European Journal of Cardiovascular Medicine

Type 2 Diabetes Mellitus (T2DM) represents a significant global health challenge, characterized by chronic hyperglycemia resulting from insulin resistance and relative insulin deficiency. The rising prevalence of T2DM is a major public health concern, given its association with severe complications, including target organ damage (TOD) involving the kidneys, heart, eyes, and peripheral nerves. Microvascular complications such as diabetic nephropathy, retinopathy, and neuropathy, along with macrovascular complications like cardiovascular disease, significantly contribute to the morbidity and mortality associated with T2DM [1,2].

Proteinuria, the presence of excess proteins in the urine, is a well-recognized marker of renal involvement and a predictor of cardiovascular events in diabetic patients [3]. The quantification of 24-hour urine protein is a critical diagnostic and prognostic tool in the management of diabetic nephropathy. The relationship between proteinuria and various clinical and biochemical parameters, including serum creatinine, estimated glomerular filtration rate (eGFR), glycated hemoglobin (HbA1c), lipid profile, and the duration of diabetes, provides insights into the extent of renal impairment and the risk of progression to end-stage renal disease (ESRD) [4].

Diabetic nephropathy, a leading cause of ESRD, is characterized by persistent albuminuria, a progressive decline in eGFR, and increased arterial blood pressure [5]. The pathogenesis involves complex interactions between metabolic and hemodynamic pathways, leading to glomerular hyperfiltration, hypertrophy, and eventual glomerulosclerosis. Hyperglycemia-induced oxidative stress, advanced glycation end-products (AGEs), and the activation of the renin-angiotensin-aldosterone system (RAAS) are key contributors to renal damage in T2DM [6].

The assessment of 24-hour urine protein is a valuable indicator of renal function and a prognostic marker for cardiovascular morbidity in T2DM patients. Elevated urine protein levels reflect increased glomerular permeability and are associated with both microvascular and macrovascular complications. Studies have shown that higher levels of proteinuria correlate with worse outcomes in diabetic patients, including a higher risk of cardiovascular events and mortality [7]. Additionally, proteinuria serves as a surrogate marker for the efficacy of therapeutic interventions aimed at reducing the progression of renal disease and preventing cardiovascular complications [8].

In clinical practice, the management of proteinuria in T2DM involves the optimization of glycemic control, blood pressure management, and the use of pharmacological agents such as angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin II receptor blockers (ARBs), which have been shown to reduce proteinuria and slow the progression of diabetic nephropathy [9]. The integration of routine 24-hour urine protein measurement into the management plan for T2DM patients enables the early identification of those at high risk for TOD and the timely implementation of strategies to mitigate these risks [10].

Aims and Objectives

The aim of this study was to investigate the association of biochemical and clinical parameters like serum creatinine, estimated glomerular filtration rate (eGFR), glycated hemoglobin (HbA1c), lipid profile, duration of diabetes, presence of diabetic retinopathy, and microvascular and macrovascular complications with 24-hour urine protein in patients with type 2 diabetes mellitus (T2DM).

This was a hospital-based prospective analytical study conducted over a period of one year from the date of approval by the Institutional Scientific and Ethical Committee. The study setting was the Medical Wards and Department of General Medicine at SVRRGGH, Tirupati.

The sample size was 100 patients with T2DM who fulfilled the inclusion and exclusion criteria. The inclusion criteria were patients with T2DM diagnosed based on the National Diabetes Data Group and WHO criteria, age >18 years, and willing to give informed written consent. The exclusion criteria were patients with acute febrile illness, glomerulonephritis due to systemic conditions, malignancies, collagen vascular disorders or any other systemic condition causing proteinuria, chronic renal failure, age <18 years, pregnant women, urinary tract infections, and type 1 diabetes mellitus.

A random sample of male and female patients with T2DM satisfying the inclusion and exclusion criteria was selected. History and physical examination were done in all the patients according to a prefixed proforma. All the patients underwent various investigations, including 24-hour urine protein (by sulfosalicylic acid method), serum creatinine (by semi-automated clinical chemistry analysis), serum cholesterol (by CHOD-PAP method), serum triglycerides (by GPO-TRINDER method), HbA1c (by HPLC-NGSP method), eGFR (calculation by MDRD equation), ECG, 2D Echo, fundoscopy, ankle-brachial index, and carotid color doppler (by ultrasonography).

