Emerging evidence suggests that sphingolipids may be involved in type 2 diabetes. However, the exact signaling defect through which disordered sphingolipid metabolism induces β-cell dysfunction remains unknown. The current study demonstrated that sphingosine-1-phosphate (S1P), the product of sphingosine kinase (SphK), is an essential factor for maintaining β-cell function and survival via regulation of mitochondrial action, as mediated by prohibitin (PHB).
We examined β-cell function and viability, as measured by mitochondrial function, in mouse insulinoma 6 (MIN6) cells in response to manipulation of cellular S1P and PHB levels.
Lack of S1P induced by sphingosine kinase inhibitor (SphKi) treatment caused β-cell dysfunction and apoptosis, with repression of mitochondrial function shown by decreases in cellular adenosine triphosphate content, the oxygen consumption rate, the expression of oxidative phosphorylation complexes, the mitochondrial membrane potential, and the expression of key regulators of mitochondrial dynamics (mitochondrial dynamin-like GTPase [OPA1] and mitofusin 1 [MFN1]). Supplementation of S1P led to the recovery of mitochondrial function and greatly improved β-cell function and viability. Knockdown of SphK2 using small interfering RNA induced mitochondrial dysfunction, decreased glucose-stimulated insulin secretion (GSIS), and reduced the expression of PHB, an essential regulator of mitochondrial metabolism. PHB deficiency significantly reduced GSIS and induced mitochondrial dysfunction, and co-treatment with S1P did not reverse these trends.
Altogether, these data suggest that S1P is an essential factor in the maintenance of β-cell function and survival through its regulation of mitochondrial action and PHB expression.
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The nuclear receptor peroxisome proliferator-activator gamma (PPARγ) is a useful therapeutic target for obesity and diabetes, but its role in protecting β-cell function and viability is unclear.
To identify the potential functions of PPARγ in β-cells, we treated mouse insulinoma 6 (MIN6) cells with the PPARγ agonist pioglitazone in conditions of lipotoxicity, endoplasmic reticulum (ER) stress, and inflammation.
Palmitate-treated cells incubated with pioglitazone exhibited significant improvements in glucose-stimulated insulin secretion and the repression of apoptosis, as shown by decreased caspase-3 cleavage and poly (adenosine diphosphate [ADP]-ribose) polymerase activity. Pioglitazone also reversed the palmitate-induced expression of inflammatory cytokines (tumor necrosis factor α, interleukin 6 [IL-6], and IL-1β) and ER stress markers (phosphor-eukaryotic translation initiation factor 2α, glucose-regulated protein 78 [GRP78], cleaved-activating transcription factor 6 [ATF6], and C/EBP homologous protein [CHOP]), and pioglitazone significantly attenuated inflammation and ER stress in lipopolysaccharide- or tunicamycin-treated MIN6 cells. The protective effect of pioglitazone was also tested in pancreatic islets from high-fat-fed KK-Ay mice administered 0.02% (wt/wt) pioglitazone or vehicle for 6 weeks. Pioglitazone remarkably reduced the expression of ATF6α, GRP78, and monocyte chemoattractant protein-1, prevented α-cell infiltration into the pancreatic islets, and upregulated glucose transporter 2 (Glut2) expression in β-cells. Moreover, the preservation of β-cells by pioglitazone was accompanied by a significant reduction of blood glucose levels.
Altogether, these results support the proposal that PPARγ agonists not only suppress insulin resistance, but also prevent β-cell impairment via protection against ER stress and inflammation. The activation of PPARγ might be a new therapeutic approach for improving β-cell survival and insulin secretion in patients with diabetes mellitus
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Hypertriglyceridemia is known to have an association with increased risks of insulin resistance and diabetes. The aim of this study was to investigate the risk of diabetes mellitus, according to changes in the concentrations of triglycerides, over time.
