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Introduction
Diabetes mellitus (DM) represents a substantial global public health challenge, exerting a widespread impact on human health. It is reported that the number of people living with diabetes worldwide is estimated at 451 million (aged 18–99 years old), with projections foreseeing an increase to 693 million by 2045 [1]. DM can lead to multiple microvascular complications including diabetic nephropathy (DN), diabetic retinopathy (DR), and diabetic cardiomyopathy [2, 3]. Among them, DN frequently progresses to end-stage renal disease (ESRD), significantly elevating the mortality risk in DM patients [4, 5]. An estimated 219,451 people worldwide died from DN in 2017 [6].
Dyslipidemia is notably widespread among individuals with DN. The mechanisms underlying dyslipidemia in DN are intricate and multifaceted. Prolonged hyperglycemia contributes to generalized vascular endothelial damage, resulting in diminished functional lipoprotein lipase. This impairment manifests as elevated levels of triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C), concurrently linked to a reduction in the glomerular filtration rate [7, 8]. Apolipoprotein B (ApoB) serves as the principal structural protein in LDL-C, facilitating the transportation of cholesterol to cells. In contrast to LDL-C, ApoB is posited as a potentially more precise indicator of cardiovascular risk and a more dependable measure of efficacy in reducing lipid levels [9, 10]. Several studies have identified independent associations between ApoB and LDL-C with chronic kidney disease (CKD) progression. However, there is limited research quantitatively exploring the threshold level of ApoB correlating with an increased incidence of DN [11, 12]. Therefore, exploring the relationship between ApoB and DN may be of great significance for the prevention and treatment of DN.
To evaluate the health and nutritional status of the population, the National Health and Nutrition Examination Survey (NHANES), a biennial survey of the United States population, uses a multi-stage probability sampling design in conjunction with questionnaires, interviews, physical examinations, and laboratory data [13]. Therefore, NHANES has provided a high-quality and nationally representative sample to explore the correlation between ApoB and DN. Mendelian randomization (MR) analysis is a tool employed to elucidate causal relationships between exposure and outcomes using genetic data [14]. Due to the random allocation of genetic alleles during meiosis, independent of environmental factors, the genetic associations observed through MR analysis are less likely to be influenced by confounding biases and reverse...