Long-term animal-protein consumption is associated with an increased prevalence of diabetes among the elderly: the Mediterranean Islands (MEDIS) study.

AIM: The role of animal-protein consumption on the prevalence of diabetes is not yet fully understood. For this reason, this study investigated the relationship between long-term animal-protein intake and diabetes in elderly individuals with no known cardiovascular disease. METHODS: During 2005-2007, 1190 men and women, aged 65-100 years, from Cyprus, Mitilini, Samothraki, Cephalonia, Crete, Lemnos, Corfu and Zakynthos were enrolled into the study. Diabetes was defined as fasting blood glucose ≥ 125 mg/dL or the use of antidiabetic medication. All participants were asked about their dietary habits through a semiquantitative food-frequency questionnaire. Assessment of protein and energy intakes was performed using food-composition tables. RESULTS: After adjusting for age, gender, obesity, history of hypertension, hypercholesterolaemia and dietary habits, a 5% increase in protein intake from meat and meat products was associated with a 34% (OR=1.338, 95% CI: 1.02-1.76) greater likelihood of diabetes, while a 5% increase in total protein intake was associated with a 29% (OR=1.288, 95% CI: 1.00-1.69) greater likelihood of diabetes. No significant associations between diabetes and protein intakes from vegetables and cereals were observed. CONCLUSION: Animal-protein consumption was associated with a higher prevalence of diabetes among the elderly, whereas protein intakes, especially from plant sources, within the recommended range appear to confer considerable protection. This suggests that reducing or controlling the burden of diabetes through dietary means in the elderly should include monitoring their daily protein intake.

Molecular modeling and functional analysis of the AtoS-AtoC two-component signal transduction system of Escherichia coli.

The AtoS-AtoC two-component signal transduction system positively regulates the expression of the atoDAEB operon in Escherichia coli. Upon acetoacetate induction, AtoS sensor kinase autophosphorylates and subsequently phosphorylates, thereby activating, the response regulator AtoC. In a previous work we have shown that AtoC is phosphorylated at both aspartate 55 and histidine73. In this study, based on known three-dimensional structures of other two component regulatory systems, we modeled the 3D-structure of the receiver domain of AtoC in complex with the putative dimerization/autophosphorylation domain of the AtoS sensor kinase. The produced structural model indicated that aspartate 55, but not histidine 73, of AtoC is in close proximity to the conserved, putative phosphate-donor, histidine (H398) of AtoS suggesting that aspartate 55 may be directly involved in the AtoS-AtoC phosphate transfer. Subsequent biochemical studies with purified recombinant proteins showed that AtoC mutants with alterations of aspartate 55, but not histidine 73, were unable to participate in the AtoS-AtoC phosphate transfer in support of the modeling prediction. In addition, these AtoC mutants displayed reduced DNA-dependent ATPase activity, although their ability to bind their target DNA sequences in a sequence-specific manner was found to be unaltered.

Characterization of ornithine decarboxylase and regulation by its antizyme in Thermus thermophilus.

Ornithine decarboxylase (ODC), the key enzyme of polyamine biosynthesis was highly purified from the thermophilic bacterium Thermus thermophilus. The enzyme preparation showed a single band on SDS-polyacrylamide gel electrophoresis, a pH optimum of 7.5 and a temperature optimum at 60 degrees C. The native enzyme which is phosphorylated could, upon treatment with alkaline phosphatase, lose all activity. The inactive form could be reversibly activated by nucleotides in the order of NTP>NDP>NMP. When physiological polyamines were added to the purified enzyme in vitro, spermine or spermidine activated ODC by 140 or 40%, respectively, while putrescine caused a small inhibition. The basic amino acids lysine and arginine were competitive inhibitors of ODC, while histidine did not affect the enzyme activity. Among the phosphoamino acids tested, phosphoserine was the most effective activator of purified ODC. Polyamines added at high concentration to the medium resulted in a delay or in a complete inhibition of the growth of T. thermophilus, and in a decrease of the specific activity of ornithine decarboxylase. The decrease of ODC activity resulted from the appearance of a non-competitive inhibitor of ODC, the antizyme (Az). The T. thermophilus antizyme was purified by an ODC-Sepharose affinity column chromatography, as well as by immunoprecipitation using antibodies raised against the E. coli antizyme. The antizyme of E. coli inhibited the ODC of T. thermophilus, and vice versa. The fragment of amino acids 56-292 of the E. coli antizyme, produced as a fusion protein of glutathione S-transferase, did not inhibit the ODC of E. coli or T. thermophilus.