- Email: [email protected]
Total Serum Cholesterol Increases Risk for Development and Progression of Nonproliferative Retinopathy in Patients with Type 1 Diabetes Without Therapeutic Intervention: Prospective, Observational Study
Archives of Medical Research
-
(2017)
-
ORIGINAL ARTICLE
Total Serum Cholesterol Increases Risk for Development and Progression of Nonproliferative Retinopathy in Patients with Type 1 Diabetes Without Therapeutic Intervention: Prospective, Observational Study Tomislav Bulum,a,b Martina Tomic,a and Lea Duvnjaka,b a
Vuk Vrhovac Clinic for Diabetes, Endocrinology and Metabolic Diseases, University Hospital Merkur, Zagreb, Croatia b Medical School, University of Zagreb, Zagreb, Croatia Received for publication April 26, 2017; accepted October 17, 2017 (ARCMED-D-17-00259).
Introduction. Results from studies investigating relationship between serum lipids and risk of development and progression of diabetic retinopathy (DR) in patients with type 1 diabetes (T1DM) are not consistent. The objective of this study was to explore the relationship between serum lipids and risk of development and progression of nonproliferative diabetic retinopathy (NPDR) in T1DM with normal renal function and with no therapeutic intervention that might influence on retinopathy and serum lipids status. Methods. A total of 103 T1DM with normal renal function (urinary albumin excretion rate !30 mg/24 h, estimated glomerular filtration rate (eGFR) O60 mL min‒11.73m‒2), and before any interventions with lipid-lowering therapy, ACE inhibitors or angiotensin II receptor blockers were included in this study and followed for 41 months. Photodocumented retinopathy status was made according to the EURODIAB protocol. Results. Patients who developed NPDR or progressed to proliferative retinopathy were older (44 vs. 33 years, p !0.001), had longer duration of diabetes (21.1 vs. 13.3 years, p !0.001), and higher serum total cholesterol level (5.1 vs. 4.5 mmol/L, p 5 0.02) compared to patients without retinopathy. In a backward stepwise Cox’s multiple regression analysis serum total cholesterol was significantly associated with risk of development or progression of NPDR in our subjects ( p 5 0.04), with odds ratios of 1.27e1.91. Conclusion. These data suggest that serum total cholesterol levels are associated with risk of development and progression of NPDR in T1DM and normal renal function. The study was conducted in patients with no therapeutic interventions. Ó 2017 Published by Elsevier Inc. on behalf of IMSS. Key Words: Retinopathy, Type 1 diabetes, Total cholesterol.
Introduction Since diabetic retinopathy (DR) is one of the leading causes of visual impairment and blindness in patients with type 1 diabetes (T1DM), identification of the determinants of the onset of DR is essential for reducing the invalidity and mortality associated with diabetes (1). With appropriate
Address reprint requests to: Tomislav Bulum, Vuk Vrhovac Clinic for Diabetes, Endocrinology and Metabolic Diseases, University Hospital Merkur, Zagreb, Croatia; Phone: þ38512353991; FAX: þ38512331515; E-mail: [email protected]
medical and ophthalmologic care visual impairment and blindness can be prevented in majority of cases (2). Well known risk factors for development and progression of DR include duration of diabetes, age, hyperglycemia and hypertension, while relationship between serum lipids and DR are not consistent (3e5). Previous crosssectional studies have shown positive associations between conventional lipid parameters, specifically total, LDLcholesterol, and triglycerides with severity and progression of DR (6,7). Results from large Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) cohort also found associations between serum lipoproteins and severity of DR in
0188-4409/$ - see front matter. Copyright Ó 2017 Published by Elsevier Inc. on behalf of IMSS. https://doi.org/10.1016/j.arcmed.2017.10.003
2
Bulum et al./ Archives of Medical Research
T1DM (2). Increased levels of total and LDL-cholesterol are not only associated with risk of DR but also with macular edema in T1DM (8,9). However, therapy with statins and fenofibrate protect against development and progression of DR and in some studies the associations between serum lipids and DR in T1DM was no longer observed after adjustment for covariates including statin use (10e13). It is assumed that retinopathy and nephropathy, as most important microvascular complications in patients with diabetes, occur at the same time and that the severity of retinopathy parallels the presence and severity on nephropathy in diabetes (14,15). Moreover, it is suggested that relationship between DR and lipid variables are influenced by concurrent renal disease and that associations between renal disease and serum lipids are strongly influenced by retinopathy status in T1DM (16). The objective of this study was to explore the relationship between serum lipids and risk of development and progression of nonproliferative diabetic retinopathy (NPDR) in T1DM with normal renal function and with no therapeutic intervention that might influence on retinopathy and serum lipids status. Subjects, Materials and Methods The study population was based on all 264 patients with T1DM who were referred to tertiary care specialist diabetes clinic between January 2010 and December 2010. T1DM was defined as an onset of diabetes before the age of 35 years, positive autoantibodies and permanent insulin treatment initiated within one year of diagnosis. The study included patients following characteristics: age of 18e65 years, minimum duration of type 1 diabetes of one year and absence of heart, liver and renal disease. Patients were excluded from the study if they had taken any of the following: lipid-lowering therapy, antihypertensive therapy including ACE inhibitor or angiotensin II receptor blockers, medications that might affect glucose metabolism such as glucocorticoids as well as patients taking oral glucose-lowering medication. Retinopathy was diagnosed by binocular indirect slit lamp fundoscopy and fundus photography after mydriasis with eye drops containing 0.5% tropicamide and 5% phenylephrine by a single grader. Final diagnosis of DR was made by fundus photographs. Color fundus photographs of two fields (macular field, disc/nasal field) of both eyes were taken with a 45 fundus camera (VISUCAM, Zeiss) according to the EURODIAB retinal photography methodology (17). In this study retinopathy was classified as NPDR or proliferative diabetic retinopathy (PDR). NPDR was defined as the presence of one or more microaneurysms, hemorrhages, and/or hard exudates. PDR was defined as any new vessels, fibrous proliferations, preretinal hemorrhage, vitreous hemorrhage, or photocoagulation scars (17). In each patient the ‘‘worse’’ eye was graded for retinopathy
-
(2017)
-
