Jung Hun Ohn

10-year trajectory of β-cell function and insulin sensitivity in the development of type 2 diabetes: a community-based prospective cohort study

BACKGROUND The relative contributions of β-cell function and insulin sensitivity in the pathogenesis of type 2 diabetes are not fully understood. We investigated the longitudinal change in β-cell function and insulin sensitivity in the development of diabetes and the role of genetic variants in deterioration of glucose tolerance. METHODS We followed up 4106 participants with normal glucose tolerance (NGT) from the Korean Genome and Epidemiology Study with oral glucose tolerance tests every 2 years for 10 years. We estimated pancreatic β-cell function with the 60 min insulinogenic index (IGI60) and insulin sensitivity with the composite (Matsuda) insulin sensitivity index (ISI). We investigated the association of 66 known type 2 diabetes genetic variants with risk of prediabetes or diabetes and impaired β-cell function and insulin sensitivity. FINDINGS During 10 years of follow-up, 1093 (27%) of 4106 participants developed prediabetes and 498 (12%) participants developed diabetes. Compared with participants who remained NGT, those who progressed to diabetes had a lower IGI60 (unadjusted data 5·1 μU/mmol [95% CI 0·5-56·1] vs 7·9 μU/mmol [0·5-113·8]; p<0·0001) and lower ISI (unadjusted data 8·2 [2·6-26·0] vs 10·0 [3·2-31·6]; p<0·0001) at baseline. Participants who had NGT at 10 years showed a decrease in ISI (adjusted data 10·1 [9·9-10·3] vs 7·4 [7·3-7·6]; p<0·0001) but a compensatory increase in IGI60 (adjusted data 6·9 μU/mmol [6·5-7·2] vs 11·7 μU/mmol [11·2-12·1]; p<0·0001) compared with baseline. By contrast, participants who developed diabetes showed a decrease in ISI (adjusted data 8·4 [8·0-8·7] vs 3·0 [2·8-3·2]; p<0·0001) but no significant compensatory increase (p=0·95) in IGI60. A genetic variant near the glucokinase gene (rs4607517) was significantly associated with progression to prediabetes or diabetes (hazard ratio 1·27, 1·16-1·38; p=1·70 × 10(-7)). INTERPRETATION Decreased β-cell function, which might be determined partly by genetic factors, and impaired β-cell compensation for progressive decline in insulin sensitivity are crucial factors in the deterioration of glucose tolerance. FUNDING South Korean Ministry of Health & Welfare.

Changes of microRNA profile and microRNA-mRNA regulatory network in bones of ovariectomized mice.

Growing evidence shows the possibility of a role of microRNAs (miRNA) in regulating bone mass. We investigated the change of miRNAs and mRNA expression profiles in bone tissue in an ovariectomized mice model and evaluated the regulatory mechanism of bone mass mediated by miRNAs in an estrogen‐deficiency state. Eight‐week‐old female C3H/HeJ mice underwent ovariectomy (OVX) or sham operation (Sham‐op), and their femur and tibia were harvested to extract total bone RNAs after 4 weeks for microarray analysis. Eight miRNAs (miR‐127, ‐133a, ‐133a*, ‐133b, ‐136, ‐206, ‐378, ‐378*) were identified to be upregulated after OVX, whereas one miRNA (miR‐204) was downregulated. Concomitant analysis of mRNA microarray revealed that 658 genes were differentially expressed between OVX and Sham‐op mice. Target prediction of differentially expressed miRNAs identified potential targets, and integrative analysis using the mRNA microarray results showed that PPARγ and CREB pathways are activated in skeletal tissues after ovariectomy. Among the potential candidates of miRNA, we further studied the role of miR‐127 in vitro, which exhibited the greatest changes after OVX. We also studied the effects of miR‐136, which has not been studied in the context of bone mass regulation. Transfection of miR‐127 inhibitor has enhanced osteoblastic differentiation in UAMS‐32 cells as measured by alkaline phosphatase activities and mRNA expression of osteoblast‐specific genes, whereas miR‐136 precursor has inhibited osteoblastic differentiation. Furthermore, transfection of both miR‐127 and miR‐136 inhibitors enhanced the osteocyte‐like morphological changes and survival in MLO‐Y4 cells, whereas precursors of miR‐127 and ‐136 have aggravated dexamethasone‐induced cell death. Both of the precursors enhanced osteoclastic differentiation in bone marrow macrophages, indicating that both miR‐127 and ‐136 are negatively regulating bone mass. Taken together, these results suggest a novel insight into the association between distinct miRNAs expression and their possible role through regulatory network with mRNAs in the pathogenesis of estrogen deficiency–induced osteoporosis.

