Abnormal Glucose Metabolism and Insulin Resistance Are Induced via the IRE1α/XBP-1 Pathway in Subclinical Hypothyroidism

Evaluation of linagliptin and insulin combined therapy on unfolded protein response in type 1 diabetic mouse heart

The aim of this study is to reveal the effects of the use of linagliptin, a DPP-4 inhibitor due to its beneficial cardiovascular effects, on endoplasmic reticulum stress (ERS) signaling, which is involved in the pathogenesis of cardiovascular complications related to type 1 diabetes. BALB/c female mice (n = 72) were divided into six groups: control, diabetes+insulin, diabetes+linagliptin, diabetes+linagliptin+insulin, diabetes+TUDCA, and diabetes+TUDCA+insulin. Immunohistochemistry and western blot method, qRT-PCR, ELISA method, and malondialdehyde (MDA) measurements were performed. Linagliptin administered to the type 1 diabetic mouse heart significantly reduced the expression levels of the total and cleaved forms of ATF6, ATF4, and p-JNK, caspase 3. Immunohistochemical and western blot analyses revealed that cleaved caspase 3 protein expression was significantly increased in the diabetes+insulin group compared to the other groups. According to ELISA findings, TUDCA was more effective in reducing NOX 1 and MDA levels than linagliptin. While linagliptin decreased the Chop mRNA level, no change was observed in the Grp78 mRNA level. Our findings showed that there was not much difference between the administration of linagliptin alone or in combination with insulin. Our study reveals that linagliptin is an effective therapeutic agent on ERS and apoptotic UPR in type 1 diabetic hearts.

Sensitivity to thyroid hormone and risk of components of metabolic syndrome in a Chinese euthyroid population

INTRODUCTION

To evaluate the association of sensitivity to thyroid hormone with metabolic syndrome (MetS) and its components in a Chinese euthyroid population.

METHODS

A total of 3573 participants from Pinggu Metabolic Disease Study were analyzed. Serum-free triiodothyronine (FT3), free thyroxine (FT4), thyrotropin (TSH), total adipose tissue (TAT), visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT) area of abdominal, and lumbar skeletal muscle area (SMA) were measured. Central thyroid hormone resistance was calculated by the Thyroid Feedback Quantile-based Index (TFQI) and Chinese-referenced Parametric TFQI (PTFQI), Thyrotroph T4 Resistance Index (TT4RI) and TSH Index (TSHI). Peripheral thyroid hormone resistance was assessed by FT3/FT4 ratio.

RESULTS

Higher values of TSHI (odds ratio [OR] = 1.167, 95% confidence interval [CI]: 1.079-1.262, p < .001), TT4RI (OR = 1.115, 95% CI: 1.031-1.206, p = .006), TFQI (OR = 1.196, 95% CI: 1.106-1.294, p < .001), PTFQI (OR = 1.194, 95% CI: 1.104-1.292, p < .001), and lower values of FT3/FT4 ratio (OR = 0.914, 95% CI: 0.845-0.990, p = .026) were associated with MetS. Increased levels of TFQI and PTFQI were associated with abdominal obesity, hypertriglyceridemia, and hypertension. Increased levels of TSHI and TT4RI were associated with hypertriglyceridemia, abdominal obesity, low high-density lipoprotein cholesterol. Reduced levels of FT3/FT4 ratio were associated with hyperglycemia, hypertension, and hypertriglyceridemia. The levels of TSHI, TFQI, and PTFQI were negatively related to SMA and positively related to VAT, SAT, and TAT (all p < .05).

CONCLUSIONS

Reduced thyroid hormone sensitivity was associated with MetS and its components. Impaired thyroid hormone sensitivity might affect the distribution of adipose tissue and muscle.

Incidence and Factors Associated with Hyperglycemia in Patients with First Hospitalization for Major Depression Disorder: A Large Cross-Sectional Sample

Purpose

Major depressive disorder (MDD) is a mood disorder characterized by persistent spontaneous depression and has a high rate of disability and mortality. There is a complex relationship between MDD and disorders of glucose metabolism, and our study aimed to investigate the prevalence and risk factors for hyperglycemia in patients with MDD who were hospitalized for the first times.