using fundus photographs. Patients with ungradable photographs for DR were excluded from the study. Urinary albumin excretion rate (UAE) was measured from at least two 24 h urine samples and determined as the mean of 24 h urine collections. Patients performed collections on two consecutive days to minimize variability. Data on serum creatinine levels, age, sex and race were used to calculate the estimated glomerular filtration rate (eGFR) using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula, which has been shown to be accurate in determining renal function in diabetic patients with normal renal function (18,19). Those with eGFR less than 60 mL min1 1.73 m2 were excluded from the study. All subjects were confirmed to be free of urinary tract infections. Numeric variables are given as means (SD) or medians (ranges) depending on the normality distribution tested using Kolmogorov-Smirnov test, or percentages and absolute numbers for nominal variables. We used the unpaired Students t test and Mann-Whithney to compare cross classified continuous variables and the c2 test to evaluate proportions when we compared baseline data in the group of patients who developed or have progression of NPDR with the group of patients who did not develop or have progression of NPDR. All tests were two sided. Cox’s proportional hazards multiple regression analyses were used to examine the baseline variables predictive of development or progression of NPDR. Results are described as relative risk (hazard ratio). A p value of less than 0.05 was regarded as significant. Results From 264 patients at baseline we excluded 161 patients: four had developed PDR, 80 used statins and fenofibrate and 77 ACE-inhibitors or angiotensin II receptor blockers who showed to have protective role in NPDR development. This left 103 patients who fulfilled the inclusion criteria of being free of lipid-lowering therapy and ACE-inhibitors or angiotensin II receptor blockers use and without DR or with NPDR were included in the study (Figure 1). The majority of patients (52.4%) had no retinopathy while 49 (47.6%) had NPDR at baseline. Baseline clinical and metabolic characteristics of patients without DR compared to those that developed NPDR or progressed to PDR are presented in Table 1. Patients who developed NPDR or progressed to PDR were older (44 vs. 33 years, p !0.001), had longer duration of diabetes (21 vs. 13 years, p !0.001) and higher serum total cholesterol (5.1 vs. 4.5 mmol/L, p 5 0.02) compared to patients without retinopathy during the study. 21 patients without retinopathy developed NPDR during 41 months of following with cumulative incidence of 38.8% and incidence ratio of 24.1%. Ten patients who had NPDR at baseline progressed to PDR with the cumulative incidence of 20.4% and incidence ratio 16.9% for the same period of time (Figure 1).
Serum Cholesterol and Retinopathy in Type 1 Diabetes
Figure 1. Number of patients with type 1 diabetes that developed nonproliferative retinopathy or progressed to proliferative retinopathy during the study.
The possible risk factors for development or progression of NPDR were examined in backward stepwise Cox’s multiple regression analysis (Table 2). Total serum cholesterol, hemoglobin A1c, and duration of diabetes were significantly associated with development or progression of NPDR. An increase in 1 mmol/L of total serum cholesterol was associated with a relative risk of 1.519 (95% confidence interval 1.27e1.91). A similar analysis was performed without the total serum cholesterol in the stepwise procedure. Duration of diabetes (relative risk of 0.92) and HbA1c (relative risk 1.61) resulted as the only significant determinants of NPDR development or progression.
Discussion The results of our study suggest that serum total cholesterol levels are associated with risk of development and progression of NPDR in T1DM and normal renal function. Patients who developed NPDR or progressed to PDR were older, had longer duration of diabetes and higher total serum cholesterol compared to patients without retinopathy during the study. In backward stepwise Cox’s multiple regression analysis total serum cholesterol was the risk factor for development or progression of NPDR. Our study included patients with normal renal function and with no therapeutic intervention that might influence on retinopathy and serum lipids status. It has been suggested that extravasation of LDL from retinal capillaries and its subsequent oxidation may be implicated in development and progression of DR although
3
in many other studies traditional serum lipids has shown an inconsistent relationship with DR (10,11,20e22). In DCCT/EDIC cohort retinopathy was positively associated with small LDL cholesterol concentration and negatively with large LDL cholesterol concentration and opposite associations of retinopathy with large and small LDL particles can explain why there was no association with LDL cholesterol in the conventional lipid panel (2). In T1DM, relationship between high lipoprotein(a) serum levels and PDR compared to NPDR have been observed, without relationship with diabetic neuropathy (23). In the retinal capillary oxidized LDL is toxic to pericytes and endothelial cells and also have prothrombic effects (24,25). The ETDRS study as well as Wisconsin Epidemiologic Study showed that retinal hard exudates, the component of DR, as well as subsequent visual deterioration, was strongly associated with total and LDL cholesterol (26e28). In addition, study that included similar number of T1DM like our study but with longer follow-up reported that high levels of LDLcholesterol were associated with incident DR (29). In our study, only total serum cholesterol was associated with NPDR incidence and progression, but all of the studied lipid variables were worst in those with NPDR than those without (even if they were not statistically significant). Treatment with statins protects against the development of diabetic macular edema and progression of DR (30). Moreover, a treatment of triglycerides with fenofibrate in patients with a background of statin use decreases the risk of progression of DR (31). Statin therapy reduces lipid leakage and improve lipid clearance in the eyes and also have anti-inflammatory effects that might slow the progression of DR (32,33). We excluded from our study patients treated with statins and fenofibrates. It has been suggested that relationship between DR and lipid variables are influenced by concurrent renal disease and that associations between renal disease and serum lipids are strongly influenced by retinopathy status in T1DM (16). These interactions between nephropathy, retinopathy status and lipid variables may reflect risk factors like oxidation, inflammation, endothelial dysfunction, cytokines and advanced glycation end products to which patients with nephropathy are exposed (34). In addition, investigators for the first time separately analyzed patients without renal disease (UAE !30 mg/24h and eGFR O60 mL min1 1.73m2) and found significant difference in the total cholesterol/HDL cholesterol ratio by DR status (16). Moreover, correlation between lipid variables and UAE were strikingly different in patients without DR or with DR. It is possible that lipid variables are more strongly associated with DR in studies that included patients with UAE O30 mg/24 compared to our study that included patients with normal UAE. As nephropathy is often a precursor to systemic complications such as retinopathy and dyslipidemia, when investigating retinopathy status it would be important taking into account nephropathy status.