SPSS software v 26 was used for statistical analysis. Spearman's correlation coefficient was used for correlation of numerical variables. Before data collection, all subjects were briefed about the purpose of the study, and written informed consent was obtained. All investigations were done free of cost, and no financial burden was imposed on the patients.

Table 1: Descriptive Statistics of the Study Population

The study included 100 patients with Type 2 Diabetes Mellitus (T2DM) to evaluate the correlation between 24-hour urine protein and various clinical and biochemical parameters. The descriptive statistics of the study population are summarized in Table 1. The mean age of the participants was 58.64 years (SD = 11.82), with a minimum age of 33 years and a maximum age of 85 years. The mean weight of the participants was 70.318 kg (SD = 8.64), with a range from 46 kg to 92 kg. The average height was 162.8 cm (SD = 4.96), ranging from 150 cm to 175 cm. The mean Body Mass Index (BMI) was 26.892 kg/m² (SD = 3.16), with a minimum of 20.0 kg/m² and a maximum of 37.9 kg/m². The mean HbA1c level was 7.813% (SD = 1.10), ranging from 6.6% to 11.0%. The mean serum creatinine level was 1.091 mg/dL (SD = 0.26), with a range from 0.7 mg/dL to 1.8 mg/dL. The mean estimated Glomerular Filtration Rate (eGFR) was 75.015 mL/min/1.73m² (SD = 22.43), with values ranging from 38.1 mL/min/1.73m² to 120.8 mL/min/1.73m². The mean 24-hour urine protein was 187.880 mg/dL (SD = 116.65), with a minimum of 50.0 mg/dL and a maximum of 520.0 mg/dL. The mean Ankle Brachial Index (ABI) was 1.055 (SD = 0.12), with values ranging from 0.9 to 1.3.

Table 2: Demographic and Clinical Characteristics

Demographic and clinical characteristics are detailed in Table 2. The age distribution showed that 9% of the patients were under 40 years old, 19% were between 41 and 50 years, 27% were between 51 and 60 years, 29% were between 61 and 70 years, 15% were between 71 and 80 years, and 1% were over 80 years old. The gender distribution indicated that 55% of the patients were male, and 45% were female. Regarding smoking history, 43% of the patients were smokers, while 57% were non-smokers. In terms of lipid profile, 53% of the patients had elevated lipid levels, and 47% had normal lipid levels. For treatment, 74% of the patients were on oral hypoglycemic agents (OHA), and 26% were on a combination of OHA and insulin.

Table 3: Clinical Examinations and Findings

Clinical examinations and findings are presented in Table 3. The electrocardiogram (ECG) results showed that 94% of the patients had a normal ECG pattern, 4% had left ventricular hypertrophy (LVH), and 2% had LVH with strain. Fundoscopic examination revealed that 73% of the patients had normal findings, 14% had mild non-proliferative diabetic retinopathy (NPDR), 4% had moderate NPDR, 1% had mild NPDR with grade 1 hypertensive (HTN) changes, 2% had moderate NPDR with grade 1 HTN changes, 3% had moderate NPDR with grade 2 HTN changes, and 3% had grade 1 HTN changes only. In terms of diabetic retinopathy, 15% of the patients had mild NPDR, 9% had moderate NPDR, and 76% had no NPDR. Carotid artery Doppler results indicated that 92% of the patients had normal findings, and 8% had mild atherosclerosis.

Table 4: eGFR and HbA1C Distribution

The distribution of eGFR and HbA1c levels is shown in Table 4. Among the patients, 34% had an eGFR greater than 90 mL/min/1.73m², 35% had an eGFR between 60 and 89 mL/min/1.73m², and 31% had an eGFR between 30 and 59 mL/min/1.73m². Regarding HbA1c levels, 37% of the patients had an HbA1c level less than 7%, and 63% had an HbA1c level greater than 7%.

