Abnormality in urinary protein excretion in Japanese men with impaired glucose tolerance

Prediabetes: A Benign Intermediate Stage or a Risk Factor in Itself?

Prediabetes is a condition when the blood glucose levels are above the normal range but below the threshold for defining diabetes. Previously considered benign, it is now recognized to be associated with various macrovascular and microvascular complications, with increases in the risk of cardiovascular events, nephropathy neuropathy, and retinopathy. Early identification of prediabetics may help detect the risk for these future complications at an earlier stage. Moreover, therapeutic options for prediabetes are available, which can retard its progression to diabetes and the subsequent development of complications. Hence, we make a case for the early identification of prediabetes through screening methods and appropriate institution of management strategies.

Urine Proteome in Distinguishing Hepatic Steatosis in Patients with Metabolic-Associated Fatty Liver Disease

Background: In patients with metabolic-associated fatty liver disease (MAFLD), hepatic steatosis is the first step of diagnosis, and it is a risk predictor that independently predicts insulin resistance, cardiovascular risk, and mortality. Urine biomarkers have the advantage of being less complex, with a lower dynamic range and fewer technical challenges, in comparison to blood biomarkers. Methods: Hepatic steatosis was measured by magnetic resonance imaging (MRI), which measured the proton density fat fraction (MRI-PDFF). Mild hepatic steatosis was defined as MRI-PDFF 5−10% and severe hepatic steatosis was defined as MRI-PDFF > 10%. Results: MAFLD patients with any kidney diseases were excluded. There were 53 proteins identified by mass spectrometry with significantly different expressions among the healthy control, mild steatosis, and severe steatosis patients. Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of these significantly changed urinary molecular features correlated with the liver, resulting in the dysregulation of carbohydrate derivative/catabolic/glycosaminoglycan/metabolic processes, insulin-like growth factor receptor levels, inflammatory responses, the PI3K−Akt signaling pathway, and cholesterol metabolism. Urine alpha-1-acid glycoprotein 1 (ORM1) and ceruloplasmin showed the most significant correlation with the clinical parameters of MAFLD status, including liver fat content, fibrosis, ALT, triglycerides, glucose, HOMA-IR, and C-reactive protein. According to ELISA and western blot (30 urine samples, normalized to urine creatinine), ceruloplasmin (ROC 0.78, p = 0.034) and ORM1 (ROC 0.87, p = 0.005) showed moderate diagnostic accuracy in distinguishing mild steatosis from healthy controls. Ceruloplasmin (ROC 0.79, p = 0.028) and ORM1 (ROC 0.81, p = 0.019) also showed moderate diagnostic accuracy in distinguishing severe steatosis from mild steatosis. Conclusions: Ceruloplasmin and ORM1 are potential biomarkers in distinguishing mild and severe steatosis in MAFLD patients.

Impaired Fasting Glucose and Chronic Kidney Disease, Albuminuria, or Worsening Kidney Function: a Secondary Analysis of the SPRINT

PURPOSE

Diabetes mellitus is a risk factor for the development and progression of chronic kidney disease (CKD). However, the association of prediabetes with adverse kidney outcomes is uncertain.

METHODS

We performed a secondary analysis of the Systolic Blood Pressure Intervention Trial (SPRINT), including 9,361 participants without diabetes at baseline. We categorized participants according to fasting glucose as having impaired fasting glucose (≥100 mg/dL [(≥5.6 mmol/L]) or normoglycemia (<100 mg/dL [(<5.6 mmol/L]). Unadjusted and adjusted proportional hazards models were fit to estimate the association of impaired fasting glucose (versus normoglycemia) with a composite outcome of worsening kidney function (≥30% decrease in eGFR to <60 ml/min/1.73 m2 in participants without baseline CKD; ≥50% decrease in eGFR or need of long-term dialysis/kidney transplantation in participants with CKD) or incident albuminuria (doubling of urinary albumin to creatinine ratio from <10 mg/g to >10 mg/g). These outcomes were also evaluated separately, and according to CKD status at baseline.

