Association between misalignment of circadian rhythm and obesity in Korean men: Sixth Korea National Health and Nutrition Examination Survey

ABSTRACT

Background: The disruption of circadian rhythm has been found to associate with obesity in vivo and in vitro. Sleep duration, eating habits, total feeding time, and nightshift work can also affect circadian rhythms. This study investigated the association between misalignment of circadian rhythm and obesity in Korean men, using a cross-sectional database.

Methods: This study used data from the Korean National Health and Nutrition Examination Survey (KNHANES), whose study population was 3,658 men aged 18 to 60 years. General and abdominal obesity was defined as a body mass index (BMI) ≥ 25 kg/m² and waist circumference ≥ 90 cm, respectively. Circadian rhythm factors were determined with a self-report questionnaire and included breakfast frequency, sleep duration, and work time. Frequency of breakfast was divided into regular breakfast (five to seven times a week) and irregular breakfast (less than five times a week). Sleep duration was divided into less than 7 hours, 7–9 hours, and over 9 hours. Working time was defined as day/evening, night shift, and other type. The adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for general and abdominal obesity were calculated using multivariable logistic regression according to the number of factors that disturb the circadian rhythm.

Results: Participants with 1 (aOR 1.34, 95% Cl 1.10–1.61) and ≥2 (aOR 1.62, 95% Cl 1.29–2.05) factors disturbing circadian rhythms were associated with elevated risk for general obesity. Similarly, those with 1 (aOR 1.33, 95% Cl 1.09–1.63) and ≥2 (aOR 1.70, 95% Cl 1.32–2.20) factors had elevated risk for abdominal obesity.

Conclusions: Factors disturbing the circadian rhythm were associated with general and abdominal obesity. Additional studies are needed, and associations with metabolic diseases should be investigated.     

Determination of rat brain buffering in vivo by 31P-NMR

Buffering capacity of most tissues is composed of both rapid and slow phases, the latter presumably due to active acid extrusion. To examine the time course of brain buffering the brain pH of Sprague-Dawley rats was measured using 31P-nuclear magnetic resonance. The effect on brain pH of 30- or 58-min exposures to 20% CO2 followed by 30- or 38-min recovery periods, respectively, was studied. Brain pH reached its lowest value after a 15-min exposure to elevated CO2, thereafter slowly and steadily increasing. During recovery brain pH rose rapidly in the first 5 min exceeding control brain pH by 0.08 pH units. Brain pH fell during the next 30 min despite increases in blood pH and decreases in blood CO2 tension. Calculated intrinsic brain buffering rose steadily threefold during the last 40 min of CO2 exposure and during the final 30 min of recovery. These data show that in rat brain there is a temporally late buffering process, most likely active acid extrusion, requiring greater than 30 min for full activation and at least 30 min for discontinuation.     

Absence of heat shock protein synthesis in isolated mitochondria and plastids from maize

Examination of the proteins synthesized by isolated mitochondria, chloroplasts, or proplastids from maize tissues showed that a heat treatment at 40 degrees C does not induce or enhance the synthesis of any protein when compared to preparations treated at the control temperature of 28 degrees C. These observations are consistent with the results obtained by labeling proteins in vivo under sterile conditions. In vivo labeling in the presence of cycloheximide during heat shock showed no heat shock protein synthesis. Labeling in the presence of chloramphenicol during heat shock showed a similar heat shock protein pattern as in the absence of the inhibitor. It is concluded that maize organelles do not synthesize heat shock proteins and that, if present, they may be due to bacterial contamination.     

Reclustering of scattered Golgi elements occurs along microtubules

Depolymerization of the interphase microtubules by nocodazole results in the scattering and apparent fragmentation of the Golgi apparatus in Vero fibroblast cells. Upon removal of the drug, the interphase microtubules repolymerize, and the scattered Golgi elements move back to the region around the microtubule-organizing center (MTOC) within 40 to 60 min. Using a fluorescent lipid analogue (C6-NBD-ceramide) as a vital stain for the scattered Golgi elements, their relocation was visualized by video-enhanced fluorescence microscopy in Vero cells maintained at 20 degrees C. The NBD-labeled structures were identified as Golgi elements by their colocalization with galactosyltransferase in the fixed cells. During reclustering, NBD-labeled Golgi elements were observed to move by discontinuous saltations towards the MTOC with velocities of 0.1 to 0.4 micron/s. Paths along which Golgi elements moved were super-imposable on microtubules visualized by indirect immunofluorescence. Neither the collapse of intermediate filaments caused by microinjection of antibodies to vimentin nor the disruption of microfilaments by cytochalasin D had an effect on the reclustering of Golgi elements or the positioning of the Golgi apparatus. These data show that scattered Golgi elements move along microtubules back to the region around the MTOC, while neither intact intermediate filaments nor microfilaments are involved.     