Patients and Methods

A total of 981 first-time inpatients with MDD were recruited, socio-demographic information, anthropometric data, and biochemical parameters were collected for each participant. The 17-item Hamilton Assessment Scale for Depression (HAMD-17), the 14-item Hamilton Anxiety Scale (HAMA-14), the Positive Syndrome Scale (PSS), and Clinical General Impressions Inventory-Severity of Illness (CGI-SI) scores were used to assess patients' clinical symptoms.

Results

The prevalence of hyperglycemia was 9.28% among patients with MDD who were hospitalized for the first time. Compared to the non-hyperglycemic subgroup, patients in the hyperglycemic subgroup were found to have more extensive and significant demographic and clinical characteristics, higher levels of metabolism-related parameters, and more severe psychological and psycho-pathological symptoms. Age, thyroid stimulating hormone (TSH), triglycerides (TG) were risk factors for hyperglycemia in MDD patients, while course of disease was a protective factor.

Conclusion

The study findings suggest that the prevalence of hyperglycemia is not high in patients with MDD who are hospitalized for the first time. The risk variables for predicting hyperglycemia include age, TSH and TG. The above three factors and course of disease have good combined diagnostic ability for hyperglycemia.

The Thyroid Hormone Axis and Female Reproduction

Thyroid function affects multiple sites of the female hypothalamic-pituitary gonadal (HPG) axis. Disruption of thyroid function has been linked to reproductive dysfunction in women and is associated with menstrual irregularity, infertility, poor pregnancy outcomes, and gynecological conditions such as premature ovarian insufficiency and polycystic ovarian syndrome. Thus, the complex molecular interplay between hormones involved in thyroid and reproductive functions is further compounded by the association of certain common autoimmune states with disorders of the thyroid and the HPG axes. Furthermore, in prepartum and intrapartum states, even relatively minor disruptions have been shown to adversely impact maternal and fetal outcomes, with some differences of opinion in the management of these conditions. In this review, we provide readers with a foundational understanding of the physiology and pathophysiology of thyroid hormone interactions with the female HPG axis. We also share clinical insights into the management of thyroid dysfunction in reproductive-aged women.

Association between thyroid dysfunction, metabolic disturbances, and clinical symptoms in first-episode, untreated Chinese patients with major depressive disorder: Undirected and Bayesian network analyses

AIMS

Thyroid dysfunction and metabolic disturbances are common in major depressive disorder (MDD) patients. We aimed to assess the relationship between thyroid dysfunction, metabolic disturbances, and clinical symptoms in Chinese first-episode, drug-naïve (FEDN) MDD patients using undirected and Bayesian network methods.

METHODS

1718 FEDN MDD patients were recruited. Serum levels of free triiodothyronine (FT3), free thyroxine (FT4), thyroid stimulating hormone (TSH), anti-thyroglobulin (TgAb), thyroid peroxidases antibody (TPOAb), total cholesterol (TC), total triglycerides (TG), high-density lipoprotein (HDL-C), low-density lipoprotein (LDL-C), and glucose were assessed. Blood pressure and body mass index were measured. Hamilton Rating Scale for Depression (HAMD), Hamilton Rating Scale for Anxiety, and positive subscale of Positive And Negative Syndrome Scales were used to detect clinical symptoms. An undirected network with EBICglasso default and a directed acyclic graph (DAG) using the Bayesian network approach was conducted.

RESULTS

The prevalence rates of clinical symptoms, thyroid dysfunction, and metabolic dysfunction were as follows: anxiety (n=894, 52%), psychotic symptoms (171, 10%), subclinical hypothyroidism (SCH, n=1041, 61%), abnormal TgAb (n=297, 17%), abnormal TPOAb (n=438, 25%), hyperthyroidism (n=5, 0.3%), hypothyroidism (n=3, 0.2%), hyperglycemia (n=241, 14%), hypertriglyceridemia (n=668, 39%), low HDL-C (n=429, 25%), hypercholesterolemia (421, 25%), abnormal TC (357, 21%), abnormal LDL-C (185, 11%). overweight or obesity (n=1026, 60%), and hypertension (n=92, 5.4%). Both networks demonstrated serum TSH and TC levels and the severity of depression played an important role in the pathophysiology of MDD.

