Yea Eun Kang

The Roles of Adipokines, Proinflammatory Cytokines, and Adipose Tissue Macrophages in Obesity-Associated Insulin Resistance in Modest Obesity and Early Metabolic Dysfunction

The roles of adipokines, proinflammatory cytokines, and adipose tissue macrophages in obesity-associated insulin resistance have been explored in both animal and human studies. However, our current understanding of obesity-associated insulin resistance relies on studies of artificial metabolic extremes. The purpose of this study was to explore the roles of adipokines, proinflammatory cytokines, and adipose tissue macrophages in human patients with modest obesity and early metabolic dysfunction. We obtained omental adipose tissue and fasting blood samples from 51 females undergoing gynecologic surgery. We investigated serum concentrations of proinflammatory cytokines and adipokines as well as the mRNA expression of proinflammatory and macrophage phenotype markers in visceral adipose tissue using ELISA and quantitative RT-PCR. We measured adipose tissue inflammation and macrophage infiltration using immunohistochemical analysis. Serum levels of adiponectin and leptin were significantly correlated with HOMA-IR and body mass index. The levels of expression of MCP-1 and TNF-α in visceral adipose tissue were also higher in the obese group (body mass index ≥ 25). The expression of mRNA MCP-1 in visceral adipose tissue was positively correlated with body mass index (r = 0.428, p = 0.037) but not with HOMA-IR, whereas TNF-α in visceral adipose tissue was correlated with HOMA-IR (r = 0.462, p = 0.035) but not with body mass index. There was no obvious change in macrophage phenotype or macrophage infiltration in patients with modest obesity or early metabolic dysfunction. Expression of mRNA CD163/CD68 was significantly related to mitochondrial-associated genes and serum inflammatory cytokine levels of resistin and leptin. These results suggest that changes in the production of inflammatory biomolecules precede increased immune cell infiltration and induction of a macrophage phenotype switch in visceral adipose tissue. Furthermore, serum resistin and leptin have specific roles in the regulation of adipose tissue macrophages in patients with modest obesity or early metabolic dysfunction.

Comparison of serum Neuregulin 4 (Nrg4) levels in adults with newly diagnosed type 2 diabetes mellitus and controls without diabetes

We explored the role of Neuregulin 4 (Nrg4), a newly described factor secreted by adipose tissue, by measuring serum Nrg4 levels in humans. Circulating Nrg4 levels were significantly higher in patients with diabetes mellitus compared with controls without diabetes and were correlated with the serum glucose level and insulin resistance.

Urinary Chiro- and Myo-Inositol Levels as a Biological Marker for Type 2 Diabetes Mellitus

Background: The aim of this study was to investigate the role of the urinary chiro- and myo-inositol levels in predicting type 2 diabetes mellitus (T2DM). Subjects and methods: A total of 212 normal controls and 101 type 2 diabetic patients were enrolled this study. The concentrations of urinary chiro- and myo-inositol were measured by high performance liquid chromatography/mass spectrometry. Results: The concentration of urinary chiro-inositol was significantly higher in the diabetic subjects (2.24 ± 5.18 ng/L) than those in the control group (0.38 ± 0.62 ng/L; p < 0.001). The urinary myo-inositol level of the diabetic subjects (36.95 ± 37.77 ng/L) was also significantly higher than that of the controls (8.17 ± 13.29 ng/L; p < 0.001). The urinary chiro-inositol multiplied by myo-inositol level of the diabetic subjects (148.10 ± 544.91) was significantly higher than in the controls (5.12 ± 24.15; p < 0.001). The area under the receiver operating characteristic curve for the urinary chiro-inositol multiplied by myo-inositol level to predict T2DM was 0.840 (confidence interval 0.789–0.891, p < 0.001). The cut-off value for the urinary chiro-inositol multiplied by myo-inositol level to predict T2DM was 2.20 (sensitivity 81.3%, specificity 70.3%). Conclusions: The urinary chiro- and myo-inositol concentrations were increased in the type 2 diabetic patients and the urinary chiro- times the myo-inositol was considered to be a sufficient marker in predicting T2DM.