A missense mutation (Asp250----Asn) in exon 6 of the human lipoprotein lipase gene causes chylomicronemia in patients of different ancestries.

We have previously reported two common lipoprotein lipase (LPL) gene mutations underlying LPL deficiency in the majority of 37 French Canadians (Monsalve et al., 1990. J. Clin. Invest. 86: 728-734; Ma et al., 1991. N. Engl. J. Med. 324: 1761-1766). By examining the 10 coding exons of the LPL gene in another French Canadian patient, we have identified a third missense mutation that is found in two of the three remaining patients for whom mutations are undefined. This is a G to A transition in exon 6 that results in a substitution of asparagine for aspartic acid at residue 250. Using in vitro site-directed mutagenesis, we have confirmed that this mutation causes a catalytically defective LPL protein. In addition, the Asp250----Asn mutation was also found on the same haplotype in an LPL-deficient patient of Dutch ancestry, suggesting a common origin. This mutation alters a TaqI restriction site in exon 6 and will allow for rapid screening in patients with LPL deficiency.     

Target-sensitive immunoliposomes: preparation and characterization

A novel target-sensitive immunoliposome was prepared and characterized. In this design, target-specific binding of antibody-coated liposomes was sufficient to induce bilayer destabilization, resulting in a site-specific release of liposome contents. Unilamellar liposomes were prepared by using a small quantity of palmitoyl-immunoglobulin G (pIgG) to stabilize the bilayer phase of the unsaturated dioleoylphosphatidylethanolamine (PE) which by itself does not form stable liposomes. A mouse monoclonal IgG antibody to the glycoprotein D of Herpes simplex virus (HSV) and PE were used in this study. A minimal coupling stoichiometry of 2.2 palmitic acids per IgG was essential for the stabilization activity of pIgG. In addition, the minimal pIgG to PE molar ratio for stable liposomes was 2.5 X 10(-4). PE immunoliposomes bound with HSV-infected mouse L929 cells with an apparent Kd of 1.00 X 10(-8) M which was approximately the same as that of the native antibody. When 50 mM calcein was encapsulated in the PE immunoliposomes as an aqueous marker, binding of the liposomes to HSV-infected cells resulted in a cell concentration dependent lysis of the liposomes as detected by the release of the encapsulated calcein. Neither uninfected nor Sendai virus infected cells caused a significant amount of calcein release. Therefore, the release of calcein from PE immunoliposomes was target specific. Dioleoylphosphatidylcholine immunoliposomes were not lysed upon contact with infected cells under the same conditions, indicating that PE was essential for the target-specific liposome destabilization.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization of non-transferrin-bound iron clearance by rat liver

Recent evidence suggests that the hepatic iron-loading characteristic of hemochromatosis may result in part from efficient hepatic clearance of non-transferrin-bound iron, which is increased in this disorder. However, this hypothesis assumes that hepatic clearance remains highly efficient despite excess iron stores. We therefore studied hepatic uptake of non-transferrin-bound iron in the single-pass perfused rat liver under varying conditions. Animals were iron loaded or depleted by dietary manipulation, but no changes in the efficiency of ferrous iron uptake or the kinetic parameters were seen (single-pass extraction, 59-74%; Km, 16-19 microM; Vmax, 30-32 nmol X min-1 X g liver-1). Added divalent zinc, cobalt, and manganese ions reversibly inhibited ferrous iron uptake and the inhibition by zinc was shown to be competitive. Uptake required calcium, was markedly temperature-sensitive (delta E = 14.3 Kcal/mol), and was relatively insensitive to inhibition of cellular energy metabolism. Particles consistent with ferritin cores were seen in lysosomes of hepatic parenchymal cells within 30 min of perfusion with ferrous iron. These results suggest that ferrous iron is cleared from plasma by a passive, saturable transport process that is not regulated by the iron content of the liver and that may be shared with other transition metal ions. Because clearance is highly efficient, increased levels of non-transferrin-bound iron in plasma may present the liver with an obligatory iron load resulting in progressive accumulation and toxicity.