Association between thyroid hormone levels, body composition and insulin resistance in euthyroid subjects with normal thyroid ultrasound: The Kangbuk Samsung Health Study.

OBJECTIVE: Thyroid hormones play crucial roles in the control of energy homoeostasis and can influence body composition. In contrast, the changes in body composition might influence thyroid hormone levels. We evaluated associations between thyroid hormone levels, body composition and insulin resistance in euthyroid subjects with normal thyroid ultrasound (US) findings. DESIGN AND PATIENTS: This retrospective cross-sectional study included 36 655 euthyroid subjects who joined the medical health check-up programme at our institution. Serum thyroid hormone levels were analysed in association with body fat percentage (BFP), skeletal muscle mass index (SMI) and homoeostatic model assessment of insulin resistance (HOMA-IR). Linear regression analyses were performed to evaluate relationships between thyroid hormone levels and anthropometric parameters. RESULTS: Mean age was 36.4 years, and 49% of subjects were female. In multiple linear regression analysis, serum-free triiodothyronine (FT3) levels exhibited positive associations with waist circumference (WC) and HOMA-IR and a negative association with body weight, body mass index (BMI) and SMI among both men and women. The association between serum-free thyroxine (FT4) levels and anthropometric markers showed inconsistent results in men and women. Serum thyroid-stimulating hormone (TSH) levels showed a positive association with HOMA-IR in both men and women. CONCLUSIONS: Lower SMI was significantly associated with higher serum FT3 levels, the active form of thyroid hormone, in both men and women. Higher insulin resistance was positively associated with serum FT3 levels and inversely associated with serum TSH levels in euthyroid subjects with normal thyroid US findings.

Glucocorticoid-Induced Hyperglycemia: A Neglected Problem.

Glucocorticoids provide a potent therapeutic response and are widely used to treat a variety of diseases, including coronavirus disease 2019 (COVID-19) infection. However, the issue of glucocorticoid-induced hyperglycemia (GIH), which is observed in over one-third of patients treated with glucocorticoids, is often neglected. To improve the clinical course and prognosis of diseases that necessitate glucocorticoid therapy, proper management of GIH is essential. The key pathophysiology of GIH includes systemic insulin resistance, which exacerbates hepatic steatosis and visceral obesity, as well as proteolysis and lipolysis of muscle and adipose tissue, coupled with ß-cell dysfunction. For patients on glucocorticoid therapy, risk stratification should be conducted through a detailed baseline evaluation, and frequent glucose monitoring is recommended to detect the onset of GIH, particularly in high-risk individuals. Patients with confirmed GIH who require treatment should follow an insulin-centered regimen that varies depending on whether they are inpatients or outpatients, as well as the type and dosage of glucocorticoid used. The ideal strategy to maintain normoglycemia while preventing hypoglycemia is to combine basal-bolus insulin and correction doses with a continuous glucose monitoring system. This review focuses on the current understanding and latest evidence concerning GIH, incorporating insights gained from the COVID-19 pandemic.

Greater Severity of Steatosis Is Associated with a Higher Risk of Incident Diabetes: A Retrospective Longitudinal Study.