CONCLUSIONS

MDD patients may have thyroid and metabolic dysfunction in the early stage. Targeting hypercholesterolemia, depressive symptoms, and SCH in MDD patients may hold promise in reducing clinical symptoms, metabolic disturbances, and thyroid dysfunction.

Hypothyroidism And Gestational Diabetes Mellitus: Is There A Relationship?

Background and Objective — Subclinical gestational hypothyroidism (SGH) and gestational diabetes mellitus (GDM) constitute two most common endocrine pathologies encountered during pregnancy. SGH and GDM have common pathophysiological mechanisms, being interrelated pathological conditions that are capable of complicating the course of pregnancy, labor and the postpartum period both on the part of the mother and on the part of the fetus. We aimed to analyze the relationship between these pathologies and to assess the risk of developing GDM against the background of hypothyroidism. Materials and Methods — the study included 200 pregnant women observed at the Perinatal Center of the Maternity Hospital the Bauman State Clinical Hospital No. 29 during 2018-2020. The main group consisted of 133 women who visited the perinatal center for hypothyroidism (both SGH and primary hypothyroidism, detected prior to pregnancy); the control group comprised 67 women without endocrine pathology. Both groups were comparable in terms of age, height, weight, and the number of pregnancies in the anamneses. The main group received levothyroxine sodium therapy with the achievement of the target trimester-specific level of thyroid-stimulating hormone (TSH). The criteria for the diagnosis of SGH were the TSH level above 2.5 μIU/mL in combination with an enlarged titer of antithyroid antibodies and/or a burdened medical history of thyroid pathology, or the TSH level above 4.0 μIU/mL in the absence of antithyroid antibodies [1]. The diagnosis of GDM was established on the basis of fasting hyperglycemia (≥5.1 mmol/L), or based on the results of an oral glucose tolerance test (OGTT) with 75 g of glucose: fasting glucose level of ≥5.1 mmol/L; the concentration 1 hour after glucose intake ≥10.0 mmol/L; the content 2 hours after glucose intake ≥8.5 mmol/l) [2]. In both groups, the frequency of developing GDM, the timing of diagnosis, and the need for insulin therapy were evaluated. Statistical data processing was carried out using the StatTech v. 2.1.0 software. Quantitative indicators were assessed for compliance with the normal distribution via Shapiro-Wilk criterion or Kolmogorov-Smirnov criterion. Intergroup comparison was performed using Mann-Whitney U test or Pearson’s chi-squared test. Results — We discovered that among women with a burdened family history of thyroid pathology and diabetes mellitus, as well as with thyroid pathology prior to pregnancy, the prevalence of hypothyroidism was higher. The presence of thyroid pathology in the anamnesis of pregnant women was associated with an earlier diagnosis of hypothyroidism. We revealed a significant difference in the prevalence of GDM between two groups of subjects. The chances of detecting GDM in the hypothyroidism group were 8.6 times higher than in the euthyroidism group. The threshold level of TSH for the first trimester, predicting the development of GDM, was identified. The sensitivity and specificity of the model were 71.4% and 63.1%, respectively. Conclusion — Hypofunction of the thyroid and GDM are interrelated endocrine pathologies. In the presence of hypothyroidism (both primary and SGH), GDM develops significantly more often. The level of TSH in the first trimester ≥2.7 μIU/mL amplifies the chance of developing GDM by over 8 times; hence, it could be considered a signal for timely prevention and detection of this pathology.

