemic control. GWC of the distal ischemic tissue from DM mice showed significantly lower probe accumulation than in non-DM mice. The immunofluorescence staining of the ischemic tissues showed a 3-fold reduction in CD31 and 4-fold reduction in the α V  β3 expression in DM vs. non-DM animals. In conclusion, we successfully demonstrated that diabetes-associated reductions in peripheral angiogenesis can be non-invasively detected with PET-CT imaging using targeted dimeric-cRGD probe.

Oxidant Mechanisms in Renal Injury and Disease

SIGNIFICANCE

A common link between all forms of acute and chronic kidney injuries, regardless of species, is enhanced generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) during injury/disease progression. While low levels of ROS and RNS are required for prosurvival signaling, cell proliferation and growth, and vasoreactivity regulation, an imbalance of ROS and RNS generation and elimination leads to inflammation, cell death, tissue damage, and disease/injury progression.

RECENT ADVANCES

Many aspects of renal oxidative stress still require investigation, including clarification of the mechanisms which prompt ROS/RNS generation and subsequent renal damage. However, we currently have a basic understanding of the major features of oxidative stress pathology and its link to kidney injury/disease, which this review summarizes.

CRITICAL ISSUES

The review summarizes the critical sources of oxidative stress in the kidney during injury/disease, including generation of ROS and RNS from mitochondria, NADPH oxidase, and inducible nitric oxide synthase. The review next summarizes the renal antioxidant systems that protect against oxidative stress, including superoxide dismutase and catalase, the glutathione and thioredoxin systems, and others. Next, we describe how oxidative stress affects kidney function and promotes damage in every nephron segment, including the renal vessels, glomeruli, and tubules.

FUTURE DIRECTIONS

Despite the limited success associated with the application of antioxidants for treatment of kidney injury/disease thus far, preventing the generation and accumulation of ROS and RNS provides an ideal target for potential therapeutic treatments. The review discusses the shortcomings of antioxidant treatments previously used and the potential promise of new ones. Antioxid. Redox Signal. 25, 119-146.

Evaluation of glycemic variability in well-controlled type 2 diabetes mellitus

AIMS

It is necessary to evaluate glucose variability and postprandial hyperglycemia in patients with well-controlled type 2 diabetes mellitus because of the limitations associated with hemoglobin A1c (HbA1c) measurements. We evaluated parameters reflecting postprandial hyperglycemia and glycemic variability in patients with optimal HbA1c.

PATIENTS AND METHODS

Thirty-nine patients with HbA1c levels below 7% were recruited to the study. A continuous glucose monitoring system (CGMS) was applied for two 72-h periods. 1,5-Anhydroglucitol (1,5-AG) and fructosamine (FA) were measured as parameters for postprandial hyperglycemia and glucose variability. Using CGMS data, the following postprandial hyperglycemia parameters were calculated: mean postprandial maximum glucose (MPMG) and area under the curve for glucose above 180 mg/dL (AUC-180). To measure glycemic variability, we calculated mean amplitude of glucose excursion (MAGE) using a classical (MAGEc) and new method (MAGE group of sign [MAGEgos]).

RESULTS

The baseline HbA1c level was 6.3±0.3%. The mean MPMG was 10.34±1.84 mmol/L, and the mean AUC-180 was 0.17±0.23 mmol/L/day. The mean MAGEgos was 3.27±1.29 mmol/L, and MAGEc was 4.30±1.43 mmol/L, indicating glycemic variability in our patients. The mean levels of 1,5-AG and FA were 16.7±7.4 μg/mL and 273.0±22.5 μmol/L, respectively. In a correlation analysis, FA was significantly correlated with MPMG, AUC-180, MAGEgos, and MAGEc. In contrast, 1,5-AG was only correlated with AUC-180.

CONCLUSIONS

This study demonstrated postprandial hyperglycemia and glycemic variability in subjects with well-controlled diabetes. FA may reflect postprandial hyperglycemia and glycemic variability, but 1,5-AG may be of limited value for assessing glucose variability in patients with well-controlled type 2 diabetes mellitus.