A total of 15,932 non-diabetic participants (mean age 43.2 years, 68% men) who attended five consecutive annual health check-ups at Kangbuk Samsung Hospital, between January 2010 and December 2014, were recruited. Participants were classified according to their triglyceride concentrations; normal (<150 mg/dL) and abnormal (≥150 mg/dL). According to the triglyceride levels in 2010 and 2012, subjects were divided into four groups: normal-normal, normal-abnormal, abnormal-normal, and abnormal-abnormal. The risk for incident diabetes was assessed in 2014.
Among the total subjects, 67.5% belonged to the normal-normal group, 8.6% to the normal-abnormal group, 9.4% to the abnormal-normal group, and 14.5% to the abnormal-abnormal group. A total of 234 subjects (1.5%) were newly diagnosed with diabetes, between 2010 and 2014. Over 4 years, 1%, 1.5%, 2.1%, and 3.0% of the subjects developed diabetes in the normal-normal, normal-abnormal, abnormal-normal, and abnormal-abnormal groups, respectively. When the risk for incident diabetes was analyzed in the groups, after adjusting the confounding variables, a 1.58-fold increase in the risk of diabetes (95% confidence interval [CI], 1.10 to 2.26) was observed in the participants with persistent hypertriglyceridemia (abnormal-abnormal group). This was attenuated by further adjustments for body mass index (BMI) (hazard ratio, 1.25; 95% CI, 0.86 to 1.80).
In this large study population, persistent hypertriglyceridemia, over a period of 2 years, was significantly associated with the risk of incident diabetes, which was attenuated after adjustment for BMI.
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Age-related decreases in lean mass represent a serious health problem. We aimed to analyze the risks of rapid decreases in lean mass by age and sex in relatively young Korean adults during a 4-year follow-up study.
A total of 65,856 non-diabetic participants (59.5% men, mean age 39.1 years) in a health screening program were subjected to bioimpedance body composition analyses and metabolic parameter analyses at baseline and after 4 years. The participants were sub-divided according to age, and additionally to six groups by age and the degree of body weight change over the 4-year period. The actual changes in body weight, lean mass, and fat mass and the percent changes over the 4-year period were assessed.
The percent change in lean mass decreased and the percent change of fat mass increased with increasing age in every age and sex group. However, the annual percent decrease in lean mass and percent increase in fat mass were significantly higher among women than among men (−0.26% vs. −0.15% and 0.34% vs. 0.42%, respectively;
Even in this relatively young study population, the lean mass decreased significantly with age, and the risk of a rapid decrease in lean mass was higher among women than among men. Furthermore, the elderly exhibited a significantly more rapid decrease in lean mass, compared with younger participants.
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We aimed to assess the risk for coronary artery calcification (CAC) according to groups subdivided by body mass index (BMI) and waist circumference (WC) in apparently healthy Korean adults.
Thirty-three thousand four hundred and thirty-two participants (mean age, 42 years) in a health screening program were divided into three groups according to BMI: <23 kg/m2 (normal), 23 to 25 kg/m2 (overweight), and >25 kg/m2 (obese). In addition, the participants were divided into two groups according to WC. Coronary artery calcium score (CACS) was measured with multi-detector computed tomography in all participants. Presence of CAC was defined as CACS >0.
When logistic regression analysis was performed with the presence of CAC as the dependent variable, the risk for CAC increased as BMI increased after adjusting for confounding variables (1.102 [95% confidence interval (CI), 1.000 to 1.216]; 1.284 [95% CI, 1.169 to 1.410]; in the overweight and obese groups vs. the normal weight group). When the participants were divided into six groups according to BMI and WC, the subjects with BMI and WC in the obese range showed the highest risk for CAC (1.321 [95% CI, 1.194 to 1.461]) and those with BMI in the overweight range and WC in the obese range showed the second highest risk for CAC (1.235 [95% CI, 1.194 to 1.461]).
Participants with obesity defined by both BMI and WC showed the highest risk for CAC. Those with BMIs in the overweight range but with WC in the obese range showed the second highest risk for CAC, suggesting that WC as a marker of obesity is more predictive of CAC than BMI.
