The effect of PPARγ agonist on SGLT2 and glucagon expressions in alpha cells under hyperglycemia.

BACKGROUND: Although sodium glucose cotransporter 2 (SGLT2) inhibitors have many beneficial effects for type 2 diabetes, including decreased cardiovascular death, recent reports that they increased glucagon through SGLT2 inhibition raised some concern. Troglitazone, Peroxisome proliferator-activated receptor γ (PPAR-γ) agonist, was reported to increase SGLT2 in renal proximal tubule cells, but its role on pancreatic alpha cells have not been reported. We investigated the effect of troglitazone on SGLT2 expression in alpha cells and subsequent glucagon regulation in hyperglycemia. METHODS: An Alpha TC1-6 cell line was cultured in control (5 mM) or hyperglycemia (HG, 15 mM) for 72 h. We applied troglitazone with or without PPARγ antagonist (GW9662 10 µM). To investigate the involvement of PI3K/Akt pathway, we applied troglitazone with or without Wortmanin. We measured sodium glucose transporter 2 (SGLT2) and glucagon (GCG) mRNA and protein expression. PPAR gamma, PI3K and Akt protein were also measured. RESULTS: Exposure of alpha TC cells to HG for 72 h increased glucagon mRNA and protein expression. HG decreased SGLT2 mRNA and protein expression. Troglitazone significantly reversed HG-induced reduction of SGLT2 expression and increase of glucagon secretion. PPARγ antagonist (GW9662 10 µM) decreased the expression of SGLT2 and increased glucagon as HG did. Hyperglycemia increased PI3K and pAkt expression in alpha cells. Wortmanin (PI3K inhibitor, 1 µM) reversed HG-induced SGLT2 decrease and glucagon increase. Troglitazone treatment decreased PI3K and pAkt expression in HG. CONCLUSION: In conclusion, PPARγ agonist, troglitazone improved glucose transport SGLT2 dysfunction and subsequent glucagon dysregulation in alpha cell under hyperglycemia. Those effects were through the involvement of PI3K/pAkt signaling pathway. This study may add one more reason for the ideal combination of PPARγ agonist and SGLT2 inhibitor in clinical practice.

Mitochondrial modulation decreases the bortezomib-resistance in multiple myeloma cells.

Multiple myeloma (MM) is an incurable hematological malignancy that causes most patients to eventually relapse and die from their disease. The 20S proteasome inhibitor bortezomib has emerged as an effective drug for MM treatment; however, intrinsic and acquired resistance to bortezomib has already been observed in MM patients. We evaluated the involvement of mitochondria in resistance to bortezomib-induced cell death in two different MM cell lines (bortezomib-resistant KMS20 cells and bortezomib-sensitive KMS28BM cells). Indices of mitochondrial function, including membrane potential, oxygen consumption rate and adenosine-5'-triphosphate and mitochondrial Ca(2+) concentrations, were positively correlated with drug resistance of KMS cell lines. Mitochondrial genes including CYPD, SOD2 and MCU were differentially expressed in KMS cells. Thus, changes in the expression of these genes lead to changes in mitochondrial activity and in bortezomib susceptibility or resistance, and their combined effect contributes to differential sensitivity or resistance of MM cells to bortezomib. In support of this finding, coadministration of bortezomib and 2-methoxyestradiol, a SOD inhibitor, rendered KMS20 cells sensitive to apoptosis. Our results provide new insight into therapeutic modalities for MM patients. Studying mitochondrial activity and specific mitochondrial gene expression in fresh MM specimens might help predict resistance to proapoptotic chemotherapies and inform clinical decision-making.

A decision tree-based approach for identifying urban-rural differences in metabolic syndrome risk factors in the adult Korean population.

AIM: The purpose of this study was to explore the difference in the pattern of metabolic syndrome (MetS) in urban and rural populations in Korea using data mining techniques. SUBJECTS AND METHODS: In total, 1013 adults >30 yr of age from urban (184 males and 313 females) and rural districts (211 males and 305 females) were recruited from Gyeongsangnam-do, Korea. Modified National Cholesterol Education Program Adult Treatment Panel III criteria were used to identify individuals with MetS. We applied a decision tree analysis to elucidate the differences in the clustering of MetS components between the urban and rural populations. RESULTS: The prevalence of MetS was 33.2% and 35.2% in urban and rural districts, respectively (p=0.598). The decision-tree approach revealed that the combination of high serum triglycerides (TG) + high systolic blood pressure (SBP), high TG + low HDL cholesterol, and high waist circumference (WC) + high SBP + high fasting plasma glucose (FPG) were strong predictors of MetS in the urban population, whereas the combination of TG + SBP + WC and SBP + WC + FPG showed high positive predictive value for the presence of MetS in the rural population. CONCLUSIONS: Although no significant difference was found for the prevalence of MetS between the two populations, the differences in the clustering pattern of MetS components in urban and rural districts in Korea were identified by decision tree analysis. Our findings may serve as a basis to design necessary population-based intervention programs for prevention and progression of MetS and its complications in Korea.