Elevated pregnancy losses at high and low extremes of maternal glucose in early normal and diabetic pregnancy: evidence for a protective adaptation in diabetes

OBJECTIVE

Early pregnancy losses increase with marked hyperglycemia in diabetic pregnancy. However, mean loss rates do not differ from those of nondiabetic pregnancy. This observation might be explained by increased fetal losses at the extremes of glycemia in diabetic and nondiabetic pregnancy. To test this hypothesis, we examined relationships of proximate measures of prior glycemia, glycated protein and fructosamine, to pregnancy loss.

RESEARCH DESIGN AND METHODS

A total of 389 diabetic and 429 nondiabetic pregnant subjects participated in the Diabetes In Early Pregnancy study. Glycated protein and fructosamine measurements were standardized as multiples of control values for each center (Z score). The logarithm of odds of pregnancy loss were plotted against Z scores and tested by logistic models.

RESULTS

Mean pregnancy loss rates were 12% in diabetic and 13% in normal pregnancies. However, over six intervals of glycated protein in diabetic pregnancy, fetal loss rates at the upper and lower extremes (24 and 33%, respectively) were approximately threefold higher than the four intervening rates (8-14%). The odds ratio of pregnancy loss for these extreme intervals to the intervening intervals is 3.0 (P = 0.01). Nondiabetic losses showed a similar pattern. In confirmation, logit pregnancy losses were increased in a J-shaped curve at the glycemic extremes in normal (P < 0.019) and diabetic (P < 0.015) pregnancy. The upper glycemic extreme in diabetic pregnancy was two- to fivefold higher than in control pregnancy.

CONCLUSIONS

Pregnancy losses are increased at the extremes of glycemia in both normal and diabetic pregnancy but at higher levels in diabetic pregnancy. The data suggest defensive adaptations against hyperglycemia in diabetic pregnancy.

Impact of chronic renal failure and peritoneal dialysis fluids on advanced glycation end product and iNOS levels in penile tissue: an experimental study

OBJECTIVES

To investigate the impact of chronic renal failure (CRF) on advanced glycation end product and inducible nitric oxide synthase (iNOS) in penile tissue, we examined the advanced glycation end product 5-hydroxy methyl furfural (5-HMF) content and iNOS expression in rats in which uremia had been produced by greater than 85% nephrectomy. In addition, the contribution of peritoneal dialysis (PD) fluids to the elevation of penile tissue 5-HMF levels and iNOS staining scores has been investigated.

METHODS

Adult male Wistar rats, aged between 10 and 12 weeks and weighing 200 to 330 g, were divided into five groups that each included 6 animals. The first group served as a control group. In the second group, CRF was induced and a peritoneal catheter was implanted, but PD was not performed. In group 3, CRF was induced and PD was performed using dialysis fluids containing 1.36% glucose and icodextrin. In group 4, CRF was also induced and PD was performed using 3.86% glucose and icodextrin. Finally, in group 5, without CRF, an indwelling catheter was implanted, and the PD procedure was performed using dialysis fluids containing 3.86% glucose and icodextrin.

RESULTS

The elevation in 5-HMF levels and iNOS staining scores in penile tissue from groups 2, 3, 4, and 5 was significant compared with group 1 (P <0.05). The elevation in 5-HMF levels and iNOS staining scores was also significant between groups 2 and 3, 2 and 4, 3 and 4, 3 and 5, and 4 and 5 (P <0.05). Moreover, the correlation between the 5-HMF levels and iNOS staining scores was statistically significant (r = 0.525, P = 0.003).

CONCLUSIONS

In the present experimental study, we found that 5-HMF levels and iNOS staining scores were significantly elevated in rat penile tissue in which uremia had been produced compared with the groups without CRF. Additionally, PD fluids containing glucose had an effect on the elevation of penile tissue 5-HMF levels and iNOS staining scores.

alpha-Dicarbonyls increase in the postprandial period and reflect the degree of hyperglycemia

OBJECTIVE

Chronic hyperglycemia is known to increase tissue glycation and diabetic complications, but controversy exists regarding the independent role of increased postprandial glucose excursions. To address this question, we have studied the effect of postprandial glycemic excursions (PPGEs) on levels of methylglyoxal (MG) and 3-deoxyglucosone (3-DG), two highly reactive precursors of advanced glycation end products (AGEs).