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Magnitude of Central Obesity and its Associated Factors Among Adults in Urban Areas of Northwest Ethiopia
The purpose of this study was to investigate the relationship between statin eligibility and the degree of renal dysfunction using the Adult Treatment Panel (ATP) III and the American College of Cardiology (ACC)/American Heart Association (AHA) guidelines in Korean adults.
Renal function was assessed in 18,746 participants of the Kangbuk Samsung Health Study from January 2011 to December 2012. Subjects were divided into three groups according to estimated glomerular filtration rate (eGFR): stage 1, eGFR ≥90 mL/min/1.73 m2; stage 2, eGFR 60 to 89 mL/min/1.73 m2; and stages 3 to 5, eGFR <60 mL/min/1.73 m2. Statin eligibility in these groups was determined using the ATP III and ACC/AHA guidelines, and the risk for 10-year atherosclerotic cardiovascular disease (ASCVD) was calculated using the Framingham Risk Score (FRS) and Pooled Cohort Equation (PCE).
There were 3,546 (18.9%) and 4,048 (21.5%) statin-eligible subjects according to ATP III and ACC/AHA guidelines, respectively. The proportion of statin-eligible subjects increased as renal function deteriorated. Statin eligibility by the ACC/AHA guidelines showed better agreement with the Kidney Disease Improving Global Outcomes (KDIGO) recommendations compared to the ATP III guidelines in subjects with stage 3 to 5 chronic kidney disease (CKD) (κ value, 0.689 vs. 0.531). When the 10-year ASCVD risk was assessed using the FRS and PCE, the mean risk calculated by both equations significantly increased as renal function declined.
The proportion of statin-eligible subjects significantly increased according to worsening renal function in this Korean cohort. ACC/AHA guideline showed better agreement for statin eligibility with that recommended by KDIGO guideline compared to ATP III in subjects with CKD.
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Diabetes can be efficiently prevented by life style modification and medical therapy. So, identification for high risk subjects for incident type 2 diabetes is important. The aim of this study is to identify the best β-cell function index to identify high risk subjects in non-diabetic Koreans.
This is a retrospective longitudinal study. Total 140 non-diabetic subjects who underwent standard 2-hour 75 g oral glucose tolerance test from January 2007 to February 2007 at Kangbuk Samsung Hospital and followed up for more than 1 year were analyzed (mean follow-up, 54.9±16.4 months). The subjects were consist of subjects with normal glucose tolerance (
Thirty subjects out of 140 subjects (21.4%) developed type 2 diabetes. When insulin-based index and C-peptide-based index are compared between progressor and non-progressor to diabetes, all C-peptide-based indices were statistically different between two groups, but only insulinogenic index and disposition index among insulin-based index were statistically different. C-peptide-based index had higher value of area under receiver operating characteristic curve (AROC) value than that of insulin-based index. "C-peptidogenic" index had highest AROC value among indices (AROC, 0.850; 95% confidence interval, 0.761 to 0.915). C-peptidogenic index had significantly higher AROC than insulinogenic index (0.850 vs. 0.731 respectively;
C-peptide-based index was more closely related to incident type 2 diabetes in non-diabetic subjects than insulin-based index.
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Effect of Anthocyanins Supplementation on Serum IGFBP-4 Fragments and Glycemic Control in Patients with Fasting Hyperglycemia: A Randomized Controlled Trial
We investigated the association between the severity of non-alcoholic fatty liver disease (NAFLD) and the estimated 10-year risk of cardiovascular disease (CVD) calculated by Pooled Cohort Equation (PCE) and Framingham risk score (FRS).
A total of 15,913 participants (mean age, 46.3 years) in a health screening program were selected for analysis. The presence and severity of fatty liver was assessed by abdominal ultrasonogram. Subjects who drank alcohol more than three times a week were excluded from the study.