Depressive symptoms of type 2 diabetics treated with insulin compared to diabetics taking oral anti-diabetic drugs: a Korean study.

OBJECTIVE: The purpose of this study was to examine the depressive symptoms of type 2 diabetic patients who were treated with insulin compared to those diabetics treated with oral anti-diabetic drugs in Korea. METHODS: A total 204 outpatients with type 2 diabetes were invited to complete a questionnaire using the Beck depression inventory (BDI) to measure depressive symptoms. Age, gender, body mass index, serum lipid profile, and a social history including marital status, occupation and educational background were also assessed. The presence of diabetic complications was evaluated by examining the patients' medical records. Diabetic patients who were not treated with anti-diabetic drugs were excluded. All the study subjects were classified into two groups based on their mode of therapy: the oral drug group and insulin group. The insulin group included patients treated with insulin-oral drug combinations as well as those treated solely with insulin. RESULTS: Overall, 32.4% of our diabetic subjects showed depressive symptoms with the criterion being a BDI score > or = 16. Compared to the oral drug group, the insulin group showed a significantly higher frequency of depressive symptoms (insulin group, 48.0%; oral drug group, 27.3%; p<0.01) and higher BDI scores (insulin group, 16.6+/-10.7; oral drug group, 12.6+/-8.7; p<0.01). Moreover, after an adjustment for social factors, the degree of hyperglycemia and the presence of diabetic complications, the insulin group showed a significantly higher frequency of depression (odds ratio 4.38, 95% CI 1.66-11.6, p=0.003), compared to the oral drug group. CONCLUSIONS: The data showed that insulin treatment is related to the presence of depressive symptoms, and the importance of more careful psychological support of Korean insulin-treated type 2 diabetic patients is strongly suggested.

Hyperglycemia per se can reduce plasma free fatty acid and glycerol levels in the acutely insulin-deficient dog.

To evaluate the in vivo effect of hyperglycemia per se on plasma free fatty acid (FFA) and glycerol concentrations, euglycemic and hyperglycemic clamp studies were performed in six overnight fasted dogs in the state of insulin deficiency produced by somatostatin (SRIF) infusion. The mean blood glucose concentrations during the steady-state (the second hour of each study) averaged 4.65 +/- 0.10 mmol/L in euglycemic clamp and 14.11 +/- 0.10 mmol/L in hyperglycemic clamp. During the SRIF infusion, plasma FFA concentrations increased from 0.32 +/- 0.05 mumol/mL at the basal state to 0.76 +/- 0.04 mumol/mL at the steady-state in euglycemic clamp and from 0.26 +/- 0.04 mumol/mL to 0.43 +/- 0.02 mumol/mL in hyperglycemic clamp. Plasma glycerol concentrations increased from the basal value of 0.07 +/- 0.01 mumol/mL to 0.15 +/- 0.01 mumol/mL during the steady-state in euglycemic clamp and from 0.06 +/- 0.01 mumol/mL to 0.08 +/- 0.01 mumol/mL in hyperglycemic clamp. The steady-state concentrations of plasma FFA and glycerol in hyperglycemic clamp were significantly lower than those in euglycemic clamp (P less than .001; respectively). These results suggest that hyperglycemia per se might decrease plasma FFA and glycerol concentrations at least in part by decreasing lipolysis in the acutely insulin-deficient dog.

Intra-abdominal fat is associated with decreased insulin sensitivity in healthy young men.