Association between Growth Differentiation Factor 15 (GDF15) and Cardiovascular Risk in Patients with Newly Diagnosed Type 2 Diabetes Mellitus

We investigated an association between serum Growth Differentiation Factor 15 (GDF15) level and cardiovascular risk in patients with newly diagnosed type 2 diabetes mellitus (T2D). A total of 107 participants were screened for T2D and divided into a T2D group and a control group (without diabetes). We used the Framingham risk score (FRS) and the New Pooled Cohort Equation score to estimate the 10-year risk of atherosclerotic cardiovascular disease. Serum GDF15 levels were measured using an enzyme-linked immunosorbent assay. Correlation analyses were performed to evaluate the associations between GDF15 level and cardiovascular risk scores. The mean serum GDF15 level was elevated in the T2D group compared to the control group (P < 0.001). A positive correlation was evident between serum GDF15 level and age (r = 0.418, P = 0.001), the FRS (r = 0.457, P < 0.001), and the Pooled Cohort Equation score (r = 0.539, P < 0.001). After adjusting for age, LDL-C level, and body mass index (BMI), the serum GDF15 level was positively correlated with the FRS and the New Pooled Cohort Equation score. The serum GDF15 level is independently associated with cardiovascular risk scores of newly diagnosed T2D patients. This suggests that the level of GDF15 may be a useful predictive biomarker of cardiovascular risk in newly diagnosed T2D patients.

Defective ciliogenesis in thyroid hürthle cell tumors is associated with increased autophagy

Primary cilia are found in the apical membrane of thyrocytes, where they may play a role in the maintenance of follicular homeostasis. In this study, we examined the distribution of primary cilia in the human thyroid cancer to address the involvement of abnormal ciliogenesis in different thyroid cancers. We examined 92 human thyroid tissues, including nodular hyperplasia, Hashimotos thyroiditis, follicular tumor, Hürthle cell tumor, and papillary carcinoma to observe the distribution of primary cilia. The distribution and length of primary cilia facing the follicular lumen were uniform across variable-sized follicles in the normal thyroid gland. However, most Hürthle cells found in benign and malignant thyroid diseases were devoid of primary cilia. Conventional variant of papillary carcinoma (PTC) displayed longer primary cilia than those of healthy tissue, whereas both the frequency and length of primary cilia were decreased in oncocytic variant of PTC. In addition, ciliogenesis was markedly defective in primary Hürthle cell tumors, including Hürthle cell adenomas and carcinomas, which showed higher level of autophagosome biogenesis. Remarkably, inhibition of autophagosome formation by Atg5 silencing or treatment with pharmacological inhibitors of autophagosome formation restored ciliogenesis in the Hürthle cell carcinoma cell line XTC.UC1 which exhibits a high basal autophagic flux. Moreover, the inhibition of autophagy promoted the accumulation of two factors critical for ciliogenesis, IFT88 and ARL13B. These results suggest that abnormal ciliogenesis, a common feature of Hürthle cells in diseased thyroid glands, is associated with increased basal autophagy.

Mitochondrial Energy Metabolism and Thyroid Cancers

Primary thyroid cancers including papillary, follicular, poorly differentiated, and anaplastic carcinomas show substantial differences in biological and clinical behaviors. Even in the same pathological type, there is wide variability in the clinical course of disease progression. The molecular carcinogenesis of thyroid cancer has advanced tremendously in the last decade. However, specific inhibition of oncogenic pathways did not provide a significant survival benefit in advanced progressive thyroid cancer that is resistant to radioactive iodine therapy. Accumulating evidence clearly shows that cellular energy metabolism, which is controlled by oncogenes and other tumor-related factors, is a critical factor determining the clinical phenotypes of cancer. However, the role and nature of energy metabolism in thyroid cancer remain unclear. In this article, we discuss the role of cellular energy metabolism, particularly mitochondrial energy metabolism, in thyroid cancer. Determining the molecular nature of metabolic remodeling in thyroid cancer may provide new biomarkers and therapeutic targets that may be useful in the management of refractory thyroid cancers.

