The Relationship Between Kidney and Retinal Microvascular Dysfunction in Ghanaians with Type II Diabetes Mellitus

Abstract

Background: Globally, the prevalence of diabetes is on the rise, with significant differences existing between different geographical zones of the world. In 2021, 24 million people in sub Saharan Africa had diabetes, and this number was expected to more than double by 2045, the highest projected rise in any region worldwide. A characteristic complication of diabetes is a microvascular disease that may affect different microcirculation including the retinal and kidney microcirculation. Based on their common pathophysiological bases, kidney and retinal microcirculation dysfunction may be related. Therefore, dysfunction in one of these microcirculations may be used as an auxiliary diagnostic/screening index for the other. Studies assessing the concordance of kidney microvascular dysfunction (KMD) and retinal microvascular dysfunction (RMD) in diabetes have yielded inconsistent results, based on the population studies. Studies assessing the concordance of KMD and RMD in different people groups including sub-Saharan Africans are lacking. Similar to ethnicity, elevated blood pressure may be a potential explanatory variable. General Aim: This study set out to assess the association between KMD and RMD in Ghanaians with T2D with and without hypertension or suboptimal blood pressure. Methodology: This was a cross-sectional study among 177 systematically sampled Ghanaians with T2D aged ≥ 35 years managed at the national diabetes management and research centre in Accra, Ghana. The sociodemographic and clinical characteristics of the study population were obtained by the use of a structured questionnaire. Anthropometric and blood pressure (BP) measurements were obtained by physical examination according to the World Health Organization’s guidelines. Fasting blood samples were obtained to assess the fasting plasma glucose, glycated haemoglobin, lipid and creatinine concentrations. KMD was based on albuminuria, defined as urinary albumin-creatinine ratio ≥ 30mg/g according to the 2012 Kidney Disease: Improving Global Outcomes guidelines. Retinal images were analyzed and graded under the supervision of a certified ophthalmologist according to the “Early Treatment Diabetic Retinopathy Study” criteria. Suboptimal BP control was defined per the “2017 American College of Cardiology/American Heart Association” guidelines criteria and “European Society of Cardiology/European Society of Hypertension” guidelines (for individuals with hypertension and diabetes) as systolic BP >/= 130mmHg and/or diastolic BP >/= 80 mmHg 15. The associations of renal and RMD were examined by the use of logistic regression with adjustments for age, sex, socioeconomic status, diabetes duration, HbA1c, smoking, systolic BP, obesity, and total cholesterol. Results: The majority of the study population (77.4%) were females. The mean (±standard deviation), age, diabetes duration, systolic BP, diastolic BP, body mass index (BMI), HbA1c concentration, and estimated glomerular filtration rate were 55.93 (±9.35) years, 11.36 (±6.75) years, 137.32 (±16.55) mmHg, 78.57 (±8.85) mmHg, 30.13 (±5.90) kg/m2, 7.83 (±1.67) % 5.03 (±1.30) mmol/L and 99.84 (±22.45) ml/min/1.73m2 respectively. The prevalence of KMD and RMD were 27% and 28.8 % respectively. RMD was more prevalent in individuals with KMD than in those with normal KMD (41.7% vs. 24.0%%, p = 0.026). All cases of moderate or severe non-proliferative diabetic retinopathy (NPDR) and high-risk or severe proliferative diabetic retinopathy (PDR) [n=6 (3.4%)] were in the impaired KMD group. In the fully adjusted model, KMD remained significantly associated with RMD (odds ratio 2.41 [95% CI:1.00-5.80], p=0.049). The association between KMD and RMD was more pronounced in individuals with hypertension (3.10[1.01-9.50], 0.048) than without hypertension (1.70[0.33 8.77], 0.523). In analyses stratified by BP levels, KMD was significantly associated with RMD in individuals with suboptimal BP (2.76[1.07-7.14],0.037) but not in individuals with optimal BP (0.24[0.00-17.04],0.512) Conclusion: This study shows positive associations between KMD and RMD among Ghanaians with T2D, with the strength of association, accentuated in individuals with hypertension/suboptimal BP. Ghanaians with T2D with KMD may benefit from more frequent evaluation of RMD (and vice-versa), to aid early detection and treatment. Future studies could further characterize the role of hypertension in the associations between KMD and RMD.