Antiglycation Effects of Carnosine and Other Compounds on the Long-Term Survival of Escherichia coli

Abstract

Glycation, or nonenzymatic glycosylation, is a chemical reaction between reactive carbonyl-containing compounds and biomolecules containing free amino groups. Carbonyl-containing compounds include reducing sugars such as glucose or fructose, carbohydrate-derived compounds such as methylglyoxal and glyoxal, and nonsugars such as polyunsaturated fatty acids. The latter group includes molecules such as proteins, DNA, and amino lipids. Glycation-induced damage to these biomolecules has been shown to be a contributing factor in human disorders such as Alzheimer's disease, atherosclerosis, and cataracts and in diabetic complications. Glycation also affects Escherichia coli under standard laboratory conditions, leading to a decline in bacterial population density and long-term survival. Here we have shown that as E. coli aged in batch culture, the amount of carboxymethyl lysine, an advanced glycation end product, accumulated over time and that this accumulation was affected by the addition of glucose to the culture medium. The addition of excess glucose or methylglyoxal to the culture medium resulted in a dose-dependent loss of cell viability. We have also demonstrated that glyoxylase enzyme GloA plays a role in cell survival during glycation stress. In addition, we have provided evidence that carnosine, folic acid, and aminoguanidine inhibit glycation in prokaryotes. These agents may also prove to be beneficial to eukaryotes since the chemical processes of glycation are similar in these two domains of life.

(p)ppGpp-Dependent Persisters Increase the Fitness of Escherichia coli Bacteria Deficient in Isoaspartyl Protein Repair

“…5). While the best-described roles of methylglyoxal as a metabolic poison do not correspond well with our metabolic measurements or with the reduced persister frequency observed in our ⌬glpD mutant, methylglyoxal has also been described as a protein-glycating agent (46), and it is interesting to speculate that the deleterious effects of glycation might be balanced either by reduced susceptibility to other protein damage or by the induction of protein maintenance and repair machinery. Possibly, a more complex effect of this nature could explain the transient but substantial increase in fitness that we observed for our ⌬pcm mutant in the presence of methylglyoxal.…”

Rich Medium Composition Affects Escherichia coli Survival, Glycation, and Mutation Frequency during Long-Term Batch Culture

“…Further, the delay in glycation in TB and SB cultures is coincident with both delay of the death phase and delay in alkalization. This is expected since glycation levels have been shown to increase with medium pH (10,13,28). Our data show that higher glycation levels early during incubation correspond to a more severe death phase, and low glycation levels are coincident with a delay in the death phase.…”

“…It has previously been shown that advanced glycation end products (AGEs) accumulate during the LTSP (2, 10-13). In the presence of increasing concentrations of sugar (i.e., glucose), both the accumulation of AGEs and the severity of the death phase increase (10). To determine how glycation is affected by growth in different rich media, we quantified the amount of carboxymethyl lysine (CML), a common glycation end product, in cells cultured in LB, YT, TB, or SB, using an ELISA with an anti-CML antibody.…”

“…Whole-cell protein was isolated as previously described (2,10). Briefly, 5-ml cultures of PFM2, grown in different media, were incubated for 1 to 3 days.…”

“…An increase in glycation is associated with increased oxidative stress levels; therefore, conditions that lead to high levels of oxidative stress also lead to higher levels of glycation. It has been demonstrated that glycation can lead to cell death in E. coli (10)(11)(12), and when glycation levels are reduced, for example, by the addition of antiglycation agents, such as carnosine or aminoguanidine, cell death also decreases (10). Another factor modulating the survival of cells in batch culture is pH (14-17).…”