Morphological and Functional Changes in the Thyroid Follicles of the Aged Murine and Humans

Background Although both thyroid histology and serum concentrations of hormones are known to change with age, only a few reports exist on the relationship between the age-related structural and functional changes of the thyroid follicles in both mice and humans. Our objectives were to investigate age-related histological changes of the thyroid follicles and to determine whether these morphological changes were associated with the functional activity of the follicles. Methods The thyroid glands of mice at 18 weeks and at 6, 15, and 30 months of age were histologically examined, and the serum levels of thyroid hormones were measured in 11-week-old and 20-month-old mice. Samples of human thyroid tissue from 10 women over 70 years old and 10 women between 30 and 50 years of age were analyzed in conjunction with serum thyroid hormone level. Results The histological and functional changes observed in the thyroid follicles of aged mice and women were as follows: variable sizing and enlargement of the follicles; increased irregularity of follicles; Sanderson’s polsters in the wall of large follicles; a large thyroglobulin (Tg) globule or numerous small fragmented Tg globules in follicular lumens; oncocytic change in follicular cells; and markedly dilated follicles empty of colloid. Serum T3 levels in 20-month-old mice and humans were unremarkable. Conclusions Thyroid follicles of aged mice and women show characteristic morphological changes, such as cystic atrophy, empty colloid, and Tg globules.

A Novel PHEX Gene Mutation in a Patient with Sporadic Hypophosphatemic Rickets

Phosphate regulating gene with homologies to endopeptidases on the X-chromosome (PHEX) is a common cause of X-linked hypophosphatemic (XLH) rickets. Diverse PHEX gene mutations have been reported; however, gene mutations in sporadic rickets are less common than in XLH rickets. Herein, we describe a 50-year-old female patient with sporadic hypophosphatemic rickets harboring a novel splicing-site mutation in the PHEX gene (c.663+1G>A) at the exon 5-intron 5 boundary. The patient had recently suffered from right thigh pain and an aggravated waddling gait. She also presented with very short stature, generalized bone pain, and muscle weakness. Despite low serum phosphate levels, her phosphate reabsorption rate was lower than normal. Additionally, her 1,25-dihydroxyvitamin D3 concentration was lower than normal, although FGF23 level was normal. After treatment with alfacalcidol and elemental phosphate, her rachitic symptoms subsided, and callus formation was observed in the fracture site on the right femur.

Serum Meteorin-like protein levels decreased in patients newly diagnosed with type 2 diabetes.

We analyzed circulating Meteorin-like (METRNL) levels in human. Serum METRNL levels were significantly lower in subjects with diabetes mellitus compared with those without diabetes. Serum METRNL was negatively correlated with the serum glucose level and insulin resistance. Metformin treatment did not increase the serum METRL levels after 12 weeks.

Regeneration of thyroid follicles from primordial cells in a murine thyroidectomized model

The functional unit of the thyroid gland, the thyroid follicle, dynamically responds to various stimuli to maintain thyroid hormone homeostasis. However, thyroid follicles in the adult human thyroid gland have a very limited regenerative capacity following partial resection of the thyroid gland. To gain insight into follicle regeneration in the adult thyroid gland, we observed the regeneration processes of murine thyroid follicles after partial resection of the lower third of the thyroid gland in 10-week-old male C57BL/6 mice. Based on sequential observation of the partially resected thyroid lobe, we found primitive follicles forming in the area corresponding to the central zone of the intact lateral thyroid lobe. The primitive thyroid follicles were multiciliated and had coarsely vacuolated cytoplasm and large vesicular nuclei. Consistently, these primitive follicular cells did not express the differentiation markers paired box gene-8 and thyroid transcription factor-1 (clone SPT24), but were positive for forkhead box protein A2 and leucine-rich repeat-containing G-protein-coupled receptor 4/GPR48. Follicles newly generated from the primitive follicles had clear or vacuolar cytoplasm with dense, darkly stained nuclei. At day 21 after partial thyroidectomy, the tall cuboidal follicular epithelial cells had clear or vacuolar cytoplasm, and the intraluminal colloid displayed pale staining. Smaller activated follicles were found in the central zone of the lateral lobe, whereas larger mature follicles were located in the peripheral zone. Based on these observations, we propose that the follicle regeneration process in the partially resected adult murine thyroid gland associated with the appearance of primitive follicular cells may be a platform for the budding of differentiated follicles in mice.