Table 5: Comparison of HbA1C with Other Parameters

Table 5 compares HbA1c levels with other parameters. Patients with HbA1c levels less than 7% had a mean BMI of 26.7 kg/m² (SD = 3.3), while those with HbA1c levels greater than 7% had a mean BMI of 27.0 kg/m² (SD = 3.1), with a p-value of 0.621, indicating no significant difference. The mean duration of diabetes for patients with HbA1c levels less than 7% was 6.8 years (SD = 4.1), compared to 8.4 years (SD = 4.4) for those with HbA1c levels greater than 7%, with a p-value of 0.061. The mean serum creatinine level for patients with HbA1c levels less than 7% was 0.9 mg/dL (SD = 0.1), compared to 1.2 mg/dL (SD = 0.2) for those with HbA1c levels greater than 7%, with a statistically significant p-value of less than 0.001. The mean eGFR for patients with HbA1c levels less than 7% was 88.7 mL/min/1.73m² (SD = 18.1), compared to 67.0 mL/min/1.73m² (SD = 20.9) for those with HbA1c levels greater than 7%, with a p-value of less than 0.001. The mean 24-hour urine protein for patients with HbA1c levels less than 7% was 108.6 mg/dL (SD = 45.6), compared to 234.4 mg/dL (SD = 120.7) for those with HbA1c levels greater than 7%, with a statistically significant p-value of less than 0.001. The mean ABI for patients with HbA1c levels less than 7% was 1.0 (SD = 0.1), compared to 1.1 (SD = 0.1) for those with HbA1c levels greater than 7%, with a p-value of 0.365.

Table 6: Correlation of 24-Hour Urine Protein with Various Parameters

Note: Correlation is significant at the 0.01 level (2-tailed).

The correlation of 24-hour urine protein with various parameters is detailed in Table 6. There was a positive correlation between smoking history and 24-hour urine protein with a Pearson correlation coefficient of 0.145, which was not statistically significant (p-value = 0.151). The correlation between the duration of diabetes and 24-hour urine protein had a Pearson correlation coefficient of 0.084, which was also not statistically significant (p-value = 0.406). The treatment history showed a statistically significant positive correlation with 24-hour urine protein, with a Pearson correlation coefficient of 0.478 (p-value < 0.0001). The correlation between BMI and 24-hour urine protein had a Pearson correlation coefficient of 0.121, which was not statistically significant (p-value = 0.229). HbA1c showed a highly significant positive correlation with 24-hour urine protein, with a Pearson correlation coefficient of 0.869 (p-value < 0.0001). Serum creatinine also showed a significant positive correlation with 24-hour urine protein, with a Pearson correlation coefficient of 0.602 (p-value < 0.0001). The correlation between ABI and 24-hour urine protein was not statistically significant, with a Pearson correlation coefficient of 0.018 (p-value = 0.859). Diabetic retinopathy showed a significant positive correlation with 24-hour urine protein, with a Pearson correlation coefficient of 0.797 (p-value < 0.0001).

These results indicate that higher levels of 24-hour urine protein are significantly associated with higher HbA1c levels, higher serum creatinine levels, diabetic retinopathy, and certain treatment histories, underscoring the importance of proteinuria as a marker for assessing the risk of target organ damage in patients with T2DM.

The present study aimed to explore the correlation between 24-hour urine protein levels and various clinical and biochemical parameters in patients with Type 2 Diabetes Mellitus (T2DM). Our findings indicate that higher levels of 24-hour urine protein are significantly associated with higher HbA1c levels, higher serum creatinine levels, diabetic retinopathy, and certain treatment histories. These results underscore the importance of proteinuria as a marker for assessing the risk of target organ damage in patients with T2DM.

Proteinuria is a well-recognized marker of diabetic nephropathy and an independent predictor of cardiovascular morbidity and mortality in diabetic patients [11]. The mean 24-hour urine protein level in our study population was 187.88 mg/dL (SD = 116.65). This is consistent with findings from previous studies, which have demonstrated that proteinuria is strongly correlated with poor glycemic control and renal function decline in T2DM patients [12, 13]. For instance, a study by Parving et al. (2006) found that elevated urine protein levels were associated with a higher risk of cardiovascular events and progression to end-stage renal disease (ESRD) [14].

Our study found a significant positive correlation between 24-hour urine protein and HbA1c levels, with a Pearson correlation coefficient of 0.869 (p < 0.0001). This finding is in line with the study by Wang et al. (2014), which reported a correlation coefficient of 0.72 (p < 0.001) between urine protein levels and HbA1c in T2DM patients [15]. High HbA1c levels indicate poor glycemic control, which exacerbates the risk of microvascular and macrovascular complications, including diabetic nephropathy. The relationship between poor glycemic control and increased proteinuria underscores the need for stringent glycemic management to mitigate the risk of renal and cardiovascular complications in diabetic patients.