To distinguish the relative role of intra-abdominal and subcutaneous abdominal fat in metabolic aberrations in upper body fat localization, we measured the relationship between regional fat distribution and insulin sensitivity in nine young men (28.6 +/- 0.7 years; body mass index [BMI], 24.7 +/- 1.3 kg/m2). Regional fat distribution was measured by anthropometric measurement and computed tomography (CT). Insulin sensitivity was measured by euglycemic hyperinsulinemic glucose clamp. Insulin sensitivity, expressed as the ratio of rate of glucose utilization to the mean plasma insulin concentration during the second hour of glucose clamp (M/I) was negatively correlated with BMI (r = -.91, P less than .001), waist to hip girth ratio (WHR) (r = -.80, P less than .01), subcutaneous abdominal fat area (r = -.90, P less than .001), and intra-abdominal fat area (r = -.88, P less than .01). Stepwise forward regression analysis showed that in addition to BMI, intra-abdominal fat area was a significant correlate of decrease in insulin sensitivity. These findings suggest that intra-abdominal fat play an important role in decreasing insulin sensitivity, even in healthy young men.

Initial role of macrophage in the development of anti-beta-cell cellular autoimmunity in multiple low-dose streptozotocin-induced diabetes in mice.

Multiple injections of low doses of streptozotocin to susceptible strains of mice produce an experimental autoimmune diabetes mellitus. To investigate the possible initial role of macrophages in the development of insulitis, we studied the effect of macrophage-toxic silica administration on the development of in vitro cellular cytotoxic immune response against pancreatic beta-cells. Multiple streptozotocin-treated mice developed hyperglycemia at day 12 and their splenocytes showed cytotoxicity against cultured rat insulinoma cells. Mice given silica and streptozotocin together remained normoglycemic and their splenocytes showed no cytotoxicity. In contrast, in vitro depletion of macrophages from the splenocytes of mice given multiple streptozotocin alone did not abolish the cytotoxicity. These results show that macrophages themselves contribute little to the cellular cytotoxicity, but are necessary for the development of cytotoxic cells. From these results we suggest that there are at least two different steps in the development of insulitis; the presentation of beta-cell autoantigen by macrophages to helper-T cells, followed by the development of beta-cell-specific cytotoxic cells.

Glucose, insulin and C-peptide kinetics during intravenous glucose tolerance test in chronic liver disease.

To elucidate the mechanism of glucose intolerance in chronic liver disease (CLD), the kinetics of plasma glucose, insulin and C-peptide were studied after intravenous glucose loading in patients with CLD. Fasting plasma insulin levels were higher in patients with CLD than in normal subjects. This hyperinsulinemia was attributed primarily to an increased pancreatic secretion of insulin. Patients with CLD were divided into two groups, one with normal fasting plasma glucose (FBS less than 100 mg/dl (Group I) and the other with higher FBS (Group II). In Group I, the glucose disappearance rate was normal and a brisk acute insulin response (AIR) to glucose was noted. The glucose disappearance rate in Group II was lower than that in normal subjects, and AIR to glucose was blunted. It is suggested that normal glucose tolerance in Group I patients could be interpreted as a state of compensation by hypersecretion of insulin. On the other hand, the glucose intolerance in Group II patients could be due to inadequate insulin secretion to overcome insulin resistance of CLD.

Clinical heterogeneity of insulin dependent diabetes mellitus in Korea.

This study was undertaken to find out how many current Korean patients with insulin dependent diabetes mellitus (IDDM) had a previous history of non-insulin requiring phase. Fasting serum C-peptide levels were measured in the 2300 diabetic patients during the visit to the Asan Medical Center, Seoul, Korea. Fifty-nine patients showed fasting serum C-peptide levels below 0.13 nmol/l. These 59 patients were classified further into two groups according to their history of insulin requirement: group A who required insulin within 1 year after diagnosis or presented initially as diabetic ketoacidosis and group B who had non-insulin requiring phase at least for 1 year (median: 5 years; range: 1-23 years). Twenty-six patients (44%) were classified into group A and 27 patients (46%) into group B. Median age of onset was 26 years (range: 10-50 years) and 45 years (range: 23-73 years) in groups A and B, respectively (P < 0.001). While the two groups had similar values in the current and maximum body mass indices, sex ratio and the prevalence of islet cell antibodies, 58% of the group A and 7% of the group B patients had histories of diabetic ketoacidosis. These results suggest a clinical heterogeneity in patients with IDDM in Korea.

Triiodothyronine induces proliferation of pancreatic ß-cells through the MAPK/ERK pathway.