4
Bulum et al./ Archives of Medical Research
-
(2017)
-
Table 1. Clinical characteristics of the patients who did not developed diabetic retinopathy during the study compared to those that developed nonproliferative retinopathy or progressed to proliferative retinopathy
Variable
Free of diabetic retinopathy (n [ 54)
Developed/progression of nonproliferative retinopathy (n [ 31)
Gender (male) Age (years) Diabetes duration (years) Hemoglobin A1c (%) Body mass index (kg/m2) Waist circumference (cm) Total serum cholesterol (mmol/L) HDL cholesterol (mmol/L) HDL-2 cholesterol (mmol/L) HDL-3 cholesterol (mmol/L) LDL cholesterol (mmol/L) Tryglicerides (mmol/L) Systolic blood pressure (mmHg) Diastolic blood pressure (mmHg) Pulse rate (beats per min) Serum creatinine (mmol/L) Urinary albumin excretion (mg/24 h) Estimated glomerular filtration rate (mL min1 1.73 m2)
38 (52.8%) 33 (18e60) 13.3 8.2 7.8 0.9 24 (19e33) 84 13.5 4.5 0.8 1.71 0.36 0.55 0.21 1.17 0.22 2.56 0.62 0.97 0.37 125 (100e170) 80 (60e100) 70 (47e98) 66.82 14.77 5.54 (2.4e405.1) 106.5 (79e132)
16 (51.6) 44 (20e73) 21.1 10.3 7.4 1.1 25 (16e37) 81 13.7 5.1 0.8 1.68 0.38 0.51 0.14 1.16 0.31 2.9 0.75 1.02 0.62 127 (100e160) 80 (65e100) 70 (52e94) 68.87 11.39 5.99 (1.8e37.8) 101 (66e129)
p 0.997 !0.001 !0.001 0.059 0.304 0.723 0.027 0.701 0.679 0.920 0.759 0.595 0.795 0.611 0.590 0.448 0.808 0.082
The present study and results have a number of potential limitations. First, the small number of patients with incidence and progression of NPDR limited our ability to generalize our results to other populations. Second, this cohort had little racial/ethnic diversity and our data would be primarily relevant to a white European population. Third, our study was single hospital-based study therefore selection bias is likely. Fourth, methods used for diagnosis of retinopathy and eGFR may influence on final results making comparisons of findings between studies difficult. In our study, we measured eGFR using CKD-EPI formula and photodocumented retinopathy status according to the EURODIAB protocol. In conclusion, we have shown that serum total cholesterol levels are associated with risk of development and progression of NPDR in T1DM and normal renal function. Patients with NPDR also had higher hemoglobin A1c and systolic blood pressure and strict control of classical risk
factors for development and progression of DR is also needed. The study was conducted in patients with no therapeutic interventions. Prospective studies with larger number of T1DM and sufficiently long follow-up are needed to confirm the present findings.
Table 2. Baseline risk factors for development or progression of nonproliferative retinopathy in 103 patients with type 1 diabetes by means of Cox’s multiple regression analysis
References
Variable Total serum cholesterol (mmol/L) Age (year) Gender (male) Duration of diabetes (year) Hemoglobin A1c (%) Body mass index (kg/m2) Urinary albumin excretion rate (mg/24 h) History of smoking
Relative risk (95% CI) 1.519 0.971 2.469 0.913 1.805 0.967 0.993
p
(1.275e1.918) (0.933e1.010) (0.927e6.576) (0.853e0.978) (1.113e2.927) (0.965e1.081) (0.971e1.016)
0.043 0.143 0.071 0.010 0.017 0.554 0.546
0.701 (0.256e1.918)
0.489
Conflict of Interest The authors disclose no conflict of interest.
Ethical Approval All procedures were in accordance with the ethical standards of the institutional committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
1. Cheung N, Mitchell P, Wong TY. Diabetic retinopathy. Lancet 2010; 376:124e136. 2. Lyons TJ, Jenkins AJ, Zheng D, et al. Diabetic retinopathy and serum lipoprotein subclasses in the DCCT/EDIC cohort. Invest Ophthalmol Vis Sci 2004;45:910e918. 3. West KM, Erdreich LJ, Stober JA. A detailed study of risk factors for retinopathy and nephropathy in diabetes. Diabetes 1980;29:501e508. 4. Bulum T, Blaslov K, Duvnjak L. Risk factors for development and progression of nonproliferative retinopathy in normoalbuminuric patients with type 1 diabetes. Diabetes Res Clin Pract 2014;106: 555e559. 5. Sinav S, Onelge MA, Onelge S, et al. Plasma lipids and lipoproteins in retinopathy of type 1 (insulin-dependent) diabetic patients. Ann Ophthalmol 1993;25:64e66.
