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.     

UHRF2, a Ubiquitin E3 Ligase,Acts as a Small Ubiquitin-like Modifier E3 Ligase for Zinc Finger Protein 131

Small ubiquitin-like modifier (SUMO), a member of the ubiquitin-related protein family, is covalently conjugated to lysine residues of its substrates in a process referred to as SUMOylation. SUMOylation occurs through a series of enzymatic reactions analogous to that of the ubiquitination pathway, resulting in modification of the biochemical and functional properties of substrates. To date, four mammalian SUMO isoforms, a single heterodimeric SUMO-activating E1 enzyme SAE1/SAE2, a single SUMO-conjugating E2 enzyme ubiquitin-conjugating enzyme E2I (UBC9), and a few subgroups of SUMO E3 ligases have been identified. Several SUMO E3 ligases such as topoisomerase I binding, arginine/serine-rich (TOPORS), TNF receptor-associated factor 7 (TRAF7), and tripartite motif containing 27 (TRIM27) have dual functions as ubiquitin E3 ligases. Here, we demonstrate that the ubiquitin E3 ligase UHRF2 also acts as a SUMO E3 ligase. UHRF2 effectively enhances zinc finger protein 131 (ZNF131) SUMOylation but does not enhance ZNF131 ubiquitination. In addition, the SUMO E3 activity of UHRF2 on ZNF131 depends on the presence of SET and RING finger-associated and nuclear localization signal-containing region domains, whereas the critical ubiquitin E3 activity RING domain is dispensable. Our findings suggest that UHRF2 has independent functional domains and regulatory mechanisms for these two distinct enzymatic activities.     

The Drosophila tissue polarity gene starry night encodes a member of the protocadherin family.

The tissue polarity genes control the polarity of hairs, bristles and ommatidia in the adult epidermis of Drosophila. We report here the identification of a new tissue polarity gene named starry night (stan). Mutations in this essential gene alter the polarity of cuticular structures in all regions of the adult body. The detailed polarity phenotype of stan on the wing suggested that it is most likely a component of the frizzled (fz) pathway. Consistent with this hypothesis, stan appears to be downstream of and required for fz function. We molecularly cloned stan and found that it encodes a huge protocadherin containing nine cadherin motifs, four EGF-like motifs, two laminin G motifs, and seven transmembrane domains. This suggests that Stan functions in signal reception, perhaps together with Fz.