Publications

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is caused by mutations in the NOTCH3 gene on chromosome 19. Previous studies showed that NOTCH3 contains mutational hotspots that can vary among individuals of different ethnic backgrounds. In this study, we investigated the spectrum of NOTCH3 mutations in Korean patients with CADASIL. We retrospectively analyzed 156 patients who underwent NOTCH3 gene testing for molecular diagnosis of CADASIL using Sanger sequencing with a tiered approach. First, we screened previously reported mutational hotspots (exons 2-6, 8, 11, 18, 19, and 22). If no mutation was detected and samples were available, we extended our analysis to additional exons (7, 9, 10, 14, 15, 20, 21, 23, and 25). In 45 of 156 patients (28.8%), 29 mutations and 16 novel variants of unknown significance (VUS) were identified. The p.R544C mutation in exon 11 of NOTCH3 was the most frequently observed mutation (n = 8), followed by p.R75P in exon 3 (n = 7), p.R332C in exon 6 (n = 3), p.R54C in exon 2 (n = 2), and p.R90C in exon 3 (n = 2). Among the VUS, p.R1175W in exon 22, p.S414C in exon 8, and p.N1207S in exon 22 were found in 5, 3, and 2 patients, respectively. Other mutations and VUS were observed in 1 patient each. Although this was not a prospective, nationwide cohort study, the results above suggested that the spectrum of NOTCH3 mutations might be different in Koreans than in individuals of Caucasian ethnicity. Therefore, further analysis of Koreans with CADASIL might be necessary to implement a Korean-specific mutation screening paradigm.

Rho kinase (ROCK) isoforms regulate insulin signaling and glucose metabolism negatively or positively in cultured cell lines and skeletal muscle. However, the in vivo function of the ROCK1 isoform in adipose tissue has not been addressed. To determine the specific role of the adipose ROCK1 isoform in the development of insulin resistance and obesity, mice lacking ROCK1 in adipose tissue globally or selectively were studied. Here, we show that insulin's ability to activate IRS-1/PI3K/Akt signaling was greatly enhanced in adipose tissue of ROCK1(-/-) mice compared with wild-type mice. These effects resulted from the inhibitory effect of ROCK1 on insulin receptor action, as evidenced by the fact that IR tyrosine phosphorylation was abolished in ROCK1(-/-) MEF cells when ROCK1 was reexpressed. Consistently, adipose-specific disruption of ROCK1 increased IR tyrosine phosphorylation in adipose tissue and modestly improved sensitivity to insulin in obese mice induced by high-fat feeding. This effect is independent of any changes in adiposity, number or size of adipocytes, and metabolic parameters, including glucose, insulin, leptin, and triglyceride levels, demonstrating a minimal effect of adipose ROCK1 on whole body metabolism. Enzymatic activity of ROCK1 in adipose tissue remained ∼50%, which likely originated from the fraction of stromal vascular cells, suggesting involvement of these cells for adipose metabolic regulation. Moreover, ROCK isoform activities were increased in adipose tissue of diet-induced or genetically obese mice. These data suggest that adipose ROCK1 isoform plays an inhibtory role for the regulation of insulin sensitivity in diet-induced obesity in vivo.

Ingestion of a meal is the greatest challenge faced by glucose homeostasis. The surge of nutrients has to be disposed quickly, as high concentrations in the bloodstream may have pathophysiological effects, and also properly, as misplaced reserves may induce problems in affected tissues. Thus, loss of the ability to adequately dispose of ingested nutrients can be expected to lead to glucose intolerance, and favor the development of pathologies. Achieving interplay of several organs is of upmost importance to maintain effectively postprandial glucose clearance, with the liver being responsible of orchestrating global glycemic control. This dogmatic role of the liver in postprandial insulin sensitivity is tightly associated with the vagus nerve. Herein, we uncover the behaviour of metabolic pathways determined by hepatic parasympathetic function status, in physiology and in pathophysiology. Likewise, the inquiry expands to address the impact of a modern lifestyle, especially one's feeding habits, on the hepatic parasympathetic nerve control of glucose metabolism.