Serum Cholesterol and Retinopathy in Type 1 Diabetes 6. Kissebah AH, Siddiq YK, Kohner EM, et al. Plasma lipids and glucose/insulin relationship in non-insulin-requiring diabetics with and without retinopathy. Lancet 1975;1:1104e1108. 7. Orchard TJ, Dorman JS, Maser RE, et al. Factors associated with avoidance of severe complications after 25 yr of IDDM, Pittsburgh Epidemiology of Diabetes Complications Study I. Diabetes Care 1990;13:741e747. 8. Miljanovic B, Glynn RJ, Nathan DM, et al. A prospective study of serum lipids and risk of diabetic macular edema in type 1 diabetes. Diabetes 2004;53:2883e2892. 9. Romero-Aroca P, Baget-Bernaldiz M, Fernandez-Ballart J, et al. Tenyear incidence of diabetic retinopathy and macular edema. Risk factors in a sample of people with type 1 diabetes. Diabetes Res Clin Pract 2011;94:126e132. 10. Klein BB, Klein R, Moss SE. Is serum cholesterol associated with progression of diabetic retinopathy or macular edema in persons with younger-onset diabetes of long duration? Am J Ophthalmol 1999; 128:652e654. 11. Klein BE, Myers CE, Howard KP, et al. Serum lipids and proliferative diabetic retinopathy and macular edema in persons with long-term type 1 diabetes mellitus. The Wisconsin Epidemiology Sudy of Diabetic Retinopathy. JAMA Ophthalmology 2015;133: 503e510. 12. Nielsen SF, Nordestgaard BG. Statin use before diabetes diagnosis and risk of microvascular disease: a nationwide nested matched study. Lancet Diabetes Endocrinol 2014;2:894e900. 13. Keech AC, Mitchell P, Summanen PA, et al. Effect of fenofibrate on the need for laser treatment for diabetic retinopathy (FIELD study): a randomised controlled trial. Lancet 2007;370:1687e1697. 14. Grunwald JE, Alexander J, Ying GS, et al. Retinopathy and chronic kidney disease in the Chronic Renal Insufficiency Cohort (CRIC) study. Arch Ophthalmol 2012;130:1136e1144. 15. Arar NH, Freedman BI, Adler SG, et al. Heritability of the severity of diabetic retinopathy: the FIND-eye study. Inv Ophthalmol Vis Sci 2008;9:3839e3844. 16. Tolonen N, Hietala K, Forsblom C, et al. Associations and interactions between lipid profiles, retinopathy and nephropathy in patients with type 1 diabetes: the FinnDiane Study. J Intern Med 2013;274: 469e479. 17. Aldington SJ, Kohner EM, Meuer S, et al. Methodology for retinal photography and assessment of diabetic retinopathy: the EURODIAB IDDM Complications Study. Diabetologia 1995;38:437e444. 18. Levey AS, Stevens LA, Schmid CH, et al. A new equation to estimate glomerular filtration rate. Ann Intern Med 2009;150:604e612. 19. Vucic Lovrencic M, Radisic Biljak V, Bozicevic S, et al. Estimating glomerular filtration rate (GFR) in diabetes: the performance of MDRD and CKD-EPI equations in patients with various degrees of albuminuria. Clin Biochem 2012;45:1694e1696.
5
20. Wu M, Chen Y, Wilson K, et al. Intraretinal leakage and oxidation of LDL in diabetic retinopathy. Invest Ophthalmol Vis Sci 2008;49: 2679e2685. 21. Vinodhini VM, Gnaneswaran S, Ebenezer WW, et al. A study on the pattern of lipid profile and apolipoproteins in patients with diabetic retinopathy. Int J Pharm Clin Res 2013;5:1e3. 22. Ankit BS, Mathur G, Agrawal RP, et al. Stronger relationship of serum apolipoprotein A-1 and B with diabetic retinopathy than traditional lipids. Indian J Endocr Metab 2017;21:102e105. 23. Gazzaruso C, Garzaniti A, Buscaglia P, et al. Lipoprotein(a) levels and apolipoprotein(a) polymorphism in type 1 diabetes mellitus: relationships to microvascular and neurological complications. Acta Diabetologica 1998;35:13e18. 24. Lyons TJ, Li W, Wells-Knecht MC, et al. Toxicity of mildly modified low density lipoproteins to cultured retinal capillary endothelial cells and pericytes. Diabetes 1994;43:1090e1095. 25. Allison BA, Nilsson L, Karpe P, et al. Effects of native, triglycerideenriched, and oxidatively modified LDL on plasminogen activator inhibitor-1 expression in human endothelial cells. Arterioscler Thromb Vasc Biol 1999;19:1354e1360. 26. Davis MD, Fisher MR, Gangnon RE, et al. Risk factors for high-risk proliferative diabetic retinopathy and severe visual loss: Early Treatment Diabetic Retinopathy Study Report 18. Invest Ophthalmol Vis Sci 1998;39:233e252. 27. Chew EY, Klein ML, Ferris FL III, et al. Association of elevated serum lipid levels with retinal hard exudate in diabetic retinopathy. Early Treatment Diabetic Retinopathy Study (ETDRS) Report 22. Arch Ophthalmol 1996;114:1079e1084. 28. Klein BE, Moss SE, Klein R, et al. The Wisconsin Epidemiologic Study of Diabetic Retinopathy XIII: relationship of serum cholesterol to retinopathy and hard exudate. Ophthalmology 1991;98:1261e1265. 29. Romero P, Salvat M, Fernandez J, et al. Renal and retinal microangiopathy after 15 years of follow-up study in a sample of type 1 diabetes mellitus patients. J Diabetes Complications 2007;21:93e100. 30. Chung YR, Park SW, Choi SY, et al. Association of statin use and hypertriglyceridemia with diabetic macular edema in patients with type 2 diabetes and diabetic retinopathy. Cardiovasc Diabetol 2017;16:4. 31. Chew EY, Ambrosius WT, Davis MD, et al, ACCORD Study Group, ACCORD Eye Study Group. Effects of medical therapies on retinopathy progression in type 2 diabetes. N Engl J Med 2010;363:233e244. 32. Gupta A, Gupta V, Thapar S, et al. Lipid-lowering drug atorvastatin as an adjunct in the management of diabetic macular edema. Am J Ophthalmol 2004;137:675e682. 33. Bu DX, Griffin G, Lichtman AH. Mechanisms for the antiinflammatory effects of statins. Curr Opin Lipidol 2011;22:165e170. 34. Macisaac RJ, Ekinci EI, Jerums G. Markers of and risk factors for the development and progression of diabetic kidney disease. Am J Kidney Dis 2014;63(Suppl. 2):S39eS62.