BACKGROUND: 3,5,3'-Triiodothyronine (T3) has a stimulatory effect on cellular growth via thyroid hormone receptors (TRs) in several cell lines. TR expression in the pancreas suggests that pancreatic beta cell proliferation might be induced by T3. The purpose of this study was to demonstrate that T3 induces pancreatic beta cell proliferation through the mitogen activated protein kinase/extracellular regulated kinase (MAPK/ERK) pathway. METHODS: INS-1 cells were plated as a monolayer at densities of 4×104, cultured in RPMI 1,640 with 10% fetal bovine serum with 2-mercaptoethanol, respectively, in 6-well multiplates. After 48 h, they were exposed to 10-7 M T3 or to vehicle alone. Viable cells were harvested after 24, 48, and 72 h of continuous exposure. Cell proliferation and TRα1 and TRß1 expression were analyzed by flow-assisted cell sorting analysis, Ki-67 staining, and Western blotting. The p38 MAPK, ERK, and Akt pathways were analyzed by Western blotting. Beta cell function was evaluated by assaying insulin secretion. RESULTS: T3 enhanced INS-1 cell proliferation at a dose of 10-7 M in a time-dependent manner via the MAPK/ERK pathway and promoted insulin secretion. CONCLUSIONS: Our results demonstrate that MAPK/ERK pathway plays an important role in the T3 induced pancreatic beta cell proliferation.

A Model and Simple Iterative Algorithm For Redundancy Analysis.

Stewart and Love proposed redundancy as an index for measuring the amount of shared variance between two sets of variables. van den Wollenberg presented a method for maximizing redundancy. Johansson extended the approach to include derivation of optimal Y-variates, given the X-variates. This paper shows that redundancy maximization with Johansson's extension can be accomplished via a simple iterative algorithm based on Wold's Partial Least Squares.

HLA and Graves' disease in Koreans.

The HLA-A, B, C and DR antigen distribution in 128 Korean patients with Graves' disease was compared with that in 220 controls. The frequency of HLA-B13, DR5 and DRw8 (relative risk 3.8, 4.4, and 2.3, respectively) was significantly increased in patients with Graves' disease. There was no significant correlation between the presence of these HLA antigens and the clinical features.

RFLP analysis of HLA-DR beta and -DQ beta genes in the Korean patients with insulin-dependent diabetes mellitus.

Human genomic DNA samples from 19 Korean patients and 31 controls of known serological DR antigen specificity were studied for insulin-dependent diabetes mellitus (IDDM)-associated variation in HLA-DR beta and -DQ beta restriction fragment length polymorphisms (RFLPs). Genotyping allowed for accurate assignment of HLA-DR types. For HLA-DRw6, a 12kb/DR beta/Taq I fragment was decreased in Korean IDDM (p less than 0.05). However, we could not find an increased frequency of a 12kb/DQ beta/Bam HI fragment or decreased frequency of a 3.7kb/DQ beta/Bam HI fragment in Korean IDDM. These results suggest a possible protective role of the HLA-DRw6 specificity in IDDM, irrespective of ethnic background, the absence of a specific DQ beta RFLP pattern associated with IDDM in Koreans, and the difference of the Korean population in the genetic of IDDM, compared to the Caucasoid population.

Differing frequency of autoantibodies to glutamic acid decarboxylase among Koreans, Thais, and Australians with diabetes mellitus.

The wide racial-geographic differences in the incidence and prevalence of insulin-dependent diabetes mellitus (IDDM) between Europids and Asian populations prompted us to compare frequencies of positivity of autoantibody to glutamic acid decarboxylase (GAD). The patients with IDDM included 41 Koreans, 30 Thais, and 45 Australian Europids; the Koreans included 14 cases regarded as atypical IDDM by reason of a delayed requirement for insulin treatment. Autoantibodies were measured by radioimmunoprecipitation using iodinated purified porcine brain GAD. The frequency of positive tests for anti-GAD of 30% (8/27) for Koreans and 51% (20/39) for Thais was significantly lower than the 84% (38/45) for Australian Europids, even after stratifying by age of onset. Correspondingly, the mean levels of anti-GAD among seropositive cases were significantly lower for Koreans than for Australian Europids. In contrast to Thais and Australians, more than half the Koreans were diagnosed at age > 20 years, but there was no significant difference in positivity for anti-GAD between those over or under the age of 20 at diagnosis. The different frequency of positivity in tests for anti-GAD among Koreans, Thais, and Australian Europids with IDDM suggests that there is a greater etiologic heterogeneity of IDDM among Asian than Europid populations, in whom autoimmune destruction of pancreatic islets predominates.