RESULTS

The mean age was 67.9 ± 9.4 years, 35.5% were female, and 31.4% were black. The median follow-up was 3.3 years and 41.8% had impaired fasting glucose. Impaired fasting glucose was not associated with higher rates of the composite outcome (HR 0.97; 95%CI 0.81-1.16), worsening kidney function (HR 1.02; 95%CI 0.75-1.37), or albuminuria (HR 0.98; 95%CI 0.78-1.23). Similarly, there was no association of impaired fasting glucose with outcomes according to baseline CKD status.

CONCLUSIONS

Impaired fasting glucose at baseline was not associated with the development of worsening kidney function or albuminuria in participants of SPRINT.

Glycated hemoglobin A1c level is associated with high urinary albumin/creatinine ratio in non-diabetic adult population

BACKGROUND

Regarding the association between glycated hemoglobin A1c (HbA1c) levels and microvascular complications, high HbA1c level in participants without diabetes mellitus (DM) may be associated with a high urinary albumin-to-creatinine ratio (UACR).

PATIENTS AND METHODS

Twelve thousand seven hundred and seventy four participants without DM were included in this study. The participants were divided into three groups according to HbA1c levels: a Low group (<5.7%), Middle group (5.7-6.0%), and High group (>6.0%). A high UACR was defined as UACR ≥3.9 mg/g for men and UACR ≥7.5 mg/g for women.

RESULTS

The proportions of participants with a high UACR in the Low, Middle, and High groups were 22.4%, 27.9%, and 38.1%, respectively. Both univariate and multivariate analyses showed that logUACR was greatest in the High group compared to the other groups. For participants without metabolic syndrome (MetS), the proportions of participants with high UACR and logUACR values were greatest in the High group compared to the other groups. For participants with MetS, no differences were found for proportions of participants with high UACR and logUACR values in the Low, Middle, and High groups.

CONCLUSION

Non-DM participants with relatively high HbA1c levels should be closely monitored for UACR, especially if participants do not have MetS. KEY MESSAGES HbA1c level was positively associated with the proportion of participants with a high UACR and logUACR in participants without DM. For participants without MetS, the proportion of participants with a high UACR was greater in the High group than in the other groups and logUACR was greatest in the High group compared to the other groups. For participants with MetS, there were significant associations between HbA1c and the proportion of participants with a high UACR as a categorical variable or logUACR as a continuous variable, but the statistical significance of this finding was weak. No differences were found for proportions of participants with high UACR and logUACR values in the Low, Middle, and High groups.

Glycated haemoglobin A1c is associated with low-grade albuminuria in Chinese adults

BACKGROUND AND OBJECTIVE

Diabetes is a strong risk factor for cardiovascular diseases, whereas few studies have investigated simultaneously the associations of glycated haemoglobin A1c (HbA1c), fasting blood glucose (fasting plasma glucose (FPG)) and 2 h postload blood glucose (2 h PG) with low-grade albuminuria, which is an earlier marker of cardiovascular diseases in the general population. Our study aimed to investigate and compare associations of HbA1c, FPG, and 2 h PG levels with risks of low-grade albuminuria in the middle-aged and elderly Chinese.

DESIGN AND METHODS

This was a cross-sectional study involving 9188 participants aged 40 years or older. All participants underwent a standard 75 g oral glucose tolerance test. Low-grade albuminuria was defined as the highest quartile of urinary albumin-to-creatinine ratio (ACR) (>6.10 mg/g in males and >8.76 mg/g in females) in respondents without microalbuminuria or macroalbuminuria.

