Validity and reliability of the 13C-methionine breath test for the detection of moderate hyperhomocysteinemia in Mexican adults.

BACKGROUND: Hyperhomocysteinemia (Hhcy) is considered an independent risk factor for vascular diseases and, more recently, for dementia. The methionine loading test (MLT) is useful for diagnosing additional subjects with moderate Hhcy. However, it is a complex and time-consuming procedure. A noninvasive test for the diagnosis of moderate Hhcy is desirable. METHODS: The study protocol consisted of three consecutive visits. During the first visit, we performed an MLT to characterize the Hhcy status of 75 healthy adult subjects. For the breath test protocol, we selected a subsample and assigned to the control group 17 subjects with fasting and post-loading homocysteine (Hcy) ≤12 and <42.3 µmol/L, respectively, and to the Hhcy group 16 subjects with fasting Hcy ≤12 and >42.3 µmol/L after loading. Selected subjects were requested to have a second visit to perform a breath test within 1-4 weeks following the MLT test and received an oral dose of 2.5 mg/kg of 1-13C-methionine dissolved in water. Breath samples were collected at basal, 20, 40, 60, 80, 100 and 120 min (test 1). The same procedure was repeated within 1 week (test 2). RESULTS: MLT was useful for diagnosing almost twice the number of individuals with Hhcy (24%) in comparison with the fasting determination alone (13.3%). The 13C-methionine breath test reported a sensitivity of 81.3% and a specificity of 64.7% against the MLT. The coefficient of variation between breath test 1 and breath test 2 was 9.0±5.4%. CONCLUSIONS: The 13C-methionine breath test is a valid and reliable method for identifying subjects with moderate Hhcy.

Adiposity and Insulin Resistance in Children from a Rural Community in Mexico.

BACKGROUND AND AIMS: The study of the incidence of overweight and obesity as well as body composition and insulin resistance in children from rural communities is scarce. The aims of the study were a) to characterize the adiposity and homeostasis model assessment of insulin resistance (HOMA-IR) in school-age children from a rural community and b) to determine factors associated with fat mass and HOMA-IR in this population. METHODS: A total of 41 school-aged children (15 males and 26 females; 9.9 ± 2.5 years old) from a Mexican rural community was studied. Trained observers had previously assessed the children's nutritional status during the first 6 months of life. Anthropometry, energy intake, physical activity, body composition and biochemical parameters were measured. RESULTS: The overall prevalence of overweight/obesity was 7.3%. The mean energy intake of children was below international recommendations (1,235 ± 400 kcal/day). A higher percentage of fat mass was observed in females (20.3 ± 8.5) than in males (14.1 ± 5.1) (p = 0.006). There were seven children with IR, but we did not observe a correlation between HOMA and BMI percentiles (Pearson's r = 0.09, p = 0.57). In a regression model, gender (females) was the primary factor associated with the percentage of fat mass. The growth velocity during the first 6 months of life was associated with HOMA-IR. CONCLUSIONS: There is a low frequency of overweight and obesity in children from rural communities in Mexico. However, these children appear to have increased risk of adiposity and insulin resistance.