RESEARCH DESIGN AND METHODS

We performed 4-month crossover studies on 21 subjects with type 1 diabetes and compared the effect of premeal insulin lispro or regular insulin on PPGEs and MG/3-DG excursions. PPGE was determined after standard test meal (STMs) and by frequent postprandial glucose monitoring. HbA1c and postprandial MG and D-lactate were measured by HPLC, whereas 3-DG was determined by gas chromatography/mass spectroscopy.

RESULTS

Treatment with insulin lispro resulted in a highly significant reduction in PPGEs relative to the regular insulin-treated group (P = 0.0005). However, HbA1c levels were similar in the two groups, and no relationship was observed between HbA1c and PPGE (P = 0.93). Significant postprandial increases in MG, 3-DG, and D-lactate occurred after the STM. Excursions of MG and 3-DG were highly correlated with levels of PPGE (R = 0.55, P = 0.0002 and R = 0.61, P = 0.0004; respectively), whereas a significant inverse relationship was seen between PPGE and D-lactate excursions (R = 0.40, P = 0.01). Conversely, no correlation was observed between HbAlc and postprandial MG, 3-DG, or D-lactate levels.

CONCLUSIONS

Increased production of MG and 3-DG occur with greater PPGE, whereas HbA1c does not reflect these differences. Reduced PPGE also leads to increased production of D-lactate, indicating a role for increased detoxification in reducing MG levels. The higher postprandial levels of MG and 3-DG observed with greater PPGE may provide a partial explanation for the adverse effects of glycemic lability and support the value of agents that reduce glucose excursions.

Measuring glycated proteins: clinical and methodological aspects

The recognition that nonenzymatic glycation, wherein free sugar condenses with certain reactive protein amino groups, is increased in hyperglycemic states has led to improved means for assessing diabetic control through the measurement of concentrations of glycated proteins in the circulation. This article reviews the chemistry, methods for measurement, and clinical relevance of circulating glycated proteins in the management of diabetes.

Post-translational non-enzymatic modification of proteins. II. Separation of selected protein species after glycation and other carbonyl-mediated modifications

There are two strategies applicable to revealing non-enzymatic post-translational modifications of proteins; while assaying of the hydrolytically stable adducts was the subject of our previous communication [1], here we attempted to review separation technologies for the unfragmented modified proteins. There are a few standard procedures used for this purpose, namely Laemmli gel electrophoresis, different modes of gel permeation chromatography and boronate affinity chromatography. The latter approach makes use of the vicinal hydroxy groups present in glycated proteins. Some (but not all) arising adducts exhibit typical fluorescence which can be exploited for detection. In most cases fluorescence is measured at 370/440 nm for the so-called advanced glycation products or at 335/385 nm for the only so far well characterized glycation marker (pentosidine). Some indication exists that, e.g., synchronous fluorescence detection will probably in the future add to the selectivity and allow the distinction of the different adducts arising during non-enzymatic post-translational modifications (glycation). The proteins reviewed are serum albumin, collagen and lens proteins while glycation of hemoglobin is the subject of another review within the present volume.

Primary structures of fungal fructosyl amino acid oxidases and their application to the measurement of glycated proteins

Fructosyl amino acid oxidase (FAOD), which is active toward model compounds of the glycated proteins in blood, N epsilon-fructosyl N sigma-Z-lysine and N-fructosyl valine, was purified to homogeneity from Aspergillus terreus GP1. Though the enzyme did not use glycated proteins directly as its substrate, it used glycated human serum albumin (HSA) when HSA was treated with a protease. Linear relationships between both the concentration and the increase in absorbance and the glycation rate of glycated HSA and the increase in absorbance were observed. cDNAs coding for FAODs were cloned from cDNA libraries of A. terreus GP1 and Penicillium janthinellum AKU 3413. The coding region for both fungal FAODs consisted of 1314 bp encoding 437 amino acids. The sequence of a dinucleotide-binding motif, GXGXXG, was in the deduced N-terminal region and a similar sequence to that the active site of bacterial sarcosine oxidases was found near the C-terminal region of FAOD. The of C-terminal tripeptides SKL and AKL of FAODs from A. terreus and P. janthinellum, respectively, represent typical peroxisomal-targeting signals. Finally, FAOD protein was produced in Escherichia coli transformants in an active form, and at the same level as in the original fungi.