See the letter "Letter: Presence of Carotid Plaque Is Associated with Rapid Renal Function Decline in Patients with Type 2 Diabetes Mellitus and Normal Renal Function (Diabetes Metab J 2019;43:840–53)" on page 201.
We appreciate your interest and comments on our article entitled “Presence of carotid plaque is associated with rapid renal function decline in patients with type 2 diabetes mellitus and normal renal function” that was published in Diabetes & Metabolism Journal [1]. You pointed out the importance of age and duration of diabetes in the progression of diabetic kidney disease (DKD). Also, you provided evidences to support that DKD and atherosclerosis share similar risk factors such as inflammation.
We want to emphasize that the ultimate goal of the study was to find means to identify patients with rapid renal function early—when renal function is normal—so interventions can be undertaken to stop or slow the decline. This study focused on the association between baseline carotid atherosclerosis and early rapid renal function decline during a 6-year follow-up in a cohort of patients with type 2 diabetes mellitus (T2DM) and baseline estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m2. Although age is one of the important factors for eGFR decline in patients with DKD, age-related loss of kidney function is mainly due to other important comorbidities, such as diabetes and hypertension [23]. Moreover, we defined rapid decline in eGFR as those who had an eGFR decline >3.3% per year, in accordance with previous studies [45]; this threshold corresponds approximately to an eGFR loss ≥2.5 mL/min/1.73 m2 per year, which reflects approximately three times more rapid decline than expected by normal aging [6]. As for the duration of diabetes, previous studies demonstrated that duration of diabetes is not associated with rapid renal function decline in patients with T2DM and preserved renal function decline after adjustment of clinical risk factors [178].
We agree that it would have better reflected renal outcome if we had included temporal changes in carotid intima-media thickness or glycosylated hemoglobin over time instead of cross-sectional baseline parameters. Further prospective trials are warranted to examine the beneficial effects of intensive medical treatment or an improvement in glycemic control and carotid atherosclerosis on prevention or delay of rapid renal function decline in patients with T2DM and preserved renal function. Nevertheless, our study clearly demonstrates that rapid renal function decline in patients with T2DM is associated with carotid atherosclerosis at baseline.
References
1. Seo DH, Kim SH, Song JH, Hong S, Suh YJ, Ahn SH, Woo JT, Baik SH, Park Y, Lee KW, Kim YS, Nam M. KNDP Study Group. Presence of carotid plaque is associated with rapid renal function decline in patients with type 2 diabetes mellitus and normal renal function. Diabetes Metab J. 2019; 43:840–853.
2. Yokoyama H, Tomonaga O, Hirayama M, Ishii A, Takeda M, Babazono T, Ujihara U, Takahashi C, Omori Y. Predictors of the progression of diabetic nephropathy and the beneficial effect of angiotensin-converting enzyme inhibitors in NIDDM patients. Diabetologia. 1997; 40:405–411.
3. Cheng SS, Wilson DM, Munn SR. Predictors of progression of diabetic nephropathy: implication for timing of kidney transplantation. Clin Transplant. 1997; 11:334–336.
4. Krolewski AS. Progressive renal decline: the new paradigm of diabetic nephropathy in type 1 diabetes. Diabetes Care. 2015; 38:954–962.
5. Pavkov ME, Knowler WC, Lemley KV, Mason CC, Myers BD, Nelson RG. Early renal function decline in type 2 diabetes. Clin J Am Soc Nephrol. 2012; 7:78–84.
6. Lindeman RD, Tobin J, Shock NW. Longitudinal studies on the rate of decline in renal function with age. J Am Geriatr Soc. 1985; 33:278–285.
7. Zoppini G, Targher G, Chonchol M, Ortalda V, Negri C, Stoico V, Bonora E. Predictors of estimated GFR decline in patients with type 2 diabetes and preserved kidney function. Clin J Am Soc Nephrol. 2012; 7:401–408.
8. Jiang G, Luk AOY, Tam CHT, Xie F, Carstensen B, Lau ESH, Lim CKP, Lee HM, Ng ACW, Ng MCY, Ozaki R, Kong APS, Chow CC, Yang X, Lan HY, Tsui SKW, Fan X, Szeto CC, So WY, Chan JCN, Ma RCW. Hong Kong Diabetes Register TRS Study Group. Progression of diabetic kidney disease and trajectory of kidney function decline in Chinese patients with type 2 diabetes. Kidney Int. 2019; 95:178–187.