Insulin Resistance Associated with Plasma Xanthine Oxidoreductase Activity Independent of Visceral Adiposity and Adiponectin Level: MedCity21 Health Examination Registry

BACKGROUND

Higher levels of uric acid production have been reported in individuals with visceral fat obesity, and obesity is known to enhance xanthine oxidoreductase (XOR) activity, although the precise mechanism remains unclear. We investigated the associations of visceral fat area (VFA), serum adiponectin level, and insulin resistance with plasma XOR activity using our novel highly sensitive assay based on [¹³C₂,¹⁵N₂] xanthine and liquid chromatography/triple quadrupole mass spectrometry.

METHODS

This cross-sectional study included 193 subjects (92 males and 101 females) registered in the MedCity21 health examination registry. Plasma XOR activity, serum adiponectin level, and VFA obtained by computed tomography were measured, and insulin resistance was determined based on the homeostasis model assessment (HOMA-IR) index.

RESULTS

The mean values for VFA, log HOMA-IR, and log plasma XOR activity were 76.8 ± 45.8 cm², 0.14 ± 0.30, and 1.50 ± 0.44 pmol/h/mL, respectively. Multiple regression analysis showed that HOMA-IR was significantly (p=0.020) associated with plasma XOR activity independent of other factors, including VFA and adiponectin level, as well as age, sex, alcohol drinking habit, smoking habit, alanine transaminase, HbA1c, and eGFR. The "sex∗HOMA - IR" interaction was not significant (p=0.020) associated with plasma XOR activity independent of other factors, including VFA and adiponectin level, as well as age, sex, alcohol drinking habit, smoking habit, alanine transaminase, HbA1c, and eGFR. The ".

CONCLUSIONS

Our results indicate that insulin resistance is associated with plasma XOR activity and that relationship is independent of visceral adiposity and adiponectin level, suggesting that the development of insulin resistance resulting from increased visceral adiposity and/or reduced serum adiponectin contributes to increased uric acid production by stimulating XOR activity.

Association of Albuminuria With Intraglomerular Hydrostatic Pressure and Insulin Resistance in Subjects With Impaired Fasting Glucose and/or Impaired Glucose Tolerance

OBJECTIVE

Little is known about the relationships between insulin resistance, intrarenal hemodynamics, and urinary albumin excretion (UAE) in humans with impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT). The aim of the current study was to examine intrarenal hemodynamic abnormalities, insulin resistance, and UAE in subjects with IFG or IGT. We hypothesized that intrarenal hemodynamic abnormalities would be associated with insulin resistance.

RESEARCH DESIGN AND METHODS

Fifty-four kidney donors underwent 75-g oral glucose tolerance and inulin and para-aminohippuric acid clearance testing. Insulin sensitivity index (ISI) was evaluated by the Matsuda index. Intrarenal hemodynamic parameters were calculated by the Gomez formulae.

RESULTS

Of the 54 subjects, 33 exhibited IFG or IGT and 31 exhibited normal glucose tolerance (NGT). Glomerular hydrostatic pressure (P_glo) and UAE were significantly higher in the IFG or IGT subjects with obesity (P = 0.015 and 0.0001, respectively). Log ISI correlated significantly and negatively with P_glo (r = -0.351, P = 0.009) in all subjects. In multiple regression analyses among all subjects, log ISI was associated significantly and independently with P_glo (β = -0.316, P = 0.015), after adjustment for age, sex, and systolic blood pressure. Further, BMI (β = 0.517, P = 0.0004), P_glo (β = 0.420, P = 0.004), and log ISI (β = -0.366, P = 0.008) were each associated significantly and independently with UAE after adjustment.

CONCLUSIONS

We demonstrated that increased insulin resistance is associated with increased P_glo and UAE in IFG or IGT subjects. These hemodynamic burdens and insulin resistance may cause injury to the glomeruli even in subjects with IFG or IGT.

Urinary Iron Excretion is Associated with Urinary Full-Length Megalin and Renal Oxidative Stress in Chronic Kidney Disease

BACKGROUND/AIMS

Megalin mediates the uptake of glomerular-filtered iron in the proximal tubules. Urinary full length megalin (C-megalin) excretion has been found to be increased in association with megalin-mediated metabolic load to the endo-lysosomal system in proximal tubular epithelial cells (PTECs) of residual nephrons. In the present study, we investigated the association between urinary iron and C-megalin in chronic kidney disease (CKD) patients, and the possible harmful effect of iron in renal tubules.

