Using a Short Food Frequency Questionnaire to Evaluate Macronutrients, Fiber, Phosphorus, Potassium, and Calcium in Adults with Stages 3-5 Chronic Kidney Disease.

The progression of chronic kidney disease (CKD) can be directly or indirectly accelerated by a poor diet and the diet's influence on risk factors for this disease. There have been no food frequency questionnaires (FFQs) developed for the assessment of diet in patients with CKD in Taiwan. This study analyzed the validity of a short FFQ (SFFQ) with 42 items for estimating patient intake of macronutrients, fiber, phosphorus, potassium, and calcium against 3-day dietary records (3-day DRs) in Taiwanese patients with stages 3-5 CKD. In an interview, 107 participants with the help of a dietician filled out an SFFQ and reviewed a 3-day DR the patients had filled out prior to the interview. Partial Pearson correlation coefficients between SFFQ and 3-day DR were 0.722, 0.619, 0.593, 0.572, 0.450, 0.611 and 0.410 for protein, fat, carbohydrate, fiber, phosphorus, potassium, and calcium, respectively, after adjusting for energy intake. Cross-classification analysis revealed 63.5-83.2% similarity in cross-tool estimated intakes of macronutrients, fiber, phosphorus, potassium, and calcium in the same quartiles or adjacent ones. Bland-Altman plots revealed good agreement between the two tools along different intake levels. In conclusion, the newly developed SFFQ had moderate relative validity in estimating the usual intake of key nutrients related to nutrition management of patients with late-stage CKD, suggesting it can be used to assess dietary intakes in a population with CKD, especially in those residing in an Asian region.

Structures of the human pyruvate dehydrogenase complex cores: a highly conserved catalytic center with flexible N-terminal domains.

Dihydrolipoyl acetyltransferase (E2) is the central component of pyruvate dehydrogenase complex (PDC), which converts pyruvate to acetyl-CoA. Structural comparison by cryo-electron microscopy (cryo-EM) of the human full-length and truncated E2 (tE2) cores revealed flexible linkers emanating from the edges of trimers of the internal catalytic domains. Using the secondary structure constraints revealed in our 8 A cryo-EM reconstruction and the prokaryotic tE2 atomic structure as a template, we derived a pseudo atomic model of human tE2. The active sites are conserved between prokaryotic tE2 and human tE2. However, marked structural differences are apparent in the hairpin domain and in the N-terminal helix connected to the flexible linker. These permutations away from the catalytic center likely impart structures needed to integrate a second component into the inner core and provide a sturdy base for the linker that holds the pyruvate dehydrogenase for access by the E2-bound regulatory kinase/phosphatase components in humans.

Analysis of chemical and enzymatic cleavage frequencies in supercoiled DNA.

Chemical and enzymatic probing methods are powerful techniques for examining details of sequence-dependent structure in DNA and RNA. Reagents that cleave nucleic acid molecules in a structure-specific, but relatively sequence-non-specific manner, such as hydroxyl radical or DNase I, have been used widely to probe helical geometry in nucleic acid structures, nucleic acid-drug complexes, and in nucleoprotein assemblies. Application of cleavage-based techniques to structures present in superhelical DNA has been hindered by the fact that the cleavage pattern attributable to supercoiling-dependent structures is heavily mixed with non-specific cleavage signals that are inevitable products of multiple cleavage events. We present a rigorous mathematical procedure for extracting the cleavage pattern specific to supercoiled DNA and use this method to investigate the hydroxyl radical cleavage pattern in a cruciform DNA structure formed by a 60 bp inverted repeat sequence embedded in a negatively supercoiled plasmid. Our results support the presence of a stem-loop structure in the expected location and suggest that the helical geometry of the cruciform stem differs from that of the normal duplex form.