Among the participants, 57.6% had no NAFLD, 35.4% had grade I, 6.5% had grade II, and 0.5% had grade III NAFLD. Mean estimated 10-year CVD risk was 2.59%, 3.93%, 4.68%, and 5.23% calculated using the PCE (
In our study of apparently healthy Korean adults, increasing severity of NAFLD showed a higher correlation with estimated 10-year CVD risk when calculated using the PCE than when calculated using FRS.
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Waist-to-height ratio (WHtR) is an easy and inexpensive adiposity index that reflects central obesity. In this study, we examined the association of various baseline adiposity indices, including WHtR, with the development of diabetes over 4 years of follow-up in apparently healthy Korean individuals.
A total of 2,900 nondiabetic participants (mean age, 44.3 years; 2,078 men) in a health screening program, who repeated the medical check-up in 2005 and 2009, were recruited. Subjects were divided into two groups according to development of diabetes after 4 years. The cut-off values of baseline body mass index (BMI), waist circumference (WC), and WHtR for the development of diabetes over 4 years were calculated. The sensitivity, specificity, and mean area under the receiver operator characteristic curve (AUROC) of each index were assessed. The odds ratio (OR) for diabetes development was analyzed for each of the three baseline adiposity indices.
During the follow-up period, 101 new cases (3.5%) of diabetes were diagnosed. The cut-off WHtR value for diabetes development was 0.51. Moreover, WHtR had the highest AUROC value for diabetes development among the three adiposity indices (0.716, 95% confidence interval [CI], 0.669 to 0.763; 0.702, 95% CI, 0.655 to 0.750 for WC; 0.700, 95% CI, 0.651 to 0.750 for BMI). After adjusting for confounding variables, the ORs of WHtR and WC for diabetes development were 1.95 (95% CI, 1.14 to 3.34) and 1.96 (95% CI, 1.10 to 3.49), respectively. No significant differences were observed between the two groups regarding BMI.
Increased baseline WHtR and WC correlated with the development of diabetes after 4 years. WHtR might be a useful screening measurement to identify individuals at high risk for diabetes.
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Abnormal Glucose Metabolism and Associated Risk Factors Among Adults in Mekelle City, Ethiopia
Anthropometric Indexes for Predicting High Blood Pressure in Vietnamese Adults: A Cross-Sectional Study
The aim of this study is to compare the risk for future development of nonalcoholic fatty liver disease (NAFLD) according to different status of metabolic health and obesity.
A total of 3,045 subjects without NAFLD and diabetes at baseline were followed for 4 years. Subjects were categorized into four groups according to the following baseline metabolic health and obesity statuses: metabolically healthy, non-obese (MHNO); metabolically healthy, obese (MHO); metabolically unhealthy, non-obese (MUHNO); and metabolically unhealthy, obese (MUHO). Being metabolically healthy was defined as having fewer than two of the following five components: high blood pressure, high fasting blood glucose, high triglyceride, low high density lipoprotein cholesterol, and being in the highest decile of the homeostasis model assessment-insulin resistance index. Obesity was defined as a body mass index >25 kg/m2. The presence of NAFLD was assessed by ultrasonography.
The proportions of subjects included in the MHNO, MHO, MUHNO, and MUHO groups were 71.4%, 9.8%, 13.0%, and 5.8%, respectively. The proportions of subjects who developed NAFLD were 10.5%, 31.4%, 23.2%, and 42% in the MHNO, MHO, MUHNO, and MUHO groups, respectively. The risk for developing NAFLD was highest in subjects who were metabolically unhealthy both at baseline and after 4 years compared with subjects who were consistently metabolically healthy during the follow-up period (odds ratio, 2.862). Using the MHNO group as reference, the odds ratios for the MHO, MUHNO, and MUHO groups were 1.731, 1.877, and 2.501, respectively.
The risk for NAFLD was lower in MHO subjects than in MUNO subjects.