METHODS

Urinary levels of iron and C-megalin were measured in 63 CKD patients using automatic absorption spectrometry and a recently-established sandwich ELISA, respectively.

RESULTS

Although both urinary C-megalin and urinary total protein levels were correlated with urinary iron (C-megalin: ρ = 0.574, p <0.001; total protein: ρ = 0.500, p <0.001, respectively), urinary C-megalin alone emerged as an independent factor positively associated with urinary iron (β = 0.520, p <0.001) (R2 = 0.75, p <0.001). Furthermore, urinary iron was significantly and positively associated with urinary 8-hydroxydeoxyguanosine, an oxidative stress marker, while no association with other markers of renal tubular injury, i.e., β2-microglobulin and N-acetyl-β-D-glucosaminidase, was noted.

CONCLUSIONS

Our findings suggest that renal iron handling may be associated with megalin-mediated endo-lysosomal metabolic load in PTECs of residual nephrons and oxidative stress in renal tubules.

Xanthine oxidoreductase activity is associated with serum uric acid and glycemic control in hemodialysis patients

Xanthine oxidoreductase activity (XOR-a) plays an important role as a pivotal source of reactive oxygen species. In the present study, we investigated factors associated with plasma XOR-a in 163 hemodialysis patients (age 67.3 ± 10.9 years; 89 males and 74 females), using a newly established, highly-sensitive assay based on [¹³C₂,¹⁵N₂] xanthine and liquid chromatography/triple quadrupole mass spectrometry. Plasma glucose and serum uric acid levels correlated significantly and positively with plasma XOR-a. In multiple regression analyses, the presence of type 2 diabetes mellitus (T2DM) and plasma glucose were associated significantly, independently, and positively with plasma XOR-a. While serum uric acid correlated significantly and positively with plasma XOR-a in hemodialysis patients without T2DM, plasma glucose and serum glycated albumin, a new marker of glycemic control in diabetic hemodialysis patients, correlated significantly and positively with plasma XOR-a in those with T2DM. Multivariate analyses in those with T2DM revealed that plasma glucose and serum glycated albumin were associated significantly and independently with plasma XOR-a, and that serum uric acid was associated significantly and independently with XOR-a in those without T2DM. Our results suggested that glycemic control in hemodialysis patients may be important in regard to a decrease in ROS induced by XOR.

Development of hyperkalemia following treatment with dapagliflozin (DAPA) in a patient with type 2 diabetes after bilateral adrenalectomy

Dapagliflozin (DAPA), a sodium-glucose co-transporter 2 (SGLT2) inhibitor, is known to have a beneficial diuretic effect, in addition to a glucose-lowering effect. Although SGLT2 inhibitor has been reported, the increase of hyperkalemia in patients treated with renin-angiotensin-aldosterone system (RAAS) inhibitors, their mechanism of action is unclear. We report the first case of a type 2 diabetes (T2DM) patient with potential mineralocorticoid deficiency who developed hyperkalemia after administration of DAPA. A 79-year-old woman underwent bilateral adrenalectomy for uncontrolled hypercortisolism due to an inoperable recurrence of Cushing's disease, and she was subsequently maintained on replacement therapy with glucocorticoid. She was diagnosed as having T2DM at 71 years of age and was treated with sitagliptin and miglitol. Since she presented with weight gain of about 5 kg over 6 months and her HbAlc level increased over 12%, 5 mg/day DAPA was added to her daily regimen. After the start of DAPA treatment, she developed hyperkalemia (6.5 mEq/L) with increased plasma renin activity of 53.1 ng/mL/h. She was diagnosed with aldosterone deficiency and started on fludrocortisone 0.1 mg daily, after which the hyperkalemia improved immediately. In this case, DAPA treatment could potentially increase the requirement for mineralocorticoid replacement, directly suggesting that the SGLT2 inhibition-induced natriuretic effect is accompanied by compensatory activation of the RAAS axis, which is essential to keep the serum potassium level within the normal range. Therefore, physicians should be careful about the development of hyperkalemia in patients when SGLT2 and RAAS inhibitors are used in combination.