BACKGRUOUND: Fatty liver is associated with increased risk of developing type 2 diabetes. We aimed to evaluate whether the severity of hepatic steatosis is associated with incident diabetes. METHODS: We conducted a longitudinal analysis using data from 1,798 participants who underwent a comprehensive health checkup and abdominal computed tomography (CT). We assessed the association between baseline liver attenuation value on non-contrast CT images and risk of incident diabetes. All the participants were categorized into three groups based on the baseline liver attenuation value on non-contrast CT images: without hepatic steatosis (>57 Hounsfield unit [HU]), mild hepatic steatosis (41-57 HU), and moderate to severe hepatic steatosis (≤40 HU). RESULTS: During a median follow-up period of 5 years, 6.0% of the study participants progressed to diabetes. The incidence of diabetes was 17.3% in the moderate to severe hepatic steatosis group, 9.0% in the mild steatosis group, and 2.9% in those without hepatic steatosis. In a multivariate adjustment model, as compared with participants without hepatic steatosis, those with moderate to severe steatosis had a hazard ratio (HR) of 3.24 (95% confidence interval [CI], 1.64 to 4.2) for the development of diabetes, and those in the mild steatosis group had a HR of 2.33 (95% CI, 1.42 to 3.80). One standard deviation decrease in mean CT attenuation values of the liver was associated with a 40% increase in the development of diabetes (multivariate adjusted HR, 1.40; 95% CI, 1.2 to 1.63). CONCLUSION: We found a positive association between severity of hepatic steatosis and risk of incident diabetes. Greater severity of steatosis was associated with a higher risk of incident diabetes.

Dose-Dependent Effect of Smoking on Risk of Diabetes Remains after Smoking Cessation: A Nationwide Population-Based Cohort Study in Korea.

BACKGROUND: This study aimed to evaluate the dose-dependent effects of smoking on risk of diabetes among those quitting smoking. METHODS: We analyzed clinical data from a total of 5,198,792 individuals age 20 years or older who received health care check-up arranged by the national insurance program of Korea between 2009 and 2016 using the Korean National Health Insurance Service database. Cumulative smoking was estimated by pack-years. Smokers were classified into four categories according to the amount of smoking: light smokers (0.025 to 5 smoking pack-years), medium smokers (5 to 14 smoking pack-years), heavy smokers (14 to 26 smoking pack-years), and extreme smokers (more than 26 smoking pack-years). RESULTS: During the study period, 164,335 individuals (3.2% of the total population) developed diabetes. Compared to sustained smokers, the risk of diabetes was significantly reduced in both quitters (hazard ratio [HR], 0.858; 95% confidence interval [CI], 0.838 to 0.878) and nonsmokers (HR, 0.616; 95% CI, 0.606 to 0.625) after adjustment for multiple risk factors. The risk of diabetes gradually increased with amount of smoking in both quitters and current smokers. The risk of diabetes in heavy (HR, 1.119; 95% CI, 1.057 to 1.185) and extreme smokers (HR, 1.348; 95% CI, 1.275 to 1.425) among quitters was much higher compared to light smokers among current smokers. CONCLUSION: Smoking cessation was effective in reducing the risk of diabetes regardless of weight change. However, there was a potential dose-dependent association between smoking amount and the development of diabetes. Diabetes risk still remained in heavy and extreme smokers even after smoking cessation.

Decreased Vagal Activity and Deviation in Sympathetic Activity Precedes Development of Diabetes.

OBJECTIVE: The objective of this study was to examine whether altered heart rate variability (HRV) could predict the risk of diabetes in Asians. RESEARCH DESIGN AND METHODS: A cohort study was conducted in 54,075 adults without diabetes who underwent 3-min HRV measurement during health checkups between 2011 and 2014 at Kangbuk Samsung Hospital. We analyzed the time domain (SD of the normal-to-normal interval [SDNN] and root mean square differences of successive normal-to-normal intervals [RMSSD]) and the frequency domain (total power, normalized low-frequency power [LF], and normalized high-frequency power [HF] and LF/HF ratio). We compared the risk of diabetes until 2017 according to tertiles of heart rate and HRV variables, with tertile 1 serving as the reference group. RESULTS: During 243,758.2 person-years, 1,369 subjects were diagnosed with diabetes. Both time and frequency domain variables were lower in the group with diabetes, with the exception of those with normalized LF and LF/HF ratio. In Cox analysis, as SDNN, RMSSD, and normalized HF tertiles increased, the risk of diabetes decreased (hazard ratios [95% CIs] of tertile 3: 0.81 [0.70-0.95], 0.76 [0.65-0.90], and 0.78 [0.67-0.91], respectively), whereas the risk of diabetes increased in the case of heart rate, normalized LF, and LF/HF ratio (hazard ratios [95% CIs] of tertile 3: 1.41 [1.21-1.65], 1.32 [1.13-1.53], and 1.31 [1.13-1.53), respectively) after adjusting for age, sex, BMI, smoking, drinking, systolic blood pressure, lipid level, CRP, and HOMA of insulin resistance. CONCLUSIONS: Abnormal HRV, especially decreased vagal activity and deviation in sympathovagal imbalance to sympathetic activity, might precede incident diabetes.

