Growth hormone signaling is necessary for lifespan extension by dietary methionine

Growth hormone significantly impacts lifespan in mammals. Mouse longevity is extended when growth hormone (GH) signaling is interrupted but markedly shortened with high‐plasma hormone levels. Methionine metabolism is enhanced in growth hormone deficiency, for example, in the Ames dwarf, but suppressed in GH transgenic mice. Methionine intake affects also lifespan, and thus, GH mutant mice and respective wild‐type littermates were fed 0.16%, 0.43%, or 1.3% methionine to evaluate the interaction between hormone status and methionine. All wild‐type and GH transgenic mice lived longer when fed 0.16% methionine but not when fed higher levels. In contrast, animals without growth hormone signaling due to hormone deficiency or resistance did not respond to altered levels of methionine in terms of lifespan, body weight, or food consumption. Taken together, our results suggest that the presence of growth hormone is necessary to sense dietary methionine changes, thus strongly linking growth and lifespan to amino acid availability.     

A genome scan for quantitative trait loci affecting the Salmonella carrier-state in the chicken

Selection for increased resistance to Salmonella colonisation and excretion could reduce the risk of foodborne Salmonella infection. In order to identify potential loci affecting resistance, differences in resistance were identified between the N and 6₁ inbred lines and two QTL research performed. In an F2 cross, the animals were inoculated at one week of age with Salmonella enteritidis and cloacal swabs were carried out 4 and 5 wk post inoculation (thereafter called CSW4F2 and CSW4F2) and caecal contamination (CAECF2) was assessed 1 week later. The animals from the (N × 6₁) × N backcross were inoculated at six weeks of age with Salmonella typhimurium and cloacal swabs were studied from wk 1 to 4 (thereafter called CSW1BC to CSW4BC). A total of 33 F₂ and 46 backcross progeny were selectively genotyped for 103 and 135 microsatellite markers respectively. The analysis used least-squares-based and non-parametric interval mapping. Two genome-wise significant QTL were observed on Chromosome 1 for CSW2BC and on Chromosome 2 for CSW4F2, and four suggestive QTL for CSW5F2 on Chromosome 2, for CSW5F2 and CSW2BC on chromosome 5 and for CAECF2 on chromosome 16. These results suggest new regions of interest and the putative role of SAL1.     

Correlation of Phenotype with the Genotype of Egg-Contaminating Salmonella enterica Serovar Enteritidis

The genotype of Salmonella enterica serovar Enteritidis was correlated with the phenotype using DNA-DNA microarray hybridization, ribotyping, and Phenotype MicroArray analysis to compare three strains that differed in colony morphology and phage type. No DNA hybridization differences were found between two phage type 13A (PT13A) strains that varied in biofilm formation; however, the ribotype patterns were different. Both PT13A strains had DNA sequences similar to that of bacteriophage Fels2, whereas the PT4 genome to which they were compared, as well as a PT4 field isolate, had a DNA sequence with some similarity to the bacteriophage ST64b sequence. Phenotype MicroArray analysis indicated that the two PT13A strains and the PT4 field isolate had similar respiratory activity profiles at 37°C. However, the wild-type S. enterica serovar Enteritidis PT13A strain grew significantly better in 20% more of the 1,920 conditions tested when it was assayed at 25°C than the biofilm-forming PT13A strain grew. Statistical analysis of the respiratory activity suggested that S. enterica serovar Enteritidis PT4 had a temperature-influenced dimorphic metabolism which at 25°C somewhat resembled the profile of the biofilm-forming PT13A strain and that at 37°C the metabolism was nearly identical to that of the wild-type PT13A strain. Although it is possible that lysogenic bacteriophage alter the balance of phage types on a farm either by lytic competition or by altering the metabolic processes of the host cell in subtle ways, the different physiologies of the S. enterica serovar Enteritidis strains correlated most closely with minor, rather than major, genomic changes. These results strongly suggest that the pandemic of egg-associated human salmonellosis that came into prominence in the 1980s is primarily an example of bacterial adaptive radiation that affects the safety of the food supply.     

Green Tea Polyphenol Epigallocatechin Gallate Inhibits Adipogenesis and Induces Apoptosis in 3T3‐L1 Adipocytes

Objective: Green tea catechins have been shown to promote loss of body fat and to inhibit growth of many cancer cell types by inducing apoptosis. The objective of this study was to determine whether epigallocatechin gallate (EGCG), the primary green tea catechin, could act directly on adipocytes to inhibit adipogenesis and induce apoptosis. Research Methods and Procedures: Mouse 3T3‐L1 preadipocytes and mature adipocytes were used. To test the effect of EGCG on viability, cells were incubated for 3, 6, 12, or 24 hours with 0, 50, 100, or 200 μM EGCG. Viability was quantitated by MTS assay. To determine the effect of EGCG on apoptosis, adipocytes were incubated for 24 hours with 0 to 200 μM EGCG, then stained with annexin V and propidium iodide and analyzed by laser scanning cytometry. Both preadipocytes and adipocytes were also analyzed for apoptosis by terminal deoxynucleotidyl transferase dUTP nick‐end labeling assay. To determine the effect of EGCG on adipogenesis, maturing preadipocytes were incubated during the 6‐day induction period with 0 to 200 μM EGCG, then stained with Oil‐Red‐O and analyzed for lipid content. Results: EGCG had no effect on either viability or apoptosis of preconfluent preadipocytes. EGCG also did not affect viability of mature adipocytes; however, EGCG increased apoptosis in mature adipocytes, as demonstrated by both laser scanning cytometry and terminal deoxynucleotidyl transferase dUTP nick‐end labeling assays. Furthermore, EGCG dose‐dependently inhibited lipid accumulation in maturing preadipocytes. Discussion: These results demonstrate that EGCG can act directly to inhibit differentiation of preadipocytes and to induce apoptosis of mature adipocytes and, thus, could be an important adjunct in the treatment of obesity.     