RESULTS

HbA1c, FPG and 2 h PG were all significantly correlated with urinary ACR after adjustment for confounders (all p values <0.0001). After adjustment for HbA1c, the relationships of FPG and 2 h PG with ACR reduced to null. HbA1c levels were still significantly associated with ACR after further adjustment for FPG and 2 h PG. Multiple logistic regression showed that risks of low-grade albuminuria were positively associated with HbA1c levels in a dose-response manner. Compared with participants with HbA1c ≤ 37 mmol/mol (5.5%), ORs (95% CIs) for low-grade albuminuria were 1.05 (0.94 to 1.18), 1.25 (1.04 to 1.50), 1.40 (1.04 to 1.90) and 2.21 (1.61 to 3.03) for HbA1c categories of 38-42 mmol/mol (5.6-6.0%), 43-48 mmol/mol (6.1-6.5%), 49-53 mmol/mol (6.6-7.0%), and >53 mmol/mol (7.0%), respectively (p for trend <0.0001).

CONCLUSIONS

HbA1c, but not FPG or 2 h PG, was independently associated with an increased risk of low-grade albuminuria in the middle-aged and elderly Chinese.

Prediabetes: a high-risk state for diabetes development

Prediabetes (intermediate hyperglycaemia) is a high-risk state for diabetes that is defined by glycaemic variables that are higher than normal, but lower than diabetes thresholds. 5-10% of people per year with prediabetes will progress to diabetes, with the same proportion converting back to normoglycaemia. Prevalence of prediabetes is increasing worldwide and experts have projected that more than 470 million people will have prediabetes by 2030. Prediabetes is associated with the simultaneous presence of insulin resistance and β-cell dysfunction-abnormalities that start before glucose changes are detectable. Observational evidence shows associations between prediabetes and early forms of nephropathy, chronic kidney disease, small fibre neuropathy, diabetic retinopathy, and increased risk of macrovascular disease. Multifactorial risk scores using non-invasive measures and blood-based metabolic traits, in addition to glycaemic values, could optimise estimation of diabetes risk. For prediabetic individuals, lifestyle modification is the cornerstone of diabetes prevention, with evidence of a 40-70% relative-risk reduction. Accumulating data also show potential benefits from pharmacotherapy.

A nanolitre method to determine the hydrodynamic radius of proteins and small molecules by Taylor dispersion analysis

The escalating number of new therapeutic biopharmaceuticals being developed and their high value increases the need for the development of novel analytical technologies. Faster analysis time, high accuracy, low sample consumption and the ability to monitor process flow are all essential prerequisites. We evaluate a novel analytical instrument that combines UV area imaging and Taylor dispersion analysis (TDA) to determine the hydrodynamic radius of proteins and small molecules in solution. Benchmarking the results against dynamic light scattering, we report the influence of injection system, injection volume, flow rates, analyte concentration and highlight the importance of washing procedures. Issues arising from the manual injection valve in the alpha laboratory system that led to high standard deviations were eliminated by incorporating an automated injector in a beta system. The hydrodynamic radii obtained show good correlation with literature values and in most cases a relative standard deviation of less than 5%. The system is fully automated after coupling to the CE which allows for multiple injections and sample/buffer changes without operator intervention. The small sample size (approx. 60 nL), the lack of sample preparation required, and the speed of analysis (approx. 2-3 mins) makes this instrument highly applicable to the real-time analysis of inherently unstable, high cost biopharmaceutical materials where understanding their aggregation state and size is important.

Dextran−Gold Nanoparticle Hybrid Material for Biomolecule Immobilization and Detection

The formation of a hybrid metal-biopolymer material is described. The synthesis of this material consists of functionalizing the surface of gold nanoparticles through a series of steps that lead to epoxy-functionalized nanoparticles. These are subsequently reacted with hydroxyl moieties of the alpha-D-glucopyranosyl groups of dextran. Subsequently, the dextran chains are carboxylated through treatment with bromoacetic acid. The resultant material combines the unique optical properties of gold nanoparticles with the versatility that carboxylated dextran offers for further functionalization with biomolecules. The interaction of this material with three proteins was then investigated through changes in the plasmon resonance properties of the gold nanoparticles. Concanavalin A, a lectin that binds glucose and mannose by means of specific molecular recognition, interacts readily with this material and such interaction is easily detected using optical absorption spectroscopy. Through reaction of the carboxyl groups with (+)-biotinyl-3,6,9,-trioxaundecanediamine, a material bearing biotin groups was obtained. This could interact with streptavidin or antibiotin by means of specific molecular recognition. Further confirmation of biospecific interactions was obtained with control experiments in which the binding sites were blocked through preincubation of the proteins with the corresponding ligand in solution. Binding of these proteins was concentration-dependent over a wide concentration range. This material provides a simple and convenient colorimetric method for biospecific interaction analysis.

