Diabetes Care 30:3083-3085, 2007 DOI: 10.2337/dc07-1092 © 2007 by the American Diabetes Association
Pregnancy-Associated Plasma Protein-A Levels Are Related to Glycemic Control but Not to Lipid Profile or Hemostatic Parameters in Type 2 Diabetes
1 Endocrinology and Nutrition Service, Department of Medicine, Germans Trias i Pujol University Hospital, Universitat Autònoma de Barcelona, Badalona, Spain Address correspondence and reprint requests to Jordi L. Reverter, MD, PHD, Endocrinology and Nutrition Service, Germans Trias i Pujol University Hospital, Via Canyet s/n, 08916, Badalona, Spain. E-mail: reverter.germanstrias{at}gencat.net
Abbreviations: ABI, ankle-brachial pressure index hsCRP, high-sensitivity C-reactive protein IL, interleukin PAPP-A, pregnancy-associated plasma protein-A TNF, tumor necrosis factor
Pregnancy-associated plasma protein-A (PAPP-A) is a zinc-binding matrix metalloproteinase that regulates extracellular matrix remodeling. PAPP-A degrades IGFBP-4, increasing levels of local IGF-1 in response to injury, and could be involved in the pathogenesis of atherosclerosis (1–6). Inflammatory cytokines tumor necrosis factor (TNF)- and interleukin (IL)-1β, implicated in insulin resistance (7), are potent stimulators of PAPP-A (8,9). The association between PAPP-A levels and metabolic parameters such as cholesterol and high-sensitivity C-reactive protein (hsCRP) is controversial (2,10,11). We aimed to study the relationship between PAPP-A, glycemic control and other metabolic and hemostatic parameters, inflammatory cytokines, and ankle-brachial pressure index (ABI) in diabetic patients.
Type 2 diabetic patients (n = 175, 65 of whom were women) with stable glycemic control (variation in A1C <10% in the last 5 years) and without diagnosis of clinical macrovascular disease, inflammatory disease, malignancies, or pregnancy were studied. Fifty-three (20 of whom were women) nondiabetic subjects without previous clinical macrovascular disease and normal ABI ( 0.9) were recruited as control subjects.
Demographic, anthropometric, and clinical data and ABI were recorded in all subjects. Laboratory data were measured by commercially available assays, hsCRP by nephelometry, ultrasensitive PAPP-A using an enzyme-linked immunosorbent assay, and TNF- Continuous variables were expressed as means ± SD or median (interquartile range). Differences between groups were examined by Students t test or Mann-Whitney and correlation between variables by Pearsons or Spearmans tests as required. Multiple logistic regression analysis was performed.
Clinical and biochemical characteristics of all study subjects are shown in Table 1. PAPP-A levels were significantly higher in male than in female subjects in both groups (median [interquartile range] 1.04 [0.6–1.47] vs. 0.52 mIU/l [0.43–0.94], P = 0.025 in control subjects and 0.49 [0.23–0.93] vs. 0.35 mIU/l [0.13–0.63], P = 0.01 in diabetic patients).
Serum PAPP-A concentrations were significantly higher in control than in diabetic subjects (median [interquartile range] 0.73 [0.48–1.33] vs. 0.45 mIU/l [0.19–0.82], respectively, P < 0.0001) and correlated negatively with A1C (r = –0.2, P = 0.03). Diabetic patients were stratified according to mean ± SD values of A1C (<5.9, 5.9–8.2, and >8.2%). PAPP-A concentration was significantly lower in patients with A1C >8.2% (0.35 mUI/l [0.07–0.43]) compared with that in patients with A1C <5.9% (0.72 mUI/l [0.2–0.92], P < 0.03) and between 5.9 and 8.2% (0.56 mUI/l [0.15–0.83], P < 0.02) and control subjects (0.73 mUI/l [0.48–1.33], P < 0.001). No differences in PAPP-A levels were observed when subjects with normocholesterolemia were compared with those with hypercholesterolemia (median [interquartile range] 0.6 [0.45–1.14] vs. 0.8 mUI/l [0.48–1.38], respectively) and with diabetic patients (0.6 [0.45–1.14] vs. 0.8 mUI/l [0.48–1.38]). On the other hand, when control subjects and diabetic patients with normocholesterolemia were compared, PAPP-A levels remained significantly higher in control subjects than in diabetic patients (0.6 [0.45–1.14] vs. 0.33 mUI/l [0.13–0.83], respectively, P = 0.04). We obtained the same results when control subjects and diabetic patients with hypercholesterolemia were compared (0.8 [0.48–1.38] vs. 0.44 mUI/l [0.22–0.78], P < 0.0001). Moreover, PAPP-A levels were similar in subjects treated with statins compared with those in untreated subjects in both groups. No differences were observed in PAPP-A levels between diabetic patients with or without a history of diabetic vasculopathy (n = 25), abnormal ABI (n = 54), nephropathy (n = 42), or retinopathy (n = 59), and no relationship was found between plasma levels of PAPP-A and those of hemostasis parameters and inflammatory cytokines. Multiple logistic regression analyses using PAPP-A as the dependent variable and age, BMI, and biochemical parameters as independent variables showed no associated factors other than A1C (P = 0.02) and glycemia (P = 0.04).
In the present study, PAPP-A levels were significantly lower in diabetic patients compared with those in age- and sex-matched control subjects without clinical macrovascular diseases, and, for the first time, a significant inverse correlation was found between PAPP-A and A1C, independent of other clinical and metabolic factors. The relationship between PAPP-A levels and A1C could reflect the influence of glycemic control on the regulation of PAPP-A expression. A possible hypothesis to consider is that PAPP-A may not be a good marker of vascular risk in chronic diseases such as diabetes. In fact, PAPP-A would be a modulator of proliferative local action of IGF-1 in atherosclerotic plaques (1–6). IGF-1 acts as a promoter of repair at damaged tissues (4,5,12), and increased PAPP-A levels may reflect a repaired mechanism against vascular damage (10). In previous articles (13), diabetic patients with hypercholesterolemia showed higher PAPP-A levels than control subjects. We do not have an explanation for this disparity in our results; however, in that previous study, PAPP-A levels were measured in diabetic patients with a wide range of A1C, without a hypercholesterolemic control group. No correlations were observed between PAPP-A and clinical and other biochemical data. In previous studies on this topic, there were discrepancies, and some authors have reported a relationship (2,10,14) between PAPP-A and hsCRP, while others have not (11).
The lack of an observed correlation between PAPP-A levels and IL-6 or TNF-
This study was supported by a grant "Ajut a la recerca en diabetis Gonçal Lloveras i Vallès" from the Catalan Diabetes Association.
Published ahead of print at http://care.diabetesjournals.org on 28 August 2007. DOI: 10.2337/dc07-1092. A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C Section 1734 solely to indicate this fact. Received for publication June 8, 2007. Accepted for publication August 21, 2007.
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