A review of the literature on common CYP17A1 mutations in adults with 17-hydroxylase/17,20-lyase deficiency, a case series of such mutations among Koreans and functional characteristics of a novel mutation.

OBJECTIVE 17α-hydroxylase/17,20-lyase deficiency is a rare form of congenital adrenal hyperplasia, characterized by hypertension and sexual infantilism and caused by loss-of-function mutations in CYP17A1. This study investigated the clinical and molecular characteristics of six adults with 17α-hydroxylase/17,20-lyase deficiency and the functional consequences of a novel CYP17A1 mutation. MATERIALS AND METHODS Six phenotypic females, three with 46,XY and three with 46,XX karyotypes, presented with primary amenorrhea and hypertension. All had elevated levels of plasma adrenocorticotropic hormone, serum gonadotropin, progesterone, and 11-deoxycorticosterone, and reduced testosterone and dehydroepiandrosterone sulfate (DHEA-S). All coding exons and flanking intronic sequences of CYP17A1 were directly sequenced using genomic DNA. Wild-type and mutant CYP17A1 cDNAs were inserted into the pcDNA3.1/V5-His-P450c17 vector, and transiently expressed in COS-7 cells. This was followed by an assessment of 17α-hydroxylase and 17,20-lyase activities by measuring the conversions of progesterone to 17-hydroxyprogesterone and 17-hydroxypregnenolone to DHEA. RESULTS The mutation analysis identified one patient with compound heterozygosity for p.H373L and p.W406L, one with compound heterozygosity for p.H373L and p.A174E, three with compound heterozygosity for p.Y329fs and p.H373L, and one with homozygosity for p.H373L. An in vitro functional analysis of the novel p.W406L mutation revealed a complete loss of 17α-hydroxylase/17, 20-lyase activities. CONCLUSIONS p.H373L was the most common mutation among these Korean patients, consistent with the high allele frequency of p.H373L in Chinese and Japanese populations, suggesting possible founder effects in Asian countries. The novel p.W406L mutation caused a complete loss of both catalytic activities, indicating that this amino acid is critical for P450c17 function.

Transformation of Nonfunctioning Pancreatic Neuroendocrine Carcinoma Cells into Insulin Producing Cells after Treatment with Sunitinib

We report a rare case of severe hypoglycemia after sunitinib treatment for pancreatic neuroendocrine carcinoma. We describe the initial clinical presentation, laboratory results, pathologic findings, and managment in a patient with a nonfunctioning pancreatic neuroendocrine carcinoma with liver metastases who developed life threatening hypoglycemia after 2 months of sunitinib therapy. A 46-year-old woman presented to the emergency department with loss of consciousness from hypoglycemia. Serum C-peptide and insulin levels at fasting state revealed that the hypoglycemia resulted from endogenous hyperinsulinemia. She had been diagnosed with nonfunctioning pancreatic neuroendocrine carcinoma based on a biopsy of metastatic cervical lymph node and was being treated with sunitinib, a small molecule tyrosine kinase inhibitor. Immunohistochemical stain of the metastatic liver mass demonstrated that the initially nonfunctioning neuroendocrine carcinoma cells had changed into insulin-producing cells after sunitinib therapy. Transarterial chemoembolization of the liver masses and systemic chemotherapy with streptozotocin/adriamycin relieved the hypoglycemia. A nonfunctioning pancreatic neuroendocrine carcinoma was transformed into an insulin-producing tumor after treatment with sunitinib, causing endogenous hyperinsulinemia and severe hypoglycemia.

Adult multisystem langerhans cell histiocytosis presenting with central diabetes insipidus successfully treated with chemotherapy.