Hwangryunhaedok-tang (Huang-Lian-Jie-Du-Tang in Chinese, Oren-gedoku-to in Japanese) is a traditional herbal medicine with a long history of use for anti-inflammatory purposes. In this study, subchronic toxicity of daily oral administration of a Hwangryunhaedok-tang water extract (HHT) at 0, 250, 750, and 2000mg/kg for 13weeks was examined in rats. Mortality, clinical signs, and changes in body weight, food consumption, clinical signs, ophthalmological examination, urinalysis, hematology, serum biochemistry, gross observation, organ weight, and histopathology were monitored in accordance with Good Laboratory Practice and OECD guidelines. We found no mortality or abnormality in clinical signs, body weight, serum biochemistry, or organ weight in HHT-treated groups in either sex. However, there were significant changes in glucose, bilirubin, urobilinogen, protein (only male) in urine after 2000mg/kg/day HHT treatment for both sexes. In hematological examinations, we found a significant decreased number of red blood cells (RBC), whereas, an increased the mean corpuscular volume, number of platelets, and rate of reticulocyte (RET) after 2000mg/kg/day HHT treatment of male rats. In male and female rats, 750 and 2000mg/kg/day HHT treatment decreased the number of RBC and increased RET. Histopathological examinations revealed stomach mucosal erosion in female rats (2000mg/kg/day). No-observed-adverse-effect levels were established for 750mg/kg HHT in rats under the conditions of this study. However, other toxicological studies are necessary to evaluate the safety of HHT fully.

Obesity-induced endoplasmic reticulum (ER) stress causes chronic inflammation in adipose tissue and steatosis in the liver, and eventually leads to insulin resistance and type 2 diabetes (T2D). The goal of this study was to understand the mechanisms by which administration of bilirubin, a powerful antioxidant, reduces hyperglycemia and ameliorates obesity in leptin-receptor-deficient (db/db) and diet-induced obese (DIO) mouse models. db/db or DIO mice were injected with bilirubin or vehicle ip. Blood glucose and body weight were measured. Activation of insulin-signaling pathways, expression of inflammatory cytokines, and ER stress markers were measured in skeletal muscle, adipose tissue, and liver of mice. Bilirubin administration significantly reduced hyperglycemia and increased insulin sensitivity in db/db mice. Bilirubin treatment increased protein kinase B (PKB/Akt) phosphorylation in skeletal muscle and suppressed expression of ER stress markers, including the 78-kDa glucose-regulated protein (GRP78), CCAAT/enhancer-binding protein (C/EBP) homologous protein, X box binding protein (XBP-1), and activating transcription factor 4 in db/db mice. In DIO mice, bilirubin treatment significantly reduced body weight and increased insulin sensitivity. Moreover, bilirubin suppressed macrophage infiltration and proinflammatory cytokine expression, including TNF-α, IL-1β, and monocyte chemoattractant protein-1, in adipose tissue. In liver and adipose tissue of DIO mice, bilirubin ameliorated hepatic steatosis and reduced expression of GRP78 and C/EBP homologous protein. These results demonstrate that bilirubin administration improves hyperglycemia and obesity by increasing insulin sensitivity in both genetically engineered and DIO mice models. Bilirubin or bilirubin-increasing drugs might be useful as an insulin sensitizer for the treatment of obesity-induced insulin resistance and type 2 diabetes based on its profound anti-ER stress and antiinflammatory properties.

The homeostatic balance of hepatic glucose utilization, storage, and production is exquisitely controlled by hormonal signals and hepatic carbon metabolism during fed and fasted states. How the liver senses extracellular glucose to cue glucose utilization versus production is not fully understood. We show that the physiologic balance of hepatic glycolysis and gluconeogenesis is regulated by Bcl-2-associated agonist of cell death (BAD), a protein with roles in apoptosis and metabolism. BAD deficiency reprograms hepatic substrate and energy metabolism toward diminished glycolysis, excess fatty acid oxidation, and exaggerated glucose production that escapes suppression by insulin. Genetic and biochemical evidence suggests that BAD's suppression of gluconeogenesis is actuated by phosphorylation of its BCL-2 homology (BH)-3 domain and subsequent activation of glucokinase. The physiologic relevance of these findings is evident from the ability of a BAD phosphomimic variant to counteract unrestrained gluconeogenesis and improve glycemia in leptin-resistant and high-fat diet models of diabetes and insulin resistance.

PURPOSE: To investigate the effectiveness of respiratory guidance system in 4-dimensional computed tomography (4 DCT) based respiratory-gated radiation therapy (RGRT) by comparing respiratory signals and dosimetric analysis of treatment plans.

METHODS: The respiratory amplitude and period of the free, the audio device-guided, and the complex system-guided breathing were evaluated in eleven patients with lung or liver cancers. The dosimetric parameters were assessed by comparing free breathing CT plan and 4 DCT-based 30-70% maximal intensity projection (MIP) plan.