Effects of hypothyroidism on the female pancreas involve the regulation of estrogen receptors

This study aimed to investigate the impact of short-time hypothyroidism on the expression of aromatase, estrogen receptors (ERα, β), and GPR30 in the pancreas of female rabbits. The formation of new islets and the expression of insulin, GLUT4, and lactate dehydrogenase (LDH) were also analyzed. This purpose is based on actions that thyroid hormones and estrogens have on β-cells differentiation, acinar cell function, and insulin secretion. Twelve Chinchilla-breed adult virgin female rabbits were divided into control (n = 6) and hypothyroid (n = 6; methimazole 10 mg/kg for 30 days) groups. In the complete pancreas, expressions of aromatase and estrogen receptors, as well as proinsulin, GLUT4, and LDH were determined by western blot. Characteristics of islets were measured in slices of the pancreas with immunohistochemistry for insulin. Islet and acinar cells express aromatase, ERα, ERβ, and GPR30. Hypothyroidism increased the expression of ERα and diminished that for aromatase, ERβ, and GPR30 in the pancreas. It also promoted a high number of extra small islets (new islets) and increased the expression of proinsulin and GLUT4 in the pancreas. Our results show that actions of thyroid hormones and estrogens on β-cells neogenesis, acinar cell function, and synthesis and secretion of insulin are linked. Thus, the effects of hypothyroidism on the pancreas could include summatory actions of thyroid hormones plus estrogens. Our findings indicate the importance of monitoring estrogen levels and actions on the pancreas of hypothyroid women, particularly when serum estrogen concentrations are affected such as menopausal, pregnant, and those with contraceptive use.

Impact of persistent subclinical hypothyroidism on clinical outcomes in non-ST-segment elevation acute coronary syndrome undergoing percutaneous coronary intervention

BACKGROUND

Data on the association of subclinical hypothyroidism (SCH) with the severity of coronary artery disease and major adverse cardiovascular and cerebral events (MACCE) in patients with non-ST-segment elevation acute coronary syndrome (NSTE-ACS) after percutaneous coronary intervention (PCI) are limited and conflicting.

OBJECTIVE

We established the baseline rate of SCH and followed the trajectory of thyroid-stimulating hormone (TSH) values during and after hospitalisation for PCI for up to six months and determined whether persistent SCH was associated with the severity of coronary artery disease and MACCE in patients with NSTE-ACS after PCI.

DESIGN

Population-based prospective cohort study.

PATIENTS

We included patients with NSTE-ACS who underwent PCI with simple balloon angioplasty or stent implantation for coronary heart disease.

MEASUREMENTS

Thyroid function tests of patients before PCI and 1 day, 1 week, 1 and 6 months after PCI were performed. Cases showing transient SCH were excluded. Patients were divided into two groups based on the results of four TSH tests: 0.27-4.2 mIU/L (n = 1472, 89.7%) and >4.2 mIU/L (n = 170, 10.4%). The risk factors for the severity of coronary artery lesions were estimated using multinomial logistic regression analysis. Univariate and multivariate Cox regression analyses were used to study the relationship between TSH and MACCE.

RESULTS

Among 1642 patients, there were 1070 males (65.2%) and 572 females (34.8%), with an average age of 62.5 ± 9.6 years. SCH patients had a wider range of diseased vessels and a higher number of diseased vessels (p < .05). TSH level was an independent risk factor for moderate [odds ratio (OR) = 1.144, 95% confidence interval (95% CI): 1.057-1.237, p = .001] and severe (OR = 1.131, 95% CI: 1.043-1.226, p = .003) coronary artery lesions. After adjusting for covariates, the risk of MACCE [hazard ratio (HR): 4.067, p < .001], nonfatal myocardial infarction (HR: 14.724, p = .003), and unplanned PCI (HR: 5.028, p < .001) were higher in the SCH group than in the euthyroidism group. There were no significant differences in the incidence of heart failure (HR: 6.012, p = .175), nonfatal stroke (HR: 2.039, p = .302), unplanned coronary artery bypass grafting (CABG) (HR: 1.541, p = .57), or cardiac death (HR: 2.704, p = .375) between the two groups.