Protective effect of smoking cessation on subsequent myocardial infarction and ischemic stroke independent of weight gain: A nationwide cohort study.

Smoking cessation reduces the cardiovascular risk but increases body weight. We investigated the risk of subsequent myocardial infarction and ischemic stroke according to weight gain after smoking cessation, using a nationwide population based cohort. We enrolled 3,797,572 Korean adults aged over 40 years who participated in national health screenings between 2009 and 2010. Subjects who quit smoking were classified into three subgroups according to the weight change between baseline and 4 years prior. Myocardial infarctions and ischemic strokes were followed until the end of 2015. We compared the hazard ratios among smoking cessation subgroups, non-smokers, and current smokers. The mean changes in weight (1.5 ± 3.9 kg) of the smoking cessation group were higher than those of the other groups (p < 0.0001). A total of 31,277 and 46,811 subjects were newly diagnosed with myocardial infarction and ischemic stroke, respectively. Regardless of weight change, all subgroups of smoking cessation had significantly less risk than current smokers. The subgroup of smoking cessation with weight gain over 4kg showed the lowest risk for myocardial infarctions (hazard ratio 0.646, 95% confidence interval 0.583-0.714, p < 0.0001) and ischemic strokes (hazard ratio 0.648, 95% confidence interval 0.591-0.71, p < 0.0001) after multivariable adjustment. In conclusion, weight gain after smoking cessation did not adversely affect the cardiovascular protective effect.

Relation between Baseline Height and New Diabetes Development: A Nationwide Population-Based Study.

BACKGROUND: Short stature and leg length are associated with risk of diabetes and obesity. However, it remains unclear whether this association is observed in Asians. We evaluated the association between short stature and increased risk for diabetes using the Korean National Health Screening (KNHS) dataset. METHODS: We assessed diabetes development in 2015 in 21,122,422 non-diabetic Koreans (mean age 43 years) enrolled in KNHS from 2009 to 2012 using International Classification of Diseases 10th (ICD-10) code and anti-diabetic medication prescription. Risk was measured in age- and sex-dependent quintile groups of baseline height (20 to 39, 40 to 59, ≥60 years). RESULTS: During median 5.6-year follow-up, 532,918 cases (2.5%) of diabetes occurred. The hazard ratio (HR) for diabetes development gradually increased from the 5th (reference) to 1st quintile group of baseline height after adjustment for confounding factors (1.000, 1.076 [1.067 to 1.085], 1.097 [1.088 to 1.107], 1.141 [1.132 to 1.151], 1.234 [1.224 to 1.244]), with similar results in analysis by sex. The HR per 5 cm height increase was lower than 1.00 only in those with fasting blood glucose (FBG) below 100 mg/dL (0.979 [0.975 to 0.983]), and in lean individuals (body mass index [BMI] 18.5 to 23 kg/m²: 0.993 [0.988 to 0.998]; BMI <18.5 kg/m²: 0.918 [0.9 to 0.935]). CONCLUSION: Height was inversely associated with diabetes risk in this nationwide study of Korean adults. This association did not differ by sex, and was significant in lean individuals and those with normal FBG levels.

Maintenance of body weight is an important determinant for the risk of ischemic stroke: A nationwide population-based cohort study.