Parallel increase in urinary excretion rates of immunoglobulin G, ceruloplasmin, transferrin, and orosomucoid in normoalbuminuric type 2 diabetic patients

OBJECTIVE

Increased urinary excretions of several plasma proteins with different molecular radii <55 A and different isoelectric points (pI), such as IgG, ceruloplasmin, transferrin, and orosomucoid, have been independently reported to precede the development of microalbuminuria in diabetic patients. We examined whether increases in urinary excretions of these proteins would be in parallel in the same patient.

RESEARCH DESIGN AND METHODS

Urinary excretion rates of proteins mentioned above in timed overnight urine samples were evaluated in 61 normoalbuminuric type 2 diabetic patients (group D) aged 40-60 years and in 17 age-matched control subjects (group C).

RESULTS

The excretion rates of these proteins were significantly higher in group D than in group C. These exhibited a strong linear correlation with each other and had a weak correlation with the excretion rate of N-acethylglucosaminidase. The excretion rate of alpha2-macroglobulin with large molecular radii of 88 A was not different between groups C and D, nor did they have any correlations with the excretion rates of the other proteins. Creatinine clearance and blood pressure levels in group D were significantly higher than those in group C.

CONCLUSIONS

In normoalbuminuric diabetic patients, excretion rates of plasma proteins with molecular radii <55 A increased in parallel with each other. In view of our previous finding that urinary excretions of these plasma proteins selectively increased in parallel with enhanced glomerular filtration rate after acute protein loading, the present finding may be explained by renal hemodynamic changes, such as increased intraglomerular hydraulic pressure.

Longitudinal association of glycemia and microalbuminuria: the Framingham Offspring Study

OBJECTIVE

To assess current and long-term associations of glycemia with microalbuminuria, a marker of generalized endothelial injury.

RESEARCH DESIGN AND METHODS

We measured clinical characteristics, fasting plasma glucose, and the urinary albumin-to-creatinine ratio (UACR) in 1,311 men and 1,518 women attending the sixth examination cycle (1995-1998) of the Framingham Offspring Study. After excluding participants with diabetes or cardiovascular disease (CVD) at the baseline examination (1971-1974), we used fasting glucose measured at baseline, examination 6, and at least two additional examinations from 1974 to 1995 in regression models to predict risk for microalbuminuria (UACR > or = 30 mg/g) associated with baseline, current, and 24-year time-integrated glycemia.

RESULTS

Microalbuminuria was present in 9.5% of men and 13.4% of women. Among men, age-adjusted odds ratios (95% CI) for microalbuminuria associated with each 0.28 mmol/l (5 mg/dl) increase in baseline, current, and time-integrated glucose levels were 1.12 (1.00-1.16), 1.08 (1.05-1.10), and 1.16 (1.11-1.21), respectively. These effects persisted after adjustment for systolic blood pressure and other confounders. Higher glucose levels also predicted incident diabetes and CVD. Mean time-integrated glucose levels were highest among men who developed both CVD and microalbuminuria (SE 6.82 +/- 0.16 mmol/l), intermediate among men with either condition (6.03 +/- 0.65 mmol/l), and lowest among men with neither condition (5.49 +/- 0.02 mmol/l; P < 0.001 for all pairwise comparisons). We observed similar associations in women.