CONCLUSIONS

Preoperative TSH levels and changes in thyroid hormone levels several months post-PCI in NSTE-ACS patients are highly significant in practice. Persistent SCH is associated with severe coronary artery lesions and MACCE, and may be a predictor for evaluating the prognosis of PCI-treated NSTE-ACS patients.

TSH Combined with TSHR Aggravates Diabetic Peripheral Neuropathy by Promoting Oxidative Stress and Apoptosis in Schwann Cells

Subclinical hypothyroidism (SCH) is associated with diabetic peripheral neuropathy (DPN); however, the mechanism underlying this association remains unknown. This study is aimed at examining neurofunctional and histopathological alterations in a type 2 diabetes (T2DM) mouse model of SCH and investigating the impact of thyroid-stimulating hormone (TSH) in an in vitro DPN cell model established using RSC96 cells under high glucose (HG) and palmitic acid (PA) stimulation. Our results indicated that T2DM, in combination with SCH, aggravated abnormal glucose and lipid metabolism in T2DM and dramatically destroyed the peripheral nervous system by increasing paw withdrawal latency, decreasing motor nerve conduction velocity, and exacerbating ultrastructural deterioration of the damaged sciatic nerve caused by diabetes. Furthermore, the results of our in vitro experiments showed that TSH intensified HG/PA-induced RSC96 cell damage by inducing oxidative stress, mitochondrial dysfunction, and apoptosis. More importantly, TSHR knockout or inhibition of PA-induced TSHR palmitoylation could alleviate the apoptosis induced by TSH. Overall, in this study, the novel mechanisms by which TSH, as an independent risk factor for DPN progression, aggravating Schwann cell apoptosis and demyelination, are elucidated. These findings indicate that TSHR could be a potential target for both the prevention and treatment of DPN and, possibly, other microvascular diseases, and have implication in the clinical management of patients with DPN.

Relation between Uric Acid Levels and Subclinical Hypothyroidism in Diabetic Patients

BACKGROUND AND AIM

Subclinical hypothyroidism (SCH) is frequently seen in diabetic patients. Elevated levels of uric acid (UA) were also reported in diabetic patients. No study assessed the relation between SCH and UA levels in diabetic patients. We aimed to evaluate this relation and the association of both conditions with other clinical and laboratory parameters in diabetic patients.

SUBJECTS AND METHODS

This cross-sectional study included 100 T2DM patients in addition to 50 age and sex matched healthy controls. Diabetic patients comprised 50 patients with SCH and 50 euthyroid patients. All participants were subjected to careful history taking, thorough clinical examination and standard laboratory work up. The performed investigations included fasting and postprandial blood sugar, fasting insulin levels, HbA1c levels, thyroid hormones (FT3, FT4 and TSH), renal profile and serum UA.

RESULTS

Comparison between the studied groups regarding serum UA levels revealed significantly higher levels in the diabetic group (5.4 ± 1.9 versus 4.2 ± 1.0 mg/dl, p<0.001). SCH + DM patients had significantly higher UA levels in comparison to DM group (6.1 ± 1.8 versus 4.8 ± 1.7 mg/dl, p<0.001) and control group (6.1 ± 1.8 versus 4.2 ± 1.0 mg/dl, p<0.001). SCH + DM patients had significantly higher HbA1c levels (8.9 ± 1.1 versus 7.6 ± 1.3 %, p<0.001), HOMA-IR (3.9 ± 0.8 versus 2.8 ± 1.0, p<0.001) and UA levels (6.1 ± 1.8 versus 4.8 ± 1.7, p<0.001). Correlation analysis identified a significant direct correlation between serum UA and HOMA-IR in DM + SCH patients (r=0.4,p=0.004). In univariate analysis, presence of SCH [OR (95% CI): 2.57 (1.07-6.15), p=0.034] and nephropathy [OR (95% CI): 4.57 (1.77-11.8), p=0.002] were significant predictors of higher (upper tertile) UA in the studied patients. However, in multivariate analysis, only nephropathy [OR (95% CI): 4.25 (1.62-11.17), p=0.003] continued to be significant while SCH showed a marginal trend [OR (95% CI): 0.43 (0.17-1.08), p=0.073].