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Metabolic health is an emerging concept that is highly correlated with various metabolic complications, and adipocytokines have been causally linked to a wide range of metabolic diseases. Thus, this study compared serum adipocytokine levels according to metabolic health and obesity status.
Four hundred and fifty-six nondiabetic subjects (mean age, 40.5 years) were categorized into four groups according to metabolic health and obesity status: metabolically healthy nonobese (MHNO), metabolically healthy obese (MHO), metabolically unhealthy nonobese (MUHNO), and metabolically unhealthy obese (MUHO). Being metabolically healthy was defined as the presence of fewer than two of the following five metabolic abnormalities: high blood pressure, high fasting blood glucose, high triglyceride, low high density lipoprotein cholesterol, and being in the highest decile of the homeostatic model assessment of insulin resistance index. Obesity status was assessed using body mass index (BMI), with obesity defined as a BMI higher than 25 kg/m2. Levels of serum interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor α (TNF-α), and adipocyte fatty acid binding protein (A-FABP) were also evaluated.
Of the 456 subjects, 247 (54.2%) were in the MHNO group, 66 (14.5%) were in the MHO group, 66 (14.5%) were in the MUHNO group, and 77 (16.9%) were in the MUHO group. There were no significant differences in IL-6 or MCP-1 levels among the groups, but levels of TNF-α and A-FABP were significantly higher in the MUHNO group compared to the MHNO group.
High TNF-α and A-FABP levels are significantly associated with metabolically unhealthiness in nonobese Korean individuals.
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Selenoprotein P (SEPP1) and fetuin-A, both circulating liver-derived glycoproteins, are novel biomarkers for insulin resistance and nonalcoholic fatty liver disease. However, the effect of exendin-4 (Ex-4), a glucagon-like peptide-1 receptor agonist, on the expression of hepatokines, SEPP1, and fetuin-A, is unknown.
The human hepatoma cell line HepG2 was treated with palmitic acid (PA; 0.4 mM) and tunicamycin (tuni; 2ug/ml) with or without exendin-4 (100 nM) for 24 hours. The change in expression of PA-induced SEPP1, fetuin-A, and endoplasmic reticulum (ER) stress markers by exendin-4 treatment were evaluated using quantitative real-time reverse transcription polymerase chain reaction and Western blotting. Transfection of cells with AMP-activated protein kinase (AMPK) small interfering RNA (siRNA) was performed to establish the effect of exendin-4-mediated AMPK in the regulation of SEPP1 and fetuin-A expression.
Exendin-4 reduced the expression of SEPP1, fetuin-A, and ER stress markers including PKR-like ER kinase, inositol-requiring kinase 1α, activating transcription factor 6, and C/EBP homologous protein in HepG2 cells. Exendin-4 also reduced the expression of SEPP1 and fetuin-A in cells treated with tunicamycin, an ER stress inducer. In cells treated with the AMPK activator 5-aminoidazole-4-carboxamide ribonucleotide (AICAR), the expression of hepatic SEPP1 and fetuin-A were negatively related by AMPK, which is the target of exendin-4. In addition, exendin-4 treatment did not decrease SEPP1 and fetuin-A expression in cells transfected with AMPK siRNA.
These data suggest that exendin-4 can attenuate the expression of hepatic SEPP1 and fetuin-A via improvement of PA-induced ER stress by AMPK.
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Tumor necrosis factor (TNF)-α and AMP-activated protein kinase (AMPK) are known to stimulate and repress lipolysis in adipocytes, respectively; however, the mechanisms regulating these processes have not been completely elucidated.
The key factors and mechanism of action of TNF-α and AMPK in lipolysis were investigated by evaluating perilipin expression and activity of protein kinase RNA-like endoplasmic reticulum kinase (PERK)/eukaryotic initiation factor 2 α (eIF2α) by Western blot and an immunofluorescence assay in 24-hour TNF-α-treated 3T3-L1 adipocytes with artificial manipulation of AMPK activation.