-
(2017)
-
ORIGINAL ARTICLE
Total Serum Cholesterol Increases Risk for Development and Progression of Nonproliferative Retinopathy in Patients with Type 1 Diabetes Without Therapeutic Intervention: Prospective, Observational Study Tomislav Bulum,a,b Martina Tomic,a and Lea Duvnjaka,b a
Vuk Vrhovac Clinic for Diabetes, Endocrinology and Metabolic Diseases, University Hospital Merkur, Zagreb, Croatia b Medical School, University of Zagreb, Zagreb, Croatia Received for publication April 26, 2017; accepted October 17, 2017 (ARCMED-D-17-00259).
Introduction. Results from studies investigating relationship between serum lipids and risk of development and progression of diabetic retinopathy (DR) in patients with type 1 diabetes (T1DM) are not consistent. The objective of this study was to explore the relationship between serum lipids and risk of development and progression of nonproliferative diabetic retinopathy (NPDR) in T1DM with normal renal function and with no therapeutic intervention that might influence on retinopathy and serum lipids status. Methods. A total of 103 T1DM with normal renal function (urinary albumin excretion rate !30 mg/24 h, estimated glomerular filtration rate (eGFR) O60 mL min‒11.73m‒2), and before any interventions with lipid-lowering therapy, ACE inhibitors or angiotensin II receptor blockers were included in this study and followed for 41 months. Photodocumented retinopathy status was made according to the EURODIAB protocol. Results. Patients who developed NPDR or progressed to proliferative retinopathy were older (44 vs. 33 years, p !0.001), had longer duration of diabetes (21.1 vs. 13.3 years, p !0.001), and higher serum total cholesterol level (5.1 vs. 4.5 mmol/L, p 5 0.02) compared to patients without retinopathy. In a backward stepwise Cox’s multiple regression analysis serum total cholesterol was significantly associated with risk of development or progression of NPDR in our subjects ( p 5 0.04), with odds ratios of 1.27e1.91. Conclusion. These data suggest that serum total cholesterol levels are associated with risk of development and progression of NPDR in T1DM and normal renal function. The study was conducted in patients with no therapeutic interventions. Ó 2017 Published by Elsevier Inc. on behalf of IMSS. Key Words: Retinopathy, Type 1 diabetes, Total cholesterol.
Introduction Since diabetic retinopathy (DR) is one of the leading causes of visual impairment and blindness in patients with type 1 diabetes (T1DM), identification of the determinants of the onset of DR is essential for reducing the invalidity and mortality associated with diabetes (1). With appropriate
Address reprint requests to: Tomislav Bulum, Vuk Vrhovac Clinic for Diabetes, Endocrinology and Metabolic Diseases, University Hospital Merkur, Zagreb, Croatia; Phone: þ38512353991; FAX: þ38512331515; E-mail: [email protected]
medical and ophthalmologic care visual impairment and blindness can be prevented in majority of cases (2). Well known risk factors for development and progression of DR include duration of diabetes, age, hyperglycemia and hypertension, while relationship between serum lipids and DR are not consistent (3e5). Previous crosssectional studies have shown positive associations between conventional lipid parameters, specifically total, LDLcholesterol, and triglycerides with severity and progression of DR (6,7). Results from large Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) cohort also found associations between serum lipoproteins and severity of DR in
0188-4409/$ - see front matter. Copyright Ó 2017 Published by Elsevier Inc. on behalf of IMSS. https://doi.org/10.1016/j.arcmed.2017.10.003
2
Bulum et al./ Archives of Medical Research
T1DM (2). Increased levels of total and LDL-cholesterol are not only associated with risk of DR but also with macular edema in T1DM (8,9). However, therapy with statins and fenofibrate protect against development and progression of DR and in some studies the associations between serum lipids and DR in T1DM was no longer observed after adjustment for covariates including statin use (10e13). It is assumed that retinopathy and nephropathy, as most important microvascular complications in patients with diabetes, occur at the same time and that the severity of retinopathy parallels the presence and severity on nephropathy in diabetes (14,15). Moreover, it is suggested that relationship between DR and lipid variables are influenced by concurrent renal disease and that associations between renal disease and serum lipids are strongly influenced by retinopathy status in T1DM (16). The objective of this study was to explore the relationship between serum lipids and risk of development and progression of nonproliferative diabetic retinopathy (NPDR) in T1DM with normal renal function and with no therapeutic intervention that might influence on retinopathy and serum lipids status. Subjects, Materials and Methods The study population was based on all 264 patients with T1DM who were referred to tertiary care specialist diabetes clinic between January 2010 and December 2010. T1DM was defined as an onset of diabetes before the age of 35 years, positive autoantibodies and permanent insulin treatment initiated within one year of diagnosis. The study included patients following characteristics: age of 18e65 years, minimum duration of type 1 diabetes of one year and absence of heart, liver and renal disease. Patients were excluded from the study if they had taken any of the following: lipid-lowering therapy, antihypertensive therapy including ACE inhibitor or angiotensin II receptor blockers, medications that might affect glucose metabolism such as glucocorticoids as well as patients taking oral glucose-lowering medication. Retinopathy was diagnosed by binocular indirect slit lamp fundoscopy and fundus photography after mydriasis with eye drops containing 0.5% tropicamide and 5% phenylephrine by a single grader. Final diagnosis of DR was made by fundus photographs. Color fundus photographs of two fields (macular field, disc/nasal field) of both eyes were taken with a 45 fundus camera (VISUCAM, Zeiss) according to the EURODIAB retinal photography methodology (17). In this study retinopathy was classified as NPDR or proliferative diabetic retinopathy (PDR). NPDR was defined as the presence of one or more microaneurysms, hemorrhages, and/or hard exudates. PDR was defined as any new vessels, fibrous proliferations, preretinal hemorrhage, vitreous hemorrhage, or photocoagulation scars (17). In each patient the ‘‘worse’’ eye was graded for retinopathy
-
(2017)
-
