Effects of insulin resistance on mitochondrial (dys)function

Association of obesity- and insulin resistance-related indices with subclinical carotid atherosclerosis in type 1 diabetes: a cross-sectional study

BACKGROUND

Obesity and insulin resistance are well-established risk factors for atherosclerosis and cardiovascular disease (CVD). Although some obesity- and insulin resistance-related indices (OIRIs) have been linked to CVD, their associations with subclinical carotid atherosclerosis (SCA) in individuals with type 1 diabetes (T1D) remain unclear. This study aims to systematically explore and compare the associations of various common OIRIs with SCA in T1D population.

METHODS

A total of 418 adult inpatients with classic T1D admitted from October 2008 to June 2021 to the First Affiliated Hospital of Air Force Medical University in Xi'an, China were included in this study. Demographic, anthropometric, and laboratory data were collected. Studied OIRIs comprised body mass index, waist-to-height ratio, waist-to-hip ratio (WHR), a body shape index, abdominal volume index, body adiposity index, body roundness index, conicity index, triglyceride-glucose index, visceral adiposity index, Chinese visceral adiposity index (CVAI), lipid accumulation product, estimated glucose disposal rate (eGDR), triglyceride-to-HDL ratio, and cardiometabolic index. Binary logistic regression, restricted cubic spline (RCS), and receiver operating characteristic curves were used to examine the associations of these indices with SCA.

RESULTS

In multivariable logistic regression analyses, after adjusting for potential confounders, per 1.0-standard deviation (SD) increase in CVAI (OR, 95% CI: 1.68, 1.16-2.47), eGDRWHR (eGDR calculated with WHR; OR, 95% CI: 0.44, 0.22-0.82), and eGDRWC (eGDR calculated with waist circumference; OR, 95% CI: 0.49, 0.24-0.93) were significantly associated with SCA. CVAI exhibited the highest area under the curve (AUC) in diagnosing SCA, with a value of 0.73 (95% CI: 0.69-0.77). RCS analyses indicated a linear and positive association between CVAI and SCA in the overall population and the females. Subgroup analyses and sensitivity analyses further supported the association between CVAI and SCA. Additionally, adding CVAI to the Steno Type 1 Risk Engine (ST1RE) improved the reclassification, but did not enhance the overall discriminative ability of ST1RE to identify SCA.

CONCLUSION

Among various OIRIs, CVAI shows the strongest association with SCA in adults with T1D. These findings suggest that CVAI may merit further longitudinal investigation as a potential marker for SCA assessment in this population.

Triglyceride-glucose index: a potent predictor of metabolic risk factors and eating behavior patterns among obese individuals

BACKGROUND

The strong potential of triglyceride to glucose index (TyG) in prediction of metabolic abnormalities is well identified in numerous disease including diabetes, metabolic syndrome and kidney disorders. However, no study is available to assess its validity and association with metabolic phenotype among obese individuals. In the current study, we aimed to evaluate the TyG index, its validity and association with metabolic parameters among obese individuals.

METHODS AND MATERIALS

In the current cross-sectional study, 300 obese individuals were enrolled. Their demographic, anthropometric measurements were done and laboratory parameters including serum lipids, glycemic markers and insulin resistance were evaluated. Blood pressure was also measured with standard methods. The TyG index was calculated as the ln (fasting triglyceride level [mg/dL] × fasting glucose level [mg/dL]/2). Eating pattern was measured with three factor eating behavior questionnaire (TFEQ). Receiver operator characteristic curve was used to assess the TyG validity.

RESULTS

Subjects at the higher TyG tertile had higher waist o hip ratio (WHR) and eating disorder compared with lowest tertiles. Also, those at the highest tertiles had significantly higher total cholesterol (TC), triglyceride (TG), and fasting blood sugar (FBS), and lower high density lipoprotein cholesterol (HDL). According to the ROC curve analysis for various metabolic parameters, TyG demonstrated the highest area under curve (AUC) value of 0.838 compared with other metabolic parameters in identification of metabolic syndrome.

CONCLUSION

The current study provides valuable insights into the relationship between TyG index, metabolic parameters, and eating behaviors among obese individuals.