U-shaped relationship between serum uric acid levels and intrarenal hemodynamic parameters in healthy subjects

Hyperuricemia has been reported to affect renal hemodynamics. In a recent study, both low and high levels of serum uric acid (SUA) were found to be associated with loss of kidney function. The goal of this study was to evaluate the relationship between SUA levels and intrarenal hemodynamic parameters in healthy subjects, using plasma clearance of para-aminohippurate (C_PAH) and inulin (C_in). Renal and glomerular hemodynamics were evaluated by simultaneous measurements of C_PAH and C_in in 48 healthy subjects (54.6 ± 13.4 yr). Intrarenal hemodynamic parameters, including efferent and afferent (R_a) arteriolar resistance, were calculated using Gómez's formulas. Relationships of SUA levels with these intrarenal hemodynamic parameters were examined. In quadratic regression analysis, SUA levels had a significant inverse U-shaped relationship with C_in (P < 0.0001, R² = 0.350) and C_PAH (P = 0.0093, R² = 0.188) and a U-shaped relationship with R_a (P = 0.0011, R² = 0.262). In multiple regression analysis with normal (3.5-6.0 mg/dl) and mildly low or high (<3.5 or >6.0 mg/dl) SUA levels entered as dummy variables of zero and one, respectively, mildly low or high SUA levels were significantly and independently associated with R_a (β = 0.230, P = 0.0403) after adjustment for several factors (R² = 0.597, P < 0.0001). Both mild hyperuricemia and mild hypouricemia are significantly associated with increased R_a, although weakly. The increase in R_a in subjects with mild hyperuricemia or hypouricemia may be related to renal hemodynamic abnormalities, possibly leading to a decline in renal function.

Association of Nocturnal Hypertension With Disease Activity in Rheumatoid Arthritis

OBJECTIVES

Both nocturnal hypertension (HT) and systemic inflammation underlying rheumatoid arthritis (RA) have been shown to be independent predictors of cardiovascular disease (CVD), although little is known on the relationship between nocturnal blood pressure (BP) and disease activity in RA patients.

METHODS

We performed 24-hour ambulatory BP monitoring (ABPM) in 71 RA patients to examine the relationship of nocturnal fall in BP and RA disease activity based on a disease activity score of 28 joint counts with C-reactive protein (CRP, 28-joint disease activity score (DAS28)-CRP). Among them, 25 RA patients whose consent obtained were reexamined by ABPM to assess the improvement of nocturnal fall in BP after RA therapeutic intervention.

RESULTS

The mean DAS28-CRP level was 4.8±1.6 in 71 RA patients. The mean nocturnal fall in BP was 5.6±8.9%. DAS28-CRP was associated significantly and independently in a negative manner with the nocturnal fall in BP (β = -0.388, P = 0.004). In 25 RA patients, DAS28-CRP improved from 5.4±1.1 to 3.5±0.8 (P < 0.0001) and the nocturnal fall in BP increased significantly from 4.5±9.2% to 10.6±5.8% (P = 0.002) with the significant decrease of nighttime systolic BP (SBP) from 121.2±22.5mm Hg to 112.5±18.8mm Hg (P = 0.02) in spite of no change in daytime BP after 4 weeks of RA treatment.

CONCLUSIONS

The present study observed that higher RA activity was associated with lower nocturnal fall in BP, but not daytime BP, in RA patients.

Comparison of the Estimated Glomerular Filtration Rate (eGFR) in Diabetic Patients, Non-Diabetic Patients and Living Kidney Donors

BACKGROUND/AIMS

We have reported that the eGFR overestimates renal function when glycemic control is poor. It has been reported that eGFR calculated by serum creatinine underestimates GFR in living kidney donors. We compared the utility of the eGFR in diabetic patients, non-diabetic patients and living kidney donors. Forty diabetic patients, 40 non-diabetic patients, and 40 living kidney donors were enrolled.

METHODS

GFR was measured by inulin clearance (C(in)). eGFR was calculated based on serum creatinine (eGFR(cr)) or serum cystatin C (eGFR(cys)). We compared the agreements between each of the eGFR and C(in) in each group.