using fundus photographs. Patients with ungradable photographs for DR were excluded from the study. Urinary albumin excretion rate (UAE) was measured from at least two 24 h urine samples and determined as the mean of 24 h urine collections. Patients performed collections on two consecutive days to minimize variability. Data on serum creatinine levels, age, sex and race were used to calculate the estimated glomerular filtration rate (eGFR) using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula, which has been shown to be accurate in determining renal function in diabetic patients with normal renal function (18,19). Those with eGFR less than 60 mL min1 1.73 m2 were excluded from the study. All subjects were confirmed to be free of urinary tract infections. Numeric variables are given as means (SD) or medians (ranges) depending on the normality distribution tested using Kolmogorov-Smirnov test, or percentages and absolute numbers for nominal variables. We used the unpaired Students t test and Mann-Whithney to compare cross classified continuous variables and the c2 test to evaluate proportions when we compared baseline data in the group of patients who developed or have progression of NPDR with the group of patients who did not develop or have progression of NPDR. All tests were two sided. Cox’s proportional hazards multiple regression analyses were used to examine the baseline variables predictive of development or progression of NPDR. Results are described as relative risk (hazard ratio). A p value of less than 0.05 was regarded as significant. Results From 264 patients at baseline we excluded 161 patients: four had developed PDR, 80 used statins and fenofibrate and 77 ACE-inhibitors or angiotensin II receptor blockers who showed to have protective role in NPDR development. This left 103 patients who fulfilled the inclusion criteria of being free of lipid-lowering therapy and ACE-inhibitors or angiotensin II receptor blockers use and without DR or with NPDR were included in the study (Figure 1). The majority of patients (52.4%) had no retinopathy while 49 (47.6%) had NPDR at baseline. Baseline clinical and metabolic characteristics of patients without DR compared to those that developed NPDR or progressed to PDR are presented in Table 1. Patients who developed NPDR or progressed to PDR were older (44 vs. 33 years, p !0.001), had longer duration of diabetes (21 vs. 13 years, p !0.001) and higher serum total cholesterol (5.1 vs. 4.5 mmol/L, p 5 0.02) compared to patients without retinopathy during the study. 21 patients without retinopathy developed NPDR during 41 months of following with cumulative incidence of 38.8% and incidence ratio of 24.1%. Ten patients who had NPDR at baseline progressed to PDR with the cumulative incidence of 20.4% and incidence ratio 16.9% for the same period of time (Figure 1).
Serum Cholesterol and Retinopathy in Type 1 Diabetes
Figure 1. Number of patients with type 1 diabetes that developed nonproliferative retinopathy or progressed to proliferative retinopathy during the study.
The possible risk factors for development or progression of NPDR were examined in backward stepwise Cox’s multiple regression analysis (Table 2). Total serum cholesterol, hemoglobin A1c, and duration of diabetes were significantly associated with development or progression of NPDR. An increase in 1 mmol/L of total serum cholesterol was associated with a relative risk of 1.519 (95% confidence interval 1.27e1.91). A similar analysis was performed without the total serum cholesterol in the stepwise procedure. Duration of diabetes (relative risk of 0.92) and HbA1c (relative risk 1.61) resulted as the only significant determinants of NPDR development or progression.
Discussion The results of our study suggest that serum total cholesterol levels are associated with risk of development and progression of NPDR in T1DM and normal renal function. Patients who developed NPDR or progressed to PDR were older, had longer duration of diabetes and higher total serum cholesterol compared to patients without retinopathy during the study. In backward stepwise Cox’s multiple regression analysis total serum cholesterol was the risk factor for development or progression of NPDR. Our study included patients with normal renal function and with no therapeutic intervention that might influence on retinopathy and serum lipids status. It has been suggested that extravasation of LDL from retinal capillaries and its subsequent oxidation may be implicated in development and progression of DR although
3
in many other studies traditional serum lipids has shown an inconsistent relationship with DR (10,11,20e22). In DCCT/EDIC cohort retinopathy was positively associated with small LDL cholesterol concentration and negatively with large LDL cholesterol concentration and opposite associations of retinopathy with large and small LDL particles can explain why there was no association with LDL cholesterol in the conventional lipid panel (2). In T1DM, relationship between high lipoprotein(a) serum levels and PDR compared to NPDR have been observed, without relationship with diabetic neuropathy (23). In the retinal capillary oxidized LDL is toxic to pericytes and endothelial cells and also have prothrombic effects (24,25). The ETDRS study as well as Wisconsin Epidemiologic Study showed that retinal hard exudates, the component of DR, as well as subsequent visual deterioration, was strongly associated with total and LDL cholesterol (26e28). In addition, study that included similar number of T1DM like our study but with longer follow-up reported that high levels of LDLcholesterol were associated with incident DR (29). In our study, only total serum cholesterol was associated with NPDR incidence and progression, but all of the studied lipid variables were worst in those with NPDR than those without (even if they were not statistically significant). Treatment with statins protects against the development of diabetic macular edema and progression of DR (30). Moreover, a treatment of triglycerides with fenofibrate in patients with a background of statin use decreases the risk of progression of DR (31). Statin therapy reduces lipid leakage and improve lipid clearance in the eyes and also have anti-inflammatory effects that might slow the progression of DR (32,33). We excluded from our study patients treated with statins and fenofibrates. It has been suggested that relationship between DR and lipid variables are influenced by concurrent renal disease and that associations between renal disease and serum lipids are strongly influenced by retinopathy status in T1DM (16). These interactions between nephropathy, retinopathy status and lipid variables may reflect risk factors like oxidation, inflammation, endothelial dysfunction, cytokines and advanced glycation end products to which patients with nephropathy are exposed (34). In addition, investigators for the first time separately analyzed patients without renal disease (UAE !30 mg/24h and eGFR O60 mL min1 1.73m2) and found significant difference in the total cholesterol/HDL cholesterol ratio by DR status (16). Moreover, correlation between lipid variables and UAE were strikingly different in patients without DR or with DR. It is possible that lipid variables are more strongly associated with DR in studies that included patients with UAE O30 mg/24 compared to our study that included patients with normal UAE. As nephropathy is often a precursor to systemic complications such as retinopathy and dyslipidemia, when investigating retinopathy status it would be important taking into account nephropathy status.