BACKGROUND: Overweight is known as a risk factor for ischemic stroke. However, the effect of weight change on the development of ischemic stroke remains controversial. We investigated the relationship between weight change and the risk of ischemic stroke using a nationwide population-based cohort. METHODS: Our study enrolled 11,084,683 participants (Mean age 49.7±13.5 years, range 20-114 years) in the Korean National Health Screening Program from 2009 to 2012. Weight change was calculated using the difference between the baseline weight and the weight at health screening four years prior to the baseline. The occurrence of newly-diagnosed ischemic stroke was observed until the end of 2015. We categorized the study population according to weight change and performed multivariable analysis to compare the risk. RESULTS: Ischemic stroke was newly diagnosed in 113,591 subjects. The crude incidence rates of ischemic stroke per 1000 person-years according to the change in body weight were 3.059, 1.906, and 1.491 in the <-5%, ±5%, and ≥+5% groups, respectively. After adjusting all variables, the hazard ratio (HR) of ischemic stroke was higher in subjects who underwent weight loss (HR 1.152) or weight gain (HR 1.087) than in those who maintained their weight. When analyzed by eight groups of 5% intervals, the risk showed a U-shaped curve with those who maintained their weight showing the lowest risk. CONCLUSIONS: The risk of ischemic stroke was gradually increased in those who lost or gained more than 5% of their weight over four years, after adjusting for confounders. We should be aware of the increased risk of ischemic stroke in people who undergo weight change and should identify and manage the cause of weight change.

The Risk of Myocardial Infarction and Ischemic Stroke According to Waist Circumference in 21,749,261 Korean Adults: A Nationwide Population-Based Study.

BACKGROUND: Waist circumference (WC) is a well-known obesity index that predicts cardiovascular disease (CVD). We studied the relationship between baseline WC and development of incident myocardial infarction (MI) and ischemic stroke (IS) using a nationwide population-based cohort, and evaluated if its predictability is better than body mass index (BMI). METHODS: Our study included 21,749,261 Koreans over 20 years of age who underwent the Korean National Health Screening between 2009 and 2012. The occurrence of MI or IS was investigated until the end of 2015 using National Health Insurance Service data. RESULTS: A total of 127,289 and 181,637 subjects were newly diagnosed with MI and IS. The incidence rate and hazard ratio of MI and IS increased linearly as the WC level increased, regardless of adjustment for BMI. When the analyses were performed according to 11 groups of WC, the lowest risk of MI was found in subjects with WC of 70 to 74.9 and 65 to 69.9 cm in male and female, and the lowest risk of IS in subjects with WC of 65 to 69.9 and 60 to 64.9 cm in male and female, respectively. WC showed a better ability to predict CVD than BMI with smaller Akaike information criterion. The optimal WC cutoffs were 84/78 cm for male/female for predicting MI, and 85/78 cm for male/female for predicting IS. CONCLUSION: WC had a significant linear relationship with the risk of MI and IS and the risk began to increase from a WC that was lower than expected.

Pioglitazone Attenuates Palmitate-Induced Inflammation and Endoplasmic Reticulum Stress in Pancreatic ß-Cells.

BACKGROUND: The nuclear receptor peroxisome proliferator-activator gamma (PPARγ) is a useful therapeutic target for obesity and diabetes, but its role in protecting ß-cell function and viability is unclear. METHODS: To identify the potential functions of PPARγ in ß-cells, we treated mouse insulinoma 6 (MIN6) cells with the PPARγ agonist pioglitazone in conditions of lipotoxicity, endoplasmic reticulum (ER) stress, and inflammation. RESULTS: 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-1ß) 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 ß-cells. Moreover, the preservation of ß-cells by pioglitazone was accompanied by a significant reduction of blood glucose levels. CONCLUSION: Altogether, these results support the proposal that PPARγ agonists not only suppress insulin resistance, but also prevent ß-cell impairment via protection against ER stress and inflammation. The activation of PPARγ might be a new therapeutic approach for improving ß-cell survival and insulin secretion in patients with diabetes mellitus.