RESULTS

There were significant and positive correlations between each eGFR and C(in) in diabetic patients and non-diabetic patients. However, the intraclass correlation coefficients (ICC) between each eGFR and C(in) in diabetic patients (ICC: eGFR(cr) 0.699, eGFR(cys) 0.604) were weaker than those in non-diabetic patients (ICC: eGFR(cr) 0.865, eGFR(cys) 0.803). The correlation coefficients between each eGFR and C(in) (eGFR(cr); r = 0.422, p = 0.0067 and eGFR(cys); r = 0.358, p = 0.0522) in living kidney donors were significantly weaker than those in non-diabetic patients. The ICCs between each eGFR and C(in) (ICC: eGFR(cr) 0.340, eGFR(cys) 0.345) in living kidney donors were significantly weaker than those in non-diabetic patients.

CONCLUSIONS

Based on C(in), eGFR was accurate in non-diabetic patients. However, eGFR was inaccurate in living kidney donors and relatively inaccurate in diabetic patients.

Association between poor glycemic control, impaired sleep quality, and increased arterial thickening in type 2 diabetic patients

Objective

Poor sleep quality is an independent predictor of cardiovascular events. However, little is known about the association between glycemic control and objective sleep architecture and its influence on arteriosclerosis in patients with type-2 diabetes mellitus (DM). The present study examined the association of objective sleep architecture with both glycemic control and arteriosclerosis in type-2 DM patients.

Design

Cross-sectional study in vascular laboratory.

Methods

The subjects were 63 type-2 DM inpatients (M/F, 32/31; age, 57.5±13.1) without taking any sleeping promoting drug and chronic kidney disease. We examined objective sleep architecture by single-channel electroencephalography and arteriosclerosis by carotid-artery intima-media thickness (CA-IMT).

Results

HbA1c was associated significantly in a negative manner with REM sleep latency (interval between sleep-onset and the first REM period) (β=-0.280, p=0.033), but not with other measurements of sleep quality. REM sleep latency associated significantly in a positive manner with log delta power (the marker of deep sleep) during that period (β=0.544, p=0.001). In the model including variables univariately correlated with CA-IMT (REM sleep latency, age, DM duration, systolic blood pressure, and HbA1c) as independent variables, REM sleep latency (β=-0.232, p=0.038), but not HbA1c were significantly associated with CA-IMT. When log delta power was included in place of REM sleep latency, log delta power (β=-0.257, p=0.023) emerged as a significant factor associated with CA-IMT.

Conclusions

In type-2 DM patients, poor glycemic control was independently associated with poor quality of sleep as represented by decrease of REM sleep latency which might be responsible for increased CA-IMT, a relevant marker for arterial wall thickening.

Significant association between glycemic status and increased estimated postglomerular resistance in nondiabetic subjects - study of inulin and para-aminohippuric acid clearance in humans

We investigated whether glomerular hemodynamic parameters in nondiabetic subjects, including healthy subjects, are associated with glycemic status indices, by simultaneous measurement of inulin (C_in) and para-aminohippuric acid (C_PHA) clearance. Twenty-six subjects (age 49.5 ± 13.3 years; 13 men and 13 women; 14 healthy subjects and 12 subjects with mild proteinuria) were enrolled. C_in and C_PAH were measured simultaneously. All 26 subjects were nondiabetics. Estimated preglomerular resistance, estimated postglomerular resistance, and estimated glomerular hydrostatic pressure (P_glo) were calculated according to Gomez’ formula. P_glo correlated significantly and positively with hemoglobin A1c (HbA1c) in both healthy subjects (r = 0.532, P = 0.0498) and subjects with mild proteinuria (r = 0.681, P = 0.015). While there was no significant correlation between estimated preglomerular resistance and HbA1c, estimated postglomerular resistance correlated significantly and positively with HbA1c both in healthy subjects (r = 0.643, P = 0.013) and subjects with mild proteinuria (r = 0.589, P = 0.044). Glomerular filtration fraction, estimated P_glo and estimated postglomerular resistance in total subjects were associated significantly with HbA1c after adjustment for age, gender, and body mass index. These results demonstrate that, even in nondiabetic subjects, glycemic status is associated with estimated postglomerular resistance, but not estimated preglomerular resistance. It is suggested that increased estimated postglomerular resistance associated with higher HbA1c levels, even within the normal range, causes increased estimated P_glo, leading to increased FF. Thus, hemodynamic abnormalities associated with higher HbA1c levels may be related to glomerular hypertension, even in nondiabetic subjects.