Change in Vascular Adhesion Protein‐1 and Metabolic Phenotypes after Vertical Banded Gastroplasty for Morbid Obesity

Objective: The association between circulating vascular adhesion protein‐1 (VAP‐1) and metabolic phenotypes has been shown to be inconsistent. The current study explored whether the changes in serum VAP‐1 levels correlate with the changes in metabolic phenotypes after weight reduction surgery. Research Methods and Procedures: Clinical characteristics and serum VAP‐1 levels in 20 morbidly obese subjects (mean BMI 38.84 kg/m²) were measured before and after vertical banded gastroplasty. Results: Before surgery, serum VAP‐1 levels correlated positively with fasting plasma glucose (γ = 0.56, p = 0.01) and negatively with insulin levels (γ = ?0.51, p = 0.021). After surgery, the changes in serum VAP‐1 levels were negatively correlated with the changes in waist circumference (γ = ?0.57, p = 0.011), diastolic blood pressure (DBP) (γ = ?0.56, p = 0.015), and mean arterial pressure (γ = ?0.46, p = 0.055). In multivariate regression, serum VAP‐1 levels were negatively correlated with waist circumference (β = ?2.36, p = 0.014) and DBP (β = ?3.02, p = 0.017) after adjusting for age and gender. The change in DBP was negatively correlated with the change in VAP‐1 levels after adjusting for age, gender, and steady‐state plasma glucose. Discussion: The results suggest that VAP‐1 levels are correlated with fasting glucose and insulin levels in morbidly obese subjects. After surgery, the changes in VAP‐1 levels were associated with changes in visceral adiposity and DBP. Serum VAP‐1 might modulate DBP independently from the changes in insulin resistance in morbidly obese people.     

Increase in the Thermic Effect of Food in Women by Adrenergic Amines Extracted from Citrus Aurantium

Objective: To compare the thermic response to a meal between men and women of varied body composition and to determine whether adrenergic amines extracted from citrus aurantium (CA) induce an increase in metabolic rate and enhance the thermic response to the meal. Research Methods and Procedures: In 30 healthy weight‐stable subjects (17 women, 13 men; BMI: 20 to 42 kg/m²), body composition was determined by bioimpedance analysis followed by resting energy expenditure for 20 minutes, and the thermic effect of food (TEF) of a 1.7‐MJ, 30‐gram protein meal was determined intermittently for 300 minutes by indirect calorimetry. In a subset of 22 subjects, the TEFs of CA alone and when added to the same 1.7‐MJ meal were determined. Blood pressure and pulse before and throughout the studies and catecholamine excretion were determined. Results: TEF was significantly lower in women than men (152 ± 7 vs. 190 ± 12 kJ and 8.8 ± 0.4% vs. 11.0 ± 0.7% of meal), independently of age and magnitude of adiposity. The thermic response to CA alone was higher in men, but, when added to the meal, CA increased TEF only in women and to values no longer different from men. CA had no effect on blood pressure and pulse rate but increased epinephrine excretion by 2.4‐fold. Discussion: A 20% lower TEF in women suggests a diminished sympathetic nervous system response to meals, because with CA, TEF increased by 29% only in women. However, this acute response may not translate into a chronic effect or a clinically significant weight loss over time.     

Profile of Overweight and Obese People in a Mediterranean Region

Objective: To assess the prevalence of excess weight (obesity and overweight) and the related environmental risk factors in a Mediterranean population. Self‐perception of body weight, attitudes toward weight‐control behaviors, and the associated factors were also examined. Research Methods and Procedures: A cross‐sectional nutritional survey was carried out in the Balearic Islands between 1999 and 2000. A random sample (n = 1200) of the adult population (20 to 60 years old) was interviewed. Dietary questionnaires and a global questionnaire incorporating questions related to sociodemographic and lifestyle variables were utilized. Anthropometric measurements were also obtained. Results: Nearly one‐half of the population of the Balearic Islands is above the normal weight range (BMI > 25). The predictors of overweight and obesity in the Balearic Islands are to be over 40 years old, to be married, to form part of the lowest educational levels, and to have a sedentary lifestyle. A large percentage of excess‐weight individuals tend to underestimate their BMI, are not concerned about their weight status, tend to snack more often, and have never dieted. Discussion: Although the likely causes of the rise in obesity prevalence are difficult to elucidate from this study, we have identified the profile of individuals with excess weight in the Balearic Islands as well as their attitudes toward their body image.