Association of urinary albumin excretion with insulin resistance in Japanese subjects: impact of gender difference on insulin resistance.

OBJECTIVE: To investigate the relationship between homeostasis model assessment for insulin resistance (HOMA-R) and urinary albumin excretion in Japanese and clarify gender difference in albuminuria-related insulin resistance. METHODS: The subject group consisted of 752 Japanese who had no history of diabetes, hypertension or dyslipidemia. After anthropometric examination, fasting blood samples were obtained to determine plasma glucose (FPG), lipids and HOMA-R. The urinary excretion of albumin in the first void urine was expressed as the creatinine ratio (ACR, mg/gCr). Estimated glomerular filtration rate (eGFR) was calculated from serum creatinine using the formula for Japanese. RESULTS: HOMA-R showed a significant correlation with ACR, and the correlation between HOMA-R and ACR was evident in the subjects with central obesity, whereas no significant correlation was found in the non-obese subjects. There was no correlation between HOMA-R and eGFR. HOMA-R increased according to the quintile of ACR and followed a significant trend. This association was obvious in males; however, in females there was no significant trend. Multiple regression analysis revealed that HOMA-R showed a significant correlation with age, waist circumference, blood pressure and serum triglyceride. In addition, ACR exhibited an independent association with HOMA-R. The association of HOMA-R and ACR was observed only in males, and was not present in females. CONCLUSION: Microalbuminuria is associated with insulin resistance in Japanese, where central obesity might play an essential role. This association is gender-specific suggesting the involvement of sex hormones in the pathogenesis of albuminuria-related insulin resistance.

[Usefulness of protein/creatinine ratio in spot urine using test strips].

The influence of concentration and dilution has been the major issue of urinalysis. This study is to evaluate the usefulness of protein (P)/creatinine (C) ratio (P/C ratio) in spot urine by test strips method. For this purpose, the basic performance of creatinine test strips is evaluated and judging criteria for the urine P/C ratio is defined. Our evaluation revealed that the creatinine test strips were basically not affected by substances which have similar composition to creatinine, such as creatine, but by some medical agents and disinfectant. Its minimum detective sensitivity was 6.0 mg/dl, while that of protein test strips was 1.3 mg/dl. We determined judging criteria for the P/C ratio as follows: Below 80 mg/gCr, Normal; 80 to 500mg/gCr, 1 +; over 500 mg/gCr, 2+. The P/C ratio based on the quantitative and test strips methods provided good consistency of 82.2%. In low-creatinine urine samples (11 to 99mg/dl), 181 of 216 samples (83.8%) were tested negative on single-protein tests; while the P/C ratio provided fewer negative results, 134 of 216(62.0%). Moreover, in high-creatinine urine samples (200 to 600 mg/dl), 70 of 122 samples (57.4%) were tested negative on single protein tests; while the P/C ratio provided negative results in almost all the samples, 120 of 122 (98.4%). These urine samples were mostly collected at a medical examination. The results above showed that the P/C ratio obtained by easy and quick test strip method is equivalent to the quantitative method in performance and useful for spot urine testing.

[Evaluation of novel test strip to measure albumin and creatinine in urine].

The purpose of this study was to evaluate the clinical usefulness of novel test strip that simultaneously measure urinary albumin and creatinine. Testing was performed on 95 random urine samples from diabetics. Each sample was assayed with following methods: test strip by instrument (AX4280) reading and by visual interpretation, quantitative method for albumin, creatinine, and alpha1-microglobulin and cellulose acetate membrane electrophoresis. The results of test strip had good correlation with quantitative results. In the case of instrument reading, the sensitivity, specificity and consistency were 91.2%, 78.9% and 86.3% for albumin and 94.5%, 87.5% and 91.6% for albumin index (albumin/creatinine ratio; A/C ratio), respectively. The percent same level agreement for creatinine was 63.2%. After correction using creatinine value on test strip, 18.4% of samples defined as negative by albumin quantitative value were turned to be positive, 12.3% of samples defined as positive were turned to be negative. The same level of creatinine correction effect as the quantitative method was obtained at the test strip. When alpha1-microglobulin/creatinine (alpha1 m/g x Cr) ratio was compared with albumin index, percent positive of alpha1 m/g x Cr ratio was 35.0% for samples with albumin index less than 30 mg/g x Cr, 59.5% for those with albumin index between 30 and 300 mg/g x Cr. In addition, on cellulose acetate membrane electrophoresis, both retinol binding protein (RBP) and beta2-microglobulin (beta2 m) were detected in 12.5% of patients in normal condition or pre-nephropathy. Among patients at early-nephropathy, the detection rate of RBP and beta2 m were 20.0% and 15.0% respectively. These results indicate that the renal tubule is also damaged at the early stages of nephropathy.