The Aryl Hydrocarbon Receptor (AhR) Is a Novel Gene Involved in Proper Physiological Functions of Pancreatic β-Cells

The Kynurenine pathway is crucial in metabolizing dietary tryptophan into bioactive compounds known as kynurenines, which have been linked to glucose homeostasis. The aryl hydrocarbon receptor (AhR) has recently emerged as the endogenous receptor for the kynurenine metabolite, kynurenic acid (KYNA). However, the specific role of AhR in pancreatic β-cells remains largely unexplored. This study aimed to investigate the expression of AhR in human pancreatic islets using publicly available RNA-sequencing (RNA-seq) databases and to explore its correlations with various metabolic parameters and key β-cell markers. Additionally, functional experiments were conducted in INS-1 cells, a rat β-cell line, to elucidate the role of Ahr in β-cell biology. RNA-seq data analysis confirmed the expression of AHR in human islets, with elevated levels observed in pancreatic islets obtained from diabetic and obese donors compared to non-diabetic or lean donors. Furthermore, AHR expression showed an inverse correlation with the expression of key β-cell functional genes, including insulin, PDX-1, MAFA, KCNJ11, and GCK. Silencing Ahr expression using siRNA in INS-1 cells decreased insulin secretion, insulin content, and glucose uptake efficiency, while cell viability, apoptosis rate, and reactive oxygen species (ROS) production remained unaffected. Moreover, Ahr silencing led to the downregulation of major β-cell regulator genes, Ins1, Ins2, Pdx-1, and Glut2, at both the mRNA and protein levels. In summary, this study provides novel insights into the role of AhR in maintaining proper β-cell function. These findings suggest that AhR could be a potential target for future therapeutic strategies in treating type 2 diabetes (T2D).

Evaluating sex-specific responses to western diet across the lifespan: impact on cardiac function and transcriptomic signatures in C57BL/6J mice at 530 and 640/750 days of age

BACKGROUND

Long-term consumption of Western Diet (WD) is a well-established risk factor for the development of cardiovascular disease (CVD); however, there is a paucity of studies on the long-term effects of WD on the pathophysiology of CVD and sex-specific responses.

METHODS

Our study aimed to investigate the sex-specific pathophysiological changes in left ventricular (LV) function using transthoracic echocardiography (ECHO) and LV tissue transcriptomics in WD-fed C57BL/6 J mice for 125 days, starting at the age of 300 through 425 days.

RESULTS

In female mice, consumption of the WD diet showed long-term effects on LV structure and possible development of HFpEF-like phenotype with compensatory cardiac structural changes later in life. In male mice, ECHO revealed the development of an HFrEF-like phenotype later in life without detectable structural alterations. The transcriptomic profile revealed a sex-associated dichotomy in LV structure and function. Specifically, at 530-day, WD-fed male mice exhibited differentially expressed genes (DEGs), which were overrepresented in pathways associated with endocrine function, signal transduction, and cardiomyopathies. At 750 days, WD-fed male mice exhibited dysregulation of several genes involved in various lipid, glucagon, and glutathione metabolic pathways. At 530 days, WD-fed female mice exhibited the most distinctive set of DEGs with an abundance of genes related to circadian rhythms. At 640 days, altered DEGs in WD-fed female mice were associated with cardiac energy metabolism and remodeling.

CONCLUSIONS

Our study demonstrated distinct sex-specific and age-associated differences in cardiac structure, function, and transcriptome signature between WD-fed male and female mice.

VascuFit: Aerobic exercise improves endothelial function independent of cardiovascular risk: A randomized-controlled trial

BACKGROUND AND AIMS

Endothelial dysfunction predicts elevated cardiovascular (CV) risk in healthy individuals. Aerobic exercise reduces endothelial dysfunction in part by improving CV risk factors. Yet, this explains less than 50 % of the effect and a direct influence of exercise training on the endothelium is discussed as possible contributor. The VascuFit study applied non-linear periodized aerobic exercise (NLPE) training to assess its multilevel effects on endothelial function including potential epigenetic endothelial modifications by circulating micro-ribonucleic acids (endomiRs).

METHODS

Sedentary adults with elevated CV risk between 40 and 60 years were randomized 2:1 and engaged in an eight-week ergometer-based NLPE training (n = 30) or received standard exercise recommendations (n = 14). Macro-, microvascular, cellular and molecular adaptations were assessed via brachial-arterial flow-mediated dilation (baFMD), static retinal vessel analysis (SVA), flow cytometry, and endomiRs regulating key pathways of endothelial function. Statistics included ANCOVA, Principal Component Analysis (PCA), and regression analyses.

RESULTS

baFMD improved by 2.38 % (CI:0.70-4.06, p = 0.007) independent of CV risk, whereas SVA parameters and circulating endothelial (progenitor) cells did not significantly change in the NLPE group. The mean distance between baseline and follow-up PCA loadings of the endomiR dataset explaining 44.2 % of dataset variability was higher in the NLPE-group compared to the control group (2.71 ± 2.02 vs. 1.65 ± 0.93). However, regression analyses showed no evidence of endomiRs explaining the improvement of baFMD.

CONCLUSIONS

The improvement of macrovascular endothelial function by aerobic exercise training was independent from CV risk factors. Increased heterogeneity among endomiRs did not explain this effect, but suggests an adaptive response to the exercise stimulus on the epigenetic level.