CONCLUSIONS

The present study suggests an association between SCH and increased UA levels in diabetic patients.

Subclinical Hypothyroidism in Patients with Diabetic Retinopathy: Role of Vascular Endothelial Growth Factor

BACKGROUND

Considering the vital role of vascular endothelial growth factor (VEGF) in the development of diabetic retinopathy (DR) in one hand and the frequent association between subclinical hypothyroidism (SCH) and DR on the other hand.

OBJECTIVE

The present study was proposed to explore the possible role of VEGF in the relation between SCH and DR, thus we investigated the relation between SCH and VEGF levels in patients with DR.

METHODS

Two hundred patients with DR were recruited in this study [100 patients with proliferative diabetic retinopathy (PDR) and 100 patients with non-proliferative diabetic retinopathy (NPDR)]. Patients with DR were divided into 2 groups according to thyroid function: patients with SCH or those with euthyroidism. Patients were subjected to careful history taking, and underwent clinical and ophthalmological examination. Fasting blood glucose, glycosylated hemoglobin, fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), TSH, FT4, FT3, VEGF and thyroid volume were assessed Results: Among all the studied patients, 21.5% (43/200) had SCH. DR patients with SCH had higher age, diabetes duration, HbA1c, HOMA-IR and VEGF than those with euthyroidism. The frequency of PDR in patients with SCH was 72.1% (31/43) and 43.9% (69/157) in those with euthyroidism, whereas the frequency of NPDR in patients with SCH was 27.9 (12/43) and 56.1% (88/157) in those with euthyroidism (P < 0.003). In multivariate analysis, PDR, HOMA-IR and VEGF levels were the significant predictor variables of SCH.

CONCLUSIONS

Increased VEGF levels may be implicated in the relationship between SCH and DR.

The Impact of Subclinical Hypothyroidism on Patients with Polycystic Ovary Syndrome: A Meta-Analysis

The association between subclinical hypothyroidism (SCH) and polycystic ovary syndrome (PCOS) has been shown in many studies. These findings are still controversial, however. It is unclear whether the co-incidence of subclinical hypothyroidism and polycystic ovary syndrome will affect the severity of metabolism. Therefore, we performed this meta-analysis to investigate the association. A comprehensive search strategy was developed to obtain all relevant studies published in PubMed, EMBASE, Cochrane Library, and Chinese Academic Journal Full-text Database (CNKI) up to 31 December 2020. We adopted the standardized mean difference (SMD) with 95% confidence intervals (CI) for evaluation, and sensitivity analysis was performed. Publication bias was analyzed and represented by a funnel plot, and funnel plot symmetry was assessed with Egger's test. Twenty-seven studies with 4821 participants (1300 PCOS patients with SCH, 3521 PCOS patients without SCH) were included in the present meta-analysis,among which 71.31% chinese patients out of the total. The results showed that PCOS patients with SCH had higher levels of HOMA-IR, TG, TC, LDL, FBG, FCP, PRL and lower levels of HDL, LH and T. It also recognized the limitation of the lack of a consistent definition of hypothyroidism in the 27 studies included. The results of this study indicated that SCH may aggravate lipid and glucose metabolism in patients with PCOS.

Subclinical hypothyroidism contributes to poor glycemic control in patients with type 2 diabetes mellitus, and ellagic acid attenuates methimazole-induced abnormal glucose metabolism in mice model

