Pathophysiology/Complications N A L A R T I C L E Effects of Aspirin or Basic Amino Acids on Collagen Cross-Links and Complications IVAN CONTRERAS, PHD KAREN M. REISER, MD NAHIR MARTINEZ, MD ELDA GlANSANTE, MD TULIO LOPEZ, MD NANCY SUAREZ, PHD SARKIS POSTALIAN, MD MIGUEL MOLINA, MD FREDDY GONZALEZ, MD MARIA R. SANCHEZ MANUEL CAMEJO MARIA C. BLANCO OBJECTIVE — To determine if long-term therapy with aspirin or basic amino acids for sub- jects with NIDDM reduces the severity of clinical complications and/or reduces tissue levels of markers of glycooxidative damage RESEARCH DESIGN AND METHODS— Subjects with NIDDM were administered either aspirin (100 mg/day) or a combination of basic amino acids consisting of L-arginine (2 g/day) plus L-lysine (0.5 g/day) for 1 year. The study was double-blind and placebo-controlled. The presence and severity of retinopathy nephropathy and neuropathy were assessed in all sub- jects at 4-month intervals, as were serum blood glucose, glycohemoglobin levels, and presence of albuminuria. Collagen cross-linking and collagen glycation were measured in skin collagen obtained by biopsy at the beginning and the end of the study. Skin biopsies were also obtained from age-matched control subjects. RESULTS — Skin samples obtained from NIDDM subjects at the beginning of the study had significantly increased levels of glucitolyllysine, pentosidine, and hydroxypyridinium, as com- pared with age-matched control subjects. Pentosidine levels were significantly correlated with severity of retinopathy and neuropathy, but not nephropathy. Subjects receiving aspirin, but not amino acids or placebo, had significantly decreased levels of skin pentosidine after 1 year of therapy. CONCLUSIONS — It is concluded that 1) low-dose aspirin may reduce glycooxidative damage in people with NIDDM, and 2) treatment may need to continue for more than 1 year before clinical status improves. S everal studies have shown that abnor- malities in collagen glycation are significantly correlated with the sever- ity of complications in diabetic subjects (1-5). Thus, there has been considerable interest in agents capable of blocking glu- cose adduct formation or interfering with formation of advanced glycation products (1,4,5). We recently investigated two such agents: aspirin and basic amino acids. In the present study, we report on the results of a placebo-controlled, double-blind 12- month clinical trial, in which subjects were administered either aspirin or a mixture of L-arginine and L-lysine. RESEARCH DESIGN AND METHODS Patient population After signing an informed consent form approved by the hospital ethics committee, 24 patients with NIDDM were enrolled in the study. There were 13 women and 11 From Luis Razetti Medical School and University Hospital (I.C, N.M., E.G., T.L., N.S., S.P, MM., EG., M.R.S., M.C., M.C.B.), Central University of Venezuela, Caracas, Venezuela; and the Department of Medicine (K.M.R.), School of Medicine, University of California, Davis, Davis, California. Address correspondence and reprint requests to Karen Reiser, MD, CRPRC, UC Davis, Davis, CA 95616. E-mail: kmreiser@ucdavis.edu. Received for publication 25 September 1996 and accepted in revised form 10 December 1996. ANOVA, analysis of variance. men aged 50 ± 7 (37-61) years (mean ± SD [range]). Patients were randomly allocated to one of three groups. On the basis of pre- viously reported effects, we calculated that a minimum of six subjects per group would be necessary to determine if a given treat- ment affected clinical status or markers of glycooxidative damage (1). We further assumed a randomly distributed attrition rate <20%. Therapeutic regimens. There were three treatment groups: aspirin (100 mg/day), basic amino acids (0.5 g L-lysine 4- 2 g L- arginine/day), or placebo. All capsules were kept in the hospital pharmacy and dis- pensed by the pharmacy Every 6 weeks, patients were interviewed and medication logs were reviewed to ensure compliance. Patients took no other medications during the study. No patients dropped out of the study because of adverse effects. Clinical studies A 4-mm punch biopsy (anterior thigh) was obtained from each patient at the start of the study; biopsies were also obtained from age-matched control subjects. The five male and six female control subjects were aged 47 ± 8 (33-61) years. Patients were subjected to physical examination, routine blood chemistries, and assessment of dia- betic complications. Retinopathy was assessed clinically and by angiography, and renal status was assessed by creatinine clearance and microalbuminuria. Neu- ropathy was assessed clinically and by elec- tromyography. Glycohemoglobin levels were determined by affinity column chro- matography Fasting blood glucose, fruc- tosamine, and glycohemoglobin were determined every 4 months. Biochemical analyses Skin samples were assessed for collagen cross-links, glucose adduct formation, and advanced glycation products by high-per- formance liquid chromatography, as previ- ously described (6). Statistical analysis Statistical analyses were performed on a microcomputer using a statistical analysis 832 DIABETES CARE, VOLUME 20, NUMBER 5, MAY 1997 Downloaded from http://diabetesjournals.org/care/article-pdf/20/5/832/584248/20-5-832.pdf by guest on 20 January 2023