Vascular disease and ischemic stroke in patients with atrial fibrillation: Temporal trends and age-related differences

BACKGROUND AND AIMS

We examined temporal trends and age-related differences in the prevalence of vascular diseases and in their association with ischemic stroke (IS) risk in patients with atrial fibrillation (AF).

METHODS

The registry-based FinACAF study covered all patients with AF in Finland during 2007-2018. Incidence rate ratios (IRRs) of IS were computed with Poisson regression, and the interaction of vascular diseases with age and calendar year period was assessed.

RESULTS

We identified 229,565 patients (50.0 % female; mean age 72.7 years) with incident AF. The overall prevalence of any vascular disease was 28.6 %, and the prevalence increased from 2007 to 2018, primarily among patients over 75 years. Overall, 5909 (2.6 %) patients experienced IS within the first year after AF diagnosis. Crude IS rate decreased continuously during the study period in both patients with and without vascular diseases, with the rates remaining consistently higher in patients with vascular diseases. Vascular diseases were independently associated with higher IS incidence among patients under 65 years (adjusted IRR with 95 % confidence interval 1.35 (1.10-1.66)), while among older patients, only peripheral artery disease was associated with IS, and other vascular conditions had no association with IS. No interactions between the calendar year period and vascular diseases with IS rate were observed.

CONCLUSIONS

The association between vascular diseases and IS has remained stable over time and vascular diseases were independently associated with higher incidence of IS particularly in patients with AF under the age of 65.

Establishment, Prediction, and Validation of a Nomogram for Cognitive Impairment in Elderly Patients With Diabetes

Objective: The purpose of this study is to establish a predictive model of cognitive impairment in elderly people with diabetes. Methods: We analyzed a total of 878 elderly patients with diabetes who were part of the National Health and Nutrition Examination Survey (NHANES) from 2011 to 2014. The data were randomly divided into training and validation cohorts at a ratio of 6:4. The least absolute shrinkage and selection operator (LASSO) logistic regression analysis to identify independent risk factors and construct a prediction nomogram for cognitive impairment. The performance of the nomogram was assessed using receiver operating characteristic (ROC) curve and calibration curve. Decision curve analysis (DCA) was performed to evaluate the clinical utility of the nomogram. Results: LASSO logistic regression was used to screen eight variables, age, race, education, poverty income ratio (PIR), aspartate aminotransferase (AST), blood urea nitrogen (BUN), serum uric acid (SUA), and heart failure (HF). A nomogram model was built based on these predictors. The ROC analysis of our training set yielded an area under the curve (AUC) of 0.786, while the validation set showed an AUC of 0.777. The calibration curve demonstrated a good fit between the two groups. Furthermore, the DCA indicated that the model has a favorable net benefit when the risk threshold exceeds 0.2. Conclusion: The newly developed nomogram has proved to be an important tool for accurately predicting cognitive impairment in elderly patients with diabetes, providing important information for targeted prevention and intervention measures.

Prediabetes Increases the Risk of Frailty in Prefrail Older Adults With Hypertension: Beneficial Effects of Metformin

BACKGROUND

Prediabetes has garnered increasing attention due to its association with cardiovascular conditions, especially hypertension, which heightens the risk of prefrailty and frailty among older individuals.

METHODS

We screened elders with prefrail hypertension from March 2021 to January 2023. We assessed the correlation linking cognitive dysfunction (Montreal Cognitive Assessment score), insulin resistance (triglyceride-to-glucose index), and physical impairment (5-meter gait speed). Then, we measured the risk of developing frailty after a 1-year follow-up period, adjusting the outcome using multivariable Cox regression analysis. We also investigated the impact of administering 500 mg of metformin once daily to a subset of frail subjects for an additional 6 months.

RESULTS

We assessed the relationship between the triglyceride-to-glucose index and the Montreal Cognitive Assessment score, observing a significant correlation (r, 0.880; P<0.0001). Similarly, we analyzed the association between the triglyceride-to-glucose index and 5-meter gait speed, uncovering a significant link between insulin resistance and physical impairment (r, 0.809; P<0.0001). Prediabetes was found to significantly (P<0.0001) elevate the risk of frailty development compared with individuals without prediabetes by the end of the 1-year follow-up, a finding confirmed via multivariable analysis with Cox regression. Furthermore, among the subgroup of subjects who developed frailty, those who received metformin exhibited a significant decrease in frailty levels (P<0.0001).

CONCLUSIONS

Insulin resistance and prediabetes play substantial roles in the development of cognitive and physical impairments, highlighting their importance in managing hypertension, even before the onset of frank diabetes. Metformin, a well-established drug for the treatment of diabetes, has shown favorable effects in mitigating frailty.