We report the rare case of an adult who was diagnosed with recurrent multisystem Langerhans cell histiocytosis (LCH) involving the pituitary stalk and lung who present with central diabetes insipidus and was successfully treated with systemic steroids and chemotherapy. A 49-year-old man visited our hospital due to symptoms of polydipsia and polyuria that started 1 month prior. Two years prior to presentation, he underwent excision of right 6th and 7th rib lesions for the osteolytic lesion and chest pain, which were later confirmed to be LCH on pathology. After admission, the water deprivation test was done and the result indicated that he had central diabetes insipidus. Sella magnetic resonance imaging showed a mass on the pituitary stalk with loss of normal bright spot at the posterior lobe of the pituitary. Multiple patchy infiltrations were detected in both lung fields by computed tomography (CT). He was diagnosed with recurrent LCH and was subsequently treated with inhaled desmopressin, systemic steroids, vinblastine, and mercaptopurine. The pituitary mass disappeared after two months and both lungs were clear on chest CT after 11 months. Although clinical remission in multisystem LCH in adults is reportedly rare, our case of adult-onset multisystem LCH was treated successfully with systemic chemotherapy using prednisolone, vinblastine, and 6-mercaptopurine, which was well tolerated.

Assessment of Diabetic Polyneuropathy and Autonomic Neuropathy Using Current Perception Threshold in Korean Patients with Diabetes Mellitus

Background The current perception threshold (CPT) could be quantified by stimulating Aβ and C fibers at 2,000 and 5 Hz, respectively. C fibers play a role in the autonomic nervous system and are involved in temperature and pain sensation. We evaluated the usefulness of CPT for diagnosing distal polyneuropathy (DPN) and cardiovascular autonomic neuropathy (CAN) in diabetic patients. Methods The CPT was measured in the index finger (C7 level) and in the third toe (L5 level) in diabetic patients aged 30 to 69 years. We assessed DPN according to the neuropathy total symptom score-6 (NTSS-6) and 10-g monofilament pressure sensation. Subjects with a NTSS-6 >6 or with abnormal 10-g monofilament sensation were defined to have DPN. CAN was evaluated by spectral analysis of heart rate variability and by Ewings traditional tests. Results The subjects with DPN had significantly higher CPT at all of the frequencies than the subjects without DPN (P<0.05). Abnormal 10-g monofilament sensation and NTSS-6 >6 could be most precisely predicted by CPT at 2,000 and 5 Hz, respectively. However, only 6.5% and 19.6% of subjects with DPN had an abnormal CPT at 2,000 Hz at the C7 and L5 levels. Although CPT at 5 Hz showed a negative correlation with the power of low and high frequency in the spectral analysis (P<0.05), only 16.7% of subjects with CAN exhibited an abnormal CPT at the same frequency. Conclusion Although the CPT is significantly associated with neuropathic symptoms or signs corresponding to the nerve fiber stimulated, it provides little additional information compared with conventional evaluations.

Expression of Thyroid Stimulating Hormone Receptor mRNA in Mouse C2C12 Skeletal Muscle Cells

Background We analyzed whether thyroid stimulating hormone receptor (TSH-R) is expressed in a skeletal muscle cell line and if TSH has influence on the differentiation of muscle cells or on the determination of muscle fiber types. Methods TSH-R gene expression was detected with nested real-time polymerase chain reaction (RT-PCR) in C2C12, a mouse skeletal muscle cell line. The effect of TSH on myotube differentiation was assessed by microscopic examination of myotube formation and through the measurement of expression of muscle differentiation markers, i.e., myogenin and myoD, and muscle type-specific genes, i.e., MyHC1, MyHC2a, and MyHC2b, with quantitative RT-PCR before and after incubation of C2C12 myotube with TSH. Results TSH-R was expressed in the mouse skeletal muscle cell line. However, treatment with TSH had little effect on the differentiation of muscle cells, although the expression of the muscle differention marker myogenin was significantly increased after TSH treatment. Treatment of TSH did not affect the expression of muscle type-specific genes. Conclusion TSH-R is expressed in a mouse skeletal muscle cell line, but the role of TSH receptor signaling in skeletal muscle needs further investigation.

