Objective: To investigate the correlation study between C-reactive protein (CRP) and the occurrence and development of diabetic nephropathy (DN). METHODS To summarize and analyze the research progress of CRP and DN in recent years. RESULTS: CRP is a pro-inflammatory factor associated with the occurrence, evolution and development of DN, and is involved in the inflammatory response. CONCLUSIONS: Significantly elevated CRP levels may be the result of long-term low inflammatory response in DN patients; CRP is an important indicator to predict the progression of DN; detection of CRP is meaningful for the diagnosis and efficacy assessment of DN. Keywords: diabetic nephropathy; diabetes mellitus; C-reactive protein; inflammatory factors I. Significance of CRP in DN Diabetic nephropathy (DN) is a specific kidney damage caused by diabetes mellitus, and is one of the common and serious complications of diabetes mellitus (DM). C-reactive protein (CRP) is a sensitive marker of non-specific inflammation. The concentration of CRP can rise tens or even hundreds of thousands of times 6-12 h after an inflammatory reaction or tissue damage. This response is not affected by radiotherapy, chemotherapy, or glucocorticoid therapy. In CRP and DN exploration and research found: CRP is directly involved in the inflammatory process and positively correlated with vascular lesions and urinary microalbumin, and DN is considered an inflammatory disease. Therefore, the detection of CRP level can monitor the occurrence and development of DN. Mogensen suggested that the natural history of DN is divided into 5 stages, before stage III, the patient is not yet clinically obvious renal damage manifestations, renal damage pathological changes can still be reversed, if timely and effective treatment can delay or stop the progress of DN? The mechanism of CRP involvement in the inflammatory response during DN CRP is an acute temporal reactive protein that is associated with systemic and local inflammatory states. CRP can cause renal injury through a variety of pathways: high concentrations of CRP directly participate in the systemic or local inflammatory response, damage vascular endothelial cells, promote their proliferation and migration, increase vascular resistance, promote atherosclerosis, and also aggravate glomerular hyperfiltration and hyperperfusion It also aggravates glomerular hyperfiltration and hyperperfusion and activates tubular epithelial cells, producing fibrogenic factors, leading to tubular interstitial fibrosis and causing kidney injury. The comprehensive analysis can confirm that the inflammatory process is involved in the pathogenesis of DN, and CRP is one of the risk factors for DN, and its mechanism needs to be studied in more detail. The mechanism of CRP-induced DN may be: (1) through local inflammation leading to vascular endothelial cell damage or dysfunction. (2) reducing the biological activity and expression of endothelial nitric oxide synthase; (3) participating in oxidative stress and enhancing the adhesion and infiltration of monocytes to the vascular endothelium; (4) stimulating the release of inflammatory factors and monocyte chemokines from the vascular endothelium, causing tissue damage; (5) activating the body’s coagulation and complement systems, disrupting the balance of the body’s coagulation and fibrinolytic systems, and triggering vascular lesions. 3.2 Practical value of CRP assay in DN clinic DN has insidious onset and it is difficult to diagnose early kidney damage, coupled with the influence of internal and external environmental factors, it is not easy to elucidate the complex condition of DN patients by CRP. CRP can be used as a predictor of renal injury and damage, and can also be used in combination with serum D-monodimer, fibrinogen and endothelin to improve the sensitivity and speed of early diagnosis of DN. In conclusion, CRP can be used as a clear and reliable index for determining inflammation and as a reference for testing the correctness and efficacy of treatment targeting. At the same time, strengthening the research on the mechanisms of joint related inflammatory factors and their receptor regulation and signal transduction pathways may provide a new theoretical basis for the treatment of DN. 3.3 Other factors affecting CRP In the course of DN, factors commonly affecting CRP: obesity, insulin resistance, metabolic syndrome. All of the above can indirectly exacerbate the inflammatory response and metabolic disorder effects, causing vascular endothelial dysfunction and reduced insulin sensitivity, etc., thus intensifying the formation of a vicious circle between inflammatory response and complications, accelerating the deterioration of DN and eventually leading to the occurrence of DM and DN complications endpoint events. Therefore, active intervention therapy can slow down the process of DN. 3.4 Western medicine intervention and treatment of CRP and DN The mechanisms associated with elevated CRP in DN patients are: chronic inflammation, insulin resistance, hyperglycemia, etc. Clinical anti-inflammatory treatments such as blood pressure and blood glucose control, dialysis, insulin therapy, and protein reduction can directly or indirectly reduce the degree of inflammatory response in DN patients and delay the development of renal lesions. With the understanding of the mechanism of inflammation in DN, it has been found in the studies of ACEI, ARB, statins, thiazolidinediones, mescaline morphine ethyl ester, tretinoin, and retinoic acid that one of their nephroprotective effects originates from the anti-inflammatory effect. Western medicine is still in the embryonic stage of research for intervention in CRP, with a narrow therapeutic scope and too much requirement for standardization of indicators, resulting in the application of a wide range of drugs and achieving clinical therapeutic effects while often bringing many adverse effects. 