CONCLUSIONS

Long-term hyperglycemia and subdiabetic glycemia increase risk for microalbuminuria. Microalbuminuria, type 2 diabetes, and CVD seem to arise together over the course of decades, consistent with the hypothesis that they share a common antecedent.

Increased urinary excretion of N-acetylglucosaminidase in subjects with impaired glucose tolerance

N-acetylglucosaminidase (NAG) is a lysosomal enzyme produced by renal proximal tubular cells and has been widely used as a marker, which indicates a degree of renal tubular damage. An increase in urinary NAG excretion is though to result from the renal tubular damage. The aim of this study was to evaluate whether even mild hyperglycemia causes an increase in urinary excretion of NAG, which is a renal tubular protein. We examined urinary NAG excretion in overnight urine in 22 Japanese men with impaired glucose tolerance (IGT) for more than two years (IGT group) and 41 healthy control subjects matched in age, gender, BMI and blood pressure (control group). Urinary NAG excretion levels of IGT group and control group were 2.89 (1.23-7.97) and 2.22 (0.60-4.93) U/g creatinine, median (range), respectively. The IGT group showed significantly higher urinary excretion of NAG compared to the control group (p < 0.01). Several studies have indicated that plasma proteins filtered through the glomerular capillary may have intrinsic renal toxicity. Recently, we have reported that urinary excretion of plasma proteins (ceruloplasmin, IgG4 and IgG) with molecular radii of approximately 45-55 A is increased in subjects with IGT compared to healthy control subjects with normal glucose tolerance. Considering the present result together with our recent finding, we suggest that increased urinary excretion of NAG in the mildly hyperglycemic subjects may be due to the adverse effects of the plasma proteins highly filtered through the glomerular capillary on tubular cells.

Fasting plasma homocysteine levels in the insulin resistance syndrome: the Framingham offspring study

OBJECTIVE

Insulin resistance, associated metabolic abnormalities, and elevated homocysteine levels are risk factors for cardiovascular disease (CVD). We examined relationships between homocysteine levels and features of insulin resistance syndrome (IRS).

RESEARCH DESIGN AND METHODS

We measured clinical characteristics, plasma levels of fasting homocysteine, folate, B vitamins, creatinine, and fasting and 2-h insulin and glucose levels after a 75-g oral glucose tolerance test in 2,214 subjects without CVD at the fifth examination (1991-1995) of the Framingham Offspring Study. After excluding 203 subjects with diabetes, the remaining 2,011 subjects were categorized as having none, one, two, or all three of the phenotypes of IRS: impaired glucose tolerance, hypertension, and/or a central metabolic syndrome (two or more traits: obesity, dyslipidemia, or hyperinsulinemia). In addition, in 1,592 subjects attending the sixth examination (1995-1998), we measured the urine albumin/creatinine ratio (UACR). Age-, sex-, creatinine-, vitamin-, and UACR-adjusted mean homocysteine levels or proportions with homocysteine >14 micromol/l in each phenotypic category and differences between categories were assessed with regression models.

RESULTS

The mean age of the subjects was 54 years (range 28-82); 55% were women, 12.3% had hyperinsulinemia, and 15.9% had two or more of the IRS phenotypes. Adjusted mean homocysteine levels were higher comparing those with hyperinsulinemia (9.8 micromol/l) and those without (9.4 micromol/l, P = 0.04) and were higher among subjects with two or more IRS phenotypes (9.9 micromol/l) compared with those with 1 or no phenotype (9.3 micromol/l, P = 0.003). Mean UACR levels were also higher among subjects with two or more IRS phenotypes (7.2 mg/g) compared with those with 1 or no phenotype (5.5 mg/g, P = 0.007).

CONCLUSIONS

Hyperhomocysteinemia and abnormal urinary albumin excretion are both associated with hyperinsulinemia and may partially account for increased risk of CVD associated with insulin resistance. Because hyperhomocysteinemia and microalbuminuria also reflect endothelial injury, these observations also support the hypothesis that endothelial dysfunction is associated with expression of the IRS.