Ramelteon for the treatment of delirium in elderly patients: a consecutive case series study

OBJECTIVE

Melatonin is effective in the prevention and treatment of delirium. Ramelteon has few adverse effects and higher affinity for MT1 and MT2 receptors than melatonin. The aim of the present study was to determine the efficacy of ramelteon in elderly patients with delirium caused by different primary diseases/conditions.

METHOD

We treated 10 consecutive elderly patients having delirium with ramelteon.

RESULTS

Of the 10 patients, six showed improvement, and no marked adverse effects were observed.

CONCLUSIONS

Our study suggested that ramelteon was a safe and useful alternative to melatonin for the treatment of delirium in elderly patients. Randomized, controlled studies are necessary to confirm the therapeutic benefits of ramelteon.

Significant association of poor glycemic control with increased resistance in efferent arterioles--study of inulin and para-aminohippuric acid clearance in humans

AIMS

To examine whether glomerular hemodynamic parameters in humans are associated with glycemic control indices, by simultaneously measuring clearance of inulin (Cin) and para-aminohippuric acid (CPHA).

METHODS

Thirty-one subjects (age 55.4±14.7 years; 15 men and 16 women; 21 diabetics and 10 non-diabetics) were enrolled. Cin and CPAH were measured simultaneously. Afferent arteriolar resistance (Ra), efferent arteriolar resistance (Re), glomerular hydrostatic pressure (Pglo) and glomerular filtration fraction (FF) were calculated according to Gomez' formula.

RESULTS

FF correlated significantly and positively with fasting plasma glucose (FPG), hemoglobin A1c (HbA1c) and glycated albumin (GA) (r=0.396, p=0.0303; r=0.587, p=0.0007; r=0.525, p=0.0070, respectively). Pglo correlated significantly and positively with FPG, HbA1c and GA (r=0.572, p=0.0008; r=0.535, p=0.0019; r=0.540, p=0.0053, respectively). Although there was no significant correlation between Ra and glycemic control indices, Re correlated significantly and positively with HbA1c and GA (r=0.499, p=0.0043; r=0.592, p=0.0018, respectively). FF, Pglo and Re were associated significantly with HbA1c and GA after adjustment for age.

CONCLUSIONS

These results demonstrate, in humans, that poor glycemic control is associated with increased Re, but not Ra. It is suggested that increased Re causes increased Pglo, leading to increased FF. Thus, hemodynamic abnormalities with poor glycemic control may be related to glomerular hypertension in humans.

Quantitative analysis of abdominal aortic calcification in CKD patients without dialysis therapy by use of the Agatston score

BACKGROUND/AIM

The aim of the present study was to quantitatively examine factors associated with aortic calcification in non-dialysis CKD patients.

METHODS

We quantitatively investigated aortic calcification from the renal artery to the bifurcation in 149 non-dialysis CKD patients (58±16 years; 96 males and 53 females, 48 diabetics; eGFR 40.3 ± 29.3 ml/min), and measured Agatston scores using multi-slice computed tomography.

RESULT

Of 149 patients, aortic calcification was present in 117. In patients with aortic calcification, age (p<0.001), C-reactive protein (p<0.001), and intact-PTH (p < 0.001) were significantly higher, estimated glomerular filtration rate (eGFR) was significantly lower (p<0.001), and diabetes was observed more often (p<0.05). In regards to the degree of aortic calcification, the Agatston scores correlated significantly and positively with age (ρ=0.438, p<0.001) and serum phosphate (ρ=0.208, p=0.024), and correlated significantly but negatively with e-GFR (ρ=-0.353, p<0.001). In multiple regression analysis, eGFR was associated significantly and independently with the log [Agatston score] (β=-0.346, p<0.01), after adjustment for several confounders including serum phosphate and the presence of diabetes.

CONCLUSIONS

Hyperphospatemia, chronic inflammation, diabetes, and decreased GFR are associated significantly with the presence of aortic calcification in non-dialysis CKD patients. Decreased eGFR was associated significantly and independently with the quantitative degree of aortic calcification.