4
Bulum et al./ Archives of Medical Research
-
(2017)
-
Table 1. Clinical characteristics of the patients who did not developed diabetic retinopathy during the study compared to those that developed nonproliferative retinopathy or progressed to proliferative retinopathy
Variable
Free of diabetic retinopathy (n [ 54)
Developed/progression of nonproliferative retinopathy (n [ 31)
Gender (male) Age (years) Diabetes duration (years) Hemoglobin A1c (%) Body mass index (kg/m2) Waist circumference (cm) Total serum cholesterol (mmol/L) HDL cholesterol (mmol/L) HDL-2 cholesterol (mmol/L) HDL-3 cholesterol (mmol/L) LDL cholesterol (mmol/L) Tryglicerides (mmol/L) Systolic blood pressure (mmHg) Diastolic blood pressure (mmHg) Pulse rate (beats per min) Serum creatinine (mmol/L) Urinary albumin excretion (mg/24 h) Estimated glomerular filtration rate (mL min1 1.73 m2)
38 (52.8%) 33 (18e60) 13.3 8.2 7.8 0.9 24 (19e33) 84 13.5 4.5 0.8 1.71 0.36 0.55 0.21 1.17 0.22 2.56 0.62 0.97 0.37 125 (100e170) 80 (60e100) 70 (47e98) 66.82 14.77 5.54 (2.4e405.1) 106.5 (79e132)
16 (51.6) 44 (20e73) 21.1 10.3 7.4 1.1 25 (16e37) 81 13.7 5.1 0.8 1.68 0.38 0.51 0.14 1.16 0.31 2.9 0.75 1.02 0.62 127 (100e160) 80 (65e100) 70 (52e94) 68.87 11.39 5.99 (1.8e37.8) 101 (66e129)
p 0.997 !0.001 !0.001 0.059 0.304 0.723 0.027 0.701 0.679 0.920 0.759 0.595 0.795 0.611 0.590 0.448 0.808 0.082
The present study and results have a number of potential limitations. First, the small number of patients with incidence and progression of NPDR limited our ability to generalize our results to other populations. Second, this cohort had little racial/ethnic diversity and our data would be primarily relevant to a white European population. Third, our study was single hospital-based study therefore selection bias is likely. Fourth, methods used for diagnosis of retinopathy and eGFR may influence on final results making comparisons of findings between studies difficult. In our study, we measured eGFR using CKD-EPI formula and photodocumented retinopathy status according to the EURODIAB protocol. In conclusion, we have shown that serum total cholesterol levels are associated with risk of development and progression of NPDR in T1DM and normal renal function. Patients with NPDR also had higher hemoglobin A1c and systolic blood pressure and strict control of classical risk
factors for development and progression of DR is also needed. The study was conducted in patients with no therapeutic interventions. Prospective studies with larger number of T1DM and sufficiently long follow-up are needed to confirm the present findings.
Table 2. Baseline risk factors for development or progression of nonproliferative retinopathy in 103 patients with type 1 diabetes by means of Cox’s multiple regression analysis
References
Variable Total serum cholesterol (mmol/L) Age (year) Gender (male) Duration of diabetes (year) Hemoglobin A1c (%) Body mass index (kg/m2) Urinary albumin excretion rate (mg/24 h) History of smoking
Relative risk (95% CI) 1.519 0.971 2.469 0.913 1.805 0.967 0.993
p
(1.275e1.918) (0.933e1.010) (0.927e6.576) (0.853e0.978) (1.113e2.927) (0.965e1.081) (0.971e1.016)
0.043 0.143 0.071 0.010 0.017 0.554 0.546
0.701 (0.256e1.918)
0.489
Conflict of Interest The authors disclose no conflict of interest.
Ethical Approval All procedures were in accordance with the ethical standards of the institutional committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
1. Cheung N, Mitchell P, Wong TY. Diabetic retinopathy. Lancet 2010; 376:124e136. 2. Lyons TJ, Jenkins AJ, Zheng D, et al. Diabetic retinopathy and serum lipoprotein subclasses in the DCCT/EDIC cohort. Invest Ophthalmol Vis Sci 2004;45:910e918. 3. West KM, Erdreich LJ, Stober JA. A detailed study of risk factors for retinopathy and nephropathy in diabetes. Diabetes 1980;29:501e508. 4. Bulum T, Blaslov K, Duvnjak L. Risk factors for development and progression of nonproliferative retinopathy in normoalbuminuric patients with type 1 diabetes. Diabetes Res Clin Pract 2014;106: 555e559. 5. Sinav S, Onelge MA, Onelge S, et al. Plasma lipids and lipoproteins in retinopathy of type 1 (insulin-dependent) diabetic patients. Ann Ophthalmol 1993;25:64e66.