Serum creatinine levels also showed a significant positive correlation with 24-hour urine protein in our study, with a Pearson correlation coefficient of 0.602 (p < 0.0001). Elevated serum creatinine is indicative of impaired renal function, and its association with proteinuria highlights the progressive nature of diabetic nephropathy. These findings are supported by the work of Gross et al. (2005), who demonstrated that higher serum creatinine levels were associated with increased urine protein excretion in T2DM patients [16].

Diabetic retinopathy was another variable significantly correlated with 24-hour urine protein in our study, with a Pearson correlation coefficient of 0.797 (p < 0.0001). This result aligns with the study by Klein et al. (2004), which found a significant association between the severity of diabetic retinopathy and the degree of proteinuria in T2DM patients (p < 0.001) [17]. Diabetic retinopathy and nephropathy share common pathogenic mechanisms, including hyperglycemia-induced oxidative stress and the formation of advanced glycation end-products (AGEs), which contribute to endothelial dysfunction and increased vascular permeability [18].

Our findings also revealed that treatment history, particularly the use of combined oral hypoglycemic agents (OHA) and insulin, was significantly correlated with 24-hour urine protein levels, with a Pearson correlation coefficient of 0.478 (p < 0.0001). Patients on combined therapy had higher mean urine protein levels (281.5 mg/dL) compared to those on OHA alone (155.0 mg/dL), indicating more advanced disease and greater risk of renal complications. This observation is consistent with the study by Bakris et al. (2003), which reported that intensified therapy in patients with poor glycemic control and significant proteinuria was associated with a slower progression of renal disease but higher baseline proteinuria levels [19].

Contrasting findings from some studies suggest variability in the degree of proteinuria among different populations and treatment regimens. For example, a study by Ruggenenti et al. (2004) found that the use of angiotensin-converting enzyme inhibitors (ACEIs) significantly reduced proteinuria levels in T2DM patients with nephropathy, highlighting the importance of renin-angiotensin system (RAS) blockade in managing diabetic kidney disease [20]. However, our study did not specifically examine the impact of ACEIs or angiotensin II receptor blockers (ARBs) on proteinuria, which could be a potential area for future research.

The lack of significant correlation between 24-hour urine protein and some parameters such as BMI, duration of diabetes, and Ankle Brachial Index (ABI) in our study suggests that these factors may not be as strongly predictive of proteinuria as HbA1c, serum creatinine, and diabetic retinopathy. Similar findings were reported by Hovind et al. (2004), who observed that while BMI and diabetes duration were important risk factors for diabetic complications, they did not show a direct correlation with proteinuria levels [21].

In conclusion, our study highlights the significant associations between 24-hour urine protein levels and key clinical and biochemical parameters in T2DM patients. These findings reinforce the utility of proteinuria as a valuable marker for assessing the risk of target organ damage and guiding therapeutic interventions. Effective management of glycemic control, along with the use of renoprotective agents, remains crucial in reducing the burden of diabetic nephropathy and associated cardiovascular complications.

The study elucidates the significant correlations between 24-hour urine protein levels and various clinical and biochemical parameters in patients with Type 2 Diabetes Mellitus (T2DM). Elevated 24-hour urine protein levels were significantly associated with higher HbA1c levels, indicating poor glycemic control, and higher serum creatinine levels, reflecting impaired renal function. Additionally, a significant association was observed between proteinuria and diabetic retinopathy, highlighting the interconnected nature of microvascular complications in diabetes. Patients undergoing combined treatment with oral hypoglycemic agents (OHA) and insulin exhibited higher proteinuria levels, suggesting more advanced disease stages.

The study emphasizes the critical role of proteinuria as a marker for assessing the risk of target organ damage (TOD) in T2DM patients. These findings reinforce the importance of routine 24-hour urine protein measurement in clinical practice for early identification of high-risk patients. Effective glycemic management and the use of renoprotective agents, such as ACE inhibitors or angiotensin II receptor blockers, are crucial strategies to mitigate the progression of diabetic nephropathy and associated cardiovascular complications.

Future research should focus on exploring the impact of different treatment regimens on proteinuria and long-term renal outcomes in T2DM patients. Additionally, investigating the role of novel biomarkers in conjunction with traditional measures may enhance the predictive accuracy for TOD and guide personalized treatment approaches.

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