Subclinical hypothyroidism (SCH) as mild thyroid disorder or comorbidity in patients with endocrine disorders is closely related with insulin resistance (IR) and poor glycemic control. The present study attempted to investigate the effect of SCH on IR and glycemic control in patients with type 2 diabetes mellitus (T2DM). In addition, the effects of ellagic acid (EA) on SCH C57BL/6J and db/db mice were also investigated to explore potential therapeutic drug against SCH-induced abnormal glucose metabolism. T2DM patients were recruited in our study and categorized into two groups according to thyroid stimulating hormone (TSH) value: T2DM without SCH group (TSH ≤4 μIU/ml; n = 30) and T2DM with SCH group (TSH >4μIU/ml; n = 60). Methimazole (MMI; 0.08 mg kg^-1  day^-1 ) was intragastrically administrated for 12 weeks to establish SCH in C57BL/6J and db/db mice. Compared with T2DM patients without SCH, poor glycemic and cholesterol control were emerged in T2DM patients with SCH and that were prominent in patients with TSH more than 10 μIU/ml. In addition, a significant positive correlation between serum TSH and fasting plasma-glucose (FPG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), or glycated hemoglobin (HbA1c) was observed in T2DM patients with SCH. Moreover, abnormal glucose metabolism in C57BL/6J and db/db mice with SCH has been attenuated by EA administration. Our findings provided data regarding the positive correlation between high TSH level with poor glycemic control in T2DM patients with SCH. EA might be a supportive strategy for preventing SCH-induced abnormal glucose metabolism. PRACTICAL APPLICATIONS: Subclinical hypothyroidism (SCH) is a potential risk factor associated with abnormal glucose metabolism in patients with type 2 diabetes mellitus (T2DM). A clinical theory of a positive correlation between high TSH level and poor glycemic control was validated in type 2 diabetes mellitus patients and mouse models. Ellagic acid (EA) might be a supportive strategy for preventing SCH-induced abnormal glucose metabolism that provided a treatment option in T2DM patients with subclinical hypothyroidism in clinical practice.

Sensitivity to Thyroid Hormones and Risk of Prediabetes: A Cross-Sectional Study

CONTEXT

Thyroid hormone influences glucose homeostasis through central and peripheral regulations. To date, the link between sensitivity to thyroid hormones and prediabetes remains unknown. We aimed to investigate the association between thyroid hormones sensitivity and risk of prediabetes in both general and euthyroid populations.

METHODS

Participants with serum free triiodothyronine (FT3), free thyroxine (FT4), and thyrotropin (TSH) measurements from the health checkup programs of the First Hospital of China Medical University were collected. We measured the parameters representing central and peripheral sensitivities to thyroid hormones (central sensitivity, assessed by calculating Thyroid Feedback Quantile-based Index (TFQI), TSH Index (TSHI), and Thyrotroph Thyroxine Resistance Index (TT4RI); peripheral sensitivity, evaluated by FT3/FT4 ratio). Associations between thyroid hormones sensitivities and risk of prediabetes were assessed with logistic regression.

RESULTS

A total of 4378 participants (mean age ± SD, 49 ± 11 years) were included, with 1457 (33%) subjects had prediabetes. The risk of prediabetes was negatively associated with levels of TSHI (odds ratio [OR] 0.91; 95% confidence interval [CI], 0.85-0.97), TT4RI (OR 0.91; 95% CI, 0.84-0.99) and Parametric TFQI (PTFQI) (OR 0.89; 95% CI, 0.83-0.95) among all subjects. The association remained significant in euthyroid subjects and euthyroid subjects with negative thyroid autoimmunity. Higher FT3/FT4 ratio was associated with a mild increased risk of prediabetes (95% CI 1.09; 1.02-1.16). Compared with subjects in the lowest quartile of PTFQI, those in the highest quartile had lower risk of prediabetes (0.70; 95% CI, 0.58-0.84).

CONCLUSIONS

Decreased central sensitivity to thyroid hormones is associated with lower risk of prediabetes. This demonstrates the complex interaction between thyroid system and glucose metabolism. Future studies are warranted to confirm our findings and underlying mechanisms.

Maternal hypothyroidism in mice influences glucose metabolism in adult offspring

AIMS/HYPOTHESIS

During pregnancy, maternal metabolic disease and hormonal imbalance may alter fetal beta cell development and/or proliferation, thus leading to an increased risk for developing type 2 diabetes in adulthood. Although thyroid hormones play an important role in fetal endocrine pancreas development, the impact of maternal hypothyroidism on glucose homeostasis in adult offspring remains poorly understood.

