Glossary

• AGEs (advanced glycation end products). Damaged proteins formed when sugars react with them. They build up with age and in diabetes.
• Anserine. Carnosine with a methyl group on the imidazole ring. The main dipeptide in poultry and tuna.
• Beta-alanine. One of carnosine’s two building blocks. Supplying it raises muscle carnosine.
• Carnosinase. The enzymes that split carnosine into beta-alanine and histidine. CN1 works in blood, CN2 inside cells.
• Carnosine synthase (CARNS1). The enzyme that joins beta-alanine and histidine to make carnosine.
• CNDP1. The gene for serum carnosinase. A repeat variation in this gene affects enzyme levels.
• Dipeptide. Two amino acids joined by one amide bond.
• Glycation. The reaction of a sugar with a protein, without an enzyme.
• Imidazole ring. The five-sided ring in histidine with two nitrogen atoms. The part of carnosine that buffers and binds metals.
• Meta-analysis. A study that pools the numbers from several trials.
• mmol/kg. Millimoles per kilogram, a measure of concentration in tissue. Dry weight and wet weight values differ by about four times.
• N-acetylcarnosine. Carnosine with an acetyl group added. Used in eye drops.
• Paraesthesia. A tingling or prickling feeling on the skin. The common side effect of beta-alanine.
• pKa. The pH at which half of a group has given up its hydrogen ion. A buffer works best near its pKa.
• Polaprezinc, zinc-L-carnosine. A zinc complex of carnosine, a gastric ulcer medicine in Japan.
• Randomised controlled trial. Participants are assigned by chance to treatment or comparison. The strongest single-study design.
• Reactive carbonyl species. Compounds such as methylglyoxal and 4-hydroxynonenal that damage proteins.