Summary ― From 3-7 weeks of age, male and female broilers were fed ad libitum on 1 of the 8 experimental diets. These diets were isoenergetic (13.6 kJ/kg) and isoproteic (186 g/kg) and provided 7 to 14 g/kg lysine. The growth performances, the abdominal fat proportion and hepatic malic enzyme activity (malate dehydrogenase with decarboxylating EC 1.1.1.40) were measured. All parameters varied when dietary lysine concentration was increased from 7 to 9 or to 11 g/kg. The lysine requirement in the finishing period for minimum abdominal fat proportion was higher than for minimum feed conversion ratio, itseful higher than for maximal growth rate. Malic enzyme activity varied with abdominal fat proportion, and this variation could explain the reduction in fatness. However, an excess of lysine did not amplify the reduction of fat deposit.

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Background and aimsIL-18 expression is up-regulated in atherosclerotic plaques, and higher levels are seen in obese and Type 2 Diabetic individuals. More recently, a possible role for IL-18 in glucose and energy homeostasis has been suggested.Methods and resultsWe investigated variation within the IL18 gene and its association with measures of obesity and the metabolic syndrome. Five IL18 tagging single nucleotide polymorphisms (rs1946519, rs2043055, rs549908, rs360729, rs3882891) were selected and genotyped in the Gene-Diet Attica Investigation on childhood obesity (GENDAI) (age range 10–14 yrs); in young European men in the second European Atherosclerosis Research offspring Study (EARSII), an offspring study (age range 18–28 yrs) and in a group of healthy women from the Greek Obese Women study (GrOW) (age range 18–74 yrs). Six common haplotypes were observed. In GrOW, Hap6 (Frequency-2.6%) was associated with higher insulin levels (p < 0.0001), estimates of HOMA-Insulin Resistance (p < 0.0001) and HOMA-β-cell (p < 0.0001) compared to the common haplotype Hap1 (Frequency-33.2%). In EARSII, rs2043055 was associated with peak and area under the curve triglycerides (p = 0.001 and p = 0.002, respectively) after an oral fat tolerance test in ‘cases’ but not ‘controls’. None of the haplotypes were associated with measures of body fatness in any of the studies.ConclusionAssociation of IL18 variation with insulin levels and estimates of insulin resistance were only observed in our adult study, suggesting that the effects of IL-18 are only associated with increasing age. Taken together with the association of IL18 variants with post-prandial measures, this provides support for IL-18 as a metabolic factor.