RESULTS: The use of complex system-guided breathing showed significantly less variation in respiratory amplitude and period compared to the free or audio-guided breathing regarding the root mean square errors (RMSE) of full inspiration (P = 0.031), full expiration (P = 0.007), and period (P = 0.007). The dosimetric parameters including V(5 Gy), V(10 Gy), V(20 Gy), V(30 Gy), V(40 Gy), and V(50 Gy) of normal liver or lung in 4 DCT MIP plan were superior over free breathing CT plan.

CONCLUSIONS: The reproducibility and regularity of respiratory amplitude and period were significantly improved with the complex system-guided breathing compared to the free or the audio-guided breathing. In addition, the treatment plan based on the 4D CT-based MIP images acquired with the complex system guided breathing showed better normal tissue sparing than that on the free breathing CT.

Hypothalamic leptin signaling plays a central role in maintaining body weight homeostasis. Here, we show that clusterin/ApoJ, recently identified as an anorexigenic neuropeptide, is an important regulator in the hypothalamic leptin signaling pathway. Coadministration of clusterin potentiates the anorexigenic effect of leptin and boosts leptin-induced hypothalamic Stat3 activation. In cultured neurons, clusterin enhances receptor binding and subsequent endocytosis of leptin. These effects are mainly mediated through the LDL receptor-related protein-2 (Lrp2). Notably, inhibition of hypothalamic clusterin, Lrp2 or endocytosis abrogates anorexia and hypothalamic Stat3 activation caused by leptin. These findings propose a novel regulatory mechanism in central leptin signaling pathways.

BACKGROUND: The aim of this study was to examine whether formal and informal social activities are associated with a lower risk of depression. Besides, we investigated which type of social activities may protect against late-life depression by gender using data from a population-based study of older Korean adults.

METHODS: Data for analysis were drawn from the 2010 Korean Longitudinal Study of Aging. Study sample included 3968 Korean adults aged ≥ 65 years. Depression was measured using the 10-item Center for Epidemiological Studies. Depression scale. Multivariate logistic regression analyses were used.

RESULTS: Among the informal activities, frequent contact by phone or letters with adult children is significantly associated with a lower risk of depression among older Korean adults, even after adjusting for potentially confounding factors. Face to face contact with close friends was negatively associated with depression in women, but not in men. Face to face contacts with adult children were not significantly associated with depression. All of formal social activities (attending religious activities, volunteering, and participating in alumni society or family councils, political or interest groups) were not significantly associated with depression in both men and women.

CONCLUSIONS: Informal social activities (contact by phone/letters with children and contact with friends) may have a greater impact on geriatric depression than formal social activities in this population. Researchers need to consider gender differences when examining the relationship between social activity and depression. More research is warranted to examine the direction of associations between particular types of social activities and late-life depression across time.

Chronic exercise training results in numerous skeletal muscle adaptations, including increases in insulin sensitivity and glycogen content. To understand the mechanism leading to increased muscle glycogen, we studied the effects of exercise training on glycogen regulatory proteins in rat skeletal muscle. Female Sprague Dawley rats performed voluntary wheel running for 1, 4 or 7 weeks. After 7 weeks of training, insulin-stimulated glucose uptake was increased in epitrochlearis muscle. As compared with sedentary control rats, muscle glycogen did not change after 1 week of training, but increased significantly after 4 and 7 weeks. The increases in muscle glycogen were accompanied by elevated glycogen synthase activity and protein expression. To assess the regulation of glycogen synthase, we examined its major activator, protein phosphatase 1 (PP1), and its major deactivator, glycogen synthase kinase (GSK)-3. Consistent with glycogen synthase activity, PP1 activity was unchanged after 1 week of training but significantly increased after 4 and 7 weeks of training. Protein expression of R(GL)(G(M)), another regulatory PP1 subunit, significantly decreased after 4 and 7 weeks of training. Unlike PP1 activity, GSK-3 phosphorylation did not follow the pattern of glycogen synthase activity. The   40% decrease in GSK-3α phosphorylation after 1 week of exercise training persisted until 7 weeks, and may function as a negative feedback mechanism in response to elevated glycogen. Our findings suggest that exercise training-induced increases in muscle glycogen content could be regulated by multiple mechanisms, including enhanced insulin sensitivity, glycogen synthase expression, allosteric activation of glycogen synthase, and PP1 activity.