3.5 Chinese medicine research on CRP intervention in DN Chinese medicine believes that DN has a long duration of disease, long-standing disease injures yin and consumes qi, and there are many deficiencies and blood stasis, so treatment is mostly based on benefiting qi and nourishing yin, resolving phlegm and eliminating stasis. Clinical observation shows that the application of prescriptions such as Modified Kidney Protection Formula II and the single herbs Huang Qi, Chuanxiong and Xin Yi can improve the clinical symptoms, reduce the rate of urinary clear protein excretion, inhibit endothelial cell inflammatory factors and lower CRP in DN patients to improve chronic inflammation of the kidney. In addition, the effect of traditional Chinese medicine with conventional western medicine treatment is also affirmed. With the deepening of the inflammatory mechanism of DN, the search for anti-inflammatory drugs with good efficacy and low or no damage to renal function will be the opportunity and advantage of TCM for DN treatment, and also raise new questions and requirements. This will promote research on the correlation between TCM and experimental testing, and will also open up new avenues for the treatment of CRP and DN. 3.6 CRP and the progression and prognosis of DN High levels of CRP are not only involved in the progression of metabolic abnormalities and renal failure in DN patients, but are also an independent predictor of morbidity and mortality. high mortality and disability in DN are mainly due to inflammatory response exacerbated by medium and small vessel lesions and complications. The study of the correlation between Chinese medicine evidence type and CRP in DN patients found that CRP levels gradually increased with the evolution of evidence type from yin deficiency and dry heat, spleen and kidney qi (yang) deficiency, qi and yin deficiency, and yin and yang deficiency. The normal CRP level is dominated by Qi and Yin deficiency; the elevated CRP level is dominated by Yin and Yang deficiency, and the organism is in a Yang deficiency state with a “cold” and “quiet” aspect, which is manifested as a “non-infectious inflammatory reaction”. With the progress and requirements of medical science, it is a more intuitive method to detect and evaluate the prognosis of DN with reference to the CRP index from the perspective of dialectical treatment in TCM, which is not the westernization of TCM, but the combination of Chinese and Western medicine, which can better utilize the advantages of TCM in the treatment of DN. V. Detection of CRP in the diagnosis of DN The main points of diagnosis of DN are based on fasting glucose (FG), oral glucose tolerance (OGTT), microproteinuria (MA), urinary albumin excretion rate (UAER). fg and OGTT are used to diagnose DM. MA is the gold standard for the diagnosis of DN, but it is applicable to the clinical nephropathy stage. uaer is applicable to the diagnosis of early nephropathy stage (early DN), but in hyperglycemia or hypertension, blood in urine, exercise, heart failure, and use of antihypertensive drugs can vary. Of the 5 stages of the natural history of DN suggested by Mogensen, I and II are preclinical (no obvious signs of kidney damage yet) and can be expected to reverse albuminuria and stop or delay the progression of DN if treated with effective interventions. Inflammatory factors are present in DM and DN, and are more pronounced in DN patients. Hint: CRP testing is particularly important for the diagnosis and treatment of early DN. Also CRP is the strongest independent predictor of cardiovascular complications (coronary artery disease). From the perspective of detection of renal damage already: transferrin and immunoglobulin may respond to renal damage earlier than U-MA, and microglobulin and endothelin are helpful for early DN diagnosis and prognosis, but all are to be confirmed by larger series of studies. The pathophysiological mechanism of MA is the systemic endothelial cell dysfunction (injury) caused by the inflammatory response (CRP) during microangiopathy, and endothelial cell dysfunction may be the intermediate link between the systemic inflammatory response and MA. The significance of MA testing tends to be diagnostic and prognostic if compared with the detection indexes from the perspective of no kidney damage or imminent progression of kidney damage, while the latter highlights the concept of treating the disease before it occurs (prevention before it occurs; prevention after it occurs), which can guide the clinic to stop, control or even reverse the progression of early kidney function damage earlier and to a greater extent. Because CRP is a sensitive marker of non-specific inflammation, regular review of CRP is important for comprehensive assessment of DN disease. Summary: Although there have been many studies on CRP and DN in recent years, the lack of standard research data and methods has resulted in limited academic breadth and depth, which has been the greatest resistance to research progress. Although this is a pressing issue, it still confirms that CRP is an underutilized indicator in terms of its sensitivity to the vascular inflammatory response and its intervention on the endothelial system. The mechanism of DN has not yet been fully elucidated, and as the study of CRP and DN progresses it may further reveal the mechanism of DN and the role of CRP in it, and provide new targets and opportunities for early diagnosis and treatment of DN, and early detection and effective prevention and treatment of DN.