Serum Cholesterol and Retinopathy in Type 1 Diabetes 6. Kissebah AH, Siddiq YK, Kohner EM, et al. Plasma lipids and glucose/insulin relationship in non-insulin-requiring diabetics with and without retinopathy. Lancet 1975;1:1104e1108. 7. Orchard TJ, Dorman JS, Maser RE, et al. Factors associated with avoidance of severe complications after 25 yr of IDDM, Pittsburgh Epidemiology of Diabetes Complications Study I. Diabetes Care 1990;13:741e747. 8. Miljanovic B, Glynn RJ, Nathan DM, et al. A prospective study of serum lipids and risk of diabetic macular edema in type 1 diabetes. Diabetes 2004;53:2883e2892. 9. Romero-Aroca P, Baget-Bernaldiz M, Fernandez-Ballart J, et al. Tenyear incidence of diabetic retinopathy and macular edema. Risk factors in a sample of people with type 1 diabetes. Diabetes Res Clin Pract 2011;94:126e132. 10. Klein BB, Klein R, Moss SE. Is serum cholesterol associated with progression of diabetic retinopathy or macular edema in persons with younger-onset diabetes of long duration? Am J Ophthalmol 1999; 128:652e654. 11. Klein BE, Myers CE, Howard KP, et al. Serum lipids and proliferative diabetic retinopathy and macular edema in persons with long-term type 1 diabetes mellitus. The Wisconsin Epidemiology Sudy of Diabetic Retinopathy. JAMA Ophthalmology 2015;133: 503e510. 12. Nielsen SF, Nordestgaard BG. Statin use before diabetes diagnosis and risk of microvascular disease: a nationwide nested matched study. Lancet Diabetes Endocrinol 2014;2:894e900. 13. Keech AC, Mitchell P, Summanen PA, et al. Effect of fenofibrate on the need for laser treatment for diabetic retinopathy (FIELD study): a randomised controlled trial. Lancet 2007;370:1687e1697. 14. Grunwald JE, Alexander J, Ying GS, et al. Retinopathy and chronic kidney disease in the Chronic Renal Insufficiency Cohort (CRIC) study. Arch Ophthalmol 2012;130:1136e1144. 15. Arar NH, Freedman BI, Adler SG, et al. Heritability of the severity of diabetic retinopathy: the FIND-eye study. Inv Ophthalmol Vis Sci 2008;9:3839e3844. 16. Tolonen N, Hietala K, Forsblom C, et al. Associations and interactions between lipid profiles, retinopathy and nephropathy in patients with type 1 diabetes: the FinnDiane Study. J Intern Med 2013;274: 469e479. 17. Aldington SJ, Kohner EM, Meuer S, et al. Methodology for retinal photography and assessment of diabetic retinopathy: the EURODIAB IDDM Complications Study. Diabetologia 1995;38:437e444. 18. Levey AS, Stevens LA, Schmid CH, et al. A new equation to estimate glomerular filtration rate. Ann Intern Med 2009;150:604e612. 19. Vucic Lovrencic M, Radisic Biljak V, Bozicevic S, et al. Estimating glomerular filtration rate (GFR) in diabetes: the performance of MDRD and CKD-EPI equations in patients with various degrees of albuminuria. Clin Biochem 2012;45:1694e1696.
5
20. Wu M, Chen Y, Wilson K, et al. Intraretinal leakage and oxidation of LDL in diabetic retinopathy. Invest Ophthalmol Vis Sci 2008;49: 2679e2685. 21. Vinodhini VM, Gnaneswaran S, Ebenezer WW, et al. A study on the pattern of lipid profile and apolipoproteins in patients with diabetic retinopathy. Int J Pharm Clin Res 2013;5:1e3. 22. Ankit BS, Mathur G, Agrawal RP, et al. Stronger relationship of serum apolipoprotein A-1 and B with diabetic retinopathy than traditional lipids. Indian J Endocr Metab 2017;21:102e105. 23. Gazzaruso C, Garzaniti A, Buscaglia P, et al. Lipoprotein(a) levels and apolipoprotein(a) polymorphism in type 1 diabetes mellitus: relationships to microvascular and neurological complications. Acta Diabetologica 1998;35:13e18. 24. Lyons TJ, Li W, Wells-Knecht MC, et al. Toxicity of mildly modified low density lipoproteins to cultured retinal capillary endothelial cells and pericytes. Diabetes 1994;43:1090e1095. 25. Allison BA, Nilsson L, Karpe P, et al. Effects of native, triglycerideenriched, and oxidatively modified LDL on plasminogen activator inhibitor-1 expression in human endothelial cells. Arterioscler Thromb Vasc Biol 1999;19:1354e1360. 26. Davis MD, Fisher MR, Gangnon RE, et al. Risk factors for high-risk proliferative diabetic retinopathy and severe visual loss: Early Treatment Diabetic Retinopathy Study Report 18. Invest Ophthalmol Vis Sci 1998;39:233e252. 27. Chew EY, Klein ML, Ferris FL III, et al. Association of elevated serum lipid levels with retinal hard exudate in diabetic retinopathy. Early Treatment Diabetic Retinopathy Study (ETDRS) Report 22. Arch Ophthalmol 1996;114:1079e1084. 28. Klein BE, Moss SE, Klein R, et al. The Wisconsin Epidemiologic Study of Diabetic Retinopathy XIII: relationship of serum cholesterol to retinopathy and hard exudate. Ophthalmology 1991;98:1261e1265. 29. Romero P, Salvat M, Fernandez J, et al. Renal and retinal microangiopathy after 15 years of follow-up study in a sample of type 1 diabetes mellitus patients. J Diabetes Complications 2007;21:93e100. 30. Chung YR, Park SW, Choi SY, et al. Association of statin use and hypertriglyceridemia with diabetic macular edema in patients with type 2 diabetes and diabetic retinopathy. Cardiovasc Diabetol 2017;16:4. 31. Chew EY, Ambrosius WT, Davis MD, et al, ACCORD Study Group, ACCORD Eye Study Group. Effects of medical therapies on retinopathy progression in type 2 diabetes. N Engl J Med 2010;363:233e244. 32. Gupta A, Gupta V, Thapar S, et al. Lipid-lowering drug atorvastatin as an adjunct in the management of diabetic macular edema. Am J Ophthalmol 2004;137:675e682. 33. Bu DX, Griffin G, Lichtman AH. Mechanisms for the antiinflammatory effects of statins. Curr Opin Lipidol 2011;22:165e170. 34. Macisaac RJ, Ekinci EI, Jerums G. Markers of and risk factors for the development and progression of diabetic kidney disease. Am J Kidney Dis 2014;63(Suppl. 2):S39eS62.