Enhancement of AMPK activity by the addition of activator minoimidazole carboxamide ribonucleotide (AICAR) suppressed TNF-α-induced lipolysis, whereas the addition of compound C, an inhibitor of AMPK phosphorylation, enhanced lipolysis. Perilipin, a lipid droplet-associated protein, was decreased by TNF-α and recovered following treatment with AICAR, showing a correlation with the antilipolytic effect of AICAR. Significant activation of PERK/eIF2α, a component of the unfolded protein response signaling pathway, was observed in TNF-α or vesicle-treated 3T3-L1 adipocytes. The antilipolytic effect and recovery of perilipin expression by AICAR in TNF-α-treated 3T3-L1 adipocytes were significantly diminished by treatment with 2-aminopurine, a specific inhibitor of eIF2α.
These data indicated that AICAR-induced AMPK activation attenuates TNF-α-induced lipolysis via preservation of perilipin in 3T3-L1 adipocytes. In addition, PERK/eIF2α activity is a novel mechanism of the anti-lipolytic effect of AICAR.
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The hypertriglyceridemic waist (HTGW) phenotype is a simple and inexpensive screening parameter to identify people at increased risk of cardiovascular disease. We evaluated whether the HTGW phenotype predicts diabetes in urban Korean adults.
A total of 2,900 nondiabetic subjects (mean age 44.3 years), comprising 2,078 males (71.7%) and 822 females (28.3%) who underwent annual medical check-ups at our center between January 2005 and December 2009, were recruited. The subjects were divided into four groups according to baseline serum triglyceride (TG) level and waist circumference (WC): normal WC-normal TG (NWNT) level, normal WC-high TG level, enlarged WC-normal TG level, and enlarged WC-high TG (EWHT) level. High serum TG level was defined as ≥150 mg/dL and enlarged WC was defined as ≥90 cm for men and ≥85 cm for women. New cases of diabetes were determined according to questionnaires filled in by participants and the diagnostic criteria of the American Diabetes Association. Cox proportional hazards model analysis was used to assess the association of HTGW phenotype with the incidence of diabetes.
A total of 101 (3.5%) new diabetes cases were diagnosed during the study period. The EWHT group had a higher incidence of diabetes (8.3%) compared with the NWNT group (2.2%). The adjusted hazard ratio for diabetes for subjects with the EWHT phenotype at baseline was 4.113 (95% confidence interval [CI], 2.397 to 7.059) after adjustment for age, and 2.429 (95% CI, 1.370 to 4.307) after adjustment for age, sex, total cholesterol, systolic blood pressure, and alcohol drinking history. It was attenuated by inclusion of baseline fasting glucose level in the model.
Subjects with the HTGW phenotype showed the highest risk of incident diabetes. This tool could be useful for identifying individuals at high risk of diabetes.
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Chronic kidney disease (CKD) is considered one of the most common risk factors for cardiovascular disease. Coronary artery calcification (CAC) is a potential mechanism that explains the association between renal function and cardiovascular mortality. We aimed to evaluate the association between renal function and CAC in apparently healthy Korean subjects.
A total of 23,617 participants in a health-screening program at Kangbuk Samsung Hospital were included in the study. Estimated glomerular filtration rate (eGFR) was assessed using the Cockcroft-Gault equation. Coronary artery calcium score (CACS) was measured via multidetector computed tomography. Subjects were divided into three groups according to the CKD Staging system with eGFR grade: stage 1, eGFR ≥90 mL/min/1.73 m2; stage 2, eGFR 60 to 89 mL/min/1.73 m2; and stage 3, eGFR 30 to 59 mL/min/1.73 m2.
The mean age of the participants was 41.4 years and the mean eGFR was 103.6±21.7 mL/min/1.73 m2. Hypertension and diabetes were noted in 43.7% and 5.5% of the participants, respectively. eGFR showed a weakly negative but significant association with CACS in bivariate correlation analysis (
In early CKD, renal function negatively correlated with the degree of CAC in Korean subjects. Age was the strongest effector for this association.
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