Dysfunctional mitochondria elicit bioenergetic decline in the aged heart

Aging represents a complex biological progression affecting the entire body, marked by a gradual decline in tissue function, rendering organs more susceptible to stress and diseases. The human heart holds significant importance in this context, as its aging process poses life-threatening risks. It entails macroscopic morphological shifts and biochemical changes that collectively contribute to diminished cardiac function. Among the numerous pivotal factors in aging, mitochondria play a critical role, intersecting with various molecular pathways and housing several aging-related agents. In this comprehensive review, we provide an updated overview of the functional role of mitochondria in cardiac aging.

Insulin resistance drives cognitive impairment in hypertensive pre-diabetic frail elders: the CENTENNIAL study

AIMS

Pre-diabetes is a condition that confers an increased cardiovascular risk. Frailty is very common in hypertensive patients, and insulin resistance has been linked to frailty in older adults with diabetes. On these grounds, our aim was to evaluate the association between insulin resistance and cognitive impairment in hypertensive and pre-diabetic and frail older adults.

METHODS AND RESULTS

We studied consecutive pre-diabetic and hypertensive elders with frailty presenting at the Avellino local health authority of the Italian Ministry of Health (ASL AV) from March 2021 to March 2022. All of them fulfilled the following inclusion criteria: a previous diagnosis of hypertension with no clinical or laboratory evidence of secondary causes, a confirmed diagnosis of pre-diabetes, age >65 years, Montreal Cognitive Assessment (MoCA) Score <26, and frailty. We enrolled 178 frail patients, of which 141 successfully completed the study. We observed a strong inverse correlation (r = -0.807; P < 0.001) between MoCA Score and Homeostatic Model Assessment for Insulin Resistance (HOMA-IR). The results were confirmed by a linear regression analysis using MoCA Score as dependent variable, after adjusting for several potential confounders.

CONCLUSION

Taken together, our data highlight for the first time the association between insulin resistance and global cognitive function in frail elders with hypertension and pre-diabetes.

Diet-Related Changes of Short-Chain Fatty Acids in Blood and Feces in Obesity and Metabolic Syndrome

Obesity-related illnesses are one of the leading causes of death worldwide. Metabolic syndrome has been associated with numerous health issues. Short-chain fatty acids (SCFAs) have been shown to have multiple effects throughout the body, both directly as well as through specific G protein-coupled receptors. The main SCFAs produced by the gut microbiota are acetate, propionate, and butyrate, which are absorbed in varying degrees from the large intestine, with some acting mainly locally and others systemically. Diet has the potential to influence the gut microbial composition, as well as the type and amount of SCFAs produced. High fiber-containing foods and supplements increase the production of SCFAs and SCFA-producing bacteria in the gut and have been shown to have bodyweight-lowering effects. Dietary supplements, which increase SCFA production, could open the way for novel approaches to weight loss interventions. The aim of this review is to analyze the variations of fecal and blood SCFAs in obesity and metabolic syndrome through a systematic search and analysis of existing literature.

Metabolic signatures of insulin resistance in non-diabetic individuals

BACKGROUND

Insulin resistance (IR) evolved from excessive energy intake and poor energy expenditure, affecting the patient's quality of life. Amino acid and acylcarnitine metabolomic profiles have identified consistent patterns associated with metabolic disease and insulin sensitivity. Here, we have measured a wide array of metabolites (30 acylcarnitines and 20 amino acids) with the MS/MS and investigated the association of metabolic profile with insulin resistance.

METHODS

The study population (n = 403) was randomly chosen from non-diabetic participants of the Surveillance of Risk Factors of NCDs in Iran Study (STEPS 2016). STEPS 2016 is a population-based cross-sectional study conducted periodically on adults aged 18-75 years in 30 provinces of Iran. Participants were divided into two groups according to the optimal cut-off point determined by the Youden index of HOMA-IR for the diagnosis of metabolic syndrome. Associations were investigated using regression models adjusted for age, sex, and body mass index (BMI).

RESULTS

People with high IR were significantly younger, and had higher education level, BMI, waist circumference, FPG, HbA1c, ALT, triglyceride, cholesterol, non-HDL cholesterol, uric acid, and a lower HDL-C level. We observed a strong positive association of serum BCAA (valine and leucine), AAA (tyrosine, tryptophan, and phenylalanine), alanine, and C0 (free carnitine) with IR (HOMA-IR); while C18:1 (oleoyl L-carnitine) was inversely correlated with IR.

CONCLUSIONS

In the present study, we identified specific metabolites linked to HOMA-IR that improved IR prediction. In summary, our study adds more evidence that a particular metabolomic profile perturbation is associated with metabolic disease and reemphasizes the significance of understanding the biochemistry and physiology which lead to these associations.