METHODS

We investigated this using a mouse model of hypothyroidism, induced by administration of an iodine-deficient diet supplemented with propylthiouracil during gestation.

RESULTS

Here, we show that, when fed normal chow, adult mice born to hypothyroid mothers were more glucose-tolerant due to beta cell hyperproliferation (two- to threefold increase in Ki67-positive beta cells) and increased insulin sensitivity. However, following 8 weeks of high-fat feeding, these offspring gained 20% more body weight, became profoundly hyperinsulinaemic (with a 50% increase in fasting insulin concentration), insulin-resistant and glucose-intolerant compared with controls from euthyroid mothers. Furthermore, altered glucose metabolism was maintained in a second generation of animals.

CONCLUSIONS/INTERPRETATION

Therefore, gestational hypothyroidism induces long-term alterations in endocrine pancreas function, which may have implications for type 2 diabetes prevention in affected individuals.

The current debate over treatment of subclinical hypothyroidism to prevent cardiovascular complications

BACKGROUND

Subclinical hypothyroidism (SCH) is an asymptomatic condition associated with increased thyroid-stimulating hormone (TSH) >4 mIU/L with normal thyroxine (T4) and triidothyronine (T3) levels. It is more common in older subjects and especially in women with an overall incidence of 10%.

OBJECTIVE

Because the normal TSH levels increase with age up to 7.5 mIU/L in older people, several studies have reported either no benefits whereas others have reported the benefits of treatment. These studies have caused a great debate over the treatment of SCH, especially in older subjects. Therefore, the objective of this study was to review the current evidence over this debate by reviewing the recent literature on the subject to discern whether treatment of SCH is necessary and under what circumstances.

METHODS

To get a better perspective on the current debate over treatment of SCH, a focused Medline search of the English language literature was conducted from 2012 to 2019 using the terms, hypothyroidism, subclinical, dyslipidaemia, cardiovascular disease, heart failure and 38 papers with pertinent information were selected.

RESULTS

The analysis of results from these papers indicated that the normal levels of TSH are increasing with the advancement of age from 4 mIU/L up to 7.5 mIU/L for patients ≥75 years of age. Also, several of reviewed studies have shown no benefits of treatment whereas, others have shown definite benefits of treatment with levothyroxine supplementation on the clinical and metabolic effects of SBH with reductions in CVD, HF and mortality. The treatment is more effective in younger persons and less so in older persons.

CONCLUSIONS

Based on the overall evidence, treatment of SCH is indicated in younger persons with a TSH level >4.0 mIU/L. In older subjects, treatment should be individualised and based on the presence of symptoms, the level of TSH, and initiated at TSH levels ≥10 mIU/L and at low doses to avoid adverse cardiovascular effects from overtreatment.

Telmisartan attenuates obesity-induced insulin resistance via suppression of AMPK mediated ER stress

Telmisartan is a known angiotensin II (Ang II) AT1 receptor blocker (ARB). While the beneficial effect of Telmisartan on glucose and lipid metabolism has been reported, the underlying molecular mechanism remained unclear. The endoplasmic reticulum (ER) stress is considered as one of important factors contributing to insulin resistance. In this study, we found that Telmisartan alleviated diet-induced obesity and insulin resistance, suppressed inflammation in adipose tissue, and alleviated hepatic steatosis. Furthermore, we showed that Telmisartan suppressed ER stress by activating AMP-activated protein kinase (AMPK) signaling pathway in vivo. In differentiated 3T3-L1 adipocytes, Telmisartan also improved palmitate acid (PA) induced ER stress. Compound C, an AMPK inhibitor, could abolish beneficial effect of Telmisartan on ER stress. Our data indicated Telmisartan improved obesity-induced insulin resistance through suppression of ER stress by activation of AMPK. These results provided the evidence that Telmisartan may have therapeutic potential for the treatment of obesity and type II diabetes.