Carnitine induces autophagy and restores high-fat diet-induced mitochondrial dysfunction

OBJECTIVE Autophagy is suppressed in skeletal muscle and the liver with insulin resistance induced by a high-fat diet. Autophagy is essential for maintaining mitochondrial function, and dysfunctional mitochondria are associated with insulin resistance. As carnitine treatment is well known to improve insulin resistance by promoting mitochondrial function, we investigated if carnitine affects autophagy in the skeletal muscle of a high-fat diet-induced rodent model of obesity. RESULTS After 6weeks on a high-fat diet (48kcal% fat), mice developed glucose intolerance, and the gastrocnemius muscle showed a decrease in insulin signaling and mitochondrial function, which was reversed after carnitine (100mg/kg/day) treatment by oral gavage for 2weeks. Swollen mitochondria with destroyed cristae were observed in the skeletal muscle of high-fat diet-fed mice but were not there after carnitine treatment. High-fat diet decreased LC3B-II, a marker of autophagosome formation, and increased sequestosome 1 (SQSTM1), expression of which was reversed after carnitine treatment. In C2C12 myotubes, prolonged treatment with palmitate suppressed autophagy, which was relieved by carnitine treatment. However, the induction of autophagy by carnitine in C2C12 myotubes was not observed after knock-down of peroxisome proliferator-activated receptor γ (PPARγ), which is known to regulate autophagy. CONCLUSION We conclude that the removal of dysfunctional mitochondria by induction of autophagy through PPARγ may be a novel mechanism by which carnitine improves insulin resistance and mitochondrial dysfunction in obesity.

DNA methylation profiles in sibling pairs discordant for intrauterine exposure to maternal gestational diabetes

ABSTRACT Intrauterine exposure to hyperglycemia is reported to confer increased metabolic risk in later life, supporting the ‘developmental origins of health and disease’ hypothesis. Epigenetic alterations are suggested as one of the possible underlying mechanisms. In this study, we compared pairwise DNA methylation differences between siblings whose intrauterine exposure to maternal gestational diabetes (GDM) were discordant. Methylation of peripheral blood DNA of 18 sibling pairs was measured using Infinium HumanMethylation450 BeadChip assays. Of the 465,447 CpG sites analyzed, 12 showed differential methylation (false discovery rate <0.15), including markers within genes associated with monogenic diabetes (HNF4A) or obesity (RREB1). The overall methylation at HNF4A showed inverse correlations with mRNA expression levels, though non significant. In a gene set enrichment analysis, metabolism and signal transduction pathways were enriched. In conclusion, we found DNA methylation markers associated with intrauterine exposure to maternal GDM, including those within genes previously implicated in diabetes or obesity.

Unprotected daily sun exposure is differently associated with central adiposity and beta-cell dysfunction by gender: The Korean national health and nutrition examination survey (KNHANES) V

BACKGROUND Ultraviolet irradiation by sun exposure has been associated with both harms and benefits to metabolic health. OBJECTIVE The objective of this study was to determine whether unprotected daily sun exposure is associated with the prevalence of diabetes and explore the underlying mechanism. METHODS We analyzed the Korean National Health and Nutrition Survey V from 2010 to 2011. Participants 19-60 years of age were asked about the average amount of time they had been exposed to direct sunlight per day since the age of 19. We categorized participants into three groups with different levels of lifetime daily sun exposure and explored the association of sun exposure with the prevalence of diabetes. RESULTS The risk of diabetes was higher in subjects with more than 5h of unprotected sun exposure per day, with an odds ratio of 2.39 (95% CI 1.75-3.25), compared to those with less than 2h of sun exposure, and the association remained significant after adjusting for diabetes risk factors. Long-term sun exposure was associated with increased central obesity and the possibility of an increase in visceral adiposity, especially among women, and with decrease in beta cell function and peripheral adiposity or percent body fat in men. CONCLUSIONS Our study provides a cutoff for upper limit of sun exposure and suggests unprotected daily sun exposure for more than 5h should be avoided to prevent diabetes. Increased central adiposity and decreased beta cell function were observed in women and men, respectively, who had long-term unprotected daily sun exposure.